Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 021505
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1105 AM EDT TUE SEP 2 2014

.SYNOPSIS...
HIGH PRESSURE WILL EXTEND OVER THE REGION  INTO THIS AFTERNOON. A
WEAK COLD FRONT TRACKS SOUTHEAST INTO OUR AREA BY THIS
EVENING...BEFORE STALLING ACROSS THE CAROLINAS AND WASHING OUT ON
WEDNESDAY. HIGH PRESSURE SETS BACK UP OVER THE EAST BY FRIDAY WITH
YET ANOTHER COLD FRONT MOVING TOWARD US THIS WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1050 AM EDT TUESDAY...

GETTING HIGHER DEWPOINTS THIS MORNING AND HAVE UPPED THESE VALUES
INTO EARLY AFTERNOON. NARROW LINE OF SHOWERS/STORMS MOVING ACROSS
NRN KY WITH ONE VORT LOBE WITH MAIN AXIS SHIFTING ACROSS SE IND TO
SOUTH OF CVG. THIS AFTERNOON WILL SEE PLENTY OF INSTABILITY WITH
SUNSHINE. WILL NOT SEE ANY WIDESPREAD THREAT OF SHOWERS OR STORMS
UNTIL LATER IN THE DAY WHEN THE UPPER SUPPORT MOVES INTO THE MTNS
OF WV. UNTIL THEN INCREASE IN CU FIELD OVER THE MTNS...WITH
SHOWERS AND STORMS DEVELOPING AFTER 1 PM...MAINLY ISOLATED UNTIL
AFTER 4 PM. HIGH TEMP FORECAST ON TRACK LOOKING AT MID 80S WEST TO
LOWER TO MID 90S SOUTHEAST. HEAT INDICES MAY APPROACH 100 TOWARD
FARMVILLE/CHARLOTTE COURT HOUSE.

PREVIOUS VALID DISCUSSION...

SPC HAS PLACED THE SLIGHT RISK OF SEVERE STORMS TO OUR WEST FROM
KENTUCKY NORTHWARD TO NEW YORK WITH MAIN THREAT DAMAGING WINDS.
BETTER INSTABILITY AND SHEAR SHOULD REMAIN ALONG THE WESTERN
SLOPES OF APPALACHIANS.

A WEAK COLD FRONT SLIDES ACROSS THE REGION TONIGHT...AND MODELS
PUSH CONVECTION TO THE EAST COAST. PREFRONTAL CONVECTION WILL
SPREAD EAST FROM THE MOUNTAINS INTO THE PIEDMONT. THE NAM AND GFS
WERE FASTER COMPARED TO ECMWF. LOW TEMPERATURES TONIGHT WILL
REMAIN MILD WITH READINGS FROM THE LOWER 60S IN THE MOUNTAINS TO
THE LOWER 70S IN THE PIEDMONT.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
AS OF 415 AM EDT TUESDAY...

NEAR TERM SHORT WAVE WILL BE LOCATED JUST EAST OF THE REGION AT
THE BEGINNING OF THIS PERIOD...WITH A WEAK WEST-EAST ORIENTED
FRONTAL BOUNDARY STALLING JUST SOUTH OF THE VA/NC BORDER AS IT
ENCOUNTERS A PERSISTENT RIDGE OF HIGH PRESSURE ALOFT...THAT
OVERALL WILL REMAIN VERY PERSISTENT ACROSS THE CENTRAL AND EASTERN
STATES SOUTH OF 40 DEG LAT WELL INTO NEXT WEEK. MOISTURE AND
INSTABILITY WILL NEVER REALLY BE REMOVED FROM THE REGION BEHIND
THE FRONT...ESPECIALLY ACROSS THE NC COUNTIES AND INTO SW VA. BY
AFTERNOON...EXPECT SHOWERS/THUNDERSTORMS TO REDEVELOP ACROSS SW
VA...NW NC...AND INTO THE PIEDMONT OF NC...SLOWLY WORKING NORTH
TOWARD THE VA BLUE RIDGE AND INTO SOUTHSIDE VA. EXTENDED RANGE
MODELS IN GENERAL AGREEMENT THAT DRYING WILL NOT PROGRESS AS FAR
SOUTH AS INDICATED WITH YESTERDAYS MODEL RUNS...SO HAVE INCREASED
POPS FURTHER NORTH SOONER THAN EARLIER THOUGHT...ESPECIALLY ACROSS
THE SW COUNTIES. WITH 850MB TEMPS HOVERING IN THE +18C TO +20C
RANGE...COOLING WILL BE MINIMAL IF ANY...WITH MAX TEMPS REMAINING
A GOOD 10 DEGREES ABOVE NORMAL...WITH STILL 90S ACROSS THE
PIEDMONT AND 80S ELSEWHERE...EXCEPT ELEVATIONS ABOVE 3500 FEET IN
THE 70S. WITH THE MINIMAL PWAT STILL RUNNING AROUND 1.5 INCH...MIN
TEMPS WILL NOT BE COOLING MUCH EITHER...REMAINING IN THE MUGGY
60S.

