Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 031150 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 750 AM EDT TUE MAY 3 2016 .SYNOPSIS... A COLD FRONT WILL CONTINUE TO SLOWLY MOVE SOUTHWARD THROUGH WEDNESDAY. MEANWHILE...LOW PRESSURE DEEPENING ACROSS THE GREAT LAKES WILL DRIFT SOUTHWARD INTO THE SOUTHERN APPALACHIANS BY THURSDAY...REMAINING OVER THE REGION UNTIL LATE IN THE WEEKEND. WIDESPREAD RAIN TODAY WILL GIVE WAY TO AN UNSETTLED WEATHER PATTERN WITH SCATTERED TO NUMEROUS SHOWERS AND UNSEASONABLY COOL TEMPERATURES DURING THE LATER HALF OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 430 AM EDT TUESDAY... UNSETTLED WEATHER PATTERN TO CONTINUE...BUT SEVERE THREAT AND FLOODING THREAT GREATLY DIMINISHED. SLOW MOVING FRONTAL SYSTEM THAT BROUGHT WIDESPREAD SEVERE WEATHER TO THE REGION MONDAY EVENING DRAPED ACROSS THE REGION FROM NEAR KDCA...TO KDAN...TO KCLT EARLY THIS MORNING. SHOWERS CONTINUE ALONG THE FRONT THIS MORNING...WITH A NEW AREA OF RAIN SHOWERS SPREADING INTO THE REGION FROM THE OH/TN VALLEY. NOTHING TO THE DEGREE OBSERVED PRIOR TO MIDNIGHT...NOR IS ANY SUCH REPEAT EXPECTED TODAY. HAVE NOT OBSERVED ANY LIGHTNING SINCE ABOUT 06Z. RAINFALL AMOUNTS NOW GENERALLY IN THE 1/4 INCH OR LESS CATEGORY...WITH THE HEAVIEST NOW MAINLY S-SE OF THE RNK CWA. BIG QUESTION FOR TODAY IS WHETHER OR NOT THERE WILL BE A RESURGENCE OF CONVECTION ALONG THE FRONT AS A WAVE OF LOW PRESSURE RIDES ALONG THE FRONT. MODELS TO VARYING DEGREES INCREASE INSTABILITY ACROSS NORTH CENTRAL NC INTO SOUTHSIDE VA...WHERE SPC HAS INDICATED A SLIGHT RISK...WITH A MARGINAL RISK AS FAR NORTH AND WEST AS THE BLUE RIDGE. HOWEVER...SFC LOW PRESSURE IS PROGGED TO RIDE MAINLY JUST S-E OF THE CWA ALONG THE FRONT AS IT CONTINUES TO SLOWLY SAG SOUTHEAST. THUS...FEEL SEVERE THREAT IS LIMITED AT BEST FOR OUR CWA...AND IF SO LIKELY CONFINED TO THE CASWELL/HALIFAX AREA. ECMWF LEAST IMPRESSIVE ABOUT THUNDER THREAT FOR TODAY...WHILE GFS/NAM MORE FAVORABLE. OVERALL...SEVERE WEATHER PARAMETERS DO NOT APPEAR FAVORABLE FOR MUCH SEVERE. HAVE INCLUDED MENTION OF THUNDER ACROSS SOUTHSIDE INTO NORTH CENTRAL NC...BUT HAVE REFRAINED FROM MENTIONING ELSEWHERE AND DID NOT MENTION SEVERE AT THIS POINT. ADDITIONAL RAINFALL SHOULD REMAIN BELOW FLASH FLOOD THRESHOLDS...WITH THE HEAVIEST RAIN FALLING ACROSS THE AREAS WITH HIGHER FFG VALUES...NAMELY EAST OF THE BLUE RIDGE. NONETHELESS...LIKELY TO CATEGORICAL POPS ARE IN ORDER FOR MUCH OF THE CWA THROUGH 00Z...DECREASING TO CHANCE AFTER MIDNIGHT FROM WEST TO EAST. MAX TEMPERATURES PROBLEMATIC...BUT THINKING THAT CLOUDS WILL BE ABUNDANT TODAY AS UPPER HEIGHTS CONTINUE TO LOWER...FRONT REMAINS QUASI-STATIONARY ACROSS THE S-SE PORTIONS OF THE REGION...AND LIGHT TO MODERATE RAIN SHOWERS CONTINUE TO MOVE ACROSS THE REGION. HAVE LEANED TOWARD THE COOLER SIDE OF GUIDANCE AS A RESULT. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... AS OF 400 AM EDT TUESDAY... THE COLD FRONT SHOULD FINALLY BE OFFSHORE BY WEDNESDAY. HOWEVER...A DEEP UPPER LEVEL TROUGH FROM HUDSON BAY IN CANADA SHOULD TRACK OVER THE GREAT LAKES DURING THE DAY. AS IT APPROACHES THE MID ATLANTIC ON WEDNESDAY NIGHT...WINDS SHOULD SHIFT TO THE NORTHWEST. A PRETTY STIFF COLD AIR ADVECTION PATTERN TAKES PLACE THROUGH THURSDAY AND FRIDAY...AS THE UPPER LEVEL TROUGH CUTS OFF FROM THE FLOW TO BECOME A CLOSED UPPER LEVEL OVERHEAD. AN OMEGA BLOCK PATTERN WILL RESIDE OVER THE UNITED STATES AS THE UPPER