Area Forecast Discussion
Issued by NWS Blacksburg, VA

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003 FXUS61 KRNK 172306 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 706 PM EDT SUN MAY 17 2015 .SYNOPSIS... HIGH PRESSURE OFFSHORE WILL MAINTAIN A MOIST SOUTHERLY FLOW OF AIR ACROSS THE REGION TONIGHT THROUGH MONDAY. A COLD FRONT WILL SLOWLY APPROACH FROM THE WEST LATE MONDAY...MOVING THROUGH THE REGION TUESDAY. COOLER...DRIER AIR WILL FILTER INTO THE REGION BY THE MID PART OF NEXT WEEK BEHIND THE FRONT. && .NEAR TERM /THROUGH MONDAY/... AT 300 PM EDT SUNDAY... HIGH PRESSURE OFF THE SOUTHEAST COAST WILL CONTINUE THE WARM MOIST SOUTHERLY FLOW INTO OUR REGION THIS AFTERNOON INTO TONIGHT. THE UPPER LEVEL RIDGE REMAINS ANCHORED FROM FLORIDA THROUGH THE GREAT LAKE INTO MONDAY. THE COMBINATION OF UPPER DISTURBANCES ROTATING AROUND THE UPPER RIDGE AND DAYTIME HEATING HAVE RESULTED IN THE DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON...MAINLY ALONG AND WEST OF THE BLUE RIDGE MOUNTAINS. IMPRESSED BY HOW THE SFC BASED CAPE AS SEEN ON THE 17Z SPC MESOSCALE ANALYIS WHERE ABLE TO REBOUND TO 1000 J/KG TO AS MUCH AS 2000 J/KG JUST TO OUR NORTHEAST IN THE WAKE OF THIS SHORTWAVE SHOWERS AND CLOUDS ALONG WITH AREAS OF MORNING FOG. SUFACE-BASED LIS WERE QUITE HEALTHY EAST OF THE BLUE RIDGE FROM MINUS 2 TO MINUS 4. STORMS THIS AFTERNOON FORMING IN THE DEEP LAYER MOISTURE CONVERGENCE MAINLY IN SOUTHWEST PORTION OF FORECAST AREA. HOWEVER...STILL BELIEVE THAT UNDER THE UPPER LEVEL RIDGE...THE THREAT FOR MORE THAN ISOLATED PULSE SEVERE THUNDERSTORMS REMAINS LOW. THE MAIN CONCERN FOR THIS AFTERNOON INTO TONIGHT WILL THREAT FOR AREAS OF HEAVY RAIN AND LOCALIZED FLASH FLOODING DUE MAINLY TO A MOIST ATMOSPHERE...PRECIPITABLE WATER VALUES IN THE 1.3 TO 1.7 RANGE(QUITE HIGH FOR THEN MONTH OF MAY ESPECIALLY AT BCB)...AND LIGHT WIND SPEEDS MAKING FOR SLOW CELL MOVEMENT. ANY ANCHORING OR TRAINING OF EFFICIENT RAIN PRODUCING CONVECTION MAY HELP THE POTENTIAL FOR WATER PROBLEMS. SIMILAR TO YESTERDAY EXPECTED CONVECTION TO DIMINISH TONIGHT WITH THE LOSS OF SOLAR HEATING WITH MOST OF THE STORMS ENDING ABOUT 02Z...BUT WILL HOLD ONTO SOME LIGHT POPS OVERNIGHT MAINLY IN THE WESTERN MOUNTAINS. THE LIGHT WEST UPSLOPE WINDS IN THE FAR WEST MAY HELP SHOWERS PERSIST TONIGHT. AREAS OF FOG WILL DEVELOP OVERNIGHT ESPECIALLY IN LOCATIONS THE RECEIVED RAINFALL SUNDAY. LOW TEMPERATURES OVERNIGHT WILL REMAIN MILD WITH READING FROM THE UPPER 50S IN THE MOUNTAINS TO THE LOWER TO MID 60S IN