Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 281934 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 334 PM EDT THU AUG 28 2014 .SYNOPSIS... A WEAK COLD FRONT WILL STALL ACROSS NORTH CAROLINA TONIGHT...THEN HEAD BACK NORTH AGAIN FOR FRIDAY INTO SATURDAY. A STRONGER UPPER SYSTEM WILL BRING A BETTER THREAT FOR SHOWERS AND STORMS TO CLOSE OUT THE LABOR DAY WEEKEND. && .NEAR TERM /THROUGH FRIDAY/... AS OF 300 PM EDT THURSDAY... BACKDOOR FRONT EXPECTED TO TRACK SLOWLY SOUTH THIS EVENING INTO NC. MODELS HAVE KEPT ISOLATED POPS ACROSS THE SOUTHERN CWA THRU LATE EVENING...ESPECIALLY EAST OF DAN. OVERNIGHT...THE 12Z NAM HAS INCREASED CLOUD COVER THINKING CU FIELD THIS AFTERNOON FLATTENS THIS EVENING THEN STICKS UNDER INVERSION OVERNIGHT. COMBINED WITH EAST-NE FLOW THIS COULD LEAD TO SOME STRATUS IN THE MORNING. KEPT SKY OVERALL TONED DOWN FROM THE NAMDNG BUT THINK AREAS OVER THE FOOTHILLS AND PIEDMONT COULD BE MOSTLY CLOUDY IN THE MORNING. PATCHY FOG WILL FORM IN THE WEST LATE TONIGHT WHERE SKIES SHOULD STAY AT WORST PARTLY CLOUDY...THOUGH CANNOT RULE OUT SOME SPILL OVER THE LOWER CLOUDS INTO THE NEW RIVER VALLEY. LOWS TONIGHT WILL BE A LITTLE COOLER IN THE NORTH PER DRIER AIR WITH READINGS IN THE MID TO UPPER 50S...WHILE MOST OF US EXPERIENCE LOWS IN THE LOWER TO MID 60S. FRIDAY...FRONT STARTS WORKING BACK NORTH ACROSS US. MODELS ARE AGREEMENT THAT LIFT AND MOISTURE WILL BE LIMITED OVER US BUT CANNOT RULE OUT ISOLATED SHRA/TSRA IN THE REGION. BEST LIFT WILL BE ACROSS THE SW VA MTNS TOWARD TN...SO HAVE 30ISH POPS HERE. ANOTHER AREA IS OVER THE RALEIGH-DURHAM AREA AND EAST...SO MAY SEE SOME SCATTERED STORMS TOWARD YANCEYVILLE. SE WINDS WILL BE KEEPING TEMPS FROM GETTING TOO HIGH...PLUS DEALING WITH POTENTIAL LOW CLOUDS INTO MORNING OVER THE EAST. HIGHS WILL MAY WORK OUT TO BE HOMOGENEOUS ACROSS THE ENTIRE CWA OUTSIDE THE HIGHER ELEVATIONS WITH LOWER TO MID 80S. SE FLOW DOWNSLOPE WARMING MAY INCREASE TEMPS OVER THE MTN EMPIRE BUT STORMS FIRING UP IN THE AFTERNOON SHOULD PREVENT IT FROM TOPPING OUT CLOSE TO THE MAV GUIDANCE OF UPPER 80S. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... AS OF 310 PM EDT THURSDAY... UPPER RIDGE EXPECTED TO SHIFT EAST AS STRONGER UPPER TROUGH MOVES FROM THE UPPER MIDWEST INTO THE GREAT LAKES. MODELS AGREE THAT A SRN STREAM UPPER SHORTWAVE WITH ENHANCEMENT IN THE JET WILL STREAK OVER THE GULF COAST STATES AND ACROSS THE WRN SLOPES OF THE APPALACHIANS SUNDAY. FOR SATURDAY THOUGH...MAINLY LOOKING WEAK FLOW ALOFT WITH SOME CONVERGENCE ACROSS THE MTNS PER SSE FLOW. MODELS ARE FAVORING A BIT OF CONVECTION WITH THE LEE TROUGH IN THE EAST...MAINLY FROM THE ERN WV PANHANDLE SOUTHEAST TOWARD THE TIDEWATER. THINK THE AIRMASS WILL BE UNSTABLE AND MOIST