917
FXUS63 KLOT 271132
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
632 AM CDT MON OCT 27 2025
KEY MESSAGES
- A PASSING STORM SYSTEM MAY PROVIDE PERIODS OF RAIN ACROSS THE
AREA DURING THE MIDDLE OF THE WEEK, FAVORING AREAS SOUTH OF
INTERSTATE 80.
- EXPECT SEASONABLE TEMPERATURES THROUGH NEXT WEEKEND.
DISCUSSION
ISSUED AT 310 AM CDT MON OCT 27 2025
AN UPPER-LEVEL LOW CENTERED NEAR THE BOOTHEEL OF MISSOURI EARLY
THIS MORNING WILL MOVE ESE TO THE CAROLINAS THROUGH TONIGHT AS
A STRONG RIDGE OVER ONTARIO REMAINS MOSTLY STATIONARY. A DEEP
RESERVOIR OF DRY AIR ADVECTING FROM THE EAST AND NORTHEAST WILL
SUPPRESS PRECIP WELL SOUTH OF THE AREA, WITH ONLY SOME CIRRUS
ATTEMPTING TO LIFT NORTHWARD THROUGH THE DAY.
A LONGWAVE TROUGH OVER WESTERN CANADA AND THE NORTHWEST U.S.
WILL BECOME CONSIDERABLY ELONGATED ACROSS THE GREAT PLAINS OVER
THE NEXT 24-48 HOURS BETWEEN THE RIDGE OVER ONTARIO AND A
RAPIDLY BUILDING WEST COAST RIDGE. A NARROW NORTH TO SOUTH
ORIENTED BAND OF RAIN IS EXPECTED TO DEVELOP WEST OF THE
MISSISSIPPI RIVER LATE TONIGHT INTO TUESDAY IN ASSOCIATION WITH
A MODEST AREA OF MID-LEVEL MOISTURE BELOW A BROAD ENTRANCE
REGION OF A NORTHWEST POINTED UPPER-JET MAXIMUM. EXTENSIVE LOW
TO MID-LEVEL DRY-AIR ADVECTION FROM A PSEUDO-HUDSON BAY HIGH TO
THE NORTHEAST WILL STEADILY ERODE THE EASTERN EDGE OF THE
PRECIP BAND TUESDAY INTO TUESDAY NIGHT BEFORE THE MAIN VORTICITY
LOBE OF THE TOUGH DETACHES AND PIVOTS SOUTHWEST OF THE AREA.
EXPECTATIONS ARE THAT MUCH OF THE AREA WILL REMAIN DRY ON
TUESDAY, WITH RAIN POTENTIAL RANGING FROM LOW-END CHANCE POPS
(30%) NEAR THE WISCONSIN LINE TO LIKELY POPS (UP TO 70%) TOWARD
CENTRAL ILLINOIS TUESDAY NIGHT INTO WEDNESDAY MORNING. IT IS
HIGHLY LIKELY THAT THERE WILL BE A SHARP NORTH TO SOUTH GRADIENT
IN PRECIPITATION SOMEWHERE OVER THE FORECAST AREA, WITH A
DISTINCT POSSIBILITY THAT MUCH OF NORTHERN ILLINOIS REMAINS DRY
WITH THIS EVENT.
THE NEWLY FORMED LOW TO THE SOUTHWEST, THE ORIGINAL LOW OVER
THE CAROLINAS, AND EVEN THE REMNANTS OF HURRICANE MELISSA WILL
CONGEAL INTO A LONGWAVE TROUGH OVER THE NORTHEAST LATE IN THE
WEEK, WITH SIGNALS OF A COUPLE REINFORCING WAVES CROSSING THE
AREA FROM THE NORTHWEST THIS WEEKEND INTO EARLY NEXT WEEK.
ENSEMBLE GUIDANCE CONTINUES TO DEPICT A LOOSE OMEGA BLOCK
DEVELOPING AS THE WEST COAST RIDGE AMPLIFIES. OUR AREA WOULD BE
SITUATED ON THE WESTERN EDGE OF THE MAIN LONGWAVE TROUGH TO THE
EAST, YIELDING SPORADIC BOUTS OF SCATTERED RAIN SHOWERS AND
PERHAPS SOME LAKE EFFECT RAIN SHOWERS DURING THIS TIME. TEMPS
WILL REMAIN SEASONABLE AS ARCTIC AIR REMAINS WELL NORTH OF THE
AREA.
KLUBER
AVIATION /12Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 630 AM CDT MON OCT 27 2025
VFR CONDITIONS ARE FORECAST THROUGH THE PERIOD.
AFTER DAYBREAK WINDS ARE EXPECTED TO INCREASE UP TO AROUND
13-15KT OUT OF THE EAST WITH AN OCCASIONAL GUST INTO THE UPPER
TEENS POSSIBLE. WINDS BEGIN TO EASE AFTER SUNSET THOUGH
SPORADIC GUSTS MAY LINGER INTO THE EVENING IN CHICAGO.
MOSTLY CLEAR SKIES ARE EXPECTED TODAY WITH INCREASING HIGH
CLOUD COVERAGE OCCURRING OVERNIGHT INTO TUESDAY MORNING AHEAD OF
AN APPROACHING WEATHER SYSTEM.
PETR
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 AM CDT WEDNESDAY FOR THE IL
NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
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