Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/16/17

Area Forecast Discussion
National Weather Service Gray ME
1051 PM EST Wed Feb 15 2017 .SYNOPSIS... Low pressure will rapidly develop in the Gulf of Maine tonight and pulls away Thursday leaving behind upslope snow showers in the mountains. High pressure will build into the region on Friday as the storm departs to the maritimes. A few upslope snow showers will linger in the mountains through Saturday but elsewhere skies will be mainly sunny. Temperatures will warm through the weekend reaching the mid 40s by Sunday. && .NEAR TERM /THROUGH THURSDAY/... 1045 pm...Second band of moderate to heavy snow extends from from around KLEW southward through the Portland area, and then offshore of York and Rockingham counties. This band should shift W through around 06Z or so before dissipating. Rates of an inch an hour are likely in this band, and could see them as high as 2" per hours. HRRR has been excellent with these bands today and tonight. Will hold the WSW for now as we will see some synoptic snow developing over the ern zones, but may be a struggle to reach warning criteria here. 8 PM...Intense sfc convergence, along with mid lvl frontogenesis have combines to produce a persistent band of heavy precip from around Casco bay NW through Cumberland and southern Oxford counties. We`ve had reports of 2-3" an hour for a couple hours in this band. Just got reports in the last hour of a changeover along the coast and in Portland, which will limit total snow accums there. Forecasts for this evening lean heavily on meso models, including HRRR, and meso model ensembles. This rotates this band of heaviest precip SSE through York county/ including NH border towns in Carroll county/ and then into Strafford and Rockingham toward midnight. The band will weaken a bit later this evening, so amounts to the south will probably not reach the totals we`ll see in interior SW ME, but should still reach warning criteria. This will also limit the snow to some degree over ern zones, and may not see warning criteria here, but will hold the warning to see how synoptic precip develops this evening. Previously...A dynamic storm is in store for this evening and overnight. Temps have pushed into the mid and upper 30s over parts of Srn NH and coastal Wrn ME. This has allowed precip to start as rain. Farther inland snow has continued in the higher terrain much of the day...with accumulations already around 6 inches. Now things really start to get interesting. As mid level low centers rapidly develop this evening...colder air will be dragged back S thru the forecast area. This will turn any rain back to snow. KGYX 88D dual-pol data is already showing low ZDR and high CC values collapsing back towards the coast as heavier areas of lift and precip move thru. At GYX we flipped from light rain to heavy snow in a matter of minutes as stronger lift moved overhead. I expect this to be the trend thru the evening...with mixed precip transition quickly to heavy snow with rapid accumulations. The coast will be the last place to flip back to snow...but when it does it will be a significant hazard for those on the road. Roads will become slippery in a hurry. The surface trof remains wedged at the NH/ME border back towards the White Mtns. I expect it to hold more or less stationary thru the early evening. For that reason I have focused the higher QPF across extreme SWrn ME into the White Mtns. Later this evening strong low pressure developing in the Gulf of ME will drag this trof Swd. This should be when the heaviest snow occurs for Srn NH. It may not last more than an hour or two...but snow could be very heavy for that short duration. For the rest of the night intensity of snow will taper off but continue into morning. Headlines remain as they were earlier today. Highest snowfall amounts should be near the NH/ME border...especially where SE facing upslope assisted in lift. The lowest confidence in snowfall amounts are just W of the current trof axis...where shorter duration of snowfall may limit totals some. Also to the E over central ME...lower snowfall totals are possible due to mixing and lack of precip. Their best snowfall may come later tonight when low pressure begins to throw moisture back NWrd. The very mesoscale nature of this event will lead to some wildly varying snowfall amounts over short distances. && .SHORT TERM /THURSDAY NIGHT/... Low pressure will gradually pull away from the area Thu. Lingering low level moisture and NW flow will lead to plenty of upslope snow showers in the mtns thru the day. An additional several inches of accumulation is possible. We stay in cyclonic flow Thu night...and that should keep the boundary layer fairly mixed. I stayed close to 2 m temp guidance for lows. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... High impact weather potential: None A rather quiet period of weather as we move into the end of the week and the weekend. The forecast begins with a relatively progressive high amplitude pattern over North American. As of Wednesday morning a large ridge was build up through western North American with above freezing surface temperatures all the way to the Northwest Territories in in Western Canada, and a trough moving through New England and southern Quebec. This ridge will move east over the weekend keeping high pressure in control through the start of next week. Friday the departing low will bring upslope snow showers to the mountains of northern New Hampshire. Have increased QPF and snow amounts slightly compared to guidance as those areas are often able to squeeze quite a bit of snow out of this pattern. Saturday a high builds into the region and temperatures will warm above freezing across most of the area. A weak system passing to the north on Sunday may bring a few scattered flurries to the mountains and increasing clouds however temperatures will again remain warm reaching the mid 40s south to upper 30s north. Those flurries and clouds will stick around into Monday. By Tuesday there is the potential for another storm to bring more widespread precipitation. Confidence is very low at this time and have gone with a consensus blend of guidance. && .AVIATION /04Z THURSDAY THROUGH MONDAY/... Short Term...Widespread IFR or lower is expected tonight in deep onshore flow. -RA along the coast will change to SN...heavy at times. Eventually this may even clip CON and snowfall drops Swd tonight. Conditions improve to MVFR and VFR early Thu...except in the mtns where SHSN will keep occasional IFR. Surface gusts around 20 to 25 kts possible at all terminals Thu. Long Term... VFR will prevail from Friday right through the weekend except in the mountains where HIE will see periods of MVFR in SHSN. && .MARINE... Short Term...Winds and seas will build especially behind rapid strengthening low pressure in the Gulf of ME. Gale warnings for the outer waters and SCAs for the bays remain in effect into Thu. Winds and seas will gradually diminish as low pressure pulls away. Long Term... Very quiet period on the waters with high pressure built overhead. Expect conditions to remain below SCA right through the start of next week. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Winter Storm Warning until 10 AM EST Thursday for MEZ012>014- 018>028. Winter Storm Warning until 7 PM EST Thursday for MEZ007>009. NH...Winter Storm Warning until 10 AM EST Thursday for NHZ004>006- 008>010-013-014. Winter Storm Warning until 7 PM EST Thursday for NHZ001>003. Winter Weather Advisory until 7 AM EST Thursday for NHZ007-011- 012-015. MARINE...Small Craft Advisory until 10 AM EST Thursday for ANZ151-153. Gale Warning until 6 PM EST Thursday for ANZ150-152-154. && $$ SYNOPSIS...Curtis NEAR TERM...Cempa/Legro SHORT TERM...Legro LONG TERM...Curtis AVIATION...Curtis/Legro MARINE...Curtis/Legro
Area Forecast Discussion
National Weather Service Marquette MI
658 PM EST Wed Feb 15 2017 .SHORT TERM...(This evening through Thursday) Issued at 408 PM EST WED FEB 15 2017 WV imagery and RAP analysis indicated an amplified pattern with a ridge from srn CA to central Canada and a trough from Quebec into the northeast CONUS resulting in nrly mid/upper level flow through the wrn Great Lakes. At the surface, a ridge from nw Ontario through ern MN was slowly building to the east as nnw flow LES continued across Lake Superior. Tonight, as the ridge builds into the area and the winds diminish, the higher res models suggest that lake induced troughing and land breezes will focus the LES bands into the n cntrl cwa and along the shoreline near Marquette by late tonight. With -16C temps at the top of the 3k ft inversion, expect mainly light snow showers but with high SLR values aoa 30/1 with the shallow convective cloud in the DGZ. Thursday, expect any remaining LES to diminish during the morning as the ridge builds into the ern cwa and winds become offshore. Otherwise, mainly cloudy conditions will prevail with low level moisture remaining below the lowering inversion. Highs will range from the lower 20s east to lower 30s west. .LONG TERM...(Thursday night through Wednesday) Issued at 249 PM EST WED FEB 15 2017 Real good agreement in the models and GEFS ensemble that upper ridge over the western Conus builds across central Plains and Great Lakes Fri into Fri night. Shortwave trough crossing northern Ontario on Sat will flattern ridge slightly but it should build again Sun into Mon with GEFS h5 heights and h85 temps both 2-3 standard deviations above normal. Ridge will result in dry weather this weekend. Main question will be how warm it will get Fri through Sun. Latest NAM indicates increasing moisture 950-900mb (500ft-1500ft agl) as early as Fri and certainly by Sat. Just not sure if this is realistic or an artifact of models trying to generate too much low- level moisture due to warming temps and expected melting snow. Previous GFS runs were showing similar idea with low-level