IWX issues Area Forecast Discussion (AFD) at Jan 4, 11:24 AM EST987
FXUS63 KIWX 041624
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1124 AM EST Sat Jan 4 2025
.KEY MESSAGES...
- Light lake effect snow showers and flurries linger into
midday.
- Snow is expected Sunday night into Monday morning, mainly
along and south of US 24 where accumulations and travel
impacts remain possible.
- Remaining cold with periods of lake effect snow next week.
&&
.DISCUSSION...
Issued at 256 AM EST Sat Jan 4 2025
Impressive lake effect snow showers earlier this evening (impressive
for their inland extent and incredible ratios) are finally tapering
off amid dry air intruding and weakening low-level flow. Winds are
forecast to back westerly through the day which ought to ultimately
end the snow showers. Until then, paltry equilibrium levels near 5k
feet (which includes the DGZ) and plenty of lift through the column
will allow for some snow showers and flurries to persist through at
least midday. Accumulations will be less than 1 inch. Otherwise,
highs today in the 20s followed by overnight lows in the teens.
The key item of interest continues to be a Midwest storm system
Sunday night and Monday. There is still ample time (24 hours) for
headline adjustments as some incongruent model guidance persists,
though the northern and western portion of the watch is in jeopardy.
For now, the watch is unchanged.
What short-term guidance is becoming available indicates the
possibility of headline-worthy snowfall within the watch while global
models and their ensembles are drier and farther south. The 75th
percentile forecast (only a 25% chance of a higher total) issued
this morning is about 6" in a line from Marion to Portland. North of
here the 75th percentile forecast is about 4 inches. Guidance
differences seem to hinge on the pace and interaction of the trough
exiting the southern Plains and how it is shunted by an impulse
digging into the eastern Great Lakes. Add to this the influence of
incoming high pressure over the Northern Plains. The latest cluster
analysis does offer one very balanced solution (among GFS, ECMWF,
and Canadian ensembles) in which there is nearly a 30/30/30
distribution. The result is a very tight gradient in snowfall from
south to north over Grant, Blackford and Jay counties. The once
northerly outlier GEFS is only north somewhat compared to others
while the ECMWF ensemble is still a southerly outlier.
Cold with lake effect snow developing in the wake of this system.
Highs Wednesday will struggle to reach 20 degrees followed by at
least a couple nights of single-digit lows outside of lake effect
clouds. What forecast soundings are available indicate a poorly
saturated DGZ could be a limiting factor of Lake Effect snow, but
otherwise a 24-hour duration of snow is plausible Wednesday into
Thursday. Another reinforcing dose of cold air is possible next
weekend.
&&
.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1122 AM EST Sat Jan 4 2025
Brief MVFR based cig invof KSBN to start will erode into VFR as
dry entrainment continues beneath encroaching high cloud shield
advecting in from the plains. Gusty w-nwrly winds this aftn
will subside toward sunset.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Storm Watch from Sunday evening through Monday evening
for INZ020-022>027-032>034.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 10 PM EST this evening for LMZ043-
046.
&&
$$
DISCUSSION...Brown
AVIATION...T
Source:
IWX issues Area Forecast Discussion (AFD) at Jan 4, 11:24 AM EST---------------
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