Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 252349 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 649 PM EST WED FEB 25 2015 .SYNOPSIS... OVERNIGHT INTO THURSDAY...LOW PRESSURE WILL TRACK FROM THE GULF COAST STATES NORTHEAST TO OFF THE COAST OF THE CAROLINAS. A CLIPPER SYSTEM WILL CROSS THE REGION THURSDAY NIGHT THROUGH FRIDAY. HIGH PRESSURE BUILDS OVER THE AREA FOR THE WEEKEND. && .NEAR TERM /THROUGH THURSDAY/...
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AS OF 630 PM EST WEDNESDAY... FOLLOWING THE LATEST HRRR/RAP SHOWS SNOW MOVING INTO THE NC MTNS SHORTLY THEN SPREADING NEWD THROUGH THE REST OF THE EVENING REACHING OUR NRN AREAS BY MIDNIGHT. MODIFIED SNOWFALL AMOUNTS AS THINK HIGHER QPF WILL OCCUR IN THE NC MTNS...BUT STILL OVERALL HEADLINES LOOK GOOD. WILL FINE TUNE THE OVERNIGHT FORECAST SOON...AS MAY SEE SOME HIGHER AMOUNTS IN THE SOUTHEAST PER 18Z NAM...AND REFLECTIVITY FORECAST PER HRRR. PREVIOUS DISCUSSION AT 330 PM... THIS EVENING AND OVERNIGHT...AN AREA OF LOW PRESSURE WILL TRACK QUICKLY EASTWARD FROM ROUND THE MOUTH OF THE MISSISSIPPI RIVER TO OFF THE COAST OF THE CAROLINAS. ON THURSDAY...THE LOW WILL CONTINUE ITS QUICK DEPARTURE INTO THE WESTERN ATLANTIC. CONCURRENT WITH THE LOWS SWEEP THROUGH THE DEEP SOUTH TONIGHT...WILL BE AN APPROACHING SHORTWAVE TROUGH THROUGH THE OHIO VALLEY. OUR REGION WILL BE IMPACTED BY THE NORTHWEST FLANK OF DYNAMICS AND MOISTURE ASSOCIATED WITH THE GULF COAST LOW. THE APPROACHING SHORTWAVE TROUGH WILL DEEPEN WITH ITS APPROACH...AND ALLOW FOR SOME OF THE GULF COAST MOISTURE TO MAKE COVER A GREATER EXPANSE NORTHWARD AND WESTERN THAN IT WOULD OTHERWISE. PRECIPITATION IS EXPECTED TO SPREAD QUICKLY ACROSS THE AREA FROM SOUTHWEST TO NORTHEAST THIS EVENING...AND EXIT QUICKLY TOWARD THE NORTHEAST THURSDAY MORNING. FROM A LOW LEVEL THERMAL PROFILE STANDPOINT...THE PRECIPITATION TYPE TONIGHT SHOULD ALL BE SNOW ONCE SURFACE AND BOUNDARY LAYER TEMPERATURE COOL ENOUGH. MUCH OF THE PIEDMONT AREA REACHED THE 40 TO 45 DEGREE RANGE THIS AFTERNOON...WITH A MIX OF MID TO UPPER 30S ACROSS THE MOUNTAINS. DEW POINTS ARE STILL IN THE 10 TO 15 DEGREE RANGE AT MOST LOCATIONS. ONCE PRECIPITATION STARTS...IT SHOULD NOT TAKE TOO LONG FOR WET BULBING TO TAKE PLACE AND TEMPERATURE AND DEW POINT SEEK AT THE WET BULB WHICH WILL BE IN THE UPPER 20S TO AROUND 30. WE EXPECT A BRIEF PERIOD OF LIGHT RAIN WITH THE ONSET OF THE PRECIPITATION ACROSS PARTS OF SOUTHSIDE VIRGINIA AND NEIGHBORING PORTIONS OF NORTH CENTRAL NORTH CAROLINA. HOWEVER...IT SHOULD NOT TAKE MUCH MORE THAN TWO OR THREE HOURS FOR THE CHANGE TO SNOW. THE FOCUS FOR THE GREATEST AMOUNT OF SNOW WILL EXTENT FROM THE SOUTHERN PART OF THE FORECAST AREA...NORTHEAST INTO THE EASTERN SECTIONS WHERE 3 TO 5 INCHES ARE EXPECTED....WITH ISOLATED 6 INCHES. THE LEAST AMOUNT OF SNOW WILL BE ACROSS SOUTHEAST WEST VIRGINIA WHERE 1 TO 3 INCHES ARE EXPECTED. WINTER STORM WARNINGS AND ADVISORIES ARE POSTED FOR PARTS OF THE AREA...AND WILL BE ALLOWED TO CONTINUE BUT ARE BEING EXPANDED. WILL ADJUST AMHERST AND BEDFORD FROM ADVISORY TO WARNING. WILL NOW INCLUDE MERCER...SUMMERS AND EASTERN