Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 260021 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 721 PM EST SUN JAN 25 2015 .UPDATE...
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ISSUED AT 706 PM EST SUN JAN 25 2015 FRESHENED UP THE GRIDS WITH THE LATEST OBSERVATIONAL DATA FOR TEMPS...DEW POINTS...AND WINDS. THIS RESULTED IN LITTLE OVERALL CHANGE FROM THE ONGOING FORECAST. BASED ON THE CURRENT RADAR RETURNS...AND THE PWAT VALUES OVERNIGHT BEING AROUND A HALF INCH OR LESS...WENT AHEAD AND REDUCED ANY MENTION OF MODERATE RAINFALL/SNOWFALL TO LIGHT. JUST NOT SEEING A WHOLE LOT OF EVIDENCE AT THIS POINT FOR MODERATE TO HEAVY INTENSITIES...THOUGH SNOW COULD HAVE SOME HEAVIER SPOTS AT TIMES TOMORROW MORNING. LATEST NAM12 FORECAST SOUNDINGS REALLY START TO LOSE MOISTURE IN THE UPPER LEVELS BETWEEN 6 AND 9 Z...WITH NOT MUCH LIFT EITHER...ALSO SUPPORTING LIGHTER INTENSITIES. OTHERWISE...FORECAST SEEMS TO BE IN PRETTY GOOD SHAPE OVER THE NEXT FEW HOURS. THE CENTER OF THE LOW IS CURRENTLY OVER SOUTH CENTRAL KY AND MOVING OUR DIRECTION...WITH THE NEXT ROUND OF LIGHT RAIN ABOUT TO SPREAD ACROSS THE CWA OVER THE NEXT 1 TO 2 HOURS.
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&& .SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT) ISSUED AT 409 PM EST SUN JAN 25 2015 SURFACE ANALYSIS AS OF 20Z ACROSS THE REGION FEATURES A SMALL LOW PRESSURE SYSTEM OVER THE LOWER MIDWEST TRACKING EAST INTO THE OH VALLEY THIS EVENING. AHEAD OF THIS...SOME SHOWER ACTIVITY HAS BEGUN TO MOVE INTO THE AREA THIS AFTERNOON WITH MORE WIDESPREAD PRECIP BACK WEST INTO WESTERN KENTUCKY AND SOUTHERN INDIANA. PLENTY OF SOUTHWEST FLOW TODAY AND WAA INTO THE AREA HAS ALLOWED FOR TEMPS TO RISE INTO THE UPPER 40S AND EVEN LOWER 50S ACROSS EASTERN KENTUCKY TODAY. MODELS SHOWING THE COLD FRONT TO MOVE THROUGH LATER TONIGHT AFTER 00Z WILL HAVE THE COLDER AIR MOVING IN LATER. THIS ADVECTION WILL BEGIN IN EARNEST JUST AFTER 06Z AS THE FRONT MOVES THROUGH. EXPECTING A CHANGE OVER IN THE HIGHER ELEVATIONS WITH ALREADY TEMPS AT BLACK MOUNTAIN REACHING ITS HIGH FOR THE DAY IN THE UPPER 30S AND IS NOW BEGINNING TO DROP OFF AT THIS HOUR. MODEL PROFILES SHOW A BRIEF PERIOD OF GOOD OMEGA THROUGH THE LAST FEW HOURS OF THE EVENT AS THE FRONT MOVES THROUGH. WITH COLD ENOUGH AIR MOVING IN...THERE COULD BE SOME QUICK BURSTS OF SNOW IN THE HIGHER ELEVATIONS AND EVEN IN THE VALLEYS WHERE COLDER AIR HAS FINALLY MOVED IN. SPEAKING OF TEMPERATURES...LATE TONIGHT AND INTO THE DAY ON MONDAY...TEMPS WILL BE FALLING INTO THE MORNING HOURS BUT SOME SLIGHT RADIATIONAL HEATING DURING THE DAY BEFORE