Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 240921 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 521 AM EDT THU APR 24 2014 .SYNOPSIS... COOL CANADIAN HIGH PRESSURE SLIDES OVER THE REGION TODAY AND BECOMES LOCATED OFF THE SOUTHEAST COAST BY THIS EVENING. THE NEXT COLD FRONT CROSSES THE MID ATLANTIC REGION ON FRIDAY...FOLLOWED BY A SERIES OF WEAK AND GENERALLY DRY FRONTS THROUGH THE WEEKEND. A PERIOD OF UNSETTLED WEATHER IS EXPECTED EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... A COOL CANADIAN SFC HIGH PRESSURE IS CENTERED OVER THE GREAT LAKES REGION AND EXTENDS ACROSS THE OHIO VALLEY EARLY THIS MORNING. THE SFC HIGH WILL SLIDE SOUTHEAST OVER THE MID ATLANTIC REGION TODAY AND BECOME LOCATED OFF THE SOUTHEAST U.S. COAST BY THIS EVENING. THE PRESSURE GRADIENT WILL REMAIN SOMEWHAT TIGHTENED ALONG THE ATLANTIC COAST TODAY AS THE HIGH MOVES IN AND A STRONG SFC LOW WELL EAST OF THE NRN NEW ENGLAND COAST SLOWLY PUSHES EWD. WITH HIGH PRESSURE OVERHEAD...SUNSHINE WILL BE PLENTIFUL AND TEMPS WILL WARM NICELY TODAY. CIRRUS CLOUDS WILL INTO THE REGION FROM THE NW AS THE AFTN PROGRESSES BUT THIS SHOULD HAVE A MINIMAL IMPACT ON HIGH TEMPERATURES TODAY. EXPECT HIGHS IN THE UPPER 60S INLAND VA/NE NC AND IN THE LOW-MID 60S CLOSER TO THE IMMEDIATE CHES BAY/ATLANTIC COASTS. IN ADDITION...DRY WEATHER AND FINE FUELS WILL PREVAIL TODAY. THE DRY CONDITIONS COUPLED WITH BREEZY NW WINDS WILL ALLOW MIN RH VALUES TO FALL INTO THE UPPER TEENS-LOW 20S MOST AREAS BY THIS AFTN. INCREASED FIRE POTENTIAL IS A CONCERN ONCE AGAIN FOR TODAY...BUT WILL BE LIMITED TO THE MD/VA EASTERN SHORE. PLEASE REFER TO THE FIRE WEATHER SECTION BELOW FOR MORE INFORMATION. WINDS WILL TURN SE-S AND BE LIGHT AS HIGH PRESSURE CONTINUES TO MOVE SEWD OVERNIGHT. MEANWHILE...A COLD FRONT AND ASSOCIATED UPPER LEVEL SHORTWAVE WILL PUSH ACROSS THE MID-MISSISSIPPI VALLEY AND INTO THE OHIO VALLEY OVERNIGHT. HIGH CLOUDS WILL INCREASE AND THICKEN OVERNIGHT AS THE SFC FRONT APPROACHES THE MID ATLANTIC REGION. THE COMBINATION OF CLOUD COVER AND INCREASING MOISTURE/DEWPOINTS WILL PREVENT TEMPS FROM DROPPING QUICKLY OVERNIGHT. LOWS SHOULD BE NEAR NORMAL WITH READINGS IN THE MID- UPPER 40S AREAWIDE (EXCEPT LOW 40S POSSIBLE FOR INTERIOR MD EASTERN SHORE). && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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TIMING OF THE FRONTAL PASSAGE HAS SLOWED AND THE UPPER LEVEL SHORTWAVE STRENGTH IS WANING AS BOTH FEATURES CROSS THE MID ATLANTIC REGION FRIDAY INTO FRIDAY EVENING. SHORT RANGE MODELS ARE IN FAIR AGREEMENT WITH SLOWING THE ONSET OF PRECIP AND LIMITING IT TO AREAS WEST OF INTERSTATE 95 FROM MID-MORNING TO EARLY AFTN. THE PRESENCE OF A THETA-E GRADIENT (AHEAD OF THE THETA-E RIDGE AXIS) MEANS THAT A SLIGHT CHANCE OF THUNDER IS POSSIBLE DURING THIS TIMEFRAME...DESPITE AN INITIAL LACK OF PREFERRED/FAVORABLE SFC INSTABILITY IN THE MORNING. CONVECTIVE POTENTIAL IMPROVES DURING THE AFTN/EARLY EVENING AS DAYTIME HEATING AND INCOMING SHORTWAVE ENERGY DESTABILIZES THE ATMOSPHERE AND DEEP LIFT/OMEGA ACCOMPANIES THE FRONTAL PASSAGE. MODEL