Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 300807 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 407 AM EDT TUE SEP 30 2014 .SYNOPSIS... WEAK HIGH PRESSURE BUILDS INTO THE AREA TODAY. A BACK DOOR COLD FRONT WILL SLIDE SOUTH INTO THE AREA WEDNESDAY. A STRONG COLD FRONT ARRIVES FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 320 AM EDT TUESDAY... PER SFC OBS/WEBCAMS AND COORDINATION WITH WFO RALEIGH HAVE EXPANDED THE DENSE FOG ADVISORY TO THE FAR SE CWA TIL 10 AM. THE FOG IS DENSE IN ENOUGH AREAS TO CONTINUE THE ADVISORY...WITH PATCHY DENSE FOG WEST OF THE NEW RIVER VALLEY LEADING TO A SPECIAL WX STATEMENT HERE. AFTER THE FOG BURNS OFF MID MORNING...EXPECT MOSTLY SUNNY SKIES. A SHORTWAVE MOVING ACROSS THE GREAT LAKES WILL SHIFT SOUTHEAST TOWARD THE MID ATLANTIC TONIGHT. APPEARS MOST OF THE AREA WILL STAY DRY WITH LITTLE CLOUD COVER. EXCEPTION WILL BE LATE TONIGHT WHEN SHORTWAVE PIVOTS SE INTO NRN VA...MAY SEE A SCATTERING OF SHOWERS AROUND AMHERST TO BUCKINGHAM...ALONG WITH MORE CLOUDS EAST OF THE BLUE RIDGE IN VIRGINIA. TEMPS TODAY WILL BE MILDER WITH MORE SUNSHINE WITH HIGHS RANGING FROM THE LOWER TO MID 70S MOUNTAINS...TO UPPER 70S/NEAR 80 EAST/ROANOKE. TONIGHT...SHOULD SEE SOME MID TO UPPER 40S SHELTERED VALLEYS IN THE SOUTHWEST WITH LESS CLOUD COVER WHILE MOST EXPERIENCE LOWS IN THE LOWER TO MID 50S. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 250 AM EDT TUESDAY... UPPER LOW PASSES WELL TO THE NE EARLY WEDNESDAY DRAGGING A WEAK SURFACE FRONT THROUGH FROM THE NW DURING THE DAY BEFORE THE BOUNDARY STALLS JUST TO THE SOUTH BY WEDNESDAY NIGHT. APPEARS JUST ENOUGH DEEP MOISTURE ALONG THE TRAILING FRONT/VORT TAIL TO WARRANT A SMALL CHANCE OF SHOWERS EXTREME NE SECTIONS CLOSER TO THE CORE OF THE UPPER SYSTEM INTO WEDNESDAY EVENING. OTRW PARTLY SUNNY AND QUITE MILD WEDNESDAY GIVEN WEAK WESTERLY FLOW ALOFT AND NOSE OF 85H WARMING ALONG THE BLUE RIDGE. NEXT WEDGE SET UP STARTS TO TAKE SHAPE LATER WEDNESDAY NIGHT AS HIGH PRESSURE OVER NEW ENGLAND NOSES SOUTH ALLOWING A MORE EASTERLY LOW LEVEL TRAJECTORY TO DEVELOP. HOWEVER HOW FAST THIS UNFOLDS STILL IFFY GIVEN SHORTWAVE RIDGING INCREASING WHILE THE MAIN AXIS OF THE SURFACE RIDGE IS FARTHER EAST. SINCE THE TREND LOOKS SLOWER TO SEE LOW CLOUDS DEVELOP...DELAYED THE ONSET OF DRIZZLE UNTIL LATE...AND TRIMMED COVERAGE TO MOSTLY THE NE AND BLUE RIDGE SECTIONS INTO THURSDAY MORNING. WEDGE WILL START TO FADE FROM WEST TO EAST DURING THURSDAY AS RETURN SOUTHERLY FLOW KICKS IN AHEAD OF THE NEXT UPSTREAM COLD FRONT. HOWEVER FLOW LOOKS WEAK ENOUGH IN THE EAST TO CAUSE DRIZZLE/FOG TO POSSIBLY LINGER INTO THE AFTERNOON AS MOST OF THE WARM ADVECTION MOVES OVER THE COOL POOL. ELSW EXPECTING INCREASING SUNSHINE WITH HIGHS BUMPING WELL INTO THE 70S...AND CLOSE TO 80 SE...WHILE THEN NORTH/NE SECTIONS MAY ONLY REACH THE LOWER 70S PENDING TIMING OF CLOUD EXODUS. COLD FRONT APPROACHES FROM THE WEST VERY LATE THURSDAY NIGHT PRECEDED BY INCREASING MOISTURE ADVECTION AND SW WINDS ALOFT. HOWEVER GUIDANCE SUGGESTS THAT THE LOW LEVEL WEDGE MAY FLOP BACK IN AREAS EAST OF THE MOUNTAINS AS THE BEST LOW LEVEL WARM ADVECTION GOES UP THE WESTERN SLOPES. GIVEN UNCERTAINTY WONT INCLUDE ANY ADDED DRIZZLE/FOG THURSDAY NIGHT BUT WILL ADD IN SOME WARM ADVECTION SHOWERS SW GIVEN THE TYPICAL RETURN FLOW CONVERGENCE SEEN ON THE PERIPHERY OF A WEDGE IN THIS TYPE SCENARIO. OTRW LOW TEMPS TO REMAIN QUITE MILD WITH READINGS PERHAPS RISING LATE AHEAD OF THE FRONT. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 345 PM EDT MONDAY... A COLD FRONT WILL SWEEP THROUGH THE REGION ON FRIDAY...CLEARING THE AREA FRIDAY EVENING. MODELS ARE EVEN FASTER TODAY WITH THE FRONT WITH RAIN OVER THE MOUNTAINS IN THE MORNING...DRYING BY EARLY AFTERNOON. SHOWERS MOVE EAST OF THE BLUE RIDGE IN THE AFTERNOON CLEARING THE PIEDMONT BY 08P/00Z. SINCE MODELS HAVE A TENDENCY TO RUN FRONTS FAST IN THE FALL...WILL MAINTAIN CURRENT FORECAST TIMING OF SHOWERS FRIDAY AND FRIDAY EVENING. WILL INCREASE POPS AS MODELS HAVE BEEN CONSISTENT WITH THE FRONTAL PASSAGE ON FRIDAY. FOLLOWING THE FRONT AND A PASSING OF A SHORT WAVE AXIS SATURDAY MORNING...A PRESSURE GRADIENT WILL BRING BREEZY AND GUSTY CONDITIONS TO THE REGION SATURDAY AFTERNOON. THESE WINDS WILL RELAX SATURDAY NIGHT AS HIGH PRESSURE BUILDS IN FROM THE SOUTHWEST. WITH HIGH PRESSURE IN THE REGION...SUNDAY AND MONDAY WILL REMAIN DRY AND LESS BREEZY. TEMPERATURES FRIDAY WILL DEPEND ON TIMING OF SHOWERS ROLLING ACROSS THE AREA. IF SHOWERS CAN HOLD OFF UNTIL LATE AFTERNOON...SOUTHSIDE COULD SEE 80F BEFORE THE DAY IS OUT. SINCE RAIN WILL ARRIVE EARLY ACROSS THE WEST...TEMPERATURES SHOULD NOT MAKE IT TO 70F. FOLLOWING THE FRONT AND OVER THE WEEKEND...TEMPERATURES WILL RUN 5F-10F COOLER THAN NORMAL. TEMPERATURES WILL BEGIN TO MODERATE TOWARDS NORMAL EARLY NEXT WEEK. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... AS OF 135 AM EDT TUESDAY... DENSE FOG WILL AFFECT MOST TERMINALS THIS MORNING...EXCEPT ROA/BLF. THERE WILL BE TIMES WHERE VSBYS WILL JUMP TO IFR/MVFR BUT MOST OF THE TIME IT SHOULD STAY 1/2SM OR LOWER. THIS FOG WILL BE DISSIPATING IN THE 12-15Z TIME FRAME WITH VFR EXPECTED THE REST OF THIS TAF PERIOD. EXTENDED AVIATION DISCUSSION... VFR CIGS AND VSBYS CAN BE EXPECTED WEDNESDAY AND THURSDAY...ALTHOUGH PERIOD OF LIFR LIKELY TO OCCUR FOR OUR MOUNTAIN VALLEY AIRPORTS...KBCB...KLWB...WHICH WILL EXPERIENCE DENSE RIVER FOG BEFORE DAYBREAK EACH MORNING. THE NEXT THREAT FOR SUB VFR CIGS/VSBYS WILL COME WITH A FRONTAL PASSAGE ON FRIDAY. THIS FRONT WILL LIKELY BE ASSOCIATED WITH A LINE OF SHOWERS AND THUNDERSTORMS...SWEEPING WEST TO EAST ACROSS THE REGION. NORTHWEST WINDS INCREASE BEHIND THIS FRONT FRIDAY NIGHT INTO SATURDAY. SATURDAY SHOULD BE VFR ALTHOUGH SOME UPSLOPE MVFR CIGS ARE POSSIBLE AT LWB/BLF. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR VAZ009-010- 012>017-022>024-032>035-043>047-058-059. NC...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR NCZ001>006- 018>020. WV...NONE. && $$ SYNOPSIS...PM/WP NEAR TERM...WP SHORT TERM...JH LONG TERM...RCS AVIATION...MBS/PM/WP

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