Forecast Discussions mentioning any of "HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 05/17/16

Area Forecast Discussion
National Weather Service Flagstaff AZ
357 PM MST MON MAY 16 2016

.SYNOPSIS...A low pressure system moving south through the western
states will bring showers and thunderstorms to northern Arizona
starting this afternoon. On Tuesday and Wednesday, the low moves
into Arizona, expect increasing shower and thunderstorm activity
spreading deeper into central Arizona. By Thursday shower activity
will diminish and be limited the the mountain areas with the best
chances for measurable rain over the White Mountains region in
eastern Arizona. Dry weather will return from Friday into the
weekend with good chances for advisory level winds on Friday
afternoon.

&&

.DISCUSSION...A cold low pressure system is currently diving south
through the western states. Today`s showers and thunderstorms were
but a taste of the leading edge of this storm. On Tuesday and
Wednesday this low moves into northern Arizona with numerous
showers and thunderstorms expanding further into central Arizona.
Shower and storm activity will continue into the overnight hours
as the instability and lift associated with the upper low will be
strong enough to overcome typical nocturnal surface cooling
effects that otherwise cause convection to decrease diurnally.
Afternoon temperatures will also be around 10 degrees colder than
normal for this time of year. We are forecasting around 0.25
inches of rainfall over our mountain regions.

The main impacts with this system will be wet roads, occasional
erratic gusty winds and small hail. The probability for flooding
or severe thunderstorms is low.

By Thursday the low will move eastward away from the state with
lingering chances for showers and afternoon thunderstorms mainly
over mountain areas. The best chances for measurable precipitation
will be in the White Mountains region on Thursday afternoon.

Friday through Sunday...Another seasonably strong low pressure
system sets up over the Pacific Northwest. This low will remain
too far north of Arizona to bring us much in the way of
precipitation. However the position of the low will increase our
surface pressure gradients leading to stronger winds. The
strongest winds for this period will develop on Friday with good
chances that our Friday afternoon wind gusts will exceed our wind
advisory thresholds.

&&

.AVIATION...For the 00Z package...TIL 02Z...expect scattered
-shra/-tsra coverage north of I-40 with isolated coverage south of
I-40. MVFR cig/vis possible. Erratic outflow wind gusts to 40kt
possible near precip shafts. Otherwise sfc winds SW-W 15-25 kts.
Btwn 02z-15Z Tues VFR with light winds. Aft 15z tues, sct
-shra/-tsra developing across northern AZ. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...A slow moving upper level low will bring
moisture and very good chances for showers and thunderstorms to
northern Arizona from Tuesday through Wednesday evening. Max temps
to be around 10 degrees below normal.

Thursday through Saturday...Chances for showers and thunderstorms
decrease from west to east on Thursday. Dry weather and increasing
south to southwest winds will return Friday and Saturday.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC...Bohlin
AVIATION...DL
FIRE WEATHER...DL


For Northern Arizona weather information visit
weather.gov/flagstaff



  [top] Area Forecast Discussion National Weather Service Phoenix AZ 255 PM MST MON MAY 16 2016 .SYNOPSIS... A large Pacific low pressure system is expected to move south from Idaho, and into Arizona late Tuesday through Wednesday. Increasing clouds with a chance of showers and thunderstorms are forecast to spread from southeast California and southwest Arizona late Tuesday afternoon, into south central Arizona Tuesday night and Wednesday. Clearing is expected Wednesday night, with dry weather and near normal temperatures developing toward the end of the work week and weekend. && .DISCUSSION... Tonight through Wednesday Night... An interesting weather pattern will develop over the region the next few days. A large former Pacific low pressure system, centered over southwest Idaho since Sunday, will start to move south toward AZ. Strong ridge building along the Pacific northwest coast, folding over into southwest Canada, bodes well for the Idaho trof to retrograde and track southwest into southern CA Tuesday and Tuesday night. Mid/hi level cyclonic shear will increase the potential for showers and thunderstorms, with increasing moisture. The San Diego sounding showed some appreciable low level moisture, and the Chihuahua Mexico balloon sounding showed a hint of a significant moisture plume visible south of the border in precip water satellite imagery. Lastly, the Phoenix and Tucson Radar VAD Wind Profiles were already detect backing south to southwest winds under 12 thsd feet. As the trof deepens from Idaho toward southern CA, low level winds will continue to back from the south, importing more moisture into the tight mid/hi level cyclonic circulation feature expected Tuesday/Tuesday night. In other words, as the trof moves slowly west to east, a threat of showers and thunderstorms will first develop in southeast CA/southwest AZ late Tuesday afternoon,then spread into south central AZ, including Phoenix, Tuesday night and Wednesday. Clearing is expected Wednesday night. Thursday and Friday... In the aftermath of Wednesdays eastward moving trof, dry west to northwesterly flow will develop Thursday over our forecast area. The flow aloft will change to dry southwesterly in advance of yet another large Pacific weather system expected to develop However another Large Pacific weather system will settle into the western states this weekend, producing gusty south to southwest winds area-wide Fri, Sat, Sun, and Mon afternoons. && .AVIATION... South-Central Arizona including KPHX...KIWA and KSDL... No aviation weather impacts expected through Tuesday afternoon. Southeasterly flow will veer to westerly this afternoon, peaking around 10 kt with occasional gusts to around 15 kt. Onset of the downslope easterly flow will occur near the climatological average of 09-10z. Southeast California/Southwest Arizona including KIPL and KBLH... Typical diurnal winds expected at the terminals, generally less than 15 kt at KIPL and KBLH. Looking ahead, scattered showers and thunderstorms will likely develop ahead of an approaching low pressure system Tuesday afternoon. The strongest storms will be capable of producing strong downdraft winds. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Wednesday through Sunday... An upper level low will begin weakening on Wednesday with just a slight chance of showers and thunderstorms east of the Lower Colorado River Valley. Temperatures will be below normal over south- central AZ and at or slightly above normal across southeast California and southwest Arizona. The system exits on Thursday for warmer temperatures and increasing winds. Another system slowly approaches from the northwest Friday into Sunday for breezy to windy conditions each day and a cooling trend. Minimum humidities will generally be in the 15-20 percent range over the lower deserts through Thursday before declining to near 10 percent by Friday. Friday afternoon, and possibly Saturday afternoon, will likely have elevated fire danger conditions over portions of the area. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...Vasquez AVIATION...Hirsch FIRE WEATHER...Kuhlman
Area Forecast Discussion National Weather Service Phoenix AZ 605 AM MST MON MAY 16 2016 .UPDATE...Updated Aviation and Fire Weather Discussions... && .SYNOPSIS... Cooler air is beginning to move into the region as a Pacific low pressure system in the northwest U.S. begins to deepen and sag further south. The Pacific low is forecast to move into the southwestern states early this week persisting through Wednesday. This will provide even cooler temperatures along with slight chances of showers and thunderstorms Tuesday. Clearing skies with rebounding temperatures are forecast for late in the week. && .DISCUSSION... Broad upper low circulation covers much of the Intermountain West this early morning with a few well-defined embedded vorticies along a weak upper jet intrusion on the western side of the low. This low pressure system will be the focus on our weather for the early part of the week, bringing a temperature cool down and shower/thunderstorm chances across the forecast area. Overnight skies remain clear and winds have subsided from their elevated westerly breezes last evening. Continued draw-down of UL heights and few degrees of cooling through the atmo profile transitioning into the area from yesterday`s cool front have generated cooler morning temperatures so far, generally 4 to 5 degrees cooler than this time Sunday. Dry conditions, afternoon southwesterly breezes and temperatures over the Deserts in the upper 80s to low 90s are expected today ahead of the southward sagging Great Basin upper low. Forecast model consistency has been fairly good with regards to this upper low - still tracking the main circulation center west across SoCal by Tuesday afternoon and into central AZ overnight Tuesday into Wednesday. 500mb heights have already retreated from their higher values late last week so the height fall differential with the intruding upper low is not as great as previous events we`ve seen this Spring. PWAT forecasts on model plots and soundings have flirted with 0.75 to 1.00 inch values, focused mainly along and either side of the CO River Valley by Tuesday evening. When comparing these values to soundings from neighboring offices of Tucson and Las Vegas these forecast values are in the upper reaches of PWAT sounding climatology. Also hard not imagine some Gulf of California moisture advection into the region with southerly flow up the river; dewpoints for sites along the River have touched the 50F mark periodically over the weekend. While that is more surface based moisture, a thin layer of mid-level moisture returns are also forecast. These are most noticeable in several inverted-V soundings for KBLH, KPHX and Wickenburg. SREF plume forecasts do generate a few hundred joules of mean MU and ML CAPE for Tuesday afternoon and overnight, in conjunction with the overhead passage of the upper cold core. Forecast 500mb and 300mb temperatures in the -16 to -17C and -40 to -44C ranges respectively. Still not an overly favorable profile to support organized convection in terms of wind and we`ll be looking for the dry sub-cloud layer to enhance evaporative processes leading to gusty outflow winds from any showers and storms that do develop. Given the latest guidance suggesting 1) sufficient moisture for some high-based activity across the western AZ deserts and 2) hi- resolution gridded wind fields indicating some outflow boundary activity emanating from the western AZ deserts, felt that slightly boosting PoPs across La Paz and western Maricopa counties for Tuesday afternoon and evening was warranted. With varying periods of partly to mostly cloudy skies, the South- Central AZ Deserts can expect a few more degrees of cooling off high temperatures from today for Tuesday and Wednesday, with widespread 80-degree readings. Tuesday will be cool for most, including locations west of the CO River Valley with some warming back into the 90s possible by Wednesday. The loosely cut-off system will begin to become more of an open wave as it clear east of the area overnight Wednesday, with some slight chances lingering for spotty thundershower activity over the eastern AZ higher terrain for Wednesday and Thursday afternoons. For the rest of the forecast area from Phoenix, Blythe, Gila Bend, Yuma and El Centro - conditions will slowly warm back up to near-normal values as very short-lived ridging passes through the area peaking 1000-500mb thicknesses back into the mid 570dm range. Upper level pattern remains active and progressive across the West for the coming weekend as a broader and deeper Pacific low moves down the West Coast out of B.C. and the Gulf of Alaska. Beginning Friday, deep southerly flow filters in across much of the Southwest states allow for healthy WAA and prolonged warming of temperatures in spite of the gradually lower UL heights in troughing upstream. What remained uncertain over previous forecast periods was the southward extent of the low. It appears now that the main circulation and cold core stays to our north across the Great Basin. Downstream ridging would lend us to think the Pacific low would dive further south over the weekend, but it now looks like ridging over the Plains will weaken while another upstream Pacific low transitions out of the Gulf of Alaska late Saturday. This should shift the Great Basin Low over the Rockies. All-in-all, some variant of troughing will generally hold over the west with several periods of breezy to gusty winds for the coming weekend and into early next week. Temperatures shouldn`t see a significant cool-down, but rather just below mid-May normals with many lower elevations sites a degree or two either side of 90F. && .AVIATION... South-Central Arizona including KPHX...KIWA and KSDL... Southeast California/Southwest Arizona including KIPL and KBLH... Light winds this morning will turn westerly and become breezy at times this afternoon, mainly at Phoenix area terminals. Dry westerly flow aloft will keep skies mainly clear into early Tuesday before the next weather system moves into the region bringing a chance of showers and thunderstorms later Tuesday. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Wednesday through Sunday... An upper level low will begin weakening on Wednesday with just a slight chance of showers and thunderstorms east of the Lower Colorado River Valley. Temperatures will be below normal over south- central AZ and at or slightly above normal across southeast California and southwest Arizona. The system exits on Thursday for warmer temperatures and increasing winds. Another system slowly approaches from the northwest Friday into Sunday for breezy to windy conditions each day and a cooling trend. Minimum humidities will generally be in the 15-20 percent range over the lower deserts through Thursday before declining to near 10 percent by Friday. Friday afternoon, and possibly Saturday afternoon, will likely have elevated fire danger conditions over portions of the area. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...Nolte AVIATION...Kuhlman FIRE WEATHER...Kuhlman
Area Forecast Discussion National Weather Service Flagstaff AZ 358 AM MST MON MAY 16 2016 .SYNOPSIS...Expect breezy west southwest winds today, along with an increasing chance of showers and thunderstorms by afternoon. A slow moving storm system will keep a chance of showers and thunderstorms over the area through at least Thursday. Temperatures will be below average through midweek and then warm back to around average second half of the week. && .DISCUSSION...A large area of low pressure over the western states will continue to move southward today...and be over the area Tuesday and Wednesday. Best chances for showers today will primarily be north of I-40...with the best lift and instability. Tuesday and Wednesday...The area of low pressure will drop southward into portions of northwest and central Arizona on Tuesday...and then be over the region on Wednesday. Stronger lift...deeper saturation...and instability will provide for good chances of showers and thunderstorms. Rainfall amounts look to be from 0.1 to 0.5 inches with this system, lighter amounts expected for the lower elevations Thursday northern Arizona is forecast to transition from a low pressure trough back to a high pressure ridge pattern, bringing drier conditions and warming daytime temperatures. Friday through Sunday...Another low pressure trough is forecast to approach northern Arizona from the west, producing a dry and windy southwest flow. By Monday of next week the low pressure trough is forecast to move across Arizona...bringing lighter winds...drying conditions...and slightly below average daytime temperatures. && .AVIATION...For the 12Z package...Expect VFR conditions overnight. After 18Z Mon...expect isolated to scattered SHRA/TSRA primarily along and north of a KFLG-KRQE line with brief MVFR cig/vis possible. Winds becoming westerly Mon afternoon 15-25 kts. In addition, collapsing TSRA may produce very strong and erratic surface winds with gusts as high as 50 knots possible in the vicinity of storms. Aviation discussion not updated for TAF amendments. .FIRE WEATHER...A slow moving low will bring increasing moisture and increasing chances for showers and thunderstorms to northern Arizona on Monday and Tuesday. Wednesday through Friday...Chances for showers and thunderstorms continue through Wednesday with a drying trend starting from Thursday onward. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC...TC AVIATION...RR FIRE WEATHER...RR For Northern Arizona weather information visit weather.gov/flagstaff
Area Forecast Discussion National Weather Service Phoenix AZ 314 AM MST MON MAY 16 2016 .SYNOPSIS... Cooler air is beginning to move into the region as a Pacific low pressure system in the northwest U.S. begins to deepen and sag further south. The Pacific low is forecast to move into the southwestern states early this week persisting through Wednesday. This will provide even cooler temperatures along with slight chances of showers and thunderstorms Tuesday. Clearing skies with rebounding temperatures are forecast for late in the week. && .DISCUSSION... Broad upper low circulation covers much of the Intermountain West this early morning with a few well-defined embedded vorticies along a weak upper jet intrusion on the western side of the low. This low pressure system will be the focus on our weather for the early part of the week, bringing a temperature cool down and shower/thunderstorm chances across the forecast area. Overnight skies remain clear and winds have subsided from their elevated westerly breezes last evening. Continued draw-down of UL heights and few degrees of cooling through the atmo profile transitioning into the area from yesterday`s cool front have generated cooler morning temperatures so far, generally 4 to 5 degrees cooler than this time Sunday. Dry conditions, afternoon southwesterly breezes and temperatures over the Deserts in the upper 80s to low 90s are expected today ahead of the southward sagging Great Basin upper low. Forecast model consistency has been fairly good with regards to this upper low - still tracking the main circulation center west across SoCal by Tuesday afternoon and into central AZ overnight Tuesday into Wednesday. 500mb heights have already retreated from their higher values late last week so the height fall differential with the intruding upper low is not as great as previous events we`ve seen this Spring. PWAT forecasts on model plots and soundings have flirted with 0.75 to 1.00 inch values, focused mainly along and either side of the CO River Valley by Tuesday evening. When comparing these values to soundings from neighboring offices of Tucson and Las Vegas these forecast values are in the upper reaches of PWAT sounding climatology. Also hard not imagine some Gulf of California moisture advection into the region with southerly flow up the river; dewpoints for sites along the River have touched the 50F mark periodically over the weekend. While that is more surface based moisture, a thin layer of mid-level moisture returns are also forecast. These are most noticeable in several inverted-V soundings for KBLH, KPHX and Wickenburg. SREF plume forecasts do generate a few hundred joules of mean MU and ML CAPE for Tuesday afternoon and overnight, in conjunction with the overhead passage of the upper cold core. Forecast 500mb and 300mb temperatures in the -16 to -17C and -40 to -44C ranges respectively. Still not an overly favorable profile to support organized convection in terms of wind and we`ll be looking for the dry sub-cloud layer to enhance evaporative processes leading to gusty outflow winds from any showers and storms that do develop. Given the latest guidance suggesting 1) sufficient moisture for some high-based activity across the western AZ deserts and 2) hi- resolution gridded wind fields indicating some outflow boundary activity emanating from the western AZ deserts, felt that slightly boosting PoPs across La Paz and western Maricopa counties for Tuesday afternoon and evening was warranted. With varying periods of partly to mostly cloudy skies, the South- Central AZ Deserts can expect a few more degrees of cooling off high temperatures from today for Tuesday and Wednesday, with widespread 80-degree readings. Tuesday will be cool for most, including locations west of the CO River Valley with some warming back into the 90s possible by Wednesday. The loosely cut-off system will begin to become more of an open wave as it clear east of the area overnight Wednesday, with some slight chances lingering for spotty thundershower activity over the eastern AZ higher terrain for Wednesday and Thursday afternoons. For the rest of the forecast area from Phoenix, Blythe, Gila Bend, Yuma and El Centro - conditions will slowly warm back up to near-normal values as very short-lived ridging passes through the area peaking 1000-500mb thicknesses back into the mid 570dm range. Upper level pattern remains active and progressive across the West for the coming weekend as a broader and deeper Pacific low moves down the West Coast out of B.C. and the Gulf of Alaska. Beginning Friday, deep southerly flow filters in across much of the Southwest states allow for healthy WAA and prolonged warming of temperatures in spite of the gradually lower UL heights in troughing upstream. What remained uncertain over previous forecast periods was the southward extent of the low. It appears now that the main circulation and cold core stays to our north across the Great Basin. Downstream ridging would lend us to think the Pacific low would dive further south over the weekend, but it now looks like ridging over the Plains will weaken while another upstream Pacific low transitions out of the Gulf of Alaska late Saturday. This should shift the Great Basin Low over the Rockies. All-in-all, some variant of troughing will generally hold over the west with several periods of breezy to gusty winds for the coming weekend and into early next week. Temperatures shouldn`t see a significant cool-down, but rather just below mid-May normals with many lower elevations sites a degree or two either side of 90F. && .AVIATION... South-Central Arizona including KPHX...KIWA and KSDL... Southeast California/Southwest Arizona including KIPL and KBLH... Gusty westerly winds to continue to gradually diminish through the rest of the evening and overnight hours as stronger winds aloft become decoupled from the surface. wind directions to become easterly later tonight at the phx area taf sites, while KBLH remains out of a southerly to sw-ly direction, and KIPL out of a westerly direction. After a period of light winds on Monday morning, stronger westerly winds to develop Monday afternoon at the phx area taf sites and at KIPL as stronger winds once again mix down to the sfc, with KBLH seeing winds picking up from a southerly direction. Dry westerly flow aloft to keep skies mainly clear through monday at all of the taf sites. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Wednesday through Sunday... An upper level low will begin weakening on Wednesday with just a slight chance of showers and thunderstorms (east of the Lower Colorado River Valley). Temperatures will be below normal over south-central AZ (at or slightly above normal west of there). Winds will be light. The system exits on Thursday for warmer temperatures and more noticeable afternoon breezes. Another system slowly approaches from the northwest Friday into Sunday for breezy conditions (especially southeast California) and a cooling trend. Minimum humidities will generally be in the 15-20 percent range on the lower deserts before declining to near 10 percent by Friday. Overnight recovery also trends down but remains fair. Portions of southeast California and the Lower Colorado River Valley may occasionally flirt with critical thresholds during the Friday-Sunday time frame. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...Nolte AVIATION...Percha FIRE WEATHER...AJ
  [top] Area Forecast Discussion National Weather Service Tucson AZ 257 AM MST MON MAY 16 2016 .SYNOPSIS...A low pressure system will move south into the desert southwest by midweek. Cooler temperatures will occur through Tuesday followed by isolated to scattered thunderstorms from Tucson eastward Wednesday. A chance of showers continues across the White mountains Thursday, then dry conditions with warmer temperatures next weekend. && .DISCUSSION...Breezy conditions again today across far southeast Arizona. Otherwise...mostly clear skies and cooler afternoon temperatures can be anticipated. Models continued to track a low pressure system south into northwest Arizona on Tuesday. Moisture associated with this system appeared to be limited but enough to warrant the mention of a few showers and thunderstorms Tuesday into Thursday. The best chance of showers will be across northern and eastern sections of the state. Cooler air will also accompany this system with high temperatures lowering to near normal readings this week. Thereafter, medium range models showed a ridge of high pressure building over the desert southwest followed by another storm system which will bring breezy to windy conditions this weekend. && .AVIATION...VALID THRU 17/12Z. Clear skies and VFR conditions will prevail through the forecast period. Surface wind less than 10 kts thru 16/14z...then increasing surface wind. Sly/swly surface wind at 15-25 kts and gusts to 23-33 kts by 16/19z...with the strongest surface wind east of KTUS in the vicinity of KALK, KFHU and especially KDUG. Surface wind diminishing aft 17/02z and generally less than 10 kts by 17/05z. Aviation discussion not updated for TAF ammendments. && .FIRE WEATHER.... Breezy conditions will persist today across the far southeastern corner of southeast Arizona...roughly southeast of a line from the Huachuca mountains to the Chiricahua mountains in Cochise county. Critical fire weather thresholds may be briefly exceeded in this area this afternoon. However, widespread conditions are not expected and therefore no fire weather headlines will be in effect. Less wind is expected elsewhere across the forecast area today, along with dry and cooler conditions. There will be a slight chance of showers and thunderstorms Tuesday into Thursday, mainly northeast and east of the Tucson metro area. The best chance of precipitation will be in the White mountains. Some afternoon breeziness is expected through the upcoming week, mainly on Tuesday and then again Friday into Sunday of next weekend. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Area Forecast Discussion National Weather Service Phoenix AZ 1030 PM MST SUN MAY 15 2016 .UPDATE...To Aviation Discussion... && .SYNOPSIS... Cooler air is beginning to move into the region as a Pacific low pressure system in the northwest U.S. begins to deepen and sag further south. The Pacific low is forecast to move into the southwestern states early this week persisting through Wednesday. This will provide even cooler temperatures along with slight chances of showers and thunderstorms Tuesday. Clearing skies with rebounding temperatures are forecast for late in the week. && .DISCUSSION... upper low pressure, that is now moving into the northern Great Basin, has begun to bring cooler temperatures to the region today, with the high at Phoenix Sky Harbor ending up at 95 today, down 6 degrees from yesterday`s high of 101. Along with the cooler temperatures, locally gusty winds also occurred today as the winds aloft increase ahead of the upper low. westerly winds in the 15-20 mph range with gusts to 30 mph were observed at many locations across South-Central and SW Arizona, with even stronger winds over parts of SE CA. Along with the winds, a few pockets of blowing dust were also observed. The latest (00z) GFS and NAM model suites continue to show the upper low moving toward the region through the early and middle parts of this week, with temperatures cooling even further, and even a chance for showers from late Tuesday into Wednesday, as the upper low center moves across the region. As far as the very short term is concerned, other then some downward adjustment in the hourly dewpoint forecasts and some minor adjustments to the other hourly grids, inherited forecasts are holding up well. && .PREVIOUS DISCUSSION... Upper low across the Great Basin continues to drift eastward this afternoon. Latest satellite imagery shows widespread cloudiness out ahead of this system across the Rockies with a smattering of showers and thunderstorms extending southward into Chihuahua. Across the desert southwest, skies have been mostly clear with temperatures in the lower 90s across the lower deserts, a drop of roughly 6 to 8 from those observed yesterday. Dewpoints are also significantly lower east of Phoenix, though moisture is already increasing again across western Arizona ahead of a vort max traversing the Mojave Desert. This vort max will also strengthen wind fields across the region and breezy conditions are anticipated through this evening across much of the area. No major changes were made to the forecast in the short-term. Temperatures tonight will be near or slightly above average with subsiding winds and mostly clear skies. && .PREVIOUS DISCUSSION... The upper low eventually will start to dig southward through the Great Basin on Monday into the Desert Southwest on Tuesday. Models have been consistent with the overall track of this system, but have shifted it further west slightly over the past 24 hours. Some moisture advection is expected over our area Tuesday into early Wednesday with PWATS increasing to between 0.50-0.75 inches. Though this system is not very cold aloft (500mb temps near -16C) there should be sufficient moisture and instability for some isolated showers and thunderstorms starting Tuesday afternoon. Overall timing has shifted a bit later, so rain chances will linger into Wednesday, especially from Phoenix eastward. Have added in slight chance POPs across south-central Arizona for Tuesday night and Wednesday morning with chances remaining through Wednesday evening across the higher terrain east of Phoenix. We could see a shot at some gusty thunderstorm winds with an inverted V forecast sounding structure, but winds aloft will be light, so would only rely on evaporative cooling effects. Temperatures through Wednesday are forecast to be at or below normals with Monday and Tuesday being the coolest days with highs mostly in the upper 80s across the lower deserts. We will start to see some warming across our western zones on Wednesday under rising heights aloft as highs climb back into the middle 90s. Model consensus continues to show a deep Pacific low digging southward into the Pacific Northwest late this week, but what happens thereafter is less certain as model spread increases into next weekend. For the Desert Southwest, heights aloft and temperatures will certainly rise on Thursday and Friday resulting in highs at or just above normals (middle to upper 90s). Have low confidence in the forecast picture for next weekend as it is not clear if the Pacific low will dig far enough south to affect the Desert Southwest. && .AVIATION... South-Central Arizona including KPHX...KIWA and KSDL... Southeast California/Southwest Arizona including KIPL and KBLH... Gusty westerly winds to continue to gradually diminish through the rest of the evening and overnight hours as stronger winds aloft become decoupled from the surface. wind directions to become easterly later tonight at the phx area taf sites, while KBLH remains out of a southerly to sw-ly direction, and KIPL out of a westerly direction. After a period of light winds on Monday morning, stronger westerly winds to develop Monday afternoon at the phx area taf sites and at KIPL as stronger winds once again mix down to the sfc, with KBLH seeing winds picking up from a southerly direction. Dry westerly flow aloft to keep skies mainly clear through monday at all of the taf sites. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Wednesday through Sunday... An upper level low will begin weakening on Wednesday with just a slight chance of showers and thunderstorms (east of the Lower Colorado River Valley). Temperatures will be below normal over south-central AZ (at or slightly above normal west of there). Winds will be light. The system exits on Thursday for warmer temperatures and more noticeable afternoon breezes. Another system slowly approaches from the northwest Friday into Sunday for breezy conditions (especially southeast California) and a cooling trend. Minimum humidities will generally be in the 15-20 percent range on the lower deserts before declining to near 10 percent by Friday. Overnight recovery also trends down but remains fair. Portions of southeast California and the Lower Colorado River Valley may occasionally flirt with critical thresholds during the Friday-Sunday time frame. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...Percha/Hirsch PREVIOUS DISCUSSION...Kuhlman AVIATION...Percha FIRE WEATHER...AJ