ENOUGH TO TRIGGER A FEW STORMS BUT OVERALL UPPER SUPPORT IS LACKING SO ONLY SEEING ISOLATED COVERAGE OVER THE MTNS AND NORTH OF A ROANOKE TO DANVILLE LINE. MORE SUN SATURDAY WILL BRING TEMPS TOWARD 90 OUT EAST WITH MID 80S WEST. SAT NIGHT...MAIN AXIS OF CONVECTION WILL RUN FROM MS-KY...WITH LITTLE TO NO CHANCE OF SHOWERS EAST OF THE BLUE RIDGE AFTER FRIDAY EVENING STORMS WANE. WITH THE UPPER SUPPORT TRACKING CLOSER WILL HAVE AT LEAST SLIGHT CHANCE INTO THE MTNS LATE. SUNDAY LOOKS ACTIVE AS THE SHORTWAVE SHIFTS ACROSS KY INTO NRN WV...WITH STRONG CONVERGENCE AND LIFT. WILL SEE HIGH CHANCE/LIKELY POPS. LOOKS LIKE CLOUD COVER COULD ARRIVE SOON ENOUGH TO KEEP INSTABILITY LOWER...BUT ENOUGH UPPER SUPPORT/SHEAR IN THE WEST WHERE A FEW STORMS COULD PRODUCE GUSTY WINDS. HIGHS SUNDAY WILL RANGE FROM THE UPPER 70S MTNS TO UPPER 80S SE. OVERALL...LABOR DAY WEEKEND LOOKING VERY WARM/HOT/HUMID. SATURDAY NOT TOO BAD RAIN WISE...BUT STAY COOL WHILE DRINKING PLENTY OF WATER IF OUTDOORS. SUNDAY APPEARS POOR FOR OUTDOOR ACTIVITIES. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 300 PM EDT THURSDAY... MUCH OF THE LONG TERM PERIOD WILL BE INFLUENCED BY A MEAN UPPER RIDGE THAT WILL INITIALLY RESIDE ALONG AND OFF THE SOUTHEAST COAST...WHICH GRADUALLY RETROGRESSES AND EXPANDS WESTWARD INTO THE GULF COAST STATES BY THE END OF THE FORECAST PERIOD. SOUTHEASTERN RIDGE WILL INITIALLY BE STRONG ENOUGH TO DEFLECT ANY NORTHERN STREAM ENERGY AWAY FROM THE BLACKSBURG FORECAST AREA...WITH MAIN BAROCLINIC ZONE REMAINING FROM THE NORTHERN PLAINS EAST INTO AND THROUGH THE GREAT LAKES INTO NEW ENGLAND. HOWEVER...TAP OF TROPICAL MOISTURE RIDING AROUND PERIPHERY OF SOUTHEASTERN RIDGE LIKELY TO REMAIN OVER/NEAR THE BLACKSBURG FORECAST AREA THROUGH AT LEAST MONDAY OR MONDAY NIGHT...MAINTAINING THREAT FOR MAINLY DIURNALLY DRIVEN SCATTERED SHOWERS AND THUNDERSTORMS...SOME OF WHICH MAY BE ACCOMPANIED BY LOCALLY HEAVY RAIN CONSIDERING RELATIVELY HIGH PRECIPITABLE WATER VALUES EXPECTED OVER THE AREA. GRADUAL RETROGRESSION OF UPPER RIDGE INTO NORTHERN GULF COAST REGION DURING THE MIDWEEK PERIOD SHOULD BE SUFFICIENT TO ALLOW WINDS ALOFT TO VEER SUCH THAT INFLUENCE OF TROPICAL MOISTURE TAP GRADUALLY WANES...ONLY TO BE REPLACED BY MORE AGGRESSIVE SOUTHWARD INTRUSION OF NORTHERN STREAM ENERGY AND ASSOCIATED SCATTERED SHOWERS/STORMS IN ADVANCE OF AN ACCOMPANYING DECAYING COOL FRONT INTO THE MID APPALACHIAN AND MID ATLANTIC REGION IN TUESDAY-WEDNESDAY TIMEFRAME. PUSH OF POST-FRONTAL SLIGHTLY DRIER AIR MAY BE STRONG ENOUGH TO REDUCE THREAT FOR PRECIPITATION ACROSS AREAS NORTH OF INTERSTATE 64 BY THURSDAY...BUT WITH AT LEAST A CHANCE THREAT FOR SHOWERS/STORMS REDEVELOPING BY AFTERNOON ACROSS THE SOUTHWESTERN MOUNTAINS CLOSER TO