IND issues Area Forecast Discussion (AFD) at Aug 16, 12:32 AM EDT106
FXUS63 KIND 160432
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
1232 AM EDT Fri Aug 16 2024
.KEY MESSAGES...
- Showers likely with few thunderstorms overnight and this morning
- Warmer tomorrow with isolated showers/storms
- Scattered showers and a few storms possible at times over the
weekend
- Another prolonged stretch of mild and dry weather likely next week
&&
.FORECAST UPDATE...
Issued at 957 PM EDT Thu Aug 15 2024
Initial round of showers and isolated thunderstorms has moved off to
the east of central Indiana this evening. Rain cooled air behind
this is keeping the northern forecast area from around 70 to the
lower 70s, with upper 70s and lower 80s noted south of this area.
Pretty quiet weather should rule for the remainder of the evening
with not much forcing in the area. Kept some mention of isolated
showers to cover anything that does manage to pop up, but the vast
majority of the area will remain dry.
As an upper trough approaches overnight, lift will increase. A
relatively weak 850mb jet will develop and bring additional lift and
moisture to the area. Thus, expect showers and some thunderstorms to
develop/move into the area overnight. Brought PoPs back up to likely
or higher category from west to east overnight, which is very
similar to the forecast issued earlier today.
Some elevated instability will advect in allowing the thunder
overnight, with some lingering surface based instability in the
southwest forecast area. A few stronger storms may be able to
develop or sustain themselves, mainly southwest where the best
surface based instability will be. However, confidence is low given
better instability remains west of the area.
Temperatures will remain near steady north and fall into the lower
70s south. Clouds should prevent fog formation in areas that saw
rain earlier.
&&
.MESOSCALE UPDATE...
Issued at 1231 AM EDT Fri Aug 16 2024
MRMS reflectivity mosaic loop was showing some convection
developing across the Wabash Valley in an area of weak surface based
instability. SPC mesoanalysis site had the stronger instability
pooled across north central Illinois with around 500 J/kg across the
Wabash Valley. Meanwhile, the stronger deep shear also resided west
of central Indiana, around the base of an upper Midwest low. CAMs
and radar trends suggest the upstream Missouri and west central
Illinois along with the northwestern Illinois activity will spread
across central Indiana after 3am and through around rush hour. This
looks reasonable. Would not rule out a strong or perhaps even severe
storm over the Wabash Valley, but with limited instability and
shear, chances seem pretty low. Precipitable water values to near 2
inches or above the 75th percentile support at least potential for
some heavy rain with any storm, although storm movement of 20+ knots
should limit any flood threat to localized.
&&
.SHORT TERM (This evening through Friday)...
Issued at 255 PM EDT Thu Aug 15 2024
Rest of Today and Tonight.
Scattered showers with an isolated rumble of thunder will continue
through the rest of the afternoon hours as residual moisture from
earlier convection continues to move eastward. Synoptically, a low
pressure system continues to slowly move eastward out of the Dakotas
into Minnesota with weaker shortwaves to the south bringing the
repeated rounds of precipitation to the area. Temperatures continue
to struggle to rise out of the 70s and based on upstream cloud
cover, it looks unlikely that anywhere outside of the southern
portions of the forecast area will be able to reach 80. Through the
evening, don't expect anything more than a rumble of thunder or two.
A slightly better chance for organized convection is expected later
into the overnight hours as convection that will initiate across
Missouri pushes eastward. Latest model guidance hasn't had the
southern dive that earlier runs has, mainly due to the fact that the
storms are expected to generally remain elevated vs surface based
and won't be as tied to the thermal and theta-e boundaries. Coverage
should peak towards 3AM with thunderstorms exiting after daybreak.
Severe weather looks unlikely with the storms expected to remain
elevated and with little instability above the stable layer, hail
larger than peas looks unlikely as well.
Friday.
Generally dry conditions are expected for Friday with skies expected
to clear out by the mid to late afternoon hours with only diurnally
driven cu by 20Z. As cold air moves in aloft, this will create a
slightly unstable atmosphere which could allow for isolated showers
and possibly a few rumbles of thunder towards the afternoon hours
along with efficient mixing of the surface moisture. Plan on
dropping afternoon dewpoints to factor in this mixing out of
moisture and will bump up gusts into the low 20 mph range. The
clearing of skies should allow for fairly warm afternoon highs in
the mid to upper 80s even as the colder air aloft moves in.
&&
.LONG TERM (Friday night through Thursday)...
Issued at 255 PM EDT Thu Aug 15 2024
Friday Night into Sunday -
A large upper level low will drift slowly through the Great Lakes
and Ohio Valley regions Friday night into Sunday, with at least some
chance for showers and thunderstorms much of this time frame, though
chances will be maximized near and just after peak heating in the
afternoons. Relatively modest at best instability and shear suggest
little to no severe threat, with primarily weak diurnally driven
convection.
Sunday night through Thursday -
As the low exits to the east and strong upper ridging persists to
the west, much of next work week looks to again be quite comfortable
for the time of year, with below normal temperatures and low
humidity as a broad surface high traverses the region, and dry/cool
northwest flow aloft on the leeward side of the ridge keeps this
pleasant airmass in place. The amplitude of the ridge will keep any
disturbances well north of the area.
&&
.AVIATION (06Z TAF Issuance)...
Issued at 1200 AM EDT Fri Aug 16 2024
Impacts:
- Showers and thunderstorms are possible mainly after 07z
and before 12z but also after 16z
- MVFR ceilings possible after 08z and through 14z
- Can not rule out high gusts to mix down in convection
overnight and this afternoon, but chances too low to
put in the TAFs.
Discussion:
Seasonably strong winds aloft around the base of an upper Midwest
low pressure system combined with a moist and unstable atmosphere
will bring a few chances for convection to the terminals.
Convective allowing models and radar trends suggest
convection will move across 07z-12z and again possibly
this afternoon. A strong or severe thunderstorm can not
be ruled either period, but chances are too low to mention
due to the elevated nature of instability noted in Hi-Res
soundings.
Winds will be SSW mostly 10 knots or less but possibly higher in
convection if higher winds can mix down despite a stable boundary
layer.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
MESOSCALE...MK
UPDATE...50
SHORT TERM...White
LONG TERM...Nield
AVIATION...MK
Source:
IND issues Area Forecast Discussion (AFD) at Aug 16, 12:32 AM EDT---------------
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