LEVEL LOW SETTLES OVER THE MID ATLANTIC. THEREFORE...COOL AND DAMP CONDITIONS ARE EXPECTED FOR THE REMAINDER OF THIS WORK WEEK. PERIODIC SHOWERS...LOW CLOUDS...AND PATCHY FOG ARE LIKELY. WITH A DEEP COOL POOL OF AIR ALOFT...TEMPERATURES SHOULD DROP TO NEAR OR BELOW NORMAL FOR THE FIRST WEEK OF MAY. FOR EXAMPLE...HIGHS ON THURSDAY SHOULD ONLY REACH THE LOWER 50S TO THE LOWER 60S. ALSO...LOWS ON FRIDAY DIP INTO THE UPPER 30S TO THE UPPER 40S. && .LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 230 PM EDT MONDAY... CUTOFF OVER THE AREA FRIDAY WILL WEAKEN AND DRIFT EAST THIS WEEKEND AS FLOW ALOFT SLOWLY EVOLVES INTO A MORE PROGRESSIVE PATTERN FOR THE SECOND WEEK OF MAY. THE WEEKEND WILL BE OUR TRANSITION BETWEEN THE TWO PATTERNS SO LOOK FOR SATURDAY TO BE THE COOLER OF THE TWO DAYS BUT STILL RESEMBLING SOMETHING CLOSER TO NORMAL WITH RESPECT TO TEMPERATURE...THEN TRENDING ABOVE NORMAL FOR SUNDAY AND MONDAY. HIGHEST ELEVATIONS...SUCH AS MOUNT ROGERS...MAY EVEN TOY WITH TEMPERATURES IN THE 30S. FOR THE WEEKEND...INCREASING SUBSIDENCE IN THE WAKE OF THE UPPER LOW FAVORS MAINLY DRY CONDITIONS...ALTHOUGH CAN`T RULE OUT A POP-UP SHOWER IN THE MOUNTAINS. SINCE POPS LESS THAN 20 PERCENT...REMOVED SHOWER THREAT FOR ALL BUT THE WV HIGHLANDS. MODELS DO HINT AT ANOTHER FRONTAL ENCROACHMENT MONDAY, SO MAINTAINED CHANCE THREAT MONDAY. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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AS OF 745 AM EDT TUESDAY... COLD FRONT CONTINUES TO SLOWLY PUSH THROUGH THE MID ATLANTIC REGION...AND APPEARS TO BE ACROSS THE FAR E-SE PORTION OF THE CWA...BUT THE ACTUAL FRONT MAY BE SOMEWHAT CONTAMINATED BY CONVECTIVE OUTFLOW FROM YESTERDAYS THUNDERSTORMS. LIGHT RAIN CONTINUES TO OVERRUN THE FRONT AS A WAVE OF LOW PRESSURE RIDES ALONG THE FRONT AND FLOW ALOFT REMAINS SOUTHWEST...AWAITING REINFORCEMENT FROM A SERIES OF UPSTREAM DISTURBANCES AND A DEEPENING UPPER LOW SAGGING SOUTHWARD ACROSS THE GREAT LAKES OVER THE NEXT FEW DAYS. GENERALLY SEEING IFR CIGS THIS HOUR AT MOST SITES. THIS WILL LIKELY CONTINUE UNTIL MID-MORNING EAST OF THE BLUE RIDGE...THEN IMPROVE TO MVFR AND EVENTUALLY VFR AS LOW PRESSURE MOVES EAST OF THE REGION AND WINDS BECOME W-NW. WEST OF THE BLUE RIDGE...IFR- MVFR CIGS MAY PERSIST MUCH OF THE DAY...ESPECIALLY KBLF AND KLWB. OVERNIGHT AS THE UPPER LOW MOVES SOUTHWARD...HEIGHTS LOWER...AND TEMPS COOL ALOFT...EXPECT REINFORCEMENT OF LOW CLOUDS AND IFR CIGS WEST OF THE BLUE RIDGE WITH OCCASIONAL -SHRA. SHOWERS SHOULD BE ENDING EAST OF THE BLUE RIDGE AFT 00Z. VSBYS MOSTLY MVFR OR BETTER THROUGH THE PERIOD. WINDS BECOMING W-NW 5-7KTS THROUGH MUCH OF THE PERIOD. MEDIUM CONFIDENCE IN CIGS AND VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD. LOW CONFIDENCE IN ANY TSRA POTENTIAL KDAN TODAY. EXTENDED AVIATION DISCUSSION... THE COLD FRONT DEPARTS OFFSHORE ON TUESDAY NIGHT...WHICH WILL ALLOW ALL TAF SITES TO RETURN TO VFR. HOWEVER...A DEEP UPPER LEVEL LOW FROM THE HUDSON BAY IN CANADA...SHOULD DIVE SOUTHWARD TOWARD THE MID ATLANTIC ON WEDNESDAY. THIS UPPER LEVEL LOW SETTLES OVER THE MID ATLANTIC THROUGH THE REMAINDER OF THIS WEEK. FLYING CONDITIONS SHOULD REMAIN RATHER POOR DURING THIS TIME DUE TO PERIODIC SHOWERS...LOW CEILINGS...AND PATCHY FOG.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...RAB NEAR TERM...RAB SHORT TERM...PW LONG TERM...PM AVIATION...PW/RAB

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