Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/14/20

Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
553 PM MDT Thu Aug 13 2020 .AVIATION... 00Z TAF CYCLE Isold evening convection is forecast to wind down an hour or two after sunset. Gusty downburst winds will be the main aviation hazard. Isolated relatively anemic convective activity will favor mountain ranges south of I-40 as well as the eastern plains Friday afternoon. Again, gusty downburst winds will be the main hazard. 33 && .PREV DISCUSSION...310 PM MDT Thu Aug 13 2020... .SYNOPSIS... Unseasonably strong high pressure over the desert southwest will continue to deliver record heat to many areas through this weekend. The greater chances for showers and thunderstorms will remain over eastern New Mexico each afternoon. Isolated showers and storms are still possible over central and western New Mexico however most activity will be light with strong gusty winds the main threat. Better moisture is expected to filter into all of New Mexico by early next week as high pressure drifts west into the Great Basin. The coverage of showers and storms may increase over the area in this pattern through next week. && .DISCUSSION... SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)... The dome of high pressure aloft has settled over southern NM today. A weak low is offshore of CA, and some batches of cirrus are squeezing northeastward between it and the high to its east. Shower and thunderstorm activity may be slightly more widespread than this time yesterday, but it is still a fairly paltry crop with minuscule rainfall amounts. Look for the current high terrain cells to collapse over the next couple of hours with outflows firing just a few additional storms into the evening. The RAP model indicates a few cells may even survive (mostly in eastern zones) beyond midnight, so this has been built into the forecast. For Friday, the high will side-step to the west into AZ. PWATs will continue to remain fairly low (0.5 to 0.75) in many northern zones Friday with slightly higher values (0.75 to 1.0) found in the south central to southeastern zones. This, coupled with the hot surface temperatures will again yield high-based dry thunderstorms, especially for areas outside of the south central to southeastern zones. Into Friday night, attention will focus on the mesoscale surface high that will likely develop from afternoon/evening convection, and a synoptically-driven backdoor cold front will also be taking shape in eastern CO/KS/OK/TX. LONG TERM...(SATURDAY THROUGH WEDNESDAY)... The unseasonably strong 596dm H5 high centered over AZ on Saturday will strengthen further to 600dm thru early next week while drifting northwest into the Great Basin. 12Z NAEFS climate percentiles show this ridge at max values observed for mid August. This upper level pattern will generate north to northwest flow along the Front Range thru next week with surface high pressure building south into the Great Plains. Moist, low level return flow will deepen westward into NM, partly aided by convective outflows each afternoon along and east of the central mt chain. Meanwhile, a lobe of H7 high pressure is shown developing over TX Sunday thru Tuesday. This will reinforce mid level south-southwest flow into NM which helps transport better moisture north from Mexico. This complicated pattern may bring a noticeable increase in storm coverage with locally heavy rainfall as PW values increase to near 1". Storm motions generally from north to south will favor greater potential for precip within the RGV next week. By late in the week, the potent upper level high center is progged to advance eastward into the Four Corners with decreasing coverage of storms and hotter temps again by next weekend. 52/Guyer && .FIRE WEATHER... The hotter than average temperatures will persist, although readings could decline a couple to a few degrees into early next week as high pressure establishes west of the Four Corners. The dry thunderstorm potential will continue into the weekend, but into early next week storms are expected to gradually become slightly more efficient at rainfall production as dewpoints and humidity climb in eastern zones and eventually seep westward. That being said, much of northwestern NM will likely miss the opportunity for wetting rainfall or relief to drying fuels. Thunderstorm outflows will present the typical short-lived and localized wind concerns each day, and there is potential for some stronger gusts as back door fronts enter the state, the first arriving Friday night into Saturday morning. 52 && .ABQ WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM MDT this evening for the following zones... NMZ236-238. && $$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
