Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 262337
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
637 PM CDT Sat May 26 2018

.SHORT TERM...(This evening through Sunday)
Issued at 258 PM CDT Sat May 26 2018

Latest satellite imagery shows clear skies overhead. Upstream,
cirrostratus in CO and KS moving northward. Water vapor imagery
shows an upper-level trough over the western CONUS with two closed
lows apparent over southern CA and northern NV and a ridge
extending from the southern High Plains into the Northern Plains.
High clouds will continue to drift northward and are expected to
move by late afternoon and persist overnight. The combination of
high clouds and light breezes will promote warm lows tonight,
60s, about 15 degrees or more above seasonable normals.

The amplified trough will remain in place tonight over the western
CONUS with an upper-level closed low in the Central Great Basin
with a ridge downstream covering the Plains. The closed low will
fill in some and see a little movement east across the Central
Great Basin Sunday with the ridge displaced more towards the
Southern Plains to Upper Midwest. A weak impulse and associated
vort lobe on the eastern periphery of the upper-level trough will
track northward across western NE late Sunday-Sunday night proving
broad ascent. This will promote storm chances, best storm chances
exist across the NEB Panhandle into far western NEB Sunday with
isolated-scattered coverage expected. Steep mid-level lapse rates
in place tomorrow, near 8.5-9 C/km, with ample instability in the
Central High Plains along and near a sharpening lee-side trough.
Moisture is sufficient with surface dew points in the mid 50s.
Multicells and some supercells possible with deep layer shear of
30-40 kts and modest sfc-3 km SRH apparent in soundings. Increased
storm chances continue then over Sunday night across western NEB
given the aid of increasing LLJ. Some uncertainty regarding how
far eastward storms will track Sunday night. Concur with previous
forecast w.r.t. convective evolution to MCS/cluster. Highs will
be hot in the upper 80s to lower 90s, about 15-20 degrees above
seasonable normals.

.LONG TERM...(Sunday night through Saturday)
Issued at 258 PM CDT Sat May 26 2018

The main concerns in the long term revolve around thunderstorms
Monday-Tuesday. Threat for damaging winds and large hail exists
Monday with additional risk of heavy rainfall/flash flooding,
mostly Monday night. Otherwise, highs cool some through Tuesday
with unsettled weather and clouds. Highs are forecast from the
upper 70s to upper 80s, warmest towards central NEB, Monday to
upper 70s to around 80 Tuesday. Highs are forecast to return to
the upper 80s by Thursday.

Little change in the amplified large scale pattern early Monday
compared to previous forecasts with a mid-level closed low over
the Central Great Basin and a ridge extending from the Southern
Plains into the Upper Midwest. The mid-level low will weaken into
an open wave over the next 24 hrs ejecting and tracking to the
northern High Plains by early Tuesday.

Scattered strong to severe thunderstorms possible Monday afternoon
and Monday night. Early Monday there may be lingering showers and
storms, some convective debris and cloudiness. Attentions turns to
late Monday nonetheless wherein overall thunderstorm potential is
more favorable with a shortwave trough providing broad ascent.
Focus is on the sharpening lee-side trough late Monday. Ample
instability is expected to come together with MLCAPEs exceeding
2200 J/kg in the afternoon with mid-level lapse rates 7.5-8 C/km.
Moisture is favorable with increasing delivery during the day with
surface dew points in the lower 60s in place by Monday afternoon.
Meanwhile, guidance in fair agreement with climbing precipitable
water values on Monday reaching 1.25-1.5 across much of the
area late Monday-Monday night, corresponding to a forecast of
150% to near 200% of normal. Kinematic profiles looks adequate,
including deep layer vertical wind shear, increasing to 30-40 kts,
supportive of multicells and some supercells being possible. Thus
strong to severe storms capable of damaging winds and large hail
are a concern. Lastly, there is some risk for heavy rainfall,
mainly Monday night, given the so-so storm motion, precipitable
water, and anticipated convective evolution to MCSs/multicell
clusters.

Surface cold front advances early Tuesday. Meanwhile, the upper
level trough will continue to lift northeastward and cross the
Upper Missouri Valley by Tuesday night. Overall, the threat for
thunderstorms shifts east to the eastern-third of the local
forecast area Tuesday. At least a risk for isolated strong-severe
storms and locally heavy rainfall are present Tuesday.

Upper-level ridge upstream shifts eastward to overhead and builds
across the Central and Northern Plains Wednesday with an
amplified large scale pattern expected again. The upper-level
ridge continues to build across the Plains Thursday with modest
500 ht rises forecast while an upper-level trough moves onshore
the West Coast by Thursday night. The upper-level trough ejects
into the Central Great Basin Friday. Of which, highs rebound into
the upper 80s Thursday with some readings forecast to see lower
90s across portions of the area Friday. Next chance for showers
and thunderstorms then appear in the afternoon and evening
Thursday and Friday, albeit low-end chances at this time.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 637 PM CDT Sat May 26 2018

Main concerns are thunderstorm chances late Sunday and LLWS
conditions tonight. Satellite imagery shows increasing cirrus
clouds across southwest Nebraska. High clouds will continue to
drift northeastward and will continue to persist overnight.
Meanwhile, LLWS conditions develop tonight associated with LLJ
starting near 04z later this evening and diminishing after 12z
Sunday morning. Upper height of the wind shear layer forecast
around 1.5 kft with a speed at the top of layer around 40-50 kts.
Partly sunny conditions expected tomorrow with VFR ceilings.
Lastly, there is potential for isolated thunderstorms in the
eastern Panhandle and far western NEB late tomorrow afternoon.

&&

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

$$

SHORT TERM...ET
LONG TERM...ET
AVIATION...Roberg


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