NWS Hastings, NE wrote its last area forecast discussion before the first event at Jun 24, 6:27 PM CST, 3 hours 27 minutes earlier.
Area forecast discussion, Jun 24, 6:27 PM CST, 3 hours 27 minutes before
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
727 PM CDT Fri Jun 24 2022
...Short Term and Aviation Update...
.UPDATE...
Issued at 726 PM CDT Fri Jun 24 2022
Some of our latest thoughts regarding thunderstorm/severe storm
trends:
- Thus far, strong capping (evidenced by 700 millibar temps in the
12-14C range) has held any "true" afternoon convection at bay
(other than a few showers/very weak storms earlier mainly east
of Hwy 281 in Nebraska). Even the attempts at high-based storms
barely south-southwest of our CWA (Hays KS area) have struggled
mightily).
- As fairly well captured by higher-res models (CAMS) such as 18Z
NAMNest/22Z HRRR, the main "action" at this time is still well
to our west over western NE up into SD along the greater low
level convergence along a north-south oriented surface trough.
- So, the million dollar question: what are WE in for tonight?
Well, to be perfectly honest and reiterate/build upon the
excellent previous afternoon discussion below...there are still
some question marks. Putting as much faith in the CAMS as we
dare, odds are fairly good that our entire CWA should largely
remain storm-free through around 10 PM.
- However, anytime beyond (roughly) 10 PM and lasting until
(roughly) 2-3 AM we begin a window of opportunity for POSSIBLE
severe storms, which if were to occur would primarily be a
function of storms to our west merging into at least a broken
(if not more solid) line, developing a decent cold pool and
charging eastward into our CWA. This would mainly foster a wind
threat, although any embedded supercell structure would perhaps
foster a large hail threat as well. It's possible some more
isolated activity or a separate storm complex could try going up
ahead of anything moving in from the west, but given such warm
air aloft overhead and also the nose of the low level jet aiming
more into northeast NE versus our area, this possibility would
appear more favored over the OAX CWA.
- IN SUMMARY: It "appears" that strong capping will most likely
"save" us from any true isolated daylight severe storm threat,
but especially the 10PM-3AM time frame bears close watching for
a possible severe storm threat in our CWA. As mentioned in the
main discussion below however, nothing appears to be a "sure
thing" tonight and we'll continue to closely monitor things as
they evolve.
&&
.DISCUSSION...(This evening through Friday)
Issued at 415 PM CDT Fri Jun 24 2022
Main forecast concerns are chances for strong/severe thunderstorms
within the next 12 hours.
Summary:
Tricky thunderstorm forecast in the short term has several
ingredients are in place for severe weather, but not all. This
results in a highly conditional and generally uncertain forecast
in the first 12 hours, or so. Generally speaking, an isolated
strong to severe thunderstorm could develop from the Tri-Cities
north and east at any time this afternoon and evening...but the
"best" chances for thunderstorms and severe weather will probably
hold off until after sunset when a line of thunderstorms MAY move
in from the west. Even this scenario, however, is uncertain as a
layer of warm air aloft (capping) could prevent most thunderstorm
activity, or at least the really strong stuff. A cold front will
move through the area Saturday AM and bring us refreshing, breezy
NW winds, drier air, and cooler temperatures for the weekend.
Temperatures will steadily warm through next week, likely
culminating with at least near-triple digit heat in about a week.
Early indications are for cooler, but potentially active, pattern
for the 4th of July weekend.
Forecast Details:
Low confidence forecast through tonight due to mixed hi-res
guidance, somewhat messy sfc/mid level pattern, and warm mid level
temperatures amidst weak forcing. Starting off aloft...area
remains in "dirty" SW upper flow with obvious connection to a
monsoonal moisture plume. A weakening, positively tilted shortwave
trough stretches from W Dakotas SW to the Four Corners, with
another stronger trough nosing S into MT. Appears the primary
upper forcing will remain across the N Plains, but much like
yesterday, at least one or two weak perturbations are likely to
work through the area through tonight. These waves could be strong
enough to support convection as early as this aftn/eve...as we're
currently seeing from Doniphan to York...but capping in the H8 to
H7 layer (as evident by 12-14C temps at H7 per latest SPC
mesoanalysis) may very well be strong enough to prevent sfc-based
activity altogether. However, IF a storm can breach the cap and
become sfc based, the aftn/eve environment would support strong-
severe convection with strong instability (MLCAPE 2-3K+ J/kg) and
modest shear (0-6km bulk shear 25-30kt, supported by significant
veering in lowest 3km) in place. Dew points in the low 70s amidst
backed low level flow could, in theory, also produce an iso
tornado. Again though, the eve tstm potential is VERY conditional
and more than likely not going to pan out.