Area Forecast Discussion National Weather Service Phoenix AZ 900 PM MST SUN MAY 15 2016 .UPDATE... Updated Aviation and Fire Weather sections. && .SYNOPSIS... Cooler air is beginning to move into the region as a Pacific low pressure system in the northwest U.S. begins to deepen and sag further south. The Pacific low is forecast to move into the southwestern states early this week persisting through Wednesday. This will provide even cooler temperatures along with slight chances of showers and thunderstorms Tuesday. Clearing skies with rebounding temperatures are forecast for late in the week. && .DISCUSSION... upper low pressure, that is now moving into the northern Great Basin, has begun to bring cooler temperatures to the region today, with the high at Phoenix Sky Harbor ending up at 95 today, down 6 degrees from yesterday`s high of 101. Along with the cooler temperatures, locally gusty winds also occurred today as the winds aloft increase ahead of the upper low. westerly winds in the 15-20 mph range with gusts to 30 mph were observed at many locations across South-Central and SW Arizona, with even stronger winds over parts of SE CA. Along with the winds, a few pockets of blowing dust were also observed. The latest (00z) GFS and NAM model suites continue to show the upper low moving toward the region through the early and middle parts of this week, with temperatures cooling even further, and even a chance for showers from late Tuesday into Wednesday, as the upper low center moves across the region. As far as the very short term is concerned, other then some downward adjustment in the hourly dewpoint forecasts and some minor adjustments to the other hourly grids, inherited forecasts are holding up well. && .PREVIOUS DISCUSSION... Upper low across the Great Basin continues to drift eastward this afternoon. Latest satellite imagery shows widespread cloudiness out ahead of this system across the Rockies with a smattering of showers and thunderstorms extending southward into Chihuahua. Across the desert southwest, skies have been mostly clear with temperatures in the lower 90s across the lower deserts, a drop of roughly 6 to 8 from those observed yesterday. Dewpoints are also significantly lower east of Phoenix, though moisture is already increasing again across western Arizona ahead of a vort max traversing the Mojave Desert. This vort max will also strengthen wind fields across the region and breezy conditions are anticipated through this evening across much of the area. No major changes were made to the forecast in the short-term. Temperatures tonight will be near or slightly above average with subsiding winds and mostly clear skies. && .PREVIOUS DISCUSSION... The upper low eventually will start to dig southward through the Great Basin on Monday into the Desert Southwest on Tuesday. Models have been consistent with the overall track of this system, but have shifted it further west slightly over the past 24 hours. Some moisture advection is expected over our area Tuesday into early Wednesday with PWATS increasing to between 0.50-0.75 inches. Though this system is not very cold aloft (500mb temps near -16C) there should be sufficient moisture and instability for some isolated showers and thunderstorms starting Tuesday afternoon. Overall timing has shifted a bit later, so rain chances will linger into Wednesday, especially from Phoenix eastward. Have added in slight chance POPs across south-central Arizona for Tuesday night and Wednesday morning with chances remaining through Wednesday evening across the higher terrain east of Phoenix. We could see a shot at some gusty thunderstorm winds with an inverted V forecast sounding structure, but winds aloft will be light, so would only rely on evaporative cooling effects. Temperatures through Wednesday are forecast to be at or below normals with Monday and Tuesday being the coolest days with highs mostly in the upper 80s across the lower deserts. We will start to see some warming across our western zones on Wednesday under rising heights aloft as highs climb back into the middle 90s. Model consensus continues to show a deep Pacific low digging southward into the Pacific Northwest late this week, but what happens thereafter is less certain as model spread increases into next weekend. For the Desert Southwest, heights aloft and temperatures will certainly rise on Thursday and Friday resulting in highs at or just above normals (middle to upper 90s). Have low confidence in the forecast picture for next weekend as it is not clear if the Pacific low will dig far enough south to affect the Desert Southwest. && .AVIATION... South-Central Arizona including KPHX...KIWA and KSDL... Southeast California/Southwest Arizona including KIPL and KBLH... Dry cool front passing across the deserts this afternoon and evening. Expect southwest winds to prevail through the evening before starting to become light and variable. Gusts of 20-25 kts will be common through 02Z before weakening. However, the Imperial valley will have stronger gusts (30-35 kts) through 04Z before beginning to weaken. Could see some local blowing dust/sand there but confidence not high enough to reflect in KIPL TAF. Winds will be lighter on Monday afternoon. Otherwise, no significant cloudiness. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Wednesday through Sunday... An upper level low will begin weakening on Wednesday with just a slight chance of showers and thunderstorms (east of the Lower Colorado River Valley). Temperatures will be below normal over south-central AZ (at or slightly above normal west of there). Winds will be light. The system exits on Thursday for warmer temperatures and more noticeable afternoon breezes. Another system slowly approaches from the northwest Friday into Sunday for breezy conditions (especially southeast California) and a cooling trend. Minimum humidities will generally be in the 15-20 percent range on the lower deserts before declining to near 10 percent by Friday. Overnight recovery also trends down but remains fair. Portions of southeast California and the Lower Colorado River Valley may occasionally flirt with critical thresholds during the Friday-Sunday time frame. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...Percha/Hirsch PREVIOUS DISCUSSION...Kuhlman AVIATION...AJ FIRE WEATHER...AJ
Area Forecast Discussion National Weather Service Phoenix AZ 221 PM MST SUN MAY 15 2016 .SYNOPSIS... Cooler air is beginning to move into the region as a Pacific low pressure system in the northwest U.S. begins to deepen and sag further south. The Pacific low is forecast to move into the southwestern states early this week persisting through Wednesday. This will provide even cooler temperatures along with slight chances of showers and thunderstorms Tuesday. Clearing skies with rebounding temperatures are forecast for late in the week. && .DISCUSSION... Upper low across the Great Basin continues to drift eastward this afternoon. Latest satellite imagery shows widespread cloudiness out ahead of this system across the Rockies with a smattering of showers and thunderstorms extending southward into Chihuahua. Across the desert southwest, skies have been mostly clear with temperatures in the lower 90s across the lower deserts, a drop of roughly 6 to 8 from those observed yesterday. Dewpoints are also significantly lower east of Phoenix, though moisture is already increasing again across western Arizona ahead of a vort max traversing the Mojave Desert. This vort max will also strengthen wind fields across the region and breezy conditions are anticipated through this evening across much of the area. No major changes were made to the forecast in the short-term. Temperatures tonight will be near or slightly above average with subsiding winds and mostly clear skies. && .PREVIOUS DISCUSSION... The upper low eventually will start to dig southward through the Great Basin on Monday into the Desert Southwest on Tuesday. Models have been consistent with the overall track of this system, but have shifted it further west slightly over the past 24 hours. Some moisture advection is expected over our area Tuesday into early Wednesday with PWATS increasing to between 0.50-0.75 inches. Though this system is not very cold aloft (500mb temps near -16C) there should be sufficient moisture and instability for some isolated showers and thunderstorms starting Tuesday afternoon. Overall timing has shifted a bit later, so rain chances will linger into Wednesday, especially from Phoenix eastward. Have added in slight chance POPs across south-central Arizona for Tuesday night and Wednesday morning with chances remaining through Wednesday evening across the higher terrain east of Phoenix. We could see a shot at some gusty thunderstorm winds with an inverted V forecast sounding structure, but winds aloft will be light, so would only rely on evaporative cooling effects. Temperatures through Wednesday are forecast to be at or below normals with Monday and Tuesday being the coolest days with highs mostly in the upper 80s across the lower deserts. We will start to see some warming across our western zones on Wednesday under rising heights aloft as highs climb back into the middle 90s. Model consensus continues to show a deep Pacific low digging southward into the Pacific Northwest late this week, but what happens thereafter is less certain as model spread increases into next weekend. For the Desert Southwest, heights aloft and temperatures will certainly rise on Thursday and Friday resulting in highs at or just above normals (middle to upper 90s). Have low confidence in the forecast picture for next weekend as it is not clear if the Pacific low will dig far enough south to affect the Desert Southwest. && .AVIATION... South-Central Arizona including KPHX...KIWA and KSDL... Southeast California/Southwest Arizona including KIPL and KBLH... Dry cool front will make its way across the region today increasing winds while promoting less cloud cover. Typical AM wind headings will transition through south to southwest during the day while increasing in speed. Gusts in the upper teens to low twenty knot range will be possible for the Phoenix area terminals and KBLH, while stronger winds off the mountains are expected for KIPL with gusts at or greater than 30kts. West winds to linger later into the evening than usual, losing their gustiness but remaining elevated. One final band of mid-level clouds will continue to track E-SE with mostly clear skies filling in behind the exiting SCT-BKN layers by the afternoon and evening. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Tuesday through Saturday... A low pressure system will be centered over northwest Arizona on Tuesday and Wednesday leading to a slight chance of thunderstorms over south-central Arizona. Temperatures will be below normal with mostly light winds. The upper low exits Thursday before another system approaches Friday and Saturday leading to breezy to windy conditions. Winds, under current forecast guidance, look to be stronger for the late week system than the one responsible for the winds over the late weekend and early in the work week. Temperatures will start off below normal Tuesday and Wednesday before climbing back to normal by Friday. Humidities begin declining Wednesday with minimum values dipping to about 10% late in the week. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...Hirsch PREVIOUS DISCUSSION...Kuhlman AVIATION...Nolte FIRE WEATHER...Nolte/AJ
Area Forecast Discussion National Weather Service Phoenix AZ 454 AM MST SUN MAY 15 2016 .UPDATE...To AVIATION and FIRE WEATHER Discussions... && .SYNOPSIS... Cooler air is beginning to move into the region as a Pacific low pressure system in the northwest U.S. begins to deepen and sag further south. Breezy conditions are expected today with highs near normals. This Pacific low is forecast to move into the southwestern states tonight persisting through Tuesday. This will provide even cooler temperatures along with slight chances of showers and thunderstorms. Clearing skies with rebounding temperatures are forecast for late in the week. && .DISCUSSION... Drier air has filtered into Arizona as westerly flow aloft moved in around the southern fringe of the upper low currently situated across the Pacific Northwest. This drier air has ended any shower or thunderstorm chances with mainly clear skies expected today. Lowering heights aloft will allow for some modest cooling to take place today and as a result highs should only top out in the lower 90s across the deserts. A deepening surface low over the Great Basin is increasing pressure gradients across the Desert Southwest resulting in some breezy winds currently across southeast California. The gradient will strengthen later today with breezy to windy southwesterly winds across the majority of the CWA. Winds will remain below advisory levels, but some gusts to 35 mph are likely across southeast California and southern Gila County. Elevated fire danger conditions for a brief time may be realized across southern Gila County this afternoon, but not enough to warrant any headlines. The upper low eventually will start to dig southward through the Great Basin on Monday into the Desert Southwest on Tuesday. Models have been consistent with the overall track of this system, but have shifted it further west slightly over the past 24 hours. Some moisture advection is expected over our area Tuesday into early Wednesday with PWATS increasing to between 0.50-0.75 inches. Though this system is not very cold aloft (500mb temps near -16C) there should be sufficient moisture and instability for some isolated showers and thunderstorms starting Tuesday afternoon. Overall timing has shifted a bit later, so rain chances will linger into Wednesday, especially from Phoenix eastward. Have added in slight chance POPs across south-central Arizona for Tuesday night and Wednesday morning with chances remaining through Wednesday evening across the higher terrain east of Phoenix. We could see a shot at some gusty thunderstorm winds with an inverted V forecast sounding structure, but winds aloft will be light, so would only rely on evaporative cooling effects. Temperatures through Wednesday are forecast to be at or below normals with Monday and Tuesday being the coolest days with highs mostly in the upper 80s across the lower deserts. We will start to see some warming across our western zones on Wednesday under rising heights aloft as highs climb back into the middle 90s. Model consensus continues to show a deep Pacific low digging southward into the Pacific Northwest late this week, but what happens thereafter is less certain as model spread increases into next weekend. For the Desert Southwest, heights aloft and temperatures will certainly rise on Thursday and Friday resulting in highs at or just above normals (middle to upper 90s). Have low confidence in the forecast picture for next weekend as it is not clear if the Pacific low will dig far enough south to affect the Desert Southwest. && .AVIATION... South-Central Arizona including KPHX...KIWA and KSDL... Southeast California/Southwest Arizona including KIPL and KBLH... Dry cool front will make its way across the region today increasing winds while promoting less cloud cover. Typical AM wind headings will transition through south to southwest during the day while increasing in speed. Gusts in the upper teens to low twenty knot range will be possible for the Phoenix area terminals and KBLH, while stronger winds off the mountains are expected for KIPL with gusts at or greater than 30kts. West winds to linger later into the evening than usual, losing their gustiness but remaining elevated. One final band of mid-level clouds will continue to track E-SE with mostly clear skies filling in behind the exiting SCT-BKN layers by the afternoon and evening. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Tuesday through Saturday... A low pressure system will be centered over northwest Arizona on Tuesday and Wednesday leading to a slight chance of thunderstorms over south-central Arizona. Temperatures will be below normal with mostly light winds. The upper low exits Thursday before another system approaches Friday and Saturday leading to breezy to windy conditions. Winds, under current forecast guidance, look to be stronger for the late week system than the one responsible for the winds over the late weekend and early in the work week. Temperatures will start off below normal Tuesday and Wednesday before climbing back to normal by Friday. Humidities begin declining Wednesday with minimum values dipping to about 10% late in the week. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...Kuhlman AVIATION...Nolte FIRE WEATHER...Nolte/AJ
Area Forecast Discussion National Weather Service Phoenix AZ 935 PM MST SAT MAY 14 2016 .SYNOPSIS... Cooler air is beginning to move into the region as a low pressure system in the northwest U.S. begins to deepen. Breezy conditions are expected again for Sunday. Another Pacific weather system is forecast to move into the southwestern states late Sunday through Tuesday. This will provide even cooler temperatures along with slight chances of thunderstorms mainly over northern and central Arizona. Clearing skies with rebounding afternoon temperatures are forecast for late next week. && .DISCUSSION... Clearing skies can be seen across southeastern California and the western half of Arizona this evening. Earlier, a few thunderstorms swept over the southeastern third of Arizona but that activity has dissipated and pushed to the east. Low pressure system now over Oregon continues to gradually deepen and spread its influence further to the south. Models indicate this system will eventually drop down towards the south, ultimately moving into northwest Arizona by Tuesday evening. This will bring a slight chance for thunderstorms to the region and keep relatively cooler air in place for a few days. Rain chances are still on the low side but at least there`s a chance for unsettled weather, particularly Tuesday afternoon through Wednesday morning. Temperatures should start to climb back above normals the rest of the week. && .PREVIOUS DISCUSSION... Latest satellite imagery shows several areas of cumulus congestus, mainly concentrated across the Mogollon Rim, the CO Plateau and portions of southeastern AZ. Isolated showers and thunderstorms have developed, but are mainly relegated to the higher terrain near Tucson and Flagstaff. Meanwhile, moisture values are running well above average with dewpoints in the mid 40s. NAEFS PWAT percentiles are also running above the 90th percentile, though ground based GPS- IPW and TPW suggest PWATS are somewhat lower. The relatively moist conditions have also kept temperatures at bay, which have generally been running in the mid to upper 90s in the lower deserts. At Sky Harbor Airport, the high has reached 100 degrees. Preponderance of hi-res CAMs including the operational and experimental HRRR continue to indicate that isolated convection will develop across Gila County this afternoon and this evening. PoPs were increased to around 10 percent in these areas, though in reality most precipitation that falls will likely evaporate and not measure at the surface. Models are in excellent agreement that much drier air will be transported northeastward this evening and overnight, with the GEFS ensemble mean indicating PWATS dropping as low as 0.40 inches. Consequently, showers and thunderstorms will dissipate shortly after sunset. && .AVIATION... South-Central Arizona including KPHX...KIWA and KSDL... Southeast California/Southwest Arizona including KIPL and KBLH... A weak weather disturbance will continue to produce scattered cumulus and altocumulus with broken-overcast cirrus this afternoon before thinning out this evening. Over northern and southeastern Arizona there will be isolated thunderstorms with some additional weaker showers which will begin dissipating after sunset. Surface winds will favor south and southwest directions through the evening (gusts of 15-20 kts Phoenix area; 20-30 kts SE CA and SW AZ). Winds will be stronger Sunday afternoon but with significantly less cloudiness. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Tuesday through Saturday... A low pressure system will be centered over northwest Arizona on Tuesday and Wednesday leading to a slight chance of thunderstorms over south-central Arizona. Temperatures will be below normal with light winds. The low exits Thursday before another system approaches Friday and Saturday leading to breezy to windy conditions. Temperatures will start off below normal Tuesday and Wednesday before climbing back to normal by Friday. Humidities begin declining Wednesday with Minimum values dipping to about 10% late in the week. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...Waters/Hirsch PREVIOUS DISCUSSION...Kuhlman AVIATION...AJ FIRE WEATHER...AJ
AREA FORECAST DISCUSSION...UPDATED
NWS LOS ANGELES/OXNARD CA
604 PM PDT MON MAY 16 2016 Updated aviation section .SYNOPSIS... The low will bring the marine layer and near normal temperatures into Tuesday with a slight chance of showers and thunderstorms in the mountains and deserts Tuesday afternoon. The offshore flow on Wednesday and Thursday will reduce clouds and be the hottest days of the week. Then on Friday a low should arrive for an increase of the marine layer and a cooling trend into early next week. && .SHORT TERM...(TDY-THU) An upper low over nrn Nevada will drop slowly south over the next 24-36 hours. As it does, some energy will wrap around it and move into our area Tuesday afternoon and evening. This combined with some mid level moisture and instability will generate at least the threat of an afternoon thunderstorm or two over the LA/Ventura mtns and Antelope Valley. There`s not a ton of moisture to work with but enough to warrant a slight chance. Steering flow is from the north so there is some chance that anything that forms will drift south into the adjacent foothills and valleys, but chances are too low to include in the forecast at this time. Otherwise, a pretty mundane forecast. A brief ridge will pop up Wed and lead to a little warming trend but still plenty of marine lyr clouds for coast and valleys, some of which may linger at the beaches through the afternoon. Models still show some instability over the mtns and deserts Wed but with little moisture to work feel that any convective threat is minimal. A trough will start to move into nrn California Thu and initiate a cooling trend for most areas except the far interior. .LONG TERM...(FRI-MON) The trough will slide south through the state Fri-Sun before shifting east Monday. Impacts will mostly be cooler temps, more clouds, mainly from a deeper marine lyr, and stronger onshore breezes. So after a brief respite May gray will likely be the dominant player through the weekend, though likely with at least some breaks in the clouds. One thing to watch is the ECMWF continues to be more bullish with moisture than the GFS on Sunday and actually spits out some light precip across SLO county. This seems an unlikely scenario and decided just add some clouds there for now. Beyond Sunday there are a fair amount of model differences in the details, but most agree that this troughy pattern will continue for several more days. && .AVIATION...17/0000Z. At 00Z, the marine layer depth was around 4300 feet at KLAX. The top of the inversion was around 5000 feet with a temperature of 16 degrees Celsius. IFR to MVFR conditions will spread into coastal and valley terminals through 13Z. Highest confidence in IFR conditions exist in terminals north and west of KSBA and for Los Angeles County Valley terminals. There is an chance of LIFR conditions at terminals north and west of KSBA between 06Z and 16Z. A slightly later clearing time is forecast on Tuesday, with VFR conditions possibly lingering until around 21Z at coastal terminals. KLAX...VFR conditions are expected through at least 03z, then MVFR conditions will spread in through 08Z. VFR conditions should redevelop between 19Z and 21Z. Due to the eddy circulation, there is a 30 percent chance of east winds greater than 7 knots between 10Z and 16Z. KBUR...VFR conditions are expected through 08Z, then IFR conditions should spread in between 07Z and 10Z. There is a 30 percent chance that IFR conditions could be MVFR. MVFR conditions could develop by 16Z at the latest. VFR conditions should develop around 18Z. && .MARINE...16/100 PM. Moderate confidence that Gale Force winds are finished for at least the next few days...though occasional gusts between 30 and 35 KT are possible tonight near Point Conception. Moderate confidence in small craft advisory winds from the Central Coast to San Nicolas Island through early Tuesday morning. with much lighter winds tomorrow and Wednesday. Expecting southeast winds to be prevalent south of Point Conception this morning and Tuesday morning with local gusts to 15 KT possible in the San Pedro Channel and the Anacapa Passage. Choppy Short period waves likely everywhere into Tuesday...with improvement expected after. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect until 9 PM PDT this evening For zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PDT Tuesday For zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...MW AVIATION...Hall MARINE...Kittell SYNOPSIS...Seto weather.gov/losangeles
