Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/01/18


Area Forecast Discussion
National Weather Service Taunton MA
1032 PM EST Wed Jan 31 2018 .SYNOPSIS... A weak warm front may bring some light snow accumulations north of the Massachusetts turnpike late tonight into Thursday morning. A cold front then may bring a period of mixed precipitation changing to snow Thursday night into Friday morning with some light accumulations possible. A brief shot of arctic air Friday night into Saturday with wind chills dropping to between zero and 10 below zero. A storm system will likely bring rain and/or snow to the region Sunday into Monday morning...but precipitation types and amounts are highly uncertain. Another storm system may bring more rain and/or snow to the region sometime Wednesday into Thursday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Abundant low level dry air still in place, but it was slowly eroding. Latest few runs of the HRRR appear to have a good handle on the timing, so used it as the basis for updating the timing of this forecast. Thinking the best window for any accumulating snow will be between 2 AM and 6 AM. Not as confident in the southern extent of snowfall, especially south of the Mass Pike. Minor tweaks to temperatures and dew points to reflect observed trends. 645 pm update... Mid level cloudiness continues to overspread the region. Temps were mainly in the 20s early this evening and will generally remain steady or slowly rise overnight...especially near the south coast as southerly flow develops. Still looks like main threat for snow will be along the east slopes of the Berks and north of MA Turnpike...mainly after midnight and into Thursday morning where some locations may receive an inch or two of snow. Greatest risk will be across east slopes of Berks/northern Worcester Hills and perhaps into Essex county. This may impact the am rush hour given cold ground temperatures and previous forecast handles this well. Previous Discussion... * Accumulating snowfall north of the Mass Pike for the Thursday morning commute * Zonal flow aloft with southwest flow in the mid-levels. This southwest flow will yield to some warm advection across the region and increase the moisture aloft. Cold surface temperatures/cold dome over the region in combination of the WAA and isentropic lift will result in snow showers for the area tonight. Light snow showers will start after 03z but the area and intensity will increase after 06-09z as LLJ begins to strengthen. NAM and GFS model soundings also indicate some lift within the snowgrowth region around 6-8 units of omega. Again, while not a lot, just enough to produce snowfall for the northern half of the region. Locations south of the Pike and east of I-84 will probably see just a flurry or two. Still a lot of dry air in place for much of the overnight and mid-morning hours. While this won`t be a significant event, the timing of snowfall appears to fall during the Thursday morning commute. Because of the cold surface temperatures, snowfall will quickly stick to area roadways, especially if untreated. Current thinking is half of an inch or less for locations around the Mass Pike and I-84. For 1-2 inch amounts, highest confidence will be across Route 2 and areas north. The east slope of the Berks and the west side of the Worcester Hills could also see 1-2 inches. This is due the southwesterly flow resulting in some upslope along the Worcester Hills. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/... Thursday afternoon into Friday Warm front to the north with cold front approaching from the west for this time period. Mid and upper flow amplifies slightly with a broad trough over much of the northern CONUS. Weak isentropic still during the day which could erode the near-surface dry layer (south of the Pike) and result in some scattered showers. P-type should mainly be rain as the boundary layer warms through much of the day. With continued warm air advection, high temperatures are expected to be several degrees above normal in the upper 30s to mid 40s. Upper level disturbance moving through the trough will push an Arctic front from the west towards southern New England late tonight into Friday. Any ongoing precip Thursday evening may transition back to snow as thermals begin to fall below freezing. Main focus for this time-frame is a little anafrontal wave which will move into the region around Friday morning. Models still show a good spread on when this could potential occur. The EC is fastest keeping the bulk of the heaviest precip confined to the immediate south coast, where as the NAM is the slowest resulting in more precip and