-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 302358
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
758 PM EDT WED JUL 30 2014

.SYNOPSIS...
AN UPPER TROUGH OF LOW PRESSURE WILL RETROGRADE WEST TO THE
MISSISSIPPI RIVER VALLEY...AND THE CENTER OF SURFACE HIGH PRESSURE
WILL SHIFT TO OUR EAST. THE RESULT THROUGH THE WEEKEND AND INTO
THE EARLY PART OF NEXT WEEK WILL BE AN INCREASED CHANCE OF SHOWERS
AND STORMS ACROSS OUR REGION STARTING ON THURSDAY.
CURRENTLY...FRIDAY INTO SATURDAY LOOKS TO BE THE TIME WINDOW WITH
THE GREATEST POTENTIAL FOR THE ENTIRE AREA.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 320 PM EDT WEDNESDAY...

WE WILL CONTINUE TO WATCH TWO POTENTIAL AREAS OF CONVECTION
HEADING INTO THE EARLY EVENING HOURS. THE ONE WILL BE CENTERED
JUST SOUTHEAST OF THE FORECAST AREA...BUT ITS INFLUENCE MAY BE
EXTEND FAR ENOUGH NORTH FOR SOME ISOLATED SHOWERS AND STORMS IN
AREAS AROUND...EAST AND SOUTH OF DANVILLE VA THROUGH ROUGHLY 800
PM. THE OTHER AREA WILL BE IN ASSOCIATION WITH SOME INSTABILITY
THAT HAS DEVELOPED JUST WEST OF THE SOUTHEAST WEST VIRGINIA
PORTION OF THE FORECAST AREA. WHILE AREAS AROUND AND WEST OF
LEWISBURG WV MAY SEE A STRAY SHOWER BETWEEN NOW AND ROUGHLY 500
PM...CHANCES WILL INCREASE AS WE APPROACH 700 PM. A DISTURBANCE
WITH AN AREA OF STEEP LAPSE RATE AIR IS CURRENTLY MOVING THROUGH
OHIO...AND SHOULD BE APPROACHING THE AREA TOWARD THE EARLY
EVENING. BOTH THE HRRR AND RNK WRF-ARW OFFER SOLUTIONS THAT BRING
THE ACTIVITY TO OUR DOORSTEP AND THEN HAVE IT DISSIPATE. HAVE
ALLOWED FOR THE POTENTIAL FOR SOME ISOLATED THUNDERSTORMS THIS
EVENING IN AREAS NEAR AND NORTH OF INTERSTATE 64 IN WV AND VA.
OTHER ISOLATED SHOWERS WILL BE POSSIBLE NEAR THE CREST OF THE BLUE
RIDGE FROM THE LATE AFTERNOON INTO THE EARLY EVENING. WHILE
INSTABILITY IS NOT STRONG IN THIS AREA...CONVERGENCE WITHIN THIS
AREA MAY BE ENOUGH FOR A FEW SHOWERS TO FORM. THE MAIN FOCUS WILL
BE ACROSS THE FAR NORTHWEST AND FAR SOUTHEAST PARTS OF THE REGION.

A HIGH PRESSURE RIDGE AXIS WAS SITUATED WEST-EAST ACROSS THE AREA
CURRENTLY. EASTERLY FLOW ON THE SOUTH SIDE OF THIS FEATURE HAS
HELPED ADVECT HIGHER DEW POINTS IN THE LOWER 60S BACK TOWARD THE
AREA AS CLOSE AS ROXBORO NC AND SOUTH HILL VA. THE CENTER OF THE
HIGH IS PROGGED TO START SHIFTING EASTWARD TONIGHT. THIS WILL HELP
ALLOW FOR A GRADUAL TREND TOWARDS LOW LEVEL WINDS WITH A GREATER
SOUTHERLY COMPONENT ACROSS THE REGION. IN TURN...HIGHER DEW POINT
AIR IS EXPECTED TO CONTINUE ITS PROGRESSION TOWARDS AND THEN INTO
THE AREA. BY DAYBREAK THURSDAY...SOME OF THIS MOISTURE WILL BECOME
BANKED AGAINST THE CREST OF THE BLUE RIDGE WITH INCREASED CLOUD
COVER OVER NORTHWEST NORTH CAROLINA AND NEIGHBORING SECTIONS OF
SOUTHWEST VIRGINIA. LOW TEMPERATURES TONIGHT SHOULD BE MILDER AS
COMPARED TO THOSE OF THIS MORNING. READINGS AROUND 50 TO THE LOWER
50S ARE EXPECTED ACROSS THE MOUNTAINS WITH A MIX OF MID TO UPPER 50S
ACROSS THE PIEDMONT. A FEW SPOTS ACROSS SOUTHSIDE VIRGINIA AND
NEIGHBORING NORTH CENTRAL NORTH CAROLINA CAN EXPECT LOWS AROUND 60.
OF OUR SIX CLIMATE SITES...LEWISBURG HAS THE POTENTIAL OF BEING
CLOSE TO A RECORD LOW TONIGHT. SEE THE CLIMATE SECTION OF THIS
DISCUSSION FOR DETAILS.

