Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 301816 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 216 PM EDT TUE JUN 30 2015 .SYNOPSIS... LOW PRESSURE WILL SLIDE NORTHEAST ACROSS THE EASTERN GREAT LAKES TODAY...WITH THE ASSOCIATED COLD FRONT APPROACHING THE AREA FROM THE NORTHWEST LATE THIS AFTERNOON INTO TONIGHT. THE FRONT WILL STALL ACROSS THE REGION WEDNESDAY THROUGH SATURDAY...WITH LOW PRESSURE TRACKING ALONG THE FRONT LATER THURSDAY AFTERNOON INTO THURSDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... THE CURRENT UPPER AIR ANALYSIS SHOWS A TROUGH OVER THE GREAT LAKES REGION...WITH A RIDGE CENTERED OVER THE SUBTROPICAL WRN ATLANTIC. AT THE SURFACE...A BROAD AREA OF LOW PRESSURE IS SITUATED OVER THE GREAT LAKES...WITH A COLD FRONT TRAILING BACK THROUGH THE OHIO VALLEY. THE PRIMARY TROUGH AXIS WILL LIFT ACROSS THE ERN GREAT LAKES TODAY...WITH A SHORTWAVE TROUGH APPROACHING FROM THE W BY LATER THIS AFTERNOON. MEANWHILE...THE SURFACE LOW WILL LIFT THROUGH THE ERN LAKES AS WELL...WITH THE COLD FRONT APPROACHING FROM THE NW. A PRE-FRONTAL TROUGH DEVELOPS OVER THE REGION TODAY WITH STRONG DIABATIC HEATING...AND THIS WILL BECOME THE FOCAL POINT FOR ISO-SCT CONVECTION LATER TODAY INTO THIS EVENING. BEST COVERAGE EXPECTED THIS EVENING AS BEST HEIGHT FALLS ARRIVE OVER THE REGION. HI-RES GUIDANCE STILL HITTING ON THE SE THIS EVENING...BUT LIMITED MOISTURE RETURN AND WARM TEMPS ALOFT PROVIDED BY OFFSHORE RIDGE (MODEST MID LEVEL LAPSE RATES) WILL HELP LIMIT COVERAGE. EFFECTIVE SHEAR VALUES ARE PROGGED TO REACH 30-35KT BY LATE THIS AFTERNOON INTO THIS EVENING COINCIDING WITH THE APPROACH OF THE SHORTWAVE TROUGH. INSTABILITY IS MORE MARGINAL (MLCAPE OF 1000-1500 J/KG) WHEN COMPARED TO THE EVENTS OF JUN 20/25. OVERALL STORM STRUCTURE SHOULD BE LESS ORGANIZED THAN THOSE EVENTS...BUT A THREAT OF DAMAGING WIND GUSTS STILL EXISTS BASED ON THE STRENGTH OF THE SHEAR IN A REGION OF STEEP LOW-LEVEL LAPSE RATES AND A WELL-MIXED BL. THE DAY SHOULD BEGIN SUNNY ACROSS THE REGION...BEFORE BECOMING PARTLY TO MOSTLY CLOUDY LATE THIS AFTERNOON INTO THE EVENING. HIGHS ARE EXPECTED TO REACH THE UPPER 80S TO LOW 90S. POPS THEN TAPER OFF AFTER MIDNIGHT WITH PARTIAL CLEAR LATE (ESPECIALLY W). MAY BE A FEW SHOWERS LINGERING ERN VA. LOWS TONIGHT ARE FORECAST TO RANGE FROM THE UPPER 60S TO MID 70S. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY/... THE FRONTAL BOUNDARY SETTLES IMMEDIATELY N OF THE REGION WEDNESDAY. OVERALL...THERE IS LITTLE FORCING...SO ONLY A ~20% POP IS FORECAST FOR MOST OF THE AREA...WITH THE EXCEPTION OF ~30% CLOSER TO THE COAST WHERE LOW-LEVEL MOISTURE WILL BE SOMEWHAT HIGHER. HIGHS ARE FORECAST TO ONCE AGAIN REACH THE UPPER 80S TO LOW 90S. PARTLY CLOUDY CONDITIONS ARE EXPECTED WEDNESDAY NIGHT WITH LOWS IN THE UPPER 60S TO LOW 70S. THE FRONT SAGS S INTO THE REGION BY THURSDAY. MEANWHILE...SHORTWAVE ENERGY IS EXPECTED TO TRACK INTO THE CENTRAL APPALACHIANS BY AFTERNOON. THE 00Z/30 NAM IS THE QUICKEST...WHILE THE 00/30 GFS/ECMWF/CMC LAG THE ENERGY TO THE W UNTIL AFTERNOON. AT THIS TIME...THE LATER CONSENSUS SOLUTION HAS BEEN FAVORED...WITH ONLY 20-30% POPS FORECAST IN THE MORNING...BEFORE BRINGING 40-50% INTO WRN PORTIONS BY LATER IN THE AFTERNOON...WITH 30-40% FARTHER E. HIGH TEMPERATURES ARE EXPECTED TO RANGE FROM THE LOW/MID 80S N...TO AROUND 90 SE WITH THE FRONT OVER THE REGION. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... UNSETTLED CONDITIONS SEEN THRU THE PERIOD AS A FRONTAL BOUNDARY BECOMES STALLED ACROSS THE REGION WITH SEVERAL S/W`S DROPPING SE IN THE OVERALL NW FLOW. TIMING OF ANY S/W (OR CONVECTIVE COMPLEX) RATHER PROBLEMATIC ATTM...SO WILL CARRY THE POPS THROUGH THE 12 HOUR PERIOD VERSUS TRYING TO GO WITH A MORE DIURNAL PATTERN. SOME CONSENSUS HAS DEVELOPED WITH RESPECT TO A SHORTWAVE TROUGH TRACKING ACROSS THE REGION THU NIGHT/EARLY FRI. THERE IS A POTENTIAL FOR HEAVY RAINFALL WITH THIS SYSTEM. A BROAD 50% POP IS FORECAST AT THIS TIME THU NIGHT/EARLY FRI...BEFORE TAPERING TO 30-40%. THEN BASICALLY 30-40% FOR THE REST OF THE PERIOD EXCEPT SUNDAY WHERE THE LATEST DATA IS HINTING AT A SOMEWHAT DRIER DAY (20-30 POP). TEMPS COOLEST FRI GIVEN WIDESPREAD CLOUD COVERAGE AND PCPN CHCS. HIGHS IN THE 80S. BOUNDARY LOCATION WILL PLAY A ROLE IN TEMPS FOR THE REST OF THE PERIOD...BUT MODEL TRENDS ARE FOR THE WARM FRONT TO EVENTUALLY LIFT NORTH OF THE FA PLACING REGION IN A MORE HUMID AIRMASS. THUS...HIGHS EACH DAY IN THE M80S-L90S. LOWS THURSDAY NIGHT U60S-L70S. OTHERWISE...LOWS IN THE 70S. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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VFR CONDITIONS PERSIST ACROSS AREA TERMINALS THROUGH THE TAF PERIOD. BEGINNING TO NOTICE SOME CU/SC PUSHING IN FROM THE W/SW ALONG A WEAK SFC TROUGH. SHRAS/TSTMS ARE PSBL THIS AFTN/EVENG ESPECIALLY AT RIC/SBY...BUT CHANCE IS TOO LO TO INCLUDE IN THE TAFS ATTM. WINDS WILL REMAIN S-SW AND COULD SEE AN OCCASIONAL GUST UP TO ~20 KT THROUGH LATE AFTN. CURRENTLY NOTING NARROW LINE OF CONVECTION LIFTING NORTHEAST FROM THE WESTERN CAROLINAS. COULD SEE A BRIEF PERIOD OF SHOWERS TONIGHT AFTER 23Z IN ASSOCIATION WITH THIS ACTIVITY, AND AS UPPER DISTURBANCE PUSHES ACROSS TONIGHT. BEST CHANCE WILL BE MAINLY TO THE W OF KRIC. HOWEVER, FORECAST CONFIDENCE REMAINS LOW THAT THIS CONVECTION WILL IMPACT ANY ONE TERMINAL AND WITH ANY CONVECTION STILL AT LEAST 6 HRS OFF, HV HELD OUT OF THE TAF FOR NOW. OUTSIDE OF ANY SHOWERS, EXPECT SOME LOWER CIGS MOVING IN OVERNIGHT ON SW FLOW, AND DROPPED DOWN TO LOW END VFR NEAR MVFR CATEGORY OVERNIGHT. OUTLOOK...A FRNTAL SYSTM SLOWLY APPROACHES FM THE W DURING THE REST OF THE WEEK. MAINLY VFR CONDS WILL PREVAIL THROUGH THE PERIOD. THERE WILL BE CHANCES FOR AFTN/EVENG SHRAS/TSTMS EACH DAY WITH THE HIGHEST CHANCES ON THU AND FRI WITH THE FRONT IN THE VICINITY, BUT THE PERIOD OF MOST WIDESPREAD RESTRICTION AND CHCS FOR VSBY RESTRICTIONS COME THURSDAY AFTN/FRIDAY MORNING.
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&& .MARINE... HI PRES REMAINS OFFSHORE TDA AS LO PRES TRAVERSES THE GREAT LAKES REGION. BETWEEN THESE TWO FEATURES...SLY FLOW WILL INCREASE THRU THE DAY ACROSS THE MID ATLC. MARGINAL SCA REMAINS IN EFFECT FOR THE BAY STARTING MIDDAY AS THE PRESSURE GRADIENT INCREASES...WITH WINDS STAYING SUB-SCA OVER THE RIVERS/SOUND/CSTL WTRS. THE SCA ENDS TNGT...WITH WEAKER SLY/SWLY FLOW (10-15 KT) EXPECTED FOR WED AHEAD OF AN APPROACHING COLD FRNT. THE FRNT DROPS INTO THE AREA FM THE NW ON THU...WITH WINDS BCMG LIGHT AND VRB THU AND FRI AS THE FRNT STALLS OVER THE REGION. WAVES AVG 1-2 FT AND SEAS AVG 2-4 FT THRU THE WEEK. SEAS MAY COME CLOSE TO 5 FT OVER NRN WTRS AT TIMES. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT WEDNESDAY FOR ANZ630>632- 634. && $$ SYNOPSIS...AJZ/MAM NEAR TERM...AJZ/SAM SHORT TERM...AJZ LONG TERM...AJZ/MPR AVIATION...MAS/MAM MARINE...MAS

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