Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 141443 AAA
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1043 AM EDT MON JUL 14 2014

.SYNOPSIS...
BERMUDA HIGH PRESSURE WILL KEEP VERY WARM AND HUMID CONDITIONS
ACROSS THE MID-ATLANTIC INTO TUESDAY. A COLD FRONT WILL CROSS THE
AREA TUESDAY NIGHT. CANADIAN HIGH PRESSURE WILL BUILD ACROSS THE
EASTERN STATES WEDNESDAY THROUGH THURSDAY NIGHT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 10AM...OBS ACROSS THE I-95 CORRIDOR W/ TEMPS IN THE M80S AND
DEWPOINTS JUST ABOVE THE 70 DEG MARK - MAKE FOR HEAT INDICES NEAR
90F. A MIX OF SCATTERED MID-LEVEL DEBRIS CLOUDS WILL DO LITTLE TO
INHIBIT THE CONVECTIVE POTENTIAL TODAY...WHICH IS INCREASING BY
THE MINUTE. 12Z KIAD SOUNDING...AS WELL AS SURROUNDING REGIONAL
OBS SHOW A FAIRLY LOADED OVERHEAD COLUMN - W/ SFC AND MUCAPES
ALREADY IN THE 2-2.5K RANGE ALREADY. FORECAST AND SOUNDING
MODIFICATIONS HAVE THESE VALUES BORDERING 4K J/KG HEADING INTO THE
MID AFTN/MAX HEATING TIMES.

WE`RE STILL UNDER THE BASE OF A LARGER UPPER TROUGH BACK ACROSS
THE GREAT LAKES...WHICH WILL SEND A MINOR SHORTWAVE KINK IN THE
UPPER FLOW TOWARD THE AREA IN THE COMING HRS. THIS FEATURE WILL
DEEPEN SLIGHTLY AS IT MOVES EWD AND CLOSER TO THE COAST...BUT WILL
BE MORE THAN ENOUGH TO BE OUR MAIN LIFTING MECHANISM TODAY AS
SCATTERED SHOWERS AND WEAK TSTMS NEAR THE APLCNS FROM THE WEST.
LOCAL GUIDANCE POINTS TOWARD A LEE SFC TROUGH DRIFTING OVER THE
APLCNS IN SHORT ORDER AND PRODUCING IT`S OWN CONVECTION FROM THE
NRN SHEN VLY AND EWD...FROM EARLY AFTN ONWARD. AS THE SHORTWAVE
TROUGH NEARS THE I-95 CORRIDOR/ERN SEABOARD...THE LOW LEVEL SHEAR
PARAMETERS WILL INCREASE LATER THIS AFTN/EVE - GIVING ONGOING
CONVECTION MORE ENERGY FOR ORGANIZATION AND POTENTIALLY
MESOVORTICES AND/OR TORNADO PRODUCTION. NERN MD APPEARS TO THE BE
MORE FAVORABLE LOCATION FOR THESE ELEMENTS TO COME TOGETHER ACROSS
OUR REGION...IN TERMS OF INSTABILITY/SHEAR/TIMING.

LOCALIZED HEAVY RAIN ALSO POSSIBLE AND EXPECTED ACROSS ISOLATED
LOCATIONS THIS AFTN...SO THE POTENTIAL FOR FLASH FLOODING - ESPEC
IN URBAN AREAS - EXISTS BUT WILL DEPEND ON RESIDENCE TIME UNDER
THE HEAVIEST RAIN AND ANY POSSIBLE TRAINING. HOLDING OFF ON THE FF
WATCH BECAUSE OF THE ISOLATED POTENTIAL AND PROGRESSIVE NATURE OF
THE INCOMING CONVECTION. HOWEVER...THE RAINFALL FROM LAST NIGHT...
TODAY AND INTO TOMORROW WILL RAMP UP THE POTENTIAL FOR A FF WATCH
FOR PARTS OF THE AREA ON TUE. HWO WILL CONTINUE TO MENTION THESE
RISKS.

FROM PREV DISC...
ORGANIZED CONVECTION/SEVERE RISK SHOULD DIMINISH/MOVE OUT OF THE
CWA THIS EVENING...BUT GENERALIZED BROAD LIFT CONTINUES ACROSS THE
CWA SO WILL CONTINUE WITH CHANCE POPS THROUGH THE OVERNIGHT.

USED A BLEND OF BIAS CORRECTED SREFS/ADJMAV FOR MAXIMA AND BIAS
CORRECTED SREFS/ADJMET FOR MINIMA.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
MOIST/UNSTABLE ENVIRONMENT PERSISTS OVER THE CWA ON TUESDAY...WITH
AN AXIS OF HIGH PRECIPITABLE WATER/THETA-E AIR EAST OF THE BLUE
RIDGE. SOME CONVECTION WILL LIKELY BE ONGOING TUESDAY MORNING...
INCREASING IN COVERAGE AGAIN FOR THE AFTERNOON AS A COLD FRONT
APPROACHES FROM THE WEST AND AS HEIGHTS LOWER IN ADVANCE OF AN
APPROACHING UPPER TROUGH.

SEVERE WEATHER /DAMAGING WIND GUSTS/ AND FLASH FLOODING WILL AGAIN
BE POSSIBLE BY AFTERNOON...ESPECIALLY WITHIN THE AFOREMENTIONED AXIS
OF MOISTURE COINCIDING WITH THE BEST INSTABILITY /EAST OF THE BLUE
RIDGE/.

