715
FXUS61 KLWX 211440
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1040 AM EDT THU AUG 21 2025
SYNOPSIS
A MEANDERING FRONTAL ZONE WILL CONTINUE TO SLIDE SOUTH OF THE
AREA TODAY. MEANWHILE, HURRICANE ERIN IS EXPECTED TO MAKE ITS
CLOSEST APPROACH TO ST. MARY'S COUNTY THIS MORNING. ERIN WILL
MOVE FURTHER OFFSHORE THIS EVENING WITH WEAK HIGH PRESSURE
BUILDING IN FOR FRIDAY INTO THE FIRST HALF OF SATURDAY. ANOTHER
COLD FRONT WILL CROSS THE AREA MONDAY MORNING BEFORE A STRONG
DOME OF HIGH PRESSURE APPROACHES FROM THE MIDWEST NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
CONTINUING TO MONITOR THE PROGRESSION OF A MEANDERING FRONTAL
BOUNDARY SOUTH AND EAST OF THE AREA THIS MORNING AND INTO THE
AFTERNOON. THIS BOUNDARY REMAINS DRAPED OVER THE SOUTHERN DELMARVA
BACK ACROSS THE CENTRAL VA PIEDMONT/SOUTHERN SHENANDOAH VALLEY AND
INTO FAR SOUTHERN WV. THE BOUNDARY WILL CONTINUE FURTHER SOUTH AND
EAST THIS EVENING AS HURRICANE ERIN MOVES FURTHER OFF INTO THE
WESTERN ATLANTIC AND WEAK HIGH PRESSURE BUILDS IN FROM THE GREAT
LAKES/OHIO RIVER VALLEY. UNTIL THIS HAPPENS EXPECT A REPEAT OF WHAT
WE SAW YESTERDAY ACROSS THE REGION WITH AMPLE OVERCAST LOW TO MID
STRATUS), POCKETS OF LIGHT DRIZZLE AND FOG, AND COOL TEMPERATURES
DUE IN PART TO STOUT ONSHORE FLOW. REDUCTIONS IN VISIBILITY ARE
POSSIBLE GIVEN THE OVERALL PATTERN ESPECIALLY TOWARD FOOTHILLS OF
THE BLUE RIDGE AND CATOCTINS AS WELL AS BACK ACROSS THE
ALLEGHENIES WITH LOWER CEILINGS IN PLACE. THESE CONDITIONS WILL
LIKELY HOLD STRONG THROUGH MID-AFTERNOON WITH SLOW IMPROVEMENTS
LATER THIS AFTERNOON/EVENING DUE IN PART TO A LACK OF SOLAR
INSOLATION AS WELL AS DRY AIR ADVECTION PUSHING INTO THE REGION.
AS FOR HURRICANE ERIN, EXPECT FURTHER ACCELERATION TO THE NORTH AND
EAST TODAY AS IT PULLS FURTHER AWAY FROM THE MID-ATLANTIC COAST AND
TOWARD THE EASTERN CANADIAN MARITIMES. ERIN REMAINS A CATEGORY 2 PER
THE LATEST ADVISORY, BUT WILL MOST LIKELY BECOME EXTRATROPICAL LATER
TODAY AND INTO FRIDAY. A CONTINUATION OF COASTAL FLOODING CONCERNS
ALONG THE WESTERN SHORE OF THE CHESAPEAKE BAY AND UP ACROSS THE
TIDAL POTOMAC WILL REMAIN OVER THE NEXT FEW HIGH TIDE CYCLES. FOR
THOSE TRAVELING TO THE DELMARVA BEACHES, BE AWARE OF CONTINUED TIDAL
FLOODING AND RIP CURRENT CONCERNS WHICH WILL LIKELY LAST
THROUGH THE WEEKEND.
