Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/31/16

Area Forecast Discussion
National Weather Service Albany NY
1021 PM EST Fri Dec 30 2016 .SYNOPSIS... High pressure will build in tonight but lake effect snow bands will continue overnight. A quick moving low pressure system will bring more snow to the area Saturday and Saturday night with a moderate snowfall expected for the western Adirondacks. High pressure will bring fair weather to the area on Sunday before an approaching low pressure system will bring some wintry precipitation to the area Monday into Tuesday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Lake Effect Snow Advisory for the western Mohawk Valley extended until 5 am. As of 1021 PM...Weather radar loop shows main lake effect snow band affecting our area is clipping southern herkimer County and extending into Schoharie, Greene, Columbia and Berkshire Counties. The band appears to be slowly lifting northward towards the advisory area. Latest HRRR has band moving northward and continuing until around 08Z so extended the LES advisory until 5 AM. Some areas in Schoharie, Greene and western Albany Counties may pick up a total of 2-3 inches of snow from this band as it has been persistent and only slowly moving northward. Outside of lake effect bands, clouds have broken or cleared. Temperatures are mostly in the 20s with teens across the western adirondacks to around 30 in far southern Ulster, Dutchess and Litchfield Counties. KENX VAD wind profile still shows 10-25 kts in the boundary layer so gusty winds are gradually diminishing. Winds will diminish more overnight. Overnight lows will run from near 10 degrees across the highest terrain of the western Adirondacks to the lower 20s in Hudson Valley from the Poughkeepsie area up into the Capital District and into northwestern Connecticut. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... Winter Weather Advisory for a moderate snowfall has been issued for 10 am Saturday until 6 am Sunday as quick moving clipper system brings another round of snow to the region. The surface ridge will quickly shift off the coast Saturday and the weak upper ridging will flatten as a short wave trough/clipper system quickly from the Great Lakes region. Guidance is in good agreement with the timing of the system. Used a blended approach to handle the QPF. Initial should get some light snow due to warm air advection as the warm front approaches with better and more widespread snowfall as the associated low level jet moves in. The highest QPF totals are expected closer to the low across the northwest portion of the forecast area. Have issued a Winter Weather Advisory for snow for the western Adirondacks for 4 to 8 inches of snowfall with lighter amounts expected as you head to the southeast with 1-2 inches for the Capital District and little if any in the mid Hudson Valley. The snow will wind down Saturday night with the passage of the short wave trough its associated cold front. Higher pressure at the surface and aloft will build in on Sunday and Sunday night with a return to fair weather. && .LONG TERM /MONDAY THROUGH FRIDAY/... Monday into Tuesday...upper level ridge is over the Eastern Seaboard, while a negatively-tilted trough moves into the central part of the US. The northern portion of this trough looks to result in strong cyclogenesis over the Upper Midwest, while the southern portion ejects toward the eastern seaboard. With the dominant low- level cyclone over the Upper Midwest, warm midlevel air will spread across the Eastern US. Isentropic lift will increase Monday, but will be pretty weak initially, so only chance PoPs are in place. The lift looks to increase Monday night into Tuesday, with good model consensus, so likely PoPs are in place for that time period. It appears that p-type will be an issue with this system. A rather strong high will be in place over Maine Monday, and will only slowly retreat Monday night and Tuesday. Models are indicating good southerly surface flow does not kick in until Tuesday at the earliest. With cold low temperatures expected Sunday night, this raises the prospects of the cold air being slow to scour out locally, and we may be more reliant on top-down processes to warm things up at the surface. Have lowered temperatures from superblend for this package. Best indication for p-type is a light mixture of snow and sleet initially Monday, then becoming rain/freezing rain as midlevel warm air advection results in melting aloft late Monday/Monday night. Expecting plain rain by some time Tuesday with precip tapering off by Tuesday night. Fairly good model agreement with the large-scale players in this system, but low confidence on the details as would be expected with a system still four days out. Will continue to mention freezing rain potential in HWO. Potentially mild day Wednesday as dry slot pushes in. Cold advection kicks in Wednesday night/Thursday with temps back toward normal by the end of the week. Possibly some lake-effect snow showers Thursday. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... Much of the overnight will see VFR conditions at the TAF sites with the exception being the occasional snow shower which may drop conditions to MVFR at KALB and KPSF overnight tonight. A fast moving low pressure system will bring some light snow to all the TAF sites except KPOU on Saturday. Snow should begin between 17 and 23Z Saturday. MVFR/IFR conditions in snow expected at KGFL, KALB and KPSF. Blustery conditions will continue this evening, with westerly winds gusting to near 30 knots at times at KALB/KPSF. Winds will gradually decrease later this evening to 8-14 kts and then to 3-7 kts late tonight. Winds shift to the south and increase to 10-20kts Saturday morning. Outlook... Saturday Night: Moderate Operational Impact. Likely SN. New Years Day: No Operational Impact. NO SIG WX. Sunday Night: No Operational Impact. NO SIG WX. Monday: Moderate Operational Impact. Chance of RA...SN...SLEET. Monday Night: Moderate Operational Impact. Likely RA...FZRA. Tuesday: High Operational Impact. Likely RA. Tuesday Night: Moderate Operational Impact. Chance of RA. Wednesday: Moderate Operational Impact. Chance of RA. && .HYDROLOGY... Active weather pattern continues. Lake effect and upslope snows wind down tonight. Looking at light to moderate snowfall Saturday and Saturday night as clipper system approaches and moves across the region. Fair weather returns for Sunday and Sunday night as high pressure builds in. However, another round of wintry precipitation expected including a period of freezing rain Monday night eventually changing over to plains rain Tuesday as a low pressure system passing well to out northwest across the Great Lakes region. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Winter Weather Advisory from 10 AM Saturday to 6 AM EST Sunday for NYZ032-033. Lake Effect Snow Advisory until 5 AM EST Saturday for NYZ038. MA...None. VT...None. && $$ SYNOPSIS...SND NEAR TERM...SND SHORT TERM...IAA LONG TERM...Thompson AVIATION...11/Thompson HYDROLOGY...IAA
