Area Forecast Discussion
Issued by NWS Northern Indiana

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739
FXUS63 KIWX 151900
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
300 PM EDT Tue Aug 15 2017

.SYNOPSIS...
Issued at 253 PM EDT Tue Aug 15 2017

Isolated showers and storms will remain possible late this
afternoon along a weak cold front. Dry conditions are then
expected tonight into Wednesday, with patchy fog possible later
tonight. Lows tonight will drop into the 60s, with highs on
Wednesday into the low to mid 80s. A couple rounds of rain and
thunderstorms will be possible Wednesday night into Thursday as a
low pressure system tracks into the Great Lakes region. Drier and
cooler air then follows in wake of this system on Friday, with
renewed chances for rain on Saturday.

&&

.SHORT TERM...(This Evening through Wednesday)
Issued at 253 PM EDT Tue Aug 15 2017

Isolated showers/storms will remain possible across nrn IN/nw OH
into the late afternoon and early evening near a remnant cold
front/aggregate lake breeze. Coverage/chances/intensity will be
limited by dry mid levels and warm profile.

Dry conditions are expected tonight into most of Wednesday as
shortwave ridging amplifies in advance of an upper trough ejecting
east into the Central US. MOS and SREF probabilities are relatively
aggressive with fog/stratus development overnight given light winds,
mainly clear skies and lingering near surface moisture near diffuse
boundary (best chances across portions of ne IN/nw OH).
Coverage/impact of any fog is uncertain at this range, especially in
the north as some drier air settles in post-frontal.

A few showers/storms may pop up during the mid-late afternoon hours
tomorrow along/southwest of US 30 near an instability gradient.
Lacking flow/forcing should keep any convection below severe limits.
Temperatures tonight/Wednesday are expected to be similar to
today otherwise.

&&

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 253 PM EDT Tue Aug 15 2017

Good surge of moisture and elevated instability (PWATS nearing 2"
and sfc dewpoints up near 70F) Wednesday night into Thursday morning
will set the stage for increasing rain/thunder chances. This will
occur as ramping southwest flow (in advance of the above mentioned
upper trough) forces a warm front northeast into the region, with
the best chances for precipitation likely later Wednesday night
into early Thursday. System cold front and/or pre- frontal trough
then becomes the potential trigger for additional convection
during the afternoon and evening on Thursday. 30-35 knots of deep
layer shear and the potential for a moderately unstable boundary
layer in warm sector may present a conditional severe risk by
Thursday aftn/eve, though expected cloud contamination and poor
lapse rates thanks to warm/moist profile appear to be limiting
factors for severe wx at this time. As a result have no problem
with SPC`s marginal risk.

Dry/less humid air will lead to fair weather and cooler temps post-
frontal into Friday. The next shortwave in persistent wnw flow aloft
amplifies through the region on Saturday with the next chance for
showers/storms. Dynamics with this system appear decent for August
standards, however, moisture return is somewhat limited resulting in
low chance PoPs for now. Subsidence/height rises then allow high
pressure to build in for Sunday and Monday with fair wx.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 257 PM EDT Tue Aug 15 2017

Isold MVFR this afternoon along and to the southeast of DFI-FWA-MCX
line. Isold -SHRA / -TSRA will pop up along the trof axis with week
boundary layer convergence.

Clouds dissipate after sunset and with light winds...decoupling will
lead to radiative fog formation...especially south of DFI-FWA-MCX
line. IFR and isold LIFR possible...and have included BR at FWA
but left out at SBN.

VRF conditions during the early part of the TAF
Wednesday...however expect to see cu formation again as convective
temps are reached mid to late morning.

&&

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

$$

SYNOPSIS...Steinwedel
SHORT TERM...Steinwedel
LONG TERM...Steinwedel
AVIATION...Lewis


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