912 PM MDT Thu Aug 13 2020 .UPDATE... Issued at 902 PM MDT Thu Aug 13 2020 Another fire has started in the mountains and the smoke plume now reaches to the eastern border of Colorado. We have increased sky coverage in the forecast grids to account for this new plume. Tomorrow, the plume is expected to travel more east-southeast with shifting synoptic winds. We expect ongoing hot and dry conditions to mean continued elevated fire danger, but winds have dropped enough not to continue the Red Flag Warning in the northern mountains. && .SHORT TERM...(This evening through Friday) Issued at 140 PM MDT Thu Aug 13 2020 Another hot afternoon across the plains with temperatures already in the lower 90s across most locales. Just some cumulus clouds so far this afternoon as airmass has already well mixed over the Front Range. Across the far northeast plains, dewpoints in the 40s/50s but expect falling dewpoints there as well during the next few hours with further mixing. Still an ever so slight chance for a storm where the moisture is still holding, generally across Logan, Phillips and Sedgwick counties. Elsewhere dry conditons through tonight. Main concern is the amount of haze and smoke expected over the region through Friday from the Pine Gulch and Grizzle Creek Fires. The westerly mid level flow will continue to influence the airmass as the smoke from the fires comes right across the Interstate 70 corridor and into the Front Range and northeast plains. Latest HRRR smoke forecast increases the smoke again towards 00z over Denver and spreads over the plains through midnight and continues through Friday morning. Will be adding more haze and smoke to the forecast to account for this. Later tonight and Friday morning an upper trof will traverse the northern high plains which will increase the mid level flow (35kt) and bring down an associated cold front across the plains during the morning hours. Unfortunately there is not really any cold air with it and no moisture to speak of along with a slightly subsident airmass. Temperatures will again be well into the 90s while precipitable water values remain around a third of an inch over the Front Range. The only good news is that the flow aloft will begin to shift northwest later in the day, so less smoke likely especially over northern sections of Colorado by afternoon. .LONG TERM...(Friday night through Thursday) Issued at 140 PM MDT Thu Aug 13 2020 The upper level ridge axis builds across the western U.S. Friday night and Saturday. The ridge amplifies and shifts eastward Saturday and remains in place through midweek. Models show a disturbance moving over the top of the ridge and flattening it a bit toward the end of the extended period. At the surface, low level upslope flow continues through the first part of the weekend. The dry and warm airmass limits chances for precipitation. Only widely scattered thunderstorms are possible Saturday afternoon on the far eastern plains. On Sunday, another frontal boundary moves south through the eastern plains. Could see a few more thunderstorms develop farther west with deeper upslope flow and slightly better moisture. Still kept pops to be in the 20-30 range. Once the ridge axis shifts farther east, expect north to northwest flow aloft across the area. Expect some thunderstorms to develop each day with moisture trapped underneath the high and weak disturbances moving through the flow. Highs on the plains will be in the mid 80s to mid 90s Saturday and Sunday. Highs drop back a few degrees for Monday through Thursday with a bit more cloud cover. Stark && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 902 PM MDT Thu Aug 13 2020 Winds are taking longer to shift to drainage than anticipated so those groups have been moved back in the terminal forecasts. Hazy skies will persist overnight and in the morning due to ongoing fires in the mountains. The smoke is not expected to reduce visibility enough to impact airport operations tonight or tomorrow. && .FIRE WEATHER... Issued at 140 PM MDT Thu Aug 13 2020 Slight recovery for humidity levels tonight while winds relaxing this evening. Mountain top flow does increase later tonight and Friday morning and could see gusts up to 30kt Friday morning. Flow decreases Friday afternoon so won`t coincide with lowest humidity levels in the afternoon. There will still be elevated fire danger with the low humidities but expect winds under 20 mph with the lowest humidities during the driest parts of the afternoon. Hence no red flag warnings will be issued at this time. Fire danger will remain elevated through Saturday, but winds will generally be light. On Sunday, moisture increases on the eastern plains with generally light winds. It will continue to be very warm and mostly dry through the middle of next week with a slight chance of thunderstorms Monday through Thursday. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Direnzo SHORT TERM...Entrekin LONG TERM...Stark AVIATION...Direnzo FIRE WEATHER...Entrekin
Area Forecast Discussion
National Weather Service Charleston SC
