Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 072004
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
404 PM EDT TUE JUL 7 2015

.SYNOPSIS...
A COLD FRONT APPROACHES FROM THE NORTHWEST TONIGHT. THE FRONT IS
EXPECTED TO STALL JUST NORTH OF THE REGION BY WEDNESDAY...THEN
LIFT BACK NORTH AS A WARM FRONT LATE IN THE WEEK...AS HIGH
PRESSURE ALOFT BUILDS ACROSS THE SOUTHEAST STATES.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 404 PM EDT TUESDAY...

THIS AFTERNOONS SPC 18Z MESOSCALE ANALYSIS SHOWED SOME MOISTURE
CONVERGENCE ALONG THE SOUTHERN BLUE RIDGE MOUNTAINS WITH LIS AROUND
MINUS 3 TO MINUS 5. SFC BASED CAPES ARE RESPECTIVE AT 1000 TO 2000
J/KG THIS AFTERNOON. DAY ONE CONVECTIVE OUTLOOK PLACED US IN GENERAL
THUNDERSTORM. HOWEVER...AN ISOLATED STRONG THUNDERSTORM WITH HEAVY
DOWNPOURS AND GUSTY WINDS MAY BE POSSIBLE FOR A SMALL WINDOW THIS
AFTERNOON INTO THIS EVENING. IN ANY CASE...ALLOWED FOR ISOLATED
TO SCATTERED SHOWERS AND THUNDERSTORMS FOR THIS AFTERNOON INTO
TONIGHT WITH BEST CHANCE IN THE WEST.

A FRONTAL BOUNDARY WILL SAG SOUTHEAST TONIGHT ACROSS THE OHIO
VALLEY...WITH THE ACTIVE WEATHER REMAINING WEST OF US. BUT
CONVECTIVE OUTFLOWS AHEAD OF THIS ACTIVITY MAY WORK INTO THE
MOUNTAINS OVERNIGHT. LEANED POPS TOWARDS THE HRRR FOR THIS EVENING
THEN GFS FOR TONIGHT INTO WEDNESDAY. LOW TEMPERATURES OVERNIGHT WILL
RANGE FROM THE LOWER 60S TO NEAR 70 DEGREES IN THE PIEDMONT.

UPPER LEVEL RIDGING ACROSS THE SOUTHEAST STATES WILL BUILD WEST
ALONG THE GULF COAST ON WEDNESDAY...ALLOWING FOR INCREASINGLY ZONAL
FLOW ACROSS THE MID ATLANTIC REGION. THIS BUILDING RIDGE WILL HELP
STALL A COLD FRONT TO OUR WEST NEAR THE WEST VIRGINIA/MARYLAND
BORDER WEST TO OHIO WEDNESDAY. SOUTH OF THIS BOUNDARY...WE WILL
REMAIN ON THE WARM/MOIST UNSTABLE SIDE OF THE FRONT...WITH
SHOWERS AND THUNDERSTORMS. INSTABILITY PARAMETERS ARE MODEST FOR
THE MOST PART...BUT INDICATE ENOUGH CAPE AND LOW LEVEL SHEAR TO
TRIGGER A FEW STRONG TO PERHAPS SEVERE STORMS...CAPABLE OF
PRODUCING HAIL AND LOCALLY STRONG WINDS. SPC DAY TWO CONVECTIVE
OUTLOOK PLACED THE BETTER POTENTIAL OF SEVERE WEATHER TO OUR WEST
WITH MARGINAL ACROSS WESTERN KENTUCKY AND TENNESSEE. HIGH
TEMPERATURES ON WEDNESDAY WILL VARY FROM THE LOWER 70S IN THE
NORTHWEST MOUNTAINS TO AROUND 90 DEGREES IN THE PIEDMONT.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 340 PM EDT TUESDAY...

FORECAST AREA WILL BE PINCHED BETWEEN HIGH PRESSURE TO OUR
SOUTH...AND WAVERING SURFACE FRONT WHICH WILL TRY TO MAKE INROADS
LATE WEDNESDAY...RETREATING THURSDAY...ONLY TO RETURN AGAIN THURSDAY
NIGHT AND FRIDAY.  THERE WILL CERTAINLY BE SHOWERS/STORMS ASSOCIATED
WITH THE FRONT...BUT DETAILS WITH RESPECT TO TIMING ARE NOT THAT
CLEAR-CUT...ESP WHEN DEALING WITH A WAVERING FRONT.

