FXUS63 KILX 170832
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
332 AM CDT SAT MAY 17 2008

.DISCUSSION...
ISSUED 330 AM CDT SAT MAY 17 2008

FORECAST CONCERN IS CONVECTION CHANCES INTO EARLY NEXT WEEK AS
SEVERAL SHORT WAVES DIVE SE ACROSS THE GREAT LAKES REGION WITH
LARGE UPPER LEVEL TROF OVER THE NORTHEASTERN U.S. EXTENDED MODELS
SHOW STRONG UPPER LEVEL RIDGE OVER THE WEST COAST TO SHIFT EAST
OVER THE MS VALLEY LATER THIS WEEK AND INTO MEMORIAL DAY WEEKEND
BRINGING SUMMER WARMTH BACK TO IL WITH HIGHS IN THE 80S. 00Z SHORT
RANGE MODELS FAIRLY SIMILAR THROUGH MON AND USED A BLEND.

SHORT TERM...TODAY THROUGH MONDAY NIGHT.

EARLY MORNING SURFACE MAP SHOWS WEAK HIGH PRESSURE OF 1018 MB OVER
TX AND RIDING NE INTO WV. A COLD FRONT EXTENDED FROM 994 MB LOW
PRESSURE NE OF LAKE SUPERIOR ACROSS CENTRAL WI AND NW IA/KS.
DECREASING AREA OF SHOWERS WAS SPREADING SE ACROSS NORTHERN IL
TOWARD I-80 WITH MID LEVEL CLOUDS JUST NORTH OF ILX CWA WHILE
CENTRAL AND SE IL HAVE CLEAR SKIES AND SW WINDS 5 TO 15 MPH. TEMPS
WERE IN THE MID TO UPPER 50S. ALOFT A STRONG UPPER LEVEL LOW
PRESSURE WAS OVER HUDSON BAY AND WESTERN ONTARIO WITH LARGE UPPER
LEVEL TROF OVER THE NE THIRD OF THE U.S. MEANWHILE STRONG 594 DM
500 MB HIGH PRESSURE RIDGE WAS OVER THE PACIFIC STATES.

MODELS SWING A WEAK COLD FRONT SE THROUGH CENTRAL IL THIS MORNING
AND INTO SE IL THIS AFTERNOON. THIS TO BRING A SLIGHT CHANCE OF
SHOWERS TO MAINLY NE AREAS. BUMPED UP HIGHS BY A FEW DEGREES INTO
THE MID TO UPPER 70S AS 850 MB TEMPS STAY NEAR 12C TODAY AND
SHOULD SEE SOME SUNSHINE. THESE READINGS ARE NEAR OR JUST ABOVE
NORMAL HIGHS. BETTER CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS
TONIGHT ESPECIALLY NORTHERN AREAS AS STRONGER SHORT WAVE DROPS SSE
INTO NORTHERN IL AND DRIVES A STRONGER COLD FRONT SE THROUGH
CENTRAL IL THIS EVENING. LINGERED A CHANCE OF SHOWERS IN EASTERN
IL SUNDAY WITH STRONG UPPER LEVEL TROF OVER THE OHIO VALLEY...
WHILE DRY IN WESTERN HALF OF IL AS WEAK HIGH PRESSURE MOVES OVER
IA/MO. 850 MB TEMPS DROP TO 2 TO 4C SUNDAY AND COOLED HIHGS INTO
THE MID TO UPPER 60S...ABOUT 10 DEGREES COOLER THAN TODAYS
EXPECTED HIGHS. SUNDAY NIGHT LOOKS DRY OVER MOST AREAS BUT HAVE
SLIGHT CHANCE OF SHOWERS LATE SUNDAY NIGHT SW OF SPRINGFIELD AS
NEXT WX SYSTEM APPROACHES.

MODELS IN AGREEMENT IN BRINGING A SHORT WAVE SE OVER IL MON WHILE
SURFACE LOW PRESSURE MOVES SE ACROSS MO AND INTO THE MID MS VALLEY
BY MON EVENING. CENTRAL/SE IL ON COOLER/NORTH SIDE OF SYSTEM WITH
GOOD CHANCE OF SHOWERS AND CHANCE OF THUNDERSTORMS BY MONDAY
AFTERNOON. COOLED MON HIGHS INTO THE 60S WITH CLOUDY SKIES. RAIN
CHANCES DIMINISH FROM THE WEST DURING MON NIGHT AS SYSTEM EXITS
EAST ACROSS THE TN VALLEY.

LONG TERM...TUESDAY THROUGH FRIDAY.
UPPER LEVEL HEIGHTS BEGINNING TO RISE TUE AND SLIGHT CHANCE OF
SHOWERS WITH UPPER LEVEL TROF CONFINED TO NE HALF OF AREA. MILDER
HIGHS BACK INTO THE MID 70S WITH MORE SUNSHINE AND WARMER 850 MB
TEMPS NEAR 10C. ECMWF AND GFS ARE SIMILAR IN SHIFTING STRONG UPPER
LEVEL RIDGE OVER THE PACIFIC STATES EAST INTO THE MS VALLEY LATER
THIS WEEK. WARM FRONT LIFTING NORTH THROUGH IL COULD BRING CHANCE
OF CONVECTION WED/THU. SUMMERLIKE WARMTH APPEARS TO SETTLE INTO IL
LATER THIS WEEK INTO MEMORIAL DAY WEEKEND WITH HIGHS IN THE 80S.

HUETTL

&&

.AVIATION...
ISSUED 1122 PM CDT FRI MAY 16 2008...FOR THE 06Z TAFS

THE MID CLOUDS AND SPRINKLES ARE ONLY GOING TO AFFECT DEC AND CMI
FOR ANOTHER HOUR OR SO...THEN SKIES SHOULD BECOME CLEAR THE REST
OF THE NIGHT. THE NEXT SHORTWAVE IS COMING QUICKLY ON IT/S
HEELS...AND IS ALREADY IN NORTHERN IOWA AND SOUTHERN WISCONSIN.
SOME LIGHTNING STRIKES HAVE DEVELOPED ACROSS THAT AREA IN THE LAST
COUPLE OF HOURS...DUE TO ELEVATED CONVECTION. WILL BE ADDING SOME
PRECIP AND VCTS IN THE TAFS FOR AT LEAST THE NORTHEAST TAF SITES
FOR LATER MORNING AND AFTERNOON. ONCE AGAIN...MOST AREAS WILL
REMAIN DRY...SO WILL NOT HIT PRECIP TOO HARD...ESPECIALLY WITH THE
VERY LIMITED MOISTURE INDICATED IN THE FORECAST SOUNDINGS.

THE LOWEST CIGS THAT MAY SHOW UP SHOULD REMAIN VFR LEVELS...4K-5K
OR SO. VIS LEVELS SHOULD REMAIN VFR AS WELL...EVEN IN ANY BRIEF
THUNDERSTORMS.

SHIMON

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$