Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 040555 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 155 AM EDT TUE AUG 4 2015 .SYNOPSIS... HIGH PRESSURE WILL REMAIN ACROSS THE REGION THIS EVENING BEFORE WEAKENING AHEAD OF A COLD FRONT THAT WILL APPROACH FROM THE WEST LATE TONIGHT. THIS FRONT SHOULD CROSS THE AREA TUESDAY BEFORE STALLING OVER THE CAROLINAS TUESDAY NIGHT INTO WEDNESDAY. LOW PRESSURE WILL RIDE ALONG THE FRONT BRINGING A BETTER CHANCE FOR MORE WIDESPREAD SHOWERS AND STORMS THURSDAY INTO FRIDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 857 PM EDT MONDAY... FOCUS FOR THE NEAR TERM FORECAST IS ON THE EVOLUTION OF THUNDERSTORM CLUSTER ACROSS NE KY/SW OH THIS EVENING. THERE ARE SEVERAL FACTORS THAT SUGGEST THIS CLUSTER WILL WEAKEN BY THE TIME IT REACHES OUR FORECAST AREA. FIRST...THIS CLUSTER IS MOVING INTO A REGION OF LOWER THETA-E AIR. SECOND...IT IS MOVING INTO A REGION OF WEAKER LOW LEVEL INFLOW/WINDS. FINALLY...AS WE LOSE THE HEATING FROM THE SUN...INSTABILITY WILL CONTINUE TO DIMINISH. ALL OF THESE FACTORS LEAD US TO LEAN TOWARD MANY OF MESOSCALE MODEL SOLUTIONS OF WEAKENING THIS CLUSTER AS IT ENTERS OUR SE WV COUNTIES AFTER 03Z/11 PM EDT. STORMS MAY PROPAGATE SOUTH INTO RICHER THETA-E AIR/HIGHER INSTABILITY AXIS IN ERN KY. WILL CONTINUE TO KEEP CHC POPS IN OUR NW COUNTIES AFTER 03Z. WITH DEBRIS CLOUDINESS MOVING OVER THE AREA TONIGHT...ESPECIALLY IN THE WEST...PUSHED UP TEMPS A DEGREE OR TWO. AS A COLD FRONT SLOWLY MOVES THROUGH OUR AREA TUESDAY EXPECT SHOWERS AND STORMS TO DEVELOP TUESDAY AFTERNOON. MODELS APPEAR MORE BULLISH ON CONVECTIVE DEVELOPMENT WITH SLIGHTLY BETTER DYNAMICS BUT INSTABILITY IS LIMITED SO SEVERE THREAT WILL BE MARGINAL AT BEST AND CONFINED TO EASTERN SECTIONS AS PER THE CURRENT SPC DAY 2 OUTLOOK. WILL KEEP POPS IN THE CHANCE CATEGORY AND WAIT TO SEE HOW THE SITUATION UNFOLDS TONIGHT TO MAKE ANY NECESSARY ADJUSTMENTS. HIGHS TOMORROW WILL BE AIDED BY WARM AIR ADVECTION AND INCREASING DOWNSLOPE WINDS...SO HIGHS TUESDAY WILL BE IN THE LOW/MID 90S EAST TO MID/UPPER 80S WEST. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... AS OF 215 PM EDT MONDAY... COLD FRONT WILL HAVE JUMPED INTO THE PIEDMONT LEE TROUGH BY EARLY TUESDAY EVENING BEFORE PUSHING EAST ALLOWING HIGH PRESSURE TO BUILD IN FROM THE NW THROUGH WEDNESDAY. WITH STRONG DOWNSLOPING IN PLACE...POPS APPEAR QUITE IFFY TUESDAY EVENING EXCEPT PERHAPS OVER THE FAR WEST WHERE CLOSER TO A DEEPER MOISTURE AXIS TO THE WEST...AND ALONG THE EASTERN PERIMETER GIVEN WEAKER DOWNSLOPE ESPCLY WHEN