665
FXUS61 KLWX 180100
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
900 PM EDT THU SEP 17 2026
WHAT HAS CHANGED
WHILE SHOWERS ARE SPOTTY IN PARTS OF NORTHEASTERN WEST VIRGINIA
AT THIS TIME, ADDITIONAL SHOWERS AND EMBEDDED THUNDERSTORMS HAVE
FORMED TWO LINEAR SEGMENTS ACROSS SOUTHWESTERN PENNSYLVANIA AND
SOUTHEASTERN PENNSYLVANIA. THESE SEGMENTS HAVE DEVELOPED ALONG A
COLD FRONT. A COOLER PATTERN STILL REMAINS A POSSIBILITY NEXT
WEEK.
KEY MESSAGES
- 1) SHOWER AND THUNDERSTORM CHANCES SHIFT SOUTHWARD WITH A COLD
FRONT THROUGH FRIDAY, WHICH WILL BE FOLLOWED BY COOLER
TEMPERATURES.
- 2) SHOWERS AND THUNDERSTORMS RETURN AT TIMES SUNDAY INTO NEXT
WEEK, WITH TEMPERATURES LIKELY FALLING BELOW NORMAL.
DISCUSSION
KEY MESSAGE 1...SHOWER AND THUNDERSTORM CHANCES SHIFT SOUTHWARD
WITH A COLD FRONT THROUGH FRIDAY, WHICH WILL BE FOLLOWED BY
COOLER TEMPERATURES.
A FEW SHOWERS ARE NOTED IN SPOTS ACROSS PARTS OF NORTHEASTERN
WEST VIRGINIA. WHILE THESE SHOWERS SHOULD COME AND GO OVER THE
NEXT HOUR OR TWO, WE WILL BE WATCHING TWO LINEAR SEGMENTS OF
SHOWERS AND EMBEDDED THUNDERSTORMS IN SOUTHWESTERN AND
SOUTHEASTERN PENNSYLVANIA. THESE SEGMENTS HAVE LOST SOME OF
THEIR LIGHTNING ACTIVITY, BUT REMAIN IN TACT ENOUGH THAT IF THEY
MOVE INTO MARYLAND IN AN HOUR OR TWO, THEY COULD BRING BRIEF
GUSTY WINDS AND DOWNPOURS. THE THUNDERSTORMS ARE NOT SEVERE.
THIS ACTIVITY THAT WE ARE WATCHING ARE ALONG A COLD FRONT THAT
WILL CONTINUE TO PUSH SOUTHWARD THROUGHOUT THE NIGHT AND DURING
THE DAY FRIDAY. SOME PATCHY FOG COULD OCCUR PARTICULARLY IN
AREAS THAT HAVE RECEIVED RAINFALL THIS PAST AFTERNOON AND EARLY
EVENING.
WHILE THE WIND SHIFT PORTION OF THE COLD FRONT LIKELY PUSHES
SOUTH OF THE AREA FRIDAY MORNING, THE MOISTURE GRADIENT MAY HANG
BACK ACROSS CENTRAL VIRGINIA UP TO THE POTOMAC HIGHLANDS. AS A
SHORTWAVE TROUGH SWINGS THROUGH DURING THE AFTERNOON, SOME
ADDITIONAL SHOWERS AND THUNDERSTORMS MAY DEVELOP IN THESE AREAS.
TEMPERATURES WILL FALL BACK INTO THE LOWER TO MID 80S WITH
NORTHERLY GUSTS UP TO 20 MPH AT TIMES. THERE MAY ALSO BE A FAIR
AMOUNT OF STRATOCUMULUS AT TIMES AS WELL. A COOLER NIGHT LIES
AHEAD AS HIGH PRESSURE CROSSES SOUTHERN QUEBEC INTO NEW ENGLAND.
FRIDAY NIGHT'S LOWS SHOULD BE IN THE UPPER 50S TO MID 60S.