THE PIEDMONT. MONDAY MORNING STARTS DREARY WITH AREAS OF FOG. THE LOW CLOUDS AND FOG SHOULD BURNING OFF RAPIDLY AFTER 9 AM AS DAYTIME HEATING INCREASES...MAKING FOR A MIXTURE OF CLOUDS AND SUNSHINE. SCATTERED SHOWERS AND THUNDERSTORMS WILL ONCE AGAIN FORM IN THE UNSTABLE AIR DRIVEN BY DAYTIME HEATING...BEGINNING PRIMARILY OVER THE MOUNTAINS. SIMILAR WEATHER PATTERN EXPECTED MONDAY WILL WITH SHOWERS AND ISOLATED THUNDERSTORMS DEVELOP IN THE MOUNTAINS MID MORNING...THEN SPREADING IN COVERAGE THROUGH THE AFTERNOON...WITH WESTERLY WINDS ALOFT CARRYING SOME OF THIS ACTIVITY ACROSS THE PIEDMONT BY LATE AFTERNOON. THE DAY TWO CONVECTIVE OUTLOOK KEEPS OUR REGION IN THE GENERAL THUNDERSTORMS WITH A AREA OF MARGINAL SEVERE TO OUR WEST ACROSS THE OHIO VALLEY WITH THE POTENTIAL FOR MARGINALLY SEVERE WIND AND HAIL. FOR HIGHS ON MONDAY...PLAYED HIGH TEMPERATURES CLOSE TO ADJMET WITH ITS COOLER HIGH VALUES IN THE WESTERN MOUNTAINS. IN GENERAL...HIGH TEMPERATURES MONDAY WILL RANGE FROM THE LOWER 70S IN THE MOUNTAINS TO THE UPPER 80S IN THE PIEDMONT. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... AS OF 330 PM EDT SUNDAY... WHILE OVERALL COVERAGE OF CONVECTION WILL DECREASE SOMEWHAT WITH LOSS OF INSTABILITY MONDAY NIGHT...THE WEAK FRONTAL BOUNDARY STILL APPROACHING FROM THE WEST MAY EITHER ALLOW LINGERING CONTINUATION OF SHOWERS IN FAR WEST...OR MAY INCREASE AGAIN TOWARD MORNING. STILL REMOVED MENTION OF THUNDER AFTER MIDNIGHT OR SO...BUT KEEPING A LIKELY POP IN THE WEST THROUGH MIDNIGHT...AND THEN HIGH CHANCE THROUGH MUCH OF THE OVERNIGHT WITH QUICKLY DIMINISHING CHANCE OF SHOWERS IN EAST OVERNIGHT. RELATIVELY MILD NIGHT WITH CLOUD COVER...ALL TEMPS IN 60S EXCEPT FOR HIGHEST RIDGES. MODELS CONTINUE TO SLOW PASSAGE OF FRONT...BUT LOOKS LIKE DURING THE AFTERNOON THE MAIN CONVERGENCE ZONE SHIFTS WELL INTO PIEDMONT AND THEN WELL EAST OF FCST AREA BY EARLY EVENING...WHILE THERE IS STILL A DEW PT GRADIENT PUSHING INTO WESTERN APPALACHIANS BY EVENING. THEREFORE NEED TO KEEP A CHANCE OF SHOWERS AND TSTORM AROUND THROUGH MUCH OF THE DAY...BUT BY LATE AFTERNOON ANY THREAT FOR THUNDER SHOULD PRIMARILY BE FAR EAST AND BY EARLY EVENING MAY BE EAST OF AREA ENTIRELY. HOWEVER WITH SLOWING TRENDS DID NOT WANT TO COMPLETELY REMOVE POPS FROM FAR SOUTHEAST UNTIL AFTER MIDNIGHT TUES NIGHT. LEFT ISOLD THUNDER IN FAR WEST EVEN INTO LATE AFTERNOON BUT INSTABILITY IS ALMOST NOTHING BY THEN SO MAY ONLY BE WORTH MENTION OF AN ISOLD SHOWER. GFS A BIT FASTER TO DRY THINGS OUT AND REDUCE PRECIP CHANCE