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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 132000
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
400 PM EDT MON MAY 13 2013

.SYNOPSIS...
-- Changed Discussion --
COLD HIGH PRESSURE WILL SETTLE OVER THE REGION TONIGHT. A SHIFT
IN THE WEATHER PATTERN TAKES PLACE BY MID-WEEK AS AN UPPER RIDGE
BUILDS OVER THE REGION...AND TEMPERATURES INCREASE TO ABOVE
NORMAL READINGS. A FRONTAL BOUNDARY WILL APPROACH THE AREA ON
THURSDAY AND STALL OVER OR NEAR THE AREA INTO THE START OF THE
WEEKEND.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TUESDAY/...
-- Changed Discussion --
AS OF 315 PM EDT MONDAY...

DESPITE SURFACE HIGH PRESSURE BUILDING INTO THE AREA...A NUMBER OF
ELEMENTS MAKE TONIGHT/S FORECAST NOT SO CUT AND DRY.

CURRENTLY WE HAVE AN UPPER SHORTWAVE TROUGH CROSSING THROUGH THE MID-
ATLANTIC STATES WITH A DECENT UPPER LEVEL COLD CORE ALONG ITS AXIS.
HEATING IN THE LOW LEVELS IS PRODUCING A STRONG LAPSE RATE THAT HAS
CREATED A GENEROUS COLLECTION OF CUMULUS CLOUD STREETS. REFLECTIVE
RETURNS FROM KFCX 88D SUGGESTS SOME ISOLATED TO SCATTERED LIGHT RAIN
SHOWERS IN THE MIX NEAR THE I-64 CORRIDOR. THIS ACTIVITY WILL
CONTINUE THROUGH THE AFTERNOON HOURS...BUT QUICKLY DISSIPATE AS
WE APPROACH SUNSET THIS EVENING.

OVERNIGHT...THIS UPPER TROUGH PROGRESSES TO THE ATLANTIC
COAST...TAKING WITH IT ANY LINGERING CLOUD COVER ASSOCIATE WITH IT.
CLOSER TO THE SURFACE...THE CENTER OF HIGH PRESSURE IS PROGGED TO BE
CENTERED OVER THE REGION BY SUNRISE TUESDAY. COLD AIR WAS ASSOCIATED
WITH IT LAST NIGHT...AND IF EVERYTHING ELSE WAS EQUAL...WE WOULD
EXPECT EVEN COLDER TEMPERATURES WITH THE POTENTIAL FOR EVEN MORE
AREAS UNDER A FREEZE WARNING OR FROST ADVISORY COMPARED TO LAST
NIGHT. HOWEVER...THERE IS A PROBLEM WITH THIS THINKING.

MODEL GUIDANCE HAS BEEN OFFERING A SOLUTION THAT BEGINS THE PROCESS
OF THE BACKING OF LOW LEVEL WINDS ACROSS THE WESTERN QUARTER OF THE
REGION AS UPPER LEVEL RIDGE MOVES INTO THE MISSISSIPPI VALLEY. THESE
WINDS WILL START THE PROCESS OF WEAK WARM AIR ADVECTION AT 850MB
ACROSS THE NORTHERN MOUNTAINS AND FOOTHILLS OF NC LATE TONIGHT...AS
WELL AS...WESTERN PARTS OF THE MOUNTAIN EMPIRE REGION OF SOUTHWEST
VIRGINIA. INCLUDED WITH THIS WILL BE INCREASING MID TO HIGH LEVEL
CLOUDINESS AFTER MIDNIGHT IN THE SAME REGION OF THE FORECAST AREA.
SO THE COMBINATION OF THESE FEATURES WILL LIMIT HOW MUCH THE
TEMPERATURE FALLS TONIGHT...AND GREATLY REDUCE THE POTENTIAL FOR
FROST.