thus snowfall for a good portions of the area. GFS is down the middle with Hi-res also on the faster side. These waves are quiet tricky as it is all about the timing of the wave and location of the front. Will continue to blend the guidance resulting in 0.5 to 2 inches of snowfall especially across the southeastern half of the region. Unfortunately this will also occur during the Friday morning commute, so a few slick spots are possible. The rest of Friday appears blustery and frigid behind the front as 850 mb temps fall below -20C. Temps at the surface may remain steady or fall during the day, as heating will be limited. Westerly winds will increase to 25-30 MPH resulting in wind chill values in the single digits. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Highlights... * Dry but a brief shot of arctic air Fri night into Sat * Storm expected Sun into Mon am but ptype highly uncertain * Another storm system possible Wed and/or Thu Details... Friday night and Saturday.... A brief shot of arctic air Friday night into Saturday as 850T drop below -20C. Low temps Friday night should drop mainly into the single digits to lower teens along with gusty northwest winds. Wind chill values should be on the order of zero to ten below zero. High temps on Saturday will be held in the 20s. Sunday into Monday morning.. Interesting and another difficult forecast Sunday into Monday morning. Models indicate an initial wave of low pressure lifting towards the Great Lakes on Sunday. This results in a burst of warm air advection aloft and at the surface. Ptype would probably be initially snow for much of the region...but might be a quick change to rain on the coastal plain depending on strength of warm air advection. Antecedent airmass is pretty cold...so will have to factor that in as well. Attention will then turn towards developing low pressure off the mid Atlantic coast. While current track is uncertain most of the data suggests something near the far southeast New England coast to around the Benchmark. One would think this would be favorable track for heavy snow given time of year/climatology. However...the initial low that tracks towards the Great Lakes appears to warm the mid levels considerably making it tough for a significant snow event along the coastal plain given GFS/ECMWF solutions. This is especially true with the lack of high pressure to our north. With that said...The GGEM indicates a colder/snowier solution Sun into Mon am as it is weaker with that initial low headed towards the Great Lakes. This limits the mid level warm advection ahead of the developing coastal storm. In a nutshell...it is too early to rule anything out but greatest risk for significant snowfall appears to be across the interior. A snowier scenario would feature a weaker initial low tracking to our west with a stronger coastal storm. A mainly rain solution would feature the opposite. Monday night and Tuesday... Quieter weather follows Monday night into Tuesday, although can not rule out a few rain/snow showers Tuesday but does not look like a big deal at this point. Wednesday into Thursday... Low confidence in this time range...but guidance indicates the potential for another storm. Ptype/timing highly uncertain given the time range. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/...High confidence. Before midnight... VFR with southwesterly flow. Midnight til Thursday...VFR with occasional MVFR across the higher terrain and north of the Pike. SHSN increasing after 06z which could result in lower vsbys and accumulating snowfall. Highest confidence is across terminals near route 2 and points north. Snow accum around 1-2 inches possible. Thursday 18z til Friday... Mixture of MVFR/VFR late in the day falling to MVFR during the overnight. A few spotty showers are possible but more widespread precip could move in after midnight. IFR conditions are possible towards the Friday morning push as any rain transition to snow resulting in an inch or two snowfall. Conditions improve to VFR by Friday afternoon. Blustery westerly winds towards the evening with gusts near 25-30 knots possible. KBOS Terminal...High confidence in TAF. Low confidence in light snow risk during the morning push...but odds favor bulk of it staying north of the terminal. KBDL Terminal...High confidence in TAF. Low confidence in light snow risk during the morning push...but odds favor bulk of it staying north of the terminal. Outlook /Friday Night through Monday/... Friday Night: VFR. Windy with gusts to 35 kt. Saturday: VFR. Windy with local gusts to 30 kt. Saturday Night: Mainly VFR, with local MVFR/IFR possible late. Breezy. Chance SHSN. Sunday: Mainly MVFR, with areas IFR possible. Breezy. RA and SN likely. Sunday Night: Mainly IFR, with local MVFR possible. Breezy. SN and RA likely. Monday: MVFR/IFR conditions possible. Windy with local gusts to 30 kt. Chance RA, chance SN, FZRA likely. