Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 021920 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 320 PM EDT TUE JUN 2 2015 .SYNOPSIS... A COLD FRONT WILL STALL TO OUR SOUTH TONIGHT THROUGH WEDNESDAY. THE BOUNDARY WILL RETURN NORTH TOWARD OUR AREA AS A WARM FRONT THURSDAY BEFORE DISSIPATING NEARBY ON FRIDAY. HIGH PRESSURE WILL BUILD NORTH OF THE REGION DURING THE WEEKEND. && .NEAR TERM /THROUGH WEDNESDAY/... A COLD FRONT WILL STALL OUT TO THE SOUTH TONIGHT THROUGH WEDNESDAY WHILE AN UPPER-LEVEL LOW REMAINS OVER THE TENNESSEE VALLEY. A SOUTHWEST FLOW ALOFT AROUND THE UPPER-LEVEL LOW WILL CAUSE WARM AND MOIST AIR TO OVERRUN THE SURFACE COOLER AIR BEHIND THE FRONT...RESULTING IN PLENTY OF CLOUDS ALONG WITH TIMES OF RAIN AND DRIZZLE. RAINFALL AMOUNTS ACROSS MOST AREAS SHOULD BE LIGHT...BUT A COUPLE HEAVIER SHOWERS AND THUNDERSTORMS MAY DEVELOP ACROSS THE CENTRAL SHENANDOAH VALLEY LATE THIS AFTERNOON...CLOSER TO THE BOUNDARY WHERE MORE INSTABILITY MAY DEVELOP. TEMPERATURES THIS AFTERNOON WILL HOLD IN THE 50S ACROSS NORTHERN MARYLAND...WITH LOWER TO MIDDLE 60S EXPECTED IN THE WASHINGTON METROPOLITAN AREA TO THE MIDDLE AND UPPER 60S IN CENTRAL VIRGINIA. MIN TEMPS TONIGHT WILL BE IN THE 50S FOR MOST AREAS AND MAX TEMPS WEDNESDAY WILL REMAIN WELL BELOW NORMAL THANKS TO THE CLOUDS AND PRECIPITATION...TOPPING OFF IN THE LOWER TO MIDDLE 60S FOR MOST AREAS. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... THE UPPER-LEVEL LOW WILL SLOWLY SLIDE EAST INTO THE CAROLINAS WEDNESDAY NIGHT...INCREASING THE EASTERLY COMPONENT TO THE LOW- LEVEL FLOW AND ALSO INCREASING LOW-LEVEL FRONTOGENTICAL FORCING. THE INCREASED FORCING AND MOISTURE WILL LEAD TO MORE WIDESPREAD RAINFALL...ESPECIALLY FOR LOCATIONS NEAR AND EAST OF THE BLUE RIDGE MOUNTAINS OVERNIGHT. THERE IS STILL DIVERGENCE AMONG THE GUIDANCE AS TO HOW CLOSE THE UPPER-LEVEL LOW GETS WHICH WILL HAVE AN IMPACT ON RAINFALL RATES. SHOULD THE LOW BE CLOSE ENOUGH...THERE CAN BE A PERIOD OF MODERATE TO LOCALLY HEAVY RAINFALL THAT OCCURS...AND WITH ALREADY SATURATED SOILS THIS MAY LEAD TO AN INCREASED THREAT FOR FLOODING. CONFIDENCE IN THIS OCCURRING AT THIS TIME IS LOW. UPR LOW DRIFTS ENE FROM NC TO SERN VA THURSDAY...BEFORE DRIFTING OFFSHORE THROUGH FRIDAY. THIS WILL MAINTAIN NELY FLOW OVER THE AREA WITH MUCH BELOW NORMAL TEMPERATURES. BLENDED THE WARMER MET WITH MAV AND PREVIOUS FORECAST FOR CONTINUED MAX TEMPS IN THE UPR 60S INLAND...LOW TO MID 70S NEAR SHORE AND LOWER SRN MD. SUBTROPICAL MOISTURE FLUX CONTINUES INTO THE AREA WITH CONVERGENCE EXPECTED OVER SRN MD. 12Z GFS SUGGESTS THIS AREA WILL HAVE SOME INSTABILITY AND SOME EXCESSIVE RAINFALL IS POSSIBLE ALONG THIS CONVERGENCE. THIS FORECAST HAS SHIFTED OVER THE PAST COUPLE DAYS...SO WILL NEED TO CONTINUE TO MONITOR FOR SPECIFIC THREATS. FOR NOW...THUNDER POSSIBLE EAST FROM INTERSTATE 95 AND IN THE ALLEGHENY HIGHLANDS IN THE AFTERNOON. LEFT A GENERAL MENTION IN BOTH SECTIONS OF THE HWO FOR FLOOD POTENTIAL. CLOUDY ACROSS THE AREA THROUGH THIS PERIOD. MIN TEMPS THURSDAY NIGHT COOL WITH NNELY FLOW STREAMLINES STRETCHING