Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/01/21

Area Forecast Discussion
National Weather Service Gaylord MI
1014 PM EST Sun Feb 28 2021 .UPDATE... Issued at 1014 PM EST Sun Feb 28 2021 993mb low is north of Georgian Bay, with a cold front extending to the south toward western Lk Erie. Cold advection is very much underway, though surface temps remain near or above freezing at this hour. That will be changing, with mid-20s temps in central upper MI, and teens and colder on the other side of Superior. Readings will fall well into the teens in eastern upper and far northern lower MI by dawn, with upper teens to mid 20s elsewhere. Winds have been a little uppity this evening. A number of gusts circa 40mph occurred with and just after fropa, with GLR the exception on the high side at 47mph. That was fine. Just in the past hour though, several gusts in the 45-50mph range have come out of eastern upper MI. Nam Bufr soundings suggest circa-45mph gusts or a touch higher are possible thru about midnight, as momentum is transfered downward in a mixed layer some 3k ft deep. Toward and after midnight, the pressure gradient and associated wind gusts should relax. Given the short duration of continued gusty winds, have issued an SPS to highlight winds late this evening, instead of issuing a very short wind advisory (though that was considered). Lake effect banding just barely starting on APX radar into nw lower MI. More prominent banding has organized east of MQT. 00Z Nam Nest output, and latest HRRR runs, continue to have the strongest band developing into Whitefish Pt/Paradise, and on se across the bay into Brimley/Kinross. Think the idea of the previous forecast is sound: fairly lousy conditions are likely tomorrow morning in the above area due to falling/blowing snow, gusty winds, and cold temps. Did fine tune the location of best snow accums a bit tomorrow, pushing a little further east away from Luce Co. Regardless, 2-6" snow accums are likely overnight into Monday in the area noted above. So posted an advisory for western Chippewa, and ultimately decided to include central Chip as well. Do not think this will be a huge event for the Sault, but places w and s of there (again, Brimley to Kinross) should get enough snow and have enough impact (including to I-75) to warrant including the central Chip zone. No need for winter wx headlines elsewhere, as least yet. Nam Nest and other near-term guidance are not bullish on snow amounts in other parts of northern MI. && .NEAR TERM...(Through Monday) Issued at 328 PM EST Sun Feb 28 2021 ...Much colder air and lake snow showers returning... High Impact Weather Potential: Colder air spills into the region tonight leading to single digit wind chills for Monday. Accumulating lake effect snow showers for the snowbelts. Pattern Synopsis/Forecast: 20Z satellite/composite analysis reveals our open short-wave circulation rolling through northern Wisconsin. Associated slowly deepening surface low pressure is passing through the Iron Mountain area heading toward the eastern U.P. with 3 hour pressure falls centered across that area. Axis of deformation/f-gen forced snowfall continues to pivot through western/central Upper Michigan along the N/NW side of the wave/surface low. Expansive warm conveyor belt/axis of rainfall stretches from Oklahoma ENE across the Mid Atlantic. Much of lower Michigan still sitting in "no-mans" land of sorts between axis of snow to the north and rain to the south. Lower cloud cover has expanding up through our area and there is some showery/drizzly looking returns on radar sliding up through northern Lower Michigan with a little better coverage in eastern Upper. But in all, precip across this CWA has been paltry thus far. Through this evening: Short-wave and surface low will track across eastern Upper Michigan over the next several hours, back- side deformation axis just skirting through eastern Upper Michigan through early- mid evening. Given the further north track of the low, precip across E.UP. will likely remain mainly liquid through early evening anyway until colder air begins to fold back into the region resulting in a few hours of light accumulating snow. South of the bridge, spotty rain showers will continue to move through northern Lower Michigan through early-mid evening with maybe a brief transition over to snow before ending. System continues quickly into eastern Canada tonight. Higher impacts follow with substantially colder air spilling into the state on gusty northwest winds...later tonight through Monday. This will drive temperatures down into the teens by Monday morning with only modest rebounding anticipated during the day Monday. But gusty winds will result in single digit above and below zero wind chill readings Monday morning, quite the change from where have been over the last few days. Lake snows are another matter. Strong cold advection tonight drives H8 temps down to -18C to -22C through Monday resulting in lake induced CAPE values of near 500 J/Kg on Michigan and a little better still on Superior (BufKit suggests a period of moderate to extreme lake effect conditions on Monday). Incoming airmass will be on the drier side however, with single digit dewpoints and PWAT values under 0.10", which might throttle lake effect to some degree. But think we will be able to muster some moderate snow accumulations in the snowbelts. Along with gusty winds and blowing snow, we may need to hoist an advisory for Monday. && .SHORT TERM...(Monday night through Wednesday) Issued at 328 PM EST Sun Feb 28 2021 High Impact Weather Potential: Minimal Pattern Synopsis/Forecast: Ridging makes a return to the Great Lakes for the start of the short strong, anomalous troughing departs (some would say, good riddance). As we get into high pressure on the back side of this troughing...lake effect should be winding down as temps aloft rise...and potential for diminishing cloud cover with still quite cold air aloft should lead to one more very cold night before things warm up again Tuesday. A weak northern stream shortwave will be the next thing to watch going into late Tuesday and early Wednesday...with a more potent shortwave staying well to our south...and that troughing from Monday, still anomalous as it spins off the coast of Nova Scotia (hold that thought till the long term). By Wednesday...upstream flow over the Pacific becomes more amplified...with troughing digging south of Alaska as ridging behind it strengthens...setting the scene for a cutoff low to get kicked eastward into Southern California. As troughing digs toward the western North American coast...will see ridging across the west- central US begin to amplify Wednesday...lending a slight troughy look to eastern portions of the US. Primary Forecast Concerns: Lingering LES, cold temps/cloud cover Monday night...gusty winds and precip chances Tuesday into Wednesday. As shortwave departs eastward Monday night...will see pressure gradient begin to slacken as surface high pressure builds in. This should act to decrease winds for a time. Will see mid-level subsidence move in during the night...which should lead to a decrease in cloud cover. Recent guidance seems to be trending things a tad warmer for Monday night...though there is still a pretty reasonable chance for some locations to bottom out below normal Monday night. Aforementioned mid-level subsidence should also help bring LES chances to a close through the night as inversion heights fall. Can`t rule out it lingering longer into the night north/northwest flow lake effect across eastern Upper and perhaps near or right off the sunrise coast of northern Lower...where 850 Ts look to stay cold enough through at least 6z. As northern stream shortwave (aka, clipper system) approaches from the northwest Tuesday...will see moisture increase from top down. the same time...southwesterly flow will be ramping up as well...between departing surface high to our southeast and low moving through southern Manitoba/Ontario...with a lot of dry air still in the midlevels...and gulf moisture kept busy to our south by potent shortwave moving through the southern stream of the flow across the Gulf coast states. Precipitation may have a hard time reaching the ground...though may have a slightly better chance further north across Eastern Upper, and maybe the tip of the mitt, where synoptic moisture from the clipper will be stronger, and where better dynamics will be located. Will at least see some increased cloud cover...but bigger news will be warmer temperatures as system drags a warm front through the region through the day. Additionally...with strengthening pressure gradient between surface high and incoming low...will likely see winds pick up again during the day Tuesday...leading to another gusty day...though warm advection will be in play this time around. Latest model runs may be trending perhaps a little cooler for Wednesday than they have the last few days...with that northern stream system dragging a west-to-east-oriented cold front into the Great Lakes. Will have to keep half an eye on this for temperature trends...though at least for now, it looks to stay dry. .LONG TERM...