Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
200 AM EDT THU APR 2 2015

.SYNOPSIS...
HIGH PRESSURE WILL PASS OVERHEAD TONIGHT PROVIDING CLEAR SKIES
AND LIGHT WINDS. A WARM FRONT WILL PUSH NORTH THROUGH THE OHIO
VALLEY THURSDAY...SUPPORTING SPOTTY SHOWER MAINLY WEST OF THE
MOUNTAINS. A STRONG COLD FRONT WILL PASS ACROSS THE AREA FRIDAY
NIGHT...PRODUCING SHOWERS AND THUNDERSTORMS...FOLLOWED BY 
BREEZY BUT DRY CONDITIONS FOR THE WEEKEND.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 330 PM EDT WEDNESDAY...

1022 MB SURFACE HIGH PRESSURE WAS CENTERED OVERHEAD. THIS FEATURE
WILL PROMOTE CLEAR SKIES TONIGHT WITH NEAR CALM WINDS. A LIGHT
SOUTHEAST BREEZE MAY DEVELOP ALONG THE RIDGETOPS TOWARD DAYBREAK
THURSDAY...BUT VALLEYS SHOULD REMAIN DECOUPLED WITH POTENTIAL 
FOR PATCHY FROST...LOWS IN THE 30S.

THE HIGH SHOULD BE CENTERED NEAR THE ATLANTIC COAST TO START THE
DAY THURSDAY. CLOCKWISE FLOW AROUND THE HIGH RESULTING IN 
INCREASING SOUTHERLY WINDS AND DEWPOINTS. MOISTURE WILL BEGIN TO
RETURN TO THE AREA AS A WARM FRONT LIFTS NORTH THROUGH THE TN/OH
VALLEYS ON THURSDAY...PROMOTING INCREASING CLOUDINESS AND THE 
THREAT FOR A FEW SPRINKLES WEST OF THE BLUE RIDGE. PENDING 
CLOUD COVER...TEMPERATURES SHOULD WARM WELL INTO THE 60S...
POTENTIALLY TESTING 70 DEGREES ACROSS THE PIEDMONT.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
AS OF 345 PM EDT WEDNESDAY...

OUR AREA WILL BE IN A WARM SECTOR SQUEEZE PLAY FOR THE LATTER 
PORTION OF THE WEEK WITH HIGH PRESSURE MOVING OFF TO OUR EAST AND A 
SLOW MOVING COLD FRONT APPROACHING FROM THE WEST. THIS WARM OUR 
TEMPERATURES IN THE 60S AND 70S ON FRIDAY AND KEEP US IN A CHANCE OF 
SHOWERS UNTIL LATE FRIDAY NIGHT WHEN SHOWERS ARE LIKELY AS THE FRONT 
MOVES THROUGH. WHILE THE BEST DYNAMICS WITH THE FRONT WILL SLIDE BY 
TO OUR NORTHWEST THE AMOUNT OF SHEAR ACROSS THE AREA FRIDAY 
AFTERNOON INTO FRIDAY NIGHT IS NOT TRIVIAL AND THE LOW LEVEL WIND 
FIELD HAS A GOOD AMOUNT OF BRISK EARLY SPRING ENERGY. THE BIG 
LIMITING FACTOR FOR CONVECTION IS THE LACK OF SIGNIFICANT 
INSTABILITY WITH CAPES AT OR BELOW 500J/KG LATE FRIDAY AFTERNOON. 
WILL CONTINUE THE FORECAST FOR SHOWERS/CHANCE OF THUNDER AND AGREE 
WITH SPC DAY THREE SEVERE OUTLOOK WHICH PLACES THE FAR WESTERN 
PORTION OF THE AREA IN A MARGINAL RISK FOR A WIND THREAT. 

SIGNIFICANTLY COLDER AIR MOVES IN BEHIND THE FRONT LATE FRIDAY NIGHT 
AND SATURDAY ON BLUSTERY NORTHWEST WINDS. THE FAR WESTERN SLOPES 
WILL SEE SOME UPSLOPE SNOW SHOWERS DEVELOP BEFORE DAYBREAK SATURDAY 
AND A MINIMAL SLUSHY COATING OF SNOW IS POSSIBLE...ESPECIALLY FOR 
WESTERN GREENBRIER COUNTY...BEFORE THE PRECIPITATION DISSIPATES AS 
WE GO THROUGH SATURDAY MORNING. CURRENTLY EXPECT WINDS BEHIND THE 
FRONT TO REMAIN BELOW ADVISORY CRITERIA BUT CONDITIONS WILL 
CERTAINLY BE QUITE GUSTY.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 345 PM EDT WEDNESDAY...