Area Forecast Discussion
National Weather Service Goodland KS
700 PM MST Fri Dec 30 2016 .SHORT TERM...(This afternoon through Saturday) Issued at 1122 AM MST Fri Dec 30 2016 18z water vapor imagery and RAP analysis indicated broad ridging ongoing across the plains with area of mountain induced cirrus forming across northeast Colorado. Approaching short trough was just crossing the Canadian border with corresponding sfc front in the Dakotas. Very warm temperatures will continue through the afternoon hours and may see a site or two near record values given how fast a few locations warmed...but think strong inversion has already mixed out which may level off additional warming. Cold front will sweep across the area and while winds above the surface will increase with its passage...front appears to be rather shallow initially with strong inversion limiting momentum transfer. Temps will be 20-25 degrees cooler tomorrow than today. There may be a small window for fog development across eastern Colorado around sunrise should winds decouple completely...but at this time chances are fairly low for significant fog development. .LONG TERM...(Saturday night through Friday) Issued at 117 PM MST Fri Dec 30 2016 An extended cold outbreak looks to be on tap for this period as a deep trough digs into the western CONUS early in the week then slowly moves across the remainder of the CONUS. Low level moisture return ahead of the system in the shallow cold air may result in some freezing fog/light freezing rain Sunday night/Monday morning. Soundings look most favorable in the northeast part of the area around McCook. The very cold air will begin to spill into the area Monday night and remain entrenched through the end of the week. There will be a chance for light snow Wednesday and Thursday as the upper trough axis swings through. Given the very cold air mass, would expect a dry snow with high liquid to snow ratios. This may boost snow amounts close to advisory criteria. However, it looks like a low end event at this time with not much in the way of wind either. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 430 PM MST Fri Dec 30 2016 For KGLD and KMCK, vfr conditions through the period. For KGLD winds quickly veer to the northwest then north in the 02z-06z timeframe at speeds around 11kts as a cold front moves through. This continues through 18z before winds start to back to the west then southwest at speeds under 10kts. For KMCK light northwest winds at taf issuance expected to continue through 19z then back to the west and southwest at similar speeds (around 6kts) for the rest of the period. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JRM LONG TERM...024 AVIATION...99
Area Forecast Discussion
National Weather Service Grand Rapids MI
941 PM EST Fri Dec 30 2016 LATEST UPDATE... Marine .SYNOPSIS... Issued at 316 PM EST Fri Dec 30 2016 Light snow accumulations are expected through the US-10 corridor late this evening into Saturday morning. Otherwise, the rest of the weekend looks pretty quiet with highs in the 30s. A strong storm system early next week will bring some decent rainfall to Lower Michigan, followed by a return of arctic air and lake effect snow by Tuesday night/Wednesday. && .SHORT TERM...(This evening through Sunday night) Issued at 316 PM EST Fri Dec 30 2016 Light snow accumulations are expected across the northern forecast area tonight, mainly north of a Pentwater to Mt. Pleasant line. New snowfall of 1 to 2 inches is expected along US-10. Heavier snowfall is forecast further north across Northern Lower Michigan. An Alberta Clipper is forecast to track from northern Wisconsin into the UP overnight. Strong warm advection ahead of the low will result in light snow breaking out across the far northern forecast area. Strong southwest flow in the low levels will actually result in surface temperature gradually rising after midnight, so low temperatures will occur this evening. Highs on Saturday will warm into the mid and upper 30s. Will feature relatively low PoPs across much of the area on Saturday as the cold front pushes through, but moisture will be limited. The rest of the weekend looks quiet with dry weather expected through late Sunday evening. Saturday night lows will be in the 20-25 range. Lower Michigan will finally get some sun to kick off 2017 with highs in the mid to upper 30s. .LONG TERM...(Monday through Friday) Issued at 316 PM EST Fri Dec 30 2016 Sfc low tracks from Southern Plains into western Great Lakes on Monday and Tuesday. Cold air is eroded pretty quickly so it doesn`t appear that freezing rain is a threat at this time. The cold air returns on the back side of the storm by Tuesday night and Wednesday with lake effect snow showers for the rest of the week. The lake effect snows should be persistent but perhaps not heavy as inversion heights are generally around 5 to 8 kft. We will have to watch the Thursday to Friday period closely as Gulf moisture streams northward and phasing of the northern and southern streams is possible. Although the current operational runs are suppressed with the trough until it reaches the Atlantic coast, it would not take much more amplification for it to bring some synoptic snows to Lower Michigan. