Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 072004 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 404 PM EDT TUE JUL 7 2015 .SYNOPSIS... A COLD FRONT APPROACHES FROM THE NORTHWEST TONIGHT. THE FRONT IS EXPECTED TO STALL JUST NORTH OF THE REGION BY WEDNESDAY...THEN LIFT BACK NORTH AS A WARM FRONT LATE IN THE WEEK...AS HIGH PRESSURE ALOFT BUILDS ACROSS THE SOUTHEAST STATES. && .NEAR TERM /THROUGH WEDNESDAY/... AS OF 404 PM EDT TUESDAY... THIS AFTERNOONS SPC 18Z MESOSCALE ANALYSIS SHOWED SOME MOISTURE CONVERGENCE ALONG THE SOUTHERN BLUE RIDGE MOUNTAINS WITH LIS AROUND MINUS 3 TO MINUS 5. SFC BASED CAPES ARE RESPECTIVE AT 1000 TO 2000 J/KG THIS AFTERNOON. DAY ONE CONVECTIVE OUTLOOK PLACED US IN GENERAL THUNDERSTORM. HOWEVER...AN ISOLATED STRONG THUNDERSTORM WITH HEAVY DOWNPOURS AND GUSTY WINDS MAY BE POSSIBLE FOR A SMALL WINDOW THIS AFTERNOON INTO THIS EVENING. IN ANY CASE...ALLOWED FOR ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS FOR THIS AFTERNOON INTO TONIGHT WITH BEST CHANCE IN THE WEST. A FRONTAL BOUNDARY WILL SAG SOUTHEAST TONIGHT ACROSS THE OHIO VALLEY...WITH THE ACTIVE WEATHER REMAINING WEST OF US. BUT CONVECTIVE OUTFLOWS AHEAD OF THIS ACTIVITY MAY WORK INTO THE MOUNTAINS OVERNIGHT. LEANED POPS TOWARDS THE HRRR FOR THIS EVENING THEN GFS FOR TONIGHT INTO WEDNESDAY. LOW TEMPERATURES OVERNIGHT WILL RANGE FROM THE LOWER 60S TO NEAR 70 DEGREES IN THE PIEDMONT. UPPER LEVEL RIDGING ACROSS THE SOUTHEAST STATES WILL BUILD WEST ALONG THE GULF COAST ON WEDNESDAY...ALLOWING FOR INCREASINGLY ZONAL FLOW ACROSS THE MID ATLANTIC REGION. THIS BUILDING RIDGE WILL HELP STALL A COLD FRONT TO OUR WEST NEAR THE WEST VIRGINIA/MARYLAND BORDER WEST TO OHIO WEDNESDAY. SOUTH OF THIS BOUNDARY...WE WILL REMAIN ON THE WARM/MOIST UNSTABLE SIDE OF THE FRONT...WITH SHOWERS AND THUNDERSTORMS. INSTABILITY PARAMETERS ARE MODEST FOR THE MOST PART...BUT INDICATE ENOUGH CAPE AND LOW LEVEL SHEAR TO TRIGGER A FEW STRONG TO PERHAPS SEVERE STORMS...CAPABLE OF PRODUCING HAIL AND LOCALLY STRONG WINDS. SPC DAY TWO CONVECTIVE OUTLOOK PLACED THE BETTER POTENTIAL OF SEVERE WEATHER TO OUR WEST WITH MARGINAL ACROSS WESTERN KENTUCKY AND TENNESSEE. HIGH TEMPERATURES ON WEDNESDAY WILL VARY FROM THE LOWER 70S IN THE NORTHWEST MOUNTAINS TO AROUND 90 DEGREES IN THE PIEDMONT. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... AS OF 340 PM EDT TUESDAY... FORECAST AREA WILL BE PINCHED BETWEEN HIGH PRESSURE TO OUR SOUTH...AND WAVERING SURFACE FRONT WHICH WILL TRY TO MAKE INROADS LATE WEDNESDAY...RETREATING THURSDAY...ONLY TO RETURN AGAIN THURSDAY NIGHT AND FRIDAY. THERE WILL CERTAINLY BE SHOWERS/STORMS ASSOCIATED WITH THE FRONT...BUT DETAILS WITH RESPECT TO TIMING ARE NOT THAT CLEAR-CUT...ESP WHEN DEALING WITH A WAVERING FRONT. MODELS ARE IN AGREEMENT THAT CONVERGENCE ALONG THE FRONT WILL PROVIDE TRACK FOR ORGANIZED DEEP CONVECTION WITH MARGINAL RISK FOR SEVERE WEATHER PER FASTER WESTERLIES ALOFT NEAR THE FRONTAL ZONE. INCREASING