GREENBRIER IN THE ADVISORY. BY THURSDAY AFTERNOON...THE AREA TRANSITIONS INTO NORTHWEST FLOW IN THE WAKE OF THE COASTAL SYSTEM...AND MORE IMPORTANTLY AS THE OHIO VALLEY SHORTWAVE TROUGH CROSSES THE REGION. ANTICIPATE SCATTERED SNOW SHOWERS ACROSS SOUTHEAST WEST VIRGINIA SOUTH INTO THE NORTHERN MOUNTAINS OF NORTH CAROLINA. LIGHT ACCUMULATING SNOWS ARE EXPECTED ALONG THE PREFERRED UPSLOPE AREAS OF THESE REGIONS. LIGHTER SNOW SHOWERS AND FLURRIES WILL BE POSSIBLE DOWNSTREAM TO THE CREST OF THE BLUE RIDGE...AND PERHAPS ONE TIER OF COUNTIES EASTWARD INTO THE PIEDMONT. HAVE FAVORED THE LOW SIDE OF GUIDANCE FOR TEMPERATURES...OR SLIGHTLY LOWER WHERE THERE IS OR IS EXPECTED TO BE...A DECENT SNOW PACK. TONIGHT EXPECT LOWS AROUND 20 TO THE LOWER 20S ACROSS THE MOUNTAINS WITH MID TO UPPER 20S ACROSS THE PIEDMONT. FOR THURSDAY...EXPECT LOW TO MID 30S ACROSS THE MOUNTAINS FOR HIGHS...WITH LOW TO MID 30S ACROSS THE PIEDMONT.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... AS OF 330 PM EST WEDNESDAY... UPPER PATTERN FLATTENS AND BECOMES ZONAL OVER THIS TIME FRAME WITH WEAK RIDGING OVER THE EASTERN UNITED STATES BY SATURDAY. 850 MB TEMPERATURES ARE THE COLDEST ON FRIDAY FROM AROUND -10 IN THE SOUTHEAST TO -17 IN THE NORTHWEST. SATURDAY WILL SEE A SMALL RISE IN 850 MB TEMPERATURES. HAVE GONE BELOW GUIDANCE ON THURSDAY NIGHT SINCE FRESH SNOW WILL BE ON THE GROUND. COLDER NIGHT WILL BE ON FRIDAY NIGHT WITH LESS CLOUD COVER AND LIGHTER WINDS. LARGE AREA OF HIGH PRESSURE AT THE SURFACE WILL MOVE FROM THE DAKOTAS ON THURSDAY NIGHT THROUGH THE OHIO VALLEY BY SATURDAY. BY FRIDAY AFTERNOON UPSLOPE WINDS DIMINISH AND ENOUGH DRY AIR MOVES IN TO END SNOW SHOWERS IN THE WEST. SURFACE WINDS BECOME LIGHT AND VARIABLE ON FRIDAY NIGHT THEN WILL HAVE AN EASTERLY COMPONENT ON SATURDAY. MODELS WERE SUGGESTING SOME LOW LEVEL MOISTURE ON IN THE SOUTHEAST COUNTY WARNING AREA...WHICH MAY EXTEND AS FAR WEST AS THE BLUE RIDGE. BUFKIT AT DAN HAD A SHALLOW LAYER OF LIFT AND LIGHT SNOW EARLY SATURDAY MORNING. CONFIDENCE IN THIS SCENARIO IS NOT HIGH ENOUGH AT THIS TIME TO INCLUDE IN THE FORECAST. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 315 PM EST WEDNESDAY... EXPECT HIGH PRESSURE TO BE CENTERED OVER THE MID ATLANTIC SATURDAY NIGHT...WITH EAST NORTHEASTERLY WINDFLOW DRAWING CHILLY AIR INTO OUR AREA. LIGHT WIND SPEEDS AND MAINLY HIGH CLOUDS WILL RESULT IN EFFICIENT RADIATIONAL COOLING...WITH OVERNIGHT LOWS RANGING FROM THE MID TEENS NEAR INTERSTATE 64...TO THE MID 20S ACROSS NORTHERN NORTH CAROLINA. FOR SUNDAY...COOL HIGH PRESSURE WILL REMAIN WEDGED AGAINST THE MOUNTAINS...AND THEREFORE UNDERCUT FORECAST MODEL TEMPERATURES BY SEVERAL DEGREES FOR AFTERNOON HIGHS...RANGING FROM THE LOW/MID 30S NORTH TO THE LOW 40S SOUTH. LIGHT RAIN WILL ENTER THE AREA DURING THE EVENING AS OUR NEXT COLD FRONT APPROACHES...AND MAY SEE POCKETS OF FREEZING RAIN DEVELOP ALONG THE INTERSTATE 64 CORRIDOR OVERNIGHT WHERE SURFACE TEMPERATURES HOLD BELOW FREEZING. AT THIS POINT...ANY ICE ACCUMULATIONS SHOULD BE MODEST AS WINDS SHIFT INCREASINGLY SOUTHWESTERLY...WITH SURFACE TEMPERATURES BEGINNING TO RISE AGAIN AFTER MIDNIGHT