IND issues Area Forecast Discussion (AFD) at Aug 21, 2:44 PM EDT919
FXUS63 KIND 211844
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
244 PM EDT Wed Aug 21 2024
.KEY MESSAGES...
- Dry with well-below normal temperatures and lower humidity
- Temperatures trending warmer with above average temperatures by
Saturday.
&&
.SHORT TERM (This evening through Thursday)...
Issued at 244 PM EDT Wed Aug 21 2024
Fall-like weather will continue for the short term as central
Indiana remains under the influence of Canadian high pressure.
Latest IND ACARs sounding shows a very dry atmospheric profile with
a subsidence inversion around 850mb/1km agl. With 850mb temps well
below normal for this time of year at 7C, max surface temperatures
are only reaching the lower to mid 70s even with steep boundary
layer lapse rates. Lowered afternoon humidity levels for today and
tomorrow as deep mixing has already resulted in dew points in the
40s for most locations. Despite lower humidity, conditions are not
meeting critical thresholds for fire weather concerns.
Tonight will likely be the coolest night of the season for a few
areas, especially low lying wind sheltered locations. Optimal
conditions expected for radiational cooling as the center of the
high pressure moves over the northern half of the state tonight.
With such a dry airmass, light winds, and clear skies, decided to go
well below guidance for min temps, towards the NBM10th percentile,
with mid to upper 40s for Central and North Central Indiana and low
50s for South Central Indiana.
Almost a copy/paste forecast for Thursday as the area of high
pressure slowly begins to shift eastward. Highs may be a degree or
two warmer during the afternoon in the mid to maybe upper 70s, but
overall expect another dry, Fall-like day.
&&
.LONG TERM (Thursday night through Wednesday)...
Issued at 244 PM EDT Wed Aug 21 2024
Thursday Night Through Sunday.
The stagnant weather pattern that has been in place for much of the
week will continue late this week into the weekend as a broad and
expansive ridge across the central US states is bookended by two
larger low pressure systems off each coast. The system on the west
coast will move into southern Canada with the ridge blocking most of
the eastward progression. There will be a low potential for
diurnally driven showers this weekend but soundings show a robust
cap in place along with fairly low instability and no lifting
mechanisms in place. As the ridge builds, temperatures will
gradually continue to warm, especially as the northerly flow gets
cut off by late Wednesday. Expect to see highs in the mid 80s by
Friday followed by 90 towards Sunday.
Monday Through Wednesday
The ridge will slowly begin to migrate eastwards towards early next
week which will keep the flow near the surface and aloft quite
stagnant and lead to temperatures climbing into the low to
potentially mid 90s by mid-week. A weak cold front may push through
Tuesday into Wednesday, but the forcing associated with this system
will be centered in Canada with only weak forcing towards the Ohio
Valley. Ensembles show quite a bit of difference on both the timing
and extent of precipitation, so plan on keeping POPs low until
better agreement on the system progression arrives.
By early next week, air quality may start to become a greater
concern late this weekend into early next week with the
aforementioned stagnant airmass and cap aloft leading to poor air
circulation and a buildup of ozone. Forecast dewpoints look a bit
aggressive in the models with the recent dryness combined with the
corn sweat season coming to an end, so plan on tapering those down a
bit to limit the afternoon heat indices and associated heat risk.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 244 PM EDT Wed Aug 21 2024
Impacts:
- None
Discussion:
VFR conditions are expected through the forecast period. Cloud cover
will remain limited to occasional high cirrus and diurnal cumulus
during the afternoon hours. NE Winds of 5 to 10 kts during the day
will fall back to near calm overnight tonight.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CM
LONG TERM...White
AVIATION...CM
Source:
IND issues Area Forecast Discussion (AFD) at Aug 21, 2:44 PM EDT---------------
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