Area Forecast Discussion
Issued by NWS Blacksburg, VA

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281 FXUS61 KRNK 081007 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 507 AM EST MON FEB 8 2016 .SYNOPSIS...
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A STRONG CYCLONE IN THE UPPER LEVELS OF THE ATMOSPHERE WILL SINK SOUTH ACROSS THE GREAT LAKES AND INTO THE OHIO VALLEY TODAY. THE AREA OF LOW PRESSURE WILL CUTOFF AND REMAIN NEARLY STATIONARY FOR THE NEXT THREE DAYS...TEMPERATURES FALLING AFTER TODAY AND REMAINING BELOW FREEZING THROUGH MUCH OF THE UPCOMING WEEK. THE LEADING EDGE OF THIS AIRMASS WILL ARRIVE IN THE FORM OF A COLD FRONT...THIS FRONT CROSSING THE MOUNTAINS THIS AFTERNOON... ASSOCIATED WITH RAIN AND SNOW SHOWERS. THE COLDEST OF THE AIR WILL NOT ARRIVE UNTIL TUESDAY. WEAK UPPER LEVEL IMPULSES WILL MOVE ACROSS THE MOUNTAINS DURING THE WEEK RESULTING IN A PROLONGED SNOW SHOWER EVENT ESPECIALLY OVER THE MOUNTAINS THROUGH MIDWEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 445 AM EST MONDAY... COLD ARCTIC LOW...SURFACE AND ALOFT...WAS CENTERED OVER WISCONSIN. TWO FRONTS TRAILED SOUTH FROM THE LOW. THE FIRST EXTENDED FROM MICHIGAN SOUTH THROUGH OHIO AND INTO CENTRAL KY/TN. THIS FIRST FRONT WAS ASSOCIATED WITH AN AREA OF RAIN... TEMPERATURES JUST AHEAD OF THE FRONT IN THE 40S...AND 30S JUST BEHIND THE FRONT. THE SECOND FRONT EXTENDED FROM WISCONSIN SOUTH THROUGH IOWA AND INTO THE CENTRAL PLAINS. THIS FRONT WAS THE LEADING EDGE OF THE ARCTIC BITTER COLD WITH TEMPERAUTRES BEHIND THIS FRONT IN THE SINGLE DIGITS AND TEENS. THE FIRST FRONT IS PROGGED TO CROSS OUR FORECAST AREA TODAY... ARRIVING IN OUR FAR WESTERN COUNTIES NEAR THE APPALACHIAN DIVIDE TOWARD NOON...THEN MOVING EAST OF THE MOUNTAINS THIS AFTERNOON...CROSSING THE PIEDMONT THIS EVENING. IN SPITE OF TEMPERATURES IN THE 20S ACROSS THE CWA EARLY THIS MORNING...WARM AIR ADVECTION AHEAD OF THE FRONT SHOULD ALLOW TEMPERATURES TO RISE ABOVE FREEZING...REACHING THE UPPER 30S TO NEAR 40 IN THE MOUNTAINS...AND UPPER 40S TO NEAR 50 IN THE PIEDMONT. WITH TEMPERATURES THIS WARM...EXPECTING ANY PRECIPITATION ASSOCIATED WITH THE FRONT TO FALL AS A MIX OF RAIN/SNOW IN THE MOUNTAINS... AND ALL RAIN EAST OF THE BLUE RIDGE. WILL MAINTAIN THE EXISTING WINTER WEATHER ADVISORY FOR OUR FAR WESTERN COUNTIES WHERE 1 TO 2 INCHES OF SNOW IS POSSIBLE TODAY. NOT OVERLY CONFIDENT ON THE ACCUMULATION SINCE IT WILL DEPEND ON WHETHER EVAPORATIONAL COOLING CAN MAINTAIN A P-TYPE OF ALL SNOW. HIGHEST ELEVATIONS WILL HAVE THE BEST CHANCE TO REMAIN ALL SNOW. LOWER ELEVATIONS WILL NOT. TOTAL MODEL QPF IN LIQUID EQUIVALENT FORM IS 0.1 TO 0.2 INCHES. ITS NOT IN THE FORECAST ATTM...BUT SOMETHING TO WATCH OUT FOR IS THE POTENTIAL FOR ISOLD THUNDER. WITH TEMPERATURES RISING INTO THE 40S IN THE BOUNDARY LAYER...THIS MAY CREATE JUST ENOUGH INSTABILITY TO DRIVE A LINE OF DEEPER CONVECTION RIGHT ALONG THE FRONT. FALLING HEIGHTS AND STEEPENING LAPSE RATES ALONG THE LEADING EDGE OF THE UPPER TROF MAY DRIVE SOMETHING MORE