HIGH PRESSURE TO THE NORTHEAST ON SATURDAY SHOULD PROVIDE ENOUGH
DRY AIR TO KEEP RAIN AT BAY. ONE EXCEPTION MAY BE ALONG THE
ALLEGHENY FRONT DUE TO CONVERGENCE IN AN INVERTED SURFACE
TROUGH. WARM ADVECTION ALOFT AND MID LEVEL PERTURBATIONS WILL
LIKELY PROVIDE CLOUD COVER AREAWIDE. TEMPERATURES WILL BE
CLOSER TO CLIMATOLOGY, RANGING FROM THE MID 70S TO LOWER 80S.
LOW PRESSURE MOVING INTO THE OHIO VALLEY MAY INCREASE RAIN
CHANCES SATURDAY NIGHT.
KEY MESSAGE 2...SHOWERS AND THUNDERSTORMS RETURN AT TIMES SUNDAY
INTO NEXT WEEK, WITH TEMPERATURES LIKELY FALLING BELOW NORMAL.
A COLD FRONT DROPS THROUGH THE FORECAST AREA ON SUNDAY BEFORE
STALLING TO THE SOUTH, BRINGING DAILY CHANCES FOR SHOWERS AND
THUNDERSTORMS. IN ADDITION TO DAILY PRECIPITATION, A COOLER AIRMASS
BUILDS OVERHEAD IN THE WAKE OF THE COLD FRONT, YIELDING COOLING
TEMPERATURES EACH DAY. ON SUNDAY, HIGH TEMPERATURES WILL BE IN THE
LOW 80S FOR MOST (70S MTNS) WITH OVERNIGHT LOWS IN THE 60S. BY
MIDWEEK, HIGH TEMPERATURES WILL TOP OUT IN THE UPPER 50S TO 60S WITH
OVERNIGHT LOWS IN THE 50S. THESE TEMPERATURES REMAIN SOMEWHAT
UNCERTAIN WITH LARGE MODEL SPREAD, BUT THE FORECAST FAVORS THE
COOLER SIDE OF GUIDANCE GIVEN A COLD AIR DAMMING SURFACE
PATTERN. OVERALL, NEARBY DISTURBANCES BRING UNSETTLED WEATHER
TO THE REGION BEGINNING SUNDAY AND PERSISTING THROUGH MIDWEEK.
AVIATION /00Z FRIDAY THROUGH TUESDAY/
IF PATCHY FOG DEVELOPS NEAR THE TERMINALS TONIGHT, IT COULD DROP
VISIBILITY TO MVFR OR IFR FOR AN HOUR OR TWO LATER TONIGHT.
OTHERWISE, A PASSING SHOWER OR EMBEDDED THUNDER COULD MOVE
THROUGH MRB OR IAD THE REMAINDER OF TONIGHT. ADDITIONAL SHOWERS
AND THUNDERSTORMS COULD DEVELOP AS THE FRONT PUSHES SOUTH
THROUGH THE DAY FRIDAY, BUT COULD MAINLY BE NEAR CHO TERMINAL.
OTHERWISE, VFR CONDITIONS ARE ANTICIPATED ACROSS TERMINALS THROUGH
MOST OF FRIDAY. PATCHY MOUNTAIN VALLEY FOG COULD BRIEFLY BRING
VSBYS DOWN AT KMRB AND KCHO TO MVFR EARLY FRIDAY MORNING BEFORE
RETURNING TO VFR THROUGH MOST OF THE DAY. WINDS SHIFT NORTHERLY
FRIDAY MORNING AND CONDITIONS REMAIN LARGELY UNCHANGED
THROUGHOUT THE DAY SATURDAY. BEGINNING SUNDAY, MORE SHOWERS AND
THUNDERSTORMS COULD INTERMITTENTLY IMPACT TERMINALS AS A TROUGH
MOVES THROUGH THE REGION WITH SOUTHERLY WINDS POTENTIALLY
GUSTING TO 20 KT.
