Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 272059
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
ISSUED BY NATIONAL WEATHER SERVICE CHICAGO IL
259 PM CST Tue Jan 27 2015

.SHORT TERM...(Through wednesday afternoon)
ISSUED AT 255 PM CST TUE JAN 27 2015

MAIN CHALLENGE IN THE SHORT/NEAR TERM REVOLVES AROUND CLOUD COVER
TONIGHT...WINDS AND TEMPS ON WEDNESDAY. A SURFACE RIDGE IS IN PLACE
OVERHEAD...AND SATELLITE PICTURES SHOW LOWER CLOUDS ERODING FROM THE
NORTHEAST THIS AFTERNOON AS DRIER AIR FILTERS IN.  BEST CHANCES FOR
EROSION WILL BE FOR EASTERN AREAS WHERE THIS DRIER AIR IS MAKING
BETTER HEADWAY. RAW MODEL GUIDANCE CONTINUES TO ADVERTISE CLEARING
MUCH SOONER THIS EVENING AREA-WIDE...WHILE RAP TIME HEIGHTS SUGGEST
IT WILL TAKE UNTIL LATER TONIGHT FOR THIS TO OCCUR...ESPECIALLY
NORTH OF I-72. MODEL SOUNDINGS SUGGEST THAT THIS LOWER LEVEL
MOISTURE WILL REMAIN TRAPPED BELOW A SUBSIDENCE INVERSION...AND THAT
IT WILL AT LEAST HOLD FIRM THROUGH THE EVENING HOURS. CLOUD BEARING
WINDS WILL BE TURNING MORE NORTHERLY AS WELL...WHICH WOULD SUPPORT
CLOUDS HANGING ON ALONG AND WEST OF HIGHWAY 51. SURFACE HIGH
PRESSURE TONIGHT WILL SHIFT OFF THE EAST TONIGHT AS THE UPPER RIDGE
IN THE PLAINS MOVE EAST AND CONTINUES TO DEAMPLIFY. EXPECT WINDS TO
SHIFT TO THE SE OVERNIGHT...WITH LOWS IN THE EAST IN THE UPPER TEENS
TO NEAR 20...WITH 20S HOLDING WEST WHERE CLOUD COVER IS EXPECTED TO
BE MORE PREVALENT.

THURSDAY...ATTENTION SHIFTS TO UPPER LEVEL LOW PRESSURE MOVING
THROUGH THE GREAT BASIN THIS AFTERNOON. THE UPPER TROUGH MOVES INTO
THE PLAINS RIDGE WHILE ADDITIONAL PACIFIC ENERGY MOVES INTO THE
NORTHERN PLAINS. LOW LEVEL WARM ADVECTION ENSUES IN THE
SOUTHWESTERLY FLOW AHEAD OF THESE SYSTEM .IT APPEARS THAT NOT ALL OF
OF THIS LOW LEVEL WARMING WILL NOT TRANSLATE TO THE SURFACE WITH A
FAIRLY STRONG INVERSION HOLDING...BUT DO EXPECT SOME WARMING FROM
TODAY`S READINGS...ESPECIALLY FOR SOUTHERN AND WESTERN AREAS WHERE
MID 40S LOOK LIKE A DECENT BET. AREAS NORTH AND EAST WILL REMAIN ON
THE COOLER SIDE STRUGGLING TO REACH 40. AHEAD OF THESE TWO
DISTURBANCES SURFACE LOW PRESSURE OF 1005 MB COMBINES WITH THE
DEPARTING HIGH TO CREATE A MODEST PRESSURE GRADIENT ACROSS THE AREA.
A VERY STRONG LOW LEVEL JET SETS UP LATE IN THE AFTERNOON...BUT
GIVEN THE LOW LEVEL INVERSION...EXPECT A BREEZY DAY WITH GUSTS IN
THE 25 KT RANGE.

KMD

&&

.LONG TERM...(Tonight through Tuesday)
ISSUED AT 326 AM CST TUE JAN 27 2015

Low clouds to decrease during the evening as 1027 mb high pressure
drifts over IL/IN by overnight. Lows tonight range from upper teens
to near 20F ne counties (where clearing may occur soonest) to mid
20s sw counties. High pressure drifts east into eastern Ohio river
valley by 18Z/noon Wed and get a breezy SSE flow developing over IL
and bringing in milder air with partly to mostly sunny skies. Highs
Wed range from lower 40s eastern IL to the upper 40s to around 50F
from Jacksonville west to the MS river.

Low pressure ejects east from northern Rockies into western Great
Lakes by dawn Thu and pulls cold front east across IL late Wed night
into Thu morning. This to bring chances of light rain overnight Wed
night into Thu morning and possibly lingering over eastern IL Thu
afternoon where light snow could mix in over northern counties
before ending. Lows Wed night of 33-38F with coolest readings in
east central IL. Highs Thu in upper 30s and lower 40s central IL and
mid 40s in southeast IL southeast of I-70.

1040 mb Canadian high pressure moves down into the Midwest Friday
and returns mostly clear to partly cloudy skies and cooler
temperatures Thu night through Fri night. Cooler highs Friday of
30-35F. Most of Saturday now appears dry over central and eastern IL
with chance of light snow/rain moving into west central IL later
Saturday ahead of next storm system. Seasonable highs Saturday in mid
to upper 30s.

00Z extended models show more phasing of southern and northern
stream system this weekend and bring better chances of light snow to
central and southeast IL Sat night into Sunday evening as surface
low deepens ne from southeast Texas into the eastern OH/TN river
valleys. This could bring a few inches of snow accumulations
especially in southeast IL where even a mix of precipitation appears
possible south of Highway 50. Another Canadian high to drift
southeast into IL early next work week bringing colder/below normal
temperatures.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 1141 AM CST TUE JAN 27 2015

MAIN AVIATION CONCERN REVOLVES AROUND EXISTING MVFR AND IFR CIGS.
IFR CIGS ARE BECOMING LESS COMMON ACROSS THE TERMINALS AS DRIER
AIR SLOWLY FILTERS IN FROM THE NORTHEAST. EXPECT KBMI WILL HANG
ONTO IFR A BIT LONGER BEFORE TRANSITION MVFR CIGS IN THE 1000-1500
FT RANGE. CHALLENGE THEN TURNS TO HOW QUICKLY THE LOWER CLOUD BASE
ERODES. HRRR AND RAP GUIDANCE ARE A BIT MIXED TO HOW QUICKLY THIS
OCCURS. THE GENERAL FEELING IS THAT SOMETIME THIS EVENING THE MVFR
DECK WILL LIFT ABOVE 2000 FT AND SCATTER OUT AS THE HRRR
SUGGESTS...BUT CONFIDENCE ON THIS TIMING IS MEDIUM. HIGHEST CONFIDENCE
ON TIMING THIS OCCURRENCE IS AT KCMI AND EASTERN LOCATIONS WHERE
DRIER AIR WILL MORE READILY ADVECT IN. MEANWHILE THE RAP AND NAM
HOLD ONTO THE CLOUDS THROUGH 6Z OR SLIGHTLY LATER AS A LOW LEVEL
INVERSION REMAINS IN PLACE. WINDS OVERNIGHT WILL VEER TO THE
SOUTHEAST AND WEAKEN BEFORE STRENGTHENING TOMORROW MORNING. SOME
PATCHY FOG MAY DEVELOP AFTER CLOUDS CLEAR BUT HELD OFF ANY MENTION
AT THIS POINT.


&&

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

$$

SHORT TERM...kmd
LONG TERM...07
AVIATION...KMD





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