Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 272000 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 400 PM EDT WED MAY 27 2015 .SYNOPSIS...
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HIGH PRESSURE OFF THE SOUTHEAST COAST WILL MAINTAIN A BROAD SOUTHERLY FLOW OF MOISTURE INTO THE REGION THROUGH THE REMAINDER OF THIS WEEK. A WEAK UPPER LEVEL DISTURBANCE AND ASSOCIATED FRONTAL BOUNDARY WILL SLIDE INTO THE REGION EARLY THURSDAY. THIS WEATHER FEATURE IN COMBINATION WITH DAYTIME HEATING AND INSTABILITY WILL RESULT IN PERIODIC ROUNDS OF SHOWERS AND STORMS OVER THE NEXT FEW DAYS.
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&& .NEAR TERM /THROUGH THURSDAY/...
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AS OF 350 PM EDT WEDNESDAY... CONVECTION STRUGGLING TO GET GOING SO FAR THIS AFTERNOON AND WILL LIKELY REMAIN ISOLATED THROUGH THIS EVENING...MAINLY IN MTNS AND FOOTHILLS...GIVEN LIMITED INSTABILITY AND DRIER AIR PUSHING IN FROM THE WEST BEHIND THE WEAK SHORT WAVE THAT HAS LIFTED NORTHEAST OVER THE NORTHEAST U.S. ANY WIDELY SCATTERED CONVECTION THAT DOES MANAGGE TO DEVELOP THE REMAINDER OF THE AFTERNOON SHOULD DIMINISH QUICKLY WITH LOSS OF HEATING. WILL NEED KEEP AN EYE ON MORE ORGANIZED CONVECTION WELL TO THE WEST AS IT MOVES INTO EASTERN KY AND TN...BUT ALL INDICATIONS ARE THAT THIS WILL DIE QUICKLY WELL BEFORE IT REACHES WESTERN SLOPES OF APPALACHIANS...WHICH WOULD BE NEAR MIDNIGHT IF IT DID SURVIVE. KEEPING A SLIGHT CHANCE POP IN THE WEST FOR THIS SMALL POSSIBILITY... AS WELL AS ALONG BLUE RIDGE MAINLY IN NW NC GIVEN SOME LINGERING INSTABILITY AND CONVERGENCE PER THE HRRR...BUT OTHERWISE DROPPING POPS AFTER MIDNIGHT. SOME SUGGESTION IN THE GUIDANCE THAT PATCHY FOG MAY BE MORE LIKELY LATE TONIGHT...BUT WITH GENERAL LACK OF RAINFALL EXPECTED REMAINDER OF THE DAY...AND SOME RESIDUAL MID DECK OVERNIGHT...THINK THIS IS NOT LIKELY AND HAVE CHOSEN NOT TO INCLUDE IT. FOR THURSDAY...WE FINALLY HAVE SOME INGREDIENTS COMING TOGETHER TO SUPPORT MORE WIDESPREAD COVERAGE OF CONVECTION...WITH WEAK UPPER WAVE MOVING INTO APPALACHIANS EARLY IN THE DAY AND ASSOCIATED WEAK FRONTAL BOUNDARY...OR REALLY MORE OF A TROUGH AXIS...WHICH WILL ADD TO SOME WEAK CONVERGENCE ALREADY GEOGRAPHICALLY FAVORED NEAR THE BLUE RIDGE. MODELS SUGGEST MODEST INSTABILITY IN PART BECAUSE OF WARMER AFTERNOON TEMPS EXPECTED...BUT STILL NOTHING SUPER IMPRESSIVE...AND PERHAPS ENOUGH DRY AIR AT MID LEVELS TO SUPPORT SOME GUSTY DOWNDRAFTS. AT THIS POINT THINK SEVERE POTENTIAL IS LIMITED...BUT MUCH BETTER THAN THE LAST COUPLE OF DAYS. HOWEVER WITH WEAKER STEERING FLOW AND WELL ABOVE AVERAGE PRECIP WATER VALUES EXPECTED...LOCALLY HEAVY RAIN WILL BE THE MAIN CONCERN. GIVEN DRY ANTECEDENT CONDITIONS...NOT ALL THAT CONCERNED ABOUT A FLASH FLOOD THREAT...BUT STILL SOMETHING TO KEEP AN EYE ON WITH ISOLATED AREAS IF ANY STORMS BECOME LOCKED ON TERRAIN. THIS WILL STILL MAINLY BE OVER THE MOUNTAINS...WITH COVERAGE JUSTIFYING SOME LIKELY POPS...BUT STORMS MAY DRIFT INTO THE PIEDMONT BY LATE AFTERNOON...SO MID CHANCE POPS BY LATE IN THE DAY THERE AS WELL.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SUNDAY/...
