Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 250853
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
353 AM CDT Fri May 25 2018

.SYNOPSIS...
Issued at 352 AM CDT Fri May 25 2018

H5 analysis from earlier this evening had a closed low off the
coast of central California. Downstream of the low, a ridge of
high pressure extended from the four corners north west into
southern British Columbia. East of the ridge, a shortwave trough
was present over southern Manitoba with a trough extending south
into western Nebraska. Further east, a low amplitude ridge
extended from Chicago north into western Ontario. At the surface:
A weak trough of low pressure extended from the eastern Dakotas
into eastern Nebraska and eastern Kansas overnight. INVOF this
feature, showers and thunderstorms were present mainly across
eastern Kansas, however, satellite imagery overnight does indicate
some mid level cloudiness from western Minnesota into eastern
Nebraska. West of the trough axis, mostly clear skies were present
across western and north central Nebraska overnight. Readings as
of 3 AM CDT ranged from 53 at Gordon, to 68 at O`Neill.

&&

.SHORT TERM...(Today and tonight)
Issued at 352 AM CDT Fri May 25 2018

Abundant sun, clear skies and a lack of precipitation, will
highlight the weather forecast over the next 24 hours across
western and north central Nebraska. Ridging aloft, currently over
the intermountain west, will transition east over the next 24
hours, with the ridge axis be oriented from far sern Colorado,
north into eastern Montana by 12z Saturday. In the meantime, H85
temps will surge into the middle 20s C this afternoon. Bufkit
soundings indicate strong mixing up to around H600 this afternoon
across the forecast area, leading to highs in the lower 90s today.
These readings are 15 to 20 degrees above normal for this time of
year, but still below record highs for may 25th. Dry conditions
are expected over the next 24 hours, with the surface trough to
the east and a building ridge aloft from the west. The inherited
forecast was dry and this was continued for the short term
forecast. Minimum relative humidity will reach around 20 percent
in far southwestern Nebraska this afternoon which would lead to
elevated fire weather concerns. However, with light winds expected
and fuels being green from recent rains, fire weather concerns
should be minimal this afternoon.

.LONG TERM...(Saturday through Thursday)
Issued at 352 AM CDT Fri May 25 2018

Western Nebraska remains in southwest flow aloft for the next
several days as an upper low over the Great Basin fills and gets
absorbed into the Western U.S. trough. The ridge over the Plains
amplifies this weekend and becomes nearly meridional, setting the
stage for the first heat wave of the season. The trough then crosses
the northern Plains mid next week, followed by another ridge. At the
surface, a lee side low and frontal system sits off the higher
terrain for the first half of the week. The cold front finally
swings through the area late Tuesday into Wednesday in association
with the upper trough.

Saturday... Bumped up highs another degree or so across the area as
guidance continues to trend warmer. NAEFS ensembles still indicate
H5 heights above 90%ile of climo (around 5860m) and H85 temps around
99%ile (25C north central to 28C panhandle). With a slight southerly
breeze, abundant sunshine, and deep/efficient mixing, should be able
to reach the lower/mid 90s for highs. Still have a concern about
moisture holding temps down a touch as southeast sfc winds help keep
dew points in the mid/upper 50s.

Sunday... Also warmed the highs due to mid-level dry air slowing
down precip chances and another day of efficient mixing with near-
record H85 warmth. Storm chances look decent in the evening/night
however. Forecast soundings suggest crazy instability (CAPE 4000+
j/kg and LI`s around -10) and continued moisture advection in the
low levels. Shear still appears to be the limiting factor in keeping
widespread severe threat at bay, but clusters of storms capable of
hail are certainly in play.

Monday/Memorial Day... Have to keep an eye on the convective
potential as this may be the highest severe threat of the period.
Slightly cooler temps (mid/upper 80s) and higher dew points
(lower/mid 60s) still result in CAPE around 4000 j/kg. In addition
to steep lapse rates (almost adiabatic H7-5), deep layer shear
increases to around 40kts as the upper trough approaches (sufficient
for supercells). Hail and wind aren`t the only concerns. If PWAT
reaches the 1.2" as suggested by GFS soundings (record value), could
be looking at flooding issues.

Tuesday and beyond... Kept chc-lkly TSRA Tue. with the cold front
passage. Strong storms still possible, but instability is a lot
lower and wind profile becomes unidirectional. Temps closer to
normal with highs around 80F. Things dry out and warm up again Wed.
with a sfc high taking over. A mid-level wave in combination with
another developing sfc low increase precip chances Thu.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1133 PM CDT Thu May 24 2018

VFR conditions will persist the next 24 hours across all of
western Nebraska. Winds will also remain light below 10 kts.


&&

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

$$

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



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