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 624 PM EST Fri Dec 30 2016 For the most part I expect VFR conditions through tonight into mid morning Saturday as the precipitation from the system passing north of here will keep that precipitation (snow) well north of the GRR TAF sites tonight. The strong southwest winds have already blown out the low level moisture so no threat for low celling either. However winds will be near 50 knots as close as 2000 above the ground so I put low level wind shear after 06z for that. Once the cold front comes through in the 15z time frame Saturday, there looks to be enough lift and moisture for some lake effect snow showers. Winds will be strong enough for the snow showers to each all TAF sites. This brief event should end just beyond 00z Sunday. && .MARINE... Issued at 941 PM EST Fri Dec 30 2016 There seems to be some question as to just how strong the winds will get in our southern near short tonight. I checked using BUFKIT with the NAM...RAP and HRRR for MKG...LWA and SBN. It seems questionable that we would actually get gales. So, I dropped the gale headline in favor of a Small Craft Advisory through Saturday afternoon. && .HYDROLOGY... Issued at 1010 AM EST Fri Dec 30 2016 Flood advisories continue at Ionia and Maple Rapids. Ionia is slowly receding, while Maple Rapids is near its crest 0.9 feet above bankfull and will begin a slow recession also. The next weather impact on the rivers will be rain totaling about a third of an inch on Monday. This may prolong the amount of time the Maple River spends above bankfull. River forecast points such as Ionia and Hastings will be below bankfull prior to the rain but still running higher than normal, so they will have to be monitored. Beyond that, colder than normal air will settle in starting on Wednesday, so concerns will shift toward river ice redevelopment. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory until 7 PM EST Saturday for LMZ844>849. && $$ SYNOPSIS...EBW SHORT TERM...EBW LONG TERM...Ostuno AVIATION...WDM HYDROLOGY...CAS MARINE...WDM
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
817 PM CST Fri Dec 30 2016 .UPDATE... Issued at 815 PM CST Fri Dec 30 2016 Went ahead and updated the forecast this evening to account for the latest observational trends. First change was to raise min temps a bit tonight, as southerly surface winds will stay up ahead of an approaching front and clouds begin to thicken up towards Saturday morning. Also lowered dewpoints quite a bit as latest obs continue to show scant low-level moisture with dewpoints in the low teens to the low 20s. Given this dry near- surface airmass, think any precipitation is going to struggle to saturate all the way to ground level. Latest NAM and HRRR guidance seem to support this thinking, thus have lowered pops for late tonight into Saturday morning. KD && .SHORT TERM... (Through Late Saturday Afternoon) Issued at 254 PM CST Fri Dec 30 2016 Surface low ahead of a sharp shortwave will move rapidly across the western Great Lakes on Saturday. Trailing cold front will approach Central MO by around 12Z Saturday. To the south, a sprawling surface high across the Gulf Coast will finally move eastward tonight and allow some return flow from the Gulf of Mexico, but this will only be for a relatively brief time before the cold front approaches. Any precipitation late tonight into Saturday will likely be limited to the far southeastern CWA generally southeast of an Salem line. Even though a few snowflakes may mix in with the rain at the onset with initially dry air at low levels, the thermal profile should limit any possibility of a significant period of rain/snow as the atmosphere will be too warm. Both lows and highs should be 10 to 15 degrees above normal tonight and Saturday over all but the far northern CWA where post-frontal afternoon temperatures will likely remain steady in the mid to upper 30s. Browning .LONG TERM... (Saturday Night through Next Friday) Issued at 254 PM CST Fri Dec 30 2016 (Saturday night into Monday) Main forecast challenge is the timing of precipitation early next week. Saturday night and Sunday still looks mainly dry as both the GFS and ECMWF show a shortwave ridge moving across Missouri and Illinois. Rain chances will increase on Sunday night as weak low level moisture convergence increase beneath increasing ascent ahead of a upper trough over the central Plains. Will keep likely PoPs on Monday as this trough moves across the area. SREF ensemble mean temperatures are in decent agreement and generally followed for temperature trends. (Tuesday through Friday) GFS and ECMWF are in decent agreement that a strong cold front will pass through the area late Monday night into early Tuesday which will bring below normal temperatures for mid-late next week. There may still be some light precipitation lingering along the front on Tuesday. While zonal upper flow will initially set up behind the front on Tuesday, both models are showing a large upper trough moving southward out of Canada into the Midwest by late next week. Ahead of the large trough, a weak shortwave will move out of the Central Plain across Missouri and Illinois bringing a slight chance of snow by Wednesday night and Thursday. By Wednesday into Friday, GFS ensemble mean temperatures are showing highs only in the 20s which is supported by 850 temperatures in the -10 to -20C range. Britt && .AVIATION... (For the 00z TAFs through 00z Saturday Evening) Issued at 522 PM CST Fri Dec 30 2016 VFR conditions will persist through the TAF period, but there will be some terminal impacts due to low-level wind shear. Low-level wind shear will develop tonight at all sites as winds around 2,000 feet increase to 40-45 knots. SSW surface winds will stay up around 10-13 knots overnight, but will become more gusty early Saturday morning ahead of a surface cold front. VFR cigs will develop ahead of the front late tonight into Saturday morning, and a stray shower around the STL sites cannot be completely ruled out. The front will move through all sites by early Saturday afternoon, bringing a wind shift to the WNW and clearing skies. SPECIFICS FOR KSTL: Main terminal impact will be wind shear tonight as winds around 2,000 feet increase to 40-45 knots. SSW surface winds will increase early Saturday morning ahead of a cold front which will move through by early Saturday afternoon. VFR cigs around FL050 will increase ahead of the front, and a stray shower cannot be ruled out Saturday morning. Winds will shift to the WNW behind the front Saturday afternoon as skies begin to slowly clear. KD && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