MIXING WEAKENS. HOWEVER INSTABILITY NOT OVERLY IMPRESSIVE SO RUNNING WITH ONLY ISOLATED EVENING POPS IN THESE SPOTS BEFORE DRY ADVECTION WINS OUT OVERNIGHT. AREA WILL REMAIN IN BETWEEN FEATURES AND UNDER A BUBBLE HIGH WEDNESDAY AIDED BY WEST/NW FLOW THROUGH THE COLUMN AND LOWER PWATS. MOST GUIDANCE INCLUDING THE LATEST ENSEMBLES HAVE LITTLE PRECIP UNDER THE SUBSIDENCE WEDNESDAY SO TRIMMED BACK TO ONLY ISOLATED POPS ACROSS THE SW AND FAR EASTERN COUNTIES LATE IN THE DAY. HIGH TEMPS WEDNESDAY DON`T APPEAR QUITE AS HOT AS EARLIER GIVEN DECENT 85H COOLING DESPITE DOWNSLOPE ALOFT AND MORE SUN. STILL THINK SOME LOW/MID 90S LIKELY EAST AND 80S WEST. MOISTURE WILL BEGIN TO INCREASE WEDNESDAY NIGHT AS AN INITIAL WAVE HEADS EAST OUT OF THE SOUTHERN PLAINS AND BEGINS TO LIFT THE FRONT BACK NORTH WITH WEAK OVERRUNNING IN PLACE. GUIDANCE REMAINS SLOW TO MOISTEN THINGS UP WEDNESDAY NIGHT WITH THE BEST FLUX OF DEEP MOISTURE NOT RETURNING UNTIL THURSDAY PER THE LATEST GFS/EURO. SINCE APPEARS BEST MOISTURE/LIFT WILL BE MAINLY OVER THE FAR WEST/NORTH WITH THE FRONT...WILL KEEP LOW CHANCE POPS MOUNTAINS WEDNESDAY NIGHT AND SLIGHTS OUT EAST. PLUME OF DEEPER MOISTURE ADVECTS IN WITH THE LEAD SHORTWAVE THURSDAY INTO THURSDAY NIGHT WITH MODELS SHOWING DECENT INSTABILITY THURSDAY AFTERNOON AS WELL AS LIFT WITH THE SURFACE WAVE THURSDAY NIGHT. HOWEVER STILL SOME UNCERTAINTY IN EXACTLY WHERE THE CORE OF THIS SYSTEM WILL TRACK WITH SOME SOLUTIONS FARTHER WEST WHICH WOULD LIMIT FOCUS UNTIL THURSDAY NIGHT AFTER LOSS OF HEATING. THEREFORE KEEPING LIKELY POPS CONFINED TO THE WEST AND CHANCE OUT EAST FOR NOW. LEFT TEMPS CLOSER TO A MORE BLENDED SOLUTION PENDING DEGREE OF SHOWER COVERAGE WHICH COULD MAKE THINGS COOLER THAN THE 80S TO AROUND 90 SE ON THURSDAY. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 100 PM EDT MONDAY... STRONG SHORTWAVE FOR EARLY AUGUST WILL PASS ACROSS OR JUST NORTH OF THE REGION TO START THE PERIOD ALLOWING A TRAILING COLD FRONT TO SLIDE SOUTHEAST INTO THE CAROLINAS BY LATER FRIDAY INTO FRIDAY NIGHT. THIS ASSOCIATED WITH ANOTHER DIGGING 5H TROUGH THAT WILL BRING THE ONSET OF THE NEXT ROUND OF SLIGHTLY COOLER TEMPERATURES FOR NEXT WEEKEND. HOWEVER NEW GUIDANCE CONTINUES TO FLIP FLOP AS SOME SOLUTIONS NOW NOT AS DEEP OR PROLONGED WITH THE EASTERN UPPER TROUGH IN HAVING A PASSING 5H COOL POOL EARLY IN THE WEEKEND BEFORE RETURNING TO MORE ZONAL FLOW AND SOME RETURN IN MOISTURE BY DAY7. THIS AHEAD OF ADDED UPSTREAM CLIPPER TYPE ENERGY THAT SHOULD GIVE THE INITIAL SYSTEM A BIT OF A BOOT TO START. THIS COULD ALSO