Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 261701 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 101 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 TONIGHT/... AS OF 945 AM EDT TUESDAY... MOISTURE CONTINUES TO INCREASE ACROSS THE REGION THIS MORNING AS EVIDENCED VIA NEARLY AN INCH JUMP IN PWATS OFF MORNING SOUNDINGS SINCE YESTERDAY ALONG WITH A MUCH DEEPER SOUTH/SW FLOW. THIS DEEPER MOISTURE ALSO IN CONJUNCTION WITH A WEAK TROUGH AXIS JUST WEST OF THE MOUNTAINS WHERE SPOTTY SHOWERS CONTINUE TO LINGER. HOWEVER CLOUD COVER ALSO QUITE WIDESPREAD ACROSS THE WEST WHERE WILL BE SLOW TO GET GOOD HEATING UNTIL EARLY/MID AFTERNOON GIVEN SURGE IN LOW LEVEL MOISTURE. THIS SHOULD LEAD TO TO SOME SCATTERING OR CLUSTERS OF SHOWERS AND STORMS PER FORECAST 1K J/KG CAPES BUT MAINLY BLUE RIDGE WEST AS LESS MOISTURE IN THE EAST PER LEFTOVER WEAK RIDGING ALOFT FOR NOW. THIS SIMILAR TO THE LATEST HRRR BUT APPEARS IT MAY BE OVERDONE WITH EASTWARD EXPANSE SO FOLLOWING CLOSER TO THE LATEST NAM WHICH HAS THE BEST COVERAGE WESTERN THIRD...AND ONLY ISOLATED OUT TO THE BLUE RIDGE AND LITTLE PIEDMONT. GIVEN RATHER WIND WINDS ALOFT AND LACK OF SHEAR/LAPSES...NOT EXPECTING MUCH SEVERE THREAT OUTSIDE OF PULSE NATURE STRONGER CELLS...WHILE APPEARS ENOUGH MOVEMENT TO LIMIT ANY FLOODING THREAT UNLESS SOME TRAINING OCCURS. OTRW CUT BACK ON WESTERN POPS TO INIT THIS MORNING...FOLLOWED BY INCREASING CHANCES EARLY/MID AFTERNOON WITH LIKELY POPS FAR WEST LATE. TEMPS MAY BE DAMPENED A BIT VIA EARLY CLOUDS AND DEVELOPING CONVECTION WESTERN MOUNTAINS...SO TRIMMED BACK HIGHS A FEW DEGREES THERE...BUT KEPT 80-85 FROM THE BLUE RIDGE EAST WHERE MORE SUN LIKELY. PREVIOUS VALID DISCUSSION AS OF 500 AM EDT TUESDAY... INCREASING CLOUD COVER IS ANTICIPATED TODAY AS SOUTHERLY WINDS TRANSPORT MOISTURE INTO THE AREA FROM THE GULF OF MEXICO. DEWPOINTS WILL TREND UPWARD AND COMBINE WITH DAYTIME HEATING TO YIELD SCATTERED SHOWERS AND THUNDERSTORMS. HIGH PRESSURE WHICH PASSED OVERHEAD DURING THE HOLIDAY WEEKEND PROVIDING THE NEAR CLOUD FREE CONDITIONS IS NOW POSITIONED JUST OFF THE SOUTHEAST ATLANTIC COAST. LOSS OF STRONG SUBSIDENCE WILL NOW OPEN THE DOOR FOR SHOWERS PER INCREASING MOIST SOUTHERLY FLOW ON THE WESTERN PERIPHERY OF THE ANTICYCLONE. DEWPOINTS CLIMBING INTO THE 60S ALONG WITH DAYTIME HEATING WILL RESULT IN INCREASING INSTABILITY AND THE FORMATION OF SCATTERED SHOWERS AND THUNDERSTORMS. SHOWER ACTIVITY TODAY IS EXPECTED TO BE MOST PRONOUNCED OVER THE MOUNTAINS...PRIMARILY ALONG AND WEST OF THE BLUE RIDGE. AN UPPER LEVEL TROUGH OF LOW PRESSURE OVER THE MID SECTION OF THE COUNTRY IS SLOWLY MOVING EAST WITH NUMEROUS SHOWERS/STORMS. OUTFLOW FROM SOME OF THIS ACTIVITY WILL LIKELY REACH OUR WESTERN MOUNTAINS TONIGHT ALLOWING FOR A CONTINUED THREAT FOR DEEP CONVECTION DURING THE OVERNIGHT. TEMPERATURES TODAY WILL BE SIMILAR TO MONDAY...MAYBE EVEN A DEGREE OR TWO LOWER IN THE MOUNTAINS PER INCREASING CLOUD COVER. DEWPOINTS HOWEVER...WILL BE ON THE INCREASE...AND OFFSET ANY PERCEIVED COOLING...THE HIGHER HUMIDITY RESULTING IN HIGHER APPARENT TEMPERATURES WITH THE AIR HAVING MORE OF A MUGGY FEEL. MINIMUM TEMPERATURES TONIGHT WILL LIKELY REMAIN AOA 60...HIGHER DEWPOINTS AND CLOUD COVER LIMITING THE RADIATIVE COOLING EFFECTS. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... AS OF 500 AM EDT TUESDAY... EXPECT SCATTERED SHOWERS AND THUNDERSTORMS FOR MUCH OF THE AREA ON WEDNESDAY AS AN UPPER LEVEL TROUGH PASSES ACROSS THE APPALACHIAN CHAIN. THE TROUGH IS EXPECTED TO BE CLOSE ENOUGH TO OUR WESTERN BORDER SUCH THAT SHOWER ACTIVITY WILL BE ONGOING AT THE START OF THE DAY ACROSS THE MOUNTAINS. BEST DYNAMICS/STRONGEST INSTABILITY ASSOCIATED WITH THE TROUGH WILL REMAIN NORTH OF THE AREA. IN ADDITION...RAINFALL AND WIDESPREAD CLOUD COVER EARLY IN THE DAY WILL LIMIT HEATING AND SURFACE-BASED INSTABILITY...AND DO NOT EXPECT ORGANIZED SEVERE THUNDERSTORM ACTIVITY...ALTHOUGH A FEW STRONG STORMS WILL STILL BE POSSIBLE DURING THE AFTERNOON AND EVENING. ON THE OTHER HAND...WITH DEEP GULF MOISTURE IN PLACE...WILL HAVE TO KEEP AN EYE OUT FOR LOCALLY HEAVY RAIN...AS WELL AS THE POSSIBILITY OF ISOLATED/MINOR FLOODING ISSUES. UPPER LEVEL RIDGING WILL REDEVELOP ON THURSDAY ACROSS THE SOUTHEAST/ MID ATLANTIC STATES. WHILE WEAK UPPER LEVEL DISTURBANCES WILL STILL PASS ACROSS THE AREA...SHOWER AND THUNDERSTORM ACTIVITY FOR THURSDAY AND FRIDAY WILL BE DRIVEN MORE BY DAYTIME HEATING OF THE SOUPY AIR. CONVECTION WILL INCREASE LATE EACH MORNING...PEAK DURING EARLY EVENING...AND WILL DIMINISH AFTER SUNSET...ALTHOUGH DO NOT THINK RAINFALL WILL GO AWAY COMPLETELY EACH NIGHT AS SPOTTY SHOWERS LINGER ACROSS THE AREA. WITH LITTLE UPPER LEVEL SUPPORT...EXPECT ONLY LOCALLY STRONG THUNDERSTORMS EACH DAY WITH NO ORGANIZED ACTIVITY. UPPER LEVEL RIDGING WILL MAKE FOR LIGHT WINDS ALOFT AND SLOW STORM MOVEMENT...SO THE THREAT OF LOCALLY HEAVY RAIN WILL CONTINUE THROUGH THE END OF THE WORKWEEK. INCREASED CLOUD COVER DURING THE PERIOD WILL LIMIT HEATING...HOLDING AFTERNOON HIGHS IN THE MID TO UPPER 70S ACROSS THE MOUNTAINS...AND THE LOW/MID 80S EAST OF THE BLUE RIDGE. WITH NO CHANGE IN AIRMASS EXPECTED...EXPECT MUGGY CONDITIONS EACH NIGHT...WITH LOWS HOLDING IN THE LOW/MID 60S AREAWIDE. && .LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 400 AM EDT TUESDAY... IN EXTENDED PERIOD THE SYNOPTIC SETUP DOES NOT REALLY CHANGE TOO MUCH. THE RIDGE OVER THE ATLANTIC COAST CONTINUES TO DIRECT A STEADY SUPPLY OF WARMTH AND MOISTURE INTO THE EASTERN SEABOARD. AT THE SAME THERE WILL BE A CHANCE FOR SOMEWHAT MORE ORGANIZED ACTIVITY ASSOCIATED WITH A SLOW-MOVING BOUNDARY TRAILING FROM A SURFACE LOW TRACKING INTO THE GREAT LAKES ON SATURDAY. THE ECMWF SHOWS THIS FEATURE BECOMING QUASI-STATIONARY TO OUR NORTH OH-PA-NJ AXIS ON LATE SATURDAY INTO MONDAY AND THEN POSSIBLY SLIDING FARTHER SOUTH INTO OUR AREA BY LATER MONDAY. GFS PERHAPS A BIT FURTHER NORTH WITH THIS FEATURE AND MORE PROGRESSIVE AND EVENTUALLY BUILDS HIGH PRESSURE OVER THE NORTHEAST WHICH PUSHES A BACKDOOR TYPE FRONT TOWARD THE AREA LATE SUNDAY. GFS ENSEMBLES SOLUTION THROUGH THIS PERIOD MOSTLY MAINTAIN THE RIDGE OVER THE SOUTHEAST IN A POSITION THAT WOULD HOLD THE BOUNDARY AND ASSOCIATED PRECIPITATION FURTHER NORTH. HPC GUIDANCE CLOSER TO EURO SOLUTION AND WAS BASICALLY FOLLOWED FOR THE EXTENDED. THIS ALL MEANS CONTINUED WELL ABOVE NORMAL TEMPERATURES...ESPECIALLY AT NIGHT...ALONG WITH ABUNDANT MOISTURE AND HIGH CHANCES FOR AT LEAST AFTERNOON/EVENING CONVECTION. && .AVIATION /18Z 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/PM NEAR TERM...JH/PM SHORT TERM...NF LONG TERM...NF/PC AVIATION...JH/PM

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