120
FXUS61 KLWX 210212
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
912 PM EST FRI DEC 20 2024
SYNOPSIS
LOW PRESSURE WILL CONTINUE TO EXIT TO THE EAST OVERNIGHT WITH
SOME LINGERING SNOW SHOWERS ALONG THE ALLEGHENIES WITH LIGHT
FLURRIES FURTHER EAST. HIGH PRESSURE RETURNS LATE SATURDAY
THROUGH MONDAY, WITH MAINLY DRIER AND VERY COLD CONDITIONS.
PRECIPITATION CHANCES INCREASE AS ANOTHER FRONT APPROACHES
DURING THE MIDDLE OF NEXT WEEK.
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/
915 PM UPDATE: RAIN AND SNOW SHOWERS HAVE DISSIPATED ACROSS NE
MD THIS EVENING, WITH LINGERING SNOW SHOWERS ACROSS THE
ALLEGHENY FRONT. THESE SHOWERS AND STREAMERS WILL CONTINUE
OVERNIGHT AND EVEN INTO EARLY SATURDAY. ACCUMULATIONS OVERNIGHT
WILL LIKELY BE A TRACE TO AROUND 2 INCHES IN ISOLATED AREAS
ALONG THE ALLEGHENIES. OVERNIGHT LOWS WILL CONTINUE TO FALL INTO
THE UPPER 20S TO LOW 30S FOR THE LOWER ELEVATIONS AND MID TO
UPPER TEENS ALONG THE ALLEGHENY FRONT. WINDS WILL ALSO INCREASE
TONIGHT, WITH THE HIGHEST GUSTS ALONG THE RIDGE TOPS GETTING
INTO THE 30 TO 35 MPH RANGE BY EARLY SATURDAY MORNING.
SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/
A LARGE HIGH WILL BUILD SOUTH INTO THE REGION BEHIND THE
DEPARTING UPPER LEVEL STORM SYSTEM. THIS HIGH WILL CIRCULATE
MORE ARCTIC AIR SOUTHEAST AND SOUTHWARD. WHILE CONDITIONS LOOK
DRY TO THE EAST OF THE MOUNTAINS, AN ADDITIONAL INCH OR 2 COULD
ACCUMULATE. MOST OF THE ACCUMULATING SNOW IS LIKELY TO COME
FROM HEAVIER SNOW SHOWERS TO SNOW SQUALLS. THERE IS STILL UNCERTAINTY
REGARDING THE EXACT PLACEMENT, INTENSITY, AND DURATION OF ANY
HEAVIER SHOWERS/SQUALLS. THESE COULD SET UP AS STREAMERS,
MEANING A LARGE GRADIENT OF SNOW ACCUMULATIONS OVER SHORT
DISTANCES. TOTAL SNOW ACCUMULATION THROUGH SATURDAY EVENING WILL
BE AROUND 2 TO 4 INCHES WITH ISOLATED 5 INCH IN A WORST- CASE
SCENARIO, FROM GARRETT INTO WESTERN GRANT/WESTERN PENDLETON
COUNTIES.
BLUSTERY CONDITIONS EXPECTED SATURDAY AFTERNOON, AS WINDS GUST
UP TO 40 MPH IN THE MOUNTAINS. COMBINED WITH HIGHS IN THE 30S,
THE RESULTING WIND CHILL VALUES DURING THE MIDDLE OF THE DAY ARE
LIKELY TO BE IN THE TEENS TO 20S, WITH SINGLE DIGITS IN THE
MOUNTAINS.
BRISK TO BLUSTERY CONDITIONS CONTINUE INTO SATURDAY NIGHT, AS LOWS
DROP TO THE 20S. GUSTY WINDS PRODUCE WIND CHILLS IN THE SINGLE
DIGITS TO LOW TEENS, WITH BELOW 0 VALUES IN THE ALLEGHENIES.
HIGHS REMAIN BELOW FREEZING FOR MOST OF THE AREA SUNDAY, WITH UPPER
20S TO LOW 30S, AND MID 30S IN CENTRAL VA. DOWNRIGHT COLD SUNDAY
NIGHT AS LOWS DIP TO THE LOW TEENS AREAWIDE, WITH SOME SINGLE DIGITS
IN THE MOUNTAINS AND ALONG THE MD/PA BORDER.
LONG TERM /MONDAY THROUGH FRIDAY/
ARCTIC AIR WILL RELEASE IT'S GRIP UPON OUR REGION MONDAY WITH
MODERATING TEMPERATURES THROUGHOUT THE HOLIDAY WEEK. OVERALL THE
UPPER LEVEL FLOW WILL BECOME MORE ZONAL WITH A FAIRLY ACTIVE
NORTHERN AND SOUTHERN JETSTREAM. SEVERAL PIECES OF SHORTWAVE ENERGY
WILL TRAVERSE THE SOUTHERN JETSTREAM EJECTING OUT OF THE SOUTHERN
U.S INTO THE MID-SOUTH AND MID-ATLANTIC WITH SUBTROPICAL RIDGING OFF
THE SOUTHEAST U.S COAST.
