Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 010915 CCA
AFDJKL

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE JACKSON KY
515 AM EDT WED JUL 1 2015

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 417 AM EDT WED JUL 1 2015

A WET PERIOD WILL BE IN STORE. WE WILL START OFF THIS MORNING
WITH A LARGE LONGWAVE TROUGH CONTINUING ACROSS THE REGION. THE
SHORTWAVE WHICH SPARKED RAIN AND STORMS YESTERDAY WILL BEGIN
SHIFTING NORTHEAST AND OUT OF THE REGION WHILE ANOTHER SMALLER
SHORTWAVE BEGINS TO TAKE FORM UPSTREAM OF EASTERN KY. THE
GFS...NAM...AND ECMWF ARE ALL IN GOOD AGREEMENT THAT AN MCS WILL
FROM AS A RESULT OF THIS SHORTWAVE...SETTLING ACROSS MISSOURI BY
12Z THIS MORNING /AS CAN ALREADY BE SEEN ON IR/. WITH NW FLOW
STILL IN PLACE...EXPECT SOME OF THE MOISTURE FROM THIS SYSTEM TO
ADVECT INTO KY...IN CONJUNCTION WITH ANY LEFT OVER MOISTURE FROM
YESTERDAY/S SYSTEM...AS THE MCS BECOMES COLD POOL AND SHEER
DRIVEN. AS WE BEGIN HEATING THROUGH THE DAY...THIS MOISTURE WILL
BEGIN RISING AND SCT SHOWERS AND THUNDERSTORMS TO START DEVELOPING
ACROSS THE REGION. WHILE A WEAK FRONTAL BOUNDARY WILL BE
POSITIONED ALONG THE OHIO RIVER VALLEY...IT SEEMS AS THOUGH THE
BEST STORM POTENTIAL WILL BE SPARKED ACROSS THE SOUTHERN
CWA...CLOSER TO THE TN BORDER AND THE COLD POOL DRIVEN OUTFLOW
BOUNDARY. ACCORDING TO SOUNDINGS ACROSS THE SW CWA...THE LAST TWO
RUNS OF THE NAM12 MODEL HAVE BEEN IN GOOD AGREEMENT WITH SHOWING
CAPE VALUES TOPPING OUT NEAR 4000 J/KG BETWEEN 18 AND 21Z...A
STRONG FAT CAPE...AND DRYING ALOFT WHICH MAY PROMOTE SOME DECENT
HAIL POTENTIAL. LI/S WILL EVEN BE TOPPING OUT AROUND -9 AT KSME
AND KLOZ...SUPPORTING THE IDEA FOR UNSTABLE CONDITIONS CONDUCIVE
TO STRONG THUNDERSTORM DEVELOPMENT. THAT BEING SAID...AS YOU HEAD
FARTHER NORTH...INSTABILITY AND WIND SHEAR DROPS SIGNIFICANTLY AS
YOU LOSE INFLUENCE FROM THE COLD POOL OF THE UPSTREAM MCS. THIS
CORRELATES WELL TO THE MRG AND SLIGHT RISK AREAS OF THE SPC DAY 1
CONVECTIVE OUTLOOK.

THE ECMWF MAY ACTUALLY HAVE THE BEST HANDLE ON THIS SYSTEM DURING
THE OVERNIGHT PERIOD...AS IT IS SHOWING A STRONG HANDLE ON THE
MESOSCALE FEATURES AND HAS VERY GOOD INITIALIZATION SO FAR THIS
MORNING. CURRENTLY...IT IS SHOWING A WELL DEFINED LLVL JET BELOW
THE NOCTURNAL INVERSION FEEDING THE MCS AS IT MOVES INTO MISSOURI.
AS WE HEAD INTO THE DAY...THE MCS WILL LIKELY BECOME MORE COLD
POOL AND SHEER DRIVEN...SHIFTING SE AND AWAY FROM THE LLVL JET AS
THE INVERSION AND WINDS BREAK DOWN. BY 0Z TONIGHT...THE ECMWF
CLEARLY SHOWS THE LLVL JET REESTABLISHING ITSELF ACROSS MISSOURI
AND REENERGIZING THE MCS ACROSS MISSOURI...WHILE THE STRONGEST
CONVECTION OVER OUR CWA BEGINS TO DISSIPATE WITH LOSS OF DAYTIME
HEATING/FORCING.

