FXUS61 KLWX 040159 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 859 PM EST Tue Dec 3 2024 .SYNOPSIS... Well below normal temperatures will continue through the end of the week. A potent area of low pressure will drag a strong cold front across the area Wednesday night into Thursday. This brings mountain snow, strong gusty winds, and colder temperatures to the area. High pressure returns Friday into the weekend, which will bring a gradual warming trend back towards normal temperatures. && .NEAR TERM /THROUGH WEDNESDAY/... Clear and cold overnight with diminishing winds. Low clouds over the mountains will gradually dissipate overnight, but there will be some increase in high clouds overnight. Previous afd... Winds will drop off markedly overnight as high pressure moves overhead. With clear skies accompanying the light winds, still setting up to be the coldest night of this stretch with widespread lows in the teens to low 20s. Rural portions of the VA Piedmont and sheltered valleys west of the Blue Ridge likely drop into the low to mid teens tonight. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... The aforementioned upper-level ridge will be overhead on Wednesday while high pressure pushes offshore. This will result in temps in the low to mid 40s (30s in the mountains). Light south-southwest winds in the morning increase through the day. Looking upstream, a powerful upper-level trough digs south out of central Canada late in the day into Wednesday evening. The surface reflection of this upper-level system will push a very strong cold front through the region Wednesday night into Thursday. The increasing pressure gradient across the Mid-Atlantic becomes noticeable by Wednesday evening as WAA allows stronger winds aloft to begin mixing down to the surface. South-southwest winds sustained at 15-20 mph and gusting 25-30 mph are expected Wednesday evening into Wednesday night. Stronger winds are anticipated for the mountains, where gusts of 40-50 mph are expected Wednesday night. Even stronger winds arrive after the front passes, with Wind Advisories and High Wind Watches/Warnings likely needed for parts of the area for Thursday. One caveat is that the winds may not quite be aligned with height, meaning there is about a 20 to 30 degree directional change from the surface to about 5 km AGL. This could prevent those strongest values from making it down. Peak gusts of 40-45 mph, with up to 55-60 mph along the highest ridges of the Alleghenies and Blue Ridge/ Catoctin Mountains are most likely through early Thursday evening. Precipitation begins to move into the area late Wednesday evening, ahead of a rapidly advancing cold front. It likely is snow in the mountains and a mix of rain/snow to the east, at least at the onset. The models indicate strong CAA in the 850-925 mb layer Wednesday night, that should allow precipitation to quickly transition to all snow for most of the areas along/west of the Blue Ridge after 12AM to 3AM Thursday morning. To the east of the Blue Ridge, temperatures are much more marginal, likely to be in the mid to upper 30s, with near freezing temps between US-15 and the Blue Ridge. The exact temperature will be critical for any potential impacts from any light accumulating snowfall Thursday morning. Also, given the gusty to windy downslope conditions that quickly develop early Thursday morning, that will help keeps temps from dropping too much. At the very least, rain/snow showers probably make their way to the I-95 corridor. The forecast maintains very light accumulations all the way to the metro areas. Thinking that with such a powerful front and upper- level forcing, there will be heavy snow showers/squalls embedded within the upslope snow; east of the mountains, a line of snow showers is possible. These could cause issues on roadways due to reduced visibility, gusty winds, and some slick spots. In the mountains, blizzard conditions are becoming likely for most areas along and west of the Allegheny Front. Very cold air and a deep moisture connection to the Great Lakes will set the stage for a potent snow squall event along the Allegheny Front. Forecast snow amounts between Wednesday night and Thursday morning are between 4 and 6 inches with potentially higher amounts up to around 9 inches along the western-facing slopes above 2500 feet. In most of the Alleghenies, winds likely gust well above 35-40 mph. With an air mass this cold, the snow/liquid ratios are going to be very high, leading to a fine, powdery snow. This paired with the aforementioned wind gusts could lead to whiteout conditions at times. Treacherous travel conditions are likely in the mountains Thursday morning. Even after snow ends, the blowing snow will make travel difficult at best through Thursday night. Highs on Thursday afternoon outside of the mountains should be in the 30s for most, with sunny conditions returning by early afternoon. Strong winds continuing throughout the day advect in colder air, meaning we are not really going to see "high temperatures" during the afternoon given wind chills in the 20s for most (single digits in the mountains). As we move into Thursday night, colder air rushes into the region resulting in lows in the 20s (teens in the mountains). Winds remain quite strong even overnight, so wind chills are going to be the coldest of the season thus far. For areas east of the Blue Ridge, wind chills will drop into the teens. Further west, wind chills drop into the single digits along and west of the Blue Ridge, and even well into the negative single digits along the ridges above 2500 feet. Cold Weather headlines are possible in the mountains during this time. Given the possibility of power outages from the strong winds, it is important to make preparations now ahead of this event and be prepared to find a way to stay warm. