Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 271847
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
247 PM EDT SUN JUL 27 2014

.SYNOPSIS...
LOW PRESSURE OVER MICHIGAN IS EXPECTED TO TRACK ACROSS PENNSYLVANIA
TONIGHT. AN ASSOCIATED COLD FRONT WILL MOVE THROUGH THE REGION
MONDAY. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT BRINGING
COOLER AND DRIER CONDITIONS DURING MIDWEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
SEVERE WEATHER IS EXPECTED FOR THE MID ATLANTIC TODAY AND TONIGHT.

A POTENT SHORTWAVE TROUGH IS MOVING ACROSS THE WESTERN GREAT LAKES
WHILE A SFC LOW RESIDES JUST AHEAD OF IT OVER SRN MI THIS AFTERNOON. AN
ASSOCIATED COLD FRONT EXTENDS FROM MI THROUGH IN/KY. AHEAD OF THIS
COLD FRONT...SOUTHERLY WINDS HAVE LED TO DEWPTS TO CLIMB AROUND 70
DEG F IN THE MID-ATLANTIC. A FEW DISTURBANCES HAVE CROSSED THE
REGION TODAY CAUSING A CHAOTIC CLOUD DECK RESULTING IN SOME AREAS
WARMING FASTER THAN OTHERS. THIS INCLUDES NRN MD AND THE POTOMAC
HIGHLANDS. TEMPS RANGE FROM THE MID TO UPPER 80S IN THIS AREA TO
THE UPPER 70S NEAR CHO.

PER THE MESOANALYSIS...INSTABILITY HAS RISEN TO 1K-2K J/KG ACROSS
THE REGION WITH 2K-3K J/KG NEAR THE MASON DIXON LINE WHERE MOST OF
THE HEATING HAS OCCURRED. 0-6 KM SHEAR HAS INCREASED TO 40-50 KTS.
THE EXIT REGION OF THE JET STREAM IS STILL BACK ACROSS THE OHIO
VALLEY BUT WILL MOVE EASTWARD THIS AFTERNOON. THUNDERSTORMS ARE
EXPECTED TO MOVE FROM OHIO AND TRACK E-SE INTO THE MID-ATLANTIC LATE
THIS AFTERNOON. CONDITIONS WILL CONTINUE TO BECOME MORE UNSTABLE AND
SUITABLE FOR STRONG THUNDERSTORM DEVELOPMENT ACROSS THE MID ATLANTIC
THIS AFTERNOON. ADDITIONAL THUNDERSTORMS WILL LIKELY FORM ON
OUTFLOW BOUNDARIES IN THE OHIO VALLEY AND MOVE EASTWARD BY THIS
EVENING. EXPECT THUNDERSTORMS TO CROSS THE APPALACHIANS LATE THIS
AFTERNOON REACHING THE I-95 CORRIDOR THIS EVENING. SUPERCELLS ARE
EXPECTED AND WILL LIKELY LEAD TO DMG WINDS...LARGE
HAILS...ISOLATED TORNADOES AND HEAVY RAINFALL. AT THIS TIME FFG IS
HIGH AND PWATS ARE MARGINAL. FLASH FLOODING IS ALWAYS A CONCERN
WITH THUNDERSTORMS THAT MOVE OVER THE SAME REGION AND THEREFORE IT
IS POSSIBLE THIS EVENING.

SHOWERS MOVING ACROSS THE CENTRAL FOOTHILLS THIS AFTERNOON HAVE
BEEN IN AN UNFAVORABLE ENVIRONMENT FOR THUNDERSTORMS DUE TO THE
LOWER INSTABILITY...AT THIS TIME. THEY ARE TRACKING INTO A
FAVORABLE AREA AND WILL BE MONITORED CLOSLY.

THE POTENT SHORTWAVE TROUGH WILL MOVE ACROSS LAKE ERIE LATE TONIGHT
WHILE THE COLD FRONT CROSSES THE MID ATLANTIC. WESTERLY WINDS WILL
MOVE IN BEHIND THE COLD FRONT AND THUNDERSTORMS WILL MOVE EAST OF
THE BAY BY EARLY MONDAY MORNING.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
THE TROUGH WILL BE OVER NY MONDAY AND WHILE THE COLD FRONT WILL BE
OFF THE COAST. AS ENERGY ROUNDS THE BASE OF THE TROUGH MONDAY
SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE MAINLY I-66 AND
NORTH MONDAY AFTERNOON. NW WINDS WITH GUSTS UP TO 30 MPH WILL BE
POSSIBLE IN THE AFTERNOON.