MONDAY FROM SOUTHWEST TO NORTHEAST. WITH SOUTHWESTERLY WINDFLOW ESTABLISHED TO START THE DAY MONDAY... AFTERNOON TEMPERATURES WILL BE THE WARMEST WE HAVE SEEN IN WELL OVER A WEEK...WITH HIGHS CLIMBING INTO THE MID AND UPPER 40S OVER THE MOUNTAINS...AND INTO THE MID 50S ACROSS THE PIEDMONT. SHOWER ACTIVITY WILL CONTINUE THROUGH THE DAY...AND WILL BEGIN TO WANE DURING THE EVENING AS THE COLD FRONT PASSES ACROSS OUR AREA... SHIFTING WINDS NORTHWESTERLY AND DOWNSLOPE. HIGH PRESSURE BEHIND THE COLD FRONT WILL PASS QUICKLY ACROSS THE GREAT LAKES...AND WILL THEN BUILD SOUTHWARD ACROSS THE MID ATLANTIC...WEDGING AGAINST THE EASTERN FACE OF THE APPALACHIANS BY SUNRISE TUESDAY. RAIN CHANCES WILL QUICKLY INCREASE AGAIN ON TUESDAY AFTERNOON AS YET ANOTHER LOW PRESSURE SYSTEM DEVELOPS OVER THE PLAINS...AND PUSHES NORTHEAST TOWARD THE GREAT LAKES. COLD SURFACE TEMPERATURES PROVIDED BY THE HIGH PRESSURE WEDGE COMBINED WITH THE WARM AIR ALOFT AND DEEP MOISTURE AS PROVIDED BY THE LOW PRESSURE SYSTEM TO OUR WEST WOULD MAKE FOR A CHANCE FOR FREEZING RAIN FROM THE INTERSTATE 64 CORRIDOR...POSSIBLY AS FAR SOUTH AS THE NEW RIVER VALLEY. && .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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AS OF 640 PM EST WEDNESDAY... CIGS WILL LOWER AND SNOW WILL BE OVERSPREADING THE AREA THROUGH THE EVENING...WITH SOME RAIN EARLY AT DANVILLE. LOOK FOR POOR FLYING CONDITIONS TO START ALONG A BLF-BCB-DAN LINE IN THE 2-3Z TIME FRAME...WITH LWB-ROA-LYH OCCURRING IN THE 3Z-5Z TIME FRAME. SNOW IS GOING TO BE HEAVY AT TIMES ALONG AND SOUTH OF BLF-BCB- DAN...POSSIBLY EVEN INTO ROA/LYH. VSBYS WILL BE LOW AT TIMES. THIS SYSTEM SHOULD EXIT THE AREA THURSDAY MORNING WITH CIGS STAYING SOCKED IN AT MVFR LEVELS FOR MOST OF THE DAY...AS MODELS KEEP THE LOW LVLS IN HIGHER RH. SNOW WILL TAPER OFF AFTER 12Z...THOUGH FLURRIES OR EVEN FZDZ/DZ COULD OCCUR ACROSS THE MTNS THROUGH THE DAY. YET ANOTHER CLIPPER MAY CROSS THE AREA THURSDAY NIGHT INTO FRIDAY RETURNING THE WESTERN AREAS TO MVFR IN SPOTTY SNOW SHOWERS. COLD HIGH PRESSURE BUILDS IN BEHIND THIS SYSTEM FRIDAY NIGHT INTO SATURDAY WITH A RETURN TO VFR EXPECTED ACROSS THE REGION. DEVELOPING LOW PRESSURE OVER THE SOUTHERN PLAINS BY SUNDAY MAY COMBINE WITH A WARM FRONT OVER THE OHIO VALLEY TO SPILL SOME MVFR CIGS INTO THE AREA INCLUDING SOME SPOTTY RAIN INTO THE MOUNTAIN BY SUNDAY AFTERNOON INTO MONDAY. OTHERWISE VFR EAST OF THE MOUNTAINS WHERE THE RESIDUAL WEDGE OF HIGH PRESSURE WILL REMAIN.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...WINTER WEATHER ADVISORY UNTIL 9 AM EST THURSDAY FOR VAZ007- 009>014-018>020-022>024. WINTER STORM WARNING UNTIL 9 AM EST THURSDAY FOR VAZ015>017- 032. WINTER STORM WARNING UNTIL 1 PM EST THURSDAY FOR VAZ033>035- 043>047-058-059. NC...WINTER STORM WARNING UNTIL 9 AM EST THURSDAY FOR NCZ001>004- 018>020. WINTER STORM WARNING UNTIL 1 PM EST THURSDAY FOR NCZ005-006. WV...WINTER WEATHER ADVISORY UNTIL 9 AM EST THURSDAY FOR WVZ042>044- 507. && $$ SYNOPSIS...DS/WP NEAR TERM...DS/WP SHORT TERM...AMS LONG TERM...NF AVIATION...DS/WP

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