FXUS61 KILN 070633
AFDILN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
133 AM EST MON DEC 7 2009
.SYNOPSIS...
A WEAK UPPER SHORTWAVE WILL TRACK ACROSS THE GREAT LAKES TONIGHT
AND MONDAY. HIGH PRESSURE WILL BRIEFLY BUILD INTO THE OHIO VALLEY
ON MONDAY NIGHT...BEFORE A STRONG SURFACE LOW TRACKS INTO THE
MIDWEST LATE TUESDAY AND WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
IN ZONAL FLOW ALOFT A WEAK EMBEDDED SHORT WAVE OVER THE CENTRAL
PLAINS WILL TRACK ACROSS THE GREAT LAKES ON MONDAY. LIFT IS WEAK
AND MOISTURE IS LIMITED WITH THIS SYSTEM. MID LEVEL CLOUDS DEVELOP
OVERNIGHT WITH ANY FLURRIES OR VERY LIGHT SNOW SHOWERS LOOKING TO
HOLD OFF UNTIL EARLY MONDAY MORNING. HAVE OMITTED ANY MENTION OF
PRECIP IN THE OVERNIGHT PERIOD AND ADJUSTED SKY COVER TO CLOUDY
WITH A THICK CIRRUS SHIELD ALREADY IN PLACE. HAVE CONTD PREV FCST
TREND GOING CLOSE TO OR SLIGHTLY ABOVE WARMER MAV NUMBERS FOR
LOWS TONIGHT.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY NIGHT/...
SHORTWAVE WILL SHEAR OUT AS IT TRACKS INTO THE LOWER GREAT LAKES
EARLY MONDAY...WITH A SIMILAR WEAKENING TREND TO THE FORCING.
COMBINED WITH THE LACK OF SIGNIFICANT LOW LEVEL
MOISTURE...LIMITED POPS TO LOW CHANCE OR SLIGHT CHANCE MONDAY
MORNING. ANY SNOW WOULD BE VERY LIGHT WITH NO ACCUM. PVA ASSTD
WITH THE MIDLEVEL TROUGH WILL SWING THROUGH THE CWA AROUND
12Z...THEN QUICKLY EXIT TO THE NORTHEAST BY 18Z WHICH SHOULD ALLOW
ANY PRECIP CHANCES TO QUICKLY TAPER OFF BY AFTERNOON. ANY
LINGERING LIGHT SHOWERS WILL MIX WITH OR CHANGE TO RAIN DURING THE
AFTERNOON AS THE BOUNDARY LAYER WARMS UP.
IN A PROGRESSIVE UPPER PATTERN...HIGH PRESSURE WILL BE QUICK TO
BUILD INTO THE OHIO VALLEY MONDAY NIGHT...THEN SHIFT TO THE EAST
EARLY TUESDAY. UPPER TROUGH WILL DIG INTO THE SOUTHERN ROCKIES ON
TUESDAY AND OBTAIN A NEGATIVE TILT AS IT SHIFTS INTO THE SOUTHERN
PLAINS AND OZARKS TUESDAY EVENING. THIS WILL RESULT IN
CYCLOGENESIS OVER THE CENTRAL PLAINS TUESDAY NIGHT. ALL MODELS
CONTINUE TO BE IN REMARKABLY GOOD AGREEMENT ON THE TRACK OF THE
SURFACE LOW...TAKING IT FROM CENTRAL MISSOURI AROUND 06Z WEDS TO
NEAR CHICAGO BY 12Z. THUS...CONFIDENCE IS HIGH ON A WIDESPREAD
RAIN EVENT UNFOLDING ACROSS THE ENTIRE CWA TUESDAY NIGHT AS A
WARM FRONT AND A STRONG LOW LEVEL JET LIFT ACROSS THE AREA.
CHANCES FOR LIGHT PRECIP WILL INCREASE FROM SOUTH TO NORTH
TUESDAY AFTERNOON IN RESPONSE TO INCREASING ISENTROPIC LIFT. WITH
SFC WETBULB TEMPS NEAR OR BELOW FREEZING...SOME OF THIS PRECIP MAY
TAKE THE FORM OF LIGHT SNOW OR SLEET AT THE ONSET...ESPECIALLY
ACROSS AREAS NORTH OF I-70. HOWEVER...LIFT WILL BE LIGHT AND NO
ACCUMULATING FROZEN PRECIP IS ANTICIPATED. PRECIP WILL BECOME ALL
RAIN AREA WIDE AFTER SUNSET TUES AS WARMER AIR ADVECTS IN FROM THE
SOUTH. AXIS OF STRONGEST LOW LEVEL CONVERGENCE AND ISENTROPIC LIFT
WILL MOVE INTO FAR SOUTHERN PORTIONS OF THE CWA BY LATE TUES
AFTERNOON...AND SHIFT INTO CENTRAL PORTIONS OF THE CWA BY 06Z
WEDS. EXPECT WIDESPREAD RAIN TO OVERSPREAD THE ENTIRE CWA THROUGH
THIS TIME. DEEP LOW LEVEL CONVERGENCE AND THE POTENTIAL FOR WEAK
CONVECTIVE INSTABILITY WILL LEAD TO ENHANCED RAINFALL RATES IN
SPOTS...WITH THE POTENTIAL FOR RAINFALL AMOUNTS TO APPROACH OR
EXCEED ONE INCH IN SOME LOCATIONS. WARM FRONT LIFTS TO NORTHERN
