Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 190050 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 850 PM EDT MON AUG 18 2014 .SYNOPSIS... A LOW PRESSURE SYSTEM WILL DEVELOP OVER VIRGINIA TONIGHT BEFORE MOVING OFF THE COAST TUESDAY. WEAK HIGH PRESSURE RETURNS ON WEDNESDAY BEFORE ANOTHER SYSTEM OVER THE GREAT LAKES MOVES INTO THE MID ATLANTIC STATES FOR THURSDAY AND FRIDAY. && .NEAR TERM /THROUGH TUESDAY/... UPDATE THIS EVENING TO DROP THE WATCH AND TWEAK THE POPS SOME OVERNIGHT. AS SECONDARY LOW DEVELOPING OVER CENTRAL NC SHOULD BECOME THE DOMINANT LOW OVERNIGHT LIFTING NORTHEAST INTO NORTHEAST NC AND SOUTHEAST VA AND LOWER BAY. TRENDING TOWARDS THE HRRR POP TRENDS WITH THE MOST WIDESPREAD SHOWERS AND STORMS ACROSS THE SOUTHERN TWO THIRDS OF THE FORECAST AREA. EXPECT SCATTERED SHOWERS AND STORMS WELL NORTH AND NORTHWEST OF RIC. ONCE THE LOW BEGINS TO DEVELOP THIS EVENING...EXPECT TO SEE MORE SHOWERS AND AREAS OF RAIN FORM ALONG AN NORTH OF THE FRONT WITH MORE CONVECTIVE PRECIPITATION TO THE SOUTH OF IT. SOME AREAS COULD SEE 0.50 - 1 INCH OF RAIN AS PW CONTINUE TO RUN A LITTLE OVER 2 INCHES IN A VERY MOIST ATMOSPHERE. HAVE ALSO BUMPED UP OVERNIGHT LOWS DUE TO THE MORE HUMID AIRMASS. FOR TUESDAY...THE LOW SLOWLY SLIDES OFF THE VA COAST AND HAS SOME WRAP AROUND MOISTURE SO HAVE HELD ON TO THE PCPN A LITTLE LONGER ACROSS THE DELMARVA AS THE 12Z NAM IS SLOWER THAN THE 12Z GFS IN PULLING THE LOW OUT. LATER IN THE AFTERNOON...WILL GET THE SFC BOUNDARY SLIDING DOWN INTO THE TIDEWATER AND NE NC SO MORE SHOWERS ARE POSSIBLE THERE. FOR TEMPERATURES HAVE LEAN A LITTLE LOW ESPECIALLY TOWARD THE NORTH THINKING THAT CLOUDS WILL LINGER AND LIMIT THE DAY TIME HEATING. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... FROM TUESDAY NIGHT THROUGH THURSDAY...THE MODELS ARE SHOWING LOTS OF VARIABLIITY WITH THE MOVEMENT OF SHORTWAVE ENERGY IN THE NORTHWEST FLOW AS THE UPPER RIDGE OVER THE MS VALLEY BUILDS AND THE UPPER LOW OVER THE GREAT LAKES IS SLOW TO MOVE EAST. WEDNESDAY LOOKS TO BE THE DRIER OF THE TWO DAY AS THE EXITING LOW OFF THE COAST ALLOWS FOR WEAK HIGH PRESSURE OVER THE NE TO NOSE SOUTHWARD INTO THE MID ATLANTIC STATES AND THE MOISTURE LESSENS. BUT BY THURSDAY...THE NW FLOW IS MORE ESTABLISHED AND WITH CONVECTION TO THE NORTHWEST AND THE REGION IN A GOOD POSITION ON THE EDGE OF THE RIDGE...COULD EASILY SEE CONVECTION DROP SE INTO THE REGION. SO HAVE VERY LITTLE PCPN ON WEDNESDAY WITH HIGHER CHANCE POPS ON THURSDAY. BUT CONFIDENCE IN THE OVER PATTERN IS LOW DUE TO THE MODEL UNCERTAINTY FROM RUN TO RUN. FOR TEMPERATURES...HAVE ALLOWED FOR SOME ADDITIONAL HEATING ON WED AND THU DUE TO MORE SUNSHINE AND ALSO DUE TO THE WEST/NW FLOW ALOFT. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... UNSETTLED WEATHER PATTERN CONTINUES INTO THE EXTENDED PERIOD AS NWLY FLOW ALOFT DEVELOPS. TEMPS WILL BE NEAR TO SLIGHTLY BELOW SEASONABLE...LATE SUMMER NORMS. WHILE MEDIUM RANGE GUIDANCE CONTINUES TO STRUGGLE HANDLING THE SPLIT/BLOCKY FLOW OVER THE HIGHER LATITUDES...MODELS HAVE BECOME MORE STABLE WITH RESOLVING SRN STREAM ENERGY OVER THE OH VALLEY AND MID-ATLANTIC REGION. THIS THANKS TO UPPER/SFC HIGH PRESSURE FROM THE SE STATES EWD OFF THE COAST. WITH THAT SAID...FLOW AMPLIFIES OVER THE ERN CONUS AS MID LEVEL HIGH PRESSURE BUILDS OVER THE CNTRL US AND LOW PRESSURE REMAINS OVER THE NE US. THIS WILL PLACE THE MID-ATLANTIC STATES IN NWLY FLOW ALOFT...OPENING THE DOOR FOR SHORTWAVE ENERGY IN THE UPPER FLOW. QUASI-STATIONARY BOUNDARY WILL LOCATE OVER THE REGION...JUST TO THE SOUTH. MOISTURE WILL NOT BE A LIMITATION WITH PWATS PROGGED AROUND 2 INCHES (+1 STD DEV) AND DEWPOINTS IN THE MID-UPPER 60S. ANTICIPATE A DIURNAL TREND WITH SHOWERS/THUNDERSTORMS...BUT UPSTREAM MCS DEVELOPMENT MAY SPILL INTO THE REGION DURING THE OVERNIGHT HOURS THRU THE WEEKEND. HIGHER POPS MAY BE WARRANTED...BUT BASED ON THE DEGREE OF UNCERTAINTY AND TIMING...WILL STICK MORE TO CLIMO WITH CHANCE POPS DURING THE AFTERNOON AND EVENING. COULD BEGIN TO SEE A DRYING TREND BY LATE IN THE WEEKEND INTO EARLY NEXT WEEK AS THE UPPER HIGH BUILDS EWD...SHUNTING THE BEST MOISTURE OFFSHORE. WITH THE LATEST MODEL RUNS PLACING THE FRONT SOUTH OF THE LOCAL AREA...NLY FLOW AND FALLING THICKNESSES WILL LIKELY YIELD TEMPS IN THE LOW-MID 80S. LOW-MID 80S TO CONTINUE THRU THE WEEKEND...WARMING BACK INTO THE MID 80S BY EARLY NEXT WEEK. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/...