607 PM CST Fri Dec 30 2016 .UPDATE... Issued at 607 PM CST Fri Dec 30 2016 Updated the grids/forecast to include scattered flurries around and to the east and south of the Twin Cities for this evening. RAP analysis is showing a rather strong band of mid level frontogenesis stretching W-E across the Twin Cities. This feature moves rather quickly to the SE this evening. The 12Z NSSL WRF picked up on this quite nicely and has the light snow/flurries out of the local area by 04z. && .SHORT TERM...(This evening through Saturday) Issued at 350 PM CST Fri Dec 30 2016 Clipper currently just north of Minot will track through Fargo and to the north of Green Bay tonight. We are within the warm sector of the system and with cloud heights only down to 8k feet, we have done very little to modify the dry layer of air below 600mb on this mornings 12z KMPX sounding. Although many of the deterministic models continue to spit out some light snow this evening in western WI, think this is overdone given the dry air and we preferred a mix of rapid updating hi-res models (RAP/HRRR/HopWRF), which looks to have a better handle on the extent of the dry air. In fact, our best chance for snow will likely come on the backside of the system. As winds turn to the northwest and we get into strong CAA advection. We`ll see the return of low stratus as well. Forecast soundings show steep lapse rates developing up to about 825mb, with the top of the cloud layer cooling into DGZ. This should create a shield of snow showers and flurries following the backside of the low tonight through the middle of Saturday morning north of I-94. For temperatures, being in the warm sector, we have been a few degrees warmer today than we were predicting overnight and we should see a swath of highs in the mid 30s in SW MN downwind of the Buffalo Ridge. Favored the warmer guidance for lows tonight, which just means a slower push of cold air behind the low. The cold trough will be working across the upper MS Valley Saturday, so highs near to slightly below normal look good. .LONG TERM...(Saturday night through Friday) Issued at 350 PM CST Fri Dec 30 2016 The big weather story in the long term remains the system coming through Monday and Tuesday. There is substantial model disagreement between the GFS and other numerical guidance. Hopefully we get some better consensus over the next 24 hours. The 12z GFS is a far western (warm) outlier. There is reasonable agreement between the Canadian/NAM/ECMWF with a low track that is roughly Kansas City to Chicago. That certainly would suggest snow, but it also means we`re sort of on the outside of the heaviest QPF that would fall across IA, far southeast MN and southern WI (although the ECMWF still has a solid 0.50" locally). The GFS sounding has rain/sleet/snow with its far western track. We introduced a wintry mix for a time across eastern MN and western WI to account for some temperature uncertainty in the forecast - because even the solutions that are farther east suggest that it will be a warmer boundary layer when the snow is falling and it will be close to the rain/snow transition. The upper pattern is fairly complex with the jet evolving from split flow to a positively tilted trough and strengthening southern stream. This transition happens on Sunday, so by tomorrow we hope the GFS/ECMWF will come more in line. We should note that although the GEFS also shows the rain/mix potential, overall more of its solutions are a bit cooler than the 12z operational run. As mentioned in previous discussions, Arctic air arrives by the middle of the week and should last through next weekend. This cold shot doesn`t look quite as cold as what we experienced in mid December, but it appears to have more staying power and is reinforced by a couple passing cold fronts over the first couple weeks in January. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 607 PM CST Fri Dec 30 2016 Two issues tonight. the first is strong mid level forcing currently stretching from the Twin Cities to Eau Claire. This feature is helping to promote some -SN to the west and north of KMSP at TAF issuance. The forcing moves rather quickly southeast this evening so the thought was to include some -SN in the KRNH...KMSP and KEAU TAFS for the first 3 hours. The second issue is a low pressure system over northern MN moving southeast. This feature will bring widespread snow to areas north of the TAF sites. However, when we transition to the backside of the low during the early morning hours, northwest winds will be on the increase along with MVFR ceilings spreading southeast. These have been handled well in the TAFS and only minor changes were made. A ridge of high pressure will spread from west to east Saturday afternoon bringing VFR conditions to the area. SE winds early tonight 10 knots or less, veering NW overnight with speeds 12-15 knots with gusts 20-25 knots. Winds slowly diminishing Saturday afternoon and backing to the SW by evening. KMSP...Added some -SN through 03z with a few sites north of the airfield indicating flurries. Otherwise, MVFR ceilings late tonight and Saturday morning with clearing during the afternoon. Winds similar to those described above. /OUTLOOK FOR KMSP/ Sun...VFR. Wind S 5-10 kts. Mon...MVFR/IFR. Wintry Mix likely. Wind NE 5-10 kts Tue...MVFR chc IFR. Chance -SN. Wind NW 10-20 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ UPDATE...RAH SHORT TERM...MPG LONG TERM...CLF AVIATION...RAH
Area Forecast Discussion
National Weather Service Marquette MI
627 PM EST Fri Dec 30 2016 .SHORT TERM...(This evening through Saturday) Issued at 403 PM EST FRI DEC 30 2016 Water vapor imagery and RAP analysis show shortwave ridging shifting over the Upper Great Lakes ahead of the next shortwave of interest moving across southern Manitoba/ne ND. Radar imagery shows a nice band of snow streaking ese with that feature, extending from southern Manitoba ese across northern MN. Some obs have indicated vis as low as 1/2sm in the snow. Closer to home, les has been winding down quickly this aftn with arrival of sfc high pres ridge axis and inversions falling to around 4kft. Diminishing les over the ne fcst area will shift offshore around 00z as high pres ridge axis shifts past the area. Attention, then quickly turns to the upstream shortwave, which should already be spreading snow into western Upper MI by 00z. Deep layer forcing per qvectors is still fcst to be quite strong as is isentropic ascent. Consistent with recent days model runs, specific humidity up to 2g/kg is avbl around 700mb, suggesting potential for a widespread 2- 4 inches of snow to the n of sfc warm front under band of fgen during a roughly 6-9hrs of forcing. Advection of steep mid level lapse rates of 7+C/KM into the backside of the pcpn area may lead to some convective elements within the snow. 850mb temps of -8 to -10C will also support lake enhancement off Lake Michigan into the se fcst area. Majority of models indicate