Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KLWX 271819
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
219 PM EDT WED AUG 27 2014

.SYNOPSIS...
A WEAK COLD FRONT OVER THE MIDWEST WILL CROSS THE AREA TONIGHT.
HIGH PRESSURE WILL BUILD ACROSS THE NORTHERN MID-ATLANTIC THURSDAY
NIGHT...LINGERING OFF THE COAST INTO THE WEEKEND. THE NEXT COLD
FRONT WILL APPROACH THE MID-ATLANTIC EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 17Z...SUNNY OVER BALT-WASH METRO FROM WEAKENING SFC HIGH. WEAK
BOUNDARY WEST OF THE BLUE RIDGE HAS CAUSED SOME STRATOCU OVER THE
SHEN VLY TO CATOCTIN MOUNTAIN. ISOLATED SHOWERS MAY DEVELOP IN THIS
AREA. OTHERWISE...ACTIVITY WILL HOLD OFF UNTIL THE ACTUAL COLD FRONT
(OVER CNTRL OHIO AND PITTSBURGH NOW) APPROACHES THE NWRN ZONES. MAX
TEMPS AROUND 90F ACROSS THE AREA. SFC HEATING AND DEWPTS IN THE MID
TO UPR 60S WILL LEAD TO 500-1000 J/KG OF MLCAPE LATE THIS AFTERNOON
AND EVENING. ISO-SCT SHOWERS AND THUNDERSTORMS ARE EXPECTED AS WEAK
FORCING. MARGINAL SHEAR OF 20 KT IS STILL EXPECTED. THE BEST CHANCE
FOR THUNDERSTORMS WILL BE IN THE POTOMAC HIGHLANDS THIS EVENING. AND
THAT IS SCATTERED AT BEST. ACTIVITY WILL DISSIPATE DUE TO THE LOSS
OF DAYTIME HEATING THIS EVENING. QUESTION IS WHETHER THE BALT-WASH
CORRIDOR WILL SEE THUNDERSTORMS. THINKING IS STILL THAT SOMETHING
MORE ORGANIZED THAN POP UP ACTIVITY WOULD BE NEEDED. STILL HAVE AN
ISO COVERAGE IN THE GRIDS FOR THE METRO THIS EVENING.

NW FLOW AND DRIER AIR WILL MOVE IN BEHIND THE FRONT. THE FRONT
SHOULD BE IN SRN VA BY THURSDAY MORNING AND CLOUDS WILL CLEAR FROM
NORTH TO SOUTH EARLY THURSDAY MORNING. IN SPITE OF SOME MIXING...FOG
IS LIKELY WHERE RAIN FALLS.

THURSDAY...NW FLOW WILL DROP DEWPTS INTO THE 50S. FCST MAX TEMPS ARE
IN THE LOW 80S NEAR THE MASON DIXON LINE TO THE MID 80S IN CENTRAL
VA...WITH MID TO UPPER 80S IN DC/BALTIMORE.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
NLY FLOW FROM HIGH PRESSURE MOVING EAST ACROSS THE NRN MID-
ATLANTIC SHOULD LIMIT FOG THURSDAY NIGHT. MIN TEMPS MID 50S NW TO
LOW 60S SE (MID 60S URBAN).

FRIDAY...MID LEVEL RIDGE AXIS LIFT OVER THE AREA WITH A RETURN OF
MOISTURE BY THAT EVENING. ISO WORDING FOR THUNDERSTORMS IN
MOUNTAINS OF THE SOUTHWEST ZONES. MAX TEMPS GENERALLY MID 80S IN
SELY ONSHORE SFC FLOW.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
SURFACE HIGH PRESSURE WILL MOVE OFF OF THE NEW ENGLAND COAST OVER
THE COURSE OF THE WEEKEND. GRADUALLY INCREASING WARM AND MOIST
SOUTHERLY FLOW COMBINED WITH HEIGHT FALLS ALOFT WILL LEAD TO
INCREASED INSTABILITY DURING THIS TIME. THUNDERSTORM ACTIVITY SATURDAY
SHOULD BE LIMITED TO THE HIGH TERRAIN ALONG THE POTOMAC HIGHLANDS
AND WESTERN MD WHERE UPSLOPE FLOW WILL PROVIDE THE BEST TRIGGER FOR
CONVECTION. LITTLE STEERING FLOW SHOULD ENSURE THAT THESE STORMS
REMAIN WEST OF THE METRO AREAS UNTIL THEY DIE OUT SHORTLY AFTER
SUNSET SATURDAY NIGHT.