1039 PM EDT Thu Aug 13 2020 .SYNOPSIS... A trough of low pressure will persist inland, while high pressure remains over the Atlantic through Friday. A weak cold front will approach the area this weekend and pass through on Monday. A trough will then redevelop over the area during the middle of next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Earlier convection has transitioned into a large area of mostly light to moderate stratiform rain with embedded heavier convective elements. The atmosphere has been largely overturned this evening except for areas along/south of I-16 where some late afternoon clearing allowed for some instability to redevelop. RAP soundings suggest the nocturnal inversion is already starting to set up in that area, but with some shortwave energy poised to pass through aloft later tonight, some redevelopment is possible later tonight. Still expect most of the convection to transition back into the coastal waters early Friday. Pops have been readjusted to take current radar trends into account, ranging from 80-100% across the Charleston Tri-County area into Colleton and Beaufort Counties to 50-70% across interior Southeast Georgia with 20-40% south of I-16. Temperatures have been heavily augmented by convection and some areas have likely already reached their overnight lows. Lows will range from the lower 70s inland to the upper 70s/near 80 at the coast. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... A fairly active pattern will continue Friday through Sunday. The upper trough axis will steadily shift east through the period, gradually pushing a weak cold front toward the area. A weak surface trough will precede the front. Atmospheric moisture will remain unseasonably high Friday and Saturday with PW around 2.2". Some drying is possible late Sunday which could result in slightly less convective coverage during the afternoon. Daytime highs will be in the lower 90s each day. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Models are in fair agreement in the long term period. A weak cold front will stall over the region during the early to middle part of next week. The upper pattern will become more amplified with time as a strong shortwave drops into the Ohio River Valley. While rain chances will be in the forecast each day, the most active convective days of the set appear to be Tuesday and Wednesday as vort energy and deeper moisture moves into the area. Temperatures will be fairly close to normal. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... The core of the strongest tstms should be south of KCHS by 00z, but may need to hang onto a mention of TSRA through 01z pending last minute radar imagery. The outflow that is helping to concentrate the convection should remain north of KSAV, but this will be monitored. Scattered showers/tstms are likely again tomorrow afternoon, but the details on the convective evolution is still a bit uncertain. No mention of TSRA will be included at this time at either KSAV or KCHS. Extended Aviation Outlook: Flight restrictions possible in showers and thunderstorms each day, mainly in the afternoon and evening. && .MARINE... Tonight: Winds have turned northwest along parts of the South Carolina waters with the passage of an outflow boundary. Winds should turn more uniformly southwest late with speeds 10-15 kt and seas 1-3 ft. Friday through Tuesday: Outside of any showers and thunderstorms, no marine concerns are anticipated through mid next week. South to southwest winds will prevail with speeds at or below 15 knots, generally highest late week into the weekend with a slightly tighter pressure gradient. Seas will average 2 to 3 feet. && .EQUIPMENT... There was no 14/00z sounding from KCHS due to unfavorable weather conditions during the launch window. The Green Pond/Beaufort NOAA Weather Radio transmitter remains off the air. Electronic technicians are working with the local phone company to resolve the problem. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$
Area Forecast Discussion
National Weather Service Grand Forks ND
843 PM CDT Thu Aug 13 2020 .UPDATE... Issued at 843 PM CDT Thu Aug 13 2020 Severe thunderstorms continue northeast of the F-M area, up toward the northwest side of the Upper and Lower Red Lakes. These storms have not been moving too much, so heavy rain may still be an issue in some areas. Radar estimated storm total precipitation shows some heavier amounts in eastern Pennington and eastern Norman counties. Otherwise, the latest SPC discussion mentions the potential for continued development over the next few hours as the low level flow picks up. UPDATE Issued at 632 PM CDT Thu Aug 13 2020 Thunderstorms have been firing from just east of the Fargo- Moorhead area, northeast toward the Upper and Lower Red Lakes. This seems to be along the western fringe of the low level jet and in the warm sector with ample instability and moisture. The SPC has issued a severe thunderstorm watch that includes most of our counties along and east of the Red River Valley. With the high amount of moisture in the area, will have to keep an eye on heavy rain, or training of storms over the same area. && .SHORT TERM...