IWX issues Area Forecast Discussion (AFD) at Nov 9, 4:05 AM EST464
FXUS63 KIWX 090905
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
405 AM EST Sat Nov 9 2024
.KEY MESSAGES...
- Dry conditions continue today, but rain chances increase
tonight into early Sunday. Rainfall amounts tonight into
Sunday may exceed one half inch, especially along and east of
Interstate 69.
- Much above normal temperatures for Sunday, but then cooling to
near seasonable levels early this work week.
- Another chance of rain for next Wednesday.
&&
.DISCUSSION...
Issued at 400 AM EST Sat Nov 9 2024
Overall, very few changes are warranted this forecast cycle as
general theme of previous forecast remains intact. A broad low
level anticyclone across the Great Lakes this morning will shift
across the Mid Atlantic into the northeast CONUS this evening
allowing for onset of low level warm advection. Still a good
deal of dry air persists immediately upstream across the
Ohio/Tennessee Valleys, with more substantial low level moisture
transport not building into western Great Lakes region until
later this evening. Some elevated moisture return could allow
for a few sprinkles south of US 24 late this afternoon. Despite
onset of low level warm advection today, highs this afternoon
will likely be slightly cooler than yesterday due to more
limited mixing heights and increase in mid and high level
cloudiness this afternoon.
For tonight, the old, vertically stacked upper level low across
central CONUS will track across northern Iowa/southern Minnesota.
This will allow for more substantial deep layer moisture advection
with PWATs increasing to 1.25 to 1.50 inches which is near the
climatological max for the date. Gradual veering of low level flow
tonight into early Sunday should shunt the best moisture axis from
western TN into east central IN by late tonight. It still appears as
though strongest DPVA will bypass the area the to the north although
strong advective forcing, broad pre-frontal confluence, and approach
of an upper jet streak should support widespread rainfall with
greatest confidence along and east of I-69 corridor. Forecast cross
sections/vertical wind profiles do indicate some signals of
some support for both slantwise/upright convection. Thunder
potential still appears quite low, especially given northward
bypass of stronger upper forcing, but could see quite a non-
uniform rainfall distribution with a few narrow bands of greater
rainfall possible across the east(~0.5-1") given nature of
elevated instability, prefrontal confluence, low level moisture
convergence, and anomalous column moisture.
On Sunday, a mid level dry slot will punch across the southern Great
Lakes, with primary low level moisture axis shifting east of the
area into southern/eastern Ohio. Despite this dry slot, some modest
recovery in low-mid level moisture is possible across the southern
Great Lakes during the afternoon as the upper low tracks across
northern Lower Michigan. Any surface-based instability will
have a very limited depth and scattered showers during the
afternoon should add only minor amounts to storm total
accumulations. Large scale subsidence and drying column should
result in diminishing rain chances after 21Z Sunday. The other
weather story for Sunday will be potential for some stronger
afternoon wind gusts (~30-35 mph), particularly across western
half of the forecast area where the potential exists for some
deeper post-frontal mixing. Sunday will feature the warmest
conditions of this period with highs expected in low to middle
60s.
A transition back to a quieter weather pattern is anticipated for
Monday and Tuesday as flow quickly deamplifies in wake of Sunday
system. Medium range guidance has exhibited a few trends regarding
the midweek system, with overall tendency in deterministic runs
closer to the idea of GFS with a little less amplitude with next
Pacific wave. Will still remain somewhat conservative with
midweek PoPs for any one 12-hour period as timing uncertainty
still exists. The GFS is a fast outlier which is a typical bias,
but trend to perhaps a little less amplitude may support
earlier arrival of rain chances Wednesday afternoon.
Colder air will advect into the region behind this system for
Thursday and Friday, but consensus guidance among
deterministic/ensemble solutions is that this would be glancing shot
of colder air with temperatures near seasonable levels for late work
week/next weekend.
&&
.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 143 AM EST Sat Nov 9 2024
A large ridge of high pressure was northeast of the area and
was helping to keep a cool and dry northeast flow over northern
Indiana. An upper level system will track northwest of the area
and should spread showers across the terminals shortly after
06Z. For now, have kept showers out of the TAFs due to the large
amount of dry air below the cloud base.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Marsili
AVIATION...Skipper
Source:
IWX issues Area Forecast Discussion (AFD) at Nov 9, 4:05 AM EST---------------
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