Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 150603 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 203 AM EDT TUE APR 15 2014 .SYNOPSIS... A COLD FRONT WILL APPROACH THE AREA FROM THE WEST LATE TONIGHT AND PASS ACROSS THE REGION DURING TUESDAY RESULTING IN WIDESPREAD SHOWERS. MUCH COLDER AIR WILL RUSH IN BEHIND THE FRONT TUESDAY AFTERNOON AS UNSEASONABLY COLD HIGH PRESSURE BEGINS TO BUILD IN ON STRONG NORTHWEST WINDS INTO TUESDAY NIGHT. THE HIGH WILL BUILD OVER THE MID ATLANTIC REGION WEDNESDAY THROUGH FRIDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 830 PM EDT MONDAY... SHOWERS HAVE BEEN SLOW TO EVOLVE THIS EVENING WITH MOSTLY LIGHT RAINFALL SEEN ACROSS THE SRN BLUE RIDGE ATTM DESPITE INCREASING MOISTURE OFF EVENING SOUNDINGS. MODELS REMAIN OVERDONE WITH DEGREE OF LIFT UNDER PASSING SHORTWAVES WELL AHEAD OF THE MAIN UPPER TROF THIS EVENING AS THE FLOW REMAINS MORE SW AND FORCING WEAK. LATEST HRRR SEEMS TO HAVE A HANDLE ON LIGHTER SHRA FOR A WHILE LONGER BEFORE THE FLOW DEEPENS/BACKS AND BETTER ISENTROPIC LIFT KICKS IN WITH AN INCREASING SOUTHERLY JET ESPCLY AFTER MIDNIGHT. HAVE ALREADY UPDATED TO LOWER POPS THIS EVENING...THEN QUICKLY REBOUND TO CATEGORICAL MOST SECTIONS OVERNIGHT AS BANDS OF SHRA BEGIN TO LIFT NORTH AHEAD OF THE WAVE AS WEAK INSTABILITY SHIFTS NORTH ACROSS SOUTHERN/EASTERN SECTIONS LATE. GIVEN THIS ALONG WITH STRONGER WIND FIELDS INCLUDED A LOW TOPPED TSRA MENTION ESPCLY FAR WEST JUST AHEAD OF THE FRONT AROUND DAWN AND OUT EAST FOR LOW TOPPED BANDS LATE AS WELL. BUMPED UP LOWS A LITTLE OUT WEST AS EXPECT THE FRONT TO BE JUST SLOW ENOUGH TO KEEP MOST TEMP FALLS FROM OCCURRING UNTIL THE MORNING. OTRW A MILD NIGHT WITH LOWS 50S TO LOWER 60S. WINDS AND LOW TOPPED SHRA THE MAIN CONCERNS DURING TUESDAY WITH STRONG ENOUGH GUSTS TO SUPPORT AT LEAST AN ADVISORY BLUE RIDGE SECTIONS WITH POSSIBLE BANDED SHRA OUT EAST DESPITE LIMITED INSTABILITY. AFTER COORDINATION WITH OTHER OFFICES HAVE DECIDED TO GIVE THE MIDSHIFT ANOTHER LOOK RATHER THAN HOISTING A WIND ADVISORY TONIGHT AS MAY BE CLOSE TO WARNING CRITERIA OVER THE SW FOR A PERIOD TUESDAY AFTERNOON. OTRW MADE SOME ADJUSTS TO TIMING OF THE HEAVIER SHRA AND POSSIBLE ISOLATED TSRA TUESDAY. PREVIOUS DISCUSSION AS OF 320 PM EDT MONDAY... SHOWERS STARTING TO ENTER THE WRN CWA THIS AFTERNOON. 12Z MODELS AND LATEST LOCAL HIGH-RES FAVOR SLOWER TIMING TO THE EAST THRU DUSK...BUT BY MIDNIGHT MOST AREAS WILL SEE LIKELY TO CATEGORICAL POPS AS SERIES OF UPPER VORTS MOVING AHEAD OF THE FRONT SHIFT FROM THE GULF COAST STATES INTO VA. APPEARS THUNDER THREAT WILL STAY ISOLATED AT BEST GIVEN INSTABILITY IS WEAK. GOOD JET DYNAMICS WILL LEAD TO POCKETS OF HEAVY RAIN OVERNIGHT INTO TUESDAY...AS FRONT APPROACHES. MODELS IN AGREEMENT EASING THE FRONT INTO THE MOUNTAINS BY 12Z-15Z TUESDAY AND SHIFTING TO THE EAST OF THE FORECAST AREA BY LATE TUE AFTERNOON. DESPITE FRONT MOVING