Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
531 AM EST TUE MAR 3 2015

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE MID ATLANTIC COAST TODAY...THEN A
WARM FRONT WILL LIFT NORTH THROUGH THE REGION THIS EVENING. LOW
PRESSURE OVER THE CENTRAL PLAINS WILL TRACK INTO SOUTHEAST CANADA
AND WILL PUSH A COLD FRONT INTO THE REGION ON WEDNESDAY. COLDER
AIR BEHIND THE FRONT WILL ALLOW FOR A TRANSITION FROM RAIN TO SNOW
WEDNESDAY NIGHT AND THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 415 AM EST TUESDAY...

LOWER CLOUDS WERE JUST FILLING IN ACROSS THE FORECAST AREA THIS 
MORNING. HAVE MADE ADJUSTMENTS TO THE TIMING OF THE PRECIPITATION 
BASED ON RADAR TRENDS AND THE TIMING SHOWN ON THE LAST FEW RUNS OF 
THE HRRR AND THE LATEST WRF GUIDANCE. HAVE THEREFORE MADE ADJUSTMENTS 
TO THE VALID TIME OF THE ADVISORIES. APPEARS A MORE ORGANIZED AREAS 
OF PRECIPITATION WILL CROSS THE NORTHERN COUNTY WARNING AREA BETWEEN 
8AM AND NOON. STILL EXPECTING A BETTER PROBABILITY OF PRECIPITATION 
ON THE EASTERN SLOPES OF THE BLUE RIDGE. OTHERWISE...NO WELL DEFINED 
FEATURES THAT WILL DEFINE WHERE AND WHEN PRECIPITATION WILL FALL. 

WHEREVER THE PRECIPITATION IS...IT WILL BE LIGHT. BUFKIT NOT
SHOWING GOOD DENDRITIC GROWTH AND BY 15Z/10AM...WARM NOSE WILL BE
WELL STRONG ENOUGH TO RESULT IN LIQUID AS THE HYDROMETEORS FALL
THROUGH THAT LAYER. SO SURFACE TEMPERATURES WILL BE THE DECIDING
FACTOR IN PRECIPITATION TYPE. NEW RIVER VALLEY THROUGH THE
ALLEGHANY HIGHLANDS WERE BELOW FREEZING. ONLY A SLOW RISE IN
TEMPERATURES EXPECTED TODAY. GUIDANCE KEPT THE NORTHEAST
COUNTIES...MAINLY FROM LYNCHBURG INTO AMHERST AND ROCKBRIDGE
COUNTY BELOW FREEZING FOR MUCH OF THE DAY. HAVE DELAYED THE START
OF THE WINTER WEATHER ADVISORY AND EXTENDED THE ADVISORY THROUGH
LATER IN THE DAY WHERE THE TEMPERATURE REMAINS BELOW FREEZING.

TONIGHT...A STRONG LOW LEVEL JET PUSHES UP TEMPERATURES AND DEW 
POINTS. LOWS WILL OCCUR IN THE EVENING. AFTER MIDNIGHT...THE COLD 
FRONT APPROACHES AND THE PROBABILITY OF MODERATE RAIN IN THE 
NORTHWEST COUNTY WARNING AREA INCREASES.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
AS OF 430 AM EST TUESDAY...

EXPECT TO START WEDNESDAY WITH A COLD FRONT SITUATED FROM THE 
ALLEGHANY HIGHLANDS THROUGH THE MOUNTAIN EMPIRE. STRONG MOISTURE 
FLOW INTO THE AREA ON A 50KT TO 60KT SOUTHWESTERLY LOW LEVEL JET 
WILL PUSH PRECIPITABLE WATER VALUES TO 1.0-1.1 INCHES IN THE 
WEST...AND AS HIGH AS 1.4 INCHES FURTHER EAST...ALL SIGNIFICANTLY 
ABOVE NORMAL FOR EARLY MARCH. 
 
DURING THE MORNING...RAIN WILL BE WIDESPREAD WEST OF THE BLUE 
RIDGE...ALTHOUGH THE STRONGEST LIFT/HEAVIEST RAINFALL IS EXPECTED TO 
BE WEST OF THE CONTINENTAL DIVIDE...JUST SKIRTING OUR SOUTHEAST WEST 
VIRGINIA COUNTIES...PARTICULARLY THE WEST FACING SLOPES. FURTHER 
EAST...WILL LIKELY SEE A BAND OF HEAVY RAIN JUST AHEAD OF THE FRONT 
AS IT SLOWLY DRIFTS EAST THROUGH THE DAY...WITH SOME DRYING TAKING 
PLACE BEHIND THE BOUNDARY AS WINDS SHIFT NORTHWESTERLY AND 
DOWNSLOPE. 

DURING WEDNESDAY AFTERNOON AND EVENING...THE COLD FRONT WILL 
SLOW/STALL ACROSS THE SOUTHSIDE AND NORTH CAROLINA PIEDMONT AS A 
STRONG WAVE DEVELOPS OVER NORTHERN GEORGIA AND PUSHES NORTHEAST 
ALONG THE BOUNDARY. THE WAVE WILL PASS JUST SOUTHEAST OF OUR AREA 
DURING THE EARLY MORNING HOURS OF THURSDAY...WITH STRONG CONVERGENCE 
DEVELOPING FROM THE ALLEGHANY HIGHLANDS SOUTHWARD ALONG THE BLUE 
RIDGE...SUPPORTING AN ADDITIONAL ROUND OF POTENTIALLY HEAVY RAIN. 

