312
FXUS63 KGID 141202
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
702 AM CDT Fri Jun 14 2024

.KEY MESSAGES...

- While mainly spotty showers/sprinkles and probably a few (most
  likely) non-severe storms will be possible during the day
  today, MUCH HIGHER chances for thunderstorms (some probably
  severe...especially west) will arrive later this evening-
  overnight in the form of a larger-scale complex.

- Although of less certainty than tonight`s storm chances, most
  of our coverage area (CWA) is under a Marginal to Slight Risk
  (level 1-2 of 5) for severe storms Saturday. This risk (IF it
  materializes) would appear to mainly favor our
  central/eastern counties and mainly 5 PM-Midnight (earlier
  than tonight`s round).

- At least for now, we are calling for a brief break in rain
  chances centered on Sunday daytime, but thereafter, a parade
  of mostly-still-highly-uncertain, daily/nightly chances return
  to various parts of area, with the overall highest chances
  (PoPs) up to 50% currently focused Tues night-Wed.

- Temperature-wise: confidence is high that especially today
  through Tuesday will feature above normal/average readings,
  with Sunday-Monday currently looking like the overall-hottest
  days with highs well into the 90s most areas and heat index
  readings near-to-slightly above 100 (but at least for now
  slightly short of our 105+ Advisory criteria).

- Very warm LOW temps in the 70s most areas both Sun night and
  Mon night COULD at least approach record-warm values for June
  17-18.

- Temperature uncertainty really grows by Wed-Thurs, with our
  official forecast calling for a bit of a cool-down into the
  70s-mid 80s, but some model data suggesting this is NOT a
  "sure thing"

&&

.DISCUSSION...
Issued at 519 AM CDT Fri Jun 14 2024

Quick "admin note" up front:
It`s this forecaster`s first of several nights on, and from a
"first impressions" perspective:

1) This is a "messy" upcoming weather pattern when it comes to
the parade of rain/thunderstorm chances that currently litter
every single day/night forecast period except Sunday daytime.
More than usual, it is highly recommended to try not taking
these chances/PoPs anything close to literally no more than 1-2
days in advance.

2) Although at least a slight cool-down is at least POSSIBLE by
Wed-Thurs, at least slightly above normal heat will clearly be
the other main story through the next several days...as we
continue flipping the switch to "summer mode" after several
weeks of overall-mild/temperature conditions that defined our
spring/early summer season up until a few days ago.


-- PRIMARY CHANGES TO THIS 7-DAY FORECAST PACKAGE VERSUS THE
 PREVIOUS ONE (issued Thurs afternoon):

- Technically, the overall-biggest/most noticeable change was a
  low-confidence one, as high temps for Wednesday were brought
  down 5-8 degrees, now very tentatively aimed mid 70s-low 80s
  most places.


-- 7-DAY FORECAST OVERVIEW/HIGHLIGHTS):

- CURRENT/RECENT WEATHER SCENE AS OF 430 AM:
Although it hasn`t quite arrived yet, an area of isolated to
scattered rain showers and a few embedded thunderstorms look to
be developing eastward into our far western zones over the next
few hours, driven by subtle, somewhat "sneaky" mid level
convergence likely rooted up in the 800-700 millibar layer. Out
ahead of this incoming activity, skies have overall averaged
mostly clear overnight most areas. In the big picture of the
mid-upper levels, water vapor satellite imagery and short term
model data confirm that our flow aloft is out of the west-
northwest, as we reside north of an upper ridge axis centered
over the Southern High Plains, and still well-downstream from a
shortwave trough heading east across western AZ. At the
surface, the cold front that tracked southward across our CWA
yesterday and divided seasonably warm (north) from downright hot
(south) has settled into southern KS. In the wake of this
front, much drier air with dewpoints well down into the upper
40s-mid 50s range reside across our CWA, and low temps are on
track to bottom out somewhere in the 60s most areas, but as cool
as upper 50s far north, to as warm as around 70 far southeast.
Early-AM breezes are generally 5-10 MPH out of the northeast.


