Severe Thunderstorm Warning 76, NWS Hastings, NE

AREA FORECAST DISCUSSION
National Weather Service Hastings NE
223 PM CDT Thu May 12 2022

.Mesoscale Discussion...
Issued at 215 PM CDT Thu May 12 2022

Complex convective evolution expected over the next couple of
hours. In general, we're off to a faster start than forecast due
to a lead wave that helped convection develop along the dry line
along CO/KS border already by late morning. This activity has
since moved NE off the dry line...in concert with the NE moving
mid level disturbance. Have already had some severe hail and wind
reports...and given recent observation trends in satellite and
local environment...don't see any reason to think this activity
won't continue to grow upscale and become more organized. Initial
hi-res model data this morning was struggling to pick up on this
trend...but more recent HRRR runs, and 12Z NAMNest/ARW, seemed to
do best...and they've been showing a gradual uptick in coverage
and intensity with time this aftn...perhaps just 1-2 hr too slow.

So what to expect going forward...MLCAPE (2500-3000 J/kg) and
deep layer shear (40-50kt) will maintain, or even incr. These
parameters, along with very steep mid level lapse rates, will make
large to very large (in excess of 2") hail likely with the most
intense cells. Also, steep low level lapse rates and tendency to
grow upscale into a large QLCS, in concert with DCAPE 1000-1500
J/kg, will likely lead to fairly widespread 60-70 MPH wind gusts,
perhaps locally higher, esp. in the portion of the QLCS that moves
more SW to NE...as this will be more normal to the 0-3km shear
vector. QLCS tornado potential is not zero, esp. with
aforementioned NEward moving segments, as they will have about
30kt of 0-3km shear to work with. However, a potential limiting
factor could be lackluster 0-3km CAPE. This initial line will
likely be most intense N of the state line, and should exit to the
NE by around 21-2130Z.

The question then becomes if another line segment can develop
along the actual cold front as it moves in from W to E. Hi-res
guidance suggests this could be around 23Z-00Z...and oriented SW
to NE from around PHG to ODX. This would move E/SE and continue to
pose a risk for large hail and dmg wind. It's uncertain how severe
this could be across Neb zones due to effects from first rd of
convection...but KS zones will likely be less affected and thus
more unstable. So if I had to guess...the worst severity with the
second round may focus along and S of the state line...but even
areas further N could see a 2nd round of svr, as well. All of this
looks to wane towards 02-04Z.

&&

.DISCUSSION...(This evening through Thursday)
Issued at 150 PM CDT Thu May 12 2022

Primary forecast challenges are severe thunderstorm and fire weather
concerns today, then occasional low to moderate rain/storm chances
this weekend into next week.

Summary: By far the greatest focus of this forecast will be in the
first 12 hours due to the potential for severe thunderstorms, and
perhaps a brief period of critical fire weather in the far W behind
a surging cold front. An initially broken line of thunderstorms will
develop/move in from the W/SW this afternoon, then spread E/NE and
increase in coverage. Damaging wind gusts and large hail look to be
the primary threats. Most, if not all, of the severe convection will
be over by 10-11PM, and dry conditions CWA-wide should return by
midnight. Friday through most of the day Saturday look to be dry and
comfortable, with highs in the 70s-80s, relatively light winds, and
limited humidity. A bit of an active pattern resumes as early as
late Sat aftn or eve, but more likely Sat night...as a series of
fairly weak disturbances move through in the zonal/NW upper flow and
interact with broad baroclinic zone draped across the Central U.S.
Models appear to be in decent agreement regarding the potential for
a stronger storm system and push of cold air late next week.

Forecast Details Beyond This Evening:
Have PoPs exiting the far SE CWA by 09Z, but think most of the
stronger activity will be over by ~04Z. Winds will decr overnight,
and with clearing skies, expect a much cooler Fri AM with lows in
the upper 40s to mid 50s. Fri daytime hours should be very pleasant
owing to plentiful sunshine, low humidity, lgt winds out of the W-N
at 10-15 mph, and highs near 80F.

Sat also looks to be a fairly pleasant and dry for most of the day.
However, recent model trends suggest incr chcs for shwrs/storms to
dev along a weak cold front that may bec draped across portions of
our Neb. zones. This would be mainly after 4-5pm. Models also
indicate additional LLJ driven shwrs/tstms Sat night, but these may
focus a bit further S across KS. Severe chcs are not great, but not
zero, either. CAPE will likely be quite limited Sat aftn/eve...but
may incr overnight along with better shear. Parts of the area are in
a Day 3 Marginal Risk, with the Slight Risk primarily SE of the CWA.

Not terribly concerned with pcpn chcs Sun into Mon...and temps will
remain pleasant (near to just above normal), with highs in the mid
70s to mid 80s, and lows comfortably in the upper 40s to 50s. This
alone is often indicative of limited humidity. Models generally
trend a bit warmer and potentially more active towards the middle of
next week...ahead of a stronger storm system that could force a
significant cold front through the area towards the end of next week
(Day 8-9). Magnitude of front and climo would suggest a strong-
severe tstm chc with the front, but details regarding moisture
quality, lapse rates, etc. are far too uncertain this far out.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Friday)
Issued at 1250 PM CDT Thu May 12 2022

Significant weather: T-storms with gusty winds and perhaps brief
dip to MVFR CIGs and IFR VSBYs, mainly within the first 6-9hrs.

Today-Tonight: A broken line of tstms over SW NE/NW KS will
continue to progress E/NE through the aftn. The strongest storms
will be capable of producing large hail and wind gusts of at least
35-45kt, perhaps higher, mainly in the 19Z to 00Z time frame.
Storms will exit to the E/SE around 00Z to 03Z as a cold front
moves through the area, and switches with from SW/W (or variable)
to the NW. The front should also clear the CWA out from all but
high-level cirrus blow-off...leaving VFR for the remainder of the
overnight. Confidence: general evolution - medium, exact
timing/impacts - low.

Friday thru 18Z: Lgt WNW to NW winds and clr skies are expected.
Confidence: High.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

Mesoscale...Thies
DISCUSSION...Thies
AVIATION...Thies

Hazardous Weather Outlook
National Weather Service Hastings NE
229 PM CDT Thu May 12 2022

KSZ005>007-017>019-NEZ039>041-046>049-060>064-072>077-082>087-
131200-
Phillips-Smith-Jewell-Rooks-Osborne-Mitchell-Valley-Greeley-Nance-
Sherman-Howard-Merrick-Polk-Dawson-Buffalo-Hall-Hamilton-York-
Gosper-Phelps-Kearney-Adams-Clay-Fillmore-Furnas-Harlan-Franklin-
Webster-Nuckolls-Thayer-
229 PM CDT Thu May 12 2022

This Hazardous Weather Outlook is for south central Nebraska and
portions of north central Kansas.

.DAY ONE...This Afternoon and Tonight.

Scattered to widespread thunderstorms are expected this afternoon
into the evening hours. Some of these will be severe...with hail
up to 2 inches in diameter winds gusts in excess of 70 mph
possible. In addition...an isolated tornado cannot be ruled out.
The main timeframe for severe weather will be until 11pm.

In addition to thunderstorms, near critical fire weather
conditions are expected this afternoon for areas along and west of
Highway 183.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Thunderstorm chances return to the forecast Saturday night, and
will continue off and on periodically through the middle of next
week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed late this afternoon and
into the evening hours. Please relay reports of hail of any size
as well as damaging wind gusts.

&&

More information may be obtained at the following web page:
   https://www.weather.gov/hastings

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