Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 311803 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 103 PM EST SAT JAN 31 2015 .SYNOPSIS... COLD HIGH PRESSURE WAS CENTERED OVER WEST VIRGINIA AND WILL DRIFT SOUTHEAST DURING THE DAY...BEFORE DRIFTING OFF THE COAST TONIGHT. MEANWHILE...AN AREA OF LOW PRESSURE WILL MOVE OUT OF THE SOUTHERN ROCKIES TODAY...CROSSING THE CENTRAL/SOUTHERN PLAINS TONIGHT...BEFORE HEADING NORTHEAST INTO THE MID MISSISSIPPI AND OHIO VALLEYS ON SUNDAY...AND EVENTUALLY REACHING THE EAST COAST BY MONDAY. THIS STORM SYSTEM WILL PROVIDE A LARGE FOOTPRINT OF PRECIPITATION...WITH HEAVY SNOW FALLING NORTH OF INTERSTATE 70 FROM ILLINOIS TO PENNSYLVANIA...AND MAINLY RAIN SOUTH OF I-70 FROM OKLAHOMA AND TEXAS TO THE MID ATLANTIC COAST. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1245 PM EST SATURDAY... COLDEST OF THE AIR ALOFT ASSOCIATED WITH YESTERDAYS SHORT WAVE TROUGH HAS ALREADY PASSED OVERHEAD. TEMPERATURES ALOFT SHOULD NOW BE WARMING...MODELS WARMING OUR M13 DEG C READING FROM YESTERDAY EVENING TO NEAR M3 DEG C TODAY...ABOUT A 10 DEGREE CHANGE. THIS SHOULD NET HIGHS ABOVE FREEZING FOR THIS AFTERNOON IN SPITE OF STARTING OFF IN THE DEEP FREEZE THIS MORNING. DEWPOINTS ON THE OTHER HAND WILL REMAIN QUITE DRY WITH READINGS REMAINING IN THE SINGLE DIGITS...AND HELPING TO YIELD AFTN RH VALUES IN THE TEENS. LITTLE OR NO CLOUD COVER THIS AFTERNOON. HIGH PRESSURE ACROSS THE CAROLINAS THIS AFTERNOON AND THEN OFF THE SOUTHEAST COAST TONIGHT. AS WE BEGIN TO TRANSITION THROUGH THE AFTERNOON...SOME INCREASE IN UPPER LEVEL MOISTURE WILL BEGIN TO OCCUR IN THE FORM OF THIN CIRROSTRATUS. THIS WILL BE THE FIRST HINT OF OUR NEXT WEATHER SYSTEM TO IMPACT THE REGION. LOOKING WELL WEST OF OUR FORECAST AREA...THERE IS A BROAD UPPER LEVEL TROUGH WITH EMBEDDED SHORT WAVE ENERGY OVER THE DESERT SOUTHWEST. SOME OF THE ENERGY FROM THIS TROUGH IS ALREADY GETTING EJECTED INTO THE CENTRAL AND SOUTHERN PLAINS WITH RAIN FALLING FROM KANSAS TO WEST TEXAS. MODELS INDICATE THIS SOUTHERN STREAM ENERGY IS GOING TO PHASE WITH A NORTHERN STREAM SHORT WAVE WHICH WILL BE DROPPING SOUTHEAST OUT OF THE NORTHERN ROCKIES THIS AFTERNOON. THIS PHASING WILL RESULT IN THE DEVELOPMENT OF A SURFACE CYCLONE WHICH WILL THEN MOVE EAST ACROSS KANSAS AND MISSOURI TONIGHT...EVOLVING INTO A MAJOR WINTER STORM AS IT HEADS EAST BOUND ON SUNDAY. ATTM IT LOOKS LIKE THE RAIN/SNOW LINE WILL BE ALONG THE INTERSTATE 70 CORRIDOR...WITH SNOW TO THE NORTH AND RAIN TO THE SOUTH. FOR OUR PART OF THE CONUS IT LOOKS LIKE WE WILL BE SPARED THE WINTRY BRUNT OF THIS SYSTEM. THE CIRROSTRATUS THAT BEGINS TO GRACE OUR WESTERN HORIZON THIS AFTERNOON WILL THICKEN THIS EVENING... BECOMING OVERCAST FOR THE OVERNIGHT. AS THE CLOUD BASES LOWER...OUR AREA MAY