Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 131136
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
636 AM EST Mon Nov 13 2017

.SYNOPSIS...
Issued at 409 AM EST Mon Nov 13 2017

Mostly cloudy skies will prevail today, with highs climbing into
the low 40s. Patchy fog and drizzle will gradually diminish this
morning. Expect decreasing cloud cover and patchy fog tonight
into Tuesday. Lows tonight will be around 30F. Highs Tuesday will
be in the mid to upper 40s.

&&

.SHORT TERM...(Today and Tonight)
Issued at 409 AM EST Mon Nov 13 2017

Expect any remaining drizzle and fog to gradually diminish through
the early morning hours as moisture dwindles and the upper level
ridge makes its way in. Cloud cover is the main concern for the
short term. With high pressure building in and fairly progressive
upstream clearing was originally planning to clear clouds out pretty
quick today, though I am hesitant to do so as we are well socked in
right now beneath the inversion. Some of the guidance shows the
inversion and thus cloud cover lingering through much of the day,
with the exception of the far western CWA. Have stuck with this
trend for now, given that this is usually the case this time of
year. We could see a bit of patchy fog overnight, particularly if we
clear out earlier than forecast. Kept high temperatures in the 40s
for now, but we may have difficulty reaching this if cloud cover
remains as thick and oppressive as it is now.

&&

.LONG TERM...(Tuesday through Sunday)
Issued at 436 AM EST Mon Nov 13 2017

A quiet start to the long term is expected, with partly cloudy skies
expected Tuesday with highs in the mid-upper 40s beneath an upper
level ridge. Meanwhile, a 500mb low pressure trough will drift
from west to east across the canadian prairie, reaching northern
Ontario by Tuesday evening. By Wednesday, this trough will dig
southward into northern Lake Huron before being forced to the New
England states Thursday evening by a building ridge. This will
bring a cold front through our forecast area Tuesday night and
Wednesday. As a result, kept going categorical pops given model
consistency for this period with respect to timing/location of
precipitation (in the form of rain). Left the previously forecast
slight chances for thunder given the steeper mid level lapse rates
during this time period. Highs on Wednesday will be in the upper
40s and low 50s.

Thursday into Thursday evening our forecast area will once again be
under the influence of an amplifying upper level ridge, keeping
conditions mild and dry. Highs will be in the 40s.

Friday into Saturday we deal with the next low pressure system to
impact our region. Models are still in disagreement as to the exact
location of the low pressure system, and the strength/placement of
mid and upper level features. That being said, they are all
outputting precipitation in the region from Friday into Saturday, so
per collaboration with neighbors left the consensus higher end pops.
The GFS is slightly more progressive and lifts the rapidly deepening
surface low from Iowa/Illinois Friday afternoon into northern Lake
Huron by Friday night, which allows for substantial moisture
advection across the CWA starting Friday AM and continuing into
Friday evening before the trailing cold front drifts in Saturday. It
also has a fairly well developed dry slot that will greatly drop
precip. chances for Saturday evening and Sunday, and brings 850mb
temps of up to -14C in for the Sunday-Monday time frame. This
solution will give us some lake effect rain/snow potential for next
weekend (W-NW Wind favored regions) and have maintained lower end
pops to deal with this possibility for now. The ECMWF starts things
a bit later than the GFS (by about 6-12 hours), and is slightly
warmer with 850mb temps(down to -12C). Thus it seems like the models
are consistent in the general progression/development of the system
but just mismatched in timing and strength of forcing.

Either way, it seems we`ll have a longer duration gale event on Lake
Michigan, starting out of the south on Friday and trending W-NW for
Saturday-Sunday, gusting to over 40 knots Saturday evening. Will
need to monitor this closely in upcoming forecasts.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
Issued at 635 AM EST Mon Nov 13 2017

IFR and LIFR cigs persist at terminals early this morning,
although highly fluctuating cigs between LIFR and VFR are
expected early this morning. Low level upward vertical motion
downwind of Lake Michigan combined with shallow moisture profiles
in wake of last night`s short wave allowed for expansive drizzle
formation, although radar trends/obs suggesting drizzle potential
should be on quick downward trend next few hours. This should also
support the end of LIFR cigs early this morning. A rather stagnant
pattern is in store for today with weak low level flow. This weak
flow combined with low level inversion should keep low clouds in
place for most of the day, although likely improving to higher end
MVFR through the late morning/afternoon. A better chance of low
cloud scattering tonight with some high clouds overspreading the
area. Some patchy fog may develop again tonight, but confidence in
extent is low at this time and will limit mention to MVFR vsbys
late in the period at KSBN.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...MCD
SHORT TERM...MCD
LONG TERM...MCD
AVIATION...Marsili


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