Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 010822 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 422 AM EDT MON JUN 1 2015 .SYNOPSIS... HIGH PRESSURE WILL REMAIN ANCHORED OFF THE MID ATLANTIC COAST TODAY AS A SLOW MOVING COLD FRONT APPROACHES FROM THE NORTHWEST. THIS COLD FRONT WILL DROP INTO THE REGION MONDAY NIGHT...AND STALL OVER THE AREA TUESDAY INTO WEDNESDAY. HIGH PRESSURE BUILDS ACROSS THE NORTHEAST WEDNESDAY...SLIDING OFFSHORE THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... LATEST GOES WATER VAPOR IMAGERY DEPICTS STUBBORN UPPER RIDGE OVER THE WRN ATLANTIC EARLY THIS MORNING. A LONGWAVE TROUGH WITH A CLOSED LOW IS OBSERVED OVER THE CENTRAL CONUS. AT THE SFC...WEAK AREA OF LOW PRESSURE HAS CENTERED OVER SRN PA/MD WITH A WARM FRONT EXTENDING EWD ALONG THE PA/MD BORDER. A TRAILING COLD FRONT WAS LOCATED OVER THE CNTRL APPALACHIANS. A WARM/HUMID AIRMASS IS IN PLACE OVER THE REGION THIS MORNING WITH TEMPS IN THE UPPER 60S-LOW 70S THIS MORNING (~10 DEGS ABOVE NORMAL). PWATS HAVE CLIMBED TO AROUND 1.5 INCHES AS MID LEVEL MOISTURE INCREASES IN INCREASING SWLY FLOW. WILL CARRY SLIGHT CHANCE POPS ACROSS THE PIEDMONT THIS MORNING AS DEEPENING MOISTURE AND WEAK FORCING ALOFT LIFT OVER THE REGION. FOR TODAY...A NRN STREAM SHORTWAVE WILL TRAVERSE THE GREAT LAKES/SRN CANADA AS THE UPPER TROUGH OVER THE MIDWEST SLOWLY PROGRESSES EWD. THE SFC LOW OVER THE NRN MID ATLANTIC WILL SHIFT EAST AND ELONGATE AS THE NRN STREAM WAVE APPROACHES...REMAINING OVER THE REGION. THE COLD FRONT WILL SLOWLY PUSH EWD AS WELL...LOCATING OVER THE ERN VA PIEDMONT LATE TODAY. AS THE UPPER RIDGE GETS SHUNTED OFFSHORE THIS AFTERNOON...DEEP LAYER SWLY FLOW WILL ALLOW FOR DEEPER MOISTURE OVER THE LOCAL AREA. PWATS PROGGED TO REACH +1 STD DEV. THETA-E ADVECTION AND INCREASING LOW LEVEL MOISTURE WILL RESULT IN BETTER INSTABILITY...WITH MLCAPE VALUES FROM 1000-1500 J/KG. NAM A LITTLE MORE ROBUST WITH MLCAPE BTWN 1500-2000 J/KG. SHEAR REMAINS RATHER WEAK (~15 KT) AS UPPER LEVEL FLOW IS RATHER UNIMPRESSIVE. EXPECT THE RIDGE TO KEEP SHOWERS/THUNDERSTORMS ISOLATED/PULSES IN NATURE UNTIL MID-LATE AFTERNOON WHEN BETTER COVERAGE IS EXPECTED. INVERTED V SOUNDINGS MAY PRODUCE GUSTY WINDS...BUT DO NOT ANTICIPATE SEVERE WEATHER. MAIN THREAT WILL BE LOCALLY HEAVY RAINFALL DUE TO WEAK FLOW AND HIGH PWATS. LIMITED INSTABILITY IN THE HAIL GROWTH LAYER MAY ALSO PRODUCE SMALL HAIL. BEST COVERAGE WILL BE MID-LATE AFTERNOON INTO THE EVENING HOURS FROM THE PIEDMONT INTO CNTRL VA AND THE MD ERN SHORE...WHERE LIKELY POPS HAVE BEEN RETAINED. CHANCE POPS SOUTH AND EAST...WITH LOW POPS ALONG THE IMMEDIATE COAST AS THE UPPER RIDGE PREVAILS. THIS MATCHES LATEST HI-RES GUIDANCE. STILL SOME DIFFERENCES IN MODELS WITH RESPECT TO QPF TODAY THROUGH THIS EVENING. SREF REMAINS ON THE CONSERVATIVE SIDE AS GEFS PLACES HIGH PROBS STORM TOTAL AMOUNTS EXPECTED TO RANGE FROM LESS THAN ONE TENTH OF AN INCH SOUTH CENTRAL VA TO HALF AN INCH IN THE NRN PIEDMONT. LOCALLY HIGHER AMOUNTS EXPECTED IN THUNDERSTORMS. A SLIGHT DROP OFF IN H85 TEMPS AND LOW LEVEL THICKNESSES WILL BE OVERCOME BY WARM RETURN FLOW. HIGHS GENERALLY IN THE MID-UPPER 80S TO AROUND 90 (COOLER ALONG THE IMMEDIATE COAST). SKY AVERAGES PARTLY CLOUDY EAST TO MOSTLY CLOUDY WEST. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... MULTI-MODEL CONSENSUS NOW SLOWLY TRACKS THE CNTRL CONUS UPPER TROUGH ACROSS THE TN/KY VALLEYS INTO THE GULF STATES THRU WEDS. THE UPPER LOW PROGGED TO CLOSE OFF OVER THE TN VALLEY MON NIGHT. NRN STREAM SHORTWAVE WILL LIFT ALONG THE SAINT LAWRENCE RIVER VALLEY TONIGHT AND OFF THE NE COAST TUESDAY NIGHT. THE COLD FRONT DROPS INTO THE LOCAL AREA MON NIGHT...BEFORE STALLING OVER THE AREA TUESDAY AND WEDNESDAY. WILL MAINTAIN CHANCE POPS OVER THE NW HALF OF THE LOCAL AREA MON NIGHT AS SCATTERED SHOWERS EXPECTED TO PERSIST ALONG THE FRONT AS IT DROPS INTO THE REGION. WARM AND HUMID TONIGHT WITH LOS N THE UPPER 60S TO AROUND 70. A BETTER CHC FOR SHOWERS/TSTMS AND BENEFICIAL RAIN ARRIVES FOR MOST OF THE AREA BY TUESDAY AFTERNOON. LARGE SCALE CONFLUENCE WILL REMAIN OVER SE CANADA...KEEPING SFC HIGH PRESSURE NORTH OF THE REGION. HOWEVER...THE HIGH WILL RIDGE SWD INTO THE LOCAL AREA AS LOW PRESSURE DEVELOPS OFF THE NE COAST DUE TO HEIGHT FALLS FROM THE NRN STREAM WAVE. LIKELY POPS ARE FORECAST FOR MOST OF THE AREA...WITH THE SURFACE BOUNDARY OVER THE REGION...AND ACTUALLY SOME UPPER SUPPORT IN THE RRQ OF A ~100KT JET OVER SE CANADA. LOCALLY HEAVY RAINFALL IS POSSIBLE AS ANOMALOUS PWATS COMBINE WITH WEAK STEERING FLOW. CLOUD COVER/PRECIP WILL LIMIT INSTABILITY...WITH ONLY 15-20 KT EFFECTIVE SHEAR EXPECTED...LIMITING THE POTENTIAL FOR SEVERE WEATHER. COOLER TUE WITH HIGHS IN THE LOW-MID 80S (COOLER ALONG THE COAST AND OVER THE NW PIEDMONT). AN INVERTED SFC TROUGH SHARPENS ALONG THE COAST TUES NIGHT AS HIGH PRESSURE BUILDS INTO NEW ENGLAND. BETTER FORCING ARRIVES WEDS AS SPOKES OF ENERGY LIFT FROM THE UPPER LOW TO COMBINE WITH ANOMALOUS MOISTURE OVER THE REGION. ISENTROPIC LIFT WILL ALSO ENHANCE PRECIP. HAVE INCREASED POPS ALONG AND WEST OF THE I-95 CORRIDOR INTO THE LIKELY CATEGORY AS A RESULT. COOLER WEDS DUE TO CLOUDS/PRECIP AND FALLING HEIGHTS/THICKNESSES. HIGHS RANGE FROM AROUND 70 NW TO THE LOW 80S SE. MORNING LOWS FORECAST IN THE 60S. TOTAL QPF THRU THE NEAR-SHORT TERM INDICATE A WIDESPREAD BENEFICIAL ONE HALF TO ONE INCH ACROSS MUCH OF THE LOCAL AREA. PIEDMONT LOCALES EXPECTED TO SEE THE MOST WITH AMOUNTS UNPWARDS OF ONE HALF INCH. SREF PROBS REMAIN ON THE LOW SIDE OF THE GUIDANCE...WHILE GEFS PROBS ARE MUCH HIGHER...INDICATING NEARLY 2 INCHES FOR RIC. TRENDED TOWARD CONSERVATIVE SREF...BUT THERE WILL BE SOME WIDE VARIATIONS IN QPF. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... HIGH PRESSURE SLIDES OFF THE NEW ENGLAND COAST WED NIGHT...KEEPING THE FRONTAL BOUNDARY STALLED ALONG THE SOUTHEAST COAST THROUGH THE UPCOMING WEEKEND. BACK TO THE WEST...AN UPPER TROUGH GETS STUCK OVER THE GULF COAST STATES AND TN VALLEY. MOISTURE AND SHORTWAVE ENERGY SPINNING AROUND THE TROUGH WILL BE SQUEEZED UP THE COASTAL PLAIN OF THE CAROLINAS AND VIRGINIA...KEEPING UNSETTLED CONDITIONS ACROSS THE MID ATLANTIC REGION DURING THE LONG TERM FORECAST TIMEFRAME. 