Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 012111 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 411 PM EST SUN FEB 1 2015 .SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT) ISSUED AT 335 PM EST SUN FEB 1 2015 19Z SFC ANALYSIS SHOWS A RATHER DEEP AREA OF LOW PRESSURE MOVING ACROSS THE MISSISSIPPI RIVER INTO ILLINOIS. A COLD FRONT FROM THIS IS STRETCHED TO THE SOUTHWEST DOWN INTO TEXAS. AS THIS LOW PUSHES FURTHER INTO THE OHIO VALLEY...THE CORE OF ITS PCPN SHIELD IS NOW ENTERING EASTERN KENTUCKY WITH LIGHT TO MODERATE RAINS OVERSPREADING THE AREA. UNDER THICK CLOUDS AND THE ARRIVING RAINS...TEMPERATURES HAVE PEAKED THIS AFTERNOON WITH READINGS IN THE MID 40S TO LOWER 50S ACROSS THE AREA. DEWPOINTS...MEANWHILE...ARE COMING UP WITH THE ARRIVING RAINS AND NOW VARY FROM THE LOW TO MID 20S IN THE EAST AND THE UPPER 30S TO LOWER 40S TO THE WEST. WIND HAVE ALSO PICKED UP WITH THE ARRIVAL OF THE RAIN WITH GUSTS TO 20 TO 25 KTS FROM THE SOUTH OVER THE CUMBERLAND VALLEY AND 15 TO 20 KTS ELSEWHERE. THE MODELS ARE IN GOOD AGREEMENT ALOFT THROUGH THE SHORT TERM PORTION OF THE FORECAST AS THEY WHIP A SHARP TROUGH THROUGH THE SOUTHERN APPALACHIANS BY MIDDAY MONDAY. IN THE NORTHWEST FLOW THAT FOLLOWS...A TRAILING SHORTWAVE WILL PASS THROUGH EASTERN KENTUCKY INTO EARLY TUESDAY MORNING...SEEN AS STRONGEST IN THE ECMWF WHEN COMPARED TO THE NAM12 AND GFS/GEM. HAVE MAINLY FOLLOWED A MODEL BLEND THROUGH MONDAY NIGHT WITH AN EMPHASIS ON THE HIGHER RESOLUTION DETAILS FROM THE NAM12 BEFORE LEANING MORE ON THE GFS AND NAM12 WITH THE TRAILING WAVE THROUGH TUESDAY MORNING. SENSIBLE WEATHER WILL FEATURE A GOOD SOAKING RAIN FOR EAST KENTUCKY THROUGH THE EVENING AND INTO THE OVERNIGHT ALONG WITH BREEZY CONDITIONS AS THE WRAPPED UP SFC LOW MOVES THROUGH. THE LOW PASSES TO THE EAST BY SUNRISE MONDAY WITH WINDS SWITCHING TO THE WEST AND INCREASING AS THE TIGHT GRADIENT ON THE LOW/S BACKSIDE EXITS THE AREA. IN ADDITION TO THE BREEZY CONDITIONS IN THE WAKE OF THE LOW...AN ARCTIC BOUNDARY WILL BRING IN MUCH COLDER AIR FROM WEST TO EAST ACROSS THE CWA BETWEEN 08 AND 13Z RESULTING IN A SWITCH OVER FOR ANY LINGERING PCPN TO SNOW. THE WINDS WILL BECOME MORE UPSLOPE WHILE THE SFC LOW FURTHER DEEPENS INTO MONDAY MORNING. THIS WILL ADD TO THE SNOW FALL FOR OUR FAR EASTERN COUNTIES WITH THE WINDS BLOWING THE SNOW AROUND KEEPING THE VIS LOW IN ANY SHOWERS. EXPECT THE SNOW TO BE WORST BETWEEN 11 AND 15Z FOR MOST OF THE AREA WITH LIGHT ACCUMULATIONS EXPECTED ASIDE FROM THE RIDGES AND LOCATIONS IN THE FAR EAST. ALONG THOSE PLACES NEAR THE VIRGINIA BORDER SOME HIGHER SNOW TOTALS WILL BE POSSIBLE WITH BETWEEN 2 AND 3 