Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 180858

Area Forecast Discussion
National Weather Service Hastings NE
358 AM CDT THU AUG 18 2016

...A Strong Cool Front for Mid-August will Introduce a
Refreshingly Cool/Less-Humid Air Mass for this Weekend and it`s
Probably Preceded by Severe Tstms Fri Afternoon/Eve...

.SHORT TERM...(Today and tonight)
Issued at 358 AM CDT Thu Aug 18 2016

Aloft: A high-amplitude ridge was over the E Pac and extended
into NW Canada. The Westerlies extended downstream from the ridge
along the US-Can border. Flow over the Srn 2/3 of the CONUS was
weak with trofiness over the Wrn USA and a subtropical ridge over
the SE States and adjacent Atlantic. The main player in our wx
will be the deepening trof over Wrn Canada. Not much will change
thru tonight except everything will get slightly suppressed to the
S as the Wrn Canada trof drops into ND/MT.

Surface: High pres was over the Ern USA. A strong cool front
extended from cntrl Canada low pres SW into ND/MT. The high will
remain over the Ern USA while the cool front conts plunging S. It
will enter the panhandle late this morning and stretch across the
Sandhills by sunset. By dawn Fri...the model consensus places the
front from OIN-HSI-OLU.

Now thru Sunrise: A 30-40 low-lvl jet has resulted in some spotty
small high-based shwrs and a couple tstms. This activity should
wane 6-9 am as the low-lvl jet weakens.

Today: P/cloudy forenoon then becoming m/sunny. A couple degs
hotter than yesterday...but with a nice breeze. SW winds gust
20-23 kts.

Tonight: M/clear except increasing clouds...especially N and W of
the Tri-Cities. Can`t rule out a few shwrs/tstms moving in late.
Elevated MLCAPE is fcst 1000-1500 J/kg. Weak unidirectional wind
profile will result in weak deep layer shear around 20 kts.

.LONG TERM...(Friday through Wednesday)
Issued at 358 AM CDT Thu Aug 18 2016

A fairly strong cold front for mid-August is expected to traverse
the local area on Friday. While the exact timing of this front
will have some impact on shower and thunderstorm coverage...
forcing from the frontal boundary should be sufficient to spark
fairly widespread coverage of thunderstorms during the late
afternoon and evening as instability builds ahead of it. Because
inherited chances for precipitation were already fairly high...
very little change was necessary to the inherited forecast...and
only fine tuned the timing/pops a bit to remain in line with

Overall...instability is expected to surge ahead of the
approaching frontal boundary by mid afternoon the
frontal boundary will be in the midst of crossing the local area.
While the best chance for more widespread and stronger
thunderstorms will be across the southeastern quadrant of the
local area...where the instability will be greatest...the entire
ares will have a decent chance for thunderstorms forced by the
passing frontal boundary and reinforcing upper level wave. While
shear values are not very significant ahead of the front...given
the instability and increasing shear values near the boundary
itself...would not be surprised to see some stronger to marginally
severe thunderstorms develop during the late afternoon and evening
hours...with strong winds likely being the main threat...with a
lesser large hail threat also anticipated later in the day. Not
surprisingly...much of the local area is highlighted with a slight
risk for severe thunderstorms by SPC.

As the day wears on Friday...a fairly significant upper level
disturbance is forecast to help push this frontal boundary
southeast and away from the local area...with chances for
precipitation rapidly ending in its wake. With this fairly strong
wave pushing the front east...thunderstorm activity is expected to
be outside of the local area by Saturday morning...with a dry and
seasonably cool weekend in store for the local area. While
temperatures are expected to be 10-15 degrees below normal over
the weekend...temperatures on Friday ahead of the front will be a
challenge with increasing cloud cover and the timing of cold air
advection. Overall...did not alter Fridays high temperatures
significantly, with the northern third of the local area being
most impacted by approaching frontal boundary.

Behind the passing cold front...expect northwesterly flow aloft
to prevail over the upcoming weekend. While embedded shortwaves in
this flow pattern can often times lead to the development of
shower and thunderstorm stable air in place will
prevent little more than some passing clouds over the upcoming
weekend into early next week. As the upper flow then shifts and
becomes more southwesterly towards the middle of next week...
expect increasing temperatures to near or slightly above climo...
along with increasing moisture and result in a
return to a more unstable weather pattern. Given the modeled
instability and shear values next Tuesday/Wednesday...we could
eventually need to add the potential for some strong to severe
thunderstorms...but at this point the predictability remains too
low to mention in the HWO.


.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Thursday)
Issued at 1250 AM CDT Thu Aug 18 2016

Significant Wx: LLWS until 14Z.

Rest of tonight: VFR with SCT altocu around 13K ft and SCT-BKN
cirrostratus around 20K ft. LLWS. Light ESE should gradually
become S under 10 kts. Confidence: High

Thu: VFR with a few altocu around 12K ft. SSW winds increase and
gust up to 23 kts. Confidence: High

Thu eve: VFR with just a few shreds of cirrostratus at 20-25K ft.
S Winds settled down to around 10 kts. Confidence: High


.GID Watches/Warnings/Advisories...


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