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000
FXUS63 KIWX 101036
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
636 AM EDT Wed Apr 10 2024

.KEY MESSAGES...

- After a dry start, rain expands northward starting as early as
  around midday. Rain continues into Friday morning before
  clearing out Friday afternoon and evening.

- A Flood Watch is in effect from 8 PM EDT Wednesday until 8 AM
  EDT Friday. This is as rainfall accumulates 1.5 to 2.25 inches
  of rain with thunderstorms most possible Thursday potentially
  increasing totals. River flooding and areas of high water are
  looking likely by the end of the week.

- Saturday certainly looks like the drier of the weekend days,
  but Sunday looks warmer, achieving 70 degrees then.

- Rain and possibly thunder could make another return Monday
  night and Tuesday of next week.

&&

.DISCUSSION...
Issued at 328 AM EDT Wed Apr 10 2024

The baroclinic boundary that traversed across our forecast area
yesterday stalls out just south of a line from Portland, IN to Lima,
OH this morning, but will begin lifting northwest again as the
warm advection wing of a low in TX lifts northeastward along
the baroclinic boundary. RAP time sections indicate dry air at
the surface likely restricts precip until late morning/midday at
the earliest in the Portland, IN area. Will restart the
northward advance of PoPs around 17 or 18z. This just appears to
be non-convective rain with little instability to work with
Wednesday afternoon. Finally, the low pressure system pushes
northeast into the forecast area during the day Thursday with
the warm sector working into areas east of I-69. 500 to 1000
J/kg of MUCAPE advances north and east especially in areas along
and east of I-69 with 6 C/km mid level lapse rates. However, a
moist low level from sfc to 700 mb likely precludes wind or hail
threats. Shear is marginally conducive for a tornado threat,
but think that mostly stays to our southeast. This instability
likely contributes more to convectively enhanced heavy rain that
leads to flooding. With the ground remaining saturated from
recent rainfall indicating a more efficient runoff process and
river flooding only recently returning to action stage or less
over the course of the last half week or so, think river and
areal flooding will likely be an issue. Thinking 1.5 to 2.25
inches of rain likely falls across the area, especially from 00z
Thu evening to 00z Fri evening, but amounts could become higher
with the convective component. PWATs are expected to be 2 to 3
SDs above normal indicating the moisture content. The surface
low track will ultimately bring the most lift/forcing to the
area thus likely highlighting where the highest precipitation
falls as the upper trough takes a neutrally to slightly
negatively tilted orientation also helps to bring in more
moisture. A GEM/ECMWF/GFS/SREF camp takes the low pressure
center right overhead with the NAM being the main outlier south
of US-24 at this time. With this in mind, have added White
northward to Starke and Marshall counties to the flood watch
where saturated ground exists based on previous departure from
normal rainfall and rivers in action stage still exist.

Another hazard from this storm will be the gradient winds which look
to pick up between Thursday afternoon and Friday afternoon. 30 to 40
mph wind gusts will be common during the diurnally enhanced peak
windows (as opposed to at night). Mixing during this time frame is a
little bit less confident and this may provide a ceiling for how
high gusts could get. Highs in the 60s will be common during the day
Wednesday and in the warm sector (east of IN-15) on Thursday with
50s more common west of the warm sector. 50s will be common on
Friday within the cooling northwest flow.

The surface low pushes into the Northern Great Lakes later Thursday
night into Friday with northwest flow and embedded vort maxes likely
continuing light to moderate rain into midday Friday, especially
south of US-30. Mid level height rises take over Friday
afternoon and night from northwest to southeast ending the rain
and clearing clouds out during that time period. Temperatures
trend warmer as a result reaching back into the 60s on Saturday
and into the the 70s on Sunday.

Within split flow for Sunday, a weak low pressure system straddles
the border between Canada and the United States and this pushes a
warm front through the forecast area. There`s some question
about how moist the area is in the low levels, especially as it
pertains to any light precipitation from the warm front and its
weak forcing. Still think slight chance PoPs from the NBM is a
good place to start, but could see this balloon as some
instability could be around to make pop storms possible. Then, a
trough from the southwest CONUS carries a surface low for
between Monday evening and Tuesday. Another chance for
thunderstorms exists with a cold front in the vicinity then.
Highs in the 70s will be possible Monday and Tuesday.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 635 AM EDT Wed Apr 10 2024

Quiet aviation conditions to begin the period will become more
active later this afternoon, and especially tonight.

Mid level cloudiness has decayed across far northern Indiana
during the overnight hours, but this will be short-lived as mid
level theta-e gradient begins to lift back northward into this
afternoon. Lowering mid level cigs today will give way to MVFR
cigs, and eventually to potential IFR cigs late tonight into
Thursday morning. This northward moisture transport will be
aided by a fairly dynamic upper level system that will lift
across the Ohio Valley on Thursday. Sfc reflection of this
system is expected to track across northern Indiana in a
deepening state, with a healthy deformation-forced area of rain
affecting the terminals through early Thursday. Large scale
ascent via the left exit region of an upper jet streak will also
enhanced rain coverage by tonight. Some weak elevated
instability is possible tonight across far NE Indiana, but
signal appears weak enough to keep thunder out of the 12Z TAFs.
Backed winds to the east/northeast will begin to acquire some
gustiness toward the end of this forecast valid period as the
approaching low pressure area deepens.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Flood Watch from this evening through Friday morning for
     INZ006>009-012>015-017-018-020-022>027-032>034-116-216.
OH...Flood Watch from this evening through Friday morning for
     OHZ001-002-004-005-015-016-024-025.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Roller
AVIATION...Marsili