PORTIONS OF THE CWA BY 12Z WEDS AS SFC LOW MOVES TO NEAR
KORD...WHICH WILL SHIFT MOST OF THE PRECIP INTO CENTRAL AND
NORTHERN OHIO BY WEDS MORNING.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
DEEPENING SURFACE LOW WILL LIFT OFF TO OUR NORTHEAST WEDNESDAY INTO
WEDNESDAY NIGHT. THIS WILL LEAD TO A DECREASING CHANCE OF SHOWERS
THROUGH THE DAY WITH PCPN THEN TAPERING OFF WEDNESDAY NIGHT. THE
ASSOCIATED TIGHTENING PRESSURE GRADIENT WILL LEAD TO VERY STRONG LOW
LEVEL WINDS WITH 925 TO 850 MB WINDS IN THE 40 TO 50 KNOT RANGE
WEDNESDAY AFTERNOON INTO WEDNESDAY EVENING. STRONG CAA WILL DEVELOP
ON THE BACK SIDE OF THE LOW. AS IT DOES...RAIN SHOWERS WILL BEGIN TO
CHANGE OVER TO SNOW SHOWERS FROM THE NORTHWEST LATE WEDNESDAY
AFTERNOON AND EARLY WEDNESDAY EVENING. BY THIS TIME THOUGH...MUCH OF
THE DEEPER MOISTURE WILL BE SHIFTING OFF TO THE NORTHEAST SO DO NOT
EXPECT MUCH IN THE WAY OF SNOW ACCUMULATION. HOWEVER...THE CAA WILL
HELP TRANSFER THE STRONG WINDS ALOFT DOWN TO THE SURFACE. WIND GUSTS
IN THE 40 TO 50 MPH RANGE WILL BE POSSIBLE WEDNESDAY AFTERNOON AND
EARLY EVENING.
A BROAD UPPER LEVEL TROUGH WILL THEN REMAIN IN PLACE ACROSS THE
EASTERN HALF OF THE UNITED STATES THROUGH NEXT WEEKEND. THIS WILL
LEAD TO A CONTINUATION OF BELOW NORMAL TEMPERATURES. HAVE TRENDED
TEMPS COOLER THAN GUIDANCE...ESPECIALLY THURSDAY INTO FRIDAY AS
SURFACE HIGH PUSHES EAST INTO OUR AREA. THE 12Z ECMWF IS FARTHER
NORTH THAN THE GFS WITH SOUTHERN SYSTEM LATE IN THE PERIOD. HAVE
OPTED TO KEEP THE FORECAST DRY AT THIS POINT FOR THE WEEKEND...BUT
IF MODELS CONTINUE TO TREND NORTH...WE MAY EVENTUALLY NEED TO
INTRODUCE SOME PCPN ACROSS AT LEAST THE SOUTH FOR SATURDAY INTO
SUNDAY.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
WATCHING BAND OF RADAR ECHO/PRECIPITATION ACROSS IL/MO/KY SPEEDING
QUICKLY TOWARD THE TAF SITES ASSOCIATED WITH DAMPENING SHORTWAVE
TROUGH. NEW 07.00Z MODEL SET FROM NCEP HAS INCREASED
LIFT/SATURATION INTO THE TAF SITES THIS MORNING AND NOW ALONG WITH
07.03Z RUC BRING A BAND OF LIGHT SNOW THROUGH THE SITES FROM 11Z-
15Z. RADAR TRENDS CERTAINLY LENDING SOME SUPPORT TO THIS
NOTION...WITH IFR SNOW NOW APPROACHING THE INDIANA/ILLINOIS
BORDER. DISTANCE/TIME EXTRAPOLATION PUTS THIS INTO CVG/LUK/DAY
AROUND 11Z...THEN POINTS NORTH/EAST A FEW HOURS LATER. WITH A SLOW
WEAKENING TREND IN THE LIFT...DID NOT CARRY IFR VSBYS INTO TAFS
YET...BUT SHOULD THESE VSBYS REMAIN INTO WRN/CNTL INDIANA...MAY
VERY WELL HAVE TO TEMPO IN AN HOUR OR TWO OF IFR SNOW. CIGS SHOULD
REMAIN MVFR THROUGH THE EVENT...THOUGH ANY DROP TO IFR VSBY WILL
LIKELY ALSO BRING A BRIEF DROP TO IFR CIGS. ACCUMULATIONS WILL
LIKELY REMAIN BELOW A HALF AN INCH...BUT GROUND OPERATIONS MAY BE
AFFECTED WITH SLIPPERY SURFACES FOR A TIME BEFORE TEMPERATURES GET
ABOVE FREEZING. SHOULD SEE MVFR CIGS LINGER MUCH OF THE DAY BEFORE
DEPARTING THIS EVENING...BUT CIRRUS SHIELD WILL BE THICKENING IN
ADVANCE OF MONSTER MIDWEST STORM.
OUTLOOK...WIDESPREAD PRECIPITATION WITH MVFR/IFR CIGS/VSBYS AND
GUSTY WINDS ARE LIKELY TUESDAY AFTERNOON THROUGH WEDNESDAY.
MVFR CIGS ARE POSSIBLE WEDNESDAY NIGHT.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...HAWBLITZEL
NEAR TERM...AR
SHORT TERM...HAWBLITZEL
LONG TERM...JGL
AVIATION...BINAU
