Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 271540
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1140 AM EDT WED APR 27 2016

.UPDATE...
ISSUED AT 1140 AM EDT WED APR 27 2016

THE FORECAST WAS UPDATED LATE THIS MORNING TO ACCOUNT FOR THE
LATEST TRENDS IN RADAR IMAGERY AND THE LATEST RUN OF THE HRRR
MODEL. RAIN SHOWERS HAVE BEEN MORE PERSISTENT AND WIDESPREAD THIS
MORNING THAN PREVIOUSLY FORECAST. WE HAVE ALSO BEEN SEEING
SPORADIC LIGHTNING STRIKES THROUGH OUT THE MORNING THAT WERE NOT
PREVIOUSLY FORECAST EITHER. THE HRRR MODEL SEEMS TO HAVE A GOOD
HANDLE ON THE EVOLUTION OF THIS MORNINGS SHOWER AND STORM
ACTIVITY...THEREFORE...PRECIPITATION CHANCES FROM 13Z THIS MORNING
THROUGH THE REST OF THE AFTERNOON WERE INCREASED TO ACCOUNT FOR
MODEL DATA AND ACTUAL OBS ACROSS THE REGION. THE PRECIPITATION
AMOUNTS FOR TODAY WERE ALSO INCREASED TO ACCOUNT FOR THE MORE
WIDESPREAD PRECIPITATION THAT WE HAVE ALREADY HAD AND ARE
ANTICIPATING THE REST OF TODAY.

UPDATE ISSUED AT 626 AM EDT WED APR 27 2016

WSR-88D IS TRACKING SCATTERED SHOWERS ACROSS A GOOD PORTION OF
EASTERN KY THIS MORNING. WE HAVE BEEN SPARED THE THUNDER THIS
MORNING UNLIKE PORTION OF CENTRAL KY...BUT DID ADD ISOLATED BY
LATE MORNING TO EARLY AFTERNOON IN CASE SOME OF THIS ACTIVITY
PROPAGATES INTO THE REGION. OVERALL ADJUSTED POPS TO REFLECT THE
RADAR TRENDS. OTHERWISE JUST A FEW MINOR ADJUSTMENTS TO
TEMPS/DEWS/WINDS WITH LATEST OBS AND TRENDS.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 400 AM EDT WED APR 27 2016

THIS MORNING WSR-88D RADAR IS SHOWING SOME RAIN SHOWER ACTIVITY
ACROSS PORTION OF EASTERN KY. MORE OF A SCATTERED COVERAGE OVERALL
AND RIGHT NOW THE LATEST HRRR SEEMS TO BE HANDLING THIS...HOWEVER
THE NMM/ARW SEEM TO BE OVERDONE ON THE UPSTREAM SHOWERS. JUST CAN
NOT JUSTIFY THE MORE ROBUST POP CAMS ARE PAINTING GIVEN THE CLOUD
TOP WARMING TREND BASED ON IR SAT.

NOW THE REST OF THE DAY STILL REMAINS IN QUESTION. CAMS DO
REDEVELOP CONVECTION THIS AFTERNOON AND WOULD PROBABLY RESIDE
ALONG LEFT OVER BOUNDARIES. HOWEVER GIVEN LACK OF UPPER LEVEL
SUPPORT AND EVEN LESS SHEAR THAN YESTERDAY...WOULD THINK ANY
CONVECTION THAT FIRES WOULD BE FAIRLY DISORGANIZED. HOWEVER FELT
LIKE SCATTERED CONVECTION COULD NOT BE RULED OUT AND PERHAPS A
ISOLATED SEVERE REPORT IF WE REALIZE THE INSTABILITY. OVERALL KEPT
BETTER POPS IN THE SW TO MATCH THE SSEO THINKING UNTIL MORE
ORGANIZED CONVECTION WOULD ONCE AGAIN RIDE EAST THIS EVENING INTO
TONIGHT. THEREFORE BRING MORE NUMEROUS SHOWERS AND SCATTERED
STORMS AFTER 00Z...AND WOULD THINK OVERALL BETTER CHANCES WOULD
RESIDE ALONG AND NORTH OF THE MOUNTAIN PARKWAY. GENERALLY THINK
CONVECTION WILL WANE OVERNIGHT AND ISOLATED STORM WOULD BE THE
STORY OVERNIGHT INTO EARLY THURSDAY.

