351
FXUS61 KLWX 201533
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1033 AM EST WED NOV 20 2024
SYNOPSIS
A STRONG COLD FRONT LOOKS TO CROSS THE REGION LATE TONIGHT INTO
EARLY THURSDAY MORNING. THE FRONT WILL DELIVER MUCH NEEDED RAIN TO
THE AREA ALONG WITH GUSTY WINDS AND BELOW NORMAL TEMPERATURES TO
ROUND OUT THE WORKWEEK. AN UPPER LEVEL LOW PRESSURE SYSTEM WILL
FOLLOW THE FRONT THURSDAY THROUGH SATURDAY, BRINGING A
PROLONGED PERIOD OF COLD TEMPERATURES, UPSLOPE MOUNTAIN SNOW,
AND GUSTY WINDS. HIGH PRESSURE RETURNS SUNDAY INTO MONDAY BEFORE
ANOTHER FRONT APPROACHES BY THE MIDDLE OF NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
MID-MORNING UPDATE: THE MAIN UPDATE THIS MORNING WAS TO UPGRADE
THE WINTER STORM WATCH TO A WINTER STORM WARNING IN GARRETT,
WESTERN GRANT, WESTERN PENDLETON, AND WESTERN HIGHLAND COUNTIES,
AND A WINTER WEATHER ADVISORY IN WESTERN MINERAL COUNTY. NO
MAJOR CHANGES WERE MADE TO THE FORECAST FOR TODAY. PREVIOUS
DISCUSSION FOLLOWS...
FOR TODAY, A FRONTAL SYSTEM WILL CONTINUE TO PUSH TOWARDS THE
MID- ATLANTIC. LOCALLY, CLOUDS WILL INCREASE THROUGHOUT THE DAY
WITH WARM AIR ADVECTION KICKING IN, ALLOWING FOR ONE MORE WARMER
DAY WITH HIGHS IN THE LOW TO MID 60S FOR MOST AREAS.
PRECIPITATION CHANCES WILL START OFF FAIRLY LOW THIS MORNING AND
EARLY AFTERNOON BEFORE POPS INCREASE FROM WEST TO EAST STARTING
LATER THIS AFTERNOON AND EARLY EVENING. THESE SHOWERS MAY TRY
TO SPAWN A LOW-TOPPED SQUALL LINE LATER THIS EVENING AND INTO
THE EARLY OVERNIGHT HOURS. CANNOT RULE OUT A STRAY RUMBLE OF
THUNDER DURING THE COLD FRONT PASSAGE LATER TONIGHT.
FOR TONIGHT, THE MAIN CONCERN WILL BE THE INCREASING/AMPLIFIED
WIND FIELD ALONG AND JUST BEHIND THE FRONTAL PASSAGE. WINDS
AHEAD OF THE COLD FRONT WILL BE PRETTY TAME BEFORE A QUICK AND
RAPID INTENSIFICATION ENSUES JUST BEHIND THE FRONTAL PASSAGE.
GUIDANCE CONTINUES TO HINT AT THE POTENTIAL FOR 50 MPH GUSTS
ALONG THE HIGHER RIDGES OF THE ALLEGHENY FRONT. GIVEN THE
INCREASED POTENTIAL, A WIND ADVISORY HAS BEEN HOISTED FOR LATE
THIS EVENING INTO THE EARLY OVERNIGHT HOURS AS THE FRONT PASSES.
THERE MAY BE THE NEED FOR FURTHER EXTENSIONS IN BOTH AREA AND
TIME WITH RESPECT TO THE WIND ADVISORY. SHOWERS WILL BE FAIRLY
SHORT-LIVED ALONG THE COLD FRONT PASSAGE BUT MAY TRY TO STICK
AROUND THROUGH THE OVERNIGHT HOURS AND HEADING INTO THURSDAY.
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
WHILE THE FIRST SHORTWAVE MOVES FURTHER NORTHEAST, PRECIPITATION
WILL LIKELY BE LACKLUSTER FOR THE MORNING HOURS ON THURSDAY.
