Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 200250
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
950 PM CDT Wed Jul 19 2017

.UPDATE...
Issued at 949 PM CDT Wed Jul 19 2017

Really only one noticeable modification has been made to the
overnight forecast:

Perhaps out of an abundance of caution more than anything, have
added some slight shower/thunderstorm chances (PoPs) to our far
north, mainly north of a Loup City-Genoa line. As expected, the
vast majority of late afternoon/evening thunderstorm activity
(including isolated severe weather) has remained slightly north
of our CWA in a west-east corridor across northern Nebraska.
However, there are signs both in radar trends and also models such
as the HRRR that at least weak elevated convection could try
brushing southward into our northern zones especially 11PM-4AM,
possibly aided by the increasing low level jet lifting over an
outflow boundary. Not anticipating anything severe, but some gusty
winds up to around 40-ish MPH probably cannot be ruled out.

Otherwise, the majority of the CWA should see a rain/thunder-
free night with seasonably-warm lows holding up in the low-mid
70s.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 155 PM CDT Wed Jul 19 2017

Hot and humid conditions will continue across the local area
through the short term periods with little relief in sight ahead
of weak cold front across the Dakotas. As this front slowly sinks
south over the next 24 to 48 hours hours...expect the pressure
gradient to weaken across the region...likely resulting in
lighter winds across the local area tomorrow. While temperatures
as well as heat index values will be similar across the region
tomorrow as we saw today...these lighter winds will likely make it
feel a bit more miserable...with either a Heat Advisory or an
Excessive Heat warning in place for the entire forecast area.

.LONG TERM...(Thursday night through Wednesday)
Issued at 155 PM CDT Wed Jul 19 2017

A weak shortwave is expected to ride over a weak cold front to our
north Thursday night...possibly sparking some convection across
portions of northern Nebraska. While the best chance appear to be
north of the local area...cannot rule a few storms temporarily
bringing some relief to areas primarily north of highway 92 across
south central Nebraska late Thursday night.

Otherwise...expect strong high pressure to slowly give way to the
aforementioned cold front late Friday night with slightly
cooler...yet seasonable...weather then forecast to return over the
upcoming weekend. Ahead of this front...however...expect
oppressive heat to continue across the local area through the
afternoon hours Friday as temperatures once again climb to near
100 degrees and heat index values soar to between 102 and 108 by
the afternoon. With some elevated instability as well as forcing
from an associated short wave...expect this spell of heat to come
to an end as a better chance for thunderstorms returns to the
local area Friday night. While severe weather parameters are a
bit questionable...much of south central Nebraska is highlighted
for a marginal risk of severe weather Friday
evening/overnight...so kept a mention of this possibility in the
HWO. With this front slow to push south across the area...expect
a continued chance of thunderstorm into Saturday...with additional
small chances for thunderstorms expected off and on again through
the extended periods.

While this is not by any means a wet pattern...there will likely
be thunderstorms around at times with a return to more seasonable
temperatures for late July.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday)
Issued at 724 PM CDT Wed Jul 19 2017

Will officially advertise a fairly "quiet" period with no formal
mention of thunderstorms and VFR ceiling/visibility, with the main
concern being a round of at least marginally-mentionable low level
wind shear (LLWS) overnight. However, there may be a few caveats
to consider, and these are mentioned in element-specific details
below.

Ceiling/visibility:
While confidence is rather high in VFR ceiling, the very high
surface dewpoints/humidity levels to bring into question the
possibility of at least light fog development. However, with
models even less favorable than last night for limited fog
formation (likely given greater boundary layer mixing), will keep
it VFR for now.

Thunderstorm potential:
While pretty much all models keep any legit thunderstorm potential
at least 50 miles north of both terminals through the period,
there is ongoing activity within 100 miles to the north, and there
are hints of at least weak convection skirting the area during the
day Thursday. Therefore, while not nearly enough evidence exists
to formally mention a thunderstorm, the chance is probably not
truly zero.

Winds (including LLWS):
Not accounting for any possible convective outflow effects,
surface winds will average from the south tonight and become more
southeasterly during the day Thursday (especially afternoon).
Sustained speeds the majority of the time should average under
12kt, but especially right away this evening some gusts closer to
20kt are possible. As a southwesterly low level jet ramps up this
evening/overnight (accelerating to 40-45kt within roughly the
lowest 1,000 ft.), this will set up a period of low level wind
shear advertised from 04z-12z.

&&

.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.

&&

$$

UPDATE...Pfannkuch
SHORT TERM...Rossi
LONG TERM...Rossi
AVIATION...Pfannkuch



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