(Wednesday night through Sunday) Issued at 328 PM EST Sun Feb 28 2021 High Impact Weather Potential: Minimal...? Remember when I said to hold that thought about Monday`s troughing lingering off Nova Scotia? Well, that pesky bugger may end up helping to bookend our week with colder it looks to linger near the St. Lawrence River/Nova Scotia through the week...and actually attm appears to retrograde for a time, swinging some lobes of colder air into the Great Lakes perhaps even as early as Wednesday night. Perhaps cold enough air aloft to bring LES chances back into the picture...especially if it pans out that the downstream trough will send little lobes of energy knocking on our northern door through the end of the week into next weekend. As such, will have to watch for another incursion of cold air for Friday into Saturday as northerly flow could be continually reinforced across the Great Lakes region for the last half of the week. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 640 PM EST Sun Feb 28 2021 Cigs improving to MVFR this evening. Drizzle/rain ending, -SHSN later tonight into Monday. Low pressure just ne of ANJ. Cold front moving across ne lower MI. Cigs will improve behind the front, with current IFR cigs/vsbys in spots improving to MVFR this evening. But eventually, the incoming air will be cold enough to spawn lake effect snow. Brief vsby restrictions will be possible late tonight into Monday at MBL/PLN and especially TVC. Otherwise a mix of MVFR to VFR cigs. Gusty w winds will veer nw tonight, remaining gusty thru the TAF period. && .MARINE... Issued at 328 PM EST Sun Feb 28 2021 ...Back into a gusty period of time on the lakes... Winds will veer around to the northwest this evening and increase. Might be a short period of gale force gusts on Lake Michigan this evening. But a longer period of gale gusts will be found on northern Lake Huron tonight through Monday. Gale warnings will remain intact as is. Winds will diminish Monday night. But another round of gusty winds is possible Tuesday with gale force gusts possible on Lake Michigan. && .APX WATCHES/WARNINGS/ADVISORIES... MI...WINTER WEATHER ADVISORY from 3 AM to 4 PM EST Monday for MIZ086- 087. LH...SMALL CRAFT ADVISORY until 9 PM EST Monday for LHZ345-349. GALE WARNING until 9 PM EST Monday for LHZ347-348. SMALL CRAFT ADVISORY until 3 AM EST Tuesday for LHZ346. LM...SMALL CRAFT ADVISORY until 9 PM EST Monday for LMZ323-341-342- 344>346. LS...NONE. && $$ UPDATE...JZ NEAR TERM...ADAM SHORT TERM...FEF LONG TERM...FEF AVIATION...JZ MARINE...ADAM
Area Forecast Discussion
National Weather Service Bismarck ND
916 PM CST Sun Feb 28 2021 .UPDATE... Issued at 916 PM CST Sun Feb 28 2021 Snow continues this evening north and east of a surface low centered in far south central North Dakota. The clipper has been pushing south a bit quicker than expected, with snow expanding through the southern James River Valley earlier than forecast, but is also lingering on the back end longer than expected, with snow still ongoing at Minot as of 3 UTC. Made some adjustments to POPs to account for the current radar trends. Snow has become more organized since the last update, maybe not quite to a legitimate banding scenario, but enough to show a moderate area of stronger radar reflectivities where visibilities have been reduced to three- quarters of a mile. UPDATE Issued at 609 PM CST Sun Feb 28 2021 The surface low bringing light snow to the area is currently centered in far west central North Dakota. Snow is ongoing from Crosby, through most of the north central, and into the Harvey/Carrington area, with visibilities dropping as low as one mile at Minot. Some isolated higher radar returns are seen in the south central, but ceilings are still around 5-7K feet, and we haven`t seen any evidence of snow making it to the ground in these areas just yet. Regardless, did go ahead and expand POPs through much of the south central to account for this. Not much change in our thinking regarding snow totals and location, but will keep an eye on things in case we start seeing significantly reduced visibilities and higher snowfall rates, especially since it looks like we`re still an hour or two from the strongest forcing seen in high-res guidance. && .SHORT TERM...(This evening through Monday) Issued at 159 PM CST Sun Feb 28 2021 Main forecast issue in the short term period will be snow amounts and placement with the clipper system tonight. Currently, low pressure is developing near Glasgow in northeast Montana. Clouds continue to thicken over western and central ND. Highs should top out in the upper 30s and lower 40s today west of the Lake and Missouri River, with only teens along the Canadian border. For tonight, the surface low that is situated over northeast Montana will track southeast through west central and south central ND and is expected to be around Aberdeen by around Midnight. This will bring a swath of light snow northwest into central and eastern North Dakota. The trend today has been for this band to shift farther west. The band of heaviest snow, squarely over eastern ND on the midnight shift, is now situated from around Bantry and Towner, to Harvey and Carrington, and southeast to Valley City. The latest few runs of the RAP/HRRR shift it even a little farther west. We are still talking amounts below advisory criteria, but we`re aiming at a moving target. There are a few additional factors complicating things as well. First, there are some indications of some possible banding precipitation along the northern edge of the snow band. The latest RAP shows a band of negative EPV, strong 2D forcing and steep lapse rates from Harvey and Carrington to just North of Jamestown in the 01-04Z timeframe. This is also congruent with strong deformation zone and at tight baroclinic zone within this same area. Second, the latest forecast RAP sounding are quite impressive with the depth of the Dendritic growth zone. Especially from Jamestown and Carrington, where the DGZ extends from the surface to around 700 MB. The DGZ is a bit deeper at Carrington, but the Omega is stronger at Jamestown. Both depict the omega throughout the depth of the DGZ. This resulted in us bumping up the snow ratio`s and finally, the QPF has been increasing with each run. This has resulted in a band of 1 to 2 inches of snow from roughly the Towner area in McHenry county south and east through Harvey and Carrington to northeast Stutsman, with Jamestown right around 1 inch and higher amounts east and north toward Valley City and Cooperstown in eastern ND. if we do get the banding, maybe we see some locally higher amounts to around 3 inches. But the limiting factor is the overall quick movement of the system, as any one area would likely see only 3-5 hours of snowfall, with the heaviest snowfall probably only lasting a couple of hours. The entire area of snow exits the southern James River Valley shortly after midnight. Evening shift will have to monitor any trends in placement and possible banding setting up. It will be cold behind the exiting clipper with lows around 10 below zero near the Turtle mountains, and single digits above or below zero for areas north and east of the big Lake and the Missouri River. The far southwest will be mild spot with lows only dropping into the teens. Monday warms nicely behind the exiting clipper with highs climbing into the 40s and maybe lower 50s west central and southwest. the Turtle Mountains into the James River Valley will be the cool spot with highs around 30. .LONG TERM...(Monday night through Sunday) Issued at 159 PM CST Sun Feb 28 2021 Mild Pacific air builds into the Northern Plains Tuesday through Wednesday with with widespread highs in the 40s northeast to 50s south and west. Upper level ridge amplifies across the Rockies and eventually moves into the Great Plains Fri-Sat. Opted to again go above NBM for daytime highs, going with 60/40 blend of NBM 75th percentile and straight NBM. This results in forecast highs into the 60s Fri-Sun for the west and south central, with 50s reaching the Turtle Mountains area over the weekend. These forecast highs are 25-30 degrees above normal for early March, and we could see a few Max temperature records reached. Also, with these warm temperatures, minimum relative humidity will drop into the upper teens and 20s late in the Work week and through the weekend, elevating fire weather concerns. At this time, the best potential for the combination of strong winds and low RH will be on Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 609 PM CST Sun Feb 28 2021 A clipper moving through is bringing snow to the area this evening and tonight, with KMOT/KJMS likely the only two terminals affected through 06Z. MVFR ceilings and visibilities are possible in any areas of snow. KBIS/KDIK/KXWA are expected to stay VFR through the TAF period. Winds will be variable southwest to southeast ahead of the clipper, then shift northerly behind the system. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...MJ SHORT TERM...TWH LONG TERM...TWH AVIATION...MJ
Area Forecast Discussion
National Weather Service Boston/Norton MA
