Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 191922 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 322 PM EDT SUN APR 19 2015 .SYNOPSIS...
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LOW PRESSURE TRACKING NORTH FROM THE MISSISSIPPI VALLEY INTO THE GREAT LAKES REGION TONIGHT...PUSHING A WARM FRONT THROUGH THE LOCAL AREA. A COLD FRONT THEN CROSSES THE AREA MONDAY NIGHT. HIGH PRESSURE BUILDS BACK IN FROM THE SOUTHWEST ON TUESDAY.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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CLDNS HAS SPREAD ACRS MOST OF THE FA AS OF MID AFTN...W/ RA MAKING STEADY PROGRESS INTO CNTRL/SRN PORTIONS. SYNOPTIC PATTERN SETTING UP FOR A WIDESPREAD SIGNIFICANT RAINFALL OVR THE FA. W/ HI PRES OFF OF NEW ENG...AND LO PRES W OF THE MTNS...A SIGNFICANT INFLO OF DP LYRD MOISTURE XPCD OVRNGT AS A WARM FRONT PROGRESSES NE THROUGH THE FA. HAVE CONTD MENTION OF HVY RA...AND MDLS DO HINT AT MINIMAL INSTABILITY PUSHING NWD INVOF ERN PORTIONS OF VA AND OVR NE NC LT THIS EVE/AFT MDNGT SO ADDED SLGT CHC-CHC THUNDER. QPF AVGG 0.75-1.50"...MAYBE LOCALLY HIGHER AMTS. PCPN AMTS TO RMN BLO 6-12 HR FLASH FLOOD GUIDANCE SO NO FLASH FLOOD WATCH WILL BE ISSUED. MAJORITY OF THE RA SHIFTS TO THE CST BY 12Z/20. THERE WILL ALSO BE GUSTY ESE WNDS TO 20-30 MPH...HIGHEST NR THE CST. ADDED AREAS OF FG (VSBYS 1-3NM) OVR THE WTRS - AFT MDNGT...DUE TO WARMER AIR SPREADING OVR COOLER WTRS. LO TEMPS TNGT FM THE M50S TO M60S.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
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THE AREA OF RAIN WILL SHIFT OFF THE COAST MON MRNG...THEN CONCERN SHIFTS TO A TROUGH ALOFT APPROACHING FROM THE WEST BY LATE MON AFTN/EVE (LIKELY LEADING TO SCT SHWRS/TSTMS). SPC CONTS TO PUT THE AREA OUTLOOKED IN A SLIGHT RISK OF SVR TSTMS MON AFTN/EVE FOR THE POTENTIAL OF ISOLD DAMAGING WIND GUSTS AND LARGE HAIL. THE POTENTIAL FOR SVR WX IS CERTAINLY THERE GIVEN ML CAPE VALUES EXPECTED TO BE IN THE 1000-1500 J/KG RANGE...STEEP LAPSE RATES...AND A MODEST SHEAR PROFILE. WILL CONT TO HIGHLIGHT POSSIBLE STRONG/ISOLD SVR STORMS IN THE HWO FOR LATE MON AFTN/EVE. OTW...VRB CLOUDS-PARTLY SUNNY AND BREEZY/WARMER MIDDAY/AFTN ON MON. HI TEMPS IN THE 70S AT THE CST...80 TO 85 ELSW. COLD FRONT CROSSES THE FA MON NGT WITH CHC POPS...THEN DRYING/COOLER WESTERLY FLOW TAKING OVR INTO TUE. PARTLY/MOSTLY SUNNY TUE WITH HI TEMPS IN THE UPR 60S TO NR 70 AT THE COAST...AND L/M70S ELSW. HI PRES MOVES TO NR THE SE CONUS CST BY WED...PROVIDING WSW FLO AND CONTG MILD WX. A WK TROUGH SFC-ALOFT WILL BE APPROACHING FM THE WNW...WHICH MAY RESULT IN INCRSG CLDNS W AND N...ALG W/ PSBL ISOLD/SCT SHRAS/TSTMS (HWVR WILL CAP POPS AT 14% THOSE AREAS FOR NOW). LO TEMPS TUE NGT M40S W AND N TO FAR L50S SE. HI TEMPS WED IN THE L/M70S N AND NW...TO M/U70S CNTRL/SE.