INCHES SEEN ON THE PEAKS ABOVE 2500 FEET AND UP TO 2 INCHES ON THE LOWER RIDGES WHILE VALLEYS GENERALLY PICK UP AN INCH OR LESS. FINALLY...IN ADDITION TO THE SNOW AND WINDS...THE COLD AIR COULD MOVE IN QUICK ENOUGH...TRAILING THE RAINS AND LIMITED DRY SLOTTING TO RESULT IN ICY CONDITIONS ON AREA ROADS. FOR THIS REASON...WILL HAVE AN SPS OR WINTER WEATHER ADVISORY OUT FOR THE ENTIRE AREA...HITTING THE EAST PROGRESSIVELY HARDER FOR AMOUNTS AND IMPACTS. OUR VIRGINIA BORDER COUNTIES WILL HAVE AN ADVISORY FOR SNOW GOING UNTIL 23Z WHILE TO THE WEST THE ADVISORY WILL RUN THROUGH 19Z WITH LESSER TOTALS. THE SNOW TAPERS OFF FROM WEST TO EAST MONDAY AFTERNOON WITH CAA SENDING TEMPS DOWN INTO THE TEENS MOST PLACES BY DAWN TUESDAY...THOUGH LOW CLOUDS WILL LIKELY KEEP READINGS FROM COMPLETELY BOTTOMING OUT FOR EASTERN PARTS OF THE AREA. USED THE BCCONSSHORT FOLLOWED BY THE SUPERBLEND AS A STARTING POINT FOR TEMPERATURES...DEWPOINTS...AND WINDS THROUGH TUESDAY MORNING. MADE ONLY MINOR ADJUSTMENTS TO WINDS AND TEMPERATURES TO ACCOUNT FOR THE TERRAIN EFFECTS OF THE CAA WINDS LATE TONIGHT INTO MONDAY MORNING. AS FOR POPS...ENDED UP ON THE HIGH SIDE OF MOS GUIDANCE THROUGH MONDAY AFTERNOON OWING TO THE TENDENCY FOR THE MODEL/MOS GUIDANCE TO UNDER DO UPSLOPE SNOW SITUATIONS. .LONG TERM...(TUESDAY THROUGH SUNDAY) ISSUED AT 410 PM EST SUN FEB 1 2015 TUESDAY WILL START OUT WITH GENERALLY ZONAL FLOW ALOFT AND SURFACE HIGH PRESSURE IN PLACE. TEMPERATURES WILL WARM FROM THE PREVIOUS DAY WITH SURFACE WINDS BECOMING MORE SRLY AND SKIES CLEARING...THOUGH STILL EXPECTED TO BE A FEW DEGREES BELOW SEASONABLE NORMALS. A SHORTWAVE WILL BEGIN TO TRAVERSE ALONG A TROUGH AXIS WELL NORTH OF THE REGION...REACHING THE UPPER GREAT LAKES BY WEDNESDAY EVENING AND STRENGTHENING AS IT SHOOTS OFF TO THE SE AND ACROSS THE EASTERN PORTION OF KY. THIS COURSE OF ACTION...INCLUDING THE AMPLITUDE AND TIMING...IS VERY MUCH A RESULT OF WHICH MODEL IS CORRECT. AS OF NOW...THERE IS STILL QUITE A BIT OF DISAGREEMENT BETWEEN THE GFS AND ECMWF...WHICH LEADS TO LOW CONFIDENCE ON THE RESULTING SURFACE FEATURES. THE GFS CONTINUES TO BE THE STRONGEST WITH THE SYSTEM...SHOWING A 1009MB LOW PRESSURE SYSTEM MOVING ACROSS NEW ENGLAND WEDNESDAY EVENING. THE ECMWF IS IN A SIMILAR LOCATION FOR THE LOW...BUT IS SLIGHTLY WEAKER AT 1013MB AS OF THE 12Z RUN. A COLD FRONT WILL EXTEND SOUTHWEST OF THIS LOW...AND BRING FRONTAL PRECIPITATION TO MUCH OF THE OHIO VALLEY WEDNESDAY EVENING THROUGH THURSDAY MORNING FOR THE GFS...AND SOMEWHAT LATER WEDNESDAY NIGHT THROUGH THURSDAY AFTERNOON FOR THE ECMWF AND GEM. REGARDLESS...THIS WILL BE A QUICK HITTING SYSTEM...WITH MUCH