IND issues Area Forecast Discussion (AFD) at Apr 9, 7:33 PM EDT587
FXUS63 KIND 092333
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
733 PM EDT Wed Apr 9 2025
.KEY MESSAGES...
- Rivers have already reached or are expected to reach moderate to
major flood stage in Central and South Central Indiana, primarily
in the White and East Fork White River basins
- Widespread, significant river flooding continuing through at
least the next 1 to 2 weeks in some spots
- Thunderstorms possible on Thursday, mainly south of I-74. A few
storms may be strong with gusty winds and small hail.
- Brief warming trend begins this weekend
&&
.SHORT TERM (This evening through Thursday)...
Issued at 301 PM EDT Wed Apr 9 2025
Another dreary, wet day across Central Indiana. Latest satellite and
observations show an area of low pressure over Northern MO with
widespread clouds and showers extending eastward into Central IL and
IN. A quasi-warm frontal 925-850mb boundary extends from the low
along the I-74 corridor while the region remains in an area of large
scale lift ahead of an approaching jet streak. A 35-45 kt
southwesterly low level jet is advecting moisture aloft over the
boundary where widespread showers have developed today. Despite a
good set up for rain, ACARs soundings reveal very dry air within the
boundary layer that is slowly saturating as precipitation falls
aloft. Wet bulbing within the lowest layer and a saturated DGZ has
allowed for snow to make it down to the surface at times this
afternoon along and north of the I-70 corridor. Despite surface
temperatures in the upper 30s to mid 40s, this set up is good for
snowflakes to reach the surface. Little to no impacts from snow
expected.
This first round of showers will move through over the next several
hours as the low to mid level boundary lifts northward ahead of the
approaching low pressure system. Surface quasi-warm frontal boundary
likely remains south of the area today as upstream ACARs and forecast
soundings keep a low level inversion over the region through tomorrow
morning. The low level jet ramps up after sunset tonight, further
strengthening the low level inversion while steepening mid level
lapse rates. Expect additional convective showers to develop along
the trailing cold front this evening. MUCAPE values are fairly weak,
so not expecting much lightning with this second round; however an
isolated lightning strike is not out of the question for portions of
South Central Indiana. Main threat will be brief periods of moderate
to heavy rain within the 8PM to 2AM timeframe tonight.
Overall rainfall amounts today should remain below a third of an
inch over the next 24 hours. This rainfall is Not expected to
exacerbate the ongoing flooding threat in Central and Southern
Indiana; however it may delay and slow down the rate water recedes
over the next several days.
Thursday...
The area of low pressure from Wednesday passes by to the east
southeast leaving the region within a west-northwesterly flow
pattern. Cold air advection behind this system is relatively weak...
in fact stronger surface heating will result in much warmer
temperatures tomorrow within the low to mid 60s. Another weak mid
level wave rounds the base of a deepening trough overhead, which may
spark off showers and a few thunderstorms tomorrow afternoon along
and southwest of the I-74 corridor. Shear is relatively weak, but
steepening lapse rates, sufficient low level moisture, and CAPE
upwards of 1000j/kg may result in an environment conducive for brief
strong storms capable of producing small hail and gusty winds. This
threat is mainly for South Central Indiana. Rainfall amounts
Thursday afternoon likely will not be uniform due to the scattered
nature of the convection. Any shower or storm may be able to produce
a quick quarter to half inch of rainfall...further slowing down the
rate of river levels receding from recent floods.
&&
.LONG TERM (Thursday night through Wednesday)...
Issued at 301 PM EDT Wed Apr 9 2025
Thursday night...
Some lingering showers or thunderstorms will be across mainly
southern sections of central Indiana during the evening hours as
forcing from the system shifts south.
Some uncertainty remains on the timing of the cold front, which
leaves some questions about the amount of instability left in the
evening hours. If the front is slower, then enough instability will
remain for a few strong to potentially severe storms in the far
southwestern portions of the area. If it's faster, the severe threat
will be south of the area. Will continue to monitor. Damaging winds
and large hail would be the severe threat.
Rain chances will diminish into the night as the system moves out of
the area.
Friday and Friday night...
Colder air will move back in for this period with upper troughing
still over the area. Clouds will diminish Friday night as high
pressure builds into the area. This will allow temperatures to fall
to around freezing by Saturday morning.
Saturday and Sunday...
The weekend will be dry and warmer with high pressure in control at
the surface and upper ridging aloft.
Monday...
As an upper low moves into the northern Great Lakes area, a surface
cold front will move through the area. This should have some
moisture to work with given southerly flow ahead of it. Thus, will
have some chance PoPs for this. Thunderstorms will be possible, but
with uncertainty remaining in just how much moisture (and thus
instability) will be present, the severe threat remains unclear.
Temperatures may climb into the lower 70s ahead of the front.
Tuesday and Wednesday...
Cooler temperatures return with an upper trough in the vicinity.
Odds of rain remain low though through the day Wednesday.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 733 PM EDT Wed Apr 9 2025
Impacts:
- Showers developing tonight
- MVFR conditions expected with periods of IFR possible late tonight
into Thursday morning
Discussion:
Weak low pressure will push through the area overnight into
Thursday, with showers expected to persist and increase in coverage
overnight. Significant low level dry air has been a limiting factor
thus far, and will likely keep much of the evening VFR.
Widespread MVFR conditions will likely develop later tonight once
precipitation moistens the lower levels from aloft. Guidance appears
a little aggressive with IFR conditions, but cannot rule it out
entirely. Will carry SCT007 at all sites and PROB30s for
showers/fog/IFR ceilings for a period late tonight to account for
this.
Conditions will return to VFR during the late morning/midday hours
Thursday, though additional showers and perhaps a thunderstorm will
become possible. These chances are far too uncertain for inclusion
at this point in the TAF cycle.
Winds will be between easterly and southerly depending upon the site
early in the period, with all gradually becoming northwesterly later
in the period as the low center passes. Sustained winds will be at
or below 10KT through the period.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CM
LONG TERM...50
AVIATION...Nield
Source:
IND issues Area Forecast Discussion (AFD) at Apr 9, 7:33 PM EDT---------------
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