Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 301431
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1031 AM EDT SAT MAY 30 2015

.SYNOPSIS...
HIGH PRESSURE WILL PERSIST OFFSHORE TODAY WITH CONTINUED WARM AND
HUMID CONDITIONS IN THE MID-ATLANTIC. A COLD FRONT WILL ENTER THE
REGION LATE SUNDAY AND STALL OVER THE REGION INTO TUESDAY. HIGH
PRESSURE IS EXPECTED TO SLIDE INTO THE REGION FOR THE MIDDLE PART
OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
PERSISTENT RIDGE OF HIGH PRESSURE REMAINS OFF THE COAST THIS
MORNING. PAIR OF SHORTWAVE TROUGHS ARE LOCATED OVER MS
VALLEY...WHILE MORE ORGANIZED FRONTAL SYSTEM OVER ONTARIO. NONE OF
THESE SYSTEMS TO DIRECTLY AFFECT THE REGION TODAY...ALTHOUGH
COMBINED EFFECTS WILL BEGIN TO CAUSE HEIGHT FALLS FROM THE WEST
TONIGHT.

A FEW LIGHT SHOWERS AND SPRINKLES ACROSS THE NW CWA THIS MORNING.
CAMS IN GOOD AGREEMENT WITH A NOON-2PM CONVECTIVE INITIATION TIME.
HOWEVER...PATCH OF MID LEVEL CLOUDS OVER THE MOUNTAINS IS DELAYING
TEMP RISES AND COULD HAVE AN EFFECT ON HOW MUCH INSTBY DEVELOPS.
BEST CHANCES OF STORMS REMAINS OVER THE POTOMAC HIGHLANDS...WITH
MORE SCATTERED COVERAGE INTO THE SHENANDOAH VALLEY. HAVE KEPT
AREAS EAST OF THE BLUE RIDGE DRY (LT 15 POP)...BUT CAN/T RULE OUT
A STRAY STORM. LAPSE RATES NOT TERRIBLY FAVORABLE TODAY AND DEEP
LAYER SHEAR AOB 20 KT. SUPPOSE IF ENOUGH INSTBY DEVELOPS A LOCALLY
DAMAGING WIND GUST IS POSSIBLE WITH STRONGER CELLS...WHICH IS
COVERED BY SPC MARGINAL RISK IN THE NW CWA. LOCALLY HEAVY RAIN
REMAINS POSSIBLE WITH PWATS AROUND 1.5 INCHES AND WEAK STEERING
FLOW. EXPECT ANY CONVECTION IN THE MOUNTAINS TO DIMINISH BY AROUND
MIDNIGHT.

WARMER GFS HAS BEEN PERFORMING BETTER FOR MAXT...AND SIDED IN
THAT DIRECTION. ADJUSTED MAX T DOWN A LITTLE WHERE THE THICKER
CLOUD COVER RESIDES THIS MORNING. SINCE DEWPTS WL REMAIN MID 60S
ON AVG...WEIGHTED TWD HIER MET MOS FOR MIN-T TNGT.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
MS VLY LOPRES EXERTING A HEAVIER INFLUENCE IN SYNOP EVOLUTION
SUNDAY...WHICH SLOWS DOWN CDFNT AND STALLS PTTN CHG. A SHARPENING
TROF W OF THE APLCNS IN TURN SUPPORTS CONTD RDGG IN THE ATLC COAST.
THAT PLACES CWFA IN WARM/HUMID AMS FOR YET ANOTHER DAY...W/ THE
INSTBLTY THAT GOES WITH IT. INVOF THE LOW...SHEAR SHUD BE A BIT
BETTER...WHICH WL BE WHERE GREATER CHC OF STRONG TSTMS RESIDES.
BUT THE FORCING OF THE FNT WL BE SUFFICIENT TO PROMPT STORM
DVLPMNT... ALBEIT A BIT LATER THAN PRVSLY ADVERTISED. HV TRIMMED
POPS FOR THE DAYTIME PD...BACKING OFF INTO THE CHC CATEGORY FOR
EAST OF THE BLURDG. BUT AMPLE MSTR STREAMING FM WRN GLFMEX WL
MAINTAIN HIGH PCPN RATES W/IN THESE STORMS.

TSRA WL EMERGE EAST OF THE BLURDG SUN EVE...PRECEDING THE FNT.
XPCT A LTL BIT OF WEAKENING DUE TO LOSS OF DAYTIME HEATING AS WELL
AS A SLGTLY LESS FVRBL ENVIRONMENT. DO NOT HV A GOOD FEEL FOR
WHETHER ACTIVITY WL CONT OVNGT OR NOT. HV MAINTAINED CHC POPS
THRUT.

