IND issues Area Forecast Discussion (AFD) at Aug 13, 10:07 AM EDT135
FXUS63 KIND 131407
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
1007 AM EDT Tue Aug 13 2024
.KEY MESSAGES...
- Becoming Partly Cloudy Today; Warmer.
- Mostly Clear Tonight.
- Numerous showers and storms Thursday afternoon into
Friday with heavy rain and lightning as the greatest threats
- Isolated to scattered showers and storms remain into the weekend
&&
.FORECAST UPDATE...
Issued at 1006 AM EDT Tue Aug 13 2024
No major changes needed to the forecast this morning. Our only
changes, though minor, are the sky cover grids for the next several
hours. We bumped sky cover in the southern portions of the CWA to
better account for persistent low to mid-level clouds. Higher-res
guidance tends to diminish these with time, but too quickly in our
opinion. So we delayed the thinning of these clouds for a few hours.
By late in the morning typical diurnal cumulus should begin to form,
especially over places not currently under cloud cover.
Additionally, some debris cirrus from a convective complex out west
may eventually begin to overspread our region this afternoon.
&&
.SHORT TERM (Today and tonight)...
Issued at 301 AM EDT Tue Aug 13 2024
Synopsis -
Surface analysis early this morning shows a large and strong area of
high pressure centered over MI/OH and Western PA. The high was
influencing the weather from the upper Midwest, through the Ohio
Valley to the east coast, as well as the deep south. Light to calm
winds were in place and dew point temperatures were a bit higher
than the past few nights, in the upper 50s and lower 60s. Aloft,
water vapor showed a short wave exiting Central Indiana, within the
NW flow aloft. A moderate ridge aloft was found exiting the Rockies.
This was resulting in lee side northwest flow and subsidence across
the plains pushing toward the Ohio Valley. Radar this morning shows
a few light showers or sprinkles over southern and eastern Central
Indiana exiting to the east.
Today -
Models today suggest the moderate ridging over the Rockies is
expected to build and push eastward today, reaching the plains
tonight. This will result in continued northwest flow across Central
Indiana along with subsidence. Little in the way of forcing dynamics
is seen today within this northwest flow. The earlier short wave
over Indiana is expected to quickly exit by mid morning. GOES16
showing mid level clouds over the southern half of Indiana early
this morning, but these clouds are expected to advect east amid the
northwest flow aloft this morning. Forecast soundings and time
heights both showing saturation within the mid levels early this
morning, show dry air arriving by late more as these clouds depart.
Forecast soundings also suggest CU development this afternoon as
convective temperatures will be reached. All of this adds up to
partly cloudy skies, with perhaps a few more clouds across southern
Indiana this morning.
850mb temperatures are expected to rise slightly warmer today than
yesterday as the high pressure center drifts farther east allowing
warmer air from the southwest to build across Indiana. This will
allow for slightly warmer high temperatures, in the lower to middle
80s.
Tonight -
Northwest flow aloft is expected to persist over Indiana as the
ridge axis builds across the Mississippi Valley. Subsidence remains
in play across Indiana on the lee side of the ridge. Meanwhile at
the surface, the center of the strong surface high is expected to
continue to drift farther east, but it/s influence will continue to
persist across Central Indiana. Forecast soundings through the night
indicate a dry column with good mid level subsidence. Thus mostly
clear skies will be expected. Lows will be in the lower to middle
60s.
&&
.LONG TERM (Wednesday through Monday)...
Issued at 301 AM EDT Tue Aug 13 2024
At the surface, the period begins with surface high pressure over
the Great Lakes Wednesday keeping conditions fairly warm and dry for
Central Indiana with highs returning to near normal in the mid 80s.
High pressure then shifts towards the Northeast CONUS as lower
pressure in the Plains approaches, setting the stage for the next
pattern change across Indiana.
Guidance has come into better agreement over the past 24 hours
regarding the weather pattern Thursday into the weekend. Broad
troughing over the Northern Plains Thursday slowly shifts east and
deepens over the Great Lake by Saturday. The associated surface low
tracks along the IA/MN border on Thursday pushing a warm front
through Central Indiana, leading to a set up with stronger moist and
warm air advection. This pattern shift will essentially kick out the
very dry, Canadian airmass that has been in place much of the week
preventing storm systems from impacting Indiana. The area will be
placed in an area of upper level divergence by Thursday afternoon
with a strengthening 25-35kt low level jet, resulting in an a
moistening environment with enhanced lift supportive of rain showers
and thunderstorms. While the greatest lift for storm development
will be further north and west near the low, there should be enough
lift along the warm front for convection to sustain itself as it
pushes into Indiana Thursday afternoon and evening. Severe weather
potential looks relatively minimal at the moment, but it is not out
of the question. Despite modest lift and wind shear, Instability may
be be lacking due to a low level warm nose and weak low to mid level
lapse rates. Currently the main threat with any storms is lightning
and repeated rounds of heavy rainfall. With confidence growing in a
wetter weather pattern, PoPs were increased Thursday a evening into
Thursday night. Best chance for the most widespread rainfall and
storms does appear further north and west, closer to the low.
Friday, the surface low pushes into the Central Great Lakes region
with a trailing front through Indiana. Guidance does show the
potential for an upper wave on the backside of the trough to
interact with the front as it is over the Ohio Valley early Friday
resulting in another round of heavy rain and storms. Again, the
greatest threat so far appears to be heavy rainfall and lightning.
Will have to watch for potential flooding issues if multiple rounds
of heavy rain develop over the same areas Thursday into Friday.
Convection becomes more scattered going into the weekend as lower
pressure slowly exits the Great Lakes region, placing Indiana back
into a northwesterly flow pattern at the surface and aloft. Expect
slightly cooler temperatures back into the upper 70s and lower 80s.
Not expecting a washout of a weekend, but showers and a few storms
could be around at times if waves of energy wrap around the backside
of the low and into the state.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 548 AM EDT Tue Aug 13 2024
Impacts:
- Mainly VFR conditions are expected this TAF period.
- Brief IFR/MVFR MIFG/BR possible at HUF and LAF til 13Z.
Discussion:
A weak short wave has exited Central Indiana along with a mid level
cloud deck associated with that feature. Clear skies, light winds
and dew point depressions at 2F or less may result in some brief
MVFR BR or MIFG at LAF and HUF, however confidence on that is low as
it has not formed at this point. Any fog will quickly dissipate
after sunrise.
As heating returns today, fog will dissipate, leading to a return to
VFR conditions. Forecast soundings suggest diurnal CU will once
again be expected during the peak heating hours of the day.
Mostly clear skies and VFR conditions are expected overnight as the
TAF sites will remain under the influence of high pressure.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
UPDATE...Eckhoff
SHORT TERM...Puma
LONG TERM...CM
AVIATION...Puma
Source:
IND issues Area Forecast Discussion (AFD) at Aug 13, 10:07 AM EDT---------------
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