Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 201513 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1113 AM EDT WED MAY 20 2015 .SYNOPSIS... HIGH PRESSURE OVER THE GREAT LAKES WILL MOVE EAST TODAY...FOLLOWED BY AN AREA OF LOW PRESSURE THAT WILL AFFECT THE REGION THURSDAY. DRY AND TRANQUIL WEATHER EXPECTED FOR FRIDAY AND SATURDAY COURTESY OF DRY HIGH PRESSURE. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1100 AM EDT WEDNESDAY... 12Z/8AM RNK UPPER AIR SOUNDING WAS REFRESHINGLY DRY...PWAT 0.35. AS SUCH...EXPECTING VERY FEW CLOUDS WITH MOSTLY SUNNY SKIES. HUMIDITY MINIMUMS THIS AFTERNOON SHOULD TEST 30 PERCENT. HIGH PRESSURE OVER THE SOUTHERN GREAT LAKES WILL DRIFT EAST TODAY PROVIDING MOSTLY SUNNY SKIES AND SEASONABLE TEMPERATURES BEFORE A FAST-MOVING SHORT-WAVE AND ASSOCIATED SURFACE LOW TRACK EASTWARD FROM THE MID- MS/TN VALLEY INTO THE CAROLINAS BY EARLY THURSDAY. THE TRACK OF THIS WEAK SURFACE WAVE LOOKS POISED TO DELIVER A MODEST QUANTITY OF OVERRUNNING RAINFALL BEGINNING AS EARLY AS AROUND MIDNIGHT TONIGHT BUT WITH POPS INCREASING MAINLY AFTER 06Z. && .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... AS OF 330 AM EDT WEDNESDAY... LOOKING TO THURSDAY...WILL START THE DAY WITH AN UPPER LEVEL TROUGH PASSING ACROSS THE APPALACHIAN CHAIN...WITH ASSOCIATED SURFACE LOW PRESSURE MOVING ACROSS THE MOUNTAINS OF NORTH CAROLINA. EASTERLY WINDFLOW WILL CARRY ATLANTIC AIR UPSLOPE INTO THE MOUNTAINS...WITH ENOUGH LIFT PRESENT TO BRING RAIN TO MOST OF THE MID ATLANTIC AND CENTRAL APPALACHIANS. CONSIDERING OUR AREA IS HOLDING ON THE COOL SIDE OF THIS SYSTEM...DO NOT ANTICIPATE MUCH IN THE WAY OF THUNDERSTORM ACTIVITY. AS THE LOW DRIFTS EAST DURING THE AFTERNOON...WINDS FOR OUR AREA WILL BEGIN TO SHIFT NORTHERLY...THEN NORTHWESTERLY DURING THE EVENING AS HIGH PRESSURE BEGINS TO TAKE CONTROL. DRIER AIR PUSHING IN WITH THE HIGH WILL BRING AN END TO ALL BUT UPSLOPE SHOWERS ALONG THE WESTERN RIDGES BY SUNSET THURSDAY. CONSIDERING THE DRAW OF COOL MARINE AIR AND WIDESPREAD CLOUD COVER...UNDERCUT MAV/MET GUIDANCE BY A FEW DEGREES...WITH AFTERNOON HIGHS RANGING FROM THE LOW 60S NEAR INTERSTATE 64...TO THE LOW/MID 70S ACROSS THE FOOTHILLS IN NORTH CAROLINA. HIGH PRESSURE WILL BE IN CONTROL THURSDAY NIGHT THROUGH SATURDAY NIGHT. MODELS ARE HINTING AT A COLD FRONT SINKING SOUTHWARD ON FRIDAY POTENTIALLY BRINGING A FEW SHOWERS TO AREAS NORTH OF HIGHWAY 460...BUT DO NOT HAVE ENOUGH CONFIDENCE TO MAKE MENTION IN THE FORECAST GIVEN THE DRY AIR THAT WILL BE IN PLACE. EXPECT DRY CONDITIONS UNDER MOSTLY CLEAR SKIES. TEMPERATURES DURING THE PERIOD WILL BE NEAR TO SLIGHTLY BELOW NORMAL FOR THE SECOND HALF OF MAY. && .LONG TERM /SUNDAY THROUGH TUESDAY/... AS OF 330 AM EDT WEDNESDAY... UPPER PATTERN WILL BE DEVELOPING A LARGE TROF OVER THE EASTERN US DURING THE EXTENDED PERIOD...WITH A BERMUDA HIGH OFF THE COAST. WILL BEGIN