Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 111744

Area Forecast Discussion
National Weather Service Northern Indiana
1244 PM EST Wed Jan 11 2017

Issued at 1228 M EST Wed Jan 11 2017

A low pressure system will move northeast across the Great Lakes
tonight and Thursday causing rain and isolated thunderstorms in
our area. Rain chances will begin to increase later this
afternoon, and especially by this evening. High pressure will
move into the Great Lakes behind this system providing dry
conditions with colder temperatures Friday. Another low pressure
system is expected to track through the Ohio Valley over the
weekend, possibly causing freezing rain, mainly along and south of
U.S. Route 24.


Issued at 1221 PM EST Wed Jan 11 2017

Warm/moist advection is now underway as low level winds have
backed more southwesterly. A couple of embedded short waves in
upper level westerlies will bring a couple of enhanced areas of
precip chances late this afternoon, one across south
central/southeast areas, and also across far northwest sections
of the area in closer proximity to stronger low level
baroclinicity. Previous forecast appears to have this trend well
in hand and only tweak of note for the afternoon update will be to
add a patchy fog mention across the south/west central areas at
leading edge of stronger moist advection.


.SHORT TERM...(Today and Thursday)
Issued at 307 AM EST Wed Jan 11 2017

Strong upstream jet streak rotating through base of potent cntrl
Canada sw trough will race ewd through James Bay by this evening.
Swwd trailing frontal zone and sfc frontal wave developing over
ern CO this morning will streak out newd in response. Thus
brief/shallow cold advection wing will rapidly modify as flow
backs quickly toward daybreak and ramps significantly higher late
this aftn and evening. Highres guidance quite bullish with
unstable low level theta-e burst ahead of sfc boundary this
evening and of which may promote a period of thunder potential
northwest half as ejecting sfc cyclone augments more
focused/deeper ascent plume although this signal remains fleeting
otherwise near term nod looks more showery this aftn. Progressive
sfc front will push through all but far se overnight with more
focused rainfall occurring with the frontal zone with blended pops
Thu morning looks inflated given vigorous post frontal drying
spreading in across the cwa.


.LONG TERM...(Friday through Tuesday)
Issued at 307 AM EST Wed Jan 11 2017

More erstwhile consensus has developed with handling of arctic ridge
dipping further down across the srn lakes Fri and swd suppression of
sfc frontal zone into the TN valley. Thus most favorable zone of
extended over running has shifted to just north of the OH river
through Sun aftn and with it the more significant icing
potential. However higher based zone of mid level frontogenesis
still heralds a potential trouble zone along and south of the
highway 24 corridor late Saturday into early Sunday and perhaps
again farther north Sunday night. Still significant spread exists
in handling and ewd projection of newd ejecting upper trough out
of the srn Rockies late weekend. Best course of action given the
noise is to follow blended approximations that capture ongoing
trends reasonably well.

Regardless strong consensus does exit with tracking deepening
cyclone well west again early next week. This allows broad warm
sector to spread well north again into the lakes with +15-20 degree
temp anomalies Mon-Tue.


.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1221 PM EST Wed Jan 11 2017

Highly anomalous moisture will advect northward across northern
Indiana later this afternoon into this evening. This axis of
stronger moisture advection will be accompanied by sharp
deterioration in aviation weather conditions this afternoon/early
evening. As of 1730Z, KFWA already beginning to experience leading
edge of IFR deck, which should lower to lower end IFR or LIFR
later this afternoon/early evening. A similar trend expected at
KSBN for mid to late afternoon, although cigs at these levels may
persist for a longer duration tonight at KSBN given low level
thermal ridge orientation. Some fog will also be concern
particularly late afternoon through the evening hours.

Scattered rain showers are expected later this afternoon, but
will become more widespread tonight as a pair of upstream
disturbance interact with strong baroclinic just off to the
northwest of the area. Some weak elevated instability too
overspread the terminals this evening which could yield isolated
thunder risk, but will continue to omit for now. Have also
maintained LLWS conditions at terminals this afternoon/evening as
another strong low level jet focuses across the area.


LM...Small Craft Advisory until 4 PM EST this afternoon for LMZ043-




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