ROBUST THIS AFTERNOON. IF THIS OCCURS THEN COLDER AIR WITHIN THE DOWNDRAFTS COULD DRIVE HEAVIER RAIN/SNOW RATES THAN WHAT IS CURRENTLY FORECAST. BY TONIGHT THE FIRST FRONT WILL BE MAKING ITS WAY ACROSS THE PIEDMONT AND HEADED FOR THE COAST. COLD AIR ADVECTION WILL BE DRAWING DOWN THE TEMEPERATURE WITH ANY LINGERING MOISTURE CHANGING OVER TO SNOW SHOWERS. ARRIVAL OF THE SECOND FRONT LATE TONIGHT INTO TUESDAY WILL THEN BRING ONSET OF A MUCH COLDER AIRMASS AND AN OPPORTUNITY FOR STEADIER HEAVIER SNOW SHOWER ACTIVITY FOR THE MOUNTAINS. WILL MAINTAIN WINTER STORM WATCH FOR WESTERN COUNTIES BEGINNING TONIGHT AND CONTINUING INTO MID WEEK. WILL FINE TUNE THIS HEADLINE ONCE WE GET PAST TODAYS PRECIPITATION EPISODE. THERE SHOULD BE A PHYSICAL BREAK BETWEEN THRE PRECIP THAT OCCURS TODAY VERSUS THE SNOW SHOWER ACTIVITY TONIGHT WHICH WILL THEN PERSIST INTO MID WEEK.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
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AS OF 400 AM EST MONDAY... UPPER TROUGH WILL SLOWLY SLIDE EAST ACROSS OUR AREA TUESDAY INTO WEDNESDAY NIGHT. SEVERAL SHORTWAVES WILL ROTATE AROUND THE UPPER TROUGH DURING THE PERIOD. THE NAM...GFS AND ECMWF SHOWED A HEALTHY SHORTWAVE IN THE MOUNTAINS TUESDAY MORNING WHICH PIVOTS EAST TUESDAY NIGHT INTO WEDNESDAY. PERSISTENT NORTHWEST WINDS FROM THE SURFACE THROUGH AROUND 700 MB...WILL RESULT IN SNOW SHOWERS AND SNOW FLURRIES. THE CHALLENGE IN THE FORECAST IS WHEN AND HOW FAR EAST BANDS OF SNOW SHOWERS PUSH. WITH GOOD COLD AIR ADVECTION AND FORECAST SOUNDINGS SHOWING PRIME ICE CRYSTAL GROWTH...WILL SPREAD THE CHANCE OF SNOW SHOWERS AND FLURRIES FURTHER EAST TUESDAY INTO THE PIEDMONT. HIGH TEMPERATURES ON TUESDAY WILL RANGE FROM AROUND 20 IN THE MOUNTAINS TO AROUND 40 IN THE PIEDMONT. WITH THE SHORTWAVE ROLLING EAST TUESDAY NIGHT...KEPT THE SNOW SHOWERS AND SNOW FLURRIES CONTINUING. LOW TEMPERATURES WILL RANGE FROM AROUND 10 DEGREES IN THE NORTHWEST MOUNTAINS TO THE MID 20S IN THE PIEDMONT. ENOUGH COLD AIR...COMBINED WITH MODERATE WINDS...WILL RESULT IN COLD WIND CHILL VALUES. IN THE MOUNTAINS...IT WILL BE COLD ENOUGH FOR WIND CHILL ADVISORIES TUESDAY NIGHT INTO WEDNESDAY MORNING. FOR TUESDAY INTO TUESDAY NIGHT...SNOW ACCUMULATIONS WILL VARY FROM A COATING TO CLOSE TO 3 INCHES IN THE WESTERN MOUNTAINS. DEEPER MOISTURE WILL ERODE FROM SOUTH TO NORTH ON WEDNESDAY AND WEDNESDAY NIGHT...WITH THE SNOW SHOWERS ENDING FIRST IN THE NORTHWEST NORTH CAROLINA MOUNTAINS AND EVENTUALLY IN SOUTHEAST WEST VIRGINIA ON THURSDAY. HIGHEST SNOW AMOUNTS AROUND A COUPLE OF INCHES WILL BE ON THE HIGHER WEST FACING SLOPES AND COLDEST WIND CHILLS WILL BE AT HIGHER ELEVATIONS WEDNESDAY NIGHT. HIGH TEMPERATURES WEDNESDAY WILL VARY FROM THE MID TEENS IN THE MOUNTAINS TO THE MID 30S IN THE PIEDMONT. LOW TEMPERATURES WEDNESDAY NIGHT WILL VARY FROM THE SINGLE DIGITS IN THE MOUNTAINS TO THE TEENS IN THE PIEDMONT. THE COMBINATION OF WIND AND TEMPERATURES WILL CREATE WIND CHILLS BELOW ZERO IN THE MOUNTAINS WEDNESDAY NIGHT INTO THURSDAY MORNING.
