858
FXUS61 KLWX 270051
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
851 PM EDT TUE MAY 26 2020
SYNOPSIS
HIGH PRESSURE REMAINS IN THE WESTERN ATLANTIC THROUGH
WEDNESDAY. A TROPICAL DISTURBANCE NEAR THE SOUTHEAST U.S. COAST
ON WEDNESDAY MORNING WILL MOVE NORTH THROUGH THE APPALACHAINS
BY THURSDAY MORNING, AND REPLACED BY SLOW MOVING UPPER LEVEL
TROUGH WHICH LINGERS ACROSS THE CWA THROUGH FRIDAY NIGHT. A
COLD FRONT WILL MOVE THROUGH OUR REGION FROM THE WEST EARLY
SATURDAY. HIGH PRESSURE BUILDS INTO THE REGION SUNDAY AND
REMAINS THROUGH EARLY NEXT WEEK.
NEAR TERM /THROUGH WEDNESDAY/
THE CWA IS CAUGHT BETWEEN THE OFFSHORE SURFACE HIGH AND THE
TROPICAL DISTURBANCE THAT'S WELL TO THE SOUTH; HOWEVER, THE LONG
SE FETCH WILL CONTINUE TO PUMP MOISTURE INTO THE REGION. AS OF
THIS EVENING, SATELLITE IMAGERY IS SHOWING HIGH CLOUDS WELL
AHEAD OF THE TROPICAL DISTURBANCE MOVING INTO THE AREA. ALSO, A
STRATUS DECK IS APPROACHING FROM THE EASTERN SHORE.
HIGH CLOUDS WILL CONTINUE TO MOVE INTO THE AREA TONIGHT, AND
WITH A PERSISTENT ONSHORE FLOW, LOW CLOUDS AND AREAS OF DRIZZLE/FOG
SHOULD SPREAD OVER THE AREA AFTER MIDNIGHT. FOG MAY BE LOCALLY
DENSE AND ANOTHER DENSE FOG ADVISORY MAY BE NEEDED LATE TONIGHT
INTO WEDNESDAY MORNING AS MOISTURE GETS TRAPPED UNDERNEATH THE
NOCTURNAL AND SUBSIDENCE INVERSIONS.
WITH BOTH WARM AIR AND MOISTURE ADVECTION ON WEDNESDAY,
SCATTERED SHOWERS SHOULD BE DEVELOPING TOMORROW MORNING ACROSS
THE SOUTHERN PORTION OF THE CWA, AND SPREADING ACROSS THE
REGION BY LATE AFTERNOON. DO NOT ANTICIPATE TOMORROW TO BE A
WASHOUT, AS WE'LL WAIT FOR WEDNESDAY NIGHT AND THURSDAY FOR THAT
POSSIBILITY.
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/
HIGHER PRECIPITABLE WATER WITH VALUES AOA 1.5 INCHES CWA-WIDE
MOVES INTO THE REGION WEDNESDAY EVENING. THESE VALUES ARE EVEN
GREATER IN THE SW PORTION OF OUR CWA, RISING TO AS MUCH AS 2.0
INCHES ALONG THE CHESAPEAKE BAY PER THE 26/12Z ECMWF. SHOWERS
WILL BECOME MORE NUMEROUS AFTER MIDNIGHT WEDNESDAY NIGHT, AND AM
LOOKING FOR TWO AREAS OF HEAVIER RAINFALL LATE WEDNESDAY NIGHT:
ONE IN THE SW PORTION OF THE CWA, FOLLOWED BY AN AXIS OF HEAVIER
RAINFALL ASSOCIATED WITH THE HIGH PWS AND PVA ALONG AND EAST OF
I-95 TOWARDS DAWN THURSDAY AND LASTING THROUGH THE AFTERNOON.
