Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 161119

Area Forecast Discussion
National Weather Service Hastings NE
619 AM CDT Fri Jun 16 2017

.SHORT TERM...(Today and tonight)
Issued at 324 AM CDT Fri Jun 16 2017

Cirrus is moving out of the area as the thunderstorms move
further to the east early this morning. There have been a few
boundaries showing up on the radar in the past few hours. These
boundaries are left over from the convection earlier in the

The main concern for today will be thunderstorm development this
afternoon and evening. There is an upper level wave that moves into
the area during the day. It is not a strong wave, but there will be
some upper level support. Models show a weak front to the northwest
of the forecast area this morning that moves into the area during
the afternoon and evening. The thunderstorms should develop along
this front. The question is where will it be? The front is very weak
and all of the little boundaries from the convection last night have
messed up the location of the front. The HRRR and 4km models have
the convection starting in the west while the NAM and GFS have it
further to the east, maybe even to the east of the forecast area.
Expect that the convection should get started in the mid afternoon
and along whatever boundaries that are out there. Expect that the
best chance will be in the eastern part of the forecast area and
that is where the higher PoPs are. The thunderstorms that do get
going should be severe. MUCAPE in the east is around 3000 to 5000
j/kg depending on the model. The one thing that all of the models
agree on is that the thunderstorms should move out of the forecast
area during the evening hours.

Before the thunderstorms...sunshine today will allow temperatures
to warm into the 90s across the area. The dew points in the south
and southeast will be the highest and heat index values will
approach 100 degrees for that area. There will be light winds and
as the front moves in the winds will be somewhat variable. Then,
after the thunderstorms...what is left of a front is expected to
stall across the southeast part of the forecast area tonight. Low
temperatures will be on the warm side tonight.

.LONG TERM...(Saturday through Thursday)
Issued at 324 AM CDT Fri Jun 16 2017

Aloft: The Westerlies will temporarily transition from zonal to
amplified this weekend into early next week. A ridge will build over
the NW USA allowing a strong +2 SD subtropical high to form
underneath. A trof will form downstream over the Ern USA. The weak
shortwave trof moving thru the Pac NW Fri night will pass over the
Cntrl Plns Sat. NW flow will be overhead in its wake.
Deamplification will occur mid next week with a shortwave ridge
slated to move thru here Wed. The Westerlies will become zonal over
the Nrn USA Thu but will be cyclonic as a fairly deep trof or low
heads E thru Srn Canada.

The last 3 runs of the UKMET/GFS/CMC/EC are tightly clustered thru
Wed with the exception of the 00Z/15 CMC which is a fast outlier
with the Srn Canada low next Wed.

Surface: A cool front will be making its way thru the NW USA today
and tonight. It will arrive into Nrn Neb by 12Z/Sat and cross the
CWA during the day. High pres over the NW USA will build in and then
emerge onto the Plns Sun. A NW-SE oriented stationary front should
then develop across the Nrn Plns Mon. There are some hints it could
come into the CWA as a backdoor...but this uncertain. Even if it
does it should be little more than a wind shift and it will rapidly
lift back N as a warm front as a low pres sys progressing thru the
NW USA approaches. The CWA will be in the warm sector Wed...but the
Canadian low should drive a decent cool front thru here Thu.

Rain: Unfortunately we have entered a summertime pattern which never
offers much. Overall the next svrl days is looking dry for most
locations. There are only limited opportunities for some very
spotty/isolated tstm activity.

Removed thunder from the fcst for Sat. The light QPF is post-frontal
Sat afternoon and night. There is insufficient instability for
thunder. Looks like some light rain could be generated by mid-lvl
fgen with cloud bases 8-10K ft.

The MRGL risk assigned by the SPC for the SE 1/2 of the CWA will
probably end up being shoved further E/S with subsequent updates. We
shouldn`t even be in general thunder. While there will be
substantial elevated instability thru about 6 pm...there will be way
too much CIN/capping to allow for convective initiation.

Sat`s FROPA will sweep away low-lvl moisture as a continental polar
air mass invades. Mstr should return to the rgn Tue. Tstm potential
could be better than we are currently indicating as the Nrn
instability gradient always seems to be an area favored by tstms

Temps: a temporary interruption to slightly cooler than normal
Sun...bounded by near normal Sat and Mon. Then it`s back to
summertime heat in the 90s Tue-Thu.

The fcst may not be hot enough for next Thu. The last 2 EC runs are
offering widespread low-mid 100s for highs. However...this is at the
upr end (75% percentile) of the spread compared to the 51 EC ens
members. The 00Z GFS is supportive of widespread 100F as well.


.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Saturday)
Issued at 616 AM CDT Fri Jun 16 2017

High clouds are expected to break up this morning. There will be a
weak front move through the area during the day, but the winds
will be fairly light. There is an outside chance for some
thunderstorms this afternoon in the vicinity of the front, but
the chance is very low.




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