598
FXUS63 KGID 120037
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
737 PM CDT Tue Jun 11 2024

...Aviation, Short Term and Key Messages Update...

.KEY MESSAGES...

- Very spotty/sneaky isolated storms into this evening mainly
  along the I-80/Hwy 6 corridor counties (see UPDATE section
  below).

- Temperatures heat up on Wednesday with highs in the 90s to
  possibly around 100 degrees. Heat index values between 100 to
  105 degrees are expected on Thursday across portions of north
  central Kansas.

- Wednesday late afternoon-evening roughly the northeast 1/4 of
  our coverage area is under a Marginal Risk of severe, BUT a
  strengthening cap COULD keep us storm-free (a conditional
  threat).

- Storm chances (15% to around 25%) increase Thursday evening
  and night along the leading edge of a cold front. Some of
  these storms may be strong to severe.

- Rain and storm chances continue Friday through early next week
  with the highest chances (20% to near 70%) Friday night.

&&

.UPDATE...
Issued at 736 PM CDT Tue Jun 11 2024

-- Regarding very isolated convection over the last few hours
 and likely next few hours:

- Although fortunately not reaching severe thresholds (largely
  due to fairly weak deep layer shear and poor mid level lapse
  rates), we have nonetheless had to do a few somewhat
  unexpected forecast/Hazardous Weather Outlook updates already
  since late afternoon to account for very "sneaky", spotty
  storms developing along a weak warm front slowly lifting north
  through our central coverage area (CWA). Instability is
  decent, with mixed-layer CAPE into the 1000-2000 J/kg range.

- Through sunset, expect the majority of this VERY SPOTTY
  activity to focus within counties along the I-80/Hwy 6
  corridors, with small hail/gusty winds not out of the
  question, but truly severe storms fairly unlikely.

- Current expectation is for ongoing activity to fade away with
  loss of diurnal heating and largely be gone by 10 PM, but with
  at least a modest southwesterly low level jet gradually
  increasing through the night, would not be surprised to see
  additional activity flare up in our northern zones later in
  the night and/or Wednesday AM (will take a closer look at this
  a bit later for another possible update to rain/storm
  chances).

 &&

.DISCUSSION...
Issued at 342 PM CDT Tue Jun 11 2024

Today and tonight...

Light and mostly variable winds along with mostly sunny to partly
cloudy skies are across south central and central Nebraska and north
central Kansas. High temperatures today are expected to mostly be in
the mid to upper 80s. Winds will increase out of the south tonight
with clear to mostly clear skies. Low temperatures tonight will be
in the 60s.

Wednesday through Saturday night...

An upper level ridge will be centered over Arizona and New Mexico on
Wednesday. Winds will increase out of the south to southwest
Wednesday afternoon as a surface low to the north of the area
strengthens. Temperatures Wednesday afternoon are expected to heat
up into the 90s with some places possibly reaching the triple
digits. The areas most likely to reach the triple digits will be
south and west of a line from Lexington to Holdrege to Phillipsburg
and Stockton. Some areas in central Nebraska may have heat index
values that are around or at 100 degrees. A cold front will begin
moving into Nebraska Wednesday night. Low temperatures Wednesday
night across south central and central Nebraska and north central
Kansas will be in the mid 60s to mid 70s.

The front will continue moving through the area on Thursday with
breezy northeasterly winds. Temperatures will be cooler from the
previous day with highs ranging from the mid 80s to around 100
degrees. Heat index values across portions of north central Kansas
may get over 100 degrees but will likely stay under 105 degrees. Low
temperatures Thursday night will range from the upper 50s to near 70
degrees. Rain and storm chances (15% to around 25%) will increase
Thursday evening and night along the leading edge of the front. Some
of these storms may become strong to severe.

Upper ridging will be over the southern and central Plains on Friday
with upper disturbances moving over Nebraska and Kansas. These
disturbances will allow for continued chances (15% to around 30%) of
showers and thunderstorms on Friday. Winds will be gusty out of the
southeast. Temperatures will continue cooling from the previous day
with highs mostly in the 80s. Upper disturbances will move over the
area Friday night with chances (20% to near 70%) of showers and
thunderstorms increasing. Low temperatures Friday night will be in
the low 60s to low 70s. An upper trough will continue over the
southern and central Plains on Saturday. This will result in
continued chances (15% to near 40%) of showers and thunderstorms.
High temperatures on Saturday will range from the mid 80s to mid
90s. Low temperatures Saturday night will be similar to those from
the previous night.

Sunday through Monday night...

A cold front will approach or begin passing through the area on
Sunday. This uncertainty in frontal position will impact high
temperatures on Sunday. At this time, am expecting high temperatures
on Sunday to range from the upper 80s to the upper 90s. Rain and
storms are expected along and behind the front. High temperatures on
Monday are expected to be in the low 80s to mid 90s with rain and
storm chances (15% to near 25%). Low temperatures early next week
will generally be in the low 60s to mid 70s.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 736 PM CDT Tue Jun 11 2024

For KGRI/KEAR Airports:
- General overview:
Confidence is high in VFR ceiling/visibility and "probably"
rain/thunderstorm-free conditions. That being said, especially
KGRI could flirt with a very rogue thunderstorm right away this
evening. Overall though, winds will be the primary aviation
concern through the period, starting with a modest (not overly-
strong) round of low level wind shear (LLWS) late tonight into
Wed AM, and then fairly strong south-southwesterly surface winds
(at least by June standards) during the day Wednesday.

- Ceiling/visibility/thunderstorm details:
Right out of the gate this evening, have gone with a few hours
of "vicinity thunderstorm" (VCTS) at KGRI as an isolated/rogue
storm could easily pass within 5 miles. Beyond this though, odds
strongly favor the remainder of the period being dry/storm-free,
although very late Wednesday afternoon (mainly after 22Z there
is a very low (10% or less) chance of additional isolated
convection, so this will need monitored. Any possible ceiling
during the period should be brief and well up into VFR range.

- Wind details:
- Surface winds:
The very lightest winds of the period are right away these first
6 hours (except for possible/brief thunderstorm outflow at
KGRI), with speeds mainly under 8KT from the southeast. Then, as
the night wears on, speeds will modestly increase as direction
trends more southerly with sustained speeds up around 10KT
(gusts possibly closer to 15KT). However, winds will definitely
kick up another gear during the day Wednesday, as especially
16-21Z will feature several hours of sustained southwesterly
speeds around 20KT/gusts 25-30KT before an approaching surface
trough allows speeds to start diminishing mainly after 21Z.

- Low level wind shear (LLWS):
Although admittedly only marginally-worthy of formal TAF
inclusion, opted to introduce a LLWS group 06-13Z as winds
within the lowest 1K ft. AGL will accelerate to around 36KT from
the south-southwest, resulting in as much as 25-30KT of shear
magnitude between the surface and this level.

&&

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

&&

$$

UPDATE...Pfannkuch
DISCUSSION...Schuldt
AVIATION...Pfannkuch