Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 210810 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 410 AM EDT TUE APR 21 2015 .SYNOPSIS... A COLD FRONT WILL CONTINUE TO MOVE EAST THROUGH VIRGINIA AND WILL REACH THE COAST THIS MORNING. HIGH PRESSURE OVER THE SOUTHERN PLAINS WILL MOVE EAST TO THE COAST BY WEDNESDAY MORNING. ANOTHER FRONT WILL MOVE THROUGH THE AREA ON WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 400 AM EDT TUESDAY... LOCAL NATIONAL WEATHER SERVICE RADAR SHOWED WIDELY SCATTERED SHOWERS IN THE MOUNTAINS EARLY THIS MORNING. EVEN THOUGH UPSLOPE FLOW CONTINUES THROUGH THE DAY...HAVE ENDED THE SHOWERS AFTER THIS MORNING AND EXPECT A CLEARING SKY THIS AFTERNOON AS THE AIR MASS DRIES OUT. HRRR SUGGESTS SHOWERS MAY BE GONE AS EARLY AT 7AM. SURFACE DEW POINTS ALREADY DROPPING INTO THE 30S AND 40S BEHIND THE COLD FRONT THAT EXTENDED FROM EASTERN PENNSYLVANIA TO THE FLORIDA PANHANDLE. DRIER AIR ALOFT MAY BE SEEN ON THE WATER VAPOR LOOP ADVANCING ACROSS THE CENTRAL AND SOUTHERN APPALACHIANS. THE DOWNSLOPE WINDS WILL AIDE IN DRYING AND WARMING THE AIR EAST OF THE BLUE RIDGE. EXPECT HIGHS IN THE EAST TO BE ON THE WARMER SIDE OF GUIDANCE. BUFKIT FORECAST SOUNDINGS SHOWED DEEP MIXING WHICH WILL AIDE IN TRANSPORTING DRIER AIR DOWN TO THE SURFACE. THE DEEP MIXING AND PRESSURE RISES OF 3 TO 6 MB IN 6 HOURS WILL RESULT IN GUSTS AS HIGH AS 35 MPH. WINDS WILL DIMINISH TONIGHT AFTER SUNSET. LATER TONIGHT CLOUDS INCREASE AHEAD OF AN APPROACHING COLD FRONT. MODELS HOLD THE POTENTIAL FOR PRECIPITATION WEST OF THE FORECAST AREA UNTIL AFTER 07Z/3AM. LOW LEVEL JET FROM THE SOUTH-SOUTHWEST ALSO INCREASES TO NEARLY 45 KNOTS BY LATE TONIGHT. HAVE STRONG GUSTS...BUT STILL UNDER ADVISORY CRITERIA...AT HIGHER ELEVATIONS AFTER MIDNIGHT. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 330 AM EDT TUESDAY... THE CLOSED UPPER LOW WILL CONTINUE TO DO A SIT AND SPIN OVER THE GREAT LAKES REGION THROUGH THE SHORT TERM PERIOD....KEEPING OUR TEMPERATURES AT OR SLIGHTLY BELOW NORMAL. BY WEDNESDAY MORNING A SPOKE OF ENERGY ROTATING AROUND THE UPPER LOW WILL BE PUSHING A COLD FRONT INTO THE AREA FROM THE WEST. MOISTURE/INSTABILITY ARE LIMITED BUT LAPSE RATES ARE STEEP SO SOME SHOWERS AND THUNDERSTORMS WILL BE ABLE TO DEVELOP AHEAD OF THE FRONT. THE BIG FEATURE OF NOTE WILL BE THE SYNOPTIC WINDS. THE LOW LEVEL WIND FIELD WILL BE RAMPING UP TO 40KTS/50KTS AND MODEL SOUNDINGS SHOW A VERY WELL MIXED AND DRY BOUNDARY LAYER THAT WILL BE EFFICIENT FOR DOWNWARD MOMENTUM TRANSFER...ESPECIALLY AS COLDER AIR STARTS TO WORK IN BEHIND THE FRONT. BELIEVE THE SITUATION WILL REMAIN BELOW ADVISORY CRITERIA BUT THE RIDGES MAY SEE GUSTS AROUND 40MPH. ANY SHOWERS/STORMS WILL ALSO HAVE PLENTY OF WIND TO MIX DOWN SO EVEN UNIMPRESSIVE CONVECTIVE CLUSTERS MAY BE QUITE GUSTY. BEHIND THE FRONT WE SHOULD GET ENOUGH HIGH PRESSURE BUILDING IN FROM THE NORTHWEST TO KEEP THINGS QUIET...THOUGH