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&& .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 250 PM EST SUNDAY... CLOSED 500 MB LOW REMAINS OVER SOUTHEAST CANADA BUT HEIGHTS RISE OVER THE REGION. LONG WAVE TROUGH REMAINS OVER THE EAST THROUGH SUNDAY WITH MODELS SHOWING DIFFERENCE IN TIMING AND INTENSITY OF SHORT WAVES EMBEDDED WITHIN THE TROUGH. SURFACE HIGH PRESSURE WILL BE CENTERED OVER THE FORECAST AREA ON FRIDAY MORNING. MORE ARCTIC AIR COMES IN SATURDAY AND SUNDAY. BOTH GFS AND ECMWF ARE SHOWING VARIATIONS OF A 1040 MB HIGH BUILDING WELL INTO THE OHIO VALLEY AND MID ATLANTIC REGION DURING THAT TIME FRAME. SNOW SHOWERS WILL BE ENDING IN THE NORTHWEST COUNTY WARNING AREA. WILL HAVE A LOW PROBABILITY OF SNOW IN THE FORECAST FOR FRIDAY OR SATURDAY THAT IS ASSOCIATION WITH A SOMEWHAT STRONGER SHORT WAVE TRACKING THROUGH THE BASE OF THE UPPER TROF. BUT AT THAT TIME FRAME...LOCATION AND TIMING ARE LIKELY TO CHANGE. && .AVIATION /09Z MONDAY THROUGH FRIDAY/... AS OF 1150 PM EST SUNDAY... THROUGH THE NIGHT...THE CWA SHOULD GENERALLY BE SANDWICHED IN BETWEEN THE DEPARTING COASTAL SYSTEM AND A DEEP UPPER LOW SAGGING SOUTHWARD THROUGH THE GREAT LAKES. THIS SYSTEM ALSO APPEARS TO BE SOMEWHAT SLOWER THAN EXPECTED YESTERDAY. CONSEQUENTLY...DEEPER ASSOCIATED MOISTURE SHOULD NOT REACH THE WESTERN CWA UNTIL AROUND DAYBREAK...AFTER DAYBREAK EAST OF THE BLUE RIDGE. SO LARGELY...ALL TAF SITES WILL SEE VFR CIGS/VSBYS THROUGHOUT THE FIRST 12 HOURS OF THE TAF VALID PERIOD. CIGS WILL BEGIN TO LOWER INTO THE MVFR CATEGORY KBLF-KLYH AND KBCB IN THE 12Z-15Z TIME FRAME WITH -SN ASSOCIATED WITH A BAND OF STRONGER DYNAMIC FORCING AND INITIAL FRONTAL BOUNDARY. ALTHOUGH THIS INITIAL BAND OF PRECIPITATION WILL SPREAD INTO THE PIEDMONT...TEMP PROFILES SUGGEST THAT IT MAY LARGELY BE RAIN IN THOSE AREAS. HAVE CARRIED ONLY -RA FOR KDAN AND KLYH...WITH A -RASN MIX KROA...WITH LOW CONFIDENCE IN SNOW THERE. KBCB SHOULD SEE MOSTLY -SN...BUT SOME -RA POSSIBLE AT THE ONSET. THE INITIAL BAND OF FRONTAL FORCED PRECIPITATION SHOULD MOVE EAST OF THE CWA BY AFTERNOON. AT THAT POINT...AND WITH COLDER ARCTIC AIR BEGINNING TO FILTER INTO THE REGION FROM THE WEST...PRECIPITATION SHOULD GENERALLY END EAST OF THE ALLEGHANY FRONT EXCEPT FOR A FEW FLURRIES LATER IN THE EVENING...BUT -SHSN SHOULD COMMENCE IN EARNEST ACROSS THE ALLEGHANYS WITH MVFR CIGS LOWERING TO IFR. CIGS SHOULD GENERALLY IMPROVE TO MVFR OR BETTER