Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 270533

Area Forecast Discussion
National Weather Service Hastings NE
1233 AM CDT Tue Jun 27 2017

.SHORT TERM...(This evening through Tuesday night)
Issued at 304 PM CDT Mon Jun 26 2017

Aloft: The Westerlies were moderately amplified with a ridge over
the Wrn USA...a trof over the E and cyclonic NW flow between over
the Plns. A low was moving onshore with the Pac NW. This low will
weaken and cont E as a trof tonight into tomorrow and arrive into
MT/WY after midday. This will force the Wrn ridge to deamplify
and move over the CWA tomorrow. The tail end of this trof will
cross the CWA Tue night.

Surface: A very week cool front was sinking S thru the CWA this
afternoon. This front will dissipate tonight. Nrn Plns high pres
will sink into the OH/TN Vlys tomorrow...putting the CWA in the
warm sector.

Tonight: The cool front has triggered sct tstms. These storms will
sink S with the front...clearing the Srn border of the CWA by 9
PM. The environment is not deal but sufficient for svr tstms. We
already saw hail up to the size of golf balls in Furnas County
with a low-top supercell.

MLCAPE will be 1000-1500 J/kg in the presence of 40 kts of deep
layer shear.

Some models are hinting that some mid-lvl shwrs could develop from
ACCAS after midnight...on the Ern fringe of the moisture plume
advecting NE across the CWA. Confidence was not high enough to
include in the fcst yet.

Tue: Possibly a few AM shwrs then becoming m/sunny and breezy.
Areas W of Hwy 281 could gust to 40 mph.

Tue night: Probably the best chance of widespread rain we`ve seen
in quite some time. Tstms will develop over the Panhandle and Ern
CO and congeal into clusters in the outflow dominant environment.
The approaching shortwave trof will aid in maintaining them as
they surge E and cross a good chunk of the CWA. The main threat
will be damaging winds...but hail can`t be ruled out W of Hwy 183.

.LONG TERM...(Wednesday through Monday)
Issued at 304 PM CDT Mon Jun 26 2017

There is a lot of reason to be pessimistic on rain chances given
how dry June has been over the rgn. However...this week offers
legit reasons for optimism. Believe we have the best chances for
widespread beneficial rainfall we`ve seen in weeks as we will have
help aloft Tue and again Thu.

With on-going tstm monitoring...will keep this section brief.

SPC has a slgt risk for the SE half of the CWA Wed.

Of greater concern is Thu with 2000-3000 J/kg MLCAPE and a
Craven-Brooks sigsvr parameter of 50-70K. These storms will have
support of a shortwave trof.


.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Wednesday)
Issued at 1221 AM CDT Tue Jun 27 2017

Mostly clear skies along with relatively light winds and
increasingly moist low levels will provide a brief window for fog
and stratus Tuesday morning. Short-term models support this trend
of low visibilities, particularly along and east of Highway 281. Therefore,
I`ve given a brief window of IFR at KGRI, and MVFR at KEAR.
Increasing winds should mix out the fog/stratus by 13z or 14z at
the latest.

This afternoon, southerly winds will gust to around 30 kts. The
pressure gradient tightens significantly 21 to 00Z, so I expect
that somewhat breezy conditions will continue into the evening and
overnight as well.

The next concern is the threat for thunderstorms Tuesday night.
Models show a complex of thunderstorms moving out of western
Nebraska and into the area in the 02-05Z timeframe, but there is
still enough uncertainty on exact timing/location that this isn`t
included in this TAF issuance

Lastly, there is a chance that we approach LLWS criteria Tuesday
night under a 50-60 kt low-level jet at 850mb. Of course, this
will depend on how much surface winds can decouple. Given the
complex forecast, I haven`t included it in this TAF and will re-
evaluate at 12Z.




LONG TERM...Kelley
AVIATION...Mangels is the U.S. government's official web portal to all federal, state and local government web resources and services.