Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 221437 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1037 AM EDT FRI MAY 22 2015 .SYNOPSIS... A COLD FRONT WILL APPROACH THE AREA TODAY BEFORE PASSING THROUGH TONIGHT. HIGH PRESSURE WILL BUILD OVERHEAD SATURDAY BEFORE MOVING OFF THE COAST SUNDAY THROUGH THE MIDDLE PORTION OF NEXT WEEK. NOTICEABLY HOTTER AND MORE HUMID CONDITIONS ARE EXPECTED NEXT WEEK AS A SUMMER-LIKE AIR MASS ENTERS THE REGION. && .NEAR TERM /THROUGH TONIGHT/... A FROST ADVISORY IS IN EFFECT FOR THE HIGHER ELEVATIONS OF ALLEGANY GRANT MINERAL AND PENDLETON TONIGHT. COLD AIR ADVECTION WILL OCCUR BEHIND THE COLD FRONT THIS EVENING. WINDS WILL SUBSIDE UNDER CLEAR SKIES LATE TONIGHT AND SENSITIVE PLANTS MAY BE DAMAGED OR DESTROYED AS TEMPS REACH THE LOW TO MID 30S. CLEAR MORNING ACROSS THE MID-ATLANTIC WITH TEMPS IN THE UPPER 50S LOW 60S...ALREADY SURPASSING THE HIGH TEMPS FROM THURSDAY. A COLD FRONT IS LOCATED JUST SOUTH OF THE EASTERN GREAT LAKES. THERE ARE A FEW SHOWERS AHEAD OF THE FRONT BUT HAVE BEEN WEAKENING AS THE AIRMASS MOVES SOUTHWARD. IS0-SCT SHOWERS ARE EXPECTED TO MOVE INTO THE NRN POTOMAC HIGHLANDS THIS AFTERNOON AS SHOWN ON THE HRRR. ISO SHOWERS MAY EVEN REACH BALTIMORE BEFORE DIMINISHING AS THEY MOVE SOUTH TOWARDS NOVA AND DC. PREVIOUS DISCUSSION... IT WILL ALSO BE BREEZY THIS AFTERNOON WITH WINDS GUSTING UP TO 25 KT UNDER A SOMEWHAT TIGHT PRES GRADIENT. UNUSUALLY CHILLY AND STRONG HIGH PRESSURE WILL BUILD QUICKLY SOUTHWARD AND BE CENTERED OVER SRN PA BY 12Z SAT. VERY COOL AND DRY AIR MASS ALONG WITH DIMINISHING WINDS WILL LEAD TO A RAPID DROPOFF IN TEMPS OVERNIGHT WITH PATCHY FROST LIKELY OVER FAR WRN AREAS. FOR NOW INCLUDED PATCHY FROST IN GRIDS BUT WILL LET DAYSHIFT MONITOR DEWPOINTS AND LET THEM DECIDE WHETHER A FROST ADVISORY WILL BE NEEDED OR NOT. LATEST MOS GUIDANCE SUGGESTS THAT TEMPS WILL FALL LOW ENOUGH FOR FROST TO FORM IN THAT AREA. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... CANADIAN HIGH PRESSURE WILL REMAIN OVER THE REGION SATURDAY...RESULTING IN PLENTY OF SUNSHINE ALONG WITH DRY CONDITIONS. AFTER A CHILLY START...THE SUNSHINE WILL ALLOW FOR TEMPS TO REBOUND INTO THE LOWER TO MIDDLE 70S FOR MOST AREAS. THE SURFACE HIGH WILL BEGIN TO SHIFT TOWARD MID-ATLANTIC COAST SATURDAY NIGHT. A LIGHT SOUTHERLY FLOW WILL ALLOW FOR TEMPS TO BE A FEW DEGREES WARMER COMPARED FRIDAY NIGHT...BUT IT WILL STILL TURN OUT CHILLY DUE TO RADIATIONAL COOLING. MIN TEMPS WILL RANGE FROM THE LOWER AND MIDDLE 40S IN SHELTERED VALLEYS TO THE MID AND UPPER 50S IN DOWNTOWN WASHINGTON AND BALTIMORE. && .LONG TERM /SUNDAY THROUGH