Special Weather Statement, NWS Blacksburg, VA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
333 PM EDT THU AUG 21 2014

.SYNOPSIS...
A STRONG UPPER LEVEL RIDGE OF HIGH PRESSURE NEAR THE GULF COAST
WILL KEEP NORTHWEST FLOW IN PLACE OVER THE REGION THROUGH THE END
OF THE WEEK. THIS WILL RESULT IN PERIODIC ROUNDS OF SHOWERS AND
STORMS INTO SATURDAY BEFORE A COLD FRONT DROPS THROUGH FROM THE
NORTH SATURDAY NIGHT. HIGH PRESSURE FOLLOWING THE FRONT SHOULD
BRING DRIER AND COOLER AIR INTO THE AREA BY EARLY NEXT WEEK.
&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 235 PM EDT THURSDAY...

DESPITE DECENT INSTABILITY OVER THE REGION THIS AFTERNOON...CONVECTION
REMAINS LIMITED VIA WESTERLY WINDS ALOFT AND LOWER THETA-E UNDER
FAINT LOW LEVEL RIDGING OVER THE MOUNTAINS. HOWEVER DECENT NW
FLOW ALOFT REMAINS IN PLACE WITH ANOTHER UPSTREAM MID LEVEL WAVE
APPROACHING FROM OHIO WHICH IS CURRENTLY PRECEDED BY A WEAK
OUTFLOW DRIVEN BAND OF SHRA/TSRA. MODELS REMAIN INCONSISTENT IN
WHERE TO BRING BEST COVERAGE OF STORMS INTO THIS EVENING BUT
APPEARS SOME CONSENSUS ON SPILLING THE CURRENT MCS FEATURE INTO
WEST VA THROUGH SUNSET BEFORE IT FADES WITH LOSS OF HEATING. THUS
WILL MAINTAIN LOW LIKELY TO HIGH CHANCE POPS FAR NW THIRD GIVEN
MORE MORE EAST THAN SE MOVEMENT OF THIS FEATURE...WITH A QUICK
DROPOFF IN CHANCES HEADING EAST INTO THE DOWNSLOPING.

THIS IMPULSE QUICKLY PASSES/WEAKENS AFTER SUNSET GIVING WAY TO
INCREASING NW FLOW ALOFT AHEAD OF ANOTHER SHORTWAVE ROUNDING THE
RIDGE LATE. ALTHOUGH FOCUS WILL BE LIMITED AFTER LOSS OF
HEATING...SOME CONCERN WITH DEGREE OF LEFTOVER INSTABILITY AND
SOME ADDED TSRA DEVELOPMENT AFTER MIXING FADES ESPCLY IF COVERAGE
IS LESS EARLY ON. THIS SUPPORTS HOLDING ON TO SOME LOW POPS INTO
THE EARLY MORNING HOURS BEFORE INCREASING AGAIN OVER THE WEST
TOWARD DAYBREAK AHEAD OF THE NEXT SYSTEM. SOME PATCHY FOG AROUND
BUT MAINLY IN THE VALLEYS GIVEN CURRENT MIXING/WARMTH AND
OVERNIGHT CLOUDS. OTRW LOWS MAINLY IN THE 60S BUT PERHAPS ONLY LOW
70S EAST IF CLOUDS PERSIST.