AS THE WAVE PASSES OUR AREA DURING LATE THURSDAY MORNING...IT WILL 
ENHANCE THE NORTHWESTERLY FLOW ACROSS THE MOUNTAINS...DRAWING COLD 
AIR ASSOCIATED WITH ARCTIC HIGH PRESSURE FURTHER ACROSS OUR AREA. 
THE SURGE OF COLDER AIR HUGGING THE SURFACE WILL CAUSE RAIN TO 
CHANGE TO SLEET AND/OR FREEZING RAIN FOR A FEW HOURS ACROSS THE 
MOUNTAINS...BEFORE FINALLY CHANGING TO SNOW BY THURSDAY AFTERNOON. 
BECAUSE WE ARE EXPECTING MORE SLEET AND FREEZING RAIN THAN 
PREVIOUSLY FORECAST...WENT WITH LOWER SNOWFALL TOTALS FOR THURSDAY. 
RIGHT NOW...LOOKING AT THE POSSIBILITY OF WINTER STORM SNOW AND 
SLEET AMOUNTS FOR WESTERN GREENBRIER...AND PERHAPS BATH AND 
ROCKBRIDGE COUNTIES IN SPOTS...BUT DO NOT HAVE ENOUGH CONFIDENCE TO 
GO WITH A WINTER STORM WATCH AT THIS POINT. WILL LET THE DAY SHIFT 
HAVE ANOTHER LOOK AT THE COMING 03/12Z MODEL RUNS.

PRECIPITATION WILL WIND DOWN THURSDAY AFTERNOON AND EVENING AS HIGH 
PRESSURE BUILDS IN FROM THE WEST...SETTLING ACROSS THE MID AND UPPER 
OHIO RIVER VALLEY BY FRIDAY MORNING. STRONG RADIATIONAL COOLING WILL 
MEAN ONE MORE SHOT OF SINGLE DIGIT TEMPERATURES TO START THE DAY 
ACROSS THE MOUNTAINS...WITH TEENS EXPECTED ACROSS THE PIEDMONT. HIGH 
PRESSURE WILL SHIFT TO NEW ENGLAND...WHERE IT WILL THEN WEDGE 
SOUTHWARD FRIDAY NIGHT...HUGGING THE EASTERN FACE OF THE 
APPALACHIANS. 

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 145 PM EST MONDAY...

HIGH PRESSURE WILL BE IN CONTROL OF OUR WEATHER PATTERN THROUGH
AT LEAST SATURDAY NIGHT. THE HIGH WILL GRADUALLY BUILD INTO THE
AREA FROM THE WEST...AND MAKE ITS WAY TO THE COAST BY SATURDAY.
THIS WILL ALLOW FOR A TREND TOWARD MILDER CONDITIONS AS THE LOW
LEVEL FLOW ACROSS THE AREA BECOMES GRADUALLY MORE SW-W...WHILE A
SHORTWAVE RIDGE AND RISING 850 TEMPS TAKE PLACE.

SUNDAY INTO MONDAY A GENEROUS AMOUNT OF VARIATIONS IN THE MODELS 
TAKE PLACE. WHILE BOTH THE GFS AND THE NAM EVENTUALLY COME INTO 
AGREEMENT OF A LONG WAVE TROUGH OVER THE EASTERN THIRD OF CONUS BY 
MONDAY OR TUESDAY OR NEXT WEEK...HOW THE SOLUTIONS COME TO BE THAT 
WAY HAVE NOTABLE DIFFERENCES. THE GFS IS MORE PROGRESSIVE IN 
ESTABLISHING THE TROUGH IN THE EAST BY SUNDAY...AND ANY SOUTHERN 
STREAM SYSTEMS EASILY BYPASS OUR REGION EXITING THE U.S. NEAR THE 
GA/FL BORDER. THE ECWMF IS NOT A QUICK TO ESTABLISH AN EAST COAST 
TROUGH...AND A SUCH...SOUTHERN STREAM SYSTEMS HAVE A BETTER 
OPPORTUNITY TO PROGRESS NORTHEAST THROUGH OUR REGION ON THE EAST 
SIDE OF AN APPROACHING SHORTWAVE TROUGH.

OUR FORECAST FOR SUNDAY INTO MONDAY WILL BE A CONSENSUS OF THESE 
TWO...WITH IT RESEMBLING A WATERED DOWN VERSION OF THE ECWMF IN 
TERMS OF PRECIPITATION POTENTIAL ON SUNDAY AND SUNDAY NIGHT...AND 
ALSO STAYING ON MORE OF THE MILD SIDE THAN COLD IN REGARDS TO 
MONDAY.

&&

.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
AS OF 1250 AM EST TUESDAY...