  [top] Area Forecast Discussion National Weather Service Reno NV 301 PM PDT MON MAY 16 2016 .SYNOPSIS... A few showers are expected this evening across Northwest Nevada as low pressure slowly pulls away. A warming trend is expected Tuesday and Wednesday with dry conditions. Another low is expected late in the week with gusty winds Thursday before more showers are expected Friday into the weekend. && .SHORT TERM... A few showers are ongoing across Northwest Nevada this afternoon with their movement to the southeast. The showers are generally east of a Alturas to Yerington line and are expected to remain that way into this evening. There are plenty of clouds west of this line, but it is more stable with very little vertical development. The upper low responsible for these showers is slowly moving south across Northeast NV and will continue to do so overnight. Expect showers to diminish with the loss of heating overnight. A few showers though will remain possible over Mono County Tuesday morning in the upslope northeast flow behind the low before clearing in the afternoon. Temps will slowly warm Tuesday into Wednesday under a short wave ridge. Wednesday looks to be the warmest day this week before the next low approaches Thursday. I removed the mention of showers/thunderstorms for the Sierra Wednesday. GFS/NAM show weak instability if at all, and the EC is showing no response. The large scale pattern is not favorable for development and the atmospheric profile also isn`t favorable for convection due to heating alone. Wallmann .LONG TERM...Thursday through Monday... Unsettled weather pattern will continue into early next week, with below average temps prevailing after Thursday. The main changes to the current extended forecast continued the trend of increasing precip chances north of I-80 late Thursday night thru Friday evening, and prolonging the cool temps and some precip chances into early next week. For Thursday, the main weather effects will be potential for strong winds ahead of the main low as it drops into the Pacific Northwest. Tightening pressure and thermal gradients with upper level jet support and 700 mb flow of 40-45 kt over the Sierra has been indicated for several days. Therefore confidence is high for a decent wind event Thursday afternoon-evening especially from I-80 southward, with possible gusts near 50 mph and Sierra ridge gusts over 80 mph. Farther north, increased cloud cover and less favorable jet position should limit wind gusts to 40 mph or less. Cold front will begin dropping south into northeast CA-northwest NV and some instability near the front may lead to some late day thunderstorms, although strong winds aloft could limit convective development. The greater chance for precip (with pops increased to likely) will arrive north of I-80 late Thursday night thru Friday as upper low center continues pushing farther south into northeast CA. Cold pool aloft and steep mid-level lapse rates may support some elevated convection north of Susanville-Gerlach overnight into early Friday. For Friday-Saturday, medium range guidance/ensemble data is in good agreement with cool and showery pattern continuing especially north of I-80, although increasing precip chances will gradually spread southward to near US-50 during each afternoon and evening with possible thunderstorms. Snow levels still could drop to near 6000- 6500 ft from Highway 50 northward, and even down to near 5500 feet in stronger shower bands. The showery nature of the precip will limit accumulations especially during the daytime, but higher passes could receive some short duration travel impacts at times. For lower elevations, some thunderstorms will produce small hail/graupel with brief accumulations possible with stronger or more persistent cells. For Sunday-next Monday, the medium range guidance begins to diverge on the track of the upper low although is main effects will still affect portions of eastern CA-western NV. Another vorticity wave may rotate around the main low on Monday, so we will keep a mention of showers and isolated afternoon-evening thunder going into next week. The overall cold pool will weaken so we will gradually increase Temperatures and raise snow levels, but highs will still remain below average. MJD && .AVIATION... VFR conditions will prevail thru midweek with generally light winds shifting from north tonight to northeast=east Tuesday, then becoming west by Wednesday afternoon. Isolated showers over northwest-west central NV will diminish this evening, but no precip is expected to affect any of the main terminals. The absence of additional rain today and northeast flow over the Sierra will limit significant fog formation around KTRK late tonight- early Tuesday, although patches of shallower fog (with limited impacts to aviation) could develop in the more fog prone portions of the Martis valley. MJD && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit... http://weather.gov/reno
  [top] Area Forecast Discussion National Weather Service Phoenix AZ 255 PM MST MON MAY 16 2016 .SYNOPSIS... A large Pacific low pressure system is expected to move south from Idaho, and into Arizona late Tuesday through Wednesday. Increasing clouds with a chance of showers and thunderstorms are forecast to spread from southeast California and southwest Arizona late Tuesday afternoon, into south central Arizona Tuesday night and Wednesday. Clearing is expected Wednesday night, with dry weather and near normal temperatures developing toward the end of the work week and weekend. && .DISCUSSION... Tonight through Wednesday Night... An interesting weather pattern will develop over the region the next few days. A large former Pacific low pressure system, centered over southwest Idaho since Sunday, will start to move south toward AZ. Strong ridge building along the Pacific northwest coast, folding over into southwest Canada, bodes well for the Idaho trof to retrograde and track southwest into southern CA Tuesday and Tuesday night. Mid/hi level cyclonic shear will increase the potential for showers and thunderstorms, with increasing moisture. The San Diego sounding showed some appreciable low level moisture, and the Chihuahua Mexico balloon sounding showed a hint of a significant moisture plume visible south of the border in precip water satellite imagery. Lastly, the Phoenix and Tucson Radar VAD Wind Profiles were already detect backing south to southwest winds under 12 thsd feet. As the trof deepens from Idaho toward southern CA, low level winds will continue to back from the south, importing more moisture into the tight mid/hi level cyclonic circulation feature expected Tuesday/Tuesday night. In other words, as the trof moves slowly west to east, a threat of showers and thunderstorms will first develop in southeast CA/southwest AZ late Tuesday afternoon,then spread into south central AZ, including Phoenix, Tuesday night and Wednesday. Clearing is expected Wednesday night. Thursday and Friday... In the aftermath of Wednesdays eastward moving trof, dry west to northwesterly flow will develop Thursday over our forecast area. The flow aloft will change to dry southwesterly in advance of yet another large Pacific weather system expected to develop However another Large Pacific weather system will settle into the western states this weekend, producing gusty south to southwest winds area-wide Fri, Sat, Sun, and Mon afternoons. && .AVIATION... South-Central Arizona including KPHX...KIWA and KSDL... No aviation weather impacts expected through Tuesday afternoon. Southeasterly flow will veer to westerly this afternoon, peaking around 10 kt with occasional gusts to around 15 kt. Onset of the downslope easterly flow will occur near the climatological average of 09-10z. Southeast California/Southwest Arizona including KIPL and KBLH... Typical diurnal winds expected at the terminals, generally less than 15 kt at KIPL and KBLH. Looking ahead, scattered showers and thunderstorms will likely develop ahead of an approaching low pressure system Tuesday afternoon. The strongest storms will be capable of producing strong downdraft winds. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Wednesday through Sunday... An upper level low will begin weakening on Wednesday with just a slight chance of showers and thunderstorms east of the Lower Colorado River Valley. Temperatures will be below normal over south- central AZ and at or slightly above normal across southeast California and southwest Arizona. The system exits on Thursday for warmer temperatures and increasing winds. Another system slowly approaches from the northwest Friday into Sunday for breezy to windy conditions each day and a cooling trend. Minimum humidities will generally be in the 15-20 percent range over the lower deserts through Thursday before declining to near 10 percent by Friday. Friday afternoon, and possibly Saturday afternoon, will likely have elevated fire danger conditions over portions of the area. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...Vasquez AVIATION...Hirsch FIRE WEATHER...Kuhlman
  [top] Area Forecast Discussion National Weather Service San Francisco Bay Area 151 PM PDT MON MAY 16 2016 .SYNOPSIS...Warming trend will likely peak on Tuesday as light offshore winds persist in the hills as high pressure builds. Onshore winds return to the coast Wednesday with coastal cooling while inland areas remain warm. More significant cooling trend starts Thursday as westerly winds develop ahead of incoming trough. Well below normal daytime highs Friday through Sunday with a chance of showers...especially in the North Bay on Saturday. && .DISCUSSION...as of 1:51 PM PDT Monday...Northerly gradient down the coast in excess of 5 mb with large scale SFO-WMC gradient now neutral. This is all setting the stage for some offshore winds in the hills and boundary layer later tonight into Tuesday morning. Already this afternoon starting to see some evidence of upcoming warming trend with places like Concord and Santa Rosa already into the 80s as of 1 pm. Developing offshore flow and warming aloft will lead to pronounced warming on Tuesday with inland highs well into the 80s and lower 90s. Given the time of year and short duration of the event the beaches of Monterey county may miss out on the warm weather but will only have to go a few miles inland to find 80s on Tuesday. The airmass aloft will actually warm Tuesday into Weds with 850 mb temps warming from 15 Celsius to around 18 Celsius...however the offshore component will be lost as winds are projected to be off the ocean for most of Weds. Some hill and inland areas may see little overall change from Tuesday to Weds but the general idea will be for cooling near the bays on Weds as onshore winds return through the afternoon. Thursday will mark the beginning of a noted cooling trend that will last right through the weekend and likely into early next week. For Thursday winds will become strong over the ocean with gusty onshore winds Thursday afternoon ahead of an unseasonably deep and cold upper trough. If current model solutions are correct Thursday evening will be blustery at the coast with dramatic 500 mb height falls and strong cold advection off the ocean. Sweatshirt sales will be strong in the city on Friday with unseasonably cold upper trough over the region...in fact temperatures will become fairly isothermal across the region with little variation in temperature from the coast to the inland valleys. 850 mb temps from 2-3 Celsius on Friday and Saturday per the latest ECMWF with the core of the cold air aloft staying over the North Bay. In general have raised pops over the North Bay and dragged precip chances down into the Bay Area and towards Santa Cruz on Saturday. MOS guidance shows pops as high as 50% but since were still 5 days out have kept official forecast in the 20-30% range. Should pattern verify t-storms will become possible with 500 mb temps from -23 to -25 Celsius over the North Bay and 700 mb around -7 Celsius (snow in the Sierra). Given its still days out and exact track of upper low will likely change didn`t want to paint t-storms into forecast with bigger impacts likely being below normal temps and showers. For reference the ECMWF has a general 0.25-0.50 of liquid for northern Sonoma County this weekend with a tenth or less for the greater Bay Area. Low should eject by Sunday with shower chances decreasing but temps still below normal...mainly in the 60s. By May standards the pattern remains active and unseasonably cool with long range models keeping a trough over the West Coast. No big storms of note but above average confidence for below normal temps through most of next week. && .AVIATION...as of 11:23 AM PDT Monday...VFR conds now prevail at all area terminals with marine stratus having retreated southward and offshore aside from some lingering patches along the southern San Mateo County coast and around Monterey Bay and the northern Big Sur coast. Onshore winds are expected to pick up significantly this afternoon... with latest HRRR model output increasing the SFO-SAC sea level pressure gradient to nearly 4 mb by the latter part of the afternoon. Tonight...Coastal stratus is projected to redevelop during the evening hours and begin extending back inland through the Bays. As the night progresses however...surface high pressure will increasingly build inland through the Pacific Northwest and into the northern Great Basin. This will turn surface flow more offshore especially over the northern half of the district eroding the marine layer and marine air influence. Consistent with latest model output and guidance latest TAFs have cig onset at KSFO and KOAK during the late evening hours...but then with early clearing on Tuesday as drier air mass works in. Vicinity of KSFO...VFR cigs through the afternoon and early evening hours...with moderate confidence will continue VFR through the evening rush. Winds increasing out of the west during the afternoon...to 20 to 25 kt with gusts 25 to 30 kt late afternoon/early evening hours. Low-to-moderate confidence in timing and details of cig development overnight. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR conds now prevail...and are expected to continue through the afternoon hours. High confidence that cigs will redevelop during the evening hours but lower confidence in details of timing. && .MARINE...as of 1:21 PM PDT Monday...Strong high pressure over the Eastern Pacific and lower pressure over the interior will result in gusty northwest winds through much of the week. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...Mry Bay until 11 PM SCA...Pigeon Pt to Pt Pinos 0-10 nm until 11 PM SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...Pt Arena to Pt Reyes 0-10 nm SCA...Pt Reyes to Pigeon Pt 0-10 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm SCA...Rough Bar Advisory for SF Bar SCA...SF Bay until 9 PM && $$ PUBLIC FORECAST: RWW AVIATION: Blier MARINE: Blier Visit us at www.weather.gov/sanfrancisco Follow us on Facebook and twitter at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea
AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
1102 PM PDT SAT MAY 14 2016 .SYNOPSIS... Breezy winds and near normal temperatures... with a chance of precipitation through Monday and possibly lingering in the mountains Tuesday afternoon. Offshore flow will make Wednesday and Thursday the hottest days of the week. By Friday there will be an increase in clouds and a cooling trend for the weekend. && .UPDATE... A cool day today with most coast and vlys temps coming in 4 to 8 degrees below normal. The marine layer is about 1800 feet and is capped by a moderate inversion. The major player today is the onshore flow which is an impressive 9.3 mb onshore to KDAG at 00Z with this strong an east push there was very slow to no clearing across the LA and VTA beaches. A little weak trof mixed the marine layer out across the central coast and it will be slower to reform. There will be plenty of low clouds over the VTA and LA coasts and vlys but the SBA south coast will stay predominately cloud free as the sun downer will keep the low clouds at bay. The wind advisories for the Antelope Valley and the SBA south coast are not too well but the SBA winds will likely pick up in a few hours and there will be some local advisory level winds in the AV but the stronger winds will be tomorrow. Overall the current fcst is in good shape and there are no updates planned. && .SHORT TERM...(TDY-MON) Upper level low currently moving eastward into Oregon and by Sunday is centered over the Oregon/Idaho border. Around that time it really becomes a split flow situation to stop its eastward progression and the low begins to dig southward into Nevada over the short term forecast. Models generally agree in placing the center somewhere near Vegas on Tuesday. This trough pattern over the west coast will result in little day to day changes through the short term. Expect only minor fluctuations in the depth of the marine layer and the extent of overnight/morning stratus. Onshore pressure gradients will be strong enough to slow the pace of afternoon clearing, with some immediate coastal areas staying in the stratus through the afternoon. Northwest flow should help keep the SBA coast clear at night. Had a few reports of drizzle in Ventura County and overnight drizzle possibilities will continue each night. Both the GFS and NAM swing a weak area of lift through the area late tonight and tomorrow morning as the tail end of a vort lobe around the upper low swings through. This may enhance the chance of drizzle for tonight mainly over the LA County coast and valleys. Decided to pull back on the slight chance of showers in Los Angeles County coast and San Gabriel Valley for Sunday afternoon/evening, keeping it instead limited to areas higher up in the foothills. High temperatures cool some on Sunday but in general will feel the same. Models warm low levels a bit on Monday to bring a few degrees warming mainly inland areas and a few degrees again on Tuesday. Some far inland areas should even be back up above normal for this time of year. Winds will be an issue for the Antelope Valley and the Santa Barbara south coast and adjacent foothills. Winds have been fairly tame in the Antelope Valley so far but are expected to pick up later this evening and stay elevated through Sunday night. For winds in SBA County, gusty northwest winds will develop this evening and again Sunday evening. Local numerical model indicates stronger winds for Sunday evening. Another wind advisory will likely be needed again for the same areas on Sunday night. Have introduced a slight chance of showers over the eastern San Gabriels for Tuesday afternoon/evening. With the position of the closed upper low forecast to be near Vegas Tuesday, there could be just enough instability and dynamics to produce some showers. GFS and NAM both showing an area of negative lifted indicies along with some CAPE. Moisture availability will be an issue however. .LONG TERM...(TUE-FRI) The closed upper low just to our NE is forecast to fill, open up, and move east on Wednesday. Just enough in the way of height rises to squeeze a few more degrees of warming Wednesday following another night of coastal stratus (northwest flow should keep the SBA south coast clear). Expecting above normal temperatures for all but the immediate coast which will remain at or just below normal. By Thursday the next closed upper low forecast to dive down the west coast will begin to increase our onshore pressure gradients, thicken up the marine layer and stratus coverage, and start a cooling trend that continues into Friday. The cooling will occur first over inland areas Thursday then spread across the forecast area Friday. Expect Saturday to be much the same as Friday as far as marine layer and high temperatures. Some differences in the east-west position of the low by 12z Saturday with the GFS along the Oregon coast and the ECMWF further east over OR/ID border. But this difference won`t impact the forecast for this long term period. && .AVIATION...15/06Z... At 05z at KLAX... the inversion was about 1500 feet deep. The top of the inversion was near 5150 feet with a temperature of thirteen degrees Celsius. Overall... Moderate confidence in the 06z TAFs. The reduced confidence is primarily due to the uncertain timing of the low cloud incursion and a bit due to uncertainty in the locations that will be impacted. Most coastal and adjacent valley locations will be impacted but there is up to a twenty percent chance that some locations will remain VFR. Some wind shear in the KSBA vicinity through 09z. Otherwise and elsewhere VFR conditions will prevail. KLAX... Moderate confidence in the 06z TAF. The reduced confidence is primarily due to the possibility of the height of the marine layer fluctuating overnight. There is a 20 percent chance of an east wind component 8-9 knots from 10Z-15z. There is a thirty percent chance of no clearing Sunday afternoon. Otherwise VFR conditions will prevail. KBUR... Moderate confidence in the 06z TAF. The reduced confidence is primarily due to the possibility of the height of the marine layer fluctuating overnight. There is a twenty five percent chance of the clearing delayed until 19z. Otherwise VFR conditions will prevail. && .MARINE...14/200 pM. Northwest winds will continue to create small craft advisory conditions from Piedras Blancas to San Nicolas island including the west portion of the Santa Barbara basin through Monday night. The strongest winds will likely occur in the vicinity of the Northern Channel islands this afternoon. The Northwest winds will increase to possible gale force from Piedras Blancas to San Nicolas island Sunday afternoon and prevail through Monday morning. Northwest winds are expected to increase Thursday from Piedras Blancas to San Nicolas island and sca conditions are likely. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory in effect until 3 AM PDT Sunday For zones 39-52. (See LAXNPWLOX). Wind Advisory in effect until 9 PM PDT Sunday For zone 59. (See LAXNPWLOX). PZ...Small Craft Advisory in effect until 3 PM PDT Sunday For zones 645-670-673-676. (See LAXMWWLOX). Gale Warning in effect from 3 PM Sunday to 4 AM PDT Monday For zones 645-670-673-676. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Sunday For zone 650. (See LAXMWWLOX). && $$ PUBLIC...Rorke AVIATION...KJ MARINE...Rorke SYNOPSIS...Munroe weather.gov/losangeles
Area Forecast Discussion National Weather Service Sacramento CA 1017 PM PDT SAT MAY 14 2016 .Synopsis... Cool down with a few showers or thunderstorms north of I-80 this weekend. Then a warmup to lower 90s again by mid week followed by another cool down and potential showers late in the week. && .Discussion (Sunday through Tuesday)... Upper low/trough tracking into/across ORE will be east of the CWA on Sunday. Northerly winds begin to dry the boundary layer out a bit on Sunday with stronger drying winds Monday into Tuesday. Both Sun nite/Mon morning and Mon nite/Tue morning look to be ideal set-ups for the formation of a modest northerly barrier jet on the west side of the Sac Valley. Max temps mostly in the 80s in the Valley on Mon or up to 5 degrees above normal will warm into the low 90s in the Valley on Tue or 7-12 degrees above normal. JClapp && .EXTENDED DISCUSSION (Wednesday THROUGH Saturday) The extended forecast models depict an upper level shortwave ridge of high pressure over the western portion of the CONUS Wednesday and Wednesday night, which will bring warm and dry conditions across NorCal. High temperatures in the valley will be about 10 degrees above normal Wednesday afternoon. The stable air over the region on Wednesday will shift southeastward as another trough of low pressure slides southward from the Pacific Northwest. Model forecasts are in good agreement to the strength and positioning of the system to move into NorCal sometime Thursday afternoon or evening. The disturbance will bring cooler temperatures and the possibility for showers and thunderstorms through the end of the workweek. High temperatures in the valley will drop to near or slightly below normal temperatures in the low to mid 70s. && .AVIATION... Mainly VFR conditions the next 24 hours. Isolated showers will diminish tonight over the Sierra, but are likely to redevelop Sunday afternoon. South to west winds up to 10 kt will become northwest on Sunday. Dang && .STO Watches/Warnings/Advisories... None. && $$
Area Forecast Discussion National Weather Service Phoenix AZ 935 PM MST SAT MAY 14 2016 .SYNOPSIS... Cooler air is beginning to move into the region as a low pressure system in the northwest U.S. begins to deepen. Breezy conditions are expected again for Sunday. Another Pacific weather system is forecast to move into the southwestern states late Sunday through Tuesday. This will provide even cooler temperatures along with slight chances of thunderstorms mainly over northern and central Arizona. Clearing skies with rebounding afternoon temperatures are forecast for late next week. && .DISCUSSION... Clearing skies can be seen across southeastern California and the western half of Arizona this evening. Earlier, a few thunderstorms swept over the southeastern third of Arizona but that activity has dissipated and pushed to the east. Low pressure system now over Oregon continues to gradually deepen and spread its influence further to the south. Models indicate this system will eventually drop down towards the south, ultimately moving into northwest Arizona by Tuesday evening. This will bring a slight chance for thunderstorms to the region and keep relatively cooler air in place for a few days. Rain chances are still on the low side but at least there`s a chance for unsettled weather, particularly Tuesday afternoon through Wednesday morning. Temperatures should start to climb back above normals the rest of the week. && .PREVIOUS DISCUSSION... Latest satellite imagery shows several areas of cumulus congestus, mainly concentrated across the Mogollon Rim, the CO Plateau and portions of southeastern AZ. Isolated showers and thunderstorms have developed, but are mainly relegated to the higher terrain near Tucson and Flagstaff. Meanwhile, moisture values are running well above average with dewpoints in the mid 40s. NAEFS PWAT percentiles are also running above the 90th percentile, though ground based GPS- IPW and TPW suggest PWATS are somewhat lower. The relatively moist conditions have also kept temperatures at bay, which have generally been running in the mid to upper 90s in the lower deserts. At Sky Harbor Airport, the high has reached 100 degrees. Preponderance of hi-res CAMs including the operational and experimental HRRR continue to indicate that isolated convection will develop across Gila County this afternoon and this evening. PoPs were increased to around 10 percent in these areas, though in reality most precipitation that falls will likely evaporate and not measure at the surface. Models are in excellent agreement that much drier air will be transported northeastward this evening and overnight, with the GEFS ensemble mean indicating PWATS dropping as low as 0.40 inches. Consequently, showers and thunderstorms will dissipate shortly after sunset. && .AVIATION... South-Central Arizona including KPHX...KIWA and KSDL... Southeast California/Southwest Arizona including KIPL and KBLH... A weak weather disturbance will continue to produce scattered cumulus and altocumulus with broken-overcast cirrus this afternoon before thinning out this evening. Over northern and southeastern Arizona there will be isolated thunderstorms with some additional weaker showers which will begin dissipating after sunset. Surface winds will favor south and southwest directions through the evening (gusts of 15-20 kts Phoenix area; 20-30 kts SE CA and SW AZ). Winds will be stronger Sunday afternoon but with significantly less cloudiness. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Tuesday through Saturday... A low pressure system will be centered over northwest Arizona on Tuesday and Wednesday leading to a slight chance of thunderstorms over south-central Arizona. Temperatures will be below normal with light winds. The low exits Thursday before another system approaches Friday and Saturday leading to breezy to windy conditions. Temperatures will start off below normal Tuesday and Wednesday before climbing back to normal by Friday. Humidities begin declining Wednesday with Minimum values dipping to about 10% late in the week. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...Waters/Hirsch PREVIOUS DISCUSSION...Kuhlman AVIATION...AJ FIRE WEATHER...AJ Area Forecast Discussion National Weather Service Denver/Boulder CO 830 PM MDT MON MAY 16 2016 .UPDATE... Issued at 830 PM MDT Mon May 16 2016 Radar shows widespread showers across the plains and Front Range. Current snow level ranged from around 7000-7500 feet in the southern foothills, to down as low as 6000 feet near the Wyoming border as Cheyenne Wyoming had switched over to snow in the last couple hours. Main precipitation shield is just east of I-25 but lots of drizzle farther west, with another batch of heavier precip and snowfall in the mountains around Summit and Park counties. The main precip area on the plains is shifting slightly westward as another surge was noted in Northeast Colorado, so rain will continue through the rest of this evening and then maybe only slowly decrease through the rest of the night as upslope component weakens. Even then, drizzle and areas of fog should remain behind and continue into Tuesday morning with the very moist and ever so slight upslope component still in place. With regard to snow in the mountains, the orographic forcing is rather weak but still convective enough for a heavy burst of snow this evening in the Summit and Park county areas. Will keep the advisories going here, but did cancel the advisory farther northwest where snow has been slow to develop in zone 31 near the Rabbit Ears Pass area. && .SHORT TERM...