ANY SHOWER COULD PRODUCE LOCALLY HEAVY RAINFALL LATE WED NIGHT
AND THURSDAY, ESPECIALLY DURING THE AFTERNOON HOURS ALONG AND
EAST OF INTERSTATE 95 WHERE MOISTURE IS MAXIMIZED.
LONG TERM /FRIDAY THROUGH TUESDAY/
A POTENT SHORTWAVE WILL DESCEND INTO THE GREAT LAKES ON FRIDAY.
FURTHER TO THE SOUTH, A DECAYING UPPER LOW WILL THIN OUT INTO AN
OPEN WAVE AND GRADUALLY BECOME ABSORBED INTO THE LARGER TROUGH
SITUATED TO OUR NORTHWEST. AS THIS PROCESS OCCURS, THE NORTHERN
STREAM SYSTEM WILL DRIVE A COLD FRONT SOUTHWARD TOWARD OUR REGION.
WHILE OUR AREA WON'T BE SITUATED BENEATH THE STRONGEST FORCING FOR
ASCENT AT UPPER LEVELS, OR IMMEDIATELY AHEAD OF THE SURFACE COLD
FRONT, GRADUAL HEIGHT FALLS WILL BE OCCURRING ALOFT. WITH WARM AND
HUMID AIR IN PLACE AT THE SURFACE, THE HEIGHT FALLS IN THE PRESENCE
OF AN UNSTABLE AIRMASS SHOULD BE SUFFICIENT TO SPARK THE DEVELOPMENT
OF SHOWERS AND THUNDERSTORMS, ESPECIALLY DURING THE AFTERNOON AND
EVENING HOURS. GUIDANCE HAS TRENDED DOWNWARD WITH QPF TOTALS ACROSS
THE AREA, SUGGESTING POTENTIALLY LOWER AREAL COVERAGE OF STORMS.
STILL THINK THERE WILL BE AT LEAST SOME THREAT FOR LOCALIZED
FLOODING FOLLOWING A SOAKING RAINFALL ON THURSDAY. PRECIPITABLE
WATER VALUES WILL BE AROUND 1.5-2 INCHES, SUGGESTING THAT ANY STORMS
THAT DO FORM ON FRIDAY COULD BE EFFICIENT HEAVY RAINFALL PRODUCERS.
A STRONGER STORM OR TWO CAN'T BE RULED OUT EITHER, WITH MLCAPE
VALUES INCREASING TO AROUND 1000 J/KG AND AROUND 20-35 KNOTS OF 0-6
KM SHEAR IN PLACE. OUTSIDE OF THE THUNDERSTORM ACTIVITY, CONDITIONS
WILL BE VERY WARM AND HUMID, WITH HIGHS IN THE MID 80S AND DEWPOINTS
IN THE UPPER 60S TO LOWER 70S.
SATURDAY'S FORECAST WILL LARGELY DEPEND ON THE SOUTHWARD PROGRESSION
OF THE AFOREMENTIONED SYSTEM'S COLD FRONT. 12Z GUIDANCE HAS THUS FAR
TRENDED FASTER WITH RESPECT TO THE PROGRESSION OF THE FRONT, WHICH
WOULD SUGGEST LOWER CHANCES FOR SHOWERS AND STORMS. HOWEVER, THERE'S
STILL ENOUGH SPREAD IN THE GUIDANCE, THAT LINGERING SHOWERS AND
STORMS CAN'T BE RULED OUT, ESPECIALLY DURING THE MORNING HOURS. IF
THE FRONT WERE TO HOLD TO OUR NORTH, THERE COULD ONCE AGAIN BE A
THREAT FOR LOCALIZED FLOODING OR A STRONGER AFTERNOON STORM, BUT THE
TREND SEEMS TO BE MOVING AWAY FROM THIS SOLUTION.
A MUCH COOLER AND DRIER AIRMASS WILL WORK IN BEHIND THE FRONT FOR
SUNDAY AND MONDAY AS UPPER LEVEL TROUGHING DIGS INTO THE EASTERN US.
