Special Weather Statement, NWS North Platte, NE

Area Forecast Discussion
National Weather Service North Platte NE
257 PM CDT Wed May 12 2021

.SHORT TERM...(This evening through Thursday night)
Issued at 253 PM CDT Wed May 12 2021

The primary concern for the short term will revolve around
convective chances this evening through tomorrow.

Currently, the area sits in northwesterly flow aloft as an upper
ridge axis slowly progresses off to the east of the area. A
shortwave is evident in GOES upper level WV imagery over E MT and W
ND. This shortwave is helping to spark showers and convection over
the higher terrain of E WY.

The aforementioned convective activity will continue to push
southeast in the mean flow through this evening. There remains
potential for a few thunderstorms generally west of Highway 83 though
any severe threat looks very low. Instability weakens with eastward
extent into the CWA, with only ~250-500J/kg west of Highway 61. This
marginal instability combined with weak vertical shear aloft has led
to a very disorganized nature to convection thus far. As convection
moves into the eastern Panhandle a gradual weakening trend is
expected. Still, cannot totally rule out gusty winds in a few of the
stronger cells given a mixed boundary layer and steep low level
lapse rates. Convection should largely remain west of Highway 61,
though can't totally rule out a stray storm or two reaching the
Highway 83 corridor this evening.

Lows overnight will be warmer than the last few days with persistent
warm advection anticipated. Any frost concerns look minimal with
overnight lows largely in the upper 30s to lower 40s. A warm front
at H7 will progress through north central Nebraska early tomorrow
morning and should lead to a few showers/isolated thunderstorms.

Convection chances return again tomorrow evening as yet another
shortwave is progged to drop into the Dakotas. Lee cyclogenesis
should begin in earnest across eastern Wyoming tomorrow morning.
Surface flow locally increases from the south and will bring in some
moisture. Model solutions show surface dewpoints in the 40-50 degree
range, which should support MUCAPE values on the order of 750-1000
J/kg by late afternoon. The surface low will eject eastward through
the evening and drag a pseudo dryline to near Highway 61. Convective
initiation will be preferred along this boundary late evening. A few
strong storms cannot be ruled out for the Sandhills and southwestern
Nebraska given adequate deep layer shear on the order of 40 to
50kts. Hodographs look largely straight, though some veering is
noted in the lowest 3km. A few splitting discrete cells are possible
early on in the convective life cycle before a transition to a
messier storm mode is possible. Cool temperatures aloft will lead to
a risk of isolated large hail as lapse rates remain steep in the mid-
levels. Additionally, any clustering of storms would likely lead to
an increased threat for damaging wind gusts as they propagate
southeast. High-res guidance shows a variety of potential convective
evolutions and confidence in mode remains low at this time.
Convection will propagate eastward through the evening and become
more widespread over central Nebraska. The severe threat should
lessen with time as the boundary layer begins to slowly stabilize
after sunset.

.LONG TERM...(Friday through Wednesday)
Issued at 253 PM CDT Wed May 12 2021

Things remain active into the long term as flow remains
northwesterly into the weekend. A generally upslope regime should
lead to thunderstorm chances across much of the area. Additionally,
a surface front will remain draped over portions of northern Kansas.
The severe risk remains unclear through the weekend, though a few
strong to severe storms remain possible given the progression and
placement of the aforementioned surface boundary. A stronger trough
is expected to dig into the Four Corners region into early next
week. Flow begins to transition southwesterly aloft and will lead to
a prolonged period of active weather. Daily chances of
thunderstorms will continue and surface moisture builds though
midweek. Trends will need to be monitored for severe potential as
we move into next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1226 PM CDT Wed May 12 2021

Cumulus clouds will continue to overspread the region this
afternoon with scattered rain showers developing late afternoon
into the evening. Ceilings should remain VFR, although locally
heavier rain showers will result in tempo visby drops. Any shower
activity should move east of KVTN-KLBF after 12/06z. Southerly
winds will be gusty at times today, then stay relatively elevated
around 10 kts overnight.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&

SHORT TERM...Brown
LONG TERM...Brown
AVIATION...Snively

Hazardous Weather Outlook
National Weather Service North Platte NE
311 PM CDT Wed May 12 2021

NEZ004>010-022>029-035>038-056>059-069>071-094-132015-
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-
311 PM CDT Wed May 12 2021 /211 PM MDT Wed May 12 2021/

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

.DAY ONE...TONIGHT.

Scattered rain showers with a possible thunderstorm will affect
the panhandle, then spread into the Sandhills through tonight.
The threat of severe weather appears low at this time.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

Daily thunderstorm chances exist Thursday through Tuesday,
primarily from the afternoon through the late evening. Some of
the storms could produce severe wind gusts or large hail Thursday.
Refer to later forecasts regarding severe potential for Friday
and beyond.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed through tonight.

&&

Get your weather, hydrological, and climate information at
http://www.weather.gov/northplatte

Special Weather Statement
National Weather Service North Platte NE
346 PM MDT Wed May 12 2021

NEZ056-122245-
Deuel NE-
346 PM MDT Wed May 12 2021

...SIGNIFICANT WEATHER ADVISORY FOR DEUEL COUNTY UNTIL 445 PM MDT...

At 346 PM MDT, Doppler radar was tracking a strong thunderstorm over
Chappell, moving northeast at 10 mph.

Winds in excess of 40 mph will be possible with this storm.

Locations impacted include...
Chappell, Barton and Mount Vernon.

This includes Interstate 80 in Nebraska between mile markers 78 and
102.

LAT...LON 4122 10261 4122 10216 4100 10215 4100 10261
TIME...MOT...LOC 2146Z 245DEG 9KT 4106 10246

Jurgensen