Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 121642

Area Forecast Discussion
National Weather Service Indianapolis IN
1242 PM EDT Mon Apr 12 2021

...Updated Aviation Discussion...

.Forecast Update...
Issued at 948 AM EDT Mon Apr 12 2021

Back edge of the lower clouds continues to spin across the northeast
half of central Indiana this morning with mainly clear skies further
to the southwest. Much of the light rain has shifted east into Ohio
but there continue to be pockets of light rain and/or drizzle
focused across northeast counties. 1330Z temperatures were generally
in the upper 40s and lower 50s.

The primary focus for the remainder of the day will be improving
conditions as the surface wave shifts into the eastern Great Lakes
and high pressure steadily builds in from the west. Lingering
cyclonic flow on the bask side of the storm system though may keep
the cloud deck and perhaps some pockets of sprinkles and/or drizzle
over far northeast counties into the early afternoon before
diminishing. Otherwise expect a gradual clearing trend with
increasing sunshine into the afternoon.

Nudged high temperatures down a couple degrees based on current
trends but overall...still anticipate low to mid 60s across the
forecast area. Westerly winds will be gusty through late afternoon
before dropping off this evening as the pressure gradient loosens.

Zone and grid updates out.


.Short Term...(Today through Tuesday)
Issued at 311 AM EDT Mon Apr 12 2021

Upper low, off the southwest Lake Erie shore per the GOES-16 global
composite water vapor loop, will continue to move slowly eastward
today. Models and CAMs suggest band of showers on the back end of
the low will move east of central Indiana near or shortly after 12z
this morning. Then, surface high pressure will build in from the
west and model time sections were showing the lower levels will be
drying up. This and layered rh progs support increasing sunshine
with just perhaps some scattered diurnal cu and increase in mid
clouds. With the increase in sunshine, temperatures should be able
to bounce back to slightly above normal and reach the middle 60s
this afternoon.

BUFKIT was showing potential for 25 knots to mix down below the
weakening inversion during the afternoon. So, it will be another
breezy day.

Tonight and Tuesday... Models in good agreement that surface high
pressure will expand over central Indiana from the northwest. That
said, models and even moreso the CAMs suggesting southern wave in
zonal flow aloft around the base of western Great Lakes upper low
will kick off some showers over the far southern tier or so tonight
and Tuesday. So, after coordination with neighboring offices,
decided to introduce small PoPs to our far southern tier tonight and
Tuesday. This may needed to be adjusted up and northward if trend
continues. Either way, instability will be lacking, so not mention
of thunder. Will keep clouds on the low end near and north of
Interstate 70 per model soundings, low level rh progs and synoptic

Low level thermals and expected cloud cover support near normal
highs in the lower and middle 60s on Tuesday. May need to adjust
temperatures over southern counties down at some point if trends


.Long Term...(Tuesday night through Sunday)
Issued at 311 AM EDT Mon Apr 12 2021

Troughing will continue over most of the US this week as energy
arrives through NW flow from the west Canadian coast. This wave
is split into two separate cut off lows, as the broad nature of
the trough interacts with two individual jet streaks. The first
low looks to pass east of central Indiana leading to
predominately NW flow. This will be the primary factor in the
cool down Tuesday through Thursday with highs in the upper 50s
over this time period. With cyclonic flow aloft, some cloud cover
is likely with breaks in the afternoon. Overnight temperatures
over this stretch should fall below 40, leading to some frost
concern. However, this aforementioned cloud cover will hinder
frost growth even if temperatures do fall into the mid 30s.

As the two lows reach similar latitudes, dynamic alignment will
promote height rises over the Great Plains this will keep any
surface disturbances south of central Indiana, producing a dry
forecast through the work week. As this ridge dissolves, and
weakens the western close low, zonal flow aloft will develop as a
result. Within zonal flow, near seasonal temperatures are
expected. This zonal flow does pose a challenge in long term
forecasting as smaller scale features play a larger role. Some
ensemble members are initiating showers along surface
disturbances over the weekend, but confidence in this occurring
is low at this time.


.Aviation...(18Z TAF Issuance)
Issued at 1242 PM EDT Mon Apr 12 2021

- MVFR ceilings scattering early this afternoon
- West to northwest wind gusts to over 20 knots through early this

DISCUSSION: The back edge of the stratocu continues to slowly lift
and scatter early this afternoon. Expect further clearing throughout
the afternoon as high pressure builds in from the west. W/NW wind
gusts briefly exceeding 20kts are possible at all terminals through
early this evening...then should see winds drop off quickly near

After a mostly clear start to the evening...likely to see an area of
mid level clouds currently over the central Plains expand into the
region late this evening and through much of the overnight. Model
soundings and RH progs highlight that skies should become partly
cloudy with just scattered pockets of mid and high level cloud cover
by midday Tuesday.




Short Term...MK
Long Term...Updike
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