494
FXUS63 KGID 140604
AFDGID

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

...Aviation Update...

.KEY MESSAGES...

- Better chances (50-80%) for storms arrive late Friday evening
  and continues overnight. Large hail and damaging wind are the
  main concerns. There is a SLIGHT Risk (level 2 of 5) mainly
  W/SW of the Tri-Cities, and a MARGINAL Risk elsewhere.

- Rest of the forecast appears somewhat active with nearly daily
  shower/storm chances, generally highest (40-50%) mid to late
  next week.

- After a brief/minor cool down for Friday, temperatures
  moderate by Saturday then become hot again (90s to low 100s)
  Sunday and Monday. Expect mainly 80s-90s next week.

&&

.DISCUSSION...
Issued at 337 PM CDT Thu Jun 13 2024

Rather interesting day out there today from a sensible weather
perspective, as conditions range from mild, dry and breezy
across central NE, to quite hot and steamy in northern KS. In
fact, ODX is in the low 80s, has a sub-60 dew point, and NE
winds a refreshing 20 MPH, gusting 30 MPH. On the flip (S) side
of the front, areas near Beloit are in the low 100s with dew
points in the upper 60s to lower 70s. At least these areas have
a breeze, as well, but out of the S. Sfc cold front has made to,
or even just S of, the NE/KS state line as of 3PM, and should
continue to sink southward this evening. Recent satellite data
shows new CU/TCU development along a WSW to ENE axis - roughly
near the I-70 corridor. This appears to be ahead of the actual
cold front, likely along some sort of pre-frontal trough/wind
shift. Hi-res guidance has been pretty consistent in that the
main convective development would indeed be just S of the area
this aftn/eve, and this seems to be what`s playing out. Have
maintained some low end PoPs in our far S (20-30%) in the event
the storms grow large enough to clip these counties before
moving SE. There have been some very small, iso and elevated
cells develop in Lincoln County this afternoon, along what appears
to be the lowest 100mb mixing ratio gradient. Hi- res guidance
has not handled this activity well, and kept out of the official
forecast at this time given recent weakening. Model soundings
suggest a narrow corridor of weak instability based above the
primary capping inversion, but don`t think this will amount to
much given primary upper support shifting away from the area.

Current cold front looks to stall out and become more diffuse by
late overnight, so the primary MUCAPE axis never really clears
the area. In fact, models show weak warm air advection returning
to W/SW zones by dawn Fri AM, so wouldn`t be shocked to see some
ACCAS and a few "sunrise surprise" storms W/SW of the Tri-
Cities. By in large, however, think much of the daytime hrs Fri
will remain dry thanks to negligible 500mb height changes and
very warm mid level air evidenced by 700mb temps around 12-15C.
SE winds should limit the mixing depth and high end potential
for temps, but low to mid 60s dew points will return to at least
the far W and SW. These higher dew points will also serve as a
good proxy of the primary instability axis for storms that
develop over the higher terrain Fri aftn to work with as they
shift E/NE Friday eve. Latest thinking is that activity will
approach far W/SW zones as an MCS around mid to late evening,
probably on the strong to severe side. Main threat should be
high wind, though some hail could still be possible too.
Activity should gradually weaken with time and E/NE extent Fri
night as activity "outruns" the aforementioned instability axis.
IF this instability axis lines up further NE, or can be advected
NE Fri eve, then the severe threat could extend/expand in
time/space. One other thing to watch, though is low confidence
at this time, is potential for pockets of iso heavy rain. There
could be some backbuilding on the SW/S flank of said MCS, and
PWATS will be elevated in the 1.5-1.7" range. How prevalent the
backbuilding/training actually is is uncertain. Models generally
dry us out by dawn Sat AM.

Forecast details beyond 48hrs become fairly murky, as they often
are in the summer months, due to effects of convection, the
weakest of upper level disturbances, and potential boundary
placement. The NAM suggests mostly uncapped moderate to strong
instability late Sat aftn and into the eve, along with modest
deep layer shear of 25-35kt. Main question is forcing and upper
level support as some of the guidance show a filling shortwave
over the N Plains, shifting away from the area by 21Z, whereas
other guidance lingers at least weak height falls later and
further SW. SREF guidance suggests the best instability axis may
lag the better shear, which makes sense given the overall setup.
The Marginal Risk on the SPC Day 3 Convective Outlook seems
reasonable enough to cover a low-confidence, non-zero chance for
severe weather Sat PM...though would expect this to be refined
and/or shifted over the coming updates. SREF calibrated guidance
would support slightly higher probs over E/NE zones vs W/SW.

Should get into a drier and hotter pattern for a couple days
Sun-Mon, with some areas along/S of the state line likely
nearing or exceeding triple digits for highs once again. May be
pushing Heat Advisory conditions for these areas one or both
days. Would think H7 temps in excess of 15C would keep us
capped off and dry, esp. Mon, but stranger things have happened.
More coherent upper level troughing and push of lower mid level
temps/heights should arrive around the middle of next week and
perhaps linger in the region through the end of the week. This
could make for a pattern of repeated rounds of convection and
more mild high temps for the second half of next week. Multiple
ensemble platforms support this idea by showing above normal
precip anomalies and above normal temperature anomalies (likely
driven by warm overnight lows) through the region next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 104 AM CDT Fri Jun 14 2024

For KGRI/KEAR Airports:
- General overview:
High confidence in VFR ceiling/visibility through the vast
majority of the period, but with a good chance for a potentially
large-scale (and possibly severe?) complex or line of
thunderstorms arriving very late in the period Friday evening,
things could trend sub-VFR very quickly. Speaking of
rain/storms, there could be spotty/brief passing showers/weak
thunderstorms perhaps as early as around 14Z, 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 the vast
majority of the period, 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 6-8 hours at most. As early
as roughly 14Z, 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 14-18Z. Between 18-03z, odds favor mainly dry conditions,
but cannot rule out some continued spotty shower/weaker
thunderstorm activity here and there. Finally, very late in the
period (mainly after 03Z KEAR/04Z KGRI), latest higher-res
models are increasingly-suggestive of a larger scale
complex/line of storms arriving from the west. Given this
activity is out toward the end of this TAF period, will only
introduce a 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.

- Winds:
Aside from any possible much stronger/erratic direction winds
caused by thunderstorms mainly late in the period, winds should
not be a significant issue. The lightest winds of the period are
right away early this morning (under 10KT out of the 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.

&&

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

&&

$$

DISCUSSION...Thies
AVIATION...Pfannkuch