Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 261044

Area Forecast Discussion
National Weather Service Hastings NE
544 AM CDT FRI AUG 26 2016

.SHORT TERM...(Today and tonight)
Issued at 349 AM CDT Fri Aug 26 2016

Focus is on thunderstorm potential and timing later today and then
on the possibility for fog and reduced visibilities overnight.

The pattern aloft featured southwest flow across the Central Plains
ahead of an upper trough translating into the Rocky Mountain region.
At the surface, high pressure was oriented from southern South
Dakota across Nebraska with the surface boundary located to our
south across far southern Kansas into Oklahoma. Convection has been
ongoing across southern Kansas during the predawn hours, and this
activity is gradually lifting north and may edge toward or into our
southeast zones this morning and have carried small pops for this.

Heading into today the surface ridge axis will slide east with winds
transitioning southeast on the back side of the ridge and ahead of a
surface trough along the high plains. Aside from the potential for
some scattered showers/storms in our south this morning, much of the
daytime hours are looking fairly dry with cloud cover expected to
increase/thicken in the afternoon. The airmass is similar to 24
hours ago and temps in the mid 70s look reasonable with the
expected cloud cover.

Showers and thunderstorms are expected to develop this afternoon and
evening along a frontal boundary across central Kansas and to our
west along the high plains as the shortwave trough emerges from the
Rockies. The convection is forecast to spread eastward as the wave
moves crosses the plains today/tonight. In general, precipitation
chances look decent given the dynamics associated with the wave,
however some models suggest convection may become more scattered vs
widespread as it tracks east. Have made adjustments on pops and
timing of convection and will need to monitor how things evolve
today. A strong to severe storm is possible mainly for our southern
zones where instability and shear parameters are higher in the
vicinity of the southern boundary, with hail/wind the primary
hazards from the storms. Precipitable water values average an inch
to an inch and a half and locally heavy rainfall may accompany the
storms and lead to areas of lowland flooding. The shortwave trough
axis edges east of our cwa toward daybreak Saturday and any
lingering precipitation should be winding down and moving off to the
east early Saturday.

Have included fog in the forecast tonight as models are pretty
consistent on indicating the potential for fog and reduced
visibilities, especially across south central Nebraska. Have went
with the potential for visibilities below one mile and some areas
could see a period of dense fog.

.LONG TERM...(Saturday through Thursday)
Issued 452 AM CDT Fri Aug 26 2016

General overview of this 6-day period:
At a quick glance of standard forecast products, it`s pretty
evident that we will be leaving the current cooler feel behind and
entering a somewhat "stagnant" and seasonably-warm summer weather
pattern with highs mainly in the 80s each day and lows in the 60s
each night, along with a plethora of mainly small/currently
low-confidence thunderstorm chances. Adding to the "return to
summer" theme will be day after day of fairly humid dewpoints
mainly in the 60s. In other words, there is just nothing very
"notable" to highlight/latch onto at this it shouldn`t
be overly hot (but certainly no cool spells of note either) and
although have little doubt that at least a few isolated severe
storm/localized flooding threats will crop up here or there, there
is nothing "obvious" enough at this time to justify specifically
highlighting in our local Hazardous Weather Outlook (and SPC also
has refrained from any severe outlooks thus far for this time

With these basics covered, will attempt to provide some semblance
of brief day-to-day thoughts, but please keep in mind that
especially thunderstorm chances are very murky/"iffy" in both
timing and placement, even in the Day 2-3 time frame let alone
beyond that, as we return to a rather tricky summer weather

Saturday/Saturday night:
By and large, the potentially widespread thunderstorm event
detailed in the short term section above is expected to have moved
east of our CWA by daybreak, in tandem with the instigating mid
level shortwave trough in our recent and persisting pattern of
west-southwest flow aloft. As a result, have greatly reduced the
areal coverage of small thunderstorm chances for Saturday morning
(relegating them only to far southeast zones for a few hours) and
potentially rolled the dice a touch by removing mentionable
chances altogether from Saturday afternoon. To be clear, the
chance of a rogue Saturday afternoon storm is not truly "zero",
but it seems to closer to 10 percent in any given area versus 20+,
and thus why it`s not in the official forecast. Of course, this
all bears watching, as actually the very latest 06z 4-kilometer
NAM suddenly seems a touch more aggressive with lingering storm in
our eastern zones for a time Saturday morning. Otherwise, for most
folks, the biggest issue Saturday might be potentially decent
coverage of at least light fog lingering until around mid- morning
in the wake of the departing convection, and have coordinated with
the short-termer to carry this fog possibility over from the
Friday night period. Otherwise, once morning fog/potentially
widespread clouds break up, expect no worse than a partly cloudy
afternoon as light southerly breezes prevail, allowing high temps
to climb back into the 80s again. Briefly turning to Saturday
night, have blanketed the majority of the CWA with a basic 20
percent chance (PoP) for isolated storms. While models such as the
ECMWF are completely dry, there are hints from the NAM and
especially GFS that the combo of a fairly weak incoming mid level
wave and a weak-modest low level jet could spark some spotty

Sunday/Sunday night:
Our basic weather pattern starts to change a bit as mid-upper flow
weakens a bit in response to an upper level ridge centered over
the southeast/mid-south states retrogrades toward the Central
Plains a bit. That being said, despite the weakening flow, there
still appears to be respectable convective instability, fairly
weak capping and signs of very subtle little disturbances working
overhead. As a result, just cannot completely rule out at least
spotty thunderstorm activity and currently have 20 PoPs during the
day and 30s at night. Southerly winds will be a bit breezier than
Saturday, and high temps were nudged up 2-3 degrees from previous.

Monday-Thursday time frame:
With so many daily uncertainties too murky to even dive into,
will just brush over these 4 days in brief...Although at a glance
the large-scale pattern becomes more "ridgy" over the central
CONUS, it`s not a huge sprawling ridge with notably hot mid level
temps/substantial capping, and subtle little waves still look to
work their way through our general area from the west or at least
brush us. Combined with at least modestly daily instability, a
parade of low storm chances continue nearly every forecast period.
At least for now, Thursday daytime remains a "dry" forecast, but
this might not last long either per the latest ECMWF.


.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Saturday morning)
Issued at 542 AM CDT Fri Aug 26 2016

Cloud cover is expected to lower/thicken today/tonight with
ifr/lifr conditions possible toward 12Z Saturday with the
potential for visibility restrictions in fog. There is the chance
for thunderstorms at the terminals primarily late this evening
into the early overnight period.


Issued at 440 AM CDT Fri Aug 26 2016

With only a handful of August/meteorological summer days are a few "random" precipitation notes of possible

- Hastings airport still needs another 0.19" of rain this month to
avoid the driest meteorological summer (Jun- Aug) on record out
of 122 years (current record is 4.34 inches in 1922).

- The generally north (drier) vs. south (wetter) disparity in
rainfall across our CWA has become even more stark over the past
few days. For example, per official NWS and CoCoRaHS stations, a
few of the wettest sites so far this month include Osborne KS
(7.56") and Hebron (6.85"). Each of these totals are far more than
the Nebraska Tri-Cities airports COMBINED: Grand Island (0.44"),
Hastings (1.19") and Kearney (1.47" per official observer).


.GID Watches/Warnings/Advisories...


LONG TERM...Pfannkuch
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