IWX issues Area Forecast Discussion (AFD) at Jan 15, 6:17 AM EST773
FXUS63 KIWX 151117
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
617 AM EST Wed Jan 15 2025
.KEY MESSAGES...
- Dry and very cold today. Morning wind chills below-zero
followed by afternoon wind chills in the single-digits.
- A clipper system will slow the Thursday morning commute with
reduced visibility and a quick accumulation of snow.
- Wind chills below zero tonight, but a brief thaw is ahead
Friday and Saturday.
&&
.DISCUSSION...
Issued at 248 AM EST Wed Jan 15 2025
A brief reprieve in sensible weather today with high pressure
over Iowa and Illinois shutting off lake effect snow locally.
Mainly clear skies as well which of course has allowed our
temperatures this morning to plummet toward 0 at some sites. The
next clipper arrives after midnight and is on schedule to
impact the Thursday morning commute. A quick burst of fluffy
snow is anticipated once again bringing reduced visibility and
quick accumulations of high- ratio (dry/fluffy) snow. Unlike
Tuesday's event, the DGZ will be about 5k to 8k FT higher though
still well saturated and colocated with robust mid-level omega.
The 500-mb flow looks stronger, pushing 90 knots and a little
further southwest of our area. Lake effect snow follows this
clipper briefly, ultimately shutting down prior to midnight
Friday morning when inversion heights crash toward 3k FT.
A brief thaw occurs Friday as 500-mb heights rise in response to an
upstream trough approaching the Four Corners. We'll see high
temperatures in the mid 30s to near 40 Lakeside. By the late
afternoon and evening a low tracking through Ontario spreads a cold
front through the Great Lakes. Meanwhile, over the mid-
Mississippi Valley, low pressure develops ahead of a shortwave
at 500mb. This results in a rain/snow mix Friday night through
Saturday. Friday night, the baroclinic zone along the cold front
is modest which reduces the risk of a flash freeze, yet
temperatures will be near 30 degrees; cold enough for a nonzero
risk of icy spots. Saturday will be mild over northwest Ohio
ahead of the front where mid-30s highs are expected.
Temperatures bottom out Saturday night thanks to a renewed
surge of Arctic air in which Saturday night lows will fall
toward 10-15 degrees. With precipitation ending Saturday
afternoon, remaining wet surfaces will freeze.
Very cold then for the remainder of the weekend through early week
with lake effect snow. The core of the 850-mb cold is overhead
Tuesday before easing. Single-digit highs are favored Monday and
Tuesday (the 50th percentile forecast is about 5 to 6 degrees both
days). Monday morning and Tuesday morning lows will be below
zero. Wind chills are forecast to be at or below -15F, resulting
in the need for Cold Weather Advisories.
&&
.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 615 AM EST Wed Jan 15 2025
Backing low level winds and lowering inversion heights have
eroded lake effect cloud cover across northern Indiana. This
trend will continue today as winds become south-southwest this
afternoon in response to an expansive ridge of high pressure
shifting eastward across the Ohio River Valley. Gust potential
is of somewhat low confidence this afternoon due to competing
effects of tightening low level height gradient and extensive
snow cover possibly hurting mixing potential. Mainly clear skies
today should give way to some increasing mid clouds this
evening as some stronger westerly flow provides some isentropic
ascent downstream of next clipper system. An upper jet streak
accompanying this clipper will dig across the western Great
Lakes tonight bringing another round of snow showers toward end
of this forecast valid period. MVFR/IFR vsbys appear likely from
late tonight into Thursday morning. Some brief lake
effect/enhancement is possible Thursday morning before more
pronounced mid level drying follows for late Thursday morning
into Thursday afternoon. Tightening gradient with this system
should also promote some 20 knot gusts tonight.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory from 3 PM this afternoon to 4 AM EST
Friday for LMZ043-046.
&&
$$
DISCUSSION...Brown
AVIATION...Marsili
Source:
IWX issues Area Forecast Discussion (AFD) at Jan 15, 6:17 AM EST---------------
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