Severe Thunderstorm Warning 337, NWS North Platte, NE

Area Forecast Discussion
National Weather Service North Platte NE
256 PM CDT Sat Sep 9 2023

...AFTERNOON FORECAST DISCUSSION...

.SYNOPSIS...
Issued at 254 PM CDT Sat Sep 9 2023

Key Messages:

- Increasing chances of rain and thunderstorms through late
  tonight with some strong to severe thunderstorms possible
  capable of large hail, damaging wind gusts, and locally heavy
  rain.

- Decreasing rain and thunderstorm Sunday afternoon into Monday,with
  much cooler temperatures for the first half of next week.

- Temperatures rebound for the late week, returning to more
  seasonable values.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 254 PM CDT Sat Sep 9 2023

This Afternoon/Tonight...isolated showers and thunderstorms have
been prevalent through the morning and early this afternoon across
portions of central and north central Nebraska. These are being
driven by the arrival of a strong cold front from the north,
encountering a moderately humid and unstable airmass across much of
western and central Nebraska on the nose of a narrow instability
gradient. Aloft, enhanced h5 flow overtop southerly low-level flow
is leading to a moderately sheared environment with 0-6km BWD values
of 30-40 knots. Latest 19z obs places the surface boundary near a
line from immediately south of ONL to immediately north of OGA. With
this southwest to northeast orientation of the boundary and
orthogonal shear vectors, expecting largely isolated convection this
afternoon. Forecast soundings show deep inverted-v profiles largely
due to dew point depressions nearing 30 degF. Steep mid-level lapse
rates will continue to advect in from the west and this will factor
into MLCAPE values hovering in the 1500-2000 j/kg range through
early this evening. Expectations going forward are for additional
thunderstorm activity to develop through early this evening as the
capping inversion weakens over time. Though DCAPE values in excess
of 1000 j/kg will support a damaging wind threat the main concern
will be large hail, perhaps exceeding golf ball size. This is due to
effective shear supporting multicell and perhaps brief supercellular
storm modes, strong mid-level shear with 2-7km BWD values exceeding
35 knots, and SHIP values from forecast soundings exceeding 1.0. As
storms merge and grow upscale in part from a growing cold pool,
expect the threat to transition to largely gusty winds. Given weak 0-
2km shear and LCLs exceeding 2000 meters AGL, believe the tornado
threat to be fairly low. That said, should a storm manage to latch
onto the boundary, a non-zero tornado threat will be present. CAMs
have been poor to handle ongoing convection early today, but believe
evolution of afternoon and evening activity they suggest is the
likely scenario...initial development early this afternoon
gradually increasing in coverage with a slight southeasterly
track. Believe storms will lose strength this evening as capping
increases. Some locally heavy rain is possible Most activity
should exit to the south and east by Midnight tonight. Attention
will then turn to activity moving off the higher terrain of
Wyoming and southwest South Dakota. Latest HRRR suggests multiple
discrete storms working in after Midnight into the western
Sandhills. Believe this activity will be weakening with time again
due to increasing capping with time. Though mid-level lapse rates
may remain favorable so cannot rule out a couple hail reports in
the early morning hours.

Sunday/Sunday Night...surface cold front will continue to shift
south through the area, settling near an Imperial to Ord line.
Modest southerly flow ahead of this feature will continue to usher
in theta-e rich air into the convergent zone. This will help bolster
increased coverage of rain and thunderstorms for our southern zones
early in the day. Expecting renewed development to favor areas east
of Highway 83 and generally south of Highway 2. Cannot completely
rule out a few hail reports with steep mid-level lapse rates of 7-8
degC/km and 2-7km BWD values of 30+ knots. Recent HREF guidance is
fairly muted with limited probabilities though this may be largely
explained by low precision within individual members. With PWAT
values hovering around 1.0" in the pre-convective environment,
will need to monitor potential for some locally heavy rain.
Limiting this concern though will be fairly progressive storm
motion and limited training of storms. Further northwest, stronger
mid-level convergence in association with an approaching
shortwave disturbance will bring increased rain and thunderstorm
probabilities in the post- frontal airmass. A few NWP solutions
depict fairly heavy rainfall in raw QPF output, notably the
NAM/Canadian solutions, so this potential will need to be
monitored. Meanwhile, the ECMWF is not as bullish and the GFS even
less so. Because of this, not overly confident that we see these
rainfall amounts in our northern zones during this period. Drier
air will begin to work in by the evening hours and this combined
with decreasing lift will allow precipitation chances to wane in
the evening. Surface high pressure will settle in during the
overnight hours, allowing winds to go light and temperatures to
fall into the low 50s and even the low 40s.

