Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 261913 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 313 PM EDT TUE MAY 26 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 WEDNESDAY/... 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 /WEDNESDAY NIGHT 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 /19Z TUESDAY THROUGH SUNDAY/... AS OF 1245 PM EDT TUESDAY... STARTING TO SEE ISOLATED CONVECTION POP UP ACROSS THE FAR WEST EARLY THIS AFTERNOON WHERE MOISTURE REMAINS DEEPER AND AIDED BY DIFFERENTIAL HEATING. EXPECT THIS AREA TO GRADUALLY FILL IN AND BECOME A BIT MORE ORGANIZED WHICH WILL AFFECT THE KBLF-KLWB CORRIDOR AND POSSIBLY AROUND KBCB IF SHRA/TSRA SPILL FARTHER EAST. THUS WILL CARRY A PREVAILING VCTS/VCSH AND TEMPO IN MORE IN THE WAY OF MVFR TO IFR CONDITIONS PENDING IF A SHOWER OR STORM DIRECTLY IMPACT ONE OF THESE LOCATIONS. OTRW EXPECTING MAINLY 4-6K FT VFR CIGS THIS AFTERNOON WITH LITTLE SHOWER COVERAGE AT KLYH/KDAN WITH ISOLATED POTENTIAL AT KROA. WINDS THIS AFTERNOON WILL REMAIN OUT OF THE SOUTH 5-10KTS...WITH GUSTS 14-18KTS. EXPECTING CONVECTION TO FADE WITH LOSS OF HEATING THIS EVENING AND IN THE WAKE OF A WEAK IMPULSE SLIDING BY TO THE NE. THIS MAY LEAVE MOST OF THE REGION IN VFR UNDER MID DECK WITH PERHAPS SOME MVFR IN FOG THIS EVENING WHERE EARLIER RAIN OCCURRED. NEXT SHORTWAVE TROUGH NOW TO THE SW WILL SLIDE INTO THE AREA LATER TONIGHT WITH AN ASSOCIATED BAND OF SHRA/ISOLATED TSRA SPREADING IN FROM THE SW AFTER MIDNIGHT. GUIDANCE HAS MOST OF THIS AFFECTING THE MOUNTAINS MAINLY KBLF/KLWB LATE AND EAST TO KBCB/KROA AROUND DAYBREAK IF NOT A BIT SOONER. THUS INCLUDING A PERIOD OF PREVAILING MVFR IN SHRA EARLY WEDNESDAY MORNING WITH SOME OF THIS PERHAPS SLIDING INTO KROA/KLYH WEDNESDAY MORNING WITH POSSIBLE MVFR. LOW CLOUDS AHEAD OF THIS FEATURE MAY ALSO BRING MVFR TO IFR CIGS ALONG AND EAST OF THE BLUE RIDGE OVERNIGHT BUT IFFY GIVEN MODEL TENDENCY TO BRING IN STRATUS SO HELD OFF GOING THAT PESSIMISTIC FOR NOW. EXTENDED AVIATION DISCUSSION... WEDNESDAY...THE UPPER DISTURBANCE WILL CONTINUE TO SHIFT EAST ACROSS THE REGION WITH DECREASING ACTIVITY OVER THE WEST BY MIDDAY LIKELY REDEVELOPING ALONG AND EAST OF THE BLUE RIDGE WEDNESDAY AFTERNOON. TIMING OF THIS WEAK TROUGH TRICKY AS COULD SEE MORE DRYING ALOFT OVER THE WEST BY AFTERNOON PER LATEST BUFKIT SOUNDINGS WITH CONVERGENCE OVER THE EAST. LATEST GUIDANCE EVEN SUGGESTS A RETURN TO VFR WEST OF THE BLUE RIDGE WEDNESDAY AFTERNOON WITH PERIODS OF MVFR/IFR OUT EAST PENDING CONVECTIVE COVERAGE. THIS BOUNDARY DRIFTS INTO EASTERN VA THU BEFORE WASHING OUT...SO ACTIVITY COULD BE SOMEWHAT MORE FOCUSED ALONG- 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. 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. WINDS REMAINING SW 5-10KTS THROUGH MUCH OF THE PERIOD...EXCEPT VARIABLE AND GUSTY IN/NEAR THUNDERSTORMS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...DS LONG TERM...DS AVIATION...JH/PM

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