Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 121750

Area Forecast Discussion
National Weather Service Northern Indiana
1250 PM EST Sun Nov 12 2017

Issued at 1239 PM EST Sun Nov 12 2017

Precipitation types will be all rain this afternoon before
transitioning back to a light mix of rain and snow early tonight
ahead of ending. Dry conditions return late tonight into Tuesday
as high pressure settles over the area. Lows tonight will be in
the upper 20s and lower 30s. The rest of the week will be warmer,
with highs climbing into the upper 40s and lower 50s by Wednesday.
Additional rain showers will move through on Wednesday as a cold
front sweeps across the area.


Issued at 905 AM EST Sun Nov 12 2017

Update to increase pops/sky cover per observations/near term
higher resolution model solutions. In addition have targeted
mention of chance sleep, per observations/mping reports. Area of
best potential within elevated warm Tw layer, along/n of route 30
lifting northward through midday as it dwindles amid adiabatic


.SHORT TERM...(Today and Tonight)
Issued at 336 AM EST Sun Nov 12 2017

This morning will start out with a mixture of rain and snow as a low
pressure system crosses our area. As of 08z, a band of precip
associated with generally weak isentropic ascent on the 285K sfc
was lifting north-northeast across the forecast area. At the
moment, most observations have been rain, but expect that we`ll
start to see more of a rain/snow mix in the coming hours as temps
fall towards sunrise. This band will continue it`s northward
progression through the first portion of the day.

The trough at 500mb currently sits to our west, and it will sweep
eastward through late this evening. Best forcing per 850-500mb
qvector convergence will begin within the next hour and increase
through 7 pm before subsidence makes its way into the western
forecast area. At the surface, a low pressure system will drift
east-southeastward with this better forcing, creating yet another
region of precipitation along our southern border. As this
occurs, expect the northern band from this AM to diminish as
moisture transport shifts more to the east and focuses near the
low in our south. Have decreasing pops generally in the north,
and an increase to likely this afternoon in our far southeast.
Once we get into the daylight hours expect temps to rise enough to
have primarily rain for the precipitation type, with a transition
back to rain/snow mix tonight before it ends all together.

While a majority of the models have struggled with this initial area
of precipitation (too much dry air), the HRRR has been pretty
steady and accurate about the evolution of this morning`s
precipitation as it moves north and eastward. Based on this, I
used the HRRR through the immediate short term for precipitation
trends. The NAM comes in line with the HRRR later this morning,
keying in on the two focuses for precipitation in the north/south,
so I did blend a bit with the NAM as well for this

Kept high temps for today on the cooler side again, given
precipitation and thick cloud cover will rule the day. Highs will
climb into the 30s and maybe low 40s further south. Lows tonight
will range from the upper 20s far NE to the low 30s elsewhere.


.LONG TERM...(Monday through Saturday)
Issued at 336 AM EST Sun Nov 12 2017

Monday into Tuesday will be dry, with decreasing clouds expected
Monday as a ridge builds into our forecast area. High temperatures
will be more seasonable than the past few days, ranging from the mid
to upper 40s.

Tuesday night into Wednesday we`ll deal with the next low pressure
system to cross through the area. We`ll be in the warm sector, with
the surface low situated over Lake Superior, and the associated cold
front draped from Upper Michigan southwestward into Illinois, Iowa,
and Missouri. This will drift eastward through Thursday morning.
Both the ECMWF/GFS are now coming into better agreement as to the
timing/placement of the precipitation so have kept likely pops for
now. At this time, with temperatures climbing into the 40s and 50s
for highs on Wednesday-I kept precipitation type as all rain.

High pressure returns for Wednesday night-Thursday, bringing another
period of dry conditions. Highs on Thursday will be in the 40s, and
overnight lows in the low to mid 30s.

Friday into Friday night features yet another low, forecast to track
from roughly Missouri into northern Lake Huron. While the general
track and overall precipitation location is similar, the GFS is much
stronger-deepening the low to 970mb by Saturday morning. The ECWMF
is weaker, with only a 981 mb low at the same time (though it
eventually deepens the low to 975 mb by Saturday night over
Ontario). Kept higher end pops per collaboration with neighbors, but
there is still uncertainty with this system being this far out.
Currently, temperatures look to be in the 40s-50s so precipitation
will be mostly rain. If this pans out, we`ll have southerly gales
Friday becoming northwest on the Lake Michigan.

Saturday into Sunday I think we`ll have a decent chance for some
light lake effect rain/snow showers in northwest/west wind favored
regions, given 850mb temps down to -10 or -11, weak forcing from
the upper level low, and decent 0-1 km theta-e lapse rates.
However, it seems like moisture will be limited so just kept pops
at low-end chance to slight chance for now.


.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
Issued at 1239 PM EST Sun Nov 12 2017

Low pressure system pushes out of the area during the first half of
the overnight allowing scattered rain at SBN and possibly mixing
with a few flakes at FWA before it pushes out.

The other hazard for the TAF sites will be lowering flight
conditions entering this afternoon/evening as the lower portion of
the atmosphere moistens up and we get into the deformation
region. Conditions to the west of the region have a smattering of
IFR conditions mixed in with MVFR conditions. Therefore, would
expect a further decrease in conditions as we go into the
overnight hours with MVFR conditions likely and there may even be
a drop into IFR conditions especially at FWA by early morning
Monday as well.





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