Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 080150
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
950 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 950 PM EDT TUESDAY...

AT 01Z/9PM COLD FRONT EXTENDED FROM LAKE ONTARIO TO SOUTHERN
MISSOURI. A FRONTAL BOUNDARY WILL SAG SOUTHEAST TONIGHT ACROSS
THE OHIO VALLEY...WITH THE ACTIVE WEATHER REMAINING MAINLY WEST
OF THE FORECAST AREA. BUT CONVECTIVE OUTFLOWS AHEAD OF THIS
ACTIVITY MAY WORK INTO THE MOUNTAINS OVERNIGHT. MADE MINOR
ADJUSTMENTS TO THE ARRIVAL TIME OF THE HIGHER PROBABILITY OF
PRECIPITATION IN THE FAR WESTERN COUNTY WARNING AREA BASED ON THE
LATEST LOCAL WRF AND HRRR GUIDANCE.

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 /02Z WEDNESDAY THROUGH SUNDAY/...
AS OF 655 PM EDT TUESDAY...

OVERALL CONTINUED VFR EXPECTED INTO TONIGHT WITH WIDELY SCATTERED
CONVECTION ALONG THE BLUE RIDGE POSSIBLY PUSHING EAST BEFORE
FADING WITH LOSS OF HEATING AFTER SUNSET. THIS MAY BRIEF MVFR TO
SPOTS WHERE WILL COVER WITH VCSH/VCTS GIVEN UNCERTAINTY. OTHER
CONCERN WITH AXIS OF MORE WIDESPREAD UPSTREAM SHRA/TSRA CLOSER TO
THE FRONT THAT COULD REACH THE KBLF/KLWB VICINITY AROUND MIDNIGHT
BEFORE WEAKENING. HOWEVER THIS AREA OF SHRA MAY LINGER INTO EARLY
WEDNESDAY SO WILL KEEP SOME PREVAILING SHRA MENTION OVER THE FAR
WEST. FOG THE OTHER ISSUE OVERNIGHT ESPCLY WHERE SOME RAIN HAS OR
WILL OCCUR OVER THE NEXT FEW HOURS. HOWEVER MUCH DRIER AIR OVER
THE REGION SHOULD PRECLUDE MUCH DENSE FOG OUTSIDE OF EARLIER
RAINFALL SO KEEPING THINGS MOSTLY MVFR AT KLWB/KBCB WITH A BRIEF
INCLUSION AT KLYH/KBLF LATE. ANY FOG OR STRATUS SHOULD BURN OFF BY
MID/LATE MORNING WEDNESDAY AS MIXING INCREASES WITH MAINLY VFR
CONDITIONS RETURNING LATE MORNING INTO THE AFTERNOON.

AS THE UPSTREAM FRONT MOVES CLOSER ON WEDNESDAY AND OLD OUTFLOW
HEADS EAST...THE RISK FOR SHRA/TSRA WILL INCREASE ACROSS MUCH OF
THE REGION ESPCLY NORTHERN AND WESTERN SECTIONS WEDNESDAY
AFTERNOON. THEREFORE HAVE ADDED IN EITHER A PREVAILING VFR MENTION
FOR SHRA OR VCTS FOR DEEPER CONVECTIVE COVERAGE AT ALL LOCATIONS
EXCLUDING KDAN WHERE SHOULD BE FARTHER REMOVED FROM THE SHOWERS.

EXTENDED AVIATION DISCUSSION...

A COLD FRONT WILL STALL NEAR THE WV/MD BORDER WEST TO OHIO BY
WEDNESDAY NIGHT. SOUTH OF THIS BOUNDARY...WE WILL REMAIN ON THE
WARM/MOIST SIDE OF THE FRONT...AND SUBJECT TO DAILY THREAT FOR
MVFR SHOWERS/STORMS. HOWEVER APPEARS COVERAGE WILL BE LESS THAN
THAT OF WEDNESDAY WITH MOSTLY VFR EXPECTED OUTSIDE OF BRIEF ROUNDS
OF MVFR/IFR IN WIDELY SCATTERED CONVECTION FROM THURSDAY AFTERNOON
THROUGH SUNDAY.

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

&&

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

&&

$$
SYNOPSIS...KK/WP
NEAR TERM...AMS/KK
SHORT TERM...PM
LONG TERM...PM
AVIATION...JH/NONE



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