1026 PM EST Sun Feb 28 2021 .SYNOPSIS... A frontal system moving northeast from the mid-Atlantic region will spread steady light rains across Southern New England tonight into Monday, clearing by Monday afternoon. A strong Arctic cold front will usher in scattered snow showers and possible snow squalls Monday night. It will also produce unseasonably cold temperatures, low wind chills and gusty winds Monday night into Tuesday. Temperatures return to above average levels for midweek, before turning cooler and unsettled late in the week into the weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 10 PM Update... No major changes in the latest update other than adjusting precipitation chances toward high res guidance. This generally keeps chances before midnight north of the MA Pike. Better opportunities of precip south of the MA Pike before 06Z. Best chances of precip are after 06Z, but precip moving in beforehand will generally act to moisten up the lower levels as we are still working on eroding the dry air. Still have the possibility of light spotty freezing rain where the previous SPS was issued and think that this is not out of the question with dewpoints in the lower 30s. After 06Z should see the temps and dewpoints climbing above 32 in the higher terrain. 635 PM Update: Regional radar shows initial slug of isentropically-forced light rains mainly across our southern coastal waters and into adjacent southern CT/Long Island. Drier air seen on morning RAOBs appears to be holding the northward advance of this rain at bay, and while some radar returns are showing up across Hartford County and western MA, looks to be diminishing on approach. Though the HRRR and the 18z NAM-3km still show the best chance of rains across central/southern RI into adjacent southeast MA/Cape thru 02z, I`ve started to decrease PoPs toward lower Chance in that same timeframe for the remainder of Southern New England. Any precipitation that falls will be on the light side, especially further north one goes. It still is possible that some very light frozen precip/freezing rain could result across the higher terrain, though it`s looking more questionable than earlier as dewpoints are rising into the low 30s and lighter precip rates that should temper stronger wet- bulb cooling. The second round of rains then arrives starting after midnight on northeast into the overnight hours, associated with a weak wave low on a frontal zone. Second round of rains should be more steadier than this initial round. It still looks like eastern and southeastern New England stands the best chance of rains from this second slug of precip closer to the track of the weak surface low. Less rains further inland (western/central MA, northern/western CT). This looks on track and didn`t make any significant change for the second half of the night. Previous discussion: Initial surge of light rain approaching southern CT/RI assocd with isentropic lift. Soundings show pronounced dry layer below 850 mb which will slow onset of rainfall but the low levels eventually moisten up this evening from SW to NE. Rain will be overspreading CT/RI and SE MA this evening then pushing northward across rest of SNE. This initial shot of rainfall will be light as best isentropic lift is forecast to pass south of New Eng. There is some concern with shallow cold air across the Berkshires and northern Worcester hills for a time tonight. Dewpoints here in the mid/upper 20s so wet bulb cooling may allow temps to fall to near 32 degrees. This could result in pockets of freezing rain later this evening but coverage is expected to be limited. No advisories planned but will issue an SPS to increase awareness. Another period of rain expected overnight as next shortwave and attendant surface wave approaches New Eng. Focus for this rainfall will be across the coastal plain and SE New Eng coast with moderate rain at times with lighter rain further in the interior. Low temps will be in the 30s, but rising into the 40s SE New Eng toward daybreak. Areas of fog will also develop overnight. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Monday... Lingering rain in the morning assocd with the shortwave passage and low track across SE New Eng. Then we expect rapid improvement in the afternoon as cold front sweeps through followed by rapid drying in the column with PWATs decreasing from around 1" to less than 0.2" by 00z. Expect partial sunshine developing from west to east in the afternoon, although strong shortwave approaching from the west may lead to a few snow showers in far western MA late in the day. Strong cold advection will result in gusty W/NW winds developing with gusts 25-35 mph. Mild temps in the pre-frontal airmass with highs 40s and even some lower 50s in the coastal plain before temps fall sharply mid/late afternoon in the cold advection. Monday night... A piece of the polar vortex will drop south across northern New Eng with shortwave energy rotating through SNE. Secondary arctic front will move south across the region 03-06z and may be accompanied by a few snow showers and locally heavy squalls. There is a good signal with the snow squall parameter and steep low level lapse rates with a shortwave passage and arctic fropa. However, 0-2km moisture is somewhat limited and the snow growth region never truly saturates. This may limit areal coverage with more widely sct activity. Potential for brief heavier snow showers but timing will be after the evening commute. Strong winds will be an issue for Mon night in strong cold advection and deep boundary layer promoting excellent mixing. Soundings show potential for wind gusts to 50+ mph after the arctic front passage. As a result a wind advisory was issued for all SNE. Arctic chill will be ushered in on these strong NW winds as 850 mb temps drop to -20 to -24C by 12z Tue which is down to the lowest 1st percentile of 850 mb temps for this time of year compared to climatology. Expect lows dropping into single numbers over the higher terrain and low to mid teens elsewhere, except upper teens outer Cape/Islands. Combined with the gusty winds, wind chills will drop to zero to -10F by Tue morning and as cold as -15F in the Berkshires and northern Worcester hills where wind chill advisories may eventually be needed. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Highlights... * Unseasonably cold and gusty Tuesday. Daytime single-digit to teens wind chills. * Temperatures rebound back into the 40s on Wed. * Mainly dry, but turning unsettled and cooler than normal late in the week into the weekend. Details: Tuesday: Sunny, but unseasonably cold temperatures and gusty conditions will be the main story as strong Arctic shortwave/lobe of the polar vortex translates into the Canadian Maritimes by Tues night. Model soundings continue to show at least very good mixing given the shot of cold air aloft (850 mb temps around -20 to -24C/-15 to -19C at 925 mb). While these temperatures do warm a bit as the day wears on and the 925/850 mb thermal trough shifts eastward/offshore, we still expect mixing to at least to 900 mb (not as deep as Monday night). BUFKIT momentum transfer still supports gusts at Advisory levels (45 to 50 mph) for at least the Tues morning hrs. By afternoon, the inversion height continues to lower, sustained winds decrease with a weakening p-gradient and mixed layer wind speeds also diminish. This should allow for decreasing winds/speeds as we move into the afternoon, a trend which will continue into the evening. Though we are looking at full sun, only looking at high temperatures in the 20s, with temps around freezing across southeast MA, eastern RI and Cape Cod/Islands. Will see single-digit wind chills thru noon (still a chance for sub-zero wind chills in the Berkshires) given the 25-35 mph sustained winds, these values "warming" to the teens by afternoon with the slackening winds. Regardless, Tues will be quite cold and more reminiscent of mid-winter than the 2nd day of climatological spring. Tuesday Night: Winds continue to slacken as a ridge of high pressure builds into SNE. This ridge axis shifts eastward for the second half of the overnight enough for a SW return flow to commence. Kept lows in the upper teens to mid 20s, but could see values in the low teens in the sheltered areas in NW MA if winds can stay light enough. Wednesday into Wednesday Night: Temperature roller-coaster continues into Wed with milder SW flow between the offshore ridge and a weak Clipper low that passes to our north. Still looking for dry conditions with 925/850 mb temps on Wed around -1 to -4C, supporting highs back into the 40s, with upper 40s towards SE MA and the metro areas. Lows mainly in the mid-20s to near freezing. Thursday into the Weekend: Deterministic and ensemble solutions point to a pattern change toward cooler than normal temperatures and generally unsettled weather for this period. The Arctic shortwave on Tuesday retrogrades into northern Quebec, establishing a broad longwave trough across the Northeastern CONUS. This longwave is reinforced by periodic shortwave disturbances aloft into the weekend, these individual shortwave features digging southward into the mid-Atlantic. We are not looking for temperatures to be as cold as Tuesday, but below average temperatures are expected each day in this period. 850 mb temps range around -13 to -17C and -9 to -13C @ 925mb support highs mainly in the upper 20s to upper 30s. Lows in the upper teens to mid 20s. Though cyclonic flow will maintain generally unsettled conditions, really isn`t much in the way of significant precipitation to speak of. That which does transpire may only be spotty/showery with the cold pool aloft and variable amounts of cloudiness. All in all, it`s a generally dry period. Models do continue to simulate a coastal low late in the weekend coming out of the Carolinas; not ready to write off this progged low as yet but the majority of ensemble low tracks are far enough SE of the 40N/70W benchmark that presently favor more of a miss at this point. Will offer a dry forecast following NBM, but will also continue to monitor subsequent guidance/trends for the late-weekend coastal system. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00Z TAF Update: Tonight: High confidence in trends, moderate on timing. Ceilings/visbys should remain at VFR levels at least through 04z. Initial precip looks quite light and shouldn`t result in restrictions either from cigs or visbys. Deterioration to IFR- LIFR then looks on track for after midnight and overnight with the next round of rains. Though the exact start time is still less clear, deteriorating flight categories should be the case starting 05-07z. SE gusts to 20 kt possible over Cape/Islands overnight. Monday...High confidence in trends. IFR/LIFR improving to VFR in the afternoon as winds shift to W/NW behind cold front. Gusts to 25-30 kt developing in the afternoon. Monday night...High confidence. VFR, but brief and localized MVFR/IFR possible in any heavier snow showers/squalls passing through. NW gusts to 35-45 kt. KBOS TAF...High confidence in trends. Expect a period of IFR/LIFR late tonight and Mon morning, improving to VFR in the afternoon. KBDL TAF...High confidence in trends. Expect a period of IFR/LIFR late tonight and Mon morning, improving to VFR in the afternoon. Outlook /Tuesday through Friday/... Tuesday: VFR. Strong winds with gusts up to 45 kt. Tuesday Night: VFR. Windy with local gusts up to 30 kt. Wednesday: VFR. Breezy. Wednesday Night: VFR. Thursday: VFR. Breezy. && .MARINE... A period of SE gusts to 25+ kt expected on the eastern waters late tonight and early Mon, but the main concern is the strong NW winds late Mon and especially Mon night. We have upgraded to a gale warning for all waters for late Mon into Tuesday behind the cold front. Strong NW gales expected with even an outside chance of marginal storm force gusts. Currently we have gusts to 45 kt with a few G50 kt possible. In addition, expect widespread moderate freezing spray Mon night into Tue morning and so a freezing spray advisory was issued. Outlook /Tuesday through Friday/... Tuesday: Moderate risk for gale force winds with gusts up to 45 kt. Rough seas up to 14 ft. Freezing spray. Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. && .TIDES/COASTAL FLOODING... Tides are astronomically high Monday, with Boston at 11.0 FT MLLW (12:36 PM), Nantucket 3.6 FT MLLW (12:02 PM), and Providence at 5.0 FT MLLW (9:23 AM). Current expectation is for a surge of less than one foot along the south coast, and perhaps around 1 foot along eastern MA coast, which would keep the total water level below the minor flood category for both coasts. In addition, winds are expected to shift to the W/NW in the morning as a cold front moves offshore, lessening the potential along E MA coast. If front ends up slowing down, it is possible we could see minor splashover (sub-Coastal Flood Advisory level) along both coasts, but that seems to be a worst case scenario right now. Does not appear to be a prolonged period of strong enough S/SE winds to build up seas offshore more than 4-5 FT, so beach erosion is not expected to be an issue right now either. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Wind Advisory from 4 PM Monday to 10 AM EST Tuesday for CTZ002>004. MA...Wind Advisory from 4 PM Monday to 10 AM EST Tuesday for MAZ002>006-008>021-026. Wind Advisory from 4 PM Monday to 1 PM EST Tuesday for MAZ007- 022>024. RI...Wind Advisory from 4 PM Monday to 10 AM EST Tuesday for RIZ001>008. MARINE...Freezing Spray Advisory from midnight Monday night to 1 PM EST Tuesday for ANZ231>237-250-251-254>256. Gale Warning from 4 PM Monday to 7 PM EST Tuesday for ANZ230>232-251-255-256. Gale Warning from 4 PM Monday to 4 PM EST Tuesday for ANZ233>237. Gale Warning from 4 PM Monday to 10 PM EST Tuesday for ANZ250- 254. && $$ SYNOPSIS...KJC/BL/Loconto NEAR TERM...KJC/BL/Loconto SHORT TERM...KJC LONG TERM...Loconto AVIATION...KJC/Loconto MARINE...KJC/Loconto TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
745 PM CST Sun Feb 28 2021 .UPDATE... Very minor updates to the ongoing forecast package. Did retrend hourly temperatures/winds to reflect the current position of the front and make some slight chances to the PoP forecast given the quiet radar at this hour, the expected showers along the front later this evening, and the anticipated thunderstorms forming across the Rio Grande and moving eastward later tonight. Looking at the brand new 00z Sounding out of KDRT there is a 2-3 Degree C inversion just above 950 mb with southwesterly wind bringing in some weak air advection at that lay. It is important to note that the front was north of KDRT at the time of the sounding. Decent shear of over 70 knots and Surface CAPE values near 100 J/kg were reported. A 700mb-500mb low crawling across Southern Arizona and New Mexico (evident on GOES-EAST/WEST Water Vapor) will come into play later this evening. The cold front is currently extending from a Rocksprings to Kerrville to Lago Vista to Taylor line as it continues to move to the south and east. Earlier in the evening a few elevated showers developed across Llano county, but these quickly died out behind the front. Additional light showers have formed to the northeast of the area near Cameron and Caldwell, and a thin line of isolated showers is show in many of the mesoscale and high resolution models forming along the front later this evening. Some aircraft soundings out of AUS and SAT still show a weak capping inversion which may work against these showers. The main show will be with the approach of the low pressure to the west. Ahead of it, as it moves into southeastern New Mexico and the Texas Panhandle later tonight the low and mid-level winds will strengthen ahead of it. This will move more air in the mid and upper atmosphere out of the way, causing air at the low levels to fill that void there-by creating lift. With the front already through the area and based on the notes about the 00z DRT sounding, any convection that does form will be elevated. With enough instability, shear, and moisture in the area a few elevated supercells remain possible. The HRRR remains consistent in showing a few developing between 10pm and midnight across Val Verde County. The 12z ARW and NMM high resolution models also supported this solution while the NSSL WRF was the least bullish, and the NAM Nest somewhere in the middle with isolated storms across the Hill Country. Even if the CAP wins out and the severe risk is conditional, the lift from the upper low should produce scattered showers and thunderstorms across the Rio Grande Plains into the Hill Country through the early morning hours, spreading eastward towards the I-35 corridor. SPC maintained their marginal risk of severe weather in their 01z update to the Convective outlook, noting that if strong to severe storms do form that hail remains the primary threat. We will monitor the trends of the 00z High Resolution models and provide further updates this evening in NWSChat and on Social Media. Rain chances continue with cool temperatures on Monday. What a change in just a few weeks...from snow/sleet/thunder sleet to the chance of strong to severe storms! && .PREV DISCUSSION... /ISSUED 523 PM CST Sun Feb 28 2021/ AVIATION... The cold front that will be the main driver of the TAF through the period is already pushing into the Hill Country producing a few showers between KAQO (Llano) and KBMQ (Burnet). Ahead of the front, the prefrontal trough have already turned winds out of the north along the I-35 corridor. Winds will pick up out of the north and be gusty once the front arrives at all terminals between 03z and 05z. Showers will be possible with ceilings dropping to MVFR as the front arrives and moves through with thunderstorm chances, at least in the vicinity, increasing between 09z at AUS and DRT and 11z at SAT/SSF. Chances for thunderstorms will linger into the mid-morning Monday with gusty north winds continuing. Rain showers, MVFR cigs, and gusty north winds will continue through much of tomorrow, before finally beginning to clear late in the day. Timing of the clearing will be the focus of future TAFs, while this set focuses on the precipitation chances. PREV DISCUSSION... /ISSUED 236 PM CST Sun Feb 28 2021/ SHORT TERM (Tonight through Monday Night)... Afternoon surface observations show a warm and moist air mass in place with current temperatures in the upper 60s to lower 80s. Dewpoint temperatures are impressive for this time of year and range from the upper 50s in the Hill Country to the upper 60s in the coastal plains. For the remainder of this afternoon, we could see a few light showers develop across portions of the Hill Country and along and east of the I-35/I-37 corridors. In addition, a cold front will move in from the north and could help generate isolated thunderstorms across portions of Burnet and Llano counties. As the above mentioned front continues to move southward this evening, a line of showers and thunderstorms is expected to develop along and especially behind the cold front. These storms will be elevated in nature, that is they will not be rooted in the flow near the surface. Favorable