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/...High confidence. Tonight into tomorrow... S-SW winds increase overnight, reaching at least 30 kt across the waters, although a few gusts could approach Gales, most winds should remain below criteria. Therefore, will continue small crafts, rather than gales at this time, but this will have to be watched. Even though winds may diminish somewhat during the day on Thu, seas will continue above 5 ft, so will maintain the advisories through Thu. Outlook /Friday Night through Monday/... Friday Night: Moderate risk for gale force winds with gusts up to 35 kt. Rough seas up to 10 ft. Freezing spray. Saturday: High risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Saturday Night: Risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Slight chance of snow showers. Local visibility 1 to 3 nm. Sunday: Winds less than 25 kt. Local rough seas. Rain likely. Local visibility 1 to 3 nm. Sunday Night: Risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Rain. Monday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 13 ft. Rain likely. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 10 PM EST Thursday for ANZ231-232. Small Craft Advisory until 7 PM EST Thursday for ANZ233-234- 236. Small Craft Advisory until 7 AM EST Thursday for ANZ230. Small Craft Advisory until 2 PM EST Friday for ANZ235-237-256. Gale Warning until 7 AM EST Thursday for ANZ250. Small Craft Advisory until 10 AM EST Thursday for ANZ251. Small Craft Advisory until 4 AM EST Friday for ANZ254-255. && $$ SYNOPSIS...Frank/Dunten NEAR TERM...Belk/Frank/Dunten SHORT TERM...Dunten LONG TERM...Frank AVIATION...Frank/Dunten MARINE...Frank/Dunten
Area Forecast Discussion
National Weather Service Burlington VT
649 PM EST Wed Jan 31 2018 .SYNOPSIS... A changeable weather pattern is in store for the remainder of the week and into the weekend and early next week. An area of low pressure will affect the region overnight into Thursday. Expect some snow that will mix with light rain on Thursday as southerly winds bring in warmer air. A cold front will bring another round of cold weather to end the week. Another front is expected to move through late Saturday with additional snow, while yet another low pressure area on Monday gives us another chance of snow. && .NEAR TERM /THROUGH THURSDAY/... As of 637 PM EST Wednesday...Massaged pops a bit through the late evening hours to account for current radar/observational trends as surface warm front lifts through the area. Most of the snow has been on the light side (visibilities 1-5sm) and leaned toward a blend of the latest BTV 4km WRF and HRRR output to govern coverage during this time frame. There were no adjustments to our minor snowfall forecast showing totals generally less than in inch in most locations this evening. Prior discussion... Interesting developments on the radar the last few hours with the development of a narrow band of moderate to heavy snow that has developed in association with a burst of warm air advection aloft. Looks like it will be moving across a good chunk of the region by early evening, and could cause the evening commute to be a little slower than normal. It won`t last too long, so accumulations should remain under 1" for the most part. HRRR also suggests the southern portion will be weakening as it moves through. For the rest of the overnight, it`s been a bit of a challenging forecast. After this initial burst of snow, there really isn`t much behind that. Radar mosaics show that, as do the hi-res models. Did use a blend of the hi-res models for the PoPs, and in general have most of the region with <25% chance of precipitation by midnight. There`s really no strong forcing overnight and the moisture depth decreases. So it`s not out of the question we`ll just see some snizzle (very light snow with very small flakes). Perhaps a touch of drizzle? If that happens, we could have a few slick spots since temperatures will be below freezing. Temperatures however will be rising all night, so by daybreak we`ll probably be pushing 30F or warmer from the Champlain Valley westward. Southerly winds will also get a bit gusty in the Champlain Valley as well (20-30 mph gusts). On Thursday, the precipitation should re-develop, especially for the southern half of the region thanks to frontogenesis across that region. Should be mostly light snow, but boundary layer temperatures at lower elevations should be warm enough for a little mix of rain at times. Despite the relatively high chances for precipitation, there won`t be a lot of moisture falling from the sky. Snowfall accumulations will generally be no more than 1" for the lucky people. Have highs into the mid/upper 30s across the Champlain Valley and much of northern NY, though some guidance indicates highs into the lower 40s for some places. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 355 PM EST Wednesday...some interesting weather changes during the period. First off will be the passage of an arctic front Thursday evening into the early overnight hours. Some differences in timing amongst all the models, but best guess is that the front will come through the St Lawrence Valley about 00z Friday (7pm Thursday), reaching the Champlain Valley about 03-05z (10pm-midnight) and then into eastern Vermont by 09z (4am). The snow squall index parameter does show some respectable positive values Thursday evening, indicative of the potential for snow squalls. There will also be a little bit of surface based instability across the St Lawrence Valley. The BTV 4km WRF model does show a couple of linear features resembling snow squalls in the radar reflectivity forecast output. On the negative side, the timing with the lack of daytime heating is not the best for maximizing the intensity of any snow squalls (just like summer thunderstorms). At this point thinking it`s a good bet that we`ll have some snow showers rolling through during the evening in association with the strong cold front, but not enough confidence to blanket a large area with a chance of heavier squalls. Still uncertain if we`ll have the situation to actually issue our first "Snow Squall Warning" product. Later shifts will fine tune that aspect. After the front, temperatures crash. 925mb temperatures by Friday will be down to -20C near the Canadian border to -14C in the south by mid afternoon. Thus surface temperatures are not expected to move much during the day, and may actually slowly fall. Plan for highs only in the teens. Still a fairly tight pressure gradient, and good low level mixing, so we`ll have breezy northwest winds gusting over 20 mph quite often. That will produce wind chills much of the day in the -5 to -15F range. Still a good amount of low level moisture around, so I`d expect the mountains will squeeze out some light snows. Speaking of the mountains, air temperatures at the higher elevations will only be in single digits, with winds producing wind chills well below zero (-20s to -30s, and pushing -45F at the highest summits). Friday night is looking cold, but we`ve seen much worse earlier this winter. Lows should range between +3 to -8F. Some wind will continue for much of the night, so wind chills will bottom out between -10F to -25F. We may end up having some wind chill advisory issuance requirements. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 232 PM EST Wednesday...Should see a cold start to the weekend with 850mb temps of -22C to -25C in place across the North Country and sfc ridge axis cresting across the region during Saturday morning. Generally looking at high temperatures of 15 to 20F Saturday afternoon with light westerly winds in place. It appears a weak frontal system developing across the Great Lakes will bring increasing clouds to the region later Saturday into Saturday night from SW-NE. Should see some developing light snow within the frontal zone, especially across nrn NY where we`ve increased PoPs to around 60% for Saturday night, and 40-50% across VT. Based on present indications, may see light snow accumulations of 1-2" Sat night, with locally up to 3" possible across nrn NY. The increasing clouds and light S-SW winds developing Saturday night will keep temperatures a bit warmer, with lows mainly in the low-mid teens. Next potential coastal low pressure system we are monitoring arrives Sunday night into Monday. Appears the 12Z GFS has shifted a bit further north and west with the sfc low tracking across Cape Cod/sern MA during Monday morning. The sfc low is also a bit deeper at 990mb or so. On the other hand, the 12Z ECMWF has shown little change with prior runs with 999mb sfc low tracking just south and east of the 40N 70W benchmark at 12Z Monday. Both operational runs indicate the system would be rather quick moving, consistent with the open nature of the associated 700-500mb shortwave trough. Appears best potential for accumulating snow would be across central and eastern VT Sunday night into Monday morning. The GFS solution would bring potential moderate snowfall (4-8") across central/ern sections of VT, and we`ll need to continue to monitor this potl. At this point, have raised PoPs, to 60-70% across central/ern VT and 45-60% elsewhere (lowest in the St. Lawrence Valley). Highs on Monday should be in the mid 20s. Should see continued seasonably cold temperatures into Tue/Wed of next week, with highs generally in the low-mid 20s. The 12Z GFS suggests another potential shortwave trough and sfc low near sern New England by Wednesday, but fast nature of the mid-level flow pattern suggests timing of any features out at day 7 will be of relatively low skill at this point. