106
FXUS61 KLWX 230156 AAA
AFDLWX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
856 PM EST FRI FEB 22 2019
SYNOPSIS
HIGH PRESSURE WILL REMAIN TO OUR NORTH THROUGH TONIGHT WHILE A
BOUNDARY STALLS OVER THE SOUTHEASTERN CONUS. LOW PRESSURE
DEVELOPING OVER THE MIDDLE MISSISSIPPI RIVER VALLEY WILL
STRENGTHEN AS IT MOVES NORTHEASTWARD ACROSS THE GREAT LAKES INTO
CANADA THIS WEEKEND. HIGH PRESSURE WILL BUILD FROM THE NORTHERN
GREAT PLAINS TOWARD THE GREAT LAKES AND EVENTUALLY INTO THE
NORTHEAST THROUGH THE FIRST HALF OF NEXT WEEK. LOW PRESSURE
DEVELOPING OVER THE TENNESSEE VALLEY COULD APPROACH THE REGION
DURING THE MIDDLE OF NEXT WEEK.
NEAR TERM /UNTIL 6 AM SATURDAY MORNING/
LOW PRESSURE WILL BEGIN TO STRENGTHEN OVER THE ROCKIES
OVERNIGHT AND HIGH PRESSURE WILL REMAIN TO OUR NORTH. THE LOW-
LEVEL FLOW WILL BEGIN TO TURN TO THE SOUTHWEST AND THIS WILL
ALLOW FOR OVERRUNNING TO INCREASE. STILL FEEL THAT MOST AREAS
ACROSS THE CENTRAL AND NORTHERN CWA WILL BE DRY...CLOSER TO THE
HIGH. HOWEVER, LIGHT RAIN WILL LIKELY SPREAD NORTH INTO THE
POTOMAC HIGHLANDS AND CENTRAL VIRGINIA TOWARD MORNING. THERE
WILL BE ENOUGH EVAPORATIVE COOLING FOR A COLD LAYER TO DEVELOP
BETWEEN ABOUT 2KFT AND 4KFT. THIS WILL CAUSE FREEZING RAIN ALONG
THE RIDGES. A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE
POTOMAC/ALLEGHENY HIGHLANDS AND CENTRAL/NORTHERN VIRGINIA BLUE
RIDGE MOUNTAINS, WHERE CONFIDENCE IS HIGHEST FOR PRECIPITATION
TO OCCUR IN THAT COLD LAYER. ICE ACCUMULATIONS WILL BE AROUND
ONE- TENTH OF AN INCH OR LESS. LOWS GENERALLY 28-38F.
SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/
LOW PRESSURE WILL INTENSIFY AS IT MOVES THROUGH THE MIDWEST
SATURDAY. THE LOW AND MID-LEVEL FLOW WILL STRENGTHEN AND TURN
MORE SOUTH TO SOUTHWESTERLY, CAUSING MORE OVERRUNNING. THIS WILL
CAUSE RAIN TO OVERSPREAD THE REST OF THE AREA FROM SOUTHWEST TO
NORTHEAST SATURDAY MORNING INTO SATURDAY AFTERNOON. A MODERATE
TO PERHAPS EVEN LOCALLY HEAVY RAIN IS EXPECTED ACROSS PORTIONS
OF THE POTOMAC HIGHLANDS AND CENTRAL VIRGINIA SOUTH OF
INTERSTATE 64. A FLOOD WATCH IS IN EFFECT FOR THESE AREAS.
ELSEWHERE, RAIN SHOULD BE LIGHT ENOUGH TO PREVENT FLOODING
SATURDAY INTO SATURDAY EVENING, BUT IT COULD BE CLOSE DURING THE
EVENING HOURS NEAR THE CHARLOTTESVILLE AREA. THE REASON WHY THE
STEADIER RAIN WILL BE TO THE SOUTHWEST IS THAT OVERRUNNING WILL
BE DEEPER FARTHER AWAY FROM THE HIGH.
WILL ALSO HAVE TO WATCH FOR FREEZING RAIN ALONG THE RIDGES AS
WELL. THE WINTER WEATHER ADVISORY CONTINUES THROUGH SATURDAY
MORNING FOR THE CENTRAL/NORTHERN BLUE RIDGE INTO THE
POTOMAC/ALLEGHENY HIGHLANDS. FURTHER EXPANSION MAY BE NEEDED
INTO WESTERN ALLEGANY COUNTY IN MARYLAND, BUT CONFIDENCE WAS
NOT HIGH ENOUGH AT THIS TIME DUE TO UNCERTAINTIES WITH THE
TIMING AND ARRIVAL OF THE STEADIER PRECIPITATION.
LOW PRESSURE WILL MOVE INTO THE GREAT LAKES SATURDAY NIGHT AND
INTO CANADA SUNDAY. THE WARM FRONT ASSOCIATED WITH THE LOW WILL
APPROACH SATURDAY NIGHT BEFORE PASSING THROUGH MIDDAY SUNDAY
AND THE COLD FRONT ASSOCIATED WITH THE LOW WILL PASS THROUGH
SUNDAY AFTERNOON.
