326  
FXUS63 KILX 271210  
AFDILX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LINCOLN IL  
610 AM CST WED JAN 27 2021  
   
SYNOPSIS
 
 
ISSUED AT 400 AM CST WED JAN 27 2021  
 
LIGHT SNOW WILL SPREAD EASTWARD ACROSS CENTRAL AND SOUTHEAST IL  
DURING THIS MORNING, AND DIMINISH TOWARD SUNSET. BETWEEN 1 AND 2  
INCHES OF SNOW IS EXPECTED ALONG AND SOUTH OF A RUSHVILLE TO  
DECATUR TO TERRE HAUTE LINE TODAY. WINTER WEATHER ADVISORIES ARE  
IN EFFECT TODAY FOR SOUTHERN AND SOUTHWEST ILLINOIS. MUCH COLDER  
TEMPERATURES WILL ARRIVE TONIGHT WITH LOWS IN THE SINGLE DIGITS TO  
TEENS, AND WIND CHILLS OF 5 BELOW TO 5 ABOVE OVER MUCH OF CENTRAL  
IL. STRONG CANADIAN HIGH PRESSURE WILL BUILD INTO IL BY THURSDAY  
AFTERNOON, RETURNING SUNSHINE THOUGH STAYING COLD THROUGH THURSDAY  
NIGHT.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 430 AM CST WED JAN 27 2021  
 
EARLY MORNING SURFACE ANALYSIS SHOWS 1037 MB CANADIAN HIGH  
PRESSURE OVER LAKE WINNIPEG AND RIDGING SOUTH INTO THE MIDWEST.  
THIS WAS GIVING A CHILLY NE FLOW OVER IL. TEMPERATURES AT 4 AM  
RANGED FROM 15 TO 20F ALONG AND NORTH OF A RUSHVILLE TO  
BLOOMINGTON LINE (WITH WIND CHILLS OF 5-10F), TO THE LOWER 30S IN  
SOUTHEAST IL. DEWPOINTS WERE ONLY IN THE LOW TO MID TEENS OVER THE  
NORTHERN CWA, WHILE UPPER 20S IN SOUTHEAST IL. ALOFT A 541 DM 500  
MB LOW WAS OVER CENTRAL KS WHILE A STRONGER 519 DM 500 MB LOW WAS  
OFF THE WA/PACIFIC NORTHWEST COAST.  
 
THE LATEST FORECAST MODEL SUITE TAKE THE CUTOFF LOW FROM CENTRAL  
KS TO THE SOUTHERN IL/IN BORDER BY SUNSET TODAY AS IT WEAKENS TO  
545 DM. WEAK FORCING AND ISENTROPIC LIFT WITH THIS WX SYSTEM OVER  
SOUTHERN HALF OF IL TODAY. CAMS SHOW ALL SNOW WITH THIS WX SYSTEM  
AS IT SPREADS LIGHT SHOW EASTWARD OVER CENTRAL/SOUTHERN IL DURING  
MID TO LATE MORNING, THEN DIMINISHES IN EAST CENTRAL/SOUTHEAST IL  
DURING LATE AFTERNOON AND EARLY THIS EVENING. MUCH DRIER AIR OVER  
NORTHERN CWA, AND MAINLY EXPECT JUST FLURRIES THERE TODAY.  
SOUTHERN/SW CWA ARE EXPECTED TO SEE 1-2 INCHES OF SNOW BY DUSK  
WITH THE HIGHEST AMOUNTS ALONG AND SOUTH OF HIGHWAY 50 IN CLAY,  
RICHLAND AND LAWRENCE COUNTIES. ABOUT A 6 HOUR PERIODS OF LIGHT  
SNOW EXPECTED TODAY. HIGHS TODAY MOSTLY IN THE UPPER 20S AND LOWER  
30S OVER CWA, BUT RANGE FROM THE MID 20S NW OF THE IL RIVER, TO  
THE MID 30S BY LAWRENCEVILLE.  
 