EVOLVING UPPER PATTERN WILL REMAIN PROGRESSIVE AND FEATURE SOME FLAT 
RIDGING THROUGH THE EXTENDED PERIOD AND LOOKS TO KEEP OUR AREA IN 
THE MILD AIR AT LEAST THROUGH MIDWEEK. HIGH PRESSURE WILL BUILD IN 
WITH QUIET WEATHER AND THE START OF A WARMING TREND ON SUNDAY TO 
CLOSE OUT THE WEEKEND. THE FIRST PART OF NEXT WEEK WILL SEE A SERIES 
OF WEAK UPPER LEVEL SHORT WAVES MOVE THROUGH AS THE AIRMASS OVER THE 
EASTERN US BECOMES WARMER AND MORE MOIST THANKS TO PERSISTENT 
SOUTHWESTERLY WINDS. THIS SHOULD SET US UP FOR BOUTS OF DIURNAL 
CONVECTION WITH A CHANCE OF SHOWERS AND THUNDERSTORMS JUST ABOUT 
EACH AFTERNOON...BECOMING MORE LIKELY ACROSS WESTERN PORTIONS OF 
THE AREA. AS WE GO OUT IN TIME MODEL GUIDANCE STARTS TO DIFFER ON 
TIMING OF WEATHER SYSTEMS BUT IT APPEARS THE NEXT COLD FRONT 
APPROACHING FROM THE WEST WILL NOT AFFECT OUR REGION UNTIL LATE 
WEDNESDAY AT THE EARLIEST.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 145 AM EDT THURSDAY...

A VERY DRY AIR MASS RESIDES OVER THE AREA EARLY THIS MORNING IN
THE WAKE OF A LARGE AREA OF HIGH PRESSURE MOVING OFF THE VA COAST
AT THIS HOUR. UPSTREAM ARE A SERIES OF SHORT WAVES EMBEDDED WITHIN
AN INCREASINGLY ZONAL AND ACTIVE UPPER FLOW. THE FIRST OF THESE
SHORT WAVES WILL SPREAD RAPIDLY TOWARD THE REGION THROUGH THE DAY.
MODELS...ESPECIALLY THE GFS...ARE WAY TO AGGRESSIVE GIVEN THE VERY
DRY AIR MASS IN PLACE...DEWPOINTS STILL IN THE SINGLE DIGITS AND
TEENS ACROSS MUCH OF THE AREA...IN GENERATING MEASURABLE QPF WITH
THIS FIRST FEATURE. FEEL LARGELY THAT THIS FIRST FEATURE WILL
SIMPLY SERVE TO MOISTEN THE ATMOSPHERE FOR MORE APPRECIABLE
MOISTURE WITH THE SECOND SHORT WAVE TO ARRIVE THU NIGHT/FRI
MORNING. MODEL TIME-HEIGHT CROSS-SECTIONS AND BUFKIT MODEL
SOUNDINGS SHOW THAT THE BULK OF THE MOISTURE THROUGH THE TAF VALID
PERIOD REMAINS AOA100. THUS...FOR NOW...HAVE IGNORED THE
WIDESPREAD 0.10-0.20 INCH 6-HR QPF GENERATED BY THE GFS AND THE
MODEL GENERATED TAFS OF CIGS AOB 025 BY 00Z. HAVE NOT INTRODUCED
ANY SUB-VFR CIGS AT THIS POINT. WILL INCLUDE A PROB30 FOR
-RA/SPRINKLES BLF- LWB WHERE THE MOISTURE SHOULD BECOME A LITTLE
DEEPER MORE QUICKLY AND ANY UPSTREAM -SHRA MAY SPREAD INTO EASTERN
WV/FAR SW VA AS SPRINKLES BEFORE DISSIPATING. VISIBILITIES WILL
NOT BE AN ISSUE THROUGH THE TAF VALID PERIOD. WINDS...LIGHT SE
MOST LOCATIONS AT THE ONSET...VEERING TO SSW THROUGH THE DAY AND
INCREASING TO 10-12KTS WITH GUSTS 20-22KTS POSSIBLE AS THE
PRESSURE GRADIENT INCREASES BETWEEN THE DEPARTING SFC HIGH AND LOW
PRESSURE DRAPED FROM THE SOUTHERN PLAINS TO THE NORTHEAST.