MUCAPE and shear should result if some strong to possibly severe thunderstorm development during the mid-evening into the overnight hours across a good portion of south central Texas. The current SPC Day 1 outlook has most of our counties in a Marginal risk (Level 1 out of 5) for severe weather. Given most storms should occur behind the boundary, the main concern with these thunderstorms will be the potential for hail up to around 1" in diameter. Mesoscale models generally agree the best chance for storm development will be from the Hill Country into the I-35 corridor. We have noted the fairly consistent trend from the HRRR model in showing some activity developing over the Serranias del Burro mountains of Mexico. Should this occur, this activity would likely remain intact as it moves into the Rio Grande plains and southern Edwards Plateau. With this in mind, we did raise precipitation chances slightly across the above mentioned areas this evening. For tomorrow morning, we should see decent coverage of post-frontal showers and thunderstorms across a good portion of south central Texas. Temperatures will also be much cooler and we have opted to trend toward the cooler guidance numbers with the expected precipitation, cloud cover and cold air advection behind the front. Highs are expected to range from the mid 40s in the Hill Country to the upper 50s in the Rio Grande and coastal plains. It will be blustery behind the front on Monday with northerly winds of 15 gusting to near 25 mph across a good portion of the region. Wind speeds will not be in any rush to decrease Monday evening, but should begin a slow, downward trend through the overnight hours. Rain chances will also be on the decrease from west to east Monday night. LONG TERM (Tuesday through Sunday)... The long term periods are looking less eventful as the deterministic models have been trending with a slower and weaker storm system to pass through the Southern Plains late in the week. The result of this trend leaves a lower amount of cloud cover for Tuesday into Wednesday and a more gradual mid-week return of southerly flow. This means wider diurnal ranges and less available moisture in advance of the late week storm system. MOS guidance trends have arrived much drier over the past 24 hours in regards to the rain chances for Friday and have all but removed any thoughts of potential rain for late Thursday. The weaker trends of the late week disturbance also signals a weaker cold air advection pattern and milder temperature trends for next weekend. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 80 48 50 42 62 / 30 70 70 30 10 Austin Bergstrom Intl Airport 81 48 51 42 63 / 30 70 70 30 10 New Braunfels Muni Airport 81 51 52 44 65 / 20 70 60 30 10 Burnet Muni Airport 78 44 48 40 60 / 30 60 70 20 10 Del Rio Intl Airport 83 52 59 41 66 / 0 40 20 - - Georgetown Muni Airport 79 46 49 42 60 / 40 70 80 30 10 Hondo Muni Airport 81 49 55 41 67 / - 60 50 20 10 San Marcos Muni Airport 80 49 51 42 63 / 20 70 60 30 10 La Grange - Fayette Regional 82 51 53 45 61 / 20 70 70 40 20 San Antonio Intl Airport 80 51 53 43 64 / 20 60 60 20 10 Stinson Muni Airport 80 51 54 43 64 / 10 60 50 20 10 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term/Aviation...Treadway Long-Term...YB
Area Forecast Discussion
National Weather Service Grand Forks ND
932 PM CST Sun Feb 28 2021 .UPDATE... Issued at 930 PM CST Sun Feb 28 2021 CLipper system moving through is bringing snowfall rates up to an inch an hour per radar estimate in portions of Barnes County this past hour. Given the shallow frontogensis and the speed of the clipper tracking to the southeast snowfall amounts will generally be an inch or less with a few locations in the southern valley expected to see a possible 2 to maybe 3 if higher intensity snowfall persists. RAP runs consistently paint the highest totals from the Valley City area southeast overnight. This would place Fargo just to the north of the risk area for the 2 to 3 inch band. UPDATE Issued at 654 PM CST Sun Feb 28 2021 Small clipper system beginning to show its hand with a more intense band snowfall setting up near Minot within a broader area of light snow. CAMs continue to paint the higher intensity snow to move to the southeast to from Minot through the Carrington and New Rockford areas towards Valley City. Some guidance then has the band move into the Fargo area and some to the southwest of Fargo. Will monitor the eastward extent this evening on radar trends and surface obs. Within the stronger echoes of the band visibility will be reduced under a mile at times and a quick 1 to 3 inches of snow will be possible depending on the residence time of any location under the band. && .SHORT TERM...(This evening through Monday night) Issued at 254 PM CST Sun Feb 28 2021 Snow amounts and placement with the clipper system tonight will be the primary challenge for the period. Main upper low has been digging down into southern Canada, with some decent snow currently going over southeastern Saskatchewan. The shortwave/clipper system will dig further into the region tonight, with a strong cold front coming with it. Several of the models indicate some pretty strong frontogenesis co-located with synoptic lift from the upper shortwave trough. The SPC meso page seems to verify the mid-level frontogenetical forcing, so banding potential looks pretty good. The main fly in the ointment will be the very fast movement of the system, as higher snowfall rates will not stay very long at one spot. Both CAMs and the larger scale models have been trending further south with the track of the snow, coming down over Fargo when previous forecasts have more along the Highway 2 corridor. At this point, think amounts that the previous shift messaged seem reasonable, generally in the trace to 1 inch range with localized 2 to 3. Some gusty winds as cold air advection kicks in behind the system, but think that they will not be high enough for substantial blowing snow impacts. Snow will be exiting the area by morning. The quick shot of cold air behind the clipper along with clearing skies will drop temps below zero overnight, but think readings should recover during the day on Monday. The surface high building down behind the front overnight will be short-lived, with winds quickly shifting back to the south by Monday afternoon. Could see some drifting in the Devils Lake Basin, but at our current wind speeds would need falling snow for any restrictions to visibility, which will not be happening. The winds will shift more southwesterly by Monday night as upper flow becomes more zonal. There will be some very strong warm air advection, and this should help keep temps in the teens to 20s above zero. .LONG TERM...(Tuesday through Sunday) Issued at 254 PM CST Sun Feb 28 2021 The Tuesday through Saturday period is expected to see quiet weather with seasonably warm temperatures. Ensemble guidance is in good agreement on a solution of zonal flow aloft on Tuesday shifting to northwesterly flow as an upper level ridge builds in to our west. The main forecast questions will ultimately revolve around the strength and location of the upper level ridging. Tuesday will see zonal flow aloft, 850 hPa temperatures above zero, and a breezy west-southwesterly wind at the surface that will help temperatures begin their rapid ascent to above normal. Resultant high temperatures should range from the 40s across the northern forecast area, to the 50s south of I-94. A shift toward more northwesterly flow aloft is expected to occur by Wednesday as an upper level ridge begins to build in to our west. The upper level ridging will be a mainstay through the rest of the extended period, but the location of this feature will have an impact on the magnitude of the impending warming trend. The CMC and ECMWF ensembles are less progressive, and place the ridge axis over MT/WY for much of the week before pushing it eastward by the weekend. The GEFS ensemble solution is more progressive in pushing the ridge aloft further eastward sooner. A more progressive solution would see our temperatures warm up more toward the 90th percentile (upper 40s to mid 50s) high temperatures, while a less progressive ridge would keep our highs closer to the 50th to 75th (40s to low 50s) percentile range. Regardless of the exact evolution, the ridge should shift east into our forecast area by the weekend at the latest. The presence of the upper level ridging over the forecast area should push our temperatures to well above normal values in the 50s to low 60s. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 544 PM CST Sun Feb 28 2021 Clipper system to bring a quick round of snow to eastern ND impacting the DVL, GFK and FAR TAFs this evening into the overnight. Will see CIGs and VSBY lower quickly as snow saturates and MVFR conditions develop. Within the strongest snow bands IFR conditions are possible for brief periods. In the wake of the snow the winds will turn to the north and some gusts will develop for a few hours overnight. Skies become VFR by morning with sfc high pressure and light winds expected for much of Monday. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...JK SHORT TERM...JR LONG TERM...Rick AVIATION...JK
Area Forecast Discussion
National Weather Service Jacksonville FL
