IND issues Area Forecast Discussion (AFD) at Aug 26, 9:41 AM EDT444
FXUS63 KIND 261341
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
941 AM EDT Mon Aug 26 2024
.KEY MESSAGES...
- Above normal heat is expected for the next several days with
an Excessive Heat Watch for Tuesday
- Record highs will be threatened Tuesday and Wednesday
- There are low chances for thunderstorms on Tuesday and Wednesday,
with high uncertainty.
- There is higher confidence for thunderstorms between late Thursday
through Friday night, with high uncertainty on timing.
- Cooler weather expected for the upcoming holiday weekend
&&
.FORECAST UPDATE...
Issued at 941 AM EDT Mon Aug 26 2024
Forecast is in good shape this morning. No significant changes were
made, with mainly tweaks to match current hourly trends.
Mid cloud across the western forecast area will drift east before
mixing out this afternoon. Some high clouds will move across the
area this afternoon along with perhaps some cumulus.
Temperatures will continue to quickly warm today, reaching the 90s
for highs. Dewpoints should be low enough that apparent temperatures
are only up to a few degrees higher than actual readings.
&&
.SHORT TERM (Today and Tonight)...
Issued at 259 AM EDT Mon Aug 26 2024
Mainly clear skies ongoing early this morning although mid level
clouds have been gradually expanding south from the lower Great
Lakes. These clouds may linger into the morning hours as a subtle
axis of moisture aloft passes through the region. 06Z temperatures
ranged from the mid 60s to the mid 70s.
Strong upper level ridge centered over the Missouri Valley this
morning will drift east into Illinois by tonight and serve as the
prominent feature influencing weather across the Ohio Valley.
Convection will remain well to the northwest of the region today in
advance of a stronger upper level low traversing the ridge periphery
from the northern Rockies today into the Dakotas tonight. Additional
storms are possible tonight into Tuesday riding overtop of the ridge
axis from the Great Lakes southeast into the upper Ohio Valley but
these will remain displaced to the northeast of the forecast area.
Hot temperatures continue today but similar to Sunday...expect
dewpoints to be tempered as drier air aloft is pulled to the surface
courtesy of a deep mixing layer likely to peak near 750mb. 850mb
temperatures will rise steadily today and should peak at 20-21C over
western counties by late day. Low level thermals support widespread
highs near readings in the Wabash Valley on Sunday that ranged from
92 to 94 degrees. The hottest air will be located over far western
Indiana again this afternoon where mid level heights and 850mb temps
are highest. Mid 90s are expected and with the presence of the cap
around 700mb...expect diurnal cu to be more flattened and scattered
with little impact to heating through the day. As mentioned above
with dewpoints expected to fall back to the low to mid 60s during
the afternoon...peak heat indices will likely cap in the mid and
upper 90s in most locations.
Cu will diminish near sunset leaving skies mostly clear again
heading into tonight. There is potential for cirrus blowoff from any
convection to our north or northeast overnight and into early
Tuesday to drift back southwest into parts of the forecast area but
confidence in this remains quite low. Raised cloud coverage a bit
across northeast counties to account for this possibility. Lows
tonight will be warm and hold in the low to mid 70s.
&&
.LONG TERM (Tuesday through Sunday)...
Issued at 259 AM EDT Mon Aug 26 2024
An amplified ridge, on the order of 2-4 sigma above the
climatological has now reached the Ohio Valley, with the axis of
this ridge expected to reach the general Indiana region sometime
late Tuesday. Within the center of this ridge is highly anomalous
850mb temperatures (99th percentile), of which will likely lead the
warmest surface temperatures of the month yet with highs expected to
be in the mid to upper 90s on Tuesday. Also of note will be the
rather impressive dew point temperatures lifted northward ahead of a
weak low level wave on Tuesday. With the support of some "Corn
Sweat" dew points are expected to push into the low to mid 70s over
much of central Indiana Tuesday afternoon. The combination of upper
90 temperatures and low to mid 70 dew points will create the
potential for dangerous heat conditions with heat indices between
105 and 110.
Beginning late Tuesday, this ridge starts to deamplify some, allowing
for a few weak short waves to develop. This will likely not impact
the overall airmass much, but increased cloud cover and potentially
scattered rain chances could suppress diurnal temperature gains
some, leading to increased uncertainty on afternoon high temperature
forecasts Wednesday and Thursday. Current expectations are for highs
in the mid 90s, but this could fluctuate 4-5 degrees depending on
clouds and any rainfall.
As mentioned, we will have a well established ridge on Tuesday. This
should inhibit the progression of lift over central Indiana, however,
with high levels of instability, any development over Northern IN/OH
has the potential to clip portion of NE central Indiana Tuesday. This
looks unlikely at this time, but 15-25% PoPs have been included to
showcase the potential. Also mentioned was the eventual flattening
of the ridge mid week. This will increase chances for convective
development Wednesday and Thursday, but greater forcing will remain
further north and west until Friday. For now, a broad 15-35 percent
chance of thunderstorms has been included on Wednesday and Thursday
with high uncertainty. Overall chances increase for Friday as the
lift from a upper wave nears, but there is still uncertainty on
timing for any thunderstorms on Friday.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 530 AM EDT Mon Aug 26 2024
Impacts:
- None
Discussion:
VFR conditions will continue through Tuesday morning. An axis of mid
level clouds will drift S/SW across the northwest half of central
Indiana this morning. Then diurnal cu will again develop for the
afternoon before diminishing near sunset tonight. There is potential
for a subtle increase in cloud coverage predawn Tuesday depending on
convective coverage over the Great Lakes.
Southwest winds up to 10kts are possible this afternoon otherwise
expect light and variable flow.
&&
.CLIMATE...
Issued at 259 AM EDT Mon Aug 26 2024
Record highs at Indianapolis:
8/26: 97 (1948)
8/27: 97 (1948)
8/28: 96 (1953)
Record highest minimum temps at Indianapolis:
8/27: 74 (1977)
8/28: 74 (2013)
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Watch from Tuesday morning through Tuesday
evening for INZ021-028>031-035>041-043>048-051>055-060-061.
&&
$$
UPDATE...50
SHORT TERM...Ryan
LONG TERM...Updike
AVIATION...Ryan
CLIMATE...Ryan/Updike
Source:
IND issues Area Forecast Discussion (AFD) at Aug 26, 9:41 AM EDT---------------
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