Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 301927
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
327 PM EDT TUE JUN 30 2015

.SYNOPSIS...
LOW PRESSURE WILL SLIDE EASTWARD OVER THE EASTERN GREAT LAKES
TODAY. A COLD FRONT WILL SLIDE SOUTHEAST INTO THE MID ATLANTIC
LATE ON WEDNESDAY...AND THEN STALL ACROSS THE REGION ON THURSDAY.
THE STALLED FRONT WILL LINGER IN THE AREA THROUGH THE WEEKEND
BEFORE LIFTING NORTHWARD AGAIN ON MONDAY.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
SVR TSTM WATCH 372 IN EFFECT FOR METRO BALT AND N-CENTRL MD TIL
8PM AND SVR TSTM WATCH 377 IN EFFECT FOR THE REST OF THE CWFA TIL
9PM.

LLVL CNVRGNC AND NOSE OF THTE RDG THE DRIVING MECHANISMS ATTM ACRS
NERN CWFA. DIURNAL HEATING...DIFFERNETIAL HEATING BNDRYS...TRRN
CIRCULATIONS...AND LEE TROF ALL PROVIDING LIFTING MECHANISMS FOR
THE REST OF THE AREA. ENVIRONMENT CONTAINS MORE THAN ENUF
CAPE/SHEAR /2000 J/KG SBCAPE AND 40 KT EFFECTIVE BULK SHEAR/. THIS
SUGGESTS THAT TSTM DVLPMNT WL BECOME MORE NMRS IN THE SHEN
VLY/BLURDG BEFORE 21Z. THESE STORMS WL THEN MIGRATE TWD THE I-95
CRRDR TWD THE END OF THE WATCH PD. THERE IS POTLENTIAL THAT STORMS
MAY LINGER BYD EXPIRATION OF WATCH. IF SO...A LCL EXTENSION MAY BE
CONSIDERED IN CONJUNCTION WITH SPC. THE PRIMARY THREAT WOULD BE
DAMAGING WIND GUSTS. GIVEN THE MAGNITUDE OF THE SHEAR...A CPL
SUPERCELLS NOT OUT OF THE QUESTION.

WHILE THERE SHOULD BE AN OVERALL EASTWARD PROGRESSION AND DIURNAL
WEAKENING OF ACTIVITY THIS EVENING...MODELS MAINTAIN ELEVATED INSTBY
OVERNIGHT AND DECENT SHEAR TNGT. MID/UPPER LEVEL TROUGH WILL BE
APPROACHING TOWARD DAYBREAK. THEREFORE SOME SHOWERS AND STORMS MAY
LINGER WELL INTO THE OVERNIGHT PERIOD. MIN TEMPS IN THE LOWER/MID
60S WEST AND UPPER 60S/LOWER 70S EAST.

THE TROF WL EMERGE OVER THE ERN SHORE BY WED MRNG. A CDFNT WL BE
APPROACHING...ATTENDENT FM LOPRES THAT WL BE TRACKING ACRS QUEBEC
BY THAT TIME. HWVR...THE CDFNT LOOKS QUITE WEAK...AND AM
STRUGGLING TO FIND FORCING MECHANISMS. AMS WL STILL BE QUITE MOIST
BUT NOT THAT UNSTBL. MID LVL LAPSE RATES WL BE DECENT. WL HOLD
ONTO LOW END CHC POPS...HIER THAN MAV/MET...AND CONT TIL SUNSET.

AM NOT MAKING ANY SUBSTANTIVE CHANGES TO TEMPS ATTM. WL STILL BE
IN THE WARM SECTOR TMRW...SO TEMPS WL BE SLGTLY MUGGY WITH HIGHS
MID-UPR 80S.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
LOW PRESSURE WILL MOVE ACROSS THE UPPER MISSISSIPPI RIVER VALLEY
THURSDAY MORNING WHILE A COLD FRONT REMAINS STALLED ACROSS MUCH OF
THE EASTERN SEABOARD. SHOWERS ARE EXPECTED TO MOVE INTO THE
HIGHLANDS THURSDAY AFTERNOON AS LOW PRESSURE MOVES ALONG THE STALLED
FRONTAL BOUNDARY. FCST MODELS HAVE SLOWED DOWN THE PROGRESSION OF
SHOWERS MOVING INTO THE REGION. SHOWERS WILL SPREAD ACROSS THE MID-
ATLANTIC THURSDAY NIGHT. HEAVY SHOWERS ARE EXPECTED AS ENHANCED LIFT
OCCURS IN THE ENTRANCE REGION OF A UPPER LEVEL JET. DUE TO THE TIME
OF DAY AND LACK OF INSTABILITY ALOFT...THUNDERSTORMS ARE NOT
EXPECTED AT THIS TIME.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
MAIN STORY THROUGH THE EXTENDED IS CONT CHCS FOR UNSETTLED WX...AS
STUBBORN FRONTAL BOUNDARY REMAINS NEAR/OVER OUR AREA. THERE REMAINS
CONSIDERABLE UNCERTAINTY AND MODEL DISAGREEMENT WITH REGARDS TO
FRONTAL LOCATION THROUGH THE EXTENDED. AS SUCH...IT IS DIFFICULT
DETERMINE THE SPATIOTEMPORAL EXTENT OF ANY ACTIVITY AND DETERMINE
CONVECTIVE VS SHOWER CHCS.

