Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 192053 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 353 PM EST WED NOV 19 2014 .SYNOPSIS...
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HIGH PRESSURE TO THE SOUTH WILL GIVE WAY TO A FAST MOVING COLD FRONT THAT WILL CROSS THE REGION FROM THE NORTHWEST LATE TONIGHT INTO THURSDAY MORNING. COLD HIGH PRESSURE SHOULD AGAIN FOLLOW THIS FRONT FOR WEEKS END RESULTING IN ADDITIONAL DRY WEATHER INTO SATURDAY. A COMPLEX LOW PRESSURE SYSTEM PASSING TO THE WEST SUNDAY WILL SWING A FRONTAL SYSTEM THROUGH THE REGION SUNDAY NIGHT BRINGING THE NEXT CHANCE FOR WIDESPREAD RAINFALL.
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&& .NEAR TERM /THROUGH THURSDAY/...
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AS OF 210 PM EST WEDNESDAY... HIGH PRESSURE TO THE SOUTHEAST WILL CONTINUE TO DRIFT SOUTH AND WEAKEN OVERNIGHT IN ADVANCE OF A FAST MOVING BUT MAINLY DRY COLD FRONT THAT LOOKS TO ARRIVE IN THE FAR WEST AROUND DAYBREAK THURSDAY. AHEAD OF THE FRONT...WILL SEE PERIODIC BANDS OF MID/HIGH CLOUDS ASSOCIATED WITH A STRONG JET ALOFT THAT MAY ALSO INDUCE SOME MOUNTAIN WAVE CLOUDS BEFORE THE FRONT ARRIVES. THIS JET WILL BE ASSOCIATED WITH A SPEED MAX RIDING THROUGH THE SOUTHERN PERIPHERY OF THE 5H TROUGH WHERE SOME CHANNELED SHORTWAVE ENERGY WILL ALSO RESIDE. GUIDANCE CONTINUES TO SHOW 40-50 KTS AT 85H LATER TONIGHT BUT MOSTLY ABOVE THE INVERSION LEVEL JUST BEFORE LOW LEVEL MOISTURE ARRIVES OVER THE WEST WITH THE ACTUAL FRONT. FOR NOW KEEPING MOST OF THE STRONGER WINDS ALOFT...BUT WOULD ONLY TAKE A BREAKING GRAVITY WAVE TO BRING SOME OF THESE WINDS DOWN TO THE RIDGES SO SOMETHING TO WATCH. OTRW MOSTLY CLEAR TO PC THIS EVENING...FOLLOWED BY A BAND OF LOWER CLOUDS WITH THE FRONT FAR WEST LATE WHERE SOME AIDED UPSLOPE ENHANCEMENT MAY PRODUCE A FEW HOURS OF SNOW SHOWERS. HOWEVER GIVEN SUCH A STRONG MORE WESTERLY TRAJECTORY AND LACK OF MOISTURE...KEEPING MOSTLY HIGH CHANCE POPS WESTERN SLOPES WHERE INCLUDING A GENEROUS HALF INCH OR SO OF SNOW MAINLY FAR NW PER PASSING WAVE ALOFT. LOW TEMPS TRICKY UNDER THE TIGHTENING PRESSURE GRADIENT THAT MAY KEEP THE RIDGES MIXED WITH LITTLE TEMP FALL WHILE THE VALLEYS/OUTLYING AREAS DROP FAST EARLY GIVEN DRY AIR. THEREFORE TRENDED UP A BIT SIMILAR TO MOS VALUES ESPCLY SPOTS LIKE BLF/ROA PER BREEZES WHILE KEEPING MOST OTHER SPOTS IN THE 20S BEFORE RISING SOME LATE. NEXT SURFACE RIDGE AXIS STARTS TO BUILD IN FROM THE WEST BEHIND THE FRONT THURSDAY ALLOWING FOR MORE SUBSIDENCE AND DRYING EXCEPT ALONG THE WESTERN SLOPES WHERE MORNING LOW CLOUDS/FLURRIES MAY HANG IN UNTIL MIDDAY. OTRW GRADIENT REMAINS RATHER TIGHT WITH DAYTIME MIXING/HEATING AIDING TRANSPORT OF STRONGER GUSTS TO THE SURFACE SO CONTINUED BREEZY/WINDY ESPCLY EARLY. HOWEVER RATHER NEUTRAL ADVECTION DESPITE SITTING UNDER THE 85H BAROCLINIC ZONE SUGGESTS BETTER DOWNSLOPE WARMING EAST WHERE HIGHS COULD TOP 50 SE. ELSW LINGERING CLOUDS UNDER COOLER AIR ALOFT LIKELY TO KEEP THE MOUNTAINS IN THE UPPER 30S TO MID 40S FOR THE MOST PART.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