EAST OF THE BLUE RIDGE. VISIBILITIES WILL BE MOSTLY MVFR DURING THE MORNING/AFTERNOON RAIN/SNOW...IMPROVING TO VFR ACROSS THE PIEDMONT DURING THE EVENING...DETERIORATING TO IFR OR PERHAPS EVEN LIFR IN THE WEST IN INCREASING SNOW SHOWERS AND PERHAPS EVEN SOME BLOWING SNOW...ALTHOUGH DID NOT ADVERTISE THAT JUST YET. WINDS WILL REMAIN CHAOTIC THROUGH THE OVERNIGHT HOURS AS THE REGION REMAINS SANDWICHED BETWEEN THE TWO LARGER SCALE SYNOPTIC SYSTEMS. GENERALLY A NNW WIND WILL PREVAIL IN MOST AREAS. TOWARD DAYBREAK...WINDS IN THE WEST SHOULD TRANSITION TO SW 5-7KTS AND THIS WILL SPREAD EAST THROUGH THE MORNING. BY EVENING...WINDS WILL BECOME WSW-WNW 10-12KTS WITH GUSTS 15-20KTS BEHIND THE FRONTAL BOUNDARY AND SLOWLY INCREASE THROUGH THE EVENING HOURS. HIGH CONFIDENCE IN CIGS THROUGH 12Z...THEN MEDIUM CONFIDENCE THROUGH THE REMAINDER OF THE TAF VALID PERIOD. HIGH CONFIDENCE IN VSBY THROUGH 12Z...THEN MEDIUM CONFIDENCE THROUGH THE REMAINDER OF THE TAF VALID PERIOD. MEDIUM CONFIDENCE IN WIND DIRECTION...MEDIUM TO HIGH CONFIDENCE IN WIND SPEED THROUGH THE TAF VALID PERIOD. EXTENDED DISCUSSION... SUB-VFR SHOULD BECOME MORE CONFINED TO THE WESTERN SLOPES MONDAY NIGHT INTO MIDWEEK WITH PROLONGED MVFR/IFR CONDITIONS AT KBLF/KLWB IN SNOW SHOWERS THROUGH AT LEAST WEDNESDAY NIGHT AS ARCTIC AIR ARRIVES. POTENTIAL ALSO FOR PERIODS OF MVFR AT KBCB/KROA AS IMPULSES ROTATE ACROSS THE MOUNTAINS AND BANDS DEVELOP DURING THE OVERNIGHT HOURS. ACCUMULATING SNOW IS LIKELY IN THE MOUNTAINS WEST OF THE BLUE RIDGE. FLURRIES MAY ALSO OCCUR AS FAR EAST AS THE PIEDMONT WHERE INTERVALS OF VFR TO MVFR CIGS COULD ALSO OCCUR. CONDITIONS SHOULD BRIEFLY RETURN TO MAINLY VFR THURSDAY/THURSDAY NIGHT AS WEAK HIGH PRESSURE BUILDS IN AND MOISTURE DECREASES. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY MORNING FOR VAZ007-009>012-015-019-020. WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR VAZ007- 009-015. NC...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY MORNING FOR NCZ001-018. WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR NCZ001- 018. WV...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY MORNING FOR WVZ042>044-507-508. WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR WVZ042- 043-508.
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&& $$ SYNOPSIS...PM NEAR TERM...PM SHORT TERM...KK LONG TERM...AMS AVIATION...JH/PM/RAB

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