Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 181830 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 230 PM EDT SAT OCT 18 2014 .SYNOPSIS... A COLD FRONT CROSSING THROUGH THE MID ATLANTIC REGION THIS MORNING WILL BE OFF THE COAST TONIGHT...FOLLOWED BY HIGH PRESSURE FOR SUNDAY. ON MONDAY AND TUESDAY LOW PRESSURE WILL TRACK FROM THE GREAT LAKES TO OFF THE VIRGINIA COAST. && .NEAR TERM /THROUGH TONIGHT/... AS OF 115 PM EDT SATURDAY... WEAK COLD FRONT HAS JUST EXITED OUR SOUTHSIDE COUNTIES AROUND NOON...BRINING WINDS FROM THE NORTHWEST WITH GUSTS AS HIGH AS 25 MPH. AT THE SAME TIME...KEEPING AN EYE ON ANOTHER COLD FRONT THAT WILL ENTER WESTERN GREENBRIER COUNTY BY 2 PM. EXPECT A FEW SHOWERS ALONG THE WESTERN RIDGES WITH THIS BOUNDARY THROUGH THE AFTERNOON AND EVENING...BUT BELIEVE THE MOST WIDESPREAD SHOWER ACTIVITY WILL OCCUR SHORTLY BEFORE MIDNIGHT FOR THE MOUNTAINS AS THE NORTHWESTERLY WIND FLOW CARRIES A SURGE OF MOISTURE IN FROM LAKE MICHIGAN. WITH WINDS NOW NORTHWESTERLY ACROSS THE AREA...AND CLOUD COVER INCREASING ACROSS THE PIEDMONT...MAY SEE ANOTHER 1 TO 2 DEGREE TEMPERATURE INCREASE OVER 1 PM OBSERVATIONS ACROSS THE SOUTHSIDE FOR THE REMAINDER OF THE DAY...HOWEVER BELIEVE LOCATIONS FURTHER WEST ARE CURRENTLY AT...OR HAVE ALREADY EXPERIENCED...THEIR HIGHS FOR TODAY. HIGHS WILL RANGE FROM THE LOW/MID 50S ACROSS THE WESTERN RIDGES...TO THE MID 60S/AROUND 70 EAST OF THE BLUE RIDGE. LOOKING INTO TONIGHT...WILL BE TRIMMING BACK ON CHANCE OF PRECIPITATION TOWARD DAWN. EXPECT 850 MB TEMPERATURES LOWERING TO 0 TO +5 BY LATE TONIGHT...WHICH IS AIR COLD ENOUGH TO SUPPORT A FEW SNOW FLAKES ACROSS WESTERN GREENBRIER COUNTY AT THE VERY TAIL END OF THE CHANCE OF PRECIPITATION. ALONG THE SAME LINES... CLOUDS DO NOT CLEAR OUT AND WIND DOES NOT DIMINISH UNTIL LATE TONIGHT. THIS WILL LIMIT THE AREAL COVERAGE OF ANY FROST. && .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... AS OF 400 AM EDT SATURDAY... TO BEGIN...STRONG SHORT WAVE WILL QUICKLY ROTATE OUT OF THE REGION SUNDAY MORNING...WITH SFC HIGH PRESSURE BUILDING IN RAPIDLY FROM THE NORTHWEST IN ITS WAKE. GUSTY NW WINDS AND STRONG CAA EARLY WILL QUICKLY GIVE WAY TO DIMINISHING WINDS AND WAA ALOFT BY AFTERNOON. UPSLOPE CLOUDS MAY LINGER FOR A FEW HOURS ACROSS THE ALLEGHANYS...BUT ALL BUT THE NAM SHOW THIS MOISTURE GONE BY EARLY AFTERNOON...AND THE NAM BY 00Z MON. THUS...WE SHOULD SEE AMPLE AMOUNTS OF SUNSHINE ALL AREAS BY AFTERNOON AND IT WILL BE CLEAR NEARLY ALL DAY EAST OF THE BLUE RIDGE. TEMPERATURES WILL BE ON THE COOL SIDE...AND AMONG SOME OF THE COOLEST SO FAR IN THIS YOUNG FALL SEASON. WITH MORNING LOWS IN THE WESTERN MOUNTAINS IN THE LOW TO MID 30S AND GUSTY NW WINDS...IT WILL FEEL LIKE A LITTLE WINTERLIKE FOR A FEW HOURS SUN MORNING WITH WIND CHILLS 20 TO 25 NW GREENBRIER FOR A AROUND SUNRISE. SUNSHINE AND WEST WINDS...ESPECIALLY EAST OF THE ALLEGHANY FRONT...WILL YIELD A MUCH NICER AFTERNOON WITH HIGHS RANGING FROM THE UPPER 40S HIGHER ELEVATIONS OF WESTERN GREENBRIER TO THE MID 60S SOUTHSIDE AND OUR NC PIEDMONT COUNTIES. THE MAIN CONCERN THROUGH THIS PERIOD WILL BE