Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 142002 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 402 PM EDT MON APR 14 2014 .SYNOPSIS...
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A STRONG COLD FRONT WILL APPROACH FROM THE WEST OVERNIGHT AND CROSSES THE REGION TUESDAY. CANADIAN HIGH PRESSURE BUILDS IN FROM THE NORTHWEST TUESDAY NIGHT AND SETTLES OVER THE MID ATLANTIC AND NORTHEAST WEDNESDAY AND THURSDAY.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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STLT IMAGERY CONTINUES TO SHOW RIDGING OVER THE WESTERN ATLANTIC AND A DEEPENING TROUGH IN THE UPPER MIDWEST. THUNDERSTORM CLUSTERS WERE OVER THE GULF COAST STATES. UPPER AIR ANALYSIS HAS A STRONG SHORT WAVE EXTENDING FROM CANADA ACROSS MINNESOTA TO THE SOUTHERN HIGH PLAINS. AT THE SURFACE...A COLD FRONT EXTENDED FROM LOW PRESSURE OVER LAKE HURON SOUTHWEST THROUGH INDIANA TO SOUTH TEXAS. HIGH PRESSURE WAS SITUATED OVER THE NORTHERN ROCKIES. ACROSS THE MID ATLANTIC STATES...A SOUTHERLY WIND FLOW PREVAILED PUTTING THE AREA WELL INTO THE WARM SECTOR. A FEW SHOWERS WERE NOTED ACROSS THE SOUTHERN APPALACHIANS. THE CHANCE FOR PCPN INCREASES SLOWLY FROM W TO E THIS EVENING AND OVERNIGHT. MOST PCPN HOLDS OFF UNTIL AFTER MIDNIGHT. HAVE A SLGT CHC TSTM OVER THE PIEDMONT COUNTIES AFT 08Z. TEMPERATURES WILL BE MILD...MAINLY IN THE LOW TO MID 60S.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
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THE SITUATION BECOMES QUITE INTERESTING BY TUESDAY AFTERNOON. THE PRIMARY TROUGH LIFTS THROUGH THE TENNESSEE AND OHIO VALLEYS TUESDAY MORNING AND BEGINS TO TAKE ON A NEGATIVE TILT AS IT APPROACHES THE MID-ATLANTIC TUESDAY AFTERNOON. MEANWHILE...THE SURFACE COLD FRONT APPROACHES THE REGION FROM THE NW DURING THE DAY...WITH INCREASING LOW-LEVEL FRONTOGENESIS. THE NAM/GFS HAVE SIMILAR TIMING OF THE FRONT...MOVING INTO FAR WESTERN COUNTIES AROUND MIDDAY AND REACHING THE COAST DURING THE EVENING. THE 0-3KM BULK SHEAR IS PROGGED TO REACH 50 TO 60KT. CAPES REACH 500 TO 800 J/KG OVER SOUTHERN PORTIONS OF THE AREA. NAM SHOWS LOW PRESSURE ALONG THE FRONT FORMING IN THE GEORGIA AREA TUESDAY MORNING AND SLOWLY INTENSIFYING AS IT MOVES TOWARD SOUTHEAST VIRGINIA LATE IN THE AFTERNOON. IF THIS IS REALIZED...THIS WOULD INCREASE LOW LEVEL HELICITY. VARIOUS TORNADO PARAMETERS INCLUDING THE 0-1KM EHI AND THE 0-3KM SHERB HAS VALUES OF 1 TO 2. SPC HAS OUTLOOKED A SIGNIFICANT PORTION OF VIRGINIA AND OUR NORTH CAROLINA COUNTIES WITH A SLIGHT RISK OF SEVERE. THE BEST CHANCE FOR SEVERE APPEARS TO BE S OF A LINE FROM EMPORIA TO JUST EAST OF RICHMOND TO NORTHAMPTON COUNTY ON THE VIRGINIA EASTERN SHORE. THE MAIN THREAT WILL BE FROM DAMAGING WINDS BUT TORNADOES ARE ALSO POSSIBILITY. THE TIME FRAME FROM 4 PM TO 8 PM EASTERN DAYLIGHT TIME WOULD HAVE THE HIGHEST CHANCE FOR SEVERE. THE POSSIBILITY OF SEVERE WILL BE HIGHEST IF BREAKS IN THE OVERCAST APPEAR IN THE THREAT AREA. THE COLD FRONT WILL END