SOUNDINGS SHOW A PRIMARILY UNIDIRECTIONAL WIND PROFILE WITH SLIGHT VEERING WITH HEIGHT IN THE LOWEST LEVELS (ROUGHLY BELOW 850-900 MB) WHICH IMPLIES THAT THUNDERSTORM LINE SEGMENTS MAY BE POSSIBLE. HOWEVER...WIND SHEAR FROM 0-6 KM IS AVERAGING ABOUT 30 KT WHICH SUGGESTS THAT THE POTENTIAL FOR ORGANIZED CONVECTION IS LOW. IN ADDITION ... SHORT-LIVED LOW LEVEL SW FLOW WILL ADVECT MODEST PWATS INTO THE REGION (0.75 TO 1.40 INCHES). THEREFORE IF ANY THUNDERSTORMS DEVELOP...THEY SHOULD PRIMARILY BE UNORGANIZED WITH PERIODS OF MODERATE TO HEAVY RAINFALL WITH SUB-SEVERE WIND GUSTS OF 30-40 MPH UNDER THE STRONGEST STORM CORES. KEEPING ONE CAVEAT IN MIND...IF THE UPPER LEVEL SHORTWAVE DIGS FARTHER SOUTH OVER THE NEXT 24 HOURS (AS OF THU MORNING)...THEN THE AMPLIFICATION OF UPSTREAM RIDGING WILL LIKELY STALL THE FRONTAL PASSAGE UNTIL FRIDAY EVENING THUS CAUSING AN ADDITIONAL DELAY IN THE ONSET OF PRECIP TO THE AREA AND DECREASING THUNDERSTORM POTENTIAL DUE TO UNFAVORABLE TIMING. WILL NEED TO MONITOR 12Z MODEL TRENDS THIS MORNING AS WELL AS SHORTWAVE PLACEMENT IN WATER VAPOR IMAGERY TO DETERMINE BEST TIMING/IMPACTS. HIGH TEMPS IN THE MID-UPPER 70S ARE ANTICIPATED MOST AREAS WHILE THE MD/VA EASTERN SHORE SHOULD BE IN THE LOW-MID 70S. THE COLD FRONT IS EXPECTED TO MOVE OFFSHORE LATE FRIDAY NIGHT AS A SECONDARY DRY COLD FRONT (ASSOCIATED WITH AN UPPER LOW OVER THE GREAT LAKES) APPROACHES FROM THE NW. GRADUALLY CLEARING SKIES FROM WEST TO EAST FRI NIGHT SHOULD RESULT IN LOWS IN THE UPPER 40S TO LOWER 50S WEST OF INTERSTATE 95 AND MID-UPPER 50S EAST OF INTERSTATE 95 (LOWER 50S MD/VA EASTERN SHORE). THE DRY FRONT WILL SAG DOWN ACROSS THE AREA ON SAT WHICH WILL RESULT IN BREEZY WLY/DOWNSLOPE FLOW AND INCREASING LOW LEVEL THICKNESSES. THIS SHOULD ALLOW DAYTIME TEMPS TO WARM INTO THE UPPER 70S (POSSIBLY 80 DEGREES) FOR NE NC AND INTERIOR VA WEST OF CHES BAY AND INTO THE MID 60S TO LOWER 70S FOR THE MD/VA EASTERN SHORE. A NARROW BAND OF MOISTURE AND MEASURABLE PRECIP IS EXPECTED TO STAY NORTH OF THE LOCAL FORECAST AREA SAT/SAT NIGHT. LOWS SAT NIGHT WILL BE AT TO SLIGHTLY ABOVE NORMAL WITH TEMPS OF 45-50 DEGREES NW OF RICHMOND AND THE MD/VA EASTERN SHORE...AND IN THE LOWER 50S ELSEWHERE.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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MODELS CONTINUE TO POINT TO A HIGHLY AMPLIFIED/BLOCKY PATTERN OVER THE CONUS NEXT WEEK...RESULTING IN AN INCREASINGLY WET PERIOD. MODELS CONTINUE TO STRUGGLE WITH THIS BLOCKY FLOW...MAINLY IN LOCATION OF FRONTAL BOUNDARY PROGGED TO BE DRAPED ACROSS THE RGN ALONG WITH TIMING OF SEVERAL BATCHES OF MSTR PROGGED TO ROTATE NE FROM THE DEEP SOUTH. WHAT TODAYS MODELS SHOW DIFFERENT FROM YSTRDYS IS A SLOWER START TO THE PCPN MON...SOMEWHAT HIGHER CONFIDENCE FOR AN EXTNDD PRD OF WETNESS FROM MON NITE THRU WED ALONG WITH A FRONTAL BOUNDARY THAT WILL LIKELY PLAY HAVOC WITH TEMPS. KEPT SUN DRY/SEASONABLE AS H5 RIDGE BUILDS ACROSS THE AREA. WARM FRONT APPRCHS THE RGN FROM THE SW SUN NIGHT...BUT GUID SUGGESTS ANY MOISTURE STAYS W OF FA THRU 12Z MON. LOWS SAT/SUN NIGHTS IN THE M40S-L50S. HIGHS