IND issues Area Forecast Discussion (AFD) at Aug 18, 10:02 AM EDT157
FXUS63 KIND 181402
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
1002 AM EDT Sun Aug 18 2024
.KEY MESSAGES...
- Showers and thunderstorms possible again this afternoon and
evening, mainly along and north of I-74
- Wind gusts of up to around 25 mph are expected this afternoon
-Dry and cooler than normal through mid week with highs in the 70s
and lows generally in the 50s
&&
.FORECAST UPDATE...
Issued at 1002 AM EDT Sun Aug 18 2024
Minor changes to today's forecast to account for ongoing radar
trends with slower onset of shower and storm chances as we await
what modest destabilization may occur today under the slowly
breaking low cloud, and an approaching secondary trough pivoting
around the larger low over the Great Lakes.
Shear and instability are minimal to non-existent this morning,
though some destabilization should occur and allow for some
scattered showers and a few rumbles of thunder this afternoon
underneath the cold pool of the upper low, though lapse rates are not
impressive and CAPE profiles should be thin. No severe threat is
anticipated, with only lightning and brief heavy downpours of any
concern.
&&
.SHORT TERM (Today and tonight)...
Issued at 313 AM EDT Sun Aug 18 2024
A low pressure system moving over the Great Lakes will exit to the
east through the day, leaving behind cooler temperatures and
backside moisture over central Indiana. This morning will see an
increase in low cloud ceilings and some fog form, mainly across
the north.
A weak boundary off of the exiting low still remains over central
Indiana, which should have a least a few showers and thunderstorms
form along later today. These will likely reform by late morning to
midday and last into the overnight hours. The best chance will be
across the northeast half of the forecast area, along and north of I-
74, but can't rule out showers creeping SW this evening. Also expect
some breezy winds this afternoon due to tighter pressure gradients
aloft mixing down. NW winds are forecasted to be sustained around 10-
15 mph with gusts of 20-25 mph.
Given the NW winds, temperatures will be cooler today with highs
near 80 and lows tonight reaching the low 60s.
&&
.LONG TERM (Monday through Saturday)...
Issued at 313 AM EDT Sun Aug 18 2024
Upper troughing continues over the eastern U.S. with a large upper
ridge over the central U.S. This puts central Indiana in line for
northwesterly cooler and drier airflow with Canadian surface high
pressure sinking southeast into the Great Lakes and Ohio Valley.
ECMWF EFI shows cooler than normal temperatures Tues and Wednesday
and into the Wednesday night/early Thursday morning lows, and this
goes along well with the GEFS ensemble members 850 mb temperature
pattern.
Ensembles show the overall pattern changing around Thursday
to Friday with the upper ridge buckling eastward and collapsing into
a more zonal flow pattern and placing a very broad upper ridge in
place over much of the eastern two thirds of the country by next
weekend. Seeing some indication in LREF and NBM probs of potential
for rain chances sometime next weekend which fits with a more zonal
pattern and potential for little ripples of shortwaves moving
through the main flow pattern, but probabilities are still pretty
low (lower than climatology) and thus not enough of a signal to
deviate from NBM which should smooth out these shortwaves overall
resulting in a dry forecast. The broad ridging should lead to
warming temperatures for the end of the week and warmer than normal
temperatures next weekend.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 658 AM EDT Sun Aug 18 2024
Impacts:
- MVFR/IFR ceilings through midday to early afternoon
- Winds gusts return Sunday afternoon
- Isolated showers Sunday afternoon
Discussion:
There should continue to be a gradual increase in MVFR/IFR cloud
ceiling coverage through the morning that are expected to last
through midday to early afternoon. Patchy fog will also be possible
this morning but limited to areas that lack clouds. Dense fog is not
expected, however. Ceilings will increase through the morning and a
return to VFR conditions is expected by mid afternoon. Mixing and
momentum transfer by afternoon will result in wind gusts up to 20-25
knots again. Isolated to scattered showers will return by midday to
mid afternoon with LAF and IND seeing the best chances to see these
showers. A few thunderstorms could form this afternoon but
confidence is low so have left any thunder mention out of TAFs for
now.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Nield
SHORT TERM...KF
LONG TERM...CP
AVIATION...KF
Source:
IND issues Area Forecast Discussion (AFD) at Aug 18, 10:02 AM EDT---------------
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