NOW FOR THURSDAY THERE LOOKS TO BE ONGOING CONVECTION EARLY ON AS
MENTIONED ABOVE. WE THEN LOOK TO AN APPROACHING COLD FRONT FROM
THE CENTRAL PLAINS...AT THE SAME TIME AN UPPER LEVEL CLOSED LOW
EJECTS NE INTO THE UPPER MS VALLEY REGION. THIS WILL LEAD TO
FALLING HEIGHTS AND LIFTING FROM THE BOUNDARY. TIMING SEEMS TO BE
THE BIGGEST QUESTION AND HOW MUCH CAN WE GET TO DEVELOP GIVEN THE
EARLY ON CONVECTION. HOWEVER THE WESTERLIES ALOFT BEGIN TO PICK
UP WITH DEEP LAYER SHEAR OF 35 TO 40 KNOTS. THE MODEL SOUNDING
FROM BOTH THE NAM AND GFS WOULD SUGGEST DCAPES APPROACHING THE
1000 J/KG RANGE...STEEP LOW LEVEL LAPSE RATES...AND AMPLY MID
LEVEL DRYING WHICH WOULD LEAD TO POTENTIAL FOR DAMAGING WIND
GUSTS. THE HAIL THREAT WOULD ALSO BE THERE WITH DECENT BUOYANCY IN
THE HAIL GROWTH ZONE...AFOREMENTIONED DEEP LAYER SHEAR...AND
FREEZING LEVELS LOWERING...BUT OVERALL THE STRONGER SIGNALS SEEM
TO POINT TO MORE OF A WIND THREAT. ALSO THERE ARE CERTAINLY SOME
SIGNALS WITH RESPECT TO THE CIPS ANALOG FOR THURSDAY. HOWEVER
RIGHT NOW GIVEN SOME OF THE UNCERTAINTY AKA MARGINAL SPC
RISK...AND WITH RESPECT TO MOST OF THE SHORT TERM MODELS MODEST
SIGNAL THURSDAY AFTERNOON...WILL HOLD OFF ON STRONGER MENTION IN
THE HWO.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 435 AM EDT WED APR 27 2016

THE MODELS HAVE COME INTO BETTER AGREEMENT THROUGH THE LONG TERM
PERIOD...WITH ACTIVE WEATHER PATTERN STILL ANTICIPATED VERY EARLY
IN THE LONG TERM PERIOD AND THEN AGAIN OVER THE WEEKEND INTO NEXT
WEEK. AN UPPER LEVEL SHORTWAVE TROUGH SHOULD DEPART TO THE
NORTHEAST THU NIGHT INTO FRIDAY WITH UPPER LEVEL RIDGING MOVING
ACROSS THE AREA RATHER QUICKLY FRIDAY INTO FRIDAY NIGHT...BRINGING
A DRY END TO THE WORK WEEK. MEANWHILE...A TROUGH IS STILL EXPECTED
TO TAKE SHAPE ACROSS THE WESTERN CONUS...WITH A SERIES SHORT WAVES
EJECTING EASTWARD AND NORTHEAST ACROSS THE PLAINS AND INTO THE MS
AND OH VALLEYS FRI INTO SUN. EARLY NEXT WEEK...A MORE SIGNIFICANT
SHORTWAVE MOVING FROM ROCKIES AND INTO THE NORTHERN AND CENTRAL
PLAINS TO END THE WEEKEND TO EARLY NEXT WEEK SHOULD INTERACT OR
MERGE WITH A NORTHERN STREAM SHORTWAVE TROUGH ACROSS EASTERN
CANADA. THIS SHOULD SHARPEN UP A TROUGH OVER ONTARIO AND QUEBEC
AND THE GREAT LAKES.

