Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/02/23

Area Forecast Discussion

National Weather Service Indianapolis IN

 930 PM EDT Mon May 1 2023

.Forecast Update...
Issued at 930 PM EDT Mon May 1 2023

Few significant updates to the going forecast this evening. Made
minor low temperature adjustments based on latest HRRR/LAMP
guidance, primarily along the Lafayette/Indy/Rushville corridor.
Minor adjustments made to PoPs to bring them in line with latest
regional radar trends and continued expectation that showers will
steadily pull eastward and likely end for most of the area late
tonight.

Otherwise, lowered wind gusts overnight as latest ACARS data show
low level inversion development has been much stronger than larger
scale models originally anticipated, which will significantly limit
gustiness overnight.

&&

.Short Term...(This evening through Tuesday)
Issued at 258 PM EDT Mon May 1 2023

* Wind gusts to 40 mph through this evening
* Widespread rain north of I-74 diminishing overnight
* Isolated showers tomorrow, but still colder than normal

.This evening and tonight...

One of the coldest beginning`s of May for much of Central and North
Central Indiana with highs struggling to get out of the 40s! An
expansive upper level low over the Great Lakes is responsible for
the low clouds, rain, and wind across the region. Latest satellite
and radar imagery vividly show an upper trough rotating about the
main upper low into Central Indiana this afternoon with steady
stratiform rain along and north of I-74. This upper feature will
keep rain and lower clouds around through this evening, then
precipitation begins to diminish in coverage and intensity
overnight.

In addition to very cold highs for this time of year, a strong 40 kt
low level jet and a strong pressure gradient are resulting in gusty
winds to 40 mph across the region as well. Strongest winds have
occurred south of the I-74 corridor where the cloud deck is thinner
and boundary layer heating has led to deeper mixing. Expect winds to
remain elevated overnight around 10 to 20 mph; however the stronger
gusts of 30 to 40 mph will likely diminish after sunset.

Overnight temperatures won`t fall too much from daytime highs as
persistent cloud cover and winds prevent significant boundary layer
cooling. Expect lows in the upper 30s to low 40s.

.Tuesday...

Similar weather pattern continues into tomorrow, albeit a few
degrees warmer and less shower coverage. The main upper low pushes
northeast towards Toronto, but multiple upper waves will continue to
rotate around it into the region. RAP cross sectional views of the
atmosphere show mid level dry air advection tomorrow afternoon,
which may lead to a few breaks in the clouds at times, especially
across the south and western portions of Indiana. Keeping at least
20 PoPs across the northern 2/3 of the region as isolated showers
will likely persist under the cyclonic flow pattern. Lower
confidence exists in the timing of these weaker waves; however it
does look like tomorrow will be significantly drier than today has
been. With a strong low level jet aloft and a bit more boundary
layer heating tomorrow, expect gusts of 20-35 mph during the
afternoon hours. Temperatures should rise into the lower 50s for
most locations, except the far northeastern counties where clouds
and showers will be more prominent. However, since there is lower
confidence in timing of smaller waves, any afternoon showers would
likely cool temperatures down back into the 40s for a brief period.
Best chance of that occurring is along and north of I-74.

&&

.Long Term...(Tuesday night through Monday)
Issued at 258 PM EDT Mon May 1 2023

The long term period will start off still under the influence of an
upper level low slowly drifting east from the Great Lakes
continuing the chilly conditions. At the surface, high pressure
will start to move in for midweek, allowing a break in rain as
well as sunnier skies than we`ve seen the last few days. The first
few nights of the long term will have a risk of additional frost
with lows in the 30s, but as the the pattern changes through the
period, there will be a warming trend into next week.

Towards the end of the week, a surface low in the central plains in
addition to return flow on the backside of the exiting high may
bring some chances for rain. Confidence is on the lower end for this
precipitation at the moment as at the upper levels a ridging pattern
will be moving in, which may suppress those rain chances. There is
quite a bit of noise in the models for next week, but central
Indiana could see another low pressure or troughing system that
would bring additional chances for rain. In terms of temperatures
for the latter half of the period, there is a high confidence in the
warming trend as there is general agreement on a regime allowing for
highs in the 60s and 70s and lows in the 40s and 50s.

&&

.Aviation...(00Z TAF Issuance)
Issued at 721 PM EDT Mon May 1 2023

Impacts:

* Showers early in the period gradually ending.

* Strong west northwesterly winds occasionally gusting above 20KT
  this evening and again on Monday.

* MVFR ceilings return to LAF/IND 09-12Z and persist through 18-20Z
  Monday.

Discussion:

Large upper low continues to spin over the eastern Great Lakes this
evening. Rain associated with this low will gradually move east of
the sites this evening. Cannot rule out additional showers at times
during the period, but chances are too low for mention at this time.

Widespread VFR ceilings will remain the rule until late tonight,
when MVFR ceilings are likely to build back into LAF/IND in the 09-
12Z time frame. These ceilings will likely persist into the early-
mid afternoon hours, 18-20Z before returning to VFR. HUF/BMG appear
likely to remain VFR throughout.

Winds will remain breezy from about 280-300 degrees. Gusts will be
much more sporadic overnight tonight and thus will not mention. More
consistent gustiness will return after daybreak Monday, with gusts
20-26KT likely at the sites through the day Monday.

No significant obstructions to visibility are expected through the
period.

&&

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

&&

$$

Update...Nield
Short Term...CM
Long Term...KH
Aviation...Nield