303
FXUS61 KLWX 161418
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1018 AM EDT SAT AUG 16 2025
SYNOPSIS
A WEAK FRONT WILL REMAIN DOWN OFF THE CAROLINA COAST THIS
WEEKEND. AT THE SAME TIME, HIGH PRESSURE BUILDS ACROSS THE MID-
ATLANTIC INTO NEW ENGLAND. THIS WILL LEAD TO A CONTINUATION OF
LATE SUMMERTIME HEAT AND HUMIDITY ALONG WITH DECREASED CHANCES
FOR THUNDERSTORMS. A COLD FRONT WILL TRACK ACROSS THE AREA SUNDAY
NIGHT INTO MONDAY MORNING BEFORE STALLING OVER THE REGION
THROUGH MID-WEEK. THIS BOUNDARY FINALLY PUSHES THROUGH AS A COLD
FRONT ON WEDNESDAY WITH A COOLDOWN EXPECTED LATER NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
ISOLATED SHOWERS CONTINUE TO POP UP AT TIMES ON EITHER SIDE OF
THE BLUE RIDGE AND CATOCTIN MOUNTAINS THIS MORNING, DUE TO SOME
LOW LEVEL CONVERGENCE, ELEVATED INSTABILITY, AND TERRAIN UPLIFT
IN THE EASTERLY FLOW. THE STRATUS ALSO REMAINS THICKEST IN THIS
AREA, WITH SIGNS OF CONVECTIVE MIXING TAKING PLACE IN SATELLITE
IMAGERY EAST OF I-95. RECENT HIGH RES GUIDANCE HAS PICKED UP ON
THIS TREND AND SUGGESTS THE SHOWER THREAT WILL END BETWEEN NOON
AND 2 PM AS THE CONVERGENCE WEAKENS AND SOME OF THE LOW LEVEL
MOISTURE MIXES OUT. FARTHER WEST, THERE IS PLENTY OF SUN, WITH
INITIAL STAGES OF CUMULUS DEVELOPMENT ALONG THE TERRAIN.
THE REGION HAS SEASONABLY MILD AND MOIST AIR IN PLACE. THIS
POST- FRONTAL AIR MASS IS SOMEWHAT DRIER WHILE BEING
CHARACTERIZED BY PRECIPITABLE WATER VALUES OF 1.50 TO 1.75
INCHES. HOWEVER, LIKE MANY SUMMERTIME BOUNDARIES, THE
THERMODYNAMIC DIFFERENCES ARE MINIMAL WHILE MOSTLY BEING DRIVEN
BY WIND SHIFTS. CONSEQUENTLY, MAINLY EAST TO SOUTHEASTERLY FLOW
WILL PERSIST THROUGH THE DAY. ANY LINGERING LOW STRATUS CLOUDS
SHOULD GRADUALLY BURN OFF DURING THE MIDDAY HOURS.
THE PRESENCE OF SURFACE HIGH PRESSURE OVER THE REGION WILL
PROMOTE MOSTLY SUNNY SKIES TODAY. ANY SHOWER CHANCES ARE
EXPECTED TO SHIFT WESTWARD RELATIVE TO FRIDAY GIVEN THE
PROLONGED ONSHORE FLOW. THE 00Z HIGH-RESOLUTION MODEL CONSENSUS
FAVORS ANY DIURNAL ACTIVITY BETWEEN THE ALLEGHENIES AND BLUE
RIDGE MOUNTAINS. VERTICAL SHEAR PROFILES ARE VERY WEAK,
GENERALLY AVERAGING 10 KNOTS IN THE 0-6 KM LAYER. ADDITIONALLY,
FORECAST SOUNDINGS DEPICT WEAK LAPSE RATES WHICH WILL LIMIT THE
DEGREE OF VERTICAL DEVELOPMENT OF AFTERNOON CONVECTION. THUS,
MOST ACTION SHOULD FOCUS CLOSER TO THE TERRAIN BEFORE UPDRAFTS
RAIN THEMSELVES OUT. HOWEVER, GIVEN HIGH MOISTURE CONTENT
(MIXING RATIOS OF 16 TO 18 G/KG), SOME LOCALLY HEAVY RAINFALL IS
NOT OUT OF THE QUESTION. ANY CONVECTIVE DEVELOPMENT FADES AFTER
DARK WHICH LEADS TO A DRY NIGHT AHEAD.
LOOKING AT TEMPERATURES, EXPECT AFTERNOON HIGHS TO STAY FAIRLY
CLOSE TO MID-AUGUST CLIMATOLOGY. THAT IS, WIDESPREAD MID/UPPER
80S ARE LIKELY WITH A FEW SPOTTY 90 DEGREE READINGS IN THE
WARMER SPOTS. FOR THE MOUNTAINS, 70S TO LOW 80S ARE EXPECTED.
