Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 311718 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 118 PM EDT SUN AUG 31 2014 .SYNOPSIS...
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THE REGION WILL STAY BETWEEN A LARGE HIGH PRESSURE SYSTEM OVER THE SOUTHEAST UNITED STATES AND A COMPLEX LOW PRESSURE SYSTEM CROSSING THE GREAT LAKES. DISTURBANCES PASSING BETWEEN THESE TWO FEATURES WILL COMBINE WITH HEAT AND HUMIDITY TO RESULT IN PERIODIC CHANCES OF SHOWERS AND STORMS INTO EARLY WEEK. A COLD FRONT FINALLY ARRIVES FROM THE NORTH WEDNESDAY INTO THURSDAY.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 950 AM EDT SUNDAY... INITIAL BAND OF EARLY MORNING SHOWERS HAS ALREADY FADED UPON CROSSING THE BLUE RIDGE SO UPDATED TO CUT BACK ON POPS THROUGH EARLY AFTERNOON. ALSO EXPECTING MORE SUNSHINE ACROSS MOST OF THE REGION THIS MORNING PER LATEST VISIBLE PICS WITH THE MAIN AXIS OF DEEP MOISTURE REMAINING WEST OF THE MOUNTAINS. THIS SHOULD ALLOW FOR A BIT MORE INSTABILITY THIS AFTERNOON GIVEN SW FLOW AND LOW LEVEL MOISTURE. HOWEVER MORNING SOUNDINGS SHOWING CAPPING JUST OFF THE SURFACE AND A MORE SIGNIFICANT MID LEVEL INVERSION ABOVE WHICH SHOULD ACT TO DETER ANY WIDESPREAD ADDED CONVECTIVE COVERAGE UNTIL PERHAPS EARLY THIS EVENING AT BEST. OTRW APPEARS BETTER AFTERNOON CHANCES WILL BE ALONG THE SOUTHERN BLUE RIDGE PER LOW LEVEL SW FLOW...HIGHER THETA-E AND FORECAST INSTABILITY...AS WELL AS OVER THE NW WHERE THE UPPER SHEAR AXIS LOOKS TO FOLD INTO LATE BEHIND THE PASSING WAVE FROM THIS MORNING. ALSO SOME ADDITION OF DIFFERENTIAL HEATING ON THE EDGE OF THE FAR WESTERN CLOUD SHIELD MAY ALONG WITH OROGRPAHICS AID INITIAL DEVELOPMENT AT LEAST ON A SCATTERED BASIS. THUS BASICALLY KEPT GOING LOW LIKELY POPS IN THESE SPOTS WHILE TRIMMING BACK OVER THE PIEDMONT WHERE MORE UNDER THE RESIDUAL RIDGE AND WITHOUT MUCH FOCUS FOR NOW SIMILAR TO THE LATEST HRRR. THICKNESS OFF 12Z RAOBS REMAINS QUITE WARM...AND GIVEN A MILD START INCLUDING MORE HEATING EARLY...WOULD EXPECT READINGS OUT EAST TO POSSIBLY REACH 90/LOW 90S WITH MID/UPPER 80S ELSW FROM THE BLUE RIDGE EAST. SHOULD BE A LITTLE COOLER FAR WEST PER CLOUDS BUT EVEN THERE APPEARS UPPER 70S/LOW 80S LIKELY. LARGER BAND OF SHOWERS WILL PIVOT ENOUGH TO REACH SOUTHEAST WEST VIRGINIA TONIGHT...SIMILAR TO ORIENTATION OF WPC QPF FORECAST AND THE 00Z GFS...SLIGHTLY FARTHER SOUTH THAN THE 00Z NAM. HUMID AIR MASS AND VERY MILD DEW POINTS WILL RESULT IN LITTLE COOLING TONIGHT. USED WARMER MET GUIDANCE FOR OVERNIGHT LOWS. && .