FOR SATURDAY NIGHT INTO EARLY SUNDAY, A SOAKING RAIN IS EXPECTED
ACROSS MOST AREAS DUE TO INCREASED OVERRUNNING AND FORCING FROM
A STRENGTHENING LOW-LEVEL JET. COPIOUS AMOUNTS OF MOISTURE
REMAIN IN PLACE. RAINFALL AMOUNTS AROUND 0.75 TO 1.50" ARE MOST
LIKELY, WITH LOCALLY 2-3" POSSIBLE. THE HIGHEST AMOUNTS FOR THE
ENTIRE EVENT (TONIGHT THROUGH SUNDAY MORNING) ARE MOST LIKELY
ACROSS THE CENTRAL SHENANDOAH VALLEY INTO THE POTOMAC HIGHLANDS.
HAVING THAT BEEN SAID, RECENT SNOW MELT HAS CAUSED SATURATED
SOILS AND FLOOD GUIDANCE IS LOW DUE TO THAT. THEREFORE, FLOODING
OF SMALL STREAMS AND CREEKS AS WELL AS LOW LYING URBAN AREAS IF
POSSIBLE ACROSS THE ENTIRE AREA SATURDAY NIGHT INTO SUNDAY.
CONFIDENCE WAS NOT HIGH ENOUGH FOR A WATCH AT THIS TIME DUE TO
THE LATER START TIME OF THE STEADIER PRECIPITATION AND THE FACT
THAT IT MAY BE SEPARATED FURTHER FROM WHEN MOST OF THE SNOW
MELTING HAS OCCURRED (THURSDAY INTO FRIDAY OF THIS WEEK). WILL
HAVE TO REASSESS ON LATER SHIFTS.
DRIER CONDITIONS WILL OVERSPREAD THE AREA FROM WEST TO EAST
SUNDAY MORNING AND LOW PRESSURE WILL INTENSIFY AS IT MOVES INTO
SOUTHERN CANADA. A STRONG GRADIENT BETWEEN THE LOW AND HIGH
PRESSURE OVER THE CENTRAL CONUS WILL CAUSE WINDY CONDITIONS
BEHIND THE COLD FRONT LATER SUNDAY MORNING INTO THE POTOMAC
HIGHLANDS AND SUNDAY AFTERNOON ELSEWHERE. THE WINDY CONDITIONS
WILL PERSIST THROUGH SUNDAY NIGHT. A HIGH WIND WATCH IS IN
EFFECT, MAINLY FOR THE RIDGES OF ALLEGHENY AND POTOMAC HIGHLANDS
AS WELL AS THE BLUE RIDGE MOUNTAINS. WIND GUSTS AROUND 60 MPH
ARE POSSIBLE. ELSEWHERE, WIND GUSTS OF 35 TO 55 MPH ARE MOST
LIKELY, ESPECIALLY ACROSS NORTHERN AND CENTRAL AREAS (INCLUDING
THE WASHINGTON AND BALTIMORE METRO AREAS). WILL CONTINUE TO
MONITOR FOR THE POTENTIAL OF WIND ADVISORIES AND/OR HIGH WIND
WARNINGS.
LONG TERM /MONDAY THROUGH FRIDAY/
STRONG CANADIAN HIGH PRESSURE WILL BE BUILDING SOUTHWARD INTO THE
CENTRAL U.S. ON MONDAY, AS LOW PRESSURE LIFTS AWAY FROM NEW
ENGLAND TO THE NORTHEAST. THIS WILL MAINTAIN A TIGHT PRESSURE
GRADIENT ACROSS THE MID ATLANTIC STATES, SO CONTINUED WINDY
CONDITIONS CAN BE EXPECTED. DRY CONDITIONS, NEAR NORMAL
TEMPERATURES AND MOSTLY CLEAR SKIES ARE LIKELY INTO MID WEEK AS
HIGH PRESSURE BUILDS OVER THE REGION. GFS HINTING AT THE
POTENTIAL FOR A WEAK AREA OF LOW PRESSURE PASSING TO OUR NORTH
ON WEDNESDAY, ALTHOUGH MOSTLY DRY CONDITIONS LOOK TO PERSIST,
OUTSIDE OF SOME UPSLOPE SHOWERS. HIGH PRESSURE LOOKS TO BUILD
BACK OVER THE REGION THROUGH THURSDAY, WITH CONTINUED DRY
CONDITIONS. WE WILL KEEP TEMPERATURES RUNNING NEAR NORMAL FOR
LATE FEBRUARY GIVEN DIFFERING SOLUTIONS BETWEEN DETERMINISTIC
AND ENSEMBLE GUIDANCE AT THIS TIME.
