Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 061345 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 945 AM EDT WED MAY 6 2015 .SYNOPSIS... UPPER LEVEL HIGH PRESSURE WILL REMAIN OVER THE AREA TODAY THROUGH THURSDAY. A WEAK BACKDOOR COLD FRONT WILL DRIFT SOUTH INTO THE AREA BY EARLY THURSDAY BEFORE DISSIPATING THURSDAY NIGHT INTO FRIDAY. DEVELOPING LOW PRESSURE OFF THE SOUTHEAST COAST SHOULD DRIFT NORTH TO ALONG THE COAST OF THE CAROLINAS BY THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 940 AM EDT WEDNESDAY... NO MAJOR CHANGES WERE MADE TO THE OVERALL FORECAST PICTURE FOR TODAY. HOWEVER...ONE ADJUSTMENT MADE WAS THE TREND OF THE CLOUD COVER THE REMAINDER OF THE MORNING INTO EARLY AFTERNOON HOURS. A SWATH OF ALTO-CU ACROSS THE NORTHERN HALF OF THE AREA HAS PERSISTED ALL MORNING. WHILE WE DO EXPECT THIS CLOUD DECK TO MIX OUT BY NOONTIME AS WE TRANSITION TO SURFACE BASED HEATING CUMULUS CLOUDS...UNTIL THAT HAPPENS...THE FORECAST WARRANTS A GREATER AMOUNT OF CLOUD COVER FORECAST IN THE NORTH THROUGH AT LEAST MIDDAY. AS OF 223 AM EDT WEDNESDAY... UPPER LEVEL RIDGING WILL REMAIN IN PLACE ACROSS THE REGION INTO TONIGHT AS A WEAK BACKDOOR COLD FRONT EDGES IN FROM THE NORTH/NE BY SUNRISE ON THURSDAY. BOOST IN MOISTURE AHEAD OF THE FRONT WITH FORECAST PWATS INCREASING TO AROUND 1.5 INCHES COMBINED WITH HIGHER 85H THETA-E OVER THE MOUNTAINS SHOULD LEAD TO A BIT MORE CONVECTIVE COVERAGE THIS AFTERNOON/EVENING. HOWEVER WITH RIDGING OVERHEAD AND MODEST CAPE VALUES OF ONLY 500-1K J/KG MAINLY FAR WEST/NORTH...DEGREE OF SHRA/TSRA COVERAGE REMAINS IFFY ESPCLY IN REGARDS TO ORGANIZATION UNDER SUCH WEAK FLOW AND MAINLY LOW LEVEL FORCING. MOST MODEL SOLUTIONS DO DEVELOP SCATTERED AFTERNOON COVERAGE...STARTING OVER THE FAR NW AROUND MIDDAY AND THEN ALONG THE BLUE RIDGE PER WEAK SE FLOW CONVERGENCE. LATEST HRRR/SPC WRF/GFS ARE THE WETTEST AND SPILL CONVECTION FARTHER EAST... WHILE THE NAM/HIRES/EC SOLUTIONS REMAIN MORE SCATTERED NATURE AND FARTHER NORTH WITH MORE ORGANIZED COVERAGE. THINK COULD BE A PERIOD OF LIKELY COVERAGE NW AND RIDGES WHERE MORE LOCALIZED DIFFERENTIAL HEATING GIVES A BOOST BUT FOR NOW HOLDING OFF...AND ONLY BOOSTING POPS TO HIGHER CHANCE MAINLY NORTH-WEST. ISOLATED STRONGER TSRA POSSIBLE BUT MORE OF AN ISOLATED HEAVY RAIN THREAT GIVEN LIGHT STEERING AND LIKELY OUTFLOW DRIVEN REDEVELOPMENT. FAR SOUTH/SE LOCATIONS MAY END UP DRY FOR THE MOST PART SO TRIMMED POPS THERE GIVEN LACK OF LIFT. OTRW PARTLY SUNNY AND STILL QUITE WARM AHEAD OF THE FRONT WITH HIGHS MOSTLY UPPER 70S TO MID 80S. COVERAGE MAY LINGER MOUNTAINS WITH PERHAPS SOME OF THIS SPILLING EAST OF THE BLUE RIDGE EARLY THIS EVENING IF A CLUSTER ORGANIZES BEFORE FADING WITH LOSS OF HEATING BEFORE MIDNIGHT. THEREFORE KEPT IN SOME LOW POPS MAINLY NORTH HALF THIS EVENING BEFORE TURNING PC WITH PATCHY FOG OVERNIGHT. LOWS MOSTLY IN THE MUGGY 50S WITH SOME SPOTS ALONG THE RIDGES LIKELY STAYING ABOVE 60 OVERNIGHT. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 315 AM EDT WEDNESDAY... AN AREA OF WEAK HIGH PRESSURE WILL REMAIN OVER THE MID ATLANTIC THROUGH THE DAY THURSDAY. THIS SHALLOW WEDGE MAY LINGER OVER THE AREA THURSDAY NIGHT WITH THE HELP OF A SUB-TROPICAL LOW WOBBLING OFF THE SOUTHEAST COAST. EASTERLY FLOW FROM BOTH SYSTEMS WILL BRING AN INCREASE IN MOISTURE INTO THE AREA EACH PERIOD. THE MORE MOISTURE THE BETTER CHANCE FOR SHOWERS. HOWEVER...WE WILL KEEP POPS LOW (20- 30 PERCENT) THROUGH THE FORECAST PERIOD FOR A COUPLE OF REASONS. THE FIRST REASON IS THAT THE EASTERN PORTION OF FORECAST AREA WILL BE UNDER A SUBSIDENCE REGION OF THE SOUTHEAST COASTAL LOW THURSDAY AND THURSDAY NIGHT. THE MOUNTAINS WILL BE JUST OUTSIDE OF THIS REGION AND COULD SEE HIT AND MISS SHOWERS THURSDAY AFTERNOON...FADING IN THE EVENING. THE SECOND REASON TO KEEP POPS LOW IS CONFIDENCE. WITH A STUBBORN UPPER LEVEL RIDGE OVER THE MID ATLANTIC...THE COASTAL LOW`S FORECAST TRACK IS UNCERTAIN AND COULD WOBBLE AROUND THE CAROLINAS OVER THE WEEKEND. THE THIRD REASON IS TIMING OF SHOWERS. IF THIS LOW TRACKS INLAND...TIMING FEEDER-BANDS TRACKING ACROSS THE AREA WILL BE DIFFICULT. THE NAM BRING THE FIRST BAND ACROSS SOUTHSIDE LATE THURSDAY NIGHT...WHILE THE GFS TIMING IS LATE IN THE DAY FRIDAY. DRY AIR ENTRAINING INTO THE LOW FRIDAY AND FRIDAY NIGHT COULD ALSO KEEP SHOWERS CLOSER TO THE CENTER AND NOT ENTER THE FORECAST AREA AT ALL. TEMPERATURES WILL ALSO BE TRICKY THROUGH THE PERIOD. WITH WEAK STEERING FLOW AND A SHALLOW WEDGE...TEMPERATURES WILL WARM TO NEAR 80F ACROSS THE AREA THURSDAY. ON FRIDAY...MORE CLOUDS AND CONTINUED EASTERLY FLOW WILL KNOCK DOWN DAYTIME TEMPERATURES INTO THE MID TO UPPER 70S. DEPENDING ON SHOWER ACTIVITY...TEMPERATURES COULD BE COOLER. DESPITE SHOWERS OR NOT...DEW POINTS WILL INCREASE THROUGH THE PERIOD SO PREPARE YOURSELF FOR MUGGY SUMMER-LIKE CONDITIONS. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 345 PM EDT TUESDAY... UPPER LEVEL RIDGING ACROSS THE SOUTHEAST AND MID ATLANTIC IS EXPECTED TO MOVE LITTLE THROUGH THE WEEKEND INTO THE BEGINNING OF THE NEXT WORKWEEK. AS SUCH...EXPECT THE TREND OF SUMMERLIKE WEATHER TO CONTINUE. THE MAIN CONCERN THROUGH THE PERIOD REMAINS THE TRACK OF A LOW APPROACHING THE CAROLINA COAST...POTENTIALLY PUSHING A PLUME OF TROPICAL MOISTURE ACROSS OUR AREA WHICH DAYTIME-HEATING DRIVEN SHOWERS AND THUNDERSTORMS MAY FEED OFF OF. THE THREAT FOR ANY SEVERE THUNDERSTORMS REMAIN ISOLATED DURING THIS TIME...HOWEVER ABUNDANT MOISTURE AND LIGHT UPPER LEVEL WINDS INDICATE A THREAT FOR SLOW MOVING CELLS CAPABLE OF PRODUCING LOCALLY HEAVY RAIN. SHOULD THE LOW REMAIN OFFSHORE...FURTHER AWAY FROM OUR AREA...THE HEAVY RAIN THREAT WILL BE REDUCED. WEATHER FORECAST MODELS ARE STILL TRYING TO GET A HANDLE ON WHAT TRACK THE LOW WILL TAKE...SO THE SITUATION WILL BE MONITORED CLOSELY OVER THE NEXT FEW DAYS. RAINFALL AND INCREASED CLOUD COVER ALSO HAS THE POTENTIAL TO AFFECT DAYTIME TEMPERATURES...AND THEREFORE AFTERNOON HIGHS ALSO REMAIN SOMEWHAT IN QUESTION. WITH THIS AFTERNOON`S FORECAST PACKAGE...HAVE AFTERNOON HIGHS RANGING FROM THE MID/UPPER 70S WEST TO THE LOW 80S EAST EACH DAY...WHILE OVERNIGHT LOWS WILL BE IN THE UPPER 50S AND LOW 60S. INCREASED RAINFALL HAS THE POTENTIAL TO KEEP AFTERNOON HIGHS A FEW DEGREES LOWER ON SATURDAY HOWEVER. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... AS OF 645 AM EDT WEDNESDAY... FOG HAS BEEN LIMITED TO MORE PATCHY NATURE EARLY THIS MORNING GIVEN DRY AIR AND MID DECK THAT HAS PERSISTED ACROSS THE NORTH/WEST FOR MUCH OF THE NIGHT. COULD STILL SEE A PERIOD OF MVFR/IFR IN FOG AT KLWB FOR ANOTHER COUPLE OF HOURS BEFORE CONDITIONS IMPROVE AND POSSIBLE BRIEF MVFR/VFR IN FOG AT KLYH/KDAN. OTRW THINKING MAINLY VFR FROM MID MORNING MORNING ONWARD WITH MID DECK GIVING WAY TO 4-6K SCTD CU FIELDS WITH HEATING BY MIDDAY...THEN BKN CIGS OVER THE NORTH AND WEST THIS AFTERNOON. CONVECTION SHOULD BE A BIT MORE WIDESPREAD ACROSS THE NORTH/WEST LATER TODAY AHEAD OF A WEAK BACKDOOR COLD FRONT AND AIDED BY LIGHT SE FLOW INCLUDING DIFFERENTIAL HEATING. MODELS SUGGEST BEST COVERAGE AROUND KLWB TO INIT AND IN A RIBBON ALONG THE BLUE RIDGE. HOWEVER ORGANIZATION STILL LOOKS TO BE RATHER SCATTERED UNTIL PERHAPS LATE IN THE DAY WHEN CLUSTERS/BANDS MERGE. THUS WILL KEEP MOST CONVECTION OUT OF THE PREVAILING GROUPS BUT INCLUDE MORE OF A VCTS FLAVOR MOUNTAINS FOR A BIT MORE THUNDER PER WEAK INSTABILITY AND MORE FORCING THAN TUESDAY. KEPT SHRA/TSRA OUT OF ALL EASTERN SITES WITH GUIDANCE SHOWING MOST FOCUS OVER THE WEST BUT COULD SEE SOME COVERAGE EVENTUALLY WORK OFF THE MOUNTAINS TOWARD KLYH LATE IN THE DAY. CONVECTION MAY LINGER INTO THE EVENING WHILE POSSIBLY WORKING INTO EASTERN SECTIONS BEFORE FADING BUT TOO IFFY TO INCLUDE VCSH/VCTS MENTION THERE FOR NOW. OTHERWISE SHOULD SEE COVERAGE END WEST BEFORE MIDNIGHT AND LIKELY GIVE WAY TO ANOTHER ROUND OF FOG/STRATUS LATE AT MOST LOCATIONS. A BACKDOOR COLD FRONT WILL IMPACT THE AREA THURSDAY WITH ADDED AFTERNOON SHOWERS AND STORMS MAINLY OVER THE FAR WESTERN SECTIONS. SUB- VFR CONDITIONS WILL BE ASSOCIATED UNDER THE CORES OF THE STRONGEST CELLS...AND THEN DURING THE LATE NIGHT AND EARLY MORNING HOURS WITH LIGHT FOG IN THE VALLEYS. CONFIDENCE IN FORECAST PARAMETERS FRIDAY THROUGH SUNDAY IS LOW TO MODERATE. MODEL GUIDANCE IS HIGHLY VARIABLE IN REGARDS TO THE IMPACT A SLOW MOVING AREA OF UPPER LEVEL LOW PRESSURE ACROSS THE SOUTHEAST U.S. WILL HAVE ON THE REGION. SOME GUIDANCE HAS THE LOW CENTERED STILL OFF THE SOUTH CAROLINA COAST ON SATURDAY INTO SUNDAY...WHILE OTHERS HAVE IT ALONG THE NORTH CAROLINA...SOUTH CAROLINA STATE LINE IN A MORE OR LESS LOOPING SCENARIO. THE FORMER SOLUTION...AND OTHERS LIKE IT...POSE LIMITED IF ANY INFLUENCE ON OUR REGION. THE LATTER AS A WETTER...WINDIER...AND ONE MORE SUBJECT TO SUB-VFR CONDITIONS FOR THE MAJORITY OF THE AREA. THE CONSENSUS SCENARIO STILL HAS DAYTIME...MOUNTAIN FOCUSED ISOLATED TO SCATTERED SHOWERS AND STORMS DEVELOPING ACROSS THE REGION...WITH MAINLY VFR CONDITIONS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...DS/JH NEAR TERM...DS/JH SHORT TERM...RCS LONG TERM...NF AVIATION...DS/JH/WP

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