(This afternoon through Tuesday) Issued at 325 AM MDT Mon May 16 2016 500mb low centered over southwest Idaho at the present time is forecast to track south-southeastward to over central Utah by 06z tonight. From there models show the low curving southwestward over the lower Colorado River valley south of Las Vegas by late Tuesday afternoon. Near zonal mid-level flow on the south side of this low continues to feed ample amounts moisture over Colorado. East of the mountains this flow curves northeastward producing a wide region of weak to moderate qg ascent. Even as the upper low tracks south across Utah tonight, models show north central and northeast Colorado under large scale ascent. Returning to this afternoon...a shortwave trough/vort lobe rotating around the southeast quad of the upper trough presently aligning from NW Colorado to SE Colorado. Models show this feature and the convection its generating swinging newrd across NE Colorado between 23z/Mon-06Z/Tue. If it were not for the heavy low cloud cover and chilly temperatures on the plains, mid-level shear, instability and lift would be adequate to spawn a few strong if not severe t-storms. As it stands, the few t-storms that have managed to form over the Palmer Divide have pretty much collapsed as they moved into the far less favorable environment on the plains. One last comment, fog blanketing much of northeast Colorado and many mountain locales since late last night has shown little signs of dissipating. Many areas along the Front Range foothills are still reporting vsbys below 5 miles. Overnight...height and pressure falls on the west slope of Colorado will further enhance the moist upslope flow up against the east face of the Front Range mountains. Models indicate weak to moderate qg ascent moving over northeast and north central Colorado with the passing shortwave this evening. Model qpf amounts on the plains by 12z/Tue in the 0.35 to 0.70 inch range. QPf for the Front Range mountains and foothills in the 0.50 to 0.95 inch range. Snow level based on wetbulb zero anywhere from 7500 to 8500 ft this evening, then anywhere from 6000 to 7000 feet after midnight. Could see snow totals by morning anywhere from 5-9 inches on east facing slopes above 9000 feet...and 3-6 inches from 7000 to 9000 feet. It`s possible we could see an inch or so of very wet snow near the base of the foothills and on the Palmer Divide. Do not expect to see any snow accumulation in the Denver metro area except maybe a dusting on lawns in the higher western and southern suburbs. Lastly, should also continue to see areas of fog with the moist upslope flow...especially up against the Front Range. On Tuesday...as the upper low slowly moves away from Colorado forcing for ascent decreases and the high plains upslope flow lessens during the afternoon. Precipitable water changes little, so another day of low clouds, fog and showery type precipitation. And, another day of unseasonably cool temperatures, especially east of the Front Range. Highs on Tuesday only in the 40s...with 20s and 30s in the high country. Additional snow amounts anywhere from 2 to 6 inches in the mountains and higher Front Range foothills. Additional rain amounts on the plains anywhere from 0.05 inch in the far northeast to around a quarter inch near the foothills. Airmass appears to be too cool and stable for t-storms tomorrow mountains and plains. Last but not least, the Winter Weather Advisory for mountain zones 31..33 and 34 will remain in effect until 18z/Tuesday. Should see snowfall rates decreasing by the afternoon. .LONG TERM...(Tuesday night through Sunday) Issued at 325 AM MDT Mon May 16 2016 Cool and cloudy start to the extended with an upper level low spinning over southern CA. This low will weaken as it travels eastward becoming an open trough by Wednesday afternoon/evening. Continuing SW flow will keep a steady stream of moisture over NE Colorado with cold fronts keeping conditions cooler and therefore more stable. Fro Tuesday night into Wednesday conditions over the plains will be cool with cloudy skies and chance of showers that continue into the evening ours before clearing out overnight. Some models suggesting the clouds will clear sooner on the far NE plains allowing for some surface heating and therefore increased instability. This could lead to isolated thunder on the plains late Tuesday with heavier showers. Wednesday temperatures will be cooler than average with highs only getting into the lower 60s. A weak surface high on the plains will help to keep precipitation out but conditions will remain cloudy. In the mountains there is a chance of rain and snow showers at higher elevations with isolated thunderstorms by the afternoon. There is a deep closed off low entering the Pacific NW that will allow ridging over NE Colorado on Thursday. There will be enough moisture in the mountains however to keep a slight chance of thunderstorms in the afternoon with rain and snow showers above 10,000 ft. Temperatures will rebound back to seasonal normals on Thursday with highs in the upper 60s to lower 70s. Friday and through the weekend starts a dry and warming trend. The upper level low over the Pacific NW will continue to spin over that region keeping prolonged ridging and therefore increasing temps over CO. Look for highs into the 70s on Friday and possibly lower 80s by Saturday and Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 830 PM MDT Mon May 16 2016 IFR conditions will persist through at least Tuesday morning with shallow upslope keeping rain showers, drizzle, and fog in place. As rain decreases later tonight, drizzle and fog is expected to become more prominent. Visibilities may drop to 1/4 to 1/2sm if fog over the Front Range airports including KDEN 08Z-15Z. Should see a slow improvement 15Z-18Z Tuesday with MVFR conditions expected to develop Tuesday afternoon with some daytime heating and weakening upslope component. && .BOU Watches/Warnings/Advisories... Winter Weather Advisory until noon MDT Tuesday for COZ033-034. && $$ UPDATE...Barjenbruch SHORT TERM...Baker LONG TERM...Bowen AVIATION...Barjenbruch
  [top] Area Forecast Discussion National Weather Service Pueblo CO 551 PM MDT MON MAY 16 2016 .UPDATE... Issued at 547 PM MDT Mon May 16 2016 Severe threat is done for this evening. Watch has been cancelled for Las Animas and Baca Counties. && .SHORT TERM...(This evening through Tuesday) Issued at 327 PM MDT Mon May 16 2016 Currently...An upper low pressure system was located over the Great Basin Mon afternoon, while at the sfc high pressure over the Dakotas was supplying a low level northeasterly push into Colorado. This was providing an ample amount of low level moisture for the forecast area today, while disturbances aloft tapped into the moisture for storm production. Isolated severe storms have already occurred along the Colorado/New Mexico state line of SE Colorado, with numerous showers and isolated storms elsewhere. Extensive cloud cover has kept temps somewhat cool, 50s to lower 60s, and has throttled the fuel for widespread severe storm activity. Tonight and tomorrow...The upper low will gradually sink to the south, then southwest, over the next 24 hrs, dropping into southern Nevada and California through the day tomorrow. Numerous showers and isolated thunderstorms are expected to continue through the evening hours, then showers will linger through the night. Tomorrow the process will repeat itself, but with the upper low a bit further to the west and south, convection should diminish over the far eastern plains while continuing over the western section of the CWA. The severe threat will also drop south, out of the forecast area. Look for cool temps tomorrow, with max temps only forecast to climb into the 50s. As for ongoing winter wx highlights, significant new accumulations of wet spring snow for the higher elevations looks reasonable, and had to issue an advisory for the SW mountains for the continued threat there until late Tue night. The best window for periods of heavy rain will likely be this evening through Tue morning, along the I-25 corridor as well as the lower eastern slopes of the southern Front Range. Moore .LONG TERM...(Tuesday night through Monday) Issued at 327 PM MDT Mon May 16 2016 Upper low settles into AZ Tue night, keeping strong upward motion over the San Juan and La Garita mountains through the night. Snow level will likely hang out around 10k-11k with several inches of accumulation over the peaks. Will keep winter wx advisory in place through the night, though impact may be limited somewhat by warm road/ground temps staying near freezing. Tough to rule out some lighter rain and snow showers across the remainder of the region, best chances generally over the mountains and interior valleys, least chance over the plains. Low turns to the corner and heads east through AZ Wed, keeping precip going over the higher terrain and most valleys through the day. Kept the advisory going for now, though snow level will likely rise to above pass level by afternoon as 700 mb temps begin to climb. Shallow upslope will keep plains generally cloudy with a few showers possible, though air mass east of the mountains looks too cool/stable for tsra. On Thu, upper low weakens as it lifts northeastward across nrn NM and srn CO. Expect precip Thu/Thu night to be fairly convective in nature as low levels warm and destabilize somewhat, and will have a mention of afternoon and evening tsra all areas in the afternoon and early evening. Upper ridge then migrates eastward through the state Fri/Sat which should suppress convection somewhat, though residual moisture will likely produce some mountain storms both days. Will need to watch for some dryline storms Sat evening as deeper moisture pushes north, with boundary along/near the KS border after 00z. Similar set-up for Sun as Pacific NW upper trough pushes eastward, with dryline lurking over the far sern plains and potential for high based tsra over the mountains. Should see max temps Fri-Sat climb back to above average readings, with 80s reappearing over portions of the plains. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 516 PM MDT Mon May 16 2016 Extended periods of mvfr to lifr are expected for the TAF sites over the next couple of days, as a low pressure system slowly moves through the region. At KALS...expect periods of mvfr...and brief periods of ifr, as rounds of showers and isold ts move through the valley through tomorrow. Freezing levels should remain about 1000-1500 ft AGL on tuesday. KPUB and KCOS...TS should weaken early this eve, but numerous showers will continue for the evening. Areas of fog likely to develop by early morning, especially vicinity KCOS, and cigs likely to remain IFR through the morning...possibly improving to MVFR by afternoon. Freezing levels will be about 1000 ft AGL by early Tue. ROSE && .PUB Watches/Warnings/Advisories... Winter Weather Advisory from noon Tuesday to midnight MDT Wednesday night for COZ066-068. Winter Weather Advisory until 6 AM MDT Tuesday for COZ058-060. Winter Weather Advisory until noon MDT Tuesday for COZ081. Winter Storm Warning until 6 AM MDT Wednesday for COZ082. && $$ UPDATE...LW SHORT TERM...MOORE LONG TERM...PETERSEN AVIATION...ROSE
  [top] Area Forecast Discussion National Weather Service Grand Junction CO 508 PM MDT MON MAY 16 2016 .SHORT TERM...(This evening through Tuesday night) Issued at 359 PM MDT Mon May 16 2016 Wet, dreary weather continues through the short term as an upper level low spinning over northern Nevada moves south into the Great Basin. However, this low will not track through the forecast area. Rather, it will drop further south into Arizona. Regardless of its track, ample moisture rotating with this storm will be pulled into the region over the next couple of days. As a result, expect a continuation of widespread showers and chance for storms plus below normal temperatures in the forecast. Guidance temperatures came in too warm so decided to bump temperatures down a few degrees to reflect current trends. As with previous model runs, best chance of precipitation is expected to be during the afternoon and evening hours so grids continue to reflect that. Seeing as how the gradient is not too impressive with this storm, and that the jet core stays well south of the area, do not expect any significant winds for the region apart from the occasional gusty outflow wind with storms. Most impressive QPF remains over the eastern Uinta mountains and right along the northern divide tonight, but upper level temps remain quite mild so not expecting any significant snowfall. Tomorrow night will see the best chance for significant snowfall especially down south. Orographics remain favorable for upslope with winds generally remaining out of the southeast through the overnight hours. However, after examining wet bulb zero heights and upper level temperatures, do not think there will be any major impacts for our mountain areas. Storm total snowfall from tomorrow through Wednesday morning show the San Juans receiving 4 to 8 inches. Seeing as how this will be over several periods and the expectation that warm road surfaces will melt any falling snow, chose to not issue any advisories at this time. Will continue to monitor the situation and let future shifts decide if highlights should be issued. .LONG TERM...(Wednesday through Monday) Issued at 359 PM MDT Mon May 16 2016 Wednesday will bring another day of widespread showers to the region. The last pull of wraparound moisture from the departing trough will keep decent shower coverage going through Thursday morning before activity shifts to the higher terrain during the afternoon. A "break" of sorts will finally arrive Friday as a weak transitory ridge builds ahead of the next storm. However, cannot rule out an afternoon shower or two during the afternoon hours. As for the next storm, after remaining stationary off the coast of the Pacific northwest for several days, it will finally move onshore beginning Friday. Models indicate this massive low pressure system will split with the lower portion following the typical spring-time track. It is projected to drop down into the Great Basin as early as Sunday night and bring yet another chance for clouds and showers. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 506 PM MDT Mon May 16 2016 Stormy weather will continue tonight and tuesday as low pressure remains over the area. Expect widespread showers and scattered thunderstorms through the period with areas of IFR cigs possible, and local ifr vsbys. mts will be obscured. Terminal sites may see periods of ILS cigs as showers move through with brief mvfr and ifr conditions. Gusty outflow winds to 40 mph and small hail will accompany the strongest storms and snow levels will be running between 9 and 10k today, falling to as low as 8k tonight. && .HYDROLOGY... Issued at 918 AM MDT Mon May 16 2016 With the forecast wet weather and expected warming temperatures toward the end of the week, river levels are expected to gradually rise over the next few weeks. Flows will generally increase due to snowpack melting with some streams reaching near bankfull at times. Use caution in and near swift currents. && .GJT Watches/Warnings/Advisories... CO...None. UT...None. && $$ SHORT TERM...MMS LONG TERM...MMS AVIATION...CC HYDROLOGY...JAM
Area Forecast Discussion National Weather Service Pueblo CO 141 PM MDT MON MAY 16 2016 .UPDATE... Issued at 140 PM MDT Mon May 16 2016 Quick update for issuance of the Severe Thunderstorm Watch for Las Animas and Baca counties until 03z tonight. Incorporated latest obs and satellite data. Moore && .SHORT TERM...(Today and tonight) Issued at 450 AM MDT Mon May 16 2016 Multiple meteorological concerns over the forecast district during the short term, including but not limited to locally heavy rainfall potential, severe potential, higher elevation snow, areas of low clouds/fog and temperatures, etc. Forecast district currently graced by generally above seasonal mid- May early morning temperatures, variable cloudiness in combination with areas of low clouds and fog and isolated shower activity. Latest forecast model soundings, real/near time data, computer simulations and PV analysis indicate that upper disturbances will combine with adequate atmospheric moisture and a moist northeasterly surface surge to allow for the development of generally scattered to numerous showers and isolated to scattered thunderstorms, once again favoring the afternoon into the evening/night hours. Some of these thunderstorms are expected to generate locally heavy rainfall and also be capable of entering the strong to to severe category as projected maximum localized capes, LI`s and 0-6 km shears challenge/exceed 1600 J/Kg, -7C and 45 knots at times respectively, especially over south-central and southeastern sections of the forecast district. At this time, the potential for stronger to severe storms favor south-central and southeastern locations of the forecast district, especially from this afternoon into this evening and have mentioned severe potential(including the potential for large hail, damaging winds and even an isolated tornado) in upcoming grids/zones over eastern Las Animas and Baca continues to account for this potential(although highest potential of organized severe storms seems to favor locations such as portions of the Texas and Oklahoma panhandles). In addition, have also depicted locally heavy rain potential over eastern portions of the forecast district, including the Interstate 25 corridor and associated burn scars, including but not limited to the Waldo Canyon burn scar, etc. As always, WFO Pueblo will closely monitor severe weather and flooding potential closely and issue necessary highlights/advisories/warnings, etc. as needed. Also, will maintain winter weather highlights from noon today into at least Tuesday for Pikes Peak, Teller county and the Rampart Range as well as for the eastern Sawatch Mountains and the Western Mosquito Range, where significant late season is anticipated over these locations during this time-frame. Will also depict areas of fog and low clouds over several locations at times during the near/short term in combination with continued below seasonal mid-May maximum temperatures and near to above seasonal minimum temperatures over the majority of the CWFA during the next 24 hours. .LONG TERM...(Tuesday through Sunday) Issued at 450 AM MDT Mon May 16 2016 On Tue a large upr level low wl be centered ovr UT, with plenty of mstr ovr the forecast area. The weather wl remain unsettled with widespread pcpn chances over the mtns and high valleys. Over the sern plains upslope flow continues and chances for light showers look good...but closer to the mtns there may be better chances for pcpn and accumulations. It looks like the swrn mtns wl be hardest hit with snow on Tue...although the rest of the mtns wl also see accumulations. Tue wl be the coolest day with highs in the mid 40s to lower 50s at the lower elevations. Tue night the upr low centered is expected to move south into AZ. Snow is expected to continue ovr the mtns, with the best accumulations still expected to be ovr the swrn mtns. the lower elevations may see some light pcpn thru the night. On Wed the upr low is expected to weaken and become an open wave and being moving eastward acrs NM and CO. The mtns, high valleys and I-25 corridor wl continue to see good chances for pcpn, while the sern plains may just see some isold pcpn. Highs on Wed are expected to be a little warmer, but wl still be below average with highs only in the 50s at the lower elevations. Wed night the upr trof is expected to move ovr far ern CO and pcpn chances are expected to decrease ovr much of the area. On Thu there wl still be enough moisture ovr the area that we should again sct or high chances for pcpn ovr the mtns and high valleys, with isold pops ovr the plains. temps should be a little warmer Thu but still below average. Finally, on Fri it looks drier ovr the area as a upr ridging develops ovr ern co ahead of an upr low ovr OR and nrn CA. The ridge shifts eastward ovr KS on Sat, with increasing southwest flow ovr the forecast area. Chances for pcpn look mostly confined to the mtn areas on Fri and Sat, but we may also see some isold showers/tstms move out ovr the ern plains Sat afternoon and evening. High temps Fri and Sat are expected to be above average. On Sun the upr trof is forecast to move ovr NV which wl keep south to southwest flow aloft ovr the forecast area and mainly dry conditions. However there may still be some isold showers/tstms ovr the mtns and the dry line may be near the KS border Sun afternoon.&& .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 450 AM MDT Mon May 16 2016 MVFR to localized IFR/LIFR ceilings and visibilities at times will be possible over the KCOS and KPUB taf sites this morning due to areas of low clouds and fog. Similar to the previous 24 hours, periods of MVFR/IFR and LIFR conditions due to shower and thunderstorm activity will be possible at times over the KALS, KCOS and KPUB taf sites into tonight. In addition, the potential for strong to severe thunderstorms exist primarily over south-central and southeastern Colorado from late this morning into this evening, although the potential does exist that stronger storms capable of producing locally heavy rainfall, hail and gusty winds may be noted in the vicinity of the KALS, KCOS, and KPUB taf sites respectively from later today into this evening && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 450 AM MDT Mon May 16 2016 MVFR to localized IFR/LIFR ceilings and visibilities at times will be possible over the KCOS and KPUB taf sites this morning due to areas of low clouds and fog. Similar to the previous 24 hours, periods of MVFR/IFR and LIFR conditions due to shower and thunderstorm activity will be possible at times over the KALS, KCOS and KPUB taf sites into tonight. In addition, the potential for strong to severe thunderstorms exist primarily over south-central and southeastern Colorado from late this morning into this evening, although the potential does exist that stronger storms capable of producing locally heavy rainfall, hail and gusty winds may be noted in the vicinity of the KALS, KCOS, and KPUB taf sites respectively from later today into this evening && .PUB Watches/Warnings/Advisories... Winter Weather Advisory from noon Tuesday to 6 AM MDT Wednesday for COZ066-068. Winter Weather Advisory until 6 AM MDT Tuesday for COZ058-060. Winter Weather Advisory from 6 PM this evening to noon MDT Tuesday for COZ081. Winter Storm Warning until 6 AM MDT Wednesday for COZ082. && $$ UPDATE...MOORE SHORT TERM...77 LONG TERM...28 AVIATION...MOORE
Area Forecast Discussion National Weather Service Denver/Boulder CO 1222 PM MDT MON MAY 16 2016 .UPDATE... Issued at 1215 PM MDT Mon May 16 2016 convection now underway over the Front Range and western sections of the Palmer Divide in Douglas County. Weather spotter just reported small hail falling from a single t-storm south-southeast of Castle Rock. Precipitation will continue to expand especially over and east of the Front Range as upslope flow deepens and qg ascent increases ahead of a vort lobe/shortwave trough rotating up from southern Colorado. On another note, fog continues to plague many areas with visibilities less than 2 miles in portions of the I-25 corridor. Fog may be slow to dissipate today. Will adjust afternoon forecast grids accordingly. UPDATE Issued at 915 AM MDT Mon May 16 2016 Fog persists at this hour across most of the greater Denver metro area...although web cams and surface obs reveal a significant improvement in visibilities in areas roughly south of Interstate 70 and east of Aurora. The thickest fog was over northwest sections of the metro area such as around Boulder and Broomfield where prevailing vsbys were still below 1/4 mile. Should see this heavy fog erode from southeast-to-northwest over the next hour or two as slightly drier air flows down off the Palmer Divide and with mixing of the boundary layer with passing rain showers. Vort lobe/shortwave trough rotating northward over the CWA during the next couple of hours will enhance this shower activity as noted in the previous discussion. Isolated t-storms also a possibility towards midday. Hail, brief heavy rain and perhaps a funnel cloud or two all possible with these cells. At this time, will make only minor adjustments to the ongoing forecast. Will also hang onto the winter weather and dense fog highlights for now. && .SHORT TERM...(Today and tonight) Issued at 402 AM MDT Mon May 16 2016 Pockets of dense fog have formed in the Denver and Boulder areas with visibilities less than a quarter mile at times. Partial clearing after last evening`s period of rain allowed for strong radiational cooling along parts of the i-25 urban corridor. Visibilities at KDEN have been less than a quarter mile since about 2 AM MDT and a co-worker driving up Davidson Mesa outside of Boulder reported visibilities less than 100 feet. Other observations from local airports show visibilities greater than a mile and a half. Have issued a dense fog advisory for zones 39 and 40 until 10 AM MDT to handle the morning rush hour. Otherwise, the forecast remains on track. A band of showers has been moving over western Colorado this morning with some embedded thunderstorms as late at 3:30 AM MDT. These showers should progress into the north central mountains in the next few hours and then over northeast Colorado later today. The approaching upper trough will place Colorado under rising motions through this evening. The airmass is plenty moist and slightly unstable at mid- levels which will allow for an extended period of precipitation through this afternoon and evening. Temperatures in the mountains are expected to cool through today with snow levels eventually coming down to 10000 feet or lower. Significant accumulations will be possible on the peaks, ridges and higher elevation roadways, so a Winter Weather Advisory will be in effect through Tuesday. Temperatures are going to be much cooler than normal due to the lack of sunshine and occurring precipitation. Areas of precipitation are expected to continue into the evening and then diminish overnight. .LONG TERM...(Tuesday through Sunday) Issued at 402 AM MDT Mon May 16 2016 Models have an upper closed low over Nevada into western Colorado at 12z Tuesday. The upper low weakens and falls apart as it moves slowly eastward and across the CWA as an open trough through Wednesday night. The flow aloft will weak all four periods. The models keep weak qg upward vertical velocity for the CWA into Wednesday night. Models have easterly low level flow for the CWA Tuesday, then southeasterly well into Wednesday. Winds should be close to normal diurnal drainage patterns Wednesday night. Models show quite a bit of moisture over the CWA well into Wednesday before decrease overnight. The qpf Fields show measurable precipitation across all the CWA Tuesday into Tuesday evening. There is very little measurable precipitation noted Wednesday and Wednesday evening for the plains, but some in the mountains. There is some CAPE mainly in the mountains and foothills late day Tuesday and late day Wednesday. Lapse rates are not very steep, especially over the plains both late days periods. will go with 30-60% pops on Tuesday and Tuesday evening. Late day Wednesday`s pops are similar in the mountains and foothills only. The plains can expected 10-20%s. for temperatures, Tuesday`s highs are 1-3 C warmer than today`s expected highs. Wednesday`s readings warm up 2-5 c above Tuesday`s readings. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1215 PM MDT Mon May 16 2016 will hang onto ils cigs and vsbys at denver area terminals for the remainder of the afternoon. may not see vsbys rising above 3 miles all day, even with passing showers and t-storms. ceilings now not expected to rise above 1000 ft agl all day at KDEN, KAPA and KBJC. && .BOU Watches/Warnings/Advisories... Winter Weather Advisory until noon MDT Tuesday for COZ031-033- 034. && $$ UPDATE...Baker SHORT TERM...Dankers LONG TERM...RJK AVIATION...Baker
