Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 290539 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 139 AM EDT WED JUL 29 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 TODAY/...
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AS OF 130 AM EDT WEDNESDAY... SHOWERS ARE ALL BUT GONE IN THE CWA...BUT WILL SEE ISOLATED COVERAGE AT TIMES IN THE PIEDMONT AND TOWARD FAR SW VA INTO SE WV PER HIGHER THETA-E RIDGE. EXPECT FOG OVERALL MOST OF THE AREA WITH SKIES CLEARING IN THE NORTH. NO CHANGES TO THE FORECAST LOWS. PREVIOUS VALID DISCUSSION... 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.
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&& .SHORT TERM /TONIGHT 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 TUESDAY/... 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 /06Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 125 AM EDT WEDNESDAY... RAIN SHOWERS HAVE ERODED OVER THE REGION THIS MORNING. CANNOT RULE OUT A STRAY SHOWER BUT TOO LOW CHANCE TO ADD TO TAFS. FOG WILL BE THE MAIN CONCERN AS MOISTURE RESIDES IN THE LOW LVLS PER RAIN AND/OR HIGHER DEWPOINTS. SOME HIGHER CLOUDS ARE MOVING ACROSS THE PIEDMONT INTO THE ROANOKE AREA...STRETCHING TOWARD LWB. SHOULD SEE SOME CLEARING ALLOWING FOG TO BECOME DENSE AT TIMES AT LWB. NOT AS CONFIDENT ON HOW LOW THE VSBYS GO AT THE OTHER SITES...BUT THINK AT LEAST MVFR/IFR RANGE EXCEPT PERHAPS ROANOKE...THOUGH THEY MAY SLIP TO MVFR BRIEFLY PRIOR TO DAWN. A WEAK FRONTAL BOUNDARY WILL BE NORTH OF THE FORECAST AREA TODAY. ONCE ANY FOG/STRATUS BURNS OFF BY 14Z WILL SEE SCT/BKN CU/SC THEN TCU/CBS IN THE MTNS AFTER 18Z...AND TOWARD THE PIEDMONT AFTER 20Z. MODELS FAVORING MORE COVERAGE ALONG AND WEST OF THE BLUE RIDGE NORTH TOWARD THE SHENANDOAH CLOSE TO THE FRONT. ADDED VCTS AT ALL SITES EXCEPT LYH/DAN FOR NOW FOR A FEW HOURS THIS AFTERNOON. ANY STORMS FADE WITH LOSS OF HEATING WED EVENING WITH FOG FORMING AGAIN BY THURSDAY MORNING. 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.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/RAB NEAR TERM...DS/JH/WP SHORT TERM...KK LONG TERM...KK AVIATION...DS/JH/WP

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