Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 271124
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
624 AM EST Sat Feb 27 2021

.SYNOPSIS...
Issued at 345 AM EST Sat Feb 27 2021

Mild temperatures will persist through the weekend with another
chance of rain late tonight into Sunday. Breezy conditions are
expected late Sunday and again Monday with gusts up to 35 mph
possible. After a brief cool down Monday into Tuesday...temperatures
will moderate again for the middle and end of next week.

&&

.SHORT TERM...(Today and Tonight)
Issued at 345 AM EST Sat Feb 27 2021

First shortwave and associated round of isentropic ascent on the way
out this morning. Chances for light rain will continue mainly in our
eastern counties until around 12Z. Bulk of today period remains dry
as midlevel ridge/AVA support increasing subsidence with transient
surface high sliding across the Ohio Valley. Main question will be
cloud cover trends and associated impact on high temps. Some concern
for low level moisture to get trapped under increasing subsidence
inversion today (especially given cold ground/residual snow) and
maintain low clouds longer than anticipated. However...not much
snowpack left across most of our area and upstream with visibilities
generally holding in the 1-3SM range. Upstream satellite and other
observational data sets also indicate a healthy surge of dry air
advection as reflected in model RH fields and forecast soundings.
May hold onto clouds through the morning (especially E/SE) but do
anticipate a period of clearing (NW by later this morning and
everywhere by early afternoon) before clouds increase again ahead of
next wave later today. This leads to a challenging high temp
forecast as numerical guidance struggling immensely with degree of
mixing given cold/moist surface conditions. Guidance varies all the
way from mid 30s to mid 50s. Stayed close to previous forecast of
mid 40s to low 50s which is on the warm end of the spectrum but has
a good cluster of support among guidance. However further
adjustments may be necessary in either direction depending on cloud
trends.

&&

.LONG TERM...(Sunday through Friday)
Issued at 345 AM EST Sat Feb 27 2021

Another very similar wave shears northeast late tonight into early
Sunday. A little better 250mb jet support seen in latest guidance
supporting a modest fgen band swiping our area with the best chances
for precip in our SE. Have therefore raised PoPs accordingly. QPF
amounts generally around a tenth will not have significant impact on
the rivers but we continue to monitor the impacts of snowmelt and
the potential for ice jams as thawing continues. Wet bulb profiles
appear sufficiently warm for an all-liquid event even in our far
northern counties. Another tricky high temp forecast on Sunday.
Anticipate mostly cloudy skies but very warm/moist air gets drawn
north ahead of the cold front and potential for our SE zones to make
a run at 60F while NW zones remain stuck in the 40s. Exact timing of
frontal passage will dictate final gradient placement and models
continue to struggle with that.

Two rounds of decent CAA anticipated late Sunday and again late
Monday. Each will bring with it a brief chance for lake effect/
enhanced precip along with gusty winds. Better moisture profiles
with deep cyclonic flow on Sunday but thermal profiles are not great
and any precip will likely fall as just rain. Much colder air
arrives Monday but moisture is lacking and time window for any light
snow showers appears very brief around midday Mon. Added some low-
end chances for both of these time periods but not anticipating any
impacts. Tight gradient, decent isentropic descent, and good mixing
in CAA regime will also lead to gusty winds both late Sun and again
on Mon. Wind gusts up to 30-35 mph possible with the highest gusts
anticipated in our northern counties.

Rest of the forecast period currently appears tranquil. After a
brief return to cold temps Mon night...temps quickly moderate back
into the 50s by mid/late week. Maintained just a slight chance PoP
in our SE Tue night out of respect for ECMWF solution. Otherwise...
period likely to remain dry (though confidence decreases by late
week as models continue to struggle with evolving longwave
pattern).

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
Issued at 623 AM EST Sat Feb 27 2021

The energy that caused the rain overnight moves northeast away from
the region as high pressure passes by overhead and to the east. This
allows drier air to overspread the area west to east pushing the
IFR/LIFR conditions out during the first few hours of the TAF period
at SBN, but it may to perhaps as late as the afternoon at FWA. VFR
conditions follow for the rest of the day until after midnight when
the next system providing rain to the area moves in. Expect another
descent through MVFR into IFR and perhaps reaching LIFR by morning
Sunday with the help of increased moisture from the melting
snowpack.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...AGD
AVIATION...Roller


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