- TODAY-EARLY EVENING (through around sunset):
While MOST areas will likely be dry MOST of the time, this is a
a classic case where it is almost impossible to guarantee that
is stays totally dry the entire time, as persistent mid-level
theta-e advection will almost assuredly continue to spark
generally northwest-southeast oriented bands or splotches of at
least sprinkles/light showers, and probably a few embedded and
largely weak thunderstorms (due to them being elevated above
capped-off lower-level instability). As a result, have blanketed
the entire CWA with at least a 20% shower/thunderstorm chance
and/or sprinkle possibility through much of the day. High temps
carry at least modest uncertainty, as at least a few degrees
will depend on whether skies average more partly cloudy or
perhaps trend more toward mostly cloudy with time. For now kept
them similar to previous forecast with mid 80s most Neb zones,
and upper 80s to around 90 more common near/south of the state
line. Winds today will trend more southeasterly with time and
become modestly-breezy...sustained 10-15+ MPH/gusts 15-25 MPH.

- LATER THIS EVENING-OVERNIGHT:
This has been long-advertised as one of our better rain chances
in a while, and overall that still looks to be on track, but
perhaps/probably at the expense of at least a limited severe
storm threat. In short, upper forcing will be on the increase as
the shortwave trough currently over AZ gradually ejects into the
Central High Plains, while a southerly low level jet develops
out ahead of it. The net result should be a fairly large-scale
complex of storms (perhaps with a well-defined linear leading
edge) that is expected to arrive in our western zones around
9-10 PM, reach central counties roughly Midnight, and then
gradually vacate our eastern zones by roughly 4 AM. Severe-
weather wise, this is not a "slam dunk" setup, as there is the
potential that convection could "lose steam" as it tracks
farther east into our area (for one thing deep layer shear is
only modestly strong at 30-40KT). However, especially our
western counties (where SPC has the Slight Risk focused) could
see a few-hours window of opportunity for 60-70 MPH wind gusts,
with a lesser threat of hail probably only to around quarter
size, and an even lesser threat (albeit non-zero) of a brief
QLCS tornado if things come together just right. While localized
higher/lower amounts are always probable with convection,
official WPC QPF is calling for most of our CWA to pick up
somewhere between 0.50-1.00", which is not expected to pose much
of a flooding threat (beyond very short-term/localized)...given
that all of the sudden these last 6 days have been very dry
(and hotter) across the vast majority of our CWA. Temp- wise,
lows tonight aimed mid-upper 60s most areas.


- SATURDAY-SAT NIGHT:
Over the course of the daytime-evening hours, the larger scale
upper trough will gradually track across the heart of the
Central Plains. With this upper forcing in place, at least
spotty showers/a few weak storms just cannot be ruled out
through much of the day (although MOST places should be dry).
The overall-biggest question mark and concern is: will at least
a few strong to severe storms try flaring up mainly within our
central/eastern zones at some point between 5 PM-Midnight?
Higher-res models offer mixed messages on this, with the often-
aggressive NAMNest more supportive of this possibility than the
latest HRRR. At least from a conditional threat perspective
though, cannot argue much with SPC assigning roughly the
southeastern 2/3rds of our CWA a Slight Risk. In other
departments Saturday, assuming that daytime convection is held
to a relative minimum, it is expected to turn fairly breezy from
the south (gusts at least 20-30 MPH), which would give temps a
generally 2-5 degree boost over today, with highs aimed upper
80s-low 90s most Neb zones and low-mid 90s in KS.

Once any possible storms vacate our eastern zones late Sat
evening-overnight, it should be a dry early Sun AM with lows
holding up mainly mid-upper 60s.


- SUNDAY-SUN NIGHT:
Officially, we have kept the daytime forecast block a dry one,
which seems plausible given that warm mid level temps should
"cap" us off pretty well, although the possible presence of a
sharp, west-east surface front near our northern edges (up
around Ord/Greeley) will bear watching. Otherwise, the main
story will be another crank up in the heat, with another 3-5
degree boost in high temps with most areas well into the 90s
(flirting with 100 especially KS). Heat index readings will be
widespread upper 90s to as high as around 103 (especially in
KS), but at least for now this would fall just short of Advisory
criteria.

Sunday evening-overnight, odds favor the majority of convection
in our region remaining north of our CWA, but officially we have
as high as 30-40% chances/PoPs returning to mainly our northern
half. Overnight low temps are forecast to hold well up into the
low-mid 70s most areas (placing possible June 17 records in
jeopardy at Grand Island/Hastings).


