Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/15/23

Area Forecast Discussion

National Weather Service Indianapolis IN

 641 PM EDT Fri Apr 14 2023

...Updated Aviation Discussion...

.Short Term...(This Evening through Saturday)
Issued at 259 PM EDT Fri Apr 14 2023

* Well above normal temperatures persist
* Slight chance of showers through this evening

Current satellite imagery this afternoon reveals scattered clouds
across Central Indiana due to an upper level low pushing northeast
through the Tennessee Valley. Southeasterly moisture advection today
was running around 5 kts stronger in the mid levels than what
guidance was previously showing. Diffluence aloft combined with weak
PVA has placed the region in an area of enhanced lift which has
aided in the development of mid and upper clouds and isolated
showers through the day. Best forcing for ascent and moisture
advection has now pushed off to the east leading to clouds breaking
up and showers diminishing in coverage. Afternoon heating has since
resulted in low level destabilization, steeper low level lapse
rates, and the development of scattered cumulus clouds. Potential is
there for an isolated shower or even thunderstorm through the
evening hours, with the best chances across Eastern Indiana where
the best forcing for ascent is. Latest ACARS soundings from the
region show SBCAPE upwards of 900 j/kg, so a thunderstorm or two is
possible; however weak forcing for ascent should keep convection
isolated. A dry pocket between 1-3km agl may allow for a brief
strong wind threat to mix down to the surface under a thunderstorm
as well. This entire system has also aided in bringing surface dew
points up 20+ degrees since yesterday, giving a very muggy feel to
the air. Expect humid conditions to persist into tomorrow ahead of a
cold front as warm, moist air continues to advect northward into the
Ohio Valley.

For tonight, the upper level low tracks east of the region with
drying conditions expected on the backside of it. A few high clouds
may linger into the overnight hours but expect any shower activity
to end due to NVA and sinking air on the backside of that system.
Light southerly winds and much higher dew points will keep overnight
lows from falling much tonight. Expect lows in the mid to upper 50s
across the region, well above average for mid April.

.Saturday...

Strong ridging aloft and warm air advection ahead of an approaching
trough will keep summer-like conditions around for one more day
across Indiana. Latest RAP soundings and cross sectional views show
steep low level lapse rates and deep mixing from strong boundary
layer heating. Low level jet is rather weak, less than 15 kts during
the day, so any winds that do mix down to the surface should be
strong. Expect highs to approach the 80 degree mark once again for
most locations. Dew points will remain in the 50s so expect a more
muggy feel to the air tomorrow as well. Main forcing for ascent
remains west of the region so not concerned with thunderstorms
developing during the day in Central Indiana. Best forcing for
precipitation arrives late Saturday night as the main cold front
approaches. More information on the rain and thunderstorm threat
below in the long term section.

&&

.Long Term...(Saturday Night through Friday)
Issued at 259 PM EDT Fri Apr 14 2023

An active second half of the weekend is expected as a strengthening
upper low lifts into the Great Lakes by Sunday. This will bring
convective chances late Saturday night into Sunday with at least a
non-zero risk for a few severe storms along a cold front late Sunday
morning through mid afternoon. In the wake of the frontal passage
will come a nasty reminder that we can still see raw and chilly
weather in mid April. Cool temperatures are expected for early next
week before quickly reverting back to a warmer and quieter regime
before rain chances increase towards the end of the 7 day period.

Model guidance continues to slow the arrival of the upper low and
associated surface wave and cold front as energy aloft from the
northern stream dives into the upper trough and carves out a
strengthening upper low with a negative tilt by Sunday. Initially
Saturday evening with the surface low and front back near the
Mississippi River...any convection ongoing will be well to the west
of central Indiana. Showers and storms will diminish in intensity
and likely in coverage as well as they move into the forecast area
after midnight. While some weak instability lingers...primary
forcing at 850mb and in the mid levels will largely remain displaced
to our west. Expect showers with embedded thunder but any threat for
severe convection looks minimal. Storms could produce localized
heavy rainfall with PWATS rising above 1.25 inches but widespread
heavier rain rates are not anticipated

The better risk for any storms to reach severe levels now is likely
to focus along and immediately ahead of the cold front as it tacks
across the forecast area late morning through mid afternoon Sunday.
Forcing aloft will strengthen on Sunday with diffluence in the mid
and upper levels noted and an increase in boundary layer flow.
While instability levels remain relatively low...model soundings do
support a brief increase in speed and directional shear along with 0-
1km SRH values above 100 m2/s2. This could be enough to generate a
few stronger cells with damaging winds being the primary concern.
Any risk for severe will shift east into Ohio by mid afternoon with
the front.

Once the front passes...much cooler air will advect into the Ohio
Valley as a broad cold pool expands into the area in association
with the upper low and surface wave over the western Great Lakes.
These features will move slowly east through late Monday...heavily
influencing weather across the forecast area into Monday night. n
Raw...brisk and windy conditions will be the rule Sunday afternoon
through Monday providing a much different feel to the air than what
we have enjoyed over the last week or so. The lower levels will
become cold enough by late Sunday night to enable flurries or light
snow to mix in with rain...primarily focused across northern
portions of the forecast area. This will linger on Monday with even
potential for graupel to mix in with showers as well as steep lapse
rates will be present through the boundary layer.

Skies will remain cloudy with slow clearing from the southwest
Monday as the upper low moves away. The potential for some sun
Monday afternoon may enable temps to warm into the low and mid 50s
across the southwest half of the area...with 40s expected elsewhere.
Lows both Monday and Tuesday night will dip into the 30s across much
of the area...but frost is likely to be largely mitigated by
continued breezy winds. There is an outside chance at frost over
northern counties Tuesday night as winds lighten.

