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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