Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 280918 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 418 AM EST WED JAN 28 2015 .SYNOPSIS...
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HIGH PRESSURE CENTERED OVER THE OHIO VALLEY THIS MORNING WILL BUILD EAST ACROSS THE APPALACHIANS THIS AFTERNOON. MEANWHILE...AN AREA OF LOW PRESSURE OVER THE NORTHERN ROCKIES WILL MOVE EAST ACROSS THE NORTHERN PLAINS TODAY. THIS FAST MOVING CLIPPER LIKE SYSTEM WILL MOVE INTO THE GREAT LAKES BY THURSDAY. A COLD FRONT TRAILING SOUTH FROM THE LOW WILL CROSS THE APPALACHIANS THURSDAY AFTERNOON. HIGH PRESSURE SHOULD AGAIN FOLLOW THIS SYSTEM WITH ANOTHER ROUND OF COLDER AIR INCLUDING STRONG NORTHWEST WINDS AND MOUNTAIN SNOW SHOWERS OR FLURRIES FOR THE END OF THE WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 415 AM EST WEDNESDAY... A COLD START TO THE DAY WITH TEMPERATURES IN THE TEENS MOUNTAINS AND 20S PIEDMONT. ADD IN A 10 MPH NORTHWEST WIND AND THE WIND CHILLS RANGE FROM THE SINGLE DIGITS IN THE MOUNTAINS TO THE TEENS ACROSS THE PIEDMONT. LINGERING LOW LEVEL MOISTURE WAS STILL RESULTING IN SCATTERED FLURRIES ACROSS THE MOUNTAINS...BUT LITTLE OR NO ACCUMULATION. OUR FORECAST AREA REMAINS ON THE SOUTHWEST PERIPHERY OF THE NEW ENGLAND UPPER LEVEL LONG WAVE TROUGH AND COASTAL WINTER STORM. THE ONLY REMNANT EFFECT IS THE WIND AND SOME FLURRIES...WHICH WILL GO AWAY TODAY AS HEIGHTS RISE AND HIGH PRESSURE BUILDS ACROSS THE AREA. AS OF DAYBREAK THIS MORNING...A 1026 MB SURFACE HIGH WAS CENTERED OVER THE OHIO VALLEY AND GREAT LAKES. THIS HIGH IS FORECAST TO MOVE EAST AND STRENGTHEN TO AROUND 1030 MB AS IT PASSES OVERHEAD THIS EVENING. NET RESULT SHOULD BE DIMINISHING WINDS AND CLEAR SKIES...TEMPERATURES CLIMBING INTO THE 30S IN THE MOUNTAINS AND LOWER 40S PIEDMONT. MEANWHILE...WELL UPSTREAM OF THE FORECAST AREA...AN AREA OF LOW PRESSURE WILL EXIT THE NORTHERN ROCKIES TODAY CROSSING THE NORTHERN PLAINS. THIS CLIPPER LIKE STORM IS PROGGED BY ALL MODELS TO REMAIN NORTH OF OUR REGION AS IT ENTERS THE GREAT LAKES TONIGHT AND THURSDAY. A COLD FRONT WILL TRAIL SOUTH FROM THE LOW...SWEEPING ACROSS THE UPPER MIDWEST AND INTO THE OHIO VALLEY TONIGHT. AS THE FRONT APPROACHES OUR AREA LATE TONIGHT...WIND FLOW WILL BECOME SOUTHWESTERLY ALOFT PROMOTING WARMING TEMPERATURES IN ADDITION TO SOME INCREASING MID/UPPER LEVEL CLOUDINESS. TEMPERATURES ACROSS OUR FORECAST AREA TONIGHT WILL LIKELY BOTTOM OUT EARLY PRIOR TO THE ARRIVAL OF ANY CLOUD COVER...LOWS IN THE 20S. IF CLOUDS ARE DELAYED...THEN WE COULD SEE TEMPERATURES DIP BACK INTO THE TEENS AS INDICATED BY SOME OF THE MODELS. FOR NOW WILL GO WITH A MODEL BLEND SINCE NOT OVERLY CONFIDENT ON THE CLOUD COVER TIMING.