GET TEASED BY A BRIEF PERIOD OF VERY LIGHT SNOW TOWARD DAYBREAK SUNDAY...BUT THE AIRMASS OVER OUR AREA IS SO DRY IN THE LOW LEVELS IT MAY ALL BE VIRGA...THE PRECIP DRYING UP BEFORE REACHING THE GROUND. DEEPER MOISTURE WILL MOST LIKELY REMAIN WELL WEST OF OUR FORECAST AREA...ARRIVING LATER SUNDAY AND ONLY AFTER WE HAVE HAD PLENTY OF TIME TO WARM UP ABOVE FREEZING. THE VERY DRY AIRMASS WOULD SUGGEST WE DROP PRETTY FAST AFTER SUNSET...BUT THE INCREASING CLOUD COVER WILL MOST LIKELY COUNTER THIS DIURNAL DIP. CHALLENGE TONIGHT WILL BE THE T-MIN...MODELS HAVING TROUBLE RESOLVING THE MINIMUM TEMPERATURE. LEWISBURG WV IS A GOOD EXAMPLE WHERE THE MAVMOS SUGGESTS 15 DEGREES FOR A MINIMUM VERSUS THE METMOS OF 27. OUR FORECASTS REFLECTS A MODEL BLEND...LOWS MAINLY IN THE 20S...WITH THE MINIMUM TEMPERATURE OCCURRING EARLY IN THE NIGHT...THEN LEVELING OFF AND POTENTIALLY RISING A DEGREE OR TWO AS CLOUDS THICKEN OVER THE FORECAST AREA. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 400 AM EST SATURDAY... HIGH PRESSURE ALONG THE SOUTH CAROLINA COAST SUNDAY MORNING WILL TRAVEL EAST INTO THE ATLANTIC OCEAN. A NORTHERN STREAM TROUGH WILL CREATE A SURFACE LOW PRESSURE OVER MISSOURI SUNDAY MORNING WITH ASSOCIATED WARM AND COLD FRONTAL BOUNDARIES. THE LOW CENTER WILL TRACK NORTHEAST ALONG THE OHIO RIVER AND THEN ACROSS NORTHERN VIRGINIA AND MARYLAND SUNDAY NIGHT. MODEL TRENDS CONTINUE TO PUSH LOW CENTER AND TRACK ALONG A NORTHERN ROUTE. THE CURRENT TRACK OF THIS LOW WILL KEEP OUR AREA IN A WARM AIRMASS THROUGH THE DAY SUNDAY. BECAUSE OF THE DRY AIRMASS IN PLACE IN WAKE OF THE HIGH PRESSURE CENTER SUNDAY MORNING...THE WAA PRECIPITATION WILL BE LIGHT SNOW OR SLEET SUNDAY MORNING AS THE WARM FRONT LIFTS NORTHWARD. ISENTROPIC LIFT MAY GENERATE LIGHT PRECIPITATION MAINLY ACROSS THE GREENBRIER VALLEY TO THE ALLEGHANY HIGHLANDS. THE WARM FRONT CONTINUES TO TRACK NORTH TO THE MASON-DIXON LINE DURING THE DAY SUNDAY...AS A COLD FRONT APPROACHES FROM THE WEST. THE ENTIRE AREA WILL BE IN THE WARM SECTOR BY SUNDAY AFTERNOON CHANGING PRECIPITATION OVER TO RAIN. HIGH TEMPERATURES SUNDAY WILL WARM INTO THE MID 30S IN THE NORTHWEST MOUNTAINS TO THE LOWER 50S IN THE PIEDMONT. THE COLD FRONT WILL ENTER MOUNTAINS SUNDAY NIGHT INTO MONDAY MORNING. FOR PTYPES LEANED TOWARDS THE GFS AND TEMPERATURE PROFILES. A BRIEF PERIOD OF FREEZING RAIN...SLEET AND SNOW MAY OCCUR JUST BEFORE THE CHANGE-OVER TO SNOW AFTER MIDNIGHT ACROSS SOUTHEASTERN WEST VIRGINIA AND THE ALLEGHANY HIGHLANDS. USED A NON DIURNAL TEMPERATURE CURVE WITH LOW TEMPERATURES SUNDAY NIGHT FROM THE MID 20S IN THE NORTHWEST MOUNTAINS TO THE LOWER 40S IN THE PIEDMONT. THE SURFACE LOW TRACKS OFF THE MID ATLANTIC COAST MONDAY MORNING WITH PRECIPITATION ENDING OVER THE PIEDMONT BY NOON. THE UPPER