Somewhat more likely, though still conditional and uncertain, is
that convection develops and organizes along sfc trough over W
Neb., then gradually shifts E this eve and overnight. The degree
to which this activity can make it into our CWA will likely depend
on cold pool development to our W this eve. IF a strong cold pool
develops, then this activity will likely have a significant
reservoir of strong MUCAPE to work with with temps in the 80s and
dew points in the 70s. This scenario would be similar to earlier
runs of HRRR and 12Z/18Z runs of NAMNest. However, if activity
fails to organize a strong cold pool, then diurnal cooling and
aforementioned warm mid level temps could prevent activity from
even making it into the area altogether...similar to recent runs
of the HRRR. So as mentioned above, run to run and model to model
consistency amongst the hi-res guidance is lacking and
contributing to low confidence. The main severe threat overnight
would probably be damaging wind gusts if a line does indeed form,
but large hail will also be possible, esp. with any convection
that remains more cellular.
The actual cold front will enter NW portions of the CWA around
sunrise and quickly progress SE through the morning. The primary
instability axis should set up S/SE of the area by Sat aftn, but
at least minor elevated instability may persist further N along
the elevated frontal slope that could support some iso to scat
weak convection roughly along and S of the NE/KS state line
through mid to late aftn. Severe weather is not expected on Sat in
our area. NW winds will be pretty brzy immediately along and
behind the front, with gusts 30-35 MPH possible for esp. south
central Nebraska. The brzy NW winds will usher much drier, more
comfortable air into the region, as well as cooler air. Highs on
Sat will range from near 80F north, to mid 80s S, but lows Sat
night will fall well into the 50s, for most, and perhaps even
upper 40s far N/W. Sun looks to be the coolest of this forecast
with highs only in the 70s, and lows Sun night again in the 50s.
Mild, dry conditions, light winds, and plentiful sunshine should
make Sun a very pleasant day for those looking for a break from
hot/humid, and even Mon will be fairly nice, though a bit warmer.
Temps become notably warmer on Tue with most areas returning to
the 90s, before even hotter temps in the upper 90s to low 100s
move in for Wed-Thu as upper ridging at least briefly amplifies
over the central/southern Rockies and Plains. Early indications
are that the ridge will break down and upper flow will turn zonal,
or even NWrly, atop a stalling front in the low-levels somewhere
over the Central Plains. Where exactly the front stalls out
remains uncertain, but there's a chance it could be over or very
close to the forecast area, which would result in cooler and
fairly active conditions for the 4th of July holiday weekend.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 726 PM CDT Fri Jun 24 2022
General overview:
A tricky TAF period with regard to several elements including:
thunderstorm potential (maybe severe?), timing of wind shifts and
also possible low ceilings. Overall though, the majority of the
period should prevail VFR ceiling/visibility and be precipitation-
free. Read on for more element-by-element details.
Thunderstorm potential:
Although we are drawing closer to POSSIBLE thunderstorms, there is
still some decent uncertainty in how things evolve. Do not have
the confidence for any TEMPO groups yet (let alone prevailing
thunder), but have confined a generic "vicinity thunderstorm"
(VCTS) mention to what appears to be the most favored 4-hour time
frames (04-08Z KEAR/06-10Z KGRI). IF storms roll in during this
time, they could be severe, with gusts around 50KT being the main
threat, along with brief heavy rain and a lesser threat of large
hail. Cannot rule out at least a few showers/weaker storms beyond
these most favored times, but the VCTS period should capture the
main time frame of concern.
Ceiling/visibility:
Although confidence is very high in VFR for these first several
hours this evening and also late in the period Saturday afternoon,
the early morning through late morning hours are a big question
mark, as at least a few sets of usually-reliable guidance are
strongly suggesting perhaps several hours of MVFR ceiling (with
brief IFR not out of the question). However, convection sometimes
has a way of "messing up" low cloud forecasts this time of year,
so opted against buying in to low ceilings wholesale just yet.
However, did introduce prevailing MVFR ceiling for anywhere from
3-7 hours on Saturday morning. Stay tuned for plenty of
adjustments here in later forecasts (possibly significant?).
Winds:
Compared to other TAF elements, this one carries higher confidence
(at least outside of thunderstorm influences). Not accounting for
any possible thunderstorm-enhanced outflow, these first several
hours will feature fairly fairly light breezes, gradually shifting
from east-southeasterly to north-northeasterly. Although passing
storms could subsequently result in a period of highly variable
direction/speed, a fairly strong cold front by summer standards
will push through around sunrise, solidly switching winds to
northerly through the entire latter half of the period (Saturday
daytime). Sustained speeds will commonly average up to around
20KT/gusts 25-30KT before speeds start to slacken late afternoon.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
UPDATE...Pfannkuch
DISCUSSION...Thies
AVIATION...Pfannkuch