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Through 00Z Friday...Some light snow is moving through the area this evening as a warm front pushes in. Ceilings are generally low VFR, temporarily becoming MVFR/IFR as bands of snow move through. Current radar shows two fairly focused bands of light snow- one falling apart as it moves eastward over the Green Mountains and a smaller band to the west over MSS/SLK pushing east. Will see another hour or so of MVFR conditions over MSS/SLK while the western band pushes through, elsewhere expect just some flurries and lingering low VFR clouds through the night. Gusty southwesterly winds will develop overnight/Thursday morning at MSS/SLK, while BTV/PBG will continue to see southerly winds channeled up through the Champlain Valley. Outlook... Thursday Night: Mainly VFR, with local MVFR possible. Chance SHSN. Friday: VFR. Slight chance SHSN. Friday Night: Mainly VFR, with local MVFR possible. NO SIG WX. Saturday: VFR. Slight chance SHSN. Saturday Night: MVFR/IFR conditions possible. Chance SHSN. Sunday: Mainly MVFR, with areas IFR possible. Chance SHSN. Sunday Night: Mainly IFR, with areas MVFR possible. Likely SN. Monday: Mainly IFR, with areas MVFR possible. Chance SN, Chance SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Nash NEAR TERM...JMG/Nash SHORT TERM...Nash LONG TERM...Banacos AVIATION...RSD
Area Forecast Discussion
National Weather Service Caribou ME
1036 PM EST Wed Jan 31 2018 .SYNOPSIS... A warm front will cross the region overnight into Thursday. A strong Arctic cold front will approach the region from the west late Thursday night and cross the region on Friday. && .NEAR TERM /THROUGH THURSDAY/... 1030 PM Update... The radar loop showed things filling in w/most of the returns being aloft. The high reflectivity across the swrn areas indicative of some light snow moving into western Piscataquis County. The activity is expected to push ne overnight as shown by the latest Canadian GEM and RAP. The latest run of the HRRR aligning closer to the obs and what the radar depicted. Pushed back the timing of steadier snowfall til around midnight. Latest indications given are that the snow will push through fairly quickly due to the 925mb jet moving across the region. Precip shield pushes to the coast and becomes aligned w/the upper flow into midday Thursday. Stayed close to the daycrew`s assessment of going with 1-2 inches of snowfall into early Thursday. Temps look like they have leveled off and are now beginning to rise. Daycrew did a fine job in showing this trend overnight. Previous Discussion... A weakening warm front that will morph into a warm occlusion overnight. A weak shortwave associated with the front will move quickly through the area later tonight. This impetus will be sufficient to generate up to an inch of snow within a few hours. The front pushes through northern zones by late tonight, but the occlusion will tend to stall towards the coast into Thursday morning as it becomes parallel to the flow and a weak baroclinic zone emerges. This means up to 2-3 inches of total snow for Bangor, southern Penobscot County and much of Hancock County by midday Thursday. There`s still a lot of NWP uncertainty as to the exactly where the front stalls and how much precip falls, but would tend to favor a position closer to the coast and the greater thermal gradients. Towards the coast, strong warm advection will create some boundary layer P-type issues during the morning and allow mixing with rain. This warm air will be drawn northward Thursday afternoon. Temperatures will reach the lower 40s on the coast and nearly 30F all the way to the Saint John Valley. The remnants of the precipitation shield will tend to lift back to the north by late morning with the warm advection, but no further accumulations are anticipated. One item to watch as this precip does move back to the north will be freezing drizzle. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... Sfc low wl be to our north by the start of the short term with a trailing cdfnt down acrs the international brdr. Expect that sctd snow showers wl be ongoing on Fri evng ahd of boundary. By Fri morning expect that cdfnt wl bisect CWA with temps falling throughout the day. Maxes wl lkly be similar to ovrngt lows Cannot rule out a snow squall along the bndry drg the mrng hrs as fropa occurs. As the time gets closer and bcms more certain wl be able to add in blowing snow to fcst. NW flow conts thru the end of the short term with hipres building off of the mid-Atlantic coast by 00z Sun. Coldest temps look to be on Sat mrng with lows blo -10F and in the single digits in Downeast. Winds wl still rmn high under strong pressure gradient and wind chills are expected to drop blo -20F north of Katahdin by midnight and into mid-morning Sat. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Hipres wl shift east offshore Sat night as cyclogenesis occurs acrs the lwr MS Vly with overrunning pcpn dvlpng aft midnight Sat night and contg thru Sun along wmfnt. All med range guidance is in good agreement that lopres wl mv up the ern seaboard on Mon tho differ slightly on location and timing. GFS ensemble mean places coastal low just south of Penobscot Bay in the Gulf of Maine which is about 300 miles northwest of operational GFS, with latest EC and CMC sw of Cape Cod by 12z Mon. Either way it appears that this wl be our next potential significant storm to effect CWA. NW flow mvs in its wake of system for Mon night with hipres briefly building in Tue morning with another potential system for mid-week. && .AVIATION /04Z THURSDAY THROUGH MONDAY/... NEAR TERM: VFR conditions prevail until shortly before midnight. At that point a burst of snow lasting several hours will create IFR conditions at all terminals until later tonight. The snow will move out of locations north of HUL...but may stall into Thursday morning and continue to provide IFR vis at locations such as BGR and BHB into late morning. By afternoon, all sites will be varying between MVFR and VFR due to cigs. SHORT TERM: MVFR/IFR expected into Fri morning at all terminals. Will see improvement to VFR Fri evening in wake of frontal passage, though expect brief IFR in blowing snow along cold front. VFR expected through the day Saturday with conditions lowering to MVFR/IFR late Sat night through the end of the period. && .MARINE... NEAR TERM: Winds will pick up ahead of a frontal system tonight with a few gusts reaching 35 kts, but did not feel that winds would exceed that threshold consistently for any extended period of time and continued with the SCA through Thursday. SHORT TERM: SCA conditions expected with seas and winds expected thru Fri with marginal gale force conditions Fri night. SCA conditions expected to continue through the weekend. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory until 4 PM EST Thursday for ANZ050>052. && $$ Near Term...Hewitt
Area Forecast Discussion
National Weather Service Gray ME
959 PM EST Wed Jan 31 2018 .SYNOPSIS... A warm front will move in from the west tonight with some light snow ahead of it continuing into Thursday. A cold front moves through from the northwest Thursday night with a return to much colder temperatures behind it through the end of the week. Low pressure may affect the region Sunday into Monday with high pressure building in thereafter. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 955 PM...Minor ESTF update to ingest the current mesonet into near term grids. Prev Disc... 720 PM...For this ESTF update I scaled back pops over the next few hours as the initial surge of warm air advection snow has largely dried up as it moved into the forecast area. Temperatures were adjusted downward a bit...especially over northern and eastern sections where thicker cloud cover has yet to arrive and put a damper on radiational cooling. I adjusted near term grids to reflect latest satellite and radar trends as well as the current mesonet. Prev Disc... A short wave trough and attendant burst of WAA moving eastward across Upstate NY as of this Wednesday afternoon will continue moving eastward this evening. Regional radar mosaic shows relatively narrow band of light to moderate snow from KART-KBGM as of 1945z. This band will progress eastward and move into portions of central and southern NH early on this evening, then progress across the rest of our northern (and perhaps central) zones through the evening hours. A little bit uncertain at this time about how well the southern end of this band will hold together, but could see an hour or two burst of snow this evening across even portions of southwestern NH. Will keep an eye on that. Either way, highest PoPs will be across the north. An inch or two of snow may fall this evening across northern