Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/16/23

Area Forecast Discussion

National Weather Service Indianapolis IN

 1023 PM EDT Mon May 15 2023

.Forecast Update...
Issued at 1022 PM EDT Mon May 15 2023

A few changes made to the forecast with this evening`s update.
Current surface analysis shows an area of high pressure centered
over Nebraska with an inverted trough across much of the
Southeastern states through the Ohio Valley. The warm and moist
environment extends northward to around the Ohio River with a sharp
cut off in dew points and instability north of there. A stark cut
off in SBCAPE also exists at the northern extent of the moist
airmass from southern MO eastward towards SE Kentucky. The latest
ACARS sounding at KIND depicts a more stable airmass across Central
Indiana with weak lapse rates through much of the column. Steeper
lapse rates were noted in the boundary layer under 1 km agl, however
expect the surface to cool and stabilize overnight.

Latest satellite and radar imagery show a cluster of showers and
thunderstorms associated with a weak MCV pushing into Southern
Illinois. These systems tend to ride instability/moisture gradients,
especially in weakly forced environments with little steering flow.
With the tightest moisture and instability gradient extending from
southern MO, south of the Ohio River towards SE Kentucky, expect
this complex to follow that similar path. Short term rapid refresh
does show precipitation from this system still making it into
Indiana by sunrise, with the best chance of rainfall south of the I-
70 corridor. Currently thinking the short term models may have a
poor handle on this system and may bring rainfall too far north,
considering the probable track of this cluster track further south
along the instability gradient. Therefore started the trend of
lowering the northern extent of PoPs tomorrow morning. Still think
the southern half of the forecast area could get rain during the
morning hours, but will have to watch the track and northern extent
of this cluster of rain and storms closely. Not too concerned with
thunder potential as soundings show a very stable column. Best
chance for any thunder would be closer to the Ohio River and in SW
Indiana.

&&

.Short Term...(This evening through Tuesday)
Issued at 220 PM EDT Mon May 15 2023

A convection-induced midlevel low and MCV over the Ozarks will move
east-northeastward toward the area tonight enhancing ascent within a
fairly moist environment. Rain is expected to expand across roughly
the southern half of Indiana in the predawn hours, and should shift
east with the midlevel perturbation. In its wake, a few showers are
possible but the bulk of the ascent will be on its eastern flank.

The warm core nature of this feature is expected to result in poor
lapse rates with any meaningful instability to support thunder
closer to the Ohio River and southward. We have therefore removed
thunder for almost all of our area. HREF mean QPF should have a good
handle on rainfall amounts, which should range from around or just
above 0.50" across the southernmost portion of the area, to around
0.10" up to the I-70 corridor, and few hundredths of an inch north
of Indy metro.

We lowered temperatures tomorrow where precipitation duration should
be the longest with lingering stratus across southeast/east-central
portions of the area.

&&

.Long Term...(Tuesday night through Monday)
Issued at 220 PM EDT Mon May 15 2023

A low-predictability synoptic pattern is expected for roughly the
second half of the long term forecast period. Our current forecast
has a broader time window for rain Friday into Saturday than will
probably actually occur, due to model differences with timing of the
next shortwave trough. We will narrow that time window once ensemble
spread decreases. Overall, weather impacts do appear to be minimal.
See details on model uncertainty and range of scenarios below.

Wednesday and Thursday:

Near normal temperatures and drier continental air mass will be
nudged further into Indiana. We should be dry enough for clear
conditions, although high level moisture plume within northwesterly
flow may reach Indiana Wednesday night into Thursday providing some
cirrus.

Friday and Saturday:

The ECMWF/EPS-weighted cluster lags the GFS/GEFS-weighted cluster
with progression of the next shortwave trough through Indiana. Even
within each camp, there is significant ensemble spread, so
predictability is low and we have no choice but to keep a fairly
broad time window for precipitation Friday into Saturday. However,
the character of the forcing suggests about a 6-9 hour window for
the majority of the precipitation somewhere in the Friday afternoon
to Saturday afternoon window. Moisture should return in at least
modest quality in a narrow band ahead of DCVA/frontal forcing, but
steeper midlevel lapse rates may hold north of the area thus
limiting a broader CAPE profile. This doesn`t appear to be a
particularly favorable pattern for intense/severe convection, as of
now.

Sunday and Monday:

High confidence on post-frontal continental air mass during this
period, with uncertainties on onset due to modeling differences with
the progression of the above system as described above. Near to
slightly below normal temperatures and low humidity are expected.

Days 8-14:

Early indications are generally quiescent synoptic pattern with
below normal zonal wind anomalies and above normal midlevel heights
at higher latitudes. There will probably be smaller embedded waves
providing minor precipitation events, but in general this period
looks to bring us near to slightly above normal temperatures and
below normal precipitation.

&&

.Aviation...(00Z TAF Issuance)
Issued at 729 PM EDT Mon May 15 2023

Impacts:

* Rain Tuesday morning

* MVFR ceilings expected across southern Indiana (including KBMG)
  Tuesday morning

* Variable wind directions expected tonight, but speeds should
  remain light

Discussion:

VFR conditions persist through the evening hours ahead of the next
chance for rainfall around sunrise Tuesday morning. Another round of
rain will start in the predawn hours Tuesday and exit by midday.
Accompanying MVFR ceilings should be confined to southern Indiana,
including KBMG, and may improve during the afternoon. Otherwise VFR
conditions will prevail.

Forecast confidence is average in all but wind direction. Weak flow
may not be uniform and well-modeled; therefore periods of variable
wind direction can be expected with speeds mainly less than 6 kts.
The TAF shows the most likely wind direction. The greatest chance of
variable direction will be through early Tuesday morning.
Thereafter, more reliable northerly or northwesterly winds are
expected.


&&

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

$$

Update...CM
Short Term...BRB
Long Term...BRB
Aviation...CM