Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 201606 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 1206 PM EDT MON APR 20 2015 .SYNOPSIS... SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL ACCOMPANY A COLD FRONT LATE TODAY AND THIS EVENING. THE COLD FRONT WILL CROSS THE AREA TONIGHT. HIGH PRESSURE BUILDS BACK IN FROM THE SOUTHWEST ON TUESDAY. ANOTHER COLD FRONT CROSSES THE AREA WEDNESDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... LATEST WX ANALYSIS DEPICTS WARM FRONT JUST NORTH OF THE LOCAL AREA WITH A TRAILING COLD FRONT EXTENDING FROM ~985MB LOW PRESSURE OVER THE GREAT LAKES SWD TO THE LOWER MS VALLEY. ALOFT...UPPER LOW HAS LOCATED OVER THE UPPER MIDWEST WITH TROUGH AXIS EXTENDING SWD ALONG THE MS VALLEY. LATEST REGIONAL RADAR MOSAIC DEPICTS LAST NIGHTS SHOWERS WELL OFFSHORE WITH DRY CONDITIONS OVER MUCH OF THE MID-ATLANTIC REGION. SKIES AVG MOSTLY CLOUDY. FOR TODAY...SFC LOW LIFTS NWD INTO SRN ONTARIO THIS AFTERNOON AS THE COLD FRONT APPROACHES THE LOCAL AREA. SEVERAL PERTURBATIONS IN INCREASING SWLY FLOW ALOFT WILL LIFT TOWARD THE REGION. THE AIRMASS OVER THE LOCAL AREA WILL BECOME INCREASINGLY WARM/MOIST AND UNSTABLE...ESPECIALLY WITH A FEW HOLES IN THE CLOUD COVER EXPECTED THIS AFTERNOON. THETA E ADVECTION ALONG WITH TEMPS IN THE LOW-MID 80S AND DEWPOINTS AROUND 60 WILL RESULT IN A MARGINALLY UNSTABLE AIRMASS...WITH MLCAPE VALUES PER RAP GUIDANCE IN THE 1000-1500 J/KG RANGE. MODELS ALSO INDICATE VERY LITTLE MLCIN. WHILE THERE WILL BE VERY LITTLE INHIBITION THIS AFTERNOON...EXPECT PRECIP TO STAY TIED TO THE FRONT/CONVERGENCE ZONE. EXPECT MOISTURE ADVECTION TO RAMP UP IN ADVANCE OF THE FRONT...WITH PRECIP WATERS APPROACHING 1-1.25 INCHES. COLD FRONT REACHES THE ERN VA PIEDMONT MID-LATE AFTERNOON. HI-RES GUIDANCE INDICATING VERY LITTLE CONVECTION ALONG THE FRONT AS IT CROSSES THE CNTRL APPALACHIANS...BUT ONCE THE FRONT REACHES THE AIRMASS OVER THE PIEDMONT...MODELS INDICATE INITIATION AROUND 3-5PM THIS AFTERNOON OVER THE PIEDMONT. MODE EXPECTED TO START OFF AS DISCRETE CELLS...BUT 30-40 KT OF EFFECTIVE BULK SHEAR WILL TRANSITION TO A LINE FROM THE PIEDMONT INTO CNTRL VIRGINIA. QUICK W-SW MID LEVEL FLOW WILL PUSH STORMS QUICKLY TO THE E-NE...WITH THE BEST CHANCES REMAINING ALONG THE INSTABILITY AXIS FROM THE PIEDMONT INTO CNTRL VA. STORMS PROGGED TO REACH CNTRL VA LATE TODAY-EARLY THIS EVENING...AND THEN POINTS EWD THRU THE EVENING. WHILE MORE INSTABILITY IS PROGGED ACROSS THE SE...EVENING TIMING AND DECREASING SHEAR IS NOT FAVORABLE TO MAINTAIN LINE SEGMENTS INTO THAT