Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 280523 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 123 AM EDT MON JUL 28 2014 .SYNOPSIS... UPPER DISTURBANCES WILL CONTINUE TO WORK ACROSS THE AREA THIS EVENING IN ADVANCE OF A STRONG COLD FRONT THAT WILL BE ARRIVING FROM THE NORTHWEST AFTER MIDNIGHT. THESE FEATURES MAY TRIGGER STRONG TO POTENTIALLY SEVERE THUNDERSTORMS INTO EARLY TONIGHT. THE COLD FRONT WILL MOVE ACROSS THE REGION BY EARLY MONDAY...RESULTING IN COOLER WEATHER INTO THE MIDDLE OF THE WORK WEEK. && .NEAR TERM /THROUGH TODAY/... AS OF 115 AM EDT MONDAY... CONVECTION APPROACHING FROM WEST VIRGINIA HAS WEAKENED OVER THE PAST FEW HOURS...AMOUNTING ONLY TO SHOWER ACTIVITY AT THIS TIME. SEE NO NEED TO PROLONG THE TORNADO WATCH...AND HAVE THEREFORE CANCELLED IT EARLY FOR THE MOUNTAIN EMPIRE THROUGH THE SHENANDOAH VALLEY. ADJUSTED RAIN CHANCES FOR THE NEXT FEW HOURS BASED ON RADAR TRENDS AND HRRR MODEL DATA WHICH APPEARS TO BE HANDLING THE CURRENT RAINFALL VERY WELL. EXPECT ONLY SPOTTY UPSLOPE SHOWERS SHOULD BE ALL THAT REMAIN BY SUNRISE. LATEST SURFACE OBSERVATIONS INDICATE THE COLD FRONT IS SITUATED NEAR THE OHIO RIVER...PROGRESSING A LITTLE SLOWER THAN PREVIOUSLY FORECAST. EXPECT THE FRONT TO ENTER OUR SOUTHEAST WEST VIRGINIA COUNTIES BY AROUND 5 AM...AND THEN CONTINUE EAST THROUGH THE MORNING. AS OF 200 PM EDT SUNDAY... 5H TROF CROSSES EAST OF THE AREA MONDAY ALLOWING HIGH PRESSURE TO START BUILDING IN FROM THE WEST DURING THE AFTERNOON. HOWEVER ANOTHER SHORTWAVE ROUNDING DOWN THE BACK OF THE COOL POOL MAY HELP TO ENHANCE THE SHOWERS AS IT COINCIDES WITH THE COLDEST 85H TEMPS AND MAX HEATING. THUS BOOSTED POPS WESTERN SLOPES TO A PERIOD OF LOW LIKELYS MONDAY AFTERNOON WITH A QUICK CUTOFF TO SHRA BLUE RIDGE AND POINTS EAST WHERE DOWNSLOPING SHOULD ALLOW FOR LESS CLOUDS. ODOR WILL BE A BREEZY AND COOL DAY FOR LATE JULY OVER THE MOUNTAINS WHERE MAY STRUGGLE TO GET OUT OF THE 60S WHERE CLOUDS PERSIST AND ALONG HIGHER ELEVATIONS. SHOULD BE ABLE TO GET WELL INTO THE 80S UNDER DRY DOWNSLOPE PIEDMONT BUT ONLY 75-82 BLUE RIDGE. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... AS OF 215 PM EDT SATURDAY... WEST TO NORTHWEST UPPER FLOW WILL PERSIST OVER THE BLACKSBURG FORECAST AREA THROUGH THE SHORT TERM PERIOD AS SERIES OF WEAK SHORT WAVE TROFS EMBEDDED IN UPPER FLOW HELP ANCHOR PIN-WHEELING UPPER TROF OVER THE GREAT LAKES. COOLER AIR ALOFT...WEAK FORCING FROM INITIAL SHORT WAVE...AND WEAK UPSLOPING MAY SUPPORT ISOLATED TO WIDELY SCATTERED SHOWERS ACROSS THE WESTERN FLANKS OF THE APPALACHIANS ON MONDAY NIGHT...AND PERHAPS DIURNALLY DRIVEN EVEN INTO TUESDAY. HOWEVER...DESPITE