THE AXIS OF THE INITIAL SHORTWAVE TROUGH GENERALLY PASSING NORTH
SHOULD BE WORKING INTO THE AREA EARLY IN THE PERIOD. THIS SHOULD
LEAD TO CONVECTION EXITING ON THURSDAY NIGHT. FRIDAY AND FRIDAY
NIGHT WILL BE DRY...WITH HIGH PRESSURE DOMINATING. HOWEVER...
ADDITIONAL MOISTURE AND FORCING ARRIVE FROM THE WEST ON SATURDAY
AS SHORTWAVES BEGIN TO  ARRIVE FROM THE SOUTHWEST. THE ECMWF AND
GFS REMAIN IN GOOD AGREEMENT WITH THE TIMING OVER THE WEEKEND...AND
WE CONTINUE TO STAY CLOSE TO THE THE MODEL BLEND. THE BEST RAIN
CHANCES SHOULD OCCUR SUNDAY INTO SUNDAY EVENING AS A MORE DEFINED
SHORT WAVE TROUGH MOVES ACROSS THE OHIO AND TENNESSEE VALLEYS AND
MOISTURE SHOULD BE DEEPEST. A GOOD SOAKING RAIN DURING THE WEEKEND
IS ANTICIPATED AND AMOUNTS NEARING OR EXCEEDING AN INCH ARE
POSSIBLE FROM SATURDAY INTO SUNDAY NIGHT. LOCALLY HIGHER AMOUNTS
WILL BE POSSIBLE IF STRONGER SHOWERS OR STORMS TRAIN.

TROUGHING WILL LINGER INTO TUESDAY...JUSTIFYING AT LEAST LOW CHANCE
POPS. THE 0Z ECMWF AND 0Z GFS HOWEVER INDICATE THE POSSIBILITY OF
A REPRIEVE FOR MUCH OF TUESDAY AND LINGERING AFTER THE PERIOD. WE
HAVE CONTINUED TO UNDERCUT THE MODEL BLEND POPS ON TUESDAY UNTIL
OR IF CONFIDENCE INCREASES THAT A DRY PERIOD OR TWO SHOULD OCCUR.

HIGH TEMPERATURES WILL AVERAGE ABOVE NORMAL THROUGH THE END OF
THE WEEK...AND THEN LOOK TO COOL SLIGHTLY BACK TO AROUND OR
SLIGHTLY BELOW NORMAL TO START NEXT WEEK. CLOUD COVER SHOULD LIMIT
DIURNAL RANGES THUS OVERNIGHT LOWS WILL AVERAGE ABOVE NORMAL.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 640 AM EDT WED APR 27 2016

PERIOD EXPECTED TO REMAIN MOSTLY VFR..BUT SOME MVFR COULD NOT BE
RULED OUT. THIS MORNING WSR-88D RADAR INDICATES SCATTERED SHOWERS
ACROSS A GOOD PORTION OF THE REGION. EVEN WITH THAT CLOUD BASES
REMAIN ON THE HIGH SIDE WITH LOWEST CIGS AT AROUND 4 KFT MAINLY
ACROSS THE NORTH. WHILE WE HAVE SEEN THUNDERSTORMS DEVELOP TO OUR
WEST ACROSS CENTRAL KY...EASTERN KY ONLY SEEING SHOWERS. DID BEGIN
TO INTRODUCE SOME VCTS TOWARD THE LATE MORNING EARLY AFTERNOON FOR
ALL SITES. BETTER COVERAGE LOOKS TO ARRIVE THIS EVENING GENERALLY
AFTER 00Z...RIGHT NOW THINK BASED ON SOME OF THE SHORT TERM
GUIDANCE THE BETTER COVERAGE WILL RESIDE ACROSS THE NORTH. THIS
ACTIVITY COULD LEAD TO BRIEF DROPS IN CIGS AND VIS TO MVFR OR
LOWER LEVELS. ACTIVITY SHOULD TAPER OFF OVERNIGHT INTO EARLY
THURSDAY.

&&

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

$$

UPDATE...AR
SHORT TERM...DJ
LONG TERM...PG/JP
AVIATION...DJ



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