IWX issues Area Forecast Discussion (AFD) at Sep 26, 2:28 PM EDT937
FXUS63 KIWX 261828
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
228 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 /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 124 PM EDT Thu Sep 26 2024
An upper low to our south will usher the energy of tropical cyclone
Helene up to the area fairly quickly between today and Friday. As
its ingredients move up here, expect an increase in cloud cover, but
expect it to stay above VFR through this taf period. The area of
rain may approach FWA early tomorrow morning, but the expectation is
that it remains a county or two south of it until the afternoon,
which is just after this taf period. Winds will be the bigger hazard
as they will be able to gust to above 20 kts at both sites as early
as around 12z Friday. FWA may be able to see 35-40 kts gusts during
the afternoon and evening period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Wind Advisory from 2 PM to 11 PM EDT Friday for INZ013-015-020-
022>026-032>034.
OH...None.
MI...None.
MARINE...Small Craft Advisory from 8 AM Friday to 8 AM EDT Saturday for
LMZ043-046.
&&
$$
DISCUSSION...Steinwedel
AVIATION...Roller
Source:
IWX issues Area Forecast Discussion (AFD) at Sep 26, 2:28 PM EDT---------------
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