Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 040441 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1141 PM EST WED FEB 3 2016 .SYNOPSIS... LOW PRESSURE WAS CENTERED OVER ONTARIO WITH A STRONG COLD FRONT TRAILING SOUTH ALONG THE SPINE OF THE APPALACHIAN MOUNTAINS. THE COLD FRONT WILL MOVE EAST OVERNIGHT BRINGING AN END TO THE RAIN. COOL HIGH PRESSURE WILL GRADUALLY BUILD INTO THE CENTRAL APPALACHIANS FROM THE WEST ON THURSDAY...PASSING OVERHEAD FRIDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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AS OF 1130 PM EST WEDNESDAY... UPDATED GRIDS TO REMOVE RAIN SHOWERS OVER THE PIEDMONT AND TO DELAY ONSET OF UPSLOPE RAIN/SNOW SHOWERS UNTIL AROUND SUNRISE IN SOUTHEASTERN WEST VIRGINIA AND SOUTHWESTERN VIRGINIA. COLD AIR REMAINS WELL BACK IN THE OHIO VALLEY WITH THE DEW POINT FRONT. WARM AIR REMAINING OVER COLD GROUND TONIGHT HAS ALSO CREATED AREAS OF FOG ALONG AND EAST OF THE BLUE RIDGE. FOG WILL SCOUR AS MIXING INCREASES WITH THE PASSING OF THE COLD FRONT DURING THE EARLY MORNING HOURS. AS OF 857 PM EST WEDNESDAY... MODIFIED TEMPERATURES FOR TONIGHT AND LOWERED OVERNIGHT LOW TEMPERATURES MAINLY IN THE WEST. ADJUSTED POPS ONCE AGAIN FOR TONIGHT INTO THURSDAY MORNING. IN GENERAL...TREND BACK THE WESTERN EDGE OF SHOWERS. REGIONAL WSR-88D CONTINUE TO HIGHLIGHT SHOWERS MOVING NORTHEAST ACROSS EASTERN PORTIONS OF FORECAST AREA. LEANED THE POPS TOWARDS THE HRRR. THE HIRESWARW-EAST AND RAP WERE JUST A LITTLE SLOWER ON THE EXIT OF THE RAIN. OVERALL...HIGHRES MODELS WERE FAIRLY CLOSE ON TIMING OF FRONTAL BOUNDARY. THE COLD FRONT WILL CONTINUE TO MOVE SLOWLY EAST TONIGHT INTO THURSDAY. THE COLD AIR WAS LAGGING BEHIND THE FRONTAL BOUNDARY. MADE ONLY MINOR CHANGES FOR THURSDAY MORNING. AS OF 655 PM EST WEDNESDAY... A COLD FRONT IN THE WESTERN MOUNTAINS THIS EVENING WILL MOVE EAST TONIGHT INTO THURSDAY MORNING. THE AXIS OF THE HEAVY RAINS HAS SHIFTED EAST OF OUR AREA INTO EASTERN VIRGINIA AND EASTERN NORTH CAROLINA. KFCX 88D SHOWED SOME SCATTERED SHOWERS ACROSS SOUTHEASTERN PORTIONS OF FORECAST AREA. SOME DRIER AIR IS PUSHING EAST INTO WESTERN PORTIONS OF THE FORECAST AREA. SHAPED POPS FOR THIS EVENING INTO TONIGHT TOWARDS THE HRRR. ADDED SOME PATCHY FOG BECAUSE CLEARING THIS EVENING INTO TONIGHT WILL RESULT IN RADIATIONAL COOLING OF THE MOIST BOUNDARY LAYER. ADJUSTED TEMPERATURES FOR THIS EVENING WITH LATEST SURFACE OBS AND TOWARDS MODEL TREND WITH TEMPERATURES READINGS RISING A FEW DEGREES THIS EVENING PRIOR TO FROPA THEN FALLING TONIGHT. THE REAL COLD AIR LAGS TONIGHT. THERE MAY BE ENOUGH COLD AIR TO HAVE A FEW SNOW FLURRIES IN WEST VIRGINIA MOUNTAINS AROUND DAYBREAK. MORE CHANGES LATER TONIGHT... AS OF 330 PM EST WEDNESDAY... FLOOD WATCH HAS BEEN CANCELLED. CONVEYOR BELT OF HEAVY RAIN HAS MOVED EAST INTO CENTRAL/EASTERN VA/NC. ACTUAL SURFACE FRONT LAGS AND IT MAY TAKE MUCH OF THE OVERNIGHT BEFORE WE BEGIN TO SWAP THE MOIST AIRMASS EAST OF THE MOUNTAINS WITH ANY DRYING COMING IN FROM THE WEST. IN THE INTERIM...MAY HAVE TO