FXUS63 KJKL 071308
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
808 AM EST MON DEC 7 2009
.SHORT TERM.../TODAY THROUGH WEDNESDAY/
TWO MAIN SYSTEMS WILL AFFECT THE REGION DURING THE PERIOD. THE FIRST
IS MOVING THROUGH THE OH AND TN VALLEYS AND BRINGING LIGHT PRECIP TO
MIDDLE TN NORTH THROUGH CENTRAL KY. THE OTHER WILL BE A SHORTWAVE
TROUGH ALONG THE PACIFIC COAST AT PRESENT THAT WILL MOVE THROUGH THE
SOUTHERN ROCKIES TONIGHT AND EMERGE INTO THE PLAINS ON TUESDAY. AN
STRONG AREA OF SFC LOW PRESSURE WILL BE ASSOCIATED WITH THIS SYSTEM
AND WILL REORGANIZE TO THE LEE OF THE ROCKIES ON TUESDAY AND THEN
LIFT ENE TOWARD THE SOUTHERN END OF LK MI BY 12Z WED. THIS SYSTEM
WILL THEN TRACK INTO THE GREAT LAKES AND POSSIBLY ENTER WESTERN
ONTARIO BY THE END OF THE PERIOD. A THIRD SHORTWAVE...A LEAD
SHORTWAVE IN SOUTHWEST FLOW WILL AFFECT THE REGION BETWEEN THE MAIN
SYSTEMS AND INTERACT WITH A DEVELOPING WARM FRONT TO THE SOUTH OF THE
AREA STARTING ON TUE AND CONTINUING INTO TUE EVENING BEFORE THE MAIN
SYSTEM NEARS.
WITH THE FIRST SYSTEM...MOISTURE AND DYNAMICS ARE LIMITED...HOWEVER...
PRECIP IS REACHING THE GROUND UPSTREAM WITH MORE SOUTHERN LOCATIONS
RECEIVING RAIN WHERE THE PRECIP HAS BEEN LIGHTER AND LESS WETBULBING
HAS OCCURRED WHILE NORTHERN AREAS ARE COLDER ALOFT AND MORE
WETBULBING HAS OCCURRED. MEANWHILE WITH GENERALLY THIN CLOUDS FOR
MUCH OF THE NIGHT...MOST LOCATIONS IN EASTERN KY ARE BELOW FREEZING
WITH SFC WETBULB TEMP BELOW FREEZING ACROSS THE BOARD AT PRESENT. THE
LIMITING FACTOR WITH THIS SYSTEM IS LIMITED MOISTURE AND SHORT PERIOD
OF ISENTROPIC LIFT AS THE SYSTEM SHEARS BY TO THE NORTHWEST. THE
INITIALLY DRY AIRMASS WILL TAKE A LITTLE WHILE TO MOISTEN UP. OPTED
TO GO WITH THE HIGHEST POPS FROM SOUTHWEST TO NORTHEAST WITH LIKELY IN
THE FAR NW FOR TODAY. THE PRECIP TYPE IS PROBLEMATIC ALSO AS INITIAL
PRECIP COULD BE SNOW OR RAIN AND SNOW NORTH...AND SNOW...FREEZING
RAIN...OR SLEET IN THE SOUTH. WITH THE SYSTEM SHEARING OUT AND THE
FACT THAT LIFT WILL BE GONE ABOUT THE TIME THE ATMOSPHERE SATURATES
IN ALL BY THE FAR NW...QPF WILL BE VERY LIGHT. A LIGHT DUSTING OF
SNOW COULD OCCUR IN THE NORTH BASED ON RECENT UPSTREAM REPORTS. OPTED
TO ISSUE AN SPS AND HIGHLIGHT IN THE HWO FOR THIS SYSTEM AS
CONFIDENCE IN AREAL COVERAGE OF PRECIPITATION IS NOT ALL THAT
HIGH...BUT RADAR TRENDS COULD NOT BE IGNORED. WE WILL CONTINUE TO
MONITOR THIS SYSTEM AS IT ARRIVES.
HIGH PRESSURE WILL BRIEFLY BUILD INTO THE AREA BETWEEN THIS SYSTEM
AND SYSTEM 3 MENTIONED ABOVE WILL LEAD TO ISENTROPIC LIFT KICKING IN
SOUTH OF THE AREA OVERNIGHT TODAY AND THIS TRANSITING INTO THE AREA
ON TUE. THIS LIFT APPEARS TO BE RATHER VIGOROUS BASED ON THE MODEL
CONSENSUS AND THIS COMBINED WITH HIGH SREF AND MOS POPS...RAISED POPS
INTO THE CAT RANGE. DOWNSLOPING COULD CUT DOWN ON TOTALS IN THE
SOUTHEAST...BUT ACROSS THE BOARD INCREASED QPF AS PW MAKES A RUN AT
ONE INCH BY THE END OF THE DAY WITH GOOD MOISTURE TRANSPORT. CLOUD
COVER WITH THIS AND THE FALLING PRECIP SHOULD HOLD DOWN TEMPS DURING
THE DAY ON TUE.
