Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 030003 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 803 PM EDT THU JUL 2 2015 .SYNOPSIS... A FRONTAL BOUNDARY WILL REMAIN DRAPED ACROSS THE AREA FOR THE NEXT SEVERAL DAYS. THERE WILL BE SEVERAL WAVES OF LOW PRESSURE PASSING ACROSS THE BOUNDARY KEEPING THE THREAT OF SHOWERS AND THUNDERSTORMS IN OUR FORECAST THROUGH THE WEEKEND. && .NEAR TERM /THROUGH FRIDAY/... AS OF 300 PM EDT THURSDAY... DESTABILIZATION OF AIRMASS OVER THE PIEDMONT HAS ALLOWED FOR DEEPER CONVECTION TO ERUPT FROM TRIAD NC AREA NE TO SOUTHSIDE VA. FURTHER NORTH AND WEST THE AIRMASS IS STABLE. THE 16Z HRRR BLENDED WITH THE RAP/NAM SEEM REASONABLE THRU EARLY EVENING. THIS SOLUTION TAKES SHOWERS EAST AND OUT OF THE PIEDMONT BY 00Z...WITH ISOLATED/SCATTERED SHOWERS AROUND FOR THE MAJORITY OF THE NIGHT. THE NEXT UPSTREAM WAVE OVER THE WRN OHIO VALLEY IS EXPECTED TO TRACK ESE INTO THE SRN/CENTRAL APPALACHIANS BEFORE DAWN. STARTING TO INCREASE POPS TO LIKELY SOUTHWEST OF BLF BY THAT TIME AND TRACK THE SHOWERS EAST TOWARD SOUTHSIDE VA BY 12Z. CONFIDENCE IS HIGH THAT SHOWERS WILL BE AROUND IN THE MORNING...THOUGH SOME MINOR TRACK DIFFERENCES ON WHERE THE NARROWER BAND OF HEAVIER SHOWER SWINGS IN. CONVECTION WILL BE LIMITED SO NOT THINKING OF ANY THUNDERSTORM OR FLOODING ISSUES AT THIS TIME. FOR FRIDAY...THE MODELS KEEP THE CLOUDS AROUND SO NOT REALLY EXPECTING SOLAR INSOLATION TO DESTABILIZE THE AIRMASS. YET ANOTHER SHORTWAVE PUSHES ACROSS KY/OHIO INTO WV/NRN VA BY AFTERNOON WHILE ANOTHER WAVE MOVES ACROSS SRN TN. MODELS ARE VARYING ON WHO GETS THE HEAVIER RAIN BUT THE OVERALL SOLUTION SUGGESTS THE ENTIRE FORECAST WILL LIKELY SEE MEASURABLE RAINFALL FRIDAY. OUR FORECAST RAINFALL TOTAL FROM THIS AFTERNOON THROUGH FRIDAY AFTERNOON SHOWS AN INCH OR LESS. SINCE WE HAVE LOWER CONFIDENCE ON EXACT TRACK OF ANY HEAVIER BANDS OF DEEP CONVECTION...THE THREAT OF FLOODING WILL BE ISOLATED...AND WILL HOLD OFF ON ANY FLASH FLOOD WATCHES. WILL CONTINUE TO MENTION HEAVY RAIN THREAT IN THE HAZARDOUS WEATHER OUTLOOK. THE AIRMASS WILL NOT CHANGE MUCH...SO LOWS TONIGHT WILL ONLY BE ABOUT 5-10 DEGREES COOLER THAN CURRENT TEMPS...AND WILL SEE SIMILAR RESULTS FOR HIGHS FRIDAY...RANGING FROM THE LOW TO MID 70S WEST TO UPPER 70S TO AROUND 80. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... A BROAD UPPER LEVEL TROUGH OVER THE GREAT LAKES AND OHIO VALLEY WILL MAKE FOR A COMPLICATED LOW CONFIDENT FORECAST THROUGH THE WEEKEND. ADDING TO THE DIFFICULT FORECAST ARE TWO AREAS OF WEAK LOW PRESSURES...ONE OVER THE OHIO VALLEY AND ANOTHER ACROSS VA/NC PIEDMONT. MODELS ARE UNSURE WHICH SURFACE LOW BECOMES THE DOMINATE ONE. THE ONE THAT DOES WILL HAVE THE STRONGER STORMS...EITHER ALONG THE WESTERN SLOPES OF APPALACHIANS OR ALONG THE COAST. FOR THIS FORECAST PACKAGE...WILL HAVE THE HIGHEST POPS ACROSS THE MOUNTAINS WITH THE UPPER LEVEL TROUGH REMAINING TO THE WEST AND A SERIES OF SHORT WAVES APPROACHING THE REGION THROUGH THE WEEKEND. WILL ALSO OPT FOR MORE SHOWERS THAN THUNDERSTORMS AS CLOUD COVER SHOULD BE THICK AND PREVAIL THROUGH MOST OF THE PERIOD. FOR OVERALL COVERAGE...SATURDAY LOOKS LIKE THE BETTER DAY. ON SUNDAY...THE OHIO VALLEY LOW MAY SHIFT EAST AND MERGER WITH THE MID ATLANTIC LOW. THIS MAY PUSH A BOUNDARY SOUTH ACROSS THE AREA...KEEPING THE SOUTHERN HALF WET WHILE BECOMING RAIN-FREE AND MOST CLOUDY NORTH. WITH RAIN AND THICK CLOUDS OVER THE REGION...TEMPERATURES WILL BE SLIGHTLY COOLER THAN NORMAL THIS HOLIDAY WEEKEND. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 305 PM EDT THURSDAY... MODELS ARE CONVERTING THE UPPER LEVEL TROUGH TO A CUT-OFF LOW OVER VIRGINIA-NORTH CAROLINA ON MONDAY. MEANWHILE AT THE SURFACE...HIGH PRESSURE OVER NEW ENGLAND WILL WEDGE DOWN THE MID ATLANTIC COAST...LIKELY TO HANG AROUND UNTIL TUESDAY. WITH A SURFACE LOW OVERHEAD...CLOUDY SKIES AND LIGHT RAIN IS A GOOD BET...ESPECIALLY ALONG AND EAST OF THE BLUE RIDGE. THE WEDGE SHOULD ERODE BY WEDNESDAY WITH THE CLOSED LOW OPENING TO A TROUGH AND LIFTING NORTH AS A COLD FRONT APPROACHES FROM THE WEST. BASED ON THE SLOWER TIMING OF THE MODELS...SHOWERS WITH THE FRONT COULD ARRIVE WEDNESDAY NIGHT OR POSSIBLY WAITING UNTIL THURSDAY. TEMPERATURES WILL BE COOLER THAN NORMAL MONDAY AND TUESDAY WITH THE WEDGE IN PLAY...THEN WARM TO NEAR NORMAL BEFORE THE FRONT MOVES THROUGH THURSDAY. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... AS OF 800 PM EDT THURSDAY... WITH THE PASSAGE OF A COLD FRONT ACROSS THE AREA INTO NORTHERN NORTH CAROLINA...WEAK HIGH PRESSURE HAS BECOME WEDGED AGAINST THE MOUNTAINS...SUPPORTING LIGHT EAST NORTHEASTERLY WIND FLOW AS FAR WEST AS KBCB. WHILE CEILINGS HAVE IMPROVED TO HIGH MVFR/VFR FOR MUCH OF THE AREA EARLY THIS EVENING...EASTERLY WIND FLOW AND SHOWER ACTIVITY WILL SUPPORT A RETURN OF LOW CEILINGS OVERNIGHT...MAINLY DURING THE 06Z TO 09Z TIMEFRAME. ALSO EXPECT POCKETS OF FOG TO DEVELOP...ALTHOUGH MID AND HIGH CLOUDS HOLDING ACROSS THE REGION WILL KEEP FOG FORMATION LIMITED. FOR FRIDAY...LOW CEILINGS WILL TAKE UNTIL LATE MORNING/EARLY AFTERNOON TO RISE TO LOW END VFR. EVEN THEN...SCATTERED MVFR CEILINGS WILL REMAIN ACROSS THE AREA. ANOTHER LOW PRESSURE SYSTEM WILL APPROACH FROM THE WEST...RESULTING IN ANOTHER ROUND OF SHOWERS EARLY IN THE AFTERNOON. SEE A POTENTIAL FOR THUNDERSTORM ACTIVITY DURING LATE AFTERNOON AND THE EVENING...ESPECIALLY ACROSS THE PIEDMONT DUE TO THE INCREASED SURFACE CONVERGENCE ASSOCIATED WITH THE EASTERLY FLOW. THUNDERSTORM CHANCES IMPROVE FURTHER STILL IF CLOUDS MANAGE TO BREAK OUT FOR A FEW HOURS DURING THE AFTERNOON... ALLOWING SUNSHINE TO REACH THE SURFACE...WHICH WILL HELP THE ATMOSPHERE DESTABILIZE. EXTENDED AVIATION DISCUSSION... THE REGION WILL REMAIN IN A GENERAL NORTHWEST FLOW PATTERN ON SATURDAY...AND AGAIN EXPECT ANOTHER ROUND OF SHOWERS AND STORMS AS ANOTHER UPPER LEVEL DISTURBANCE PASSES ACROSS THE FORECAST AREA. VFR CONDITIONS ARE EXPECTED FOR THE MOST PART. THE EXCEPTIONS WILL COME AS TEMPORARY DECREASES WITHIN ANY HEAVIER RAIN SHOWERS OR THUNDERSTORMS...AND THEN LATE AT NIGHT AND EARLY MORNING DUE TO RIVER OR MOUNTAIN VALLEY FOG...ESPECIALLY IN AREAS THAT RECEIVED PRECIPITATION THE DAY BEFORE. SUNDAY INTO MONDAY...WHILE UPPER LEVEL HEIGHTS RISE DURING THE PERIOD...THERE REMAINS AN UPPER TROUGH MOVING OVER THE MID ATLANTIC DURING THIS TIME...SO STORMS ARE NEVER OUT OF THE FORECAST. && .EQUIPMENT... IT APPEARS THAT OBSERVATIONS FROM NON-NWS AWOS SITES ARE COMING BACK IN...BUT NO OFFICIAL WORD ON IF THE ISSUE IS FINALLY FIXED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...MBS/WP NEAR TERM...WP SHORT TERM...RCS LONG TERM...RCS AVIATION...NF/WP EQUIPMENT...

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