OVERNIGHT LOWS DROP OFF BY A FEW DEGREES AND DEW POINTS DROP A
TAD. NOCTURNAL MOISTENING OF THE BOUNDARY LAYER MAY LEAD TO SOME
PATCHY FOG FROM THE CENTRAL VIRGINIA PIEDMONT AND POINTS
WESTWARD.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/
MODEL GUIDANCE CONTINUE TO FAVOR SUNDAY BEING THE WARMEST DAY OF
THE PERIOD. AIDED BY A SHIFT TO WEST-NORTHWESTERLY FLOW IN THE
COLUMN, A DOWNSLOPING COMPONENT TO THE WINDS WILL HELP CARRY
TEMPERATURES INTO THE LOW 90S. MANY FORECAST SOUNDINGS SHOW A
FAIRLY DEEP MIXED LAYER WITH INVERTED-V PROFILES EXTENDING
BETWEEN THE SURFACE TO 750-MB. IF THIS WERE TO OCCUR, THE
CURRENT DEW POINT FORECAST MAY BE A TAD HIGH. FOR NOW, EXPECT
THE COMBINATION OF HEAT AND HUMIDITY TO CARRY HEAT INDICES INTO
THE MID/UPPER 90S ON SUNDAY AFTERNOON.
CHANGES DO BEGIN TO UNFOLD THROUGH THE SECOND HALF OF THE DAY
WITH THE APPROACH OF A COLD FRONT. EXPECT CLOUDS TO INCREASE
FROM THE NORTH AND WEST WITH AN UPTICK IN SHOWER AND
THUNDERSTORM CHANCES. AMONG THE MORE AGGRESSIVE OF THE HIGH-
RESOLUTION MODELS IS THE 00Z NAM NEST WHICH CARRIES A BROKEN
LINE OF CONVECTION ACROSS THE AREA SUNDAY EVENING. ANY THREAT
FOR SEVERE THUNDERSTORMS WOULD BE LIMITED BY ONLY MODEST DCAPE
VALUES (500-700 J/KG) AND VERTICAL WIND FIELDS TOPPING OUT
BETWEEN 15 AND 25 KNOTS. FURTHER, WITH SHOWERS ON THE MOVE WHILE
TRACKING TOWARD THE SOUTHEAST, ANY FLOODING THREATS WOULD BE
LIMITED BY THE PROGRESSIVE NATURE OF CELLS. ANY THREAT OF
SHOWERS SHOULD SUBSIDE BY MIDNIGHT, IF NOT EARLIER. NIGHTTIME
LOWS RISE BY A COUPLE OF DEGREES BUT REMAIN QUITE SEASONABLE.
THE POST-FRONTAL AIR MASS BECOMES EVIDENT IN MONDAY'S
TEMPERATURE FORECAST AS HIGHS STAY IN THE LOW/MID 80S (70S FOR
MOUNTAIN LOCALES). WHILE MUCH OF THE DAY SHOULD BE DRY, SOME
ADDITIONAL DISTURBANCES IN THE MID/UPPER ATMOSPHERE COULD SPAWN
ISOLATED SHOWERS (15 TO 25 PERCENT) ACROSS THE AREA. OTHERWISE,
A MIX OF CLOUDS AND SUN IS LIKELY, ACCOMPANIED BY NORTHEASTERLY
WIND GUSTS OF 10 TO 15 MPH. THE FRONTAL ZONE MAY STALL NEARBY
WHICH WARRANTS A LINGERING SHOT OF OVERNIGHT SHOWERS. OVERNIGHT
LOWS WILL BE IN THE 60S, WITH LOW 70S ACROSS D.C. AND BALTIMORE.
LONG TERM /TUESDAY THROUGH FRIDAY/
TUESDAY THROUGH THE MIDDLE OF THE WEEK, HIGH PRESSURE WILL SLIDE BY
TO OUR NORTH AND EVENTUALLY OFF THE NORTHEAST COAST. THIS WILL TURN
SURFACE WINDS OUT OF THE NORTH, THEN NORTHEAST, AND EVENTUALLY
EASTERLY AS HIGH PRESSURE BECOMES WEDGED ACROSS THE REGION. THE
OVERALL UPPER-LEVEL PATTERN REMAIN SOMEWHAT LOCKED IN DURING THIS
PERIOD, WITH A FEW WEAK SHORTWAVES SLIDING BY IN NW FLOW ALOFT. THIS
WILL BRING SHOWERS AND A FEW STORMS, WITH THE BEST CHANCE FOR
THUNDER BEING WEST OF I-81, ROUGHLY WHERE THE WESTERN PERIPHERY OF
THE WEDGE BOUNDARY WILL SETUP.
AS WE HEAD TOWARDS THE END OF NEXT WEEK, WHAT IS NOW HURRICANE ERIN
SHOULD BE WELL OFFSHORE AND BRING LITTLE TO NO IMPACT TO OUR AREA.