SOME LIGHT SNOW OR FLURRIES IN EASTERN IL/WABASH RIVER VALLEY  
EARLY THIS EVENING, THEN CLOUDS EXPECTED TO DECREASE FROM THE NW  
DURING TONIGHT. MUCH COLDER TEMPS ARRIVE OVERNIGHT WITH LOWS  
2-7F NW OF THE IL RIVER (COLDEST IN KNOX AND STARK COUNTIES), TO  
THE UPPER TEENS IN SOUTHEAST IL. NNW WINDS TO GIVE WIND CHILLS OF  
ZERO TO 5 BELOW NORTHERN CWA AND AROUND 10F SOUTHEAST OF I-70.  
   
LONG TERM
 
(THURSDAY THROUGH TUESDAY)  
ISSUED AT 430 AM CST WED JAN 27 2021  
 
STRONG 1037 MB CANADIAN HIGH PRESSURE OVER SOUTHERN MANITOBA TO  
STRENGTHEN TO AROUND 1042 MB AS IT SETTLES INTO WESTERN ONTARIO BY  
DAWN THU AND RIDGES SOUTHWARD INTO IL THU AFTERNOON. THIS WILL  
BRING AMPLE SUNSHINE TO AREA THU AS NNW WINDS GRADUALLY DIMINISH  
AS HIGH PRESSURE SETTLES IN. BELOW NORMAL HIGHS ON THU, IN THE MID  
20S NORTHERN CWA AND LOWER 30S FROM I-72 SOUTH, WITH MID 30S FROM  
HIGHWAY 50 SOUTH. TEMPS TO FALL QUICKLY THU EVENING WITH LOWS IN  
THE LOW TO MID TEENS NORTHERN CWA AND UPPER TEENS TO NEAR 20F SW  
CWA AND SOUTHEAST IL.  
 
A STRONG UPPER LEVEL RIDGE SHIFTS EASTWARD INTO THE MS RIVER  
VALLEY BY SUNSET FRIDAY. MEANWHILE STRONG SURFACE HIGH PRESSURE  
SHIFTS EAST OF IL ON FRIDAY WITH RETURN SE FLOW STARTING TO MODIFY  
TEMPS CLOSER TO NORMAL WITH PARTLY TO MOSTLY SUNNY SKIES, MORE  
CLOUDS NORTHERN/NE CWA FRI AS MID/HIGH CLOUDS STREAM SE FROM THE  
UPPER MS RIVER VALLEY. HIGHS FRI IN THE MID TO UPPER 30S, WITH SE  
IL AND SPRINGFIELD SW NEAR 40F. MID AND HIGH CLOUDS INCREASE FROM  
THE WEST DURING FRIDAY NIGHT AHEAD OF A STRONG STORM SYSTEM OFF  
THE WEST COAST THAT EMERGES OVER THE SOUTHERN PLAINS BY DAWN SAT.  
 
MODELS OVERALL HAVE TRENDED SLOWER AND FURTHER SOUTH WITH THIS  
STRONG STORM SYSTEM, NOW APPEARING TO MOVE NEAR SOUTHERN IL  
OVERNIGHT SAT NIGHT. GFS IS QUICKER SPREADING QPF EAST INTO IL  
DURING SAT MORNING, WHILE ECMWF AND GEM MODELS WAIT UNTIL SAT  
AFTERNOON TO BRING QPF INTO THE AREA. LEANING ON THE SLOWER ECMWF  
AND GEM MODELS DUE TO DEEP UPPER LEVEL TROF/LOW DIGGING INTO THE  
SOUTHERN PLAINS. SLOW MOVEMENT WOULD LIKELY LINGER PCPN THRU  
SUNDAY OVER CWA. IF FURTHER SOUTH STORM TRACK VERIFIES, THIS  
WOULD FAVOR BETTER CHANCE OF WINTRY PRECIPITATION AND POSSIBLE  
SNOW ACCUMULATIONS OVER CENTRAL IL. FOR NOW HAVE RAIN SAT  
AFTERNOON, MIXED WITH SNOW NORTHERN CWA, THEN MIXED PCPN SPREADING  
SOUTHWARD INTO CENTRAL IL DURING SAT NIGHT INTO SUNDAY. SOUTHERN  
IL MAINLY SEEING RAIN AND COULD BE ISOLATED THUNDERSTORMS IN  
SOUTHERN IL SAT AFTERNOON INTO SAT NIGHT. QPF OF 1 INCH OR MORE  
STILL LOOKS LIKELY WITH THIS STORM SYSTEM AS IT WILL HAVE DEEP  
GULF MOISTURE ADVECTING NORTHWARD AHEAD OF IT INTO IL.  
 