NEXT WAVE SLIDES DOWN THE RESIDUAL BOUNDARY FRIDAY WITH A
POSSIBLE FADING MCS ON THE DOORSTEP ACROSS THE NW EARLY ON BEFORE
IT WEAKENS CROSSING THE RIDGES. HOWEVER CONFIDENCE LOW ON THIS
OUTCOME GIVEN GUIDANCE UNCERTAINTY BUT DOES APPEAR BETTER COVERAGE
IN ORDER ESPCLY NW EARLY AND THEN AGAIN IN THE AFTERNOON AS MAY
SEE MORE WIDESPREAD CONVECTIVE BANDS FORM ALONG RESIDUAL OUTFLOW
PENDING TIMING. VERY STRONG NW JET ALOFT FOR LATE AUGUST WOULD
SUPPORT MORE LINEAR BOWING TYPE STORMS WITH POTENTIAL FOR SOME OF
THIS COVERAGE TO CROSS THE BLUE RIDGE DESPITE THE DEEP DOWNSLOPE
COMPONENT IF CAN GET ENOUGH BREAKS TO ENHANCE AFTERNOON
INSTABILITY. HOWEVER MODELS REMAIN DRIER WITH MORE DEBRIS CLOUDS
AROUND IN THE MORNING...AND A MIXED OUT SCENARIO IN THE AFTERNOON
WHICH WOULD AGAIN LIMIT POPS TO THE NORTH/NW. THUS TRENDED IN THAT
DIRECTION WITH LIKELYS EXTREME NW AND CHANCE ELSW. HIGH TEMPS
REMAIN QUITE IFFY AS WARM ENOUGH ALOFT TO ZIP INTO THE 90S EAST
GIVEN MORE SUN WHILE COULD GET STUCK IN THE 70S FAR WEST IF SHRA
ARRIVES EARLIER AND PERSISTS. FOR NOW USED A BLEND OF THE MAV/MET
MOS WITH SUPPORT FROM THE EARLIER SLIGHTLY COOLER EC 2 METER
VALUES.
&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 245 PM EDT THURSDAY...

SYNOPTIC SCALE PATTERN CHANGING TO A HIGH AMPLITUDE TROF IN THE WEST
AND RIDGE IN THE EAST. BY SUNDAY THE 591 DM CENTER OF THE 500 MB
RIDGE IS OVER THE TENNESSEE VALLEY.

BEST PUSH OF THE COLD FRONT AND DEEPER MOISTURE TO THE SOUTHWEST
WILL BE SATURDAY NIGHT AND SUNDAY. UNTIL THEN FORECAST AREA REMAINS
IN BAROCLINIC ZONE WITH THE BEST PROBABILITY OF PRECIPITATION
DEPENDENT ON UPSTREAM STORMS AND TIMING OF SHORT WAVES. WILL HAVE
HIGHEST PROBABILITY OF PRECIPITATION IN FOR FRIDAY NIGHT.

AS HIGH PRESSURE BUILDS IN...A SURFACE LOW TRACKS DOWN THE EAST
COAST. BY SATURDAY THE LOW WILL BE OVER THE CAROLINA COAST WHICH
WILL HELP BRING SURFACE AND LOW LEVEL WINDS OVER THE FORECAST AREA
AROUND TO THE EAST. THIS LOW MOVES WELL OFFSHORE AS THE WEDGE
STRENGTHENS ON SATURDAY NIGHT AND SUNDAY.

SINCE FORECAST AREA WILL BE WELL INTO THE WEDGE ON SUNDAY HAVE KEPT
MAXIMUM TEMPERATURES BELOW MOST GUIDANCE.
&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 1130 AM EDT THURSDAY...

SURFACE HIGH PRESSURE WILL BE IN A FAVORABLE LOCATION OVER NEW
ENGLAND TO WEDGE WELL DOWN THE EAST SLOPES OF THE APPALACHIANS
SUNDAY NIGHT AND MONDAY. SUPPORT FOR THE WEDGE WEAKENS BY TUESDAY.
HIGH PRESSURE WILL REMAIN OVER THE FORECAST AREA THROUGH WEDNESDAY.
WEDNESDAY NIGHT AND THURSDAY A COLD FRONT WILL APPROACH THE AREA.
LARGE 500 MB RIDGE ALOFT WILL COVER MUCH OF THE LOWER MISSISSIPPI
VALLEY ACROSS THE EASTERN UNITED STATES THROUGH THE PERIOD.