and some central zones with this feature. After midnight, jet dynamics increase a bit and mid level frontogenesis strengthens - mainly from central NH eastward to southern ME and then northeastward to the Midcoast. Again, we are somewhat uncertain how strong the forcing for ascent will be with this but it should be enough for light snow to break out in these areas especially given the modest omega in a saturated dendritic snow growth zone predicted by several deterministic models. The best chance of accumulating snowfall will likely remain north of the ASH/MHT (and possibly CON) but we are still going with at least high chance to low likely PoPs there due to the uncertainty in positioning of narrow zone of ample forcing. Will be good to watch hourly trends in the HRRR as the evening wears on. In any event it appears that the morning commute could be a slippery one across mainly central NH eastward to southern ME and the Mid coast. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Band of mainly light but accumulating snow should be ongoing at the beginning of the period early Thursday morning across central and southern zones with a relatively narrow band of frontogenetical forcing. Therefore, as mentioned in the paragraph above, the morning commute could be slippery in these areas. This band should lift northward as the day progresses with temperatures rising to above freezing across southern zones as well as along the coast. A cold front approaches from the west Thursday evening and crosses the region during the night. Snow squalls may accompany this front - especially across NH. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Overview: Looking ahead to the end of the week and the weekend the overall pattern remains fairly constant through the start of next week. Aloft, a broad trough remains over the eastern portion of the CONUS with a high over low block in the Gulf of Alaska. This is once again setting it up for the cold polar air to funnel southward across the Canadian prairies and into our area over the weekend. This airmass is slightly warmer than what we saw at the beginning of January but will still bring a return to below freezing temperatures. As we move into the end of the weekend the long wave trough will set up allowing for a storm track to move up the east coast drawing good moisture out of the southeast US. The first waves drops around this trough late Sunday initiating cyclogensis for Monday along the eastern seaboard with additional waves bringing more snow potential later in the week. Friday: A cold front will cross the area Friday morning ushering cold air advection and gusty winds for the remainder of the day. A few snow squalls are possible in the morning along the frontal boundary, especially over southern New Hampshire. By Friday night cold air is firmly in place as 500mb temperatures fall to around -25C. Overnight low temperatures will be back below zero in the north with single digits all the way to the coast. With the strong pressure gradient in place expect winds to continue through the overnight hours. While this will limit radiational cooling and likely keep temperatures a bit warmer, the combination of wind and cold temperatures will likely necessitate a wind chill advisory across the northern portion of the area. Saturday- Sunday: Saturday will be clear and cold as high pressure crests over the region. That high pressure will shift east overnight Saturday starting the return southwesterly flow and increasing temperatures for Sunday. Monday: Confidence is increasing for a coastal low to impact the area on Monday. Ensemble members and deterministic guidance all have cyclogensis occuring somewhere near Delmarva and moving northeast up the coast through the day in a classic nor`easter track. As with any coastal storm, the exact track will be paramount to determining the precipitation type along the coast. While some mixing is certainly possible, have leaned a bit colder with the surface temperatures with this forecast package keeping the rain/snow line just offshore as models tend to be aggressive in bringing warm air inland. Another wave moves in with additional snow possible Wednesday into Thursday. