Flash Flooding and Hail in Nebraska, July 16 to 18, 2018

Area Forecast Discussion
National Weather Service North Platte NE
1227 PM CDT Mon Jul 16 2018

.UPDATE...
Issued at 633 AM CDT Mon Jul 16 2018

Update to the forecast to include areas of fog in portions of the
western and central Sandhills. Visibility may be rapidly changing
and as low as a quarter mile per latest observations and
satellite imagery. The fog should burn off by around 9 am cdt.

&&

.SHORT TERM...(Today and tonight)
Issued at 342 AM CDT Mon Jul 16 2018

Surface high pressure will shift east of the area today, with return
southerly low level flow advecting moist air northward into the
area. Some sunshine is expected, which will lead to fairly unstable
conditions by later this afternoon. A shortwave approaching from the
northwest will help increase mid level flow late this afternoon into
this evening. Scattered thunderstorms are likely to develop across
the higher terrain in Wyoming late this afternoon as large scale
ascent overspreads the area with the approach of the shortwave. CAMs
suggest that these storms will grow upscale into an MCS across
western NE by mid evening tonight. As the low level jet increases,
the MCS will likely turn more south to southeast into the jet and
move across northeast CO and southwest NE late this evening into the
early morning hours Tuesday. There is at least some potential of
damaging winds as this occurs, with a lesser chance of hail up to
possibly quarter size. Wind though would be the main severe weather
threat. Locally heavy rainfall is also a possibility.

.LONG TERM...(Tuesday through Sunday)
Issued at 342 AM CDT Mon Jul 16 2018

With the subtropical ridge anchored across the southwest CONUS for
much of the week, west to northwest flow aloft will persist across
the area. GFS/ECMWF continue to advertise a strong shortwave
crossing the Dakotas Tuesday night into Wednesday. Likely pops will
be maintained across northern NE during this time. There is some
concern that the NAM is mainly dry during this period. This is
likely due to a meso-high in the wake of the tonight into Tuesday
morning MCS. Will not go any higher than 60 percent with pops at
this time due to the NAM scenario.

As the shortwave moves east toward the Great Lakes Thursday, drier
air aloft will bring clearing skies. West to northwest flow aloft
will continue around the upper level ridge anchored to our
southwest, but no notable shortwaves within the flow should keep
conditions mainly dry Thursday into weekend. Highs though mid week
will be in the 80s, warming into the upper 80s to mid 90s by week's
end.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1227 PM CDT Mon Jul 16 2018

Low stratus over western Nebraska, mainly from KAIA to KOGA, will
continue to lift and dissipate this afternoon. VFR conditions and
generally light southeast surface winds are expected through the
evening. Thunderstorms will move into northwest Neb late this
evening and spread southeast overnight, resulting in erratic gusty
winds and brief drops in visby/cigs.

&&

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

UPDATE...Roberg
SHORT TERM...Taylor
LONG TERM...Taylor
AVIATION...Snively

Hazardous Weather Outlook
National Weather Service North Platte NE
500 AM CDT Mon Jul 16 2018

NEZ004>010-022>029-035>038-056>059-069>071-094-171000-
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-
500 AM CDT Mon Jul 16 2018 /400 AM MDT Mon Jul 16 2018/

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

.DAY ONE...TODAY AND TONIGHT.

Strong to locally severe thunderstorms are possible tonight,
mainly west of highway 83. Damaging winds, and hail up to one
inch in diameter are possible. Heavy rain is also possible, as
prolonged downpours may lead to localized flooding.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

Thunderstorm chances continue Tuesday into Tuesday night across
the area. Heavy rain is the primary threat, as prolonged
downpours may lead to localized flooding. Some storms will also be
capable of producing hail and strong winds, mainly west of
Valentine through Broken Bow.

Additional thunderstorms are possible Wednesday. The threat of
severe weather is low at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation should not be needed tonight. However, spotter
reports of heavy rainfall would be appreciated.

&&

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

Roberg