Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 201656

Area Forecast Discussion
National Weather Service Northern Indiana
1156 AM EST Fri Jan 20 2017

Issued at 1152 AM EST Fri Jan 20 2017

Overcast skies accompanied with some patchy fog and drizzle will
remain this afternoon and temperatures will be in the mid 40s to
lower 50s. Chance for light rain returns tonight along with areas
of fog by Saturday morning. Unseasonably mild temperatures are
expected over the weekend with highs in the 50s and lows in the


.SHORT TERM...(Today and Tonight)
Issued at 336 AM EST Fri Jan 20 2017

Widespread rain associated with potent shortwave energy and
abundant low level theta-e advection will shift northward and
dissipate by later this morning. Very good agreement among latest
numerical guidance that rain will end by mid-late morning as brief
period of AVA/shortwave ridging and abruptly veering low-midlevel
flow yield a decisive loss of deep-layer moisture and ascent. Sped
up the end time of precip chances with latest hi-res/rapid refresh
indicating precip entirely gone by 15Z. There will be a fair
amount of moisture trapped below 850mb inversion but saturation
depth and quality appear marginal for drizzle production. More
likely scenario is just an impermeable stratus deck with some
pockets of 3-7 mile BR and have left out any daytime drizzle
mention for now. That does change by tonight though as approach of
next shortwave currently exiting the Southern Rockies brings a
renewed surge of 295K isentropic lift and theta-e advection.
Lingering dry air aloft and overall lackluster forcing for ascent
will prevent any meaningful or widespread rain but worthy of low
chance PoPs. Areas of fog also likely given warm/moist air
advection and relatively cool ground. Widespread/dense fog a
possibility by early Sat morning based on latest MOS guidance and
underlying forecast soundings/RH fields. Mild conditions will
persist today, although did lower the diurnal range a bit with
abundant low clouds remaining in place. Highs today likely to
remain stuck in the mid/upper 40s, save for our far SE where some
lower 50s possible. Very little drop expected overnight given
warm/moist air advection and abundant clouds/fog.


.LONG TERM...(Saturday through Thursday)
Issued at 336 AM EST Fri Jan 20 2017

Main story for the weekend will be unseasonably (and near record)
mild temps. Deep SW flow engulfs the Ohio Valley during the day
Saturday with 925mb temps around 10C (record territory based on KDTX
upper air climatology). Mixing will obviously be quite limited given
low sun angle, overcast skies, and strong inversion but degree of
mild air flooding the region should still support highs in the mid-
upper 50s on Saturday. Not likely to see much sun but even a few
peaks could allow a run at 60F. Slightly cooler on Sun as thermal
trough is shunted eastward but still unseasonably mild with
concensus blends offering low/mid 50s. Overnight lows
correspondingly mild with mid/upper 40s Sat night and around 40F
Sunday night. Unfortunately, several low chances for rain during
this period as well given pockets of weak isentropic ascent and
abundant low level moisture. Best chance will be Sat night as models
show weak shortwave ejecting north. However, as previously stated,
main closed low and jet energy remains well to our south, along with
better precip chances.

Slight chance for a few showers on Monday with some wraparound
moisture from passing cutoff low to our south. Otherwise, just
slightly cooler through the early part of next week. Longwave trough
over western CONUS then begins piecemeal ejection during the middle
of next week. Main vort max will pass through the Great Lakes on
Wed. Chance for some light rain with this feature but more important
will be the change of airmass behind it. N/NW flow develops later
next week and gradually increasing CAA will bring a return to more
seasonable conditions. Light rain and snow showers possible through
much of this period as well given persistent moist, cyclonic flow
and increasing lake contribution. Looking even further ahead, models
still hinting at even colder air returning by next weekend/end of
the month.


.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1152 AM EST Fri Jan 20 2017

IFR and LIFR flight conditions will persist for the next 24
hours. Drizzle and fog is expected to keep visibility and ceilings
low this afternoon. Guidance is suggesting fog to develop
overnight that may further reduce visibility early Sat morning but
confidence in timing and duration is low at this time, hence kept
out of forecast.





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