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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