IND issues Area Forecast Discussion (AFD) at Aug 16, 8:04 PM EDT378
FXUS63 KIND 170004
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
804 PM EDT Fri Aug 16 2024
.KEY MESSAGES...
- A few showers around overnight
- Scattered showers and storms possible at times over the weekend
- A couple of strong storms with gusty winds possible Saturday
afternoon and early evening
- Another prolonged stretch of mild and dry weather likely next week
&&
.FORECAST UPDATE...
Issued at 804 PM EDT Fri Aug 16 2024
Isolated convection has ended across central Indiana early this
evening. The remaining evening will stay dry. Some elevated smoke
will move in from the west providing a hazier look to the sky.
Forcing from an upper feature is currently producing some showers
and storms across northern Illinois. As this forcing arrives in
central Indiana overnight, it might be able to squeeze out some
isolated showers. Latest hi-res models show a broken line of showers
moving in early overnight as well.
Given the above, have went ahead and isolated showers to the
forecast for overnight, mainly for areas north of Interstate 70
where better forcing will be. Cannot rule out some thunder, but not
yet confident enough to add to the forecast.
&&
.SHORT TERM (This evening through Saturday)...
Issued at 259 PM EDT Fri Aug 16 2024
Muggy afternoon in progress with an abundance of stratocu/cu
lingering across the forecast area with the upper trough overhead.
Despite the lower clouds...temps had risen into the 80s as of 18Z
with dewpoints in the upper 60s and lower 70s.
Rest of This Afternoon and Tonight
While the deeper plume of moisture over the forecast area earlier
has moved off to the east...the presence of the aforementioned upper
level trough over the region has left cooler air aloft and enabled
the dense coverage of clouds over much of the area. Current water
vapor imagery shows drier air aloft and eventually model soundings
indicate that the drier air and subsidence should work down into the
boundary layer. This will lead to a gradual decrease in cu coverage
late afternoon into the evening from west to east.
There remains a low threat for a few showers and storms over the
region through early evening with mesoanalysis and the KIND ACARS
both showing SBCAPEs up into the 1500-2000 j/kg range. The
instability however will be the only driving factor for convective
development as a lack of more appreciable forcing aloft and
diminishing levels of low level moisture both work against more
widespread convective redevelopment. Will maintain a low pop for
isolated convection into the early evening but as has been mentioned
a few times already today...most locations will remain dry.
Cu will diminish this evening leaving mostly clear skies for the
first half of the night and just pockets of cirrus. Focus though
will shift to low pressure aloft and at the surface currently over
the upper Midwest which is set to drift southeast into southern
lower Michigan by Saturday morning. Deeper moisture will advect
south into the region late tonight and Saturday and likely to see an
increase in mid and high level clouds in particular across northern
counties prior to daybreak.
Saturday
The upper low will track slowly east across lower Michigan and
amplify on Saturday in tandem with the surface low. Waves aloft will
rotate around the base of the upper low and through the parent
trough with a surface boundary tracking into the region as well.
These features will serve as catalysts for convective development by
the afternoon as muted surface heating enables a weakly unstable
environment. Most of the morning should be dry across the forecast
area with rain chances increasing particularly across the northeast
half of the forecast area for the afternoon and evening.
PWATs climbing back up to near 1.50 inches will support brief heavy
downpours and that along with cloud to ground lightning will be the
primary impediments to outdoor activities during the afternoon and
early evening. That being said...there remains potential for any
stronger cells to toss out higher winds with DCAPE values in the 500-
1000j/kg range by late afternoon and steepening lapse rates through
about 700mb. Will continue to highlight the low threat for damaging
winds as a result. Once again as peak heating wanes into Saturday
evening...convection will also diminish in coverage.
Temps...it will remain muggy tonight with lows holding largely in
the upper 60s. There could be a modest spread in highs on Saturday
as clouds and greater convective coverage combine to keep highs
primarily in the lower 80s over northern counties. Further south
with more sun expected...highs will rise into the mid and upper 80s
with a few spots even around 90 over south central Indiana.
&&
.LONG TERM (Saturday night through Friday)...
Issued at 259 PM EDT Fri Aug 16 2024
Guidance remains consistent in gradually moving a large upper level
low through the Great Lakes and Ohio Valley this weekend, with
potential for showers and a few thunderstorms Saturday evening and
again during the day on Sunday.
Instability profiles on Sunday are tall and thin, with some steep
low level lapse rates providing the only small hint that perhaps an
isolated strong gust cannot be ruled out, but anticipate no severe
threat given minimal deep layer shear.
Beyond Sunday, the work week looks mild and pleasantly dry, with
unseasonably low humidity for a prolonged stretch. Broad surface
high pressure much of the week will provide strong subsidence for
mostly clear skies. Late in the week, the strong upper ridge to our
west will nudge eastward into the area and provide opportunity for
temperatures to rise back closer to seasonal normals in the mid 80s,
but any opportunity for precipitation looks to remain beyond the end
of the forecast period.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 652 PM EDT Fri Aug 16 2024
Impacts:
- Isolated showers possible overnight, mainly northern sites
- Occasional wind gusts over 20kt Saturday afternoon
Discussion:
Isolated convection looks to stay way from the sites this evening,
but a broken line of showers may move into the sites after 04Z.
For now have put in a VCSH mention at the northern sites overnight.
Confidence is low to medium.
Scattered to broken cumulus and stratocumulus will move in on
Saturday, with VFR ceilings developing at KLAF and likely KIND
during the day. Winds will increase on Saturday with gusts over 20kt
likely during the afternoon.
Looking ahead...MVFR ceilings may arrive overnight Saturday night.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...50
SHORT TERM...Ryan
LONG TERM...Nield
AVIATION...50
Source:
IND issues Area Forecast Discussion (AFD) at Aug 16, 8:04 PM EDT---------------
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