LEVEL PORTION OF THIS SYSTEM WILL TRACK OVER THE AREA DURING THE AFTERNOON. THE COMBINATION OF A DEFORMATION ZONE AND UPSLOPE FLOW WILL BRING SCATTERED SNOW SHOWERS AND SNOW FLURRIES TO THE MOUNTAINS THROUGH MONDAY AFTERNOON...THEN HIGH PRESSURE MOVES OVER THE OHIO VALLEY SHUTTING OFF MOISTURE FEED. BECAUSE TEMPERATURES PROFILES SHOULD BE WARM ENOUGH FOR RAIN DURING THE PERIOD OF PEAK QPF...OVERALL SNOW TOTALS WILL BE RELATIVELY LIGHT. ACCUMULATIONS FROM A COATING TO NEAR 3 INCHES IN THE UPSLOPE FAVORED AREAS OF GREENBRIER COUNTY MAY BE POSSIBLE. IN THE WAKE OF THE FRONT...A SURGE OF ARCTIC AIR WILL RESULT IN FALLING TEMPERATURES MONDAY. HIGHS WILL BE REACH DURING THE MORNING WITH VALUES FROM AROUND 30 IN THE NORTHWEST TO THE MID 40S IN THE SOUTHEAST. STRONG PRESSURE RISES AND COLD AIR ADVECTION WILL RESULT IN GUSTY WINDS FOR OUR REGION. A 1030 MB HIGH PRESSURE WILL BUILD EAST ACROSS OUR REGION MONDAY NIGHT. LOW TEMPERATURES MONDAY NIGHT WILL BE COLD WITH READINGS FROM THE SINGLE DIGITS IN THE NORTHWEST MOUNTAINS TO THE LOWER 20S IN THE PIEDMONT. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 400 AM EST SATURDAY... THE LONG TERM PERIOD BEGINS QUIET WITH COLD HIGH PRESSURE DRIFTING ACROSS THE REGION BEHIND THE EARLY WEEK COASTAL LOW. 850MB TEMPS BOTTOM OUT EARLY TUE MORNING IN THE -13C RANGE GREENBRIER COUNTY TOWARD -6C ACROSS THE PIEDMONT. RADIATIONAL COOLING UNDER THE SFC HIGH SHOULD BE IDEAL...ESPECIALLY WESTERN AREAS WHERE THERE SHOULD BE AMPLE SNOW COVER ON THE GROUND...LEADING TO LOW TEMPS IN THE SINGLE DIGITS VALLEYS WESTERN MOUNTAINS TO THE UPPER TEENS AND LOW 20S ACROSS THE PIEDMONT. GIVEN THAT THE AIR MASS IS NOT BITTERLY COLD...AS IN SOME PREVIOUS EVENTS WITH 850MB TEMPS -20C OR BETTER...AS HIGH PRESSURE SLIDES EAST OF THE REGION BY AFTERNOON/EVENING...WE SHOULD SEE TEMPERATURES MODERATE IN THE 30S WEST TO LOWER 40S EAST. WEDNESDAY...OUR ATTENTION TURNS TO THE NEXT POTENTIAL WINTER WEATHER SYSTEM. AS WITH THE PAST SEVERAL...THERE DO NOT APPEAR TO BE ANY CLEAR ANSWERS FOR THIS EVENT EITHER. DISTINCT NORTHERN STREAM AND SOUTHERN STREAM SYSTEMS ARE EVIDENT WED...WITH AN ARCTIC COLD FRONT FROM NEAR CHI-MCI...REASONABLY CONSISTENT AMONG BOTH MODELS. WHAT IS NOT CONSISTENT...HOWEVER...IS A POTENT SOUTHERN STREAM SYSTEM. THE GFS HAS THIS SYSTEM RACING INTO THE SOUTHEAST STATES...WHILE THE ECMWF STILL HAS THIS BACK ALONG THE TX COAST. THE ECMWF TRACKS THIS FEATURE WELL SOUTH KEEPING IT ACROSS GA/SC...THEN INTO THE WESTERN ATLANTIC AS IT PLUNGES AN ARCTIC HIGH SOUTHEAST INTO THE OH/TN VALLEY...CLEARLY FOCUSING ON THE NORTHERN STREAM. MEANWHILE...THE GFS TRACKS THIS NORTHEAST TOWARD THE SC/NC COAST AND GENERATES A COASTAL LOW NEAR THE OUTER BANKS OF NC. THE GFS HAS AN EQUIVALENT ARCTIC HIGH...BUT HOLDS IT