(This afternoon through Friday night) Issued at 352 PM CDT Thu Aug 13 2020 Warm front continues to work north, but so far we appear to remain capped with only elevated showers/weak storms transitioning north early this afternoon. As the surface trough continues to slide east and the CAP weakens we should see combination of low level convergence and at least some synoptic support associated with trough passage through southern Canada. This should allow thunderstorm initiation in highly unstable air mass this evening (ML CAPE already over 4000 J/KG according to SPC RAP mesoanalysis). Effective shear is shown by SPC Mesoanalysis in the 30-45 kt across northeast ND into northwest MN, and if concurrent with thunderstorm activity could help with discrete supercell potential before mergers take place and activity transitions east. Best signal is still mainly in northwest MN based on CAMs, but I wouldn`t want to rule out severe potential anywhere this evening along convergence zone (may be more isolated further into eastern ND). Stronger synoptic/mesoscale ascent arrives after 03Z as shortwave moves along the ND/SD border, with very high shear associated with LLJ and strong mid level speed max. WIth lingering high moisture/instability there will be a potential for elevated discrete cells and eventually upscale growth potential into another MCS that would then transition into eastern ND and northwest MN 4-9AM period. This period may actually have the best overall potential for severe convection in eastern ND. Regarding impacts this evening/overnight tonight: Where supercells develop environment could support potential for hail to 2 inch, downburst potential to 75 mph and tornadoes. While activity may mainly be elevated late tonight considering the high shear/CAPE environment there is at least a conditional risk for tornadogenesis and large hail with discrete cells. If more of an upscale trend occurs then a transition to a widespread wind event may become favored. How this potential MCS late tonight/Friday morning holds together and tracks eastward ahead of the main cold front will likely determine impacts and timing of any redevelopment during the day Friday and Friday afternoon. If this moves through quick enough, we may see a window for destabilization and another round of supercells/discrete storms ahead of the cold front in our east. If this complex lingers through the day then the tendency may be embedded pulse type convection with widespread heavy rain through the afternoon. Cold front should push east of our CWA based on current model timing by late Friday afternoon/early Friday evening with drier/more stable conditions then ending thunderstorm and severe threat. .LONG TERM...(Saturday through Thursday) Issued at 352 PM CDT Thu Aug 13 2020 Saturday... The upper level trough will begin to exit the CWA overnight Friday and into Saturday. A weak shortwave is expected to move across the northern part of the CWA during the afternoon on Saturday and some spotty rain showers in this area cannot be completely ruled out. Otherwise, temperatures look to stay in the upper 70s/low 80s with dewpoints in the mid to upper 50s. Sunday through Thursday... Northwesterly flow will begin to dominate the upper levels and will usher in a calmer weather pattern to close the weekend and move into the beginning of the work week. Along with the upper level ridging, high pressure at the surface will persist for much of the forecast period. Calmer, cooler, and drier conditions will accompany this transition with high temperatures in the mid 70s/low 80s and dewpoints in the 50s for much of the forecast area. Towards the end of the forecast period the chance for a slightly more active weather pattern appears to emerge and could bring with it the chance for rain once again. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 632 PM CDT Thu Aug 13 2020 With limited time due to the recent issuance of a severe thunderstorm watch, have basically gone with continuity from the previous set of TAFs. Added some definition for the first few hours, and will take a closer look beyond the first 6 hours with the next TAF issuance. As it stands right now, KTVF and KBJI look to have the best chance for storms this evening. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...Godon SHORT TERM...DJR LONG TERM...NCR/DJR AVIATION...Godon
National Weather Service Hastings NE
