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000
FXUS63 KLBF 241138
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
638 AM CDT Thu May 24 2018

.SYNOPSIS...
Issued at 334 AM CDT Thu May 24 2018

A fairly chaotic H5 pattern was present across the western CONUS
tonight. Low pressure was located over central Montana with a
shortwave trough of low pressure extending to the southeast into
western Nebraska. Other shortwaves were noted over southern
Colorado and northern Arizona. Further west, a trough of low
pressure was present from northwestern British Columbia south into
the eastern Pacific off the coast of northern California. Across
the eastern half of the CONUS, a ridge of high pressure extended
form eastern Iowa, north into western Ontario. East of the ridge,
a trough extended from eastern Quebec into portions of New England
and the Canadian Maritimes. At the surface, a weak inverted
trough of low pressure was present across the Nebraska Panhandle.
Low pressure was noted over western North Dakota and southeastern
Colorado. From northeastern into southwestern Nebraska, winds were
generally from the south, while west of this line, winds were
variable. Temperatures as of 3 AM CDT were in the 60s across
western and north central Nebraska.

&&

.SHORT TERM...(Today and tonight)
Issued at 334 AM CDT Thu May 24 2018

Precipitation chances over the next 24 hours is the main forecast
concern. For this morning: Mid level warm air advection will
remain favorable for showers and thunderstorms through mid morning
in the east and will continue to mention the threat for pcpn
through 15z this morning. For the remainder of today, most of the
forecast area will be west of the wind shift line, mentioned above
in the synopsis section. With the development of westerly winds
later today, drier air will begin to infiltrate western portions
of the forecast area. That being said, the threat for
thunderstorms will be significantly limited this afternoon.
Further east, the threat for showers and thunderstorms will
increase during the late afternoon and evening hours as a mid
level shortwave trough enters western Nebraska. Based on the
latest NAM12 and WARW solutions, the surface boundary (aka wind
shift line) will be oriented from Frontier county to Boyd county
around 21z this afternoon. With this in mind, will place pops
along and east of this line. As for the severe threat today and
tonight, deep layer shear is meager this afternoon, on the order
of 20 to 25 KTS. This would favor a strong storm or two through
mid evening. However, the threat for severe storms appears low
attm.

.LONG TERM...(Friday through Wednesday)
Issued at 334 AM CDT Thu May 24 2018

Upper level flow transitions from southwest to nearly meridional as
a closed low reaches the SF Bay Area on Friday, then stalls over the
Great Basin over the weekend. The amplifying ridge over the Plains
is still progged to bring the first heat wave of the season. The low
eventually lifts northeast onto the northern Plains, helping to
sweep a cold front through the area toward midweek.

Friday and Saturday... H5 heights reach 5860m (above 90%ile of
climo) and H85 temps exceed 25C across the Sandhills (around
99%ile), which keeps confidence high on the heat wave. These two
days have consistently been the warmest in the guidance. With
downslope flow on Friday and strong southerly winds on Saturday
combined with fair skies and deep mixing (to H7 or higher), highs
should reach the lower 90s (about 15 degrees above avg). A couple
concerns with max temps however... one would be a cirrus shield
overspreading from the Rockies and another is increasing moisture
advection in the low levels leading to dew points in the upper
50s.

Sunday and beyond... A couple mid-level waves and a slow-moving
boundary will be the focus for several days of precip chances. The
continued warmth of highs in the 80s to near 90 and moisture of dew
points in the 50s/60s result in abundant instability Sun-Tue.
Forecast soundings suggest MUCAPE of 2500+ j/kg, LI`s around -10,
and mid-level lapse rates around 8c/km. With that said, any
thunderstorm that develops each evening could easily become strong.
The limiting factor for widespread severe is shear as deep-layer is
generally limited to 30 kts. Low-level shear appears highest on
Monday, which could support the relatively greatest threat of severe
over this period. The LLJ sets up over Nebraska each night as well,
but the nose is pointed toward the Dakotas, keeping the greatest
convergence north of the area.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 638 AM CDT Thu May 24 2018

Showers and thunderstorms will continue to exit portions of north
central Nebraska this morning. This activity is expected to remain
east of the KLBF and KVTN terminals. For the remainder of the
forecast period, expect scattered high cloudiness with ceilings
around 25000 FT AGL. Some mid level clouds may develop late this
afternoon and early this evening with ceilings around 12000 FT
AGL.

&&

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

$$

SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Snively
AVIATION...Buttler