MILLION DOLLAR QUESTION IS WHAT WILL THE WX BE LIKE ON SAT...FOR NOW
HAVE KEPT CHC POPS AND THUNDER...THOUGH THERE IS CERTAINLY BUST
POTENTIAL WITH THIS...AS FRONT COULD BE FAR ENOUGH TO OUR
SOUTH...WHICH WOULD LIMIT INSTABILITY (ELEVATED).

AS MENTIONED YESTERDAY...TEMPS PROGGED TO REMAIN AOB CLIMO NORMS
THROUGH THE EXTENDED...WITH A GRADUAL WARMING TREND THROUGH THE
PERIOD. DEWPOINTS ALSO EXPECTED TO REMAIN AOB 70F...SO NOT EXPECTING
CONDITIONS TO BE VERY OPPRESSIVE.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
VFR CONDS PREVAILING ATTM. TSRA DVLPMNT WL BE IN THE
NEIGHBORHOOD...BUT CONFIDENCE IN IMPACT AT A TERMINAL A BIT MORE
UNCERTAIN. AM USING VCTS TO COVER THRU EVENING PUSH...AND WL INCL
A TEMPO FOR SPECIFICS ONCE ITS MORE CERTAIN A TERMINAL WL BE
DIRECTLY AFFECTED. POTL FOR WINDS GUSTS 40-50 KT IN THE STRONGEST
STORMS.

BELIEVE OVERALL INTENSITY WL DECLINE OVNGT...BUT SUSPECT THERE WL
BE SOME ACTIVITY. FLGT RESTRICTIONS WL THEREFORE REMAIN PSBL...
BUT MORE LKLY MVFR. HWVR...CONFIDENCE NOT HIGH IN STORM EVOLUTION.

TSRA CVRG LOOKING MUCH LWR ON WED...AS TROF WL BE EAST OF
TERMINALS. A WEAK CDFNT WL BE DROPPING SWD IN THE AFTN-EVNG. ITS
ENTIRELY PSBL THAT THERE WL BE NO TSRA AT ALL. TAFS VFR W/ CIGS
BKN-OVC050-060.

SUB-VFR CONDITIONS POSSIBLE THURSDAY NIGHT AS RAIN MOVES INTO THE
REGION

MAIN CONCERN THROUGH EXTENDED IS POTENTIAL FOR SCATTERED
THUNDERSTORMS EACH DAY...WITH SUB-VFR CONDS POSSIBLE NEAR TSTMS. VFR
CONDS EXPECTED OUTSIDE OF TSTMS.

&&

.MARINE...
S/SE CHANNELING OCCURING OVER THE WATERS ATTM. SCA REMAINS IN
EFFECT. SEVERE THUNDERSTORM WATCH ALS IN EFFECT FOR ALL WATERS FOR
THE POTENTIAL OF STRONG WIND GUSTS. GRADIENT WINDS WILL DIMINSH
OVERNIGHT. SW FLOW THROUGH WED AROUND 10 KT...ALTHOUGH MAY BE
SLIGHTLY STRONGER TOWARD TANGIER SOUND. LOWER CHANCE OF STORMS
THROUGH WED.

SHOWERS WILL OVERSPREAD THE REGION THURSDAY NIGHT AND MAY CAUSE
REDUCED VSBYS.

WINDS EXPECTED TO REMAIN BELOW SCA CRITERIA THROUGH THE
EXTENDED...THOUGH WILL NEED TO MONITOR AS FRONT WILL BE NEAR AREA
EACH DAY. SHOWERS AND TSTMS ARE ALSO POSSIBLE EACH DAY...WHICH
COULD IMPACT MARINE CONCERNS

&&

.TIDES/COASTAL FLOODING...
WATER LVLS RUNNING ABT A FOOT ABV ASTRO NORMS. THE LOWER OF THE
TWO HIGH TIDES ROLLING IN NOW...WHICH WL KEEP LEVELS BELOW ADVY
CRITERIA. HWVR...ISSUES WUD RESULT FROM THE NEXT TIDE...MIDNGT TO
NOON. TOO SOON TO ISSUE ADVY ATTM...BUT ONE MAY BE REQD BEFORE
EVNG OVER.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT WEDNESDAY FOR ANZ531>534-
     537-539>543.
     SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ530-
     535-536-538.

&&

$$
SYNOPSIS...HTS
NEAR TERM...HTS
SHORT TERM...HAS
LONG TERM...MSE
AVIATION...HTS/HAS/MSE
MARINE...HTS/HAS/MSE
TIDES/COASTAL FLOODING...HTS


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