FXUS63 KLOT 250837 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 337 AM CDT Fri Oct 25 2024 .KEY MESSAGES... - Shower and storms will move east of our area by mid-morning. - Today and tomorrow will feature highs in the upper 50s to around 60, with partly cloudy skies today and sunny skies tomorrow. - Elevated fire danger Monday and Tuesday, with Tuesday having the potential to be a critical fire weather day due to strong southerly winds gusting up to 40+ mph. - Widespread rain/showers Wednesday night into early Thursday, *hopefully* clearing out in time for trick or treating. && .DISCUSSION... Issued at 301 AM CDT Fri Oct 25 2024 Through Saturday: Regional radar and water vapor imagery depict a somewhat unusual (as of recently) sight this morning with widespread showers and storms moving across the Lower Great Lakes. As the associated upper- level trough shifts eastward this morning, so will the highest coverage of showers and storms with all areas expected to be dry by mid- morning. By then, a cold front (currently stretching from northwestern Wisconsin through central Iowa) will sweep across the area, leading to breezy northwest winds and lowering humidity levels. Ephemeral mid to upper-level clouds in tandem with cold air advection behind the front should keep highs in the upper 50s (northwest) to lower 60s (southeast) this afternoon. Tonight through tomorrow, a surface high pressure system will slowly slide through the Great Lakes region. Light winds (at least over land) and clearing skies tonight will hence support efficient decoupling and radiational cooling with overnight lows expected to reach the low to mid 30s (save for the lower 40s lakeside). Tomorrow will feature sunny skies and northerly winds, with highs generally in the upper 50s. Borchardt Saturday Night through Thursday: Expansive, seasonably strong high pressure around 1030 mb overhead on Saturday night will help play a role in our warm, windy, and dry period Monday and Tuesday. First, Saturday night's lows will be fairly chilly, and exactly how cold will be determined by the extent of high cloud cover. Given the otherwise favorable radiational cooling setup, suspect that the typical cold spots will be able to dip into the upper 20s, with low-mid 30s elsewhere, except upper 30s to lower 40s in Chicago. The patch of high clouds will exit southeast by sunrise on Sunday, with return flow southerly warm advection developing and allowing a recovery to comfortable lower 60s in the afternoon. The surface high will be close enough to our east Sunday night to bring one more relatively chilly night before the next surge of warmth in our exceptionally mild fall. Moisture trajectories will remain blocked off on Monday given the strong surface high pressure ridging extending all the way to the central and eastern Gulf Coast. A moisture starved positively tilted short-wave will bring some mid-level cloud cover, but more importantly induce a strengthening southwesterly low level jet. Trended dew points toward the lower, better verifying ECMWF, Canadian, and MOS guidance (low-mid 30s F at peak heating). Unless the mid deck arrives earlier, the parched air mass and dried out ground will support temps quickly rising to the upper 60s to around 70F by early afternoon. Paired with southerly gusts up to 25-35 mph (strongest NW 1/2 of the CWA), RHs dropping into the 25-30% range should translate to an elevated danger for brush and grass fire spread. Dew points lower and/or temps higher than currently forecast could increase the risk somewhat, though winds may remain just low enough to preclude red flag concerns. Gusty southerly winds will continue Monday night, keeping temps at or above normal highs (upper 50s-lower 60s) and setting the stage for potential record warmth on Tuesday. By Tuesday, cyclogenesis over the Plains (elongated 995-1000 mb low pressure), the strong surface high over the east, and a stout 50-60 kt 850 mb southwesterly low level jet, will result in a windy and remarkably warm day. Again suspect that dew points will run solidly lower than guidance indicating upper 50s as moisture trajectories remain mostly blocked. Only some cirrus, summer-like 850/925 mb temps, and the strong south-southwest winds should support highs around 80F/lower 80s, a good chance to set new records for the date. Speaking of the winds and fire danger on Tuesday, forecast soundings suggest 40+ kt of flow in the mixed layer, so we could conceivably be pushing wind advisory criteria (45+ mph gusts). Even if the dew points tick just high enough to stay above critical thresholds (25% or less), the high winds could still enable brush fires to grow out of control. The winds will only come down slightly Tuesday night and keep temps incredibly mild for this time of year in the mid to upper 60s, if not warmer! Wednesday's temps will make a run at 80F again, though cloudy skies may keep things in check a bit. Confidence is fairly high this far out in a period of widespread rain Wednesday night in this setup as a surface low pressure wave rides ahead of a cold front. The cold front will sweep across the area Halloween morning, with cooler and breezy conditions for trick or treaters. Shower coverage is expected to peak in the early morning and trend downward through the afternoon. Castro && .AVIATION /06Z TAFS THROUGH 12Z SATURDAY/... Issued at 1256 AM CDT Fri Oct 25 2024 Main Concerns: - Embedded TS early this morning, SHRA ending by mid morning - Period of MVFR CIGs following the steady rain - Wind shift to northwest in the mid to late morning An extensive area of rain with embedded thunderstorms over the terminals early this morning will become more showery ahead of and immediately behind a cold front passage after sunrise. The most concentrated area of +TS will tend to sag south of the terminals, so maintained TEMPO TS with MVFR VSBY in the TAFs. Expect about 3 hours of MVFR CIGs after the stead rain tapers off, scattering in the wake of the cold front passage by the early afternoon. Winds will occasionally gust into the 15-20 kt range behind the front, especially at RFD. Castro && .CLIMATE... Issued at 337 AM CDT Fri Oct 25 2024 Record Warmth Possible Early to Mid Next Week: Near record to record high temperatures are in the forecast on Tuesday October 29th, with record warm low temperatures also in jeopardy on Tuesday October 29th and Wednesday October 30th. Here are the current daily records at Chicago and Rockford: Chicago: 10/29: Record High: 78F in 1999; Record Warm Low: 65F in 1946 10/30: Record High: 85F in 1950; Record Warm Low: 62F in 1974 Rockford: 10/29: Record High: 81F in 1922; Record Warm Low: 61F in 2004 10/30: Record High: 83F in 1950; Record Warm Low: 56F in 1924 NWS Chicago && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory from 7 PM this evening to 4 AM CDT Saturday for the IL nearshore waters. Small Craft Advisory from 7 PM this evening to 4 PM CDT Saturday for the IN nearshore waters. && $$ Visit us at weather.gov/chicago