After the early week cool temperatures...high pressure and ridging
aloft will enable a quick warmup with highs back into the 70s by
Wednesday. A frontal boundary will move into the lower Great Lakes
by Thursday and Friday with the potential for scattered convection
across the region.

&&

.Aviation...(00Z TAF Issuance)
Issued at 641 PM EDT Fri Apr 14 2023

Impacts:

* Isolated convection will diminish before 03Z.

* Low chances for fog where rain fell today

Discussion:

Scattered showers and isolated thunderstorms will diminish early in
the period as instability wanes with loss of sunshine. Will monitor
for any need of a VC mention at issuance time.

VFR conditions are expected through the period outside of any
convection early. Cumulus will diminish this evening leaving behind
some mid and high clouds, which will persist into Saturday.

There is a low chance for some fog/stratus late tonight near KBMG
where rain fell today, with light winds expected. However, at the
moment, believe odds are too low to mention.

&&

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

$$

Short Term...CM
Long Term...Ryan
Aviation...50



...Update to aviation forecast discussion...



 .DISCUSSION...
Issued at 235 PM CDT Fri Apr 14 2023

Key Messages:

- Severe storms possible this evening & tonight

- Extreme fire danger Sunday

Detailed Discussion:

Severe weather continues to look possible across especially
northern Kansas this evening. Surface moisture return has been
about as expected, with dewpoints generally reaching the low 50s
throughout the eastern half of the state. Temperatures continue to
warm in the 850-700 hPa layer as the EML advects east (evident on
ACARS soundings and low-level water vapor imagery), while boundary
layer destabilization also occurs, indicated by the isolated cu
development in the open warm sector. Pretty striking gravity waves
have emanated out of western KS and into northern OK, possibly
assisting quicker and slightly deeper cu development across
northwest OK early this afternoon. A little elevated convection
has developed along a weak pre-frontal trough/wind shift in
northeast KS this morning, but is not expected to amount to much
more than perhaps a few sprinkles. Given increasing inhibition
across the region, it is likely some increased forcing from the
dryline and/or approaching cold front will be necessary for deep
convective initiation to occur.

The dryline, currently just east of a line from Pratt to Russell,
continues to tighten and mix just slightly eastward, but isn`t
expected to make much progress eastward. Any isolated storms that
form along this boundary would mainly develop west and southwest
of the forecast area, but could progress into central KS by 6 or 7
this evening. Deep layer shear of 25-30 kts that`s cross boundary
could allow initial storm mode to be isolated supercells, with
both significant hail and wind as primary threats. High storm
bases and lots of DCAPE should lead to strong downdrafts and
preclude any tornado risk.

The cold front/inverted trough axis, currently stretching from
Ulysses to the north side of the Omaha metro, will make initially
slow progress as surface low pressure in central KS transitions
northeast. This boundary could also serve as a focus for
convective initiation, especially later this evening as the upper
trough provides additional lift. Storm motion will be more along-
boundary with this feature, encouraging more upscale growth and
linear segments. Hail could be an initial threat, but the primary
hazard with these outflow-driven segments will be damaging
straight line winds. As the dryline starts to retreat this
evening, the cold front will become the primary focus for
additional storm initiation, and northern to northeast KS the most
likely area for a continued severe risk.

Storms will likely separate from the cold front as outflow drives
them east and southeast, indicated pretty consistently by storm
modes among HREF members. This should decrease severe threat with
time as storms gust out and new updrafts struggle to develop in a
worked-over environment. Therefore, most likely window for a
severe weather threat is 7-10 PM. Widely scattered showers and
embedded thunderstorms may linger behind the initial push of
stronger storms tonight, but coverage will limit widespread rain
amounts to less than a half inch in most locations. Frontal
passage will finally occur in the morning hours Saturday, but
some wrap around showers and perhaps even a flake or two of non-
accumulating snow will linger into Saturday night.

Fire danger Sunday will depend a bit on how much wetting rain
occurs on Friday and Saturday, but atmospheric conditions look
very supportive of extreme fire danger throughout the area. RH is
progged to drop into the teens to near 20 percent, and northwest
winds will gust to 40+ mph in the afternoon. Sunday should also be
monitored for a possible wind advisory given recent trends with
the depth and location of the low over the Northern Plains/Great
Lakes region. Winds should lessen on Monday, hopefully limiting
the window for wildfire danger to just the Sunday afternoon and
early evening period.

After a chilly and dreary Saturday, temperatures will warm into
next week, returning to above-normal values by Tuesday. Shower and
thunderstorm chances return Tuesday as well, and linger on-and-off
through the remainder of the forecast period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 632 PM CDT Fri Apr 14 2023

A messy TAF period is expected with a couple of rounds of rain and
storms. Storms south of KTOP/KFOE could impact terminals within
the next hour or two. Another round of storms moves through later
this evening and may linger behind a cold front through the early
morning hours of Saturday. Additional showers and storms are expected
during the late morning into the afternoon before shifting east of
the area near the end of the TAF period. Winds switch to the north-
northwest behind the front and become gusty through the day Saturday.
MVFR or possibly IFR cigs also build in behind the front.

&&

.FIRE WEATHER...
Issued at 235 PM CDT Fri Apr 14 2023

Very high fire danger continues this afternoon, although relative
humidity should start increasing by early evening as moisture
surges northward into the area. Attention then turns to Sunday,
when minimum afternoon RH in the 15 to 20 percent range is
expected, along with gusty northwest winds reaching sustained
speeds of 25 to 30 mph and gusts reach 40+ mph. Recent rainfall
will at least prevent any ongoing fires from lingering into
Sunday, but fuels will dry out quickly, and should still burn
efficiently.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

DISCUSSION...Laflin
AVIATION...Flanagan
FIRE WEATHER...Laflin