000
FXUS61 KRNK 081046 AAA
AFDRNK

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BLACKSBURG VA
646 AM EDT WED SEP 8 2010

.SYNOPSIS...
A COLD FRONT WILL MOVE ACROSS THE REGION FROM THE NORTHWEST TODAY
AND PASS WELL TO THE SOUTH THIS EVENING. HIGH PRESSURE WILL
FOLLOW THE FRONT OVERNIGHT BRINGING DRIER AND SOMEWHAT COOLER
WEATHER THROUGH LATE WEEK. OUR NEXT CHANCE FOR PRECIPITATION TO
COVER A SIGNIFICANT PORTION OF THE AREA WILL BE THIS COMING
WEEKEND AS BOTH A WARM FRONT AND COLD FRONT TRAVERSE THE REGION.

&&

.NEAR TERM /THROUGH TONIGHT/...
QUICK UPDATE TO UP POPS OVER PARTS OF THE SW AND EXTEND CHANCES
FARTHER EAST THIS MORNING GIVEN INCREASING SHRA COVERAGE ALONG THE
I-77 CORRIDOR AND POINTS NORTH ATTM. REMAINDER UNCHANGED FOR NOW.

PREVIOUS DISCUSSION BELOW...

COLD FRONT CROSSING INTO WVA WILL SLIDE ACROSS THE APPALACHIANS
EARLY THIS MORNING BEFORE PASSING SE OF THE BLUE RIDGE THIS
AFTERNOON. NARROW BAND OF DEEPER RH/THETA-E JUST AHEAD OF THE
BOUNDARY LOOKS TO PUSH INTO THE WESTERN SLOPES BY DAYBREAK BEFORE
ENCOUNTERING DEEP WEST/NW FLOW ALOFT AND WEAKENING. THIS ALONG WITH
WEAK LOW LEVEL CONVERGENCE LIKELY TO KEEP AT LEAST SCTD SHRA/ISOLD
THUNDER GOING INTO SE WVA/FAR WESTERN VA EARLY ON BEFORE MOST OF THE
FOCUS SHIFTS DOWN THE RIDGES INTO SW VA/NW NC LATER THIS MORNING.
FRONT PASSES OFF THE BLUE RIDGE EARLY THIS AFTERNOON INTO AN AREA OF
SLIGHTLY BETTER INSTABILITY ACROSS SOUTHERN VA/NW NC PROVIDED SOME
HEATING. MODELS CONTINUE TO HAVE DIFFERENCES IN WHETHER OR NOT
RENEWED CONVECTION WILL DEVELOP WITH BOTH THE NAM/GFS MORE ROBUST
WHILE LOCAL GUIDANCE BASICALLY DRY WITH STRONGER DOWNSLOPE IN PLACE.
NAM CERTAINLY LOOKS QUITE OVERDONE WITH QPF BUT GIVEN A SMALL WINDOW
FOR SOME LOW LEVEL BACKING TO TAKE PLACE OVER THE SOUTH...WILL
INCLUDE A LOW POP ESPCLY SINCE BOTH THE ENSEMBLES AND EURO HAVE SOME
LIGHT QPF. OTRW EXPECT QUICK POST FRONTAL AFTERNOON DRYING WITH
DECENT SHOT OF SUBSIDENCE RIGHT BEHIND THE FRONT BRINGING CLEARING
SKIES AND GUSTY WESTERLY BREEZES AS DEEP MIXING DEVELOPS FROM NW TO
SE. LOWERED HIGH TEMPS SLIGHTLY DUE TO EXPANSIVE MID/HIGH CLOUDS
THIS MORNING AND POSSIBLY A FEW SHRA SOUTH LATER ON. HOWEVER IF MORE
SUN TAKES SHAPE EARLIER THEN STRONG DOWNSLOPE/HEATING OF DRY AIR COULD
BOOST READINGS FROM ROANOKE EAST INTO THE LOW 90S.