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&& .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
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AS OF 400 AM EST WEDNESDAY... 1028 MB SFC HIGH PRESSURE IN EASTERN NORTH CAROLINA THURSDAY MORNING WILL SLIDE EAST INTO THE ATLANTIC COAST...AS CLIPPER APPROACHING FROM THE UPPER MIDWEST. THE LOW CENTER WILL CONTINUE TO MOVE EAST AND IS PROGGED TO PASS WELL TO THE NORTH LATER THURSDAY...WHILE SWINGING ASSOCIATED COLD FRONT INTO THE REGION THURSDAY AFTERNOON. KEPT THE HIGHEST POPS IN THE MOUNTAINS WITH BEST DYNAMICS AND LIFT HEADING BY TO THE NORTH. A BAND OF SNOW/RAIN WILL ARRIVE OVER THE FAR WEST BY MIDDAY AND ATTEMPT TO CROSS THE RIDGES UNDER A QUICKLY VEERING WESTERLY FLOW. PTYPE LIKELY TO START AS LIGHT SNOW MOUNTAINS BEFORE SWITCHING TO MORE LIQUID NATURE AS BOTH 85H AND BOUNDARY LAYER WARMING TAKE OVER. DURING THE DAY...SNOWFALL AMOUNTS OF PERHAPS AN INCH OR SO IN WESTERN GREENBRIER WITH OVERALL QPF OF LESS THAN A TENTH OF AN INCH...MAINLY WEST. HIGH TEMPERATURES THURSDAY WILL RANGE FROM THE MID 30S IN THE NORTHWEST TO AROUND 50 DEGREES IN THE PIEDMONT. MAXIMUM TEMPERATURES ARE A CHALLENGE WITH CLOUDS AND PRECIPITATION. TIMING OF THE COLD FRONT WAS SIMILAR ON BOTH THE ECMWF AND GFS AND FAIRLY CONSISTENT. THE COLD FRONT WILL MOVE EAST THROUGH OUR REGION THURSDAY EVENING OR EARLY THURSDAY NIGHT...USHERING IN MUCH COLDER AIR. IN THE WAKE OF THE FRONT...NORTHWEST UPSLOPE SNOW SHOWERS AND SNOW FLURRIES ARE EXPECTED WEST OF THE BLUE RIDGE. A WINTER WEATHER ADVISORY MAY BE NEEDED FOR WESTERN GREENBRIER THURSDAY NIGHT INTO FRIDAY MORNING. BUT...IT IS TOO EARLY FOR ANY HEADLINES. WILL MENTION SNOW POTENTIAL IN THE HWO. SNOW ACCUMULATIONS FOR THE FAR WESTERN SLOPES SHOULD BE AN INCH OR TWO...BUT WESTERN GREENBRIER COUNTY SHOULD PICK UP A TOTAL OF AROUND 5 INCHES BEFORE THINGS START TO WIND DOWN FRIDAY MORNING INTO FRIDAY AFTERNOON. LOW TEMPERATURES THURSDAY NIGHT WILL VARY FROM THE UPPER TEENS IN THE NORTHWEST MOUNTAINS TO AROUND FREEZING MARK IN THE SOUTHEAST. HIGH TEMPERATURES FRIDAY WILL REMAIN COLD WITH READINGS FROM THE UPPER TEENS IN THE NORTHWEST TO THE LOWER 40S IN THE SOUTHEAST. ANOTHER ISSUE TO WATCH OUT FOR THURSDAY NIGHT INTO FRIDAY IS VERY STRONG WINDS. BOTH THE GFS AND NAM SHOWED A 50 KNOT LOW LEVEL JET WHICH COULD MIX DOWN LATE THURSDAY NIGHT INTO FRIDAY MORNING. LEANED TOWARDS HPCGUIDE FOR LOWS FRIDAY NIGHT FROM THE SINGLE DIGITS TO THE LOWER 20S. WITH THE COMBINED WIND AND COLD...WIND CHILL VALUES MAY BE AS COLD AS ZERO TO TEENS WEST OF THE BLUE RIDGE TO THE 20S IN THE EAST. HIGH PRESSURE WILL BUILD EAST ACROSS OUR AREA SATURDAY INTO SATURDAY NIGHT. HIGHS SATURDAY WILL VARY FROM THE MID 20S IN THE NORTHWEST TO THE LOWER 40S IN THE SOUTHEAST. UNDER INCREASING CLOUDS SATURDAY NIGHT...LOWS WILL GENERALLY BE FROM THE TEENS IN THE MOUNTAINS TO AROUND 30 DEGREES ALONG THE SOUTHERN BLUE RIDGE.
