Area Forecast Discussion
Issued by NWS Blacksburg, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KRNK 270637 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 237 AM EDT WED MAY 27 2015 .SYNOPSIS... HIGH PRESSURE OFF THE SOUTHEAST COAST WILL MAINTAIN A BROAD SOUTHERLY FLOW OF DEEP MOISTURE INTO THE REGION THROUGH MUCH OF THIS WEEK. AN UPPER LEVEL TROUGH OF LOW PRESSURE TO THE NORTHWEST WILL GRADUALLY SLIDE EAST AND INTERACT WITH THIS MOISTURE ACROSS THE AREA. THIS WILL RESULT IN PERIODIC ROUNDS OF SHOWERS AND STORMS OVER THE NEXT FEW DAYS. && .NEAR TERM /THROUGH TODAY/... AS OF 600 PM EDT TUESDAY... MADE SOME ADJUSTMENTS...MAINLY TO POP/WX GRIDS AT THIS TIME IN CONCERT WITH LATEST HRRR AND NSSL WRF SIMULATED RADAR FORECASTS...WHICH SEEM TO BE IN LINE WITH LATEST SYNOPTIC SCALE MODEL TRENDS AS WELL REGARDING PRECIPITATION. INITIAL AREA...NOW EXITING THE SOUTHERN SHENANDOAH VALLEY INTO LWX CWA...WILL CONTINUE TO MOVE NORTHEAST AWAY FROM THE AREA. THE NEXT AREA TO WATCH IS NOW DOWN IN GEORGIA PACKING QUITE A PUNCH THERE. FEEL THAT THE REMNANTS OF THIS WILL WORK ITS WAY NORTHEAST INTO OUR CWA TOWARD MIDNIGHT AND SEVERAL HOURS THEREAFTER...ALBEIT IN A DIMINISHING STATE. THUS...HAVE DECREASED POPS FOR THE NEXT FEW HOURS...THEN INCREASED FROM THE SOUTHWEST FROM 06Z ONWARD TOWARD DAYBREAK WESTERN HALF. USED A BLEND OF SYNOPTIC AND MESOSCALE MODEL POPS THROUGH 12Z...LEANING HEAVILY TOWARD THE HRRR. TEMPS WERE A LITTLE TOO WARM IN RAIN COOLED AREAS AND A LITTLE TOO COOL ACROSS THE PIEDMONT. MADE SOME MINOR ADJUSTMENTS TO BRING BETTER IN LINE WITH CURRENT OBSERVATIONS. OTHERWISE...REMAINING GRIDS LOOK GOOD AT THIS TIME AND DID NOT NEED ADJUSTMENT. AS OF 215 PM EDT TUESDAY... BANDS OF CONVECTION CONTINUE TO DEVELOP AND PUSH SLOWLY NE MAINLY JUST WEST OF THE BLUE RIDGE WHERE 1000 J/KG ML CAPE EXISTS AND MOISTURE IS DEEPER NEAR A FAINT SHORTWAVE LIFTING NE. MOST SHORT TERM GUIDANCE CONTINUES TO FOLLOW SUIT WITH THE LATEST HRRR AND HIRES MODELS SLIDING CLUSTERS OF DEEPER CONVECTION NE...PASSING ACROSS THE HIGHLANDS AND SRN SHENANDOAH VALLEY BY EARLY THIS EVENING. EITHER SIDE OF THIS AXIS...EXPECTING ONLY ISOLATED COVERAGE MAINLY ALONG THE BLUE RIDGE WITH LITTLE OVER THE FAR EAST PER RIDGING...AND FAR WEST WHERE IN BETWEEN LIFT SOURCES. THUS WILL HAVE CONTINUED LIKELY POPS FOR A WHILE LONGER OVER PARTS OF THE WEST INTO THIS EVENING AND LOW TO SLIGHT ELSEWHERE BEFORE TRIMMING BACK TOWARD SUNSET. MAIN CONCERN OVERNIGHT SHIFTS TO ENERGY NOW WELL TO THE SW ALONG THE LEADING EDGE OF THE NEXT UPSTREAM 5H TROUGH THAT