Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 292036 CCA
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
324 PM CDT MON AUG 29 2016
...CORRECTION...

.SHORT TERM...(This evening through Tuesday)
Issued at 324 PM CDT Mon Aug 29 2016

Tonight and tomorrow.  The primary focus in the short term forecast
will be a heavy rainfall threat with a secondary focus centered on
the fog potential Tuesday morning.

The latest water vapor image reveals a mature cyclone over southern
Colorado with it`s baroclinic leaf rotating north into southwest
Nebraska/central Sandhills.  At the surface, an inverted trough
bisects southwest Nebraska northeast into the Sandhills. Convection
has been ongoing across Kansas for much of the day, with the
activity moving northward as well.

Near term guidance continues to indicate the potential of weak multi-
cell convection this afternoon and evening across much of the cwa.
Bufkit analysis from the central Sandhills and points southeast
reveal an increase in PWATS from the actual 12z KLBF sounding this
morning. The atmosphere is moderately unstable...but the
contribution of CAPE is spread thin through a large portion of the
troposphere.  Warm cloud depths are not overly impressive, but given
storm motions of 10kts or less, appreciable rainfall is possible
where convection develops.  Current thinking is that the trough will
serve as a focus for storm development until diurnal heating
subsides, with a secondary focus on the storms to the south and
southeast of the cwa as they rotate north.  Just as an FYI, 3hr
flash flood guidance across the cwa is generally 2-3" for non-
sandhills locations across the cwa. Over the Sandhills, the FFG is
as much as 5 or 6 inches. So at this point, flash flooding is not a
concern.

For Tuesday, the focus for storms lies just south and southeast of
the cwa along a warm front.  However at this point we cannot rule
out storms across our southeast, especially over Frontier County. If
storms are realized, heavy QPF is possible.

The fog potential is somewhat uncertain at this point.  The latest
guidance indicates the potential of at least patchy wording for
southeastern portions of the cwa with a source of low level moisture
and expected light winds overnight.  The latest SREF favors mvfr
stratus rather than fog, so will go with patchy wording for now.

Otherwise high temperatures will largely be held in check by the
expected cloud cover.  Although, a few mid-80s are possible across
our northern zones on Tuesday.

.LONG TERM...(Tuesday night through Monday)
Issued at 324 PM CDT Mon Aug 29 2016

Tuesday night through Thursday...a subtropical disturbance has moved
into Srn Colorado this afternoon and the models continue to shear it
out across the Cntl Plains Tuesday. The disturbance appears to exit
Wednesday morning with just isolated showers and thunderstorms
across Srn Neb. Canadian high pressure will build south thorugh the
Upper midwest Wednesday with low pressure forming on the Nrn High
plains. The low pressure will remain across the High plains Thursday
and draw the cooler air west through Nebraska. The net result is
highs in the low to mid 80s and less humidity than earlier forecast.

The model consensus suggests dew points in the lower 60s during the
day which fall into the 50s at night. This supports lows in the 50s
Wednesday and Thursday morning. The NAM12...GFS20 and ECM are giving
the signal for stratus Thursday morning. Low pressure on the high
plains will draw moisture north through Wrn Neb. The NAM and ARW/NMM
models suggest patchy fog both mornings. The feeling is the fog
would probably be patchy since rain is not expected to become
widespread so the forecast will omit this feature for now.

Thursday night through Monday...a decent long wave trof moves
through the Wrn U.S. Thursday and Friday. The trof moves into the
Cntl Plains Saturday presenting the best opportunity for
thunderstorms Saturday night and Sunday. Winds aloft increase and
lapse rates steepen suggesting strong thunderstorm development with
some potential for severe weather. Conditions support storm
development Friday evening across the Panhandle.

The warmest days are Friday through Sunday with highs in the mid 80s
most areas. Deterministic and bias corrected data suggest dew points
in the 60s ahead of the trof and the GFS advertises precipitable
water of around 1.50 inches. MLCAPE in the GFS is 1500-2500 J/KG
which would support at least a marginal severe weather potential.

Cooler and less humid weather develops Monday with highs in the 70s.
Pacific high pressure will be in place.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1222 PM CDT Mon Aug 29 2016

A disturbance moving northeast across the central plains will
spark off additional showers and thunderstorms across southwest
Nebraska this afternoon/evening. None of the storms are expected
to be severe, but the available guidance suggests some heavy rain
potential, leading to reduced visibility. The guidance holds the
majority of the rain south and east of the klbf, but close enough
to the terminal for at least a 30% mention in the forecast.
Otherwise there`s a fog signal setting up late tonight and early
tomorrow. At this point, mvfr ceiling and visibility looks
possible at klbf and other southwest Nebraska terminals.


&&

.LBF Watches/Warnings/Advisories...
None.
&&

$$

SHORT TERM...Jacobs
LONG TERM...CDC
AVIATION...Jacobs



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