THE FROST/FREEZE POTENTIAL LATE SUNDAY NIGHT/EARLY MONDAY MORNING. WHILE CONDITIONS ARE EXPECTED TO BE THE MOST CONDUCIVE TO SUCH SINCE THE OCT 5 EVENT...THEY ARE FAR FROM IDEAL. PROGRESSIVE FLOW ALOFT WILL ALLOW THE COLD SFC HIGH TO QUICKLY SHIFT EAST OF THE REGION SUN NIGHT AS THE NEXT UPSTREAM/ALBERTA CLIPPER SYSTEM RAPIDLY APPROACHES FROM THE NW. TEMPERATURES MAY ACTUALLY BOTTOM OUT AROUND MIDNIGHT AND THEN SLOWLY RISE AFTERWARDS AS WAA ENSUES FAIRLY QUICKLY WITH RETURN SW FLOW EVIDENT. THE EXCEPTION WILL BE THE DECOUPLED AREAS IN DEEPER VALLEYS. AT THIS POINT...GIVEN THE PATTERN...THE POTENTIAL FOR FROST OR A VERY LIGHT FREEZE MAY BE GREATEST EAST OF THE ALLEGHANY FRONT IN DECOUPLED AREAS OF THE GREENBRIER VALLEY/NEW RIVER VALLEY.SOUTHERN SHENANDOAH VALLEY...AND EVEN SOME AREAS OF THE PIEDMONT CLOSER TO THE HIGH CENTER WITH LIGHTER WINDS. FROST POTENTIAL IS LIKELY GREATER THAN FREEZE POTENTIAL GIVEN MOIST GROUND FROM ALL OF THE RECENT RAIN. HAVE DECIDED NOT TO ISSUE ANY HEADLINES AT THIS POINT IN COORDINATION WITH NEIGHBORING OFFICES AND ONLY PATCHY GRID PIXELS OF 30-32. A FROST ADVISORY FOR MUCH OF THE CWA...AND PERHAPS SOME COUNTIES...E.G. EASTERN GREENBRIER COUNTY...MAY NEED A FREEZE WARNING...BUT NOT ENOUGH CERTAINTY OR AGREEMENT TO ISSUE THE HEADLINE AT THIS POINT. WILL CONTINUE TO HIGHLIGHT IN THE HWO AND LIKELY INCLUDE MUCH IF NOT ALL OF THE CWA GIVEN AFOREMENTIONED POSSIBILITIES EVEN ACROSS THE PIEDMONT. ON OCT 5...LYH WAS ACTUALLY COOLER THAN BCB/BLF WITH A LOW OF 33F. FOR THE REMAINDER OF THE SHORT TERM...THE FOCUS WILL BE ON THE NEXT CLIPPER/UPPER TROUGH TO DIVE SOUTHEAST TOWARD THE AREA LATE MON-TUE. MODELS HAVE CONVERGED ON A MORE NORTHERN SOLUTION AND...INITIALLY AT LEAST... A LESS CLOSED LOW SOLUTION WITH THIS EVENT. THIS WILL LEAVE THE RNK CWA LARGELY ON THE SOUTHWEST/DRIER SIDE OF THIS SYSTEM...RESULTING IN LESS RAINFALL THAN PREVIOUSLY EXPECTED WITH THIS EVENT. INSTEAD OF THE UPPER LOW CLOSING OFF OR MIGRATING ACROSS SW VA/SE WV INTO CENTRAL VA...IT APPEARS DESTINED FOR A MUCH MORE NORTHERN LOCATION SUCH AS PA/NY/MD. STILL...THOUGH THIS WILL LEAVE AN UNSETTLED CYCLONIC FLOW SETUP ACROSS THE REGION WITH VARIABLE CLOUDINESS...SCATTERED MAINLY DAYTIME SHOWERS...AND COOL TEMPERATURES...FAIRLY TYPICAL FOR BEING ON THE SOUTHWEST/SOUTH SIDE OF A COLD CORE CLOSED LOW. THE POTENTIAL FOR RAINFALL SHOULD END SOONER WITH THESE LATEST MORE N/NE SOLUTIONS. THROUGHOUT THE PERIOD...THE BEST POTENTIAL FOR -SHRA WILL BE ACROSS THE MOUNTAINS OF SE WV. TEMPERATURES WILL BE TOO COOL TO SUPPORT ANY INSTABILITY...HENCE THUNDER...BUT ON THE OTHER HAND WILL BE TOO WARM...850MB TEMPS GENERALLY AOB +1C THROUGHOUT THE EVENT AT THE COLDEST...TO SUPPORT ANY WINTER PRECIPITATION. USED A MODEL BLEND FOR TEMPERATURES THROUGHOUT THE SHORT TERM...AS THE GFS MOST WAS TOO COLD AND THE ECMWF MOS WAS TOO WARM. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 430 AM EDT SATURDAY... MOST...IF NOT ALL OF THE PERIOD...WILL BE DOMINATED BY THE AFOREMENTIONED DEEP CLOSED LOW ACROSS THE NE STATES. WITH A HIGH AMPLITUDE UPPER RIDGE ACROSS THE WESTERN STATES...THE UPPER LOW WILL BE SLOW TO MOVE OUT. THE CENTRAL/SOUTHERN APPALACHIAN REGION WILL THUS BE LOCATED FOR SEVERAL DAYS ON THE SW SIDE OF THE UPPER LOW...AN INCREASINGLY DRY POSITION AS THE LOW DRIFTS FURTHER NE. BETWEEN WED AND FRI THE UPPER LOW ONLY DRIFTS VERY SLOWLY FROM CENTRAL/SOUTHERN PA TO OFF THE DELMARVA PENINSULA. SFC HIGH PRESSURE WILL SLOWLY APPROACH FROM THE CENTRAL U.S. EXPECT VARIABLE CLOUDS TO CONTINUE...SLIGHTLY LESS EACH DAY AND GREATEST ACROSS THE MOUNTAINS WITH SLIGHTLY ABOVE NORMAL MIN TEMPS AND BELOW NORMAL MAX TEMPS. OVERALL...A RELATIVELY BENIGN...QUIET WEATHER PERIOD. AGAIN...USED A BLEND OF MODEL TEMPS THROUGHOUT THE PERIOD. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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AS OF 200 PM EDT SATURDAY... OBSERVING GUSTY NORTHWEST WINDS THIS AFTERNOON AS ONE COLD FRONT HAS ALREADY PASSED ACROSS THE AREA. STRONGEST GUSTS ARE FOUND ACROSS THE PIEDMONT...OCCASIONALLY TOPPING 20KT...WITH SPEEDS TAPERING DOWN TO LESS THAN 10KT ALONG THE WESTERN RIDGES...WHERE A SECOND COLD FRONT IS ENTERING THIS AFTERNOON. CEILINGS RANGING 2-4KFT ARE WIDESPREAD ACROSS THE MOUNTAINS...BECOMING HIGHER AND INCREASINGLY SCATTERED EAST OF THE BLUE RIDGE. THE COLD FRONT WILL CONTINUE TO PASS SOUTHEAST ACROSS THE AREA THIS AFTERNOON...TRIGGERING UPSLOPE SHOWERS ALONG THE WESTERN RIDGES. MOST LIKELY TO BE IMPACTED WITH RAINFALL WILL BE KBLF/KLWB...AND KBCB LATER THIS EVENING. THE NORTHWESTERLY FLOW HAS PICKED UP A SLUG OF MOISTURE FROM LAKE MICHIGAN...WHICH RAPID UPDATE MODELS INDICATE WILL ARRIVE IN OUR AREA SHORTLY BEFORE MIDNIGHT...AND INCREASE THE COVERAGE OF SHOWER ACTIVITY ACROSS THE MOUNTAINS OVERNIGHT. TEMPERATURES WILL BECOME COLD ENOUGH TOWARD DAWN THAT A FEW SNOW FLAKES WILL BE POSSIBLE AT THE TAIL END OF THE SHOWER ACTIVITY FOR KLWB...HOWEVER NO ACCUMULATIONS ARE EXPECTED. IFR CEILINGS WILL BECOME WIDESPREAD ACROSS THE MOUNTAINS OVERNIGHT... BUT WILL BREAK UP FURTHER EAST IN THE DOWNSLOPE FLOW. RAINSHOWERS WILL ALSO LOWER VISIBILITIES FOR EXTENDED PERIODS OF TIME. TOWARD DAWN...SHOWER ACTIVITY WILL DIMINISH AND LOW LEVEL MOISTURE WILL BECOME INCREASINGLY SHALLOW FROM EAST TO WEST...ALLOWING CEILINGS TO GRADUALLY BREAK UP DURING THE REMAINDER OF THE MORNING. EXPECT VFR TO RETURN BY LATE SUNDAY MORNING FOR KROA AND POSSIBLY KBCB...HOWEVER KBLF/KLWB WILL REMAIN AT LEAST LOW MVFR INTO SUNDAY AFTERNOON. MEDIUM TO HIGH CONFIDENCE IN CIG THROUGH THE TAF VALID PERIOD. HIGH CONFIDENCE IN VSBYS THROUGH THE TAF VALID PERIOD. HIGH CONFIDENCE IN WIND DIR/SPD THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... VFR CONDITIONS ARE EXPECTED SUNDAY EVENING INTO MONDAY. ANOTHER UPPER LOW WILL SETTLE INTO THE REGION FROM THE NORTH LATE MONDAY AND LINGER THROUGH MID-WEEK WITH SCT -SHRA AND MOSTLY MVFR CEILINGS AND BRIEF PERIODS OF MVFR VISIBILITIES IN -SHRA. IMPROVING CONDITIONS ARE EXPECTED TOWARD THE VERY END OF THE WEEK.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS/NF SHORT TERM...RAB LONG TERM...DS/RAB AVIATION...NF/RAB

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