Area Forecast Discussion National Weather Service Grand Junction CO 1129 AM MDT MON MAY 16 2016 updated aviation section .UPDATE... Issued at 918 AM MDT Mon May 16 2016 Rain/Snow line is at about 8300 feet this morning, but will rise throughout the day. Snow accumulation level on roads as of 9am looks to be above 10,000 ft at the high passes, so have refrained from issuing any advisories today with impacts minimal. Will keep an eye on precipitation development, but expecting short lived convective showers and thunderstorms this afternoon. Short term forecast models indicate downturn in activity after sunset when snow would accumulate on the roads again. Expecting the best thunderstorms to develop across the Four Corners today with hail the main threat. && .SHORT TERM...(Today through Tuesday night) Issued at 254 AM MDT Mon May 16 2016 Energy rotating around an upper level low located over southern Idaho will continue to bring showers and thunderstorms to much of eastern Utah and western Colorado through Tuesday. First wave working through the area this morning with showers and thunderstorms driving east into the central mountains. Snow levels remain above 9k and bulk of activity has been light so far, so no plans on hoisting any winter highlights for narrow stretches of our high mountain passes. Could see a few inches accumulate above 10k by this evening, but road surfaces remain warm and impact should be minimal. Otherwise, it`s looking like another unsettled day with a few stronger storms again expected as moisture and additional energy pass through. Wind gusts to 50 mph not out of the question along with small hail. Models have remained aggressive with pops and QPF values peaking during the afternoon and evening hours. See no reason to stray far from that thinking and pop grids will be geared this direction. As the low drops or sags south into Utah, colder air will slide south with it. This will lower snow levels a bit by Tuesday morning, possibly as low as 8k, but levels rise throughout the day back to near 10k by afternoon. Overall a very similar weather day is expected with showers and thunderstorms throughout the region and some accumulating snowfall for the highest peaks. Best shot at more significant snowfall will push into the San Juans late Tuesday and Tuesday night when we see another stronger wave rotate out of the digging low with a period of favorable orographics and dynamics coming into play. This will generate more persistent precipitation that may eventually lead to more significant snowfall accumulations from Telluride southeast to Wolf Creek Pass. Main impacts would be overnight Tuesday into Wednesday morning and later shifts can take a look at the need for any sort of winter highlights. Temperatures will be running on the cool side of normal through mid-week and have undercut guidance values a bit today and again on Tuesday due to cloud cover and showers. .LONG TERM...(Wednesday through Sunday) Issued at 254 AM MDT Mon May 16 2016 The upper level low will slowly fill over the southern Great Basin by the end of the week with the cool and unsettled weather slowly abating as we close out the week. The low fills on Wednesday with remnants getting kicked out by late Thursday. This will lead to a decrease in the showers and also send in some warmer air aloft which lifts snow levels back up to near 10k by Wednesday afternoon. Scattered activity then lingers through Thursday afternoon, favoring the higher terrain. By Friday, the Pacific Northwest gets a taste of what we`ve been experiencing as a deep area of low pressure sets up just off the coast and gets cutoff. This system barely moves from Thursday through Sunday. The location of the low will cause a ridge to form to our east pushing the trough to the plains and keeping us `relatively` dry. Some afternoon convection can`t be ruled out as ample moisture will remain while daytime heating will help to destabilize the atmosphere. After the first half of the week though, the weather will show a marked improvement. Temperatures will slowly warming up through the weekend. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1129 AM MDT Mon May 16 2016 Stormy weather continues across the region through the end of the week. Expect widespread showers and isolated thunderstorms through the period with areas of IFR cigs possible, especially over the higher elevations. Terminal sites may see periods of ILS cigs as showers move through. Gusty outflow winds to 50 mph and small hail will accompany the strongest storms and snow levels will be running between 9 and 10k today, falling to as low as 8k tonight. Mountain obscuration likely over the next 24 hours. && .HYDROLOGY... Issued at 918 AM MDT Mon May 16 2016 With the forecast wet weather and expected warming temperatures toward the end of the week, river levels are expected to gradually rise over the next few weeks. Flows will generally increase due to snowpack melting with some streams reaching near bankfull at times. Use caution in and near swift currents. && .GJT Watches/Warnings/Advisories... CO...None. UT...None. && $$ UPDATE...JAM SHORT TERM...JDC LONG TERM...TGR/JDC AVIATION...TGJT HYDROLOGY...JAM
Area Forecast Discussion National Weather Service Grand Junction CO 918 AM MDT MON MAY 16 2016 .UPDATE... Issued at 918 AM MDT Mon May 16 2016 Rain/Snow line is at about 8300 feet this morning, but will rise throughout the day. Snow accumulation level on roads as of 9am looks to be above 10,000 ft at the high passes, so have refrained from issuing any advisories today with impacts minimal. Will keep an eye on precipitation development, but expecting short lived convective showers and thunderstorms this afternoon. Short term forecast models indicate downturn in activity after sunset when snow would accumulate on the roads again. Expecting the best thunderstorms to develop across the Four Corners today with hail the main threat. && .SHORT TERM...(Today through Tuesday night) Issued at 254 AM MDT Mon May 16 2016 Energy rotating around an upper level low located over southern Idaho will continue to bring showers and thunderstorms to much of eastern Utah and western Colorado through Tuesday. First wave working through the area this morning with showers and thunderstorms driving east into the central mountains. Snow levels remain above 9k and bulk of activity has been light so far, so no plans on hoisting any winter highlights for narrow stretches of our high mountain passes. Could see a few inches accumulate above 10k by this evening, but road surfaces remain warm and impact should be minimal. Otherwise, it`s looking like another unsettled day with a few stronger storms again expected as moisture and additional energy pass through. Wind gusts to 50 mph not out of the question along with small hail. Models have remained aggressive with pops and QPF values peaking during the afternoon and evening hours. See no reason to stray far from that thinking and pop grids will be geared this direction. As the low drops or sags south into Utah, colder air will slide south with it. This will lower snow levels a bit by Tuesday morning, possibly as low as 8k, but levels rise throughout the day back to near 10k by afternoon. Overall a very similar weather day is expected with showers and thunderstorms throughout the region and some accumulating snowfall for the highest peaks. Best shot at more significant snowfall will push into the San Juans late Tuesday and Tuesday night when we see another stronger wave rotate out of the digging low with a period of favorable orographics and dynamics coming into play. This will generate more persistent precipitation that may eventually lead to more significant snowfall accumulations from Telluride southeast to Wolf Creek Pass. Main impacts would be overnight Tuesday into Wednesday morning and later shifts can take a look at the need for any sort of winter highlights. Temperatures will be running on the cool side of normal through mid-week and have undercut guidance values a bit today and again on Tuesday due to cloud cover and showers. .LONG TERM...(Wednesday through Sunday) Issued at 254 AM MDT Mon May 16 2016 The upper level low will slowly fill over the southern Great Basin by the end of the week with the cool and unsettled weather slowly abating as we close out the week. The low fills on Wednesday with remnants getting kicked out by late Thursday. This will lead to a decrease in the showers and also send in some warmer air aloft which lifts snow levels back up to near 10k by Wednesday afternoon. Scattered activity then lingers through Thursday afternoon, favoring the higher terrain. By Friday, the Pacific Northwest gets a taste of what we`ve been experiencing as a deep area of low pressure sets up just off the coast and gets cutoff. This system barely moves from Thursday through Sunday. The location of the low will cause a ridge to form to our east pushing the trough to the plains and keeping us `relatively` dry. Some afternoon convection can`t be ruled out as ample moisture will remain while daytime heating will help to destabilize the atmosphere. After the first half of the week though, the weather will show a marked improvement. Temperatures will slowly warming up through the weekend. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 254 AM MDT Mon May 16 2016 Unsettled weather will remain in the region through Tuesday. Expect widespread showers and isolated thunderstorms through the period with areas of IFR cigs possible, especially over the higher elevations. Terminal sites may see periods of ILS cigs as showers move through. Gusty outflow winds to 50 mph and small hail will accompany the strongest storms and snow levels will be running between 9 and 10k today, falling to as low as 8k tonight. Mountain obscuration likely over the next 24 hours. && .HYDROLOGY... Issued at 918 AM MDT Mon May 16 2016 With the forecast wet weather and expected warming temperatures toward the end of the week, river levels are expected to gradually rise over the next few weeks. Flows will generally increase due to snowpack melting with some streams reaching near bankfull at times. Use caution in and near swift currents. && .GJT Watches/Warnings/Advisories... CO...None. UT...None. && $$ UPDATE...JAM SHORT TERM...JDC LONG TERM...TGR/JDC AVIATION...JDC HYDROLOGY...JAM
Area Forecast Discussion National Weather Service Denver/Boulder CO 821 PM MDT SUN MAY 15 2016 .UPDATE... Issued at 659 PM MDT Sun May 15 2016 The second band of showers today is now moving off the foothills. some lightning persisted to near Jefferson County Airport...but for the most part these showers are again weakening as they move to the plains. This is part of a large band of clouds that extend to the west slope...but satellite loops show a large dry slot moving into southwest Colorado. The HRRR and RAP models both show a dry period from around 06z to 13z for the metro area. The surface pattern has been weak this evening...but a surface low is forecast to develop near trinidad late tonight and intensify tomorrow morning. This will result in increasing upslope flow along the urban corridor and palmer divide...with showers redeveloping Monday morning and continuing through the day. Coordinated with adjoining offices on winter weather advisory...and will issue one for the higher mountain passes for late tonight through noon Tuesday. Models indicate that some higher elevations may see up to 30 inches of snow by the time the storm is done with us. It is likely to be a very wet sloppy mess with daytime highs in the higher passes reaching 32 tomorrow. All in all the previous forecast has a good handle on system development...but mav guidance is 5 degrees colder than met guidance. With the clouds...upslope...and moisture am going to lower max temps in eastern Colorado on Monday and drop higher passes a degree or two. && .SHORT TERM...(This evening through Monday) Issued at 322 PM MDT Sun May 15 2016 Initial shower band moving east on the plains but has mostly dissipated. A larger batch of showers and thunderstorms over the mountains will spread onto the plains this evening. This has more forcing and since it is a large area of rain it will bring higher dew points with it, so it should survive better. Still expecting a bit of a break later tonight, but then the low on the east side of the mountains will start to wind up. Some question about the amount of low level moisture that persists through the night. Models seem a bit overdone, so I am showing mostly cloudy skies but not into the fog/drizzle regime yet, at least around Denver. During the night the best moisture convergence will be across Wyoming and the Nebraska panhandle, but this should all slide southward Monday morning with the lower levels saturating, upslope winds, and persistent lift. Some uncertainty about the timing of this progressing from north to south but at this time it looks like this will be happening during the morning hours. Generally expecting light but steady rainfall, but with upslope enhancement over the east slopes of the Front Range. Snow level should also be lowering a bit during the day, settling somewhere around 7-8 thousand feet on the east slopes with warmer low levels holding it higher on the west side. Could be some heavy snow in the afternoon, but warm temps will limit the impact in populated areas so just the highest roads are of concern. .LONG TERM...(Monday night through Sunday) Issued at 322 PM MDT Sun May 15 2016 Monday night...a broad closed upper low will stretch from Northwest NV into northwest CO. Weak QG ascent will be over the cwa overnight as this trough makes its way south into AZ by 00z Wednesday. At the surface...a secondary surge will enhance the upslope along the Front Range Monday night. The mdls show moderate to strong QG ascent at the surface through the evening...with the east to southeast upslope fm the surface to around 600 mb. NAM12 forecast sounding show moist adiabatic lapse rates with the airmass saturated through the layer. There could be an isolated tstm in the mountains Monday evening but it looks too stable across the Urban Corridor and northeast plains with the possible exception of the Palmer Divide. Overrunning type of setup Monday night with the colder air below undercutting a fairly strong inversion just above 700 mb. east and southeast facing aspects above 9 thousand feet could receive 8 to 12 inches of snowfall by tuesday morning...but not as much west of the Continental Divide. No highlights yet but am learning more towards advisory type snowfall vs warning at this time for the Front Range east of the Continental Divide and possibly the higher foothills. The foothills will see a accumulating snowfall above 8 thousand feet with a steady mix of rain and snow down to 6500 feet. We could possibly see a mix of rain/snow over the palmer divide above 6 thousand feet by tuesday morning. The mix of rain/snow in the foothills should help alleviate any potential flooding risk as well. Tuesday...a deep southeasterly upslope flow will be present but the wind will not be as strong. Wl keep some light snow or rain/snow mix in the mountains through the day...with higher pops for light rain in and near the foothills/Palmer Divide as well. Wl keep the mention of tstms in the grids but mainly over the mountains. Tuesday night into Wednesday...the main area of pcpn continues to get dragged to the south. There is still enough moisture and some weak forcing around for showers...especially over the mountain but the overall coverage will be decreasing. The weakening trough finally shifts to the east of CO by Thu with a drier and more subsident northwesterly flow aloft. An upper level ridge will finally set up over the region late Thursday and continue into Saturday. It will be much warmer by the weekend with the more typical pattern of aftn/evng thunderstorms on Friday and Saturday. The mdls continue to show a large upper trough over the Pacific Northwest by the weekend...with an increasing southwesterly flow aloft over CO by Sunday. && .AVIATION...(For the 18Z TAFS through 18Z Monday afternoon) Issued at 322 PM MDT Sun May 15 2016 The showers moving through the metro area will be followed by one or two more bands of rain this evening...but it looks dry from 06z until at least 13z. The winds have been the big question today...other than the gusty winds with showers...it has been difficult to pin down directions. This will become easier tomorrow with the deepening upslope flow we will settle on north to northeast winds for much of the day. Ceilings of 030 to 060 with the showers will rise a bit overnight...then drop to mvfr monday morning...with areas of ifr. && .BOU Watches/Warnings/Advisories...winter weather advisory for mountain zones...31...33...34 from 3am tonight to noon Tuesday. && $$ UPDATE...RTG SHORT TERM...Gimmestad LONG TERM...Cooper AVIATION...Gimmestad Area Forecast Discussion National Weather Service Denver/Boulder CO 830 PM MDT MON MAY 16 2016 .UPDATE... Issued at 830 PM MDT Mon May 16 2016 Radar shows widespread showers across the plains and Front Range. Current snow level ranged from around 7000-7500 feet in the southern foothills, to down as low as 6000 feet near the Wyoming border as Cheyenne Wyoming had switched over to snow in the last couple hours. Main precipitation shield is just east of I-25 but lots of drizzle farther west, with another batch of heavier precip and snowfall in the mountains around Summit and Park counties. The main precip area on the plains is shifting slightly westward as another surge was noted in Northeast Colorado, so rain will continue through the rest of this evening and then maybe only slowly decrease through the rest of the night as upslope component weakens. Even then, drizzle and areas of fog should remain behind and continue into Tuesday morning with the very moist and ever so slight upslope component still in place. With regard to snow in the mountains, the orographic forcing is rather weak but still convective enough for a heavy burst of snow this evening in the Summit and Park county areas. Will keep the advisories going here, but did cancel the advisory farther northwest where snow has been slow to develop in zone 31 near the Rabbit Ears Pass area. && .SHORT TERM...(This afternoon through Tuesday) Issued at 325 AM MDT Mon May 16 2016 500mb low centered over southwest Idaho at the present time is forecast to track south-southeastward to over central Utah by 06z tonight. From there models show the low curving southwestward over the lower Colorado River valley south of Las Vegas by late Tuesday afternoon. Near zonal mid-level flow on the south side of this low continues to feed ample amounts moisture over Colorado. East of the mountains this flow curves northeastward producing a wide region of weak to moderate qg ascent. Even as the upper low tracks south across Utah tonight, models show north central and northeast Colorado under large scale ascent. Returning to this afternoon...a shortwave trough/vort lobe rotating around the southeast quad of the upper trough presently aligning from NW Colorado to SE Colorado. Models show this feature and the convection its generating swinging newrd across NE Colorado between 23z/Mon-06Z/Tue. If it were not for the heavy low cloud cover and chilly temperatures on the plains, mid-level shear, instability and lift would be adequate to spawn a few strong if not severe t-storms. As it stands, the few t-storms that have managed to form over the Palmer Divide have pretty much collapsed as they moved into the far less favorable environment on the plains. One last comment, fog blanketing much of northeast Colorado and many mountain locales since late last night has shown little signs of dissipating. Many areas along the Front Range foothills are still reporting vsbys below 5 miles. Overnight...height and pressure falls on the west slope of Colorado will further enhance the moist upslope flow up against the east face of the Front Range mountains. Models indicate weak to moderate qg ascent moving over northeast and north central Colorado with the passing shortwave this evening. Model qpf amounts on the plains by 12z/Tue in the 0.35 to 0.70 inch range. QPf for the Front Range mountains and foothills in the 0.50 to 0.95 inch range. Snow level based on wetbulb zero anywhere from 7500 to 8500 ft this evening, then anywhere from 6000 to 7000 feet after midnight. Could see snow totals by morning anywhere from 5-9 inches on east facing slopes above 9000 feet...and 3-6 inches from 7000 to 9000 feet. It`s possible we could see an inch or so of very wet snow near the base of the foothills and on the Palmer Divide. Do not expect to see any snow accumulation in the Denver metro area except maybe a dusting on lawns in the higher western and southern suburbs. Lastly, should also continue to see areas of fog with the moist upslope flow...especially up against the Front Range. On Tuesday...as the upper low slowly moves away from Colorado forcing for ascent decreases and the high plains upslope flow lessens during the afternoon. Precipitable water changes little, so another day of low clouds, fog and showery type precipitation. And, another day of unseasonably cool temperatures, especially east of the Front Range. Highs on Tuesday only in the 40s...with 20s and 30s in the high country. Additional snow amounts anywhere from 2 to 6 inches in the mountains and higher Front Range foothills. Additional rain amounts on the plains anywhere from 0.05 inch in the far northeast to around a quarter inch near the foothills. Airmass appears to be too cool and stable for t-storms tomorrow mountains and plains. Last but not least, the Winter Weather Advisory for mountain zones 31..33 and 34 will remain in effect until 18z/Tuesday. Should see snowfall rates decreasing by the afternoon. .LONG TERM...(Tuesday night through Sunday) Issued at 325 AM MDT Mon May 16 2016 Cool and cloudy start to the extended with an upper level low spinning over southern CA. This low will weaken as it travels eastward becoming an open trough by Wednesday afternoon/evening. Continuing SW flow will keep a steady stream of moisture over NE Colorado with cold fronts keeping conditions cooler and therefore more stable. Fro Tuesday night into Wednesday conditions over the plains will be cool with cloudy skies and chance of showers that continue into the evening ours before clearing out overnight. Some models suggesting the clouds will clear sooner on the far NE plains allowing for some surface heating and therefore increased instability. This could lead to isolated thunder on the plains late Tuesday with heavier showers. Wednesday temperatures will be cooler than average with highs only getting into the lower 60s. A weak surface high on the plains will help to keep precipitation out but conditions will remain cloudy. In the mountains there is a chance of rain and snow showers at higher elevations with isolated thunderstorms by the afternoon. There is a deep closed off low entering the Pacific NW that will allow ridging over NE Colorado on Thursday. There will be enough moisture in the mountains however to keep a slight chance of thunderstorms in the afternoon with rain and snow showers above 10,000 ft. Temperatures will rebound back to seasonal normals on Thursday with highs in the upper 60s to lower 70s. Friday and through the weekend starts a dry and warming trend. The upper level low over the Pacific NW will continue to spin over that region keeping prolonged ridging and therefore increasing temps over CO. Look for highs into the 70s on Friday and possibly lower 80s by Saturday and Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 830 PM MDT Mon May 16 2016 IFR conditions will persist through at least Tuesday morning with shallow upslope keeping rain showers, drizzle, and fog in place. As rain decreases later tonight, drizzle and fog is expected to become more prominent. Visibilities may drop to 1/4 to 1/2sm if fog over the Front Range airports including KDEN 08Z-15Z. Should see a slow improvement 15Z-18Z Tuesday with MVFR conditions expected to develop Tuesday afternoon with some daytime heating and weakening upslope component. && .BOU Watches/Warnings/Advisories... Winter Weather Advisory until noon MDT Tuesday for COZ033-034. && $$ UPDATE...Barjenbruch SHORT TERM...Baker LONG TERM...Bowen AVIATION...Barjenbruch
  [top] Area Forecast Discussion National Weather Service Pueblo CO 551 PM MDT MON MAY 16 2016 .UPDATE... Issued at 547 PM MDT Mon May 16 2016 Severe threat is done for this evening. Watch has been cancelled for Las Animas and Baca Counties. && .SHORT TERM...(This evening through Tuesday) Issued at 327 PM MDT Mon May 16 2016 Currently...An upper low pressure system was located over the Great Basin Mon afternoon, while at the sfc high pressure over the Dakotas was supplying a low level northeasterly push into Colorado. This was providing an ample amount of low level moisture for the forecast area today, while disturbances aloft tapped into the moisture for storm production. Isolated severe storms have already occurred along the Colorado/New Mexico state line of SE Colorado, with numerous showers and isolated storms elsewhere. Extensive cloud cover has kept temps somewhat cool, 50s to lower 60s, and has throttled the fuel for widespread severe storm activity. Tonight and tomorrow...The upper low will gradually sink to the south, then southwest, over the next 24 hrs, dropping into southern Nevada and California through the day tomorrow. Numerous showers and isolated thunderstorms are expected to continue through the evening hours, then showers will linger through the night. Tomorrow the process will repeat itself, but with the upper low a bit further to the west and south, convection should diminish over the far eastern plains while continuing over the western section of the CWA. The severe threat will also drop south, out of the forecast area. Look for cool temps tomorrow, with max temps only forecast to climb into the 50s. As for ongoing winter wx highlights, significant new accumulations of wet spring snow for the higher elevations looks reasonable, and had to issue an advisory for the SW mountains for the continued threat there until late Tue night. The best window for periods of heavy rain will likely be this evening through Tue morning, along the I-25 corridor as well as the lower eastern slopes of the southern Front Range. Moore .LONG TERM...(Tuesday night through Monday) Issued at 327 PM MDT Mon May 16 2016 Upper low settles into AZ Tue night, keeping strong upward motion over the San Juan and La Garita mountains through the night. Snow level will likely hang out around 10k-11k with several inches of accumulation over the peaks. Will keep winter wx advisory in place through the night, though impact may be limited somewhat by warm road/ground temps staying near freezing. Tough to rule out some lighter rain and snow showers across the remainder of the region, best chances generally over the mountains and interior valleys, least chance over the plains. Low turns to the corner and heads east through AZ Wed, keeping precip going over the higher terrain and most valleys through the day. Kept the advisory going for now, though snow level will likely rise to above pass level by afternoon as 700 mb temps begin to climb. Shallow upslope will keep plains generally cloudy with a few showers possible, though air mass east of the mountains looks too cool/stable for tsra. On Thu, upper low weakens as it lifts northeastward across nrn NM and srn CO. Expect precip Thu/Thu night to be fairly convective in nature as low levels warm and destabilize somewhat, and will have a mention of afternoon and evening tsra all areas in the afternoon and early evening. Upper ridge then migrates eastward through the state Fri/Sat which should suppress convection somewhat, though residual moisture will likely produce some mountain storms both days. Will need to watch for some dryline storms Sat evening as deeper moisture pushes north, with boundary along/near the KS border after 00z. Similar set-up for Sun as Pacific NW upper trough pushes eastward, with dryline lurking over the far sern plains and potential for high based tsra over the mountains. Should see max temps Fri-Sat climb back to above average readings, with 80s reappearing over portions of the plains. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 516 PM MDT Mon May 16 2016 Extended periods of mvfr to lifr are expected for the TAF sites over the next couple of days, as a low pressure system slowly moves through the region. At KALS...expect periods of mvfr...and brief periods of ifr, as rounds of showers and isold ts move through the valley through tomorrow. Freezing levels should remain about 1000-1500 ft AGL on tuesday. KPUB and KCOS...TS should weaken early this eve, but numerous showers will continue for the evening. Areas of fog likely to develop by early morning, especially vicinity KCOS, and cigs likely to remain IFR through the morning...possibly improving to MVFR by afternoon. Freezing levels will be about 1000 ft AGL by early Tue. ROSE && .PUB Watches/Warnings/Advisories... Winter Weather Advisory from noon Tuesday to midnight MDT Wednesday night for COZ066-068. Winter Weather Advisory until 6 AM MDT Tuesday for COZ058-060. Winter Weather Advisory until noon MDT Tuesday for COZ081. Winter Storm Warning until 6 AM MDT Wednesday for COZ082. && $$ UPDATE...LW SHORT TERM...MOORE LONG TERM...PETERSEN AVIATION...ROSE
  [top] Area Forecast Discussion National Weather Service Grand Junction CO 508 PM MDT MON MAY 16 2016 .SHORT TERM...(This evening through Tuesday night) Issued at 359 PM MDT Mon May 16 2016 Wet, dreary weather continues through the short term as an upper level low spinning over northern Nevada moves south into the Great Basin. However, this low will not track through the forecast area. Rather, it will drop further south into Arizona. Regardless of its track, ample moisture rotating with this storm will be pulled into the region over the next couple of days. As a result, expect a continuation of widespread showers and chance for storms plus below normal temperatures in the forecast. Guidance temperatures came in too warm so decided to bump temperatures down a few degrees to reflect current trends. As with previous model runs, best chance of precipitation is expected to be during the afternoon and evening hours so grids continue to reflect that. Seeing as how the gradient is not too impressive with this storm, and that the jet core stays well south of the area, do not expect any significant winds for the region apart from the occasional gusty outflow wind with storms. Most impressive QPF remains over the eastern Uinta mountains and right along the northern divide tonight, but upper level temps remain quite mild so not expecting any significant snowfall. Tomorrow night will see the best chance for significant snowfall especially down south. Orographics remain favorable for upslope with winds generally remaining out of the southeast through the overnight hours. However, after examining wet bulb zero heights and upper level temperatures, do not think there will be any major impacts for our mountain areas. Storm total snowfall from tomorrow through Wednesday morning show the San Juans receiving 4 to 8 inches. Seeing as how this will be over several periods and the expectation that warm road surfaces will melt any falling snow, chose to not issue any advisories at this time. Will continue to monitor the situation and let future shifts decide if highlights should be issued. .LONG TERM...(Wednesday through Monday) Issued at 359 PM MDT Mon May 16 2016 Wednesday will bring another day of widespread showers to the region. The last pull of wraparound moisture from the departing trough will keep decent shower coverage going through Thursday morning before activity shifts to the higher terrain during the afternoon. A "break" of sorts will finally arrive Friday as a weak transitory ridge builds ahead of the next storm. However, cannot rule out an afternoon shower or two during the afternoon hours. As for the next storm, after remaining stationary off the coast of the Pacific northwest for several days, it will finally move onshore beginning Friday. Models indicate this massive low pressure system will split with the lower portion following the typical spring-time track. It is projected to drop down into the Great Basin as early as Sunday night and bring yet another chance for clouds and showers. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 506 PM MDT Mon May 16 2016 Stormy weather will continue tonight and tuesday as low pressure remains over the area. Expect widespread showers and scattered thunderstorms through the period with areas of IFR cigs possible, and local ifr vsbys. mts will be obscured. Terminal sites may see periods of ILS cigs as showers move through with brief mvfr and ifr conditions. Gusty outflow winds to 40 mph and small hail will accompany the strongest storms and snow levels will be running between 9 and 10k today, falling to as low as 8k tonight. && .HYDROLOGY... Issued at 918 AM MDT Mon May 16 2016 With the forecast wet weather and expected warming temperatures toward the end of the week, river levels are expected to gradually rise over the next few weeks. Flows will generally increase due to snowpack melting with some streams reaching near bankfull at times. Use caution in and near swift currents. && .GJT Watches/Warnings/Advisories... CO...None. UT...None. && $$ SHORT TERM...MMS LONG TERM...MMS AVIATION...CC HYDROLOGY...JAM
