Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 100248

Area Forecast Discussion
National Weather Service Northern Indiana
948 PM EST Fri Dec 9 2016

Issued at 735 PM EST Fri Dec 9 2016

Lake effect snow showers will continue tonight, although
additional accumulations are expected to be less than an inch. Then,
low pressure will move northeast from the Southern Plains towards
the region Saturday night and Sunday, and possibly into Monday,
with snow. The snow is expected to change over to rain south of
Route 30 before ending. Significant snow accumulations are
possible Saturday night through Sunday night. Even colder air
comes in behind a cold front expected to move through around
midweek next week.


Issued at 934 PM EST Fri Dec 9 2016

Lake effect snow showers will continue through the remainder of
the overnight. Additional accumulations should be less than an
inch with fairly dry 850-700 mb profiles. Fetch will remain
favorable for continued lake effect snow showers overnight but
will be lessened in magnitude by slight backing of low level winds
toward Saturday morning. No major forecast changes will be made at
this time.


.SHORT TERM...(This Evening through Saturday)
Issued at 242 PM EST Fri Dec 9 2016

Dry entrainment along srn periphery of ongoing lake effect shsn
continues to mitigate significant additional snow accumulations.
Thus with aftn issuance will sandbag remain advisory counties.
That said expect light snow showers will continue for much of the
night across sw MI particularly through Berrien and Cass county
within short fetch wrly flow. Hwvr overall poor moisture
depth/shallow inversion will yield 1/2 inch or less additional.

Otherwise primary attention turns toward potent sw disturbance off
the WA coast this aftn coming onshore tonight. Rapid development of
downstream waa seen in all model guidance by late Sat aftn although
forcing/moisture advection overtop cold dome minimal initially and
does not ramp appreciably until daybreak Sun in response to ewd
translation of intensifying low level jet. Regardless accumulating
snow expected late Sat night.


.LONG TERM...(Saturday Night through Friday)
Issued at 242 PM EST Fri Dec 9 2016

Just enough spread in solution scope aloft...esp with thermal
profiles tied to general intensity differences among individual
model solutions to prevent an agreeable watch coordination this
aftn. That said... did bump pops much higher in consideration of
general agreeable consensus scope. While details still sketchy...
satellite depiction of upstream sw over the nepac ocean this aftn
gives a preferred nod toward stronger solutions aloft. This would
yield to a threat of mixed precip through srn areas by Sun
aftn/evening yet also point to a period of heavy snow potential
Sun morning through Sun aftn (north). In the least will issue a
Winter Storm Outlook this aftn to highlight the potential for
significant snowfall accumulations (6-10") late this weekend
especially US 30 north.

Thereafter perturbed nrn stream flow develops within stout north to
south baroclinic zone stretching from the central plains east
through the OH valley. Lots of signal noise/spread indicated mid
period (Tue) with potential sys streaking through the TN/OH valley
and again toward next Fri/Sat. Most consistent signal has been for
gradual swd suppression of bitterly cold arctic airmass bottled up
through nw Canada and blended temps at this range look like a good
start... some 20 to 25 degrees below normal for this time of year.


.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 735 PM EST Fri Dec 9 2016

Lake effect snow showers continue this evening, although becoming
progressively more cellular in nature. Intermittent IFR vsbys are
possible at KSBN over the next few hours but expecting most of the
IFR vsbys to remain northeast of KSBN. Light lake effect snow
showers may persist at KSBN through much of the night. Flurries
may also persist at KFWA over the next few hours but conditions
should remain primarily VFR. No other major concerns for this
aviation forecast period with low level warm advection eventually
ramping up later Saturday afternoon/Saturday evening. Warm
advection- forced snow should overspread terminals Saturday
evening, but not likely until after this forecast valid period.





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