STRONG LOW PRESSURE TRACKS OFF THE MID ATLANTIC COAST BY MIDDAY  
MONDAY, WHILE A LARGE UPPER LEVEL TROF/LOW WILL BE OVER THE OH/TN  
RIVER VALLEYS. SOME MODELS STILL LINGER SOME LIGHT QPF IN EASTERN  
IL ON MONDAY ON WESTERN FRINGE OF DEEP UPPER LEVEL TROF. ANY UPPER  
LEVEL SHORT WAVES TRACKING SE FROM THE WESTERN GREAT LAKES COULD  
KEEP CHANCE OF LIGHT SNOW/FLURRIES OVER EASTERN/NE IL ON MONDAY  
ALONG WITH KEEPING LOW CLOUDS AROUND LONGER. CHILLY HIGHS MONDAY  
IN THE LOW TO MID 30S.  
 
UPPER LEVEL RIDGE SHIFTING EAST INTO THE MS RIVER VALLEY BY SUNSET  
TUE ALONG WITH WEAK HIGH PRESSURE SETTLING INTO THE AREA, TO  
RETURN DRY WEATHER AND RETURN OF SOME SUNSHINE TO THE AREA WITH  
TEMPS STAYING ON THE CHILLY SIDE ON TUE. TEMPS TO LIKELY MODIFY  
NEXT WED AS HIGH PRESSURE DRIFTS EAST OF IL, WHILE YET ANOTHER  
LARGE STORM SYSTEM DIGS INTO THE ROCKIES AND MAY IMPACT THE  
MIDWEST LATER NEXT WEEK.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)  
ISSUED AT 600 AM CST WED JAN 27 2021  
 
AN AREA OF LIGHT SNOW OVER MO AT DAWN WILL SPREAD EAST ACROSS  
CENTRAL IL DURING MID/LATE MORNING AND MAINLY IMPACTING THE I-72  
AIRPORTS ESPECIALLY SPI AND DEC FROM LATE MORNING INTO MID  
AFTERNOON WITH VSBYS LOWERING TO 1-2 MILES. MAINLY FLURRIES WILL  
OCCUR AT NORTHERN PIA AND BMI AIRPORTS THIS AFTERNOON. MVFR  
CEILINGS ALREADY AT BMI, CMI AND DEC WILL SOON RETURN AT SPI,  
WHILE PIA WILL BE ON NW EDGE OF MVFR CLOUDS TODAY. CEILINGS COULD  
LOWER TO AROUND 1K FT WITH THE LIGHT SNOW AT SPI AND DEC THIS  
AFTERNOON. VFR CONDITIONS RETURN DURING THIS EVENING WITH CLOUDS  
SCATTERED OUT DURING THE NIGHT. NORTH TO NE WINDS 5-10 KTS EARLY  
THIS MORNING TO INCREASE TO 8-13 KTS AND FEW HIGHER GUSTS TODAY  
AND VEER MORE NORTHERLY. NNW TO NW WINDS OF 5-10 KTS EXPECTED  
TONIGHT.  
 

 
   
ILX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SYNOPSIS...07  
SHORT TERM...07  
LONG TERM...07  
AVIATION...07  
 
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