Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 261740
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
140 PM EDT SUN APR 26 2015

.SYNOPSIS...
WITH THE DEPARTURE OF AN UPPER LEVEL SYSTEM FROM THE MID ATLANTIC
THIS MORNING...HIGH PRESSURE BUILDING IN FROM THE MIDWEST REGION
WILL BECOME THE MAIN WEATHER FEATURE FOR OUR AREA TODAY. ANOTHER LOW
PRESSURE SYSTEM IS EXPECTED TO AFFECT THE SOUTHEAST AND MID ATLANTIC
REGION DURING THE MIDDLE OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1045 AM EDT SUNDAY...

MORNING SOUNDING FROM RNK SHOWS THE WEDGE STILL VERY WELL
ENTRENCHED ACROSS THE AREA WITH A FAIRLY DEEP LAYER OF COOL AND
MOIST AIR IN THE BOUNDARY LAYER. RADAR HAS BEEN SHOWING MAINLY
LIGHT RETURNS IN SPRINKLES/DRIZZLE WITH SOME STEADIER LIGHT
SHOWERS AROUND THE NC/VA BORDER. AS LOW PRESSURE TO OUR SOUTH
WITH AN INVERTED EXTENDING INTO OUR AREA CONTINUES TO PULL AWAY
AND WINDS BACK TO NORTH AND NORTHWEST...BELIEVE THE TREND WILL BE
FOR AREAS OF FOG AND DRIZZLE TO MORPH INTO SPRINKLES FROM THE BLUE
RIDGE WEST DURING THE AFTERNOON. SATELLITE IMAGES SHOW A GOOD
AMOUNT OF CLEARING JUST TO OUR NORTH MOVING IN OUR DIRECTION BUT
GUIDANCE INDICATES THIS WILL BE A VERY SLOW PROCESS SO WILL GO A
BIT MORE PESSIMISTIC WITH CLOUD COVER TODAY AND EXPECT SOME
GENERAL BRIGHTENING INSTEAD OF CLEARING WITH SOME LATE DAY BREAKS
FAR NORTH. THE GENERAL BRIGHTENING AND LESSENING PRECIPITATION
SHOULD HELP TEMPERATURES SLOWLY INCH UPWARD BUT IT WILL STILL BE A
VERY COOL AND DAMP DAY.

PREVIOUS AFD...

WITH THE DEPARTURE OF THE UPPER LEVEL DISTURBANCE...HIGH PRESSURE
BUILDING IN FROM THE MIDWEST STATES WILL GRADUALLY TAKE OVER AS OUR
DOMINATING WEATHER FEATURE. CLOUDS WILL START TO BREAK UP DURING
LATE AFTERNOON/EARLY EVENING EAST OF THE BLUE RIDGE...WITH CLOUD
COVER DECREASING ACROSS THE MOUNTAINS AFTER DARK. THE ARRIVAL OF
HIGH PRESSURE WILL ALSO CAUSE THE PRESSURE GRADIENT TO INCREASE
FOR THE CENTRAL APPALACHIANS...AND WE CAN EXPECT WINDS TO BECOME
BREEZY AFTER MIDNIGHT. LOOKING ONCE AGAIN AT ANOTHER COOL
NIGHT...WITH SUNDAY NIGHT LOWS RANGING FROM THE MID 40S ACROSS THE
FOOTHILLS IN NORTH CAROLINA...TO THE LOW AND MID 30S ALONG THE
INTERSTATE 64 CORRIDOR. MAY BE A FEW SPOTS WHERE TEMPERATURES FALL
BELOW FREEZING IN THE NORTH...HOWEVER THE INCREASED WIND SPEEDS
WILL LIKELY PREVENT FROST FORMATION. WILL LET THE DAY SHIFT TAKE A
LOOK AT ANOTHER BATCH OF MODEL DATA...AND DETERMINE IF ANY
FROST/FREEZE STATEMENTS ARE NECESSARY FOR TONIGHT.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
AS OF 400 AM EDT SUNDAY...

