Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 202040
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
340 PM CDT Sun May 20 2018

.SHORT TERM...(This evening through Monday)
Issued at 339 PM CDT Sun May 20 2018

With the upper low pulling northeast of Nebraska tonight and surface
high pressure in place, mainly dry and seasonably mild conditions
are in store through Monday afternoon. A broken deck of
stratus/stratocu along with lighter north winds/limited mixing kept
highs cool in the lower 60s today. A few sprinkles were observed
north central Neb this afternoon due to slightly stronger forcing
from the nearby low.

This evening and tonight... Clouds slowly clear across the north
while a thick stratus deck redevelops across the south. As winds
wane and gradually shift south/southeast, moisture begins to pool
into the area again. Introduced patchy fog for areas south of Hwy 2
overnight where the conditions are most favorable (southeast winds,
higher dew points) and suggested by SREF and LAMP guidance. Made
little change to min temps as the warmer end of blended guidance
seemed reasonable. Lows generally in the mid/upper 40s.

Monday... Sfc high over the Miss Valley continues to pull moisture
into the Plains as shown by dew points rising into the mid 50s
across western Neb. Meanwhile, a closed low over central Calif. and
Western U.S. trough places Nebraska in southwest flow aloft.
Strengthening south winds and temps exceeding 15C at H85 result in a
nice rebound for highs. Bumped up max temps a degree or so across
the board to mid/upper 70s (and 80 far SW), which is consistent with
MAV and MET. Forecast soundings suggest mixing to around 750mb. One
concern with temps is if fog lasts longer than expected (mainly
Lincoln/Frontier/Custer), but increasing winds should mix it out by
15z. Precip-wise, kept PoP out of the area as the soundings show a
slight cap remaining through the afternoon.

.LONG TERM...(Monday night through Sunday)
Issued at 339 PM CDT Sun May 20 2018

The GFS and NAM are lifting a warm front through Nebraska Monday
evening. The warm front could be the focus for isolated to low end
scattered thunderstorm development. Any storms which develop will be
in a favorable environment for severe weather. Winds aloft at 500mb,
near 30 kts, and ML CAPE around 2500 J/KG set the environment.
BUFKIT suggests supercells and the bulk Richardson number in both
models is below 50 suggesting isolated coverage.

SPC is favoring the srn Plains for storm development Monday and this
is consistent with the slower ECM which develops no convection
across Nebraska until Tuesday and Wednesday. The forecast leans on
the NAM and GFS for a marginal severe weather threat Monday evening,
mainly along and south of Interstate 80. The model consensus
indicates dew points around 60F Monday evening.

If the GFS and NAM verify, the warm front could be north and east of
wrn and ncntl Nebraska Tuesday. Rain chances are limited to diurnal
heating as instability is more modest with a punch of less moist air
in the wake of the warm front Monday. Storm activity might pick up
Wednesday evening with the approach of a Pacific cold front. Winds
aloft are mostly unidirectional and this would lessen the severe
weather threat with a multicell environment in place. Precipitable
water across ncntl Nebraska increases to between 1.25 and 1.50
inches in the GFS which would support locally heavy rainfall.

Post-frontal thunderstorms are possible Thursday as shown by the
GFS, or frontal storms indicated in the slower ECM. The forecast is
generally dry Friday and beyond with just isolated thunderstorm
chances.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1228 PM CDT Sun May 20 2018

Low/mid level stratus will continue this afternoon and evening
across most of western Nebraska (clearing in the panhandle),
along with a few sprinkles or light rain showers for the northern
terminals (KANW, KONL). Cigs will slowly lift late this evening to
VFR. However, light southeast winds and plenty of remnant surface
moisture will likely result in fog across southwest Nebraska
Monday morning. Brought KLBF to MVFR visby, but may also affect
KOGA, KBBW, and KIML.


&&

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

$$

SHORT TERM...Snively
LONG TERM...CDC
AVIATION...Snively


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