UPPER TROF PASSES THIS EVENING ALLOWING MORE OF A NW TRAJECTORY TO
DEVELOP IN ITS WAKE WHICH SHOULD PUSH MOST RESIDUAL CLOUDS TO THE
SOUTH OVERNIGHT. THIS IN COMBO WITH VERY DRY HIGH PRESSURE
BUILDING IN FROM THE NW AND COOL ADVECTION SHOULD SPELL FOR A
COOLER NIGHT WITH LOWS MAINLY IN THE 50S...WITH SOME 40S VALLEYS
UNDER CLEAR SKIES AND LIGHTER WINDS. HOWEVER STAYED CLOSER TO THE
WARMER MOS SOUTH GIVEN THE LAGGING 85H BOUNDARY ACROSS THE NORTH
THRU MORNING AND SOME RESIDUAL MIXING.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
HIGH PRESSURE WILL RIDGE INTO THE AREA THROUGH THE PERIOD WITH A DRY
NORTHWEST WIND PREVAILING. AN UPPER LEVEL LOW WILL CONTINUE TO SPIN
OVER NEW ENGLAND WITH TROUGHINESS EXTENDING SOUTH INTO THE
CAROLINAS. THIS TROUGH WILL BRING BREEZY CONDITIONS TO THE AREA
THURSDAY...AND TO A LESSER EXTENT FRIDAY. NO RAIN IS FORECASTED BUT
A FEW FAIR WEATHER CUMULUS CLOUDS WILL PASS OVER THE MOUNTAINS
DURING THE AFTERNOON HOURS.

TEMPERATURES AROUND NORMAL ALONG AND WEST OF THE BLUE RIDGE ON
THURSDAY. DOWNSLOPE FLOW WILL HELP EASTERN LOCATIONS WARM A FEW
DEGREES ABOVE NORMAL. LESS WINDS ON FRIDAY WITH 85H TEMPERATURES
WARMING A FEW DEGREES. FRIDAY AFTERNOON HIGHS SHOULD MODERATE 3F
OR SO FROM THURSDAY...MAINLY ACROSS THE MOUNTAINS. GUIDANCE COMING
IN COOLER...PARTICULARLY IN THE PIEDMONT...FRIDAY DESPITE 85H
TEMPERATURES WARMING. ONLY EVIDENCE OF COOLING IS WEAK COLD AIR
ADVECTION. FROM MY POINT OF VIEW...SEEING ABUNDANT SUNSHINE...DRY
GROUND/AIR MASS AND SOME WEAK DOWNSLOPING IN THE EAST TO GO WARMER
THAN GUIDANCE FRIDAY AFTERNOON. RADIATIONAL COOLING WILL ALLOW
THURSDAY NIGHT LOWS TO DROP AROUND 5F BELOW NORMAL. MILDER
CONDITIONS EXPECTED FRIDAY NIGHT WITH LOWS NEAR NORMAL.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
A WARM FRONT WILL APPROACH THE REGION OUT OF THE TENNESSEE VALLEY ON
SATURDAY. THE REMNANTS OF TROPICAL STORM HERMINE MAY BE ENOUGH TO
FORM A WAVE ALONG THE FRONT BUT EVEN IF THERE IS ONLY LIMITED
REFLECTION AT THE SURFACE SHOW THE UPPER SYSTEM POSSIBLY CROSSING
INTO NORTHWEST NORTH CAROLINA WHICH MAY HELP ENHANCE RAINFALL ALONG
THE WARM FRONT. BY SATURDAY NIGHT...LOW LEVEL WINDS COME AROUND TO
THE SOUTHEAST SO MOISTURE WILL BE INCREASING ACROSS THE AREA. WILL
KEEP THE BEST CHANCE OF RAIN IN FOR SATURDAY NIGHT AND SUNDAY. WILL
ALSO LOWER MAXIMUM TEMPERATURES FOR SATURDAY AND SUNDAY.

BY MONDAY MORNING...A SYSTEM IN THE NORTHERN JET STREAM WILL PUSH A
COLD FRONT THROUGH THE MID ATLANTIC REGION. EXPECT A DRIER AIRMASS
BEHIND THIS SYSTEM WILL THE UPPER FLOW BECOMING ZONAL.

