Area Forecast Discussion
Issued by NWS Blacksburg, VA

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295 FXUS61 KRNK 182248 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 648 PM EDT MON MAY 18 2015 .SYNOPSIS... A COLD FRONT EXTENDS FROM MICHIGAN TO SOUTHERN MISSOURI. THIS FRONT WILL MOVE EAST ACROSS THE OHIO VALLEY OVERNIGHT...CROSSING THE MID ATLANTIC REGION TUESDAY. MOIST SOUTHERLY FLOW AHEAD OF THE FRONT WILL HELP FUEL SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS. ONCE THE FRONT PASSES EAST OF THE AREA TUESDAY...COOLER...DRIER AIR WILL FILTER INTO THE REGION FOR MID WEEK. && .NEAR TERM /THROUGH TUESDAY/...
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AS OF 640 PM EDT MONDAY... NO MAJOR CHANGES TO THE FORECAST AS WE HEAD INTO THE EVENING HOURS. WE STILL EXPECT SCATTERED SHOWERS AND SOME STORMS ACROSS MUCH OF THE REGION. WHAT DID CHANGE WAS THE FOCUS FOR WHERE THE BEST CHANCES WOULD BE IN THE NEXT COUPLE OF HOURS BASED UPON WHERE THE GREATEST CONCENTRATION IS CURRENTLY LOCATED...FROM FRANKLIN COUNTY VA SOUTHWEST TO AROUND PILOT MOUNTAIN IN NORTH CAROLINA...AND WEST TO THE GRAYSON HIGHLANDS OF SOUTHWEST VIRGINIA. ALSO...ANOTHER GENEROUS REGION OF PRECIPITATION WAS MOVING THROUGH ROCKBRIDGE COUNTY VA...AND THERE WAS ANOTHER ONE APPROACHING WESTERN GREENBRIER COUNTY AND SUMMERS COUNTY IN SOUTHEAST WEST VIRGINIA. AS WE PROGRESS INTO THE LATE EVENING AND TOWARDS MIDNIGHT....FORECAST CHANGES WERE A LITTLE MORE EXPANSIVE. BASED UPON THE LATEST HRRR AND RNK WRF. THE FORECAST WILL NOW REFLECT LITTLE OR NO COVERAGE OF PRECIPITATION OUTSIDE SOUTHEAST WEST VIRGINIA AND NEIGHBORING PORTIONS OF SOUTHWEST VIRGINIA ONCE WE REACH THAT TIME TONIGHT. AS OF 330 PM EDT MONDAY... PWATS 2-3 STANDARD DEVIATIONS ABOVE NORMAL WILL HELP FUEL SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS THIS EVENING. THE AIRMASS IS UNSEASONABLY JUICY BUT LACK OF ANY GOOD DYNAMICS SHOULD KEEP ACTIVITY UNORGANIZED. NEVER THE LESS...SLOW MOVEMENT WILL YIELD HEAVY DOWNPOURS FOR ANY PASSING SHOWER/STORM. FORECAST AREA REMAINS UNDERNEATH A VERY SHARP UPPER LEVEL RIDGE...WHICH IS PROMOTING VERY LIGHT STEERING WINDS...0-8KM MEAN WIND OF ONLY 11 KTS...FROM 290 DEGREES. THIS UPPER RIDGE IS EXPECTED TO WEAKEN AS WE TRANSITION THROUGH THE NEXT 12-18 HOURS...AS LOW PRESSURE MOVES ACROSS THE GREAT LAKES AND INTO ONTARIO CANADA. AT THE SURFACE...A COLD FRONT WILL TRAIL SOUTH FROM THE LOW...CROSSING THE OHIO VALLEY TONIGHT. AS THE FRONT APPROACHES...IT WILL FOCUS THE DEEPER MOISTURE FROM THE OH/TN VALLEYS INTO THE WEST SIDE OF THE APPALACHIANS. THIS SQUEEZE PLAY OF DEEPER MOISTURE IN ADDITION TO LINGERING INSTABILITY OVER THE MOUNTAINS WILL RESULT IN GOOD COVERAGE OF SHOWER ACTIVITY THROUGH THIS EVENING. COVERAGE AND INTENSITY OF SHOWER AND THUNDERSTORM ACTIVITY WILL DECREASE WITH THE LOSS OF DAYTIME HEATING. HOWEVER...WITH THE COLD FRONT CONTINUING ITS APPROACH OVERNIGHT...SHOWER THREAT WILL NOT SUBSIDE ALTOGETHER. MOISTURE TRANSPORT AND CONVERGENCE PER SOUTHWEST WIND FLOW AHEAD OF THE FRONT WILL CONTINUE TO GENERATE ACTIVITY INTO THE LATE NIGHT. SURFACE FRONT IS EXPECTED TO REACH THE WESTERN