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... UPPER LOW REMAINS IN VIC OF THE GREAT LAKES THRU THE EXTENDED PERIOD THANKS TO BLOCKY FLOW OVER THE HIGHER LATITUDES. FAST WLY/ZONAL FLOW PROGGED OVER THE LOCAL AREA. SFC HIGH PRESSURE BUILDS OVER THE SE STATES/SRN MID ATLANTIC TUES NIGHT-WEDS MORNING...SLIDING OFFSHORE WEDS AFTERNOON. THE RESULT IS A MOSTLY SUNNY TO PARTLY CLOUDY SKY WEDS WITH HIGHS RIGHT AROUND NORMAL...UPPER 60S TO 70 INLAND AND MID- UPPER 60S COASTAL AREAS. POTENT SHORTWAVE ROUNDS THE BASE OF THE STACKED UPPER LOW INTO THE OH VALLEY LATE WEDS-WEDS NIGHT. ASSOCIATED FAST MOVING COLD FRONT REACHED THE CNTRL APPALACHIANS WEDS NIGHT...CROSSING THE LOCAL AREA EARLY THURS. FRONT EXPECTED TO STALL VIC NC THURS NIGHT DUE TO WLY FLOW ALOFT. QUESTION WILL BE HOW MUCH MOISTURE RETURN THERE IS THURS AS ECMWF REMAINS DRY AND THE GFS RATHER MOIST. DIFFERENCE IS LOW LEVEL SWLY FLOW IN GFS COMPARED TO WLY FLOW IN THE ECMWF. TRENDED TOWARD DRIER ECMWF...DROPPING POPS TO SILENT THURS-THURS NIGHT. HIGHS THURS REMAINING AROUND NORMAL...GENERALLY IN THE MID-UPPER 60S. COOL CANADIAN HIGH PRESSURE PROGGED TO BUILD INTO THE OH VALLEY THURS NIGHT-FRI...EXTENDING INTO THE MID-ATLANTIC REGION. THE RESULT WILL BE DRY CONDITIONS...NWLY WINDS AND BELOW NORMAL TEMPS FRI...GENERALLY IN THE LOW-MID 60S INLAND TO UPPER 50S-LOW 60S COASTAL AREAS. MODELS PICKING UP ON A SRN STREAM SYSTEM CROSSING THE SE STATES SAT. MENTIONED SLIGHT CHANCE POPS SRN VA/NE NC...CLOSEST TO THE FRONTAL BOUNDARY AND BEST MOISTURE RETURN. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/... A BACKDOOR COLD FRONT HAS DROPPED SOUTH INTO THE CAROLINAS RESULTING IN ENE WINDS OF 10 TO 15 KT BEHIND THE FRONT. WINDS NEAR THE COAST WILL INCREASE TO 15-20KT THROUGH LATE AFTERNOON AND EARLY EVENING. THE FRONT WILL LIFT BACK NORTH AS A WARM FRONT LATER THIS EVENING AND TONIGHT AHEAD OF A COMPLEX LOW PRESSURE SYSTEM OVER THE OHIO RIVER VALLEY. THIS WILL RESULT IN MVFR AND IFR CONDITIONS SPREADING RAPIDLY NORTHEAST ACROSS THE ENTIRE AREA LATER THIS AFTERNOON AND THROUGH THE EVENING/OVERNIGHT HOURS. IFR CEILINGS AND OCCASIONAL HEAVY RAIN ARE EXPECTED THIS EVENING AND ESPECIALLY OVERNIGHT AT ALL TAF SITES. EXPECT SEVERAL HOURS OF IFR CONDITIONS TO PERSIST ACROSS THE REGION FROM AROUND 00-03Z THROUGH AT LEAST 12-15Z. WIDESPREAD RAIN WHICH IS ALREADY MOVING INTO SOUTH CENTRAL VA WILL SPREAD NORTHEAST AND WILL NOT DIMINISH FROM SW- NE UNTIL 09Z TO 12Z MONDAY. ANOTHER IMPULSE TRACKS ACROSS THE REGION MONDAY AFTERNOON/EVENING BRINGING A CHC OF SHRA/TSRA. THERE IS A SLIGHT RISK OF SEVERE STORMS MONDAY AFTERNOON/EVENING WITH THE MAIN THREAT BEING STRONG TO DAMAGING WIND GUSTS. HIGH PRESSURE BUILDS ACROSS THE SOUTHEAST STATES TUESDAY AND WEDNESDAY AS LOW PRESSURE LINGERS OVER THE GREAT LAKES. THIS WILL ALLOW DRY CONDITIONS TO RETURN. A WEAK COLD FRONT DROPS ACROSS THE REGION THURSDAY. && .MARINE... A BACKDOOR COLD FRONT PRESENTLY