SUN 70-75 WEST OF THE BAY...M-U60S ALONG THE COAST. FORECAST RATHER PROBLEMATIC NEXT WEEK AS THE MODELS DIFFER ON WHERE THIS FRONTAL BNDRY SETS UP. THIS WILL LIKELY DETERMINE TMPS AND PCPN TYPES (CONVECTIVE VS STRATIFORM RAIN). UPR LVL LOW PROGGED TO SLOWLY EJECT EAST FROM THE NATIONS MID SECTION MON NIGHT ONLY TO THE OHIO VLLY BY WED. A MOIST E-SE FLOW WILL LIKELY ADD TO THE MOISTURE CONTENT RESULTING IN PERIODIC CHCS FOR PCPN THRU THE PRD. FRNTL BNDRY MAY ALSO TRY TO MAKE A RUN FARTHER NORTH BY WED AS SFC LOW BEGINS TO CROSS THE MTS. TRAILING COLD FRONT WILL EVENTUALLY PUSH ALL THIS OUT TO SEA...BUT THAT MIGHT NOT BE UNTIL THURSDAY. UPSHOT WILL CARRY HIGH CHC POPS (SHWRS) MON THROUGH WED. TMPS COOLEST (L-M60S) ALONG THE COAST DUE TO AN ONSHORE FLOW. HIGHS U60S-L70S WEST OF THE BAY. LOWS IN THE 50S.
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&& .AVIATION /09Z THURSDAY THROUGH MONDAY/... HI PRES CONTG TO BUILD OVR THE RGN THROUGH TDA...RESULTING IN DCRSG NNW WNDS. A LTL BIT GUSTY TO BETWEEN 15 TO 20 KT INTO THIS MRNG...ESP NR THE CST. WNDS DIMINISH OVR INLAND LOCATIONS TO AROUND 5 KT BY LT TDA. VFR TDA THROUGH TNGT. AN AREA OF LOW PRESSURE AND AN ASSOCIATED COLD FRONT WILL BRING SCATTERED SHOWERS AND A FEW THUNDERSTORMS FRIDAY. BRIEF PERIODS OF IFR WILL BE PSBL AT THE TAF SITES. HIGH PRESSURE BUILDS INTO THE REGION DURING THE WEEKEND WITH VFR AND DRY WEATHER TAKING OVER THROUGH MONDAY. THE NEXT WEATHER SYSTEM BRINGS A GOOD CHANCE FOR PCPN BY TUESDAY. && .MARINE... LINGERING SCAS ON THE BAY INTO MID/LT MRNG HRS...ON THE OCN UNTIL MID/LT AFTN. SFC HI PRES IS SLO TO BUILD OVR THE WTRS THIS AFTN/EVE...RESULTING IN GUSTY NNW WNDS THIS MRNG WANING THIS AFTN. VRB WNDS TNGT LESS THAN 10 KT...BECOME SSE ON FRI AHEAD OF APPROACHING LO PRES FM THE W. SPEEDS TO INCRS FRI INTO FRI NGT... THOUGH WILL KEEP BLO SCA...THEN BECOME WNW FRI NGT AND CONT THROUGH SAT. && .FIRE WEATHER... DRY CONDITIONS (MIN RH VALUES 15-25%) WILL OCCUR AGAIN TODAY. HOWEVER...WINDS WILL BE LIGHTER THAN WEDNESDAY. THIS WILL PRECLUDE THE NEED FOR ANY RED FLAG WARNINGS OVER THE LOCAL AREA. NW WINDS DO INCREASE TO AROUND 15 MPH WITH GUSTS OF 20-25 MPH DURING THE LATE MORNING/EARLY AFTN HOURS ON THE LOWER MD/VA EASTERN SHORE. GIVEN HOW LOW RH VALUES WILL BE THURSDAY AFTN COUPLED WITH LOW FUEL MOISTURE CONDITIONS...HAVE CONTINUED THE INCREASED FIRE DANGER STATEMENT FOR OUR MD COUNTIES (AFTER COORDINATION WITH MD FIRE OFFICIALS) AND ADDED VA EASTERN SHORE COUNTIES TO THE INCREASED FIRE DANGER STATEMENT. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...INCREASED FIRE DANGER FROM 11 AM EDT THIS MORNING THROUGH THIS AFTERNOON FOR MDZ021>025. NC...NONE. VA...INCREASED FIRE DANGER FROM 11 AM EDT THIS MORNING THROUGH THIS AFTERNOON FOR VAZ099-100. MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR ANZ630>632-634. SMALL CRAFT ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR ANZ650- 652-654-656-658. && $$ SYNOPSIS...BMD NEAR TERM...BMD SHORT TERM...BMD LONG TERM...MPR AVIATION...ALB/LSA MARINE...ALB FIRE WEATHER...

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