Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 160456 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1156 PM EST MON DEC 15 2014 .SYNOPSIS... HIGH PRESSURE SHIFTS EAST OFF THE COAST OVERNIGHT. A COLD FRONT WILL CROSS THE AREA TUESDAY WITH AN OPPORTUNITY FOR SHOWERS. HIGH PRESSURE IS EXPECTED TO RETURN FOR MIDWEEK. ANOTHER LOW PRESSURE STORM APPROACHES FRIDAY AND PUSHES NORTHEAST INTO THE COMING WEEKEND. && .NEAR TERM /THROUGH TUESDAY/... AS OF 930 PM EST MONDAY... WILL BE SEEING LOWER TEMPS THANKS TO DRY AIRMASS (00Z RNK SOUNDING 0.22" PWAT) AND LACK OF SIGNIFICANT CLOUD COVER OR WIND. HOWEVER...AS MID CLOUDS...THEN LOWER CLOUDS ARRIVE FROM THE WEST AND SFC GRADIENT TIGHTENS ALLOWING FOR MORE SOUTHERLY INFLOW...DEWPOINTS WILL RISE AND TEMPS WILL STALL OUT THEN RISE SOME TOWARD DAWN. ISSUE COMES WITH TEMPS OUT EAST AS THINK WILL SEE SOME LOCATIONS BOTTOM OUT AROUND 30F. AS THE MOISTURE MOVES IN THERE COULD BE PATCHY FZRA HOWEVER THREAT IS SMALL GIVEN DRY AIRMASS AND NOT MUCH EWD PUNCH TO RAINFALL TIL AFTER DAWN. MADE SOME ADJUSTMENTS AGAIN TO LOWER POPS AS RADAR SHOWING NRN BAND SHOWERS HAD FADED OVER NE TN...TAPERING TO MORE SCATTERED OR ISOLATED COVERAGE. PREVIOUS VALID DISCUSSION... ON TUESDAY...ONE LOBE OF UPPER TROF OVER THE GREAT LAKES REGION WILL BE OPENING UP AS IT MOVES NORTHEAST INTO NEW ENGLAND. SFC LOW WILL FOLLOW A SIMILAR PATH...WHICH KEEPS BEST DYNAMIC SUPPORT OFF TO OUR NORTHWEST...AS IT PUSHES A COLD FRONT THROUGH OUR AREA TUESDAY AFTERNOON. THE COLD FRONT WILL REACH THE MOUNTAINS BY 18Z TUESDAY AND EXIT THE CWA BY TUESDAY NIGHT. DO NOT BELIEVE THAT THERE IS ENOUGH INSTABILITY TO ADD THE MENTION OF THUNDERSTORMS TO THE PIEDMONT FOR TOMORROW AFTERNOON AT THIS TIME. HIGH TEMPERATURES ON TUESDAY WILL RANGE FROM THE MID 40S IN THE MOUNTAINS TO THE MID 50S IN THE PIEDMONT. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... AS OF 330 PM EST MONDAY... EXTENSIVE AREA OF MOISTURE BELOW 700MB ON THE WEST SIDE OF THE APPALACHIANS THROUGH WEDNESDAY MORNING. WILL MAINTAIN PRECIPITATION IN THE FAVORED UPSLOPE AREAS OVERNIGHT TUESDAY NIGHT. BUFKIT SOUNDINGS SHOWED MOISTURE WAS TOO SHALLOW FOR CRYSTAL GROWTH. BUT ONLY A SMALL AREA IN WESTERN GREENBRIER COUNTY AND THE NORTHWEST NORTH CAROLINA MOUNTAINS WAS COLD ENOUGH TO SUPPORT A CHANCE OF FREEZING RAIN. MORE LIKELY PRECIPITATION WILL BE VERY LIGHT...DRIZZLE AND POSSIBLE FREEZING DRIZZLE. WENT BELOW GUIDANCE FOR MAXIMUM TEMPERATURES ON WEDNESDAY IN THE WESTERN MOUNTAINS