638 PM CDT Thu Aug 13 2020 .SHORT TERM...(This evening through Friday) Issued at 333 PM CDT Thu Aug 13 2020 Scattered cumulus remains over portions of central and eastern Nebraska, largely a result of the residual moisture from this morning`s stratus. This should continue to diminish as we head into the late afternoon and evening. At the same time, visible satellite and radar show additional convection developing along and west of a line from Goodland to Thedford. CAMs continue to support strong to severe storms in this vicinity, but they have also been very consistent in weakening and dissipating storms as they approach the local area. We have maintained some slight PoPs as far east as Buffalo, Kearney, and Franklin counties, but this may end up being too generous. For Friday, the advancing upper trough will push a cold front into the region. The 18Z HRRR shows this front sliding into central Nebraska in the early afternoon, therefore we should still see a good warmup to around 90 degrees ahead of it. Scattered thunderstorms are anticipated to develop along the front by mid afternoon. Models disagree slightly on timing and location, but the overall consensus is that the better chances will be roughly southeast of a line from Phillipsburg to Hastings to Columbus. MUCAPEs over 4000J/kg and 0-6 shear around 35kts are supportive of some severe updrafts and perhaps a few isolated supercellular structures. The main threats will be large hail and damaging wind. Given poor low-level shear, the tornado threat remains pretty low. With the progressive nature of the front, I do not expect a significant risk for flooding, and dry conditions will prevail across most of the area by around midnight Friday night. Models have also trended cooler for Friday night, with lows now expected to be in the 50s for most of central Nebraska. .LONG TERM...(Friday night through Thursday) Issued at 333 PM CDT Thu Aug 13 2020 As the post-frontal high pressure slides to the east on Saturday and we see more easterly, upslope flow, southwestern portions of the area could see an isolated storm or two. That said, most of the area will likely stay dry. Beyond that, chances for rain and thunderstorms remain rather low. Periodic perturbations moving through the northwesterly flow will keep at least a few small PoPs in the forecast, but overall the pattern appears rather dry. Seasonable temperatures will also continue through the weekend and into next week due to continued northwesterly flow aloft. High temperatures will generally be in the low to mid 80s each day, only possibly reaching back into the upper 80s late next week. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday) Issued at 636 PM CDT Thu Aug 13 2020 Thunderstorms should remain to the west of the terminals tonight. There will be some MVFR ceilings in the morning for a few hours. A cold front will move into the area toward the end of the TAF period. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ SHORT TERM...Mangels LONG TERM...Mangels AVIATION...JCB
Area Forecast Discussion
National Weather Service North Platte NE
654 PM CDT Thu Aug 13 2020 .SHORT TERM...(This evening through Friday night) Issued at 301 PM CDT Thu Aug 13 2020 Near-term concerns revolve around the potential for isolated to widely scattered strong storms later this afternoon and evening across portions of southwest through central Nebraska. Current satellite imagery shows a line of bubbling cumulus stretching from just east of Mullen southwest into Arthur County with additional cu located over far northeast Colorado into portions of Deuel County. This is along a weak convergent boundary/pseudo dryline in place. Morning sounding analysis from LBF depicts a warm layer of air between the h85 and h7 levels maxing out around 22-24 degrees celsius. RAP guidance suggests these temperatures will remain similar if not increase through the daytime hours thus increasing the capping. Instability is not lacking with steep mid-level lapse rates overtop a warm and humid airmass. RAP guidance advertises MLCAPE values in excess of 3000 j/kg. Limiting factor will be shear, given lagging mid-level jet max not anticipated to arrive until this evening. Because of this, 0-6km BWD will be less than 25 knots until these stronger winds arrive. Given relatively weak shear, thinking damaging wind gusts from multicell clusters will be the main threat as DCAPE values will be in excess of 1600 j/kg and 0-3km max theta-e differences approach 30-40k. Cannot rule out some hail as well given the steep lapse rates and SBLI values approaching -8 to -10, but believe this will be more isolated in nature. Shortly after sunset as the boundary layer stabilizes, believe storms will weaken as capping increases. Even with the development of a stout LLJ, thinking this will not be enough to sustain convection well into the evening and as such have PoPs ending by 14/03z. Did bump up temperatures tonight with lows generally ranging from the low 60s in the west to near 70 in the east. Surface boundary associated with northern high plains system will enter the local area on Friday bringing an abrupt wind shift from the southwest to northwest. This will