IND issues Area Forecast Discussion (AFD) at Jul 26, 12:56 AM EDT635
FXUS63 KIND 260456
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
1256 AM EDT Fri Jul 26 2024
.KEY MESSAGES...
- Slightly cooler and less humid through Friday
- Increasing rain chances Sunday
- Increasing threat for multiple storm clusters to impact the region
next week
&&
.FORECAST UPDATE...
Issued at 933 PM EDT Thu Jul 25 2024
- Mostly Clear and Mild Overnight
- Patchy Fog possible
Surface analysis late this evening shows high pressure in place over
Lake Michigan and the Great Lakes. Cool and dry northeasterly flow
was found across Central Indiana. This was resulting in mostly clear
skies across most of Central Indiana. A tropical plume of moisture
was found over the lower Mississippi valley, then streaming
northeast to southern Indiana and KY. GOES16 showed these high
clouds on the southern edges of our forecast area. Dew points across
our area were in the upper 50s and lower 60s.
Overnight the strong surface high to the north is expected to slowly
drift east. This will keep Central Indiana under its influence,
providing mostly clear skies across the forecast area. The high
clouds over southern Indiana will also persist. Forecast soundings
through the night continue to show a dry column. Dew point
depressions overnight look to fall to 1-3F, which should be
sufficient for some patchy fog in rural and low lying areas.
Overnight lows mainly in the upper 50s to lower 60s are expected.
Overall, ongoing forecast remains on track.
&&
.SHORT TERM (This evening through Friday)...
Issued at 224 PM EDT Thu Jul 25 2024
The position of a mid-upper shortwave trough favors continental air
mass that is slightly cooler and drier nudging into central Indiana
today. Elevated convection over Illinois diminished with weakening
warm/moist advection regime, and diurnal destabilization has
resulted in isolated to scattered convection. This is mostly
concentrated southwest of our area where richer PBL moisture and
thus greater instability are.
Radiative conditions aren't optimal but sufficient for us to end up
on the cool side of model mean with regards to temperatures. This
will mean some locations will fall into the mid and perhaps lower
50s by dawn. We have adjusted accordingly.
Tomorrow, cool relatively dry easterly low level flow will hold
temperatures a few degrees below late July climatology. A slight
amplifying of the subtropical jet stream may result in cirrus across
at least the southern half of the area. Otherwise, PBL moisture may
be enough for some diurnal cumulus, but not as much as today.
&&
.LONG TERM (Friday night through Thursday)...
Issued at 224 PM EDT Thu Jul 25 2024
An upper level trough over the Plains will move toward our region on
Saturday, accompanied by a fairly substantial subtropical moisture
surge that will arrive Saturday night, per model IVT progs. These
meridional flow events where the trough is most pronounced in the
upper levels is notorious for weak midlevel lapse rates and limited
instability. While some thunder will be present, intense/severe
convection seems unlikely. Core of the richer/deeper moisture and
the ascent may be misaligned for a more productive rain event, and
so most ensembles have mean QPF up to around 0.50". Given the the
moisture profiles favoring high rainfall efficiency and the rather
broad window of ascent, this may be under-representing the potential
amounts and we may need to trend amounts up further.
Early next week, multi-model ensemble mean shows an amplifying mid-
upper ridging retrograding from the southern Plains to the central
Rockies. Flow aloft will be enhanced across our region on the
periphery of the ridge. Trajectories will favor residual plume of
steep midlevel lapse rates coupled with seasonally high PBL moisture
for moderate instability.
This is a favorable pattern for multiple MCSs to impact our area,
including progressive damaging convective wind events and upshear
propagation-driven flooding potential. Details on timing and track
placement are unclear at this time range and will be refined in
subsequent forecasts. It does appear that one or more perturbations
within peripheral enhanced flow will be more amplified and stronger
than the previous MCS pattern earlier this month. Once the ensemble
spread lessens we should be able to add more precision to the
precipitation probabilities next week.
This synoptic pattern also appears to result in favorable
trajectories for Canadian wildfire smoke to at least increase
haziness, and potentially impact air quality. This may especially be
the case later in the week as further ridge amplification occurs.
For the Day 8-14 period, cluster analysis and ensemble data point
toward extensive ridging to our west continuing. Above normal
temperatures and near normal precipitation will be favored in this
synoptic pattern.
&&
.AVIATION (06Z TAF Issuance)...
Issued at 1256 AM EDT Fri Jul 26 2024
Impacts:
- Brief MVFR Fog possible near daybreak at KLAF/KHUF/KBMG
Discussion:
Some lingering low level moisture may allow fog to form at all but
KIND near daybreak. Confidence is not high though, but will keep
continuity and maintain the mention of MVFR fog.
Otherwise, a few clouds around 4500FT will be around to go along
with some high clouds at times.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Puma
SHORT TERM...BRB
LONG TERM...BRB
AVIATION...50
Source:
IND issues Area Forecast Discussion (AFD) at Jul 26, 12:56 AM EDT---------------
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