OF THE MOISTURE FALLING ALONG OR JUST BEHIND THE FRONTAL PASSAGE. IF THIS HOLDS TRUE...WINDS WILL MAKE A QUICK SHIFT TO THE N AND BEGIN PULLING IN MUCH COLDER AIR AROUND THE TIME THE PRECIPITATION STARTS. THIS WILL QUICKLY DROP TEMPS BELOW FREEZING...SO EXPECT ANY PRECIP THAT FALLS TO BE MAINLY IN THE FORM OF SNOW...WITH MAYBE A SMALL AMOUNT OF RAIN AT THE ONSET. HIGHS ON THURSDAY ARE ONLY EXPECTED TO REACH THE UPPER 20S TO AROUND 30. DRY AIR WILL THEN QUICKLY WORK IN AND CUT OFF ANY REMAINING SNOW POTENTIAL SOMETIME THURSDAY AFTERNOON. DO NOTE...GIVEN THE DISCREPANCIES BETWEEN THE MODELS...THE TIMING OF ONSET AND DEPARTURE IS LIKELY TO CHANGE. THIS WILL THEN LIKELY AFFECT THE SNOW TOTALS. AT THIS TIME...FORECASTING GENERALLY A HALF INCH OR LESS ACROSS THE CWA...WITH THE HIGHEST AMOUNTS IN THE SE WHERE SNOW WILL LINGER THE LONGEST AND SOME UPSLOPE FLOW WILL TAKE PLACE. AFTER THIS SYSTEM PASSES THROUGH THE REGION...UPPER LEVELS WILL SLOWLY TRANSITION BACK TO ZONAL FLOW. COLDER CANADIAN AIR FLOWING INTO THE REGION WILL EVENTUALLY GIVE WAY TO MORE SEASONABLE NORMS BY SATURDAY. HIGH PRESSURE WILL BE IN CONTROL THROUGH MUCH OF THE REMAINDER OF THE EXTENDED. OUR NEXT THREAT FOR PRECIP WILL OCCUR SOMETIME SATURDAY NIGHT/SUNDAY ON DAY 7 OF THE FORECAST AS MODELS HINT AT ANOTHER SHORTWAVE DEVELOPING OVER THE CENTRAL PLAINS. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON) ISSUED AT 115 PM EST SUN FEB 1 2015 VFR CONDITIONS WILL PERSIST THROUGH MOST OF THE AFTERNOON. HOWEVER... THE CIGS WILL BEGIN TO DROP AS MODERATE RAINFALL BEGINS TO MOVE INTO THE AREA ALONG WITH A LOWERING OF THE VISIBILITY. IN GENERAL...IFR AND BELOW CONDITIONS CAN BE ANTICIPATED THROUGH THE AREA AFTER 00Z WITH THE MODERATE RAINS MOVING THROUGH. THE RAIN WILL THEN CHANGE TO SNOW AS THE COLDER AIR MOVES IN WITH REDUCED VISIBILITY AND LOWER VIS BEING THE MAIN AVN CONCERN. WINDS WILL BE INCREASING THROUGH THE AFTERNOON AND EVENING FROM THE SOUTH TO SOUTHWEST. THESE WILL START SHIFTING TO THE SOUTHWEST AND LATER TONIGHT AND THEN TO THE WEST PREDAWN. GUSTY WINDS WILL BLOW AS HIGH AS 25 KTS THROUGH THE NIGHT AND INTO THE DAY MONDAY AS THE SYSTEM MOVES ON THROUGH. THESE WINDS...COMBINED WITH SNOWFALL WILL KEEP THE VIS RATHER LOW THROUGH MID MORNING IN MOST PLACES. LOOK FOR CONDITIONS TO START IMPROVING BY MIDDAY FROM WEST TO EAST. && .JKL WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM 6 AM TO 6 PM EST MONDAY FOR KYZ088- 118-120. WINTER WEATHER ADVISORY FROM 3 AM TO 2 PM EST MONDAY FOR KYZ086- 087-104-106>117-119. && $$ SHORT TERM...GREIF LONG TERM...JMW AVIATION...GREIF

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