Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 251925

Area Forecast Discussion
National Weather Service Northern Indiana
325 PM EDT Sat Mar 25 2017

Issued at 325 PM EDT Sat Mar 25 2017

Scattered showers will increase in coverage overnight into Sunday
morning. A brief break in rain is expected Sunday night into Monday
but another round will arrive Monday night. A few isolated storms
and moderate rain are possible but no impacts are expected. Lows
tonight will generally be in the upper 40s to lower 50s. Highs on
Sunday will be in the low to mid 60s.


.SHORT TERM...(This Evening through Sunday)
Issued at 325 PM EDT Sat Mar 25 2017

Healthy band of 925-850mb fgen clipping our north earlier today in
right-rear quadrant of 140kt upper jet streak has largely dissipated
and shifted out of the area as jet axis pulls rapidly eastward.
Chances for a few SCT showers will continue through the evening as
upper low slowly drifts into the region with a very moist airmass
(850mb dewpoints near 10C on 12Z KILX sounding) advected into place.
However, center of upper low is still over Missouri and subtle
downstream ridging is preventing most, if not all, UVM/precip,
especially in our eastern zones. Hi-res guidance still suggests a
few SCT showers possible this evening (with minor elevated
instability possibly supporting a few isolated thunderstorms) but
much better chances look to arrive later tonight into Sunday morning
as differential CVA bullseye and midlevel deformation/fgen swing
through the CWA. Overall lackluster, moist adiabatic lapse rates but
forecast soundings indicate just enough instability based at 925mb
to refrain from pulling thunder mention altogether. Some moderate
rainfall rates possible at times with an additional half inch or so
basin-average QPF but not anticipating any impacts.

Suspect there will be a break in steadier precip from west to east
by tomorrow afternoon as center of dampening/opening upper low moves
overhead and slightly drier air wraps around. 12Z NAM appears to be
overdoing diurnal destabilization as per usual and resultant
convective QPF seems overzealous. However, sufficient residual
moisture/decreased stability and small, pinwheeling vort lobes will
maintain chance for some SCT showers through the afternoon with an
isolated storm not impossible. Should see a fairly quick end to
precip Sunday evening with lifting wave and loss of diurnal heating.
Extreme, marine layer-driven temp gradient today will be washed out
by tomorrow with highs for most of the CWA in the low to mid 60s.
Lows tonight will stay in the 50s, save for the far N/NE where
stubborn marine layer has current temps still in the 40s.


.LONG TERM...(Sunday Night through Saturday)
Issued at 325 PM EDT Sat Mar 25 2017

After a brief break early Monday, secondary southern stream wave,
currently over the southwest CONUS, will lift into the area with
another round of light/moderate rain. Footprint of this wave is much
smaller and weaker so precip will be in and out by around 12 hours
with limited total QPF of around a quarter inch. Tuesday and
Wednesday looking pleasant as midlevel ridge and Canadian surface
high settle over the Great Lakes. Will be slightly cooler but still
near/slightly above average for this time of year. Active southern
stream wavetrain continues into the end of the week but latest
models split on whether next upper low will lift into our region
(ECMWF and Canadian) or stay confined to the Tennessee Valley (GFS).
Will hold with concensus high chance PoPs for now given the time


.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 139 PM EDT Sat Mar 25 2017

Distinct warm front located near both taf sites with KFWA in the
warm sector and KSBN in the cooler air. Area of showers and
isolated storms have shifted north of both sites, which may allow
for a mainly dry afternoon. Hi res models still suggest
development of additional showers and storms late afternoon into
tonight as low pressure moves closer. VFR conditions have
dominated past few hours and present indications are (albeit low
confidence) that return to MVFR/IFR conditions may wait until
after 6Z. No mention of thunder has been added, but threat will be
there and may warrant at least a VCTS mention if indications of
development are apparent.





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