COLD FRONT STARTS TO PUSH EASTWARD THROUGH THE CWA IN THE
EVENING...LIKELY RESIDING EAST OF THE INTERSTATE 95 CORRIDOR BY
DAYBREAK WEDNESDAY. TREND WILL BE FOR LOWERING POPS FROM WEST TO
EAST THROUGH THE NIGHT AS POST-FRONTAL NORTHWEST WINDS BEGIN TO
BRING DRIER AIR INTO THE CWA.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
MAY HV A LINGERING CLDS/A SHRA OF TWO E OF I-95 AT THE START OF
WED...BUT COOLER AND PARTICULARLY DRIER AIR WL BE ADVECTING EWD
THRUT THE DAY...WHICH WL COAX UNSETTLED CONDS TWD THE DELMARVA.
ANOMALOUSLY SHARP H5 LOW WL PIVOT TWD CWFA WED...AND THAT CUD BE A
CONCERN IN TERMS OF EITHER STALLING CDFNT OR PROVIDING STEEP ENUF
LAPSE RATES TO REINVIROGATE DIURNAL CU IF NOT A POP-UP SHRA. WL BE
TAKING THE OPTIMISTIC RTE ATTM...BANKING ON UPR LVL ENERGY KEEPING
FNT SOMEWHAT PROGRESSIVE AND DOWNSLOPE FLOW TO INHIBIT CLD GROWTH.
IT APPEARS AS THO THE TROF AXIS ITSELF WL RECEDE BACK INTO CNDA
W/O CROSSING MID ATLC...SO WONT BE DROPPING TEMPS TREMENDOUSLY.
ACTUALLY...RAISED WED MAXT BY A CPL...BUT TEMPS IN THE UPR 70S-LWR
80S /LWR-MID 70S IN THE MTNS/ WITH DEWPTS DROPPING THRU THE 50S
ISNT A COMMON OCCURENCE.

SFC HIPRES WL BLD BHD FNT...AND WL MOST DIRECTLY AFFECT CWFA WED NGT
THRU THU NGT. MOSUN/MOCLR AND DRY WX THRUT. THU MAXT COMPARABLE TO
WED. MIN-T BOTH NGTS IN THE 50S TO LWR 60S.

FRI INTO THE WKND...S/WV ENERGY EJECTS EWD FM THE CENTER OF THE
CONUS TWD THE MID ATLC. EXACTLY HOW THAT TRANSPIRES WL DETERMINE THE
FCST OUTCOME. HWVR...NEED TO INCL POPS IN THE FCST FOR THE PD. WL
HOLD BACK SGFNT TEMP INCREASES...BUT THAT CUD HPPN IF A WMFNT CAN
ACTUALLY MAKE IT THRU.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
EXPECT LEE TROUGH AND MOIST/UNSTABLE ATMOSPHERE TO INSTIGATE
NUMEROUS SHRA/TSRA BY AFTERNOON...SOME WITH HEAVY RAIN/STRONG
WINDS. CONVECTION SHOULD DIMINISH IN COVERAGE AFTER DARK...BUT A
FEW SHOWERS WILL REMAIN POSSIBLE OVERNIGHT.

THUNDERSTORMS ARE LIKELY AGAIN TUESDAY AFTERNOON/EVENING...THEN A
COLD FRONT MOVES THROUGH WITH A WIND SHIFT TO THE NORTHWEST /AND
DRYING/ TUESDAY NIGHT.

OUTLOOK...
WED-THU...VFR UNDER HIPRES.
FRI...SHUD BE VFR TOO...BUT THERE IS AN OUTSIDE CHC AT A SHRA/TSRA.

&&

.MARINE...
WINDS SHOULD DIMINISH BELOW SCA THRESHOLDS INTO EARLY AFTN...HOWEVER
STRONG GUSTY WINDS MAY ACCOMPANY THUNDERSTORMS THIS AFTERNOON/EVENING
AND AGAIN ON TUESDAY. COLD FRONT IS EXPECTED TO APPROACH THE
CHESAPEAKE BAY LATE TUESDAY NIGHT.

COOLER AND DRIER AIR OVERSPREADS WATERS WED. HWVR...GDNC SUGGESTS
THAT WNDS WONT EXCEED SCA CRITERIA. SINCE THERES A LTL UNCERTAINTY
AS TO WHETHER CDFNT MAY GET HUNG UP NEAR THE WATERS...WL KEEP GUSTS
CAPPED AT 15 KT.

HIPRES CRESTS OVER WATERS THU AND MVS OFFSHR FRI. NW WNDS LESSEN AND
BACK SLY.

&&

.TIDES/COASTAL FLOODING...
A CPL ROUNDS OF TSTMS SUN EVE PUSHED A LTL WATER AWAY FM THE WRN
SHORE OF THE BAY. WHILE ITS ONLY A MATTER OF A FEW INCHES...THATS
ENUF OF A MARGIN TO SUGGEST THAT HIGH TIDE AT ANNAPOLIS WL COME IN
JUST UNDER MINOR CRITERIA. WATER LEVELS AOB A HALF-FOOT ABV ASTRO
PREDICTIONS ATTM...AND HIGHT IDE SHOULDNT BE A PROBLEM THIS MORNING.
PERHAPS THE ONLY OTHER SITE TO WATCH IS SW DC...BUT DO NOT HV THE
CONFIDENCE TO ISSUE ADVYS ANYWHERE ATTM.

&&

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

&&

$$
UPDATE...GMS
PREV DISCUSSION...BPP/HTS







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