904 PM EST Sun Feb 28 2021 .UPDATE... Winds are dropping with sunset. Mesoscale models continue to indicate shower activity developing over north-central Florida and moving north through dawn. At this time, just not seeing any indications that that is going to happen nor is there an obvious lifting mech to get them going. So right now not going to amend the Zones to account for this possibility but will keep VCSH in the TAFs. && .PREV DISCUSSION [618 PM EST]... .NEAR TERM [Through Tonight]... ...DENSE FOG POTENTIAL FOR INTERIOR SE GA & SUWANNEE VALLEY TONIGHT... Low stratus decks from this morning have broken up leaving a layer of flat cumulus amid south to southwesterly flow induced by the persistent surface high pressure to the east over the Atlantic. Despite extensive cumulus and cirrus drifting overhead on WSW flow aloft, filtered sunshine and deep-layer ridging will lead to another afternoon of near-record highs. Strong temperature contrast with record-level heat and cool coastal Atlantic waters will be able push inland this afternoon, combating the background southwesterly flow. Another sea breeze will sweep eastward from the Gulf, colliding with the Atlantic sea breeze along the I-95 corridor. Converging fronts may provide enough lift to overcome the weak capping inversion resulting in a few light showers late this afternoon and early evening, mainly along and east of the I-95 corridor from St Augustine southward. Low level flow will veer further southwesterly tonight ahead of a cold front approaching from the northwest and high pressure ridge axis to the south. Weak isentropic ascent in southwesterly flow will generate another batch of showers after midnight for areas south of I-10 with chances around 20-30%. In addition to shower chances, there will be potential for low stratus and fog across SE GA and the Suwannee Valley as sea fog advects inland from the northwestern Gulf of Mexico. Patchy fog may develop across the rest of NE FL but shower activity may disrupt development. Warm, moist airmass and intrusion of low stratus will limit cooling again tonight with lows only reaching the mid 60s. .SHORT TERM [Monday Through Tuesday Night]... ...HEAVY RAINFALL POSSIBLE TUESDAY NIGHT ACROSS PORTIONS OF SE GA... A cold front will continue to move southeastward, reaching the Altamaha River basin during the mid afternoon Monday before it slowly continues southward and eventually stalls across north-central FL early Tuesday morning. Ahead of the front, southwesterly flow will increase, breaking up morning low stratus by noon Monday. Showers chances will increase from northwest to southeast along the front Monday. HiRes guidance indicates a potential for embedded storms across SE GA as the front pushes southward, but due to the loss of heating and appreciable instability, t-storm potential will be very low once the front enters NE FL Monday evening. Overrunning southwesterly flow and associated isentropic lift will continue rain chances through Monday night, primarily across SE GA. A surface low will develop across the northwestern Gulf Tuesday morning as an upper low pivots over the lower Mississippi River valley. The surface low will drift into the northeast Gulf coast by Tuesday evening with an associated stationary front draped across SE GA. Elevated showers are expected in the vicinity of the front through Tuesday afternoon, with rain chances favoring locations north of I-10. As the surface low tracks inland Tuesday evening, it will shift across SE GA as it develops northeastward toward the Carolina coast. Strong forcing for ascent amid PWATs of 1-1.5" will bring a chance for heavy rainfall across northern zones of SE GA through Tuesday night, where rainfall totals of 1-2" are possible with localized higher amounts (WPC has outlined this area with a marginal risk for excessive rain). The cold front will trail behind the low as it shifts from the Gulf to the Atlantic through the predawn hours on Wednesday, bringing a chance of showers and slight chances of elevated t-storms across Suwannee Valley and SE GA. Another unseasonably warm day is expected on Monday ahead of the first cold front. Cloudy conditions in tandem with a cooler airmass settling into the area on Tuesday will bring a much cooler afternoon with highs ranging in the mid/upper 50s across SE GA and mid/upper 60s across NE FL. There could be some variability in the temperatures with the stationary boundary stretched somewhere across north-central FL. Southerly flow will quickly shunt that boundary back to the north as warm front Tuesday evening, restricting low to the upper 50s and low 60s across NE FL whereas the cold side of the boundary will let temps drop to the upper 40s and low 50s across SE GA. .LONG TERM [Wednesday Through Sunday]... Aforementioned trailing cold front will exit into the Atlantic by Wednesday afternoon. As it does so, skies will clear from northwest to southeast as cooler and slightly drier filters into the area on the periphery of an expanding surface high pressure northwest of the area. Surface high pressure will develop southward toward the Tennessee Valley on Friday with broad longwave troughing aloft. This will promote increasing onshore flow and potential coastal trough development. Still significant uncertainity this weekend, with a stark contrast in the medium range guidance compared to 24 hours ago. Sparing the details, another cold front is still progged to cross the region this weekend as an upper shortwave pivots into the northern Gulf and into the Florida Peninsula. This system will bring the next chance of rain to the area after a quiet, sligtly cooler than average end to the week. .AVIATION... [Through 00Z Tuesday] The sea breeze is pinned over KJAX at this time will make little further headway inland. HRRR is insistent upon developing some showers along the sea breeze convergence zone and moving then north toward the KSGJ/KJAX metro area. If showers move over any of the fields it is most likely to be KSGJ and have added a brief tempo overnight there. Otherwise included VCSH for the JAX Metro fields. Might see some fog in the Gainesville area and given that field`s propensity for briefly dropping down below guidance toward sunrise did go to 1sm in a tempo. Visibility restrictions should be very brief if it does happen. As the frontal system approaches tomorrow evening have a brief tempo for showers after 1800 utc but timing looks closer to 21-24 utc for most fields. Ceilings should be in the 2.5-5.0 kft range tomorrow afternoon. .MARINE... Southerly breezes will become more southwesterly overnight and through Monday afternoon ahead of a cold front, which will reach the southern Georgia waters by late Monday afternoon and continue southward across north Florida coastal waters Monday evening. Scattered showers are likely along the leading edge of the front with winds quickly shifting northerly then northeasterly behind it. Winds and combined seas will elevate in the northeasterly flow on Tuesday with winds between 15-20 kts across near shore waters and 20- 25 knots offshore. A Small Craft Advisory headline may need to be considered for this period. Another cold front will pass over the waters Wednesday with winds shifting to the south ahead of it and northerly behind it. Rip Currents: Moderate Risk at area beaches through Monday, with an increase to High Risk Tuesday with increasing onshore flow. .FIRE WEATHER... Southerly surface and transport winds will increase as the become more southwesterly through Monday ahead of an approaching cold front. This will allow peak daytime dispersion between 40-60 units on Monday. Showers and embedded storms are possible across SE GA along the cold front through Monday afternoon; showers will continue into NE FL Monday evening with limited potential for storms. Overrunning will favor rain chances continuing Monday evening and into Tuesday across SE GA. Despite limited mixing on Tuesday with overcast conditions, easterly transport flow will lead to marginal dispersion on Tuesday, except across north-central FL where weaker transport wind will lead to low dispersions. .HYDROLOGY... Potential for heavy rainfall across portions of southeast Georgia between Monday and Tuesday night may prolong or exacerbate ongoing flooding in area river systems. MODERATE RIVER FLOODING: Mod flooding that is ongoing along the upper Alapaha is expected to lower into minor flooding this week. Moderate flooding is expected on Santa Fe River near Three Rivers Estates this evening and is forecast to persist into early next week. MINOR RIVER FLOODING: Ongoing along most of the Satilla, Altamaha, Santa Fe, and lower portions of the Suwannee Rivers. Minor flooding is expected to continue through this week and potentially into next weekend along the lower portions of the Suwannee River. && .PRELIMINARY POINT TEMPS/POPS... AMG 62 80 51 56 48 / 0 60 40 70 80 SSI 62 79 54 60 54 / 0 40 40 70 80 JAX 64 83 57 64 57 / 10 20 30 50 60 SGJ 64 82 60 67 60 / 30 30 20 40 40 GNV 63 83 60 69 60 / 20 20 20 40 40 OCF 64 84 62 76 63 / 30 10 20 30 30 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. &&
Area Forecast Discussion
National Weather Service Marquette MI