LIKE SAT...STUCK TO THE WARMER END OF GDNC FOR TEMP FCSTG. THAT
YIELDS A SIZEABLE ADJUSTMENT TO THE SUN NGT LOW.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
LOW PRESSURE SHOULD BE IN THE VICINITY OF CENTRAL NY/PA MONDAY
MORNING WITH A COLD FRONT EXTENDING SOUTH BISECTING THE MID-
ATLANTIC. THE DETERMINISTIC GFS AND ECMWF ARE IN AGREEMENT THAT THE
COLD FRONT WILL SLOWLY MOVE EASTWARD MONDAY AFTERNOON. TEMPS WILL
LIKELY RISE INTO THE UPPER 60S TO MID 70S WEST OF THE BLUE RIDGE AND
INTO THE UPPER 70S TO NEAR 80 AROUND THE I-95 CORRIDOR. SUBTLE
CHANGES IN THE PLACEMENT OF THE FRONT MONDAY MORNING WILL IMPACT THE
TEMP FORECAST FOR SOME LOCALES. STRONG MOISTURE ADVECTION ALONG THE
FRONT WILL LEAD TO HEAVY RAIN AT TIMES AND INSTABILITY WILL INCREASE
AHEAD OF THE FRONT MONDAY AFTERNOON. THUNDERSTORMS WILL BE POSSIBLE
DURING THIS TIME. BEST CHANCE FOR STRONG TO SEVERE THUNDERSTORMS
WILL BE NEAR THE HIGHER TEMPS AND DEWPS...ACROSS THE PIEDMONT...
SOUTHERN MARYLAND AND SURROUNDING WATERS. HEAVY RAIN MAY CAUSE
LOCALIZED FLOODING MAINLY EAST OF THE BLUE RIDGE MONDAY.

THE FRONT SLOWLY MOVES EASTWARD MONDAY NIGHT. SHOWERS AND
THUNDERSTORMS MAY PERSIST NEAR THE I-95 CORRIDOR AND EAST INTO
TUESDAY MORNING. BEHIND THE FRONT...COOL AND DRY AIR WILL FILTER
INTO THE REGION. THE COLD FRONT SHOULD BE OFF THE COAST BY TUESDAY
AFTERNOON. A FEW LINGERING SHOWERS POSSIBLE NEAR THE CHESAPEAKE BAY
ARE POSSIBLE. TEMPS SHOULD BE IN THE 70S TUESDAY WITH A FEW SPOTS
NEARING 80 IN THE PIEDMONT AND FOOTHILLS.

HIGH PRESSURE EXPECTED MID WEEK WITH NRLY WINDS KEEPING TEMPS COOLER
THAN THE RECENT WEEKS. TERRAIN INDUCED SHOWERS AND THUNDERSTORMS ARE
POSSIBLE IN THE AFTERNOON TOWARDS THE END OF THE WEEK. TEMPS SHOULD
STAY AROUND 80 DURING THIS TIME.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
VFR SHUD PREVAIL FOR THE DAYTIME PD. SCT TSRA SHUD DVLP. MRB WUD
HV THE GREATEST CHC AT SEEING ONE. WHILE BRIEF MVFR/IFR PSBL...
DURATION TOO LIMITED AND PLACEMENT TOO UNCERTAIN TO MENTION IN ANY
TAF ATTM. INSTEAD HV SCT-BKN CU DVLPG...BASES 050. SLY FLOW WL
INCR TO 10-15 KT.

ONCE AGAIN...AREAS OF FOG SHUD BE DVLPG LT TNGT...SPCLY WHERE ANY
TSRA PASSED THRU DURING THE DAY. LCL IFR PSBL.

TSRA SHUD BE MORE NMRS SUN...TIMING A BIT LATER THAN PRVSLY THOUGHT.
AFTN-EVE HRS WL BE PREFERRED...BUT CAN NOT RULE OUT AN OVNGT STORM.

SUB-VFR CONDITIONS POSSIBLE MONDAY ESPECIALLY AT CHO-DCA-BWI-MTN
WHERE CONFIDENCE IS HIGHER THAT HEAVY RAIN WILL CAUSE LOW VSBYS.
WINDS BECOME W-NW MONDAY AFTERNOON.

&&

.MARINE...
SLY FLOW TO PREVAIL THIS WKND. EACH DAY WINDS WL BE INCREASING W/
DAYTIME MIXING...BRINGING THE MD BAY/INLETS UP TO THE CUSP OF SCA
CRITERIA. HV ISSUED A PAIR OF ADVYS TO COVER THE AFTN-EVE HRS.
TSRA SHUD BE SPARSE ON SAT...MORE NMRS ON SUN. SOME STORMS WL
CARRYING A LCL HIGH WIND RISK...AND SMW/S WL BE PSBL. BUT THE
CDFNT WL BE DELAYED...AND S/SWLY FLOW WL DOMINATE THRU THE WKND.

S-SW WINDS EXPECTED ON THE WATERS MONDAY AS A COLD FRONT NEARS. SCA
CONDITIONS ARE POSSIBLE MONDAY AND AGAIN ON TUESDAY AS THE COLD
FRONT CROSSES THE WATERS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT SUNDAY FOR ANZ530>534-
     537>543.
     SMALL CRAFT ADVISORY FROM 2 PM TO 8 PM EDT SUNDAY FOR
     ANZ530>534-537>543.

&&

$$
SYNOPSIS...HTS
NEAR TERM...ADS/HTS
SHORT TERM...HTS
LONG TERM...HAS
AVIATION...HAS/HTS
MARINE...HAS/HTS



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