GIVEN THE DECREASING COLD AIR LOCKED IN OVER THE HIGHER TERRAIN,
SNOW SHOWERS WILL LIKELY TAKE AIM FOR THE ALLEGHENY FRONT
ESPECIALLY, STARTING DURING THE DAY ON THURSDAY. WITH SOME
LIMITED INSTABILITY ACROSS THE DGZ, THESE SNOW SHOWERS COULD BE
FAIRLY SQUALLY HEADING INTO THE LATER PART OF THE DAY
ESPECIALLY. THIS MULTIPLEX FRONTAL SYSTEM WILL BRING SEVERAL
ROUNDS OF SIGNIFICANT ACCUMULATING SNOWFALL ACROSS THE ALLEGHENY
FRONT IN PARTICULAR. WINTER STORM WATCHES REMAIN IN EFFECT OVER
THE AFOREMENTIONED AREAS STARTING THURSDAY AFTERNOON AND INTO
SATURDAY. FURTHER EAST OF THE MOUNTAINS, EXPECT MOSTLY DRY
CONDITIONS BUT CANNOT RULE OUT A FEW MIXED PRECIPITATION
DROPLETS HEADING INTO THE AFTERNOON HOURS. HIGHS ON THURSDAY
WILL LIKELY STAY IN THE UPPER 20S TO JUST BELOW FREEZING ALONG
THE ALLEGHENY FRONT, WITH 40S AND 50S FURTHER EAST.
UPPER LEVEL LOW PRESSURE WILL SIT JUST NORTH OF THE MID-
ATLANTIC REGION FRIDAY BEFORE PUSHING OFF THE NEW ENGLAND COAST
DURING THE FRONT HALF OF THE WEEKEND. A POTENT PIECE OF
SHORTWAVE ENERGY WILL SWING AROUND THE BACK END OF THE UPPER
LEVEL LOW LATE FRIDAY INTO EARLY SATURDAY. THE PIECE OF
SHORTWAVE ENERGY WILL PROVIDE A REINFORCING SHOT OF COLD AIR ON
GUSTY NORTHWEST FLOW AND AN ENHANCED PERIOD OF UPSLOPE SNOW.
WINTER STORM WATCHES CONTINUE AS A RESULT FOR THE MOUNTAIN
COUNTIES WEST OF THE ALLEGHENIES THROUGH SATURDAY AFTERNOON.
UPGRADES TO THESE WATCHES WILL LIKELY COME LATER THIS MORNING
PENDING COORDINATION WITH NEIGHBORING OFFICES.
THE STEADIEST AND HEAVIEST UPSLOPE MOUNTAIN SNOW SHOWER ACTIVITY
LOOKS TO OCCUR FRIDAY INTO SATURDAY MORNING. THIS IS WHEN THE
STRONGEST PIECE OF SHORTWAVE ENERGY PIVOTS THROUGH AS THE
CUTOFF UPPER LOW PROGRESSES NORTH AND EAST TOWARD NEW ENGLAND.
00Z AND 06Z DETERMINISTIC AND ENSEMBLE GUIDANCE CONTINUE TO
FOLLOW THIS NOTION WITH INCREASED WEST TO NORTHWEST LOW-LEVEL
FLOW IN THE WAKE OF THE DEPARTING SHORTWAVE EARLY SATURDAY
MORNING.
