IWX issues Area Forecast Discussion (AFD) at Sep 29, 2:50 PM EDT056
FXUS63 KIWX 291850
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
250 PM EDT Sun Sep 29 2024
.KEY MESSAGES...
- Rain continues to dissipate for all areas, including southeast
of US-24 into tonight. A slight chance for rain exists on
Monday for areas southeast US-24 again. Otherwise, we'll have
to wait for another slight chance for rain on Tuesday as a
cold front moves through.
- Hazardous swimming conditions are expected on Lake Michigan
beaches until this evening. There is a high swim risk and
beach hazards statement in effect for beaches in La Porte
County, IN. Those visiting the beach should plan to stay out
of the water. There is a moderate swim risk for beaches in
Berrien County, MI.
- Drier weather moves in for Wednesday and Thursday with
Wednesday being much cooler. Wednesday may just nick 70
degree highs by the end of the day.
&&
.DISCUSSION...
Issued at 246 PM EDT Sun Sep 29 2024
The upper low that absorbed the remnants of tropical cyclone
Helene continues to churn over the Tennessee River Valley today.
As we head into the work week, the trend will be fore this
system to weaken and become diffuse as a trough approaches from
the west and kicks it eastward, eventually allowing dry air back
into the area.
But for today, though, expect times of rain to continue, especially
south of US-24. The NAM especially, but there are also hints in the
other models, are keying into a thermal gradient/convergent area
sliding southwest in the flow that may provide a quick enhancement
to the rain this afternoon. Instability is still fairly weak (500
J/kg at most on the NAM compared to 100 J/kg or less on the ECMWF)
limiting thunderstorm intensity and coverage. Times of drizzle may
still be possible north of US-24 as shallow moisture pairs with
times of weak lift in the moisture column.
As the vorticity from the upper low shifts southeast between tonight
and Monday, expect coverage of rain to shift southeast, out of the
area. The aforementioned trough kicking the upper low eastward
ushers a cold front in here for Tuesday. Models have around 500 J/kg
of MUCAPE, but less than 30 kts of effective shear. As such, SPC has
bounded along and east of I-69 with general thunder in their severe
weather outlook. Given the early arrival of the cold front, think
this makes sense.
Cooler air comes into the area behind the front with single digit
850 mb temperatures. This means our near normal to slightly above
normal high temperatures, in the mid to upper 70s, will drop back
into the upper 60s to low 70s for highs on Wednesday. One thing that
may help highs to warm back into low 70s before the day is done is
the arrival of the low teens 850 mb temperatures in the evening,
especially with the decent mixing forecast for the day. Dry weather
takes over Wednesday and continues Thursday. A warm front moves in
Thursday signaling the continued rise in high temperatures.
This may also signal a return to rainy weather come as early
Thursday night, but probably waiting until Friday. There's still
some timing differences on bringing a cold front through the
area, which may come early Friday or during the evening. Then,
while Saturday looks dry, differing strengths of a forecast wave
to either dive south or continue through Canada provides a low
chance for showers on Sunday at this point.
&&
.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 132 PM EDT Sun Sep 29 2024
Flight conditions have been rather puzzling this morning with
KFWA the most favorable for MVFR/occasional IFR closer to the
upper low. Yet it is KSBN that has been socked in MVFR cigs the
past several hours while KFWA is VFR. Models seem to suggest
additional mixing through the afternoon that should hopefully
allow some improvement at KSBN so have trended that direction.
Moisture will be lingering around tonight as inversion sets back
up with signs pointing towards MVFR stratus redeveloping at KFWA,
with potential for a period of IFR cigs. Bit more questionable
at KSBN, especially given current cig challenges. Have went with
VFR for now at KSBN with later forecasts possibly needing to
introduce lower cigs.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement until 7 PM CDT this evening for INZ103.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Roller
AVIATION...Fisher
Source:
IWX issues Area Forecast Discussion (AFD) at Sep 29, 2:50 PM EDT---------------
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