Area Forecast Discussion National Weather Service Pueblo CO 141 PM MDT MON MAY 16 2016 .UPDATE... Issued at 140 PM MDT Mon May 16 2016 Quick update for issuance of the Severe Thunderstorm Watch for Las Animas and Baca counties until 03z tonight. Incorporated latest obs and satellite data. Moore && .SHORT TERM...(Today and tonight) Issued at 450 AM MDT Mon May 16 2016 Multiple meteorological concerns over the forecast district during the short term, including but not limited to locally heavy rainfall potential, severe potential, higher elevation snow, areas of low clouds/fog and temperatures, etc. Forecast district currently graced by generally above seasonal mid- May early morning temperatures, variable cloudiness in combination with areas of low clouds and fog and isolated shower activity. Latest forecast model soundings, real/near time data, computer simulations and PV analysis indicate that upper disturbances will combine with adequate atmospheric moisture and a moist northeasterly surface surge to allow for the development of generally scattered to numerous showers and isolated to scattered thunderstorms, once again favoring the afternoon into the evening/night hours. Some of these thunderstorms are expected to generate locally heavy rainfall and also be capable of entering the strong to to severe category as projected maximum localized capes, LI`s and 0-6 km shears challenge/exceed 1600 J/Kg, -7C and 45 knots at times respectively, especially over south-central and southeastern sections of the forecast district. At this time, the potential for stronger to severe storms favor south-central and southeastern locations of the forecast district, especially from this afternoon into this evening and have mentioned severe potential(including the potential for large hail, damaging winds and even an isolated tornado) in upcoming grids/zones over eastern Las Animas and Baca continues to account for this potential(although highest potential of organized severe storms seems to favor locations such as portions of the Texas and Oklahoma panhandles). In addition, have also depicted locally heavy rain potential over eastern portions of the forecast district, including the Interstate 25 corridor and associated burn scars, including but not limited to the Waldo Canyon burn scar, etc. As always, WFO Pueblo will closely monitor severe weather and flooding potential closely and issue necessary highlights/advisories/warnings, etc. as needed. Also, will maintain winter weather highlights from noon today into at least Tuesday for Pikes Peak, Teller county and the Rampart Range as well as for the eastern Sawatch Mountains and the Western Mosquito Range, where significant late season is anticipated over these locations during this time-frame. Will also depict areas of fog and low clouds over several locations at times during the near/short term in combination with continued below seasonal mid-May maximum temperatures and near to above seasonal minimum temperatures over the majority of the CWFA during the next 24 hours. .LONG TERM...(Tuesday through Sunday) Issued at 450 AM MDT Mon May 16 2016 On Tue a large upr level low wl be centered ovr UT, with plenty of mstr ovr the forecast area. The weather wl remain unsettled with widespread pcpn chances over the mtns and high valleys. Over the sern plains upslope flow continues and chances for light showers look good...but closer to the mtns there may be better chances for pcpn and accumulations. It looks like the swrn mtns wl be hardest hit with snow on Tue...although the rest of the mtns wl also see accumulations. Tue wl be the coolest day with highs in the mid 40s to lower 50s at the lower elevations. Tue night the upr low centered is expected to move south into AZ. Snow is expected to continue ovr the mtns, with the best accumulations still expected to be ovr the swrn mtns. the lower elevations may see some light pcpn thru the night. On Wed the upr low is expected to weaken and become an open wave and being moving eastward acrs NM and CO. The mtns, high valleys and I-25 corridor wl continue to see good chances for pcpn, while the sern plains may just see some isold pcpn. Highs on Wed are expected to be a little warmer, but wl still be below average with highs only in the 50s at the lower elevations. Wed night the upr trof is expected to move ovr far ern CO and pcpn chances are expected to decrease ovr much of the area. On Thu there wl still be enough moisture ovr the area that we should again sct or high chances for pcpn ovr the mtns and high valleys, with isold pops ovr the plains. temps should be a little warmer Thu but still below average. Finally, on Fri it looks drier ovr the area as a upr ridging develops ovr ern co ahead of an upr low ovr OR and nrn CA. The ridge shifts eastward ovr KS on Sat, with increasing southwest flow ovr the forecast area. Chances for pcpn look mostly confined to the mtn areas on Fri and Sat, but we may also see some isold showers/tstms move out ovr the ern plains Sat afternoon and evening. High temps Fri and Sat are expected to be above average. On Sun the upr trof is forecast to move ovr NV which wl keep south to southwest flow aloft ovr the forecast area and mainly dry conditions. However there may still be some isold showers/tstms ovr the mtns and the dry line may be near the KS border Sun afternoon.&& .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 450 AM MDT Mon May 16 2016 MVFR to localized IFR/LIFR ceilings and visibilities at times will be possible over the KCOS and KPUB taf sites this morning due to areas of low clouds and fog. Similar to the previous 24 hours, periods of MVFR/IFR and LIFR conditions due to shower and thunderstorm activity will be possible at times over the KALS, KCOS and KPUB taf sites into tonight. In addition, the potential for strong to severe thunderstorms exist primarily over south-central and southeastern Colorado from late this morning into this evening, although the potential does exist that stronger storms capable of producing locally heavy rainfall, hail and gusty winds may be noted in the vicinity of the KALS, KCOS, and KPUB taf sites respectively from later today into this evening && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 450 AM MDT Mon May 16 2016 MVFR to localized IFR/LIFR ceilings and visibilities at times will be possible over the KCOS and KPUB taf sites this morning due to areas of low clouds and fog. Similar to the previous 24 hours, periods of MVFR/IFR and LIFR conditions due to shower and thunderstorm activity will be possible at times over the KALS, KCOS and KPUB taf sites into tonight. In addition, the potential for strong to severe thunderstorms exist primarily over south-central and southeastern Colorado from late this morning into this evening, although the potential does exist that stronger storms capable of producing locally heavy rainfall, hail and gusty winds may be noted in the vicinity of the KALS, KCOS, and KPUB taf sites respectively from later today into this evening && .PUB Watches/Warnings/Advisories... Winter Weather Advisory from noon Tuesday to 6 AM MDT Wednesday for COZ066-068. Winter Weather Advisory until 6 AM MDT Tuesday for COZ058-060. Winter Weather Advisory from 6 PM this evening to noon MDT Tuesday for COZ081. Winter Storm Warning until 6 AM MDT Wednesday for COZ082. && $$ UPDATE...MOORE SHORT TERM...77 LONG TERM...28 AVIATION...MOORE
Area Forecast Discussion National Weather Service Denver/Boulder CO 1222 PM MDT MON MAY 16 2016 .UPDATE... Issued at 1215 PM MDT Mon May 16 2016 convection now underway over the Front Range and western sections of the Palmer Divide in Douglas County. Weather spotter just reported small hail falling from a single t-storm south-southeast of Castle Rock. Precipitation will continue to expand especially over and east of the Front Range as upslope flow deepens and qg ascent increases ahead of a vort lobe/shortwave trough rotating up from southern Colorado. On another note, fog continues to plague many areas with visibilities less than 2 miles in portions of the I-25 corridor. Fog may be slow to dissipate today. Will adjust afternoon forecast grids accordingly. UPDATE Issued at 915 AM MDT Mon May 16 2016 Fog persists at this hour across most of the greater Denver metro area...although web cams and surface obs reveal a significant improvement in visibilities in areas roughly south of Interstate 70 and east of Aurora. The thickest fog was over northwest sections of the metro area such as around Boulder and Broomfield where prevailing vsbys were still below 1/4 mile. Should see this heavy fog erode from southeast-to-northwest over the next hour or two as slightly drier air flows down off the Palmer Divide and with mixing of the boundary layer with passing rain showers. Vort lobe/shortwave trough rotating northward over the CWA during the next couple of hours will enhance this shower activity as noted in the previous discussion. Isolated t-storms also a possibility towards midday. Hail, brief heavy rain and perhaps a funnel cloud or two all possible with these cells. At this time, will make only minor adjustments to the ongoing forecast. Will also hang onto the winter weather and dense fog highlights for now. && .SHORT TERM...(Today and tonight) Issued at 402 AM MDT Mon May 16 2016 Pockets of dense fog have formed in the Denver and Boulder areas with visibilities less than a quarter mile at times. Partial clearing after last evening`s period of rain allowed for strong radiational cooling along parts of the i-25 urban corridor. Visibilities at KDEN have been less than a quarter mile since about 2 AM MDT and a co-worker driving up Davidson Mesa outside of Boulder reported visibilities less than 100 feet. Other observations from local airports show visibilities greater than a mile and a half. Have issued a dense fog advisory for zones 39 and 40 until 10 AM MDT to handle the morning rush hour. Otherwise, the forecast remains on track. A band of showers has been moving over western Colorado this morning with some embedded thunderstorms as late at 3:30 AM MDT. These showers should progress into the north central mountains in the next few hours and then over northeast Colorado later today. The approaching upper trough will place Colorado under rising motions through this evening. The airmass is plenty moist and slightly unstable at mid- levels which will allow for an extended period of precipitation through this afternoon and evening. Temperatures in the mountains are expected to cool through today with snow levels eventually coming down to 10000 feet or lower. Significant accumulations will be possible on the peaks, ridges and higher elevation roadways, so a Winter Weather Advisory will be in effect through Tuesday. Temperatures are going to be much cooler than normal due to the lack of sunshine and occurring precipitation. Areas of precipitation are expected to continue into the evening and then diminish overnight. .LONG TERM...(Tuesday through Sunday) Issued at 402 AM MDT Mon May 16 2016 Models have an upper closed low over Nevada into western Colorado at 12z Tuesday. The upper low weakens and falls apart as it moves slowly eastward and across the CWA as an open trough through Wednesday night. The flow aloft will weak all four periods. The models keep weak qg upward vertical velocity for the CWA into Wednesday night. Models have easterly low level flow for the CWA Tuesday, then southeasterly well into Wednesday. Winds should be close to normal diurnal drainage patterns Wednesday night. Models show quite a bit of moisture over the CWA well into Wednesday before decrease overnight. The qpf Fields show measurable precipitation across all the CWA Tuesday into Tuesday evening. There is very little measurable precipitation noted Wednesday and Wednesday evening for the plains, but some in the mountains. There is some CAPE mainly in the mountains and foothills late day Tuesday and late day Wednesday. Lapse rates are not very steep, especially over the plains both late days periods. will go with 30-60% pops on Tuesday and Tuesday evening. Late day Wednesday`s pops are similar in the mountains and foothills only. The plains can expected 10-20%s. for temperatures, Tuesday`s highs are 1-3 C warmer than today`s expected highs. Wednesday`s readings warm up 2-5 c above Tuesday`s readings. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1215 PM MDT Mon May 16 2016 will hang onto ils cigs and vsbys at denver area terminals for the remainder of the afternoon. may not see vsbys rising above 3 miles all day, even with passing showers and t-storms. ceilings now not expected to rise above 1000 ft agl all day at KDEN, KAPA and KBJC. && .BOU Watches/Warnings/Advisories... Winter Weather Advisory until noon MDT Tuesday for COZ031-033- 034. && $$ UPDATE...Baker SHORT TERM...Dankers LONG TERM...RJK AVIATION...Baker
Area Forecast Discussion National Weather Service Grand Junction CO 1129 AM MDT MON MAY 16 2016 updated aviation section .UPDATE... Issued at 918 AM MDT Mon May 16 2016 Rain/Snow line is at about 8300 feet this morning, but will rise throughout the day. Snow accumulation level on roads as of 9am looks to be above 10,000 ft at the high passes, so have refrained from issuing any advisories today with impacts minimal. Will keep an eye on precipitation development, but expecting short lived convective showers and thunderstorms this afternoon. Short term forecast models indicate downturn in activity after sunset when snow would accumulate on the roads again. Expecting the best thunderstorms to develop across the Four Corners today with hail the main threat. && .SHORT TERM...(Today through Tuesday night) Issued at 254 AM MDT Mon May 16 2016 Energy rotating around an upper level low located over southern Idaho will continue to bring showers and thunderstorms to much of eastern Utah and western Colorado through Tuesday. First wave working through the area this morning with showers and thunderstorms driving east into the central mountains. Snow levels remain above 9k and bulk of activity has been light so far, so no plans on hoisting any winter highlights for narrow stretches of our high mountain passes. Could see a few inches accumulate above 10k by this evening, but road surfaces remain warm and impact should be minimal. Otherwise, it`s looking like another unsettled day with a few stronger storms again expected as moisture and additional energy pass through. Wind gusts to 50 mph not out of the question along with small hail. Models have remained aggressive with pops and QPF values peaking during the afternoon and evening hours. See no reason to stray far from that thinking and pop grids will be geared this direction. As the low drops or sags south into Utah, colder air will slide south with it. This will lower snow levels a bit by Tuesday morning, possibly as low as 8k, but levels rise throughout the day back to near 10k by afternoon. Overall a very similar weather day is expected with showers and thunderstorms throughout the region and some accumulating snowfall for the highest peaks. Best shot at more significant snowfall will push into the San Juans late Tuesday and Tuesday night when we see another stronger wave rotate out of the digging low with a period of favorable orographics and dynamics coming into play. This will generate more persistent precipitation that may eventually lead to more significant snowfall accumulations from Telluride southeast to Wolf Creek Pass. Main impacts would be overnight Tuesday into Wednesday morning and later shifts can take a look at the need for any sort of winter highlights. Temperatures will be running on the cool side of normal through mid-week and have undercut guidance values a bit today and again on Tuesday due to cloud cover and showers. .LONG TERM...(Wednesday through Sunday) Issued at 254 AM MDT Mon May 16 2016 The upper level low will slowly fill over the southern Great Basin by the end of the week with the cool and unsettled weather slowly abating as we close out the week. The low fills on Wednesday with remnants getting kicked out by late Thursday. This will lead to a decrease in the showers and also send in some warmer air aloft which lifts snow levels back up to near 10k by Wednesday afternoon. Scattered activity then lingers through Thursday afternoon, favoring the higher terrain. By Friday, the Pacific Northwest gets a taste of what we`ve been experiencing as a deep area of low pressure sets up just off the coast and gets cutoff. This system barely moves from Thursday through Sunday. The location of the low will cause a ridge to form to our east pushing the trough to the plains and keeping us `relatively` dry. Some afternoon convection can`t be ruled out as ample moisture will remain while daytime heating will help to destabilize the atmosphere. After the first half of the week though, the weather will show a marked improvement. Temperatures will slowly warming up through the weekend. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1129 AM MDT Mon May 16 2016 Stormy weather continues across the region through the end of the week. Expect widespread showers and isolated thunderstorms through the period with areas of IFR cigs possible, especially over the higher elevations. Terminal sites may see periods of ILS cigs as showers move through. Gusty outflow winds to 50 mph and small hail will accompany the strongest storms and snow levels will be running between 9 and 10k today, falling to as low as 8k tonight. Mountain obscuration likely over the next 24 hours. && .HYDROLOGY... Issued at 918 AM MDT Mon May 16 2016 With the forecast wet weather and expected warming temperatures toward the end of the week, river levels are expected to gradually rise over the next few weeks. Flows will generally increase due to snowpack melting with some streams reaching near bankfull at times. Use caution in and near swift currents. && .GJT Watches/Warnings/Advisories... CO...None. UT...None. && $$ UPDATE...JAM SHORT TERM...JDC LONG TERM...TGR/JDC AVIATION...TGJT HYDROLOGY...JAM
Area Forecast Discussion National Weather Service Grand Junction CO 918 AM MDT MON MAY 16 2016 .UPDATE... Issued at 918 AM MDT Mon May 16 2016 Rain/Snow line is at about 8300 feet this morning, but will rise throughout the day. Snow accumulation level on roads as of 9am looks to be above 10,000 ft at the high passes, so have refrained from issuing any advisories today with impacts minimal. Will keep an eye on precipitation development, but expecting short lived convective showers and thunderstorms this afternoon. Short term forecast models indicate downturn in activity after sunset when snow would accumulate on the roads again. Expecting the best thunderstorms to develop across the Four Corners today with hail the main threat. && .SHORT TERM...(Today through Tuesday night) Issued at 254 AM MDT Mon May 16 2016 Energy rotating around an upper level low located over southern Idaho will continue to bring showers and thunderstorms to much of eastern Utah and western Colorado through Tuesday. First wave working through the area this morning with showers and thunderstorms driving east into the central mountains. Snow levels remain above 9k and bulk of activity has been light so far, so no plans on hoisting any winter highlights for narrow stretches of our high mountain passes. Could see a few inches accumulate above 10k by this evening, but road surfaces remain warm and impact should be minimal. Otherwise, it`s looking like another unsettled day with a few stronger storms again expected as moisture and additional energy pass through. Wind gusts to 50 mph not out of the question along with small hail. Models have remained aggressive with pops and QPF values peaking during the afternoon and evening hours. See no reason to stray far from that thinking and pop grids will be geared this direction. As the low drops or sags south into Utah, colder air will slide south with it. This will lower snow levels a bit by Tuesday morning, possibly as low as 8k, but levels rise throughout the day back to near 10k by afternoon. Overall a very similar weather day is expected with showers and thunderstorms throughout the region and some accumulating snowfall for the highest peaks. Best shot at more significant snowfall will push into the San Juans late Tuesday and Tuesday night when we see another stronger wave rotate out of the digging low with a period of favorable orographics and dynamics coming into play. This will generate more persistent precipitation that may eventually lead to more significant snowfall accumulations from Telluride southeast to Wolf Creek Pass. Main impacts would be overnight Tuesday into Wednesday morning and later shifts can take a look at the need for any sort of winter highlights. Temperatures will be running on the cool side of normal through mid-week and have undercut guidance values a bit today and again on Tuesday due to cloud cover and showers. .LONG TERM...(Wednesday through Sunday) Issued at 254 AM MDT Mon May 16 2016 The upper level low will slowly fill over the southern Great Basin by the end of the week with the cool and unsettled weather slowly abating as we close out the week. The low fills on Wednesday with remnants getting kicked out by late Thursday. This will lead to a decrease in the showers and also send in some warmer air aloft which lifts snow levels back up to near 10k by Wednesday afternoon. Scattered activity then lingers through Thursday afternoon, favoring the higher terrain. By Friday, the Pacific Northwest gets a taste of what we`ve been experiencing as a deep area of low pressure sets up just off the coast and gets cutoff. This system barely moves from Thursday through Sunday. The location of the low will cause a ridge to form to our east pushing the trough to the plains and keeping us `relatively` dry. Some afternoon convection can`t be ruled out as ample moisture will remain while daytime heating will help to destabilize the atmosphere. After the first half of the week though, the weather will show a marked improvement. Temperatures will slowly warming up through the weekend. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 254 AM MDT Mon May 16 2016 Unsettled weather will remain in the region through Tuesday. Expect widespread showers and isolated thunderstorms through the period with areas of IFR cigs possible, especially over the higher elevations. Terminal sites may see periods of ILS cigs as showers move through. Gusty outflow winds to 50 mph and small hail will accompany the strongest storms and snow levels will be running between 9 and 10k today, falling to as low as 8k tonight. Mountain obscuration likely over the next 24 hours. && .HYDROLOGY... Issued at 918 AM MDT Mon May 16 2016 With the forecast wet weather and expected warming temperatures toward the end of the week, river levels are expected to gradually rise over the next few weeks. Flows will generally increase due to snowpack melting with some streams reaching near bankfull at times. Use caution in and near swift currents. && .GJT Watches/Warnings/Advisories... CO...None. UT...None. && $$ UPDATE...JAM SHORT TERM...JDC LONG TERM...TGR/JDC AVIATION...JDC HYDROLOGY...JAM
Area Forecast Discussion National Weather Service Denver/Boulder CO 821 PM MDT SUN MAY 15 2016 .UPDATE... Issued at 659 PM MDT Sun May 15 2016 The second band of showers today is now moving off the foothills. some lightning persisted to near Jefferson County Airport...but for the most part these showers are again weakening as they move to the plains. This is part of a large band of clouds that extend to the west slope...but satellite loops show a large dry slot moving into southwest Colorado. The HRRR and RAP models both show a dry period from around 06z to 13z for the metro area. The surface pattern has been weak this evening...but a surface low is forecast to develop near trinidad late tonight and intensify tomorrow morning. This will result in increasing upslope flow along the urban corridor and palmer divide...with showers redeveloping Monday morning and continuing through the day. Coordinated with adjoining offices on winter weather advisory...and will issue one for the higher mountain passes for late tonight through noon Tuesday. Models indicate that some higher elevations may see up to 30 inches of snow by the time the storm is done with us. It is likely to be a very wet sloppy mess with daytime highs in the higher passes reaching 32 tomorrow. All in all the previous forecast has a good handle on system development...but mav guidance is 5 degrees colder than met guidance. With the clouds...upslope...and moisture am going to lower max temps in eastern Colorado on Monday and drop higher passes a degree or two. && .SHORT TERM...(This evening through Monday) Issued at 322 PM MDT Sun May 15 2016 Initial shower band moving east on the plains but has mostly dissipated. A larger batch of showers and thunderstorms over the mountains will spread onto the plains this evening. This has more forcing and since it is a large area of rain it will bring higher dew points with it, so it should survive better. Still expecting a bit of a break later tonight, but then the low on the east side of the mountains will start to wind up. Some question about the amount of low level moisture that persists through the night. Models seem a bit overdone, so I am showing mostly cloudy skies but not into the fog/drizzle regime yet, at least around Denver. During the night the best moisture convergence will be across Wyoming and the Nebraska panhandle, but this should all slide southward Monday morning with the lower levels saturating, upslope winds, and persistent lift. Some uncertainty about the timing of this progressing from north to south but at this time it looks like this will be happening during the morning hours. Generally expecting light but steady rainfall, but with upslope enhancement over the east slopes of the Front Range. Snow level should also be lowering a bit during the day, settling somewhere around 7-8 thousand feet on the east slopes with warmer low levels holding it higher on the west side. Could be some heavy snow in the afternoon, but warm temps will limit the impact in populated areas so just the highest roads are of concern. .LONG TERM...(Monday night through Sunday) Issued at 322 PM MDT Sun May 15 2016 Monday night...a broad closed upper low will stretch from Northwest NV into northwest CO. Weak QG ascent will be over the cwa overnight as this trough makes its way south into AZ by 00z Wednesday. At the surface...a secondary surge will enhance the upslope along the Front Range Monday night. The mdls show moderate to strong QG ascent at the surface through the evening...with the east to southeast upslope fm the surface to around 600 mb. NAM12 forecast sounding show moist adiabatic lapse rates with the airmass saturated through the layer. There could be an isolated tstm in the mountains Monday evening but it looks too stable across the Urban Corridor and northeast plains with the possible exception of the Palmer Divide. Overrunning type of setup Monday night with the colder air below undercutting a fairly strong inversion just above 700 mb. east and southeast facing aspects above 9 thousand feet could receive 8 to 12 inches of snowfall by tuesday morning...but not as much west of the Continental Divide. No highlights yet but am learning more towards advisory type snowfall vs warning at this time for the Front Range east of the Continental Divide and possibly the higher foothills. The foothills will see a accumulating snowfall above 8 thousand feet with a steady mix of rain and snow down to 6500 feet. We could possibly see a mix of rain/snow over the palmer divide above 6 thousand feet by tuesday morning. The mix of rain/snow in the foothills should help alleviate any potential flooding risk as well. Tuesday...a deep southeasterly upslope flow will be present but the wind will not be as strong. Wl keep some light snow or rain/snow mix in the mountains through the day...with higher pops for light rain in and near the foothills/Palmer Divide as well. Wl keep the mention of tstms in the grids but mainly over the mountains. Tuesday night into Wednesday...the main area of pcpn continues to get dragged to the south. There is still enough moisture and some weak forcing around for showers...especially over the mountain but the overall coverage will be decreasing. The weakening trough finally shifts to the east of CO by Thu with a drier and more subsident northwesterly flow aloft. An upper level ridge will finally set up over the region late Thursday and continue into Saturday. It will be much warmer by the weekend with the more typical pattern of aftn/evng thunderstorms on Friday and Saturday. The mdls continue to show a large upper trough over the Pacific Northwest by the weekend...with an increasing southwesterly flow aloft over CO by Sunday. && .AVIATION...(For the 18Z TAFS through 18Z Monday afternoon) Issued at 322 PM MDT Sun May 15 2016 The showers moving through the metro area will be followed by one or two more bands of rain this evening...but it looks dry from 06z until at least 13z. The winds have been the big question today...other than the gusty winds with showers...it has been difficult to pin down directions. This will become easier tomorrow with the deepening upslope flow we will settle on north to northeast winds for much of the day. Ceilings of 030 to 060 with the showers will rise a bit overnight...then drop to mvfr monday morning...with areas of ifr. && .BOU Watches/Warnings/Advisories...winter weather advisory for mountain zones...31...33...34 from 3am tonight to noon Tuesday. && $$ UPDATE...RTG SHORT TERM...Gimmestad LONG TERM...Cooper AVIATION...Gimmestad Area Forecast Discussion National Weather Service Grand Junction CO 403 PM MDT TUE MAY 17 2016 .SHORT TERM...(Tonight through Wednesday night) Issued at 403 PM MDT Tue May 17 2016 Southerly flow continues to pump in moisture thanks to the low pressure that is to our west. Instability wasn`t as strong today so the intensity of the showers and storms was weaker than seen yesterday though a few heavier showers have popped. Most of the precipitation will end a few hours after sunset though some showers, generally south, will continue overnight. Some snow can be expected above 10,000 feet tonight but expect minimal impacts on roadways so held off on issuing any advisories. By Wednesday morning, the low will have shifted to southern Arizona but moisture will continue to stream into the area. Once again, afternoon showers and storms will form mid-morning onwards. H7 winds remain light so gusty winds not too much of a concern with storms that fire though some small hail is possible along with heavier rain at times. .LONG TERM...(Thursday through Tuesday) Issued at 403 PM MDT Tue May 17 2016 By Thursday morning, finally, the low pressure center will open up, become an open wave, and shift to eastern Colorado. A ridge will build in but plenty of moisture will remain in the atmosphere allowing the more usual afternoon showers and storms to form. As this occurs, a very deep area of low pressure will drop down into the Pacific northwest and become somewhat stationary. Model runs have changed where the low will set up so confidence a bit shaky in that regard. One thing that has remained constant though is that this low will tighten the pressure gradient considerably causing gusty winds across much of the Great Basin. Our area can expect to see winds picking up Friday and continue each afternoon through Sunday. Best upper level support for this system looks to stay to our north so expect some showers at times through Tuesday but nothing too widespread. Temperatures will jump to near or above normals Friday and Saturday before dropping a few degrees below Sunday onwards thanks to increased clouds. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 335 PM MDT Tue May 17 2016 The threat of precipitation will remain in place over much of western Colorado and eastern Utah over the next 24 hours. Thunderstorm activity will expand through this afternoon. ILS break points may be exceeded at times as showers work over the forecast terminals, but for the most part VFR conditions will prevail. Storms will intensify in response to daytime warming resulting in increased rainfall rates and some lowered flight criteria may be possible at times during the afternoon and early evening. Expect areas of terrain obscuration over the next 24 hours as well in this wet pattern. && .HYDROLOGY... Issued at 400 AM MDT Tue May 17 2016 Wet weather through midweek combined with rising temperatures toward the end of the week are expected to drive river levels gradually higher. In fact, over the next few weeks increased flows will primarily be the result of melting snowpack. This will cause rivers and streams to swell causing some streams to reach bankfull. Use caution in and near swift currents. && $$ SHORT TERM...TGR LONG TERM...TGR AVIATION...JAM HYDROLOGY...NL