AVIATION /02Z SATURDAY THROUGH WEDNESDAY/
VFR CONDITIONS ARE EXPECTED THROUGH TONIGHT AT ALL TERMINALS.
CHANCES THEN BEGIN TO INCREASE FOR MVFR AT CHO SATURDAY MORNING.
LOW CLOUDS AND RAIN WILL THEN OVERSPREAD THE TERMINALS SATURDAY
AFTERNOON INTO SATURDAY NIGHT, AND LAST INTO SUNDAY MORNING WITH
IFR CONDITIONS LIKELY AND SUBIFR CONDITIONS POSSIBLE. A COLD
FRONT WILL PASS THROUGH THE TERMINALS SUNDAY, AND STRONG WINDS
ARE POSSIBLE BEHIND THE COLD FRONT LATER SUNDAY AFTERNOON AND
SUNDAY NIGHT.
VFR CONDITIONS EXPECTED MONDAY AND TUESDAY AS HIGH PRESSURE
BUILDS TO OUR WEST. THE GRADIENT WILL REMAIN TIGHT ON MONDAY
WITH THE EXITING LOW OFF OF NEW ENGLAND AND THE BUILDING HIGH,
SO STRONG GUSTY NORTHWEST WINDS CAN BE EXPECTED. THE GRADIENT
WILL WEAKEN MONDAY NIGHT, WITH LIGHT NORTHERLY WINDS FORECAST
THROUGH TUESDAY.
MARINE
HIGH PRESSURE WILL BUILD TO THE NORTH THROUGH SATURDAY AND WINDS
SHOULD REMAIN BELOW SCA CRITERIA. LOW PRESSURE WILL PASS BY TO
THE WEST SATURDAY NIGHT INTO SUNDAY AND THE COLD FRONT
ASSOCIATED WITH THE LOW WILL PASS THROUGH LATER SUNDAY
AFTERNOON. WINDS MAY APPROACH SCA CRITERIA SATURDAY NIGHT, BUT
CONFIDENCE IS TOO LOW FOR A HEADLINE AT THIS TIME.
STRONGER WINDS ARE EXPECTED SUNDAY, ESPECIALLY SUNDAY AFTERNOON
THROUGH SUNDAY NIGHT BEHIND THE COLD FRONT. A GALE WARNING WILL
LIKELY BE NEEDED FOR THE WATERS DURING THIS TIME.
GALE CONDITIONS LIKELY ON MONDAY AS THE GRADIENT REMAINS QUITE
STRONG BETWEEN AN EXISTING LOW OFF OF NEW ENGLAND AND HIGH
PRESSURE BUILDING INTO THE CENTRAL U.S. SCA CONDITIONS LIKELY
PERSIST INTO MONDAY NIGHT BEFORE DROPPING BELOW CRITERIA TUESDAY
AND TUESDAY NIGHT AS HIGH PRESSURE BUILDS TOWARD THE REGION.
HYDROLOGY
GIVEN RECENT SNOWMELT AND SATURATED GROUND, 0.75" TO AROUND 1.5"
OF RAIN MAY BE ENOUGH TO RESULT IN MINOR FLOODING ISSUES THIS
WEEKEND, PARTICULARLY OVER EASTERN WEST VIRGINIA. THE OVERALL
TREND HAS BEEN FOR SLIGHTLY LESS RAIN, BUT NOT SO MUCH LESS TO
COMPLETELY AVOID A FLOOD THREAT. DESPITE THE SLIGHTLY LOWER QPF
TOTALS IN THE 12Z MODEL SUITE, MMEFS STILL INDICATES >50%
CHANCE OF MINOR FLOOD AT SEVERAL RIVER FORECAST POINTS LATER
THIS WEEKEND.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...HIGH WIND WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING FOR
MDZ501.
HIGH WIND WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY MORNING
FOR MDZ003-004-502.
VA...FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH LATE SATURDAY
NIGHT FOR VAZ025-036-037-503-504-508.
WINTER WEATHER ADVISORY FROM 3 AM TO NOON EST SATURDAY FOR
VAZ503-504-508.
HIGH WIND WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING FOR
VAZ503-504-507-508.
WINTER WEATHER ADVISORY FROM 7 AM TO NOON EST SATURDAY FOR
VAZ507.
WV...WINTER WEATHER ADVISORY FROM 3 AM TO NOON EST SATURDAY FOR
WVZ505-506.
HIGH WIND WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING FOR
WVZ501>503-505-506.
HIGH WIND WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY MORNING
FOR WVZ050>052-055-504.
WINTER WEATHER ADVISORY FROM 7 AM TO NOON EST SATURDAY FOR
WVZ501-503.
MARINE...NONE.
SYNOPSIS...BJL
NEAR TERM...BJL/MM
SHORT TERM...BJL
LONG TERM...BKF
AVIATION...BJL/MM/BKF
MARINE...BJL/MM/BKF
HYDROLOGY...BJL
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