Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 271134
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
734 AM EDT MON APR 27 2015

.SYNOPSIS...
AN UPPER DISTURBANCE MOVES ACROSS THE AREA TODAY INTO THIS
EVENING KEEPING THE REGION IN A COOL AIR MASS. LOW PRESSURE OVER
TEXAS WILL SHIFT EAST INTO THE GULF COAST STATES AND TN VALLEY TO
BRING OUR NEXT ROUND OF RAIN BY MIDWEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 715 AM EDT MONDAY...

POOL OF HIGHER DEWPOINTS...WEAK CONVERGENCE KEEPING A FEW STRATOCU
ALONG THE SE WV MTNS INTO FAR SW VA THIS MORNING. DRIER AIR WILL
ENTRAIN INTO THIS AREA LATER THIS MORNING CLEARING IT OUT.

TRACKING NEXT UPSTREAM FROM NY/PA TO OHIO. SEEING MAINLY CLOUDS
ASSOCIATED WITH THIS FEATURE JUST SOUTH OF LAKE ERIE INTO PA. FOR
THIS AFTERNOON...EXPECT TO SEE INCREASING CLOUDS AS PREVIOUSLY
ADVERTISED...AND NO NEED TO MAKE ANY SUBSTANTIAL CHANGES TO THE
GOING FORECAST. MAY SEE MORE CLOUDS WELL EAST OF THE HIGHLANDS
THOUGH...BUT STILL MORE SUN TODAY THAN CLOUDS.

PREVIOUS DISCUSSION AT 400 AM...

UPPER PATTERN SHOWS AMPLIFIED YET SPLIT FLOW WITH LOW OFF THE COAST
OF NOVA SCOTIA THIS MORNING...WITH TROUGH AXIS EXTENDING WSW INTO
THE GREAT LAKES...WHILE REX BLOCK OVER THE MIDDLE OF THE COUNTRY IS
EXPECTED WITH HIGH OVER THE CORNBELT AND LOW OVER THE TX PANHANDLE.
DURING THE DAY THE TROUGH AXIS SHIFTS SOUTH AND ACROSS OUR  AREA.
THIS WILL BE PROVIDING INCREASING CLOUDS AND BRISK CONDITIONS
ESPECIALLY OVER THE MTNS. THIS MORE LIKE A WINTER PATTERN. NOT
SEEING A GOOD DEAL OF MOISTURE/LIFT BUT THE UPPER VORT SEEMS
SUFFICIENT ENOUGH IN STRENGTH TO BRING SHOWERS TO THE MTNS OF SE WV
WITH SPRINKLES AS FAR SOUTHEAST AS THE NEW RIVER VALLEY. THERE COULD
EVEN BE SOME GRAUPEL OR ICE PELLETS IF ENOUGH SUN CAN WARM THE LOW
LVLS TO INCREASE LAPSE RATES. ATTM...THE OVERALL THREAT IS LOW SO NO
THUNDER OR WINTRY WX IN THE GRIDS.

TONIGHT...THIS SHORTWAVE EXITS AND SHOWERS DIMINISH OVER THE MTNS
AND WINDS WILL SUBSIDE SOMEWHAT. SKIES CLEAR SO TEMPS SHOULD BE
DROPPING TOWARD THE MID TO UPPER 30S MTNS...TO AROUND 40 ACROSS THE
PIEDMONT. ISSUE TONIGHT WILL BE FROST/FREEZE POTENTIAL. HAVE ONLY
THE HIGHEST RIDGES OF SE WV/MT ROGERS CLOSE TO 32F. WHILE A FEW
POCKET OF FROST ARE POSSIBLE...THINK ENOUGH OF A GRADIENT INHIBITS
FROST FORMATION. THOSE WHO LIVE IN DEEPER/SHELTERED VALLEYS WILL BE
PRONE TO FROST.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 300 AM EDT MONDAY...

GFS/ECMWF WERE SIMILAR IN BRINGING THE UPPER LOW SLOWLY EAST FROM
THE OK/TX AREA TUESDAY MORNING INTO THE TN VALLEY BY WED MORNING. AT
THE SFC...LOW PRESSURE WILL RIDE ALONG THE GULF COAST TUE-WED...THEN
SHIFT OFF THE GA COAST BY WED EVENING. WHILE THIS OCCURS A NRN
STREAM TROUGH MOVES ACROSS THE GREAT LAKES AND JUST NORTH OF US.
MODELS KEEP THESE TWO STREAMS SPLIT...BUT ENOUGH OF INVERTED TROUGH
IN THE AREA PLUS ATLANTIC FLOW TO THROW RAINFALL INTO AREA BY
TUESDAY NIGHT...AND ESPECIALLY INTO WEDNESDAY. NUDGED POPS UP AND
HAVE CATEGORICAL POPS ALONG THE BLUE RIDGE SOUTH OF ROANOKE
WEDNESDAY WITH HIGH CHANCE POPS FROM THE GREENBRIER VALLEY TO THE
PIEDMONT NORTHEAST OF LYH. AS WE HEAD INTO WEDNESDAY NIGHT THE GFS
BECOMES MORE AMPLIFIED AND STRONGER WITH THE NORTHERN LOW THAN OTHER
GUIDANCE...AND THEREFORE DRIVES THE TROUGH FURTHER SOUTH AND BRINGS
THE SFC LOW NE ALONG THE NC COAST. THE ECMWF MORE OPEN WILL TAKE THE
LOW FURTHER OUT TO SEA. ATTM...AM COMPROMISING THE TWO AND KEEPING
HIGHER POPS OVER THE SE CWA WED NIGHT.