ENTERTAIN AREAS OF FOG AS ANY CLEARING THIS EVENING WILL PROMOTE RADIATIONAL COOLING OF THE MOIST BOUNDARY LAYER. RUNOFF FROM TODAYS RAINFALL WILL ALSO REMAIN A CONCERN. EVEN THOUGH SMALL STREAMS WILL BE RECEDING...THE LARGER RIVERS WILL ACTUALLY RISE. FLOOD WARNINGS HAVE BEEN ISSUED FOR THE LOWER ROANOKE AND LOWER DAN RIVERS. OTHERS ARE BEING WATCHED CLOSELY..SEE HYDRO SECTION OF THIS DISCUSSION FOR DETAILS. TEMPERATURES TONIGHT WILL BE NON-DIURNAL AND ABOVE NORMAL... READINGS ACTUALLY RISING A FEW DEGREES THIS EVENING PRIOR TO FROPA. COLD AIR LAGS...SO NO PTYPE ISSUES TONIGHT. MAY SEE SOME FLURRIES IN THE MOUNTAINS OF WV TOWARD DAYBREAK BUT THATS ABOUT IT. ELSEWHERE...ANY REMAINING MOISTURE WOULD BE LIQUID...WITH MAIN THREAT FOR ANY LINGERING RAINFALL EAST OF HIGHWAY 29.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/... AS OF 330 PM EST WEDNESDAY... THE MAIN WEATHER RELATED CONCERNS WILL BE FOUND AT THE FAR WESTERN AND FAR EASTERN PORTIONS OF THE AREA THROUGH THE END OF THE WEEK. THE FRONTAL BOUNDARY THAT MOVED THROUGH THE REGION WEDNESDAY NIGHT WILL CONTINUE TO LINGER JUST OFF TO OUR EAST AS A VIGOROUS SHORT WAVE DEVELOPS A LOW ALONG THE COAST. THIS WILL BUCKLE THE FRONTAL BOUNDARY BACK TOWARD THE NORTHWEST AND BRING A CHANCE OF PRECIPITATION TO THE PIEDMONT AND SOUTHSIDE LATE THURSDAY AND THURSDAY NIGHT. MEANWHILE ALONG THE FAR WESTERN SLOPES...COLDER AIR MOVING IN ON NORTHWEST FLOW WILL BE GENERATING SOME MIXED RAIN/SNOW SHOWERS THURSDAY MORNING...THEN SNOW SHOWERS ON THURSDAY NIGHT AS ANOTHER SURGE OF LOW LEVEL MOISTURE MOVES IN FROM THE OHIO VALLEY. SOME LOCATIONS AT THE HIGHER ELEVATIONS MAY SEE A DUSTING OF SNOW BUT NO SIGNIFICANT ACCUMULATIONS ARE EXPECTED. HIGH PRESSURE WILL THEN BUILD IN FOR FRIDAY AND INTO THE FIRST PART OF THE WEEKEND WITH FAIR WEATHER AND SEASONABLE TEMPERATURES. TEMPERATURES WILL GENERALLY BE AT OR SLIGHTLY ABOVE NORMAL THROUGH THE SHORT TERM. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 330 PM EST WEDNESDAY... PROGRESSIVE FLOW WILL ALLOW A VIGOROUS UPPER TROF TO MOVE OVER THE EASTERN US AND DEVELOP A STRONG COASTAL LOW OFF THE SOUTHEAST COAST. ALL GUIDANCE CURRENTLY KEEPS THE PRECIPITATION SHIELD ASSOCIATED WITH THIS LOW TO THE EAST OF THE REGION WITH JUST SOME SPRINKLES POSSIBLE FOR THE FAR SOUTHEASTERN PORTIONS OF SOUTHSIDE LATE ON SUNDAY. BY MONDAY A MUCH DEEPER TROF WILL MOVE INTO THE EASTERN US AND SET UP A SIGNIFICANTLY COLDER PATTERN...WHILE A COMPLEX SURFACE PATTERN DEVELOPS AS LOW PRESSURE APPROACHES FROM THE GREAT PLAINS...FOLLOWED BY A TRANSFER OF ENERGY TO A DEVELOPING LOW OFF THE MIDDLE ATLANTIC COAST. THE COMBINATION OF THE COLDER AIR AND DEVELOPING SURFACE FEATURES LOOKS LIKE IT MAY BRING SOME LIGHT SNOW/SNOW SHOWERS TO THE AREA MAINLY WEST OF THE BLUE RIDGE. THE PATTERN DOES NOT FAVOR DEVELOPMENT OF A STRONG STORM SYSTEM TO AFFECT THE REGION SO WIDESPREAD WINTER WEATHER ISSUES ARE NOT LIKELY. BY THE MIDDLE OF NEXT WEEK WHEN THE COLDER AIR ARRIVES...HIGH TEMPERATURES WEST OF THE BLUE RIDGE WILL GENERALLY BE IN THE MIDDLE 20S WITH READINGS IN THE MIDDLE 30S EAST OF THE RIDGE. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 700 PM EST WEDNESDAY... LOWER THAN NORMAL CONFIDENCE IN CIG/VIS CONDITIONS AT TAF SITES EARLY IN THE PERIOD...THEN CONFIDENCE INCREASING WITH TIME. THE MODERATE TO HEAVY SHOWERS THAT IMPACTED THE REGION EARLIER IN THE DAY WEDNESDAY HAVE SINCE PUSHED EAST OF THE FORECAST AREAS. THUS...HAVE ENDED RESIDUAL SHRA FROM THE EASTERN PORTION OF THE TAF AREA. EXPECT A HIGH DEGREE OF VARIABILITY IN CONDITIONS THROUGH EARLY TONIGHT AS THE COLD FRONT FINISHES ITS PASSAGE TO THE EAST...WITH NORTHWEST WINDS BECOMING PREDOMINANT. NORTHWEST FLOW WILL ESTABLISH UPSLOPE CONDITIONS FROM THE BLUE RIDGE WEST WITH MVFR/IFR CONDITIONS EXPECTED THROUGH DAYBREAK. INCREASING CONFIDENCE THAT THE WEDGE WILL HOLD EAST OF THE BLUE RIDGE...SO KEPT LYH/DAN ENTERING INTO IFR CONDITIONS THROUGH THE EARLY MORNING HOURS. LOWER CONFIDENCE WEST...WERE CONDITIONS CONTINUE TO JUMP AROUND...AND MIXING IS MORE LIKELY TO OCCUR OVERNIGHT. I EXPECT ALL SITES TO BE VFR FROM THURSDAY MORNING THROUGH THE END OF THE TAF PERIOD...WITH EXCEPTIONS POSSIBLE IN UPSLOPE AREAS THAT MAY SEE A BRIEF SNOW SHOWER. EXPECT WINDS TO BECOME A BIT GUSTY AS THEY SHIFT TO THE NORTHWEST ESPECIALLY AT KBLF...KROA...AND KBCB. EXTENDED DISCUSSION... BY LATE THURSDAY...HIGH PRESSURE WILL BUILD OVERHEAD TO PROVIDE COLDER AND DRIER CONDITIONS...AND WILL KEEP VFR CONDITIONS AT ALL TAF SITES THROUGH SATURDAY. ANOTHER SYSTEM MOVING ACROSS THE SOUTHEAST APPEARS TO STAY JUST SOUTH OF US SUNDAY WITH POSSIBLE LIGHT PRECIP AND MVFR CIGS EDGING TOWARD THE VA/NC BORDER SUNDAY AFTERNOON. && .HYDROLOGY... AS OF 330 PM EST WEDNESDAY FLASH FLOOD THREAT ON THE WANE THIS EVENING INTO TONIGHT AFTER A BUSY MORNING AND AFTERNOON WITH SEVERAL FLASH FLOOD WARNINGS AND FLOOD ADVISORIES ISSUED. SEVERAL OF THESE WILL REMAIN IN EFFECT FOR A FEW MORE HOURS BUT THE HEAVY RAIN WILL SHIFT EAST OF THE CWA BY EARLY EVENING. WE ARE THEN LEFT WITH THE AFTERMATH AS SMALL CREEKS AND STREAMS WILL RECEDE QUICKLY BUT NUMEROUS ROADS WILL REMAIN CLOSED DUE TO STANDING WATER AND PONDING. MEANWHILE RUNOFF INTO LARGER STREAMS AND MAINSTEM RIVERS WILL BE ON THE INCREASE WITH MANY RIVERS RISING VERY RAPIDLY. RIVER FLOODING IS CURRENTLY FORECAST ONLY ALONG THE LOWER DAN AND ROANOKE RIVERS WITH MINOR CATEGORY FLOODING EXPECTED THURSDAY INTO FRIDAY ON THESE RIVERS. SEE FLOOD WARNING PRODUCTS /WBCFLWRNK/ FOR DETAILS ON THIS FLOODING. ESSENTIALLY EVERY OTHER MAJOR RIVER...INCLUDING THE YADKIN...JAMES...GREENBRIER AND UPPER NEW (ABOVE RADFORD) ARE FORECAST TO SEE SIGNIFICANT RISES BUT ONLY TO NEAR OR SLIGHTLY ABOVE ACTION STAGE...REMAINING SEVERAL FEET BELOW FLOOD STAGE. THESE RIVERS WILL HAVE TO BE CLOSELY MONITORED FOR SIGNIFICANT DEVIATIONS FROM THE FORECAST AS MINOR FLOODING NOT OUT OF THE QUESTION. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...KK/PM/RCS SHORT TERM...MBS LONG TERM...MBS AVIATION...MBS/WP HYDROLOGY...PC

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