Special Weather Statement, NWS North Platte, NE

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
628 PM CDT Sat Jul 29 2017

.SYNOPSIS...
Issued at 314 PM CDT Sat Jul 29 2017

H5 pattern across the CONUS today has an elongated area
of high pressure extending from Texas west to California. A low
amplitude ridge of high pressure was located across the western
CONUS with a closed low over New Brunswick and a trough of low
pressure extending south into the Carolinas. Within the low
amplitude ridge, numerous weak disturbances were noted and have led
to convective development across the central and southern Rockies
this afternoon. Across the central and northern plains this
afternoon, a surface trough of low pressure extended from the
western Dakotas, south into eastern Colorado and the far
northwestern Texas panhandle. Across western and north central
Nebraska, winds were generally from the east or southeast, which
forced abundant low level moisture into the forecast area this
afternoon. PWAT's from this morning were running from around an inch
in the panhandle to an inch and a half in the eastern forecast area.
Under partly to mostly cloudy skies this afternoon, 2 PM CDT
temperatures ranged from 78 at Broken Bow, to 88 at Imperial.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 314 PM CDT Sat Jul 29 2017

Tonight and Sunday: In the near term precipitation
chances tonight is the main forecast concern. Current LAPS data
indicates a nice area of 1500 to 2000 J/KG SB CAPE extending from
Swrn Nebraska into north central Nebraska with a very weak cap
present. This area of CAPE is in decent agreement spatially with the
latest NAM12 21z forecast which has this feature handled well. At
the surface, a weak wind boundary extended from far northeastern
Colorado into southwestern Nebraska. INVOF this area, mid level
lapse rates were highest across swrn Nebraska and were running 8.5
to 9.5C. Right now, based on the current situation, am expecting
convective development to initiate across southwestern Nebraska into
portions of central Nebraska (ie. Custer county) INVOF of the
surface boundary. Wind shear this afternoon and this evening is weak
on the order of 20 KTS so am not anticipating much of a severe
threat. However, with weak mid level flow and high PWATS, heavy rain
will be a threat and will hit this in the HWO. The latest NAM12 and
WARW linger some precipitation across the southern cwa tomorrow
morning into the afternoon hours and will hold onto this mention in
the new forecast. By late afternoon and evening, thoughts here are
to shift the highest threat for thunderstorms to the northwestern
forecast area. This is where a low level frontal boundary will set
up tomorrow evening and is colocated with an area of mid level warm
air advection. Like this evening, the severe threat should be low as
deep layer shear is limited.

.LONG TERM...(Monday through Saturday)
Issued at 314 PM CDT Sat Jul 29 2017

Monday through Tuesday...Drier conditions are expected
for most of the forecast area early next week. The h5 pattern will
amplify somewhat and the theta e ridge will be forced west into the
panhandle and western sandhills. Lapse rates will be steepest in the
west with developing convection expected generally west of highway
83. North northwesterly steering winds, will track the convection to
the sse, keeping most of it west of the Highway 83 corridor. Deep
layer shear remains marginal in the west and weak in the central
forecast area, so the severe threat appears minimal attm.

Tuesday night through Saturday...A somewhat active pattern will
remain in place in the extended forecast. Beginning Tuesday night a
strong shortwave traversing the Great Lakes, will force a cold front
through the forecast area Tuesday night leading to an increased
threat for thunderstorms. The front will then stall across the
forecast area late next week leading to a threat for thunderstorms
each day. There are some differences between the GFS and ECMWF
solutions from this morning that will have to be ironed out. The EC
forces the front through the forecast area into eastern Colorado and
Eastern Wyoming with one main upper level piece of energy. The GFS
solution, has two smaller disturbances followed by a stronger wave
next weekend. These differences will need to be ironed out, but in
the meantime, favored the GFS solution, with its weaker disturbances
and an increased threat for pcpn next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 628 PM CDT Sat Jul 29 2017

An upper level disturbance moving through the Central Rockies is
expected to be the catalyst for thunderstorms tonight. VFR is
expected after 15z Sunday.

Scattered to numerous thunderstorms are expected overnight along
and south of a line from KAIA-KMCK...just west of KLBF. Isolated
thunderstorms are expected overnight elsewhere.

The SREF suggests MVFR cigs 06z-16z along and south of a line
from KAIA-KLBF-KLXN.

&&

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

SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC

Hazardous Weather Outlook
National Weather Service North Platte NE
344 PM CDT Sat Jul 29 2017

NEZ004>010-022>029-035>038-056>059-069>071-094-302045-
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-
344 PM CDT Sat Jul 29 2017 /244 PM MDT Sat Jul 29 2017/

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

.DAY ONE...TONIGHT.

There is a threat for isolated strong to severe thunderstorms this
evening over northern Sheridan county and far northwestern Cherry
county. Gusty winds and heavy rain will be the main severe threats
with storms in these areas. Elsewhere, there is a threat for
thunderstorms with the main impact being heavy rain.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

Thunderstorms are possible at times Sunday through Friday across
western and north central Nebraska. At this time, the threat for
severe storms is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed through tonight.

&&

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

CLB

Special Weather Statement
National Weather Service North Platte NE
630 PM CDT SAT JUL 29 2017

NEZ035-036-057-300045-
Arthur NE-McPherson NE-Keith NE-
630 PM CDT SAT JUL 29 2017

...SPECIAL WEATHER STATEMENT...

At 629 PM CDT/529 PM MDT/, Doppler radar was tracking a strong
thunderstorm 17 miles north of Sarben, or 21 miles southeast of
Arthur, moving north at 5 mph.

Frequent lightning and 2 inches of rainfall is expected in 1 hour
from this storm.

Locations impacted include...
Big Bald Hill, Diamond Bar Lake, Bucktail Lake and Schnick Lake.

This includes Highway 92 between mile markers 187 and 190.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4158 10121 4140 10117 4139 10118 4140 10127
      4134 10127 4127 10140 4146 10156
TIME...MOT...LOC 2329Z 165DEG 6KT 4142 10133

CDC