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A broad trough of low pressure across the eastern half of the U.S. will linger Friday and Saturday. A strong surface high will build eastward across the region. This high will help to continue to circulate cold air from the northwest into the region Friday and Saturday. Dry conditions both days with exception to some snow showers in the mountains early Friday. Temperatures both days will be below average by about 15 degrees. Highs in the upper 30s to near 40 both days. Lows near 20 to lower 20s both nights. The high will move to the East Coast as the trough of low pressure flattens and shifts to the east as well. A southerly flow is expected to develop Sunday and Monday to allow for our temperatures to modify to near average to slightly above average both days. Some rain could move into our western zones Sunday night and early Monday, before spreading east across the rest of the region through the day Monday. Highs Sunday upper 40s to lower 50s. Highs Monday middle 50s. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... VFR conditions are expected through Wednesday. Winds then taper off overnight as high pressure moves overhead and eventually offshore. This will turn winds out of the S/SW heading into Wednesday. A strong area of low pressure approaches the area late Wednesday into Thursday, causing winds to increase once again, with gusts of 20-25 knots out of the S/SW likely Wednesday afternoon into Wednesday night. A significant wind surge comes along and behind a cold front into Thursday morning. Winds will quickly shift out of the W/NW between 09z and 13z Thursday with gusts to around 35 to 45 knots. Some snow is also possible on Thursday morning at all terminals, especially at MRB, IAD, DCA, BWI, and MTN. CHO may be a bit too far south to get any snow, but can't completely rule it out. There are even some indications that some streamers could even drop some brief heavier snow in isolated spots. Should one of these move over a terminal, it could certainly result in issues with VSBY and runway conditions, albeit briefly. VFR conditions through the period. Winds northwest 10 to 15 knots gusts up to 25 knots Friday, diminishing Friday night. Winds becoming southwest 5 to 10 knots Saturday. && .MARINE... Have upgraded the Gale Watches to Gale Warnings for Wednesday night into Thursday. Gusty northwest winds are expected to continue across all the waters through this evening before tapering off overnight as high pressure approaches. Small Craft Advisories are in effect for all the waters through the evening. Winds drop below SCA conditions for a brief time period Wednesday morning, then begin to increase substantially on Wednesday afternoon as a strong area of low pressure approaches the region. SCA conditions begin again Wednesday afternoon, with south-southwest gusts of 20-25 knots likely, then increasing to 25-30 knots over most of the waters Wednesday night. Some gusts to near gale force, around 35 knots, are likely over the open waters of the Chesapeake Bay. Still think the best chance for gale-force winds comes on Thursday as winds turn out of the NW as cold air rushes in behind the aforementioned cold front. SCAs will certainly be needed into Thursday night, but still not sure if gale conditions continue that long. For that reason, currently ending the Gale Warning at 7PM Thursday. Small Craft Advisories likely Friday into Friday evening. No marine hazards expected overnight Friday through Saturday night. Winds northwest 15 to 20 knots gusts 25 to 30 knots Friday and Friday evening. Winds becoming southwest around 10 knots gusts 15 knots Saturday and Saturday night. && .TIDES/COASTAL FLOODING... The main period of interest will be Wednesday evening into Thursday as a powerful cold front pushes across the area. Expect a marked increase in water levels ahead of this system. This places a few of the more sensitive locations into Action around the time of high tide. In the wake of this boundary, a blustery westerly wind will quickly lower water levels. Further drops are possible on Friday as winds turn more northwesterly. During this phase on Thursday and Friday, there is some potential for blowout tides. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Small Craft Advisory until 10 PM EST this evening for MDZ008. Small Craft Advisory from 11 AM Wednesday to 6 AM EST Thursday for MDZ008. Gale Warning from 6 AM to 7 PM EST Thursday for MDZ008. Winter Storm Watch from Wednesday evening through Thursday afternoon for MDZ001. VA...None. WV...Winter Storm Watch from Wednesday evening through Thursday afternoon for WVZ501-505. MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ530>532-538>540. Small Craft Advisory from 11 AM Wednesday to 6 AM EST Thursday for ANZ530-531-535-536-538-539-542. Gale Warning from 6 AM to 7 PM EST Thursday for ANZ530-531-535- 536-538-539-542. Small Craft Advisory from 11 AM to 6 PM EST Wednesday for ANZ532>534-537-540-541-543. Gale Warning from 6 PM Wednesday to 7 PM EST Thursday for ANZ532>534-537-540-541-543. Small Craft Advisory until 3 AM EST Wednesday for ANZ533-534- 537-541>543. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...DHOF/CJL/KRR LONG TERM...KLW AVIATION...LFR/KLW MARINE...LFR/KLW TIDES/COASTAL FLOODING...LWX