KEEP MORE CLOUDS AROUND AT TIMES DESPITE WEAK SURFACE RIDGING IN PLACE...ALONG WITH POSSIBLE ISOLATED SHOWERS SW SUNDAY AND MAINLY OVER THE WEST MONDAY AHEAD OF THE NEXT WAVE. THUS AFTER HIGHER CHANCE TO LOW LIKELY POPS ESPCLY NORTH/WEST WITH THE FRONTAL PASSAGE FRIDAY...WILL HANG ONTO SOME ISOLATED TO LOW CHANCE POPS SATURDAY AND OVER THE FAR SW SUNDAY DESPITE THE SURFACE FRONT WELL TO THE SOUTH. OTRW THINKING THAT MUCH OF THE WEEKEND INTO MONDAY WILL REMAIN DRY PENDING LATER TRENDS WITH THE TIMING OF THE FRONTAL PROGRESSION FROM LATE IN THE WEEK. TEMPS TO COOL BACK TO JUST BELOW SEASONAL LEVELS BUT NOT QUITE AS COOL AS SEEN YESTERDAY FOR NOW. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... AS OF 200 AM EDT TUESDAY... VFR CONDITIONS PREVAILED ACROSS THE NWS BLACKSBURG FORECAST AREA AT 02Z/2 AM EDT AS OUR REGION IS CURRENTLY SANDWICHED BETWEEN SYSTEMS. A COLD FRONT WAS NOTED ACROSS THE OHIO VALLEY...WITH A WEAK WARM FRONT NOTED ACROSS SOUTHEAST VA/EASTERN NC. SCATTERED SHOWERS AND THUNDERSTORMS REMAIN ONGOING ALONG COLD FRONT WITH POTENTIAL FOR BRIEF PERIOD OF MVFR/IFR POSSIBLE THROUGH DAYBREAK MAINLY IN THE MOUNTAINS OF WV AND FAR WRN VA. MULTI- LAYERED CLOUD BASES ARE LIKELY...BUT MAINLY VFR. OVER THE PIEDMONT...DEWPOINTS HAVE BEEN CREEPING UP VCNTY OF WARM FRONT. NO PRECIP WAS NOTED ATTM BUT LIGHT FOG WITH MVFR RESTRICTIONS CERTAINLY POSSIBLE AROUND DAYBREAK. FOR TUESDAY...THE FRONTAL BOUNDARY WILL CROSS THE MOUNTAINS...WINDS TENDING WESTERLY AND THEN NORTHWESTERLY WITH TIME. MAIN CONVERGENCE ALONG FRONT WILL SET UP OVER THE PIEDMONT DURING THE AFTERNOON...AND THIS IS WERE SCT-BKN LINE OF DEEP CONVECTION IS EXPECTED TO DEVELOP. THERE IS STILL UNCERTAINTY WITH THE TIMING AND LOCATION...BUT SIGNALS IN THE MODELS SUGGEST BEST CHANCE FOR STORM DEVELOPMENT WILL BE FROM DANVILLE EASTWARD. AS SUCH ADDED VCTS TO KDAN. WINDS THIS AFTERNOON WILL BE WESTERLY WITH SOME LOW LEVEL GUSTS POSSIBLE...TENDING MORE NORTHWESTERLY LATE IN THE AFTERNOON AND DURING THE EVENING WITH FROPA. EXTENDED AVIATION FORECAST... MOSTLY VFR OUTSIDE OF ANY DEEP CONVECTION THROUGH THE PERIOD. A FRONT WILL STALL ACROSS THE MID ATLANTIC BY LATE WEEK WHICH COULD BRING A BIT MORE COVERAGE OF SHOWERS/THUNDERSTORMS THURSDAY AND ESPECIALLY FRIDAY. THE THREAT OF SUB-VFR REMAINS LOW UNTIL THURSDAY...EXCEPT FOR THE TYPICAL FOG POTENTIAL AT KLWB/KBCB EACH MORNING BETWEEN 09-13Z. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...MBS/PH SHORT TERM...JH LONG TERM...JH AVIATION...PM

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