336
FXUS63 KLOT 150558
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1258 AM CDT THU OCT 15 2026
KEY MESSAGES
- A FALL STORM SYSTEM WILL MOVE THROUGH THE AREA THURSDAY AND
FRIDAY, BRINGING PERIODS OF RAIN SHOWERS AND GUSTY
NORTHWESTERLY WINDS (THE LATTER PRIMARILY ON FRIDAY).
- FROSTY AND NEAR-FREEZING CONDITIONS ARE FAVORED AWAY FROM
LAKE MICHIGAN FRIDAY NIGHT INTO SATURDAY.
- AFTER THE BRIEF PERIOD OF CHILLY WEATHER, THERE WILL BE A
WARMING TREND THIS WEEKEND INTO EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 310 PM CDT WED OCT 14 2026
THROUGH THURSDAY NIGHT:
OTHER THAN A FEW SPITS OF DRIZZLE NEAR LAKE MICHIGAN, MOST OF
THE AREA HAS SINCE DRIED OUT FROM THE OVERNIGHT AND EARLY
MORNING SHOWERS AND THUNDERSTORMS. THE COMBINATION OF OVERCAST
SKIES AND PERSISTENT ONSHORE NORTHEASTERLY WINDS HAVE HELD
TEMPERATURES IN THE LOW TO MID 60S NEAR/NORTH OF I-80. FARTHER
SOUTH, A THINNING OF THE STRATUS LAYER WITH OCCASIONAL PEEKS OF
SUNSHINE HAS ALLOWED TEMPERATURES TO WARM INTO THE UPPER 60S
AND LOWER 70S. GENERALLY EXPECT THE CLOUD COVER TO FILL BACK IN
THROUGH THIS EVENING AND OVERNIGHT WITH TEMPERATURES ONLY
DROPPING INTO THE 50S.
A FALL STORM SYSTEM REMAINS ON TRACK TO LIFT ACROSS THE REGION
ON THURSDAY WHICH WILL BRING WIDESPREAD SHOWERS AND A FEW
RUMBLES OF THUNDER TO THE AREA. THE GREATEST SHOWER COVERAGE IS
CURRENTLY FAVORED LATE MORNING THROUGH THE AFTERNOON. HI-RES
GUIDANCE CONTINUES TO DEPICT A RELATIVE MINIMUM IN PRECIPITATION
DEVELOPING ON THE SOUTHWEST SIDE OF THE SURFACE LOW DURING THE
LATE AFTERNOON AND EARLY EVENING. DEPENDING ON HOW FAR NORTH THE
LOW TRACKS, INCREASING INSTABILITY SOUTHEAST OF THIS DRY WEDGE
MAY LIFT INTO THE FAR SOUTHERN FORECAST AREA, SOUTH OF A PONTIAC
TO RENSSELAER LINE. WHILE THE BETTER INSTABILITY REMAINS
FARTHER SOUTH INTO CENTRAL AND SOUTHERN ILLINOIS, AN ISOLATED
STRONGER STORM CAN'T BE RULED OUT. ANY MORE ROBUST SHOWERS AND
EMBEDDED THUNDERSTORMS WILL BE CAPABLE OF EFFICIENT RAINFALL
RATES FOR THIS TIME OF YEAR IN THE PRESENCE OF PWATS
POTENTIALLY UPWARDS OF 1.5-2". THE LIMITED COVERAGE OF STRONGER
SHOWERS/STORMS SHOULD KEEP ANY FLOODING POTENTIAL TIED MAINLY TO
PONDING ON ROADWAYS AND POOR DRAINAGE SPOTS.
FRIDAY:
IN THE WAKE OF THE DEPARTING STORM SYSTEM AND ASSOCIATED STRONG
COLD FRONT, THE SURFACE PRESSURE GRADIENT INCREASES MARKEDLY
ACROSS THE AREA ON FRIDAY. THIS WILL LEAD TO BLUSTERY NORTHWEST
WINDS GUSTING UP TO 30-40+ MPH, HIGHEST ALONG THE NORTHWEST
INDIANA LAKESHORE. IN ADDITION, MODEL GUIDANCE HAS TRENDED
SLIGHTLY MORE SATURATED WITHIN THE LOW-CLOUD LAYER WHICH MAY
SUPPORT THE REDEVELOPMENT OF GUSTY DIURNAL SHOWERS. WEAK
INSTABILITY WITHIN THE LAYER AND COLDER CLOUD TOPS MAY SUPPORT
SOME GRAUPEL AS WELL. TEMPERATURES ON FRIDAY WILL LIKELY
STRUGGLE TO WARM OUT OF THE LOW TO MID 50S, MAKING FOR THE
COLDEST DAY OF THE SEASON SO FAR.