WITH THE FRONT AND UPPER TROUGH NEARBY AND HURRICANE ERIN JUST
OFFSHORE EXPECT A TIGHTENED PRESSURE GRADIENT ACROSS THE AREA THIS
AFTERNOON AND EVENING. THIS WILL LEAD TO A BUMP IN THE OVERALL
SYNOPTIC WIND FIELD ACROSS THE ENTIRETY OF THE AREA (ESPECIALLY
ALONG AND EAST OF I-95) THIS AFTERNOON INTO EARLY EVENING. WINDS
WILL GENERALLY BE OUT OF THE NORTH AND NORTHEAST WITH GUSTS HOVERING
BETWEEN 20-25 MPH. LOCALLY HIGHER GUSTS ARE POSSIBLE OVER FAR
SOUTHERN MD AND THE NORTHERN NECK OF VA AS WELL AS ADJACENT OPEN
WATERS OF THE LOWER CHESAPEAKE BAY (SEE MARINE SECTION).WITH SOME
RESIDUAL MOISTURE AND WEAK LIFT (DEPARTING FRONT/UPPER TROUGH)
OVERHEAD, ISOLATED TO WIDELY SCATTERED SHOWERS MAY POP UP. LIKE
EARLIER THIS MORNING, ANY SUCH SHOWER WOULD TRACK TOWARD THE
SOUTHWEST (MAINLY ACROSS THE CENTRAL VA PIEDMONT, WESTERN SHORE OF
THE BAY, AND SOUTHERN MD). A COUPLE RUMBLES OF THUNDER CANNOT BE
RULED OUT IN NELSON, HIGHLAND, AND AUGUSTA COUNTIES GIVEN CLOSER
PROXIMITY TO THE FRONT. ANY CONVECTIVE THREATS WIND DOWN BY AROUND 6-
8 PM.
AMPLE OVERCAST AND STOUT NORTH/NORTHEASTERLY FLOW WILL HOLD
TEMPERATURES BACK INTO THE LOW TO MID 70S TODAY WITH MID TO UPPER
60S ACROSS THE MOUNTAINS. RELATIVE TO MID/LATE AUGUST CLIMATOLOGY,
THIS FORECAST IS AROUND 8 TO 12 DEGREES BELOW AVERAGE. WIND FIELDS
WEAKEN TONIGHT WITH GRADUALLY CLEARING SKIES AS AMPLE DRY AIR
ADVECTION FUNNELS IN. CLOUDS WILL HANG ON THE LONGEST WEST OF US-
15/THE BLUE RIDGE. SOME FOG IS POSSIBLE ESPECIALLY IN THE RIVER
VALLEYS ALTHOUGH CONFIDENCE IN WIDESPREAD FOG IS LOW ESPECIALLY WEST
OF THE METROS GIVEN THE RESIDUAL CLOUD COVER. LOW TEMPERATURES ARE
FORECAST TO BE IN THE UPPER 50S TO MID 60S.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
WITH WEAK HIGH PRESSURE BUILDING INTO THE AREA ON FRIDAY, EXPECT
TRANQUIL WEATHER WITH MOSTLY SUNNY SKIES. THE PRONOUNCED
NORTHERLY FLOW WILL HAVE A NOTABLE EFFECT ON MOISTURE LEVELS AS
DEW POINTS FALL INTO THE MID 50S TO LOW 60S ON FRIDAY.
ADDITIONALLY, WINDS TURN MUCH LIGHTER AS THE IMPACTS FROM THE
TROUGH/TROPICAL CYCLONE COMBINATION SHIFT WELL OFFSHORE.
FORECAST HIGH TEMPERATURES SHOULD RETURN TO THE UPPER 70S TO LOW
80S (5 TO 10 DEGREES COOLER FOR MOUNTAIN LOCALES). THE
COMBINATION OF HIGH PRESSURE AND A DRY AIR MASS WILL ENCOURAGE
ANOTHER COOL NIGHT AHEAD. FRIDAY NIGHT'S TEMPERATURES WILL
MAINLY BE IN THE UPPER 50S TO LOW 60S (MID 60S INSIDE D.C. AND
BALTIMORE). AREAS THAT FULLY RADIATE COULD EVEN SEE SOME SPOTTY
MID 50S.
ON SATURDAY, A FORMIDABLE UPPER TROUGH ACCELERATING ACROSS
ONTARIO WILL SPREAD AMPLE HEIGHT FALLS ACROSS THE GREAT LAKES
INTO THE OHIO VALLEY. WHILE THE MOST NOTABLE EFFECTS WAIT UNTIL
SUNDAY, THE INITIAL APPROACH OF THIS SYSTEM WILL INTRODUCE
SHOWER AND THUNDERSTORM CHANCES FOR WESTERN LOCATIONS. A RETURN
SOUTHERLY FLOW AT THE SURFACE SHOULD INCREASE LOW-LEVEL MOISTURE
CONTENT. SOME UPTICK IN INSTABILITY IS LIKELY GIVEN THE
WARM/MOIST ADVECTION REGIME. HOWEVER, WITH THE MAIN FORCING OFF
TO THE WEST, EXPECT MUCH OF THE CONVECTIVE ACTION TO FOCUS BACK
TOWARD THE ALLEGHENIES. TERRAIN CIRCULATIONS WILL LIKELY BE THE
TRIGGER BEFORE ACTIVITY SPREADS DOWNSTREAM. AT THIS POINT, STORM
CHANCES GENERALLY SHUT OFF JUST EAST OF I-81.