AREA. HI-RES GUIDANCE ALSO BACKS THIS UP. HAVE INCREASED POPS TO LIKELY ACROSS THE PIEDMONT NEWD TO THE MD ERN SHORE...WITH HIGH END CHANCE SOUTH AND EAST. DAMAGING WIND GUSTS AND LARGE HAIL ARE POSSIBLE THANKS TO DEEP INSTABILITY...FAVORABLE LAPSE RATES AND A RELATIVELY LOW FREEZING LEVEL. TORNADO RISK REMAINS LOW THANKS TO GOOD MIXING AND HIGH LCL HEIGHTS. THE BEST RISK FOR SEVERE WEATHER WILL BE ACROSS THE LIKELY POP AREA WITH ISOLATED STRONG TO SEVERE STORMS STILL POSSIBLE OVER THE SE. BRIEF HEAVY RAINFALL ALSO EXPECTED...BUT MOVEMENT WILL LIMIT ANY FLOODING POTENTIAL. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... A COLD FRONT CROSSES THE FA TONIGHT WITH CHC POPS...THEN DRYING/COOLER WESTERLY FLOW TAKING OVR INTO TUE. PARTLY/MOSTLY SUNNY TUE WITH HIGH TEMPS IN THE UPR 60S TO NR 70 AT THE COAST...AND LOW/MID 70S ELSEWHERE. HIGH PRES MOVES TO NR THE SE CONUS COAST BY WED...PROVIDING WSW FLOW AND CONTINUING MILD WX. A WEAK TROUGH WILL BE APPROACHING FROM THE WNW...WHICH SHOULD RESULT IN INCREASING CLOUDS AND THE POSSIBILITY OF AFTERNOON SHOWERS (ISOLD TSTMS). LOW TEMPS TUE NGT MID 40S WEST AND NORTH TO LOW 50S SE. HIGH TEMPS WED IN THE LOW/MID 70S...EXCEPT 60S AT THE IMMEDIATE COAST. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... BROAD CYCLONIC FLOW PREVAILS THRU THE EXTENDED PERIOD AS UPPER CLOSED LOW REMAINS IN VIC OF THE GREAT LAKES AND NEW ENGLAND. TO BEGIN THE PERIOD...FAST MOVING COLD FRONT CROSSES THE REGION LATE WEDS NIGHT-EARLY THURS MORNING. GFS CONTINUES TO REMAIN ON THE SLOWER SIDE OF MODEL GUIDANCE WRT FRONTAL PASSAGE...WITH THE ECMWF QUICKER. BASED ON WLY FLOW ALOFT AND HIGH PRESSURE BACK OVER THE MIDWEST...OPTED TO REINTRODUCE SLIGHT CHANCE POPS WEDS NIGHT OVER THE NRN AND NERN ZONES AND THEN THURS SOUTH AND EAST OF RICHMOND...TRENDING SLIGHTLY TOWARD THE SLOWER GFS. HIGHS THURS AROUND NORMAL...LOW-MID 60S. THEREAFTER...COOL HIGH PRESSURE BUILDS SWD FROM THE CANADIAN PRAIRIES INTO THE MIDWEST...EXTENDING INTO THE MID-ATLANTIC REGION FRI. HIGHS FRI GENERALLY IN THE UPPER 50S NE TO MID 60S SE UNDER A PARTLY CLOUDY SKY AND NWLY WINDS. SRN STREAM SHORTWAVE PROGGED TO LIFT INTO THE MIDWEST FRI NIGHT-SAT WITH ASSOCIATED SFC LOW FORECAST TO PROGRESS EWD ALONG A STATIONARY BOUNDARY OVER THE GULF STATES SAT. MOISTURE RETURNS SAT TO GO ALONG WITH OVERRUNNING AND WEAK PERTURBATIONS ALOFT. INCREASED POPS TO SLIGHT CHANCE N TO CHANCE S. HIGHS SAT GENERALLY AROUND 60 ACROSS THE REGION. SFC LOW MOVES OFF THE CAROLINA COAST SAT NIGHT...WITH ANY REMAINING PRECIP EXPECTED ACROSS THE SE