734
FXUS61 KLWX 201440 AAA
AFDLWX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1040 AM EDT SUN SEP 20 2026
WHAT HAS CHANGED
NEW COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR ANNE ARUNDEL
COUNTY. NEW SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR TONIGHT.
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.
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 /14Z SUNDAY THROUGH THURSDAY/
PREVAILING VFR CONDITIONS ARE EXPECTED TODAY, ALTHOUGH A FEW
MVFR CLOUDS MAY BRIEFLY BE POSSIBLE THIS MORNING. 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 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
NEW COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR ANNE ARUNDEL
COUNTY FOR TONIGHT. 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 6 AM EDT MONDAY FOR MDZ014.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EDT THIS AFTERNOON FOR
ANZ530>534-537>543.
SMALL CRAFT ADVISORY FROM 6 AM TO NOON EDT MONDAY FOR
ANZ531>534-539>541-543.
DISCUSSION...LFR/KJP/KVH
AVIATION...LFR/KJP/KVH
MARINE...LFR/KJP/KVH
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