482
FXUS61 KLWX 130755
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
355 AM EDT TUE APR 13 2021
SYNOPSIS
A WEAK AREA OF HIGH PRESSURE WILL MOVE IN TODAY, BEFORE AN
UPPER LEVEL LOW IMPACTS OUR AREA DURING THE MIDDLE TO LATTER
PORTIONS OF THE WEEK.
NEAR TERM /THROUGH TONIGHT/
A FEW VERY LIGHT SHOWERS PERSIST EARLY THIS MORNING ACROSS
EASTERN AREAS ON THE BACKSIDE OF AN UPPER LOW SPINNING OFF OF
THE DELMARVA COAST, BUT SHOULD DISSIPATE SOON AS MID-LEVEL
SUBSIDENCE STRENGTHENS. OTHERWISE, WEAK SURFACE HIGH PRESSURE
AND MID-UPPER LEVEL RIDGING WILL BUILD OVER THE AREA DURING THE
NEXT 24 HRS AND SUPPORT FAIR WEATHER CONDITIONS. HOWEVER, VERY
COOL MID-LEVEL TEMPS AND RESIDUAL LOW-LEVEL MOISTURE COMBINED
WITH DAYTIME HEATING WILL SUPPORT BKN STRATOCUMULUS FIELD AND,
HENCE, MOSTLY CLOUDY SKIES.
SOME PATCHY FOG IS POSSIBLE LATE TONIGHT ESPECIALLY IN AREAS
THAT HAVE RECEIVED THE MOST RAIN LATELYT. MID- HIGH LEVEL
CLOUDS WILL INCREASE LATE TONIGHT IN ADVANCE OF CLOSED UPPER LOW
DROPPING FROM THE GREAT LKS.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
A LOW PRESSURE CENTER AND ASSOCIATED FRONTAL ZONE IS EXPECTED TO
DEVELOP WED AFTERNOON INTO THU ACROSS SRN VA AND THE CAROLINAS
AS HEIGHTS FALL IN ADVANCE OF UPPER LOW DROPPING FROM THE GREAT
LKS INTO THE NORTHERN MID-ATLC IN AN AREA OF INCREASING UPPER
LEVEL DIFFLUENCE. SHOWERS ARE EXPECTED WED INTO THU ALONG
STRENGTHENING FRONTAL ZONE AND DEVELOPING LOW PRESSURE CENTER.
SHOWERY AND UNSETTLED WX WILL PERSIST THU INTO FRI IN THE
VICINITY OF UPPER LOW OVER THE NRN MID-ATLC BUT GUIDANCE HAVE
TRENDED DRIER FOR THURSDAY GIVEN MORE NORTHWARD TRACK OF UPPER
LOW AWAY FROM OUR AREA. SOME SNOW MAY ACCUMULATE ACROSS THE
HIGHEST ELEVATIONS THU NIGHT WITH PASSAGE OF UPPER TROUGH AXIS.
LONG TERM /FRIDAY THROUGH MONDAY/
BY FRIDAY, THE AFOREMENTIONED LOW PRESSURE SYSTEM WILL BE DEPARTING
TO THE EAST AS THE STRONG UPPER LOW SLOWLY PUSHES OFFSHORE.
MEANWHILE, WELL TO OUR WEST, ANOTHER UPPER LEVEL SHORTWAVE WILL
BE EXITING THE CENTRAL/SOUTHERN ROCKIES, INDUCING SURFACE
CYCLOGENSIS ACROSS THE CENTRAL PLAINS. THIS WILL MOVE IN OUR
DIRECTION LATER IN THE WEEKEND. FOR OUR AREA, THOUGH, SHOULD
REMAIN DRY ON FRIDAY FOR THE MOST PART. HOWEVER, COULD SEE SOME
SHOWERS ASSOCIATED WITH THE UPPER LOW, PARTICULARLY ALONG/WEST
OF THE ALLGHENY FRONT AND ALONG THE MASON-DIXON LINE.
AN UPPER RIDGE MOVES INTO THE REGION BRIEFLY ON FRIDAY NIGHT AND
SATURDAY, LEADING TO A BRIEF DRY PERIOD AREA-WIDE. LOWS FRIDAY NIGHT
WILL BE RIGHT AROUND SEASONAL AVERAGES, WITH LOWS IN THE LOWS 30S IN
THE MOUNTAINS AND LOW 40S ELSEWHERE. AS THE UPPER RIDGE BUILDS IN
SATURDAY, AND THE AFOREMENTIONED LOW OVER THE CENTRAL PLAINS
APPROACHES, TEMPERATURES ARE EXPECTED TO WARM SLIGHTLY INTO THE
MID 60S.
