Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 241815
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
215 PM EDT SUN APR 24 2016

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE COAST THROUGH MONDAY. A COLD FRONT
WILL APPROACH FROM THE NORTHEAST ON TUESDAY BEFORE PASSING THROUGH
THE AREA TUESDAY NIGHT INTO WEDNESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
HIGH PRESSURE OVERHEAD EARLY THIS AFTERNOON WILL CONTINUE TO SHIFT
TOWARD THE MID-ATLANTIC COAST LATE. PLENTY OF SUNSHINE AND
SEASONABLE CONDITIONS ARE EXPECTED AND THE SURFACE WIND WILL
GRADUALLY VEER TOWARD THE SOUTH LATE THIS AFTERNOON. WIND SPEEDS
SHOULD REMAIN LIGHT...GENERALLY UNDER 10KT.

HIGH PRESSURE WILL CONTINUE TO SHIFT EAST OFF THE MID-ATLANTIC
COAST TONIGHT. A LIGHT SOUTHERLY FLOW WILL ALLOW FOR MILDER
CONDITIONS COMPARED TO LAST NIGHT. MIN TEMPS WILL BE IN THE MID TO
UPPER 40S FOR MOST LOCATIONS.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
HIGH PRESSURE WILL CONTINUE TO MOVE OUT INTO THE ATLANTIC OCEAN
MONDAY AND A SOUTHWEST FLOW WILL USHER IN NOTICEABLY WARMER
CONDITIONS ALONG WITH MORE MOISTURE. A WESTERLY FLOW IS EXPECTED
ALOFT...BUT MOST OF THE SHORTWAVE ENERGY WILL BE WELL OFF TO THE
NORTH. THEREFORE...MONDAY WILL TURN OUT DRY FOR MOST AREAS ALONG
WITH SUNSHINE. THERE MAY BE A COUPLE POPUP SHOWERS LATE MONDAY
AFTERNOON IN THE POTOMAC HIGHLANDS INTO THE VIRGINIA PIEDMONT DUE
TO DAYTIME HEATING. HOWEVER...MOISTURE WILL BE LIMITED SO ANY
COVERAGE WOULD BE ISOLATED AT BEST AND MOST AREAS WILL END UP DRY.

A SOUTHWEST FLOW WILL CONTINUE THROUGH MONDAY NIGHT...AND IT WILL
REMAIN QUITE MILD. A FEW SHOWERS ARE POSSIBLE ACROSS THE NORTHERN
PORTIONS OF THE CWA...BUT COVERAGE WOULD REMAIN ISOLATED TO
SCATTERED DUE TO LIMITED FORCING.

POTENT LOW PRESSURE BOTH AT THE UPPER-LEVELS OF THE ATMOSPHERE AND
THE SURFACE WILL MOVE EAST FROM THE ROCKIES INTO THE PLAINS ON
TUESDAY. THIS WILL ALLOW FOR RIDGING UPSTREAM TO STRENGTHEN OVER
THE MIDWEST AND GREAT LAKES. A CONFLUENCE ZONE BETWEEN THE UPPER-
LEVEL RIDGING AND UPPER-LEVEL LOW PRESSURE OVER EASTERN CANADA
WILL STRENGTHEN...AND THIS WILL CAUSE HIGH PRESSURE TO STRENGTHEN
OVER NEW ENGLAND. A BACKDOOR BOUNDARY WILL DEVELOP AHEAD OF THE
BUILDING HIGH THAT SEPARATES WARM AND MOIST AIR OVER OUR AREA FROM
MUCH COOLER AIR OVER NEW ENGLAND. THIS BOUNDARY SHOULD REMAIN TO
OUR NORTH TUESDAY...WHICH MEANS THAT A SOUTHWEST FLOW WILL ALLOW
FOR WARM AND MOIST CONDITIONS. MAX TEMPS WILL REACH THE UPPER 70S
AND LOWER 80S FOR MOST AREAS AND DEWPOINTS IN THE UPPER 50S AND
60S ARE EXPECTED. THIS WILL LEAD TO AT LEAST SOME INSTABILITY. THE
UNSTABLE ATMOSPHERE WILL COMBINE WITH A PRESSURE
TROUGH...TRIGGERING A FEW SHOWERS AND THUNDERSTORMS. SUFFICIENT
SHEAR PROFILES SUGGEST THAT A FEW THUNDERSTORMS COULD BECOME
SEVERE...WITH LOCALLY DAMAGING WIND GUSTS AND LARGE HAIL BEING THE
PRIMARY THREATS. AT THIS TIME...CURRENT THINKING IS THAT ANY
SEVERE COVERAGE WOULD BE LOCALIZED DUE TO LIMITED
INSTABILITY...GENERALLY LESS THAN 1KJ/KG. HOWEVER...SHOULD
INSTABILITY BE HIGHER THAN ANTICIPATED THEN THE SEVERE COVERAGE
WOULD INCREASE SIGNIFICANTLY.

