Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 140520
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
120 AM EDT Sat Apr 14 2018

.SYNOPSIS...
Issued at 350 PM EDT Fri Apr 13 2018

Scattered showers and isolated thunderstorms are possible this
evening, but showers and embedded thunderstorms will become more
widespread overnight into Saturday morning. A brief lull in the
intensity of rain showers is expected Saturday afternoon before
showers and embedded thunderstorms increase in coverage again
Saturday night into Sunday. Locally heavy rainfall will be
possible from late tonight through Sunday morning with storm total
rainfall amounts of 2 to 3 inches. Colder air will work into the
area behind this system late in the weekend into early next week
with scattered rain and snow showers.

&&

.SHORT TERM...(This Evening through Saturday Night)
Issued at 350 PM EDT Fri Apr 13 2018

Heavy rain/flood potential will continue to be the main focus of the
short term period, with some river flooding issues into early
next week.

Surface boundary has slowly crept northward this afternoon with
sharp south to north temp gradient persisting across extreme
northern Indiana/southern Lower Michigan. South of this boundary,
fairly deep mixing has pushed winds to near advisory criteria at
times across northwest Indiana. With development of northeast flow
level flow north of this boundary, sharp late afternoon cooling
will continue downwind of Lake Michigan across northwest Indiana
where temps will drops into the upper 40s to mid 50s. An
additional boundary is expected to bring cooling this evening off
Lake Erie across portions of northwest Ohio.

A weak embedded short wave in southwest upper flow combined with
broad advective forcing has allowed for bands of showers and
embedded thunderstorms across central Illinois/west central
Indiana this afternoon. This forcing should lift across remainder
of northwest Indiana late afternoon-early evening with a period of
rain showers and perhaps an isolated thunderstorm with a pocket
of weak elevated instability.

Main period of concern will be late evening and especially into the
overnight as stronger low level jet develops and noses across the
southern Great Lakes region toward morning. Locally heavy
rainfall will be possible, especially in association with strong
moisture flux convergence via the low level jet. Potential of
heavy rainfall will continue into Saturday morning with the
1 to 2 inches of rain a possibility from late tonight through
Saturday morning.

Shorter term guidance trends continue to be slightly more suppressed
with primary amplified mid level wave across the Plains on
Saturday, and continued idea of cooler conditions for Saturday as
easterly flow deepens through the day. Sfc boundary will likely
become anchored across extreme south, or more likely just south of
local area Saturday afternoon with widespread rainfall during the
morning also aiding in a more suppressed sfc features. Have
continued idea of previous forecast in trending to cooler
afternoon temps given above trends.

Still some indications that a lull in heavier rainfall will set up
from Saturday afternoon into early evening, before large scale
upper support increases with approach of upper level trough axis,
and a larger scale frontal response. This second round of heavier
precip could bring another 0.5 to 1.5 inches of rain to the area,
with greatest rainfall amounts in this second round more likely
along and east of the I-69 corridor. With forecasted storm total
rainfall amounts of 2 to 3 inches expected and river flooding
likely to occur, have issued an ESF for river flooding along with
the possibility of some lowland/areal flooding. No areal
headlines will be issued with this shift and will have to see how
much rainfall occurs tonight into early Saturday to assess areal
flood concerns for 2nd half of this event Saturday night/Sunday.
Potential of isolated strong storms across the south still seems
on the low side Saturday given downward trend in sfc based
instability progs. However, may need to watch for some isolated
hail potential across the south.

One other item that may need to be watched in preference to more
suppressed sfc features is the potential of a brief window of
freezing rain potential Saturday night as extreme low level
inversion develops. Have limited mention to slight chance at this
time with low confidence in occurrence and impacts.

&&

.LONG TERM...(Sunday through Friday)
Issued at 350 PM EDT Fri Apr 13 2018

Frontal forcing will shift east of the area during the day Sunday
with an extended period of scattered rain/snow showers on cold
side of this system. With marginal thermal/moisture profiles, not
expecting this portion of the storm to have much impact despite
some lake enchancement. Little if any change made to remainder of
forecast with periodic chances of rain/snow showers as additional
eastern Pacific waves help reinforce mean low level baroclinic
zone south of the area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 120 AM EDT Sat Apr 14 2018

First wave of steady precip currently entering the area with
occasional thunderstorms at KSBN through the next 3-4 hours. KFWA
will be on the edge of this initial activity but expect a good
chance of thunderstorms in the 09-14Z period. Thunder chances end
by 13-16Z at both TAF sites and expect a lull in overall precip
as well with just a few periodic showers. However...ceiling
heights will deteriorate rapidly this morning with IFR likely at
both sites through much of the day. Second wave of steady precip
not expected until the very end of this TAF period and did not
include any mention yet.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory from 4 AM early this morning to 2 PM EDT
     this afternoon for LMZ043-046.

     Small Craft Advisory from 2 AM to 6 PM EDT Sunday for LMZ043-046.

     Gale Warning from 2 PM this afternoon to 2 AM EDT Sunday for
     LMZ043-046.

&&

$$

SYNOPSIS...Marsili
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...AGD


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