834
FXUS63 KGID 170614
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
114 AM CDT Mon Jun 17 2024

...Aviation Update...

.KEY MESSAGES...

- Highs in the 90s on Monday with heat index values near 100 and gusty
  southerly winds of 25-35mph and gusts to 45mph.

- Strong to severe thunderstorms possible Monday evening across western
  portions of the area.

- Record warm low temperatures are possible on Monday for Grand
  Island and Hastings: See climate section for more detail.

- The highest chance for rainfall comes Tuesday night into
  Wednesday as a cold front stalls across southern portions of
  the area, with heavy rainfall possible.

&&

.DISCUSSION...
Issued at 334 PM CDT Sun Jun 16 2024

This afternoon and Overnight...

Temperatures this afternoon have climbed into the 90s across most of
the area, with heat index values approaching the low 100s. A weak
front has kept northwestern portions of the area slightly cooler,
with in the 80s.

There continues to be large uncertainty with the potential
thunderstorm development this afternoon. The HRRR has remained
consistent over the past several model runs, keeping the environment
capped, with warm air aloft inhibiting thunderstorm development.
Other CAMs and HREF members indicate weaker capping, with
thunderstorms developing along the front in the McCook vicinity and
moving east into the area. Among the models with thunderstorms this
afternoon, there additional uncertainty to how widespread these
storms will be (due to capping). Some models indicate that only
isolated thunderstorms will be possible, with others showing a more
widespread cluster moving into the area. Areas in the SPC slight
risk have the highest chances to see thunderstorms this afternoon-
evening.

Strong to severe thunderstorms are possible with thunderstorms that
occur this afternoon/evening. Robust instability with SBCAPE values
around 4000 J/Kg will allow for storms to quickly become severe. 0-6
Km shear will be weak (30Kts or less) which will help to limit how
strong storms are able to get. The main concerns with thunderstorms
this afternoon will be for large hail and damaging wind gusts.

As the low level jet develops this evening/overnight, thunderstorm
chances will shift to northern portions of the area. While the
heaviest concentration thunderstorms will be north of the forecast
area, scattered thunderstorms will be possible for areas mainly
along and north of I-80.


Monday...

Any lingering thunderstorms across northern portions of the area
will come to an end Monday morning. Highs will climb into the 90s,
with dewpoints in the upper 60s. Heat index values will be similar
to today, as they peak around 100 degrees. Winds will be gusty
throughout the day on Monday, with sustained winds of 25-35mph and
gusts to 45mph.

Scattered thunderstorms that develop along the western High Plains
will move into western portions of the area during the evening hours
on Monday. While instability will be plentiful, with SBCAPE values of
3000-3500 J/Kg, storms will be entering an environment with
decreasing shear. Storms are expected to weaken as they move
northeast across the area, with rain coming to an end Monday night.
The main concern for these storms will be for damaging wind gusts,
though some large hail is possible if storms remain more discrete.

Tuesday and Wednesday...

A cold front will move across the area during the daytime hours on
Tuesday, bringing cooler weather to the area. Scattered showers and
thunderstorms are expected to develop along and behind the cold
front during the afternoon and evening hours. The cold front will
stall just to the southeast of the forecast area Tuesday night, with
storms becoming more widespread along and north of the front. PWAT
values 150% of normal along with the potential for training storms
will lead to an increased risk for flooding. The entire area is in a
WPC slight risk for excessive rainfall due to this potential for
flooding. Areas that receive multiple rounds of thunderstorms could
see rainfall in excess of 2". Modest instability and weak shear
could allow for a few strong to severe thunderstorms as well.

Showers and thunderstorms will continue through the day on Wednesday
and into Wednesday night. Precipitation is expected to become more
scattered over time. The potential for flooding will continue into
Wednesday, but will likely depend on precipitation Tuesday night.
Temperatures will be cooler on Wednesday with persistent cloud
coverage and precipitation. Highs will range from the mid 60s
(northwest) to the low 80s (southeast).

Thursday Through The Weekend...

The upper level trough over the Rockies which brought precipitation
on Tuesday and Wednesday will gradually lift north and begin to exit
the area Thursday night into Friday. Highs on Thursday and Friday
will return to the 80s along with breezy southerly winds. Scattered
precipitation chances continue on Thursday and Friday. Warmer
weather continues into the weekend with highs in the mid to upper
80s. Scattered thunderstorm chances continue into the weekend,
mainly during the evening-overnight hours.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 114 AM CDT Mon Jun 17 2024

For KGRI/KEAR Airports:
- General overview:
Although there are small chances (mainly 10-20%) for a few
passing showers/thunderstorms both at some point this morning
and perhaps again Monday evening, odds favor an overall-dry
period and confidence is overall very high in VFR
ceiling/visibility throughout. That leaves moderately-strong
southerly surface winds and even stronger low-level winds as by
far the main concern (including two separate low level wind
shear/LLWS groups).

- Ceiling/visibility/rain and thunderstorm potential details:
Particularly between 10-17Z, there is a chance that a few
showers/likely weak thunderstorms will pass through, but with
overall-probability of occurrence and expected impacts fairly
low, will only include a generic "vicinity shower" (VCSH)
through part of this time frame for now. Although a few to
scattered lower-level VFR clouds are possible at times,
confidence is overall-high in VFR ceiling/visibility throughout.

- Winds:
- Surface winds:
By mid-June standards, this will be a fairly windy period.
Assuming no unexpected influences from convective outflow
boundaries, speeds will prevail southerly throughout, with
sustained speeds commonly 15-25KT/gusts 25-35KT.

- Low level wind shear (LLWS):
There are two separate periods of TAF-worthy LLWS during the
period, even despite the surface winds being plenty breezy
themselves.

1) Right away this morning through around 14Z, southwesterly
winds within roughly the lowest 2K ft. AGL will top out around
50KT, promoting roughly 30-35KT of shear magnitude between the
surface and this level.

2) This evening (02Z onward), if anything an even stronger
southerly low level jet will kick in, with speeds within roughly
the lowest 1,500 ft. AGL accelerating to around 55KT, causing
fairly strong shear magnitude at least 35-40KT between the
surface and this level.

&&

.CLIMATE...
Issued at 550 AM CDT Sun Jun 16 2024

-- Regarding possible RECORD WARM LOW TEMPS on Monday
(June 17th):

Both tonight-Monday morning and Monday night-Tues morning are
expected to remain very warm, with most of our CWA not dropping
any cooler than the low-mid 70s. As a result, calendar day
(midnight-to-midnight) records for warmest low temperature
COULD be threatened at Grand Island/Hastings airports (the 2
sites for which we issue formal Record Event Reports/RERs).

Any such records are most likely to be threatened on Monday,
because a cold front arriving Tuesday is currently expected to
drop temps safely below record territory by midnight that night.

- GRAND ISLAND
                   Record Warm Low      Latest Forecast
Monday June 17th     74 (1906)               71


- HASTINGS
                   Record Warm Low      Latest Forecast
Monday June 17th  72 (2020/2014/1946)        72


NOTE/REMINDER: in order for a new record warm low/minimum
temperature to become official it has to "survive" the entire
24-hour calendar day (in other words, it is not always based
solely on the early-AM low temp).

&&

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

&&

$$

DISCUSSION...Davis
AVIATION...Pfannkuch
CLIMATE...Pfannkuch