THE DEEPEST MOISTURE SHIFTS SOUTHWEST OUT OF THE FORECAST AREA ON
MONDAY AND TUESDAY. WILL HAVE THESE DAYS DRY IN THE FORECAST. THE
CHANCE OF PRECIPITATION RETURNS TO THE AREA ON WEDNESDAY AND
THURSDAY AHEAD OF THE FRONT. EXPECT MAXIMUM TEMPERATURES TO BE
WARMEST ON WEDNESDAY AND THURSDAY WITH THE WEDGE GONE AND MORE
POTENTIAL TO MIX DOWN WARM 850 MB TEMPERATURES.
&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
AS OF 1245 PM EDT THURSDAY...

OVERALL VFR TO PREVAIL THROUGH MUCH OF THE AFTERNOON UNDER WEAK
HIGH PRESSURE AND NW FLOW ALOFT. WILL GRADUALLY SEE CU FIELDS
INCREASE AS WELL AS ISOLATED CONVECTION FROM WEST TO EAST BUT
THINKING CIGS TO REMAIN VFR OUTSIDE OF ANY WESTERN SHRA/TSRA.
APPEARS BEST CHANCE AT SEEING A TSRA EARLY WILL BE AROUND KBLF
WITH UPSTREAM COVERAGE APPROACHING...AND THEN MID/LATE AFTERNOON
AT KLWB. FARTHER EAST...LOTS OF UNCERTAINTY IN HOW FAR ANY
ISOLATED EARLY COVERAGE MIGHT GET AND THEN WHETHER OR NOT
SOMETHING MORE ORGANIZED DEVELOPS OVER WV/OH AND TRANSLATES
SE...CROSSING MUCH OF THE REGION THIS EVENING. LATEST GUIDANCE
KEEPS THE MAJORITY TO THE WEST AND NORTH PER LACK OF CONSOLIDATION
OF SHRA/TSRA. FOR NOW PLAN TO KEEP AT LEAST A TEMPO MENTION FOR A
PERIOD OF MVFR IN TSRA FOR THE WV TERMINALS BETWEEN 19-21Z/3-5PM
THEN INTO THE VA TERMINALS BETWEEN 21-24Z/5-8PM. GUSTY WINDS ALSO
POSSIBLE WITH ANY OF THE STORMS PER INVERTED V TYPE SOUNDINGS SO
INCLUDED MENTION.

EXPECT WILL GET A BREAK IN STORMS BY MIDNIGHT FOR THE MOST PART
BEFORE ANOTHER IMPULSE APPROACHES EARLY FRIDAY IN THE INCREASING
NW FLOW ALOFT. SHOULD AGAIN SEE AREAS OF MVFR/IFR IN FOG PENDING
DEGREE OF CLOUD COVER LATE WITH THE WORST CONDITIONS AGAIN AT KLWB
AND ANY SPOT THAT SEES A DOWNPOUR THROUGH THIS EVENING. GIVEN THE
STRONGER FLOW ALOFT...ADDED SHRA COULD DEVELOP BEFORE DAWN WEST
AND STREAM SE ESPCLY ALONG THE KBLF-KDAN CORRIDOR FRIDAY MORNING
SO INCLUDED A VCSH IN THOSE LOCATIONS FOR NOW. ELSW APPEARS LOTS
OF MVFR/VFR STRATO-CU CIGS UNDER MID DECK WHICH SHOULD SLOWLY
ERODE INTO VFR DURING THE AFTERNOON AFTER EARLY FOG FADES.

EXTENDED AVIATION...