AS FOR ACCUMULATION (THURSDAY 11/21/24 THROUGH SATURDAY AFTERNOON
11/23/24), WE ARE LIKELY LOOKING AT THE FIRST SIGNIFICANT/PLOWABLE
MOUNTAIN EVENT OF THE SEASON WITH 8 TO 12 INCHES OF SNOW ALONG AND
WEST OF THE ALLEGHENY FRONT. HIGHEST SNOW TOTALS WILL BE CONFINED TO
ELEVATIONS ABOVE 3000 FEET WITH LOWER TOTALS DOWN IN THE HIGHER
VALLEY LOCATIONS ALONG WEST OF A LINE FROM BIG SAVAGE MOUNTAIN IN MD
SOUTH TOWARD SPRUCE KNOB, WV. HIGHER RIDGE LOCATIONS FROM HOYES
CREST AND INTO CANAAN VALLEY COULD SEE LOCALIZED TOTALS OVER 12"
GIVEN INTENSE SNOW RATES OF 1-2"/HR LATE FRIDAY NIGHT INTO EARLY
SATURDAY MORNING AS LIFT WITHIN THE DGZ IS MAXIMIZED. SNOW RATIOS
WILL FAVOR CLIMATOLOGY WITH LOWER RATIOS IN THE 10:1 TO 13:1 RANGE
DURING THE DAYLIGHT HOURS INCREASING TO 16:1 TO 18:1 DURING THE
EARLY MORNING AND OVERNIGHT PERIODS. THIS WILL LEAD TO PERIODS OF
COMPACTION ALTHOUGH MOST OF THE SNOW FRIDAY SHOULD BE OF FLUFFIER
CONSISTENCY GIVEN THE COLDER AIRMASS IN PLACE. OUTSIDE OF THE
SIGNIFICANT SNOW ACCUMULATION, BLOWING AND DRIFTING WILL BECOME
A PROBLEM. THIS IS DUE LARGELY IN PART TO INCREASING WINDS
FRIDAY AFTERNOON INTO SATURDAY AS THE SHORTWAVE DISTURBANCE
LIFTS OUT OF THE REGION. GUSTS WILL BE CLOSE TO WIND ADVISORY
CRITERIA (UP TO 50 MPH) ALONG THE HIGHER RIDGES WITH 30 TO 40
MPH GUSTS DOWN BELOW. THIS WILL YIELD WIND CHILLS IN THE TEENS
AND 20S FRIDAY INTO SATURDAY.
FROUDE NUMBERS WILL SIT AT OR LESS THAN 1 THROUGH THE BULK OF THE
EVENT, BLOCKING ANY SUBSTANTIAL SPILLAGE EASTWARD ACROSS THE
ALLEGHENIES AND TOWARD THE BLUE RIDGE OR METRO AREAS. EVEN WITH THAT
SAID, SOME GRAUPEL OR WET SNOW COULD MIX WITH SOME RAIN EARLY FRIDAY
MORNING ACROSS NORTHERN AND CENTRAL MD, NORTHERN VA, AND THE EASTERN
WV PANHANDLE. OUTSIDE OF SOME MORNING RAIN AND SNOW, DRY CONDITIONS
WILL PREVAIL UNDER WEST TO NORTHWEST DOWNSLOPE FLOW. EXPECT WIND
GUSTS 30-40 MPH WITH GUSTS UP TO 50 MPH ALONG THE CREST OF THE BLUE
RIDGE. THE STRONGEST WINDS EAST OF THE MOUNTAINS WILL OCCUR LATE
FRIDAY NIGHT INTO SATURDAY MORNING.
HIGH TEMPERATURES WILL RANGE FROM BELOW FREEZING OVER THE MOUNTAINS
TO MID TO UPPER 40S AND LOW 50S FURTHER EAST FRIDAY. LOWS FRIDAY
NIGHT INTO SATURDAY MORNING WILL FALL INTO THE 30S AND 40S.
LONG TERM /SATURDAY THROUGH TUESDAY/
SNOW SHOWER ACTIVITY WILL BEGIN TO DECREASE SATURDAY MORNING INTO
SATURDAY AFTERNOON AS THE SHORTWAVE TROUGH KICKS EAST AND THE UPPER
LEVEL LOW EXITS OFF COASTAL NEW ENGLAND. ADDITIONAL LIGHT SNOW
ACCUMULATIONS ARE POSSIBLE DURING THIS TIME ALONG THE HIGHEST RIDGES
WEST OF THE ALLEGHENY FRONT ALTHOUGH THE HEAVIEST SNOWS WILL HAVE
COME TO AN END. SOME UNCERTAINTY REMAINS INTO HOW MUCH SNOW WILL BE
LEFTOVER AS TEMPERATURES WILL BE AT OR ABOVE FREEZING WHICH WILL
DECREASE SNOW RATIOS AND IN TURN ANY ADDITIONAL ACCUMULATIONS DURING
THIS TIME. AREAS FURTHER EAST WILL SEE DRY CONDITIONS UNDER
DOWNSLOPING FLOW. WINDS WILL REMAIN GUSTY OUT OF THE WEST AND
NORTHWEST AT 25 TO 35 MPH. GUST UP TO 40 MPH REMAIN POSSIBLE OVER
THE RIDGES AND OPEN WATERS OF THE BAY AS THE GRADIENT WILL REMAIN
TIGHTENED BETWEEN THE DEPARTING LOW PRESSURE SYSTEM OVER NEW ENGLAND
AND THE INCOMING HIGH PRESSURE SYSTEM OVER THE CENTRAL APPALACHIANS
REGION.