FOR THU...WHAT IS LEFT OF THE FRONT TO THE SOUTH WASHES OUT AND
RETURNS NORTH ALONG WITH INCREASINGLY HIGH MOISTURE CONTENT FROM
THE SOUTH. THE UPPER RIDGE EXPANDS NORTHWARD AGAIN WITH 500MB
HEIGHTS CLOSING IN ON 592DM ACROSS THE REGION AND 850MB TEMPS IN
THE +20 TO +21C RANGE. ONLY THE LOWER SUN ANGLE IS SPARING US FROM
MORE WIDESPREAD 90S THIS LATE IN THE SUMMER. AS INDICATED
YESTERDAY...THE MAIN FOCUS FOR PRECIPITATION THU AND FRI WILL BE
MAINLY ALONG TO EAST OF THE BLUE RIDGE WHERE BETTER MOISTURE
CONTENT PREVAILS. THIS WILL BE THE PATTERN UNTIL THE NEXT UPPER
SHORT WAVE TROUGH APPROACHES FROM THE NW LATE FRIDAY...BUT WILL
NOT APPRECIABLY IMPACT THE CWA UNTIL THE WEEKEND. THUS...FOR THU
AND FRI...SCATTERED...TYPICAL SUMMERTIME DIURNAL CONVECTION
APPEARS TO BE THE RULE...WITH THE MAIN FOCUS ALONG-EAST OF THE
BLUE RIDGE. TEMPERATURES WILL REMAIN WELL ABOVE NORMAL AGAIN.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 430 AM EDT TUESDAY...

THE NEXT IN THE SERIES OF UPPER SHORT WAVE TROUGHS WILL MOVE INTO
THE REGION SATURDAY ALONG WITH THE ASSOCIATED COLD FRONT. THE
BROAD AND STRONG SUBTROPICAL UPPER RIDGE WILL PERSIST ACROSS THE
SOUTHERN STATES...BUT SHOWS SIGNS OF WEAKENING SOME AND THE CENTER
OF WHICH WILL RELOCATE MORE TOWARD THE SOUTH CENTRAL INSTEAD OF
THE SOUTHEAST STATES. THIS IN RESPONSE TO THE UPPER TROUGH
IMPINGING ON THE NORTHERN FRINGES OF THE UPPER HIGH FRI-SAT.
HOWEVER...ONCE AGAIN...THE FRONT APPEARS TO STALL ACROSS
TN/NC...WITH DEEPER MOISTURE/INSTABILITY PRECARIOUSLY CLOSE SUCH
THAT...AT A MINIMUM...POPS CANNOT BE REMOVED FROM THE SOUTHERN
SECTIONS. BY FAR AT THIS POINT...THE BEST CHANCE FOR
SHOWERS/THUNDERSTORMS WILL COME WITH THE FRONT FRI NIGHT INTO
SATURDAY. GFS/ECMWF AT ODDS AS TO HOW MUCH...IF ANY DRYING FROM
THE NORTH WILL PENETRATE THE REGION INTO EARLY NEXT WEEK...SO
HAVE NOT MADE ANY CHANGES TO EARLIER ADVERTISED POPS BEYOND SAT.
TEMPERATURES WILL REMAIN ON THE WARM SIDE AND ABOVE NORMAL. 850MB
TEMPS SHOW A SLIGHT COOLING INTO THE +16C TO +18C RANGE OVER THE
WEEKEND...BUT COULD SURGE BACK TOWARD +20C EARLY NEXT WEEK AS THE
UPPER RIDGE AMPLIFIES BACK INTO THE SOUTHEAST/MID-ATLANTIC REGION
AND HEIGHTS RISE ABOVE 590DM ONCE AGAIN.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
AS OF 735 AM EDT TUESDAY...