BY TUES AFTERNOON THAN NAM...AND WE MAY BE ABLE TO DROP ALL POPS EVEN IN FAR SOUTHEAST BEFORE 00Z. CERTAINLY DRYING OUT BEHIND FRONT TUES NIGHT INTO WED AS MAIN DEW PT BOUNDARY PUSHES THROUGH BY EARLY WED MORNING AND 850 WINDS FROM WEST PICK UP BEHIND WEAK UPPER WAVE FOR PERHAPS SOME GUSTY WINDS AT RIDGE TOP LEVEL IN MORNING...BUT ONLY TALKING ABOUT 15-25 MPH TOPS. COMFORTABLE WEATHER WEDNESDAY WITH HIGHS BACK INTO THE LOWER 70S MOUNTAINS TO LOWER 80S EAST BUT WITH DEW PTS INTO THE 40S...AND SO MAY SEE SOME 40S FOR LOWS IN SOME OF THE MOUNTAIN VALLEYS. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 345 PM EDT SUNDAY... FRONTAL BOUNDARY REMAINS TO OUR SOUTHEAST THROUGH END OF THE WEEK AND FOR NEXT WEEKEND AS WELL WITH FAIRLY LOW AMPLITUDE UPPER TROUGH AND HIGH PRESSURE KEEPING THINGS DRY AND SEASONABLE TEMPERATURES THROUGH THE PERIOD. HOWEVER...THE BOOKENDS OF THIS PERIOD...THURSDAY AND THEN SUNDAY...THERE ARE SOME QUESTIONS. THURSDAY AN UPPER WAVE PASSES BY TO THE SOUTH AND MOST OF THE LONG RANGE GUIDANCE SUGGESTS AN AREA OF SHOWERS WILL SPREAD INTO AT LEAST THE SOUTHERN PORTION OF THE FCST AREA. 12Z GFS IS FARTHER SOUTH WITH THIS WAVE AND SUGGESTS ONLY FAR SOUTHERN FRINGE MAY GET CLIPPED WITH SOME SHOWERS ON THURSDAY AND THURSDAY NIGHT. ECMWF HAS BEEN CONSISTENT WITH IDEA OF LIGHT PRECIP SPREADING ACROSS MUCH OF AREA...AND CANADIAN IS THE WETTEST. DECIDED TO KEEP SLIGHT CHC FOR MOST OF AREA WITH LOW CHC IN FAR WEST...UPSLOPE AIDED...AND FAR SOUTHERN FRINGES INTO THURS EVENING...BUT IF ANYTHING DOES OCCUR NOT LIKELY TO HAVE THUNDER GIVEN MORE STABLE ATMOSPHERE AND LIMITED DEW PTS NORTH OF THE STATIONARY FRONTAL BOUNDARY...WHICH IS LIKELY TO REMAIN OVER SOUTH CAROLINA OR EVEN FARTHER SOUTH. SFC HIGH PUSHES IN MORE STRONGLY FOR FRIDAY AND RIGHT NOW BOTH FRIDAY AND SATURDAY STAND A VERY GOOD CHANCE OF BEING RAIN FREE FOR EVERYONE. BY SUNDAY THE SFC HIGH SHIFTS OFF THE MID ATLANTIC COAST AND SOME RETURN FLOW BEGINS BACK AGAIN FROM THE SOUTHWEST...BUT SFC RIDGE IS STILL RATHER ELONGATED AND ECMWF IS SLOWER MOISTURE RETURN AS WELL...SO WE MAY SNEAK ONE MORE DRY DAY OUT OF THE HOLIDAY WEEKEND...AND EAST OF THE BLUE RIDGE WILL VERY LIKELY BE DRY SUNDAY. HOWEVER DID INTRODUCE A VERY LOW CHANCE POP BACK INTO THE WEST FOR SUNDAY BUT ACTIVITY SHOULD NOT BE WIDESPREAD...IF ANYTHING FORMS AT ALL. HOWEVER TEMPS AND HUMIDITY WILL BEGIN TO CREEP BACK UP BY SUNDAY. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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AS OF 645 PM EDT SUNDAY... SHOTGUN TYPE CLUSTERS OF HEAVIER SHRA/TSRA MAINLY FROM THE BLUE RIDGE WEST WILL PERSIST A WHILE LONGER BEFORE LOSS OF HEATING CAUSES MUCH OF THE COVERAGE TO FADE. HOWEVER GIVEN DEGREE OF DEEP MOISTURE AND UPSTREAM WEAK ENERGY...CANT TOTALLY RULE OUT ADDED SHRA THROUGH MUCH OF THE NIGHT OVER THE MOUNTAINS AND PERHAPS ACROSS NE SECTIONS PER LINGERING INSTABILITY. THIS WILL CONTINUE TO YIELD OVERALL VFR ACROSS THE REGION WITH EMBEDDED AREAS OF BRIEF MVFR/IFR NEAR CONVECTION THIS EVENING. AFTER 02Z/10 PM EXPECTING MOSTLY VFR IN MID DECK FOLLOWED BY THE ONSET OF FOG AND STRATUS AFTER MIDNIGHT. THIS SHOULD RESULT IN MVFR TO IFR CONDITIONS ESPCLY MOUNTAINS AND WHERE EARLIER HEAVY RAIN OCCURRED. LOCAL LIFR ALSO LIKELY IN SPOTS SUCH AS KLWB/KBCB. LOW CLOUDS AND FOG SHOULD AGAIN BREAK BY MID MORNING MONDAY WITH LINGERING MID DECK AND PERHAPS A FEW -SHRA GIVING WAY TO CU DEVELOPMENT AND THE ONSET OF SHRA/TSRA ONCE AGAIN IN THE AFTERNOON. COVERAGE LOOKS MORE WIDSPREAD AS UPPER HEIGHTS WEAKEN AND THE UPSTREAM COLD FRONT APPROACHES. THIS SHOULD BE ENOUGH TO BRING PERIODS OF PREVAILING MVFR TO IFR IN SHRA/TSRA KBLF/KLWB MONDAY AFTERNOON...AND PERHAPS OUT TO THE BLUE RIDGE LATER IN THE DAY INCLUDING KROA/KBCB. EXPECTING CONVECTION TO PUSH A BIT FARTHER TO THE EAST LATE MONDAY WITH DEEPER CONVECTION POSSIBLE AT BOTH KLYH/KDAN WHERE INSERTING A VCTS MENTION. OTRW OUTSIDE OF THE WESTERN MOUNTAINS...APPEARS SHOULD AGAIN BE VFR INTO THE AFTERNOON BEFORE CONVECTION BECOMES MORE WIDESPREAD. WESTERLY WINDS EXPECTED MONDAY AT 5 TO 10 KTS...LOCALLY HIGHER NEAR STORMS. MEDIUM TO HIGH CONFIDENCE IN CEILINGS...VISIBILITIES AND WIND DURING THE TAF PERIOD. EXTENDED AVIATION DISCUSSION... MONDAY NIGHT INTO TUESDAY...A COLD FRONT MOVES THROUGH. THUNDERSTORMS SHOULD BE MOST NUMEROUS IN COVERAGE AND STRONGEST IN INTENSITY DURING MONDAY EVENING AS PERHAPS A MORE LINEAR BAND OF CONVECTION PUSHES OFF THE MOUNTAINS. THIS MAY BRING LONGER PERIODS OF MVFR CIGS/VSBYS INTO MONDAY NIGHT. MOST SHOWERS ALONG THE FRONT SHOULD DEVELOP IN THE EASTERN SECTIONS TUESDAY AFTERNOON WITH ONLY KLYH/KDAN POSSIBLY SEEING A PERIOD OF MVFR IN SHRA TUESDAY AFTERNOON BEFORE THE DRIER AIR SWEEPS EAST. BEHIND THE COLD FRONT...DRIER/COOLER CONDITIONS ARE EXPECTED WED-FRI WITH MOSTLY VFR CONDITIONS AS HIGH PRESSURE SLIDES IN FROM THE NW.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/SK NEAR TERM...KK SHORT TERM...SK LONG TERM...SK AVIATION...JH/KK/RAB

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