Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 100514 AAA AFDRNK AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BLACKSBURG VA 114 AM EDT THU JUL 10 2014 .SYNOPSIS... A SLOW MOVING COOL FRONT WILL SLIDE SOUTHEAST ACROSS THE REGION OVERNIGHT BEFORE STALLING ACROSS NORTHERN NORTH CAROLINA THURSDAY. WEAK AREAS OF LOW PRESSURE RIDING ALONG THE FRONT WILL KEEP UNSETTLED WEATHER GOING INTO LATE THURSDAY BEFORE WEAK HIGH PRESSURE SPILLS SOUTH INTO THE REGION FOR FRIDAY AND SATURDAY. DEEPER MOISTURE WILL RETURN LATER IN THE WEEKEND AND EARLY NEXT WEEK AHEAD OF A MUCH STRONGER COLD FRONT THAT WILL BE PASSING THROUGH THE REGION BY NEXT TUESDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 1250 AM EDT THURSDAY... SENT AN UPDATE TO RAISE POPS TO HIGH CHANCE/LIKELYS ACROSS THE SW AHEAD OF THE NEXT WAVE OF CONVECTION SEEN HEADING NE INTO NW NC. LATEST HRRR SPREADS THIS PRECIP NE INTO SOUTHERN VA AND PERHAPS EVEN OUT INTO THE PIEDMONT LATE PENDING HOW MUCH SURVIVES STABILITY OUT EAST. THUS ALSO INCLUDING CHANCE POPS SOUTHERN TIER DURING THE NEXT FEW HOURS MORE IN LINE WITH THE LATEST 4KM NAM. WILL KEEP SOME THUNDER MENTION AS WELL GIVEN LINGERING CAPE SEEN FEEDING INTO NW NC ATTM...BUT THINK SHOULD SEE DEEPER CONVECTION FADE IN THE NEXT COUPLE OF HOURS WITH MORE OF A HEAVY RAIN SCENARIO. AS OF 955 PM EDT WEDNESDAY... SHOWERS AND ISOLATED STORMS HAVE WEAKENED. STILL GOING TO SEE A THREAT ALONG A BOUNDARY STRETCHED FROM ERN KY SOUTHEAST TOWARD NC/VA OVERNIGHT. WILL KEEP THE ISOLATED/LOW CHANCE THREAT HERE WHILE HAVING IT MAINLY DRY ELSEWHERE. PATCHY FOG EXPECTED AS WELL WHERE SKIES CLEAR OUT SOME WHICH FAVORS THE NW CWA. NOT MUCH CHANGE TO THE OVERNIGHT FORECAST IN TERMS OF TEMPS. PREVIOUS VALID DISCUSSION... OVERNIGHT DRIER AIR AS SEEN ON THE WATER VAPOR LOOP WILL PUSH INTO THE REGION AS THE LEADING WEAK COLD FRONT DRIFTS SOUTH INTO NORTH CAROLINA AND STALLS. MODELS CONTINUED TO SHOW A LOW ALONG THE FRONT LATE TONIGHT THAT PUSHES THE DEEPER MOISTURE BACK INTO THE FORECAST AREA AFTER MIDNIGHT. HAVE A LULL IN THE PRECIPITATION... ESPECIALLY IN THE NORTHWEST HALF OF THE FORECAST AREA THIS EVENING...THEN BRING BETTER PROBABILITIES BACK IN BY MORNING. TEMPERATURES WILL DEPEND ON CLOUD COVER. WITH LITTLE DROP IN DEW POINTS TONIGHT MINIMUM TEMPERATURES WILL REMAIN MILD. IF CLEARING DOES OCCUR...MAY BE ADDING FOG BACK INTO THE FORECAST IN LOCATIONS THAT HAD RAIN THIS AFTERNOON. CLOUDS AND SHOWERS WILL ALSO LIMIT RISE IN TEMPERATURES...ESPECIALLY ACROSS THE SOUTH AND EAST ON THURSDAY. STAYED CLOSER TO COOLER SIDE OF GUIDANCE FOR MAXIMUM