THE BACKDOOR BOUNDARY WILL DROP THROUGH MOST OF THE AREA TUESDAY
NIGHT. A NORTHEAST FLOW BEHIND THE BOUNDARY WILL CAUSE NOTICEABLY
COOLER CONDITIONS FOR MOST AREAS...BUT IT WILL LIKELY REMAIN WARM
NEAR AND AHEAD OF THE BOUNDARY ACROSS THE POTOMAC HIGHLANDS INTO
THE SHENANDOAH VALLEY. A COUPLE SHOWERS AND THUNDERSTORMS ARE
POSSIBLE IN THE EVENING...BUT COVERAGE WILL BECOME MORE LIMITED
OVERNIGHT BEHIND THE BOUNDARY AND EVEN AHEAD OF THE BOUNDARY DUE
TO THE LOSS OF DAYTIME HEATING.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A BACKDOOR COLD FRONT WILL CONTINUE TO PUSH SOUTHWARD WEDNESDAY
AND WEDNESDAY NIGHT. THERE IS A BETTER CHANCE OF ENCOUNTERING RAIN
SHOWERS ACROSS THE VIRGINIA PIEDMONT AND CENTRAL SHENANDOAH VALLEY
THAN NORTHEAST MARYLAND AND THE MASON-DIXON REGION THROUGHOUT THIS
PERIOD.

THE FRONT WILL TRY TO WORK ITS WAY NORTHWARD THURSDAY THROUGH
FRIDAY...KEEPING THE THREAT FOR SHOWERS AND A COUPLE OF
THUNDERSTORMS ACROSS THE REGION. AN AREA OF HIGH PRESSURE OVER THE
GREAT LAKES WILL NUDGE THE FRONT TO THE SOUTHEAST AND OFFSHORE
FRIDAY NIGHT AND SATURDAY BEFORE THE FRONT CAN REACH THE MASON-DIXON
LINE.

THE HIGH WILL MOVE INTO SOUTHERN NEW ENGLAND AND OFFSHORE NEW JERSEY
TO ALLOW FOR A SOUTHERLY FLOW TO DEVELOP AND BRING IN ADDITIONAL
WARMTH AND MOISTURE INTO THE REGION SATURDAY AND SATURDAY NIGHT.
THERE IS A CHANCE FOR SOME STRATIFORM RAIN AND PERHAPS A CLAP OF
THUNDER AS A WARM FRONT DEVELOPS ACROSS THE SOUTHERN SHENANDOAH
VALLEY AND PROPAGATES NORTHWARD.

THROUGHOUT THE DAY SUNDAY...THE INSTABILITY OF THE ATMOSPHERE
BECOMES MORE PRONOUNCED AND THE CHANCE OF RAIN SHOWERS AND
THUNDERSTORMS BECOMES MORE SCATTERED IN THE REGION.

