Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 221133 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
733 AM EDT WED APR 22 2015

.UPDATE...
ISSUED AT 725 AM EDT WED APR 22 2015

HOURLY GRIDS WERE FRESHENED UP BASED ON RECENT OBSERVATIONS.
RECENT RADAR TRENDS AND SHORT TERM MODEL RUNS POINT TOWARD THE
BEST SHOWER CHANCES ACROSS THE NORTH AND EAST THIS MORNING...AND
ACROSS THE FAR SOUTH AS WELL. THERE MAY BE PORTIONS OF THE WEST
CENTRAL CWA THAT ARE LARGELY MISSED OR RECEIVE ONLY SPRINKLES.
LIGHTNING HAS RECENTLY BEEN DETECTED BETWEEN SDF AND FFT AND ALSO
NORTH OF BNA...SO SLIGHT CHANCE OF THUNDER WILL BE ADDED FOR THIS
MORNING IN THE NORTH...LINGERING INTO THE EARLY AFTERNOON IN THE
SOUTH.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 330 AM EDT WED APR 22 2015

AN UPPER LEVEL LOW HAS NOW MOVED TO A POSITION OVER ONTARIO JUST
NOT THE GREAT LAKES. A COUPLE OF DISTURBANCES WERE ROTATING AROUND
THIS UPPER LOW INTO THE LOWER OH VALLEY REGION. MEANWHILE...A SFC
COLD FRONT WAS NEARING THE OH RIVER. FURTHER WEST...A RIDGE
EXTENDED FROM THE GULF OF MEXICO NORTH INTO THE NORTHERN ROCKIES
REGION. A CLOSED UPPER LOW WAS OVER SOUTHERN CA WITH A TROUGH
ENTERING THE PACIFIC NORTHWEST AND ADJACENT AREAS OF CANADA.

THROUGH THE NEAR TERM PERIOD...THE UPPER LEVEL LOW WILL MEANDER TO
NORTHERN NEW ENGLAND/ST LAWRENCE VALLEY REGION. THE UPSTREAM
SHORTWAVE WILL ROTATE THROUGH THE OH VALLEY AND APPALACHIAN REGION
TODAY. AS THE UPPER LOW MOVES FURTHER EAST...HEIGHTS WILL BEGIN TO
SLOWLY RISE ACROSS THE REGION LATER TONIGHT AND INTO THE DAY ON
THURSDAY AS THE RIDGE AXIS SHIFTS EAST INTO THE PLAINS. AT THE
SFC...THE COLD FRONT SHOULD PRECEDE THE SHORTWAVE INTO THE REGION
MOVING INTO THE COMMONWEALTH OVER THE NEXT COUPLE OF HOURS AND
ACROSS EASTERN AND SOUTH CENTRAL KY THROUGH EARLY THIS AFTERNOON.
HIGH PRESSURE WILL BUILD IN BEHIND THE COLD FRONT...ESPECIALLY
LATE TONIGHT AND INTO THE DAY ON FRIDAY.

A FEW STRAY SHOWERS CONTINUE TO WORK EAST ACROSS MAINLY THE
SOUTHERN HALF OF THE CWA ATTM. HOWEVER...MORE ORGANIZED SHOWER
ACTIVITY IS LOCATED NEAR THE COLD FRONT ITSELF. THERE HAD BEEN
SOME LIGHTNING IN THIS AREA EARLIER IN THE NIGHT...BUT THIS HAS
DIMINISHED OVER THE PAST COUPLE OF HOURS. ANY OF THE SHOWERS WILL
CONTINUE TO PRODUCE BRIEF GUSTY WINDS AT A LOCATION AS THEY PASS
THROUGH THE REMAINDER OF THE OVERNIGHT.

