Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 281905
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
305 PM EDT TUE JUL 28 2015

.SYNOPSIS...
A DIFFUSE FRONTAL BOUNDARY WILL LINGER ACROSS THE REGION THROUGH
WEDNESDAY BEFORE ANOTHER STRONGER COLD FRONT ARRIVES FROM THE
NORTHWEST THURSDAY. SCATTERED SHOWERS AND THUNDERSTORMS WILL
CONTINUE IN THE FORECAST UNTIL THE SECONDARY FRONT MOVES SOUTH OF
THE REGION FRIDAY. SOMEWHAT DRIER AIR SHOULD FOLLOW THE FRONT FOR THE
WEEKEND AS HIGH PRESSURE BUILDS IN FROM THE NORTHWEST.
&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 205 PM EDT TUESDAY...

CLUSTERS OF DEEPER CONVECTION CONTINUE OVER THE SE ALONG AN AXIS
OF HIGHER SURFACE BASED THETA-E/INSTABILITY AND OVER THE NW IN
ASSOCIATION WITH THE RESIDUAL FRONT AND A WEAK WAVE ALOFT. MODELS
AGAIN STRUGGLING WITH WHERE TO PAINT THE BEST CONVECTIVE COVERAGE
INTO TONIGHT GIVEN WEAK FEATURES AND DIURNAL NATURE OF MORE
OUTFLOW DRIVEN STORMS. HOWEVER SOME CONSENSUS OFF THE HRRR AND
ENSEMBLES AS WELL AS THE GFS TO HAVE BEST HEAVY RAIN PRODUCING
SHRA/TSRA OVER THE EAST AS THE WEAK SHORTWAVE TO THE NW DROPS
THROUGH THE REGION GIVEN LINGERING INSTABILITY WELL INTO THE
EVENING. THIS AREA THOUGH MAY BE TOO WORKED OVER BY THEN SO WILL
TREND WITH HIGHER POPS THERE AFTER SUNSET BUT MAINLY OF THE HIGH
CHANCE VARIETY AS ADDED PRECIP AFTER DARK MAY BE VOID OF DEEP
CONVECTION. OTRW KEEPING THE SCATTERED NATURE REGIME GOING THROUGH
ABOUT MIDNIGHT WEST...AND PERIODS OF LIKELYS OR HIGHER OUT EAST A
WHILE LONGER BEFORE CUTTING TO PC/FOG LATE. AGAIN QUITE WARM/MUGGY
WITH MANY EASTERN LOCATIONS STAY ABOVE 70 UNLESS SPOTS SEE A COOLING
SHOWER INTO THIS EVENING.

5H HEIGHTS WILL BUILD A BIT ON WEDNESDAY AS THE AREA REMAINS IN A
MOISTURE LADEN ENVIRONMENT UNDER WEAK SURFACE HIGH PRESSURE BUT WITH
LESS FOCUS GIVEN THE WASHING OUT OF THE NEARBY FRONT. GUIDANCE SHOWS
SOME CONVERGENCE ACROSS THE RIDGES DURING THE AFTERNOON ESPCLY AS THE
FLOW TURNS MORE SW ALOFT WHICH SHOULD HELP FOCUS ADDED CONVECTION ALONG
THE RIDGES. HOWEVER WITH THE NEXT UPSTREAM SHORTWAVE TROUGH WELL TO THE
NW WITH THE NEXT COLD FRONT...APPEARS LIFT WILL BE LESS BUT LIKELY
ENOUGH GIVEN STRONG INSTABILITY TO RESULT IN SCATTERED COVERAGE
MOUNTAINS AND A BIT LESS IN THE EAST. STEERING REMAINS ON THE
WEAK SIDE SO MAIN THREAT AGAIN WITH HEAVY RAINFALL. HIGH TEMPS IN
LINE WITH THE LATEST MAV/MOS MIX SO ONLY MADE SMALL TWEAKS TO BUMP
UP VALUES A LITTLE IN THE EAST WHERE SOME LOW 90S POSSIBLE. OTRW
MUGGY 80S IN STORE.
&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 300 PM EDT TUESDAY...