SINCE THAT AREA WILL BE STARTING OUT THE DAY WITH CLOUD COVER. SUBTLE...PACIFIC ORIGIN SHORT WAVE CROSSES THE TENNESSEE VALLEY AND MID ATLANTIC STATES WEDNESDAY NIGHT AND THURSDAY. ASSOCIATED JET WITH THIS FEATURE WILL PROVIDE SOME UPPER DIFFLUENCE. NO DEEP MOISTURE BUT ENOUGH FOR AMPLE MID AND HIGH LEVEL CLOUDS. WILL ADD LOW PROBABILITY OF PRECIPITATION IN FOR LATE WEDNESDAY NIGHT INTO THURSDAY. SREF GUIDANCE AND BUFKIT SUGGEST THE POTENTIAL FOR LIGHT SNOW ON THE NORTHERN EDGE OF ANY PRECIPITATION SHIELD. ANY AMOUNTS FOR RAIN OR SNOW LOOK TO BE LIGHT. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... AS OF 300 PM EST MONDAY... FOR THURSDAY EVENING...MAY SEE A FEW LIGHT RAIN SHOWERS DRIFTING ACROSS THE FORECAST REGION...POSSIBLY LIGHT SNOW OVER HIGHER RIDGES OF THE MOUNTAINS...BEFORE MIDNIGHT AS A WEAK UPPER LEVEL DISTURBANCE PASSES OVERHEAD. NO ACCUMULATIONS ARE EXPECTED. HIGH PRESSURE WILL THEN PASS ACROSS THE GREAT LAKES THURSDAY NIGHT...AND THEN BUILD SOUTHWARD ACROSS THE MID ATLANTIC ON FRIDAY TO WEDGE AGAINST THE EASTERN FACE OF THE APPALACHIANS. AS THE HIGH BUILDS IN...WE WILL NOTICE WINDS SHIFTING INCREASINGLY NORTHEASTERLY...WHICH WILL DRAW COOLER AIR INTO OUR AREA FROM NEW ENGLAND. THE OTHER MAJOR FEATURE WE WILL SEE TAKE SHAPE ON FRIDAY IS THE PASSAGE OF A LARGE UPPER LEVEL TROUGH FROM THE ROCKIES EASTWARD ACROSS THE PLAINS. THIS TROUGH WILL SUPPORT DEVELOPMENT OF A LOW PRESSURE SYSTEM ALONG THE TEXAS COAST THAT WILL PUSH EAST NORTHEAST FRIDAY NIGHT AND SATURDAY. THIS LOW PRESSURE SYSTEM WILL BE A MAJOR FACTOR IN OUR WEATHER FOR THE COMING WEEKEND...LIKELY BRINGING WINTER STORM CONDITIONS TO PORTIONS OF OUR AREA. WEATHER FORECAST MODELS ARE IN BETTER AGREEMENT WITH ONE ANOTHER TODAY CONCERNING THIS SYSTEM...BUT HAVE NOTICEABLY SHIFTED IN THE TRACK THAT THE STORM IS EXPECTED TO FOLLOW. MOST CONSISTENT OVER THE PAST COUPLE DAYS HAS BEEN THE ECMWF...AND HAVE STEERED THE LONG- RANGE FORECAST IN ITS FAVOR THIS AFTERNOON...ALONG WITH THE SIMILAR CANADIAN MODEL. HOWEVER...UNCERTAINTY STILL REMAINS AND HAVE NOT COMPLETELY BOUGHT INTO THE ECWMF/CANADIAN SOLUTIONS AS THE 15/12Z RUNS HAVE SHIFTED THE LOW EAST FROM THE PREVIOUS RUNS...WITH THE LOW NOW EXPECTED TO PASS NORTHEAST ALONG THE COAST RATHER THAN FURTHER INLAND. THE SHIFT IN TRACK KEEPS OUR AREA FURTHER AWAY FROM THE WARM AIR WRAPPING AROUND THE LOW...WHICH NOW INTRODUCES A STRONGER POTENTIAL FOR SNOW AND SLEET FURTHER EAST...POSSIBLY TO INCLUDE THE SOUTHSIDE...AS