661 
FXUS63 KILX 272338
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
638 PM CDT WED MAR 27 2013

.DISCUSSION...
ISSUED 250 PM CDT WED MAR 27 2013

UPPER NORTHWEST FLOW WILL PERSIST THROUGH MUCH OF THE FORECAST
VALID PERIOD. BIGGEST DIFFERENCES IN 12Z MODEL SUITES INVOLVE THE
STRENGTH OF WAVES IN NW FLOW AND THE RESULTANT ARCTIC AIR SURGES
OVER THE NEXT SEVEN DAYS. 

SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT

SFC RIDGE OVER MISSISSIPPI RIVER VALLEY WILL PUSH ONLY SLOWLY EAST
OVER THE NEXT 24 HOURS. ALTHOUGH...LATE MARCH SUNSHINE TODAY CONTINUES
TO PUT A MAJOR DENT IN SNOW COVER...LIGHT WINDS AND CLEAR SKIES UNDER
THE RIDGE SHOULD ALLOW TEMPS TO FALL WELL BELOW NORMAL. KSPI
RECORD IS 14F TONIGHT. WILL PROBABLY NOT SEE THE MERCURY DIP THAT
LOW...BUT SOME TEENS ARE LIKELY IN LOW SPOTS THAT RETAIN
WIDESPREAD SNOW COVER.

SURFACE RIDGE SHOULD REACH APPALACHIANS BY LATE FRIDAY NIGHT
ALLOWING SOME WAA TO PUSH INTO ILLINOIS. CLOUDS SHOULD TEMPER
WARMING SOMEWHAT...BUT HIGHS SHOULD CLIMB SEVERAL DEGREES EACH
DAY...REACHING UPPER 40S TO LOWER 50S. NORMAL THIS TIME OF YEAR IS
MOSTLY UPPER 50S.

LONG TERM...SATURDAY THROUGH WEDNESDAY

COLD AIR CURRENTLY POOLING OVER ALASKA...CURRENTLY 20-30 DEGREES
BLO NORMAL...IS PROGGED TO GET CAUGHT IN GENERAL NORTHWEST FLOW
AND SPILL DOWN INTO MIDWEST BY SUNDAY NIGHT. AHEAD OF THE COLDEST
AIR...SEVERAL SURGES WILL PUSH ACROSS ILLINOIS BEGINNING
SATURDAY...EACH COLDER. THE INITIAL FRONT ON SATURDAY
AFTERNOON/EVENING SHOULD INTERACT WITH GULF MOISTURE TO PRODUCE
GOOD CHANCE/LIKELY POPS. INSTABILITY AXIS REMAINS TO OUR WEST AND
REACHES ILLINOIS AFTER SUNSET...SO WITH CURRENT TIMING THUNDER NOT
EXPECTED...BUT LATER SHIFTS WILL NEED TO MONITOR.

FINAL SURGE ON SUNDAY NIGHT BRINGS UNSEASONABLY COLD 850 TEMPS...
AROUND -10C...BACK INTO ILLINOIS. WOULD NOT BE SURPRISED TO SEE
SOME SNOW MIXED IN WITH ANY LIGHT PRECIP ACCOMPANYING THIS FRONT
LATE SUNDAY NIGHT OR MONDAY MORNING. HOWEVER...MOISTURE SHOULD BE VERY
LIMITED GIVEN THAT THE FIRST FRONT IS EXPECTED TO SHUNT THE GULF
MOISTURE EAST WELL BEFORE THE COLD AIR ARRIVES.

BY MONDAY 12Z...850 TEMPS ARE EXPECTED TO HAVE DROPPED 15-20C IN
APPROXIMATELY 24 HOURS. CURRENTLY HOLDING ON TO 40S FOR MONDAY AND
TUESDAYS HIGHS...BUT THE RUN-TO-RUN TREND HAS BEEN GOING COLDER.
THE 00Z ECMWF HAD BEEN A BIT WARMER THAN THE GFS AND GEFS
MEAN...BUT THE 12Z ECMWF IS NOW ALSO TAPPING THE COLD AIR AND
PLUNGING A 5100 M 500 MB LOW INTO ONTARIO SIMILAR TO THE GFS BY
MONDAY SUGGESTING THAT HIGHS MAY REMAIN IN THE 30S ACROSS CENTRAL
ILLINOIS FOR THE FIRST FEW DAYS OF APRIL.

BARKER
&&

.AVIATION...
ISSUED 638 PM CDT WED MAR 27 2013

VFR CONDITIONS WILL PREVAIL AT ALL SITES NEXT 24HRS. SKIES WILL BE
CLEAR OVERNIGHT INTO EARLY TOMORROW MORNING. HOWEVER...MID CLOUDS
AROUND 10KFT WILL ADVECT INTO THE AREA AND AFFECT ALL SITES FOR
LATE MORNING INTO THE AFTERNOON. NOT SURE IF CLOUDS WILL BE BROKEN
SO WILL BE GOING WITH SCATTERED FOR NOW AND TAKE ANOTHER LOOK FOR
THE 06Z TAFS. WINDS SHOULD REMAIN LIGHT AND VARIABLE THROUGH THE
PERIOD AS HIGH PRESSURE RIDGE MOVES OVER THE AREA.

AUTEN
&&

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

$$