FOR THE THIRD DAY IN A ROW...ONCE SOLAR INSOLATION BEGINS...WINDS
WILL BECOME GUSTY AND SUSTAINED SPEEDS WILL ALSO PICK UP BY MID TO
LATE MORNING. GUSTS INTO THE 20 TO 30 MPH SHOULD BE COMMON WITH
SUSTAINED SPEEDS EASILY IN THE 10 TO 15 MPH RANGE AS MOMENTUM IS
AGAIN TRANSFERRED DOWN TO THE SURFACE. THERE SHOULD BE JUST
ENOUGH MOISTURE AND DYNAMICS FOR A GOOD CHANCE OF SHOWERS IN MOST
LOCATIONS...IN THE MORNING ACROSS THE NORTH...AND MIDDAY AND
LINGERING INTO MID AFTERNOON ALONG THE VA BORDER. QPF WILL BE
CONSIDERABLY LOWER THAN SEVERAL PREVIOUS SYSTEMS THIS MONTH...AS
THE AIRMASS WILL ONLY HAVE PW AROUND 0.6 INCHES. ONLY ABOUT A
TENTH OF AN INCH OR LESS. ALSO...ACROSS THE SOUTHEAST...THERE IS
AN OPPORTUNITY FOR SOME HEATING THROUGH LATE MORNING. IN THIS
AREA...SREF PROBABILITIES FOR LI LESS THAN 0 ARE IN THE 40 TO 70
PERCENT RANGE LATE IN THE MORNING INTO THE EARLY AFTERNOON. CAPE
WILL BE LIMITED TO 500 MB OR LESS ON AVERAGE THOUGH. THIS MAY BE
SUFFICIENT FOR A STRAY RUMBLE OR TWO...ALTHOUGH CHANCES APPEAR
BETTER TO OUR SOUTH AND EAST.

HIGH PRESSURE WILL NOSE EAST INTO THE OH VALLEY REGION
TONIGHT WITH CLEARING FROM WEST TO EAST CONTINUING. THE DRIEST
AIR WILL REACH THE WESTERN AND NORTHWESTERN CWA FIRST. THE
PRESSURE GRADIENT ALSO SHOULD BE WEAK ENOUGH THAT AT LEAST THE
NORMALLY COLDER LOCATIONS IN THIS AREA AND MORE SHELTERED AREAS
COULD NEAR THE FREEZING MARK. THERE REMAINS UNCERTAINTY AS TO
WHETHER OR NOT THERE MAY BE JUST ENOUGH OF A GRADIENT FOR A LIGHT
PUFF OF WIND AND OR DEWPOINT DEPRESSIONS BEING TOO LARGE FOR THE
THREAT OF FROST FORMATION. HOWEVER...WITH THE UNCERTAINTY IN BOTH
OF THESE...WE HAVE OPTED TO KEEP FROST AT JUST PATCHY IN THE GRIDS
FOR THOSE MORE FAVORED LOCATIONS. THIS THREAT WILL BE ADDED TO
THE HWO.

HIGH PRESSURE AT BOTH THE SFC AND MID LEVELS WILL BECOME MORE
FIRMLY IN PLACE ACROSS THE REGION WITH MID LEVEL HEIGHT RISES ON
THURSDAY. THIS SHOULD LEAD TO MOSTLY SUNNY TO SUNNY SKIES AND WITH
1000 TO 500 MB MEAN LAYER RH DOWN TO ABOUT THE 20 TO 30 PERCENT
RANGE AND PW ONLY ABOUT 0.18 TO 0.28 INCHES.. THIS PW IS BELOW THE
25TH PERCENTILE FOR THIS TIME OF YEAR ACROSS THE REGION AND OVER
1.5 STD BELOW NORMAL. ALL THIS POINTS TO RH ON THE LOW SIDE AS
WELL AS DEWPOINTS SHOULD EASILY BE IN THE 20S. CURRENT UPSTREAM
OBSERVATIONS OF DEWPOINTS TO OUR NORTHWEST BEHIND THE FRONT ALSO
SUPPORT THIS. THE DRY AIRMASS SHOULD ALSO WARM A TAD MORE THAN THE
MOS GUIDANCE WOULD SUGGEST. THIS HAS BEEN THE CASE FOR SOME OF THE
DRIER AIRMASSES THIS SPRING.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 300 AM EDT WED APR 22 2015

