Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1234 PM 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 /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1233 PM CDT Fri Oct 25 2024
Other than FEW/SCT high-end MVFR cumulus this afternoon, VFR
conditions are expected through Saturday. NW winds will
sporadically gust above 15 knots through sunset, then settle NW
around 5 knots tonight. Winds will then veer NNW/N up to 10
knots Saturday morning, with the potential to periodically vary
to just east of north. Winds will ultimately shift NNE/NE under
10 knots sometime Saturday afternoon as a surface high pressure
passes over or just north of the terminals.
Kluber
&&
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.
&&
$$
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