AS THE NORTHWESTERLY WINDS BEGIN TO TURN MORE NORTHERLY OVER
LAKE MICHIGAN, A BROKEN BAND (OR BANDS) OF LAKE EFFECT RAIN
SHOWERS WILL FOCUS INTO NORTHWEST INDIANA LATE FRIDAY AFTERNOON
THROUGH THE EVENING. WAVES ARE ALSO EXPECTED TO INCREASE AND MAY
LEAD TO MINOR LAKESHORE FLOODING OR EROSION, PARTICULARLY ALONG
THE PORTER COUNTY SHORE.
FRIDAY NIGHT ONWARD:
SKIES WILL QUICKLY CLEAR OUT AFTER MIDNIGHT FRIDAY, WHICH WILL
ALLOW FOR EFFICIENT RADIATIONAL COOLING AMIDST AN ALREADY COOLER
AIRMASS. THIS WILL LIKELY LEAD TO AREAS OF FROST DEVELOPMENT
OUTSIDE OF CHICAGO AND AWAY FROM LAKE MICHIGAN, COVERAGE
DEPENDENT UPON HOW LIGHT WINDS END UP. CAN'T RULE OUT
TEMPERATURES IN PORTIONS OF INTERIOR NORTHERN ILLINOIS DROPPING
INTO THE LOWER 30S. HOWEVER, CONFIDENCE IS NOT HIGH ENOUGH FOR A
FREEZE WATCH WITH THIS UPDATE.
WHILE STILL COOLER ON SATURDAY WITH TEMPERATURES IN THE 50S TO
AROUND 60, A RETURN OF SOUTHWESTERLY LOW-LEVEL FLOW WILL BEGIN A
GRADUAL WARMING TREND THAT CONTINUES THROUGH EARLY NEXT WEEK,
BRINGING A RETURN TO ABOVE NORMAL TEMPERATURES.
PETR
AVIATION /06Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 1258 AM CDT THU OCT 15 2026
FORECAST CONCERNS FOR THE TERMINALS...
- VFR TO HIGH END MVFR CEILINGS TONIGHT.
- STORM SYSTEM WILL ARRIVE THURSDAY MORNING AND BRING PERIODS OF
SHOWERS AND IFR CONDITIONS, AT TIMES LIFR, THROUGH THURSDAY
EVENING.
- IMPROVING CEILINGS THURSDAY NIGHT WITH INCREASING NORTHWEST
WINDS GUSTING 20-25 KTS.
A BUSY TAF PERIOD WEATHER WISE IS AHEAD AS THE DEVELOPING STORM
SYSTEM IN THE SOUTHERN PLAINS WILL BE MOVING INTO AND THROUGH
THE GREAT LAKES THURSDAY MORNING THROUGH THURSDAY EVENING. PRIOR
TO THE SYSTEM'S ARRIVAL, EXPECT VFR TO HIGH END MVFR (2500-4000
FT) CEILINGS TO PERSIST OFF AND ON THROUGH TONIGHT WITH EASTERLY
WINDS AROUND 8-10 KTS. WHILE A FEW WARM ADVECTION SHOWERS MAY
DEVELOP AS EARLY AS 09-10Z TONIGHT, IT SEEMS THE BULK OF THE
RAIN SHOWERS WILL HOLD OFF UNTIL MID TO LATE MORNING THURSDAY AS
THE CORE OF THE AFOREMENTIONED STORM SYSTEM ARRIVES. ONCE THE
RAIN SHOWERS ARRIVE THEY WILL PERSIST IN AN OFF AND ON CAPACITY
THROUGH THURSDAY EVENING RESULTING IN MVFR VISIBILITIES AND IFR
CEILINGS. THAT SAID, WITH THE SURFACE LOW FORECAST TO TRAVERSE
DIRECTLY OVERHEAD CONFIDENCE CONTINUES TO GROW IN A PERIOD OF
DRIZZLE AND LIFR CONDITIONS FOR A FEW HOURS LATE THURSDAY
AFTERNOON THROUGH EARLY THURSDAY EVENING. GIVEN THAT THERE IS
STILL SOME UNCERTAINTY AS TO THE DURATION OF THE DRIZZLE AND
LIFR CONDITIONS HAVE OPTED TO MAINTAIN PROB30S FOR THIS
POTENTIAL FOR NOW. ADDITIONALLY, THERE IS ALSO A LOW END CHANCE
(10-15%) FOR AN ISOLATED RUMBLE OR TWO OF THUNDER NEAR AND SOUTH
OF I-80 (MAINLY EFFECTING GYY) BETWEEN 21Z-01Z AS A PLUME OF
INSTABILITY OOZES NORTHWARD BUT CONFIDENCE REMAINS TOO LOW FOR
ANY FORMAL TAF MENTION.
