Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 020853 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 453 AM EDT TUE SEP 2 2014 .SYNOPSIS...
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HIGH PRESSURE WILL EXTEND OVER THE REGION THIS MORNING INTO THIS AFTERNOON. A WEAK COLD FRONT TRACKS SOUTHEAST INTO OUR AREA BY THIS EVENING...BEFORE STALLING ACROSS THE CAROLINAS AND WASHING OUT ON WEDNESDAY. HIGH PRESSURE SETS BACK UP OVER THE EAST BY FRIDAY WITH YET ANOTHER COLD FRONT MOVING TOWARD US THIS WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 400 AM EDT TUESDAY... BERMUDA HIGH PRESSURE REMAINS IN CONTROL OVER THE REGION TODAY. THE HRRR...RAP3 AND NAM SHOWED A SHORTWAVE LIFTING NORTH ACROSS THE NORTHERN PORTIONS OF FORECAST AREA THIS MORNING. PLACED SOME LIGHT POPS IN THE WEST THIS MORNING WITH THIS FEATURE AND SOME DECENT CAPE. TRIMMED BACK THE EASTERN EXTENT OF POPS FOR THIS MORNING INTO THIS AFTERNOON ESPECIALLY EAST OF THE BLUE RIDGE. IN THE WAKE OF THIS MORNING SHORTWAVE...EXPECT GOOD SUBSIDENCE INTO THIS AFTERNOON. ANOTHER SHORTWAVE AND THE FRONT WILL EDGE CLOSER TOWARD THIS EVENING...WHICH WILL BRING A BETTER THREAT OF SHOWERS AND THUNDERSTORMS TO THE MOUNTAINS WITH ISOLATED TO WIDELY SCATTERED COVERAGE OVER THE FOOTHILLS AND PIEDMONT. WEAK SHEAR AND NOCTURNAL STABILIZATION SHOULD HELP LIMIT THE INTENSITY OF THE CONVECTION FOR OUR AREA. THE SWODY1 HAS PLACED THE SLIGHT RISK OF SEVERE STORMS TO OUR WEST FROM KENTUCKY NORTHWARD TO NORTH YORK WITH MAIN THREAT DAMAGING WINDS. BETTER INSTABILITY AND SHEAR SHOULD REMAIN ALONG THE WESTERN SLOPES OF APPALACHIANS. ANOTHER HOT AFTERNOON WITH HIGH TEMPERATURES FROM THE LOWER TO MID 80S IN THE WEST TO THE LOWER TO MID 90S IN THE EAST. A WEAK COLD FRONT SLIDES ACROSS THE REGION TONIGHT...AND MODELS PUSH CONVECTION TO THE EAST COAST. PREFRONTAL CONVECTION WILL SPREAD EAST FROM THE MOUNTAINS INTO THE PIEDMONT. THE NAM AND GFS WERE FASTER COMPARED TO ECMWF. LOW TEMPERATURES TONIGHT WILL REMAIN MILD WITH READINGS FROM THE LOWER 60S IN THE MOUNTAINS TO THE LOWER 70S IN THE PIEDMONT.
