Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 201736
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1236 PM CDT Tue Jun 20 2017

.SHORT TERM...(Today and tonight)
Issued at 335 AM CDT Tue Jun 20 2017

A plume of rich moisture across West TX moves north-northeast today
and should enter scntl Neb during the afternoon or early evening.
Dew points would rise into the upper 50s to lower 60s with
precipitable water north of 1.25 inches. Steep lapse rates are
supporting k-indices in the 40s. SPC suggested areas south of
Frontier County for storm development. This is close to the HRRR.

The forecast leans on the RAP...NAM...SREF...HRRR EXP and NAM nest
for isolated storms across Scntl Neb...generally east of North
Platte. Winds aloft at 500mb are reasonably strong...35 to 40kt and
this produces a BRN around 50 with 2500-3500 J/KG of MLCape. This
would support severe storm development.

The temperature forecast today leans on the warmest model...the HRRR
EXP model which verified best Monday. Highs in the mid to upper 90s
are expected along and south of I-80.

Blended guidance plus bias correction produces lows in the 60s
tonight. A MCS may form off the Tetons this afternoon and the model
blend carries a portion of this convection into Nrn Neb late
tonight.

.LONG TERM...(Wednesday through Monday)
Issued at 335 AM CDT Tue Jun 20 2017

Strong to severe thunderstorms are possible Wednesday afternoon
along a trough/stalling frontal boundary.  The greatest likelihood
of storms lies east of a Eustis to O`Neill line where the models
indicate a moderate to strongly unstable atmosphere and sufficient
shear for organized storm development.  The models suggest the
eastward advection of an EML while boundary layer moisture pools
ahead of the stalling front.  A modest cap will be in place, but the
latest solutions indicate the eventual eroding of the lid with the
focus of storms along the front.  Large hail and gusty erratic wind
will be the primary threats.  At least initially, very large hail
will be possible as soundings reveal significant contribution of
CAPE in the HGZ.  Will need to monitor the further development of
convection overnight, albeit much lesser severe risk, as the models
indicate the development of a high plains LLJ.  At this point the
focus of additional storm development appears to favor the Cheyenne
Ridge and points north, but we cannot rule out storms across our
northwest and north into early Thursday.  The stalled front will
slowly retrograde north as a warm front and serve as a focus for
additional convective development Thursday afternoon and early
Friday.  The atmosphere remains solidly unstable south of the front
with the potential of severe hail along and south of I80 and east
through Garfield County.  SPC has outlooked parts of the CWA both in
Day 2 and Day 3.

A northern plains wave will shunt the boundary south of the forecast
area on Friday allowing for lesser instability and much cooler
temperatures.  Highs are projected to fall from the 90s on Wednesday
to just the 60s and lower 70s by Saturday.  Spotty showers are
possible Friday and Saturday as several pertabation pass through
the mean flow, but again, the convective threat is minimal.
Temperatures remain below average through Sunday, but warm early
next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1232 PM CDT Tue Jun 20 2017

VFR and scattered high level clouds are expected the next 24 hrs.
An isolated tstm is possible but nothing widespread. Low level
wind shear is expected tonight as a southerly low level jet
develops just off the surface.

&&

.HYDROLOGY...
Issued at 1232 PM CDT Tue Jun 20 2017

High water continues on the North Platte river upstream of Lake
Mcconaughy due to increased releases from upstream reservoirs in
Wyoming. The higher flows will gradually decrease over the next
several days. The gauge at Lewellen currently reads 7.0 feet and
this should fall to around 6.5 feet this weekend. Flood stage is
7.5 feet.

&&

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

$$

SHORT TERM...CDC
LONG TERM...Jacobs
AVIATION...Taylor
HYDROLOGY...Taylor



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