COLD AND DRY CONDITIONS LOOK TO CONTINUE THROUGH MONDAY AS STRONG
CANADIAN HIGH PRESSURE MAINTAINS IT'S PRESENCE OVER THE REGION. HIGH
PRESSURE WILL PUSH OFFSHORE LATE MONDAY INTO TUESDAY AS A NORTHERN
STREAM LOW PRESSURE SYSTEM RACES EAST FROM THE CENTRAL GREAT LAKES
REGION. THIS LOW PRESSURE SYSTEM COULD BRING RENEWED SNOW SHOWER
CHANCES TO THE ALLEGHENIES AS EARLY AS MONDAY NIGHT. ANY WIDESPREAD
PRECIPITATION LOOKS TO HOLD OFF UNTIL TUESDAY AND WEDNESDAY AS THE
LOW PRESSURE SYSTEM TRACKS NORTH OF THE AREA. SOME UNCERTAINTY
REMAINS AMONGST BOTH THE DETERMINISTIC AND ENSEMBLE GUIDANCE OF WHAT
THE MAIN PRECIPITATION TYPE WILL BE DURING THE TUESDAY AND WEDNESDAY
TIMEFRAME. AS IT STANDS NOW, IT LOOKS AS IF TEMPERATURES APPEAR COLD
ENOUGH AT ONSET FOR A LIGHT WINTRY MIX TUESDAY AFTERNOON INTO EARLY
WEDNESDAY MORNING (CHRISTMAS EVE/CHRISTMAS DAY) ESPECIALLY IN
LOCATIONS ALONG AND NORTH OF I-66/US-50. BEYOND THIS POINT,
UNCERTAINTY REMAINS TO HOW MUCH COLD AIR WILL BE LEFTOVER CHRISTMAS
DAY, AS THE BULK OF THE 12Z GUIDANCE SUGGESTS A WARMER SOLUTION
AHEAD OF THE SLOW MOVING COLD FRONTAL BOUNDARY. ANY RESIDUAL FROZEN
PRECIPITATION CHRISTMAS MORNING WILL LIKELY CHANGE OVER TO PLAIN
RAIN OUTSIDE THE MOUNTAINS WHICH COULD HOLD ONTO THE COLD AIR
LONGER. OVERALL THE PROBABILITY FOR A WHITE CHRISTMAS ACROSS THE
AREA REMAINS LOW, BUT NOT ZERO ESPECIALLY FOR THOSE WEST OF THE
ALLEGHENIES. A SLIGHT CHANCE OF RAIN SHOWERS (SNOW AT HIGHER
ELEVATIONS) PERSIST THROUGH THURSDAY AS THE COLD FRONT STALLS JUST
SOUTH OF THE AREA.
BELOW NORMAL TEMPERATURES LOOK TO CONTINUE THROUGH MONDAY BEFORE
TRENDING BACK TOWARD NORMAL FOR THE MIDDLE OF THE UPCOMING HOLIDAY
WEEK. HIGHS WILL GENERALLY REMAIN IN THE 30S AND 40S WITH LOWS IN
THE 20S AND 30S. BY FRIDAY, SOME LOCATIONS COULD PUSH 50 DEGREES.
AVIATION /02Z SATURDAY THROUGH WEDNESDAY/
A LULL IN PRECIPITATION WILL ALLOW FOR CEILINGS TO BECOME MVFR
OR VFR LATER THIS EVENING AND OVERNIGHT. A COLD FRONT MOVES
THROUGH TONIGHT, WITH VFR CONDITIONS RETURNING FOR SATURDAY AND
SUNDAY FOR ALL SITES. NORTHWEST WINDS INCREASE, GUSTING AROUND
25 TO 35 KNOTS SATURDAY AFTERNOON.
VFR CONDITIONS CONTINUE THROUGH TUESDAY AS HIGH PRESSURE REMAINS
NEARBY. THE NEXT CHANCE FOR SUB-VFR CONDITIONS ARRIVES TUESDAY
EVENING (CHRISTMAS EVE) AND WEDNESDAY (CHRISTMAS DAY) AS AN AREA OF
LOW PRESSURE AND FRONT CROSS THE REGION. VFR CONDITIONS RETURN WITH
BRIEF HIGH PRESSURE THURSDAY BEFORE ANOTHER WAVE OF LOW PRESSURE
CROSSES FRIDAY.
MARINE
SCAS ARE IN EFFECT THROUGH EARLY SUNDAY DUE TO THE EXPECTATIONS
OF GUSTY NORTHWEST TO NORTH WINDS THROUGHOUT MUCH OF THE
PERIOD. GUSTS COULD REACH 30 KNOTS ACROSS THE WATERS SATURDAY.
WINDS DECREASE SATURDAY NIGHT, DROPPING BELOW SCA LEVELS IN THE
UPPER POTOMAC WATERS, BUT STILL GUSTING UP TO 25 KNOTS OVER THE
BAY. THESE ELEVATED WINDS CONTINUE THROUGH SUNDAY AFTERNOON,
BEFORE FINALLY DROPPING BELOW SCA LEVELS SUNDAY EVENING.
SUB-SCA LEVEL WINDS ARE EXPECTED MONDAY AND TUESDAY. SOUTHERLY WINDS
LESS THAN 15 KTS MONDAY WILL SHIFT TO THE NORTHWESTERLY DIRECTION
TUESDAY. SHOWER CHANCES LOOK TO RETURN TO THE WATERS DURING THIS
TIME AND CONTINUE THROUGH THE WEDNESDAY (CHRISTMAS) HOLIDAY.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...SMALL CRAFT ADVISORY UNTIL 10 AM EST SUNDAY FOR MDZ008.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EST SUNDAY FOR ANZ530>532-536-
538>540-542.
SMALL CRAFT ADVISORY UNTIL 4 PM EST SUNDAY FOR ANZ533-534-537-
541-543.
SMALL CRAFT ADVISORY FROM 6 AM TO 7 PM EST SATURDAY FOR ANZ535.
SYNOPSIS...KLW
NEAR TERM...KLW/ADM
SHORT TERM...KLW
LONG TERM...EST
AVIATION...KLW/ADM/EST
MARINE...KLW/EST
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