OVERALL VFR SHOULD PREVAIL THIS MORNING AT THE TAF LOCATIONS WITH
EXTENSIVE MID/HIGH CLOUDS SPREADING ACROSS THE REGION FROM THE
WEST IN ADVANCE OF THE NEXT UPPER SHORT WAVE/FRONT. DO NOT EXPECT
MUCH PRECIPITATION UNTIL LATER IN THE AFTERNOON AS THE FRONT
APPROACHES. IN THE 18Z-22Z TIME FRAME...EXPECT BKN LINE OF
CONVECTION...POSSIBLY A FEW STRONG CELLS...TO REACH EASTERN WV
INCLUDING BLF/LWB TAF SITES. GUSTY WINDS AND POTENTIALLY BRIEF
PERIOD OF MVFR CIGS/VSBYS IN TSRA DURING THIS TIME FRAME.
HOWEVER...CONFIDENCE TOO LOW TO INCLUDE IN A PREVAILING GROUP AT
THIS POINT. FURTHER EAST...POTENTIAL FOR CONVECTION WILL BE LATER
AND EVEN LESS CERTAIN. THUS...FOR NOW HAVE OPTED FOR PROB30 OR
VCTS WITH MOSTLY VFR CIGS. SEVERAL MODELS HINT AT POTENTIAL FOR
CONVECTION REDEVELOPING OR LINGERING ACROSS THE PIEDMONT DURING
THE LATE EVENING/EARLY OVERNIGHT HOURS. FOG DEVELOPMENT OVERNIGHT
ALSO UNCERTAIN AS MUCH POTENTIAL WILL DEPEND ON HOW MUCH RAIN
OCCURS DURING THE EVENING AND ALSO CLEARING...IF ANY OVERNIGHT.
MOST MODELS SHOW DENSE MID CLOUDS REMAINING. LOW CLOUDS WILL
LIKELY DEVELOP IN UPSLOPE AREAS WEST OF THE ALLEGHANY FRONT WITH
POTENTIAL MVFR CIG AFT 06Z BLF-LWB. WINDS...MOSTLY SW-WSW 7-10KTS
WITH LOW END GUSTS WEST OF THE ALLEGHANY FRONT POSSIBLE THROUGH
THE DAYTIME.

MEDIUM TO HIGH CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS
THROUGH THE TAF VALID PERIOD.

EXTENDED AVIATION DISCUSSION...

FRONT SETTLES CLOSER TUESDAY NIGHT INTO WEDNESDAY...WHEN BETTER
COVERAGE OF SHRA/TSRA IS EXPECTED. HOWEVER LOW CONFIDENCE ON THE
TIMING AND SOUTHWARD POSITION OF THE BOUNDARY ON WEDNESDAY AT THIS
POINT PENDING PRE-FRONTAL COVERAGE FROM TUESDAY NIGHT. FOR NOW APPEARS
MAINLY VFR OUTSIDE OF EARLY MORNING FOG WEDNESDAY...THEN PERIODS
OF MVFR WEDNESDAY AFTERNOON ESPECIALLY SOUTHERN SECTIONS...AND
MAINLY ACROSS THE SOUTH/SOUTHWEST THURSDAY AFTERNOON FOR MORE
ISOLATED NATURE COVERAGE. FRONT WASHES OUT TO THE SOUTH OF THE
AREA FRIDAY WITH MORE WIDELY SCATTERED DIURNAL NATURE SHOWERS AND
STORMS...THEN PERHAPS BECOMING MORE WIDESPREAD SATURDAY WITH
PERIODIC MVFR IN MORE ORGANIZED COVERAGE AHEAD OF ANOTHER COLD
FRONT ARRIVING FROM THE NORTHWEST LATE. OTRW WILL SEE A DAILY
TREND OF EARLY MVFR/IFR IN FOG...FOLLOWED BY BRIEF VFR...THEN
INCREASING AFTERNOON/EVENING CONVECTION WHEN MVFR TO LOCAL IFR
WILL BE POSSIBLE.

&&

.EQUIPMENT...
AS OF 730 AM EDT FRIDAY ...

THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...WILL
BE OUT OF SERVICE UNTIL FURTHER NOTICE. A PART HAS BEEN BACK-ORDERED.

&&

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

&&

$$
SYNOPSIS...KK
NEAR TERM...KK/WP
SHORT TERM...RAB
LONG TERM...RAB/RCS
AVIATION...KK/RAB
EQUIPMENT...RAB


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