SCATTERED SHOWERS AND THUNDERSTORMS WILL DIMINISH WEDNESDAY EVENING
INTO WEDNESDAY NIGHT. A COLD FRONT WILL APPROACH FROM THE WEST LATE
WEDNESDAY NIGHT INTO THURSDAY MORNING. LOW TEMPERATURES WEDNESDAY
NIGHT WILL RANGE FROM THE MID 60S IN THE MOUNTAINS TO LOWER 70S IN
THE PIEDMONT.

THE COLD FRONT WILL PUSH EAST ACROSS OUR AREA THURSDAY INTO THURSDAY
NIGHT. AS HIGHLIGHTED IN SPC MARGINAL RISK...SOME STRONG TO SEVERE
THUNDERSTORMS WILL BE POSSIBLE THURSDAY AFTERNOON AND EARLY EVENING.
THE GREATEST THREAT WILL BE FOR PULSE SEVERE THUNDERSTORMS WITH
DOWNBURST/LOCALIZED WIND DAMAGE POTENTIAL AS LOW-LEVEL LAPSE RATES
STEEPEN THURSDAY AFTERNOON. THE SLIGHTLY STRONGER MID-LEVEL FLOW
SHOULD REDUCE THE FLOOD POTENTIAL. HIGH TEMPERATURES THURSDAY WILL
VARY FROM THE MID 70S IN THE NORTHWEST MOUNTAINS TO THE LOWER 90S IN
THE PIEDMONT. PLACED THE HIGHEST POPS IN THE EAST THURSDAY NIGHT.
LOW TEMPERATURES THURSDAY NIGHT WILL DROP INTO THE LOWER 60S IN THE
MOUNTAINS TO THE LOWER 70S IN THE PIEDMONT.

THE AMPLIFICATION OF THE SUBTROPICAL RIDGE INTO THE SOUTHWEST U.S.
WILL RESULT IN STRENGTHENING NORTHWEST FLOW ALOFT ACROSS THE EAST
COAST. THIS WILL PUSH THE COLD FRONT FURTHER SOUTH BEFORE STALLING
IN SOUTHEAST LATE FRIDAY. COOLER HIGHS EXPECTED FRIDAY WITH READINGS
FROM THE MID 70S IN THE NORTHWEST MOUNTAINS TO THE UPPER 80S IN THE
PIEDMONT.  LOWS TEMPERATURES FRIDAY NIGHT WILL VARY FROM THE UPPER
50S IN THE WEST TO THE MID 60S IN THE EAST.
&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 300 PM EDT TUESDAY...

A GOOD WEEKEND EXPECTED WITH DRY SEASONABLE TEMPERATURES AND
HUMIDITY LEVELS...AS HIGH PRESSURE BUILD EAST OUT OF THE OHIO VALLEY.

THERE ARE SEVERAL OTHER KEY PLAYERS IN THE MEDIUM RANGE FORECAST
ESPECIALLY THE DEEPENING UPPER TROUGH AND PSEUDO-TROPICAL LOW. A
BROAD UPPER TROUGH IS PROGGED TO REMAIN ACROSS EASTERN CANADA AND
SHOULD DEEPEN INTO THE EASTERN UNITED STATES....THEN FLATTEN OUT
EARLY NEXT WEEK. ANOTHER CONCERN FOR THIS PERIOD WILL BE AN AREA OF
LOW PRESSURE WHICH DEVELOPS ACROSS FLORIDA OR IN THE GULF AND THE
INTERACTION WITH STALLED FRONTAL BOUNDARY LOCATED ACROSS THE
SOUTHEAST STATES.