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A COMPLEX AREA OF LOW PRESSURE AND FRONTAL SYSTEMS COVERED THE MID ATLANTIC STATES MONDAY EVENING. LOW PRESSURE MOVES OFF THE COAST TUESDAY MORNING WITH WEAK HIGH PRESSURE BUILDING FROM THE NORTH THROUGH WEDNESDAY. UNSETTLED WEATHER RETURNS LATE IN THE WEEK. THE LINE OF TSTMS THAT AFFECTED SOUTHEAST VIRGINIA MOVED OFF THE COAST JUST PRIOR TO THE 00Z TAF ISSUANCE MORE SHOWERS WERE DEVELOPING BUT NO SIGNIFICANT TSTMS ARE EXPECTED OVERNIGHT. WITH MOIST CONDITIONS... MVFR WITH AREAS OF IFR CAN BE EXPECTED IN THE LATE EVENING AND OVERNIGHT. MVFR SHOULD END BY LATE MORNING. WIDELY SCT SHOWERS AND TSTMS WILL BE PSBL TUESDAY BUT NOT NEARLY AS WIDESPREAD AS THEY WERE MONDAY. OUTLOOK...SCT AFTN/EVENING TSTMS RETURN TO THE FCST THURSDAY THROUGH SATURDAY. THERE WILL BE THE POSSIBILITY OF MVFR/IFR CONDS WITHIN A FEW HOURS OF SUNRISE EACH MORNING.
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&& .MARINE... UNSETTLED WEATHER PATTERN WILL PREVAIL OVER THE WATERS THRU THE FORECAST PERIOD...BUT SCA CONDITIONS ARE NOT ANTICIPATED. AREA OF LOW PRESSURE HAS LOCATED OVER WV WITH A FRONTAL BOUNDARY EXTENDING EWD OVER SRN VA AND THE LOWER BAY. MEANWHILE...HIGH PRESSURE BUILDS OVER THE NE STATES. THE RESULT IS GENERALLY ONSHORE AROUND 10 KT. WAVES/SEAS AVG 1-2 FT. SFC LOW WEAKENS OVER THE CNTRL APPALACHIANS AS AN ADDITIONAL AREA OF LOW PRESSURE DEVELOPS OVER THE WATERS. WITH THE SFC LOW OVER THE WATERS...FLOW OVER THE COASTAL WATERS (ON THE ERN PERIPHERY OF THE LOW) WILL BE SW OVER THE SRN WATERS...VEERING TO E OVER THE NRN WATERS...AVG 10-15 KT. SCA CONDITIONS ARE NOT ANTICIPATED. SEAS WILL BUILD ONLY TO 2-3 FT WITH WAVES AVG 1-2 FT. SFC LOW SLOWLY PUSHES OFFSHORE LATE TUES-TUES NIGHT AS HIGH PRESSURE OFF THE NE COAST RIDGES SWD OVER THE NRN WATERS. FLOW REMAINS GENERALLY ONSHORE...AOB 15 KT. LOW PRESSURE LINGERS OFF THE MID-ATLANTIC COAST THRU THE END OF THE WORK WEEK AND INTO THE WEEKEND AS A FRONTAL BOUNDARY REMAINS SOUTH OF THE WATERS. THE RESULT WILL BE ONGOING ONSHORE/NELY FLOW. GRADIENT WILL REMAIN WEAK (AOB 15 KT)...BUT PERSISTENT NE FETCH MAY PUSH SEAS UPWARDS OF 5 FT IN THE NRN COASTAL WATERS FRIDAY NIGHT THRU THE WEEKEND. UNDERCUT WAVEWATCH AS GFS IS NOT THE PREFERRED MEDIUM RANGE MODEL. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...ESS NEAR TERM...ESS/JAO SHORT TERM...ESS LONG TERM...SAM AVIATION...LSA MARINE...SAM

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