CONVOLUTED UPPER AIR PATTERN REMAINS IN PLACE THROUGH THE PERIOD.
THE MAIN FEATURES BEING A DEEP 529DM UPPER LOW OFF THE NORTHEAST
U.S. COAST EXTENDING WELL BACK INTO THE OH VALLEY/MID-ATLANTIC
REGION...A CLOSED LOW COMING OUT OF THE DESERT SOUTHWEST INTO
TEXAS...AND A ELONGATED RIDGE IN BETWEEN BETWEEN THE CENTRAL
CANADIAN PROVINCES DOWN INTO THE CENTRAL U.S...THEN THE SOUTHEAST
U.S. FOR MON AND TUE...OUR REGION WILL REMAIN LARGELY UNDER THE
INFLUENCE OF THE NORTHEAST U.S./NORTHERN MID-ATLANTIC UPPER LOW. A
SPOKE OF PVA/SHORT WAVE WILL ROTATE THROUGH THE REGION FROM THE
NORTH ON THE WEST SIDE OF THE ELONGATED UPPER LOW. WITH 850MB
TEMPS CONTINUING TO HOVER NEAR 0C AND COLD 500MB TEMPS -20 TO -24C...
THE ATMOSPHERE WILL BE QUITE UNSTABLE. ANY MORNING SUNSHINE WILL
QUICKLY RESULT IN CU/SC DEVELOPING AND LIKELY -SHRA ACROSS THE
MOUNTAINS BY LATE MORNING THROUGH THE EARLY EVENING. TEMPERATURES
WILL REMAIN WELL BELOW NORMAL...AND ANY SHOWERS WILL EASILY BRING
THOSE AREAS BACK DOWN INTO THE 40S DURING THE AFTERNOON. IN
FACT...850MB TEMPS COULD SUPPORT SOME -SN AT THE HIGHEST ELEVATIONS
MON MORNING...BUT HAVE NOT INCLUDED IN THE GRIDS AT THIS TIME.
SHOWERS WILL BE CONSIDERABLY LESS LIKELY IN THE DOWNSLOPE PIEDMONT
AREAS. LESS CLOUDS IN THIS AREA WILL ALSO ALLOW MAX TEMPS TO WARM
BACK INTO THE 60S...YET STILL BELOW NORMAL.

FOR TUE...THE DEEP UPPER LOW FINALLY BEGINS TO DRIFT EAST FURTHER
OUT TO SEA...WHILE THE UPPER LOW ACROSS TX DRIFTS INTO THE
ARKLATEX REGION. A NEW UPPER LOW BEGINS TO DRIFT SOUTH OUT OF THE
CENTRAL CANADIAN PROVINCES...WHILE THE SKINNY/COMPLICATED UPPER
RIDGE DRIFTS INTO OUR REGION. THIS SHOULD BE THE ONE DAY WITH
LITTLE TO NO -SHRA ACTIVITY WITH NO FORCING EVIDENT ALOFT AND WEAK
RIDGING. INCREASED SUNSHINE SHOULD ALLOW TEMPS TO WARM A TAD
CLOSER TO NORMAL...BUT 850MB TEMPS ONLY WARM A FEW DEGREES TO
ABOUT +4C ACROSS MUCH OF THE CWA.

FOR WED...THE ARKLATEX UPPER LOW DRIFTS INTO THE SOUTHEAST STATES
WHILE LOW PRESSURE ALOFT DRIFTS SOUTHWARD INTO THE GREAT LAKES.
THESE TWO SYSTEM WILL MERGE ACROSS THE REGION INTO THU AS YET
ANOTHER UPPER LOW FORMS ACROSS THE MID-ATLANTIC BY THU. LIGHT
RAIN WILL BEGIN TO SPREAD INTO THE REGION WED AS HEIGHTS ALOFT
LOWER AS THE UPPER LOWS CONVERGE ACROSS THE REGION. THIS...ALONG
WITH CLOUD COVER AND INCREASED PRECIPITATION WILL ENSURE CONTINUED
WELL BELOW NORMAL TEMPERATURES. QPF DOES NOT APPEAR TO BE AN ISSUE
AT THIS POINT AS THE HEAVIEST RAINFALL WILL REMAIN WELL SOUTH OF
THE REGION.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
AS OF 430 AM EDT SUNDAY...