BY THURSDAY...THE MCS WILL FOLLOW THE SHORTWAVE AND ROUND THE
LONGWAVE TROUGH AXIS. IN THIS SCENARIO...WOULD TEND THE LEAN
TOWARDS THE ECMWF AND THE NAM 12...SINCE THE GFS SEEMS TO BE
PULLING THE TROUGH AXIS MUCH FURTHER SOUTHWARD...AND THEREBY
PRODUCING A STRONGER SYSTEM...COMPLETE WITH A DEVELOPING SURFACE
LOW TRACKING UP THE OHIO RIVER. THIS PEGS THE HIGHEST QPF ACROSS
THE NORTHERN CWA AND ALONG AND NORTH OF THE OHIO RIVER
VALLEY...WHICH IS OUT OF AGREEMENT WITH EVERY OTHER MODEL...AND
WAS HIGHLIGHTED BY THE WPC MODEL DIAGNOSTIC DISCUSSION AS BEING
UNREALISTIC. INSTEAD...EXPECT THE MCS AND BEST MOISTURE TO RIDE
ALONG THE TIGHTEST THICKNESS PATTERN...WITH BEST INSTABILITY AND
QPF THEREFORE LOCATED ACROSS OUR SOUTHERN CWA AND IN THE TN
VALLEY.

CONCERNING THE AMOUNT OF MOISTURE...PWATS IN THE 1.75 TO 2.00 INCH
RANGE ARE POSSIBLE THROUGH THE DAY THURSDAY...WITH WPC PEGGING
AROUND AN INCH OF PRECIP OVER A 6 HOUR PERIOD DURING THE DAY NEAR
THE TN BORDER. SOME OF THE HEAVIER STORMS/SHOWERS MAY PRODUCE
LOCALLY HIGHER AMOUNTS AS WELL. THIS MAY CREATE SOME PROBLEMS AS WE
HEAD INTO THURSDAY NIGHT AND THE HEART OF THE MCS TRAVELS ACROSS
EASTERN KY AND BRINGS WIDESPREAD HEAVY RAINFALL. EXPECT FLASH
FLOODING TO BE A CONCERN...ESPECIALLY ACROSS THE SOUTHERN CWA
WHERE PWATS ARE EXPECTED TO TOP OUT BETWEEN 2.1 AND 2.25 INCHES.
AFTER SOME DISCUSSION WITH MRX ABOUT WHETHER OR NOT TO GO AHEAD
AND ISSUE A FLASH FLOOD WATCH...ULTIMATELY DECIDED TO HOLD OFF
UNTIL DURING THE DAY TOMORROW. THE PRIMARY REASON BEING THAT THE
MODELS ARE STILL SHOWING SOME DISAGREEMENT AND EACH ONE HAS SOME
UNREALISTIC SCENARIOS...NOT TO MENTION THIS LATEST RUNS OF THE
ECMWF SHOWED SOME INCONSISTENCIES COMPARED TO THE PREVIOUS RUN.
WOULD HOPE THAT IN THE NEXT ONE TO TWO RUNS...AS THE MCS GETS
GOING TODAY...THE MODELS WILL START TO GET A BETTER HANDLE ON THE
UPCOMING SITUATION...AS WELL AS HOW FAR NORTH INTO OUR CWA FLASH
FLOODING MIGHT BE OF CONCERN.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 515 AM EDT WED JUL 1 2015