INSTABILITY OUTSIDE OF THE HIGHER WIND ENVELOPE WILL ALSO SUPPORT PULSE STRONG-SEVERE STORMS DURING THE PEAK HEATING THURSDAY. FORECAST FOR THE AREA WILL REFLECT HIGHER POPS ACROSS THE NORTHERN CWA CLOSER TO THE FRONT...AND TO A MUCH LESSER DEGREE ACROSS THE SOUTH UNTIL THE FRONT GETS CLOSER FRIDAY. TEMPERATURES FOR THURSDAY FAVOR ABOVE NORMAL READINGS PER INCREASING HEIGHTS/THICKNESSES AND A WESTERLY WIND COMPONENT WHICH SHOULD AID IN ADIABATIC WARMING EAST OF THE BLUE RIDGE. WITH 85H TEMPS APPROACHING +20 DEG C...SURFACE READING SHOULD EASILY CLIMB WELL INTO THE 80S AND POSSIBLY THE L-M 90S PENDING SUNSHINE. WITH THE FRONT OVER THE AREA FRIDAY...CLOUDS/SHOWERS SHOULD KEEP HIGH TEMPS A FEW DEGREES COOLER. MINIMUM TEMPERATURES WILL AVERAGE ABOVE NORMAL...PER THE HIGH MOISTURE CONTENT OF THE ATMOSPHERE. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 340 PM EDT TUESDAY... MODELS ARE IN AGREEMENT THE SUBTROPICAL RIDGE OVER THE SOUTHEAST STATES WILL RETROGRADE TOWARD TEXAS/OKLAHOMA FOR THE WEEKEND THEN EXPAND NORTHWEST INTO THE ROCKIES FOR NEXT WEEK...JULY 13-17. SHORT WAVE ENERGY PASSING DOWNSTREAM FROM THIS RIDGE IS THEN EXPECTED TO CARVE OUT FULL LATITUDE TROUGH OVER THE EASTERN CONUS WITH MODELS HINTING THIS FEATURE WILL CUTOFF OVER THE REGION FOR THE MIDDLE OF NEXT WEEK. DURING THE FORECAST PERIOD...AN ACTIVE FRONTAL ZONE IS EXPECTED TO REMAIN CLOSE TOO OR DRAPED ACROSS THE REGION PROMOTING DAILY THREAT FOR SHOWERS/STORMS...DETAILS WITH RESPECT TO TIMING/PATH OF DEEP CONVECTION LACKING. AS SUCH LONG TERM FORECAST REFLECTS A SHOTGUN STANCE...ALTHOUGH DID FAVOR THE PEAK HEATING OF THE DIURNAL CYCLE FOR GREATEST POPS/THUNDER COINCIDENT WITH PEAK INSTABILITY. TEMPERATURES...ALTHOUGH NOTHING EXTREME...WILL FAVOR THE WARM SIDE OF GUIDANCE THIS WEEKEND...THEN RETREAT TO SOMETHING NEAR OR JUST BELOW NORMAL FOR THE MIDDLE OF NEXT WEEK AS THE UPPER TROUGH BECOMES THE DOMINANT WEATHER FEATURE. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... AS OF 115 PM EDT TUESDAY... VFR EXPECTED THROUGH THE REST OF THIS AFTERNOON WITH CU AND STRATOCU INVOF THE HIGHER TERRAIN. SHOWERS/TSTMS ACROSS ERN KY AND NRN/WRN WV ARE PROGGED TO WEAKEN AS THEY MOVE EAST...SO FOR NOW HAVE KEPT THEM OUT OF THE TAFS. AS THE FRONT MOVES CLOSER TONIGHT AND EALRY WED...THE RISK FOR RAIN AND SUB-VFR CONDITIONS WILL INCREASE...ESP AT BLF AND LWB. EXTENDED AVIATION DISCUSSION... A COLD FRONT WILL STALL NEAR THE WV/MD BORDER WEST TO OHIO BY WEDNESDAY. SOUTH OF THIS BOUNDARY...WE WILL REMAIN ON THE WARM/MOIST SIDE OF THE FRONT...AND SUBJECT TO DAILY THREAT FOR MVFR SHOWERS/STORMS. EXPECT WIDESPREAD LATE NIGHT/EARLY MORNING LOW CLOUDS/FOG WITH IFR-LIFR CIGS/VSBYS. OVERALL...CONDITIONS SHOULD IMPROVE TO MVFR- VFR OUTSIDE SHRA/TSRA ACTIVITY DURING THE AFTERNOONS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...KK/WP NEAR TERM...KK SHORT TERM...PM LONG TERM...PM AVIATION...RAH

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