BREEZY...THROUGH THE END OF THE WORKWEEK. TEMPERATURES HAVE BEEN TRENDING COLDER FOR BOTH MAX/MIN TEMPS THURSDAY AND FRIDAY...SO WILL BE SHADING GRIDS IN THAT DIRECTION. SOME OF THE HIGHER TERRAIN WEST OF THE BLUE RIDGE WILL BE FLIRTING WITH TEMPERATURES APPROACHING THE FREEZING MARK BOTH MORNINGS. HOWEVER...THE AG PROGRAM WILL NOT BE IN FULL SWING WEST OF THE RIDGE UNTIL MAY 1 SO THIS IS NOT LIKELY TO CAUSE ANY SIGNIFICANT PROBLEMS. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... AS OF 130 PM EDT MONDAY... NOT MUCH CHANGE TO THIS FORECAST. A SOUTHERN STREAM LOW ARRIVES OVER THE AR/OK BORDER BY SATURDAY MORNING WITH OVERRUNNING CLOUDS WORKING INTO THE AREA FRIDAY AHEAD OF A WARM FRONT. BY SATURDAY ENOUGH MOISTURE TO ALLOW FOR SHOWERS TO FORM BY SATURDAY MORNING WITH BEST FORCING ACROSS THE CAROLINAS. THIS SYSTEM EXITS BY SAT NIGHT WITH SUNDAY BEING A DRY AND COOL/MILD DAY WITH HIGHS IN THE 50S MOUNTAINS TO 60S EAST. HIGH PRESSURE TO ASSUME POSITION OVER THE OHIO VALLEY INTO THE SRN APPALACHIANS MONDAY TO KEEP THINGS DRY. NEXT SOUTHERN STREAM SYSTEM MAY WORK SOME SHOWERS OUR WAY BY TUESDAY. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... AS OF 145 AM EDT TUESDAY... COLD FRONT WAS EAST OF THE BLUE RIDGE EARLY THIS MORNING AND WAS CLOSE TO CROSSING THROUGH KLYH AND KDAN AT 06Z/2AM. HAVE THE FRONT PASSING THROUGH THESE STATIONS AND WINDS BECOMING WEST BY 08Z/4AM. PRESSURE RISES BEHIND THE FRONT WILL BRING WIND GUSTS OF 20 TO 30 KNOTS THROUGH MID TO LATE AFTERNOON. AFTER SUNSET WINDS WILL DIMINISH TO LESS THAN 10 KTS. CURRENTLY SOME MVFR CEILINGS IN THE MOUNTAINS AND RAPIDLY DISSIPATING SHOWERS. LOWER CONFIDENCE ABOUT HOW WIDESPREAD MVFR CEILINGS WILL BE BEFORE 12Z/8AM. VFR CONDITIONS WILL RETURN THIS AFTERNOON WITH HIGH PRESSURE BUILDING IN BEHIND THE FRONT. EXTENDED AVIATION... THEN THE NEXT CHANCE OF MVFR CONDITIONS AND PRECIPITATION WILL BE IN THE MOUNTAINS ON WEDNESDAY AND THURSDAY WITH THE PASSAGE OF A COLD FRONT. HIGH PRESSURE AT THE SURFACE BUILDS SOUTHEAST FROM THE OHIO VALLEY THURSDAY NIGHT INTO FRIDAY. OVERRUNNING CLOUDS WORK INTO THE AREA FRIDAY AHEAD OF A WARM FRONT. BY SATURDAY...ENOUGH MOISTURE TO ALLOW FOR SHOWERS WITH BEST FORCING ACROSS THE CAROLINAS. && .HYDROLOGY... AS OF 405 AM EDT TUESDAY... AFTER THE IMPRESSIVE RAINFALL SINCE SUNDAY MORNING...WHICH SAW OVER 6 INCHES AT A FEW GAGES IN ALLEGHANY COUNTY NC...RIVERS AND LARGE CREEKS IN THE NEW RIVER AND UPPER ROANOKE VALLEYS HAVE MOSTLY CRESTED AND ARE FALLING. STAGES ALONG THE MAINSTEM NEW RIVER WILL CONTINUE TO FALL. ALLISONIA AND RADFORD HAVE RECEDED BACK BELOW FLOOD STAGE. RIVER FLOOD WARNINGS CONTINUE FOR THE LOWER ROANOKE RIVER AT RANDOLPH AND AT DANVILLE AND SOUTH BOSTON ON THE DAN FOR MINOR FLOODING. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...MBS LONG TERM...WP AVIATION...AMS/JH HYDROLOGY...AMS/PC

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