ON THURSDAY...THE TREND TOWARDS E-SE LOW LEVEL FLOW AND GREATER
MOISTURE WILL CONTINUE. INCREASING CLOUDS WILL BE THE NORM
THROUGHOUT THE DAY WITH UPSLOPE RAIN SHOWERS DEVELOPING AND GROWING
IN COVERAGE. THE GREATEST CONCENTRATION WILL BE ACROSS THE NORTHERN
MOUNTAINS OF NORTH CAROLINA...NORTHEAST ALONG THE CREST OF THE BLUE
RIDGE TO NEAR FLOYD VA. HIGH TEMPERATURES WILL RANGE FROM THE MID
70S TO AROUND 80 IN THE MOUNTAINS TO THE LOW TO MID 80S ACROSS THE
PIEDMONT.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 330 PM EDT THURSDAY...

MODELS CONSISTENT BRINGING A SHORT WAVE THROUGH THE SOUTHWEST FLOW
ALOFT THURSDAY NIGHT THROUGH FRIDAY NIGHT. THURSDAY NIGHT AND FRIDAY
THERE IS ALSO SOME SUPPORT FROM THE DIFFLUENT AREA OF THE UPPER JET.
MAY KEEP PROBABILITY OF THUNDERSTORMS LOW SINCE GUIDANCE IS SHOWING
LITTLE CAPE AND INSTABILITY OVER MUCH OF THE FORECAST AREA. BY
FRIDAY MORNING...PRECIPITABLE WATER VALUES WILL BE BACK IN THE 1.0
TO 1.5 INCH RANGE WITH SURFACE DEW POINTS IN THE 60S. WPC 24 HOUR
QPF FROM 12Z FRIDAY TO 12Z SATURDAY OF 0.25 TO 0.50 INCHES LOOKS
REASONABLE. HOWEVER...MODELS DO NOT HAVE A PARTICULARLY GOOD
CONSENSUS OF WHERE THE HEAVIEST AMOUNTS WILL BE. EASTERLY COMPONENT
OF LOW LEVEL WINDS FAVORS THE EASTERN SLOPES OF THE BLUE RIDGE.
PUTTING THE HIGHEST PROBABILITY OF PRECIPITATION IN FROM LATE
THURSDAY NIGHT THROUGH LATE MORNING ON FRIDAY.

WIDE RANGE IN GUIDANCE FOR MAXIMUM TEMPERATURES ON FRIDAY. WITH ALL
THE CLOUDS AND PRECIPITATION EXPECTED...HAVE TRENDED TOWARD THE
COOLER BIAS CORRECTED MAV NUMBERS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 330 PM EDT THURSDAY...

FRONT AT THE SURFACE REMAINS ALONG THE COAST SATURDAY NIGHT THROUGH
MONDAY. ON TUESDAY AND WEDNESDAY...A COLD FRONT WILL PUSH INTO THE
REGION FROM THE NORTHWEST.

UNTIL THIS FRONT GOES THROUGH...THERE WILL BE A DAILY THREAT OF
SHOWERS AND THUNDERSTORMS EACH AFTERNOON AND EVENING. CHALLENGING TO
NARROW DOWN WHICH DAY OF TIME FRAME WILL BE MORE FAVORABLE FOR
PRECIPITATION...ALTHOUGH MODELS SUGGEST A SHORT WAVE COMING THROUGH
THE OHIO VALLEY ON SUNDAY MAY BRING A MORE ORGANIZED AREA OF SHOWERS
AND THUNDERSTORMS TO THE COUNTY WARNING AREA.

POCKET OF WARMER 850 MB AIR WITH +20 TEMPERATURES COMES OUT OF THE
MISSISSIPPI VALLEY...REACHING THE FORECAST AREA ON WEDNESDAY BASED
ON THE ECMWF.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
AS OF 745 PM EDT WEDNESDAY...