WINDS SHIFT TO NORTH/NORTHEASTERLY ON MONDAY IN THE WAKE OF THE
FRONT, GUSTING 10 TO 15 KNOTS IN THE AFTERNOON. SHOWERS AND
THUNDERSTORMS ARE POSSIBLE EACH DAY, WITH RESTRICTIONS EXPECTED
DURING HEAVIEST PRECIPITATION.
MARINE
IF THE LINEAR SEGMENT OF SHOWERS AND EMBEDDED THUNDER OVER
SOUTHEASTERN PENNSYLVANIA MOVES INTO NORTHERN ZONES OF THE
CHESAPEAKE BAY LATE THIS EVENING INTO THE OVERNIGHT, IT COULD
PROMPT MARINE WEATHER STATEMENTS OR A SPECIAL MARINE WARNING.
THE LATTER HAS A LOW CHANCE OF OCCURRING. A SMALL CRAFT
ADVISORY REMAINS IN EFFECT FOR THE WIDER WATERS UNTIL 11 PM.
WINDS SHIFT TO NORTHERLY ON FRIDAY MORNING BEHIND THE COLD
FRONT. SOME NORTHERLY CHANNELING EFFECTS ARE POSSIBLE ON FRIDAY
MORNING INTO THE AFTERNOON DUE TO THE FRONTAL SURGE. SMALL CRAFT
ADVISORIES MAY BE NEEDED FOR SUCH AN EVOLUTION, ALTHOUGH CURRENT
GUIDANCE DOES NOT OFFER ENOUGH CONFIDENCE IN MORE THAN
OCCASIONAL MARGINAL GUSTS. A SECOND SURGE COULD ALSO OCCUR
FRIDAY EVENING. AS HIGH PRESSURE PASSES BY TO THE NORTH, WINDS
SHIFT FROM NORTHEASTERLY TO EAST- SOUTHEASTERLY ON SATURDAY.
THIS COULD BRING A FEW GUSTS TO NEAR 20 KNOTS WHICH COULD
APPROACH ADVISORY LEVELS, ESPECIALLY BY SATURDAY NIGHT.
SMALL CRAFT ADVISORY CONDITIONS ARE POSSIBLE ON SUNDAY AS
SOUTH/SOUTHWEST WINDS GUST UP TO 20 KNOTS ACROSS THE WATERS. WINDS
DIMINISH OVERNIGHT BEFORE SHIFTING TO NORTH/NORTHEASTERLY ON MONDAY
WITH SCA CRITERIA WIND GUSTS POSSIBLE. ADDITIONALLY, SHOWERS AND
THUNDERSTORMS EACH DAY MAY LEAD TO SMWS.
TIDES/COASTAL FLOODING
WITH WINDS REMAINING OUT OF THE SOUTH TO SOUTHEASTERLY DIRECTION,
THIS FLOW REGIME HAS KEPT TIDAL ANOMALIES AROUND 0.50 TO 0.75
FEET. THIS HAS BEEN ENOUGH TO PUSH A FEW OF THE MORE SENSITIVE
LOCATIONS INTO THE ACTION STAGE. UNTIL A COLD FRONT MOVES
THROUGH EARLY FRIDAY, WATER LEVELS WILL REMAIN SOMEWHAT
ELEVATED. ALTHOUGH NO TIDAL SITE IS SHOWN TO EXPERIENCE ANY
COASTAL FLOODING, IT WILL NEED TO BE MONITORED. THIS IS
PARTICULARLY THE CASE AT ANNAPOLIS, ESPECIALLY DURING THE HIGHER
OF THE TWO ASTRONOMICAL HIGH TIDES TONIGHT. EXPECT ANOMALIES TO
DROP ON FRIDAY INTO SATURDAY BEHIND THE MENTIONED COLD FRONT,
THOUGH ANOMALIES MAY INCREASE AGAIN DUE TO SOUTHERLY FLOW
SATURDAY NIGHT INTO SUNDAY.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR
ANZ532>534-543.
DISCUSSION...ADS/AVS/KLW
AVIATION...ADS/AVS/KLW
MARINE...ADS/AVS/KLW
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