114
FXUS63 KIWX 092358
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
758 PM EDT Thu May 9 2024

.KEY MESSAGES...

-Rain chances continue into tonight before sliding south and
 east.

-A quick moving system provides another chance for rain later
 tonight into Saturday morning

-Yet another chance for rain slowly slides southeast Monday
 night and Tuesday. Some thunder is possible Monday afternoon.

&&

.DISCUSSION...
Issued at 257 PM EDT Thu May 9 2024

A trough continues swinging southeastward through the Great Lakes
and Ohio Valley areas today and this pushes a surface low pressure
system eastward towards the Mid Atlantic States today. Large scale
ascent begins to wane this afternoon and dry air advection gets
under way in the low levels as the main moisture plume shifts
southeastward as well. As such, we`ll see a reduction in rain
chances into tonight, especially after a final vort max swings
through after 00z and northern stream flow gets underway. Friday is
expected to be dry, but with cloudy skies in the morning scattering
out by the afternoon. Height rises ensue especially midday Friday
with noticeable mid level ridging moving through. As mixing
commences Friday morning, could see some gusty winds to start,
achieving 15 to 20 mph, before the gradient begins to relax for the
midday and afternoon hours. Temperatures will be slightly warmer
with the increased mixing and diminished rain, allowing for low to
mid 60s for highs.

Those aformentioned mid level height rises become height falls again
Friday night as another trough moves into the area with a potent
vort max embedded within it. An thin area of large scale ascent
associated with the surface low pressure and its attendant frontal
system provides ample forcing for this event. However, the wave is
fairly quick-moving and the moisture plume is rather thin, which
will help to restrict total precipitation output to a quarter inch
or less before it departs. Mid level height rises ensue midday
Saturday and subsidence occurs during the morning hours allowing a
transition back to drier weather through the morning. As such, cloud
cover decreases through the afternoon Saturday. Expect similar to
slightly warmer high temperatures to Friday with low to mid 60s.
Additionally, a lingering tight gradient allows for gusts between 20
and 30 mph Saturday.

Mid level height rises and ridging provide a drier day Sunday as
surface high pressure edges into the area. This is the pick of the
weekend with plenty of sunshine expected along with some high
clouds. Warm advection ensues during the daytime Sunday allowing
high temperatures to rise back into the 70s.

Monday is expected to be affected by a moisture stream in from the
south with a Gulf of Mexico connection. With forcing far enough away
from the area, am a little hard pressed to have PoPs associated with
it Sunday night into Monday morning, especially given the relatively
dry atmospheric column in that area. However, instability does
appear to build to between 900 and 1200 J/kg on the ECMWF so perhaps
a stray shower/storm could be around during the afternoon/evening.
During this time, a boundary slows down just into MI as an upper
level low pressure system passes by to our south. On Tuesday, a
surface low pressure system develops through the Ohio River/
Tennessee River valley area and there`s a disjointed setup similar
to a TROWAL as this occurs. However, the placement of the upper low
to our south is in question to some extent with the ECMWF out on a
limb with it farther south, but also a little bit odd in that it
could siphon all of the moisture away from its northern
periphery as long as surface convergence doesn`t further enhance
that northern periphery. There is still time for this get
smoothed out over the coming days. This timing and placement of
the energy for the Tuesday system affects what happens later
Wednesday and Thursday with the GFS currently out on its own
with rain on Thursday. The NBM will be allowed to handle this
period for now given the disagreement in modeling.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 751 PM EDT Thu May 9 2024

An upper level trough extending from southeast Ontario into west
central Illinois will continue to sag southeast this evening.
Low level winds will back to the north as this occurs allowing
for the influx of some drier low level air from the north. A
fairly strong low/mid level front will allow for band of light
rain showers to affect terminals through the early overnight.
Some MVFR cigs will accompany this progression, eventually
transitioning to VFR late tonight as the drier air shifts to the
south. Mid level trough dropping across the Great Lakes should
allow for some diurnal cu to form Friday, but bases with this cu
field will be VFR. Lingering gusty northeast at KFWA to begin
this forecast valid period will sharply drop off as low level
front continues shifting south. Northwest winds around 10 knots
will continue on Friday.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Roller
AVIATION...Marsili