FXUS63 KLOT 170800
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 AM CDT SAT MAY 17 2008

.DISCUSSION...
248 AM CDT

AS THE UPPER LOW OVER ONTARIO ROTATES ACROSS THE PROVINCE...THE NW
FLOW ALOFT IS MAINTAINED...LOOKING MORE LIKE A PRE-SPRING PATTERN.
HIGH SUN ANGLE IS ONLY FACTOR PUTTING TEMPS NEAR NORMAL AT TIMES
DURING THE WEEKEND. AS TYPICAL IN THE PATTERN...SHORTWAVES TRAVEL
DOWN THIS NW FLOW...GENERATING LIFT AHEAD OF EACH LOBE. WUD
GENERALLY EXPECT WAVES OF SHOWERS AS IS THE CASE PRESENTLY DIVING SE
THRU NRN IL. YET SOME THUNDER APPEARED EARLIER IN THE EVENING IN
THIS LINE OF SHOWERS. CAN EXPECT ANOTHER WAVE TO DROP DOWN FROM WI
THIS EVENING AND CANNOT RULE OUT THUNDER WITH THIS WAVE EITHER. SO
HAVE UPPED THE ANTE TO INCLUDE THUNDER. HAVE ALSO RAISED POPS A BIT
MORE EARLY TONIGHT TO LIKELY BASED ON TRACK RECORD OF RECENT
DEVELOPMENT AND MODEL OUTPUT OF SEVERAL HUNDRED JOULES OF CAPE. WILL
CONTINUE THE RISK OF SHOWERS AFTER MIDNIGHT TONIGHT AND MOST OF
SUNDAY WITH CAA SWINGING DOWN BEHIND THIS MORE IMPRESSIVE SHORT
WAVE. ANOTHER WAVE DROPPING DOWN THRU THE UPR MIDWEST MONDAY WILL
PROMPT ANOTHER THREAT OF RAIN AND THUNDER MONDAY NIGHT INTO
TUESDAY.

THE LATTER HALF OF THE WEEK WILL SEE A SIGNIFICANT PATTERN CHANGE AS
UPPER RIDGING BUILDS ACROSS THE PLAINS AND INTO THE MS VLY
WEDNESDAY. THIS UPR RIDGE FINDS LTL ROOM FOR EASTWARD PROGRESS AND
ANCHORS OVER THE MS VLY THRU THURSDAY...SHIFTING ONLY SLIGHTLY EAST
BY FRIDAY. A WARM FRONT PUSHING THIS WAY FROM THE SW ON THE WEST
SIDE OF THIS RIDGE WILL BE SUPPORTED BY A RATHER STRONG LOW LVL JET
FEEDING GULF MSTR UP THE MS VLY. THIS MSTR WILL LIKELY OVERRUN THIS
FRONT AND PRODUCE SOME ELEVATED CONVECTION FROM WEDNESDAY ON INTO
THE WEEKEND. TEMPERATURES WILL LIKELY MOVE ABOVE THE SEASONAL NORM
TO THE MID 70S BY THURSDAY...PSBLY TAPPING 80 BY FRIDAY IF MORE
SUNSHINE WUD BE AVAILABLE.

RLB

&&

.AVIATION...

06Z TAFS...MAIN CONCERN FOR THE REMAINDER OF THE OVERNIGHT HOURS
WILL FOCUS ON PCPN POTENTIAL WITH THE WEAK COLD FRONT DROPPING SWD
THROUGH SRN WISCONSIN. LATEST RADAR IMAGERY INDICATES A BAND OF
SHRA MOVING THROUGH SRN WI/NERN IA AND APCHG THE WI/IL BORDER. IN
THE UPPER LEVELS...A LARGE UPPER LOW IS SLOWLY MOVING THROUGH THE
UPPER GREAT LAKES AND A SERIES OF IMPULSES IS ROTATING AROUND THE
WESTERN PERIPHERY OF THE SYSTEM. ONE OF THESE IMPULSES IS ENHANCING
SOME OF THE SHOWERS AND ISOLD EMBEDDED TS HAS BEEN OBSERVED IN
THE WESTERN EXTREME OF THE PCPN BAND OVER NERN IOWA. CURRENTLY
FEEL THAT THE TS WILL REMAIN WEST OF THE RFD TERMINAL AND ANY
PCPN OBSERVED WITH JUST BE SHRA. THE UPPER LEVEL SUPPORT
ASSOCIATED WITH THIS SYSTEM IS WEAKENING SO THE SHRA SHOULD BECOME
LESS DEFINED BY THE TIME THEY APPROACH THE TERMINALS. SO...WILL GO
WITH A 2 HOUR TEMPO GROUP FOR SHRA. WITH THE APPROACH AND PASSAGE
OF THE SFC BOUNDARY...WINDS WILL GRADUALLY SHIFT FROM SWLY TO WLY-
WNWLY. THE PRESSURE GRADIENT BEHIND THE BOUNDARY IS ILL DEFINED
AND WINDS MAY BECOME VARIABLE IN DIRECTION FOR A TIME DURG THE
LATE MORNING HOURS AS ANOTHER IN THE SERIES OF UPPER LEVEL
IMPULSES MOVES OVER THE REGION. THIS WILL BRING ANOTHER CHANCE FOR
SHOWERS DURG THE LATE AFTERNOON AND EARLY EVENING HOURS.

KREIN

&&

.MARINE...
300 AM CDT

LOW PRESSURE OVER SOUTHERN ONTARIO WILL CONTINUE TO MOVE EAST
WITH A TRAILING COLD FRONT DROPPING SOUTHEAST ACROSS LAKE MICHIGAN
THIS MORNING. A REINFORCING PUSH OF COLD AIR BEHIND THE FRONT WILL
MIX DOWN TO THE SURFACE...CAUSING WINDS TO INCREASE TO LOWER END
GALES OVER THE NORTHERN TWO THIRDS OF THE LAKE.  THE LOW WILL
CONTINUE EAST INTO QUEBEC BY SATURDAY AFTERNOON. THE GALES WILL
SUBSIDE EARLY SUNDAY MORNING AS HIGH PRESSURE BUILDS OUT OF THE
CANADIAN PRAIRIES AND INTO THE NORTHERN PLAINS. THE HIGH PRESSURE
WILL SPREAD EAST ACROSS THE WESTERN GREAT LAKES SUNDAY NIGHT AND
MONDAY.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.

&&

$$