BACK NORTH IN THE UPPER MIDWEST UNTIL A SECONDARY SHORT WAVE LIFTS OUT OF THE CENTRAL PLAINS. HENCE...THERE ARE CONSIDERABLE DIFFERENCES BETWEEN THE PRECIPITATION AMOUNTS ADVERTISED WITH THESE TWO PATTERNS. THE GFS WOULD SUGGEST WIDESPREAD RAIN/SNOW TRACKING ACROSS MUCH OF THE CWA WED NIGHT/THU...WITH UPSLOPE SNOW SHOWERS INTO THU/FRI. MEANWHILE...THE ECMWF SOLUTION WOULD INDICATE LITTLE MORE THAN SOME LIGHT SNOW ALONG THE ARCTIC FRONT...FOLLOWED BY TYPICAL UPSLOPE MOUNTAIN SNOW SHOWERS INTO THU. HAVE TAKEN A MIDDLE OF THE ROAD APPROACH FOR NOW...WHICH GENERALLY AGREES WITH THE SUPERBLEND OUTPUT...AS OPPOSED TO ANY ONE MODEL. IF THE GFS SOLUTION IS RIGHT...THERE IS MORE SIGNIFICANT POTENTIAL FOR WINTER PRECIPITATION ACROSS THE CWA...AND AGAIN ISSUES WITH P-TYPE. FOR THE REMAINDER OF THE EXTENDED...THE NEXT SYSTEM OF INTEREST DOES NOT ARRIVE UNTIL LATE IN THE WEEKEND OR EARLY NEXT WEEK...SO AT THIS POINT THE WEEKEND LOOKS DRY WITH NEAR TO BELOW NORMAL TEMPERATURES. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... AS OF 1255 PM EST SATURDAY... VFR THIS AFTERNOON THROUGH SUNDAY AFTERNOON. HIGH THIN CLOUDS THIS AFTERNOON WILL THICKEN AND CEILINGS WILL LOWER TONIGHT AND SUNDAY MORNING. HIGH CONFIDENCE THAT CEILINGS WILL REMAIN ABOVE 5000 FEET THROUGH 4AM SUNDAY. THERE IS SOME POTENTIAL FOR SOME VERY LIGHT SNOW TO OCCUR OVER SOUTHEAST WEST VIRGINIA AND NORTHERN VIRGINIA LATE TONIGHT. PROBABILITY WAS TOO LOW TO INCLUDE AT KLWB BUT JUST TO THE NORTH THERE MAY BE LIGHT SNOW AFTER 09Z/4AM. A DEVELOPING STORM SYSTEM OVER THE CENTRAL U.S. WILL MOVE EAST ON SUNDAY...THE SURFACE LOW TRACKING ALONG I-70 FROM STL 12Z/7AM SUNDAY TO NEAR HGR BY 12Z/7AM MONDAY. THIS TRACK KEEPS THE FORECAST AREA ON THE WARM SIDE OF THE SYSTEM ON SUNDAY NIGHT. HIGH CONFIDENCE OF WIDESPREAD RAIN AND MVFR OR LOWER CEILINGS. TIMING ON THE MODELS IS SLIGHTLY SLOWER THAN BEFORE. DO NOT EXPECT RAIN TO REACH KBLF AND KLWB BEFORE 21Z/4PM ON SUNDAY. A COLD FRONT WILL CROSS THROUGH THE AREA ON SUNDAY NIGHT TURNING WINDS TO THE WEST THEN NORTHWEST. AHEAD OF THE FRONT...A STRONG SOUTHWEST LOW LEVEL JET DEVELOPS AFTER 00Z/7PM ON SUNDAY NIGHT. LLWS IS POSSIBLE...ESPECIALLY AT KROA/KLYH AND KDAN. EXTENDED DISCUSSION... MONDAY...AFTER RAIN AND MVFR CONDITIONS IN THE MORNING...CEILINGS WILL LIFT IN THE AFTERNOON. EXPECT GUSTY WINDS BEHIND THIS SYSTEM WITH GUSTS OF 25 TO 40 KNOTS AT HIGHER ELEVATIONS. TUESDAY AND WEDNESDAY...HIGH PRESSURE PASSES OVERHEAD WITH VFR WX. THURSDAY...LOW PRESSURE MOVING ACROSS THE SOUTHEAST U.S. MAY BRING SUB-VFR CONDITIONS AND PRECIPITATION...POSSIBLY SNOW TO THE REGION. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...AMS/PM SHORT TERM...KK LONG TERM...RAB AVIATION...AMS

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