Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 181144 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 644 AM EST THU DEC 18 2014 .SYNOPSIS... HIGH PRESSURE OVER THE UPPER MIDWEST WILL GRADUALLY BUILD EAST ACROSS THE AREA RESULTING IN OVERALL DRY WEATHER THROUGH FRIDAY. HOWEVER PASSING UPPER LEVEL DISTURBANCES WILL RESULT IN PERIODS OF MID AND HIGH CLOUDINESS OVER THE NEXT COUPLE OF DAYS. A WEAK AREA OF LOW PRESSURE WILL EVENTUALLY DEVELOP ALONG THE GULF COAST STATES LATER FRIDAY AND MOVE EAST...PERHAPS BRINGING A PERIOD OF LIGHT WINTRY PRECIPITATION ON SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 215 AM EST THURSDAY... OVERALL DRY WEATHER AND SEASONAL TEMPS TO CONTINUE OVER THE NEXT 24 HOURS WITH WEAK SURFACE RIDGING IN PLACE UNDER A FAST/CONFLUENT FLOW ALOFT. HOWEVER THE DEGREE OF CLOUDS AND WHETHER OR NOT ANY SPRINKLES/FLURRIES WILL OCCUR REMAINS IN QUESTION GIVEN THE APPROACH OF DECENT MID LEVEL ENERGY FROM THE WEST TODAY OVERTOP VERY DRY AIR IN PLACE. LATEST GUIDANCE SHOWING LITTLE IN THE WAY OF PRECIP...WITH THIS WAVE NOW BACK OVER THE MIDWEST...MAKING IT ACROSS THE MOUNTAINS BUT DO HAVE QUITE A BIT OF MID/HIGH CLOUDS PER RH SECTIONS. LATEST FORECAST SOUNDINGS ALSO SHOW EXTENSIVE DRY AIR BENEATH THE MID DECK SO DOUBTING MUCH IN THE WAY OF LIGHT PRECIP EXCEPT POSSIBLY THE FAR WESTERN SLOPES. THUS TRIMMED BACK THE GOING COVERAGE OF SPRINKLES WITH ONLY A BRIEF MENTION FAR WEST THIS AFTERNOON. OTRW LOOKING AT INTERVALS OF SUN EARLY...OUTSIDE LINGERING UPSLOPE LOW CLOUDS WESTERN SLOPES... WITH A PERIOD OF MORE MID DECK CLOUDS INTO THE AFTERNOON/EARLY EVENING. BRIEF FLUX OF FAINT WARM ADVECTION AHEAD OF THE SHORTWAVE MAY PUSH TEMPS OVER THE SE TO AROUND 50...WHILE MOST OTHER LOCATIONS STRUGGLE IN THE UPPER 30S TO MID 40S ESPCLY IF CLOUDS ARE FASTER TO ARRIVE WHICH COULD MEAN MORE 30S FOR HIGHS MOUNTAINS. WAVE ALOFT PASSES EAST OVERNIGHT LEAVING WEAK SUBSIDENCE IN PLACE AS HIGH PRESSURE TO THE NW NOSES BACK IN LATE. THIS WILL ALSO INTRO ANOTHER ROUND OF WEAK COLD ADVECTION ALLOWING UPSLOPE CLOUDS TO REDEVELOP FARTHER EAST...PERHAPS REACHING THE BLUE RIDGE BY DAYBREAK. OTRW EXPECTING SLOW CLEARING OF THE MID/HIGH CLOUDS FROM WEST TO EAST AFTER MIDNIGHT WITH INFILTRATION OF LOW DECK ACROSS THE FAR WEST LATE. WENT CLOSER TO THE SLIGHTLY WARMER MET MOS AGAIN TONIGHT FOR TEMPS PER LINGERING GRADIENT GIVEN THE PARENT HIGH TO THE NW AND SOME CLOUDS PERSISTING AT TIMES. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... AS OF 300 AM EST THURSDAY... FRIDAY LOOKS TO BE ON THE DRY SIDE AS HIGH PRESSURE STRETCHING FROM THE GREAT LAKES THROUGH THE OHIO RIVER VALLEY REMAINS THE MAIN FEATURE IN OUR WEATHER PATTERN. MOSTLY SUNNY SKIES AND LIGHT NORTHWESTERLY DOWNSLOPE WINDS WILL ALLOW AFTERNOON TEMPERATURES TO RANGE FROM THE UPPER 30S ALONG THE WESTERN RIDGES...TO AROUND 50 OVER THE SOUTHSIDE AND THE NORTH CAROLINA PIEDMONT. EXPECT TO SEE HIGH CLOUDS INCREASING DURING THE EVENING...WITH WINDS BECOMING INCREASINGLY NORTHEASTERLY AFTER MIDNIGHT...AS THE HIGH SHIFTS EAST ACROSS THE GREAT LAKES AND BEGINS TO BUILD SOUTHWARD AGAINST THE EASTERN FACE OF THE APPALACHIANS. COOL AIR FLOWING IN FROM THE NORTH AND RADIATIONAL COOLING DESPITE THE HIGH CLOUDS WILL ALLOW OVERNIGHT LOWS TO FALL INTO THE UPPER 20S TO LOW 30S. 18/00Z FORECAST MODELS CONTINUE TO TREND WEAKER AND SLOWER WITH THE UPPER LEVEL TROUGH MOVING EAST OVER THE GREAT PLAINS AND ITS ASSOCIATED SURFACE LOW DEVELOPING ALONG THE GULF COAST FRIDAY NIGHT. MODELS ARE IN GENERAL AGREEMENT FOR PRECIPITATION TO ENTER THE NORTH CAROLINA HIGHLANDS SHORTLY BEFORE DAWN ON SATURDAY. FOR THIS MORNING`S FORECAST...STILL PRETTY CONFIDENT THAT MOST AREAS WILL SEE MEASURABLE PRECIPITATION DESPITE MODELS TRENDING TOWARD A DRIER SYSTEM...SO WILL MAINTAIN HIGH PRECIPITATION CHANCES. HOWEVER...HAVE CUT DOWN ON PRECIPITATION AMOUNTS...WITH MOST LOCATIONS BELOW 0.25 INCHES OF LIQUID EQUIVALENT PRECIPITATION. PRECIPITATION TYPE IS ALSO A CHALLENGE. THE ATMOSPHERE WILL START THE NIGHT OUT DRY...WITH THE TEMPERATURE PROFILE IN THE LOWEST FEW THOUSAND FEET OF THE ATMOSPHERE HOVERING WITHIN A FEW DEGREES OF EITHER SIDE OF THE FREEZING MARK...DEPENDING ON LOCATION. IF HEAVIER PRECIPITATION MOVES INTO THE AREA...IT WILL CAUSE THE ATMOSPHERE TO MOISTEN AND THE TEMPERATURE PROFILE TO COOL...MAKING IT MORE LIKELY TO START AS SLEET OR SNOW. LIGHT PRECIPITATION MAY MANAGE TO START AS RAIN...ESPECIALLY ACROSS THE SLIGHTLY WARMER EASTERN HALF OF THE AREA...BEFORE CHANGING OVER TO SLEET/SNOW TOWARD DAWN. ULTIMATELY WENT ON THE PESSIMISTIC SIDE...TRENDING MORE TOWARDS FROZEN PRECIPITATION TO START THE EVENT. BEST BET FOR ACCUMULATING SNOWFALL WILL BE ON THE HIGHER RIDGES...WITH UP TO 2 INCHES POSSIBLE ALONG THE BLUE RIDGE AND OTHER HIGHER RIDGELINES...AND LOCALLY HIGHER AMOUNTS. PRECIPITATION WILL PASS ACROSS THE AREA SATURDAY AND THE EARLY HALF OF SATURDAY NIGHT. UNDERCUT MODEL GUIDANCE BY SEVERAL DEGREES FOR FORECAST HIGHS CONSIDERING PRECIPITATION MOVING ACROSS THE AREA IN EAST NORTHEASTERLY WIND FLOW. MOST PRECIPITATION WILL BE EAST OF THE AREA AFTER MIDNIGHT SUNDAY...WITH YET ANOTHER HIGH PRESSURE WEDGE BUILDING OVER THE MID ATLANTIC. ANOTHER LOW PRESSURE SYSTEM WILL DEVELOP ALONG THE GULF COAST SUNDAY NIGHT...RADIATING MOISTURE NORTHWARD AND INTRODUCING ANOTHER CHANCE OF RAIN...AND POTENTIALLY FREEZING PRECIPITATION TO THE MOUNTAINS. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... AS OF 400 AM EST THURSDAY... THIS PORTION OF THE FORECAST HAS THE POTENTIAL TO BE AN ACTIVE WEATHER PATTERN BASED UPON THE VARIOUS MODELS. HOWEVER...THESE SAME MODELS OFFER ENOUGH DIFFERENCES TO MAKE THE DETAILS OF THE SENSIBLE WEATHER ENOUGH OF CHALLENGE THAT CONFIDENCE IN THE SPECIFICS IS NOT HIGH. BY MONDAY...LATEST MODELS SHOW LOW PRESSURE ALONG THE NORTH CAROLINA COAST WITH ANOTHER AXIS OF PRECIP MOVING NORTH ASSOCIATED WITH INCREASING WARM ADVECTION AHEAD OF THE DEVELOPING LONGWAVE TROUGH TO THE WEST. DEPENDING UPON HOW MUCH OR LITTLE THIS SYSTEM DEEPENS WILL CORRELATE TO HOW LONG ANY ASSOCIATED PRECIPITATION REMAINS OVER OUR REGION. THE PRECIPITATION TYPE ACROSS THE AREA IS ALSO A QUESTION. EACH MODEL HAS A DIFFERENT TAKE ON THE MAGNITUDE OF THE WARM NOSE OVER OUR REGION. THE ONLY CONSISTENT ELEMENT IS THE EXISTENCE OF A WARM NOSE. GIVEN THIS...WILL OFFER RAIN VERSUS FREEZING RAIN FORECAST DURING MUCH OF THE MONDAY PORTION OF THE FORECAST. HOWEVER DESPITE QUITE A BIT OF WARMING ALOFT OFF THE LATEST 00Z EC MODEL...THERMAL PROFILES SUGGEST SOME POTENTIAL FOR LIGHT FREEZING RAIN OR SLEET ACROSS THE VIRGINIA HIGHLANDS AND SOUTHERN SHENANDOAH VALLEY SECTIONS ESPCLY MONDAY MORNING. PRECIPITATION CHANCES THOUGH WILL BE ON THE LOW SIDE...MAINLY RANGING IN THE SLIGHT CHANCE CATEGORY FOR NOW WHICH MAY HAVE TO BE RAMPED UP LATER TODAY. BY MONDAY NIGHT...GUIDANCE IS IN FAIRLY GOOD AGREEMENT OF BRINGING A CANADIAN LOW PRESSURE SYSTEM INTO THE NORTHERN MISSISSIPPI VALLEY. FROM THAT POINT...A DEEP LONGITUDINAL TROUGH DEVELOPS SOUTH TO THE GULF OF MEXICO BY TUESDAY AFTERNOON WITH INCREASING SOUTHERLY LOW LEVEL FLOW ACROSS OUR REGION...ACCOMPANIED BY AN INCREASING MOISTURE FETCH. BY TUESDAY NIGHT INTO EARLY WEDNESDAY...BOTH THE GFS AND ECWMF CONTINUE TO DEEPEN THE UPPER LOW AND ASSOCIATED TROUGH AND NEGATIVELY TILT THE FEATURE SO THAT THE TROUGH AXIS SHIFTS TO OFF THE COAST OF THE CAROLINAS...COINCIDENT TO THE POSITION OF THE ASSOCIATED SURFACE OCCLUDED FRONT....WITH THE TRIPLE POINT PASSING SOMEWHERE NEAR OR JUST SOUTH OF OUR REGION. THIS PAINTS A PICTURE OF VERY ACTIVE WEATHER ACROSS OUR REGION LATE TUESDAY NIGHT INTO WEDNESDAY WITH PLENTY OF SHOWERS...VERY GUSTY...IF NOT DAMAGING... WINDS...AND IF THE TRIPLE POINT PROGNOSTIC IS ACCURATE...SEVERE WEATHER...OR AT LEAST A RUMBLE OR TWO OF THUNDER...OVER OR VERY CLOSE TO OUR REGION OF THE COUNTRY. HOWEVER...THIS SCENARIO STILL IS DAY 6 INTO DAY 7 OF THE FORECAST...AND THERE IS PLENTY OF TIME FOR CHANGES IN THE OPERATIONAL MODELS TO TREND TOWARD A LESS AGGRESSIVE SYSTEM. GIVEN THIS...WILL OFFER A FORECAST LATE MONDAY NIGHT INTO TUESDAY THAT OFFERS INCREASING CHANCES OF LIGHT RAIN OR FREEZING RAIN