&&

.AVIATION /10Z WEDNESDAY THROUGH SUNDAY/...
COLD FRONT PUSHING INTO WVA WILL CROSS THE WESTERN MOUNTAINS EARLY
THIS MORNING. AXIS OF MOISTURE JUST AHEAD OF THE FRONT PER MSAS
ENOUGH TO SUPPORT SCTD SHRA AND PERHAPS AN ISOLATED -TSRA THRU
MID MORNING AS STILL SEEING A RIBBON OF INSTABILITY JUST AHEAD OF
THE BOUNDARY. LATEST BUFKIT RAOBS ALSO ARE A BIT WETTER SO LOWERED
CIGS AT BOTH KBLF/KLWB FOR A PERIOD OF MVFR AND KEPT/INCLUDED A
VCSH/CB MENTION AT BOTH SPOTS EARLY THIS MORNING. ELSW SHOULD
REMAIN VFR THIS MORNING UNDER A RATHER EXPANSIVE MID/HIGH CLOUD
DECK. FRONT DROPS ACROSS THE BLUE RIDGE AROUND MIDDAY AND THEN OFF
TO THE SE BY MID/LATE AFTERNOON. LATEST MODELS HAVE AGAIN SHOWN A
BIT MORE LIFT ACROSS THE SW THIS MORNING AND THEN SLIDE AN AXIS OF
SHRA EAST ALONG THE BOUNDARY TO AROUND KDAN EARLY IN THE
AFTERNOON. THIS LOOKS OVERDONE GIVEN STRONG WEST WINDS ALOFT.
HOWEVER FORECAST INSTABILITY ALONG WITH AXIS OF HIGH PWATS AND SOME
BRIEF LOW LEVEL BACKING COULD SUPPORT A FEW SHRA/TSRA OUT EAST SO
ADDING IN A VICINITY SHRA MENTION INCLUDING A PERIOD OF BKN CIGS AT
KDAN.

SW WINDS SHIFT TO THE WEST AT BLF/LWB THIS MORNING...AND AT
ROA/LYH/DAN IN THE MIDDAY TIME FRAME. WINDS WILL PICK UP BEHIND
THIS FRONT BY MIDDAY WEDNESDAY WITH GUSTS TO 20-28 KNOTS POSSIBLE
ESPECIALLY AROUND ROANOKE.

HIGH PRESSURE WILL SETTLE IN FOR WED NIGHT INTO THURSDAY. OTHER
THAN SOME LOCALIZED LATE NIGHT MOUNTAIN VALLEY/RIVER FOG...VFR
CONDITONS ARE EXPECTED THROUGH FRIDAY.

SATURDAY AND SUNDAY...ORGANIZED SHOWERS RETURN TO THE REGION SAT
NIGHT INTO SUNDAY AS A WARM THEN A COLD FRONT MOVE THROUGH THE
AREA. COULD SEE SOME AREAS OF MVFR ASSOCIATED WITH THE
PRECIPITATION...ESPECIALLY IN THE MOUNTAINS.

&&

.FIRE WEATHER...
GIVEN APPROACHING SHOWERS ACROSS THE NW ATTM WILL DELAY UPDATING
THE GOING FIRE WEATHER WATCH TO A WARNING TO SEE THE DEGREE OF
WETTING THAT TAKES PLACE ACROSS THE SRN SHENANDOAH VALLEY EARLY
THIS MORNING.

OTRW IN THE WAKE OF A PASSING COLD FRONT...MINIMUM RELATIVE
HUMIDITIES WILL BE BETWEEN 25 AND 30 PERCENT LATER THIS
AFTERNOON...AND SOME SUSTAINED WINDS AROUND 20 MPH ARE
POSSIBLE...ALTHOUGH MOST WILL BE IN THE 15 TO 20 MPH RANGE. ALSO
10 HR FUELS ARE EITHER AT OR JUST BELOW THE 7 PERCENT MARK BUT
COULD FALL EVEN LOWER FOR A PERIOD THIS AFTERNOON.

AFTERNOON RELATIVE HUMIDITIES AND FUEL MOISTURE WILL REMAIN ON THE
LOW SIDE AGAIN THURSDAY AND FRIDAY AFTERNOONS. HOWEVER...WINDS WILL
BE SOMEWHAT WEAKER.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...FIRE WEATHER WATCH FROM 10 AM EDT THIS MORNING THROUGH THIS
     AFTERNOON FOR VAZ019-020-022>024.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...DS/JH/WP
NEAR TERM...JH
SHORT TERM...RCS
LONG TERM...AMS/RCS
AVIATION...DS/JH/WP
FIRE WEATHER...

NWS Office Area Forecast Discussion

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