ADDITIONAL WEAK STREAM ENERGY...ARRIVAL OF SURFACE RIDGE AND AMPLIFICATION OF SUBSIDENCE INVERSION SHOULD BE SUFFICIENT TO LIMIT THREAT FOR ANY ADDITIONAL SHOWER ACTIVITY TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. UPSLOPING CLOUDS ACROSS THE WEST SHOULD MAINTAIN UNSEASONABLY COOL TEMPERATURES IN THE MOUNTAINS...WITH DAYTIME HIGHS NOT LIKELY TO CLIMB OUT OF THE 60S ON EITHER TUESDAY OR WEDNESDAY ACROSS THE HIGHEST TERRAIN. EAST OF THE BLUE RIDGE...ANY INFLUENCE OF COLD ADVECTION WILL BE OFFSET BY DOWNSLOPING/COMPRESSIONAL HEATING AND GOOD INSOLATION SUCH THAT HIGHS REACH INTO THE LOWER TO MID 80S...YET STILL ~5F LOWER THAN CLIMATOLOGICAL AVERAGES. NIGHTTIME LOWS WILL BE LARGELY GOVERNED BY EXTENT OF MIXING AND CLOUD COVER. HIGHER ELEVATIONS WHERE/IF CLOUDS CAN CLEAR...AND ESPECIALLY THE MOUNTAIN VALLEYS WHERE BOUNDARY LAYER DECOUPLING WILL MORE READILY OCCUR...SHOULD EXPERIENCE AT LEAST SPOTTY READINGS DOWN INTO THE 40S. READINGS EAST OF THE BLUE RIDGE WILL BE A BIT MILDER...MAINLY 50S...YET STILL 5-10F BELOW CLIMATOLOGICAL AVERAGES. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 1200 PM EDT SUNDAY... A SURFACE HIGH THURSDAY OVER SOUTHERN MICHIGAN WILL SHIFT EAST TOWARDS NEW ENGLAND BY FRIDAY AND SATURDAY. AT THE MID LEVELS A PERSISTENT TROUGH IS SET UP OVER THE EASTERN US WITH A RIDGE OVER THE WESTERN US. THURSDAY LACKS LOW AND MID LEVEL MOISTURE SO EXPECT THE DAY TO BE DRY. MOISTURE AND INSTABILITY INCREASE FOR FRIDAY AND THROUGH THE REST OF THE PERIOD AS SEVERAL DISTURBANCES PIVOT ACROSS THE REGION AROUND THE BASE OF THE TROUGH. EXPECT SCATTERED SHOWERS AND THUNDERSTORMS TO DEVELOP EACH AFTERNOON/EVENING AND TAPER OFF TO JUST SCATTERED SHOWERS DURING THE EVENING. FOCUS OF THE HIGHEST CHANCE POPS ARE OVER THE MOUNTAINS WHERE THE BEST CONVERGENCE WILL BE LOCATED...WITH LOWER CHANCE POPS OUT EAST. THURSDAY WILL BE THE WARMEST DAY OF THE PERIOD WITH 850MB TEMPS AROUND +16C. THIS WILL CORRESPOND TO SURFACE HIGH TEMPS IN THE MID 80S OUT EAST AND NEAR 80 ACROSS THE MOUNTAINS. AS THE HIGH SHIFTS EAST ON FRIDAY THE WINDS WILL SHIFT FROM N/NW TO AN EASTERLY DIRECTION. THIS WILL WEDGE THE AREA IN THROUGH THE REMAINDER OF THE PERIOD. WITH THE INCREASED LOW/MID LEVEL MOISTURE EXPECT CLOUDY CONDITIONS. THIS ALONG WITH EXPECTED SCATTERED PRECIP AND 850MB TEMPS FALLING TO +11-14C...SURFACE HIGH TEMPS WILL BE 5-10 DEGREES BELOW NORMAL FRIDAY THROUGH SUNDAY. && .AVIATION /05Z MONDAY THROUGH FRIDAY/... AS OF 745 PM EDT SUNDAY... STILL AWAITING POTENTIAL ARRIVAL OF MORE SIGNIFICANT CONVECTION INTO THE CWA AS THE EVENING PROGRESSES WITH STRONG STORMS STILL POSSIBLE...MAINLY IN AREAS OF BETTER