THE CORE OF THE AIR MASS MOVES IN MONDAY AFTERNOON AND INTO MONDAY NIGHT WILL RESULT IN TEMPS RISING A DEGREE OR TWO OR HOLDING STEADY THROUGH THE DAY TOMORROW. TEMPS OVER THE HIGHER TERRAIN SHOULD SLOWLY FALL THROUGH THE DAY. WINDS AFTER FRONTAL PASSAGE MONDAY MORNING WILL THEN SWITCH AROUND TO THE NORTHWEST FOR A FAVORABLE DIRECTION FOR SOME UPSLOPE SNOW SHOWERS THROUGH MONDAY AFTERNOON. MOISTURE DEPTH HANGS AROUND THROUGH MONDAY MORNING AND INTO THE AFTERNOON WITH SOME DECENT LIFT REMAINING ACCORDING TO THE NAM AND GFS SO SOME DECENT SNOW SHOWERS WILL HANG AROUND THROUGH THE DAY ON MONDAY BEFORE TAPERING OFF TO FLURRIES FROM WEST TO EAST INTO MONDAY NIGHT. THE CORE OF THE AIR MASS MOVING IN WILL CAUSE TEMPS TO PLUMMET INTO THE MID 20S MONDAY NIGHT AND WILL LIKELY ADD TO THE THREAT OF HAZARDOUS AND SLICK ROADS. THEREFORE...HAVE ISSUED AN SPS TO HIGHLIGHT THIS THREAT. .LONG TERM...(TUESDAY THROUGH SUNDAY) ISSUED AT 420 PM EST SUN JAN 25 2015 A RATHER AMPLIFIED PATTERN IS EXPECTED TO BEGIN THE PERIOD. MODELS REMAIN IN GENERALLY IN GOOD AGREEMENT FOR MOST OF THE PERIOD...WITH DIFFERENCES INCREASING TOWARD THE END OF THE PERIOD. AT THE START OF THE PERIOD A TROUGH IS EXPECTED TO BE IN PLACE FROM THE GREAT LAKES SOUTH INTO THE MID ATLANTIC SATES AND OFF THE SOUTHEASTERN US COAST...WITH A RIDGE OF HIGH PRESSURE FROM MEXICO NORTH INTO THE SOUTHERN PLAINS AND ROCKIES. AT THE SFC THE A DEEP SFC LOW/BLIZZARD WILL BE MOVING ALONG THE NORTHEAST US COAST TO START THE PERIOD WITH A RIDGE OF HIGH PRESSURE AT THE SFC EXTENDING FROM ONTARIO INTO THE GREAT LAKES AND MS VALLEY REGION. A SERIES OF SHORTWAVES IN NW FLOW BETWEEN THE TWO WILL DROP FROM THE GREAT LAKES AND THROUGH THE OH VALLEY AND APPALACHIANS TUESDAY INTO TUESDAY NIGHT. THIS WILL BRING CHANCES FOR SNOW SHOWERS AND REINFORCE A COLD AIRMASS WITH 850 MB TEMPS TO FALL TO THE -8C TO -10C RANGE BY LATE TUE AFTERNOON AND TUE EVENING. AS THE TROUGH AXIS LIFTS TO THE NORTH AND EAST AND THE SFC LOW MOVES FURTHER UP THE EASTERN SEABOARD...HIGH PRESSURE WILL GRADUALLY BUILD INTO THE LOWER OH VALLEY REGION AND APPALACHIANS TUE NIGHT INTO WED. THE INFLUENCE OF THE RIDGING WILL WANE BY LATE WED NIGHT AS A SHORTWAVE MOVING AROUND THE RIDGE OVER THE ROCKIES AND A NORTHERN STREAM TROUGH BEGIN TO JOIN FORCES AND APPROACH THE GREAT LAKES AND MS VALLEY REGION AS WELL AS THE LOWER OH VALLEY REGION. THE ASSOCIATED SFC LOW SHOULD TRACK WELL NORTH OF THE AREA JUST TO THE SOUTH OF THE SOUTHERN GREAT LAKES AND INTO THE MID ATLANTIC STATES FROM WED NIGHT INTO THU NIGHT. THIS SYSTEM WILL HAVE SOMEWHAT LIMITED MOISTURE...AND THIS SHOULD BE