HIGH PRESSURE OFF THE COAST WILL SETTLE INTO A MORE TYPICAL
BERMUDA HIGH LOCATION BY SUNDAY EVENING...ALLOW LEE TROUGHING TO SET
UP LOCALLY AHEAD OF AN APPROACHING WEAK COLD FRONT SUNDAY. THIS
LIFTING MECHANISM WILL LEAD TO AN INCREASE IN SHOWERS AND
THUNDERSTORM COVERAGE AHEAD OF THE FRONT BY SUNDAY AFTERNOON.
INSTABILITY LESS THAN 1000 J AND RELATIVELY WEAK SHEAR SUNDAY SHOULD
LIMIT THE SEVERE POTENTIAL OF THUNDERSTORMS THAT DO FORM. THE
FRONTAL BOUNDARY WILL ESSENTIALLY STALL AND DETERIORATE OVER THE
AREA THROUGH MONDAY...SO CHANCE POPS AND THUNDERSTORMS WILL REMAIN
IN THE FORECAST FOR MONDAY WITH SLIGHTLY MORE INSTABILITY
THAN ON SUNDAY.

MONDAY NIGHT SHOULD BE DRY AS LITTLE DYNAMIC ENHANCEMENT WILL REMAIN
OVER THE AREA AS THE FRONT WILL HAVE MOSTLY DETERIORATED. SOUTHERLY
FLOW AROUND THE BERMUDA HIGH AND THE RESULTING LEE TROUGH WILL
RESUME TUESDAY AND AFTERNOON THUNDERSTORMS WILL BE POSSIBLE ONCE
AGAIN. A REINFORCING COLD FRONT SHOULD MOVE THROUGH
WEDNESDAY...BRINGING SHOWERS AND THUNDERSTORMS FOR THE MIDDLE OF THE
WORKWEEK.

HIGH TEMPS WILL BE NEAR 90 SATURDAY...SUNDAY AND TUESDAY...AS
PREFRONTAL SOUTHERLY FLOW AND LEE TROUGHING SET UP LOCALLY. HIGHS ON
MONDAY AND WEDNESDAY WILL BE IN THE MID TO UPPER 80S AS FRONTS
APPROACH AND CROSS THE AREA.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
VFR INTO TONIGHT FOR MOST TERMINALS. KMRB HAS BEST CHANCE FOR
SHRA/TSRA THIS EVENING...ONLY SCATTERED COVERAGE THOUGHT. DC METROS
SHOULD BE DRY TONIGHT IN SPITE OF A COLD FRONTAL PASSAGE. NWLY FLOW
AROUND 10 KT BEHIND THE FRONT LATE TONIGHT. HIGH PRESSURE BUILDS
THROUGH THURSDAY NIGHT WITH VFR CONDS THROUGH FRIDAY.

CONFIDENCE IS LOW IN THE OCCURRENCE OF ANY HAZARDS TO AVIATION IN
THE LONG TERM.

&&

.MARINE...
BAY BREEZE THIS AFTERNOON BECOMES NWLY TONIGHT BEHIND A DRY COLD
FRONT. 10 TO 15 KT NWLY FLOW THURSDAY AS HIGH PRESSURE BUILDS FROM
THE GREAT LAKES. LIGHTER NLY FLOW THURSDAY NIGHT...BECOMING ONSHORE
FOR FRIDAY.

A SMALL CRAFT ADVISORY MAY BE NECESSARY SUNDAY IN BREEZY PREFRONTAL
SOUTHERLY FLOW.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...BAJ
NEAR TERM...BAJ
SHORT TERM...BAJ
LONG TERM...CEB
AVIATION...BAJ/CEB
MARINE...BAJ/CEB



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.