THE LOW LEVEL JET WILL INCREASE TO AROUND 30 TO 35 KT BY THE END OF
THE PERIOD...AND STRENGTHENING FURTHER TO THE 50 TO 70KT+ RANGE
OVERNIGHT TUE NIGHT. MODELS PROJECT THE PW TO CLIMB TO ABOUT 1.2
INCHES ON AVERAGE OR ABOUT 250 PERCENT OR MORE ABOVE NORMAL. IN
ADDITION...LAPSE RATES ABOVE 850 AND ABOVE STEEPEN TO AT LEAST MOIST
ADIABATIC BETWEEN ABOUT 2Z AND 9Z...WITH PLENTY OF DYNAMICS AND
SHEAR. THE 0Z GFS FORECASTS BEST LI OF -1C TO -2C CENTERED AROUND 6Z
AND THE 0Z NAM HAS BL BEST LI APPROACHING 0 C. THE GFS ALSO HAS MU
CAPE GENERALLY IN THE 140 J/KG S TO OVER 500 J/KG IN THE NORTH AROUND
6Z...WHILE THE NAM HAS VALUES OF 100 TO 200 J/KG...ESPECIALLY ACROSS
THE SOUTH. SO LOCATION IS NOT CONSISTENT BETWEEN THE 0Z NAM AND
GFS...BUT POTENTIAL FOR AT LEAST A FEW LIGHTNING STRIKES IS THERE AN
OPTED TO PUT THUNDER BACK IN THE FORECAST FOR TUE NIGHT. THE MODELS
ALSO HINT AS SOME POSSIBLE COUPLING OF A JET STREAK TO OUR NORTH AND
ONE MOVING INTO THE TN AND LOWER OH VALLEY AROUND 6Z TO 12Z ON TUE
NIGHT. THIS COMBINATION WILL LEAD TO A VERY REAL POSSIBILITY OF QPF
EXCEEDING ONE INCH ACROSS MOST OF IF NOT ALL OF THE CWA CONSIDERING
THE ANOMALY OF PW AND SUCH A DYNAMIC SYSTEM. LOCALLY HEAVY RAIN
SEEMED LIKE A VERY REAL POSSIBILITY GIVEN THE FORECAST STRENGTH OF
THE LLJ AND DYNAMICS AND OPTED TO INSERT. IF CONVECTION OR ENHANCED
SHOWERS DO DEVELOP EVENT TOTAL QPF OVER TWO INCHES IN A FEW AREAS
CANNOT BE RULED OUT. THE RATHER QUICK PROGRESSION OF THE SYSTEM
BEING A LIMITING FACTOR. WENT WITH CAT POPS ON TUE NIGHT AS PLENTY OF
RAIN IS EXPECTED.
WINDS WILL BR STRONG ALOFT...BUT STABLE LOWER LEVELS SHOULD LIMIT
GUST POTENTIAL ON TUE NIGHT...WITH THE VA BORDER AND IMMEDIATE
DOWNSLOPE AREAS AND FAR WEST THE GUSTIEST AND SOME POTENTIAL FOR A
COUPLE OF GUSTS IN ANY HEAVIER SHOWERS OR THUNDERSTORMS.
HOWEVER...DURING THE DAY ON WED...BEHIND THE FRONT SUSTAINED WINDS OF
OVER 20 MPH ARE POSSIBLE AND MIXING WILL BE RATHER DEEP IN MANY
AREAS...ESPECIALLY WHERE THE MOST CLEARING OR PARTIAL CLEARING CAN
OCCUR WITHIN THE DRY SLOT. GUSTS NEAR 50KT ARE NOT OUT OF THE
QUESTION...ESPECIALLY IN THE NW AND THE HIGHEST ELEVATIONS.
CONFIDENCE IN THE EXACT SPEED IS NOT EXTREMELY HIGH BUT THERE IS A
VERY HIGH POTENTIAL OF AT LEAST WIND ADVISORY WIND GUSTS. WE WILL
HIGHLIGHT THIS IN THE SPS.
