Hail in Nebraska, July 12, 2020

Area Forecast Discussion
National Weather Service North Platte NE
652 AM CDT Sun Jul 12 2020

.SYNOPSIS...
Issued at 412 AM CDT Sun Jul 12 2020

Weak ridging was noted from the central Rockies into the High Plains
though height rises on evening soundings were minimal. Upper low has
moved onshore in BC with a separate band of enhanced westerlies with
embedded PV anomalies across the central Rockies. Mainly clear skies
across the area early this morning.

&&

.SHORT TERM...(Today through Monday)
Issued at 412 AM CDT Sun Jul 12 2020

As ridging continues to build eastward in advance of the upper
level low over BC, surface pressures have begun to lower across
the High Plains of eastern CO into eastern MT per latest RAP
analysis. Short range models suggest this trend will continue
through the morning hours allowing for a response via LLJ
development along the High Plains this morning. Although moisture
from evening soundings is fairly limited until you get south into
KS, initially this moisture return should be fairly quick in a
narrow ribbon from western KS into the Panhandle. As a result
elevated instability has already increased early this morning.
Models including CAMs are consistent in developing at the very
least shallow convection in response to the increasing LLJ through
noon in the presence of good deep layer shear. Though it may take
awhile for parcels to ascend to LCLs and eventually LFC it does
seem possible to see convective development this morning along and
east of this returning moisture axis. The limiting factor will be
the degree of deep layer forcing as well as llimited moisture
initially. There POPs were limited to some degree as confidence is
about mid range at the moment on this development. If convection
develops it should be fairly progressive through the morning
primarily across north central NE and the central Sandhills. In
it's wake mainly clear skies should prevail allowing a quick
warmup of temps by afternoon especially in the west.

As the band of aforementioned westerlies drifts south later today
would expect the best deep layer forcing to be south of the area.
Small POPs included in far southwest portion of the forecast area
but confidence is low on any development further north.

For Monday...upper low continues to move eastward toward the
northern Plains. Placed above the strong but flattening ridge to the
south will increase the resultant southwesterly flow aloft.
Attendant cold front will develop eastward across the Dakotas but
stall further south due to the southerly low level flow in response
to lowering heights. A surface trough associated with the surface
thermal ridge will develop ahead of the main cold front over the
state and will become the focus for convective development by Monday
afternoon. Some disagreement among models in that time frame as to
how much dry air will be shunted eastward over the Panhandle and
with the upper forcing encaountering the higher terrain further west
first may see initial convective development try to move east into
the Panhandle by mid afternoon. Thinking for now is any convection
there would struggle early in the well-mixed environment. However as
low level convergence focuses further on the surface trough and deep
layer shear increases in the prescence of good instability,
thunderstorms appear favorable by late afternoon across the
southwest and western Sandhills initially, then spreading eastward
through the evening. As per SPC ouitlook, large hail and damaging
winds will be primary threats, and will have to pay attention to
landspout potential with stalled trough co-located with surface
thermal axis by mid afternoon.

Afternoon temps by Monday will be quite a bit warmer and well above
average for this time of year especially in the west, approaching
upper 90s in the southwest.

.LONG TERM...(Monday night through Saturday)
Issued at 412 AM CDT Sun Jul 12 2020

Precipitation from Monday's activity could linger across the
northeastern CWA into late Tuesday morning before surface ridging
slides into the area behind the cold front. This will lead to a dry
Tuesday afternoon, but this break in precipitation will be short
lived as a shortwave ejects off of the northern Rockies late Tuesday
evening into the overnight hours. Shower/thunderstorm development
should occur across the Panhandle and northeast Colorado with the
approach of this shortwave, and will gradually move into the CWA
with time. SPC has placed a marginal risk largely south and east of
an Ogallala to O'Neill line, so will have to watch for the potential
for strong to severe storms with this activity. However, the timing
of the shortwave may hinder severe potential somewhat with the best
forcing not reaching the CWA until after 0Z Wednesday. Temperatures
will be rather pleasant on Tuesday and Wednesday in the post-frontal
airmass, with highs expected to top out in the upper 70s to low 80s,
which is around 10 degrees below average for this time of the year.

The pattern looks to stay active beyond Wednesday, with largely
zonal flow aloft expected. This leaves the area on the periphery of
a large upper level ridge centered over the southern CONUS, and
keeps us in an area of faster upper level flow. This leads to
shortwaves traversing across the central/northern Plains, and keep
things rather active. A general warming trend is expected after
midweek as well, with persistent southerly surface flow, with most
locations returning to the 90s by late week.

A shortwave is expected to eject into the northern Plains Thursday
afternoon but looks to leave the area with just a glancing blow from
the best forcing for ascent. With this in mind, went with only
chance POPs confined to the northern CWA. The first half of the
weekend looks dry in the wake of Thursday's system, but confidence
wanes through the end of the period in placement and timing of
potential shortwaves.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 648 AM CDT Sun Jul 12 2020

VFR conditions expected through the forecast period. Increasing
cloud cover at LBF may gradually lead to scattered showers and
weak thunderstorms during the late morning hours. Will continue to
monitor for potential impacts to the terminal but at this time
confidence in this is too low for inclusion at this time. Any
shower and thunderstorm that develops will quickly push off to the
east and weaken by late afternoon. Aviation concerns overnight
will then turn to the development of LLWS and isolated strong
convection. Will include LLWS in the LBF TAF but keep out of VTN
for now with any late convection staying out of the terminals.

&&

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

SYNOPSIS...Stoppkotte
SHORT TERM...Stoppkotte
LONG TERM...Brown/Stoppkotte
AVIATION...Jurgensen

Hazardous Weather Outlook...UPDATED
National Weather Service North Platte NE
941 AM CDT Sun Jul 12 2020

NEZ004>010-022>029-035>038-056>059-069>071-094-131445-
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-
941 AM CDT Sun Jul 12 2020 /841 AM MDT Sun Jul 12 2020/

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

.DAY ONE...TODAY AND TONIGHT.

Isolated strong storms will be possible during the late afternoon
and evening across the southern Panhandle into far southwest
Nebraska. Main concerns will be small hail and gusty winds along
with occasional lightning.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

Scattered thunderstorms are likely across much of central and
western Nebraska Monday afternoon and evening. Some storms may
become strong to severe with large hail and damaging winds the
main concerns though an isolated brief tornado cannot be ruled
out. All thunderstorms will be capable of heavy downpours and the
potential for training thunderstorms may lead to locally heavy
rainfall favoring portions of central and north central Nebraska.

Daily thunderstorm chances exist for Tuesday through Sunday. At
this time the threat for severe weather through this timeframe is
low.

.SPOTTER INFORMATION STATEMENT...

Please relay any information about observed severe weather to the
NWS.

&&

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