winds may be backed enough for a time to even bring lake enhancement into Menominee county. So, the area near Lake Michigan will see the most snowfall from this event, probably upwards of 6 inches. A few spots may exceed warning threshold of 6in/12hr. Will be something to monitor. There could even be a little lake enhancement off Lake Superior into the Keweenaw for a time tonight under shallow ese winds. Snow will diminish w to e late tonight into Sat morning. Winter wx advys have been issued for the entire fcst area tonight. Fcst for Sat has some issues and potential surprises. Sfc low pres associated with shortwave will be situated somewhere over w or central Upper MI at 12z with indications of sharp sfc trof developing northwestward over Lake Superior. With 850mb temps of -10 to -12C, sharp convergence and deep moisture, band of mdt to hvy snow could certainly develop along trof and impact the western fcst area. Based on wind fields/convergence, area around KIWD is a concern early in the morning and then the Keweenaw morning through early aftn. A number of high res models point toward the Keweenaw as the area of greatest potential impact. So for now, opted to run tonight`s advy thru 21z for Keweenaw County. Not out of the question that some areas could see very hvy snow for a time. As mdt/hvy snow along trof shifts se, it will begin to diminish in the aftn as increasing large scale subsidence overspreads the area. However, portions of northern and eastern Marquette County and western Alger County could see a burst of snow in the aftn. .LONG TERM...(Saturday night through Friday) Issued at 329 PM EST FRI DEC 30 2016 Models suggest that a mid/upper level ridge building from the northeast Pacific into Alaska will result in pattern amplification across the CONUS with a trough over the wrn CONUS expanding eastward through the week. The pattern will also favor the intrusion of another very cold arctic airmass by midweek that may linger through next weekend. Temperatures near or above normal into Tuesday will drop below normal with LES increasing for nw to wnw snowbelts. Sat night through Sun night, LES will shift offshore under backing winds and diminish w-e Sat night as the high pres ridge moves through the area. 850mb temps climbing to around -5C on Sun will bring moderating temps after a cold early morning with light winds and partial clearing under the passing sfc high pres ridge. Although the sfc high pres is fcst to build into New England Sun night, enough low level dry air will persist under the sfc ridge axis extending back into the Upper Lakes to maintain dry conditions through the night. More mid/high clouds will result in a warmer night. Monday-Tuesday, The models suggest that a low pressure wave will lift northeast from the plains to the western Great Lakes. However, the 06z/12z GFS remained significantly stronger and farther west (sfc low over northern MN at 12z Tue compared to nrn Lake Huron) than the 00z/12z ECMWF/ECENS, GEM, and UKMET. So, the forecast leaned more toward the non NCEP models, per WPC. Nevertheless, there still may enough of a warm layer into the se cwa to support mixed pcpn, including sleet and freezing rain along with the snow. ECMWF/GEM QPF into the 0.50-0.75 inch range suggest potential for heavy snow. As the low departs significant lake effect or lake enhanced snow for n to nw flow favored areas will also be possible with 850 mb temps falling to -15C and a shortwave trough moving through. Wednesday-Friday, Once the low moves farther e on Wed, long duration les off Lake Superior will persist with 850 mb temps dropping to -20 to -25C late in the week. Locations affected each day will depend on daily wind directions with nw winds only gradually backing to wnw or w by Thursday and Friday. However, the Keweenaw will see the most persistent LES. Eastern shoreline areas may also get into some of the heavier LES accumulation. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 627 PM EST FRI DEC 30 2016 Next disturbance and associated area of snow will quickly reach the area tonight, leading to period of IFR at all terminals. Some improvement is expected overnight as main snow area departs, but will likely see IFR cigs set in, which may linger for much of Sat morning. Conditions will improve Sat afternoon at all sites as snow moves out. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 329 PM EST FRI DEC 30 2016 As a clipper system moves across Upper Michigan, southeast winds will increase to around 30 knots from west to east across Lake Superior before diminishing in speed briefly and veering to the northeast behind the surface trough and increasing again to 30 knots over north central Lake Superior. With a ridge building into the Great Lakes, winds will diminish Saturday night into Sunday. Northeast winds are expected to increase to 30 knots Monday night and back to northerly Tuesday as a low pressures system lifts toward from the plains through the region. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Winter Weather Advisory from 10 PM this evening to 10 AM EST Saturday for MIZ006-007-014-085. Winter Weather Advisory until 7 AM EST Saturday for MIZ003>005. Winter Weather Advisory until 4 AM EST /3 AM CST/ Saturday for MIZ002-009>011-084. Winter Weather Advisory from 10 PM EST /9 PM CST/ this evening to 7 AM EST /6 AM CST/ Saturday for MIZ012-013. Winter Weather Advisory until 4 PM EST Saturday for MIZ001. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Rolfson LONG TERM...JLB AVIATION...07 MARINE...JLB
Area Forecast Discussion
National Weather Service Norman OK