GENERALLY VFR CONDITIONS EXPECTED THROUGH THE TAF VALID
PERIOD...WITH THE EXCEPTION BEING POTENTIAL FOR BR HZ DURING THE
LATE NIGHT/EARLY MORNING HOURS AT THE USUAL SPOTS...BUT ESPECIALLY
WEST OF THE BLUE RIDGE. UPPER TROUGH WILL CONTINUE ACROSS THE
REGION. A DISTURBANCE...NOW LOCATED IN THE SOUTHERN PLAINS WILL
MOVE THROUGH THE BASE OF THE TROUGH THU...THEN BEGIN TO APPROACH
THE REGION FROM THE SOUTHWEST THU NIGHT/FRI. LINE OF THUNDERSTORMS
ACROSS WESTERN WV NORTHWARD INTO CENTRAL PA WILL DISSIPATE PER ALL
MODEL SOLUTIONS AS IT MOVES TOWARD THE APPALACHIANS NOT AFFECTING
ANY TAF SITES. HOWEVER...CI SHIELD MAY AFFECT LWB FOR A WHILE THIS
EVENING. OTHERWISE...SCT AC/SC WILL DISSIPATE OVER THE NEXT COUPLE
OF HOURS. MVFR BR CAN BE EXPECTED AGAIN TONIGHT AT LWB/BCB AND
POTENTIALLY DAN/LYH...WITH LWB LIKELY SEEING A PERIOD OF IFR-LIFR
ONCE AGAIN IN THE 08Z-13Z TIME FRAME. FOG IS NOT EXPECTED AT ROA
OR BLF AT THIS TIME. FOR THU...LAYER OF MOISTURE WILL PERSIST IN
THE 040-060 RANGE...RESULTING IN CONTINUATION OF SCT-BKN CU/SC/AC
DURING THE MID DAY/AFTERNOON. LATE IN THE DAY...CI SHIELD WILL
SPREAD NORTHEASTWARD TOWARD THE REGION FROM THE SOUTHEAST STATES.
WILL HOLD OFF ON MENTIONING ANY SHRA/TSRA THIS TAF VALID PERIOD AS
IT APPEARS TO REACH NO FURTHER THAN NW NC LATE IN THE DAY.
WINDS...MOSTLY SW THROUGH THE TAF VALID PERIOD...BUT
BCB/LYH/DAN/LWB WILL LIKELY SEE CALM WINDS MUCH OF THE NIGHT.
SPEEDS THU REMAINING MOSTLY 5KTS OR LESS EVEN AFT 14Z.

MEDIUM TO HIGH CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD.
MEDIUM CONFIDENCE IN VSBYS THROUGH 14Z...THEN HIGH CONFIDENCE IN
VFR CONDITIONS.
MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID
PERIOD.

EXTENDED AVIATION DISCUSSION...
A BROAD TROUGH OF LOW PRESSURE WILL BE ACROSS THE EASTERN UNITED
STATES THROUGH SUNDAY. IT WILL SLOWLY RETROGRADE FROM THE
EASTERN/CENTRAL GREAT LAKES TO THE WESTERN GREAT LAKES BY THE
WEEKEND. THIS WILL BEGIN TO TURN THE UPPER FLOW TO THE SOUTHWEST
WITH TIME. THE AFOREMENTIONED DISTURBANCE COMING FROM THE SE
STATES THU...WILL MOVE NORTHEASTWARD ACROSS THE REGION FRI.
EXTENSIVE OVERRUNNING LIKELY WITH EMBEDDED ISOLD TSRA. SFC AIR
MASS REMAINS QUITE STABLE...ESPECIALLY EAST OF THE ALLEGHANY
FRONT...SO THUNDER APPEARS ISOLD AT THIS POINT.
HOWEVER...WIDESPREAD MVFR CIGS/VSBYS WILL BE POSSIBLE FRI WITH
THIS SCENARIO IN -RA -DZ BR. FOR SAT-SUN...AIR MASS WILL SLOWLY
BECOME WARMER AND MORE UNSTABLE. SCT SHRA/TSRA AGAIN SAT WITH ONLY
LIMITED INSTABILITY EVIDENT. FOR SUN...BETTER CHANCE OF TSRA WITH
CAPES EXCEEDING 1000 J/KG ACROSS MUCH OF THE CWA...SW FLOW
ALOFT...AND INCREASING MOISTURE LEVELS. THUS...BRIEF PERIODS OF
MVFR-IFR CIGS/VSBYS EXPECTED IN SHRA/TSRA SAT AND MORE LIKELY SUN
AFTERNOON. OTHERWISE...POTENTIAL FOR LATE NIGHT/EARLY MORNING
IFR-LIFR BR/FG INCREASES THROUGH THE PERIOD...BUT MAINLY AT THE
USUAL SITES...LWB/BCB/LYH.

&&

.CLIMATE...
JULY 31ST RECORD LOWS:

ROANOKE......49...1914
BLUEFIELD....49...1997
DANVILLE.....55...1966
LEWISBURG....48...1997
LYNCHBURG....49...1997
BLACKSBURG...44...1997

&&

.EQUIPMENT...
THE NOAA WEATHER RADIO AT WYTHEVILLE VA...WZ2500...BROADCASTING
ON A FREQUENCY OF 162.450 MHZ...IS OFF THE AIR. TECHNICIANS ARE
WAITING ON DELIVERY OF PARTS TO MAKE REPAIRS. THE EARLIEST THE
RADIO WILL BE WORKING AGAIN IS FRIDAY.

&&

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

&&

$$
SYNOPSIS...DS
NEAR TERM...DS
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...RAB
CLIMATE...PH
EQUIPMENT...DS