WILL HELP EJECT A SHORTWAVE NE INTO THE WESTERN PORTIONS AFTER MIDNIGHT. MODELS DISAGREE ON THE DEGREE OF RESIDUAL DEEP CONVECTION WITH THIS FEATURE WITH SOME HOLDING IT TOGETHER OVER THE FAR WEST LATE AND OTHERS FIZZLING COVERAGE INTO LIGHTER SHOWERS BY DAYBREAK. GIVEN SPEED OF MOVEMENT WITH THIS FEATURE AND PROGGED STRONG 85H THETA-E ALONG WITH GOOD MOISTURE TRANSPORT OFF MOST GUIDANCE WILL REINTRODUCE LIKELY POPS WEST AFTER THIS EVENING...AND SLIDE BETTER COVERAGE TOWARD THE BLUE RIDGE EARLY IN THE MORNING AS CONVECTION WEAKENS. LEFT TEMPS CLOSE TO THE LATEST MAV MOS WITH LOWS MOSTLY IN THE 60S PER DEEP MOISTURE AROUND. WEAK DAMPENING WAVE SLIDES EAST ACROSS THE REGION WEDNESDAY FOLLOWED BY ANOTHER WEAK SHORTWAVE OVER THE SW LATE IN THE DAY. DESPITE DEEP MOISTURE AND HIGH PWATS ESPCLY EAST...TIMING OF THIS FEATURE AND DEGREE OF HEATING/INSTABILITY REMAINS IN QUESTION. LATEST SREF CONSENSUS WOULD SUGGEST INITIAL BATCH OF SHRA WILL FADE NEAR THE BLUE RIDGE WED MORNING FOLLOWED BY REDEVELOPMENT ACROSS EASTERN SECTIONS IN THE AFTERNOON WHERE HEATING AND FORECAST CAPES APPEAR BEST. POTENTIAL MORE OF A WEST WIND AND DRYING ALOFT PER LATEST SOUNDINGS COULD LIMIT THINGS IN THE MOUNTAINS WHERE CLOUDS MAY LINGER LONGER. THEREFORE TRIMMED BACK POPS A BIT BUT UPPED ALONG/JUST EAST OF THE BLUE RIDGE WHERE CONVERGENCE LOOKS BETTER. HOWEVER OVERALL LIKELY TO CHANCE POPS WITH SOME HEAVY RAIN POTENTIAL GIVEN EVEN LIGHTER STEERING THAT TODAY. FOLLOWED CLOSER TO THE COOLER MAV TEMPS GIVEN MORE CLOUDS AND MOISTURE/SHRA AROUND EARLY. && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... AS OF 225 PM EDT TUESDAY... THE AREA RESETS IN THE SENSE THAT THE EXTRA INFLUENCE OF AN UPPER TROUGH HEADING THROUGH THE NORTHERN END OF THE UPPER RIDGE ENDS. WHAT IS LEFT OF THE TROUGH IS ALMOST WASHED OUT AND HEADS THROUGH SOUTHEAST CANADA WEDNESDAY NIGHT INTO THURSDAY. WHAT REMAINS IS THE PERSISTENT SOUTHEAST U.S. UPPER RIDGE...AND THERE WILL BE A NEW UPPER TROUGH DEEPENING IN NORTHERN PLAINS STATES. THIS WILL PLACE OUR AREA IN A SCENARIO COMPARABLE TO THE CONDITIONS OF TODAY. THERE WILL BE PLENTY OF MOISTURE IN THE LOW LEVELS WITH GOOD DAYTIME HEATING. UPPER LEVEL SUPPORT WILL BE AT A MINIMUM...SO SHOWER AND THUNDERSTORM ACTIVITY DURING THIS PORTION OF THE FORECAST WILL BE PRIMARILY DIURNAL IN NATURE. A ROUGE BIT OF ENERGY COULD GET EJECTED EASTWARD OFF THE MAIN UPPER TROUGH TO HELP ENHANCE OR PROLONG COVERAGE...BUT AT THIS TIME...PROJECTING ACCURATELY WHEN OR IF THAT HAPPENS WOULD BE CHALLENGING. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 300 PM EDT TUESDAY... SATURDAY INTO SUNDAY THE NEXT UPPER TROUGH MAKES HEADWAY INTO THE RIDGE...JUST LIKE ITS PREDECESSOR A FEW DAYS PRIOR. ANTICIPATE THIS FEATURE TO GENERATE A GREATER COVERAGE OF SHOWERS AND STORMS...ESPECIALLY ACROSS THE WESTERN HALF OF THE AREA. THIS ASSOCIATED SURFACE COLD FRONT IS EXPECTED TO THE AREA SUNDAY NIGHT....AND STALL OVER OR JUST TO OUR SOUTH ON MONDAY. THE FRONT WILL BUCKLE BACK NORTH EARLY NEXT WEEK AS SOUTHERLY FLOW AROUND THE WEST SIDE OF THE HIGH RE-ESTABLISHES ITSELF. THIS WILL KEEP THE CHANCE OF SHOWERS AND STORMS IN THE FORECAST...AGAIN WITH THE FOCUS WITH THE GREATEST CONCENTRATION IN THE WEST. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
AS OF 200 AM EDT WEDNESDAY... FORECAST AREA WAS WELL INTO A MOIST AIR MASS WITH MULTI-LAYER CLOUD COVER. MOST CLOUD BASES ARE AOA 5KFT AGL...BUT THERE IS A SCT LAYER BETWEEN 1500-2500 FT THAT MAY BECOME BKN ATTMS ESP WHEN ASSOCIATED WITH SHRA. WITH MOIST ENVIRONMENT CAN`T RULE OUT POTENTIAL FOR SHRA BUT NOT CONFIDENT ON COVERAGE. SHOWERS ACROSS THE AREA DURING THE OVERNIGHT HAVE BEEN DECREASING. ONCE SOLAR INSOLATION BEGINS WEDNESDAY...EXPECT RENEWED ACTIVITY WITH INCREASING COVERAGE DURING THE AFTERNOON AND EVENING. NAM BUFKIT AND OTHER SHORT TERM MODELS BRING MVFR CLOUDS INTO KLYH AND KDAN OVERNIGHT. LOW CONFIDENCE AS TO HOW LOW CEILINGS WILL BE BUT ANY MVFR CLOUDS WILL ERODE AFTER SUNRISE ON WEDNESDAY. WINDS NEAR THE SURFACE ARE MAINLY OUT OF THE SOUTH BUT MAY BRIEFLY TURN TO THE WEST OVER THE MOUNTAINS WEDNESDAY AFTERNOON AS THE SHOWERS AND THUNDERSTORMS DEVELOP OVR MTNS AND PROGRESS INTO THE FOOTHILLS AND PIEDMONT. EXTENDED AVIATION DISCUSSION... SHOWERS AN THUNDERSTORMS MAY BE SOMEWHAT MORE FOCUSED ALONG AND EAST OF THE BLUE RIDGE THURSDAY. FOR THE REMAINDER OF THE PERIOD...A MOIST UNSTABLE AIR MASS REMAINS ACROSS THE REGION WITH WEAK TRIGGERING MECHANISMS AND DYNAMICS. A FRONTAL SYSTEM WILL APPROACH FROM THE NORTH BY THE WEEKEND...BUT WILL LIKELY REMAIN WELL NORTH OF THE CWA THROUGH SUNDAY. THUS...NO CHANGE IN AIR MASS OR THE OVERALL SYNOPTIC PATTERN IS EXPECTED THROUGH THE PERIOD. EARLY MORNING LOW CLOUDS/FOG AND ASSOCIATED IFR-LIFR CIGS/VSBYS BECOME INCREASINGLY MORE LIKELY THROUGH THE PERIOD...ESPECIALLY FOLLOWING ANY LATE DAY RAINFALL. OTHERWISE...EXPECT MOSTLY VFR-MVFR CIGS OUTSIDE HEAVIER SHOWERS/THUNDERSTORMS.
-- End Changed Discussion --
&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH/RAB SHORT TERM...DS LONG TERM...DS AVIATION...PM

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.