000
FXUS63 KILX 131757
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1257 PM CDT MON MAY 13 2013

.DISCUSSION...
ISSUED 1044 AM CDT MON MAY 13 2013

FORECAST LOOKS PRETTY GOOD TODAY AND BUMPED UP HIGHS JUST A
DEGREE IN SPOTS BUT NOT ENOUGH TO WARRANT A FORECAST UPDATE WITH
THE ZFP PRODUCT (THIS WAS UPDATED SHORTLY AFTER 7 AM TO END THE
FROST ADIVSORY). A NICE SPRING DAY UNFOLDING OVER CENTRAL/SE IL
WITH SUNNY SKIES THIS MORNING BECOMING PARTLY TO MOSTLY SUNNY THIS
AFTERNOON WITH MORE MID/HIGH CLOUDS ARRIVING NORTH OF I-72 LATER
TODAY. CURRENTLY TEMPS AT 1030 AM ARE IN THE UPPER 50S AND LOWER
60S. HIGHS 65 TO 70F BY 21Z/4 PM WITH COOLEST READINGS AROUND 65F
ALONG THE INDIANA BORDER AT DANVILLE AND PARIS AND MILDEST
READINGS NEAR 70F OVER WEST CENTRAL IL. AFTER W/NW BREEZY WINDS
THE PAST TWO DAYS...TODAY THE WINDS WILL BE FAIRLY LIGHT NEAR 10
MPH OR LESS AS WNW WINDS TURN SSW. THIS DUE TO 1026 MB HIGH
PRESSURE OVER THE LOWER MS VALLEY AND RIDGING NORTHWARD INTO IL
LATE THIS MORNING...AND SHIFTS EASTWARD OVER THE OHIO VALLEY BY
SUNSET. SOME MID AND HIGH CLOUDS OVER MN AND CENTRAL/NW IA TO
SPILL SE INTO CENTRAL IL LATER TODAY AND BECOME MORE PREVALENT
OVER THE IL RIVER VALLEY FROM I-55 NW.

07

&&

.AVIATION...
ISSUED 1255 PM CDT MON MAY 13 2013

VFR CONDITIONS ARE FORECAST TO CONTINUE ACROSS THE CENTRAL IL
TERMINAL AIRPORTS THROUGH TUE. SCATTERED TO BROKEN MID/HIGH CLOUDS
OVER IA TO SPREAD ACROSS CENTRAL IL LATER THIS AFTERNOON AND EVENING
AND THEN SCATTER OUT TUE MORNING. WNW WINDS 7-11 KTS TO TURN SSW
DURING THE AFTERNOON AND SSE BY SUNSET. EXPECT SW WINDS 10-15 KTS
WITH GUSTS 17-22 KTS AFTER 13Z/TUE. NO FOG EXPECTED OVERNIGHT.
1026 MB HIGH PRESSURE OVER MS AND RIDGING NORTHWARD INTO IL TO SHIFT
EASTWARD ACROSS THE OHIO VALLEY THIS EVENING AND INTO THE SE
STATES AND RIDGING INTO THE ATANTIC STATES BY 18Z/TUE AS 998 MB LOW
PRESSURE MOVES INTO WEST CENTRAL MN. INCREASING WAA PATTERN OVER
CENTRAL IL TO GIVE SOME PASSING MID/HIGH CLOUDS LATER TODAY INTO
TONIGHT WITH CEILINGS STAYING VFR. INCREASING PRESSURE GRADIENT
SUPPORTS GUSTIER SW WINDS TUE TO AROUND 20 KTS.

07

&&

.PREV DISCUSSION...
ISSUED 309 AM CDT MON MAY 13 2013

SHORT TERM...TODAY THROUGH TUESDAY

THERMAL MODERATION BEGINS TODAY AS SFC RIDGE AXIS EDGES EAST AND LIGHT
RETURN FLOW DEVELOPS BY LATE DAY. ELEVATED WARM ADVECTION MID/HIGH
CLOUDS ALREADY EVIDENT IN IR SAT IMAGERY OVER THE DAKOTAS INTO
WESTERN IA EARLY THIS MORNING...AND THIS ACTIVITY IS EXPECTED TO
SPILL DOWN ACROSS THE CWA THROUGH THE DAY. MORE FOCUSED ISENTROPIC
LIFT AND THETA-E ADVECTION FOR ANY SPRINKLES OR LIGHT SHOWERS
SHOULD REMAIN JUST TO OUR NORTH LATER TODAY AND TONIGHT. HIGHS ARE
EXPECTED TO BE A FEW DEGREES BELOW NORMAL...GENERALLY 65-70 WITH
WARMEST READINGS IN WEST CENTRAL IL. STRONGER LOW AND MID LEVEL
WARM ADVECTION COMMENCES ON TUESDAY AS SOUTH TO SOUTHWEST FLOW
STRENGTHENS AHEAD OF A COLD FRONT ADVANCING THROUGH THE UPPER
MIDWEST. LATE AFTERNOON 850 MB TEMPS REACH 18-22 C AND THIS
SUPPORTS WIDESPREAD MID 80S AIDED BY PLENTY OF STRONG MID MAY SUN.

LONG TERM...WEDNESDAY THROUGH SUNDAY

THE PATTERN THROUGH THE EXTENDED FORECAST FEATURES ZONAL MID LEVEL
FLOW WITH A QUASI-STATIONARY BOUNDARY WAVERING ACROSS THE MIDWEST.
THIS FAVORS FREQUENT CHANCES OF SHOWERS AND THUNDERSTORMS AND
ABOVE NORMAL TEMPS. THE INITIAL COLD FRONT MOVES INTO THE CWA ON
WEDNESDAY...AND HAVE HIGHER CHANCE POPS FOR THE CENTRAL AND
SOUTHERN CWA WHERE THE FRONT IS EXPECTED TO BE DURING PEAK DIURNAL
HEATING. SOME INCREASE IN LIFT WILL ALSO BE PROVIDED BY AN OPEN
MID LEVEL SOUTHERN STREAM TROF WHICH SHIFTS THROUGH THE LOWER/MID
MISSISSIPPI VALLEY LATE WED /GFS/ OR THU /ECMWF/. LOW PRESSURE IS
FORECAST TO DEVELOP OVER THE HIGH PLAINS FRIDAY AHEAD OF A MORE
SIGNIFICANT TROF SETTING UP OVER THE WESTERN US. THIS WILL SEND
THE FRONT BACK NORTH AS A WARM FRONT WITH ATTENDANT SHOWER/STORM
CHANCES FOR THE END OF THE WEEK. IF THIS FRONT CAN SHIFT FAR
ENOUGH NORTH...SEVERAL PERIODS OF DRY WEATHER WOULD BE POSSIBLE
AND THIS IS SUGGESTED BY THE 00Z ECMWF. MEDIUM RANGE MODELS AND
ENSEMBLES SHOW THE MAIN LOW TO BE A SLOW MOVER...TRACKING THROUGH
THE UPPER MIDWEST LATE IN THE WEEKEND OR EARLY NEXT WEEK. THUS
WILL HAVE TO KEEP SOME MENTION OF POPS IN THROUGH SUNDAY GIVEN
DIFFLUENT MID LEVEL FLOW...WARM AND RATHER HUMID AIR IN PLACE...
AND UNCERTAINTY IN BOUNDARY LOCATION. FORECAST CHALLENGE WILL BE
TO PIN DOWN HIGHER POPS AND POTENTIAL DRY PERIODS FRI-SUN AS THE
PATTERN EVOLVES.

25

&&

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

&&

$$