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000
FXUS63 KGID 230546
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1246 AM CDT Tue Apr 23 2024

.KEY MESSAGES...

- Can`t rule out a few isolated/scattered showers and
  thunderstorms this evening into tonight across mainly the
  southern half of the forecast area. Not anticipating any
  severe weather, but some storms could be strong with small
  hail and gusty winds.

- Near-critical fire weather conditions (potentially spots of
  brief critical conditions) are expected across much of the
  forecast area Tuesday afternoon, with relative humidity values
  falling into the low-mid 20s and wind gusts around 30 MPH.

- A more active weather pattern looks to develop Thursday and
  continue on through the weekend. Severe weather is possible
  Thursday evening/night, then potentially again Friday/Friday
  evening depending on the timing of upper level and surface
  features.

&&

.UPDATE...
Issued at 833 PM CDT Mon Apr 22 2024

-- Comments solely focused on overnight thunderstorm potential
 (still looks like a few could be on the stronger side):

- Potential still exists for isolated to scattered, elevated
  (very high-based) storms overnight almost anywhere in our
  coverage area/CWA (except perhaps least likely far northern
  counties), with the last few HRRR runs starting to hone in on
  the the most favored zone might reside roughly 30 miles
  either side of the I-80 corridor (including the Tri Cities).

- The most favored time frame for storms is 10 PM-4 AM
  (instability really fades away/shifts east of our CWA beyond
  then).

- This is a classic case of modest elevated instability
  (primarily based up around 700 millibars or 10K ft. above the
  surface) being released as parcels are forced upward by
  strengthening southwesterly flow into an elevated frontal zone
  (and mainly a few counties north of the well-defined surface
  front currently settling southward through our far south-
  southeast zones.

- Based on a look at instability/shear progs from latest RAP13
  (both plan-view and forecast soundings), and as supported by
  HRRR modeled radar reflectivity, there is certainly a chance
  that a few storms could be on the stronger side (perhaps even
  TRY to become marginally-severe?). Most unstable CAPE (MUCAPE)
  values are progged to peak as high as 400-800 J/kg, in the
  presence of strong effective deep-layer wind shear at least
  40-50KT. Even with this limited instability, could easily
  envision a few storms producing hail to at least penny/nickel
  size, with a lower (but non-zero) threat of gusty winds at
  least 40-50 MPH making it to the surface.

- IF progged elevated instability/CAPE were only a few hundred
  J/kg higher (and for sure if 500 J/kg higher), this setup
  almost certainly been a would a candidate for an official SPC
  Marginal Risk (level 1 of 5) mainly for marginally-severe
  hail. As we see it here from the local level, we support the
  official overnight outlook remaining as "general thunder", but
  we could easily foresee a few stronger cores warranting
  Special Weather Statements (SPS), and the latest 21Z SREF
  "calibrated severe thunderstorm" parameter suggests a non-zero
  chance that a few storms could even try breaching severe
  levels (again mainly from a quarter to ping pong ball size
  hail perspective).

&&

.DISCUSSION...
Issued at 441 PM CDT Mon Apr 22 2024

Currently through tonight...

Upper air and satellite data showing generally zonal flow in
place across the region this afternoon, as we sit on the
southern side of low pressure spinning over the ND/Canada
border. Elsewhere across the CONUS, broad ridging remains near
the West Coast...another low pressure system is making its way
off the coast of VA/SC. The main impact from the system to our
north up to this point has been the accompanying surface cold
front pushing south...which at 3PM is roughly along a Silver
Creek to Beaver City line. Ahead of the front, southwesterly
winds gusting anywhere from 35-45 MPH have been common, even a
few gusts were closer to 50 MPH. Behind the front, winds switch
to the north-northwest, with gusts closer to 25-30 MPH. Overall
temperatures have worked out pretty well, a quicker passage of
the front would have made for a wider gradient across the
area...as it sits at 3 PM, north-northwest areas are right
around 70 degrees, with right around 80 in the south-southeast.

This evening into tonight, this cold front will continue to
gradually sink south into north central Kansas...and models
still showing the potential for a few isolated/scattered
showers and storms to develop along it. While there are some
minor differences with the exact time things develop and the
overall coverage, models are in pretty good agreement keeping
things focused south of Highway 6 and into north central Kansas.
Models continue to show meager instability through this
evening, but deep layer shear is strong...so while severe
weather is not anticipated, can`t totally rule out some strong
storms with small hail/gusty winds. A few models hint at some
showers try to reach further north later this evening and on, so
kept some low end precipitation chances in the forecast. Any
activity that develops is expected to taper off/move out by
sunrise Tuesday. The surface front loses its initial upper level
push and stalls out across far southern portions of our
forecast area late this evening...with winds area-wide
diminishing...before getting another push and reinforcing those
northerly winds as we get into that 09-12Z time frame. Skies are
expected to be partly-mostly cloudy, and even with winds
diminishing/remaining northerly, overnight lows are forecast to
be in the low-mid 40s.