AS FOR TEMPS...THERE WILL BE PLENTY OF NON DIURNAL CURVES TO GO
AROUND WITH TEMPS LIKELY RISING LATE TONIGHT...ESPECIALLY VALLEYS AND
THEN HIGHS ON TUE LATE IN THE DAY JUST PRIOR TO 0Z WED. THEN TEMPS
SHOULD CLIMB THROUGH TUE NIGHT...WITH HIGHS ON WED BY MIDDAY...WITH
FALLING TEMPS ON STRENGTHENING COLD AIR ADVECTION LATE AS 850 MB
TEMPS DROP VERY LATE IN THE PERIOD.
.LONG TERM.../WEDNESDAY THROUGH SUNDAY/
STRONG SURFACE LOW WILL QUICKLY MOVE NORTHEAST NEAR NEW ENGLAND WITH
A BROAD AND NEARLY FULL LATITUDE TROUGH OVER THE MUCH OF THE CONUS.
COLD FRONT WILL BE WELL TO THE EAST OF THE AREA AND ARCTIC AIRMASS
WILL BE POISED TO USHER INTO EAST KENTUCKY ON STRONG WESTERLY FLOW.
MODEL TIME HEIGHTS WITH POTENTIAL TEMPERATURE OVERLAY SUGGEST THAT
STRONG WINDS UP TO 35 MPH WILL STILL BE POSSIBLE AT THE START OF THE
PERIOD...GRADUALLY SLACKENING BUT STILL STRONG UP TO 25 MPH ON
THURSDAY AFTERNOON. HAVE STUCK CLOSE TO RAW MODEL TEMPERATURES AND
DEW POINTS IN THROUGH THE END OF THE WEEK AS THEY SEEM TO DO BETTER
WITH ARCTIC AIRMASSES ENTERING THE REGION. THIS WILL ALLOW FOR
TEMPERATURES WELL BELOW MEX GUIDANCE AS A RESULT. EXPECT NEAR STEADY
OR EVEN FALLING TEMPERATURES ON THURSDAY AFTERNOON AND ONLY AROUND
THE FREEZING MARK. DEPENDING ON INCREASING CLOUD COVER ON THURSDAY
NIGHT...TEMPERATURES COULD ONCE AGAIN FIND THEMSELVES SOLIDLY IN THE
TEENS AS TD/S FALL TO THE UPPER TEENS AND A FEW SINGLE DIGITS. WILL
STAY RIGHT AROUND THE 20 DEGREE MARK FOR NOW FOR CONSISTENCY BUT
WOULD NOT BE SURPRISED TO SEE A LOWER FORECAST AT SOME POINT.
FRIDAY NIGHT COULD ONCE AGAIN BECOME INTERESTING AS A SOUTHERN
STREAM SYSTEM THROUGH MOISTURE NORTHWARD TOWARD EAST KENTUCKY. WITH
THE COLD AIR IN PLACE THIS SHOULD FALL IN THE FORM OF SNOW...AND
DEPENDING ON QPF...POSSIBLY ACCUMULATING SNOW. THERE IS MODEL
DISAGREEMENT IN HOW STRONG THE HIGH REMAINS OVER THE AREA FOR THIS
EVENT AND A DELAYED/DRIER ECMWF/CMC WOULD ALLOW FOR MORE TIME FOR
TEMPERATURES TO MODERATE AND THEREFORE A BETTER CHANCE AT LIQUID
PRECIPITATION. HOWEVER...AT THIS POINT FEEL THE POTENTIAL IS THERE
FOR BOTH GFS/PARALLEL GFS SOLUTION TO VERIFY DUE TO HIGHLY ACTIVE
SOUTHERN STREAM. WILL MENTION CHANCES FOR SNOW IN THE ZFP.
&&
.AVIATION.../12Z TO 12Z/...UPDATED
A LIGHT MIXED PRECIP EVENT WILL OCCUR EARLY IN THE PERIOD...ESPECIALLY
EAST OF INTERSTATE 75. BRIEF MVFR VIS AND CIGS WILL OCCUR AS THIS
BAND TRANSITIONS ACROSS THE AREA THROUGH 15Z. AFTER 15Z...POST
FRONT...THE LOW LEVELS WILL REMAIN SATURATED FOR A WHILE...BASED ON
UPSTREAM OBS...SOME UPPER END OF MVFR RANGE OR THE LOWER END OF THE
VFR RANGE IS EXPECTED...FOLLOWED BY VFR ACROSS THE BOARD IN ALL BY
THE HIGHEST TERRAIN BY 18Z. VFR IS THEN EXPECTED AS SOME BRIEF
CLEARING OR CLEARING IS EXPECTED 0Z TO 6Z...AND THEN SOME MID AND
HIGH LEVEL CLOUDS WILL INCREASE LATE AHEAD OF THE NEXT MORE POTENT
SYSTEM.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...JP
LONG TERM....SCHOETTMER
AVIATION...JP