CONFIDENCE IN FORECAST IS DECENT THROUGH THE WEEKEND...WITH
SIGNIFICANT MODEL DIFFERENCES LEADING TO MUCH MORE UNCERTAINTY
HEADING INTO NEXT WEEK. HIGH PRESSURE WILL YIELD ANOTHER CHILLY
NIGHT THURSDAY NIGHT WITH LOWS AGAIN FALLING INTO THE LOWER 30S
YIELDING ANOTHER POTENTIAL NIGHT FOR SOME FROST.

HIGH WILL SHIFT EAST ON FRIDAY WITH CLOUDS ON THE INCREASE. AN AREA
OF LOW PRESSURE WILL THEN PUSH INTO THE OHIO RIVER VALLEY FRIDAY
NIGHT INTO SATURDAY WITH A WARM FRONT CROSSING EASTERN KENTUCKY LATE
FRIDAY NIGHT. SOME QUESTION AS TO HOW MUCH MOISTURE WILL MAKE ITS
WAY INTO THE AREA WITH THE POSSIBILITY OF DOWNSLOPING
SOUTH/SOUTHEAST FLOW. FORCING WILL EVENTUALLY OVERCOME ANY LOW LEVEL
CONCERNS...BUT ITS JUST A MATTER OF HOW QUICKLY THIS OCCURS. AT THIS
POINT...IT LOOKS LIKE PRECIPITATION SHOULD SPREAD INTO THE AREA
SOMETIME SATURDAY MORNING AND CONTINUE INTO SATURDAY NIGHT...MAKING
FOR A DAMP START TO THE WEEKEND. A QUICK HITTING UPPER LEVEL WAVE
WILL PUSH ACROSS EASTERN KENTUCKY SATURDAY NIGHT KEEPING THE THREAT
OF RAIN IN THE FORECAST. WE SHOULD DRY OUT ON SUNDAY AND MONDAY.
HOWEVER...THIS IS WHERE MODELS DIVERGE ON THE PLACEMENT OF A CUT OFF
UPPER LOW. DEPENDING ON WHERE IT SETS UP...OUR WEATHER COULD REMAIN
QUITE UNSETTLED...OR WE COULD BE LOOKING AT AN EXTENDED DRY PERIOD.
SAFE TO SAY...CONFIDENCE IS LOW BEYOND MONDAY.

TEMPERATURES WILL REMAIN ON THE COOL SIDE INTO NEXT WEEK WITH NO
POTENTIAL WARM UPS ON TAP.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 735 AM EDT WED APR 22 2015

MAINLY VFR CIGS AND VIS ARE EXPECTED OVER THE NEXT 24 HOURS. A
COLD FRONT WILL CROSS THE AREA THROUGH ABOUT 18Z...AND BRIEF
REDUCTIONS OF MVFR CIGS AND OR VIS ARE POSSIBLE...ESPECIALLY IF
SCATTERED SHRA ARE INTENSE OR IN ANY THUNDERSTORMS. SOUTHWEST TO
WEST WINDS WILL TURN GUSTY AGAIN BETWEEN 12Z AND 15Z...WITH GUSTS
AS HIGH AS 25 TO 30KT. HIGH PRESSURE WILL BUILD IN BEHIND THE
FRONT...WITH VFR OR A RETURN TO VFR FOR THE LAST 18 HOURS OF THE
PERIOD. THE PRESSURE GRADIENT WILL SLACKEN AROUND 0Z...WITH WINDS
DURING THE LAST 12 HOUR PERIOD OF 10KT OR LESS.

&&

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

$$

UPDATE...JP
SHORT TERM...JP
LONG TERM...KAS
AVIATION...JP



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