moisture but 12z run looks more realistic with minimal moisture. With ridge overhead, main low and cyclonic flow well to the north across northern Ontario and sfc dwpnts Fri into Sat staying mainly below freezing, have doubts that either day will have bkn-ovc low clouds as NAM would indiate. Could see sct cumulus clouds though. Mixing to 925mb as soundings (even from the drier GFS) show seems too low with upper ridge overhead and plenty of dry air in mid-upper levels. For the warm Monday we saw earlier this week (set record high at NWS MQT that day of 44F) the forecast soundings leading up to that day were indicating similar scenario as NAM indicates on Fri and Sat (low clouds and limited mixing height). Instead INL and GRB RAOBs at 00z Tue indicated a mixing depth to 875mb to 850mb was achieved. Skies were mostly sunny. Though there was stronger mixing on Mon in lowest 5kft compared to what should occur on Sat, think it could end up just as warm if not warmer since h85 temps are much warmer (-2c on Mon and at least +8c on Sat). Will continue to use 900mb temps as gage for high temps which supports highs Fri mainly in the 40s and mainly in the upper 40s to middle 50s Sat and Sun. Since is it forecast to be drier in low-levels on Sun that day may end up the warmer day. Lake breezes are possible either day which would result in falling temps in the aftn locally near the Great Lakes. Overall this weekend will feel more like spring instead of winter. Record highs this weekend are mostly in the 50s to low 60s. Here is a sampling of the record highs for Fri 2/17 through Sun 2/19. Record highs seem possible. Ironwood: 2/17 is 60 (2011), 2/18 is 58 (1981) and 2/19 is 60 (1930) Irn Mtn: 2/17 is 58 (1981), 2/18 is 51 (1930) and 2/19 is 62 (1930) NWS MQT: 2/17 is 61 (1981), 2/18 is 52 (1997) and 2/19 is 46 (1988) Mqt city: 2/17 is 55 (2011), 2/18 is 52 (1954) and 2/19 is 62 (1930) Newberry: 2/17 is 47 (1954), 2/18 is 46 (1997) and 2/19 is 47 (1994) Shortwave trough moving over the Pacific Northwest later this weekend deepens as it tracks across the northern Plains on Mon and over the Great Lakes Mon night into Tue. Sfc trough over the plains on Mon deepens to 995-1000mb low while lifting across northern Ontario by Tue morning. With enough morning sunshine on Monday could see temps again rise well into the 40s if not reach the 50s. Clouds should thicken later in the day though as shortwave comes closer. Upper Great Lakes will be well within warm sector of this system on Mon night with h85 temps up to +10c and sfc dwpnts rising toward 40F. SW H85 winds over 50 kts will pump PWATs over 1 inch or roughly 4-5 standard deviations above normal. The abundant deep moisture should help to develop rain showers over Upper Michigan late Mon into Mon night. Timing still varies, though would expect a period of rain sometime from late Mon aftn through daybreak on Tue. Given strength of theta-e ridge just upstream and moisture advection suppose there could also be thunder. Sfc dwpnts over 40F advecting over the melting snowpack could result in areas of fog Mon night. Sfc trough crossing the area on Tue morning will shift winds to the W or NW pushing a drier and cooler airmass across Upper Michigan through the day. Tue into Wed the shortwave trough will head east across Quebec and New England while weakening. Upper flow will become more zonal again which casts doubt on the cold air that was showing up for mid to late next week in model runs 24 hour ago. GFS remains cooler than ECMWF and GEM especially for middle of the week, but consistency in the ECMWF and GFS runs is lacking. Will leave consensus for now given the poor run to run continuity, but overall think models are heading toward zonal pacific flow pattern with temps at least slightly above normal. Beyond the end of the long term, recent runs of GFS and ECMWF including latest runs hint at stronger storm system over ncntrl Conus late next week (24-25 Feb). That system could bring snow to portions of northern Plains and snow and/or mixed precipitation across Upper Great Lakes. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 631 PM EST WED FEB 15 2017 Lake effect snow showers have diminished this evening and are now only affecting KSAW while light snow approaching the western U.P has also diminished as it moved into the drier air mass in place over the area. Look for MVFR conditions at all the TAF sites to improve to VFR later this evening/overnight as drier air continues to diminish -sn and erode lower cloud cover. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 408 PM EST WED FEB 15 2017 With high pressure building into the region, winds to around 25 knots over the ern lake will continue to diminish tonight. Winds through the weekend will remain at or less than 25 knots as the pressure gradient remains week across the area in the absence of any major pressure systems. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...JLA AVIATION...Voss MARINE...JLB