Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 161731
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1231 PM CDT Sun Jul 16 2017

.SHORT TERM...(Today and tonight)
Issued at 346 AM CDT Sun Jul 16 2017

At 08z, radar indicated a subtropical upper level low near Goodland
KS. Heavy convection fired south of the upper low this evening
across southeast Colo. This is the result of outflow from the
daylong rain over east-central Colo and Wrn KS. The models lift the
upper low into Swrn Neb tonight and ambient precipitable water
increases to over 1.60 inches which is very high. The NAM Bufkit
suggests high conditional heavy rainfall potential with a 30 to 40
kt low level jet and deep warm cloud rain processes. If
thunderstorms form then the resulting cold pool and mesohigh would
support heavy rainfall for areas near and south of Interstate 80.

The forecast uses a blend of the HRRR, RAP and NAM models but caps
POPs at 50 percent. WPC suggests the best rain chance will be across
NW KS. The excessive rainfall discussion from WPC is still under
development.

The temperature forecast today uses a blend of HRRR and RAP models
which supports highs in the upper 90s to 100 across Ncntl Neb and
upper 80s to lower 90s elsewhere. This strategy worked quite well
Saturday. Lows tonight are a guidance blend plus bias correction.

.LONG TERM...(Monday through Saturday)
Issued at 346 AM CDT Sun Jul 16 2017

An H5 high remains anchored over the southern Plains all week,
placing Nebraska on the northern edge of the ridge. At the surface,
a series of lows cross the forecast area along a meandering front.
Virtually the entire long term forecast can be characterized by
above normal temperatures and daily (nightly) thunderstorm chances.

Monday... Kept schc to chc PoP for SW and central Neb. early as a
relatively compact H5 low moving northeast into the state will
enhance lift. Low level moisture advection is shown by southerly
flow at H85 and sfc dew points rising into the 60s. A surface low
will provide extra forcing toward the evening, providing another
chance of TSRA across the Sandhills. Forecast soundings suggest CAPE
of at least 1000 j/kg, sufficient for strong to briefly severe
thunderstorms. 0-3 km shear increases after dark with the arrival of
the LLJ. Cloud cover will limit temps somewhat during the day, and
did not move too much from the previous forecast highs in the
lower/mid 90s.

Tuesday and Wednesday... General agreement in the models trending
even warmer. With mostly fair conditions during the day, a deep
mixed layer, and H85 temps near 30C, widespread upper 90s are
likely. Dew points remain in the 60s, primarily east of Hwy 83, and
will push some locations to 100F heat indices. NAEFS climo plots
also show H5-8 temps exceeding 90 percentile for much of this
time frame. GFS soundings indicate little to no low level lift and
a cap through 00z, which will greatly limit convection chances
during the day. The LLJ returns each night, generally around 25 to
30 kts, with the nose somewhere in the forecast area. Similar to
Monday evening, isolated strong to severe storms are possible due
to elevated CAPE and slightly better shear. Another threat will be
heavy rain as forecast PWATs are near 90ile climo values across
the Sandhills.

Thursday through Saturday... A couple weak cold fronts drop south,
gradually cooling highs back toward 90F and maintaining chances of
TSRA. The current trajectory and timing of one sfc low takes it
right over SW Neb Friday evening, which is conducive for more
widespread storms.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1230 PM CDT Sun Jul 16 2017

VFR conditions today into this evening. For the overnight into
Monday morning, increasing chances for thunderstorms at the KLBF
terminal, mainly after 12z. Visibility reductions are poossible
from brief heavy rain, which is yet to be determined in the TAF.
KVTN will be unaffected by this activity.

&&

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

&&

$$

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



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