AS YOU HEAD NORTHEAST FROM THIS PART OF THE FORECAST
AREA...TEMPERATURE ADVECTION IS MORE NEUTRAL TO STILL SLIGHTLY ON
THE SIDE OF COLD...PLUS CLOUD COVER WILL BE LESS AFTER THE
DEPARTURE OF THE UPPER TROUGH. THIS TRANSLATES TO AREAS NEAR THE
I-64 CORRIDOR OF WV AND VA...THE CURRENT FREEZE WATCH AREA...WILL
LIKELY HAVE THE COLDEST TEMPERATURES FOR THE NIGHT...BUT ALSO HAVE
SOME OF THE MID TO HIGH LEVEL CLOUDS PREVIOUSLY MENTIONED.
THEREFORE...FROST IS LESS LIKELY OUTSIDE OF THOSE AREAS THAT ARE
AT OR BELOW FREEZING. HAVE PLACED SUMMERS CO WV IN A FROST
ADVISORY TO REFLECT THE POTENTIAL FOR FROST IN THOSE SUB-FREEZING
AREAS...BUT THE COVERAGE IS EXPECTED TO BE TOO LITTLE TO HAVE THIS
COUNTY AS PART OF THE FREEZE WARNING.

AREAS ALONG AND EAST OF A BEDFORD VA TO LEXINGTON VA LINE AND ALONG
AND NORTH OF THE ROANOKE RIVER BASIN WILL RECEIVE LITTLE IF ANY OF
THE CLOUD COVER ADVANCING FROM THE SOUTHWEST BY DAYBREAK.
HOWEVER...BY DAYBREAK...THE CLOUDS ASSOCIATED WITH THE UPPER
SHORTWAVE TROUGH WILL BE EAST OF THE AREA...ALLOWING FOR AT LEAST
MOSTLY CLEAR...IF NOT CLEAR SKIES. LOW TEMPERATURES HERE ARE NOT
EXPECTED TO REACH FREEZING...BUT THERE WILL BE AN ABUNDANCE OF MID
30S ALONG WITH CALM WINDS. THIS REGION OF THE FORECAST AREA WILL BE
SLATED FOR A FROST ADVISORY.

ON TUESDAY...THE BACKING OF THE LOW LEVEL WINDS THAT STARTED IN THE
SOUTHWEST LATE MONDAY NIGHT...WILL CONTINUE THROUGHOUT THE DAY
TUESDAY ALONG WITH GENEROUS WARM AIR ADVECTION. BY THE LATE
AFTERNOON 850 MB TEMPS ARE EXPECTED BE AROUND +12C IN THE WEST AND
AROUND +6 IN THE EAST...AS COMPARED TO THE 0C TO +4 C RANGE THAT
EXIST THIS AFTERNOON. EXPECT INCREASING MID TO HIGH LEVEL CLOUDS
THROUGH THE DAY. HIGHS WILL RANGE FROM THE LOW TO MID 60S IN THE
MOUNTAINS WITH UPPER 60S TO AROUND 70 DEGREES EAST OF THE CREST OF
THE BLUE RIDGE.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
-- Changed Discussion --
AS OF 345 PM EDT SUNDAY...

MODELS SHOWING HIGHER AMOUNT OF MOISTURE WITH THE WARM FRONT WHICH
CROSSES THE FORECAST AREA TUESDAY AFTERNOON THROUGH LATE TUESDAY
NIGHT. HAVE INCREASED THE AREAL COVERAGE OF LOW PROBABILITY OF
PRECIPITATION IN THE NORTHERN COUNTY WARNING AREA...SIMILAR TO WHAT
WAS SHOWN ON THE SREF AND 00Z ECMWF. ISENTROPIC FORECAST IN THE 295K
LAYER SHOWED GOOD LIFT IN THE 850 TO 700 MB RANGE WITH PLENTY OF
MOISTURE IN THAT LAYER.

COUNTY WARNING AREA WILL BE WELL INTO THE WARM SECTOR ON WEDNESDAY
WITH A LARGE RISE IN 850 MB TEMPERATURES AND SURFACE TO LOW LEVEL
WINDS WITH A DOWNSLOPE WESTERLY COMPONENT. WENT CLOSE TO WARMER
GUIDANCE EAST OF THE BLUE RIDGE FOR MAXIMUM TEMPERATURES ON
WEDNESDAY.

