National Weather Service Weather Forecast Office

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

000
FXUS63 KIND 240545
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
145 AM EDT Wed Apr 24 2024

.KEY MESSAGES...

- Afternoon/evening rain expected. Total QPF under a half inch;
Cooler

- Becoming Partly Cloudy on Wednesday.

- Cooler mid-week, with some frost possible Wednesday night for
  northern portions of Central Indiana

- Active pattern returns Friday into next week with above normal
  temperatures and frequent rain chances

&&

.FORECAST UPDATE...
Issued at 1028 PM EDT Tue Apr 23 2024

Made minor adjustments to account for the location of rain and
current surface observations. Radar shows that the rain has almost
completely moved out of the forecast area. The front itself still
hasn`t made it`s way through central Indiana but it sits just off to
the NW and will move through overnight. Until then, the majority of
clouds have also exited with the rain but while we still sit in a
humid and relatively warm sector, a patchy stratus deck is forming
over the area. Satellite shows that much of the stratus is
currently over the NE counties, but there are some spots of
stratus forming over the Indy metro and areas both north and NE.
Can`t rule out shallow patchy fog in low lying areas as well.

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 235 PM EDT Tue Apr 23 2024

Synopsis:

Surface analysis early this afternoon shows low pressure over the
Central Great Lakes and a second area of low pressure was in place
over OK and the TX panhandle. A cold front across WI, SE IA and
eastern KS connected these two lows. Broad and elongated high
pressure was found across the east coast and stretching west across
the gulf coast. This was resulting in southerly flow across Central
Indiana, however the high pressure system was effectively blocking
moist gulf flow from reaching the Ohio Valley. Aloft, a moderate
short wave was found over WI and MN, with a trough axis extending SW
across IA. This was resulting in moderate westerly flow aloft across
Indiana. This short wave was being influenced by the broader
cyclonic flow across northeast North America as a deep upper low was
anchored near Hudson Bay. Water Vapor showed moisture ahead of the
trough over IL and Indiana and MI. GOES16 shows abundant cloud cover
ahead of the frontal boundary, pushing toward Central Indiana. An
area of rain was found over North Central Indiana, sagging
southward. Dew points ahead of the line have reached the 40s, but
current dew point depressions of 15-20F still exist.

Tonight...

Models suggest the forcing with the approaching short wave will pass
across Indiana this evening as the trough axis and the associated
surface cold front lag behind, passing overnight. Given the recent
radar trends showers over the northern parts of the forecast area
and the expected southern progression of the upper trough, the band
of showers will sag southward to nearly the I-70 corridor by 4-5pm
and farther south by 8p-9p. Forecast soundings through this time
period continue to a saturated column through the late afternoon and
early evening hours. Thus will continue with the ongoing near 100
pops with this band as it sags southward late this afternoon and
evening.

After the forcing clears, residual lingering clouds will be left in
the wake of the rain, as clearing skies will hold off until the wake
of the front  overnight. HRRR Suggests lower level saturation toward
12Z hence some lingering lower clouds may still remain during the
late overnight and early morning hours.

Cold air advection will be in place overnight as winds become
northerly. Ongoing lows in the lower to middle 40 appear on the
mark.

Wednesday...

Models on Wednesday show the upper trough departing. Strong ridging
is shown to build across the Rockies, leading to NW flow aloft and
lee side subsidence over the upper midwest, Great Lakes and Ohio
Valley. A strong area of surface high pressure is shown to build
behind the front, reaching the Great Lakes by Wednesday afternoon.
This appears to be a large area of high pressure, extending its
influence from Ontario across the Ohio Valley to the Gulf of Mexico.
Models show relatively high RH within the column in the area as the
day begins, but as heating and mixing resumes, a dry column is
realized. Hence we will look for skies to become partly cloudy as
the day progresses and the surface high builds across the area.
Given the ongoing cold air advection highs will only reach the lower
to middle 50s.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 235 PM EDT Tue Apr 23 2024

Wednesday night and Thursday...

Quiet weather can be expected during this period with high pressure
in control at the surface and rising upper heights.

The main question is frost potential Wednesday night. Winds will be
light, and the cooler airmass will remain in place. However,
uncertainty remains in how much cloud cover there will be. There
will be likely some high clouds moving in over the ridge, but they
may be initially thin.

Will go with lows in the mid 30s north and continue to mention some
frost. Lows will be in the upper 30s elsewhere. On Thursday,
filtered sunshine will boost temperatures into the upper 50s to mid
60s.

Friday and beyond...

A couple of upper systems will eject out of the southwestern USA
during this period. The first on Friday will bring a warm front
northeast through the area. Good southwest flow aloft will bring in
moisture for the front to work with. Will go with likely PoPs most
areas on Friday and Friday night.

Forcing weakens on Saturday but there will still be some around, so
will keep chance PoPs then.

The next upper system will begin influencing the area on Sunday,
with better forcing arriving with a front on Sunday night into
Monday. Continued southwest flow will keep moisture available, so
will go with likely PoPs again.

Of course, some uncertainty in timing of the best forcing remains
this far out, so details could change.

CSU Machine Learning is hinting at some potential for strong to
severe storms at times, but feel that the better threat will remain
west of central Indiana (closer to stronger forcing and better
instability) at least through the first half of the weekend. Will
have to watch the Sunday/Monday system to see if things align better.

Temperatures will be above normal through much of the period. With
the stronger southwest flow aloft, mixing will allow some breezy
conditions through much of the long term period.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 145 AM EDT Wed Apr 24 2024

Impacts:

- Pockets of IFR cigs and fog through sunrise, mainly for KLAF and
KBMG

- Winds shifting from SW to N, sustained at 7 to 10 kts. Gusts 15 to
20kts mid morning to early afternoon.


Discussion:

Latest satellite imagery shows the main area of rainfall and clouds
moving southward into Kentucky, leaving behind a nearly saturated
atmosphere. Patchy fog with IFR cigs and vis has been reported
across Central Indiana overnight; however confidence is low in exact
locations and duration of fog development as winds are still
elevated. Current thinking is that low lying areas in the Wabash
River Valley will see the worst conditions overnight. Best potential
for brief periods of IFR conditions from fog will be at KLAF and
KBMG, lower confidence at KHUF, but cannot rule it out there as
well. Expect conditions to rapidly improve around and just after
sunrise at all locations.

Winds will shift from SW to NW to N behind the front through the
morning hours. Wind shift line looks to still be up near Chicago
according to recent observations, so expect SW to W winds for at
least the next few hours at all TAF sites. Winds shift to the NW
then N later this morning. Guidance shows an increase in speeds to
10-15 kts mid morning through early afternoon as the main front/wind
shift passes through the region. Expect winds to begin diminishing
late afternoon to around and under 10 kts.

&&

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

$$

UPDATE...KF
SHORT TERM...Puma
LONG TERM...50
AVIATION...CM