Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 282334 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 734 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 650 PM EDT TUESDAY... A GENEROUS COVERAGE OF SHOWERS AND SOME SCATTERED STORMS ARE ACROSS THE REGION THIS EVENING. MOST OF THEM ARE ALONG AND EAST OF A HOT SPRINGS VIRGINIA...ROANOKE VIRGINIA...MARION VIRGINIA LINE. THE GREATEST CONCENTRATION IS BOUNDED INSIDE THE AREA TO THE RIGHT OF A ROANOKE VIRGINIA...HOT SPRINGS VIRGINIA...AMHERST VIRGINIA...BEDFORD VIRGINIA...ROANOKE VIRGINIA LINE. AS THE EVENING PROGRESSES...BOTH DIAGNOSTIC GUIDANCE AND MESO-SCALE MODELS SUGGEST A GENERAL TREND OF THE ACTIVITY PROGRESSING SLOWLY SOUTHEAST...AND DISSIPATING THROUGH THE LATE EVENING. BY EARLY WEDNESDAY MORNING...MAINLY ISOLATED SHOWERS ARE EXPECTED TO EXIST...WITH THE BULK OF THESE BETWEEN THE CREST OF THE BLUE RIDGE AND SOUTHSIDE VIRGINIA...AND NEIGHBORING PARTS OF NORTH CENTRAL NORTH CAROLINA. 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 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 /00Z WEDNESDAY THROUGH SUNDAY/... AS OF 725 PM EDT TUESDAY... SHOWERS AND THUNDERSTORMS WERE SCATTERED ACROSS THE REGION WITH THE GREATEST COVERAGE ALONG AND EAST OF A KMKJ...KROA...KHSP LINE. WITHIN THE STRONGER CELLS...LOCALIZED IFR/MVFR CONDITIONS EXISTED. WITHIN THE LIGHTER CELLS...AND OUTSIDE OF THE PRECIPITATION REGION...VFR CONDITIONS PREVAILED. AS WE HEAD INTO THE OVERNIGHT HOURS...THE COVERAGE OF SHOWERS AND STORMS WILL DECREASE...AND THE DEW POINT DEPRESSION WILL START TO LESSEN. THE RESULT WILL BE AN INCREASING COVERAGE OF SUB-VFR CONDITIONS...NOT BECAUSE OF PRECIPITATION...BUT BECAUSE OF THE FORMATION OF BR/FG AND STRATUS CLOUDS. ANTICIPATE MOST AREAS TO TREND TOWARD MVFR CONDITIONS OVERNIGHT...WITH SEVERAL LOCATIONS IN THE IFR...OR EVEN LIFR...RANGE BY EARLY WEDNESDAY MORNING. FLIGHT CATEGORIES WILL BE SLOW TO IMPROVE AFTER SUNRISE...BUT MOST LOCATIONS WILL BE VFR BY NOONTIME. IN THE AFTERNOON...ANOTHER ROUND OF SHOWERS AND SOME THUNDERSTORMS ARE EXPECTED. AGAIN...LOCALIZED MVFR/IFR CONDITIONS WILL BE POSSIBLE UNDER THE HEAVIER CELLS...WITH THE REMAINDER OF THE REGION STAYING IN VFR. EXTENDED AVIATION FORECAST... AS OF 1235 PM EDT TUESDAY... 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...DS/JH SHORT TERM...KK LONG TERM...KK AVIATION...DS/JH

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