NWS Hastings, NE wrote its last area forecast discussion before the first event at May 30, 6:27 AM CST, 1 hour 3 minutes earlier. Its key messages:
Area forecast discussion, May 30, 6:27 AM CST, 1 hour 3 minutes before
Area Forecast Discussion
National Weather Service Hastings NE
727 AM CDT Thu May 30 2024
...Aviation Update...
.KEY MESSAGES...
- More active pattern expected for the rest of the week and
through early next week, though official forecast likely
sounds worse/wetter than what reality will be for most.
- Some of the thunderstorms may be strong to severe, at times,
but there currently aren't any strong indications for
organized and/or widespread severe weather.
- Rainfall amounts will be HIGHLY variable across the region, as
is typical for the warm season. Reasonable high end amounts
over the next 5 days (ensemble 90-95th percentile) are 3-5",
which could lead to isolated hydro concerns if that pans out.
- Temperatures will remain remarkably steady in the 70s-80s
(highs) and 50s-60s (lows) for most of the next 7-10 days,
though areas SW of the Tri-Cities may make a run into the low
90s at times Sun-Tue.
&&
.DISCUSSION...
Issued at 450 AM CDT Thu May 30 2024
Much more "messy", almost summer-like, upper pattern is
forecast to settle in for the next several days with shower and
thunderstorm chances for at least portions of the forecast area
essentially a daily/nightly occurrence. The pattern won't come
with the summer-like heat, however.
Today - Tonight:
Convection has largely played out as expected over the past 9-12
hours and is indeed scattered and fairly weak currently. Several
MCVs are evident in regional mosaic radar loops, and to some
extent surface observations, which will "muddy the waters" for
forecasting convective trends today. The most obvious MCV
locally is currently just NW of Kearney, but additional MCVs are
also noted in northern Neb. and central Kan. These will slowly
shift E throughout the morning and continue to provide weak
ascent for iso-scat new development within a generally uncapped,
weak elevate CAPE environment. Shear is also weak through at
least midday, so really not much of a severe risk this morning.
Assuming some subsidence behind departing MCVs allows for at
least a few hrs of mixed sunshine, should be able to develop
some moderate instability (1000-1500 J/kg MLCAPE) immediately
along and just ahead of the front by late aftn/early eve as low
levels gradually moisten on continued Srly flow. SREF deep layer
bulk shear increases to ~30kt this eve, but appears the
strongest mid-level flow will remain well post-frontal.
Nonetheless, this CAPE/shear parameter space will probably be
adequate for marginally severe hail and wind. Capping is weak
thanks to H7 temps of 8C or less, so would expect relatively
early development along the sfc convergence zone from near Ord
to Lexington around 20Z. Activity should move E and SE through
the evening, probably still on a scattered basis through 03Z.
Some uptick in coverage will be possible thereafter, either from
MCVs moving off the high plains, or from increasing low level
jet. This could keep the marginal severe threat going well into
the overnight. PWATs are forecast to pool around 1.5" along the
frontal zone this eve/overnight, so with complex storm mergers
and/or slow effective forward motions, could have some locally
heavy rainfall. General consensus of model data suggests areas
along and S of the state line would be most at risk for isolated
2-4" of rain in short amount of time. Rainfall amounts,
however, will be HIGHLY variable across the region with many
areas staying mostly dry. This looks to be general idea each of
the next several days - some see isolated heavy rain, many
others miss out completely.
Friday-Friday Night:
Lingering showers and thunderstorms in the morning should
gradually end/shift S-SE with the composite front/outflow
through the daytime hours as upper support becomes increasingly
meager. Can't rule out an iso pop-up storm anytime in the aftn
or eve thanks to uncapped moist BL, as evident by light and
spurious QPF in various model output. Also, EC has been
insistent that an MCS could clip areas SW of the Tri-Cities Fri
night, though confidence on this is low given weak 850mb flow.
Weekend:
Rain chances continue through the entire weekend, but definitely
don't want to give the impression that either day is a washout.
In fact, think most will stay dry through late aftn Sat as the
main risk locally should come from scattered storms that develop
in central Nebraska then move SE during the evening - perhaps in
the form of one or two MCSs. Belt of stronger deep layer shear
remains just off to the N, so think severe threat should be
fairly similar to today and mostly of the marginal variety.
Overnight convection should have more LLJ to work with. Kind of
a wash, rinse, repeat for Sunday in terms of expecting timing
and location of initial development. This round of activity
could have more organization/intensity with it, though, given
higher values of both instability and shear, as well as more
coherent shortwave trough and possibly a front. Confidence in
the higher CAPE/shear overlap occurring this far S is too low
for a formal outlook from the SPC, but something to monitor for
potential impacts to Sunday evening outdoor activities.
Next week:
Forecast confidence continues on the low side early week, at
least in terms of shower/thunderstorm details on Monday, thanks
to weak zonal flow and potential for one or more boundaries to
linger in the region from previous rounds of convection.
Ensembles have started to come into better agreement regarding a
stronger shortwave trough moving through the central/northern
Plains in the Tuesday-ish time frame - which would likely send
at least a moderately strong cold front through the region and
possibly bring an end to the frequent rain chances for a few
days. Ahead of this front, some areas could make a run at the
low 90s Sun-Tue, but otherwise much of the next 7-10 days look
to be mainly mid 70s to 80s for high temperatures. Fairly
seasonable for late May - early June.
&&
.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 727 AM CDT Thu May 30 2024
- General overview for KGRI/KEAR:
Although the majority of the period will likely feature VFR
ceiling/visibility and rain/thunderstorm-free conditions,
particularly the 23-06Z time frame (this evening) could feature
at least brief (but perhaps strong to severe) thunderstorm
potential, and particularly the 06-12Z time frame (early Fri AM)
could bring sub-VFR ceiling and visibility in low clouds/light
fog. Aside from any potential short-term gustiness/erratic
direction shifts associated with thunderstorm activity, winds
will not be a major issue, with even gusts topping out mainly no
more than 15-20KT.
- Ceiling/visibility/precipitation/thunderstorm details:
Right out of the gate this morning, KGRI will have about another
hour of passing rain shower potential, but for the most part,
latest higher-res models are more suggestive that these first
10-12 hours will prevail dry/storm-free with any possible
ceiling no lower than low-end VFR. The main time frame for
possible, isolated to scattered thunderstorm activity appears to
focus 23-06Z. Given inherent uncertainty in any finer details,
have simply kept with generic "vicinity thunderstorm" (VCTS) for
now, and defer any more refined TEMPO/prevailing groups to later
issuances. There is an outside chance that KGRI/KEAR could see a
severe storm during this time, with the main hazards being
gusts to around 50KT and/or hail to around quarter size.
Once convective potential largely ends by around 06Z, there are
increasing chances for sub-VFR ceiling/visibility late in the
period. Although it is possible that visibility could be as poor
as IFR and ceiling as low as IFR/LIFR, opted to not go quite
this pessimistic quite yet, and thus went with MVFR
ceiling/visibility for now.
- Wind details:
Aside from any enhanced gustiness/erratic directional changes
from thunderstorm activity (which would be most favored between
23-06Z), winds through the first half of the period today will
mainly be 10-15KT/gusts 15-20KT out of the south-southeast. Then
overnight into early Fri AM, directional will shift more
northeasterly at speeds under 10KT.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
DISCUSSION...Thies
AVIATION...Pfannkuch