IND issues Area Forecast Discussion (AFD) at Aug 16, 9:41 AM EDT433
FXUS63 KIND 161341
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
941 AM EDT Fri Aug 16 2024
.KEY MESSAGES...
- A few strong thunderstorms possible later today
- 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 940 AM EDT Fri Aug 16 2024
Back edge of the early morning convection is set to depart our
far southeast counties by 14Z or shortly after. Minor residual
flooding lingers in a few spots over south central Indiana where
rainfall amounts of 2 to 3 inches occurred earlier. Low clouds
persisted in the wake of the convection across the area but were
mixing out and becoming more scattered. Humid morning with 13Z
temperatures in the low and mid 70s.
Boundary that aided in the convection early this morning is
shifting away to the east in tandem with the deeper moisture plume.
Drier air and subsidence in its wake has led to a broad area of
clearing across Missouri and Iowa east into central Illinois and
expect this to expand into the forecast area into the afternoon.
Subtle waves aloft remain within the broad upper trough...but
overall forcing will be minimal through the afternoon. Any
convection will largely rely on CAPEs at 1500-2000 j/kg and will
remain isolated and disorganized in the absence of forcing aloft and
deeper BL shear. Will maintain isolated pops through the afternoon
but expect most will remain dry the rest of the day.
The humidity is back in full force this morning with dewpoints in
the upper 60s and lower 70s. Dewpoints will remain elevated through
the day before beginning to slide back slightly this evening. This
will make for a muggy afternoon with highs in the mid 80s over much
of the region.
Zone and grid updates out.
&&
.MESOSCALE UPDATE...
Issued at 621 AM EDT Fri Aug 16 2024
MRMS reflectivity mosaic loop was showing some convection
moving ENE from Kokomo to Bedford and more convection further west,
moving back into the the Wabash Valley, both areas associated with
deep convergence and marginal instability and shear. SPC
mesoanalysis site had the stronger instability pooled across south
central and southwestern parts of central Indiana with around 650
to marginally severe J/kg. CAMs and radar and lightning trends
suggest the trailing Wabash Valley convection should be through
the area around 15z or so. Would not rule out a strong or perhaps
even severe storm over the next hour or so before the instability
is depleted even further but chances are low. Precipitable water
values to near 2 inches or above the 75th percentile support the
potential for more heavy rain with any storm, although storm
movement of 30+ knots should limit any flood threat to localized.
MRMS was estimating in excess of 2 inches has already fallen
overnight over parts of Warren, Howard, Morgan and Bartholomew
counties. No flooding has been reported.
&&
.SHORT TERM (Today and tonight)...
Issued at 258 AM EDT Fri Aug 16 2024
Rest of the overnight and this morning...
Early this overnight, MRMS reflectivity mosaic loop was showing
scattered thunderstorms have developed in an arc from around
Danville, Illinois to near Bloomington. Additional activity was
moving northeast across southern Illinois and north central
Illinois. The upstream activity was associated with higher surface
based instability while the Indiana activity was associated mostly
with CAPE below 1000 J/kg and was elevated per Hi-Res soundings.
CAMs and radar trends support the upstream activity moving in after
3 and exiting around or shortly after rush hour. Meanwhile, SPC
mesoanalysis suggests better mid level lapse rates will move in
overnight potentially allowing some higher wind to mix down to the
surface, especially over the Wabash Valley, closer to surface based
instability and better instability. Finally, slightly higher 0-6km
bulk shear of 35 knots, associated with an approaching speed max
around the base of an upper Midwest low seen on H20 imagery, will be
approaching this area toward daybreak. So, would not rule out a
strong or perhaps even severe storm over the Wabash Valley, but with
limited surface based 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.
Will start the morning off with 60% PoPs over far east central
sections and taper off to 20% over the upper Wabash Valley.
Today...
The upper low is expected to move across Minnesota this morning and
northern Wisconsin this afternoon. Belt of higher wind speeds around
the base of the trough will move across central Indiana this
afternoon resulting in 40-50 knot 0-6km shear to go along with a
destabilizing atmosphere and elevated CAPEs to 2000 J/kg. Potential
boundaries associated with overnight convection along with an
approaching synoptic front and the upper forcing could be enough to
ignite some afternoon and convection with potentially a few strong
and or marginally severe thunderstorms per the SPC Day1 marginal
risk for severe weather. Drier mid levels and Hi-Res soundings
support afternoon clearing prior to convective re-development and
low convective coverage. This should allow temperatures to reach the
mid to upper 80s, or around normal. 70+ dew points, on the other
hand, will make for unfortunately high humidity.
Tonight...
Isolated convection may linger into the evening, in the wake of the
cool front. Winds will not shift a lot in the wake of the front
which should keep temperatures from falling any lower than the
middle 60s despite clearing.
&&
.LONG TERM (Saturday through Thursday)...
Issued at 258 AM EDT Fri Aug 16 2024
Near to below normal temperatures return for the long term period.
This weekend will see multiple chances for rain, mainly during the
afternoon hours, as a low pressure system moves over the Great
Lakes. While any rain is welcome in the current dry pattern, it
doesn't look like central Indiana will receive much with this
system as much of the moisture will stay to both the north and
south of the area. Expecting around half an inch of rain or less
across Saturday and Sunday, although locally higher amounts could
be possible.
The upper low will exit to the east with strong and persistent
ridging setting up over the south-central Plains. This will place
the region under upper NW flow which will bring in the cooler, dry
airmass for next week. The quiet weather next week will be
reinforced by surface high slowly passing through the region.
Saturday will see highs from the low to upper 80s but will drop to
the upper 70s to near 80 the remainder of the period. Again, lows
will start off in the mid 60s and drop to 50s for the rest of the
time.
&&
.AVIATION (12Z TAF Issuance)...
Issued at 549 AM EDT Fri Aug 16 2024
Impacts:
- Showers and thunderstorms are possible mainly this morning but
also after 18z
- MVFR ceilings possible through 15z
- Can not rule out high gusts to mix down in convection
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 through 15z and again possibly
this afternoon and evening. 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.
&&
$$
UPDATE...Ryan
SHORT TERM...MK
LONG TERM...KF
AVIATION...MK
Source:
IND issues Area Forecast Discussion (AFD) at Aug 16, 9:41 AM EDT---------------
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