DECAYING FRONTAL BOUNDARY AND PROXIMITY TO HIGHER THETA-E AIR. PLENTY OF CLOUD COVER AND DEWPOINTS PRIMARILY IN THE 60S SHOULD ENSURE THAT TEMPERATURES REMAIN CLOSE TO SEASONAL AVERAGES...MAINLY MID 70S TO LOWER 80S ACROSS THE HIGHER ELEVATIONS BY DAY WITH UPPER 80S ACROSS THE PIEDMONT...WITH MAINLY 60S AT NIGHT. INTRUSION OF SLIGHTLY COOLER/DRIER POST-FRONTAL AIR FROM THE NORTHEAST MAY ALLOW TEMPERATURES TO BE A FEW DEGREES COOLER ON THURSDAY. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... AS OF 130 PM EDT THURSDAY... EXPECT MAINLY SCT CU FIELD THIS AFTERNOON IN THE 3-5KFT RANGE...BKN AT TIMES SOUTH OF A BLF-BCB-DAN LINE. ISOLATED/SCATTERED SHRA/TSRA TO FORM FROM GEV/TNB ENE TOWARD DAN/FVX THIS AFTERNOON. COVERAGE IS SUCH THAT NO MENTION IN TAFS NEEDED. THIS EVENING FRONT WILL SLOW OVER THE NC/VA LINE...GRADUALLY SINKING SWWD THROUGH FRI MORNING. MAY STILL SEE SHOWERS/STORMS LINGERING SOUTH AND EAST OF DAN. MAIN CONCERN OVERNIGHT IS HOW MUCH OF A HIGH PRESSURE WEDGE SETS UP FROM THE NORTH...WITH THE 12Z NAM SHOWING MODEST AMOUNT OF LOWER CIGS FROM THE NEW RIVER VALLEY/BCB EAST TO LYH/DAN. GIVEN DRY NATURE OF THE AIRMASS TO THE NORTH...WHILE TAKING INTO ACCOUNT THE MOIST AIRMASS OVERHEAD NOW...THINK A LEANING TOWARD THE NAM IS NEEDED...BUT TAKING INTO THE OTHER MODELS LACKING IN CLOUD COVER. WILL ADVERTISE SCT/BKN VFR CIGS AT LYH/DAN WITH SOME FOG POSSIBLE AT DAN IF IT STORMS NEARBY. FURTHER WEST...THE LACK OF CLOUD COVER AND SOME GROUND MOISTURE MAY ALLOW FOR FOG FORMATION...SO ADDED IFR/MVFR VSBYS AT BLF/LWB AND BCB AFTER 08Z. SHOULD SEE IMPROVEMENTS TO VFR AFTER 13-14Z AT ALL SITES FRIDAY. EXTENDED DISCUSSION... THE WEAK FRONT IS FORECAST TO RETURN NORTH AS A WARM FRONT FRIDAY. WIDELY SCATTERED SHRA/TSRA ARE EXPECTED ALONG THIS BOUNDARY FRIDAY AND SATURDAY...WITH THE GREATEST COVERAGE DURING THE PEAK HEATING OF THE DAY. WHERE SHRA/TSRA OCCUR EXPECT BRIEF PERIODS OF SUB VFR CONDITIONS. AN AREA OF LOW PRESSURE IS FORECAST TO MOVE THROUGH THE GREAT LAKES SATURDAY NIGHT AND SUNDAY...THE ASSOCIATED COLD FRONT TRAILING SOUTH AND MOVING ACROSS THE OHIO/TN VALLEYS. SHOWERS AND THUNDERSTORMS WILL LIKELY BE ASSOCIATED WITH THIS FRONT...THIS ACTIVITY SPREADING EAST INTO THE CENTRAL APPALACHIANS SUNDAY AND MONDAY. SHOWER COVERAGE SUNDAY/MONDAY IS EXPECTED TO BE MORE WIDESPREAD AS COMPARED TO FRIDAY AND SATURDAY. && .EQUIPMENT... AS OF 100 PM EDT THURSDAY ... THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...REMAINS OUT OF SERVICE. A PART HAS BEEN ORDERED. REPAIRS WILL BE DONE THIS FRIDAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS/WP NEAR TERM...WP SHORT TERM...WP LONG TERM...WERT AVIATION...AMS/WP EQUIPMENT...AMS

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