INSTABILITY/HEATING ACROSS SOUTHSIDE/PIEDMONT. THIS COULD IMPACT ROA/LYH/DAN IN THE 02Z-06Z TIME FRAME...BUT CONFIDENCE IN THIS OCCURRING IS LOW AS CIRRUS SHIELD FROM UPSTREAM CONVECTION AND MORNING ACTIVITY HAS ESSENTIALLY PUT A LID ON CONVECTIVE ACTIVITY TO THIS POINT ACROSS MOST OF THE CWA THIS AFTERNOON/EVENING. OF GREATER LIKELIHOOD IS THAT A LINE OF MOST LIKELY SUB SEVERE SHRA/TSRA WILL DEVELOP ALONG THE FRONT/UPPER TROUGH AS ITS SWINGS RAPIDLY THROUGH THE CWA IN THE 04Z-08Z TIME FRAME. GIVEN THAT THERE WILL BE A LARGE UPSLOPE COMPONENT AT THAT TIME...EXPECT THE GREATEST LIKELIHOOD OF SHRA/TSRA TO BE ACROSS THE WV COUNTIES...BUT ENOUGH DYNAMICS TO SUPPORT MENTION OF SHRA EASTWARD EVEN INTO THE PIEDMONT. MOST LIKELY THIS WILL BE ACCOMPANIED BY MVFR CIGS LWB-BLF...TO LOW END VFR CIGS FURTHER EASTWARD. ALL PCPN SHOULD BE ENDING BY 10Z MON...BUT EXTENSIVE UPSLOPE SC WILL CONTINUE THROUGHOUT WV MON WITH A WINTERLIKE SETUP AND STRONG NW FLOW AND STRONG CAA. EXPECT MVFR CIGS TO PREVAIL ALL DAY LWB-BLF...AND POTENTIALLY EVEN BCB AT TIMES. FURTHER EAST...CLOUDS SHOULD SCT OUT AND CIGS WILL BE MOSTLY VFR. VSBYS MOSTLY VFR OUTSIDE ISOLD MVFR IN TIME AND LOCATION DURING SHRA/TSRA. MAIN CONCERN AFT 06Z AND THROUGH THE DAY MON WILL BE STRONG NW WINDS AT SPEEDS OF 10-15KTS WITH GUSTS 25-30KTS...ESPECIALLY AFT 14Z MON. WINDS WILL BEGIN TO DIMINISH TOWARD THE END OF THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND SPD/HIGH CONFIDENCE IN WIND DIR THROUGH THE TAF VALID PERIOD. LOW CONFIDENCE IN TSRA POTENTIAL THROUGH 10Z MON. EXTENDED AVIATION DISCUSSION...DRIER AIR PUSHING IN FOR TUESDAY- WEDNESDAY WILL BRING MAINLY VFR CONDITIONS...BUT CANNOT RULE OUT LATE NIGHT FOG KBCB/KLWB ALTHOUGH THE LOW LEVELS MAY STAY DRY ENOUGH FOR LESS FOG COVERAGE. VARIABLE CIGS EXPECTED UNDER ANOMALOUS UPPER LOW THROUGHOUT THE REST OF THE WEEK. A FEW -SHRA NOT COMPLETELY OUT OF THE QUESTION ACROSS EASTERN WV...ALONG WITH OCCASIONAL MVFR CIGS. TYPICAL FOG POTENTIAL LESS THAN NORMAL FOR THIS TIME OF YEAR THROUGHOUT THE WEEK BECAUSE OF TURBULENT MIXING AND PREVAILING CYCLONIC FLOW. TOWARD THE END OF THE WEEK...AS THE UPPER LOW RETROGRADES JUST WEST OF THE REGION...INCREASING POTENTIAL FOR SHRA/TSRA BUT MAINLY SW OF THE TAF SITES INTO FRIDAY. && .EQUIPMENT... THE WEATHER RADIO AT HINTON WEST VA TRANSMITTING ON FREQUENCY 162.425 MHZ REMAINS OFF THE AIR LIKELY DUE TO PHONE LINE PROBLEMS. RESTORATION OF SERVICE IS NOT EXPECTED BEFORE NOON ON MONDAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/NF NEAR TERM...JH/RAB SHORT TERM...WERT LONG TERM...CF AVIATION...JH/RAB EQUIPMENT...JH

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