UPPER LEVEL DISTURBANCES WILL BE MOVING THROUGH PERIODICALLY AND
INTERACTING WITH A STATIONARY FRONT OVER THE AREA FOR THE NEXT FEW
DAYS...RESULTING IN PERIODS OF SHOWERS AND THUNDERSTORMS. DUE TO
THE HIGH MOISTURE CONTENT OF THE AIR...EXPECT STRATUS AND FOG
DURING THE OVERNIGHT PERIODS WITH AREAS OF MVFR/IFR MOST
PRONOUNCED BETWEEN MIDNIGHT AND 9AM EACH DAY. MODELS ARE INDICATED
THAT A DEEPER EASTERLY SORT OF WIND FLOW WILL SETUP FOR THIS
UPCOMING WEEKEND. THIS SUGGEST THAT LOW CIGS MAY PERSIST EVEN
DURING THE DAYTIME PERIODS...SATURDAY AND SUNDAY...WITH WIDESPREAD
MVFR CONDITIONS ACROSS THE AREA THIS WEEKEND DUE TO MOISTURE
BANKING UP AGAINST THE EAST SIDE OF THE APPALACHIANS. BETTER PUNCH
OF DRY AIR WITH HIGH PRESSURE BUILDING IN FROM THE NE MAY BE
ENOUGH WITH MIXING/HEATING TO ALLOW FOR INCREASING VFR MONDAY
INTO TUESDAY UNDER MAINLY DRY CONDITIONS.
&&

.EQUIPMENT...
THE ASOS AT LYNCHBURG (LYH) VA REMAINS PARTIALLY INOP DUE TO A
BOARD FAILURE. PARTS WILL LIKELY NEED TO BE ORDERED WITH THE
RETURN OF COMPLETE SERVICE UNKNOWN AT THIS TIME.

&&

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

&&

SYNOPSIS...JH
NEAR TERM...JH
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...JH/PM
EQUIPMENT...JH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BLACKSBURG VA
524 PM EDT THU AUG 21 2014

VAZ007-009>014-018>020-WVZ042>045-222130-
TAZEWELL-SMYTH-BLAND-GILES-WYTHE-PULASKI-MONTGOMERY-CRAIG-
ALLEGHANY VA-BATH-MERCER-SUMMERS-MONROE-GREENBRIER-
524 PM EDT THU AUG 21 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWEST VIRGINIA...WEST
CENTRAL VIRGINIA AND SOUTHEAST WEST VIRGINIA.

.DAY ONE...TONIGHT.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS INTO TONIGHT AS
COMPLEXES OF STORMS DROP SOUTHEAST FROM KENTUCKY. THE PRIMARY
THREAT WOULD BE DAMAGING WINDS WITH ISOLATED LARGE HAIL POSSIBLE.
IN ADDITION...HEAVY RAINS FROM THESE STORMS COULD PRODUCE
LOCALIZED FLOODING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

PERIODIC ROUNDS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS
THE REGION THROUGH THIS UPCOMING WEEKEND...BRINGING A RISK OF
STRONG THUNDERSTORMS AND EXCESSIVE RAINFALL.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

NCZ001>006-018>020-VAZ015>017-022>024-032>035-043>047-058-059-222130-
ASHE-ALLEGHANY NC-SURRY-STOKES-ROCKINGHAM-CASWELL-WATAUGA-WILKES-
YADKIN-GRAYSON-CARROLL-FLOYD-ROANOKE-BOTETOURT-ROCKBRIDGE-PATRICK-
FRANKLIN-BEDFORD-AMHERST-HENRY-PITTSYLVANIA-CAMPBELL-APPOMATTOX-
BUCKINGHAM-HALIFAX-CHARLOTTE-
524 PM EDT THU AUG 21 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL NORTH
CAROLINA...NORTHWEST NORTH CAROLINA...CENTRAL VIRGINIA...SOUTH
CENTRAL VIRGINIA...SOUTHWEST VIRGINIA AND WEST CENTRAL VIRGINIA.

.DAY ONE...TONIGHT.

BANDS OR CLUSTERS OF STRONG TO ISOLATED SEVERE THUNDERSTORMS WILL
BE POSSIBLE INTO TONIGHT. SOME OF THESE COULD PRODUCE DAMAGING
WINDS ALONG WITH WITH ISOLATED LARGE HAIL.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

PERIODIC ROUNDS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS
THE REGION THROUGH THIS UPCOMING WEEKEND...BRINGING A RISK OF
STRONG THUNDERSTORMS AND EXCESSIVE RAINFALL.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

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