THUNDERSTORMS AND DIMINISH PCPN. TEMPERATURES WILL DROP FAIRLY QUICKLY BEHIND THE FRONT...FALLING TO THE 50S IN THE PIEDMONT BY 00Z. HIGH TEMPERATURES TUESDAY ARE FORECAST TO REACH NEAR 70 IN THE WEST AND THE MD EASTERN SHORE TO THE UPR 70S IN THE FAR SE. RAIN ENDS IN THE SOUTHEAST TUESDAY NIGHT WITH CLEARING SKIES FROM W TO E OVERNIGHT. TEMPERATURES ARE FORECAST TO DROP TO 30 TO 35 WELL INLAND TO NEAR 40 IN THE SOUTHEAST. FUTURE ISSUANCES MAY REQUIRE FREEZE HEADLINES IN COUNTIES WEST OF INTERSTATE 95 IF CONFIDENCE IS HIGH ENOUGH THAT 3 HOURS OF 32 OR BELOW WILL OCCUR. IT APPEARS THAT MODEL GUIDANCE IS TOO LOW WITH THEIR NUMBER. AT THIS POINT...IT APPEARS MARGINAL. FROST IS NOT AN ISSUE DUE TO THE WIND. WEDNESDAY THROUGH THURSDAY WILL HAVE A CLEAR TO PARTLY CLOUDY SKY. MOST OF THE CLOUDS WILL BE IN THE SOUTHEAST. THERE IS A POSSIBILITY FOR LIGHT RAIN NEAR THE NORTH CAROLINA COAST BY THURSDAY BUT KEPT FORECAST DRY FOR NOW. TEMPERATURES AGAIN MAY FALL TO AROUND FREEZING OVER INLAND COUNTIES WITH THE MODEL GUIDANCE POSSIBLY TOO HIGH. WILL ASSESS AS WE GET CLOSER. TEMPERATURES WEDNESDAY AND THURSDAY ARE FORECAST TO TOP OFF GENERALLY IN THE 50S.
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&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... STRONG SFC HIGH PRESSURE REMAINS ANCHORED OVER NEW ENGLAND TO BEGIN THE MEDIUM RANGE FORECAST PERIOD, RESULTING IN CONTINUED NE FLOW OVER THE MID ATLANTIC FRIDAY. TEMPERATURES WILL BE COOL TO BEGIN THE PERIOD FRIDAY...ABOUT ONE STANDARD DEVIATION BELOW NORMAL...WITH TEMPS MODERATING A BIT SATURDAY. ALOFT, NORTHERN STREAM SHORTWAVE TROUGH, AND ATTENDANT SFC LOW IS EXPECTED TO PUSH ACROSS THE MID MS VLY TOWARDS THE EASTERN GREAT LAKES FRI-SAT, EVENTUALLY PUSHING A MAINLY DRY COLD FRONT THROUGH SAT NGT AND EARLY SUNDAY. BOTH MODELS DO TAKE A PIECE OF SHORTWAVE ENERGY ACROSS THE MID-SOUTH TOWARDS THE CAROLINA COAST FRIDAY-SATURDAY, WITH RESULTANT WEAK INVERTED TROUGHING THAT DEVELOPS PROMPTING SOME LOW POPS LATER FRIDAY AND SATURDAY. THE 12Z/14 EURO SOLUTION REMAINS A BIT WETTER THAN THE PROGRESSIVE GFS SOLUTION. HAVE SPLIT THE DIFFERENCE BETWEEN THE GFS/UKMET FOR THIS PACKAGE. RIGHT NOW, IT APPEARS THAT THE BEST RAIN CHC WOULD BE OVER EASTERN SECTIONS ALONG THE COASTAL TROUGH FRIDAY NIGHT THROUGH MIDDAY SATURDAY. UPPER TROUGH EJECTS NORTHEAST LATER SATURDAY, WITH SHORTWAVE RIDGING ARRIVING FROM THE WEST SHUNTING SYSTEM OFFSHORE. QUICK CLEARING EXPECTED THEREAFTER TOWARDS THE TAIL END OF THE PERIOD (EASTER SUNDAY AND MONDAY). && .AVIATION /20Z MONDAY THROUGH SATURDAY/... VFR CONDITIONS ACROSS AREA TERMINALS THIS AFTERNOON WITH GUSTS TO 20-25KT WHICH SHOULD BRIEFLY DIMINISH THIS EVENING.CIGS SLOWLY DETERIORATE TO MVFR TONIGHT...W/PERIODIC IFR CIGS POSSIBLE TOWARDS SUNRISE AS MOISTURE ADVECT IN ADVANCE OF THE FRONT. BREEZY SOUTHERLY WINDS CONTINUE TUESDAY (GUSTS OF 30-35 KT) AS THE FRONT APPROACHES FROM THE WEST. COLD FRONT CROSSES THE REGION TUESDAY, ACCOMPANIED BY WIDESPREAD RAINFALL TUES-TUES NIGHT