THE GFS AND CANADIAN HAVE COME INTO BETTER AGREEMENT WITH THE
ECMWF ON DEVELOPMENT AND EVOLUTION OF A COASTAL LOW/ALMOST
MILLER-A TYPE SETUP OFF THE SOUTHEAST U.S. COAST THU. THIS WILL
SPREAD RAIN INTO THE REGION FROM THE SOUTH. AS THE SOUTHERN STREAM
LOW BECOMES ABSORBED INTO SOUTHWARD MOVING UPPER LOW FROM THE
GREAT LAKES...A DEEP 540DM UPPER LOW WILL EVOLVE ACROSS WV/VA INTO
EARLY FRI. THIS WILL PROLONG THE LIGHT RAIN...NORTHERLY FLOW...AND
UNSEASONABLY COOL TEMPERATURES RIGHT INTO FRI. WITH THE REGION
LARGELY UNDER A COOL/STABLE/NORTHERLY FLOW...PWATS ACROSS THE
REGION ARE GENERALLY AROUND 1/2 INCH DURING THIS TIME FRAME...SO
HEAVY RAIN DOES NOT APPEAR TO BE A CONCERN. THAT SHOULD REMAIN
WELL SOUTHEAST ALONG COASTAL AREAS AND THEN OFF THE VA/MD COAST
WITH TIME. BUT...850MB TEMPS WILL CONTINUE TO HOVER NEAR 0C
THROUGHOUT THE PERIOD AS THE UPPER LOW DUMBBELLS ACROSS THE MID-
ATLANTIC...KEEPING MAX TEMPS FOR SURE WELL BELOW NORMAL...BUT MIN
TEMPS SLIGHTLY BELOW NORMAL BECAUSE OF CLOUD COVER

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AS OF 130 PM EDT SUNDAY...

SURFACE LOW TO OUR SOUTH WITH ASSOCIATED INVERTED TROF EXTENDING
NORTH INTO THE AREA CONTINUES TO PULL AWAY FROM THE REGION. RADAR
AND OBSERVATIONS INDICATE ONLY SOME LINGERING SPRINKLES AND
VISIBLE SATELLITE IMAGES SHOW IMPROVING VFR CONDITIONS SLOWLY
WORKING IN FROM THE NORTH. AS LOW/TROF CONTINUE TO PULL AWAY AND
HIGH PRESSURE BUILDS IN...MED/HIGH CONFIDENCE THAT WE WILL SEE
CIGS IMPROVE TO VFR AT MOST LOCATIONS AFTER 00Z. THE ONE EXCEPTION
IS KBLF WHERE INDICATIONS ARE THAT AS WINDS BACK AROUND TO A NWLY
DIRECTION THIS SHOULD GENERATE ENOUGH UPSLOPE TO KEEP MVFR THROUGH
THE OVERNIGHT...THOUGH THIS IS A MEDIUM CONFIDENCE PROPOSITION AT
BEST. ALSO...AS OTHER SITES IMPROVE TO VFR THIS MAY ALLOW FOR
DEVELOPMENT OF FOG AND POSSIBLY SOME LOW CIGS TOWARD DAYBREAK.

ONCE WE GET INTO MONDAY HIGH CONFIDENCE ALL SITES SHOULD SEE VFR
CONDITIONS BY LATE MORNING WITH A CIG DEVELOPING. ALSO...SHORT
WAVE ENERGY ROTATING AROUND THE LARGE UPPER TROF OVER THE
NORTHEAST US WILL COMBINE WITH THE POOL OF COLD AIR ALOFT TO HELP
GENERATE SOME SHOWERS...WITH ISOLATED THUNDER A POSSIBILITY DURING
THE AFTERNOON WITH SUCH STEEP LAPSE RATES. HOWEVER ANY ACTIVITY
WILL LIKELY BE CONFINED NORTHERN SECTIONS FROM THE BLUE RIDGE
WESTWARD. THE BOUNDARY LAYER WILL ALSO BE VERY WELL MIXED TOMORROW
AND GENERATE SOME GUSTY NW WINDS BUT NOTHING EXCESSIVE IS
EXPECTED.

EXTENDED AVIATION DISCUSSION...

BREEZY NORTHWEST FLOW IS EXPECTED THROUGH EARLY TUESDAY AS HIGH
PRESSURE BUILDS IN FROM THE NORTHWEST. VFR CONDITIONS ARE
EXPECTED TUE BEFORE CONDITIONS WORSEN ONCE AGAIN WED-THU AS A LOW
PRESSURE SYSTEM PASSES ACROSS THE SOUTHEAST STATES...WHICH WILL
AFFECT THE MID ATLANTIC ON WEDNESDAY INTO THURSDAY. CONFIDENCE IS
GROWING THAT THIS SYSTEM WILL RESULT IN WIDESPREAD RAIN FOR THE
FORECAST AREA...AS WELL AS PERSISTENT MVFR/IFR CONDITIONS. AN
UPPER LOW WILL ALSO BUILD SOUTHWARD FROM THE GREAT LAKES AT THE
SAME TIME.

&&

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

&&

$$
SYNOPSIS...NF
NEAR TERM...MBS/NF
SHORT TERM...RAB
LONG TERM...PM/RAB
AVIATION...MBS/RAB


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