Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 151918 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 318 PM EDT TUE APR 15 2014 .SYNOPSIS...
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AN EXCEPTIONALLY COLD AIRMASS FOR THIS TIME OF YEAR WILL QUICKLY TAKE HOLD OF THE AREA BY LATE THIS EVENING. HIGH PRESSURE WILL BUILD OVERHEAD DURING THE MIDDLE OF THE WEEK...THEN MOVE OFFSHORE LATE IN THE WEEK. AN AREA OF LOW PRESSURE MAY AFFECT THE AREA DURING THE FIRST HALF OF THE WEEKEND.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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COLD FRONT HAS MADE IT THROUGH DCA AND BWI AS OF 2PM..AND PRESSING QUICKLY SE. TEMPS DROP QUICKLY FROM THE 60S AND LOW 70S INTO THE 50S...WITH 40S SOON TO FOLLOW. DROPPED FROM 68 TO 53 HERE AT STERLING VA IN 90 MINS. GOOD THING THE COLD FRONT DID WAS UNDERCUT THE LINE OF CONVECTION THAT WAS DUMPING HEAVY RAIN FOR A TIME OVER THE METRO AREAS. END OF THE PRECIP IS NOT EXPECTED UNTIL LATER TONIGHT AND WITH THE COLD AIR CONTINUING TO COME IN...THERE WILL BE SOME SNOW IN AREAS...MAINLY ABOVE 1500 FEET...BUT COULD EVEN BE SOME WET NON ACCUM SNOWFLAKES IN THE METRO AREAS AFTER DARK BEFORE THE PRECIP ENDS. FREEZE WARNING FOR LATE TONIGHT INTO WED MORNING FOR VEGETATION...BUT ALSO COULD BE SOME ICY SPOTS WED MORN IN AREAS THAT DONT DRY IN THE OVERNIGHT WIND. HIGHS ONLY AROUND 50 ON WED UNDER SUNNY SKIES.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
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HIGH PRESSURE WEDNESDAY NIGHT ALONG WITH CLEAR SKIES/LIGHT WINDS WILL PRODUCE A MORE TYPICAL RADIATIONAL COOLING NIGHT AND THEREFORE TEMPERATURES ARE EXPECTED TO BOTTOM OUT AGAIN. FREEZE WATCH HAS BEEN ISSUED EAST OF THE BLUE RIDGE INTO THURSDAY MORNING. HIGH PRESSURE CENTER MOVES OFF THE NORTHEAST COAST AND THEN WEDGES DOWN THROUGH THE MID-ATLANTIC TO END THE WEEK. TEMPS MAY REBOUND SOME...BUT WILL STILL BE BELOW AVERAGE THROUGH FRIDAY. CLOUDS LIKELY INCREASE THURSDAY NIGHT INTO FRIDAY WITH A WEAK DISTURBANCE OFF THE COAST AND ALSO AHEAD OF THE NEXT UPSTREAM SHORTWAVE TROUGH BUT FAVOR A DRY FORECAST ATTM.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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A COUPLE AREAS OF LOW PRESSURE WILL BRUSH PAST THE REGION FOR THE FIRST PART OF THIS WEEKEND...WITH A CHANCE OF RAIN MAINLY DURING THE DAY SATURDAY. THE MODELS HAVE MOST RECENTLY TRENDED DOWNWARD WITH THE PROBABILITY OF RAIN AND WITH RAINFALL AMOUNTS AS A RESULT OF ENERGY FROM THE NORTHERN AND SOUTHERN BRANCHES OF THE JET STREAM REMAINING SPLIT INSTEAD OF PHASING. THIS LEAVES TO TWO WEAKER WAVES OF LOW PRESSURE...ONE PASSING TO THE NORTHWEST ACROSS THE GREAT LAKES AND THE OTHER MOVING OFFSHORE INTO THE ATLANTIC. ANOTHER PUSH OF COOL AIR WILL ACCOMPANY HIGH PRESSURE MOVING DOWN FROM CENTRAL CANADA FOR THE SECOND HALF OF THE WEEKEND...THOUGH NOT NEARLY AS COLD OF AN AIRMASS AS IS EXPECTED DURING THE MIDDLE OF THIS WEEK. LOW PRESSURE WILL APPROACH THE AREA FROM THE WEST EARLY NEXT WEEK BRINGING A CHANCE OF RAIN MONDAY INTO TUESDAY.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/...