THROUGH APPEARS ENOUGH LIFT AROUND THE BACKSIDE WITH SOUTHERLY JET TO KEEP THREAT OF RAIN WELL INTO TUESDAY AFTERNOON. RUSH OF COLDER AIR WORKS IN ABOUT 2-4 HOURS BEHIND THE FRONT CHANGING ANY LINGERING PRECIP TO SNOW SHOWERS IN THE HIGHER ELEVATIONS. GIVEN WARMER GROUND THE SNOW AMOUNTS THROUGH TOMORROW WILL BE LESS THAN AN INCH OVER THE RIDGETOPS ABOVE 3000 FT. WILL HAVE TO WATCH FOR ISOLATED FLOODING GIVEN WAVES OF LOW PRESSURE ALONG THE FRONT AND POTENTIAL FOR SOME TRAINING...ALTHOUGH SPEED OF FRONT MAY HINDER IT SOME. STILL QPF LOOKING ON THE ORDER OF 1 TO 1.5 INCHES...THOUGH LOCALLY HIGHER SEEMS LIKELY IN HEAVIER DOWNPOURS. WILL HOLD OFF ON ANY FLOOD WATCHES. EVEN THE RIVER ENSEMBLE FORECASTS ARE NOT TAKING ANY RIVER STAGES ABOVE FLOOD STAGE. WILL HAVE TO WATCH SOUTH BOSTON ON THE DAN THOUGH...GIVEN AMOUNTS SEEM SIMILAR TO LAST WEEK. THE OTHER ISSUE SHOULD BE WINDS BEHIND THE FRONT AS 6 HR PRESSURE RISES ON THE ORDER OF 6 TO 12 MB ARE EXPECTED. MADE SOME ADJUSTMENTS UP IN WIND GUSTS TO 40 KNOTS ACROSS THE SRN BLUE RIDGE AND ADJACENT AREAS. WILL ALLOW FOR ONE MORE RUN OF THE MODELS AS CLOUD COVER WILL TEMPER SOME OF THE GUSTS ABOVE INVERSION. HWO WILL MENTION WIND ADVISORY POTENTIAL. AS FOR TEMPS WILL BE SEEING SLOW FALLING AT BEST OVERNIGHT WITH CONTINUED SOUTH FLOW...WITH SHOWERS HELPING TO COOL IT SOME. TOMORROW WILL BE MILD IN THE FAR EAST BUT TEMPS WILL BE FALLING TO THE FREEZING MARK INTO THE UPPER 30S ACROSS THE MOUNTAINS BY DUSK. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... AS OF 355 PM EDT MONDAY... H85 TEMPS PLUNGE BEHIND STRONG COLD FRONT TUESDAY NIGHT...NEARING -12C PER THE GFS. MOISTURE DRIES OUT RATHER QUICKLY ALOFT...BUT SHOULD BE ENOUGH TO GENERATE AN HOUR OR TWO OF UPSLOPE SNOW SHOWERS ACROSS WESTERN GREENBRIER WHERE A QUICK HALF INCH OR LESS MAY FALL ABOVE 2500 FEET. SNOW SHOWERS/FLURRIES MAY FALL FOR A BRIEF TIME DOWN TO BLUEFIELD...BUT NO ACCUMULATION IS EXPECTED. SKIES SHOULD CLEAR RAPIDLY....WITH STRONG DOWNSLOPE...AND H85 JET NEAR 50KTS SHOULD PRODUCE WIND ADVISORY CRITERIA ACROSS NW NC/EXTREME SW VA AT THE VERY LEAST. POSSIBLY A SMALL WINDOW TUESDAY EVENING WITH HIGH WIND CRITERIA GUSTS NW NC. 1030MB HIGH PRESSURE NOSES ACROSS THE MOUNTAINS QUICKLY...AND MOS GUIDANCE IS SOLIDLY AT OR BELOW 32F FOR LOWS WED MORNING EVEN ACROSS THE PIEDMONT/SOUTHSIDE. BECAUSE OF THIS ISSUED A FREEZE WATCH EAST OF THE BLUE RIDGE. WINDS SHOULD HOLD THROUGH MUCH OF THE NIGHT...AND SOMETIMES LOWS COME IN A FEW DEGREES WARMER IN THIS SETUP. THUS THE CHANCE OF A WIDESPREAD FREEZE MAY BE MARGINAL ACROSS THE SOUTHEASTERN CWA...SOUTHSIDE/NC PIEDMONT. MUCH BETTER CHANCE NORTH OF THIS REGION. SURFACE HIGH PRESSURE WEDGING DOWN THE APPALACHIANS IS PRETTY MUCH LOCKED IN THROUGH THURSDAY NIGHT...WITH DRY SUNNY DAYS AND COLD NIGHTS EXPECTED. WITH LESS WIND WEDNESDAY NIGHT AND DEWPOINTS INTO THE TEENS WED PM...CONDS MAY BE EVEN MORE FAVORABLE FOR MORE WIDESPREAD FREEZE...WITH ANOTHER WATCH NECESSARY WED NIGHT/THURS MORNING. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 355 PM EDT MONDAY... WEAK TROUGH THROUGH THE MIDWEST EVENTUALLY PUSHES EAST...AND WEDGING HIGH PRESSURE EVENTUALLY DEPARTS THIS WEEKEND. WITH A RATHER DRY ANTECEDENT AIRMASS...QUESTIONABLE IF THIS MIDWEST TROUGH PRODUCES ANY PRECIP ONCE IT ARRIVES ACROSS THE OHIO VALLEY AND MIDDLE ATLANTIC THIS WEEKEND. OP GFS IS FAR MORE WET THAN THE ECMWF. THUS...POPS WERE KEPT RATHER LOW. A ZONAL UPPER FLOW TAKES SHAPE BY LATE WEEKEND INTO EARLY NEXT WEEK...WITH UNEVENTFUL AND DRY WEATHER CONTINUING ACROSS THE REGION. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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AS OF 150 AM EDT TUESDAY... MVFR TO IFR CIGS/VSBYS IN AREAS OF RAIN SHOWERS AND FOG EXPECTED THROUGH AROUND 18Z...AT WHICH POINT A STRONG COLD FRONT WILL MOVE THROUGH...IMPROVING CIGS TO VFR AFT 18Z PIEDMONT...BUT WITH CONTINUED MVFR CIGS IN UPSLOPE FLOW AND -SHRA OR EVEN POSSIBLY -SHSN EASTERN WV TAF SITES. BCB WILL SEE PERIODS OF MVFR CIGS CONTINUING THROUGH EVENING. MVFR VSBYS MAY CONTINUE AT BLF FOR A WHILE IN THE AFTERNOON/EARLY EVENING...BUT SHOULD IMPROVE TO VFR AT ALL OTHER SITES BY 20Z. WINDS WILL BE ONE OF THE GREATEST CONCERNS THIS TAF VALID CYCLE...MAINLY BEHIND THE FRONT. AHEAD OF THE FRONT...A GENERAL INCREASE OF SSE-SSW WINDS OF 10-20KTS CAN BE EXPECTED...BUT BEHIND THE FRONT...EXPECT WNW-NW 15-20KTS WITH GUSTS 30-40KTS. IT APPEARS THAT THIS WILL ONLY BE FOR A FEW HOURS...THEN DIMINISHING FAIRLY RAPIDLY AFT 02Z. MEDIUM CONFIDENCE IN CIGS/VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND DIR/SPD THROUGH THE TAF VALID PERIOD. LOW CONFIDENCE IN POTENTIAL FOR TSRA ROA/LYH/DAN AND LOW CONFIDENCE FOR -SHSN AT BLF/LWB THROUGH TAF VALIDP PERIOD. EXTENDED AVIATION DISCUSSION... MUCH DRIER AIR WORKS IN BEHIND THE FRONT WEDNESDAY WITH STRONG HIGH PRESSURE WEDGED IN FROM THE NE. THIS SHOULD ALLOW A RETURN TO WIDESPREAD VFR WITH THIS SCENARIO CONTINUING THURSDAY WITH HIGH PRESSURE RIDGING IN FROM OFF NEW ENGLAND AND THE NEXT COLD FRONT TO THE NW. THIS FRONT APPROACHES FROM THE WEST FRIDAY BUT APPEARS SLOW AND WEAK ENOUGH TO MAINTAIN VFR DURING THE DAY FOR NOW. THIS SYSTEM MAY BRING MVFR CIGS TO THE MOUNTAINS SATURDAY ALONG WITH A FEW SHOWERS OTRW VFR ELSW TO START THE WEEKEND.
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&& .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...FREEZE WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING FOR VAZ022>024-032>035-043>047-058-059. NC...FREEZE WATCH FROM LATE TONIGHT THROUGH WEDNESDAY MORNING FOR NCZ003>006-019-020. WV...NONE.
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&& $$ SYNOPSIS...AMS/JH/WP NEAR TERM...JH/WP SHORT TERM...KM LONG TERM...KM AVIATION...JH/RAB

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