also bring contrasting temperatures across the area with slightly cooler daytime highs expected across the region. The frontal boundary will clear the area by the afternoon but as fgens encounters the more humid airmass to the southeast, rain and thunderstorms will become possible during the afternoon. General thoughts are that the majority of this activity will remain east to southeast of the area. Because of this, have limited PoPs to the eastern tier of counties and only Slight Chance at that. SPC covers much of central Nebraska in a Day 2 Marginal risk of severe weather. Thinking this is adequate with any favored changes being to trim it further east and out of the area but will defer to later forecasts to address this. High temperatures tomorrow will range from the low 80s across the north to low 90s in the far south. Any precipitation chances will exit the area by late evening leaving the area dry for the overnight hours into Saturday. Lows will fall into 50s thanks in part to the drier air. .LONG TERM...(Saturday through Thursday) Issued at 301 PM CDT Thu Aug 13 2020 Beginning 12z Saturday. Period begins with modest northwest flow aloft as upper ridge across the desert southwest strengthens through the weekend. Mid-level flow amplifies as aforementioned ridge shifts slightly north into early Sunday. While strength of the developing ridge varies between the global models, placement is in fairly good agreement. For Saturday evening, on the backside of departing weak surface high pressure, southerly low-level flow should return across portions of central and southwest Nebraska helping advect some better moisture into far southwest Nebraska. This may set the stage for some thunderstorm chances, limited to areas south of I-80 and west of Highway 83. The ECMWF is slightly more bullish on this potential, likely due to cooler mid-level temperatures and thus weaker capping. Meanwhile, the GFS advertises most if not all precipitation chances remain south of the local area. With the NAM playing the middle ground, will keep PoPs in place for now. Given enhanced flow at h5, will have to monitor for potential for a few strong storms, however, given limited moisture this remains a low- confidence threat. Temperatures will generally be near normal values for mid-August with highs in the low 80s northeast to upper 80s south and west. Strengthening low-level jet will allow for rain and thunderstorms to persist into the early morning hours on Sunday with gradual decrease by mid-day Sunday. Weak high pressure works through the area on Sunday with precipitation chances possible in the afternoon, though consensus between models vary a bit. Will keep additional low-end PoPs for this time frame, mainly driven by diurnal heating so peaking during the afternoon hours and waning in the evening. Additional ridge riding shortwaves are likely to move across the high plains in the Tuesday through Friday period. During this time, the upstream ridge is expected to strengthen to near 600 dam with highly amplified flow across the central plains. As the ridge begins to weaken and shift slowly south and east, the ridge axis and with it the thermal ridge will approach towards the weekend suggesting an upwards trend in daytime temperatures for the latter half of the week. Periodic thunderstorm chances will exist owing to the lack of any substantial surface boundary that will scour out any local moisture. Timing of this activity is difficult at range but situations like this tend to follow diurnal swings so will keep day-to-day PoPs highest during the afternoon and early evening hours. Temperatures look to return to above normal values by the end of the forecast period. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 652 PM CDT Thu Aug 13 2020 VFR conditions expected to prevail at both terminals for the TAF period. Have included VCTS at LBF with a few anvil strikes in the area though convection will largely stay off to the west and northwest of the terminal. Otherwise, expect backing winds at both LBF and VTN into Friday with the approach of a cool front. Winds look to be gusty from the north tomorrow afternoon behind the front. Have included LLWS at VTN into tomorrow morning but left it out of LBF for now. Future LLWS inclusion appears possible at LBF if confidence can grow. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Jurgensen LONG TERM...Jurgensen AVIATION...Brown
Area Forecast Discussion
National Weather Service Phoenix AZ