BACK TO THE GULF OF MAINE WHERE THE WATER TEMPERATURE IS CURRENTLY 50F. WENT WITH A MAV/MET/SREF BLEND OF MID/UPR 50S WEST OF THE BLUE RIDGE AND UPR 50S TO LOW 60S EAST (MID 60S NEAR SHORE). FRIDAY...CONTINUED N/NE FLOW WITH WEAK LOW OFFSHORE WARMUP SHOULD BE ONGOING. HOWEVER...WITH CONTINUED CLOUDS LIMITED MAX TEMPS TO MID 70S. LITTLE IN THE WAY OF RAIN...JUST SOME CHANCES. && .LONG TERM /FRIDAY THROUGH TUESDAY/... LOW PRESSURE WILL MOVE OFF THE EAST COAST FRIDAY. THERE IS A CHANCE THAT A COUPLE OF SHOWERS WILL LINGER. A COLD FRONT WILL SAG SOUTHEASTWARD ACROSS THE EASTERN GREAT LAKES AND ACROSS THE REGION FRIDAY NIGHT. ADDITIONAL RAIN SHOWERS WILL DEVELOP AND CONTINUE TO PERSIST SATURDAY AS THE FRONT SLIDES INTO SOUTHEAST VIRGINIA. TEMPERATURES EACH PERIOD WILL BE NEAR NORMAL. HIGH PRESSURE WILL BUILD OVER NEW ENGLAND AND WEDGE SOUTHWARD ALONG THE EAST COAST SATURDAY NIGHT AND SUNDAY. A FEW RAIN SHOWERS COULD DEVELOP ON THE COOL SIDE OF THE FRONT WITH SOME UPSLOPE RAIN SHOWERS OVER THE POTOMAC HIGHLAND. TEMPERATURES WILL BE NEAR NORMAL. THE NEXT COLD FRONT WILL DRAG ACROSS THE OHIO VALLEY SUNDAY NIGHT THEN PUSH ACROSS THE REGION MONDAY. SHOWERS AND PERHAPS A THUNDERSTORM COULD DEVELOP ALONG AND AHEAD OF THE FRONT. SHOULD MOST OF THE RAIN ACTIVITY INCREASE IN COVERAGE DURING THE MID AFTERNOON HOURS...THEN SOME THUNDERSTORMS COULD BE STRONG TO SEVERE. TEMPERATURES WILL BE ABOVE NORMAL. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... A BOUNDARY WILL REMAIN TO OUR SOUTH THROUGH WEDNESDAY NIGHT. WARM AND MOIST AIR WILL OVERRUN THE SURFACE COOLER AIR IN PLACE...RESULTING IN LOW CLOUDS ALONG WITH TIMES OF RAIN AND DRIZZLE. IFR CONDITIONS ARE EXPECTED MOST OF THE TIME. HOWEVER...CIGS MAY MIX OUT TO MVFR LEVELS FOR A PERIOD THIS AFTERNOON AND AGAIN WEDNESDAY AFTERNOON. CONTINUED IFR/MVFR CIGS WITH NELY FLOW PERSISTING THURSDAY INTO FRIDAY. RAIN LIKELY THURSDAY...LESS FOR FRIDAY. MVFR CONDITIONS POSSIBLE FRIDAY THROUGH SATURDAY WITH RAIN SHOWERS SCATTERED ABOUT THE AREA. && .MARINE... A BOUNDARY WILL REMAIN STALLED TO OUR SOUTH THROUGH WEDNESDAY NIGHT. A NORTH TO NORTHEAST FLOW IS EXPECTED DURING THIS TIME. A SMALL CRAFT ADVISORY IS IN EFFECT THROUGH TONIGHT FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER. THE SMALL CRAFT ADVISORY CONTINUES WEDNESDAY FOR THE MIDDLE PORTION OF THE BAY AND LOWER TIDAL POTOMAC RIVER. SMALL CRAFT ADVISORIES MAY NEED TO BE EXTENDED THROUGH WEDNESDAY NIGHT FOR PORTIONS OF THE WATERS. NELY FLOW 15 GUST 20 KT WITH SCA EXPECTED THURSDAY AS LOW PRESSURE SHIFTS SOUTH OF THE AREA. THUNDERSTORMS LIKELY AND POSSIBLY GUSTY... PARTICULARLY FOR SRN MD WATERS. NORTH FLOW AROUND 10 KT THEN THURSDAY NIGHT AND FRIDAY. NO MARINE HAZARDS ARE EXPECTED FRIDAY THROUGH THE WEEKEND. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ530-531- 536-538-539. SMALL CRAFT ADVISORY UNTIL 6 PM EDT WEDNESDAY FOR ANZ532>534- 537-540>543. && $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BAJ/BJL LONG TERM...KLW AVIATION...BAJ/BJL/KLW MARINE...BAJ/BJL/KLW

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