COLDER AIR IS DRAWN ACROSS OUR AREA TOWARD THE LOW CENTER. ALSO SEE A POSSIBILITY OF REDUCED PRECIPITATION FOR OUR AREA AS THUNDERSTORM ACTIVITY DEVELOPING ALONG THE GULF COAST MAY ABSORB SOME OF THE MOISTURE RIDING NORTHWARD INTO THE MID ATLANTIC. AT ANY RATE...THE FORECAST FOR THIS SYSTEM IS FAR FROM SET IN STONE...AND ADDITIONAL CHANGES/ADJUSTMENTS ARE LIKELY OVER THE NEXT COUPLE OF MODEL RUNS. THE LOW PRESSURE SYSTEM IS EXPECTED TO AFFECT OUR AREA MAINLY FROM THE PREDAWN HOURS OF SATURDAY THROUGH LATE SATURDAY EVENING. AS THE LOW MOVES AWAY SATURDAY NIGHT...WINDS WILL SHIFT NORTHWESTERLY... RESULTING IN LINGERING UPSLOPE SNOW SHOWERS ACROSS THE WESTERN RIDGES...WHILE CLEARING CONDITIONS CAN BE EXPECTED FURTHER EAST. HIGH PRESSURE WILL BEGIN TO SETTLE ACROSS OUR AREA LATE SUNDAY EVENING. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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AS OF 1144 PM EST MONDAY... CHANGES FROM PREVIOUS FORECAST WAS TOO DELAY TIMING OF MVFR CIGS/VSBYS AND SHOWERS FOR THE WRN CWA AND IMPROVE THE CIGS FURTHER EAST. STILL LOOKS LIKE A BATCH OF SHOWERS MOVES ACROSS THE AREA BY DAWN INTO LATE MORNING THEN DRYING OUT BEHIND FRONT WITH SUB VFR CIGS REMAINING OVER THE BLF/LWB AREA THRU THE PERIOD. WINDS WILL SHIFT LIGHT SOUTH TO SW AT 4-10KTS LATER THIS MORNING THEN WEST AND GUSTY...ESPECIALLY AT ROA/BCB TUE AFTERNOON. MEDIUM CONFIDENCE IN VISIBILITIES...CEILINGS AND WINDS DURING THE PERIOD. EXTENDED DISCUSSION... UPSLOPE MOISTURE WILL KEEP SOME SUB VFR CIGS AT BLF PERHAPS LWB THRU INTO THURSDAY MORNING BEFORE DRIER AIR PUSHES IN. EXPECT VFR EAST...THOUGH BCB COULD SEE SOME MVFR CIGS TUESDAY NIGHT/WED MORNING. ANOTHER FAST MOVING UPPER LEVEL SYSTEM SLIDES ACROSS THURSDAY THOUGH BULK OF MOISTURE WILL BE ABOVE 3KFT...THOUGH SOME SUB VFR CIGS ARE EXPECTED SOUTH OF A BLF-DAN LINE. GOING TO FRIDAY INTO SATURDAY THE THREAT OF A WINTER STORM LOOMS FOR THE SOUTHEAST AND MID ATLANTIC AS LOW PRESSURE FORMS ACROSS THE GULF COAST STATES AND MOVES ALONG THE SOUTHEAST STATES/COAST FRIDAY NIGHT INTO SATURDAY. AT THIS TIME...AVIATION INTERESTS WILL NEED TO MONITOR THIS SITUATION AS LATER FORECASTS BECOME AVAILABLE. THIS COULD HAVE A HIGH IMPACT FOR TRAVEL OVER THE WEEKEND...FROM THE SOUTHERN APPALACHIANS AND CAROLINAS NORTH TO THE MID ATLANTIC.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...KK/PM NEAR TERM...KK/WP SHORT TERM...AMS LONG TERM...NF AVIATION...WP

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