440 PM MST Thu Aug 13 2020 .UPDATE...Updated aviation discussion. && .SYNOPSIS... Strong high pressure will remain situated across the Southwestern U.S. into next week bringing continued hot conditions. High temperatures across the lower deserts will approach or exceed 115 degrees starting today and lasting through at least early next week. Isolated showers and thunderstorms are possible today before chances decrease tomorrow. Potential for a slightly better monsoon set-up will develop this weekend or early next week. && .DISCUSSION... Latest water vapor imagery reveals an increase in mid and upper-level moisture across the Desert Southwest associated with remnants of post-TC Elida. Meanwhile, streamline analysis depicts a southwesterly flow around a strong anticyclone centered across southern New Mexico. Although conditions are drier than average at the surface, overall PWATs above 1.3 inches are sufficiently high to yield a large area of MLCAPE exceeding 500+ J/kg across the lower deserts. Isolated convection has already initiated across the higher terrain east of Phoenix, and additional isolated activity is expected across the lower deserts this afternoon and evening. Latest HREF suggests any storms that develop have the potential to produce heavy rain and strong/severe wind gusts. DCAPE values above 1500 J/kg, per the latest mesoanalysis also point to the potential for blowing dust. Most recent runs of the HRRR are still highlighting western Maricopa County for the highest potential. Latest ECMWF ensemble mean indicates the aforementioned anticyclone will lift northward over the next several days with height anomalies becoming more prominent across the Rockies. Excessive Heat will remain the big story through the weekend. Latest NBM forecast for Phoenix Friday is 116 deg, which would fall only one degree short of the daily record. Models remain consistent indicating the Monsoon High will drift into southern Utah as soon as Sunday. This will give us our first taste of northeasterly/easterly steering flow, which is generally more favorable for lower desert convection. This pattern will persist through much of next week, resulting in a continuation of the well-above normal temperatures and increasing chances of precipitation. The Excessive Heat Warning was extended through next Wednesday, however there is a chance it may need to be canceled a day or two early if widespread storms do materialize. && .AVIATION...Updated at 2340Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: High confidence that winds will remain westerly through the evening hours. TS activity well to the west is not expected at this point to directly affect the terminals due to the existence of drier air over the greater Phx area. A more likely impact from these storms will be to just enhance the westerly winds that are already in place. However, significant blowing dust is not expected at this point. TS activity is expected to pretty much end around/just below 03Z. Typical diurnal wind shift to easterly is expected around/shortly after midnight. As far as the outlook for Friday is concerned, a period of light southerly crosswinds is possible between 17Z and 20Z before winds become westerly. TS activity on Friday afternoon is expected to remain well to the east of the greater Phx area. Southeast California/Southwest Arizona including KIPL and KBLH: For KIPL, winds are expected to follow typical diurnal trends at speeds mostly AOB 10 kts. At KBLH, light westerly winds through the night to become southerly during the day on Friday. Otherwise, there may also be extended periods of a light/variable wind at both sites. && .FIRE WEATHER... Sunday through Thursday: High pressure will persist across the Desert Southwest next week, resulting in a continuation of the above normal temperatures. The pattern is expected to become more favorable for thunderstorm activity, even across the lower deserts. Minimum humidities through the period will drop into the teens each day with overnight recoveries generally between 25 and 50%. Winds will generally remain light aside from some typical afternoon breezes. However, any storms that develop have the potential to produce gusty, erratic winds. && .CLIMATE... Record high temperatures: Date Phoenix Yuma El Centro ---- ------- ---- --------- 8/13 115 in 2012 117 in 2012 116 in 2012 8/14 117 in 2015 115 in 2019 116 in 2015 8/15 115 in 2015 117 in 2015 118 in 2019 8/16 113 in 2013 115 in 1992 117 in 2016 8/17 114 in 2013 114 in 1992 115 in 2015 8/18 112 in 2011 116 in 1960 115 in 2015 && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Excessive Heat Warning until 8 PM MST Wednesday for AZZ530>556- 559>562. Heat Advisory until 8 PM MST Wednesday for AZZ557-558-563. CA...Excessive Heat Warning until 8 PM PDT Wednesday for CAZ565>567- 569-570. Excessive Heat Warning from 10 AM Friday to 8 PM PDT Wednesday for CAZ560>564-568. && $$ DISCUSSION...Hirsch AVIATION...Percha/Rogers FIRE WEATHER...Hirsch CLIMATE...MO
Area Forecast Discussion
National Weather Service Pueblo CO