THE INFLUENCE OF UPSTREAM HEIGHT FALLS START TO KICK IN
OVERNIGHT ON SATURDAY. THIS SUPPORTS INCREASING SHOWER AND
THUNDERSTORM CHANCES THROUGH THE NIGHT ACROSS THE ENTIRE AREA.
AFTER A SEASONABLY MILD DAY, NIGHTTIME LOW TEMPERATURES FALL
INTO THE 60S (UPPER 50S FOR THE MOUNTAIN RIDGES).
LONG TERM /SUNDAY THROUGH WEDNESDAY/
A DEEP UPPER TROUGH WILL DIG OVER THE GREAT LAKES ON SUNDAY AS LOW
PRESSURE AT THE SURFACE TRACKS TOWARD HUDSON BAY. WINDS ALOFT WILL
START TO INCREASE AS THE UPPER TROUGH APPROACHES, ATOP WHAT WILL
ALSO BE AN UNSTABLE PRE-FRONTAL AIRMASS. SHOWERS AND THUNDERSTORMS
APPEAR LIKELY SUNDAY AFTERNOON AHEAD OF THE SYSTEM'S APPROACHING
COLD FRONT, AND SOME OF THESE STORMS COULD POTENTIALLY BE STRONG TO
SEVERE, GIVEN THE OVERLAP OF INSTABILITY AND DEEP LAYER SHEAR.
TEMPERATURES WILL BE SEASONABLE, WITH HIGHS IN THE UPPER 70S TO MID
80S, BUT IT WILL BE QUITE HUMID, WITH DEWPOINTS IN THE UPPER 60S AND
LOWER 70S.
THE VAST MAJORITY OF GUIDANCE HAS THE SYSTEM'S COLD FRONT MOVING
THROUGH PRIOR TO PEAK HEATING ON MONDAY, WITH STRONG DRY ADVECTION
ENSUING IN ITS WAKE. IF THE FRONT CLEARS THE AREA, DRY CONDITIONS
WILL ENSUE ON MONDAY, BUT IF THE FRONT WERE TO PROGRESS SLOWER OFF
TOWARD THE EAST, A SHOWER OR THUNDERSTORMS COULD BE POSSIBLE MONDAY
AFTERNOON. THE FRONT WILL SURELY CLEAR THE AREA PRIOR TO TUESDAY.
MOSTLY SUNNY, COOLER, AND MUCH LESS HUMID CONDITIONS ARE EXPECTED
BEHIND THE FRONT, WITH HIGHS ONLY IN THE 70S TO NEAR 80, AND
DEWPOINTS DROPPING INTO THE 40S TO NEAR 50 FOR TUESDAY AND
WEDNESDAY.
AVIATION /15Z THURSDAY THROUGH MONDAY/
WHILE THERE WAS SOME REPRIEVE FROM THE PROLONGED LOW CEILINGS,
THE MAIN FRONTAL ZONE HAS AGAIN MOVED SOUTH OF THE REGION. THE
POST-FRONTAL NORTHEASTERLY FLOW HAS LED TO ANOTHER ROUND OF IFR
CEILINGS (SPOTTY LIFR AT TIMES). SOME REDUCTIONS IN VISIBILITY
FROM DRIZZLE AND PASSING SHOWERS ALSO ARE NOTED. THIS PATTERN
HOLDS THROUGH MUCH OF THE MORNING HOURS WITH RESTRICTIONS
CONTINUING. A RETURN JUST TO MVFR CONDITIONS IS NOT LIKELY UNTIL
THE EARLY AFTERNOON, WITH VFR BY THE EARLY EVENING.
ADDITIONALLY, THE COMBINATION OF THIS FRONT/TROUGH WITH
HURRICANE ERIN OFFSHORE WILL INCREASE NORTH-NORTHEASTERLY
WINDS. GUSTS UP TO 20 TO 25 KNOTS ARE POSSIBLE TODAY BEFORE
DECREASING INTO THE NIGHT. HIGH PRESSURE RETURNS ON FRIDAY WITH
VFR CONDITIONS LIKELY. CONVECTIVE CHANCES COME BACK ON SATURDAY,
BUT ONLY FOR THE WESTERN TERMINALS. THIS COME WITH SOUTHERLY
WINDS GUSTING TO AROUND 10 TO 15 KNOTS. SOME EXPANSION IN
SHOWERS IS LIKELY INTO THE OVERNIGHT HOURS.