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AS OF 330 PM EDT WEDNESDAY... UPPER PATTERN WILL BE IN TRANSITION DURING THE SHORT TERM WITH FLATTENING OF THE EAST COAST RIDGE AND A TROF DEVELOPING INTO A CLOSED LOW OVER THE MISSISSIPPI VALLEY. THIS WILL KEEP US IN A WEAKLY FORCED WARM/MOIST/UNSTABLE ENVIRONMENT WITH A DIURNAL TREND AND MOUNTAIN BIAS FOR SHOWERS/THUNDERSTORMS. A WEAK COLD FRONT WILL BE APPROACHING FROM THE NORTHWEST BY THE WEEKEND BUT UNCERTAINTY WILL BE INCREASING AS GUIDANCE DIFFERS IN HANDLING THE SPEED OF THIS FEATURE. BELIEVE THE SCENARIO WILL LEAD TO INCREASING CHANCES FOR FOR CONVECTION DURING THE LATTER PORTION OF THE WEEKEND. BIGGEST CONCERN WILL BE THE POSSIBILITY OF LOCALLY HEAVY RAIN GIVEN PRECIPITABLE WATER VALUES OF 1.0 TO 1.5 INCHES ACROSS THE REGION. TEMPERATURES WILL REMAIN ABOVE NORMAL WITH READINGS TRENDING UP A FEW DEGREES THROUGH THE WEEKEND... GENERALLY LOOKING FOR MID/UPPER 80S EAST OF THE BLUE RIDGE LOWER 80S WEST WITH THE USUAL COOLER READINGS AT THE HIGHER ELEVATIONS.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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AS OF 330 PM EDT WEDNESDAY... BY SUNDAY NIGHT THE UPPER PATTERN WILL BE WELL ON ITS WAY TO DEVELOPING A SPLIT FLOW REGIME ACROSS THE NORTHERN TIER OF STATES AS A CLOSED LOW DEVELOPS OVER THE MISSISSIPPI VALLEY AND SLOWLY SINKS SOUTHWARD THROUGH THE MIDDLE OF NEXT WEEK. SOME RIDGING WILL ALSO BE TAKING PLACE OVER THE MID ATLANTIC REGION AND SET UP A SLUGGISH BLOCKY PATTERN. AT THE SURFACE HIGH PRESSURE WILL BUILD THROUGH THE NORTHEAST AND WEDGE DOWN THE EASTERN SEABOARD...BRINGING COOLER/NEAR NORMAL TEMPERATURES TO THE REGION. HOWEVER...THE PATTERN WILL KEEP US MOIST WITH DEEP SOUTHEASTERLY FLOW AND EXPECT ENOUGH FORCING BETWEEN OROGRAPHIC UPSLOPE AND DIURNAL EFFECTS TO KEEP SOME SHOWER ACTIVITY...AND POSSIBLY A THUNDERSTORM... IN THE FORECAST THROUGH THE PERIOD.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... AS OF 143 PM EDT WEDNESDAY... MOIST ATMOSPHERE WITH VFR CUMULUS FIELD AND SCATTERED CIRRUS LAYERS FOR REMAINDER OF AFTERNOON. SCATTERED SHOWERS WITH SOME THUNDER POSSIBLE VCNTY OF BLUE RIDGE BY 18-20Z...DRIFTING WEST INTO FOOTHILLS THROUGH ABOUT 00Z. CONFIDENCE FAIRLY HIGH THESE WILL NOT IMPACT FAR WESTERN AIRPORTS OF KBLF AND KLWB...BUT CANNOT RULE OUT COMPLETELY. KEPT A VCSH MENTION AT KBCB AND KROA...WITH TEMPO GROUP FOR A LITTLE LATER AT KLYH...BUT LEFT OUT OF DANVILLE AS MUCH GUIDANCE STRUGGLES TO GET MUCH THAT FAR EAST BEFORE DYING. STILL...SOMETHING COULD BE IN VCNTY BY LATE THIS AFTERNOON...BUT CONFIDENCE TOO LOW AT THIS TIME TO MENTION IN TAF. OTHERWISE VFR CONDITIONS PREVAIL REST OF TODAY AND EVENING UNLESS A HEAVIER SHOWER OR STORM PASSES RIGHT OVER AN AIRPORT. OVERNIGHT ANY SHOWER ACTIVITY EXPECTED TO DIMINISH...WITH ONLY VERY SMALL CHANCE OF AN ISOLATED SHOWER IN FAR WEST OF FAR EAST. SOME MID LEVEL RESIDUAL CLOUDS SHOULD PREVENT FOG FROM FORMING...BUT GUIDANCE IS QUITE LOW NOW FOR PLACES LIKE LWB AND BCB...AND IF ANY SITE GETS RAINFALL FROM A PASSING SHOWER OR STORM...THEY WOULD SEE A MUCH HIGHER CHANCE BY MORNING. GENERALLY LEFT THIS OUT...EXCEPT FOR SOME LIGHT MVFR FOG AT KLWB...KBCB...AND KLYH. THURSDAY A WEAK UPPER LEVEL DISTURBANCE WILL HELP TO DRAG A WEAK SURFACE BOUNDARY ACROSS THE REGION...HARD TO CALL IT EVEN A FRONT...BUT THIS APPEARS LIKELY TO RESULT IN ENOUGH CONVERGENCE TO HELP DEVELOP MORE WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY BY MIDDAY IN MTNS. ADDED VCSH FOR WESTERN TAF SITES BY 16 OR 17Z...AND GOOD CHANCE THAT NEXT ISSUANCE OF TAFS WILL ADD TEMPO OR PREVAILING GROUPS FOR THUNDERSTORMS AT SEVERAL OF THESE LOCATIONS FOR THE AFTERNOON. EXTENDED AVIATION DISCUSSION... 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. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM/SK NEAR TERM...PM/SK SHORT TERM...MBS LONG TERM...MBS AVIATION...PM/SK

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