Severe Thunderstorm Warning 166, NWS Hastings, NE

Area Forecast Discussion
National Weather Service Hastings NE
848 PM CDT Thu Jun 20 2019

...Short Term Update...

.UPDATE...
Issued at 847 PM CDT Thu Jun 20 2019

Some commentary about the next 12-24 hours:

1) Overnight severe storm potential still on track:
Per the latest Mesoscale Discussion from SPC, we are still very
much anticipating at least one or more clusters/rounds of strong-
to-severe storms overnight (mainly after 11 PM), and a Severe
Thunderstorm Watch for most/all of the CWA is anticipated to be
issued sometime in the next few hours. From our local perspective,
things are still very much on track from the main afternoon
discussion below. We have apparently "dodged" the slim possibility
of any early-evening storm development in our southern zones
(although a severe storm did develop slightly east of our CWA in
northeast KS a few hours ago). Thus, nearly our full attention is
focused westward, where isolated severe convection is well-
underway in the NE/KS/CO border region. With time, this convection
will roll east into our CWA, and likely grow upscale into one or
more lines/clusters, with more isolated activity probably
developing behind these larger-scale complexes in response to lift
along the residual elevated cold pool/along axis of southerly low
level jet evident at 850 millibars. Even late in the night,
elevated instability/CAPE in the 850-700 millibar layer is progged
to remain quite stout (2000-4000 J/kg) per the latest RAP13, so
it's a semi-volatile environment around here (at least by late-
night standards). Did tweak our Hazardous Weather Outlook (HWOGID)
to increase severe wind potential to 70 MPH, especially if storms
form into bowing segments. Hail up to around golf ball size
remains on track, but this will probably be the larger exception.
Not expecting widespread flooding issues, but some areas could
pick up a quick 1-2" of rain, with localized/short-term flooding
certainly a possibility.

IN SUMMARY: Several strong to severe storms are likely overnight,
starting around roughly 11 PM in our far west and spreading
eastward overnight. At least an isolated severe storm threat could
even last past sunrise (perhaps to around 7 AM).

2) Friday trending somewhat cloudier/cooler:
Not as pressing as number 1 above, but latest model data has been
trending cloudier and thus at least slightly cooler for Friday. In
an earlier update, increased sky cover and lowered high temps
generally 2-3 degrees from initial afternoon forecast package, and
could easily see our overnight forecast shaving a few more degrees
off. If these cloudier trends do in fact verify, it may be tough
for much of the northwest 2/3 of our CWA to exceed 80 degrees, and
with low 90s less likely over our far south in KS.

&&

.SHORT TERM...(This evening through Friday)
Issued at 226 PM CDT Thu Jun 20 2019

This main focus for this forecast is multiple rounds of
potentially severe thunderstorms.

Currently, a surface cold front is dropping south across the
area, shifting winds from the south to the northwest and north.
This feature is forecast to stall out across the area this
evening. A few CAMs still show isolated storms near the late this
afternoon and evening, but these chances remain low.

The stronger signal in the near-term models has been for one or
more clusters of thunderstorms to develop over western Nebraska
and Kansas and track through the local area late tonight. Activity
will likely then persist into Friday morning as we will be on the
nose of a 30-35kt low-level jet. These storms should be elevated
in nature so I believe the main threat will be large hail. RAP
soundings show 2500-3000J of elevated CAPE above 850mb along with
ample shear, therefore the strongest storms could easily have hail
to the size of golf balls...or larger. The strongest organized
cold pools may allow for isolated severe wind gusts as well. The
HRRR shows the initial line of storms to be pretty progressive,
but shows additional scattered showers and storms developing
behind it. As a result some isolated locations could also pick up
some heavy rainfall totals as well.

Storms may linger into Friday morning, but we should mostly dry
conditions return by mid to morning into the early afternoon.
Areas near and south of the the surface boundary will have plenty
of instability to work with as temperatures surge into the 80s and
low 90s. Convective development remain somewhat uncertain,
though. For the most part, models show our area remaining free of
surface-based convection during the afternoon and evening with
developing southeast of the local area. Then additional convection
may move in from the west again overnight.

.LONG TERM...(Friday night through Thursday)
Issued at 226 PM CDT Thu Jun 20 2019

Convective details continue to get more uncertain into Saturday.
That being said, it appears that at least southeastern portions of
the area still have a shot to see severe storms with the front
stalled nearby and the upper trough over the Rockies slowly
pushing eastward.