525 PM CST Fri Dec 30 2016 .AVIATION... South winds will remain rather gusty much of the night before decreasing ahead of a cold front that will move through taf sites late tonight through Saturday morning. North winds will not be quite as strong as wind speeds were today. Otherwise, VFR conditions to continue with only some mid and high clouds expected. 30 && .PREV DISCUSSION... /ISSUED 505 PM CST Fri Dec 30 2016/ .UPDATE... && .DISCUSSION... We have updated the short term grids based on trends of RH values late this afternoon, and for this evening/overnight based on the latest short term model guidance. Spatial details of slightly higher surface dew point plumes will be potentially important for determining RH recovery overnight given the ongoing fires. Based on LAPS analysis and expected trajectories, the RAP seems to have the best handle on the current situation. HRRR is similar but slightly too dry over western north Texas. Current thinking is the area of higher dew points (low/mid 30s) over the southeast Texas Panhandle extending barely into far northwest Oklahoma will continue to advect northeast into the evening and this is where the greatest RH recovery will occur. Further east across central Oklahoma, dew point trends will probably be neutral and may even decrease some into the evening (though probably not to the extent the HRRR depicts) as drier air moves north. As temperatures cool, RH values should rise above 40 percent at all locations except the far southeast shortly after 9pm. Max RH values by morning may only be around 60 percent across the southeast half of the area. The plans are to let the Red Flag Warning expire at 6pm as cooling occurs and RHs begin to rise. A lee surface low is expected to shift southeast into northwest Oklahoma later tonight and southwesterly winds will not decrease much through early tonight, but gustiness should subside just after sunset. A surface trough/developing cold front will progress through the northwest part of the state during the morning. Pressure rises behind this front may be sufficient for 15- 20 knot sustained northerly winds immediately behind the front. BRB && .PREV DISCUSSION... /issued 254 PM CST Fri Dec 30 2016/ DISCUSSION... Although relative humidities are rising across our southwestern counties we will--for now--retain the Red Flag Warning across our entire forecast area. The evening shift will re-evaluate it, and make any necessary revisions. In any case, the Warning is set to expire at 6 pm. A relatively minor cold front will move through Oklahoma and north Texas overnight into Saturday, causing only minor changes in temperature, but will shift winds to northerly and will provide higher relative humidities. A much stronger storm system will organize Sunday into Monday, with its surface low deepening over the central High Plains. For Oklahoma and north Texas, this will bring warmer and more humid air back for a couple of days. There may be sufficient instability for a few thunderstorms in the southeast parts of our forecast area Sunday night and early Monday. If storms do develop, they will be in an environment with quite a bit of low-level wind, and could generate strong, maybe severe, wind gusts. As this storm system`s center moves northeast, a cold front will advance quickly southeast across the southern Plains. It will likely cross Oklahoma from about midnight Monday night into Tuesday afternoon. This will be the beginning of a much colder period. Various reinforcements of the colder air will hold temperatures about 10 to 20 degrees below the average for this time of year. While models disagree on details, it does appear fairly likely that some moisture will be pushed over the cold surface air by southwest winds aloft. This scenario can produce any type of winter-style precipitation, and the exact type depends on the temperature profile at the time. It is way too early to be able to forecast the exact type, so our forecast is somewhat oversimplified, and may change significantly before those days actually arrive. At this points, it appears that precipitation amounts will be relatively light, but if any of the precipitation is freezing rain/drizzle, even light amounts can be dangerous. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 39 51 32 58 / 0 0 0 0 Hobart OK 37 50 29 57 / 0 0 10 0 Wichita Falls TX 43 56 33 64 / 0 0 10 10 Gage OK 31 46 24 57 / 0 0 0 0 Ponca City OK 35 47 27 54 / 0 0 0 10 Durant OK 45 62 43 64 / 10 10 10 20 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...Red Flag Warning until 6 PM CST this evening for OKZ004>048- 050>052. TX...Red Flag Warning until 6 PM CST this evening for TXZ083>090. && $$ 12/30
Area Forecast Discussion
National Weather Service Phoenix AZ
605 PM MST Fri Dec 30 2016 .SYNOPSIS... Periodically unsettled weather will affect the region through Sunday as a result of two low pressure systems. The first will bring the best chances for rain tonight into early Saturday while the second colder system will move in Saturday night and early Sunday. Rain will be likely Saturday night and Sunday morning with lingering showers across eastern Arizona Sunday afternoon. Mostly dry but continued cool and somewhat unsettled conditions are likely for much of next week. && .DISCUSSION... A compact vorticty center was penetrating into inland California early this evening, and moisture flux through the H7 layer was spreading into western AZ faster than most models had previously suggested. While vorticity advection was somewhat lagging this slug of moisture, subtle H7 frontogentical forcing and isentropic ascent around the 300K layer were supporting rather widespread light showers through much of La Paz/western Maricopa counties. For the most part, rainfall accumulations have been solidly in the 0.05-0.20 range. Accordingly, have substantially increase POPs in these areas while also making some modest increases downstream as vorticity forced ascent should better overspread central AZ and further help midlevel showers develop later this evening. && .PREVIOUS DISCUSSION... /248 PM MST Fri Dec 30 2016/ Latest runs of the HRRR are not nearly as bullish with regard to the potential for precipitation, while the local WRFs still suggest a batch of scattered shower activity will move through overnight albeit with less QPF than earlier projections. Forecast rain totals have consequently been lowered slightly in the line with the latest multi-model consensus. Although CAPE will certainly be lacking overnight, sufficient instability associated with the cold pool aloft could produce a few lightning strikes and thunder was introduced in the forecast. Latest guidance also indicates that showers will clear the lower deserts in the morning, but linger across the higher terrain east of Phoenix into the afternoon. Next shortwave trough, fast on the heels of the first one is currently located off the Oregon coast. This system is comparable to the first in terms of moisture transport but stronger in terms of vorticity-forced ascent. Models have exhibited a discernible trend towards a slower arrival and a slower exit. Highest forecast PoPs were consequently shifted into the early and late morning Sunday for much of the area. This second and stronger "kicker" low will move southeast along the California coast Saturday with the low center eventually moving into far SE California