Tuesday and Wednesday...

Dry conditions are expected as we get into the daytime hours on
Tuesday, with upper level flow a bit more northwesterly as the
system currently to our north digs south into the Midwest and
that broad ridging slides east into the Rockies. Breezy
northerly winds are expected area-wide, with gusts 25-35 MPH
expected, then diminishing late in the afternoon as surface high
pressure sinks south into the region. Expecting partly cloudy
skies...with cooler highs ranging from the mid 60s in the north
to low-mid 70s in the south. Tuesday continues to have the
potential for widespread near- critical (potentially a few brief
spots of critical?) conditions...though cooler, dewpoints look
to be in the 20s, resulting in relative humidities dropping into
the low-mid 20 percent range. Didn`t issue any fire wx
headline, but any change up in temp or down in dewpoint may
result in needing one.

Precipitation chances return to the forecast late Tuesday night
and continue on into Wednesday...but overall confidence
remains on the lower side, so chances are still in the 20-30
percent range. Models showing a fairly subtle mid-level
disturbance sliding through the region and forecast chances are
broad in nature, but better chances look to be focused across
the the SSW half of the area and more so totally south. Little
instability is expected to be in place, so thunder continues to
be left out at this point. At the surface, high pressure sliding
east and low pressure organizing over the Rockies bring a
switch in winds back to the south for Wednesday...and breezy
conditions are expected, especially across the western half of
the area. Forecast highs are in the mid-upper 60s, but if there
does end up being more widespread light precipitation through
the day, wouldn`t be surprised to see that trend down a bit.

Thursday and on...

By Wednesday evening, models are in pretty good agreement
showing an upper level low pressure system moving onto the
central/southern CA coast...with this system being our main
weather driver in the Thursday-Friday time frame. Late Wednesday
night-Thursday morning, though the main low is well west,
precipitation chances start increasing as a lead shortwave
disturbance moves in from the southwest and warm air/moisture
advection picks up. Forecast preciptiation chances increasing
into the 50-70 percent range during the daytime hours, but the
better chances look to be during the evening/overnight hours,
when the main upper level emerges out onto the Plains...aided by
a 45-50ish kt low-level jet. Though not in the more
typical/ideal afternoon/early evening time for severe
weather...this evening/overnight activity continues to have the
potential to be strong/severe, with models showing MUCAPE values
exceeding 1500 j/kg and deeper layer shear around 35-40 kts.
The better instability looks to be focused across the southern
half of the forecast area...which is included in the SPC Day 4
15 percent area (slight risk). Outside of the storm chances,
Thursday is expected to have gusty south-southeasterly winds,
with gusts of 30- 40 MPH not out of the question. Confidence in
highs isn`t high...current forecast is in the mid 60s-near 70
for most locations.

How Friday ends up panning out is still a little
uncertain...driven by questions with how Thursday/Thursday
night evolves and the overall timing of the upper low itself.
Looking at deterministic models...at 12Z Friday the main upper
low could be over the Sandhills of Nebraska or be further
southwest over northeastern CO. A slower/more southern track
would keep better preciptiation chances around the forecast area
longer...but would also be slower to clear the main surface
features out, keeping severe weather as potentially more of an
issue...mainly for areas east of Highway 14. The quicker/more
northern track dries us out and pushes the threat further east
by mid-late afternoon. No matter the timing, gusty southwesterly
winds ahead of the front will give way to gusty west- northwest
winds as the front passes through. Highs are forecast in the
70s for most locations...but like Thursday`s highs, confidence
in on the lower side.

Forward to the upcoming weekend, late Friday night into the
daytime hours on Saturday still looking to bring a brief break
in the action between the departing Thu/Fri system and another
system expected to move in Sat night. Models show this next
upper level closed low pressure system coming out of the Rockies
and onto the Plains a little further south than the Thu/Fri
system...but still brings another chance for widespread
precipitation to the area late Saturday night into the day on
Sunday. Being several days out yet, hard to have a high degree
of confidence.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1245 AM CDT Tue Apr 23 2024

Band of mid level clds with bases 10-15k ft and iso shwrs/storms
will continue for a few more hrs before shifting E/SE. Kept VCTS
at GRI, but removed from EAR as vast majority should remain to
their E. Expect decr clds near/after sunrise such that most of
the daytime hours will be at least mostly clear. NErly winds now
will bec gusty out of the N/NW after sunrise once again.
Sustained winds 15-20kt and gusts 25-30kt are expected from mid
morning through mid to late aftn. Winds will decr to 5-9kt and
turn slightly to N/NNE around sunset. Confidence: High.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.

&&

$$

UPDATE...Pfannkuch
DISCUSSION...ADP
AVIATION...Thies