Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 231006
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
606 AM EDT Fri Jun 23 2017

.SYNOPSIS...
Issued at 340 AM EDT Fri Jun 23 2017

Showers and thunderstorms will become more numerous early this
morning. A few of the storms may produce brief periods of heavy
rain and wind gusts over 30 mph. Showers and thunderstorms will
diminish from northwest to southeast later this morning into this
afternoon as a cold front tracks southeast across the region.
Drier and cooler conditions can be expected tonight through the
weekend behind the cold front. A few disturbances will bring a
potential of some isolated showers at times from Saturday through
Monday. High temperatures today will range from the mid 70s to
around 80. Low temperatures tonight will drop back into the upper
50s.

&&

.SHORT TERM...(Today and Tonight)
Issued at 340 AM EDT Fri Jun 23 2017

Forecast still appears to be on track for greater coverage
showers/storms this morning, just slightly delayed from previous
thinking.

Complicated flow pattern this morning with more active northern
stream short wave trough beginning to increase large scale lift
across the northern Great Lakes into southern Wisconsin. Additional
sheared short waves continue to emanate from remnants of tropical
depression Cindy across the mid MS Valley. Anomalous deep layer
moisture will be in place this morning with primary moisture axis
downstream of Cindy and better low level moisture pooling
associated with approaching cold frontal boundary from the Corn
Belt to the central Great Lakes. Frontal boundary should become
more progressive over the next several hours in response to the
progression of the northern stream short wave which will allow
showers and storms to overspread northern Indiana/southern Lower
Michigan in the 11Z-15Z timeframe. With large scale lift on the
increase, pre-frontal confluence zone should also become more
active through daybreak with additional showers/scattered storms
expected to fill in from east central Illinois into northwest
Ohio.

With PWATS in the 1.75 to 2+ inch range and warm cloud depths in
excess of 12K feet, will likely have to monitor for brief periods of
heavier rainfall and some localized flooding potential. Currently
not expecting significant hydro concerns at this time given quite
dry antecedent conditions and more progressive nature of forcing
mechanisms. It still appears as though axis of heaviest rainfall
will be displaced south/southeast of the local forecast area where
deeper moisture and more favorable low level confluence/moisture
convergence persist into the afternoon hours. Destablization still
looks to be rather limited today due to high coverage of
clouds/precip. Other limiting factors for strong/severe storms
include better shear profiles more post-frontal in nature and
gradual erosion of steeper mid level lapse rates this morning. Few
cells may produce wind gusts of 30 to 40 mph today, but currently
not expecting any appreciable severe threat. Otherwise, diurnal
swing in temps will be limited today by clouds/precip this morning
followed by onset of cold air advection this afternoon. This
should limit high temperatures to the 75 to 80 degree range today.

Few lingering showers possible across the extreme southeast early
this evening, but overall quiet weather expected tonight with
cooler/drier air advecting across the Great Lakes/Ohio Valley.

&&

.LONG TERM...(Saturday through Thursday)
Issued at 340 AM EDT Fri Jun 23 2017

Longwave pattern of western CONUS ridging and eastern CONUS
troughing will be maintained through much of the upcoming weekend.
Several short wave are expected to translate through upstream ridge
into the Great Lakes region this weekend into the first part of next
week. This will allow for an extended residence time of low level
thermal troughing across the region and much below normal
temperatures. The coolest days of the long term period are still
shaping up to be Sunday/Monday when highs may struggle to reach 70
across portions of the area. While moisture will be more limited
this weekend, forcing with the series of short waves and gradual
reinforcement of cold pool aloft argue for maintaining periodic
slight chance/low chance shower PoPs through Monday. The strongest
of these waves may affect the area Monday, where have maintained
the highest chance PoPs along with chance thunder mention.

Longwave pattern to break down Tue-Wed as series of Pacific waves
dampen the upper ridge, eventually allowing downstream moderation of
temperatures across central CONUS as this dampened upper ridge axis
shifts eastward. An active northern stream wave pattern for the
Wed-Fri period should result in renewed thunder chances with
episodic stronger theta-e advective/frontal forcing. Have followed
consensus blended solution for temps for Days 5-7 with highs back
around 80 by Wed-Thu, although potential does exist for an upward
adjustment in later forecast iterations, particularly by
Thursday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday Morning)
Issued at 605 AM EDT Fri Jun 23 2017

Series of weak waves associated with both a cold front and
remnants of Tropical Storm Cindi causing a slow expansion in
showers and thunderstorms. Main thunder focus has been setting up
SW to NE (Logansport to Fort Wayne). Will handle with tempo group
for an hour. Focus will then shift to line of showers and storms
dropping rapidly SE to bring a few hour period of impacts to both
sites. Opted for tempo now as actual impacts from thunder may only
last 30 to 60 minutes. Torrential rainfall and possible wind gusts
to 30 kts with the strongest cells. Conditions will slowly improve
through the day with a return to MVFR and eventually VFR this
afternoon and evening.


&&

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

$$

SYNOPSIS...Marsili
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...Fisher


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