SOME MODELS SHOWING THE FRONT FROM PENNSYLVANIA INTO THE OHIO VALLEY
POTENTIALLY STARTING TO DROP SOUTH ON THURSDAY. WHILE CONVECTIVE
COMPLEXES ALONG THE FRONT MAY MOVE THE BOUNDARY...ZONAL FLOW DOES
NOT SEEM FAVORABLE FOR MUCH OF A SOUTHERN PUSH.
-- End Changed Discussion --

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
-- Changed Discussion --
AS OF 345 PM EDT MONDAY...

TIMING OF THE SHORT WAVE COMING OUT OF THE SOUTHERN PLAINS SOMEWHAT
SIMILAR TO PAST FEW RUNS BRINGING SOME ENHANCED LIFT INTO THE AREA
THURSDAY NIGHT AND FRIDAY. CHALLENGING TO NARROW DOWN BEST CHANCE OF
PRECIPITATION FRIDAY NIGHT THROUGH SUNDAY NIGHT. LITTLE CHANGE IN THE
AIR MASS AND DAILY HIGHS AND LOWS THROUGH SUNDAY.

NEXT LONG WAVE UPPER TROF DIGGING INTO THE CENTRAL UNITED STATES ON
SUNDAY AND MONDAY. THIS PUSHES A COLD FRONT INTO THE REGION ON
MONDAY. SO HAVE A HIGHER PROBABILITY OF PRECIPITATION FOR MONDAY AND
MONDAY NIGHT.
-- End Changed Discussion --

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
AS OF 115 PM EDT MONDAY...

VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST WEDNESDAY.

ISOLATED SHOWERS ARE POSSIBLE ALONG AND NORTH OF A KLWB-KLYH LINE
THE REMAINDER OF THIS AFTERNOON AND VERY EARLY THIS EVENING THANKS
TO A STEEP LAPSE RATE ASSOCIATED WITH A PASSING SHORTWAVE TROUGH.

OUR NEXT CHANCE OF ORGANIZED PRECIPITATION AND AREAS OF SUB-VFR
CONDITIONS WILL BE THURSAY NIGHT THROUGH SATURDAY WHEN A FONTAL
SYSTEM MOVES INTO AND THEN STALLS NEAR THE REGION.

&&

.CLIMATE...
A NEW RECORD LOW WAS ESTABLISHED AT DANVILLE THIS MORNING WITH 37
DEGREES. THE PREVIOUS RECORD WAS 38 DEGREES FROM 1989. ALSO...A
LOW OF 35 DEGREES THIS MORING TIED THE RECORD LOW AT LYNCHBURG.
THE LAST OCCURRENCE WAS IN 1969.

LOW TEMPERATURES TUESDAY MORNING WILL FLIRT WITH RECORD LOW
TEMPERATURES AT ALL CLIMATE LOCATIONS. THE FOLLOWING ARE THE
CURRENT RECORD LOW TEMPERATURES FOR MAY 14 ALONG WITH THE YEAR OF
THAT RECORD.

MAY 14
ROA...37...1996
LYH...33...1997
RNK...31...1996
DAN...38...2007
BLF...33...1996

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
VA...FREEZE WARNING FROM 1 AM TO 9 AM EDT TUESDAY FOR VAZ019-020-
     024.
     FROST ADVISORY FROM 3 AM TO 9 AM EDT TUESDAY FOR VAZ034-035-
     045>047-059.
NC...NONE.
WV...FREEZE WARNING FROM 1 AM TO 9 AM EDT TUESDAY FOR WVZ045.
     FROST ADVISORY FROM 1 AM TO 9 AM EDT TUESDAY FOR WVZ043.
-- End Changed Discussion --

&&

$$
SYNOPSIS...DS
NEAR TERM...DS
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...DS
CLIMATE...CF/DS