IN THE WAKE OF MONDAY'S FRONT, AS HIGH PRESSURE WEDGES INTO OUR
REGION, COOLER THAN AVERAGE TEMPERATURES CAN BE EXPECTED ALONG WITH
A CONTINUED CHANCE FOR SOME SHOWERS. A FEW THUNDERSTORMS ARE
POSSIBLE WEST OF I-81, BUT GENERALLY SHOULD BE TOO STABLE FOR
THUNDERSTORMS FOR MUCH OF THE AREA.
IT IS IMPORTANT TO KEEP UP WITH THE LATEST UPDATES AT HURRICANES.GOV
HOWEVER, AS THE FORECAST CAN STILL CHANGE AT THIS TIME FRAME. IT IS
NEVER A BAD IDEA DURING HURRICANE SEASON TO PRACTICE YOUR PLAN AND
BE READY FOR ONE, SHOULD ACTION BE NECESSARY IN THE FUTURE.
AVIATION /14Z SATURDAY THROUGH WEDNESDAY/
MVFR STRATUS IS STARTING TO MIX OUT FROM DCA TO MTN, BUT IS A
BIT MORE SOLID TO THE WEST, WITH CHO REMAINING IFR AS OF 14Z.
EVEN IN THESE AREAS, SHOULD START TO SEE CLOUDS LIFT AND BREAK
UP BY 16Z, THOUGH CAN'T RULE OUT THAT IT TAKES AN HOUR OR TWO
LONGER. SOME ISOLATED CONVECTIVE SHOWERS CONTINUE TO DEVELOP
BETWEEN IAD AND MRB AND NORTH OF CHO, THOUGH THE AIRPORTS MAY
NOT RECEIVE ANY DIRECT IMPACTS.
ONCE THE MARINE LAYER MIXES OUT, VFR CONDITIONS ARE EXPECTED
FOR THE REST OF THE AFTERNOON. THE ONE EXCEPTION WOULD BE KMRB
WHERE ISOLATED SHOWERS OR THUNDERSTORMS MAY FIRE UP WITH DAYTIME
HEATING. THE LATEST GUIDANCE DOES NOT INCREASE CONFIDENCE THAT
THIS CHANCE IS ANY HIGHER THAN 20 PERCENT. NIGHTTIME CONDITIONS
WARRANT SOME PATCHY FOG, PARTICULARLY ACROSS KCHO AND KMRB.
EXPECT MAINLY VFR CONDITIONS FOR SUNDAY AND MONDAY. A COLD FRONT
MOVES IN LATE SUNDAY INTO MONDAY MORNING WHICH YIELDS A SHIFT TO
NORTH/NORTHEASTERLY FLOW. SOME SHOWERS ARE POSSIBLE AS THIS
BOUNDARY PUSHES THROUGH WHICH MAY WARRANT SOME BRIEF
RESTRICTIONS.
DAILY CHANCES FOR SHOWERS CONTINUE ON BOTH TUESDAY AND WEDNESDAY,
WHICH COULD BRING SUB-VFR CONDITIONS AT TIMES. HOWEVER, SHOULD
PRIMARILY REMAIN VFR DURING THIS TIME.
MARINE
BACKGROUND WIND FIELDS REMAIN BLOW SMALL CRAFT ADVISORY LEVELS
THROUGH AT LEAST SUNDAY EVENING. ANY CONVECTIVE CHANCES STAY OUT
ACROSS THE MOUNTAINS TODAY. A BROKEN LINE OF SHOWERS ARE
POSSIBLE AS A COLD FRONT TRACKS THROUGH SUNDAY NIGHT. SOME
UPTICK IN WINDS MAY WARRANT MARINE WEATHER STATEMENTS. BY
MONDAY, POST-FRONTAL NORTHEASTERLY FLOW ENSUES WITH GUSTS AROUND
10 TO 15 KNOTS, PERHAPS SLIGHTLY HIGHER AT TIMES.
SUB-SCA WINDS ARE EXPECTED ALONG WITH DAILY CHANCES FOR SHOWERS
ON BOTH TUESDAY AND WEDNESDAY. NO MARINE HAZARDS ARE EXPECTED
AT THIS TIME.
TIDES/COASTAL FLOODING
ELEVATED TIDAL ANOMALIES LOOK TO CONTINUE THROUGH THE WEEKEND WITH
SOME UPTICK FORECAST DUE TO ONSHORE WINDS. ANNAPOLIS MAY APPROACH OR
EXCEED MINOR FLOOD FOR MULTIPLE UPCOMING TIDE CYCLES. WHILE
OTHER LOCATIONS AREN'T CURRENTLY FORECAST TO FLOOD, SOME COULD
COME CLOSE, ESPECIALLY SUNDAY EVENING. A PASSING COLD FRONT
SHOULD REDUCE WATER LEVELS SLIGHTLY HEADING INTO MONDAY.
LWX WATCHES/WARNINGS/ADVISORIES
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.
SYNOPSIS...BRO
NEAR TERM...ADS/BRO
SHORT TERM...BRO
LONG TERM...CJL
AVIATION...ADS/BRO/CJL
MARINE...BRO/CJL
TIDES/COASTAL FLOODING...
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