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 AM EDT SUNDAY... PROGRESSIVE NORTHERN STREAM FLOW WILL PRODUCE TROUGHING ACROSS THE NORTHEAST BY MONDAY MORNING. SEVERAL SHORTWAVES TRAVERSE ACROSS THE MID ATLANTIC REGION. THESE UPPER DISTURBANCES WILL SHAPE THE TIMING OF CONVECTION. AN UPPER DISTURBANCE WILL SHIFT ACROSS THE GREAT LAKES FROM THE OHIO RIVER VALLEY MONDAY MORNING...ENHANCING THE CHANCES OF SHOWERS IN THE WEST-NORTHWEST. THE SUBTROPICAL BERMUDA HIGH PRESSURE WILL REMAIN IN PLACE. A VERY MOIST SOUTHWEST FLOW WILL CONTINUE LABOR DAY. HIGH TEMPERATURES MONDAY WILL RANGE FROM THE UPPER 70S IN THE MOUNTAINS TO THE LOWER 90S IN THE PIEDMONT. SCATTERED SHOWERS AND THUNDERSTORMS REDEVELOP MONDAY AFTERNOON WITH SOLAR HEATING. SOME OF THE THUNDERSTORMS MAY CONTAIN LOCALLY HEAVY RAINS. RAINFALL WILL DIMINISH QUICKLY AS THE SUN SETS AND SHOULD SEE DRY...ALBEIT WARM AND MUGGY...CONDITIONS PERSIST THROUGH MONDAY NIGHT. LOW TEMPERATURES MONDAY NIGHT WILL VARY FROM THE LOWER 60S IN THE WEST TO THE AROUND 70 IN THE EAST. DEEP LAYER MOISTURE INCREASES TUESDAY AS ANOTHER LOW PRESSURE SYSTEM MOVING ACROSS EASTERN CANADA WILL DRAG A COLD FRONT SOUTH OF THE GREAT LAKES. BETTER CHANCES FOR CONVECTION WILL BE FOUND ACROSS THE HIGHER TERRAIN...WHERE STRONGER UPPER LEVEL SUPPORT WILL BE LOCATED. HIGHS TUESDAY WILL CLIMB INTO THE LOWER 80S IN THE MOUNTAINS TO THE LOWER 90S IN THE PIEDMONT. MODEL TREND HAVE BEEN SLOWING THE TIMING OF THE FRONT AND EXPECT THE COLD FRONT WILL STALL FURTHER NORTH TUESDAY NIGHT DUE TO THE UPPER LEVEL RIDGING IN PLACE ACROSS THE SOUTHEAST STATES. LOWS WILL FALL INTO THE MID 60S TO THE LOW 70S TUESDAY NIGHT. KEPT THE HIGHEST POPS ACROSS THE SOUTH WEDNESDAY ALONG THE STALLED FRONTAL BOUNDARY. WHILE...HIGH PRESSURE PASSING ACROSS THE GREAT LAKES SHOULD KEEP THE NORTHERN HALF OF OUR AREA DRY. HIGHS WEDNESDAY WILL BE FROM THE LOWER 80S IN THE WEST TO AROUND 90 DEGREES IN THE EAST. SLOWLY DRY THINGS OUT WEDNESDAY NIGHT FROM NORTH TO SOUTH. LOW TEMPERATURES WILL DROP INTO THE UPPER 50S IN THE NORTHWEST MOUNTAINS TO NEAR 70 DEGREES IN THE PIEDMONT. && .LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 330 PM SATURDAY... UPPER LEVEL RIDGING WILL SHIFT NORTHWARD FROM THE SOUTHEAST STATES OVER THE MID ATLANTIC DURING THE SECOND HALF OF THE WEEK...RESULTING IN BOTH WARMER TEMPERATURES AND WEAKER WINDS ALOFT. THIS WILL MAKE FOR MORE STABLE CONDITIONS THAT WILL KEEP SHOWER AND THUNDERSTORM ACTIVITY DISORGANIZED THROUGH THE PERIOD. ANY RAINFALL WHICH DEVELOPS WILL BE DRIVEN MAINLY BY DAYTIME HEATING...WHICH WILL ALLOW THIS ACTIVITY TO FIZZLE AFTER SUNSET. HIGH PRESSURE WILL PASS OFF THE NEW ENGLAND COAST ON THURSDAY... RESULTING IN A WEAK WEDGING PATTERN WITH EASTERLY FLOW OFF THE ATLANTIC. THIS WILL LIKELY BE THE DRIEST DAY OF THE PERIOD. WINDS WILL SHIFT SOUTHWESTERLY AGAIN ON FRIDAY AS ANOTHER COLD FRONT SINKS SOUTH FROM THE GREAT LAKES. STRONGER FLOW OFF THE ATLANTIC WILL RESULT IN INCREASED MOISTURE...AND WILL EXPECT SPOTTY SHOWER AND THUNDERSTORM ACTIVITY DURING THE AFTERNOON AND EVENING. EXPECT TEMPERATURES TO REMAIN SLIGHTLY ABOVE NORMAL FOR THE PERIOD. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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AS OF 1255 PM EDT SUNDAY... OVERALL VFR CONDITIONS WILL BE DETERIORATING FROM WEST TO EAST THROUGH THE REST OF THE AFTERNOON AS AN AXIS OF LOWER CLOUDS JUST ENTERING THE MOUNTAINS PUSHES EAST. THIS SHOULD BRING A FEW HOURS OF MVFR TO KLWB/KBLF THE REMAINDER OF THE AFTERNOON WITH PASSING SHRA/ISOLATED TSRA POSSIBLY RESULTING IN LOCAL MVFR VSBYS INTO EARLY THIS EVENING. CANOPY LIKELY TO DIMINISH SOME HEADING EAST TO THE BLUE RIDGE SO KEEPING ELSW VFR WHILE DELAYING TIMING OF ANY SHRA/TSRA A COUPLE HOURS AT KBCB/KROA/KLYH...AND LEAVING OUT MENTION AT KDAN FOR NOW. LATEST GUIDANCE SUGGESTS THAT THE BEST COVERAGE OF CONVECTION WILL BE OVER THE NW THIS EVENING WITH PERHAPS A BAND MOVING EAST OFF THE RIDGES BEFORE FADING BY MIDNIGHT. THUS LEFT IN EITHER HIGH END MVFR TO LOW END VFR CIGS OVER THE WEST THIS EVENING WITH SOME PREVAILING VFR/MVFR VSBYS IN SHRA POSSIBLE. OTRW WILL KEEP A VCSH MENTION FOR A FEW HOURS THIS EVENING THEN TREND TOWARD MORE PATCHY FOG/STRATUS OVERNIGHT. HOWEVER LATEST SREF PROGS SUGGEST LIMITED DENSE FOG COVERAGE GIVEN MID CLOUDS SO ONLY LOWERING KLWB TO IFR BY MORNING WITH BRIEF MVFR AT MOST OTHER LOCATIONS EXCLUDING KROA BY DAYBREAK MONDAY. LAST MID LEVEL WAVE WILL PASS TO THE NW BY EARLY MONDAY LEAVING THE AREA IN BETWEEN THIS FEATURE AND THE NEXT UPSTREAM COLD FRONT. DEEP WESTERLY FLOW COMBINED WITH LACK OF FOCUS AND DECENT MIXING SHOULD INHIBIT MUCH CONVECTION DURING MONDAY ESPCLY IF EARLY MID DECK PERSISTS. THIS SUPPORTS GOOD FLYING CONDITIONS FOR MUCH OF MONDAY AFTER EARLY LOW CLOUDS/FOG FADE WITH ONLY ISOLATED CONVECTION LIKELY. EXTENDED DISCUSSION... UPPER TROUGH AND ITS ASSOCIATED COLD FRONT WILL APPROACH FROM THE NORTHWEST TUESDAY WITH SIMILAR ISOLATED SHOWERS/STORMS EXPECTED DURING THE DAY AHEAD OF THE BOUNDARY. FRONT SETTLES CLOSER TUESDAY NIGHT INTO WEDNESDAY...WHEN BETTER COVERAGE OF SHRA/TSRA IS EXPECTED...AND THEN ACROSS THE SOUTH THURSDAY WHERE THE BOUNDARY STALLS. HOWEVER LOW CONFIDENCE ON THE TIMING AND SOUTHWARD POSITION OF THE BOUNDARY AT THIS POINT. THUS APPEARS MAINLY VFR ON TUESDAY...WITH PERIODS OF MVFR WEDNESDAY-THURSDAY IN MORE ORGANIZED MAINLY AFTERNOON/EVENING CONVECTION...AND MVFR/IFR UNDER EARLY MORNING FOG IN THE VALLEYS AND WHERE EARLIER HEAVY RAIN OCCURRED. FRONT WASHES OUT TO THE SOUTH OF THE AREA FRIDAY WITH MORE DIURNAL NATURE SHOWERS AND STORMS...OTRW VFR.
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&& .EQUIPMENT... AS OF 730 AM EDT FRIDAY ... THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...WILL BE OUT OF SERVICE UNTIL FURTHER NOTICE. A PART HAS BEEN BACK-ORDERED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS/JH NEAR TERM...AMS/JH SHORT TERM...KK LONG TERM...NF AVIATION...AMS/JH EQUIPMENT...AMS

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