WITH LIGHT TO MODERATE RAIN ON TUESDAY...WITH MODERATE RAIN SHOWERS TUESDAY NIGHT INTO EARLY WEDNESDAY ALONG WITH GUSTY WINDS. TIMING OF THE PUSH OF COLDER AIR INTO THE REGION AS WELL AS THE MAGNITUDE OF THAT COLDER AIR VARIES BETWEEN THE GFS AND ECWMF. HOWEVER...THE FORECAST WILL ALLOW FOR THE POTENTIAL FOR COLD ENOUGH AIR TO REACH WESTERN...HIGHER PARTS OF THE AREA LATE TUESDAY NIGHT INTO WEDNESDAY FOR ACCUMULATING SNOW SHOWERS. TEMPERATURES DURING THIS PORTION OF THE FORECAST WILL TREND MILDER THROUGH AT LEAST TUESDAY. WEDNESDAY MAY BE A BIT MILDER IN THE EAST...AND SLIGHTLY COOLER IN THE WEST AS COMPARED TO TUESDAY. ALL DAYS OF THIS PORTION OF THE FORECAST ARE EXPECTED TO BE ABOVE NORMAL FOR THIS TIME OF YEAR. && .AVIATION /11Z THURSDAY THROUGH MONDAY/...
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AS OF 620 AM EST THURSDAY... MOST OF THE REGION WILL EXPERIENCE VFR CONDITIONS THROUGH THE NEXT 24 HOURS WITH MAINLY INTERVALS OF MID AND HIGH CLOUDS PASSING ACROSS. THE EXCEPTION WILL BE THE THOSE AREAS MAINLY ALONG AND WEST OF A KBLF-KLWB LINE WHERE LINGERING LOW LEVEL MOISTURE WILL MAKE FOR LOWER STRATO-CU CIGS THIS MORNING. HOWEVER MODELS FAVOR KBLF LIFTING TO VFR AFTER 15Z/10AM SO KEPT SIMILAR TIMING TO PREVIOUS ON LIFTING OUT THE LOW DECK. GUSTY NW WINDS WINDS THIS MORNING WILL ALSO WEAKEN WITH SPEEDS MAINLY IN THE 8-15 KT RANGE THIS AFTERNOON. HIGH PRESSURE EXTENDING INTO THE AREA FROM THE NW WILL MAINTAIN MAINLY VFR CONDITIONS OVERNIGHT INTO FRIDAY. HOWEVER LOW LEVEL MOISTURE MAY AGAIN CAUSE UPSLOPE INDUCED MVFR CIGS ACROSS SE WEST VA TO SPILL EAST TOWARD THE BLUE RIDGE LATE TONIGHT INTO FRIDAY MORNING. SOME CHANCE FOR KBLF TO DROP INTO IFR LATE TONIGHT OTRW KEEPING MVFR LEVELS MOSTLY AT KBLF/KLWB. EXTENDED DISCUSSION... THE FRI NIGHT-SAT SYSTEM NOW HAS TRENDED WEAKER BUT WILL STILL NEED TO BE WATCHED AS IT WILL LIKELY BRING A PERIOD OF SUB VFR WINTRY WEATHER ESPECIALLY FROM THE BLUE RIDGE WEST SAT. AVIATION INTERESTS WILL NEED TO MONITOR THIS SITUATION AS LATER FORECASTS BECOME AVAILABLE. THIS WILL LIKELY HAVE AN IMPACT ON AIR TRAVEL OVER THE WEEKEND...FROM THE SOUTHERN APPALACHIANS AND CAROLINAS NORTH TO THE MID ATLANTIC. ON THE HEELS OF THIS FRIDAY/SATURDAY SYSTEM WILL BE ANOTHER SYSTEM TO POTENTIALLY IMPACT MAINLY THE EASTERN PORTION OF THE REGION MONDAY INTO TUESDAY. ANOTHER AREA OF LOW PRESSURE IS EXPECTED TO HEAD NORTH ALONG THE EAST COAST WITH SCATTERED PRECIPITATION ON ITS WESTERN FLANKS ENTERING THE REGION. AT THIS POINT A WINTRY MIX IS POSSIBLE ALONG WITH LOCALIZED MVFR CIGS.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...NF LONG TERM...DS/JH AVIATION...DS/JH/PM/WP

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