Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 230803 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 403 AM EDT TUE SEP 23 2014 .SYNOPSIS...
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HIGH PRESSURE STRETCHED FROM ILLINOIS TO NEW YORK THIS MORNING. THIS HIGH WILL REMAIN OVER THE MID ATLANTIC REGION THROUGH WEDNESDAY. MEANWHILE LOW PRESSURE WILL DEVELOP ALONG THE SOUTHEAST COAST TODAY...AND DRIFT SLOWLY TOWARD THE CAROLINA COAST BY FRIDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 345 AM EDT TUESDAY... WATER VAPOR LOOP SHOWED AN UPPER LOW OVER NORTHEAST GEORGIA. MODELS INDICATED THIS LOW WILL FILL SLIGHTLY AND DRIFT NORTHEAST BY WEDNESDAY MORNING. SURFACE HIGH PRESSURE WILL MOVE FROM THE OHIO VALLEY INTO NEW ENGLAND BY WEDNESDAY MORNING. THE HIGH WILL WEDGE DOWN THE EAST SLOPS OF THE APPALACHIANS TODAY THEN WINDS WILL BEGIN TO RESPOND MORE TO THE DEVELOPING LOW OFF THE SOUTHEAST COAST TONIGHT. EXPANSIVE SHIELD OF CIRRUS OVER THE MID ATLANTIC REGION THIS MORNING WITH THE WESTERN EDGE CLOSE TO THE VIRGINIA/WEST VIRGINIA BORDER. DEEPEST MOISTURE WILL REMAIN JUST TO THE SOUTHEAST OF THE FORECAST AREA...BUT NET RESULT OF UPPER AND SURFACE PATTERN WILL BE EXTENSIVE CLOUD COVER AND GRADUALLY INCREASING PRECIPITABLE WATER VALUES THROUGH TONIGHT. WILL BE GREATLY INCREASING CLOUD COVER TODAY AND TONIGHT. BASED ON THE EXPECTED CLOUD COVER TODAY...HAVE LOWERED MAXIMUM TEMPERATURES IN THE EASTERN HALF OF THE FORECAST AREA. THE WESTERN EXTENT OF THE CLOUDS TONIGHT WILL IMPACT HOW MUCH TEMPERATURES DROP IN THE MOUNTAINS. STAYED CLOSER TO BIAS CORRECTED MET GUIDANCE FOR OVERNIGHT LOWS.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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AS OF 300 AM EDT TUESDAY... WEDNESDAY STARTS OUT WITH SURFACE HIGH PRESSURE OVER NEW ENGLAND WEDGING SOUTH INTO THE CAROLINAS. OVER THE SOUTHEASTERN USA...AN UPPER LEVEL LOW WILL HELP SPAWN A DISTURBANCE OFF THE SOUTHEAST COAST. THESE THREE SYSTEMS WILL INTERACT WITH EACH TO BRING AN INCREASE IN CLOUDS OVER THE ENTIRE AREA WITH LIGHT RAIN/DRIZZLE ALONG AND EAST OF THE BLUE RIDGE FROM WEDNESDAY AFTERNOON INTO THURSDAY MORNING. COMPLICATING THE ISSUE IS AN UPPER LEVEL BLOCKING RIDGE IN THE WESTERN ATLANTIC. THIS RIDGE WILL SLOWLY DIRECT THE UPPER LEVEL AND THE SURFACE LOW NORTHWARD IN TANDEM. BY THURSDAY AFTERNOON...THESE LOWS WILL BE NORTH OF THE AREA WITH DRY NORTHWEST FLOW CLEARING THE AREA OUT OF RAIN. THE DEFORMATION ZONE BETWEEN THESE LOWS SHOULD KEEP THE HEAVIEST RAIN ALONG THE COAST...WITH A POSSIBLE QUARTER OF AN INCH /0.25/ OF RAIN OVER THE PIEDMONT. LATEST MODELS ARE NOW BRING MORE RAIN INLAND WEDNESDAY AFTERNOON AND NIGHT...THEREFORE INCREASED POPS IN THE EAST. MODELS ARE ALSO DRYING THE REGION OUT ON THURSDAY WITH THE LOW TRACKING INTO THE NORTHERN MID ATLANTIC REGION. CLOUDS LIKELY TO LINGER THROUGH MUCH OF THE DAY THURSDAY BUT HAVE LOWERED POPS TO AROUND 10 PERCENT. TEMPERATURES WILL BE TRICKY FOR EACH AFTERNOON THROUGH THE PERIOD. ON WEDNESDAY...THE WEDGE AND EASTERLY FLOW WILL KEEP THE EAST COOL BUT COULD BE SIGNIFICANTLY COOLER IF RAIN FALLS EARLY IN THE DAY. TIMING THE DEPARTURE OF THE WEDGE AND LOW PRESSURE SYSTEMS TO THE NORTH THURSDAY WILL BE DIFFICULT. GUIDANCE IS WARMING THE AREA WITH ABOVE NORMAL TEMPERATURES. SINCE THE WEATHER PATTERN IS NOT CONDUCIVE TO A SIGNIFICANT WARMUP...WILL LEAVE TEMPERATURES CLOSE TO PREVIOUS FORECAST AND IN LINE WITH SURROUNDING OFFICES.