MODELS ARE IN AGREEMENT THAT CONVERGENCE ALONG THE FRONT WILL
PROVIDE TRACK FOR ORGANIZED DEEP CONVECTION WITH MARGINAL RISK FOR
SEVERE WEATHER PER FASTER WESTERLIES ALOFT NEAR THE FRONTAL ZONE.
INCREASING INSTABILITY OUTSIDE OF THE HIGHER WIND ENVELOPE WILL ALSO
SUPPORT PULSE STRONG-SEVERE STORMS DURING THE PEAK HEATING THURSDAY.
FORECAST FOR THE AREA WILL REFLECT HIGHER POPS ACROSS THE NORTHERN
CWA CLOSER TO THE FRONT...AND TO A MUCH LESSER DEGREE ACROSS THE
SOUTH UNTIL THE FRONT GETS CLOSER FRIDAY.

TEMPERATURES FOR THURSDAY FAVOR ABOVE NORMAL READINGS PER INCREASING
HEIGHTS/THICKNESSES AND A WESTERLY WIND COMPONENT WHICH SHOULD AID
IN ADIABATIC WARMING EAST OF THE BLUE RIDGE.  WITH 85H TEMPS
APPROACHING +20 DEG C...SURFACE READING SHOULD EASILY CLIMB WELL
INTO THE 80S AND POSSIBLY THE L-M 90S PENDING SUNSHINE.  WITH THE
FRONT OVER THE AREA FRIDAY...CLOUDS/SHOWERS SHOULD KEEP HIGH TEMPS A
FEW DEGREES COOLER.  MINIMUM TEMPERATURES WILL AVERAGE ABOVE
NORMAL...PER THE HIGH MOISTURE CONTENT OF THE ATMOSPHERE.


&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 340 PM EDT TUESDAY...
MODELS ARE IN AGREEMENT THE SUBTROPICAL RIDGE OVER THE SOUTHEAST
STATES WILL RETROGRADE TOWARD TEXAS/OKLAHOMA FOR THE WEEKEND THEN
EXPAND NORTHWEST INTO THE ROCKIES FOR NEXT WEEK...JULY 13-17. SHORT
WAVE ENERGY PASSING DOWNSTREAM FROM THIS RIDGE IS THEN EXPECTED TO
CARVE OUT FULL LATITUDE TROUGH OVER THE EASTERN CONUS WITH MODELS
HINTING THIS FEATURE WILL CUTOFF OVER THE REGION FOR THE MIDDLE OF
NEXT WEEK.

DURING THE FORECAST PERIOD...AN ACTIVE FRONTAL ZONE IS EXPECTED TO
REMAIN CLOSE TOO OR DRAPED ACROSS THE REGION PROMOTING DAILY THREAT
FOR SHOWERS/STORMS...DETAILS WITH RESPECT TO TIMING/PATH OF DEEP
CONVECTION LACKING. AS SUCH LONG TERM FORECAST REFLECTS A SHOTGUN
STANCE...ALTHOUGH DID FAVOR THE PEAK HEATING OF THE DIURNAL CYCLE
FOR GREATEST POPS/THUNDER COINCIDENT WITH PEAK INSTABILITY.

TEMPERATURES...ALTHOUGH NOTHING EXTREME...WILL FAVOR THE WARM SIDE
OF GUIDANCE THIS WEEKEND...THEN RETREAT TO SOMETHING NEAR OR JUST
BELOW NORMAL FOR THE MIDDLE OF NEXT WEEK AS THE UPPER TROUGH
BECOMES THE DOMINANT WEATHER FEATURE.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
AS OF 115 PM EDT TUESDAY...

VFR EXPECTED THROUGH THE REST OF THIS AFTERNOON WITH CU AND
STRATOCU INVOF THE HIGHER TERRAIN. SHOWERS/TSTMS ACROSS ERN KY AND
NRN/WRN WV ARE PROGGED TO WEAKEN AS THEY MOVE EAST...SO FOR NOW
HAVE KEPT THEM OUT OF THE TAFS. AS THE FRONT MOVES CLOSER TONIGHT
AND EALRY WED...THE RISK FOR RAIN AND SUB-VFR CONDITIONS WILL
INCREASE...ESP AT BLF AND LWB.

EXTENDED AVIATION DISCUSSION...

A COLD FRONT WILL STALL NEAR THE WV/MD BORDER WEST TO OHIO BY WEDNESDAY.
SOUTH OF THIS BOUNDARY...WE WILL REMAIN ON THE WARM/MOIST SIDE OF
THE FRONT...AND SUBJECT TO DAILY THREAT FOR MVFR SHOWERS/STORMS.

EXPECT WIDESPREAD LATE NIGHT/EARLY MORNING LOW CLOUDS/FOG WITH
IFR-LIFR CIGS/VSBYS. OVERALL...CONDITIONS SHOULD IMPROVE TO MVFR-
VFR OUTSIDE SHRA/TSRA ACTIVITY DURING THE AFTERNOONS.

&&

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

&&

$$
SYNOPSIS...KK/WP
NEAR TERM...KK
SHORT TERM...PM
LONG TERM...PM
AVIATION...RAH



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