Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 201135
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
635 AM CDT Thu Jul 20 2017

...Serious Heat Conts thru Fri then Temps Ease to Near Normal
with Sct Tstms Possible Along and Behind the Cool Front Fri-Sat...

.SHORT TERM...(Today and tonight)
Issued at 418 AM CDT Thu Jul 20 2017

Aloft: 00Z RAOB data show a hot subtropical high centered over
the Srn Plns but encompassing most of the Srn USA. The Westerlies
were zonal along the US-Can border and will remain far N of the
rgn thru tonight. The high will gradually inch E into the Mid MS
Vly.

Surface: A quasi-stationary front extended from the lower GtLakes
thru IL/IA and along the Neb/SD border into WY. It appears a heat
low was over NE CO. This low is fcst to migrate into SW Neb (btwn
IML-MCK) today and then remain quasi-stationary. Tstm activity
over Nrn/Wrn Neb has generated an outflow boundary that was
advancing S and was located roughly along Hwy 6 at 09Z. What
exactly happens to this boundary is uncertain...but the 08Z HRRR
suggests deep mixing S- SE of the low/incrsg S winds should force
the boundary to lift back N to near I-80 this afternoon.

Today: There is substantial high cloudiness over S-cntrl Neb
associated with waning overnight tstms far to the N. This
cloudiness will cont to thin leaving m/sunny skies.

Heat: High temps were nudged down 1-2F from the prvs fcst...but
they should still be 1-2F higher than yesterday. The biggest fcst
concern: are dwpts close to what will occur today? That will play
a huge role in peak Heat Index values. Yesterday...dwpts were in
the mid 70s N of Hwy 6...and that resulted in oppressive HI`s as
high as 113F. See Public Info Statement (PNS) issued at 335 AM.
Even though dwpts were increased above fcst guidance...concern is
that they are not high enough.

Tonight: M/clr but becoming p/cldy N of Hwy 6. 03Z SREF QPF
probabilities suggest sct tstms will develop over the Sandhills NW
of the CWA...and head E across Nrn Neb. Most if not all of this
activity should remain N of the CWA...but did include a slight
chance from LXN-ODX just in case it drops a little further S than
currently expected.

Another warm night with temps remaining in the 80s much of the
night with lows ultimately in the 70s.


.LONG TERM...(Friday through Wednesday)
Issued at 418 AM CDT Thu Jul 20 2017

Biggest challenge will be determining thunderstorm chances in
relation to the timing of a weak cold front Friday afternoon/
Saturday.

Subtropical ridge will be in the process of weakening as multiple
disturbances in mid-levels rake across the northern plains. With
these height falls combined with a cold front moving through
Friday/Saturday, we stand a shot at some showers and
thunderstorms, with a small potential for severe storms,
especially near peak heating and destabilization during the
afternoon, continuing into the evening. Although flow remains
weak, we could get a couple of strong to severe storms. Highs on
Friday could still be quite warm ahead of the cold front with
highs near 100 to 105 and heat index of 105 or a bit higher
possible in some areas, especially south, so a heat headline is in
effect.

A similar story for Saturday and perhaps Sunday, but chance for
storms shifts south with the southward moving cold front, that may
eventually stall, and temps relax with weaker upper level ridge
and sagging weak cold front. Temps could still be near 100 for our
far south, if still south of the surface front.

Periodic chances of severe weather exist into next week as the
slightly weakened ridge aloft allows more disturbance to affect
our general area from time to time, but temps will be closer to
normal with highs in the upper 80s to near 90.

&&

.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Friday)
Issued at 635 AM CDT Thu Jul 20 2017

Significant Wx: LLWS 05Z-12Z/Fri.

Today: VFR with no clds AOB 10K ft. Lgt/vrbl winds will become SE
around 7-10 kts. Confidence: High

Tonight: VFR with no clds AOB 10K ft. LLWS develops by 05Z. S-SE
winds 8-12 kts. Confidence: High

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Excessive Heat Warning until 8 PM CDT Friday for NEZ064-076-077-
     085>087.

     Heat Advisory until 8 PM CDT Friday for NEZ039>041-046>049-
     060>063-072>075-082>084.

KS...Excessive Heat Warning until 8 PM CDT Friday for KSZ006-007-018-
     019.

     Heat Advisory until 8 PM CDT Friday for KSZ005-017.

&&

$$

SHORT TERM...Kelley
LONG TERM...Heinlein
AVIATION...Kelley



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