Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 020211 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
911 PM EST SUN FEB 1 2015

.UPDATE...
ISSUED AT 835 PM EST SUN FEB 1 2015

AS OF 8 PM...AN AREA OF LOW PRESSURE WAS CENTERED OVER EASTERN
INDIANA WITH A STATIONARY FRONT EXTENDING EAST INTO THE MID ATLANTIC
STATES WITH A COLD FRONT EXTENDING SOUTH JUST TO THE WEST OF THE
INTERSTATE 65 CORRIDOR. A DRY SLOT EXTENDED FROM EASTERN OK NORTH AND
NORTHEAST INTO SOUTHERN IL WITH RADAR RETURNS ACROSS KY EAST OF THIS
AREA. A SFC TROUGH WHICH IS THE LEADING EDGE OF THE MUCH COLDER AIR
EXTENDED WEST INTO SOUTHERN IL AND EASTERN MO.SOME SNOW IS ALSO
FALLING NEAR AND BEHIND THE SFC TROUGH WHICH IS LOCATED IN ADVANCE OF
THE UPPER LEVEL SHORTWAVE. TEMPERATURES HAVE RISEN FROM THE MID 30S
TO UPPER 30S ON TOP OF BLACK MOUNTAIN IN THE WARM ADVECTION AHEAD OF
THE COLD FRONT.

THE BACK EDGE OF THE STEADIER SHOWERS IS ENTERING THE JKL CWA WITH
ANOTHER AREA OF SHOWERS IN ADVANCE OF AND JUST BEHIND THE COLD
FRONT. AS THE COLD FRONT WORKS EAST...WE EXPECT A RELATIVE LULL IN
THE PRECIPITATION FOR A TIME IN MANY AREAS AFTER IT PASSES DURING THE
OVERNIGHT UNTIL THE UPPER LEVEL TROUGH AND SFC TROUGH NEARS AND LAPSE
RATES STEEPEN. ATTM...IT LOOKS LIKE THE ATMOSPHERE WILL BEGIN TO
COOL TO COLD ENOUGH LEVELS FOR A MIX WITH OR CHANGEOVER TO SNOW OF
ANY LINGERING SHOWERS JUST BEHIND THE COLD FRONT IN THE FAR NW
GENERALLY BETWEEN 2 AND 5 AM. THE HIGHEST TERRAIN ABOVE 2500 FEET
COULD ALSO CHANGEOVER DURING THAT TIME.

SOMEWHAT MORE ORGANIZED SNOW SHOWERS ARE ANTICIPATED WITH THE SFC
TROUGH AND IN ADVANCE OF THE SHORTWAVE AS THE COLDEST AIR WORKS IN
ALOFT SHOULD ARRIVE OR DEVELOP AND ENHANCE AS IT INTERACTS WITH THE
TERRAIN RISE AT THE ESCARPMENT IN OUR WESTERN OR NW CWA AROUND 6 OR 7
AM AND THEN GENERALLY TRANSLATE ACROSS THE AREA. ADDITIONAL LESS
ORGANIZED SHOWERS OR RAIN OR SNOW OR A MIX MAY BE ONGOING AT THAT
TIME AS WELL. RECENT MODEL GUIDANCE DOES NOT PROVIDE MUCH CONFIDENCE
IN THIS EVOLUTION AS THERE ARE HINTS OF SNOW SHOWERS AS THE
RELATIVELY STRONG SHORTWAVE MOSES THROUGH AND THE LOW HAS AN UPSLOPE
COMPONENT. HOWEVER...HRR RUNS AND SHORT TERM GUIDANCE SUCH AS THE NAM
AND THE RAP ARE NOT ALL THAT IMPRESSIVE. THE STRENGTH OF THE
SHORTWAVE...ASSOCIATED LAPSE RATES AND UPSLOPE FLOW THOUGH ARGUE FOR
GENERALLY HIGH CHANCE TO LIKELY POPS FOR THE NORTH AND SOUTHEAST FOR
MONDAY MORNING. AT THIS TIME...WE PLAN TO NOT ADD ANY ADDITIONAL
AREAS TO THE WSW. HOWEVER...UPSTREAM TRENDS WILL BE MONITORED ALONG
WITH TIMING INTO THE NW COUNTIES WHICH ON AVERAGE SHOULD BE THE
COLDEST DURING THE MORNING COMMUTE FOR POSSIBLE AREAL ADDITION TO THE
WSW.

IN ORDER TO ACCOUNT FOR THE HIGHER TERRAIN OF FONDE MTN AREA OF
WESTERN BELL COUNTY WHICH SHOULD BE FAVORED IN THE NW UPSLOPE FLOW
AND BETTER MATCH START TIMES TO MY SOUTH...WE HAVE STARTED THE WSW A
COUPLE OF HOURS EARLIER FOR THE VA BORDER COUNTIES.


&&

.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 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 739 PM EST SUN FEB 1 2015

CIGS INITIALLY WILL BE MAINLY IN THE MVFR RANGE OR FALL INTO THE VFR
RANGE EARLY IN THE PERIOD. DETERIORATION TO IFR AND BELOW CONDITIONS
ARE ANTICIPATED AFTER 06Z. THE RAIN WILL THEN CHANGE TO SNOW THROUGH
ABOUT 13Z AS THE COLDER AIR MOVES IN WITH REDUCED VISIBILITY AND
LOWER VIS BEING THE MAIN CONCERN. SOUTH TO SOUTHWEST WINDS WILL
START SHIFTING TO THE WEST SOUTHWEST AND LATER TONIGHT TO THE WEST.
GUSTS AS HIGH AS 25 KT WILL BE POSSIBLE THROUGH AT LEAST 18Z ON
MONDAY AS THE SYSTEM MOVES ON THROUGH. CONDITIONS SHOULD IMPROVE BACK
INTO THE MVFR RANGE BETWEEN 15Z AND 21Z IN MOST LOCATIONS.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 5 AM TO 6 PM EST MONDAY FOR KYZ087-
088-118-120.

WINTER WEATHER ADVISORY FROM 3 AM TO 2 PM EST MONDAY FOR KYZ086-
104-106>117-119.

&&

$$

UPDATE...JP
SHORT TERM...GREIF
LONG TERM...JMW
AVIATION...JP



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