Area Forecast Discussion National Weather Service Grand Junction CO 1142 AM MDT TUE MAY 17 2016 .UPDATE... Issued at 1142 AM MDT Tue May 17 2016 Shower and thunderstorm activity is increasing as expected. Storm motion today will be mainly from south to north or from the southeast to northwest over NE Utah and NW Colorado. Small hail, frequent lightning and gusty winds will be possible with stronger thunderstorms. && .SHORT TERM...(Today through Wednesday) Issued at 400 AM MDT Tue May 17 2016 Moisture will continue to move over the area through midweek as a low pressure system featuring a distinct pair of low centers circulates over the west. For today, the low circulation over east-central Utah will shift to the northwest as the Nevada circulation drops southeastward toward Las Vegas. The resultant south to north component of mid-level flow will continue to supply moisture to the area and precipitable water values are expected to remain near 0.50 of an inch. Daytime warming combined with divergence aloft will provide the instability and lift for scattered to numerous coverage of showers and embedded thunderstorms. As mentioned in the previous discussion, the pressure gradient in the lower levels flow will remain relatively weak with light winds the result with the exception of outflow from thunderstorms. Moist convection will decline overnight as the airmass over the region cools and becomes more stable. However, as the Las Vegas low center moves to southern Arizona, the southern half of the forecast area will fall under increased diffluence/divergence aloft. As a result, showers and a few embedded thunderstorms are expected to persist into Wednesday morning while precipitation largely ends north of the i-70 corridor. Snow levels dip below pass levels in the San Juan mountains, however expect the relatively mild temperatures will limit impact to road surfaces. The slowly moving low center will shift to west-central New Mexico Wednesday resulting in continued unsettled conditions over the area. Expect daytime temperatures to remain below normal through midweek in response to cloudy/showery weather with lows near normal again tonight. .LONG TERM...(Wednesday night through Monday) Issued at 400 AM MDT Tue May 17 2016 The last pull of wraparound moisture from the departing trough will keep decent shower coverage going through Thursday morning before activity shifts to the higher terrain during the afternoon. A "break" of sorts will finally arrive Friday as a weak transitory ridge builds ahead of the next storm. However, cannot rule out an afternoon shower or two. As for the next storm, after remaining stationary off the coast of the Pacific northwest for several days, it will finally move onshore beginning Friday. Models indicated this massive low pressure system will split with the lower portion following the typical springtime track. This system is projected to drop down over the Great Basin as early as Sunday night, bringing yet another chance for clouds and showers Monday. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1142 AM MDT Tue May 17 2016 The threat of precipitation will remain in place over much of western Colorado and eastern Utah over the next 24 hours. Thunderstorm activity will expand through this afternoon. ILS break points may be exceeded at times as showers work over the forecast terminals, but for the most part VFR conditions will prevail. Storms will intensify in response to daytime warming resulting in increased rainfall rates and some lowered flight criteria may be possible at times during the afternoon and early evening. Expect areas of terrain obscuration over the next 24 hours as well in this wet pattern. && .HYDROLOGY... Issued at 400 AM MDT Tue May 17 2016 Wet weather through midweek combined with rising temperatures toward the end of the week are expected to drive river levels gradually higher. In fact, over the next few weeks increased flows will primarily be the result of melting snowpack. This will cause rivers and streams to swell causing some streams to reach bankfull. Use caution in and near swift currents. && .GJT Watches/Warnings/Advisories... CO...None. UT...None. && $$ UPDATE...JAM SHORT TERM...NL LONG TERM...MMS/NL AVIATION...JAM HYDROLOGY...JAM/NL
  [top] Area Forecast Discussion National Weather Service Denver/Boulder CO 830 PM MDT MON MAY 16 2016 .UPDATE... Issued at 830 PM MDT Mon May 16 2016 Radar shows widespread showers across the plains and Front Range. Current snow level ranged from around 7000-7500 feet in the southern foothills, to down as low as 6000 feet near the Wyoming border as Cheyenne Wyoming had switched over to snow in the last couple hours. Main precipitation shield is just east of I-25 but lots of drizzle farther west, with another batch of heavier precip and snowfall in the mountains around Summit and Park counties. The main precip area on the plains is shifting slightly westward as another surge was noted in Northeast Colorado, so rain will continue through the rest of this evening and then maybe only slowly decrease through the rest of the night as upslope component weakens. Even then, drizzle and areas of fog should remain behind and continue into Tuesday morning with the very moist and ever so slight upslope component still in place. With regard to snow in the mountains, the orographic forcing is rather weak but still convective enough for a heavy burst of snow this evening in the Summit and Park county areas. Will keep the advisories going here, but did cancel the advisory farther northwest where snow has been slow to develop in zone 31 near the Rabbit Ears Pass area. && .SHORT TERM...(This afternoon through Tuesday) Issued at 325 AM MDT Mon May 16 2016 500mb low centered over southwest Idaho at the present time is forecast to track south-southeastward to over central Utah by 06z tonight. From there models show the low curving southwestward over the lower Colorado River valley south of Las Vegas by late Tuesday afternoon. Near zonal mid-level flow on the south side of this low continues to feed ample amounts moisture over Colorado. East of the mountains this flow curves northeastward producing a wide region of weak to moderate qg ascent. Even as the upper low tracks south across Utah tonight, models show north central and northeast Colorado under large scale ascent. Returning to this afternoon...a shortwave trough/vort lobe rotating around the southeast quad of the upper trough presently aligning from NW Colorado to SE Colorado. Models show this feature and the convection its generating swinging newrd across NE Colorado between 23z/Mon-06Z/Tue. If it were not for the heavy low cloud cover and chilly temperatures on the plains, mid-level shear, instability and lift would be adequate to spawn a few strong if not severe t-storms. As it stands, the few t-storms that have managed to form over the Palmer Divide have pretty much collapsed as they moved into the far less favorable environment on the plains. One last comment, fog blanketing much of northeast Colorado and many mountain locales since late last night has shown little signs of dissipating. Many areas along the Front Range foothills are still reporting vsbys below 5 miles. Overnight...height and pressure falls on the west slope of Colorado will further enhance the moist upslope flow up against the east face of the Front Range mountains. Models indicate weak to moderate qg ascent moving over northeast and north central Colorado with the passing shortwave this evening. Model qpf amounts on the plains by 12z/Tue in the 0.35 to 0.70 inch range. QPf for the Front Range mountains and foothills in the 0.50 to 0.95 inch range. Snow level based on wetbulb zero anywhere from 7500 to 8500 ft this evening, then anywhere from 6000 to 7000 feet after midnight. Could see snow totals by morning anywhere from 5-9 inches on east facing slopes above 9000 feet...and 3-6 inches from 7000 to 9000 feet. It`s possible we could see an inch or so of very wet snow near the base of the foothills and on the Palmer Divide. Do not expect to see any snow accumulation in the Denver metro area except maybe a dusting on lawns in the higher western and southern suburbs. Lastly, should also continue to see areas of fog with the moist upslope flow...especially up against the Front Range. On Tuesday...as the upper low slowly moves away from Colorado forcing for ascent decreases and the high plains upslope flow lessens during the afternoon. Precipitable water changes little, so another day of low clouds, fog and showery type precipitation. And, another day of unseasonably cool temperatures, especially east of the Front Range. Highs on Tuesday only in the 40s...with 20s and 30s in the high country. Additional snow amounts anywhere from 2 to 6 inches in the mountains and higher Front Range foothills. Additional rain amounts on the plains anywhere from 0.05 inch in the far northeast to around a quarter inch near the foothills. Airmass appears to be too cool and stable for t-storms tomorrow mountains and plains. Last but not least, the Winter Weather Advisory for mountain zones 31..33 and 34 will remain in effect until 18z/Tuesday. Should see snowfall rates decreasing by the afternoon. .LONG TERM...(Tuesday night through Sunday) Issued at 325 AM MDT Mon May 16 2016 Cool and cloudy start to the extended with an upper level low spinning over southern CA. This low will weaken as it travels eastward becoming an open trough by Wednesday afternoon/evening. Continuing SW flow will keep a steady stream of moisture over NE Colorado with cold fronts keeping conditions cooler and therefore more stable. Fro Tuesday night into Wednesday conditions over the plains will be cool with cloudy skies and chance of showers that continue into the evening ours before clearing out overnight. Some models suggesting the clouds will clear sooner on the far NE plains allowing for some surface heating and therefore increased instability. This could lead to isolated thunder on the plains late Tuesday with heavier showers. Wednesday temperatures will be cooler than average with highs only getting into the lower 60s. A weak surface high on the plains will help to keep precipitation out but conditions will remain cloudy. In the mountains there is a chance of rain and snow showers at higher elevations with isolated thunderstorms by the afternoon. There is a deep closed off low entering the Pacific NW that will allow ridging over NE Colorado on Thursday. There will be enough moisture in the mountains however to keep a slight chance of thunderstorms in the afternoon with rain and snow showers above 10,000 ft. Temperatures will rebound back to seasonal normals on Thursday with highs in the upper 60s to lower 70s. Friday and through the weekend starts a dry and warming trend. The upper level low over the Pacific NW will continue to spin over that region keeping prolonged ridging and therefore increasing temps over CO. Look for highs into the 70s on Friday and possibly lower 80s by Saturday and Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 830 PM MDT Mon May 16 2016 IFR conditions will persist through at least Tuesday morning with shallow upslope keeping rain showers, drizzle, and fog in place. As rain decreases later tonight, drizzle and fog is expected to become more prominent. Visibilities may drop to 1/4 to 1/2sm if fog over the Front Range airports including KDEN 08Z-15Z. Should see a slow improvement 15Z-18Z Tuesday with MVFR conditions expected to develop Tuesday afternoon with some daytime heating and weakening upslope component. && .BOU Watches/Warnings/Advisories... Winter Weather Advisory until noon MDT Tuesday for COZ033-034. && $$ UPDATE...Barjenbruch SHORT TERM...Baker LONG TERM...Bowen AVIATION...Barjenbruch
  [top] Area Forecast Discussion National Weather Service Pueblo CO 551 PM MDT MON MAY 16 2016 .UPDATE... Issued at 547 PM MDT Mon May 16 2016 Severe threat is done for this evening. Watch has been cancelled for Las Animas and Baca Counties. && .SHORT TERM...(This evening through Tuesday) Issued at 327 PM MDT Mon May 16 2016 Currently...An upper low pressure system was located over the Great Basin Mon afternoon, while at the sfc high pressure over the Dakotas was supplying a low level northeasterly push into Colorado. This was providing an ample amount of low level moisture for the forecast area today, while disturbances aloft tapped into the moisture for storm production. Isolated severe storms have already occurred along the Colorado/New Mexico state line of SE Colorado, with numerous showers and isolated storms elsewhere. Extensive cloud cover has kept temps somewhat cool, 50s to lower 60s, and has throttled the fuel for widespread severe storm activity. Tonight and tomorrow...The upper low will gradually sink to the south, then southwest, over the next 24 hrs, dropping into southern Nevada and California through the day tomorrow. Numerous showers and isolated thunderstorms are expected to continue through the evening hours, then showers will linger through the night. Tomorrow the process will repeat itself, but with the upper low a bit further to the west and south, convection should diminish over the far eastern plains while continuing over the western section of the CWA. The severe threat will also drop south, out of the forecast area. Look for cool temps tomorrow, with max temps only forecast to climb into the 50s. As for ongoing winter wx highlights, significant new accumulations of wet spring snow for the higher elevations looks reasonable, and had to issue an advisory for the SW mountains for the continued threat there until late Tue night. The best window for periods of heavy rain will likely be this evening through Tue morning, along the I-25 corridor as well as the lower eastern slopes of the southern Front Range. Moore .LONG TERM...(Tuesday night through Monday) Issued at 327 PM MDT Mon May 16 2016 Upper low settles into AZ Tue night, keeping strong upward motion over the San Juan and La Garita mountains through the night. Snow level will likely hang out around 10k-11k with several inches of accumulation over the peaks. Will keep winter wx advisory in place through the night, though impact may be limited somewhat by warm road/ground temps staying near freezing. Tough to rule out some lighter rain and snow showers across the remainder of the region, best chances generally over the mountains and interior valleys, least chance over the plains. Low turns to the corner and heads east through AZ Wed, keeping precip going over the higher terrain and most valleys through the day. Kept the advisory going for now, though snow level will likely rise to above pass level by afternoon as 700 mb temps begin to climb. Shallow upslope will keep plains generally cloudy with a few showers possible, though air mass east of the mountains looks too cool/stable for tsra. On Thu, upper low weakens as it lifts northeastward across nrn NM and srn CO. Expect precip Thu/Thu night to be fairly convective in nature as low levels warm and destabilize somewhat, and will have a mention of afternoon and evening tsra all areas in the afternoon and early evening. Upper ridge then migrates eastward through the state Fri/Sat which should suppress convection somewhat, though residual moisture will likely produce some mountain storms both days. Will need to watch for some dryline storms Sat evening as deeper moisture pushes north, with boundary along/near the KS border after 00z. Similar set-up for Sun as Pacific NW upper trough pushes eastward, with dryline lurking over the far sern plains and potential for high based tsra over the mountains. Should see max temps Fri-Sat climb back to above average readings, with 80s reappearing over portions of the plains. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 516 PM MDT Mon May 16 2016 Extended periods of mvfr to lifr are expected for the TAF sites over the next couple of days, as a low pressure system slowly moves through the region. At KALS...expect periods of mvfr...and brief periods of ifr, as rounds of showers and isold ts move through the valley through tomorrow. Freezing levels should remain about 1000-1500 ft AGL on tuesday. KPUB and KCOS...TS should weaken early this eve, but numerous showers will continue for the evening. Areas of fog likely to develop by early morning, especially vicinity KCOS, and cigs likely to remain IFR through the morning...possibly improving to MVFR by afternoon. Freezing levels will be about 1000 ft AGL by early Tue. ROSE && .PUB Watches/Warnings/Advisories... Winter Weather Advisory from noon Tuesday to midnight MDT Wednesday night for COZ066-068. Winter Weather Advisory until 6 AM MDT Tuesday for COZ058-060. Winter Weather Advisory until noon MDT Tuesday for COZ081. Winter Storm Warning until 6 AM MDT Wednesday for COZ082. && $$ UPDATE...LW SHORT TERM...MOORE LONG TERM...PETERSEN AVIATION...ROSE
Area Forecast Discussion National Weather Service Grand Junction CO 508 PM MDT MON MAY 16 2016 .SHORT TERM...(This evening through Tuesday night) Issued at 359 PM MDT Mon May 16 2016 Wet, dreary weather continues through the short term as an upper level low spinning over northern Nevada moves south into the Great Basin. However, this low will not track through the forecast area. Rather, it will drop further south into Arizona. Regardless of its track, ample moisture rotating with this storm will be pulled into the region over the next couple of days. As a result, expect a continuation of widespread showers and chance for storms plus below normal temperatures in the forecast. Guidance temperatures came in too warm so decided to bump temperatures down a few degrees to reflect current trends. As with previous model runs, best chance of precipitation is expected to be during the afternoon and evening hours so grids continue to reflect that. Seeing as how the gradient is not too impressive with this storm, and that the jet core stays well south of the area, do not expect any significant winds for the region apart from the occasional gusty outflow wind with storms. Most impressive QPF remains over the eastern Uinta mountains and right along the northern divide tonight, but upper level temps remain quite mild so not expecting any significant snowfall. Tomorrow night will see the best chance for significant snowfall especially down south. Orographics remain favorable for upslope with winds generally remaining out of the southeast through the overnight hours. However, after examining wet bulb zero heights and upper level temperatures, do not think there will be any major impacts for our mountain areas. Storm total snowfall from tomorrow through Wednesday morning show the San Juans receiving 4 to 8 inches. Seeing as how this will be over several periods and the expectation that warm road surfaces will melt any falling snow, chose to not issue any advisories at this time. Will continue to monitor the situation and let future shifts decide if highlights should be issued. .LONG TERM...(Wednesday through Monday) Issued at 359 PM MDT Mon May 16 2016 Wednesday will bring another day of widespread showers to the region. The last pull of wraparound moisture from the departing trough will keep decent shower coverage going through Thursday morning before activity shifts to the higher terrain during the afternoon. A "break" of sorts will finally arrive Friday as a weak transitory ridge builds ahead of the next storm. However, cannot rule out an afternoon shower or two during the afternoon hours. As for the next storm, after remaining stationary off the coast of the Pacific northwest for several days, it will finally move onshore beginning Friday. Models indicate this massive low pressure system will split with the lower portion following the typical spring-time track. It is projected to drop down into the Great Basin as early as Sunday night and bring yet another chance for clouds and showers. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 506 PM MDT Mon May 16 2016 Stormy weather will continue tonight and tuesday as low pressure remains over the area. Expect widespread showers and scattered thunderstorms through the period with areas of IFR cigs possible, and local ifr vsbys. mts will be obscured. Terminal sites may see periods of ILS cigs as showers move through with brief mvfr and ifr conditions. Gusty outflow winds to 40 mph and small hail will accompany the strongest storms and snow levels will be running between 9 and 10k today, falling to as low as 8k tonight. && .HYDROLOGY... Issued at 918 AM MDT Mon May 16 2016 With the forecast wet weather and expected warming temperatures toward the end of the week, river levels are expected to gradually rise over the next few weeks. Flows will generally increase due to snowpack melting with some streams reaching near bankfull at times. Use caution in and near swift currents. && .GJT Watches/Warnings/Advisories... CO...None. UT...None. && $$ SHORT TERM...MMS LONG TERM...MMS AVIATION...CC HYDROLOGY...JAM
Area Forecast Discussion National Weather Service Pueblo CO 141 PM MDT MON MAY 16 2016 .UPDATE... Issued at 140 PM MDT Mon May 16 2016 Quick update for issuance of the Severe Thunderstorm Watch for Las Animas and Baca counties until 03z tonight. Incorporated latest obs and satellite data. Moore && .SHORT TERM...(Today and tonight) Issued at 450 AM MDT Mon May 16 2016 Multiple meteorological concerns over the forecast district during the short term, including but not limited to locally heavy rainfall potential, severe potential, higher elevation snow, areas of low clouds/fog and temperatures, etc. Forecast district currently graced by generally above seasonal mid- May early morning temperatures, variable cloudiness in combination with areas of low clouds and fog and isolated shower activity. Latest forecast model soundings, real/near time data, computer simulations and PV analysis indicate that upper disturbances will combine with adequate atmospheric moisture and a moist northeasterly surface surge to allow for the development of generally scattered to numerous showers and isolated to scattered thunderstorms, once again favoring the afternoon into the evening/night hours. Some of these thunderstorms are expected to generate locally heavy rainfall and also be capable of entering the strong to to severe category as projected maximum localized capes, LI`s and 0-6 km shears challenge/exceed 1600 J/Kg, -7C and 45 knots at times respectively, especially over south-central and southeastern sections of the forecast district. At this time, the potential for stronger to severe storms favor south-central and southeastern locations of the forecast district, especially from this afternoon into this evening and have mentioned severe potential(including the potential for large hail, damaging winds and even an isolated tornado) in upcoming grids/zones over eastern Las Animas and Baca continues to account for this potential(although highest potential of organized severe storms seems to favor locations such as portions of the Texas and Oklahoma panhandles). In addition, have also depicted locally heavy rain potential over eastern portions of the forecast district, including the Interstate 25 corridor and associated burn scars, including but not limited to the Waldo Canyon burn scar, etc. As always, WFO Pueblo will closely monitor severe weather and flooding potential closely and issue necessary highlights/advisories/warnings, etc. as needed. Also, will maintain winter weather highlights from noon today into at least Tuesday for Pikes Peak, Teller county and the Rampart Range as well as for the eastern Sawatch Mountains and the Western Mosquito Range, where significant late season is anticipated over these locations during this time-frame. Will also depict areas of fog and low clouds over several locations at times during the near/short term in combination with continued below seasonal mid-May maximum temperatures and near to above seasonal minimum temperatures over the majority of the CWFA during the next 24 hours. .LONG TERM...(Tuesday through Sunday) Issued at 450 AM MDT Mon May 16 2016 On Tue a large upr level low wl be centered ovr UT, with plenty of mstr ovr the forecast area. The weather wl remain unsettled with widespread pcpn chances over the mtns and high valleys. Over the sern plains upslope flow continues and chances for light showers look good...but closer to the mtns there may be better chances for pcpn and accumulations. It looks like the swrn mtns wl be hardest hit with snow on Tue...although the rest of the mtns wl also see accumulations. Tue wl be the coolest day with highs in the mid 40s to lower 50s at the lower elevations. Tue night the upr low centered is expected to move south into AZ. Snow is expected to continue ovr the mtns, with the best accumulations still expected to be ovr the swrn mtns. the lower elevations may see some light pcpn thru the night. On Wed the upr low is expected to weaken and become an open wave and being moving eastward acrs NM and CO. The mtns, high valleys and I-25 corridor wl continue to see good chances for pcpn, while the sern plains may just see some isold pcpn. Highs on Wed are expected to be a little warmer, but wl still be below average with highs only in the 50s at the lower elevations. Wed night the upr trof is expected to move ovr far ern CO and pcpn chances are expected to decrease ovr much of the area. On Thu there wl still be enough moisture ovr the area that we should again sct or high chances for pcpn ovr the mtns and high valleys, with isold pops ovr the plains. temps should be a little warmer Thu but still below average. Finally, on Fri it looks drier ovr the area as a upr ridging develops ovr ern co ahead of an upr low ovr OR and nrn CA. The ridge shifts eastward ovr KS on Sat, with increasing southwest flow ovr the forecast area. Chances for pcpn look mostly confined to the mtn areas on Fri and Sat, but we may also see some isold showers/tstms move out ovr the ern plains Sat afternoon and evening. High temps Fri and Sat are expected to be above average. On Sun the upr trof is forecast to move ovr NV which wl keep south to southwest flow aloft ovr the forecast area and mainly dry conditions. However there may still be some isold showers/tstms ovr the mtns and the dry line may be near the KS border Sun afternoon.&& .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 450 AM MDT Mon May 16 2016 MVFR to localized IFR/LIFR ceilings and visibilities at times will be possible over the KCOS and KPUB taf sites this morning due to areas of low clouds and fog. Similar to the previous 24 hours, periods of MVFR/IFR and LIFR conditions due to shower and thunderstorm activity will be possible at times over the KALS, KCOS and KPUB taf sites into tonight. In addition, the potential for strong to severe thunderstorms exist primarily over south-central and southeastern Colorado from late this morning into this evening, although the potential does exist that stronger storms capable of producing locally heavy rainfall, hail and gusty winds may be noted in the vicinity of the KALS, KCOS, and KPUB taf sites respectively from later today into this evening && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 450 AM MDT Mon May 16 2016 MVFR to localized IFR/LIFR ceilings and visibilities at times will be possible over the KCOS and KPUB taf sites this morning due to areas of low clouds and fog. Similar to the previous 24 hours, periods of MVFR/IFR and LIFR conditions due to shower and thunderstorm activity will be possible at times over the KALS, KCOS and KPUB taf sites into tonight. In addition, the potential for strong to severe thunderstorms exist primarily over south-central and southeastern Colorado from late this morning into this evening, although the potential does exist that stronger storms capable of producing locally heavy rainfall, hail and gusty winds may be noted in the vicinity of the KALS, KCOS, and KPUB taf sites respectively from later today into this evening && .PUB Watches/Warnings/Advisories... Winter Weather Advisory from noon Tuesday to 6 AM MDT Wednesday for COZ066-068. Winter Weather Advisory until 6 AM MDT Tuesday for COZ058-060. Winter Weather Advisory from 6 PM this evening to noon MDT Tuesday for COZ081. Winter Storm Warning until 6 AM MDT Wednesday for COZ082. && $$ UPDATE...MOORE SHORT TERM...77 LONG TERM...28 AVIATION...MOORE
