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...
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.

&&

.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...(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.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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





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