SPEAKING OF HIGH PRESSURE, IT LOOKS TO BUILD BACK OVER THE AREA LATE
SATURDAY INTO SUNDAY. THIS WILL ALLOW FOR QUIET WEATHER TO RETURN
ALONG WITH DECREASING WINDS ACROSS THE REGION. DRY WEATHER
CONDITIONS AND MODERATING TEMPERATURES ARE EXPECTED HEADING INTO
MONDAY AS HIGH PRESSURE DRIFTS OFF THE SOUTHEAST U.S COAST.
MEANWHILE, LOW PRESSURE OVER THE CENTRAL U.S WILL TRACK NORTH AND
EAST INTO THE GREAT LAKES MONDAY INTO TUESDAY. THIS WILL SEND
ANOTHER FRONT INTO OUR REGION FOR THE MIDDLE OF NEXT WEEK. AS IT
STANDS NOW, THE FRONT LOOKS TO STALL SOMEWHERE IN THE VICINITY OF
OUR REGION TUESDAY INTO WEDNESDAY. THIS WILL LEAD TO INCREASED
PRECIPITATION CHANCES DURING THIS TIME. ACTIVE WEATHER CONTINUES
THROUGH THE EXTENDED INTO THE UPCOMING HOLIDAY AHEAD.
TEMPERATURES WILL REMAIN BELOW AVERAGE THROUGH THE WEEKEND WITH SOME
MODERATION BACK TOWARD NORMAL TO SLIGHTLY ABOVE NORMAL EARLY NEXT
WEEK. EXPECT HIGHS IN THE 40S AND 50S SATURDAY WARMING INTO THE 50S
SUNDAY OUTSIDE THE MOUNTAIN. LOWS WILL FALL INTO THE 30S. HIGHS
RETURN TOWARD THE 60 DEGREE MARK MONDAY AND TUESDAY UNDER INCREASED
SOUTHERLY FLOW.
AVIATION /15Z WEDNESDAY THROUGH SUNDAY/
CONDITIONS HAVE IMPROVED BACK TO VFR IN MOST LOCATIONS, AND
SHOULD REMAIN VFR THROUGH MUCH OF THE DAY. WINDS TODAY WILL
GENERALLY BE LIGHT OUT OF THE EAST TO SOUTHEAST. A BRIEF LINE
OF HEAVIER SHOWERS OR STORMS MAY ACCOMPANY A COLD FRONTAL
PASSAGE LATER THIS EVENING, WITH SHOWERS POTENTIALLY LINGERING
FOR A FEW HOURS BEHIND THE FRONT. SUB-VFR CONDITIONS MAY BE
POSSIBLE FOR A BRIEF TIME IN ASSOCIATION WITH THESE SHOWERS.
CONDITIONS SHOULD IMPROVE BACK TO VFR BEHIND THE FRONT, BUT
WINDS WILL BECOME GUSTY OUT OF THE WEST THROUGH THE REMAINDER OF
THE NIGHT. THE WIND SHIFT WILL BE ABRUPT, WITH WINDS GOING FROM
LIGHT OUT OF THE SOUTHEAST TO GUSTING TO AROUND 30-40 KNOTS OUT
OF THE WEST OVER A VERY SHORT TIME PERIOD. LLWS WILL ALSO BE
POSSIBLE THIS EVENING IMMEDIATELY BEHIND THE FRONT.
VFR CONDITIONS AND WESTERLY WINDS ARE EXPECTED ON THURSDAY. A
PASSING RAIN OR MIXED RAIN/GRAUPEL/SNOW SHOWER CAN'T BE RULED
OUT THURSDAY AFTERNOON, BUT THE VAST MAJORITY OF THE DAY SHOULD
REMAIN DRY.
