385
FXUS61 KLWX 200803
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
403 AM EDT SUN SEP 20 2026
WHAT HAS CHANGED
THE SMALL CRAFT ADVISORY WAS EXTENDED THROUGH 1 PM. PROB30
GROUPS WITH -TSRA WERE INTRODUCED FOR THIS AFTERNOON AT MANY OF
THE TAF SITES.
KEY MESSAGES
- 1) SCATTERED SHOWERS AND PERHAPS A FEW THUNDERSTORMS ARE
EXPECTED TODAY.
- 2) COOL AND WET CONDITIONS CONTINUE THROUGH THE END OF THE
WEEK.
DISCUSSION
KEY MESSAGE 1...SCATTERED SHOWERS AND PERHAPS A FEW THUNDERSTORMS
ARE EXPECTED TODAY.
AS OF 330 AM, RADAR IMAGERY SHOWS NUMEROUS SHOWERS AND
THUNDERSTORMS ONGOING ACROSS MUCH OF SOUTHERN OHIO AND NORTHERN
WEST VIRGINIA. THIS ACTIVITY WILL CONTINUE TO TRACK EASTWARD
TOWARD OUR AREA OVER THE NEXT SEVERAL HOURS, BUT IS EXPECTED TO
WEAKEN AS IT MOVES EAST OF THE APPALACHIANS INTO AN ENVIRONMENT
CHARACTERIZED BY LESSER INSTABILITY. HOWEVER, IT'S LIKELY THAT
AT LEAST SOME SHOWERS AND MAYBE AN EMBEDDED THUNDERSTORMS OR TWO
WILL TRACK EASTWARD ACROSS THE AREA THIS MORNING. THIS ACTIVITY
IS EXPECTED TO EVENTUALLY DISSIPATE ENTIRELY, BUT IT DOES CAST
SOME UNCERTAINTY REGARDING WHETHER ADDITIONAL THUNDERSTORM
ACTIVITY WILL BE ABLE TO FORM IN ITS WAKE THIS AFTERNOON.
ON THE SYNOPTIC SCALE, A WARM FRONT WILL BE LIFTING NORTHWARD
THROUGH THE FORECAST AREA TODAY, WITH HIGHER DEWPOINT AIR
STREAMING IN FROM THE SOUTH AND WEST. MOST GUIDANCE DOES SHOW AT
LEAST SOME DESTABILIZATION TODAY AS THE DEEPER MOISTURE WORKS
IN AND LIMITED SURFACE HEATING OCCURS THROUGH A BROKEN CLOUD
DECK. TEMPERATURES ARE FORECAST TO CLIMB INTO THE LOW TO MID 80S
THIS AFTERNOON, WITH DEWPOINTS REACHING INTO THE LOWER 70S.
THIS YIELDS AROUND 500-1000 J/KG OF MLCAPE. MODEL GUIDANCE ALSO
SHOWS A WEAK SHORTWAVE DISTURBANCE MOVING THROUGH AROUND PEAK
HEATING. THE BEST FORCING FOR ASCENT ASSOCIATED WITH THIS
FEATURE AND THE GREATEST INSTABILITY ARE BOTH FORECAST TO BE
ACROSS THE SOUTHERN HALF OF THE FORECAST AREA. WHILE AN
AFTERNOON THUNDERSTORM CAN'T BE RULED OUT ANYWHERE, THE GREATEST
CHANCE FOR A STORM APPEARS TO BE ROUGHLY SOUTH OF I-66 AND EAST
OF THE BLUE RIDGE. HOWEVER, FORECAST UNCERTAINTY REMAINS HIGH
WITH THE ACTIVITY FROM WV/OH MOVING THROUGH THIS MORNING, WHICH
ISN'T BEING HANDLED PARTICULARLY WELL BY MODEL GUIDANCE. EVEN IF
STORMS DO FORM, THE BACKGROUND ENVIRONMENT DOESN'T LOOK
FAVORABLE FOR SEVERE STORMS.
A COLD FRONT WILL MOVE THROUGH THE AREA TONIGHT, CAUSING WINDS
TO SHIFT AROUND TO OUT OF THE NORTH. LOW CLOUDS WILL BUILD IN
OVERNIGHT, WITH LOW TEMPERATURES FORECAST TO BE IN THE UPPER 50S
TO MID 60S.