Saturday evening. The low will bring 100m or more of 500mb height falls into far SE California and far western AZ on Saturday night along with an even more impressive mid level Q convergence bullseye. UVV/RH cross-sections from the GFS depict 15- 20 ubar/s from the surface to over 500mb combined with a nearly saturated column moving across far SE CA Saturday night. As such, widespread showers of light to moderate rain will develop Saturday night out west, and we have raised POPs to around 80 percent accordingly. QPF values were also raised based on the dynamical potential of the approaching low in conjunction with QPF forecasts from WPC and the GFS/ECMWF. GEFS ensemble members are in very good agreement through the weekend with both lows and confidence in the expected weather pattern is rather high at this time. Rainfall amounts from the southwest AZ deserts into far SE California will range from one quarter inch to one half inch. The widespread rains will spread east and into Arizona during the day on Sunday as the upper low center swings by along the AZ/Mexican border. At this time, we expect the weather to come in the form of showers. However, thunder is not completely out of the question but it appears a bit too stable to warrant mentioning storms in the forecast at this time. Of course, we are expecting much cooler high temperatures this weekend given the influence of the cooler air mass and the considerable clouds/widespread showers. High temps in the central deserts should drop into the low to mid 60s Saturday and then into the upper 50s to low 60s Sunday - well below seasonal normals. For the early portion of next week - Monday into Tuesday - cooler and unsettled conditions will remain in the weather picture as a large area of low pressure develops over the western CONUS centered north of Arizona. A moist westerly flow will set up across the area with weak impulses moving quickly through the flow. Given the fact the the boundary layer remains somewhat moist, we can expect a persistent slight chance of showers both days over the lower Arizona deserts with just single digit POPs into the far SE California deserts. High temperatures remain in the low 60s for the most part each day over the lower deserts under mostly cloudy skies. For the latter portion of the extended, Wednesday into Thursday, we can expect continued cool and somewhat unsettled conditions under the influence of the large western CONUS upper trof. GEFS ensemble members become very chaotic and differences develop between the operational GFS and ECMWF with the GFS wetter and more aggressive with more disturbances moving through the trof and across Arizona. We will go with a middle ground and have our POP trends more or less mirror the NAEFS POP trends, keeping single digit to slight chance POPs in the forecast where the best precip threats remain over higher terrain to the east of Phoenix. A couple of additional mentions: at this time, we do not expect any significant wind during this unsettled period. It will breezy at times, but winds should remain well below advisory levels each day. Also, snow levels remain rather high into early next week; and as such, we don`t expect any snow issues during the periods of heaviest QPF. Snow levels do fall well below 5000 feet later next week as colder air continues to filter in from the northwest, but by then precip chances are low and as such no snow issues. && .AVIATION... South-Central Arizona including KPHX, KIWA, and KSDL: Showers will begin to affect the Phoenix terminal generally staring in the 02-04Z time frame (somewhat earlier than previous thought), and persisting into the overnight hours. Confidence is fairly good that cigs will drop into a 5K-6K ft range with these rain bands. There may be a brief period of MVFR vsby in any more moderate showers, but not temporally persistent. Conditions should improve into higher VFR conditions by late tonight. Some showers may linger over the eastern parts of the terminal footprint Saturday morning with clouds/mist leading to at least partial mountain obscuration. Otherwise, cigs in a 4K-5K ft range should redevelop Saturday afternoon with partial daytime heating. Sfc winds will remain rather light, and be quite variable depending on positioning of shower activity. Southeast California/Southwest Arizona including KIPL and KBLH: Showers will clear SE CA terminals by mid Friday evening with 8K-10K ft cigs becoming more scattered overnight. Some early morning patchy ground fog could be possible near sunrise, though confidence is far too low to include in this TAF package. Otherwise, sfc winds will favor a S/SW component ahead of the next weather system which will affect these terminals Saturday night. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Sunday through Thursday: The second and more potent weather system will make a swift exit to the east, but lingering trough heights and still moist airmass will allow for light shower potential over south-central AZ districts and portions of the Rim/eastern AZ higher terrain through midweek. Much cooler temperatures will prevail for much of the week, closer to or below seasonal normals for a change. Unsettled storm pattern will remain over the western U.S., allowing for cool temperatures and only modest drying to settle into the districts by midweek. Winds speeds overall will follow typical drainage and diurnal patterns while remaining rather light and generally under 10mph. && .SPOTTER INFORMATION STATEMENT... Skywarn Radio Net activation is not expected this week. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at DISCUSSION...MO/Hirsch/CB AVIATION...MO FIRE WEATHER...Nolte
For frequently asked questions about the Area Forecast Discussion
Area Forecast Discussion
National Weather Service Tucson AZ