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&& .LONG TERM /SUNDAY THROUGH TUESDAY/...
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AS OF 400 AM EST WEDNESDAY... BELOW NORMAL TEMPERATURES TRENDING TO MUCH BELOW THROUGH THE EXTENDED...ALONG WITH POSSIBILITY OF MORE STRONG NORTHWEST WINDS SUNDAY NIGHT THROUGH MONDAY. UPPER LEVEL PATTERN FOR THE EXTENDED WILL BE SPLIT FLOW WITH A DOMINANT NORTHERN STREAM TROF IN THE EAST AND RIDGE FOR THE PAC NW. THERE IS ENOUGH GENERAL AGREEMENT BETWEEN THE GFS AND ECMWF MEMBERS...WHICH ARE SUPPORTED BY NAEFS ANOMALIES...TO LEAN TO THE COLD SOLUTION. THE UPPER TROF IN THE CENTRAL US WILL SLIDE EAST SUNDAY. LOW PRESSURE WHICH DEVELOPS TO OUR WEST AND TRACKS INTO NEW ENGLAND WITH A TRAILING COLD FRONT SWEEPING THROUGH THE REGION SUNDAY NIGHT. WILL NOT SPLIT HAIRS ABOUT PTYPE THIS FAR OUT BUT THE GENERAL TRACK TO OUR WEST AND NORTH WILL KEEP US ON THE WARM SIDE OF THE STORM. POSSIBLE HYBRID WEDGE IN PLACE AT THE ONSET MAY HELP COOL THINGS FOR WINTRY MIX AT ONSET GOING TO RAIN FOR THE BULK OF SUNDAY THEN BACK TO WINTRY AS PCPN TAPERS OFF...THOUGH TYPICAL NW FLOW UPSLOPE SNOW SHOWERS WEST OF THE BLUE RIDGE BECOME ESTABLISHED IN THE COLD AIR BEHIND THE COLD FRONT. MAY ALSO BE LOOKING AT ANOTHER STRONG NW WIND EVENT AS WE GO THROUGH SUNDAY NIGHT AND INTO MONDAY BUT THERE IS PLENTY OF TIME TO WATCH THIS AND SEE HOW LATER MODEL RUNS HANDLE THE EVOLUTION OF LOW LEVEL WINDS. HIGH PRESSURE WILL PROVIDE DRY WEATHER TUESDAY...BEFORE MOISTURE TRYS TO RETURN FROM THE SOUTHWEST WEDNESDAY.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... AS OF 1145 PM EST TUESDAY... DEEP COASTAL LOW NORTHEAST U.S. AND ASSOCIATED UPPER TROUGH/CYCLONIC FLOW STILL DOMINATING THE WEATHER ACROSS THE REGION. A COUPLE OF EMBEDDED NORTHWEST FLOW SHORT WAVES AND UPSLOPE FLOW CONTINUING TO ENHANCE CLOUDS ACROSS THE ALLEGHANYS...WITH CLOUDS OCCASIONALLY SPILLING OVER INTO THE NEW RIVER/ROANOKE VALLEY. THIS SHOULD BE THE TREND THROUGH THE NIGHT AS THESE SYSTEMS TRACK SOUTHEAST. LYH/DAN SHOULD REMAIN MOSTLY SKC...WITH SCT-BKN VFR CLOUDS AT ROA...SCT-BKN MVFR CLOUDS FOR BCB...AND BKN-OVC