KEY MESSAGE 2... COOL AND WET CONDITIONS CONTINUE THROUGH THE
END OF THE WEEK.
CONTINUING NORTHEASTERLY FLOW, STRONG HIGH PRESSURE TO OUR
NORTH, AND A DEVELOPING LOW PRESSURE SYSTEM TRAILING UP THE
EASTERN SEABOARD SETS UP A CLASSIC COLD AIR DAMMING ENVIRONMENT
ACROSS THE MID- ATLANTIC THROUGH MUCH OF THE WEEK. TEMPERATURES
REMAIN WELL- BELOW LATE-SEPTEMBER AVERAGES DUE TO PERSISTENT
CLOUD COVER AND A STABLE COOL AIRMASS REMAINING TRAPPED AGAINST
THE BLUE RIDGE. SEVERAL SHORT- WAVE DISTURBANCES TRACKING ACROSS
THE MID- ATLANTIC SUSTAIN ON AND OFF SHOWERS THROUGH THE END OF
THE WEEK. SUBSTANTIAL CLOUD COVER THURSDAY AND FRIDAY REDUCE
INSTABILITY AND THUNDERSTORM POTENTIAL.
THIS COASTAL LOW PRESSURE SYSTEM OFFSHORE CONTINUES TO MOVE
NORTHWARD COINCIDING WITH A STRENGTHENING HIGH PRESSURE SYSTEM
LINGERING IN QUEBEC. TIGHTENING PRESSURE GRADIENTS OVER OUR
REGION PARTICULARLY ACROSS OUR COASTAL PLAINS, COULD LEAD TO
BREEZIER WINDS LATE THURSDAY AND FRIDAY. CONTINUED ONSHORE FLOW
COMBINED WITH STRONGER TIDAL INFLUENCE COULD INCREASE COASTAL
FLOOD RISK DURING THIS PERIOD. REFER TO THE COASTAL FLOODING
SECTION BELOW FOR MORE DETAILS.
AS THIS SYSTEM TRACKS TO THE NORTH OF OUR REGION BY THE WEEKEND,
WINDIER CONDITIONS FADE. SHIFTING NORTHWESTERLY WIND USHERS IN DRIER
CONDITIONS AND DECREASING SHOWER POTENTIAL TO START OF THE
WEEKEND.
AVIATION /07Z SUNDAY THROUGH THURSDAY/
PREVAILING VFR CONDITIONS ARE EXPECTED TODAY, ALTHOUGH A FEW
MVFR CLOUDS MAY BRIEFLY BE POSSIBLE THIS MORNING. AS OF 330 AM
WE CONTINUE TO MONITOR ONGOING THUNDERSTORMS ACROSS WEST
VIRGINIA AND OHIO. THESE STORMS SHOULD TEND TO WEAKEN AS THEY
CROSS THE APPALACHIANS AND MOVE INTO AN ENVIRONMENT
CHARACTERIZED BY LESSER INSTABILITY, BUT A FEW SHOWERS MAY
PERSIST. A MAJOR FORECAST QUESTION FOR TODAY IS WHETHER STORMS
FORM AGAIN THIS AFTERNOON IN THE WAKE OF THIS MORNING SHOWER
ACTIVITY/CLOUD COVER. PROB30 GROUPS FOR -TSRA HAVE BEEN
INTRODUCED AT MANY OF THE TERMINALS THIS AFTERNOON TO ACCOUNT
FOR THE POTENTIAL OF THUNDERSTORM DEVELOPMENT, BUT CONFIDENCE
REMAINS LOW. WINDS TODAY WILL START OUT OF THE SOUTH, BEFORE
SHIFTING TO THE SOUTHWEST THIS AFTERNOON. A COLD FRONT WILL MOVE
THROUGH TONIGHT, CAUSING WINDS TO SHIFT AROUND TO OUT OF THE
NORTH. CEILINGS SHOULD GRADUALLY LOWER TONIGHT IN NORTHERLY
FLOW, BUT THERE'S DISAGREEMENT IN MODEL GUIDANCE WITH RESPECT TO
JUST HOW LOW CEILINGS GET. SOME SOLUTIONS SHOW MVFR CONDITIONS
LATER TONIGHT THROUGH THE DAY MONDAY, WHILE OTHERS SHOW IFR. FOR
NOW HAVE MVFR CEILINGS IN THE TAFS, BUT HAVE HINTED AT THE
POTENTIAL FOR IFR. IFR CONDITIONS APPEAR EVEN MORE LIKELY ON
TUESDAY WITHIN NORTHEASTERLY FLOW. SHOWERS WILL BE POSSIBLE ON
AND OFF THROUGH BOTH MONDAY AND TUESDAY.
