Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 221717

Area Forecast Discussion
National Weather Service Northern Indiana
1217 PM EST Sun Jan 22 2017

Issued at 1208 PM EST Sun Jan 22 2017

Areas of fog, dense in spots, are likely through the through early
afternoon in portions of NW Indiana. Afternoon highs today will
generally be in the 50s south of US 30 and cooler north due to
persistent fog. A weather system will bring a good chance for
rain later tonight into Monday. Then a trend towards colder, more
seasonable conditions, is expected through the rest of the week.


.SHORT TERM...(Today)
Issued at 314 AM EST Sun Jan 22 2017

Weak/subtle embedded shortwave currently rippling through the area
and responsible for lighting up area of convection along baroclinic
zone draped over our SE CWA. This activity will gradually diminish
through the early morning as shortwave trough lifts rapidly NE and
is replaced by weak ridging and AVA/subsidence downstream of notable
Tennessee Valley trough seen in morning water vapor. Visibilities
along and south of this boundary remain high. Will have to watch for
possible expansion of fog as rain tapers off later this morning but
latest HRRR keeps fog in check with frontal boundary making almost
no eastward progress as it is divorced from parent wave and aligned
parallel to mean flow. Will hold with current advisory delineation
for now but will watch for possible expansion later this morning.
15Z expiration also may be cutting it a bit close and could see
dense fog persisting for an hour or two later given light wind and
low sun angle but will not make any adjustments to end time right

Other concern for today will be precip chances once current showers
dissipate. Bulk of the latest guidance indicates a primarily dry day
with potent closed low and associated jet energy digging far enough
south to prevent most if not all precip in our area. Best CVA and
deformation certainly remain well to our south. Will see steadily
increasing moisture as easterly flow ramps up late in the day and
some subtle convergence may be able to touch off a few light showers
along remnant boundary in our S/SE but bulk of the daytime does
appear dry thanks to aformentioned downstream ridge building/AVA.
Made some drastic cuts to inherited PoPs and further cuts may be
necessary. Highs today will still be above normal but nowhere near
yesterday`s values with cooler profiles and much more cloud cover.
Large gradient expected with near 60F in the SE and upper 40s near
the lake.


.LONG TERM...(Tonight through Saturday)
Issued at 314 AM EST Sun Jan 22 2017

Precip chances a little better by tonight and into Monday,
especially in our eastern counties, as closed low begins to lift NE
with Atlantic moisture pouring inland and vorticity spoke making a
run at our area. Still some question exactly how far W/NW this
activity will push but most deterministic guidance members agree it
will reach at least the I-69 corridor by Monday. Tempered tonight`s
PoP forecast a bit based on slower arrival but still expect areas of
rain in our eastern half by Monday morning and preserved likely
PoP`s there. Rain amounts will not be particularly heavy (a few
tenths east of I-69) but this may slow the fall of river levels.
Increasing gradient will likely prevent any widespread/dense fog
concerns for Monday morning but some patchy fog not outside the
realm of possibility. Temps take another step down on Mon as N/NE
flow advects cooler air into our CWA.

Dry conditions anticipated on Tue but next elongated/positively
tilted wave will arrive on Wed with healthy left exit jet (150+ kts)
dynamics. Will have to keep an eye on exact surface low track as
latest NAM and Canadian solutions could introduce a chance for some
snow in our Michigan counties with healthy deformation/fgen band
during the day but thermal profiles are very marginal and GFS and
ECMWF remain further north. Left precip types all liquid during the
day for now. Colder air will filter south Wed night though and could
be some light snow accums. Steady CAA will bring temps back to near
normal by the end of the week and perturbed NW, cyclonic flow will
bring periodic chances for light snow showers, enhanced by Lake MI
as colder temps filter south. Any snow accums will be very light and
difficult to pinpoint timing of best chances this far out. Could be
an extended period of just SCT flurries/light snow showers Thu-Sun.


.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
Issued at 1208 PM EST Sun Jan 22 2017

Widespread fog will remain in place over northeast portions of
Indiana for the rest of the afternoon. As a result LIFR conditions
at KSBN with visibility below 1 SM expected until 00z and
remaining IFR for the remainder of the forecast period. At KFWA
areas of fog will remain north of the terminal for the beginning of
the forecast period. But it will progress southward around 00z and
associated with light rain will decrease flight conditions to MVFR
and trend to IFR by 02z and likely remain IFR until the end of the
forecast period.


IN...Dense Fog Advisory until 4 PM EST /3 PM CST/ this afternoon for

MI...Dense Fog Advisory until 4 PM EST this afternoon for MIZ077>080.




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