Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 231153
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
653 AM CDT Wed May 23 2018

.SYNOPSIS...
Issued at 345 AM CDT Wed May 23 2018

H5 analysis from tonight had a closed low along the Utah/Nevada
border, with a trough extending south into northern portions of
Baja California. North of the low and trough, a ridge of high
pressure was present across western Canada. This ridge extended
north into northern portions of the NW Territories of Canada. East
of these features, a low amplitude trough of low pressure was
present across Quebec, south into the Mid Atlantic states. East of
this trough, high pressure was anchored over the western
Atlantic. At the surface, a trough of low pressure extended from
northeastern Wyoming, south into eastern Colorado. A warm front
extended across southern South Dakota. A secondary area of low
pressure was noted over southeastern Colorado. Winds were from the
south overnight, and with partly to mostly cloudy skies, readings
as of 3 AM CDT ranged from the middle 60s to around 70 degrees.

&&

.SHORT TERM...(Today and tonight)
Issued at 345 AM CDT Wed May 23 2018

Thunderstorm chances and the threat for severe storms will be the
main forecast challenges over the next 24 hours. The previously
mentioned upper level low, will lift northeast into southern
Montana today, deepening the surface trough along the front range
of Wyoming and Colorado. East of the trough, southerly winds will
increase with breezy conditions expected this afternoon. Good
mixing will facilitate highs well into the middle and upper 80s
this afternoon. By late afternoon, a decent shortwave will lift
across the central Rockies, emerging onto the northeastern
Colorado Plains. Strong southerly winds crossing the Palmer
Divide, will result in subsidence on the north side of the divide,
enhancing a dryline bulge over nern Colorado by 21z this
afternoon. The latest NAM12, WARW, and HREF products, initiate
convection on the nose of this dryline bulge, then lift this
activity north northeast into the Nebraska panhandle through mid
evening. Additional convection is expected to develop from mid
evening into the overnight hours east of the panhandle into North
Central Nebraska. The best chances for storms overnight will be
across northern portions of the forecast area where the nose of an
H85 jet streak sets up overnight. As for the threat for severe
storms, the greatest threat will be over the northwestern forecast
area INVOF the surface trough. Modest deep layer shear of 30 to
40 KTS in the northwestern forecast area, should support some
strong to severe storms with the main threat being from large hail
and damaging winds. The severe threat will diminish east of the
panhandle, as deep layer shear weakens east of highway 83.

.LONG TERM...(Thursday through Tuesday)
Issued at 345 AM CDT Wed May 23 2018

As an upper low comes onshore in California and the main trough digs
across the Desert Southwest, a ridge builds over the Great Plains.
The pattern of amplifying southwest flow aloft helps lead to the
warmest stretch of the season so far for western Neb. Meanwhile, a
weak cool front crosses the forecast area Thursday, setting the
stage for additional thunderstorm development before high pressure
takes over. The next lee side low lines up for late in the holiday
weekend.

Thursday... Continued chc TSRA east of Hwy 83, along/ahead of the
front. Can`t rule out a strong or briefly severe storm on the
account of good surface moisture (dew points near 60F) and
instability (MUCAPE 1500+ j/kg, LI near -7). However, shear is
meager (0-6km up to 30 kts) and the wind profile is primarily
unidirectional. Made little change to max temps in the mid/upper
80s, which is close to a MAV/MET blend. H85 temps approach 25C
across the Sandhills as there is little CAA post fropa.

Friday and Saturday... The building upper ridge and surface high
leads to consistent southerly flow, fair skies, and deep mixing
(above H7). The result is widespread highs near 90F, almost 20
degrees above normal and nearing record heat for late May. NAEFS
ensembles indicate H85 temps near the 99%ile, supportive of the warm
forecast. However, hedged toward the slightly cooler end of guidance
Saturday due to dew points rising to 60F again. If return flow of
moisture is delayed and dry air sticks around longer, could be
within reach of record highs.

Sunday and beyond... Temps stay seasonably warm but are tempered a
bit as precip chances increase. Confidence is greater for strong
moisture advection ahead of the slowly approaching upper low and
developing sfc trough.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 652 AM CDT Wed May 23 2018

For the KLBF terminal: Expect scattered mid to high level
cloudiness today with ceilings ranging from 12000 to 20000 ft AGL.
The threat for thunderstorms will increase by mid evening with the
best chances from 3z to 10z Thursday. Ceilings associated with the
storms will be around 8000 FT AGL. For the KVTN terminal: Partly
to mostly cloudy skies are expected over northern Nebraska with
ceilings ranging from 12000 to 20000 FT AGL. The threat for
thunderstorms will increase after 2z, continuing into the late
evening hours. Ceilings associated with thunderstorms will be
around 3000 Ft AGL and visbys may fall off to around 4sm.

&&

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

$$

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



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