- MON-MON NIGHT:
Under continued southwesterly flow aloft, odds strongly favor
the vast majority of our CWA remaining dry under very warm mid-
level temps. However, given strong heating and weak/subtle
disturbances in the flow, at least spotty storms cannot be ruled
out (especially in our north). However, barring a big change,
this looks like a hot and fairly windy day (especially by June
standards), with highs similar to Sunday (solidly 90s most
areas), but with southerly gusts perhaps as high as 30-40 MPH as
surface low pressure deepens to our west. At least spotty heat
index of 100+ again possible, especially in KS.


- TUES-THURS:
Simply taking a brief overview of these last three days of our
7-day, the bottom line is that uncertainty starts growing
(especially temperature-wise, and especially Wed-Thurs). If the
latest ECMWF/GFS agree on anything, it`s that our next larger
scale/synoptic cold front should sag southward into our region
Tues night into Wednesday, promoting our next "best chance"
rain/thunderstorm chances beyond the one tonight. Depending on
frontal timing, Tuesday could be another rather hot day
(currently depicted to be a few degrees cooler than Mon). Then,
especially by early-summer standards, Wed and Thurs carry above-
average temperature uncertainty, with some models/guidance as
cool as 70s and others are warm as 90s. This will depend mainly
on whether the front heads back north or stalls out over our
area, and also to some degree how much convection/outflow is
around. A whole lot yet to sort out in this time range.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 701 AM CDT Fri Jun 14 2024

For KGRI/KEAR Airports:
- General overview:
High confidence in VFR ceiling/visibility through at least the
first 12-15 hours of the period, but with a good chance for a
potentially large-scale (and possibly severe?) complex of
thunderstorms arriving very late in the period Friday evening,
things could trend sub-VFR very quickly both during the
convection and also afterwards as a low ceiling possibly
materializes. Speaking of rain/storms, there could be
spotty/brief passing showers/weak thunderstorms perhaps as early
as around 15Z, but these chances are far less of a "sure thing"
than the aforementioned later ones. Aside from any
gusty/erratic thunderstorm outflow, winds do not look to be a
significant factor, with most of the period featuring an east-
southeasterly direction, with especially afternoon gusts likely
into the 20-25KT range.

- Ceiling/visibility/rainfall/thunderstorm details:
High confidence in VFR ceiling/visibility through at least the
first 12-15 hours, with any potential ceiling most likely at-
or-above 8K ft. until late evening when a larger-scale line or
complex of storms is expected to arrive from the west. Once this
occurs, sub-VFR ceiling/visibility both could clearly come into
play.

As for shower/thunderstorm potential, honestly can only really
"guarantee" dry weather these first 2-3 hours. As early as
roughly 15Z, there are hints that at least spotty, high-based
showers/weaker thunderstorms could develop overhead, and have
hinted at this potential with a basic "vicinity shower" (VCSH)
group 15-00Z. Odds more strongly favor higher-confidence dry
conditions 00-03Z before the main complex of thunderstorms
arrive. Latest higher-res models have been consistent in
showing the MAIN window of opportunity for thunderstorms 03-08Z
KEAR/04-09Z KGRI. Given this activity is still out in the latter
half of the TAF period, will only maintain generic "vicinity
thunderstorm" (VCTS) for now, but this activity could easily
produce at least small hail, heavy rain and wind gusts into the
30-50KT range depending on how it evolves (obviously later TAFs
can introduce TEMPO/prevailing thunderstorm groups).

Mainly in the wake of departing convection, various
models/guidance are fairly insistent that a low ceiling (MVFR
and perhaps IFR) could settle in, but forecaster experience has
proven many times that this is not a "sure thing". However,
given the signal is present, will introduce an MVFR ceiling 08Z
KEAR/09Z KGRI.

- Winds:
Aside from any possible much stronger/erratic direction winds
caused by thunderstorms mainly later in the period, winds should
not be a significant issue. The lightest winds of the period are
right away these first few hours (under 10KT out of the east-
northeast), but a steadier east-southeast wind will pick up
during the day, with especially this afternoon featuring
sustained speeds around 15KT/gusts 20-25KT. Winds overnight will
obviously be heavily modulated by convective outflow etc.

&&

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

&&

$$

DISCUSSION...Pfannkuch
AVIATION...Pfannkuch