Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/21/23

Area Forecast Discussion

National Weather Service Indianapolis IN

 1021 PM EDT Mon Mar 20 2023

.Forecast Update...
Issued at 1021 PM EDT Mon Mar 20 2023

Little changes made to the short term forecast with this evening`s
update. High pressure remains southeast of the region and continues
to shift eastward as a dynamic system develops in the Plains.

While increasing high clouds tonight and into the day tomorrow may
limit daytime heating, still expecting mixing to occur in the lowest
3-4 kft. Latest IND ACARS soundings still show a very dry profile
from the surface up to the tropopause. Guidance tends to saturate
the atmosphere too fast when antecedent conditions are very dry.
Therefore, lowered dew point and RH values tonight through tomorrow
evening. On top of that, mixing tomorrow during peak heating of the
day will likely bring even drier air aloft down to the surface,
further slowing down the rate of moisture return northward and
keeping conditions drier than what guidance suggests. RH values may
once again dip down into the 20s for a few hours Tuesday afternoon,
resulting in a slightly elevated fire risk once again. Afternoon
wind gusts up to 20-25 mph are also expected during peak heating of
the day due to stronger winds mixing down to the surface from aloft.

The rest of the forecast appears on track with light rain arriving
from the south and west late Tuesday evening.

&&

.Short Term...(This evening through Tuesday)
Issued at 255 PM EDT Mon Mar 20 2023

* Warmer temperatures into Tuesday
* Rain chances arrive later Tuesday afternoon

Quiet conditions continue across central Indiana this afternoon,
with high pressure in control. A few high clouds were moving across
the area, with more upstream.

As some weak upper energy interacts with a front to the northwest,
an increase in high clouds will occur for the rest of the afternoon,
especially north closer to the front. With some mixing occurring,
wind gusts to 30 mph will continue at times.

Tonight, high clouds will increase across the entire area ahead of
the next system. Southerly winds will continue with high pressure
off to the southeast and the cold front to the northwest. The clouds
and the winds will help keep low temperatures in the upper 20s to
lower 30s.

On Tuesday, southwest winds will continue with some gusts around 20
mph. An upper wave will approach from the west during the day, and
mid and high clouds will thicken as this wave approaches. Low levels
will remain dry.

Isentropic lift will increase late Tuesday afternoon, mainly west.
This lift will interact with the available moisture and produce some
patchy light rain late in the period. Will have some chance PoPs
across roughly the southwest half of the area, with highest PoPs in
the far west.

Warm advection will continue on Tuesday, but increasing cloud cover
will keep temperatures in the lower to middle 50s. Minimum humidity
will dip to around 30 percent. If clouds are thinner than expected
allowing warmer temperatures, humidity levels could be even lower.
This would cause an increase in fire danger, but fuels are still
moist enough to not warrant any kind of statement at this time. Will
continue to monitor.

&&

.Long Term...(Tuesday night through Monday)
Issued at 255 PM EDT Mon Mar 20 2023

*Light rain Tuesday night to Wednesday night
*Heavy rain and flooding Thursday into Friday

Tuesday Night Through Wednesday Night.

An active weather pattern will be in place for much of the week with
multiple rounds of rain expected.  By Tuesday night the first round
of precipitation will be arriving with a weak and fairly subtle
upper level wave being pushed forward by a strong 50kt LLJ at 850mb.
Much of the forcing for this system is being driven by isentropic
lift along the LLJ, but soundings show only modest moisture
availability which will limit rain amounts to generally at or less
than 1/4 of an inch.

Rain will then stick around into Wednesday with temperatures
continuing to warm as more robust WAA arrives.  It`ll also be a
little breezy during the daytime hours with southerly wind gusts to
25 mph at times.  Skies will remain cloudy or mostly cloudy from
Tuesday morning through the rest of the work week, so take advantage
of the sun today if you can.

Thursday Through Monday.

Many of the details regarding the heavy rain event for Thursday into
Friday remain uncertain, but what isn`t uncertain is that a heavy
rain event will be impacting the Ohio Valley with significant rain
accumulations expected across at least portions of central Indiana.
Synoptically the system doesn`t look very impressive with only a
weak upper level trough associated with this rain, but digging a
little deeper shows very strong moisture advection into a narrow
axis of convergence with robust lift. Timing of a front associated
with this system remains uncertain with models varying by 6-12 hours
on the frontal passage.