WITH RESPECT TO THE PSEUDO-TROPICAL LOW DEVELOPING ACROSS THE
EASTERN GULF AND SOUTHEAST STATES...MODELS ARE IN BETTER AGREEMENT
WITH THE UPPER TROUGH.  THE ECMWF REMAINS THE MOST ROBUST COMPARED
TO OTHER SOLUTIONS IN DEVELOPING A CLOSED SFC LOW...AND THEN
TRACKING IT NORTHEAST ALONG THE SOUTHEAST COAST INTO EARLY NEXT
WEEK.

QUESTIONS REMAIN IN THE FORECAST ON WHETHER A WEAK FRONTAL BOUNDARY
EARLY NEXT WEEK COULD PULL THE SOUTHEAST LOW PRESSURE CENTER AND ITS
ASSOCIATED MOISTURE FURTHER INLAND ACROSS THE PIEDMONT OR BLOCK IT
EAST OF THE AREA. IN ANY CASE...THE CHANCE FOR RAIN WILL BE
INCREASING HEADING INTO EARLY NEXT WEEK. THE LOCATIONS WITH THE
BETTER CHANCE OF RAIN WILL BE ACROSS THE PIEDMONT.
&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
AS OF 1235 PM EDT TUESDAY...

OVERALL SHOTGUN PATTERN TO DEVELOPING CONVECTION WILL CONTINUE
THROUGH MID AFTERNOON BEFORE PERHAPS SHRA/TSRA ORGANIZES A BIT
MORE AND HEADS EAST OFF THE BLUE RIDGE. HOWEVER STILL TOO IFFY TO
INCLUDE PREVAILING CONVECTION AT ANY ONE TAF SITE PENDING RELEASE
SO KEEPING MOSTLY VCTS GOING AT MOST LOCATIONS INTO EARLY THIS
EVENING. COULD BE ENOUGH COVERAGE THIS EVENING FOR MORE OF A
PREVAILING MVFR GROUP IN SHOWERS OUT EAST BUT LOW CONFIDENCE. OTRW
EXPECT MOST SITES TO FINALLY IMPROVE TO VFR LEVELS OUTSIDE OF
CONVECTION EARLY THIS AFTERNOON WITH LOCALIZED MVFR/IFR IF A
HEAVIER SLOW MOVING SHRA/TSRA MOVES OVER OR NEAR A TAF LOCATION
DURING THE NEXT FEW HOURS.

SHOWERS MAY LINGER WELL PAST MIDNIGHT TONIGHT ESPCLY IN THE EAST
WITH A WEAK WAVE PASSING. THIS SHOULD GRADUALLY TREND TOWARD MORE
FOG IN THE VALLEYS AND WHERE HEAVIER RAINFALL OCCURRED LATE. THIS
SUPPORTS IFR/LIFR IN THE VALLEY SPOTS SUCH AS KLWB/KBCB AND
OVERALL MVFR ELSW WITH EVEN SOME FOG POSSIBLE AT KROA IF THEY SEE
AFTERNOON/EVENING RAINFALL.

WEDNESDAY WILL BE ANOTHER DAY OF MVFR TO IFR VALLEY FOG IN THE
MORNING AND SCATTERED AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS. HOWEVER COVERAGE MAY BE LESS AND MORE
OROGRAPHIC/OUTFLOW DRIVEN WEDNESDAY AFTERNOON WITH AGAIN LOCAL
SUB-VFR IN AND NEAR ANY CONVECTION.

EXTENDED AVIATION FORECAST...

MORE WIDESPREAD SHOWERS AND THUNDERSTORMS ARE EXPECTED ON THURSDAY
AS A COLD FRONT CROSSES THROUGH REGION FROM THE NORTHWEST. THIS
FRONT SHOULD PUSH SOUTH OF THE AREA AND ALLOW FOR DRIER AND MOSTLY
VFR CONDITIONS FRIDAY THROUGH SUNDAY.

&&

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

&&

$$
SYNOPSIS...JH/RAB
NEAR TERM...JH
SHORT TERM...KK
LONG TERM...KK
AVIATION...AMS/JH/MBS/RAB


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