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IFR CONDITIONS UNDER SHOWERS THIS AFTERNOON INTO EVENING. THEN CLEARING. WINDS ALREADY NW AND GUSTING 18 TO 32KT AT TAF SITES... EXCEPT MTN WHICH IS IMMINENT. HIGH PRESSURE WED MOVES OFF THE COAST TOWARD THE END OF THE WEEK. ONSHORE FLOW MAY LEAD TO FLIGHT RESTRICTIONS IN LOW CLOUDS THURSDAY NIGHT INTO FRIDAY. SUB-VFR POSSIBLE IN RAIN SATURDAY...THEN VFR SUNDAY. EASTERLY WINDS 5 TO 10 KNOTS SATURDAY BECOME WEST OR NORTHWEST AROUND 10 KNOTS BY SUNDAY.
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&& .MARINE...
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GALES UP ON THE WATERS...FIRST FOR GUSTY SHOWERS...THEN FOR THE NW BLAST AFTER THE FRONT WHICH BEGINS MOVING OVER THE WATERS DURING THE MID AFTERNOON. GALE WARNING IN EFFECT THROUGH THE NIGHT. SCA CONTINUES INTO MUCH OF WEDNESDAY...BEFORE GRADIENT RELAXES LATER IN THE AFTERNOON FOR DIMINISHING WINDS. NO SCA CONDITIONS ARE EXPECTED WEDNESDAY NIGHT. MARGINAL SCA POSSIBLY AGAIN LATE THURSDAY OR THURSDAY NIGHT WITH EAST WINDS. SMALL CRAFT ADVISORY LEVEL WIND GUSTS ARE POSSIBLE FOR PARTS OF THE WATERS SATURDAY NIGHT INTO SUNDAY IN A TIGHTENING PRESSURE GRADIENT BETWEEN LOW PRESSURE DEPARTING TO THE NORTH AND HIGH PRESSURE BUILDING IN FROM THE WEST.
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&& .CLIMATE...
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JUST A DAY AFTER RECORD HIGH MINIMUM TEMPERATURES WERE OBSERVED...AN EXCEPTIONALLY COLD AIRMASS FOR THIS TIME OF YEAR COULD APPROACH RECORD MINIMUM TEMPERATURES EARLY TOMORROW MORNING. BELOW IS A TABLE OF RECORD MINIMUM TEMPERATURES FOR APRIL 16 ALONG WITH THE FORECAST MINIMUM TEMPERATURE FOR EARLY TOMORROW MORNING. SITE...PREVIOUS RECORD...FORECAST MINIMUM... DCA....29 F IN 1928......33 F............... BWI....30 F IN 1962......31 F............... IAD....28 F IN 1981......31 F...............
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...FREEZE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY MORNING FOR DCZ001. FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR DCZ001. MD...FREEZE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY MORNING FOR MDZ004>007-009>011-013-014-016>018. FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR MDZ011-013- 014-016>018. FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT WEDNESDAY FOR MDZ004>007-009-010. VA...FREEZE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY MORNING FOR VAZ036>040-042-050>057-501-502. FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR VAZ052>057. FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT WEDNESDAY FOR VAZ036>040-042-050-051-501-502. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EDT WEDNESDAY FOR ANZ531>534-537-539>541-543. GALE WARNING UNTIL 6 AM EDT WEDNESDAY FOR ANZ530>543. SMALL CRAFT ADVISORY FROM 6 AM TO 2 PM EDT WEDNESDAY FOR ANZ530-535-536-538-542.
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&& $$ SYNOPSIS...DFH NEAR TERM...CAS SHORT TERM...BPP LONG TERM...DFH AVIATION...BPP/CAS MARINE...BPP/CAS CLIMATE...DFH

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