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 300 PM EDT MONDAY... CONSIDERABLE UNCERTAINTY EXISTS IN THE EXTENDED PERIOD AS A FAIRLY COMPLEX UPPER LEVEL PATTERN DEVELOPS BY THE WEEKEND WITH HIGHLY AMPLIFIED UPPER RIDGE OVER THE NORTH CENTRAL U.S. EXTENDING INTO CANADA WITH TROUGHING OVER THE WESTERN ATLANTIC AND ACROSS THE WESTERN STATES. THE 12Z EURO IS MUCH FURTHER WEST WITH ATLANTIC TROUGH WITH RESULTANT SURFACE LOW MEANDERING ALONG THE MID- ATLANTIC COAST FRI-SAT BUT NOT FAR ENOUGH WEST FOR PRECIP THIS FAR INLAND. BUT WOULD LIKELY SEE SUBSTANTIAL CLOUDINESS FROM THIS ALONG WITH THE CAD-LIKE EFFECTS FROM A VERY SLOW-MOVING SURFACE HIGH OVER THE NORTHEAST. IN FACT THE UPPER RIDGE TO THE NORTH RETARDS THE NORTHWARD MOVEMENT OF THIS COASTAL SYSTEM WELL INTO SUNDAY. GFS IS MUCH LESS DEVELOPED WITH ANY COASTAL SYSTEM WITH DRY HIGH PRESSURE IN CONTROL THROUGH WEEKEND. ELECTED TO REFLECT MORE OPTIMISTIC GFS SOLUTION AT THIS POINT WITH MORE SUN. TEMPS NEAR TO ABOVE NORMAL WITH MAINLY 70S AND 50S FOR HIGHS/LOWS. BOTH GFS/EURO SHOW SURFACE LOW OR INVERTED TROUGH DEVELOPING OVER THE LOWER MISSISSIPPI VALLEY BY EARLY NEXT WEEK WITH GRIDS SHOWING CLOUDS SPREADING IN FROM SW TO NE AS EARLY AS SUNDAY NIGHT. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... AS OF 125 AM EDT TUESDAY... EXPECTING VFR CONDITIONS TO PREVAIL OVERNIGHT AT KROA/KLYH/KBLF AND KDAN. SCATTERED TO BROKEN HIGH CLOUDS WILL MUCH OF CENTRAL AND EASTERN VIRGINIA AND NORTH CAROLINA TODAY AND TONIGHT. GOOD RADIATIONAL COOLING WILL LEAD TO PATCHY RIVER BOTTOM FOG. THIS WILL RESULT IN A FEW HOURS OF LIFR CONDITIONS AT KLWB. MVFR/IFR CONDITIONS POSSIBLE AT KBCB FOR AN HOUR OR TWO RIGHT AROUND DAWN. BY 14Z/10AM TUESDAY ALL TAF LOCATIONS WILL BE VFR AND HIGH CONFIDENCE THAT CONDITIONS WILL STAY VFR THROUGH THE REMAINDER OF THE TAF PERIOD. EXTENDED AVIATION DISCUSSION... HIGH PRESSURE AND DRIER AIR IN THE REGION THROUGH WEDNESDAY WILL RESULT IN MAINLY VFR CONDITIONS. RIVER VALLEY FOG WILL STILL BE POSSIBLE AT NIGHT AS WINDS DIMINISH AND COOL AIR MASS DECOUPLES. THERE IS STILL SOME MODEL DIFFERENCES REGARDING A LOW PRESSURE SYSTEM FORMING FROM THE GULF COAST LATER THIS WEEK. SEVERAL MODELS SHOW MOISTURE INCREASING OVERNIGHT WEDNESDAY THROUGH THURSDAY EVENING WHICH MAY RESULT IN PERIODS OF IFR/MVFR CEILINGS AND VSBYS. APPEARS HIGH PRESSURE WILL AGAIN RE-ESTABLISH OVER THE REGION LATE IN THE WEEK RESULTING IN RETURN TO WIDESPREAD VFR BY THE WEEKEND. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...RCS LONG TERM...PC AVIATION...AMS/JH

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