Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 280046
AFDLWX

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

.SYNOPSIS...
LOW PRESSURE WILL 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 /UNTIL 6 AM MONDAY MORNING/...
SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR PORTIONS OF NORTHERN
AND WESTERN MARYLAND...THE EASTERN WEST VIRGINIA PANHANDLE AND
INTO THE NORTHERN SHENANDOAH VALLEY OF VIRGINIA UNTIL 2 AM.

THUNDERSTORMS HAVE BEEN SLOWER TO MOVE INTO/DEVELOP ACROSS THE CWA
THAN SOME GUIDANCE HAD EARLIER SUGGESTED. HAVE HAD ONE CELL IN WV /IN
THE WATCH AREA/ THAT WE HAVE WARNED ON AND THAT HAS BEEN THE
STRONGEST CELL WITHIN OUR CWA THUS FAR.

18Z KIAD RAOB REVEALED A CAP ACROSS THE CWA /AND SOME DRY AIR TOO/...BUT
THAT CAP HAD DISAPPEARED BASED ON THE 00Z KIAD RAOB. DESPITE THE
SETTING OF THE SUN...EXPECTATION IS FOR AN INCREASE IN CONVECTION
DURING THE MID TO LATE EVENING AS LARGER SCALE LIFT AND SHEAR
INCREASE. WITH THIS...THE SEVERE RISK WILL CONTINUE WITHIN THE
WATCH AREA AND COULD ALSO EVENTUALLY SPREAD FURTHER DOWNSTREAM OF
THE CURRENT WATCH EARLY TONIGHT.

ACTUAL COLD FRONT LIKELY WON/T MAKE IT INTO THE POTOMAC HIGHLANDS
UNTIL LATE TONIGHT.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
THE TROUGH WILL BE OVER NY MONDAY AND WHILE THE COLD FRONT WILL
MOVE 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 /01Z MONDAY THROUGH FRIDAY/...
CHALLENGING THUNDERSTORM FORECAST THIS EVENING. HAD BACKED OFF ON
TSRA A COUPLE OF HOURS IN 00Z TAFS. WHILE THERE STILL REMAINS SOME
UNCERTAINTY IN COVERAGE AND TIMING...CONTINUED THE OVERALL TREND IN
AN INCREASE IN COVERAGE DURING THE MID TO LATE EVENING...WITH
POTENTIAL IMPACT AT HUBS MAINLY 02Z-06Z TIME FRAME.

N-NW WINDS WILL MOVE IN AS A COLD FRONTAL PASSAGE OCCURS 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...
SOUTHERLY CHANNELLING WILL LIKELY SUPPORT OCCASIONAL SCA GUSTS UP
THE BAY THROUGH THE OVERNIGHT. ANY LATE EVENING/OVERNIGHT
THUNDERSTORMS MAY ALSO PRODUCE STRONG GUSTY WINDS. WINDS WILL
BECOME NWLY MONDAY BEHIND A COLD FRONT. 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.

&&

.TIDES/COASTAL FLOODING...
ANOMALIES HAVE DECREASED TO AROUND 1/2 FT ON THE WESTERN SHORE OF
THE CHESAPEAKE BAY. AT HIGH TIDE...WATER LEVELS WOULD REMAIN BELOW
MINOR TIDAL FLOOD THRESHOLDS WITH THESE ANOMALIES.

&&

.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...BPP/HAS
SHORT TERM...HAS
LONG TERM...DFH
AVIATION...BPP/HAS/DFH
MARINE...BPP/HAS/DFH
TIDES/COASTAL FLOODING...BPP






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