325 PM MDT Thu Aug 13 2020 .SHORT TERM...(This evening through Friday) Issued at 323 PM MDT Thu Aug 13 2020 Dry line has been gradually mixing eastward with dew points having dropped into the 30s along the I-25 corridor with single digits to 20s across the mountains. Some 50 to near 60 dew points still linger across the far eastern counties as of 21z. This has led to CAPE values to near 1500 J/kg near the KS border and with with deep layer shears running around 40-50 kts...can`t rule out an isolated strong to near severe storm across eastern portions of Kiowa and Prowers counties where a few CAMs runs have shown some convection develop through the evening. Better odds will be just north and east of the CWA. Elsewhere, convection will be high based and more likely to produce gusty winds up to 40 mph and only some spotty sprinkles. Activity will diminish with loss of heating this evening. Once again, dry line will retreat back westward overnight across the plains. Will have to monitor the potential for some stratus or patchy fog near the eastern border, but high res models keep northerly winds off the Palmer Divide into KCOS and KPUB which should keep any stratus to our east. Have also introduced some smoke from the Pine Gulch and Grizzly Creek fires into portions of Chaffee, Lake and Teller counties based on output from the hrrr smoke runs. This may spread eastward into portions El Paso county by early Friday morning which then spreads southward across a large portion of the southeast plains during the day on Friday as a front moves through the plains. This will more likely produce some hazy skies so have not introduced smoke into the Friday morning grids just yet. For tomorrow...upper high out west will put CO under west northwest flow aloft with some increase in mid level moisture across southern and western portions of the area. Winds across the plains will shift out of the northeast then east behind the front, but moisture actually mixes out along the I-25 corridor and adjacent plains in the afternoon which keeps best CAPE values near the Kansas border. GFS and NAM differ with sfc dew points along the eastern border with CAPE values ranging from under 1000 J/kg in the GFS to over 1500- 2000 J/kg in the NAM12. NamNest runs suggest potential for one or two severe storms near the Kansas border Friday afternoon and will carry some isolated pops to account. With the increase in moisture across the southern mountains within the upper high, there will be a better chance for some high based showers and thunderstorms. Main risks will be gusty winds up to 45 mph and lightning along with some brief light rainfall. Temperatures tomorrow should be pretty similar to today with not much cooling expected behind the front until a stronger moves in Friday night. -KT .LONG TERM...(Friday night through Thursday) Issued at 323 PM MDT Thu Aug 13 2020 Friday night and Saturday...The upper-level ridge is expected to continue sliding northwest to the Great Basin region, resulting in northwest flow aloft over Colorado. Meanwhile, post-frontal easterly flow is expected at the surface, advecting some low-level moisture to the area, especially across the plains. The increase in moisture is expected to bring isolated to scattered showers and thunderstorms to much of the area for Saturday afternoon and evening. Afternoon highs are also expected to drop compared to the past several days across the plains where temperatures are expected to reach the upper 80s to low 90s. Highs in the high valleys are expected to remain about the same in the 80s to around 90. Sunday through Thursday...The ridge is expected to remain over the western U.S. with the high centered over the Great Basin through late next week, keeping northwest flow over Colorado. Periodic shortwaves are anticipated to propagate around the upper-level high during this time. The periodic shortwaves, along with moisture being recirculated around the high pressure, are expected to bring isolated to scattered PM showers and thunderstorms to much of the area each day. A gradual increase in moisture as the week progresses is plausible as the circulation around the high is able to tap into additional Pacific moisture, which would increase the instability and potential for some of the storms to be strong to severe at times next week. Afternoon highs are expected to be in the mid 80s to lower 90s across the plains, and lower to mid 80s in the high valleys. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 323 PM MDT Thu Aug 13 2020 VFR conditions expected overnight though areas of smoke may spread over the mountains into the Pikes Peak region towards morning. Not expecting a significant reduction in vis, but some VFR haze will be possible Friday morning for KCOS and possibly for KPUB by mid day. Winds will generally remain light and diurnally driven until the front moves through the plains Friday morning bringing a wind shift from the north to northeast 10-20 mph by afternoon. Overall, TAF sites are more likely to stay dry with isolated afternoon thunderstorms confined to the southern mountains and far eastern plains. -KT && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...KT LONG TERM...CARLBERG AVIATION...KT