&&

.AVIATION /17Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS ARE EXPECTED THROUGH MONDAY. A SOUTHERLY FLOW WILL
DEVELOP LATE THIS AFTERNOON AND EVENING...BUT WIND SPEEDS SHOULD
REMAIN LIGHT. WINDS WILL INCREASE A BIT MONDAY WITH GUSTS AROUND
15 TO 20 KNOTS EXPECTED IN THE AFTERNOON. THE SOUTHWEST FLOW WILL
CONTINUE TUESDAY WITH GUSTS AROUND 20 TO 25 KNOTS EXPECTED. THERE
IS A CHANCE FOR AFTERNOON THUNDERSTORMS. SOME THUNDERSTORMS MAY
CONTAIN GUSTY WINDS AND HAIL ALONG WITH SUBVFR CIGS/VSBYS.

A COLD FRONT WILL PASS THROUGH THE TERMINALS TUESDAY NIGHT. WINDS
WILL SHIFT TO THE NORTHEAST BEHIND THE BOUNDARY. SUBVFR CIGS ARE
POSSIBLE BEHIND THE BOUNDARY.

MVFR TO IFR CONDITIONS POSSIBLE WITH RAIN SHOWERS IN THE VICINITY
NEAR CHO TERMINAL WEDNESDAY...THEN AT ANY TERMINAL WEDNESDAY NIGHT.
WINDS NORTHEAST AROUND 5 KNOTS WEDNESDAY...BECOMING SOUTHEAST AROUND
5 KNOTS WEDNESDAY NIGHT.

&&

.MARINE...
A SOUTHERLY FLOW WILL INCREASE TONIGHT INTO MONDAY. WINDS WILL BE
CLOSE TO SCA CRITERIA FOR THE MIDDLE PORTION OF THE BAY AND LOWER
TIDAL POTOMAC RIVER DURING THIS TIME. DID NOT ISSUE AN SCA AT THIS
TIME BECAUSE CONFIDENCE WAS TOO LOW GIVEN THE RELATIVELY COOLER
WATERS. HOWEVER...IT WILL BE CLOSE AND THIS WILL HAVE TO BE
MONITORED.

THE SOUTHERLY FLOW WILL INCREASE MONDAY NIGHT...AND A SMALL CRAFT
ADVISORY IS IN EFFECT FOR THE MIDDLE PORTION OF THE BAY AND LOWER
TIDAL POTOMAC RIVER. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED
FOR ALL OF THE WATERS TUESDAY. A FEW SHOWERS AND THUNDERSTORMS ARE
POSSIBLE TUESDAY AFTERNOON INTO TUESDAY EVENING. THUNDERSTORMS
WILL BE CAPABLE OF PRODUCING GUSTY WINDS AND HAIL. A BACKDOOR
COLD FRONT WILL PASS THROUGH THE WATERS TUESDAY NIGHT AND WINDS
WILL SHIFT TO THE NORTHEAST BEHIND THE BOUNDARY.

A NORTHEAST FLOW WILL CONTINUE BEHIND THE BOUNDARY FOR WEDNESDAY
INTO THURSDAY. WIND SPEEDS SHOULD REMAIN BELOW SCA CRITERIA.

&&

.FIRE WEATHER...
VERY DRY CONDITIONS WILL CONTINUE THIS AFTERNOON WITH RH VALUES
DROPPING 20S AND TEENS. HOWEVER...WINDS WILL REMAIN LIGHT. A
SOUTHWEST FLOW WILL INCREASE MONDAY WITH GUSTS AROUND 15 TO 20
MPH EXPECTED. THE SOUTHWEST FLOW WILL LEAD TO MORE ATMOSPHERIC
MOISTURE WHICH SHOULD KEEP RH VALUES ABOVE 30 PERCENT. A FEW
SHOWERS AND THUNDERSTORMS ARE POSSIBLE TUESDAY. A COOLER AND
WETTER WEATHER PATTERN MAY DEVELOP FOR THE MIDDLE AND LATTER
PORTIONS OF THE WEEK.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 8 PM MONDAY TO 6 AM EDT TUESDAY FOR
     ANZ532>534-537-540>543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...BJL
LONG TERM...KLW
AVIATION...BJL/KLW
MARINE...BJL/KLW
FIRE WEATHER...BJL



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