THURSDAY/... THE SURFACE HIGH WILL CONTINUE TO SHIFT EAST INTO THE ATLANTIC OCEAN FOR SUNDAY THROUGH THE MIDDLE PORTION OF NEXT WEEK. UPPER- LEVEL HIGH PRESSURE WILL BUILD OVER THE SOUTHEASTERN CONUS AND THE UPPER-LEVEL RIDGE AXIS WILL EXTEND NORTH INTO THE MID-ATLANTIC. THE SOUTHWEST FLOW AROUND THE HIGH WILL ALLOW FOR A WARMING TREND SUNDAY AND MONDAY. DRY CONDITIONS ALONG WITH PLENTY OF SUNSHINE ARE EXPECTED DUE TO THE UPPER-LEVEL RIDGE AXIS EXTENDING INTO OUR AREA. HOT AND HUMID CONDITIONS ARE EXPECTED FOR THE MIDDLE PORTION OF NEXT WEEK AS THE SOUTHWEST FLOW CONTINUES. THE HOT AND HUMID CONDITIONS WILL LEAD TO AN INCREASED CHANCE FOR THUNDERSTORMS TUESDAY THROUGH THURSDAY...ESPECIALLY DURING THE AFTERNOON AND EVENING HOURS EACH DAY. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... VFR CONDITIONS EXPECTED EVERYWHERE NEXT 30 HRS. SCT AFTERNOON CLOUDS EXPECTED OVER MRB WITH CIGS 040-050. WINDS GUSTING 20-25 KT AT ALL TAF SITES XCPT LIGHTER WINDS AT KCHO. HIGH PRESSURE WILL BRING VFR CONDITIONS AND LIGHT WINDS FOR SATURDAY THROUGH SATURDAY NIGHT. THE HIGH WILL MOVE OFF THE COAST SUNDAY AND MONDAY. A SOUTHWEST FLOW IS EXPECTED...BUT VFR CONDITIONS WILL PERSIST. THERE IS A BETTER CHANCE FOR THUNDERSTORMS TUESDAY AFTERNOON AND EVENING AS HOT AND HUMID CONDITIONS INCREASE INSTABILITY. && .MARINE... SOLID SCA CONDITIONS THIS AFTERNOON WITH GUSTS 20-25KT ESPECIALLY NORTH. HIGH PRESSURE WILL REMAIN OVER THE WATERS SATURDAY BEFORE MOVING OFF THE COAST SUNDAY AND MONDAY. A SOUTHERLY FLOW WILL RETURN DURING THIS TIME. HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC OCEAN THROUGH THE MIDDLE PORTION OF NEXT WEEK...ALLOWING FOR THE SOUTHERLY FLOW TO CONTINUE. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS MONDAY THROUGH TUESDAY NIGHT...BUT IT WILL BE MARGINAL DUE TO THE RELATIVELY COOLER WATERS. && .CLIMATE... UNUSUALLY COOL HIGH TEMPERATURES WERE OBSERVED THURSDAY...MAY 21ST. WASHINGTON DULLES BROKE A DAILY RECORD FOR LOW MAXIMUM TEMPERATURE. THE MAXIMUM TEMPERATURE WAS 58 DEGREES AND THIS BREAKS THE OLD RECORD OF 59 DEGREES SET BACK IN 2002. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM EDT SATURDAY FOR MDZ501. VA...NONE. WV...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM EDT SATURDAY FOR WVZ501-503-505. MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT SATURDAY FOR ANZ531>534- 537-539>543. SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ530- 535-536-538. && $$ SYNOPSIS...BJL NEAR TERM...HAS/LFR SHORT TERM...BJL LONG TERM...BJL AVIATION...BJL/LFR MARINE...BJL/LFR CLIMATE...

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