IWX issues Area Forecast Discussion (AFD) at Jan 25, 6:24 PM EST
948
FXUS63 KIWX 252324
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
624 PM EST Sat Jan 25 2025
.KEY MESSAGES...
- Temperatures the next 7 days will generally remain above
normal, with a few post frontal dips Sunday and Thursday.
- Small chance for lake effect snow showers Wednesday into
Wednesday evening. Little if any accumulation.
- Deeper system looks to arrive for start of Feb, but exact
impacts and timing remain uncertain.
&&
.DISCUSSION...
Issued at 255 PM EST Sat Jan 25 2025
Peeks of sunshine across the area have allowed temperatures to
warm above freezing, even where snowpack exists (albeit a few
degrees cooler than other areas). Cold front, extending from NE
Wisconsin into central IL and taking its time working east.
Best chances for any light snow as the front passes will reside
across portions of WI into Lower MI (N of our area) this evening
so maintained a dry forecast.
A brief cool off is in store for Sun into Sun night behind the
front, before WAA makes its first attempt of the upcoming work week
across the area Monday. Decent temp gradient may setup Mon and
Tues due to impacts from fast moving trough Mon afternoon into
Mon evening limiting NE extent of warmer low level air until
later Tuesday. The surge of WAA will be aided by a increasing
low level flow with 925 mb winds 45 to 50 kts and 850 mb winds
50 to 60 kts. Some questions remains as to how much of this can
mix to the sfc, but consensus is to increase winds somewhat over
land and water.
A slightly stronger trough dives into the Great Lakes Wednesday,
temporarily shunting the warm air back SW and maybe bringing a
narrow window for lake effect snow showers (low confidence given
limited moisture).
A larger shift in the pattern begins to take shape late Thursday
and moreso into the weekend as models generally agree on a
cutoff upper low sitting in the Four Corners region 12Z Fri and
increasing upper level ridging across the forecast area. As
would be expected this far out, model agreement is no where as
strong in the low levels with timing issues on arrival of strong
WAA as well as increasing moisture to bring precip chances into
the area. Model blends carrying slgt chc to chc pops as early as
late Thursday night, but dry airmass should remain and likely
slower trend to the upper low ejecting as it becomes negatively
tilted and deepens. Pattern recognition points towards delaying
onset of precip with majority of offices in concensus. Have
limited measurable pops until Fri night. By this point, warm air
aloft should be more established across the area with at least
some concern for freezing precip briefly Friday night. A non-
diurnal temp trend was introduced by most offices Fri night with
lows happening early then warming overnight into Sat. Plenty of
time to monitor evolution of the system.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 623 PM EST Sat Jan 25 2025
An area of vorticity that exists across the northern Great Lakes to
start the period, swings eastward and vacates the area by the
end of the taf period. However, another trough also laden with
vorticity swings into the area just after this taf period. The
initial trough sets off cold air advection and time sections
show a subtle area of low cloudiness starting around 9 or 10z at
SBN and 13 or 14z at FWA and that lasts into the early to mid
afternoon period. The NBM has about 50 percent chance for low
MVFR CIGs or lower. Meanwhile, CONSShort guidance, which is the
conventional aviation short term blended guidance, along with
LAV guidance has values staying in VFR for that same time
period. So some differences exist with respect to potential
outcomes and it may be that that layer is just too thin to get
CIGs anyway. Given the low confidence on this happening, have
opted to put a tempo group in with the lower CIGs in this
issuance.
As far as winds go, expect generally west southwest winds overnight
staying above 5 kts, but it appears that shallow enough mixing
exists to keep gusts at bay.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Fisher
AVIATION...Roller
Source: IWX issues Area Forecast Discussion (AFD) at Jan 25, 6:24 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202501252324-KIWX-FXUS63-AFDIWX)
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