735 PM EST Sun Feb 28 2021 .SHORT TERM...(This evening through Monday) Issued at 403 PM EST SUN FEB 28 2021 Quick-moving winter storm is now beginning to exit the area. Surface obs show cyclonic flow over the south-central pointing to the surface low being centered over south-central Marquette County. Correspondingly, radar shows the dryslot doing its dirty work causing the precip shield to erode quickly across the central U.P. Totals will end up being more impressive across the west half where the better fgen banding set up this morning. The synoptic precip shield will be out of the central U.P. by 00z and out of the CWA entirely by around 02z. Because snow is still ongoing even in the southern tier counties, left the Winter Weather Advisories as they were. However, evening shift can probably cancel the southern tier counties in about an hour. Tonight, as the system continues to pull away to the northeast, a strong northern stream short wave will dig into Northern Ontario. This wave and the associated surface cold front will usher in unseasonably cold air. Any wet or slushy surfaces will flash-freeze tonight which could lead to additional icy spots and slippery travel for the Monday morning commute. In addition, tightening pressure gradient and 3-hour pressure rises of 5-7 mb on the western flank of the deepening/departing low will lead to gusty winds. These gusty winds will be short-lived in most areas, except over the eastern U.P. where they will persist through the night where model soundings show the PBL remaining mixed to around 2-3 kft. Went with the HRRR over there which is near the highest in gusts, showing 30-35 mph gusts through the night. This wind will lead to waves building to as high as 14 feet on the east half of Lake Superior, so have issued a Lakeshore Flood Advisory for Alger & Luce counties. Winds, and thus waves, will decrease slightly early Monday morning before ramping back up during the day Monday with the strong CAA push. Waves should fall below criteria by mid afternoon Monday. Once this cold air settles in, lake effect snow showers will develop in the NW wind LES belts, mainly east half. The question for the west half will be how much over western Lake Superior is covered in ice and how well the CAMs are resolving it. Right now based on the GLERL ice cover analysis it looks like there is enough ice cover to inhibit most LES. However, it could shift around, and the analysis could be off. Model soundings across the west half snow belts are mostly dry except for just a thin saturated layer/cloud deck. Nonetheless, manually increased POPs to get at least chance snow showers in the forecast. However, between the lack of open water and heights rising/the column drying out, do not think there will be enough moisture to see anything more than scattered light snow showers west. East half, where there is more open water and a longer fetch, should see persistent LES through Monday afternoon, amounting to generally 1-3". Some CAMs hint at a more dominant band clipping northern and eastern Luce County which could produce up to 5" but most of the heavy snow with this band, if it develops, will fall just east of the CWA. With 850 mb temps around -22 to -24 C midday, even mixing out to 1 km AGL only gives highs around 12-14 F most areas. So March will indeed come in like a lion this year. .LONG TERM...(Monday night through Sunday) Issued at 222 PM EST SUN FEB 28 2021 Long term period continues to suggest a busy beginning of the week followed by a slower and dry middle to end of week. Initially, with the outgoing Monday shortwave and ridge axis shifting east over the region, clear skies, recent snowfall and dry conditions will help send Monday night temps near or just below zero for the interior regions and single digits above by the lakeshores. The culprits for the busier Tuesday look to be the aforementioned ridge axis tied to a weakening 1031mb high shifting into the Ohio Valley and a surface low and shortwave moving through Ontario. Being caught in the middle of these systems, a tight pressure gradient with a stout LLJ will move over the forecast area during the day. Winds at 850mb within this jet look to be near 60kts. Model soundings suggest we could mix up to around 900-875mb, which could bring widespread 25-30 mph winds to the surface. Some areas, particularly the higher terrain and near Lake Michigan could see gusts approaching 35 mph during the day. These winds will also raises concerns for lakeshore flooding and beach erosion along the Lake Michigan lakeshores. This regime will also bring strong WAA into the area which should quickly bounce temps into the mid- upper 30s by afternoon. Some places in the west and south could even climb into the low 40s. By the evening, winds should begin settling down as the low over Ontario skates southeast just north of Lake Superior and we lose the dinural mixing. Expect lows Tuesday night to bottom out in the 20s with some isolated high teens possible in the interior portions of central Upper Michigan. An amplifying pattern over the CONUS begins to develop as ridging sets up over the western Plains and slowly shifts eastward into the weekend, and deep troughing associated with an upper level low over western Greenland shifts westward. This will initially put Upper Michigan in near zonal flow on Wednesday, but will develop into NW flow mid-upper level flow beginning Wednesday night. At the surface, various highs are progged to dip south and keep the region mostly dry with the exception of potential light drizzly or flurries developing downwind of Lake Superior. Despite light surface flow generally off Lake Superior in some form with a few cold punches at 850mb being possible, slightly normal to slightly above normal highs are largely expected. Daytime highs look to largely be in the 30s with some high 20s possible on Friday. Overnight lows in the teens to single digits in the interior west are generally expected, with low 20s by the lakeshores. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 735 PM EST SUN FEB 28 2021 The fast moving snow storm has ended at all terminals with just flurries being reported at SAW. Expect MVFR cigs to prevail at all TAF sites tonight into Monday morning with brief periods of VFR cigs possible, especially at IWD around 00z. Gusty northwest winds are expected to continue tonight resulting in a steady stream of lake effect clouds and a few light snow showers at IWD and CMX. A drier air mass is expected to move in Monday afternoon with cigs improving to VFR at all terminals. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 222 PM EST SUN FEB 28 2021 As today`s low pressure system moves through the lake, expect increasing northwesterly winds to develop. In the east gales to 40kt look possible this evening and into tomorrow. Additionally as this low lifts, increasing CAA will surge cold air back into the area, prompting heavy freezing spray concerns lake-wide tonight into tomorrow. Both gale and heavy freezing spray warnings are in affect tonight and tomorrow. Tuesday southeasterly winds are expected as a low moves into Ontario and high shifts into the Ohio Valley. Winds should increase again with widespread 30kts to low end gales during the day as a stout LLJ moves over the Upper Great Lakes. As high pressure builds in after the low to the north skates away, expect calm winds below 20kts to settle in late Tuesday night and linger through at least Friday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Lakeshore Flood Advisory from midnight tonight to 3 PM EST Monday for MIZ006-007. Lake Superior... Heavy Freezing Spray Warning until 1 AM EST Tuesday for LSZ243>251-264>267. Gale Warning until 7 PM EST Monday for LSZ249>251-266-267. Heavy Freezing Spray Warning until 7 PM EST /6 PM CST/ Monday for LSZ162-240>242-263. Gale Warning from 1 AM to 1 PM EST Monday for LSZ243>248-264-265. Gale Warning from 4 AM EST /3 AM CST/ to 10 AM EST /9 AM CST/ Monday for LSZ240>242-263. Lake Michigan... None. && $$ SHORT TERM...RJC LONG TERM...JP AVIATION...EK MARINE...JP
Area Forecast Discussion
National Weather Service Pittsburgh PA
943 PM EST Sun Feb 28 2021 .SYNOPSIS... Crossing low pressure will promote periods of rain through early Monday morning. Building high pressure should then support mainly dry and cool conditions through the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Recent RAP analysis at 700mb suggests boundary layer saturation (RH >70%) has commenced across the forecast area, with precipitation gradually increasing as moisture advection in srly flow ensues ahead of an approaching cold front. Strong warm advection is evident in recent sfc temperature observations in the upper 50s / low 60s across srn portions of the region, with the 00Z sounding out of KPIT suggesting steepening mid-level lapse rates above a strong sfc temperature inversion. As the cold front nears, categorical PoPs should overspread the forecast area after midnight. With elevated instability evident; enhanced rainfall rates may occur at times, especially across sern portions of the forecast area where convergence associated with frontogenesis remains. In this area, an additional 0.50 to 1.00 inches may be realized, contributing to ongoing hydro concerns. Both areal and river flood hazards should persist with anticipated rainfall and continued snowmelt runoff. Please see the Hydrology section below for more information related to river rises. Precipitation will quickly end with the passage of the cold front Monday morning, potentially mixing with snow in the higher elevations as cold nwly flow ensues. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY NIGHT/... Remaining vorticity advection associated with a mature upper level trough will rotate southward and contribute to the chance for snow showers for a brief period of time on Monday north of Pittsburgh. Pressure rises, with isallobaric acceleration will create breezy conditions, with wind gusts of 25 to 30 mph at times on Monday afternoon. Given environmental conditions and a shortwave temperature trough, the possibility for convective snowbands does exist but lack of moisture is likely to limit any long term organization. Accumulation will be minimal and confined to locations north of I-80. High pressure should then support minimal precipitation chances through Wednesday, with flattening flow aloft supporting below average temperature through Tuesday before moderating under gradual rising heights by Wednesday. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Long term pattern suggests high pressure will maintain quiet weather for the majority of the period. Troughing near Hudson Bay, Canada may contribute to lower than normal temperature into the weekend. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... IFR/MVFR restrictions continue this evening with a brief lull in rainfall. Cigs will all lower into IFR within the next several hours as a second wave of rainfall moves into the area ahead of a cold front. SE`ly wind should veer to the SW/W with frontal passage. A return to VFR is expected by late Monday morning with dry post- frontal advection. .Outlook... Restriction potential returns Wed S of PIT with low pres. && .HYDROLOGY... An additional 0.50 to 1.00 inches of rain is forecast through early Monday in the Flood Watch area. Combined with snowmelt, this is likely to promote ongoing flooding on some area small creeks and streams. River Flood Warnings have also been posted at several points along the Monongahela and Cheat Rivers. The Cheat in particular will have to be watched closely, as snowmelt and rainfall will be highest in that basin. Flooding in the major category is currently forecast at Rowlesburg and Point Marion. Minor flooding is also expected at Parsons on the same river, and minor to moderate flooding is foreseen at Point Marion, Charleroi, and Elizabeth on the Monongahela. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...Flood Watch until 4 AM EST Monday for PAZ075-076. OH...None. WV...Flood Watch until 4 AM EST Monday for WVZ021-509>514. && $$
Area Forecast Discussion...UPDATED
National Weather Service Blacksburg VA
933 PM EST Sun Feb 28 2021 .SYNOPSIS... Low pressure moving northeast through the Great Lakes tonight will push a cold front through the Mid Atlantic region along with moderate to heavy showers and isolated thunderstorms. The weather turns windy and colder behind the front on Monday and Monday night. High pressure and dry weather build in for Tuesday and Tuesday night. && .NEAR TERM /THROUGH MONDAY/... As of 915 PM Sunday... Line of showers and embedded convective elements is now moving into the Blue Ridge and gradually shifting ESE. A large area of stratiform rain had spread across WV, with some stronger cells to our southeast in KY and TN. Have expanded isolated thunder across western and west central VA as the front continues to push through tonight. We have issued a flash flood warning for portions of Greenbrier County WV and Bath County VA. In these areas rainfall totals of up to 2" have fallen in the last 24 hrs, and we are expecting localized higher amounts before the rain ends. Ahead of the front, there was a sharp gradient in PoPs, with nothing falling yet across much of central VA and northern NC. The rain will eventually push through during the overnight and morning hours Monday as a short wave kicker deepening in Ontario Province shoves the surface system and associated front into the Atlantic and Gulf of Mexico. Have added some dense fog and also put up a dense fog advisory for the central Piedmont of VA- south of the convective line and still in a shallow in-situ wedge. This will eventually be scored out by the FROPA, with temperatures and dew points gradually falling during the day tomorrow. As of 310 PM EST Sunday... Flood Watch in effect through Monday morning for areas along and west of a Marion to Pearisburg to Lexington line. Low clouds and fog remained in the foothills and piedmont of Virginia late this afternoon. The wedge had eroded over the rest of southwest Virginia into southeast West Virginia and the mountains and foothills of North Carolina. Outside of the wedge winds were gusting from the southwest at 15 to 30 mph. HREF and HRRR guidance have the main axis of showers from central West Virginia through western Tennessee through midnight. Between midnight and noon the band of showers and associated cold front cross the Appalachians and will move in eastern sections of Virginia and North Carolina. Temperatures will be mild overnight as dew points rise across the area. However, temperatures will drop during the day behind the front in the mountains. There will be a sharp gradient in rainfall amounts on the western slopes of the central Appalachians. The heaviest rainfall through Monday morning will be west of a western Bath County, VA to western Watauga County, NC line. No changes have been made to the Flood Watches that are in effect or will go into effect at 7PM this evening. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM EST Sunday... A brief touch of wintry weather in the mid-week... A transient surface high will enter the area from the upper midwest late Monday and begin to clear out sky cover from north to south. Behind Monday`s front, winds will pick up for the overnight hours into Tuesday. Higher elevation areas will experience gusts 25-35 kt, and lower valley areas and east into the Piedmont will gust more int the 15-25 kt range. Most of Tuesday will remain clear with zonal flow dominating the eastern half of the CONUS. An eye will be kept on a small cut off low set to come out of the southern states Wednesday morning. This little system will approach the region Wednesday morning and restore cloud cover, but ought to get swept east and off the coast by Wednesday night/early Thursday morning. Most of the action from this smaller system will remain south of the NC/VA border and will be shortlived. The NC Highlands may see a quick inch or so of snow, up to 2 in the very upper elevations. Elsewhere in the mountains, a dusting is the most to be expected. Snow will become rain as temperatures warm on Wednesday. East of the Blue Ridge this will be an entirely rain event. By Thursday morning the cut off low will be out to sea, and calmer weather will prevail. Temperatures will be above normal for this forecast period, with even a slight warming trend. Daytime highs will be in the 40s and 50s. The temperature profile will cool just enough Tuesday night/Wednesday morning to allow that bit of snow in the mountains, but most will stay above freezing in the mid 30s for overnight lows. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 215 PM EST Sunday... A much calmer second half of the week and weekend... A broad ridge will move into place over much of the CONUS. This will provide us with dry mild weather through the end of the forecast period. The only disruption could be another low forming in the southern states late on Sunday and moving north to bring more rain to the area. However, this currently seems a less likely scenario than the broad ridge extending its influence almost as far south as the Gulf. This will serve to fend off any encroaching low pressure systems from approaching us from that direction. High temperatures will be slightly above normal for this entire portion of the forecast, while lows look to be right around normal. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... As of 645 PM EST Sunday... Wedge conditions are holding fast east of the Blue Ridge to include KROA and KLYH with LIFR conditions. However, the wedge retreated just a bit this afternoon so all other locations are outside of the wedge with VFR conditions. Believe KROA and KLYH will remain with very poor flight conditions until the approaching cold front finally dislodges the wedge late tonight. Expect conditions at other sites will be trending down as the front approaches and lower CIGs and showers move in. The front will clear the region early Monday morning with steadily improving conditions to VFR all sites. However, expect winds will increase significantly across the entire region by the afternoon with gusts at or above 30kt for KROA possible. Extended Aviation Discussion... Drier weather and VFR conditions are expected to across the region Tuesday and Tuesday night. A quick moving low pressure system moving across the southeastern U.S. Wednesday and Wednesday night may bring VFR clouds to the Carolinas. Some MVFR upslope clouds are possible in southeast West Virginia Wednesday. Tranquil VFR weather is expected for Thursday and Friday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Flood Watch through Monday morning for VAZ007-009>011-018-023. Flood Watch until 7 AM EST Monday for VAZ019-020-024. Dense Fog Advisory until 4 AM EST Monday for VAZ022>024-034- 035-045>047-059. NC...None. WV...Flood Watch until 7 AM EST Monday for WVZ042>044-507-508. && $$ SYNOPSIS...AMS NEAR TERM...AMS/SH/MBS SHORT TERM...VFJ LONG TERM...VFJ AVIATION...AMS/MBS