TO SEE WARMER TEMPERATURES AND HUMIDITY MOVING BACK INTO THE REGION BY SUNDAY...WITH THE TRULY UNCOMFORTABLE CONDITIONS HOLDING OFF UNTIL THE FIRST PART OF NEXT WEEK. HOWEVER THE CHANCES FOR SHOWERS AND THUNDERSTORMS WILL BE ONLY MODEST AS SIGNIFICANT DYNAMIC FORCING WILL BE ABSENT...LEAVING US TO RELY ON OROGRAPHIC FORCING FROM THE BLUE RIDGE WEST TO FOCUS LIFT AND GENERATE SOME CONVECTIVE ACTIVITY. PWATS WILL ONCE AGAIN BE RISING ABOVE ONE INCH SO THE POSSIBILITY OF LOCAL DOWNPOURS WILL BE INCREASING. BY TUESDAY A COLD FRONT WILL BE APPROACHING FROM THE WEST AND LOOKS TO BRING GREATER COVERAGE OF PRECIPITATION TO THE REGION TUESDAY AFTERNOON AND EVENING. EXPECT RISING TEMPERATURES TO BE ABOUT 10 DEGREES ABOVE NORMAL AS WE HEAD INTO NEXT WEEK. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... AS OF 730 AM EDT WEDNESDAY... VFR CONDITIONS EXPECTED TO PREVAIL TODAY AS HIGH PRESSURE OVER THE GREAT LAKES RIDGES INTO CENTRAL MID-ATLANTIC REGION. HIGH OVERCAST IN ADVANCE OF FAST-MOVING SYSTEM EXPECTED BY THE LATE AFTERNOON/EVENING WITH LOWERING CIGS TO MVFR RANGE BY AROUND 05-07Z RANGE AND CHANCES FOR LIGHT RAINFALL INCREASING THEREAFTER. EXPECT CONDITIONS TO DETERIORATE EARLY THURSDAY WITH LOWER CIGS/VSBYS...AS RAINFALL OVERSPREADS THE TAF SITES IN ASSOCIATION WITH WEAK SURFACE LOW TRACKING ACROSS THE CAROLINAS. EXTENDED AVIATION DISCUSSION... SURFACE/UPPER LEVEL SYSTEM EXITS OFF THE COAST LATE THURSDAY WITH VFR CONDITIONS RETURNING FRIDAY AFTERNOON AND CONTINUING THROUGH NEXT WEEKEND. BUILDING RIDGE ALONG THE EASTERN SEABOARD EARLY NEXT WEEK MAY KEEP CHANCES FOR RAIN AND LOW CLOUDS TO THE WEST AND NORTH OF THE AREA UNTIL TUESDAY AFTERNOON. && .HYDROLOGY... AS OF 400 AM EST WEDNESDAY... THE FORECAST RAINFALL OF A LITTLE LESS THAN 0.25 INCHES STORM TOTAL IN THE UPCOMING `EVENT` BY LATE IN THE DAY THURSDAY WILL BE HARDLY ENOUGH TO ARREST A SIGNIFICANT DECLINE IN STREAMFLOWS ACROSS THE HYDROLOGIC SERVICE AREA. MAY HAS SEEN A COMPLETE TURNAROUND FROM THE WET APRIL IN THE PRECIPITATION FORTUNES OF THE AREA. USING DATA FROM ALL THE AVAILABLE COOP SITES...MAY IS NORMALLY THE 2ND WETTEST MONTH IN THE HSA WITH A 30-YEAR (1981-2010) AVERAGE OF 4.22 INCHES (JULY IS THE WETTEST MONTH AT 4.41 INCHES). DESPITE SOME LOCALLY HEAVY DOWNPOURS IN RECENT DAYS HOWEVER THE BULK OF THE AREA HAS SEEN WELL BELOW NORMAL RAINFALL IN MAY. PARTS OF THE PIEDMONT ARE BELOW 25 PERCENT OF NORMAL MAY RAINFALL...INCLUDING THE CLIMATE SITE AT DANVILLE WITH ONLY 0.51 INCHES THIS MONTH VERSUS NORMAL OF 2.24 BY THIS DATE. USGS STREAM GAGES...ESPECIALLY ACROSS THE PIEDMONT...HAVE FALLEN BACK TO BELOW OR WELL BELOW NORMAL FLOWS AFTER A SHORT REBOUND TO NEAR NORMAL IN LATE APRIL. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...PC/PM SHORT TERM...NF LONG TERM...MBS AVIATION...AMS/PC HYDROLOGY...PC

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