Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 240421 AAB
AFDLBF

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
1121 PM CDT Wed Aug 23 2017

.SYNOPSIS...
Issued at 312 PM CDT Wed Aug 23 2017

H5 analysis this morning had closed low pressure over
Quebec with a trough of low pressure extending south into the
central Appalachian Mountains. High pressure was south of the
trough over the western Atlantic, off the coast of northern
Florida. High pressure extended west to northern Mexico, where a
secondary high pressure was located south of Arizona. A ridge
extended north of this feature into the northern Rockies and into
northern Alberta. At the surface, high pressure was located over
southeastern Nebraska near Falls City. A surface trough of low
pressure was located across eastern Wyoming into eastern Colorado.
Between these two features, a nice pressure gradient had
developed this morning across the western sandhills and north
central Nebraska. This has resulted in breezy southerly winds this
afternoon. Under clear skies this afternoon, 2 PM CDT
temperatures ranged from 80 at O`Neill, Broken Bow and North
Platte to 87 at Valentine.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 312 PM CDT Wed Aug 23 2017

In the near term, Thunderstorm chances tonight and
Thursday is the main forecast concern. For tonight: Current surface
obs from eastern Colorado, indicate a thin band of low level
moisture surging north into far southwestern Nebraska and the
southern panhandle this afternoon. The latest NAM12 soln does
indicate an adequate amount of moisture and convective potential
this afternoon to support storms in the sern panhandle and far
swrn zones, however a glance at mid level lapse rates and fcst
soundings, indicates a decent cap and plenty of cin in these areas
at peak heating. Further west, a more favorable set up for
convective development appears along the Cheyenne ridge of se
Wyoming and am expecting convective development there. As this
activity moves east it is expected to dissipate as the low level
jet is anchored well east of the panhandle. Overnight lows will be
in the mid to upper 50s. A more favorable set up for
thunderstorms will push into the forecast area on Thursday. Thanks
to a continuation in southerly winds late tonight into Thursday
morning, increased low level moisture will overspread southwest
and western Nebraska. With surface heating Thursday afternoon, SB
capes will reach 2000 to 3000 J/KG with very limited CIN noted. At
the same time, a mid level disturbance will enter the panhandle
late morning Thursday with mid level warm air advection increasing
from the western sandhills into southwestern Nebraska.
Precipitation chances will increase from midday Thursday into
Thursday evening. Deep layer shear is fairly weak mid day into the
early afternoon hours, but increases to 25 to 30 KTS late
afternoon. This will provide a limited severe weather threat from
21z to 03z Friday given the forecast CAPE of 2000 to 3000 J/KG and
25 to 30 KTS of deep layer shear.

.LONG TERM...(Thursday night through Wednesday)
Issued at 312 PM CDT Wed Aug 23 2017

Thursday night through Saturday night:
There will be a continued threat for thunderstorms Friday night
into Saturday night as persistent southerly winds allow moisture
to remain anchored across the forecast area. Additionally, a
surface trough will remain anchored across the panhandle and
eastern Colorado, and weak disturbances will track east of the
central Rockies with a continuation of zonal flow aloft. Timing
will be tricky with respect to the disturbances, and have hedged
the highest pops toward the late afternoon and early evening
hours. Shear will weaken Friday into Saturday, so any severe
threat should be minimal attm.

Sunday through Wednesday: Like yesterday, the mid range model
solutions trend toward the development of an upper level high across
the intermountain west Sunday. This feature will remain anchored
across the west through the remainder of the forecast period. this
will lead to northerly flow aloft and a limited threat for
precipitation after Sunday. Temperatures will be seasonal with highs
in the 80s and lows in the 50s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1120 PM CDT Wed Aug 23 2017

VFR is generally expected tonight and Thursday morning.

Isolated thunderstorms across Wrn Neb, west of highway 83, may
last for several hours given the low level jet underway. This
forcing mechanism should veer off to the east around 09z.

Another area of concern for thunderstorms tonight is Ncntl Neb
along and north of highway 20 east of Valentine where a small
cluster of showers and thunderstorms may develop according to the
RAP and HRRR models.

Scattered to numerous thunderstorms are expected to develop 18z
Thursday through 06z Thursday evening. These storms would
generally affect Wrn Neb 18z-00z and Ncntl Neb 00z-06z.

&&

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

$$

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


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