FCST MIN TEMPS MONDAY NIGHT RANGE FROM THE MID 50S IN THE HIGHLANDS
TO THE LOW 60S NEAR THE METROS AND WATERS. NRLY WINDS WIL CONTINUE
TUESDAY AND TEMPS WILL ONLY RISE INTO THE UPPER 70S WHICH WILL FEEL
LIKE A FALL DAY FOR THE MID-ATLATNIC.


&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
MEAN TROUGHING WILL PERSIST ALOFT OVER THE EASTERN CONUS THROUGH THE
REMAINDER OF THE UPCOMING WEEK. DRY AIR AND NORTHWEST FLOW AROUND
HIGH PRESSURE AT THE SURFACE WILL KEEP THE REGION DRY AND COOLER
THAN NORMAL DURING THIS PERIOD.

MODELS INDICATE THE TROUGH AXIS WILL SLOWLY RETROGRADE BACK WEST OF
THE AREA LATE IN THE WEEK INTO NEXT WEEKEND AS SUBTROPICAL RIDGING
RE-ESTABLISHES ITS HOLD OVER THE WESTERN ATLANTIC. AS THE TROUGH
MOVES BACK/REDEVELOPS TO OUR WEST...WINDS WILL BECOME SOUTHERLY
INCREASING THE HEAT AND HUMIDITY AS WELL AS THE CHANCES OF SHOWERS
AND THUNDERSTORMS. THE LONGWAVE PATTERN BY THE END OF NEXT WEEKEND
WOULD SUGGEST A POTENTIAL FOR HEAVY RAIN GIVEN THE LONG AND
PERSISTENT TRAJECTORY OF WIND OUT OF THE GULF OF MEXICO RIDING ALONG
A STALLED OR SLOW-MOVING FRONT.


&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS AFTERNOON.
COVERAGE WILL INCREASE THIS EVENING AND LIKELY IMPACT THE
TERMINALS. MVFR/IFR IS LIKELY IN THUNDERSTORM ACTIVITY. SOME
THUNDERSTORMS ARE EXPECTED TO BE STRONG TO SEVERE RESULTING IN
STRONG WINDS...LARGE HAIL AND ISOLATED TORNADOES. HEAVY RAIN WILL
ALSO CAUSE LOW VSBYS. THIS ACTIVITY ALL AHEAD OF A COLD FRONT WILL
MOVE FROM WEST TO EAST TONIGHT. ACTIVITY SHOULD BE THROUGH MRB
THE EVENING TO THE DCA-BWI-MTN BY MIDNIGHT.

N-NW WINDS WILL MOVE IN BEHIND THE FRONT MONDAY. SHRA AND -TSRA IS
POSSIBLE MONDAY AS ENERGY MOVES ACROSS THE AREA. NW WINDS AROUND
10-15KTS WITH GUSTS UP TO 25KTS EXPECTED AT THE TERMINALS.

NW FLOW GENERALLY 10 KTS OR LESS W/ VFR TUE-THU.

&&

.MARINE...
S-SW FLOW EXPECTED ON THE WATERS THIS AFTERNOON AND EVENING.
SHOWERS AND THUNDERSTORMS ARE EXPECTED LATE TONIGHT AND INTO
MONDAY MORNING AHEAD OF A COLD FRONT. WINDS WILL BECOME NWLY
MONDAY. A SCA IS IN EFFECT FOR THE WATERS THIS AFTERNOON. PORTIONS
OF THE UPPER TIDAL POTOMAC AND CHESAPEAKE BAY WILL DROP LATE
TONIGHT. A SCA IS IN EFFECT FOR ALL THE WATERS MONDAY.

RELATIVELY BENIGN SURFACE PRESSURE GRADIENT WITH HIGH PRESSURE
NEARBY OR OVERHEAD TUE NIGHT-FRI IS EXPECTED TO RESULT IN SUB-SCA
CONDITIONS ON THE WATERS. WINDS BECOME SOUTHERLY AND INCREASE NEXT
WEEKEND...POSSIBLY TO SCA LEVELS BUT THAT IS UNCLEAR THIS FAR OUT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ530-531-
     535-536-538-539-542.
     SMALL CRAFT ADVISORY FROM 10 AM TO 7 PM EDT MONDAY FOR ANZ530-
     531-535-536-538-539-542.
     SMALL CRAFT ADVISORY UNTIL 7 PM EDT MONDAY FOR ANZ532>534-537-
     540-541-543.

&&

$$
SYNOPSIS...HAS
NEAR TERM...HAS
SHORT TERM...HAS
LONG TERM...DFH
AVIATION...HAS/DFH
MARINE...HAS/DFH






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