Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 261153 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 753 AM EDT TUE MAY 26 2015 .SYNOPSIS... HIGH PRESSURE IS CENTERED JUST OFF THE SOUTHEAST ATLANTIC COAST. AN UPPER LEVEL TROUGH OF LOW PRESSURE IS OVER THE CENTRAL UNITED STATES AND WILL SLOWLY PROGRESSING EASTWARD TOWARD THE APPALACHIANS. SOUTHERLY WIND FLOW BETWEEN THESE TWO FEATURES WAS TRANSPORTING MOISTURE NORTHWARD FROM THE GULF OF MEXICO AND RESULTING IN AREAS OF CLOUD COVER...SHOWERS AND THUNDERSTORMS. && .NEAR TERM /THROUGH TONIGHT/... 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 /12Z TUESDAY THROUGH SATURDAY/...
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AS OF 800 AM EDT TUESDAY... SFC HIGH IS CENTERED JUST OFF THE MID-ATLANTIC COAST AND IS NOW IN A POSITION TO ALLOW WARM/MOIST GULF AIR TO SPREAD INTO THE REGION FROM THE SOUTHWEST. THIS WILL RESULT IN INCREASING CLOUDINESS WITH POTENTIAL FOR MVFR CIGS DEVELOPING ACROSS MUCH OF THE AREA THIS MORNING. WITH DAYTIME HEATING...THESE CLOUDS WILL GRADUALLY LIFT INTO LOW END VFR RANGE BY LATE MORNING/EARLY AFTERNOON. THE CLOUDS WILL LIKELY PREVENT MUCH IN THE WAY OF FOG DEVELOPMENT...BUT CANNOT TOTALLY IGNORE THE HIGHER DEWPOINTS AND THE POTENTIAL FOR LIGHT FOG AROUND DAYBREAK THIS MORNING. WITH INCREASING MOISTURE COMES THE POTENTIAL FOR DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS...FAVORING THE MOUNTAINS TODAY...THEN AREAWIDE WEDNESDAY AS AN UPPER LEVEL DISTURBANCE MOVES ACROSS THE REGION. WINDS TODAY WILL BE OUT OF THE SOUTH 5-10KTS...WITH GUSTS 14-18KTS. EXTENDED AVIATION DISCUSSION... WEDNESDAY...A SIGNIFICANT UPPER DISTURBANCE...NOW ACROSS OK/TX AND GENERATING WIDESPREAD SEVERE WEATHER AND FLOODING IN THAT REGION...WILL REACH OUR REGION. THIS ALONG WITH A WEAK BOUNDARY...EVIDENT IN SEVERAL OF THE MODELS...SHOULD ENHANCE SHRA/TSRA ACTIVITY ACROSS THE REGION...ESPECIALLY WED AFTERNOON. 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.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...PM SHORT TERM...NF LONG TERM...NF/PC AVIATION...PM

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