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Short Term...VFR conditions early on this evening will deteriorate to MVFR or lower at most terminals as the evening progresses into the overnight hours as light snow develops. These conditions should remain in place during the day on Thursday for most areas - however MHT and CON may escape with low-end VFR. Long Term...Brief chance for snow squalls MHT and CON Friday morning and the front moves into the region. Thereafter cold air advection will bring gusty northwesterly winds with VFR conditions. Winds will diminish late Friday night with VFR returning through the weekend. A coastal low impacts the area on Monday bringing widespread snow and IFR. && .MARINE... Short Term...Gales have been posted for a relatively short period of time tonight (midnight to 7 am) for the ocean waters as southerly flow with gusts around 35 kt occurs. These winds should diminish early Thu morning but SCA conditions are still likely. Long Term...A cold front will cross the waters on Friday. Behind the front cold air advection will lead to gust northwesterly winds. A gale warning will likely be needed, but due to the existing Gale headline for tonight no watch was issued at this time. Winds will subside on Saturday as high pressure moves over the waters for the weekend. Onshore flow develops Monday night with increasing wind and waves ahead of the next system. && .TIDES/COASTAL FLOODING... Will continue to monitor water levels through the remainder of the week as astronomically high tides continue through Saturday. Very light winds should preclude any issues tonight...but a southerly component to the flow suggests at least a low risk for minor flooding with both the Thursday and Friday morning high tides. Astronomical tides peak on Thursday (11.6 feet at 1120 am in Portland Harbor). && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until noon EST Thursday for ANZ151-153. Gale Warning until 7 AM EST Thursday for ANZ150-152-154. && $$ ES
Area Forecast Discussion
National Weather Service Topeka KS
936 PM CST Wed Jan 31 2018 .UPDATE... Issued at 936 PM CST Wed Jan 31 2018 The last couple runs of the RAP and the 00Z NAM show pretty good cold air advection through the day tomorrow with mostly cloudy or overcast skies at least through the morning. Looking at OBS upstream and there is a much colder airmass across the Dakotas poised to advect into the area. Because of this have lowered highs for Thursday and only show a slight diurnal warmup in the afternoon when clouds should thin. If mid clouds hold in through the afternoon, this may be a little optimistic. && .SHORT TERM...(This evening through Thursday) Issued at 335 PM CST Wed Jan 31 2018 As of 21Z Wednesday afternoon the stubborn northwest mid level flow continues across the Plains states. Mid level Pacific moisture continues to stream across central US, yielding scattered mid and high level clouds. A surface cold front traversed the CWA through the morning hours and now resides across far southeastern KS. Little CAA behind the front has allowed temperatures to reach the low 50s this afternoon. Tonight - Tomorrow: Surface ridge axis will traverse the CWA overnight, ushering in the initial push Canadian air. Low temperatures will reach mid 20s to near 30. Northerly winds will increase behind the surface ridge to 10-15kts with gusts upwards of 20-25kts. The continued CAA will only allow high temperatures to reach the upper 20s to mid 30s Thursday afternoon. .LONG TERM...(Thursday night through Wednesday) Issued at 335 PM CST Wed Jan 31 2018 Transitioning into the extended period, the pesky northwest mid level flow will remain across the central Plains. The aforementioned surface ridge axis will position overhead Thursday night/Friday morning, allowing temperatures to bottom out in the low teens. Surface high pressure will move into the mid- Mississippi valley Friday allowing southerly surface flow to return to the central Plains. Continued southerly flow will allow high temperatures to reach the 40s and 50s Saturday afternoon! A mid level shortwave trough and associated surface trough are progged to traverse the central and northern Plains Saturday night/Sunday. EC/GFS/Canadian solutions all bring a few hundredths of QPF to the entire CWA, which would fall as all snow. The active northwest flow looks to continue into next week with a secondary shortwave trough traversing the area Monday night/Tuesday. Great uncertainty exists amongst guidance regarding QPF amounts, although any precipitation would fall as all snow. Otherwise, temperatures look to remain in the 30s for Tuesday and Wednesday of next week. && .AVIATION...(For the 00Z TAFS through 00Z Friday) Issued at 502 PM CST Wed Jan 31 2018 Models are trying to develop some light QPF across central KS with the FROPA Thursday morning. However forecast soundings do not really moisten up. So even flurries appear improbable. Still would anticipate VFR conditions prevailing even if there is some light precip. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Wolters SHORT TERM...Baerg LONG TERM...Baerg AVIATION...Wolters