MEDIUM TO HIGH CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD.
HIGH CONFIDENCE IN VFR VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM
CONFIDENCE IN WIND DIR THROUGH THE TAF VALID PERIOD. MEDIUM TO
HIGH CONFIDENCE IN WIND SPD THROUGH THE TAF VALID PERIOD.

EXTENDED AVIATION FORECAST...
A SLOW MOVING...INCREASINGLY WEST-EAST ORIENTED COLD FRONT WILL
APPROACH THE REGION FROM THE NORTHWEST FRI...MOVING THROUGH THE
REGION FRI NIGHT/SAT MORNING AS AN UPSTREAM NORTHERN STREAM SHORT
WAVE FINALLY KICKS THE FRONT SOUTHEAST. MUCH OF THE DAY
FRIDAY...EXPECT THE PRECIPITATION TO REMAIN MOSTLY NORTHWEST OF
THE CWA...MOVING INTO EASTERN WV DURING THE AFTERNOON...SPREADING
ACROSS THE REMAINDER OF THE CWA AS A NARROW LINE OF CONVECTION FRI
EVENING/EARLY SATURDAY. A FEW THUNDERSTORMS ARE POSSIBLE...MAINLY
WESTERN AREAS. SEVERE WEATHER IS NOT EXPECTED. COLDER TEMPERATURES
AND UPSLOPE -SHRA...POSSIBLY -SHSN AT THE HIGHER ELEVATIONS...ARE
POSSIBLE EARLY SATURDAY BEFORE CLEARING TAKES PLACE. GUSTY
NORTHWEST WINDS ARE EXPECTED SATURDAY BEHIND THE FRONT. HIGH
PRESSURE WILL BUILD INTO THE REGION SAT AFTERNOON-SUN WITH VFR
CONDITIONS EXPECTED.

AN EXTENDED PERIOD OF SUB-VFR CONDITIONS APPEARS LIKELY MUCH OF
NEXT WEEK AS THE AREA REMAINS TRAPPED UNDER AN ACTIVE STORM TRACK
FROM A BROAD AREA OF LOW PRESSURE IN THE SOUTHWEST U.S. MULTIPLE
ROUNDS OF SHOWERS AND A FEW THUNDERSTORMS APPEAR LIKELY THROUGH
THE PERIOD.

&&

.FIRE WEATHER...
HIGH PRESSURE WILL PASS OVERHEAD EARLY TONIGHT RESULTING
IN CLEAR SKIES AND NEAR CALM WINDS.  AS THE HIGH MOVES TO 
ALONG THE ATLANTIC COAST...A SOUTHEAST WIND WILL DEVELOP
ALONG THE RIDGE TOPS...BUT REMAINING NEARLY CALM IN THE 
VALLEYS.

SOUTHERLY WIND SPEEDS AND CLOUD COVER WILL INCREASE ON 
THURSDAY AS A COLD FRONT MOVES ACROSS THE MIDWEST STATES.
LITTLE OR NO PRECIPITATION IS EXPECTED THURSDAY. 

BY FRIDAY...THE FRONT WILL BE CLOSE ENOUGH TO PRODUCE 
SCATTERED SHOWERS...AND BY FRIDAY NIGHT SHOWERS WILL BECOME
LIKELY WITH THE OPPORTUNITY FOR THUNDERSTORMS. THIS IS EXPECTED
TO BE A STRONG FRONTAL PASSAGE WITH GUSTY SOUTHWEST WINDS AHEAD
OF THE FRONT...FOLLOWED BY GUSTY NORTHWEST WINDS BEHIND THE
FRONT FROM SATURDAY INTO SUNDAY MORNING.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...PM
NEAR TERM...PM
SHORT TERM...MBS
LONG TERM...MBS
AVIATION...RAB/RCS
FIRE WEATHER...PM

National Weather Service Glossary of Abbreviations