Any severe weather risk would require the frontal passage to be late
Thursday vs earlier in the day.  Current thoughts are that the
overall severe threat is fairly low with only minimal instability to
go along with the more favorable shear. For impacts of the rain and
flooding along with additional possible outcomes of the rain, see
the Hydro discussion below.

The aforementioned trough will continue to deepen as it moves into
the Upper Midwest which will allow for additional rain Friday into
Friday night.  Some models are hinting that snow may mix in early
Saturday, but without more robust post frontal CAA, it looks to be
too warm for any snow mixing in. Generally mild temperatures and
quiet weather then are expected for Sunday before another weaker
rain producing system arrives late Monday.

&&

.Aviation...(00Z TAF Issuance)
Issued at 740 PM EDT Mon Mar 20 2023

Impacts:

* Wind gusts around 15-20 kts Tuesday afternoon

Discussion:

High pressure located south of the region is responsible for VFR
conditions tonight and tomorrow across Central Indiana. Mixing shuts
off right after sunset this evening resulting in gusty winds
diminishing below 10 kts at all sites tonight. Expect winds to
increase again after 15z tomorrow as low level mixing brings down
stronger winds aloft. Expect gusts in the 15-20 kt range tomorrow
afternoon, but persisting into the tomorrow night period as a front
approaches from the west. Despite increasing high clouds, VFR
conditions are expected to persist through 00z Wednesday.


&&

.Hydrology...
Issued at 255 PM EDT Mon Mar 20 2023

*Flooding likely Thursday night into the weekend

Potential for flooding arrives Thursday evening into the overnight
hours with very heavy rain expected in an axis along a frontal
boundary.  Current forecasts are showing that the axis will be
across south central Indiana with model ensembles hinting that a
slightly more southern track for where the axis of heavy rain may be
the final outcome. This far out though things remain fairly
uncertain. Rainfall amounts within the heavier axis may exceed 3
inches with widespread 1-2 inches outside of the heavier axis.

Heavy rain with the second portion of the event looks to set up
closer to the Tennessee Valley Friday into Friday night but if the
GFS solution which has it further north verifies, an additional 1-2
inches of rain is possible which may lead to more significant and
widespread flooding. MMEFS ensembles show that widespread minor
river flooding is likely with the potential for some moderate
flooding if the GFS solution of higher rain amounts is the final
outcome.  Either way, expect travel issues and flooded roads at
times.

&&

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

$$

Update...CM
Short Term...50
Long Term...White
Aviation...CM
Hydrology...White



Area Forecast Discussion

National Weather Service North Platte NE

 605 PM CDT Mon Mar 20 2023

...Aviation discussion...

.SYNOPSIS...
Issued at 420 PM CDT Mon Mar 20 2023

Key Messages:

- A warm front brings the threat of freezing rain and wintry mix
tonight into tomorrow, which could result in hazardous conditions.
Winter Weather Advisory in effect for much of the area.

- The next system arrives Wednesday into Thursday, which could bring
light accumulations of snow to northern Nebraska.

- Temperatures remain near or below normal for the next several
  days. (normal highs are generally in the mid 50s)

Synopsis:

Western Nebraska remains in quasi-zonal flow aloft as the primary
northern stream lies near the Canadian border and the subtropical
jet cuts across the Desert Southwest. A week upper low is moving
into the Inland Northwest, while an H7 low near the Black Hills
drags an elevated front or shortwave near northern CWA. At the
surface, a quasi-stationary front cuts right across the Sandhills,
roughly from KCDR to KLBF, then back toward KOMA. Temperatures as of
20z remain near freezing in the far north and have risen into the
mid 50s near and south of the front.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 420 PM CDT Mon Mar 20 2023

This evening and tonight... East/southeast upslope low level flow
continues on both sides of the surface boundary, resulting in modest
moisture advection. Expect surface dew points to rise from the lower
20s into the upper 20s by sunrise. Isentropic upglide is prevalent
at 280-290K along the front, which coincides with the increasing
moisture. Guidance suggests the boundary to lift north as a warm
front, anchored by the surface low near the Black Hills. Expect some
precip development as the low levels moisten and forcing increases,
although fog and/or drizzle may precede the activity. Forecast
soundings suggest a very shallow saturated layer to start before
further saturation occurs after sunrise. Capped PoP to schc or low
end chc through 12z. Did not mention fog in the official forecast
due to a brief window for optimal development and lower confidence
for placement. For min temps, stuck with the general model blend
which also lines up with the middle of the NBM envelope. Forecast
values range from the lower 20s in the far north to lower 30s far
southwest.