MOSTLY SUNNY SKIES ARE EXPECTED, ALONG WITH HIGHS IN THE UPPER 60S
TO LOWER 70S, AND DEWPOINTS IN THE 40S.
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
VFR FOR MOST OF THE TERMINALS THROUGH MIDNIGHT, THEN CONDITIONS
DETERIORATE TO AOB IFR AFTER MIDNIGHT WITH LOW CIGS LIKELY AND
POSSIBILITY OF LOW VSBY AND DRIZZLE. THESE IFR CONDITIONS WILL
LIKELY LAST THROUGH MID- MORNING WEDNESDAY. SUBIFR CONDITIONS
ARE ALSO POSSIBLE DURING THIS TIME. CIGS/VSBYS SHOULD GRADUALLY
IMPROVE TO VFR LEVELS LATE IN THE MORNING INTO THE AFTERNOON,
BUT SCATTERED SHOWERS ARE POSSIBLE THROUGHOUT THE DAY.
SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE FRIDAY INTO FRIDAY
NIGHT. A COLD FRONT WILL PROGRESS THROUGH THE AREA LATE FRIDAY
NIGHT INTO SATURDAY. DEPENDING ON THE PROGRESSION OF THE FRONT,
SHOWERS AND THUNDERSTORMS MAY BE POSSIBLE AGAIN ON SATURDAY, BUT
THE TREND HAS BEEN FOR THE FRONT TO CLEAR THE AREA EARLIER,
WHICH WOULD IN TURN LEAD TO DRIER CONDITIONS.
MARINE
A SOUTHEAST FLOW WILL CONTINUE THROUGH WEDNESDAY NIGHT, BUT
WINDS WILL REMAIN BELOW SCA CRITERIA FOR MOST OF THE TIME. FOG
IS EXPECTED TO DEVELOP TONIGHT ACROSS THE MARYLAND PORTION OF
THE CHESAPEAKE, REDUCING VSBY BELOW 1 MILES ON THE WATER, AND
CONTINUE THROUGH MUCH OF THE DAY WEDNESDAY AS DEWPOINTS RISE TO
MEET OR EXCEED THE WATER TEMPERATURE.
ON THURSDAY, A LOW LEVEL JET WITH 35KTS AT 2.5KFT ON THURSDAY
IS APPARENT ON THE 12Z BUFKIT PROFILE FOR BWI, BUT IT IS ABOVE
THE INVERSION. HOWEVER, THE POTENTIAL FOR IT TO MIX DOWN IN
HEAVIER SHOWERS IS THERE, AND SCA MAY BE REQUIRED THURSDAY.
WINDS MAY APPROACH SCA LEVELS ON FRIDAY IN SOUTHERLY FLOW, BUT
ARE EXPECTED TO REMAIN MOSTLY SUB- SCA IN MAGNITUDE.
THUNDERSTORMS WILL BE POSSIBLE OVER THE WATERS FRIDAY INTO
FRIDAY NIGHT, WITH THE HIGHEST COVERAGE OF STORMS OCCURRING
DURING THE AFTERNOON AND EVENING HOURS. GUSTY WINDS WILL BE
POSSIBLE IN ASSOCIATION WITH ANY OF THESE THUNDERSTORMS.
DEPENDING ON THE PROGRESSION OF THE SYSTEM'S COLD FRONT, SHOWERS
AND THUNDERSTORMS MAY BE POSSIBLE AGAIN ON SATURDAY. HOWEVER,
THE TREND HAS BEEN FOR THE COLD FRONT TO MOVE THROUGH QUICKER,
WHICH WOULD LEAD TO DRIER CONDITIONS.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.
SYNOPSIS...LEE
NEAR TERM...BJL/LEE
SHORT TERM...BJL/LEE
LONG TERM...KJP
AVIATION...BJL/LEE/KJP
MARINE...BJL/LEE/KJP
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