ANOTHER EVENT WHERE THE ATMOSPHERE MOISTENS FROM THE TOP DOWN. AT THE ONSET...SOME SNOW COULD MIX IN PENDING THE STRENGTH OF WARM AIR ADVECTION AND MOISTURE ADVECTION LATE WED NIGHT INTO THU MORNING. THE CLOUDS ALSO MAY NOT THICKEN QUICK ENOUGH TO PREVENT AT LEAST A MINOR RIDGE/VALLEY SPLIT FOR THE VALLEYS ON WED EVENING. AT THIS POINT...A LOW IN THE MID TO UPPER 20S OCCURRING AROUND 6Z ON THU IS EXPECTED. COLDER AIR WILL WRAP BACK INTO THE REGION BEHIND THIS SYSTEM AND POSSIBLY CHANGE ANY PRECIP BACK TO SNOW AS IT DEPARTS. HIGH PRESSURE SHOULD THEN BUILD IN TO BRING A DRY START TO THE WEEKEND. THE ECMWF LOWERS HEIGHTS MORE SIGNIFICANTLY ACROSS THE REGION AS WELL AS THE GREAT LAKES AND EASTERN SEABOARD AT THE END OF THE PERIOD AND IS THUS MUCH COLDER WITH THE AIRMASS. ANY SHORTWAVES AT THE END OF THE PERIOD SHOULD BE RATHER MOISTURE STARVED WITH THE MODEL CONSENSUS FAVORING ANYTHING THAT FALLS BEING SNOW. FOR TEMPS LATE IN THE PERIOD...OPTED TO GO A TAD COLDER THAN THE CONSENSUS BLEND...MORE IN LINE WITH ISC CONSENSUS AND GIVING A BIT MORE CREDIT TO THE PAST 2 ECMWF RUNS. && .AVIATION...
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(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING) ISSUED AT 717 PM EST SUN JAN 25 2015 AVIATION CONCERNS WILL INCLUDE DROPPING CIGS THROUGH THIS EVENING AND INTO TONIGHT. WENT A BIT MORE OPTIMISTIC THROUGH ABOUT 6Z COMPARED TO THE PREVIOUS FORECAST...GIVEN THE SLOW MOVEMENT OF THE SYSTEM RESULTING IN A LONGER TIME FOR LOWER CIGS DOWNSTREAM TO REACH THE TAF SITES. EXPECT MVFR CIGS TO NOW REACH THE AREA BETWEEN 4 AND 7Z TONIGHT...SLOWLY DROPPING THROUGH THE NIGHT AND INTO THE MORNING AS THE HEAVIER PRECIP ARRIVES AND THE THE LOWER LEVELS MOISTEN UP. EXPECT AIRFIELD MINIMUM CIGS /OR JUST A COUPLE HUNDRED FEET ABOVE/ TO ARRIVE BETWEEN 12 AND 14Z AND REMAIN THROUGH MUCH OF THE AFTERNOON. IT IS ALSO AT THIS POINT THAT RAIN WILL LIKELY MAKE THE TRANSITION TO ALL SNOW AS TEMPS DROP BELOW FREEZING ACROSS THE REGION. LOWEST VISIBILITIES MAY ACTUALLY OCCUR DURING THIS CHANGEOVER PERIOD...BUT COULD FLUCTUATE ANYWHERE BETWEEN MVFR AND AIRPORT MINIMUMS DEPENDING ON THE INTENSITY OF THE BAND OF PRECIP PASSING OVERHEAD. WINDS THROUGH THE NIGHT WILL BEGIN TO SHIFT AROUND TO THE NORTHWEST WITH GUSTS UP TO 20 KNOTS POSSIBLE BY TOMORROW IN SOME LOCATIONS. SNOW SHOULD LIGHTEN UP AND TAPER OFF LATE IN THE TAF PERIOD WITH IMPROVING CONDITIONS EXPECTED...GENERALLY AFTER 18Z.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JMW SHORT TERM...SHALLENBERGER LONG TERM...JP AVIATION...JMW

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