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&& .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
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AS OF 415 AM EDT TUESDAY... NEAR TERM SHORT WAVE WILL BE LOCATED JUST EAST OF THE REGION AT THE BEGINNING OF THIS PERIOD...WITH A WEAK WEST-EAST ORIENTED FRONTAL BOUNDARY STALLING JUST SOUTH OF THE VA/NC BORDER AS IT ENCOUNTERS A PERSISTENT RIDGE OF HIGH PRESSURE ALOFT...THAT OVERALL WILL REMAIN VERY PERSISTENT ACROSS THE CENTRAL AND EASTERN STATES SOUTH OF 40 DEG LAT WELL INTO NEXT WEEK. MOISTURE AND INSTABILITY WILL NEVER REALLY BE REMOVED FROM THE REGION BEHIND THE FRONT...ESPECIALLY ACROSS THE NC COUNTIES AND INTO SW VA. BY AFTERNOON...EXPECT SHOWERS/THUNDERSTORMS TO REDEVELOP ACROSS SW VA...NW NC...AND INTO THE PIEDMONT OF NC...SLOWLY WORKING NORTH TOWARD THE VA BLUE RIDGE AND INTO SOUTHSIDE VA. EXTENDED RANGE MODELS IN GENERAL AGREEMENT THAT DRYING WILL NOT PROGRESS AS FAR SOUTH AS INDICATED WITH YESTERDAYS MODEL RUNS...SO HAVE INCREASED POPS FURTHER NORTH SOONER THAN EARLIER THOUGHT...ESPECIALLY ACROSS THE SW COUNTIES. WITH 850MB TEMPS HOVERING IN THE +18C TO +20C RANGE...COOLING WILL BE MINIMAL IF ANY...WITH MAX TEMPS REMAINING A GOOD 10 DEGREES ABOVE NORMAL...WITH STILL 90S ACROSS THE PIEDMONT AND 80S ELSEWHERE...EXCEPT ELEVATIONS ABOVE 3500 FEET IN THE 70S. WITH THE MINIMAL PWAT STILL RUNNING AROUND 1.5 INCH...MIN TEMPS WILL NOT BE COOLING MUCH EITHER...REMAINING IN THE MUGGY 60S. FOR THU...WHAT IS LEFT OF THE FRONT TO THE SOUTH WASHES OUT AND RETURNS NORTH ALONG WITH INCREASINGLY HIGH MOISTURE CONTENT FROM THE SOUTH. THE UPPER RIDGE EXPANDS NORTHWARD AGAIN WITH 500MB HEIGHTS CLOSING IN ON 592DM ACROSS THE REGION AND 850MB TEMPS IN THE +20 TO +21C RANGE. ONLY THE LOWER SUN ANGLE IS SPARING US FROM MORE WIDESPREAD 90S THIS LATE IN THE SUMMER. AS INDICATED YESTERDAY...THE MAIN FOCUS FOR PRECIPITATION THU AND FRI WILL BE MAINLY ALONG TO EAST OF THE BLUE RIDGE WHERE BETTER MOISTURE CONTENT PREVAILS. THIS WILL BE THE PATTERN UNTIL THE NEXT UPPER SHORT WAVE TROUGH APPROACHES FROM THE NW LATE FRIDAY...BUT WILL NOT APPRECIABLY IMPACT THE CWA UNTIL THE WEEKEND. THUS...FOR THU AND FRI...SCATTERED...TYPICAL SUMMERTIME DIURNAL CONVECTION APPEARS TO BE THE RULE...WITH THE MAIN FOCUS ALONG-EAST OF THE BLUE RIDGE. TEMPERATURES WILL REMAIN WELL ABOVE NORMAL AGAIN.
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&& .LONG TERM /SATURDAY THROUGH MONDAY/...
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AS OF 430 AM EDT TUESDAY... THE NEXT IN THE SERIES OF UPPER SHORT WAVE TROUGHS WILL MOVE INTO THE REGION SATURDAY ALONG WITH THE ASSOCIATED COLD FRONT. THE BROAD AND STRONG SUBTROPICAL UPPER RIDGE WILL PERSIST ACROSS THE SOUTHERN STATES...BUT SHOWS SIGNS OF WEAKENING SOME AND THE CENTER OF WHICH WILL RELOCATE MORE TOWARD THE SOUTH CENTRAL INSTEAD OF THE SOUTHEAST STATES. THIS IN RESPONSE TO THE UPPER TROUGH IMPINGING ON THE NORTHERN FRINGES OF THE UPPER HIGH FRI-SAT. HOWEVER...ONCE AGAIN...THE FRONT APPEARS TO STALL ACROSS TN/NC...WITH DEEPER MOISTURE/INSTABILITY PRECARIOUSLY CLOSE SUCH THAT...AT A MINIMUM...POPS CANNOT BE REMOVED FROM THE SOUTHERN SECTIONS. BY FAR AT THIS POINT...THE BEST CHANCE FOR SHOWERS/THUNDERSTORMS WILL COME WITH THE FRONT FRI NIGHT INTO SATURDAY. GFS/ECMWF AT ODDS AS TO HOW MUCH...IF ANY DRYING FROM THE NORTH WILL PENETRATE THE REGION INTO EARLY NEXT WEEK...SO HAVE NOT MADE ANY CHANGES TO EARLIER ADVERTISED POPS BEYOND SAT. TEMPERATURES WILL REMAIN ON THE WARM SIDE AND ABOVE NORMAL. 