.LONG TERM...(Monday through Saturday)
Issued at 254 PM CDT Sat Sep 9 2023

Monday-Tuesday...expect the bulk of any precipitation to be out of
the area by early Monday. The exception to this would be portions of
the eastern Panhandle into southwest Nebraska. Dry air intrusion
will continue to push PWAT values well below 0.75" for much of the
area with considerable mid-level dry air overspreading the area by
the afternoon. This will support gradually clearing skies from north
to south. With h85 temperatures settling to around 10-12 degC, will
see a much cooler day again with highs only slightly warmer than
Sunday ranging in the 60s to low 70s. Large scale troughing across
the Great Lakes will continue to shift east with mid-level heights
filling in behind this feature. Resulting subsidence will keep the
forecast dry for Tuesday with only modest increases in afternoon
highs, creeping into the low to middle 70s.

Wednesday and beyond...ridging across southwest Canada will begin to
amplify during the late week. While this will slowly bleed east with
increasing mid-level heights as well, the biggest local impact will
come via amplified northwest flow aloft. Though no large-scale
system is appearing on the horizon, a weak disturbance around the
middle to latter half of the week may reintroduce some low-end PoPs
to the forecast. Though the greatest upper-level dynamics looks to
remain south of the forecast area, a trailing frontal boundary may
be the main lifting mechanism locally. NBM and EPS/GEFS
probabilities don't signal widespread wetting rain event, but
details are murky at range so continue to monitor later forecasts
for the latest. For now, have greatest PoPs inherited from the model
blend Wednesday evening and again Thursday evening, but limited to <
30% either of the days. Ensembles also continue to highlight
anomalously cool temperatures in the low and mid-levels. This likely
explains the only modest warm-up for the latter half of the week as
highs only manage to climb into the upper 70s to potentially the low
80s by Friday and the weekend. This should keep temperatures closer
to seasonable norms and limit any threat for a return to well above
normal values.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1236 PM CDT Sat Sep 9 2023

Winds will be gusty out of the south this afternoon across
portions of southwest Nebraska with wind gust of 25 to 30 kts.
Across the northern Sandhills winds will be out of the north this
afternoon around 5 to 10 kts. There will also scattered
thunderstorms this afternoon and evening, with the greatest threat
along and east of a line from Ainsworth to North Platte to
Imperial, any area impacted by the thunderstorms may have erratic
winds and MVFR or lower conditions. Rain Sunday morning may lower
cigs and visibility, at this time there is still some uncertainty
with how widespread coverage will be Sunday morning through early
afternoon, but MVFR or lower conditions will be possible across
portions of the forecast area.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SYNOPSIS...NMJ
SHORT TERM...NMJ
LONG TERM...NMJ
AVIATION...Gomez

Hazardous Weather Outlook
National Weather Service North Platte NE
317 PM CDT Sat Sep 9 2023

NEZ004>010-022>029-035>038-056>059-069>071-094-102030-
Sheridan-Eastern Cherry-Keya Paha-Boyd-Brown-Rock-Holt-Garden-Grant-
Hooker-Thomas-Blaine-Loup-Garfield-Wheeler-Arthur-McPherson-Logan-
Custer-Deuel-Keith-Perkins-Lincoln-Chase-Hayes-Frontier-
Western Cherry-
317 PM CDT Sat Sep 9 2023 /217 PM MDT Sat Sep 9 2023/

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

.DAY ONE...This afternoon and tonight.

Scattered thunderstorms are likely this afternoon across portions of
central and southwest Nebraska. Strong to severe thunderstorms are
possible with large hail up to two inches in diameter and damaging
wind gusts the main concerns. Areas at greatest risk of seeing these
hazards are east of Highway 61 and south of Highway 2. Storms are
expected to weaken by early evening with the threat for severe
weather ending by late this evening.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Scattered rain and thunderstorms are likely Sunday across much of
western and north central Nebraska. At this time, the threat for
severe weather is low but locally heavy rain will be possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated, but reports relayed to the NWS
North Platte are appreciated.

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Preliminary Local Storm Report
National Weather Service North Platte NE
442 PM CDT Sat Sep 9 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0322 PM     Hail             6 ENE Gandy             41.51N 100.36W
09/09/2023  E1.00 inch       Logan              NE   Public

            caller reports holes punched in outbuilding
            roof. time estimated from radar.

&&

Special Weather Statement
National Weather Service North Platte NE
501 PM CDT Sat Sep 9 2023

NEZ059-092230-
Lincoln NE-
501 PM CDT Sat Sep 9 2023

...A STRONG THUNDERSTORM WILL IMPACT EAST CENTRAL LINCOLN COUNTY
THROUGH 530 PM CDT...

At 500 PM CDT, Doppler radar was tracking a strong thunderstorm near
Maxwell, or 10 miles east of North Platte, moving east at 20 mph.

HAZARD...Wind gusts up to 50 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Maxwell and Keith.

This includes Interstate 80 in Nebraska between mile markers 182 and
197.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

A Severe Thunderstorm Watch remains in effect until 900 PM CDT for
southwestern Nebraska.

&&

LAT...LON 4110 10068 4120 10063 4116 10031 4096 10044
TIME...MOT...LOC 2200Z 283DEG 21KT 4112 10056

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...50 MPH

Gomez