489
FXUS63 KIWX 270019
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
819 PM EDT Thu Sep 26 2024

.KEY MESSAGES...

* Windy conditions are expected Friday into Friday evening,
  especially south of US 30 in Indiana where northeast winds may
  gusts in excess of 45 mph Friday afternoon into Friday evening.

* Showers overspread the area from southeast to northwest Friday
  afternoon into Friday evening.

* Chances for scattered rain showers linger through this weekend.

&&

.DISCUSSION...
Issued at 228 PM EDT Thu Sep 26 2024

An upper low over the western TN Valley, and Hurricane Helene over
the eastern Gulf of Mexico, will be the features of interest later
tonight through this weekend. The center of Helene is still on
target to continue northward, making landfall near the big bend area
of Florida this evening, reaching the southern Appalachians by 12z
Friday. The Fujiwara interaction with the western TN upper low then
takes over Friday into Friday night with Helene`s low center
retrograding north-northwest to near or just south of Evansville
IN by 00z Sat.

The quick movement of Helene`s remnants, and eventual merging with
the aformentioned upper low will allow for a slower weakening trend
than normally observed with tropical remnants reaching the TN
and/or lower OH Valleys. NAEFS return intervals for MSLP outside
of the CFSR climate database, with ensemble guidance in good
agreement in a low center nearly 6 standard deviations below
average lend increased ensemble support for this anomalous
synoptic evolution.

The impacts locally will be increasing east-northeast winds
late tonight into Friday on its northern fringe thanks to a
tightening low level height gradient (925 mb winds peaking 45-55
knots Friday afternoon-evening). HREF/NBM probabilistic data
suggests high confidence in gusts in the 35-45 mph range during
this time, with a 12z HREF increase to 50-60 percent probs for
headline level gusts (45 mph plus) in the south. Low level
lapse rates and mixing depths look limited and may keep the bulk
of gusts below 45 mph, though the stronger solutions and
unusual setup mentioned above are worth mentioning for what
could be a least a brief period of advisory level gusts, best
chances south of US 30 in Indiana Friday afternoon and early
evening on the leading edge of rain. Per collaboration, did opt
for a Wind Advisory mid Friday afternoon through Friday evening
in our southwest. Have gusts mainly in the 30-45 mph range
elsewhere with some northward expansion potentially needed.

A narrowing band of rain should also accompany the system warm
conveyor and associated plume of deeper moisture/isentropic upglide.
Guidance remained in general agreement in this precip shield lifting
into areas along/south of US 24 Friday afternoon, then narrowing and
slowly drying up with its pivot into our north-northwest zones
Friday night. No hydro concerns are anticipated.

Big closed low after the full merger does fill and attempt to wobble
slowly east in the vicinity of the Ohio River Valley this weekend
into early next week. This will keep clouds and chances for showers
in the forecast, though winds will diminish and temperatures will be
pleasant. Mainly quiet/dry otherwise next week with temp
fluctuations as a more active high-lat northern stream drops a cold
front through around mid week, and possibly another just beyond this
forecast period.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 810 PM EDT Thu Sep 26 2024

No significant changes were made to the 00Z TAFs with continued
focus on deteriorating conditions in terms of winds during the
day Friday, and toward the end of this forecast valid period
with precip/cigs. Mid level moisture will continue to stream
northwestward from the Mid Atlantic tonight as remnants of
tropical system eventually get ingested into the Ohio River
Valley Friday night. Low level easterlies will keep best low
level moisture locked up south of the terminals through early
Friday afternoon. By late Friday afternoon/Friday evening, warm
frontal type feature and associated low level moisture
convergence will help spread better chance of rain showers into
northeast Indiana. Strong low pressure with the tropical
remnants and broad weak background anticyclone across northern
tier of CONUS will provide quite a strong low level height
gradient for northern Indiana and gusty/strong wind potential.
Strongest winds are expected to affect KFWA with some mid
afternoon/early Friday evening easterly gusts to around 40
knots possible. VFR conditions are expected to persist through
most of this period, with better chance of MVFR working into
KFWA late this valid period. May also need to eventually
consider LLWS conditions for a brief time Friday evening as some
diurnal weakening of low level lapse rates and strong low level
winds could meet criteria (particularly at KFWA).

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Wind Advisory from 2 PM to 11 PM EDT Friday for INZ013-015-020-
     022>026-032>034.
     Beach Hazards Statement from Friday afternoon through late
     Friday night for INZ103.
OH...None.
MI...Beach Hazards Statement from Friday afternoon through late
     Friday night for MIZ177-277.
MARINE...Small Craft Advisory from 8 AM Friday to 8 AM EDT Saturday for
     LMZ043-046.

&&

$$

DISCUSSION...Steinwedel
AVIATION...Marsili