WITH PERIODIC IFR VSBY RESTRICTIONS IN HEAVY RAIN. THERE IS ALSO THE POTENTIAL FOR A STRONG LINE OF CONVECTION ON THE LEADING EDGE OF THE FRONT TUES AFTERNOON MAINLY ACROSS SOUTHEASTERN TERMINALS (PHF-ORF-ECG)W/ HEAVY RAIN AND STRONG WIND GUSTS UP TO 50 KT POSSIBLE. OUTLOOK...BEHIND THE FRONT, LOOK FOR WINDS TO BACK TO THE NW AND REMAIN GUSTY. SOME GUSTS UP TO 40 KT POSSIBLE ALONG THE COAST. IMPROVING CONDITIONS WED THRU FRIDAY AS HIGH PRESSURE BUILDS INTO THE REGION FROM THE NORTH. && .MARINE... HIGH PRESSURE REMAINS ANCHORED OVER THE WRN ATLANTIC AS A STRONG COLD FRONT SLOWLY APPROACHES FROM THE WEST. BREEZY...BUT SUB SCA...SLY WINDS CONTINUE OVER THE WATERS...AVERAGING 10-15 KT. WAVES AVERAGE 1-2 FT WITH SEAS 2-3 FT. NRN COASTAL WATERS HAVE BUILT TO NEAR 4 FT 20 NM OUT...BUT ARE EXPECTED TO REMAIN BELOW 5 FT THRU THIS AFTERNOON DUE TO SLY FLOW. CONDITIONS WILL REMAIN SUB-SCA TODAY AS THE FRONT SLOWLY APPROACHES FROM THE WEST...WITH THE STRONGEST HEIGHT FALLS OCCURRING TUESDAY. HOWEVER...A FEW GUSTS APPROACHING 20 KT CANNOT BE RULED OUT. AS THE FLOW OVER THE WATERS BECOMES MORE SELY...SEAS WILL LIKELY BUILD TO 3-5 FT IN THE NRN WATERS...NORTH OF CAPE CHARLES LIGHT...BY LATE TODAY. LOW LEVEL GRADIENT WILL ALSO STRENGTHEN LATE TODAY-TONIGHT AS THE FRONT REACHES THE OH VALLEY. WHILE A STEEP LOW LEVEL INVERSION STILL EXISTS OVER THE WATERS...EXPECT PRESSURE FALLS AND GRADIENT WINDS TO PROVIDE BETTER MIXING OVER THE WATER. WHILE STILL MARGINAL...HAVE OPTED TO HOIST SCA HEADLINES TONIGHT FOR THE BAY. STRONGEST PRESSURE FALLS ARRIVE EARLY TUES...WITH LOW-END SCA CONDITIONS OVER THE BAY/SOUND/ERN VA RIVERS. SEAS ALSO EXPECTED TO BUILD TO 3-5 FT IN THE SRN WATERS (HIGHEST 20 NM OUT) TUES MORNING. SEAS WILL BUILD TO 5-8 FT TUES AFTERNOON. IN ADDITION...A LINE OF CONVECTION IS POSSIBLE ALONG THE LEADING EDGE OF THE FRONT TUES AFTERNOON. WITH WINDS A FEW THOUSAND FT OFF THE WATER REACHING 45-50 KT...CONVECTION WILL LIKELY BE ABLE TO MIX THESE HIGHER VELOCITY WINDS DOWN. WILL HANDLE THIS WITH SHORT FUSED PRODUCTS. THE MAIN IMPACT WILL BE BEHIND THE FRONT TUESDAY NIGHT AS A MUCH COLDER/DRIER AIRMASS SURGES INTO THE REGION. GALE CONDITIONS ARE EXPECTED OVER ALL WATERS...WITH NW GUSTS REACHING 35-40 KT. HAVE HELD OFF ON A GALE WATCH ATTM AS IT WILL STILL BE DURING THE 4TH PERIOD FORECAST. HIGH PRESSURE QUICKLY BUILDS BACK OVER THE WATERS EARLY WEDS MORNING...RESULTING IN IMPROVING CONDITIONS OVER THE BAY. FLOW VEERS AROUND TO THE NE WEDS...RESULTING IN PERSISTENT ONSHORE FLOW THRU THE END OF THE WEEK. THIS WILL RESULT IN ELEVATED SEAS THRU THE END OF THE WEEK. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT TUESDAY FOR ANZ633- 635>638. SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ630>632-634- 650-652-654. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EDT TUESDAY FOR ANZ656-658. && $$ SYNOPSIS...LSA NEAR TERM...LSA SHORT TERM...LSA LONG TERM...MAM AVIATION...MAM MARINE...SAM

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