IWX issues Area Forecast Discussion (AFD) at Mar 1, 2:30 AM EST369
FXUS63 KIWX 010730
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
230 AM EST Sat Mar 1 2025
.KEY MESSAGES...
- Lake effect snow showers are expected for much of the area
today but any accumulation will be less than an inch.
- After a brief shot of cold air today temperatures slowly
rebound through early next week.
- Widespread soaking rain is expected Tuesday into Wednesday.
&&
.DISCUSSION...
Issued at 230 AM EST Sat Mar 1 2025
Potent CAA now well underway with strong NNW flow pushing 850mb
temps to around -15C locally and near -20C just to our N/NE.
Calendar-day highs have already been reached with temps steadily
falling since midnight and continuing to fall into the mid 20s
everywhere by late morning. Temps will then hold steady in the upper
20s/low 30s for the rest of the day. This CAA will support a decent
lake response already starting per latest radar mosaic. Fetch is
nearly ideal with a wind direction of 340 degrees but it would be
better if it were slightly more northerly, particularly upstream.
Streamlines don't indicate a good Lake Superior connection for our
area with a lot of dry air entrainment from northern WI where
surface dewpoints are in the single digits. Inversion heights are
decent but not spectacular at around 5-6 kft. The problem is the
degree of dry air which will cause high LCL's and limited cloud
depths. Theta-e lapse rates reflect the impact of dry air
entrainment as well. Strong lower level winds will limit lake-
induced convergence as well which will limit the development of a
single dominant band. However, the boundary layer will remain very
well mixed over our entire CWA today with reduced low level
stability extending well inland. Therefore expect what LES bands do
develop will extend across most of the area with many locations
likely to see at least flurries at some point today. This is
especially true given best omega and cloud-bearing layer resides
squarely within the DGZ. Accumulation will be difficult given recent
warm conditions and the expectation for a few peaks of sun between
bands. A quick half-inch on grassy/elevated surfaces is likely the
limit for most with perhaps isolated areas seeing around an inch if
a stronger band manages to develop.
Lake effect snow winds down quickly this evening as winds back and
subsidence/high pressure build. Light winds expected but a few
clouds may remain with lows generally mid/upper teens. Sunday will
be dry and mostly sunny as low level ridge axis moves overhead.
Increasing sun angle and some light, late-day WAA will push highs
into the mid/upper 30s. Monday will be warmer still as high pressure
exits and return flow/WAA ramps up. This could yield a few sprinkles
in our NW on Mon but chances are low given overall dry/stable
environment.
Far better chances for rain arrive late Tue as deep upper level low
ejects out of the SW CONUS taking on a negative tilt as it lifts
through the Midwest. Highly efficient moisture advection, excellent
forcing for ascent, and reduced stability aloft all point to a
widespread soaker late Tue into Tue night. Instability profiles look
meager and elevated at this point so will hold off on a thunder
mention for now. Will have to keep an eye on the potential for heavy
rain and isolated flooding but at this point the track favors a
relatively quick hit for us with midlevel dry slot limiting the
duration of the heaviest rain in our area. Light wraparound precip
continues into Wed and could mix with some snow before ending Wed
evening. Temps will be on the typical March roller coaster next week
with 50s Tue/Wed dropping to the 30s on Thu.
&&
.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1251 AM EST Sat Mar 1 2025
VFR to MVFR conditions are expected at the TAF sites, with the
best potential for MVFR ceilings/visibilities at KSBN. A trough
cycling around the exiting low pressure system will swing
through overnight into the day Saturday. This will provide an
extra boost for light lake rain/snow showers to develop [more
likely to be snow as we continue into the period]. Ceilings
upstream of both sites are in the 2500 to 4000 ft range, so have
a tempo for periods of MVFR for both-with highest confidence in
KSBN. Light flurries or snow showers may persist through the day
until dry air moves in later tomorrow afternoon. West-northwest
winds will continue to gust to around 25 knots through the
night, especially behind the trough. Otherwise, since we've
decoupled the gusts may be more intermittent than they were
earlier today.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 11 PM EST this evening for LMZ043-
046.
&&
$$
DISCUSSION...AGD
AVIATION...MCD
Source:
IWX issues Area Forecast Discussion (AFD) at Mar 1, 2:30 AM EST---------------
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