Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 191033
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
633 AM EDT Thu Oct 19 2017

.SYNOPSIS...
Issued at 159 AM EDT Thu Oct 19 2017

Mostly sunny skies will give way to high temperatures in the upper
60`s and low 70`s today. Lows tonight will be in the mid to upper
40`s. Quiet weather will continue through Saturday, with
temperatures warming to well above normal. Highs through the rest
of the week will range from the upper 60`s to the mid to upper
70`s.

&&

.SHORT TERM...(Today and Tonight)
Issued at 159 AM EDT Thu Oct 19 2017

A colossal upper level ridge will expand expeditiously over the
forecast area later today into Friday as the vertically stacked low
pressure system over Hudson Bay drifts eastward. A weak cold front
that was sprawled across Upper Michigan, WI, IA, and into the plains
last night will progress southward today and across our north
central CWA-but gradually wash out. This will ensure a lack of
precipitation through the short term, and the first portion of the
long term.

Things are heating up temperature wise on Friday. Highs today will
be in the upper 60`s and low to mid 70`s. Friday we`ll see highs in
the 70`s, with the southwest portions of our CWA seeing highs into
the upper 70`s. Most areas will see temperatures about 5-15 degrees
above normal for the end of October.

&&

.LONG TERM...(Friday through Wednesday)
Issued at 159 AM EDT Thu Oct 19 2017

High pressure will linger over our CWA through Saturday, where we
will mainly see a slow increase in cloud cover as the next system
approaches the area. Highs will be in the low to mid 70`s, and
lows Saturday night will drop into the mid-upper 50`s.

Our stellar spell of warmer, dry weather will come to an end
Sunday morning as the first of two cold fronts swing through the
area. Models are still a little in disagreement with regards to
the exact timing with the first front, but confidence in the
general pattern is higher than it has been previously. Decent
upper level divergence takes place in our far northwestern CWA
thanks to the right entrance region of a 300MB Jet, and a mid
level shortwave swings through along the western periphery of our
eastward drifting ridge. The best lift, per 850-500mb Qvector
convergence is focused north of US 30 (and actually better aligned
over Lower Michigan), but PWATS climb to nearly 1.6 inches as
return flow around the high to our southeast assists with moisture
transport from the gulf. That being said, we should still see
precipitation chances along the entirety of the surface cold front
as it moves through our area from west to east. High temperatures
on Saturday will be a little cooler due to precip and cloud
cover-mainly in the 60`s west, and the low 70`s across the central
and east.

After the first frontal boundary moves through Monday morning, may
see a brief break in the precipitation for the afternoon before the
next system arrives (depending on whether the ECMWF is correct or
the GFS). Unfortunately, this is where the disagreement between
models leads to much lower confidence. Both the 12Z ECMWF/00Z GFS
develop a cut off low near the gulf, and develop a separate trough
to the west of our area. However, the ECMWF has precipitation
developing over our area Monday afternoon with the surface low
pressure as it lifts northeastward and merges with our first front.
The GFS has this occurring slightly east from the ECMWF, placing
most of the precipitation outside of our CWA. So Monday is still a
bit uncertain, as is Tuesday into Wednesday in terms of exact
precipitation locations-but it appears both models form a decent
upper level low that lingers over the Great Lakes region through
Wednesday night. Behind the secondary push of cold air Monday, we`ll
see 850 mb temps fall just below zero. With sufficient instability
off the lake, kept the higher pops near Lake Michigan as models hint
at a few bands of lake effect rain showers developing. Given the
projected pattern, feel this is a likely scenario. Highs towards the
end of the week will only be in the low to mid 50`s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
Issued at 626 AM EDT Thu Oct 19 2017

VFR conditions through the period with winds 10 knots or less,
becoming calm tonight.

&&

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

$$

SYNOPSIS...MCD
SHORT TERM...MCD
LONG TERM...MCD
AVIATION...Fisher


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