Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 251601

Area Forecast Discussion
National Weather Service Hastings NE
1101 AM CDT Thu May 25 2017

Issued at 1052 AM CDT Thu May 25 2017

Updated the forecast for late morning and early afternoon to put
some isolated showers/thundershowers in our north, especially near
Ord as we seem to be getting as much out of any mid-level
instability that we can as steep mid-level lapse rates favor
convection. Cloud bases are high, so we probably will not end up
with much rain where rain does happen to fall in the north.
brought sprinkles as far south as just north of Kearney and Grand
Island. I also increased sky cover in our west/north today.


.SHORT TERM...(Today and tonight)
Issued at 407 AM CDT Thu May 25 2017

Aloft: WV imagery and 00Z upr-air data show two over
the TN Vly and the other over Sask with a ridge between over the
Plns. Progression will occur over the next 24 hrs. As the ridge
moves E...the flow will become WSW. A potent shortwave trof
trailing the Sask low will cont to dig across the Nrn Rockies
today and then lift into the Dakota`s tonight. 80
kt jet streak has been advancing thru the Desert SW overnight. The
LFQ of this jet will extend into KS this afternoon.

Surface: A cool front extended from ND-WY-UT-NV at 07Z. This
front will slowly press to the E and S...crossing the CWA tonight.
Low pres will form over Ern CO today. This low will be dislodged
by the front and be pushed into OK tonight.

Now: a 40-50 kt low-lvl jet was over the rgn. Mid-lvl moistening
resulted in the development of a N-S oriented band of mid-lvl
ACCAS that produced some sprinkles and even a rumble or two of
thunder up by ODX around 745Z. This band should be E of the CWA by

Today: M/sunny to start but becoming p/cldy as mid-lvl altocu
move in and afternoon CU develop. Could see a few sprinkles from
the altocu deck skirt N and W of the Tri-Cities roughly 16Z-20Z
per the HRRR/HRRRX.

It will become breezy this AM as the boundary layer becomes
unstable and mixes down the eastward moving low-lvl jet. Winds
will rapidly diminish after midday.

Warmer as temps climb back to near normal (mid-upr 70s)...though
there a few spots from Cambridge-Plainville KS will probably reach
the low 80s.

The combination of strong heating/terrain-induced circulations
and convergence invof the front and CO low will result in sct tstm
development far to the W this afternoon. As long as tstms are in
close enough proximity and there`s enough of them...sub-cloud
evaporation will result in cold pool formation and one or two tstm
clusters moving in this evening and crossing the CWA tonight.
This is based on the last 3 runs of the NAM Nest and HRRR/HRRRX
which are the most aggressive with cold pool formation and forced

The ARW/NMM suggest far less tstm development (much more sct or
even isolated). Fcst soundings show a substantial cap/EML. So a
fairly decent cold pool will be necessary for force parcels to the

As for this fcstr`s opinion...I don`t have a good feel one way or
the other. It all depends on how great tstm coverage is out W.
The more limited...the lower the chance of tstms here.

Low-lvl mstr leaves much to be desired with a continental polar
air mass over the rgn...but models are indicating sufficient mstr
should develop in place to result in MLCAPE of 1000-1500 J/kg from
I-80 S with the highest amts over N-cntrl KS. Have to wonder if
this mstr is solely from fcst tstms. These storms will be moving
into a highly unfavorable/dry air mass. There could be a narrow
wind of opportunity for svr winds/marginally svr hail this eve.

Tonight: M/cldy with a period of gusty tstms is possible with
gradually diminishing intensity as they cross the CWA...or just a
few small tstms or tstm clusters with much of the CWA remaining
dry. Stay tuned to fcst adjustments and later assessment from the
day shift and SPC. The main weakness of this fcst: if the more
widespread tstm evolution occurs...this fcst will be too low on

.LONG TERM...(Friday through Wednesday)
Issued at 445 AM CDT Thu May 25 2017

Seasonably nice temperatures and occasional chances for showers
and thunderstorms remain in the forecast through the extended
periods. Overall...expect west north westerly flow aloft to start
the period as a ridge of high pressure tries to establish itself
across the intermountain west. This will result in a more
northwesterly flow pattern aloft late in the extended...with a
weak disturbance forecast to undercut the ridge and transition
into the plains over the middle potion of next week. While the
period is not expected to be overly active expect
multiple chances for showers and thunderstorms over the next week
as temperatures fluctuate within a couple of degrees of normal.

For Friday...expect one of the more active days of the period as
an upper level disturbance across the pacific northwest swings
into the plains late in the day. While dry weather is anticipated
to start the day...this should change by late afternoon as the
aforementioned disturbance tracks into the plains. With around
1500 Joules of CAPE expected to be present above a modest
CAP...expect forcing from the approaching wave to be sufficient to
initiate some convection locally. In addition...with modest low
level shear...could see a few organized storms late in the
day...with marginally severe hail and strong wind gusts being the
primary concerns.

While instability beings to wane some on Saturday...expect the
possibility of some showers and thunderstorms lingering across the
area throughout the day...before high pressure to the west begins
to spread its influence locally by Sunday afternoon. This should
result in a string of very nice days to start next week...with
seasonable temperatures and dry conditions. By mid-week...expect
an upper level low to undercut the ridge and bring a chance for
showers and thunderstorms back to the local area.


.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Friday)
Issued at 636 AM CDT Thu May 25 2017

Significant Wx: LLWS ends by 14Z. Then S winds gust up to 30 kts.

Today: VFR. SCT altocu around 14K ft will be joined by a few CU
around 5K ft in the afternoon. LLWS ends 13Z-14Z. A period of
gusty winds will occur 14Z-18Z as mixing transfers the diminishing
low-lvl jet to the sfc. S winds will increase to 17-30 kts then
diminishing to around 10 kts. Confidence: High

Thu Eve: VFR. Few CU linger around 5K ft with SCT-BKN altocu
around 15K ft. There is a low probability for a brief 4SM TSRA
with G40KT. Lgt SE winds become N. Confidence: Medium




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