LOCAL AREA. HIGH PRESSURE RETURNS SUN...BUT COOL CONDITIONS PERSIST WITH HIGHS IN THE UPPER 50S NE TO LOW 60S SE. && .AVIATION /15Z MONDAY THROUGH FRIDAY/... THE FRONTAL RAINBAND IS MOVING OFFSHORE THIS MORNING. CONDITIONS ARE IMPROVING AND SHOULD CONTINUE THROUGH THE MORNING. CLOUD COVER ACTUALLY SCATTERING OUT BY THIS AFTERNOON...ALONG WITH A GUSTY SW WIND. A SECONDARY IMPULSE TRACKS ACROSS THE REGION LATE THIS AFTERNOON AND EVENING BRINGING A CHC OF SHOWERS/TSTMS. ANY TSTMS COULD CONTAIN STRONG WIND GUSTS. A COLD FRONT THEN MOVES OFF THE COAST LATER TONIGHT...WITH HIGH PRESSURE BUILDING INTO THE REGION TUESDAY...BEFORE MOVING OFFSHORE WEDNESDAY. A COLD FRONT CROSSES THE AREA WEDNESDAY NIGHT WITH A SLIGHT CHC OF SHOWERS. HIGH PRESSURE RETURNS THURSDAY AND FRIDAY. && .MARINE... LOW PRESSURE IS LIFTING NNE OVER THE GREAT LAKES EARLY THIS MORNING...WITH SECONDARY LOW PRESSURE OVER THE MID ATLANTIC. 3 TO 5 FT WAVES IN THE MOUTH OF THE BAY WILL CONTINUE THROUGH THE AFTN. SEAS HAVE RISEN TO 5-8FT...AND WILL LIKELY REACH 6-9FT EARLY TODAY...BEFORE SLOWLY SUBSIDING LATER TODAY THROUGH TUESDAY. A FRONTAL BOUNDARY IS PRESENTLY CROSSING THE AREA AND SHOULD MOVE OFFSHORE BY 12Z (15Z FARTHER NE). EXPECT THE WIND TO BECOME SOUTHERLY BEHIND THE FRONT WITH SPEEDS RELAXING TO 10-15KT. INHERITED SCA FLAGS REMAIN AS IS. HOWEVER...THE RIVERS COULD POTENTIALLY END EARLIER THAN THE CURRENT 10 AM TIME. THIS WILL BE RECONSIDERED AT THE 11Z/7 AM UPDATE. OTHERWISE...A COLD FRONT APPROACHES FROM THE W THIS AFTERNOON/EVENING...AND MOVES ACROSS THE COAST LATE TONIGHT. 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 WITH HIGH PRESSURE RETURNING THURSDAY AND FRIDAY. && .HYDROLOGY... AVG QPF 0.75-2.00"...LOCALLY UP TO 2.50" OVR MOST OF THE RIVER BASINS WILL RESULT IN RIVER LVLS TO PSBLY RISE TO 1/2-NR FULL BANKFULL TUE INTO WED. && .TIDES/COASTAL FLOODING... SOUTHERLY FLOW TODAY INTO THIS EVENING WILL HELP MAINTAIN ~1.0 FT ANOMALIES IN THE MIDDLE BAY THROUGH TONIGHT. TIDAL ANOMALIES WILL BEGIN TO SUBSIDE TUESDAY AS THE FLOW BECOMES OFFSHORE. NO STATEMENTS HAVE BEEN ISSUED AT THIS TIME...BUT BISHOPS HEAD WILL COME CLOSE TO THEIR 3.25FT MINOR THRESHOLD. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR ANZ634. SMALL CRAFT ADVISORY UNTIL 7 AM EDT TUESDAY FOR ANZ654-656-658. SMALL CRAFT ADVISORY UNTIL 1 PM EDT TUESDAY FOR ANZ650-652. && $$ SYNOPSIS...JDM NEAR TERM...JDM/SAM SHORT TERM...ALB/JDM LONG TERM...SAM AVIATION...AJZ MARINE...AJZ HYDROLOGY... TIDES/COASTAL FLOODING...

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