TEMPERATURES. && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... AS OF 300 PM EDT WEDNESDAY... EXPECT AN AREA OF PRECIPITATION TO BE COVERING THE SOUTHEAST PORTION OF THE BLACKSBURG CWA AT THE START OF THE SHORT TERM PERIOD...WITH GOOD LOW LEVEL MOISTURE CONVERGENCE ALONG A SFC BOUNDARY IN THIS AREA. THIS REGION WILL ALSO FALL UNDER THE RIGHT REAR QUAD OF AN UPPER LEVEL AND GOOD UPPER LEVEL DIVERGENCE.THIS AREA OF PRECIP WILL GRADUALLY WANE DURING THE OVERNIGHT HOURS. FOR FRIDAY...THE UPPER LEVEL TROF AXIS WEAKENS AND SHIFTS SLIGHT EAST...PLACING THE BEST UPPER LEVEL SUPPORT EAST OF THE BLACKSBURG FORECAST AREA. STILL EXPECT WIDELY SCATTERED SHOWERS AND STORMS IN THIS AREA WITH WEAK CONVERGENCE ALONG THE DYING BOUNDARY. A SECOND AREA FOR PRECIP DEVELOPMENT WILL BE POSSIBLE IN THE MOUNTAINS...WITH AN UPSLOPE FLOW AND A SFC BOUNDARY FORECAST BY THE GFS/NAM/SREF/ECMWF NEAR THE VA/WV BORDER. AS THE DEEPEST MOISTURE AND BEST UPPER LEVEL SUPPORT SHIFT EAST...THE COVERAGE OF PRECIPITATION FRIDAY SHOULD BE LESS...AS WELL AS THE AMOUNT OF CLOUD COVER. GENERALLY FOLLOWED THE GFS MOS GUIDANCE FOR HIGHS WITH HAS PERFORMED THE BEST IN OUR AREA OVER THE PAST FEW DAYS. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 245 PM EDT WEDNESDAY... AS SFC HIGH PRESSURE SHIFTS EAST ON SATURDAY...THE LOW LEVEL FLOW BECOMES EAST/SOUTHEAST BRINGING WEAK UPSLOPE FLOW. AT THIS POINT...THE DEEPEST MOISTURE WILL BE SOUTH AND EAST OF OUR AREA...BUT ENOUGH LOW LEVEL CONVERGENCE SHOULD SPARK ISOLATED/WIDELY SCATTERED SHOWERS/STORMS ACROSS THE SOUTHERN BLUE RIDGE. BY SUNDAY AND MONDAY...A LOW LEVEL THETA-E AXIS SURGES INTO OUR AREA WHICH WILL INCREASE COVERAGE OF DIURNALLY DRIVEN SHOWERS AND STORMS. BUT SIMILAR TO WHAT WE HAVE EXPERIENCED RECENTLY...A DEEP WEST/SOUTHWEST FLOW SHOULD KEEP THE CONVECTION SCATTERED. TOWARD THE END OF THE LONG TERM PERIOD THE MEDIUM RANGE MODELS CONTINUE TO FORECAST A BROAD UPPER TROF AND AN ASSOCIATED CUT OFF LOW OVER THE NORTHERN GREAT LAKES BY TUESDAY. THIS FEATURE HELPS DRIVE A COLD FRONT THROUGH OUR AREA ON TUESDAY. THERE ARE STILL DIFFERENCES WITH REGARD TO THE TIMING OF THIS FRONT...WITH THE 06Z GFS FASTER THAN THE 00Z ECMWF. USING A BLEND OF THESE SOLUTIONS...WILL CONTINUE TO CARRY A CHANCE OF SHOWERS/STORMS ON TUESDAY. TEMPERATURES SHOULD CLIMB IN ADVANCE OF THE FRONT TO NEAR OR SLIGHTLY ABOVE NORMAL...BEFORE FALLING BELOW NORMAL TUESDAY NIGHT INTO WEDNESDAY WHEN DRIER AIR ARRIVES. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 100 AM EDT THURSDAY... COMMS ISSUES REMAIN AT KDAN DESPITE AN INTERMITTENT RETURN OF OBSERVATION DATA. AMD NOT SKED CONTINUED IN THE TAF. BATCH OF SHRA/TSRA HEADING NE INTO NW NC WILL BE THE MAIN CONCERN OVERNIGHT OUTSIDE OF DENSE FOG/STRATUS IN AREAS THAT SAW EARLIER HEAVY RAIN. EXPECT SOME OF THE SHOWERS TO THE SW TO LIKELY AFFECT KDAN AND PERHAPS AS FAR NORTH AS THE KBLF-KROA CORRIDOR THROUGH ABOUT 09Z/5AM...THEN NE TO AROUND KLYH BEFORE DAWN. THEREFORE HAVE INCLUDED A VCSH MENTION IN THESE SPOTS OR A FEW TEMPO HOURS FOR REDUCED VSBY IN BOTH SHRA/FOG OVERNIGHT. OTRW FOG SHOULD BECOME AN ISSUE AT TIMES OVERNIGHT ESPECIALLY WHERE IT RAINED...WHICH WILL BE ALL SITES. ATTM...THE FOG WILL ALSO BE DEPENDENT ON CLOUDS. THINK ENOUGH BREAKS TO ALLOW FOG FORMATION. WILL GO MAINLY MVFR/IFR LATE TONIGHT BUT NOT AS WIDESPREAD AS EARLIER GIVEN THICKER CLOUD CANOPY HEADING UP FROM THE SW. FOG WILL FADE BY MID MORNING EXCEPT IN AREAS OVER THE EAST THAT MIGHT STILL BE SEEING SOME SHRA BANDS LINGER. APPEARS CIGS WILL ALSO BE SLOWER TO LIFT GIVEN SO MUCH MOISTURE AROUND SO INCLUDED MORE LOW END VFR BASES AT MOST SPOTS DURING THE MORNING BEFORE BREAKING OUT TO A 4-5K CU FIELD AFTER MIDDAY. KDAN MAY BE THE EXCEPTION WHERE LOWER CIGS LINGER BEFORE MORE SHRA/TSRA DEVELOPS. MODELS KEEPING THE THREAT OF SHRA/TSRA AROUND OVER THE SOUTHEAST CWA THURSDAY...SO KEPT VCTS AT ROA/LYH/DAN...AND ADDED AT KBCB WITH A VCSH AT KBLF/KLWB PER SLOWNESS OF THE FRONT TO PUSH SE AND LINGERING LOW LEVEL MOISTURE WITH HEATING WHICH SHOULD BE BETTER OVER THE WEST/NW. OTRW EXPECT VFR OUTSIDE OF ANY STORMS FOR THE MOST PART. WAVE SHOULD FINALLY TAKE THE NEXT ROUND OF SHRA/TSRA TO THE SE THURSDAY EVENING WITH PERHAPS ENOUGH DRYING TO END CONVECTION AT ALL LOCATIONS AFTER MIDNIGHT. EXTENDED AVIATION... A LOWER PROBABILITY OF PRECIPITATION IS EXPECTED ACROSS THE AREA ON FRIDAY AND SATURDAY AS WEAK HIGH PRESSURE SLIDES IN FROM THE NORTH. MOISTURE AND MORE WIDESPREAD SHRA/TSRA LIKELY TO RETURN FOR THE END OF THE WEEKEND AS THE FRONT RETURNS NORTH RESULTING IN PERIODS OF MVFR CONDITIONS. OTRW PATCHY FOG RESULTING IN LOCAL MVFR TO IFR CONDITIONS LIKELY DURING THE LATE NIGHTS AND EARLY MORNINGS ESPCLY VALLEY LOCATIONS AND WHERE EARLIER AFTERNOON RAINFALL OCCURRED. && .EQUIPMENT... AS OF 100 AM EDT THURSDAY... COMMUNICATIONS OUTAGE CONTINUES WITH KDAN ASOS NOT TRANSMITTING. THE FAA IS AWARE OF THE OUTAGE AND WILL BE WORKING ON IT...BUT NO ESTIMATED TIME OF WHEN IT WILL BE WORKING AGAIN. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS/JH NEAR TERM...AMS/JH/WP SHORT TERM...PH LONG TERM...AMS/PH/WERT AVIATION...AMS/JH/WP EQUIPMENT...WP

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