MVFR CIGS WILL START PROGRESSES NORTHEAST ACROSS THE REGION IN
CONJUNCTION WITH A WARM FRONT HEADING TOWARD THE AREA. ALONG WITH
THE FRONT WILL COME LIGHT WINTRY PRECIPITATION IN THE FORM OF
PATCHY LIGHT FREEZING RAIN AND SLEET. BY DAYBREAK TUESDAY...MANY
AREAS WILL HAVE LOWERED TO LIFR/IFR CIGS AND MVFR VSBYS DUE TO THE
PRECIPITATION AND MIST. THE BULK OF THE WINTRY PRECIPITATION WILL
BE CONFINED TO NORTH A LINE FROM KBLF-KROA-KLYH DURING THE LATE
MORNING. BY THE AFTERNOON...SURFACE TEMPERATURES SHOULD BE MILD
ENOUGH FOR A WIDESPREAD AREA OF RAIN. 

WINDS WILL REMAIN LIGHT THROUGH THE NIGHT AND GRADUALLY VEER TO
THE SOUTHEAST. ON TUESDAY...WINDS WILL INCREASE DURING THE DAY
FROM THE SOUTHWEST...AND WINDS AT 850 MB WILL INCREASE TO AROUND
45 TO 50 KTS. LOW LEVEL WIND SHEAR WILL BE POSSIBLE DURING THE
AFTERNOON...ESPECIALLY AT TERMINALS AT HIGHER ELEVATION.

MEDIUM CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS DURING THE
PERIOD. 

EXTENDED FORECAST...

ANOTHER LOW PRESSURE SYSTEM THAT WILL IMPACT ALL OF THE REGION
WILL TRACK FROM THE CENTRAL PLAINS INTO NEW ENGLAND TUESDAY NIGHT
INTO WEDNESDAY. THIS WILL RESULT IN SUB-VFR CONDITIONS WEDNESDAY
AND THURSDAY WITH WIDESPREAD RAIN AHEAD OF THE FRONT ON WEDNESDAY
AND WINTER PRECIPITATION BEHIND THE FRONT WEDNESDAY NIGHT AND
THURSDAY.

FRIDAY SHOULD SEE A RETURN TO HIGH PRESSURE AND VFR WEATHER.

&&

.HYDROLOGY...
AS OF 300 PM EST MONDAY

LIKELY TO SEE SOME SUBSTANTIAL RISES ON AREA RIVERS AND STREAMS IN 
RESPONSE TO UPCOMING RAIN EVENT AND SNOWMELT IN THE 
MOUNTAINS...QUESTIONS REMAIN ABOUT HOW SUBSTANTIAL. SIGNIFICANT SNOW
AMOUNTS ARE NOW CONFINED TO PARTS OF THE UPPER JAMES AND
GREENBRIER RIVER BASINS WHERE THE LATEST AVAILABLE ESTIMATES FROM
THE NATIONAL OPERATIONAL REMOTE SENSING CENTER SHOW ROUGHLY 1 TO 3
INCHES OF SNOW WATER EQUIVALENT WITH ISOLATED 4 INCHES IN THE
HIGHEST ELEVATIONS OF THE GREENBRIER. IN THE OTHER MAJOR RIVER
BASINS...NEW...ROANOKE/DAN AND TENNESSEE... MELTING OVER THE
WEEKEND AND TODAY HAS REDUCED THE SNOW TO LESS THAN 1 INCH OF SNOW
WATER AND IN MOST PLACES ZERO. 

THE OTHER ELEMENT OF COURSE IS THE QPF. 12Z MODELS (INCLUDING
LATEST EC) HAVE NUDGED THE HEAVIEST QPF A LITTLE MORE TO THE
WEST...REDUCING AMOUNTS IN THE JAMES AND GREENBRIER SOME. IT STILL
APPEARS AS IF 1 TO 2 INCHES COULD FALL ACROSS THE WESTERN BASINS
BY 12Z THURSDAY AND COMBINED WITH SNOWMELT THIS COULD PRODUCE AT
LEAST MINOR RIVER FLOODING ALONG THE GREENBRIER AND POSSIBLY THE
UPPER JAMES. GUIDANCE RECEIVED FROM OHRFC THIS MORNING SUGGESTED
MINOR FLOOD STAGE AT ALDERSON WV ON THE GREENBRIER LIKELY BY EARLY
THURSDAY WITH THE COMBINED SNOWMELT AND QPF. HOWEVER...GIVEN THE
CONTINUED UNCERTAINTIES WILL HOLD OFF ON A FLOOD WATCH AT THIS
POINT.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WINTER WEATHER ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR 
     VAZ011-013-014-017>019-022-023-032>034-043-045.
     WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR 
     VAZ007-009-010-012-015-016.
     WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 4 PM EST 
     THIS AFTERNOON FOR VAZ020-024-035-046-047.
NC...WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR 
     NCZ001-002-018.
WV...WINTER WEATHER ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR 
     WVZ043-044-507-508.
     WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR 
     WVZ042.

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...NF
LONG TERM...DS
AVIATION...AMS/DS/KK
HYDROLOGY...PC

National Weather Service Glossary of Abbreviations