SEEING MORE SIGNIFICANT DIFFERENCES IN THE DETERMINISTIC ECMWF
AND GFS THROUGH THE EXTENDED. OVERALL UPPER LEVEL PATTERN BECOMES
LESS AMPLIFIED THROUGH THE PERIOD. GFS IS MORE AMPLIFIED...
STRONGER WITH SHORT WAVE ENERGY DROPPING INTO THE MID-MISSISSIPPI
AND OHIO VALLEY AT THE START OF THE EXTENDED...FRI INTO SAT.
NATIONAL GUIDANCE SUGGEST THE OPERATIONAL GFS IS TOO STRONG WITH
THIS SYSTEM CONSIDERING UPSTREAM ENERGY AND ITS INFLUENCE ON
EVOLUTION OF THE WAVE THROUGH THE OHIO VALLEY. A BLEND OF
SOLUTIONS/GUIDANCE APPEARS TO BE THE BEST APPROACH FOR THE
EXTENDED PORTION OF THE FORECAST...PERHAPS WITH A NUDGE TOWARDS
THE DETERMINISTIC ECMWF.

SENSIBLE WEATHER STILL LOOKS UNSETTLED WITH AT LEAST A CHANCE OF
RAIN EACH DAY. BAROCLINIC...OR FRONTAL ZONE APPEARS TO STALL OUT
ACROSS THE REGION. MODELS ARE SHOWING SUBTLE DIFFERENCES IN THE
EXACT LOCATION OF THIS ZONE OF UNSETTLED WEATHER. MOST LIKELY
LOCATION APPEARS TO BE SOUTH OF THE OHIO RIVER BUT NORTH OF THE TENN
VALLEY. THE WEATHER WILL BE QUITE ACTIVE WITHIN THIS SECTOR WHICH
INCLUDES THE COMMONWEALTH. CONSIDERING THE RECENT RAINFALL WE HAVE
EXPERIENCED OVER THE LAST FEW DAYS...HYDRO ISSUES COULD BECOME A
CONCERN AS MULTIPLE DISTURBANCES TRACK THROUGH THE AREA.
TEMPERATURES WILL PROBABLY TREND A BIT CLOSER TO NORMAL THROUGH THE
PERIOD...ESPECIALLY TOWARDS THE END OF THE FORECAST WINDOW.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 200 AM EDT WED JUL 1 2015

SHOWERS CONTINUE TO DIMINISH ACROSS THE REGION OVERNIGHT WITH LOSS
OF HEAT INDUCED INSTABILITY. HOWEVER...A LARGE AMOUNT OF MOISTURE
HAS BEEN LEFT OVER ACROSS MUCH OF EASTERN KY...ESPECIALLY IN AREAS
THAT RECEIVED RAINFALL THIS EVENING. AS TEMPERATURES CONTINUE TO
COOL OVERNIGHT...FOG WILL CONTINUE TO FORM AND THICKEN. SEVERAL
TAF SITES ARE ALREADY REPORTING FOG...AND IF THEY CONTINUE TO DROP
IN VISIBILITY SOME MAY ACTUALLY GO BELOW AIRPORT MINS FOR A PERIOD BY
LATE TONIGHT/EARLY MORNING. THAT BEING SAID...SOME TAF SITES MAY
CONTINUE TO FLUCTUATE BETWEEN CATEGORIES DEPENDING ON THE VARYING
DEGREE OF THE FOG OVERNIGHT. AS THE FOG BURNS OFF IN THE
MORNING...IT WILL BE REPLACED BY A RENEWED CHANCE OF SHOWERS AND
THUNDERSTORMS...ESPECIALLY IN THE AFTERNOON AND EVENING. TRIED TO
GEAR TAFS TOWARD THIS IDEA...BUT ACTUAL VIS AND CIGS WILL VARY
THROUGHOUT THE DAY AS STORMS DEVELOP AND PASS NEARBY...OR EVEN
OVER THE TAF SITE. A HEAVIER AREA OF RAIN WILL MOVE IN LATE IN THE
EVENING...WITH ALL TAF SITES EXPECTED TO BE AFFECTED. THE EXACT
IMPACTS ARE STILL UNCERTAIN...BUT TRENDED TOWARDS MVFR CIGS AND
MVFR/HIGH END IFR VIS AT THIS TIME.

&&

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

&&

$$

SHORT TERM...JMW
LONG TERM...RAY
AVIATION...JMW


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