RAIN IS EXPECTED TO GRADUALLY TAPER FROM WEST TO EAST AROUND AND
AFTER MIDNIGHT THURSDAY NIGHT. CEILINGS WILL ALSO IMPROVE AS THE
RAIN ENDS WITH MVFR CONDITIONS EXPECTED TO RETURN AROUND
MIDNIGHT AND PERSIST THROUGH THE REST OF THE TAF PERIOD.
AS FOR WINDS, DIRECTIONS WILL BECOME MORE SOUTHEASTERLY THURSDAY
MORNING AS THE SYSTEM ARRIVES BEFORE BECOMING LIGHT AND SOMEWHAT
VARIABLE AS THE SURFACE LOW PASSES OVERHEAD. THOUGH, DIRECTIONS
BENEATH THE LOW SHOULD GENERALLY FAVOR A SOUTH-SOUTHEAST
DIRECTION (170-180 DEGREES). IN THE WAKE OF THE SYSTEM'S COLD
FRONT WIND DIRECTIONS WILL TURN WEST-SOUTHWEST AND THEN FINALLY
NORTHWESTERLY AROUND MIDNIGHT THURSDAY NIGHT. SPEEDS WILL ALSO
BE INCREASING IN THE WAKE OF THE COLD FRONT WITH GUSTS PEAKING
AROUND 20-25 KTS THURSDAY NIGHT, THOUGH SOME LOCALLY HIGHER
GUSTS MAY BE SEEN IF DEEPER MIXING IS ACHIEVED. THESE GUSTY
NORTHWEST WINDS WILL PREVAIL THROUGH THE DAY ON FRIDAY AS WELL.
YACK
MARINE
ISSUED AT 310 PM CDT WED OCT 14 2026
STRONG NORTHWESTERLY GALES TO 40 KT AND VERY HAZARDOUS WAVES
ARE FORECAST TO DEVELOP FRIDAY AFTERNOON IN THE WAKE OF A
DEPARTING FALL STORM SYSTEM, BECOMING MORE NORTHERLY INTO FRIDAY
EVENING. ACCORDINGLY, A GALE WATCH HAS BEEN ISSUED FOR THE
ILLINOIS AND NORTHWEST INDIANA NEARSHORE WATERS FROM 1 PM FRIDAY
THROUGH 1 AM SATURDAY.
INCREASING LAKE INDUCED INSTABILITY WILL BECOME SUPPORTIVE OF
THE DEVELOPMENT OF A BAND OF LAKE EFFECT SHOWERS OVER LAKE
MICHIGAN FRIDAY AFTERNOON AND EVENING. WATERSPOUTS ALSO CANNOT
BE RULED OUT WITHIN THE STRONGEST SHOWERS.
PETR
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 3 PM CDT THIS AFTERNOON FOR
WINTHROP HARBOR TO WILMETTE HARBOR IL.
GALE WATCH FROM FRIDAY AFTERNOON THROUGH LATE FRIDAY NIGHT FOR
THE IL AND IN NEARSHORE WATERS.
SMALL CRAFT ADVISORY UNTIL 10 AM CDT THIS MORNING FOR WILMETTE
HARBOR TO NORTHERLY IS. IL.
SMALL CRAFT ADVISORY UNTIL 4 AM CDT EARLY THIS MORNING FOR
NORTHERLY IS. IL TO MICHIGAN CITY IN.
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