SLOPES OF THE APPALACHIANS BY DAYBREAK TUESDAY...THEN MOVE OVER AND EAST OF THE MTNS MID-DAY...CLEARING THE CWA BY TUESDAY EVENING. WILL MAINTAIN THREAT FOR SHOWERS UNTIL THE PASSAGE OF THE FRONT...FOLLOWED BY CLEARING AND DRYING WITH FROPA. MET/MAV TEMPERATURE GUIDANCE LOOKS GOOD...AND USED A BLEND FOR TONIGHT`S LOWS AND TUESDAYS HIGHS...READINGS REMAINING QUITE MILD TONIGHT...AOA 60 FOR LOWS...FOLLOWED BY ANOTHER WARM DAY TUESDAY WITH HIGHS RANGING IN THE 70S MTNS TO THE 80S IN THE LOWER ELEVATIONS. ANY SIGNIFICANT COOLING/DRYING WILL NOT TAKE PLACE UNTIL WE CHANGE AIRMASSES LATER TUESDAY...BECOMING NOTICEABLE ONCE THE SUN GOES DOWN TUESDAY EVENING.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... AS OF 300 PM EDT MONDAY... ANY LINGERING CONVECTION IN THE FAR SOUTHEAST PORTIONS OF FORECAST AREA WILL TAPER OFF BY 06Z WEDNESDAY. LOW TEMPERATURES TUESDAY NIGHT WILL RANGE FROM THE UPPER 40S IN THE NORTHWEST MOUNTAINS TO THE LOWER 60S IN THE PIEDMONT. HIGH PRESSURE IN THE MIDWEST WILL RIDGE SOUTHEAST INTO OUR AREA FOR WEDNESDAY PROVIDING A BREAK FROM THE ACTIVE CONVECTION. THE COOLER HIGH TEMPERATURES ON WEDNESDAY WILL ALSO BE A WELCOME CHANGE WITH READINGS FROM THE LOWER 60S IN THE NORTHWEST MOUNTAINS TO THE MID 80S IN THE PIEDMONT. WITH A WEAK SHORTWAVE ROTATING EAST ACROSS THE REGION WEDNESDAY NIGHT...ALLOW FOR SOME LIGHT POPS IN THE WEST. LOW TEMPERATURES WEDNESDAY NIGHT WILL VARY FROM THE UPPER 40S IN THE WEST TO THE UPPER 50S IN THE EAST. THURSDAYS FORECAST REMAINS A CHALLENGE WITH THE LATEST MODEL RUNS ALL DEPICT A STRONGER SHORTWAVE TRACKING ACROSS THE AREA...BUT WITH WIDELY VARYING DEGREES OF INTENSITY AND RESULTANT MOISTURE/PRECIPITATION. WITH CAUTION...ELECTED TO USE A BLEND OF SUPERBLEND AND HPCGUIDE WITH SCATTERED POPS FOR THURSDAY. HIGH TEMPERATURES THURSDAY WILL WARM TO AROUND 60 DEGREES IN THE NORTHWEST TO AROUND 80 DEGREES ALONG THE SOUTHERN BLUE RIDGE. SHORTWAVE WILL EXIT TO THE SOUTHEAST THURSDAY NIGHT AS SFC HIGH PRESSURE SLIDES FROM THE PLAINS TO THE GREAT LAKES. OVERALL...THE AIRMASS APPEARS TO BE TOO STABLE AND DRY IN THE LOWER LEVELS TO SUPPORT MUCH THUNDER WITH THIS EVENT. HOWEVER...A NOSE OF INSTABILITY SUPPORT ISOLATED THUNDERSTORM ACROSS SOUTHERN PORTIONS OF FORECAST AREA. DIURNAL CONVECTION TAPERS OFF QUICKLY THURSDAY NIGHT. LOW TEMPERATURES THURSDAY NIGHT WILL GENERALLY VARY FROM THE UPPER 40S IN THE MOUNTAINS TO THE UPPER 50S IN THE PIEDMONT. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 300 PM EDT MONDAY... MOISTURE...WARMTH...AND HUMIDITY ARE POISED TO RETURN BY EARLY NEXT WEEK AS YET ANOTHER DEEP UPPER LOW BUILDS INTO THE SOUTHWEST UNITED STATE...THE NORTHEAST TROUGH PUSHES EASTWARD INTO THE NORTHERN ATLANTIC...AND AN ELONGATED RIDGE BETWEEN THESE TWO FEATURES DRIFTS INTO OUR REGION. HIGH TEMPERATURES FRIDAY WARM INTO THE MID 60S IN THE MOUNTAINS TO THE MID 70S IN THE PIEDMONT. LOW TEMPERATURES WILL DROP INTO THE MID 40S TO THE 50S IN GENERAL. ON SATURDAY...CANADIAN HIGH PRESSURE SHIFTS OFF THE MID-ATLANTIC COAST...AS FRONTAL BOUNDARY IS CENTRAL U.S. LIFTS NORTHEAST. KEPT SATURDAY DRY...WITH HIGH TEMPERATURES RANGING FROM THE MID 60S IN THE