On Sunday, the upper trough finally pushes through the area. This
will bring us another day with shower and storm chances. The area
should then finally see a couple dry days Monday and Tuesday as
the system departs and we see rising heights aloft. As we return
to westerly flow aloft and southwesterly flow at the surface,
temperatures should be able to return to the upper 80s and 90s.

A few subtle disturbances move through the area Tuesday night
through Thursday bringing low-end chances for rain. Better chances
will likely hold off until the next trough moves over the Rockies
the following weekend.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 719 PM CDT Thu Jun 20 2019

General overview:
There are clearly two main issues during the period: 1) A good
chance of thunderstorms (potentially severe) overnight, especially
during the 05-10Z time frame...2) What appears to be increasing
chances for sub-VFR ceiling through much of the latter half of the
period (Friday daytime). Otherwise, OUTSIDE of thunderstorm
outflow/influences, surface winds should not be a big issue, with
speeds generally at-or-below 10KT and direction generally some
variation of easterly through much of the period, but more
northerly by late Friday afternoon. Read on for more details
regarding thunderstorm/ceiling issues...

Thunderstorms:
Confidence is high in storm-free conditions through at least these
first 4-5 hours, but after that expect a somewhat "bumpy ride"
overnight, as there is a decent chance that one or more
clusters/lines of storms will pass through. Decided to introduce
TEMPO groups covering the 05-10Z period to highlight the overall
best window of opportunity for convection, with a "vicinity"
(VCTS) mention covering hours slightly before and after. Severe
storms are possible with damaging winds/hail, and for now have
gone with a basic "VRB30KT" wind mention during the TEMPO
timeframe, along with an MVFR visibility mention (although it
could certainly be well-below this for brief times). Although the
chance of at least isolated showers could linger past sunrise, the
majority of the latter 12 hours should be dry, and have refrained
from introducing any additional thunderstorm mention into Friday
afternoon for now.

Ceiling trends/uncertainty:
High confidence in VFR through at least the first 4-6 hours, and
moderately-high confidence in predominantly VFR through the first
12 hours. However, there are increasing signals that much of the
latter half of the period (Friday daytime) will feature MVFR
ceiling, with even some potential for periodic IFR. For now, have
not bought fully into the most pessimistic solutions, but have
introduced MVFR to most of Friday daytime.

&&

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

UPDATE...Pfannkuch
SHORT TERM...Mangels
LONG TERM...Mangels
AVIATION...Pfannkuch

Hazardous Weather Outlook...CORRECTED
National Weather Service Hastings NE
814 PM CDT Thu Jun 20 2019

KSZ005>007-017>019-NEZ039>041-046>049-060>064-072>077-082>087-
211100-
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-
814 PM CDT Thu Jun 20 2019

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

.DAY ONE...Overnight.

There is a good chance of thunderstorms across most of the outlook
area between 11 PM and sunrise, with some storms likely to be
severe. The general expectation is for one or two larger-scale
lines or clusters of storms to sweep across the area from west-
to-east, with perhaps more isolated to scattered activity
redeveloping behind them. The main severe weather threats
overnight will be damaging wind gusts up to around 70 MPH and
large hail up to around golf ball size. Although flooding is not
expected to be a major issue, localized areas could receive a
quick 1 to 2 inches of rain, which could promote at least brief,
minor flooding.

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

A few thunderstorms may linger across portions of the outlook
area into Friday morning, but better chances will return once
again late Friday afternoon and mainly Friday night. There will
again be the potential for strong to severe storms, with large
hail, damaging winds and locally heavy rain the primary hazards.

There are additional chances for thunderstorms Saturday through
Sunday, then again Tuesday night into Wednesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed across various portions of the
outlook area overnight.

&&

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

Pfannkuch

Special Weather Statement
National Weather Service Hastings NE
1019 PM CDT Thu Jun 20 2019

NEZ072-082-210400-
Gosper NE-Furnas NE-
1019 PM CDT Thu Jun 20 2019

...SIGNIFICANT WEATHER ADVISORY FOR GOSPER AND NORTHWESTERN FURNAS
COUNTIES UNTIL 1100 PM CDT...

At 1018 PM CDT, Doppler radar was tracking a strong thunderstorm near
Cambridge, or 27 miles east of McCook, moving northeast at 35 mph.

Penny size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Cambridge, Arapahoe, Elwood and Holbrook.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 400 AM CDT for
south central Nebraska.

LAT...LON 4035 10010 4044 10009 4044 9998 4055 9998
      4065 9982 4039 9964 4038 9964 4018 10019
      4035 10020
TIME...MOT...LOC 0318Z 242DEG 32KT 4032 10012

Pfannkuch

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