INCREASING LOW AND MID-LEVEL CLOUDS AND POTENTIAL OFF AND ON SHOWERS
COULD LEAD TO SUB-VFR CONDITIONS THROUGH THE END OF THE WEEK DUE TO
ONSHORE FLOW. GUSTY WINDS REMAIN A POSSIBILITY MID TO LATE NEXT
WEEK WITH WINDS CONTINUING TO FLOW OUT OF THE NORTH AND
NORTHEAST BEFORE THE WEEKEND.
MARINE
SMALL CRAFT ADVISORIES CONTINUE FOR THE BAY AND LOWER TIDAL
POTOMAC WITHIN SOUTHERLY FLOW THROUGH 1 PM. WINDS DECREASE
SLIGHTLY AND SHIFT TO OUT OF THE SOUTHWEST THIS AFTERNOON. A
COLD FRONT MOVES OVER THE WATERS TONIGHT, WITH WINDS SHIFTING TO
OUT OF THE NORTH. WINDS ARE EXPECTED TO STAY JUST BELOW SCA
CRITERIA TONIGHT. WINDS SHIFT TO OUT OF THE NORTHEAST AND
GRADUALLY PICK UP IN MAGNITUDE FOR MONDAY AND TUESDAY. SCA
CONDITIONS APPEAR LIKELY MONDAY INTO TUESDAY, WITH GUSTS
POTENTIALLY NEARING 30 KNOTS BY TUESDAY AFTERNOON.
NORTH TO NORTHEASTERLY WIND GUSTS REMAIN ELEVATED THROUGH THURSDAY
AS AN AREA OF LOW PRESSURE TRAVELS ALONG THE EAST COAST, WITH
SHOWERS POSSIBLE OVER THE WATERS DURING THIS PERIOD. AS THIS
SYSTEM BEGINS TO TRACK PAST OUR COASTLINE LATE IN THE WEEK,
WINDS COULD DECREASE HEADING INTO THE WEEKEND.
TIDES/COASTAL FLOODING
A COASTAL FLOOD ADVISORY REMAINS IN EFFECT FOR ANNAPOLIS THROUGH
5 AM. ANOMALIES ARE EXPECTED TO DECREASE WITHIN NORTHERLY FLOW
BEHIND A COLD FRONTAL PASSAGE TONIGHT, BUT ANNAPOLIS MAY COME
CLOSE TO MINOR FLOOD STAGE AGAIN TONIGHT. NO COASTAL FLOODING IS
ANTICIPATED ON MONDAY, BUT TIDAL ANOMALIES WILL INCREASE AGAIN
WITHIN ONSHORE FLOW FOR TUESDAY AND WEDNESDAY. WITH FLOW MORE
OUT OF THE NORTHEAST THAN EAST, ANOMALIES SHOULD BE HIGHER THE
FURTHER SOUTH YOU GO IN THE BAY. AT LEAST MINOR FLOODING APPEARS
LIKELY AT SOME LOCATIONS ON TUESDAY AND WEDNESDAY. MODERATE
FLOODING LOOKS LESS LIKELY, BUT CAN'T BE COMPLETELY RULED OUT AT
THIS POINT.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...SMALL CRAFT ADVISORY UNTIL 1 PM EDT THIS AFTERNOON FOR MDZ008.
COASTAL FLOOD ADVISORY UNTIL 5 AM EDT EARLY THIS MORNING FOR
MDZ014.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EDT THIS AFTERNOON FOR
ANZ530>534-537>543.
DISCUSSION...KJP/KVH
AVIATION...KJP/KVH
MARINE...KJP/KVH
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