Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 270152 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 952 PM EDT TUE APR 26 2016 .SYNOPSIS... A FRONTAL BOUNDARY FROM CENTRAL ILLINOIS THROUGH CENTRAL NEW JERSEY WILL SLOWLY PUSH SOUTHWARD AND INTO THE MID ATLANTIC TONIGHT AND INTO WEDNESDAY AS WAVES OF LOW PRESSURE TRACK ALONG IT. ONE WAVE WILL MOVE ACROSS WEDNESDAY MORNING FROM THE WEST...AND A MORE SIGNIFICANT WAVE WILL TRACK JUST NORTHWEST OF OUR AREA ON THURSDAY...BRINGING ADDITIONAL MOISTURE BACK ACROSS THE SURFACE BOUNDARY STILL DRAPED OVER THE REGION. && .NEAR TERM /THROUGH WEDNESDAY/... AS OF 950 PM EDT TUESDAY... CONVECTIVE WATCH NO. 111 HAS BEEN CANCELLED FOR ALLEGHANY AND BATH COUNTIES OF VIRGINIA...AND FOR MERCER...MONROE...AND SUMMERS COUNTIES OF WEST VIRGINIA. POPS AND QPF WERE ALSO LOWERED CONSIDERABLY FOR THE NEXT FEW HOURS...AS THE CWA REMAINS IN A MINIMUM OF CAPE AND PRECIPITABLE WATER BASED ON THE LATEST MESOANALYSIS RUNS. GREENBRIER REMAINS IN THE WATCH FOR NOW...BUT CONFIDENCE REMAINS LOW ON ANY SEVERE STORMS FIRING THERE. THERE IS THE POTENTIAL FOR AN UPSTREAM MCS TO REACH WEST VIRGINIA BY WEDNESDAY MORNING TO PROVIDE DIMINISHING RAIN SHOWERS AND A LITTLE THUNDER...BUT INSTABILITY WILL BE RATHER WEAK. AT THE SAME TIME...THE SFC BOUNDARY TO THE NORTH BEGINS TO BACK DOOR FROM THE NORTHEAST THROUGH THE LYNCHBURG AREA DURING THE DAY WEDNESDAY...AND REMNANTS OF THIS WAVE FROM THE WEST COULD INTERSECT THIS IN THE EAST EITHER ALLOWING CONVECTION TO CONTINUE...OR REDEVELOPING IN THE PIEDMONT. DECIDED TO JUST MAINTAIN LOW LIKELY TO HIGH CHANCE POPS MOST OF THE DAY TOMORROW...WITH CHC THUNDER PRETTY MUCH ALL DAY. MIDNIGHT SHIFT CAN REASSESS AS THIS WAVE FROM THE WEST APPROACHES AND WE MAY NEED TO REMOVE THUNDER CHANCES DURING THE MORNING...AND RE-INTRODUCE LATER IN AFTERNOON. BUT IN GENERAL MOST LOCATIONS STAND A GOOD CHANCE OF SEE A PERIOD OF SHOWERS AND MAYBE A THUNDER STORM AS WELL. SEVERE CHANCES APPEAR MINIMAL...AND WILL DEPEND ON HEATING...BUT NOT A ZERO THREAT. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... AS OF 230 PM EDT TUESDAY... A FRONTAL BOUNDARY WILL REMAIN STALLED AROUND OR JUST SOUTH OF THE VA/NC BORDER WEDNESDAY NIGHT INTO THURSDAY. DISTURBANCES FROM THE MIDDLE MISSISSIPPI VALLEY WILL PINWHEEL EASTWARD FROM A PARENT UPPER TROUGH LOCATED OVER THE UPPER MISSISSIPPI VALLEY. THESE FEATURES WILL RIDE ALONG THE BOUNDARY BRINGING EXTRA ENERGY TO THE REGION TO SUPPORT BETTER ORGANIZATION OF SHOWERS/STORMS. ONE SUCH FEATURE IS PROGGED TO ARRIVE THURSDAY MORNING IN THE WEST AND TRANSLATE ACROSS THE REGION DURING THE COURSE OF THE DAY. NOTABLE SURFACE BASED INSTABILITY AND WEAK LOW LEVEL SHEAR WILL BE SUFFICIENT FOR SOME STORMS TO BE ON THE STRONG SIDE. NORTHEAST PARTS OF THE AREA ARE EXPECTED TO EXPERIENCE THE LEAST COVERAGE OF STORMS. HERE...A NOSING RIDGE OF HIGH PRESSURE WILL HELP TO KEEP AT LEAST SURFACE BASED CONVECTION AT BAY. BY THURSDAY EVENING...A COLD FRONT ASSOCIATED WITH THE PARENT UPPER LOW WILL BE REACHING THE WESTERN PART OF THE AREA...AND MOVE TROUGH THE REGION THURSDAY NIGHT. LOOK FOR A CONTINUATION OF SHOWERS INTO THE OVERNIGHT HOURS...WITH ISOLATED STORMS STILL POSSIBLE IN THE EVENING. BY FRIDAY...THE UPPER LEVEL TROUGH AXIS WILL CROSS THE REGION. THE BEST DYNAMICS ARE PROGGED TO STAY NORTH OF THE AREA. HOWEVER...ENOUGH INSTABILITY IS EXPECTED TO REACH A LEAST THE NORTHERN HALF THE AREA FOR THE FOCUS FOR SHOWERS...AND A FEW STORMS...TO BE THERE. ALSO...DAYTIME HEATING IN THE EAST WILL COINCIDE WITH THE PASSAGE OF THE TROUGH...SO EXPECT ISOLATED TO SCATTERED COVERAGE OF SHOWERS AND ISOLATED STORMS IN THE EAST AS WELL. TEMPERATURES DURING THIS PORTION OF THE FORECAST WILL AVERAGE A FEW DEGREES ABOVE NORMAL. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... AS OF 310 PM EDT TUESDAY... FRIDAY NIGHT...ANTICIPATE SOME LINGERING ISOLATED SHOWERS AS THE UPPER TROUGH AXIS DEPARTS THE REGION. THE FOCUS FOR ANY ACTIVITY WILL BE IN THE NORTHEAST PART OF THE FORECAST AREA. OVER THE WEEKEND...UPPER RIDGING WILL TAKE PLACE ACROSS THE REGION AS ANOTHER LOW WITH ASSOCIATED FRONTAL FEATURES DEVELOPS IN THE CENTRAL PORTION OF THE COUNTRY. THIS FEATURES WILL ADVECT MOISTURE AND BITS OF SHORTWAVE ENERGY TOWARDS THE REGION. WHILE IT WILL INITIALLY BE DAMPENED BY THE RIDGE...BY THE END OF THE WEEKEND...THE RIDGE WILL HAVE BEEN DISPLACED BY ZONAL FLOW...AND BY MONDAY...LOW/TROUGH SYSTEM PROGRESSING THROUGH THE REGION. ANTICIPATE INCREASING CHANCES OF SHOWERS DURING THE WEEKEND...WITH THE GREATEST COVERAGE IN THE WEST. ISOLATED THUNDERSTORMS ARE POSSIBLE WITH THE BEST CHANCES OF THESE IN THE WEST AND SOUTH. BY LATE SUNDAY NIGHT INTO MONDAY...MODERATE RAIN SHOWERS ARE LIKELY WITH ISOLATED STORMS AS THE UPPER SYSTEM PASSES THE REGION. ANOTHER SYSTEM ON THE HEELS OF THE MONDAY ACTIVITY IS PROGGED TO SWING THROUGH THE AREA ON TUESDAY...HELPING TO MAINTAIN OUR CHANCES OF SCATTERED SHOWERS. TEMPERATURES DURING THIS PORTION OF THE FORECAST WILL AVERAGE FIVE DEGREES ABOVE NORMAL THROUGH MONDAY. ON TUESDAY...NEAR NORMAL TEMPERATURES ARE FORECAST. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... AS OF 800 PM EDT TUESDAY... VERY LOW CONFIDENCE THROUGH THE TAF VALID PERIOD. NORTHWEST TO SOUTHEAST ORIENTED FRONTAL BOUNDARY WILL DRIFT SLIGHTLY FURTHER SOUTH OVERNIGHT AND THEN BECOME QUASI-STATIONARY ACROSS THE REGION WED. IT WILL CERTAINLY SERVE AS THE FOCUSING MECHANISM FOR CONVECTION WITH A MARGINALLY UNSTABLE ATMOSPHERE. MORE IMPORTANTLY WILL NEED TO KEEP AN EYE ON UPSTREAM CONVECTION/MCS RIDING ALONG THE BOUNDARY/BAROCLINIC ZONE FROM THE OH VALLEY OVERNIGHT/EARLY THURSDAY. TIMING...INTENSITY...AND WHETHER OR NOT THESE FEATURES WILL EVEN HOLD TOGETHER TO REACH THE RNK CWA IS QUESTIONABLE. HOWEVER...ENOUGH MODELS SUGGEST THAT PRECIPITATION WILL AT LEAST REACH THE NW PART OF THE CWA LATE TONIGHT/EARLY WED THAT IT WARRANTED INCLUDING IN THE TAFS. BETTER THREAT FOR REDEVELOPMENT OF CONVECTION WED AFTERNOON AFT 16Z ACROSS MUCH OF THE CWA NEAR THE FRONTAL BOUNDARY. WITH RESPECT TO CIGS/VSBYS...POTENTIAL EXISTS FOR MVFR IN -SHRA/-TSRA BR OVERNIGHT/EARLY WED...BUT OVERALL EXPECTING VFR CIGS/VSBYS OUTSIDE CONVECTION. GREATER POTENTIAL FOR LOCAL MVFR- IFR CIGS/VSBYS IN SHRA/TSRA WED AFTERNOON AFT 18Z...BUT AGAIN CONFIDENCE IN TIMING/EXTENT/DURATION IS LOW. WINDS MOSTLY SW-WSW 5-7KTS WITH SOME LOW END GUSTS THROUGH THE PERIOD...BUT POTENTIALL BECOMING E-NE AT KLYH WED AFTERNOON BEHIND THE FRONTAL BOUNDARY WITH SOME POTENTIAL FOR WEDGE DEVELOPMENT LATE IN THE PERIOD. LOW CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD. LOW TO MEDIUM CONFIDENCE IN VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... BACK DOOR FRONT WILL SLOWLY PUSH THROUGH WEDNESDAY NIGHT AND THEN REMAIN STALLED OR SLOWLY DRIFT BACK NORTH ON THURSDAY...BEFORE A STRONGER COLD FRONT ENTERS FROM THE WEST TO PUSH THE WEAKER FRONT OFFSHORE LATE THURSDAY. DURING THIS TIME...SCATTERED SHOWERS WITH A FEW AFTERNOON THUNDERSTORMS APPEAR LIKELY. THE GREATEST CHANCE OF RAIN AND MVFR/IFR CONDITIONS WILL ACCOMPANY THE STRONGER COLD FRONT ON THURSDAY. SOME CLEARING SHOULD TAKE PLACE DURING FRIDAY...ALTHOUGH A FEW MOUNTAIN SHOWERS AND MVFR CLOUDS ARE POSSIBLE. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PW NEAR TERM...PW/SK SHORT TERM...DS LONG TERM...DS AVIATION...AMS/DS/RAB/SK

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