Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 311405 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1005 AM EDT SUN MAY 31 2015 .SYNOPSIS... LOW PRESSURE WILL TRACK UP THE OHIO VALLEY TODAY AND ACROSS SOUTHERN PENNSYLVANIA TONIGHT. A COLD FRONT EXTENDING SOUTH FROM THIS LOW WILL SLOWLY CROSS THE AREA MONDAY INTO EARLY TUESDAY. HIGH PRESSURE IS EXPECTED TO SLIDE INTO THE REGION FOR THE MIDDLE AND LATTER PORTIONS OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... SFC LOW PRESSURE LOCATED NEAR RICHMOND IND THIS MORNING BENEATH A COMPACT SHORTWAVE TROUGH. STRONG BLOCKING RIDGE OF HIGH PRESSURE REMAINS OFFSHORE. THE LOW WILL TRACK ALONG A STALLED FRONT ACROSS PA INTO TONIGHT. EARLY MORNING GUIDANCE DOES NOT SUPPORT ANY SUBSTANTIAL CHANGES TO THE FORECAST. REGIONAL 12Z SOUNDINGS INDICATE AN AIRMASS THAT SUPPORTS MODERATE INSTBY AND DEEP LAYER SHEAR ON THE LOWER END OF THE SPECTRUM (AOB 25 KT). HOWEVER BOTH VALUES SLIGHTLY HIGHER THAN PREVIOUS DAYS...AND MID LEVEL LAPSE RATES A BIT STEEPER. CONVECTION EXPECTED TO DEVELOP OVER THE TERRAIN FIRST...AND ARE ALREADY SEEING SHOWERS NEAR CATOCTIN MTN. COVERAGE MAY BE FAIRLY SCATTERED UNTIL THE LOW APPROACHES LATE THIS AFTERNOON AND EVENING. STILL THINKING MOST AREAS EAST OF THE MOUNTAINS REMAIN DRY MOST OF THE DAY. THINK THE OVERALL SEVERE THREAT WILL BE HIGHER IN PA WHERE STRONGER SHEAR WILL EXIST IN COMBINATION WITH THE LLVL BOUNDARY. HOWEVER SOME PULSE SEVERE POSSIBLE INTO FAR NORTHERN MD AND EASTERN WVA IF INSTBY MAXIMIZED. WITH PWATS REMAINING NEAR 1.5 INCHES...LOCALLY HEAVY RAIN WILL ALSO BE POSSIBLE. HOWEVER STORMS SHOULD HAVE SOME MOTION TO THEM. A GOOD DEAL OF SUNSHINE THIS MORNING WILL ALLOW TEMPERATURES TO CLIMB QUICKLY AND HIGHS IN THE UPPER 80S TO AROUND 90 WILL OCCUR WHERE THUNDERSTORMS DO NOT OCCUR. AS THE SFC LOW APPROACHES TNGT...HV ENUF FUEL TO BE ABLE TO GET STORMS TO SPREAD EWD AND HV POPS AREAWIDE... LKLY METRO BALT AND N-CENTRL MD/CHC MOST EVERYWHERE ELSE. USED MET AS GUIDE FOR MIN-T. DEWPTS WL BE THE LIMITING FACTOR. WHERE RAIN FALLS...WL LKLY GET THERE QUICKER...AND THEN HOLD AS PATCHY FOG DVLPS. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... FRNTL BNDRY WL SLOWLY CROSS THE CWFA MON...SERVING AS A FOCUS FOR MULT ROUNDS OF SHRA/TSRA. WL BE ON THE WARM/MOIST SIDE OF THE BNDRY...SO PDS OF HVY RAFL WL BE A PRIMARY CONCERN. THE BNDRY WL ALSO SERVE AS A SOURCE OF CNVGNC...MAKING FULL USE OF ANY UNSPENT INSTBY. BELIEVE THAT THERE STILL CUD BE SOME STRONGER STORMS AFTER BRIEF SPLASHES OF INSOLATION. WL CARRY WIND AND RAIN THREATS IN HWO. GIVEN AVBL FORCING AND DIURNAL HEATING...HV BUMPED UP POPS INTO LKLY/CAT RANGE MON...AND CARRIED THAT INTO I-95 FOR MON EVE. THINK ACTIVITY WL BECOME A LTL LESS WIDESPREAD OVNGT MON...BUT AM NOT CONFIDENT THAT IT/LL CEASE OUTRIGHT. THEREFORE WL BE CARRYING CHC POPS THRU THE OVNGT HRS. SINCE AMS WL BE ABOUT THE SAME...AM CONTG THE NEAR TERM TEMP FCSTG STRATEGY INTO DAY 2. ONLY COMPLICATING FACTOR WL BE IMPACT FM NMRS SHRA/TSRA. NONETHELESS...MAXT FOR MON WAS RAISED BY SEVRL DEGF... INTO THE 80S. MAY EVEN SEE UPR 80S NEAR EZF/SRN MD. SHUD HV SLGTLY COOLER/DRIER AIR ADVECTING EWD BY MON NGT...AND MIN-T NOT QUITE AS MUGGY. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AN UPPER LEVEL CUT-OFF LOW WILL SPIN ACROSS THE GULF COAST STATES THROUGH MID-WEEK WHILE LOW PRESSURE RIDES ALONG A QUASI-STATIONARY BOUNDARY ACROSS THE MID-ATLANTIC TUESDAY. A PLUME OF HIGH PWATS WILL CONTINUE TO RIDE ALONG THE BOUNDARY AND LEAD TO CLOUDS AND SHOWERS TUESDAY. A TEMP CONTRAST BETWEEN THE NW AND SE WILL LIKELY OCCUR DUE TO COOLER AIR MOVING IN ON THE BACKSIDE OF THE THE FRONTAL BOUNDARY TUESDAY. TEMPS WILL RANGE FROM THE LOW 70S TO THE UPPER 70S. INSTABILITY WILL INCREASE ON THE WARM SIDE OF THE BOUNDARY AND THUNDERSTORMS WILL BE POSSIBLE. MAIN IMPACT WILL BE HEAVY RAIN FROM STORMS AND DEPENDING ON HOW MUCH RAIN THE AREA RECEIVES SUN AND MON...LOCALIZED FLOODING IS POSSIBLE. RAINFALL AMTS OF 0.5-1.5 INCHES POSSIBLE TUESDAY INTO WEDNESDAY. SLOW MOVEMENT OF THE FRONT WILL OCCUR TUESDAY NIGHT AND SHOWERS WILL LIKELY CONTINUE AS THE UPPER LEVEL PATTERN REMAINS LOCKED. NRLY WIND WILL EVENTUALLY SPREAD THE ENTIRE MID-ATLANTIC BY WEDNESDAY NIGHT AS HIGH PRESSURE MOVES INTO THE REGION. SHOWERS SHOULD END ACROSS THE REGION WEDNESDAY. TEMPS WILL REACH THE LOW TO MID 70S WEDNESDAY. HIGH PRESSURE WILL WEDGE DOWN INTO THE REGION WEDNESDAY AND THURSDAY BEFORE MOVING OFF THE COAST FRIDAY. SHOWERS AND THUNDERSTORMS RETURN TO THE FORECAST FRIDAY-SATURDAY AS DISTURBANCES MOVE INTO THE REGION. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/... SCT TSRA WL BE DVLPG ONCE AGN TDA DUE TO DAYTIME HEATING FM THE SUN. CVRG LKLY WL BE IMPROVING INTO ELY EVNG AS BETTER SUPPORT ARRIVES. HV REDUCED CONFIDENCE IN SPECIFIC TIMING/PLACEMENT...BUT MRB ONCE AGN STANDS THE BEST CHC AT SEEING TSRA. THAT THE ONLY PLACE WHERE ANY WEATHER OUTRIGHT MENTIONED. CHO/IAD HV A MORE LIMITED CHC...WHICH DROPS FURTHER TWD DCA/BWI. THIS FCST LKLY TO BE REFINED THRUT THE DAY. ADDITIONAL COMMENTS WL BE ADDED TO TAFS ONCE CONFIDENCE SUFFICIENT. BRIEF IFR RESTRICTIONS PSBL W/IN ANY STORM. JUST LIKE PAST SVRL DAYS...CVRG OF AFTN-EVE STORMS WL DICTATE WHEN/WHERE/HOW MUCH FOG WL DVLP OVNGT. AS A START HV MVFR IN CLIMO FVRD AREAS ATTM. AS A CDFNT APPROACHES...CVRG OF TSRA WL BE MORE NMRS TO EVEN WIDESPREAD MON...SPCLY DURING THE AFTN-EVE HRS. MORE FREQUENT FLGT RESTRICTIONS WL BE PSBL...BUT STILL BELIEVE THAT THERE WL BE INTERVALS OF VFR DURING THE DAY. HWVR...CIGS LKLY TO LWR IN THE EVNG. SUB-VFR CIGS POSSIBLE TUESDAY INTO WEDNESDAY AS SHRA VCTS CONTINUES. HEAVY RAIN MAY LEAD TO REDUCED VSBYS DURING THIS TIME. WINDS BECOME NRLY FROM N TO S TUESDAY INTO WEDNESDAY. && .MARINE... SLY FLOW WL CONT ACRS THE WATERS TDA-TNGT...AND MIXING WL RESUME AFTER DAYBREAK. ALREADY A NUMBER OF 10-15 KT GUSTS...SO WILL MONITOR IF THE SCA NEEDS TO GO INTO EFFECT BEFORE 2 PM. WILL KEEP EXPIRATION AT 2 AM MONDAY FOR NOW. IN ADDITION...A TSRA THREAT WL INCREASE TNGT...MAKING FOR A FEW MARINE WRNGS PSBL INVOF STRONGER STORMS. CDFNT ARRIVES MON-MON NGT. SHRA/TSRA WL BE MORE NMRS...AND SOME MAY CONTAIN GUSTY WINDS. VERT TRANSFER WL BE LESS FVRBL DUE TO ATMOSPHERIC MSTR...AND THEREFORE WL NOT BE RAISING ANOTHER SCA FOR THE PM HRS. HWVR...ANOTHER AFTN-EVE OF MARINE WRNGS PSBL. WINDS BECOME NRLY ON THE WATERS TUESDAY INTO WEDNESDAY BUT SHOULD STAY BELOW SCA CRITERIA. SHOWERS EXPECTED TUESDAY AND WEDNESDAY WITH A CHANCE OF THUNDERSTORMS. SOME SHOWERS MAY BE HEAVY AND REDUCE VSBYS. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 2 AM EDT MONDAY FOR ANZ530>534-537>543. && $$ SYNOPSIS...HTS NEAR TERM...ADS/HTS SHORT TERM...HTS LONG TERM...HAS AVIATION...HAS/HTS MARINE...ADS/HAS/HTS

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