IWX issues Area Forecast Discussion (AFD) at Oct 31, 2:53 AM EDT
126
FXUS63 KIWX 310653
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
253 AM EDT Fri Oct 31 2025
.KEY MESSAGES...
- Light lake effect rain showers are possible this morning and
again overnight into Saturday, mainly for areas north of
US-24.
- Temperatures remain cool over the weekend with highs in the
low/mid 50s and lows in the low/mid 30s.
- Mainly dry conditions with seasonable temperatures are
expected next week.
&&
.DISCUSSION...
Issued at 253 AM EDT Fri Oct 31 2025
Some light lake effect rain showers trying to spread across the area
this morning given cool NW flow over very warm Lake MI (water temps
near 14C). Confluent, cyclonic flow aiding ascent somewhat but very
marginal delta-T's (850mb temps only around 0C) and some dry air
entrainment both near the surface and aloft are taking a heavy toll.
This will keep rainfall amounts light and isolated but may penetrate
pretty far inland given confluent flow and reduced stability inland
(particularly after sunrise) per 0-2km theta-e lapse rates. Have
expanded the PoP's some but keeping in slight chance category and
QPF amounts very light. Flow backs westerly by the afternoon with
some brief shortwave ridging. This should cut off any remaining lake
effect precip (ideally timed for early evening outdoor activities).
Precip chances return again by late evening though and continue into
Sat as a potent upper low dives into IL. Low level flow remains
generally westerly over southern Lake MI but inversion
heights/convective depths soar to near 10 kft. This should promote a
healthy lake response but the question remains where. Most hi-res
guidance shows just a glancing blow to our NW counties tonight with
best lake enhanced precip remaining N/NW of our area on Sat. Very
weak and convergent flow could even develop a mesolow over central
Lake MI during this time. Models suggest any mesolow would likely
remain out of our area but they are difficult to predict more than a
few hours out. Shortwave itself could squeeze out some sprinkles
away from the lake but this seems highly unlikely given degree of
dry air below 850mb and lack of appreciable forcing. Have therefore
trimmed NBM PoP's for Sat. Temps remain on the cool side through the
weekend with highs in low/mid 50s and lows well into the 30s.
Another trough then digs into the northern Lakes late Sun into Mon.
Still some timing and strength differences amongst various NWP
guidance here so will acquiesce to NBM low chance PoP's across the
north. If it does rain, not expecting much given limited moisture
return and best CVA forcing locked to our north. There is a very
similar story on Wed but otherwise the forecast for most of next
week remains quiet with temps near to slightly above early Nov
norms.
&&
.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1231 AM EDT Fri Oct 31 2025
The latest GLERL Lake Michigan surface water temperature analysis
from yesterday (Thursday) showed the surface water temperatures
warmer than normal (13.57C for the entire lake). These mild
temperatures were causing delta T values to be around 14C given
the latest HRRR thermal fields. Lake enhanced showers were
favorable given a long lake fetch and these fairly large delta
T values. Have continued with the mention of showers at SBN
throughout the entire 24 hour TAF period with a TEMPO MVFR
group, PROB30 group and VCSH. Surface winds should be from 270
to 310 with velocities from 6 to 14 kts with gusts up to 22
knots at FWA.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ043-
046.
&&
$$
DISCUSSION...AGD
AVIATION...Skipper
Source: IWX issues Area Forecast Discussion (AFD) at Oct 31, 2:53 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202510310653-KIWX-FXUS63-AFDIWX)
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