Tomorrow... A rather complex scenario is in store as the warm front
lifts into South Dakota during the morning, and a cold front is
quick on its heels, crossing the Sandhills during the afternoon.
Meanwhile, a mid-level shortwave brushes the northern Sandhills
later in the day. Increased PoP a bit along the Hwy 83 corridor to
account for the warm front passage and far north central for both
fronts and shortwave. Trended the PoP forecast toward the more
aggressive solutions (HREF, NAM), as there is quite a discrepancy in
coverage and overall potential for precip amongst the 20/12z model
suite. For instance, GFS and HRRR suggest very little recordable
moisture and keep it confined to far northern Neb. Did not feel
comfortable with the "optimistic" solutions due to the environmental
setup of a warm front passage in the wintertime. The current
forecast favors a rather quick-hitting round of precip during the
morning for western Neb and perhaps some lingering showers in the
afternoon for far north central. As for ptype, things could be a
mess. The thermal profile changes from very shallow and cold
saturation (freezing drizzle), to deeper moisture but with a warm
nose and cold surface (freezing rain or wintry mix), to deeper
moisture but entirely cold profile (snow), to drier but slightly
warmer air (rain/snow mix). Essentially, nearly all types are in
play for the heart of the forecast area from 6am-noon. With that in
mind, issued a Winter Weather Advisory. Do not expect much snow
accumulation due to marginal ground temps and very low SLR`s (1-
4:1), but am concerned about the potential for a glaze of ice. As
for the cold front, temp advection is delayed as an H85 thermal
ridge actually sets up on the leading edge. In all likelihood, the
cool front may merely act as a dry line. With negligible 24 hr H85
temp changes, highs should be fairly similar or slightly milder than
today. Winds may also gust over 30 mph behind the front in the
panhandle and northern Sandhills. When combined with the influx of
drier air, fire weather conditions may be locally elevated in the
panhandle.

Tomorrow night... A brief lull in activity is anticipated as the
cool front exits the CWA, high pressure settles in at the surface,
and flow aloft transitions to southwesterly. Weak cool air advection
begins with northerly flow at H85. Forecast lows range from the
upper teens far north to upper 20s far southwest.

.LONG TERM...(Wednesday through Monday)
Issued at 420 PM CDT Mon Mar 20 2023

The main forecast beyond tomorrow revolves around the next storm
system slated to affect western and north central Nebraska Wednesday
into Thursday. A lee side surface low spins up in eastern Colorado
later Wed and rides the NE/KS border through early Thu. The subtle
upper low approaches from the north during the same time, and the
main H3 jet noses right into the CWA. The jet may be particularly
intense with a streak of 140 kts. Currently, the most favorable
location for persistent precipitation and cold enough temps for snow
is Hwy 2 and north. The greatest potential for accumulating snow,
mainly on the order of 1 to 3 inches, lies closer to Hwy 20. Across
southwest Neb, the air may stay warm enough to keep precip as
rain/snow mix or all rain. The synoptic pattern remains unsettled
heading into the weekend as well, with low end PoP to round out the
forecast period. Highs should stay in the 40s or 50s the next
several days (or 30s far north), while lows stay in the 20s to
around 30.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 605 PM CDT Mon Mar 20 2023

VFR early, trending to IFR/LIFR towards daybreak with icing
possible.

Satellite and surface observations indicate generally mid/high clouds
across central and western Nebraska early this evening, and expect
this will remain the case until low clouds surge in from the east
late tonight. Expect IFR/LIFR due to low cigs and vsbys, with a
wintry mix of precipitation and a glaze of ice on aircraft surfaces
from just before daybreak through Tuesday morning. While precipitation
will diminish by early Tuesday afternoon, Do not expect significant
improvement in flight conditions until late Tuesday morning with
VFR conditions becoming established once again toward the end of
the valid period.

Winds may be a bit gusty at issuance but expect laminar conditions
to become established early with a light easterly surface wind
thorugh tonight. Winds veer around to the west late in the period
but look to remain 10kt or less.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 4 AM CDT /3 AM MDT/ to 4 PM CDT /3
PM MDT/ Tuesday for NEZ005-006-008-009-023>026-035>037-057-059-
094.

&&

$$

SYNOPSIS...Snively
SHORT TERM...Snively
LONG TERM...Snively
AVIATION...MBS