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AS OF 300 PM EST WEDNESDAY... FINAL WEAK SHORT WAVE EXPECTED TO SCOOT RAPIDLY EAST THROUGH NEW ENGLAND ON THURSDAY NIGHT...MAINTAINING COLD ADVECTION PATTERN ALONG WITH UPSLOPING CLOUDS AND THE THREAT OF ADDITIONAL FLURRIES OVER THE WEST FACING SLOPES OF THE APPALACHIANS...MOST NOTABLY ACROSS WESTERN GREENBRIER COUNTY. DOWNSLOPING WINDS EAST OF THE BLUE RIDGE SHOULD SUPPORT MAINLY CLEAR SKIES ACROSS THE PIEDMONT. SURFACE HIGH PRESSURE WILL THEN BUILD OVER THE AREA FROM THE WEST FRIDAY INTO FRIDAY NIGHT...THEN DRIFT EAST OFF THE MID ATLANTIC COAST LATER SATURDAY INTO SATURDAY NIGHT. THIS SYSTEM WILL MAINTAIN DRY AND CONTINUED COLD WEATHER OVER THE ENTIRE FORECAST AREA FRIDAY INTO SATURDAY MORNING BEFORE SOUTHERLY WINDS ON BACKSIDE OF THE DEPARTING SYSTEM ALLOW TEMPERATURES TO BEGIN A MODERATION BACK CLOSER TO SEASONAL AVERAGES BY MID AFTERNOON. NEXT SIGNIFICANT SHORT WAVE TROF EXPECTED TO BEGIN LIFTING NORTHEAST OUT OF THE SOUTHERN PLAINS AND WESTERN GULF COAST STATES ON SATURDAY NIGHT...PRECEDED BY INCREASING MID AND HIGH LEVEL CLOUDS. LOWER AND MID TROPOSPHERE OVER THE MID ATLANTIC AND MID APPALACHIAN REGION IN PROXIMITY TO COASTAL SURFACE RIDGE EXPECTED TO REMAIN SUFFICIENTLY DRY THROUGHOUT THE NIGHT SUCH THAT ANY LATE-NIGHT PRECIPITATION LIKELY TO REMAIN ALOFT (VIRGA) IN BLACKSBURG AREA OF CONCERN. IF ANY GROUND-BASED PRECIPITATION DOES OCCUR...IT SHOULD BE CONFINED TO THE HIGHER ELEVATIONS OF THE NW NC MOUNTAINS TOWARD DAYBREAK SUNDAY...WHICH WILL BE CLOSEST TO THE APPROACHING SYSTEM. ATMOSPHERIC PROFILE EXPECTED TO BE RAPIDLY WARMING DURING THIS PERIOD SUCH THAT P-TYPE THREAT WILL BE MINIMIZED...ALTHOUGH A BRIEF PERIOD OF SOME SLEET CAN NOT BE ENTIRELY RULED OUT DUE TO WET- BULBING INFLUENCES OF AN INITIALLY VERY DRY ATMOPSHERE. AT THE PRESENT TIME...FORECAST SOUNDINGS DO NOT SUPPORT ANY SLEET OR FREEZING RAIN ALONG THE LEADING EDGE OF THE ADVANCING PRECIPITATION SHIELD...SO ONLY RAIN IS CURRENTLY BEING REFLECTED IN GRIDS...IF ANY FALLS AT ALL BEFORE DAYBREAK SUNDAY.
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&& .LONG TERM /SUNDAY THROUGH TUESDAY/...
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AS OF 330 PM EST WEDNESDAY... EXPECT TO START SUNDAY OFF WITH ATLANTIC MOISTURE RIDING NORTH ACROSS OUR AREA AHEAD OF A DEEP LOW PRESSURE SYSTEM APPROACHING FROM THE CENTRAL PLAINS. LIKELY TO SEE POCKETS OF DRIZZLE OR LIGHT RAIN ACROSS THE AREA AT SUNRISE...POSSIBLY WITH ISOLATED SPOTS OF VERY LIGHT FREEZING RAIN ACROSS PORTIONS OF THE GREENBRIER AND SHENANDOAH VALLEYS IF THE PRECIPITATION ARRIVES EARLIER THAN EXPECTED. HEAVIER...MORE WIDESPREAD RAIN WILL WORK NORTHWARD ACROSS THE AREA BY LATE MORNING...BECOMING WIDESPREAD RAIN ACROSS THE ENTIRE AREA DURING AFTERNOON. HAVE ENOUGH CONFIDENCE GIVEN THE CONSISTENCY BOTH AMONG THE VARIOUS WEATHER MODELS...AS WELL AS FROM MODEL RUN TO RUN...TO GO CLOSE TO 100% CHANCE OF RAIN FOR SUNDAY AFTERNOON. THIS WILL BE A DEEP LOW PRESSURE SYSTEM...SUPPORTED ALOFT BY A INTENSE NEGATIVELY TILTED TROUGH THAT WILL PRODUCE 50KT TO 60KT OF WIND SHEAR IN THE LOWEST KILOMETER OF THE ATMOSPHERE. THE GREATEST ENERGY ASSOCIATED WITH TROUGH WILL PASS ACROSS OUR REGION DURING THE AFTERNOON AND EVENING...HOWEVER IT IS DIFFICULT TO GET MORE SPECIFIC IN THE TIMING AND MOST AFFECTED LOCATIONS THIS FAR INTO THE FUTURE. WILL