IFR CIGS FOR LWB/BLF. THE UPPER SHORT WAVE TRACKING THROUGH WV/ALONG WITH UPSLOPE MAY SUPPORT OCCASIONAL -SN MAINLY FOR LWB FOR A FEW MORE HOURS. LWB HAS BEEN REPORTING AN MVFR VSBY FOR SEVERAL HOURS...WHICH SEEMS HARD TO BELIEVE GIVEN RADAR COVERAGE...BUT POSSIBLE SINCE RADAR OVERSHOOTING VERY LOW TOPPED ECHOES. WILL INCLUDE A TEMPO MVFR GROUP FOR A FEW HOURS AT BEGINNING OF TAF VALID PERIOD...THEN EXPECT AS UPPER SUPPORT/UPSLOPE DIMINISHES...VFR VSBYS SHOULD PREVAIL. VFR VISIBILITIES ARE EXPECTED ELSEWHERE THROUGH THE TAF VALID PERIOD. VFR CIGS SHOULD RETURN TO EASTERN WV MID-LATE MORNING WED AS WELL AS HIGH PRESSURE BUILDS IN FROM THE WEST. EXPECT VFR CIGS AT ALL TAF SITES AFT 15Z WED MORNING. WINDS WILL CONTINUE TO BE AN ISSUE FOR A FEW MORE HOURS. NW WINDS 10-13KTS WITH GUSTS 18-23KTS PERSIST WEST OF THE BLUE RIDGE...AND LIKELY WILL THROUGH THE NIGHT. MODELS SHOW AN ENHANCEMENT AREA TO THE WINDS NEAR ROANOKE/FLOYD COUNTIES THROUGH THE NIGHTTIME. EVEN DAN HAS BEEN SEEING LOW END GUSTS FOR THE PAST FEW HOURS. WINDS WILL VEER TO THE NNW THROUGH THE DAY WED AND DECREASE TO 5-7KTS BY EVENING...BECOMING CALM/LIGHT AND VARIABLE MOST SITES BY 23Z. MEDIUM TO HIGH CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD. HIGH CONFIDENCE IN VSBYS THROUGH THE TAF VALID PERIOD...EXCEPT MEDIUM TO HIGH CONFIDENCE AT LWB. HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD. EXTENDED DISCUSSION... ANOTHER CLIPPER SYSTEM ARRIVES ON THURSDAY...BRINGING A CHANCE OF SUB-VFR CIGS AND VSBYS...WITH A CHANCE FOR -SHRA...-SHSN IN THE MOUNTAINS. MVFR CIGS LIKELY TO LINGER OVER THE MOUNTAINS THURSDAY NIGHT INTO FRIDAY IN THE WAKE OF THIS SYSTEM WITH STRONG NW WINDS ALSO PERSISTING INTO FRIDAY EVENING. ANOTHER AREA OF HIGH PRESSURE SHIFTS EAST INTO THE AREA SATURDAY WITH VFR EXPECTED INTO SATURDAY NIGHT. THE NEXT LOW PRESSURE SYSTEM HEADING OUT OF THE SW STATES WILL BRING A RETURN OF CLOUDS AND SOME PRECIPITATION ON SUNDAY WITH WIDESPREAD MVFR TO IFR LIKELY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...PM SHORT TERM...KK LONG TERM...MBS AVIATION...JH/RAB

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