850MB TEMPS SHOW A SLIGHT COOLING INTO THE +16C TO +18C RANGE OVER THE WEEKEND...BUT COULD SURGE BACK TOWARD +20C EARLY NEXT WEEK AS THE UPPER RIDGE AMPLIFIES BACK INTO THE SOUTHEAST/MID-ATLANTIC REGION AND HEIGHTS RISE ABOVE 590DM ONCE AGAIN.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/... AS OF 140 AM EDT TUESDAY... OVERALL VFR SHOULD PREVAIL THIS MORNING AT THE TAF LOCATIONS. A FEW SHOWERS MAY MAKE A RUN AT KLWB OVER THE NEXT COUPLE OF HOURS BUT LIKELY TO DISSIPATE CROSSING THE RIDGES SO LEAVING OUT MENTION. WELL MIXED LOW LEVELS WILL LIKELY INHIBIT MUCH FOG DEVELOPMENT THIS MORNING. CANT TOTALLY RULE OUT SOME BRIEF VALLEY FOG AT KLWB/KBCB ALTHOUGH FORECAST FOG STABILITY VALUES SHOW ONLY SPOTTY COVERAGE AT BEST. UPPER TROUGH AND ITS ASSOCIATED COLD FRONT WILL APPROACH FROM THE NORTHWEST THIS AFTERNOON WITH MOSTLY ISOLATED MOUNTAIN SHOWERS/STORMS EXPECTED DURING THE DAY AHEAD OF THE BOUNDARY. HOWEVER MAY SEE A MORE ORGANIZED BAND DROP IN FROM THE NW WITH THE LEADING PRE- FRONTAL CONVERGENCE...SO INCLUDING A VCTS MENTION ACROSS THE SOUTHEAST WEST VA SITES AROUND MID AFTERNOON AND LATE AT KBCB. OTRW EXPECTING MOSTLY VFR AFTER EARLY MID DECK ERODES AND SCATTERED- BROKEN CU FIELDS BETWEEN 4-6K FT TAKE SHAPE WITH HEATING. WIDELY SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS EVENING INTO TONIGHT. MEDIUM TO HIGH CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS DURING THE PERIOD. EXTENDED AVIATION DISCUSSION... FRONT SETTLES CLOSER TUESDAY NIGHT INTO WEDNESDAY...WHEN BETTER COVERAGE OF SHRA/TSRA IS EXPECTED. HOWEVER LOW CONFIDENCE ON THE TIMING AND SOUTHWARD POSITION OF THE BOUNDARY ON WEDNESDAY AT THIS POINT PENDING PRE-FRONTAL COVERAGE FROM TUESDAY NIGHT. FOR NOW APPEARS MAINLY VFR OUTSIDE OF EARLY MORNING FOG WEDNESDAY...THEN PERIODS OF MVFR WEDNESDAY AFTERNOON ESPECIALLY SOUTHERN SECTIONS...AND MAINLY ACROSS THE SOUTH/SOUTHWEST THURSDAY AFTERNOON FOR MORE ISOLATED NATURE COVERAGE. FRONT WASHES OUT TO THE SOUTH OF THE AREA FRIDAY WITH MORE WIDELY SCATTERED DIURNAL NATURE SHOWERS AND STORMS...THEN PERHAPS BECOMING MORE WIDESPREAD SATURDAY WITH PERIODIC MVFR IN MORE ORGANIZED COVERAGE AHEAD OF ANOTHER COLD FRONT ARRIVING FROM THE NORTHWEST LATE. OTRW WILL SEE A DAILY TREND OF EARLY MVFR/IFR IN FOG...FOLLOWED BY BRIEF VFR...THEN INCREASING AFTERNOON/EVENING CONVECTION WHEN MVFR TO LOCAL IFR WILL BE POSSIBLE. && .EQUIPMENT... AS OF 730 AM EDT FRIDAY ... THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...WILL BE OUT OF SERVICE UNTIL FURTHER NOTICE. A PART HAS BEEN BACK-ORDERED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...KK NEAR TERM...KK SHORT TERM...RAB LONG TERM...RAB/RCS AVIATION...JH/KK EQUIPMENT...RAB

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