HIGHS ARE EXPECTED TO STAY BELOW NORMAL WITH WEDNESDAY APPEARING THE
COOLEST...THOUGH THE ERN CWA MAY STAY MILD ENOUGH WITH MID
60S...WHILE THE BLUE RIDGE SOUTH OF ROANOKE ONLY GETS INTO THE UPPER
40S TO MID 50S...AND COULD BE COOLER IF RAIN MOVES IN FASTER.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 330 PM EDT SUNDAY...

WHILE THERE ARE STILL DIFFERENCES IN TIMING...THE LONG RANGE MODELS
SHOW A SIMILAR SOLUTION OF LIFTING THE DEEP EASTERN U.S. TROF TO
THE EAST AND SLOWLY BUILDING AN UPPER RIDGE ACROSS THE OHIO VALLEY
BY THE END OF THE WEEKEND.

THE GFS APPEARS OVERDONE AND TOO FAR NORTH WITH ITS PLACEMENT OF THE
AXIS OF HEAVY RAIN IN OUR FORECAST AREA. OBVIOUSLY THIS WILL NEED TO
BE MONITORED...BUT LEANED TOWARD THE ECMWF AND CANADIAN SOLUTIONS OF
KEEPING THE AXIS OF HEAVIEST RAIN CLOSER TO THE FORECAST POSITION OF
THE SFC LOW IN THE SOUTHERN CAROLINAS.

WRAP AROUND MOISTURE WILL KEEP CLOUDS...MUCH COOLER THAN NORMAL
TEMPS...AND LIGHT PRECIP THROUGH THURSDAY AND THURSDAY NIGHT. WITH
THE DEEPENING COASTAL SFC LOW...AND PASSING OF A WEAK UPPER VORT
LOBE ON THE WEST SIDE OF THE UPPER TROF AXIS...BUMPED UP WINDS LATE
THURSDAY AND FRIDAY...BUT NOTHING THAT APPEARS TO WARRANT HEADLINES
ATTM.

AS THE DEEP SFC LOW CONTINUES TO MOVE NORTHEAST...WE SHOULD FINALLY
SEE SOME CLEARING FRIDAY...THEN TEMPS CLOSER TO AVERAGE FOR EARLY
MAY BY THE WEEKEND.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
AS OF 725 AM EDT MONDAY...

SOME FOG THIS MORNING HAS IMPACTED BLF/LWB AND EVEN IN LYH. THINK
THE FOG WILL BE GONE SHORTLY WITH VFR EXPECTED THRU MOST OF THE
DAY. SOME BKN 4KFT CIGS NEAR BLF WILL ALSO CLEAR OUT IN THE NEXT
TWO HOURS.

THE WINDS WILL BE MIXING IN AFTER 14Z...FROM THE NW WITH SOME
GUSTS TO 20-25 KTS THIS AFTERNOON. UPSTREAM DISTURBANCE LOOKS TO
BRING VFR CIGS TO THE MTNS...AND PERHAPS ROA/LYH THIS AFTERNOON.

THE FORECAST WILL KEEP VFR CIGS AT ALL SITES EVEN AFTER PASSAGE OF
THIS WAVE. THE GFS IS SHOWING LOW CIGS AT BLF TONIGHT IN THE NW
FLOW...BUT THE MOISTURE EXPECTED TO BE HINDERED BY DRIER AIR...SO
FOR NOW KEEPING OPTIMISTIC VFR AT BLF.



EXTENDED AVIATION DISCUSSION...
VFR CONDITIONS ARE EXPECTED THROUGH TUESDAY BEFORE CONDITIONS
WORSEN ONCE BY LATE TUESDAY NIGHT. MODELS WERE SPEEDING UP
MOISTURE INTO THE AREA...ESPECIALLY SOUTH OF A BLF-DAN LINE BY WED
MORNING. ATTM...THE GFS IS MOST AGGRESSIVE IN HANGING THE STORM
BACK CLOSER TO THE COAST INTO FRIDAY WHICH COULD KEEP THE AREA
SOCKED INTO SUB VFR WEATHER LONGER. THE ECMWF IS MORE
PROGRESSIVE...AND ALL IN ALL LOOKS LIKE WED-THU ARE SUB VFR
DAYS...WITH SOME IMPROVEMENT FRIDAY.

&&

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

&&

$$
SYNOPSIS...WP
NEAR TERM...WP
SHORT TERM...WP
LONG TERM...PH/RAB
AVIATION...WP



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