National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KIND 201650
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1250 PM EDT Sat Apr 20 2024

.KEY MESSAGES...

- Some frost potential Sunday morning, more widespread frost
  possible Monday morning.

- Increasing rain chances next Tuesday

- Temperatures generally near seasonal next week, but brief cooldown
  is possible Wednesday into Thursday

&&

.FORECAST UPDATE...
Issued at 923 AM EDT Sat Apr 20 2024

- Mostly Sunny and Cool

Surface analysis late this morning shows strong high pressure in
place over eastern Montana. A surface ridge extended southeast from
the high, stretching across NB, northern MO to SW Indiana and
Central KY. Cool northwest surface flow was in place across Central
Indiana, along with a moderate pressure gradient. Dew points were in
the dry mid 20s. GOES16 shows clear skies in place across the
forecast area. Aloft, a deep area of low pressure was found east of
Hudson Bay. This feature was providing a nearly zonal westerly flow
in place aloft across Indiana and water vapor imagery showed only
Pacific moisture aloft within that flow.

Thus afternoon, models continue to suggest a dry column and
subsidence as high pressure is expected to continue to provide
surface ridging across Indiana. No forcing aloft is expected to
pass. Forecast soundings hint a few CU may be possible late this
afternoon, but this should be quite limited, as the soundings show a
dry column for much of the day. Thus Mostly Sunny will be the best
forecast. Ongoing cold air advection continues today on NW winds.
Given this, highs in the lower to middle 50s will be expected.
Ongoing forecast handles that well.

&&

.SHORT TERM (Today and tonight)...
Issued at 301 AM EDT Sat Apr 20 2024

Elongated upper level low over Canada will pivot upon its eastward
departure just enough to nudge a second round of colder upstream air
mass southward into Indiana. It will modify, but should still result
in temperatures about 5-7 degrees cooler than yesterday.

Ascending subtropical moisture within phasing jet should bring
increasing cirrus throughout the day persisting into the night.
Despite colder air mass, cirrus coverage and enough of an MSLP
gradient to limit radiative cooling will hold most of the area in
the upper 30s for low temperatures. The best chance of mid-30s for 2-
m temperatures and some frost potential would be north of thicker
cirrus shield and deeper within the cold air mass, across northern
portions of central Indiana.

&&

.LONG TERM (Sunday through Friday)...
Issued at 301 AM EDT Sat Apr 20 2024

.Sunday and Monday...

A cooler and drier pattern continues this weekend and into early
next week for Central Indiana. Currently focusing on the potential
for patchy frost both Sunday and Monday morning for wind sheltered
and low lying areas.

Surface high pressure centered over the Central Plains Sunday slides
southeast by Monday becoming centered over Arkansas with a weak low
level pressure gradient extending into the Ohio Valley. Cold air
advection through the weekend will keep temperatures below average
with highs struggling to reach the 60 degree mark despite drier air
and sunshine. Watching early Sunday and Monday morning for the
potential for frost; however with the center of the surface high to
the south and west, winds should remain elevated enough to prevent
widespread frost formation. Also for Sunday morning, a weak upper
level shortwave passing by in addition to the right entrance region
of the jet directly overhead may result in upper level clouds. These
factors will limit the overall frost threat and keep lows in the
upper 30s to near 40. A few wind sheltered and low lying locations
may see frost Sunday morning, but confidence is low at this point.
Better chance for frost comes Monday morning as upper troughing and
associated clouds push south and east. Winds Monday morning fall to
5 kts or less, with South Central Indiana having the best chance for
calm winds and better radiational cooling. Higher confidence exists
in patchy frost Monday morning, so have added it into the forecast
for low lying and wind sheltered locations away from urban areas.

Other that potnetial for frost, no other hazards expected through
Monday.

.Tuesday through Next Weekend...

Brief ridging builds in Tuesday ahead of another upper trough diving
into the Great Lakes region from the northwest. Warm air advection
ahead of the associated surface low tracking through Michigan should
lead to temperatures near average in the mid 60s, but with the
threat for rain. Sufficient moisture return combined with increasing
dynamics supports likely POPs on Tuesday. There is still timing
discrepancies between models regarding the speed of the front and
time of arrival for rainfall with the GFS being a good 6 hours
faster than the Euro or Canadian. Going with the slower solutions
for the forecast as more members and guidance depict this, with the
faster GFS being an outlier. Still think the highest PoPs will be
midday Tuesday, but will watch model trends closely and adjust the
timing of the expected rain in future forecast packages. Model CAPE
values for Tuesday are still fairly low, so not concerned with
severe weather at this moment, but a few thunderstorms may be
possible.

Cold air advection and surface high pressure building in behind the
departing low will allow for quiet weather conditions to return
briefly Wednesday and Thursday. Another chance for frost returns
Thursday morning as high pressure becomes centered over the Great
Lakes. Watching North Central Indiana for the best chance for frost.

Expect a gradual moderating pattern for temperatures late week and
into next weekend with multiple chances for rainfall coming back
into the forecast.

One thing to note, Indianapolis is already in the top 13 for wettest
April`s on record. Numerous chances for rainfall Tuesday, and then
again the weekend of April 27-28th will likely push Indianapolis at
least into the top 10 for wettest April`s on record.

&&

.AVIATION (18Z TAF Issuance)...
-- Changed Discussion --
Issued at 1250 PM EDT Sat Apr 20 2024

Impacts:

- VFR Conditions are expected this TAF Period.

Discussion:

Strong high pressure over the plains states will allow for a surface
ridge axis to build across the TAF sites through this period.
Forecast soundings remain very dry within the lower levels and
ceiling and visibility restrictions are not expected.

Within the flow aloft, high clouds amid the flow aloft are expected
to push into Indiana this evening and overnight, before clearing
shortly after daybreak on Sunday. Again with these high clouds, no
restrictions are expected.
-- End Changed Discussion --

&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Puma
SHORT TERM...BRB
LONG TERM...CM
AVIATION...Puma