12Z MODELS CONTINUE TO SHOW ENOUGH VARIABILITY REGARDING THE EXACT PLACEMENT OF THE UPPER TROUGH VERSUS A POTENTIAL SFC LOW DEVELOPING OFF THE SE COAST AND TRAVELLING UP THE CAROLINA COAST... PRIMARILY ALONG THE STALLED FRONTAL BOUNDARY. OVERALL...PERIODS OF SHOWERS AND THUNDERSTORMS SHOULD BE ANTICIPATED REGARDLESS OF WHETHER OR NOT THE REGION IS IMPACTED BY THE POTENTIAL COASTAL LOW OR THE UPPER TROUGH DURING THE TIME. LIGHT STEERING FLOW ALOFT ON THE ORDER OF 5-15/20KT THROUGHOUT THE LONG TERM FORECAST PERIOD LENDS A LITTLE MORE CREDENCE TO BEING IMPACTED BY A COASTAL SYSTEM...HOWEVER IT IS STILL TOO SOON TO NAIL DOWN THE EXACT TIMING AND PLACEMENT OF PRECIPITATION. WILL CONTINUE TO MAINTAIN A 10-40 PERCENT CHANCE POP THROUGHOUT THE EXTENDED FORECAST PERIODS. WITH THE PERIODIC SHOWERS/STORMS WILL COME PERIODS OF CLOUDS AND SUN. LOWS WILL GENERALLY BE IN THE 60S. INLAND HIGHS WILL GENERALLY BE IN THE LOW-MID 80S THU/FRI...MID-UPPER 80S SAT. HIGH TEMPS AT THE IMMEDIATE COAST WILL BE AROUND 5 DEGREES COOLER THAN INLAND TEMPS. && .AVIATION /09Z MONDAY THROUGH FRIDAY/... SCT-BKN HIGH LVL MSTR ARND THE AREA ERLY THIS MORNING FROM CONVECTION TO THE NW. INCRG AMTS OF MSTR WILL COMBINE WITH THE APPRCHG FRNTL BNDRY AND JUICY AIRMASS TO PRODUE SCT CONVECTION NEXT FEW DAYS. TIMING OF ANY CONVECTION RTHR PROBLEMATIC TODAY WITH BEST CHCS ACROSS NW AREAS ONCE AGAIN. WENT WITH A BKN CU DECK AT BOTH RIC/SBY TO TREND CLOUDIER BUT KEPT PCPN OUT OF TAFS FOR NOW. DRY ACROSS SERN TAF SITES CLOSER TO OFFSHORE RIDGE. OUTLOOK...SHWRS / TSTRMS WILL BE LIKELY TUESDAY. ONSHORE FLOW BEGINNING TUES NIGHT COULD RESULT IN MARGINAL CIGS/VSBYS OVR SRN PORTIONS. CHC FOR AFTN TSTMS CONTS THROUGH THE WEEK. && .MARINE... WILL KEEP A PERSISTANT S WIND FCST TODAY AS OFFSHORE RIDGE CONTS TO DOMINATE. ONLY CONCERN ARE FOR OCNL GUSTS TO 20 KTS AS PRS GRDNT BEGINS TO TIGHTEN AHEAD OF APPRCHG FRNT. HAVE AN MWS FOR THESE NOW AND MAY NEED TO REACCESS THE NEED FOR MINIMAL SCA HEADLINES IF THESE GUSTS CONT. MODELS NOW COMING TO A SOLN OF HAVING THE COLD FRONT SLOWLY CROSS THE WATERS STARTING TUE AFTRN ACROSS NRN WATERS THEN TUE NIGHT ACROSS THE SOUTH. LATEST DATA SHOWG A MORE NOTICABLE WIND SHIFT TO THE N THEN NE TUE NIGHT AND WED ALONG WITH A MINIMAL NRLY SURGE. ALTHOUGH THE DATA KEEPS WINDS BLO SCA LVLS ATTM...WUD NOT BE SURPRISED IF LATER MODELS SHOW THE NEED FOR A SCA ACROSS THE NRN WATERS BY 12Z WED. KEPT CNDTNS BLO SCA LVLS WITH THIS FCST PACKAGE BUT INDCTD SOME 5 FT SEAS JUST AT 20 NM. OTW...PERSISTANT S FLOW KEEPS WAVES IN THE BAY BTWN 2-3 FT...CSTL WTR SEAS BTWN 3-4 FT AHEAD OF FROPA. LIGHTER ONSHORE WINDS CONT THRU FRI AS THE HIGH PRS TO THE NORTH SLOWLY MOVES EAST. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...AJZ/SAM NEAR TERM...AJZ/SAM SHORT TERM...AJZ/SAM LONG TERM...BMD AVIATION...MPR MARINE...BMD/MPR

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