Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 170555

National Weather Service Hastings NE
1255 AM CDT Tue May 17 2022

.DISCUSSION...(This evening through Monday)
Issued at 405 PM CDT Mon May 16 2022

Main forecast concerns are strong to severe thunderstorm chances
with a pair of fronts Tuesday and Thursday, then cool down for
late week.

Mild, dry and pleasant conditions will continue through
this evening. A low level jet will bring gradually increasing
moisture over the next 24 hrs, which may help to sustain
convection as it rolls off the high plains late tonight and into
Tuesday morning. Exactly how this pans out will play a role in
the afternoon/evening convective potential, and there remains
considerable amount of uncertainty. Wednesday appears dry before
another, but stronger, cold front arrives at some point Thursday
into Thursday evening. Storms may develop along this front as
well, but moisture quality may be lacking which could limit
coverage and severity. Much colder temperatures and chilly NW wind
will settle in for Fri into Sat, and there`s a non-zero chc that
at least portions of the forecast area may have to deal with
patchy frost early Saturday morning.

Forecast Details:
It`s been a quiet, mild, and breezy day thus far, and don`t see
any reason this conditions won`t continue through the evening hrs.
Convection can be seen developing over the higher terrain of
WY/CO, as a weak upper disturbance rounds the top of shortwave
ridging. Some of this activity will try to organize as moves off
the higher terrain to the E...but quality moisture is severely
lacking with sfc Tds only in the mid 40s to low 50s. So have my
doubts at how successful this activity will be at sustaining
itself after sunset further E. There will be an incr low level
jet, but the best convergence on the nose of the speed max looks
to be further N, closer to perhaps convection sustains
and/or develops more efficiently in that area. Nonetheless,
various short-term and convective allowing models have non-zero
chcs for QPF after midnight and into Tue AM, so have maintained
some slgt chc PoPs. Am not expecting anything real widespread or
organized, and I think the lacking moisture and elevated nature of
convection would keep things below severe levels.

Assuming remnant cld cover isn`t overly thick/widespread, should
see another mild day on Tue with highs in the low 80s to near 90F.
Will state up front that details surrounding convection potential
Tue aftn/eve remain highly uncertain, including timing, placement,
coverage, and severity. In a general sense, looks like moisture
quality will improve, with time, which should combine with steep
mid level lapse rates and at least pockets of stronger insolation
to produce moderate instability ahead of a S/SE moving cold front.
Models are in good agreement that will be in zonal or slight NW
flow by peak heating, with several weak upper waves and neutral
or slight height falls towards eve. One potential source of
uncertainty will be any lingering vort maxima from Mon eve/night
convection. Some models have hinted at shortwave subsidence behind
one of these waves for our area, effectively limiting new dev for
peak heating. However, if convection remains weak, this may be
overdone. In terms of shear, deep layer flow remains weak by May
standards. Several forecast soundings indicate speeds less than
40kt thru the column, but do indicate strong directional shear
with low level SSE flow veering to WNW or even NW in the mid/upper
levels...resulting in 30-40kt of eff shear. So if convection can
dev, it falls within the CAPE/shear parameter space favorable for
at least iso strong to svr. As for coverage, timing, and
placement...hi-res models are all over the map...with some dev a
sold line, but mainly S of the KS/NE border...whereas others like
18Z HRRR and 12Z ARW and further N into central/sc Neb. May just
have to be one of those days where we don`t know a whole lot until
the details of tonight/tmrw AM shake out. Gut feeling is that 5pm
to midnight would be most likely time for strong/svr storms...and
that large hail and locally dmg winds would be main threats.

Nrly flow should clear us out for Wed, as well as bring us
slightly cooler temps in the upper 70s to low 80s and drier air.
Nothing to complain about for this time of year, for sure.

A stronger cold front is set to move through the region at some
point Thu into Thu night, but there`s still some spread on the
exact timing. It should be late enough that we see warm/hot
temps in the upper 80s to mid 90s ahead of the front. There is a
non-zero chc for storms to develop along the front by late aftn or
eve, but not sold that it will be widespread for our area owing to
lacking moisture. Decent SWrly low level flow will probably mix
out a lot of our BL moisture and shunt the greatest plume of
moisture off to our E. This could make it difficult to overcome
CIN until perhaps late in the day when mid-level height falls move
in. Mid to upper level flow is stronger, so if we can develop
better moisture/instability, there would likely be strong shear to
work with for large hail considering Srly sfc flow veering and
incr to 40-50kt NWrly flow at H5. Dmg wind would also be a concern
given LCLs near 3km and steep lapse rates/inverted V profiles.

Much cooler air is likely for late in the week and into the
weekend, with stiff/chilly NW wind likely on Fri. Pretty good chc
highs will remain in the 60s for one or both days near and N of
I-80, with perhaps southern areas making a run towards the low
70s. The good news is that it won`t feel at all humid,...the bad
news is that the cool/dry air will be at least a non-zero chc for
at least patchy frost Sat AM to our N/NW zones with lows in the
mid to upper 30s. Stay tuned if you have sensitive vegetation.


.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Wednesday)
Issued at 1248 AM CDT Tue May 17 2022

We have some showers and thunderstorms northwest of our TAF sites
at 1 AM CDT that will continue to die out as they slide east
southeast. Could see a brief shower or vicinity thunderstorm early
this morning either from this dieing line or from a few new storms
that models indicate could also pop up. However, by mid morning
any thunderstorms should have passed east of our TAF sites and
expect primarily dry weather from late morning through late
afternoon. Additional strong to severe thunderstorms will form
northwest of our TAF sites late this afternoon/early evening and
then slide southeast into our TAF sites this evening. The wind
will generally be southerly today and then turn north northeast
behind the thunderstorms this evening. Winds will be gusty in and
around thunderstorms. Strong low level wind shear is expected
through around 8 AM this morning.




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