PREVAILING VFR CONDITIONS ARE EXPECTED ON SUNDAY AND MONDAY,
ALTHOUGH BRIEF DROPS TO SUB-VFR MAY BE POSSIBLE ON SUNDAY AS
THUNDERSTORMS MOVE THROUGH. WINDS WILL BE OUT OF THE SOUTH ON
SUNDAY, AND THEN OUT OF THE WEST TO NORTHWEST ON MONDAY.
MARINE
THE MEANDERING FRONTAL ZONE HAS AGAIN SHIFTED SOUTH OF THE AREA
EARLY THIS MORNING. IT WILL REMAIN LIKE THAT AS THE FRONT SLIDES
SOUTHEASTWARD AS A COLD FRONT. THE COMBINATION OF THIS
FRONT/TROUGH WITH THE PRESENCE OF HURRICANE ERIN OFFSHORE WILL
EXPAND OVERALL WIND FIELDS. A GUSTY NORTH-NORTHEASTERLY WIND
OVERSPREADS THE WATERS TODAY WITH GUSTS AROUND 20 TO 25 KNOTS
(25 TO 30 KNOTS OVER THE SOUTHERN WATERS). SMALL CRAFT
ADVISORIES GO INTO EFFECT FOR ALL WATERS. DEPENDING ON HOW
GUSTY CONDITIONS GET, OCCASIONAL GALE-FORCE WINDS ARE CERTAINLY
POSSIBLE LATE THIS MORNING INTO THE AFTERNOON. IF BRIEF IN
NATURE, THIS UPTICK WOULD BE HANDLED BY A MARINE WEATHER
STATEMENT.
THESE WINDS REMAIN SLIGHTLY ELEVATED INTO TONIGHT AND FRIDAY
MORNING. SMALL CRAFT ADVISORIES MAY GET EXTENDED INTO FRIDAY
MORNING ACROSS THE MORE SOUTHERN WATERS. WINDS DECREASE FOR
THE REMAINDER OF FRIDAY AS HIGH PRESSURE SETTLES OVER THE
WATERS. THIS RIDGE DOES WEAKEN INTO SATURDAY AS THE NEXT FRONTAL
SYSTEM APPROACHES FROM THE WEST. SOUTHERLY WINDS INCREASE IN
EARNEST WITH GUSTS TO AROUND 15 KNOTS OR SO.
SUB-SCA LEVEL WINDS ARE EXPECTED ON BOTH SUNDAY AND MONDAY. WINDS
WILL BE OUT OF THE SOUTH ON SUNDAY, AND THEN OUT OF THE WEST TO
NORTHWEST ON MONDAY. SMWS MAY POTENTIALLY BE NEEDED AS THUNDERSTORMS
PASS OVER THE WATERS SUNDAY AFTERNOON INTO SUNDAY EVENING.
TIDES/COASTAL FLOODING
TIDAL ANOMALIES WILL STEADILY RISE FOR THE NEXT 12 TO 24 HOURS
AS ONSHORE FLOW STRENGTHENS IN RESPONSE TO HURRICANE ERIN
TRACKING SOUTHEAST OF THE AREA.
AS WINDS SLACKEN FRIDAY NIGHT INTO SATURDAY, A SNAP-BACK EVENT
IS EXPECTED TO OCCUR RAISING WATER LEVELS FURTHER. MODERATE
COASTAL FLOODING IS LIKELY AT ANNAPOLIS AND WIDESPREAD MINOR
COASTAL FLOODING ELSEWHERE. WATER LEVELS LIKELY REMAIN ELEVATED
UNTIL THE COLD FRONTAL PASSAGE THAT COMES IN EARLY MONDAY.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...SMALL CRAFT ADVISORY UNTIL 3 AM EDT FRIDAY FOR MDZ008.
COASTAL FLOOD ADVISORY FROM 2 AM TO 4 AM EDT FRIDAY FOR MDZ014.
COASTAL FLOOD WATCH FROM LATE TONIGHT THROUGH SATURDAY MORNING
FOR MDZ014.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 3 AM EDT FRIDAY FOR ANZ530>533-
538>542.
SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ534-537-543.
SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ535-
536.
SYNOPSIS...BRO
NEAR TERM...BRO/EST
SHORT TERM...BRO
LONG TERM...KJP
AVIATION...BRO/KJP/EST
MARINE...BRO/KJP/EST
TIDES/COASTAL FLOODING...LWX
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