NORTHWEST MOUNTAINS TO THE UPPER 70S IN THE PIEDMONT. AS THE HIGH CENTER MOVES EAST...AN EAST TO SOUTHEAST RETURN FLOW ON THE BACKSIDE MAY DEVELOP A WEDGE ACROSS THE REGION OVER THE WEEKEND. WITH THE POTENTIAL OF OVERRUNNING PRECIPITATION DEVELOPING FROM THE WEST. ADDED A SLIGHT CHANCE OF SHOWERS IN THE NORTHWEST MOUNTAINS OF NORTH CAROLINA. MODERATED LOW TEMPERATURES SATURDAY NIGHT WITH VALUES MAINLY IN THE 50S...WITH INCREASED CLOUD COVER. SCATTERED SHOWERS CONTINUED ON SUNDAY WITH THE BEST CHANCES IN THE NORTHWEST. THE UPPER RIDGE WILL SHIFT SOUTHEAST BY MONDAY...ALLOWING AN ACTIVE BAROCLINIC ZONE TO SHIFT SOUTH AND EAST INTO THE REGION FROM THE OH/TN VALLEY. CONTINUED THE POTENTIAL FOR SCATTERED CONVECTION ON TUESDAY. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... AS OF 200 PM EDT MONDAY... A VERY MOIST AIR MASS REMAINS ACROSS THE REGION STUCK UNDER AN UPPER RIDGE AS THE PAST SEVERAL DAYS. HOWEVER...THE PATTERN IS FINALLY ABOUT TO CHANGE. THE UPPER LOW THAT HAS PLAGUED THE CENTRAL U.S. THE PAST SEVERAL DAYS IS SHEARING OUT AND MOVING TOWARD THE GREAT LAKES WHERE IT WILL AID IN THE DEVELOPMENT OF A DEEP UPPER LOW ACROSS SOUTHEAST CANADA BY MIDWEEK. THIS WILL PUSH A FRONT INTO OUR REGION BY EARLY TUESDAY...THEN EAST OF THE REGION BY TUE EVENING. FOR THIS AFTERNOON AND EVENING...SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED IN ADVANCE OF THE UPPER TROUGH/FRONT. THE ACTIVITY WILL EXTEND FROM THE OH/TN VALLEYS EASTWARD INTO THE MID ATLANTIC...AND FARTHER EAST INTO THE PIEDMONT AS COMPARED TO THE PAST FEW AFTERNOONS. DURING THE AFTERNOON/EVENING...THUNDERSTORMS SHOULD BE MOST NUMEROUS WEST OF THE BLUE RIDGE...SOME WITH LOCALLY HEAVY RAINFALL. THE STRONGER STORMS WILL CONTAIN LOCALIZED OUTFLOW WINDS OF 25-30KTS IN ADDITION TO MVFR CIGS AND BRIEF PERIODS OF MVFR-IFR VSBYS. LACK OF ORGANIZATION MAKES IT DIFFICULT TO PINPOINT TIMING AT ANY OF THE TERMINALS...ESP THOSE EAST OF THE BLUE RIDGE. AS SUCH...WILL CONTINUE TO MENTION VCNTY SHRA/TSRA AND AMEND TAFS PER RADAR TRENDS. COVERAGE OF THE SHOWERS/THUNDERSTORMS WILL DECREASE AFTER SUNSET...BUT GIVEN THE SYNOPTIC PATTERN WOULD EXPECT SOME ACTIVITY TO LINGER ALL NIGHT ACROSS MUCH OF THE CWA. WITH WINDS BECOMING NW...UPSLOPE MVFR CIGS APPEAR LIKELY ACROSS EASTERN WV INTO FAR SOUTHWEST VA...WITH MODELS SUGGESTING PERIOD OF IFR CIGS PRIOR TO DAYBREAK TUESDAY AT KBLF/KLWB. MVFR VSBYS WILL ALSO PREVAIL IN MANY AREAS OVERNIGHT IN A NEAR SATURATED BOUNDARY LAYER WITH MOIST/WET GROUND AND LIGHT WSW-WNW WINDS. ANY LOW CIG/VSBY ELEMENTS SHOULD QUICKLY IMPROVE AFTER 13Z/9AM TUESDAY WITH RETURN OF VFR FOR THE AFTERNOON. SURFACE FRONT WILL PASS THROUGH ALL TERMINALS TUESDAY WITH SKIES CLEARING AND WINDS BECOMING NORTHWEST 6 TO 12 KTS. EXTENDED AVIATION DISCUSSION... DRIER/COOLER CONDITIONS ARE EXPECTED TUESDAY NIGHT AND WEDNESDAY. AN UPPER DISTURBANCE WILL LIKELY BRING SOME MVFR CIGS AND -SHRA BACK INTO THE AREA THU...MOVING OUT FRIDAY WITH VFR CONDITIONS RETURNING FRI-SAT. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...DS/PM SHORT TERM...KK LONG TERM...KK AVIATION...PM

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