836 PM MST Fri Dec 30 2016 .SYNOPSIS...As the first in a pair of storm systems approaches the area, valley rain showers and high peaks snow showers are expected to develop through early Saturday morning. Then a second system will bring more significant showers and mountain snow late Saturday night into Sunday. Beyond that, cooler temperatures and a few showers are possible through much of next week. && .DISCUSSION... Quite a variety of conditions across the region this evening as very isolated showers developed and moved through Tuscon shortly after sunset. While the majority of the metro didn`t see any rain whatsoever, some locations saw anywhere from a few sprinkles to a third of an inch. Radar mosaic as of 0330Z continued to indicate isolated showers north and east of Tucson along with some additional showers moving into far western Pima Co. These western showers were associated with an upper low/trough that was slowly making its way inland and was located over the lower Colorado River. Incoming 00Z model guidance continues to suggest that showers will develop across the area late tonight as the upper trough traverses the state and based upon observational trends to the north and west, this seems to be playing out as expected. The normally reliable HRRR is much less enthused about precip chances as the trough moves through Tucson and points east, but nearly every other available convective allowing model suggests scattered showers across the region. As such, I will retain the inherited PoPs and only make slight adjustments near Ajo where rain will likely be wrapping up sooner than later. Otherwise the forecast for the rest of the night looks in decent shape with no significant revisions necessary. && .AVIATION...Valid through 01/06Z. A bit of a break across the area as of 0330Z however showers will develop after 06Z with occasional periods of showers affecting TUS and OLS. Chances at DUG are a bit less. Conditions will improve a bit during the daytime hours but 5-8kft cigs are likely to hang on throughout the day at all sites. The previously mentioned system progged to arrive late Saturday will likely not affect any of the TAF sites until early Sunday morning, thus it`s too early to introduce any precip into the forecast. Could be some late day breeziness across the area, but aviation impacts should be minimal. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...An approaching weather system will spread showers across the region tonight with an outside chance of lightning strike or two. After a break in the showers Saturday afternoon and the first 2/3rds of Saturday night a second system will spread showers and mountain snows across the area late Saturday night into Sunday. The snow level with this system will generally be above 6000 ft with the bulk of the snow above 7000 ft. Mostly dry weather with seasonable temperatures is expected Monday through Wednesday. Then there is a potential for colder air to invade the area late in the week. Other than a SW breeze Saturday and Sunday no significant winds expected. && .PREV DISCUSSION... Dry weather continues across most of AZ early this afternoon with plenty of cloud cover limiting the rise in temperatures. The first of a pair of storms to affect the region is just now moving onshore in the vicinity of Los Angeles with a band of showers entering far western AZ. This entire system will translate eastward pushing into western NM late Saturday morning. Showers will develop eastward later this evening...reaching the Tucson metro area before midnight and the eastern part of Cochise county several hours before dawn. SPC has us in the Day 1 (12Z-12z) chance of thunderstorms and looking at the model data there is a small chance with the system as it rolls across tonight with rather low capes. Convective allowing high res models indicate there is some potential. With all that I added a slight chance of storms to the forecast for tonight. With rather high snow levels and unimpressive QPF would only expect a few inches of snow across the highest peaks about 8000 ft on up with 1-4 inches Sky Islands and a bit more over the White mountains 3-6 inches. Once this system pushes east early Saturday we will have a relative break later Saturday until the early morning hours Sunday. With shortwave ridging passing overhead I dropped pops back to basically chance mountains and slight chance valleys. With the amount of moisture we will have available and some low level instability can`t rule out a shower or two especially north, they will just be rather limited. The second system continues to be modeled rather consistently with the GFS tracking just a tiny bit further south. Precipitation from this system is expected to hold off till well after the celebrated midnight hour passes and I adjusted the forecast to account for that. Basically this is looking like a somewhat weaker version of the strong frontal system that passed through last week with a bit more moisture. Based on current timing the associated front should pass Ajo around dawn, Tucson around 11 am and the eastern border near sunset with a decent temperature drop following. High temp in tucson could be around 10-11 am. The bigger story with this system is the precipitation and the lower snow levels, that is if the QPF forecast works out and that is problematic. Model QPF solutions have a very large spread and recent SREF plumes have dropped back a bit. I tweaked a bit here and there to account for the above timing/POP thoughts and we remain a bit on the higher side of median at the moment. Some concern we may be bit high. With that said going with the idea of 0.10-0.50 inches of rain in the valleys and 0.75-1.25 liquid equivalent for the mountains which would be good for the 6-12 inches of snow we have forecast above 7000 feet for Sunday for the southern mountains and a bit less over the Whites. The bulk of the precipitation will fall a few hours either side of the front and mountain snowfall near the time of the frontal passage could fall at the rate of 2-4 inches per hour for short periods of time. Held off on an advisory headline at this time to avoid confusion with tonights system and earlier mentioned QPF concern. This system will quickly move east Sunday evening with showers coming to an end and cooler temperatures settling in. For the Monday through Wednesday time period a large mass of very cold arctic air will settle over the northern part of the west and central part of the country leaving our area in some decent westerly flow aloft that is a bit moist. hard to rule out a few light showers or mountain flurries through this time frame so have slight chance POPs running mainly northern areas. Temperatures near or slightly below seasonal averages. Interest then turns toward the end of next week where there is some potential for some of that cold air to spill south over our area. Long range models trending in that direction for Thursday through Friday for a short shot of colder temperatures. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ PUBLIC...Leins/Cerniglia AVIATION....Leins FIRE WEATHER...Cerniglia Visit us on Facebook...Twitter...YouTube...and at