Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 151134 AAA
AFDLBF

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
634 AM CDT Sat Jul 15 2017

.SHORT TERM...(Today and tonight)
Issued at 351 AM CDT Sat Jul 15 2017

A weak sfc frontal boundary across SD will settle into the Sandhills
this afternoon. The HRRR and RAP models suggest steep lapse rates
develop with isolated thunderstorms forming for a few hours. These
models were the basis for the POP forecast. Storm activity develops
21z-03z and no organized severe weather is expected. The RAP model
indicates bulk shear less than 10 kts. An isolated brief severe
storm may develop with damaging winds and marginally severe hail.

The temperature forecast leans on the HRRR experimental model which
is the warmest model for highs in the 90s to 100. This model was
about 2 degrees too cool Friday. Lows tonight are a guidance blend
plus bias correction.

.LONG TERM...(Sunday through Friday)
Issued at 351 AM CDT Sat Jul 15 2017

The amplified ridge aloft over the Rockies on Saturday will flatten
early in the week, placing Nebraska on the northern periphery. At
the surface, a boundary will meander across the northern Plains,
which will be the focus for precipitation chances for western
Nebraska during the week.

Sunday... The evening model suite is now in consensus with pushing a
weak closed low from northwest KS into Neb. WV and IR imagery
currently show a swirl in CO that has been slow to move. Held off on
PoP early in the day, but moisture and lift profiles are more
favorable for at least iso TSRA for SW Neb in the evening. Forecast
ambient PWAT values are slightly above climo, and with weak steering
flow and slow storm motion, any convection that develops will have a
heavy rain threat. The LLJ may help expand convection into central
Neb overnight. However, soundings indicate a relatively weak jet at
around 25 kts, so convergence will be rather limited. Severe threat
is low due to minimal CAPE and shear. Temperature wise, reluctantly
backed off highs as the WAA scheme is weaker than previous model
trends. H85 temps now max out at 27C in the warmest guidance, plus
any precip will hold temps down.

Monday through Friday... The interaction of the quasi stationary
front and passing disturbances aloft along the ridge periphery will
basically generate summery popcorn convection during the day and
more organized systems at night with the help of the LLJ. Confidence
in exact placement and timing of the convection remains low. Temps
have trended warmer, especially Tue and Wed, with decent southerly
flow ahead of the front. GFS and ECM are in general agreement with
moisture advection, most prevalent across the eastern half of the
CWA where dew points reach the mid 60s. Will have to watch for
possible heat headlines as locally 100+ heat indices could be
reached. A weak cool front crosses the area Thursday, providing
another chance of TSRA and slightly lower temps. There is also a bit
of an upslope component in the H85 flow, enhancing moisture
convergence and lift. Same ridge riding pattern for Friday equates
to another round of iso T.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 634 AM CDT Sat Jul 15 2017

VFR is generally expected today and tonight.

Local LIFR in fog in the Platte Valley this morning should
dissipate 15z.

A weak sfc frontal boundary across SD will settle into the Sandhills
this afternoon. The HRRR and RAP models suggest isolated thunderstorms
forming for a few hours 21z-03z.

&&

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

$$

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



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