Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 270346

Area Forecast Discussion
National Weather Service Northern Indiana
1046 PM EST Sun Feb 26 2017

Issued at 730 PM EST Sun Feb 26 2017

A series of systems will impact the region starting Monday night,
each one bringing increasing temperatures, moisture and rain
chances. Isolated thunderstorms are also possible Tuesday night
into Wednesday morning. Highs by Tuesday are expected to reach
the upper 50s to lower 60s. Colder air will arrive by later
Wednesday into Thursday with chances for snow showers lingering
through the end of the week.


Issued at 730 PM EST Sun Feb 26 2017

Low amplitude wave across the Central Plains will track across the
Ohio Valley into early Monday morning. Slight positive nature of
this feature should somewhat limit northward progression of
downstream mid cloud deck, but did slightly nudge up cloud cover
across southeast third of the area as some enhanced mid level
moisture advects across these locations. Dry low level airmass has
allowed for rapid decoupling and lost of more substantial gusts,
and some concern a few locations could drop a bit colder than
forecast, particularly northwest half of the area that should be
more divorced from better mid level cloud cover. Secondary area of
more focused cloud cover through the remainder of the evening from
northwest Illinois to far northern Indiana is tied more toward
weak low level fgen forcing with weak northern stream wave
tracking across northern Great Lakes. Currently not expecting any
measurable precip with this feature with dry subcloud layers and
weak forcing however.


.SHORT TERM...(This Evening through Monday)
Issued at 222 PM EST Sun Feb 26 2017

Weak disturbance passing through with little more than some
increase clouds and locally gusty winds. Conditions should remain
dry with clearing skies/diminishing winds tonight. Highs will be
several more degrees warmer on Monday with highs in the middle 40s
to around 50. Clouds will increase in the SE with an area of light
rain passing just outside out area. Kept a mention of some
sprinkles at best in the far SE.


.LONG TERM...(Monday Night through Sunday)
Issued at 222 PM EST Sun Feb 26 2017

Warm front will surge north Monday night into Tuesday and bring
at least a chance of showers with it. Differences then begin after
this point with track of surface low and resultant
thermal/moisture profiles key to rain/storm chances into
Wednesday. Models agree on sharp trough digging into the region in
response to 120+ kt 300 mb jet streak with some indications of a
period of a coupled jet structure. This will cause rapid
cyclogenesis somewhere across the Great Lakes with track of
surface from anywhere from U.P. of Michigan to across our NW
areas. SWODY3 has the area in a marginal risk for severe Tuesday
night. While the chance exists, concerned that best moisture may
be cut off to the south along the Ohio River where convection may
be ongoing (and likely stronger). Have changed little from overall
forecast for now, leaving mention of thunder in Tuesday night and
adding on Wednesday in the SE.

Colder air will stream southeast behind the system and bring snow
showers chances back to the area. Exact evolution of lake effect
potential still up in the air with fast moving wave dropping SE in
the flow to bring a chance for snow to the area. Models still vary
on impacts from the system, but should bring at least some
enhancement to any lake effect precip that may be ongoing. Chances
diminish quickly into the weekend as flow becomes more zonal.


.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
Issued at 1045 PM EST Sun Feb 26 2017

A few very light rain showers or sprinkles across northeast
Illinois will continue to diminish over next few hours as weak
fgen forcing associated with northern stream trough passage
wanes. Low/mid level moisture advection will continue through
Monday morning in advance of next short wave approaching the
central Rockies with VFR cigs expected to overspread northeast
Indiana overnight into Monday. Precip associated with this wave
should remain south of the terminals on Monday with a weaker
southerly gradient persisting across the region.




LONG TERM...Fisher

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