FOR SATURDAY NIGHT THROUGH SUNDAY, THE FORECAST BECOMES A BIT MORE
UNCERTAIN, ALBEIT WITH A LOW IMPACT REGARDLESS. FLOW ALOFT BECOMES
RATHER ZONAL ACROSS THE ENTIRE SOUTHERN UNITED STATES, WITH THE
SHORTWAVE MOVING OUT OF THE CENTRAL PLAINS BECOMING SOMEWHAT
WASHED OUT. A WEAK SURFACE LOW WILL TRAVERSE THE SOUTHEASTERN
UNITED STATES, THOUGH IT COULD TRACK JUST FAR ENOUGH NORTH TO
BRING SOME SHOWERS TO THE REGION. MOST LIKELY TIMEFRAME WOULD BE
SUNDAY, AND WOULD, PERHAPS, BE MORE ASSOCIATED WITH SOME
FAVORABLE JET DYNAMICS OVER THE REGION RATHER THAN THE SURFACE
LOW ITSELF, PERHAPS SPARKING SOME SHOWERS. HIGHS ON SUNDAY AGAIN
IN THE MID 60S, BUT PERHAPS SLIGHTLY WARMER THAN SATURDAY, WITH
OVERNIGHT LOWS SATURDAY AND SUNDAY NIGHT IN THE MID 30S
(MOUNTAINS) TO MID 40S (ELSEWHERE).
ANOTHER UPPER LOW MAY IMPACT THE REGION DURING THE BEGINNING PORTION
OF NEXT WEEK, WHICH COULD BRING ANOTHER CHANCE FOR SOME LIGHT
PRECIPITATION TO THE REGION.
AVIATION /07Z TUESDAY THROUGH SATURDAY/
GENERALLY EXPECTING VFR CONDITIONS ON FRIDAY AND SATURDAY. SOME
LINGERING SHOWERS COULD CAUSE SOME BRIEF REDUCED VSBYS EARLIER IN
THE DAY FRIDAY, BUT SHOULDN'T BE TOO MUCH OF AN ISSUE, AS LOW
PRESSURE IS OFFSHORE BY THIS TIME. WINDS BEHIND THAT AREA OF LOW
PRESSURE COULD BE GUSTY ON FRIDAY, WITH GUSTS TO 25 KNOTS POSSIBLE.
WINDS WILL RELAX FRIDAY NIGHT INTO SATURDAY AS AN UPPER RIDGE BUILDS
IN OVERHEAD. SHOULD SEE DRY CONDITIONS DURING THIS PERIOD AS
WELL.
MARINE
WINDS WILL BEGIN TO STRENGTHEN WED AFTERNOON AND EVENING WITH A
BRIEF LULL LATE WED NIGHT AND THU MORNING IN THE VICINITY OF
DEVELOPING LOW PRESSURE. WINDS STRENGTHEN AGAIN THU NIGHT WITH
SOLID SCA CONDITIONS EXPECTED. RISK OF GALES APPEARS LOW AT THIS
TIME.
SMALL CRAFT ADVISORIES ARE LIKELY GOING TO BE NEEDED ON FRIDAY, AND
PERHAPS INTO FRIDAY NIGHT, IN THE WAKE OF A LOW PRESSURE SYSTEM
PUSHING OFFSHORE. HOWEVER, AS THE GRADIENT LOOSENS OVERNIGHT FRIDAY
INTO SATURDAY, AND AN UPPER RIDGE BUILDS IN, EXPECT WINDS TO LIGHTEN
UP INTO SATURDAY. NO MARINE HAZARDS ARE EXPECTED ON SATURDAY.
TIDES/COASTAL FLOODING
WATER LEVELS ARE ON THE RISE WITH ANOMALIES RUNNING AROUND A
FOOT IN THE UPPER BAY TO 1.5 FT IN ANNAPOLIS TO 1.9 FT AT
DAHLGREN. MINOR COASTAL FLOODING WILL CONTINUE TO BE A CONCERN
INTO THU MORNING UNTIL WINDS BECOME MORE NW.
LWX WATCHES/WARNINGS/ADVISORIES
DC...COASTAL FLOOD ADVISORY FROM 7 AM THIS MORNING TO NOON EDT
TODAY FOR DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR
MDZ016-017.
COASTAL FLOOD ADVISORY UNTIL 11 AM EDT THIS MORNING FOR MDZ014.
VA...COASTAL FLOOD ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR
VAZ057.
WV...NONE.
MARINE...NONE.
SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...CJL
AVIATION...LFR/CJL
MARINE...LFR/CJL
TIDES/COASTAL FLOODING...
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