SAY AT THIS POINT THAT THERE IS A POTENTIAL FOR SOME SEVERE ACTIVITY ON SUNDAY AS A FEW CELLS MAY CARRY STRONGER WINDS ALOFT TO THE SURFACE. BECAUSE OF THE STRONG LOW LEVEL SHEAR...MAY ALSO SEE A FEW ROTATING CELLS PASS ACROSS THE AREA. THE LOW PRESSURE SYSTEM WILL LIFT NORTH TOWARD THE GREAT LAKES SUNDAY NIGHT...SHIFTING WINDS SOUTHWESTERLY ACROSS OUR AREA. THE SOUTHWESTERLY FLOW WILL BRING STRONGER HEATING FOR MONDAY AFTERNOON AS HIGHS RANGE FROM THE LOW 60S WEST TO AROUND 70 EAST. EXPECT A COLD FRONT TO ARRIVE AS EARLY AS MONDAY EVENING TO RETURN OUR TEMPERATURES CLOSER TO NORMAL FOR TUESDAY.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... AS OF 1145 AM EST WEDNESDAY... EXPECT VFR CONDITIONS INTO THIS EVENING AS HIGH PRESSURE SHIFTS TO THE SOUTHEAST WHILE A DEVELOPING LOW PRESSURE SYSTEM APPROACHES THE GREAT LAKES FROM THE NORTHERN PLAINS. THE TRANSIT OF THESE SYSTEMS WILL CAUSE AN INCREASING SOUTHWEST TRAJECTORY THIS AFTERNOON WITH GUSTS INTO THE 15 KT TO 20 KT RANGE POSSIBLE AS THE PRESSURE GRADIENT BETWEEN THE TWO SYSTEMS TIGHTENS. MID AND HIGH CLOUDS WILL ALSO INCREASE ACROSS MUCH OF THE REGION THIS AFTERNOON AND EVENING. A COLD FRONT WILL TRACK INTO WESTERN AREAS AROUND DAYBREAK THURSDAY. MOISTURE AHEAD OF THE FRONT WILL BRING BKN/OVC VFR CIGS AT KBLF/KLWB AFTER MIDNIGHT...WITH BASES POSSIBLY LOWERING INTO MVFR ALONG AND JUST BEHIND THE BOUNDARY EARLY THURSDAY. SOME SNOW SHOWERS ALSO POSSIBLE AT TIMES BETWEEN DAWN AND MID MORNING THURSDAY BUT NOT ENOUGH TO INCLUDE MUCH MENTION OUTSIDE OF PERHAPS KBLF IN THE TAFS FOR NOW. SOME OF THESE VFR/OCNL MVFR CIGS COULD ALSO SPILL OUT TO THE BLUE RIDGE...AFFECTING KBCB/KROA EARLY THURSDAY MORNING AS WELL WITH MAINLY CLEAR SKIES TO THE EAST. OTRW MAIN CONCERN WITH POTENTIAL LLWS THIS EVENING/OVERNIGHT AS A STRONG JET MOVES ATOP A WEAK SURFACE INVERSION. THIS WOULD AFFECT ALL TAF LOCATIONS EXCLUDING KDAN AT THIS POINT AND WHERE BETTER MIXING SUCH AS AT KBLF LOOKS TO KEEP SURFACE WINDS RATHER GUSTY ALONG THE RIDGES. THUS INCLUDING A PERIOD OF LLWS AT THE OTHER FOUR TAF SITES STARTING THIS EVENING AND CONTINUING OVERNIGHT UNTIL THE JET PASSES AND MORE CLOUDS ARRIVE LATE. MVFR/VFR CIGS LIKELY TO LINGER THURSDAY MORNING IN THE WEST BEFORE DRYING ALLOWS ALL LOCATIONS TO RETURN TO VFR IN THE AFTERNOON. WILL AGAIN BE GUSTY BEHIND THE PASSING FRONT WITH WESTERLY WINDS LIKELY TO GUST TO 20-25 KTS FROM MID MORNING THURSDAY THROUGH MUCH OF THE AFTERNOON. EXTENDED DISCUSSION... THURSDAY NIGHT THROUGH SATURDAY WILL AGAIN BE VFR...WITH HIGH PRESSURE IN THE REGION. A MORE SIGNIFICANT SYSTEM WILL APPROACH THE AREA WITH RAIN AND SUB-VFR CONDITIONS SUNDAY INTO SUNDAY NIGHT. MAY SEE A BRIEF RETURN TO VFR DURING MONDAY OUTSIDE OF THE MOUNTAINS AS A DRY SLOT DEVELOPS BETWEEN THE EXITING FRONT FROM SUNDAY AND THE NEXT UPSTREAM COLD FRONT. && .EQUIPMENT... AS OF 355 AM EST WEDNESDAY... THE VISIBILITY SENSOR AT KLYH...LYNCHBURG AIRPORT...WILL BE OUT OF SERVICE UNTIL PARTS ARRIVE TO REPLACE THE SENSOR. UNTIL THEN THE VISIBILITY WILL ONLY BE REPORTED WHEN THE CONTROL TOWER IS STAFFED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...WERT LONG TERM...NF AVIATION...JH/WP EQUIPMENT...

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