ENTERING THE NRN OCEAN ZONES WILL DROP N-S ALONG THE COAST EARLY THIS MORNING. THIS WILL PRODUCE A WIND SHIFT TO NE. SPEEDS ARE EXPECTED TO AVERAGE 10- 15KT...ALTHOUGH SPEEDS COULD BRIEFLY REACH 20KT IN THE IMMEDIATE WAKE OF THE BOUNDARY THIS MORNING. OTHERWISE...LOW PRESSURE LIFTS INTO THE ERN GREAT LAKES THIS AFTERNOON/EVENING...WITH SECONDARY LOW PRESSURE DEVELOPING OVER THE MID ATLANTIC TONIGHT. THIS IS A FAVORABLE PATTERN FOR A SHORT DURATION (~3-5 HR)OF STRONG SCA CONDITIONS IN SE FLOW. AT THIS TIME IT APPEARS TO BE CENTERED AROUND 09Z TONIGHT. WIND SPEEDS ARE EXPECTED TO INCREASE TO 15-20KT THIS AFTERNOON AND EVENING...BEFORE INCREASING TO 20-25KT WITH GUSTS ~30KT LATER TONIGHT INTO EARLY MONDAY. SEAS BUILD TO 4-5FT TODAY...AND THEN 5-7FT TONIGHT...BEFORE BEGINNING TO GRADUALLY SUBSIDE MONDAY AS THE FLOW BECOMES SOUTHERLY AND THE PRESSURE GRADIENT RELAXES. INHERITED SCAS REMAIN SIMILAR. THE MAIN CHANGES WERE TO ADD THE UPPER JAMES...AND EXTEND THE BAY/SOUND/RIVERS SEGMENTS THROUGH 10AM MONDAY. ADDITIONALLY...THE NRN OCEAN ZONES (N OF PARRAMORE ISLAND) WERE EXTENDED THROUGH MONDAY NIGHT WHERE SEAS WILL REMAIN 4-5FT. A COLD FRONT APPROACHES FROM THE W MONDAY AFTERNOON/EVENING...AND MOVES ACROSS THE COAST LATE MONDAY NIGHT. THIS FRONT IS EXPECTED TO TRIGGER SHOWERS/TSTMS...WHICH WILL HAVE THE POTENTIAL OF PRODUCING STRONG WIND GUSTS. HIGH PRESSURE BUILDS ACROSS THE SOUTHEAST TUESDAY AND WEDNESDAY AS LOW PRESSURE LINGERS OVER THE GREAT LAKES. A WEAK COLD FRONT CROSSES THE REGION WEDNESDAY NIGHT INTO THURSDAY. && .HYDROLOGY...
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AVG QPF 0.75-1.50" TNGT OVR MOST OF THE RIVER BASINS WILL RESULT IN RIVER LVLS TO PSBLY RISE TO 1/2-NR FULL BANKFULL TUE INTO WED.
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&& .TIDES/COASTAL FLOODING... A PERIOD OF ONSHORE FLOW TODAY FOLLOWED BY MODEST SE FLOW TONIGHT WILL ALLOW TIDAL ANOMALIES TO BUILD TO ~1.0FT ABOVE NORMAL LATER TONIGHT PRIMARILY IN THE MIDDLE BAY AND ALONG THE ATLANTIC COAST OF THE MD ERN SHORE. SOUTHERLY FLOW MONDAY INTO MONDAY EVENING WILL HELP MAINTAIN ~1.0FT ANOMALIES IN THE MIDDLE BAY THROUGH MONDAY NIGHT. TIDAL ANOMALIES WILL BEGIN TO SUBSIDE TUESDAY AS THE FLOW SHIFTS TO OFFSHORE. THE COMBINATION OF TIDAL ANOMALIES AND HIGH ASTRO TIDES (NEW MOON PHASE) WILL PUSH MOST SITES OVER HAT DURING HIGH TIDE SUNDAY NIGHT AND MONDAY. PORTIONS OF THE MIDDLE BAY AND OCEAN CITY WILL APPROACH MINOR FLOODING THRESHOLDS. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EDT MONDAY FOR ANZ630>638. SMALL CRAFT ADVISORY UNTIL 7 AM EDT TUESDAY FOR ANZ654-656-658. SMALL CRAFT ADVISORY UNTIL 1 PM EDT TUESDAY FOR ANZ650-652. && $$ SYNOPSIS...ALB/JDM NEAR TERM...ALB/JDM SHORT TERM...ALB/JDM LONG TERM...SAM AVIATION...AJZ/JAO MARINE...SAM HYDROLOGY...AKQ TIDES/COASTAL FLOODING...AKQ

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