330
FXUS63 KILX 021713
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1213 PM CDT TUE JUN 2 2026
KEY MESSAGES
- A HIGH PRESSURE SYSTEM WILL RESULT IN LOW HUMIDITY AND
SEASONABLE TO SLIGHTLY ABOVE NORMAL TEMPERATURES THROUGH
WEDNESDAY, WITH HIGHS IN THE LOW TO MID 80S.
- A PATTERN CHANGE OCCURS LATE IN THE WEEK, RESULTING IN
INCREASING HEAT, HUMIDITY, AND STORM CHANCES (30-60%) FRIDAY
INTO NEXT WEEK. AFTERNOON HEAT INDICES COULD CLIMB INTO THE
LOW TO MID 90S AT TIMES.
DISCUSSION
ISSUED AT 117 AM CDT TUE JUN 2 2026
*** THROUGH WEDNESDAY ***
06Z/MIDNIGHT SFC ANALYSIS SHOWS AN EXPANSIVE 1026-MB SFC HIGH PRESSURE
OVER ONTARIO. THIS FEATURE WILL SINK SOUTH AND DRIVE THE LOCAL
CONDITIONS THROUGH WED. IN THE UPPER LEVELS, AN OMEGA BLOCK
PERSISTS, WITH A MERIDIONALLY-ORIENTED RIDGE AXIS WEST OF IL, AN
UPPER LOW OVER MT, AND A POSITIVELY-TILTED TROUGH OVER THE
EASTERN US EXTENDING INTO THE OHIO VALLEY. THE PROXIMITY OF THIS
TROUGH (AND THE COOLER TEMPS ALOFT ASSOCIATED WITH IT) SHOULD
LEAD TO SLIGHTLY COOLER TEMPS TODAY, ALTHOUGH I REMAIN CONCERNED
ABOUT THE PERSISTENT COOL BIAS THE NBM HAS EXHIBITED OVER THE
LAST WEEK.
ON MONDAY (YESTERDAY), TEMPS ONCE AGAIN WOUND UP WARMER THAN FORECAST,
WHILE DEWPOINTS DROPPED MUCH LOWER THAN GUIDANCE, FALLING INTO
THE 30S ACROSS NORTHERN IL. THE DRY, NE FLOW REGIME WILL PERSIST
TODAY, SO RAISED TEMPS A FEW DEGREES (LOW TO MID 80S) AND MADE
AN EFFORT TO TREND DEWPOINTS LOWER. THESE FORECAST EDITS NOW
HAVE DEWPOINTS NEAR 40F ALONG/NORTH OF I-74 THIS AFTERNOON. THAT
WILL RESULT IN MINIMUM RH VALUES DROPPING INTO THE 20-30%
RANGE, BUT WIND GUSTS LESS THAN 20 MPH SHOULD MITIGATE ELEVATED
FIRE RISK.
THE SFC HIGH WILL CONTINUE TO SHIFT SOUTH ON WED, RESULTING IN A
SE COMPONENT TO THE WIND. THIS MAY RESULT IN TEMPS AND
DEWPOINTS BEING INCREMENTALLY HIGHER THAN TODAY, BUT OVERALL
SIMILAR CONDITIONS CAN BE EXPECTED. PRECIP IS NOT EXPECTED TODAY
OR WED.
*** LATE WEEK PATTERN SHIFT ***
A PATTERN SHIFT IS STILL ANTICIPATED DURING THE LATTER HALF OF
THE WEEK AS THE UPPER RIDGE BECOMES FLATTENED. AN UPPER HIGH
AND THE ASSOCIATED SFC HIGH PRESSURE STILL PERSIST OVER THE SE
CONUS, WHILE THE NORTHERN BRANCH OF THE JET STREAM BECOMES ZONAL
AND EMBEDDED WAVES BECOME MORE PROGRESSIVE. THE LOCATION OF THE
SFC HIGH IN THE SE US FAVORS MOISTURE ADVECTION INTO IL,
GRADUALLY BOOSTING DEWPOINTS FROM THE MID 50S ON THURS TO NEAR
70F BY SUN/EARLY NEXT WEEK.
THE BUILDING INSTABILITY COMBINED WITH THE PROGRESSIVE NORTHERN
JET STREAM RESULTS IN DAILY SHOWER AND STORM CHANCES, BEGINNING
FRI PM AND CONTINUING INTO EARLY NEXT WEEK. THE NBM PROBABILITY
OF AT LEAST 0.25" OF RAIN FRIDAY THROUGH SUNDAY NIGHT IS 50-80%
AREA-WIDE. THE SEVERE STORM POTENTIAL WILL NEED TO BE
MONITORED, BUT FOR NOW DEEP LAYER SHEAR CONTINUES TO BE THE MOST
QUESTIONABLE INGREDIENT, WITH GUIDANCE GENERALLY OUTPUTTING
VALUES LESS THAN 30 KTS. MACHINE LEARNING GUIDANCE LOWERED THE
SEVERE PROBS COMPARED TO THE PREVIOUS FORECAST.
COMBINED WITH ABOVE NORMAL TEMPS, THE INCREASING HUMIDITY PUSHES
THE FORECAST HEAT INDICES INTO THE LOW 90S BY SUN/MON. WHILE
BELOW TRADITIONAL HEAT ADVISORY CRITERIA (HEAT INDEX AROUND
105F), THE MULTI-DAY NATURE OF THIS HEAT, AND THE FACT THAT IT
IS THE FIRST SUCH EVENT OF THE YEAR, COULD LEAD TO IMPACTS FOR
SENSITIVE POPULATIONS. THE PRESENCE OF SHOWERS AND STORMS DOES
AT LEAST PROVIDE AN "OUT", WHERE ONE OR MORE DAYS IN THE
EXTENDED COULD BE COOLER THAN FORECAST OWING TO CLOUD COVER OR
PRECIP BEING MORE EXTENSIVE THAN CURRENTLY RESOLVED BY GLOBAL
MODELS. PROBABILISTIC HEAT RISK CONTINUES TO FOCUS THE HIGHEST
PROBS ON SUN-NEXT TUES, WHEN THERE IS A 40-70% CHANCE OF
MODERATE HEAT IMPACTS (SENSITIVE POPULATIONS) EACH DAY.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1209 PM CDT TUE JUN 2 2026
ASIDE FROM THIN CIRRUS AND A LOW CHANCE OF FEW-SCT VFR CU,
MOSTLY CLEAR SKIES WILL CHARACTERIZE THE FORECAST PERIOD. WINDS
WILL BLOW FROM THE EAST AROUND 10-13 KT WITH A FEW SPORADIC
GUSTS THIS AFTERNOON, THEN EASE TO 5-9 KT AFTER SUNSET.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...ERWIN
DISCUSSION...ERWIN
AVIATION...BUMGARDNER
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