VFR CONDITIONS ARE EXPECTED AT MOST TERMINALS FRIDAY, ALTHOUGH
SOME BRIEF PERIODS OF MVFR ARE POSSIBLE AT TIMES ESPECIALLY WEST
OF KMRB/KHGR. GUSTY WEST TO NORTHWEST WINDS WILL BE THE
PREDOMINANT ISSUE FOR AVIATION HEADING INTO THE START OF THE
WEEKEND. EXPECT SUSTAINED SPEEDS OF 10-20 KTS DURING THE DAY AND
NIGHTTIME HOURS WITH GUSTS 20 TO 30 KTS ON BOTH FRIDAY AND
SATURDAY AFTERNOONS. OUTSIDE OF THE WIND, PRECIPITATION CHANCES
REMAIN LOW WITH UPSLOPE SNOW SHOWERS MAINLY CONFINED WEST OF
THE ALLEGHENY FRONT. A FEW SHOWERS WITH PERHAPS A FEW WET
SNOWFLAKES OR EVEN A LITTLE GRAUPEL ARE POSSIBLE AT KMRB, KHGR,
KOKV, AND KFDK FRIDAY MORNING ALTHOUGH CONFIDENCE IS LOW.
VFR CONDITIONS ARE EXPECTED SUNDAY AND MONDAY WITH DECREASING
WINDS AS HIGH PRESSURE BUILDS OVER THE REGION.
MARINE
MUCH OF THE DAY TODAY WILL BE MET WITH FAIRLY LIGHT EASTERLY
WINDS. A STRONG COLD FRONT WILL MOVE OVER THE WATERS LATER THIS EVENING,
LEADING TO AN ABRUPT WIND SHIFT TO WESTERLY, WITH STRONG WINDS
IMMEDIATELY BEHIND THE FRONT. A GALE WARNING IS IN EFFECT FOR
ALL WATERS STARTING LATER THIS EVENING AND INTO THURSDAY MORNING.
A SPECIAL MARINE WARNING MAY ALSO BE NEEDED DUE TO THE SUDDEN
ONSET OF THE GALE GUSTS. SCA CONDITIONS ARE EXPECTED IN
WESTERLY FLOW THURSDAY THROUGH THURSDAY NIGHT.
HIGH END SCAS ARE LIKELY TO CONTINUE THROUGH SATURDAY NIGHT WITH
FREQUENT GUSTS OF 20 TO 30 KTS EXPECTED ACROSS ALL WATERS. GALE
FORCE GUSTS ARE POSSIBLE OVER THE OPEN WATERS OF THE BAY AND LOWER
TIDAL POTOMAC LATE FRIDAY NIGHT INTO SATURDAY AS WINDS SURGE BEHIND
A DEPARTING SHORTWAVE TROUGH. WINDS DECREASE BELOW SCA LEVELS SUNDAY
AND MONDAY AS HIGH PRESSURE BUILDS NEARBY.
TIDES/COASTAL FLOODING
MINOR COASTAL FLOODING IS POSSIBLE AT THE MORE SENSITIVE TIDAL
SITES LIKE ANNAPOLIS AND DC SW WATERFRONT OVER THE NEXT COUPLE
TIDE CYCLES. WATER LEVELS WILL DECREASE TONIGHT THROUGH THE
UPCOMING WEEKEND AS WINDS TURN WESTERLY.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...GALE WARNING FROM 6 PM THIS EVENING TO 6 AM EST THURSDAY FOR
MDZ008.
WINTER STORM WARNING FROM 10 AM THURSDAY TO MIDNIGHT EST
FRIDAY NIGHT FOR MDZ001.
VA...WIND ADVISORY FROM 6 PM THIS EVENING TO 1 AM EST THURSDAY FOR
VAZ503.
WINTER STORM WARNING FROM 10 AM THURSDAY TO 6 AM EST SATURDAY
FOR VAZ503.
WV...WIND ADVISORY FROM 6 PM THIS EVENING TO 1 AM EST THURSDAY FOR
WVZ501-505.
WINTER STORM WARNING FROM 10 AM THURSDAY TO 6 AM EST SATURDAY
FOR WVZ501-505.
WINTER WEATHER ADVISORY FROM 10 AM TO 10 PM EST THURSDAY FOR
WVZ503.
MARINE...GALE WARNING FROM 6 PM THIS EVENING TO 6 AM EST THURSDAY FOR
ANZ530>543.
SYNOPSIS...ADM/EST
NEAR TERM...KJP/ADM
SHORT TERM...ADM/EST
LONG TERM...EST
AVIATION...ADM/EST
MARINE...ADM/EST
TIDES/COASTAL FLOODING...LWX
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