Area Forecast Discussion National Weather Service Denver/Boulder CO 1222 PM MDT MON MAY 16 2016 .UPDATE... Issued at 1215 PM MDT Mon May 16 2016 convection now underway over the Front Range and western sections of the Palmer Divide in Douglas County. Weather spotter just reported small hail falling from a single t-storm south-southeast of Castle Rock. Precipitation will continue to expand especially over and east of the Front Range as upslope flow deepens and qg ascent increases ahead of a vort lobe/shortwave trough rotating up from southern Colorado. On another note, fog continues to plague many areas with visibilities less than 2 miles in portions of the I-25 corridor. Fog may be slow to dissipate today. Will adjust afternoon forecast grids accordingly. UPDATE Issued at 915 AM MDT Mon May 16 2016 Fog persists at this hour across most of the greater Denver metro area...although web cams and surface obs reveal a significant improvement in visibilities in areas roughly south of Interstate 70 and east of Aurora. The thickest fog was over northwest sections of the metro area such as around Boulder and Broomfield where prevailing vsbys were still below 1/4 mile. Should see this heavy fog erode from southeast-to-northwest over the next hour or two as slightly drier air flows down off the Palmer Divide and with mixing of the boundary layer with passing rain showers. Vort lobe/shortwave trough rotating northward over the CWA during the next couple of hours will enhance this shower activity as noted in the previous discussion. Isolated t-storms also a possibility towards midday. Hail, brief heavy rain and perhaps a funnel cloud or two all possible with these cells. At this time, will make only minor adjustments to the ongoing forecast. Will also hang onto the winter weather and dense fog highlights for now. && .SHORT TERM...(Today and tonight) Issued at 402 AM MDT Mon May 16 2016 Pockets of dense fog have formed in the Denver and Boulder areas with visibilities less than a quarter mile at times. Partial clearing after last evening`s period of rain allowed for strong radiational cooling along parts of the i-25 urban corridor. Visibilities at KDEN have been less than a quarter mile since about 2 AM MDT and a co-worker driving up Davidson Mesa outside of Boulder reported visibilities less than 100 feet. Other observations from local airports show visibilities greater than a mile and a half. Have issued a dense fog advisory for zones 39 and 40 until 10 AM MDT to handle the morning rush hour. Otherwise, the forecast remains on track. A band of showers has been moving over western Colorado this morning with some embedded thunderstorms as late at 3:30 AM MDT. These showers should progress into the north central mountains in the next few hours and then over northeast Colorado later today. The approaching upper trough will place Colorado under rising motions through this evening. The airmass is plenty moist and slightly unstable at mid- levels which will allow for an extended period of precipitation through this afternoon and evening. Temperatures in the mountains are expected to cool through today with snow levels eventually coming down to 10000 feet or lower. Significant accumulations will be possible on the peaks, ridges and higher elevation roadways, so a Winter Weather Advisory will be in effect through Tuesday. Temperatures are going to be much cooler than normal due to the lack of sunshine and occurring precipitation. Areas of precipitation are expected to continue into the evening and then diminish overnight. .LONG TERM...(Tuesday through Sunday) Issued at 402 AM MDT Mon May 16 2016 Models have an upper closed low over Nevada into western Colorado at 12z Tuesday. The upper low weakens and falls apart as it moves slowly eastward and across the CWA as an open trough through Wednesday night. The flow aloft will weak all four periods. The models keep weak qg upward vertical velocity for the CWA into Wednesday night. Models have easterly low level flow for the CWA Tuesday, then southeasterly well into Wednesday. Winds should be close to normal diurnal drainage patterns Wednesday night. Models show quite a bit of moisture over the CWA well into Wednesday before decrease overnight. The qpf Fields show measurable precipitation across all the CWA Tuesday into Tuesday evening. There is very little measurable precipitation noted Wednesday and Wednesday evening for the plains, but some in the mountains. There is some CAPE mainly in the mountains and foothills late day Tuesday and late day Wednesday. Lapse rates are not very steep, especially over the plains both late days periods. will go with 30-60% pops on Tuesday and Tuesday evening. Late day Wednesday`s pops are similar in the mountains and foothills only. The plains can expected 10-20%s. for temperatures, Tuesday`s highs are 1-3 C warmer than today`s expected highs. Wednesday`s readings warm up 2-5 c above Tuesday`s readings. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1215 PM MDT Mon May 16 2016 will hang onto ils cigs and vsbys at denver area terminals for the remainder of the afternoon. may not see vsbys rising above 3 miles all day, even with passing showers and t-storms. ceilings now not expected to rise above 1000 ft agl all day at KDEN, KAPA and KBJC. && .BOU Watches/Warnings/Advisories... Winter Weather Advisory until noon MDT Tuesday for COZ031-033- 034. && $$ UPDATE...Baker SHORT TERM...Dankers LONG TERM...RJK AVIATION...Baker
Area Forecast Discussion National Weather Service Grand Junction CO 1129 AM MDT MON MAY 16 2016 updated aviation section .UPDATE... Issued at 918 AM MDT Mon May 16 2016 Rain/Snow line is at about 8300 feet this morning, but will rise throughout the day. Snow accumulation level on roads as of 9am looks to be above 10,000 ft at the high passes, so have refrained from issuing any advisories today with impacts minimal. Will keep an eye on precipitation development, but expecting short lived convective showers and thunderstorms this afternoon. Short term forecast models indicate downturn in activity after sunset when snow would accumulate on the roads again. Expecting the best thunderstorms to develop across the Four Corners today with hail the main threat. && .SHORT TERM...(Today through Tuesday night) Issued at 254 AM MDT Mon May 16 2016 Energy rotating around an upper level low located over southern Idaho will continue to bring showers and thunderstorms to much of eastern Utah and western Colorado through Tuesday. First wave working through the area this morning with showers and thunderstorms driving east into the central mountains. Snow levels remain above 9k and bulk of activity has been light so far, so no plans on hoisting any winter highlights for narrow stretches of our high mountain passes. Could see a few inches accumulate above 10k by this evening, but road surfaces remain warm and impact should be minimal. Otherwise, it`s looking like another unsettled day with a few stronger storms again expected as moisture and additional energy pass through. Wind gusts to 50 mph not out of the question along with small hail. Models have remained aggressive with pops and QPF values peaking during the afternoon and evening hours. See no reason to stray far from that thinking and pop grids will be geared this direction. As the low drops or sags south into Utah, colder air will slide south with it. This will lower snow levels a bit by Tuesday morning, possibly as low as 8k, but levels rise throughout the day back to near 10k by afternoon. Overall a very similar weather day is expected with showers and thunderstorms throughout the region and some accumulating snowfall for the highest peaks. Best shot at more significant snowfall will push into the San Juans late Tuesday and Tuesday night when we see another stronger wave rotate out of the digging low with a period of favorable orographics and dynamics coming into play. This will generate more persistent precipitation that may eventually lead to more significant snowfall accumulations from Telluride southeast to Wolf Creek Pass. Main impacts would be overnight Tuesday into Wednesday morning and later shifts can take a look at the need for any sort of winter highlights. Temperatures will be running on the cool side of normal through mid-week and have undercut guidance values a bit today and again on Tuesday due to cloud cover and showers. .LONG TERM...(Wednesday through Sunday) Issued at 254 AM MDT Mon May 16 2016 The upper level low will slowly fill over the southern Great Basin by the end of the week with the cool and unsettled weather slowly abating as we close out the week. The low fills on Wednesday with remnants getting kicked out by late Thursday. This will lead to a decrease in the showers and also send in some warmer air aloft which lifts snow levels back up to near 10k by Wednesday afternoon. Scattered activity then lingers through Thursday afternoon, favoring the higher terrain. By Friday, the Pacific Northwest gets a taste of what we`ve been experiencing as a deep area of low pressure sets up just off the coast and gets cutoff. This system barely moves from Thursday through Sunday. The location of the low will cause a ridge to form to our east pushing the trough to the plains and keeping us `relatively` dry. Some afternoon convection can`t be ruled out as ample moisture will remain while daytime heating will help to destabilize the atmosphere. After the first half of the week though, the weather will show a marked improvement. Temperatures will slowly warming up through the weekend. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1129 AM MDT Mon May 16 2016 Stormy weather continues across the region through the end of the week. Expect widespread showers and isolated thunderstorms through the period with areas of IFR cigs possible, especially over the higher elevations. Terminal sites may see periods of ILS cigs as showers move through. Gusty outflow winds to 50 mph and small hail will accompany the strongest storms and snow levels will be running between 9 and 10k today, falling to as low as 8k tonight. Mountain obscuration likely over the next 24 hours. && .HYDROLOGY... Issued at 918 AM MDT Mon May 16 2016 With the forecast wet weather and expected warming temperatures toward the end of the week, river levels are expected to gradually rise over the next few weeks. Flows will generally increase due to snowpack melting with some streams reaching near bankfull at times. Use caution in and near swift currents. && .GJT Watches/Warnings/Advisories... CO...None. UT...None. && $$ UPDATE...JAM SHORT TERM...JDC LONG TERM...TGR/JDC AVIATION...TGJT HYDROLOGY...JAM
Area Forecast Discussion National Weather Service Grand Junction CO 918 AM MDT MON MAY 16 2016 .UPDATE... Issued at 918 AM MDT Mon May 16 2016 Rain/Snow line is at about 8300 feet this morning, but will rise throughout the day. Snow accumulation level on roads as of 9am looks to be above 10,000 ft at the high passes, so have refrained from issuing any advisories today with impacts minimal. Will keep an eye on precipitation development, but expecting short lived convective showers and thunderstorms this afternoon. Short term forecast models indicate downturn in activity after sunset when snow would accumulate on the roads again. Expecting the best thunderstorms to develop across the Four Corners today with hail the main threat. && .SHORT TERM...(Today through Tuesday night) Issued at 254 AM MDT Mon May 16 2016 Energy rotating around an upper level low located over southern Idaho will continue to bring showers and thunderstorms to much of eastern Utah and western Colorado through Tuesday. First wave working through the area this morning with showers and thunderstorms driving east into the central mountains. Snow levels remain above 9k and bulk of activity has been light so far, so no plans on hoisting any winter highlights for narrow stretches of our high mountain passes. Could see a few inches accumulate above 10k by this evening, but road surfaces remain warm and impact should be minimal. Otherwise, it`s looking like another unsettled day with a few stronger storms again expected as moisture and additional energy pass through. Wind gusts to 50 mph not out of the question along with small hail. Models have remained aggressive with pops and QPF values peaking during the afternoon and evening hours. See no reason to stray far from that thinking and pop grids will be geared this direction. As the low drops or sags south into Utah, colder air will slide south with it. This will lower snow levels a bit by Tuesday morning, possibly as low as 8k, but levels rise throughout the day back to near 10k by afternoon. Overall a very similar weather day is expected with showers and thunderstorms throughout the region and some accumulating snowfall for the highest peaks. Best shot at more significant snowfall will push into the San Juans late Tuesday and Tuesday night when we see another stronger wave rotate out of the digging low with a period of favorable orographics and dynamics coming into play. This will generate more persistent precipitation that may eventually lead to more significant snowfall accumulations from Telluride southeast to Wolf Creek Pass. Main impacts would be overnight Tuesday into Wednesday morning and later shifts can take a look at the need for any sort of winter highlights. Temperatures will be running on the cool side of normal through mid-week and have undercut guidance values a bit today and again on Tuesday due to cloud cover and showers. .LONG TERM...(Wednesday through Sunday) Issued at 254 AM MDT Mon May 16 2016 The upper level low will slowly fill over the southern Great Basin by the end of the week with the cool and unsettled weather slowly abating as we close out the week. The low fills on Wednesday with remnants getting kicked out by late Thursday. This will lead to a decrease in the showers and also send in some warmer air aloft which lifts snow levels back up to near 10k by Wednesday afternoon. Scattered activity then lingers through Thursday afternoon, favoring the higher terrain. By Friday, the Pacific Northwest gets a taste of what we`ve been experiencing as a deep area of low pressure sets up just off the coast and gets cutoff. This system barely moves from Thursday through Sunday. The location of the low will cause a ridge to form to our east pushing the trough to the plains and keeping us `relatively` dry. Some afternoon convection can`t be ruled out as ample moisture will remain while daytime heating will help to destabilize the atmosphere. After the first half of the week though, the weather will show a marked improvement. Temperatures will slowly warming up through the weekend. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 254 AM MDT Mon May 16 2016 Unsettled weather will remain in the region through Tuesday. Expect widespread showers and isolated thunderstorms through the period with areas of IFR cigs possible, especially over the higher elevations. Terminal sites may see periods of ILS cigs as showers move through. Gusty outflow winds to 50 mph and small hail will accompany the strongest storms and snow levels will be running between 9 and 10k today, falling to as low as 8k tonight. Mountain obscuration likely over the next 24 hours. && .HYDROLOGY... Issued at 918 AM MDT Mon May 16 2016 With the forecast wet weather and expected warming temperatures toward the end of the week, river levels are expected to gradually rise over the next few weeks. Flows will generally increase due to snowpack melting with some streams reaching near bankfull at times. Use caution in and near swift currents. && .GJT Watches/Warnings/Advisories... CO...None. UT...None. && $$ UPDATE...JAM SHORT TERM...JDC LONG TERM...TGR/JDC AVIATION...JDC HYDROLOGY...JAM
Area Forecast Discussion National Weather Service Denver/Boulder CO 821 PM MDT SUN MAY 15 2016 .UPDATE... Issued at 659 PM MDT Sun May 15 2016 The second band of showers today is now moving off the foothills. some lightning persisted to near Jefferson County Airport...but for the most part these showers are again weakening as they move to the plains. This is part of a large band of clouds that extend to the west slope...but satellite loops show a large dry slot moving into southwest Colorado. The HRRR and RAP models both show a dry period from around 06z to 13z for the metro area. The surface pattern has been weak this evening...but a surface low is forecast to develop near trinidad late tonight and intensify tomorrow morning. This will result in increasing upslope flow along the urban corridor and palmer divide...with showers redeveloping Monday morning and continuing through the day. Coordinated with adjoining offices on winter weather advisory...and will issue one for the higher mountain passes for late tonight through noon Tuesday. Models indicate that some higher elevations may see up to 30 inches of snow by the time the storm is done with us. It is likely to be a very wet sloppy mess with daytime highs in the higher passes reaching 32 tomorrow. All in all the previous forecast has a good handle on system development...but mav guidance is 5 degrees colder than met guidance. With the clouds...upslope...and moisture am going to lower max temps in eastern Colorado on Monday and drop higher passes a degree or two. && .SHORT TERM...(This evening through Monday) Issued at 322 PM MDT Sun May 15 2016 Initial shower band moving east on the plains but has mostly dissipated. A larger batch of showers and thunderstorms over the mountains will spread onto the plains this evening. This has more forcing and since it is a large area of rain it will bring higher dew points with it, so it should survive better. Still expecting a bit of a break later tonight, but then the low on the east side of the mountains will start to wind up. Some question about the amount of low level moisture that persists through the night. Models seem a bit overdone, so I am showing mostly cloudy skies but not into the fog/drizzle regime yet, at least around Denver. During the night the best moisture convergence will be across Wyoming and the Nebraska panhandle, but this should all slide southward Monday morning with the lower levels saturating, upslope winds, and persistent lift. Some uncertainty about the timing of this progressing from north to south but at this time it looks like this will be happening during the morning hours. Generally expecting light but steady rainfall, but with upslope enhancement over the east slopes of the Front Range. Snow level should also be lowering a bit during the day, settling somewhere around 7-8 thousand feet on the east slopes with warmer low levels holding it higher on the west side. Could be some heavy snow in the afternoon, but warm temps will limit the impact in populated areas so just the highest roads are of concern. .LONG TERM...(Monday night through Sunday) Issued at 322 PM MDT Sun May 15 2016 Monday night...a broad closed upper low will stretch from Northwest NV into northwest CO. Weak QG ascent will be over the cwa overnight as this trough makes its way south into AZ by 00z Wednesday. At the surface...a secondary surge will enhance the upslope along the Front Range Monday night. The mdls show moderate to strong QG ascent at the surface through the evening...with the east to southeast upslope fm the surface to around 600 mb. NAM12 forecast sounding show moist adiabatic lapse rates with the airmass saturated through the layer. There could be an isolated tstm in the mountains Monday evening but it looks too stable across the Urban Corridor and northeast plains with the possible exception of the Palmer Divide. Overrunning type of setup Monday night with the colder air below undercutting a fairly strong inversion just above 700 mb. east and southeast facing aspects above 9 thousand feet could receive 8 to 12 inches of snowfall by tuesday morning...but not as much west of the Continental Divide. No highlights yet but am learning more towards advisory type snowfall vs warning at this time for the Front Range east of the Continental Divide and possibly the higher foothills. The foothills will see a accumulating snowfall above 8 thousand feet with a steady mix of rain and snow down to 6500 feet. We could possibly see a mix of rain/snow over the palmer divide above 6 thousand feet by tuesday morning. The mix of rain/snow in the foothills should help alleviate any potential flooding risk as well. Tuesday...a deep southeasterly upslope flow will be present but the wind will not be as strong. Wl keep some light snow or rain/snow mix in the mountains through the day...with higher pops for light rain in and near the foothills/Palmer Divide as well. Wl keep the mention of tstms in the grids but mainly over the mountains. Tuesday night into Wednesday...the main area of pcpn continues to get dragged to the south. There is still enough moisture and some weak forcing around for showers...especially over the mountain but the overall coverage will be decreasing. The weakening trough finally shifts to the east of CO by Thu with a drier and more subsident northwesterly flow aloft. An upper level ridge will finally set up over the region late Thursday and continue into Saturday. It will be much warmer by the weekend with the more typical pattern of aftn/evng thunderstorms on Friday and Saturday. The mdls continue to show a large upper trough over the Pacific Northwest by the weekend...with an increasing southwesterly flow aloft over CO by Sunday. && .AVIATION...(For the 18Z TAFS through 18Z Monday afternoon) Issued at 322 PM MDT Sun May 15 2016 The showers moving through the metro area will be followed by one or two more bands of rain this evening...but it looks dry from 06z until at least 13z. The winds have been the big question today...other than the gusty winds with showers...it has been difficult to pin down directions. This will become easier tomorrow with the deepening upslope flow we will settle on north to northeast winds for much of the day. Ceilings of 030 to 060 with the showers will rise a bit overnight...then drop to mvfr monday morning...with areas of ifr. && .BOU Watches/Warnings/Advisories...winter weather advisory for mountain zones...31...33...34 from 3am tonight to noon Tuesday. && $$ UPDATE...RTG SHORT TERM...Gimmestad LONG TERM...Cooper AVIATION...Gimmestad
AREA FORECAST DISCUSSION
National Weather Service New Orleans LA
310 PM CDT TUE MAY 17 2016 .SHORT TERM... Active weather period continues across the forecast area. Radar imagery over the last few hours shows quite a jump in intensity along with coverage as daytime heating warmed the surface. Most of the storms remain in the warm sector south of the stall frontal boundary that was draped along a line from near Baton Rouge to Hattiesburg. The GFS shows activity shifting south and east through the rest of this afternoon as the very weak upper trough that initialized the convection shifts east. The HRRR shows the same depiction and this also matches up well with current radar trends. So have increased pops over SELA and coastal MS through the remainder of the afternoon and significantly dropped rain chances for late this evening and overnight to slight chance as little if any showers expected with drier mid level air moving in. The main threat thru the afternoon will still be water spouts and isolated tornadoes, mainly near the coastline. Although there`s not a lot of strong wind in the mid and upper levels, there is sufficient low level vertical and horizontal shear to potentially see these hazards in the coastal waters and adjacent land areas. Areas west of I-55 will not see much in the way of convection, just a few showers. .LONG TERM... The lull in rain will carry over into Wednesday morning as there will be not be as much lift from any upper level features to enhance convection. However, daytime heating and possibly residual frontal boundary could induce afternoon showers and storms. So, went with 40 to 50% coverage during that period. Thursday does not look all that different locally and thus kept the same or slightly higher rain chances. Friday still looks to be the most active day of the forecast period as a more significant upper level trough tracks across the southern plains and mid Mississippi Valley. Exactly when the widespread showers begins in still not completely certain but current models show something similar to yesterday with convection moving in from the Gulf of Mexico/SW LA and spreading across the entire forecast area. The widespread activity will likely last through Friday afternoon and thus have carried likely pops through then. How much rain is still uncertain at this time. The ECMWF shows maybe an inch for most places. The GFS indicates a number much much higher than that. Realistically thinking in the neighborhood of 1 to 4 inches with isolated higher amounts. If this trend continues, flash flood watch may be needed for Friday. The upper level trough will amplify as it tracks east across the United States Saturday and Sunday. Post trough cold front will usher in drier air and likely keep the region rain free. So, have dropped rain chances for those days. Some nice and slightly cooler mornings will be possible as well. MEFFER && .AVIATION... Scattered SHRA and TSRA this afternoon with most of the activity east of Interstate 55 at this time. Most terminals with MVFR ceilings this afternoon. Precipitation occasionally reducing visibilities to 1SM. Expect most of the convection to weaken and/or dissipate near sunset. May see some improvement to VFR conditions during the evening hours, but should return to IFR/MVFR ceilings around 09Z. Should see MVFR ceilings after 15z Wednesday...with potential for scattered convection Wednesday afternoon. This will be addressed in the 00Z TAF package. 35 && .MARINE... Current marine issue is waterspout potential over the tidal lakes and sounds. This should die out with convection this evening. Winds should ease tonight with the departure of the upper impulse currently moving across southern Mississippi and Louisiana. Will allow Exercise Caution headline to expire...although it may be borderline for another hour or two. Should be a light wind regime until Thursday night when front approaches from the northwest. Likely to need headlines at that time over much of the coastal waters into Friday. Relatively quiet conditions after Friday for the weekend. 35 && .DECISION SUPPORT... DSS code: Blue. Deployed: None. Activation: None. Activities: Monitoring convection. Decision Support Services (DSS) Code Legend Green = No weather impacts that require action. Blue = Long-fused watch, warning, or advisory in effect or high visibility event. Yellow = Heightened impacts with short-fused watch, warning or advisory issuances; radar support. Orange = High Impacts; Slight to Moderate risk severe; nearby tropical events; HazMat or other large episodes. Red = Full engagement for Moderate risk of severe and/or direct tropical threats; Events of National Significance. && .PRELIMINARY POINT TEMPS/POPS... MCB 65 82 65 84 / 20 50 20 60 BTR 68 83 68 84 / 20 50 20 60 ASD 69 84 70 85 / 20 50 20 50 MSY 72 83 72 83 / 20 40 20 50 GPT 69 83 70 84 / 20 40 20 40 PQL 69 84 69 85 / 20 40 20 40 && .LIX Watches/Warnings/Advisories... LA...None. GM...None. MS...None. GM...None. && $$