Area Forecast Discussion
Issued by NWS Hastings, NE

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049
FXUS63 KGID 240358
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1058 PM CDT SAT JUL 23 2016

.UPDATE...
Issued at 1058 PM CDT Sat Jul 23 2016

Updated the forecast to lower chances of precipitation a bit for
the rest of the night.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 430 PM CDT Sat Jul 23 2016

In the interest of time, won`t be digging overly-deep into the
"weeds" of these next 36 hours, but the bottom line remains the
same: Although we still have at least an outside shot for a few
strong to perhaps severe storms late this afternoon into tonight
(the entire CWA remains in the SPC Day 1 Marginal Risk), the big
story for most folks is that this afternoon is our "last hurrah"
of truly well-above-average heat before we finally settle back
toward more "typical" late July values. Please note, this is not
going to be an incredibly "dramatic" cool-down by any
means...it`s simply more of a return to normalcy. The Excessive
Heat Warning will likely run it`s course through 7 PM this
evening.

A brief look at recent/current weather today:
As of this writing, the radar screen is essentially void of
anything over our CWA, as the pesky light showers/sprinkles from
this morning have large moved off to the east and the true leading
edges of the much-anticipated surface cold front entering northern
Nebraska has yet to breach a formidable cap (as evidenced by 700
millibar temps of 14-16C) and yield legitimate storms. There is
also a thus-far inactive surface trough oriented southwest-
northeast across our CWA. As anticipated in the morning update
discussion, high temps do in fact look like they will fall at
least a few degrees short of early-morning expectations, but that
being said, temp rises were impressive this afternoon and most Neb
zones should at least tag the mid-90s with low-100s more common in
KS. With several sites currently seeing heat index values in the
99-104 range, will certainly allow the last few hours of the
Excessive Heat Warning to run its course. In the mid- upper
levels, the flow locally is quasi-zonal as we reside to the south
of a stronger disturbance tracking across the southern
Canada/North Dakota border area.

Now quickly glossing over expectations through these next 3
forecast periods:

This evening/tonight (including late this afternoon):
Uncertainty on when and even if more than a very isolated storm or
two will affect the CWA is still very much in question, but enough
potential remains to at least leave a token slight PoP in all
areas, and slightly higher 30 PoPs in southern/southwest zones. At
the surface, the cold front will slowly-but-steadily cross the
CWA, gradually turning breezes north-northeasterly in its wake.
Even behind the front, expect plenty of lingering elevated
instability, so even though things currently appear rather capped
to near-surface based parcels, the approach of 1 or more weak
disturbances from the west could eventually allow at least
"something" to form, which could possibly even be strong to
severe. In the near-term late this afternoon, our far southern
zones in KS may be more favored than the northern zones nearer
the front to pop a storm or two, thanks to steeper low level
lapse rates in the very hot/more mixed environment. Despite the
frontal passage, still a rather mild night with lows aimed from
mid 60s northwest to mid 70s far southeast.

Sunday daytime:
At least we DO have high confidence that it will be cooler by
several degrees. In the wake of the front, winds will average 5-15
MPH from an easterly direction most of the day. High temps were
changed fairly little, aimed from mid-upper 80s in most Neb zones,
to low-mid 90s in KS. Unfortunately, confidence in shower/storm
chances remains shaky, and have blanketed day-long slight chances
in most areas, and slightly higher 30 PoPs in southern zones
during the morning per the suggestion of some models such as the
18z NAM/12Z NSSL WRF. With slightly cooler air aloft and weak
disturbances moving in from the west, it will likely not take as
much to get at least spotty convection going, and probably cannot
even rule out a few stronger storms as well.

Sunday night:
Much the same as the daytime hours, have 20-30 PoPs broad-brushed
across most of the CWA through the night, as low level
southeasterly/upslope flow appears that it could foster the
development of High Plains convection to our west that could track
east-southeast into the area. In addition, at least spotty
elevated activity could continue to fester from the daytime hours.
For being less than 36 hours out, there are still plenty of
question marks here precip-wise. Temp-wise, rather light east
breezes should promote a slightly cooler night than tonight as
long as clouds aren`t overly abundant, and have aimed from low 60s
far northwest to upper 60s far southeast.

.LONG TERM...(Monday daytime through Saturday)
Issued at 430 PM CDT Sat Jul 23 2016

General overview of this 6-day period:
Although excessive, advisory/warning-worthy heat thankfully does
not appear to be an issue next week, there are still plenty of
forecast challenges, mainly revolving around a return to a parade
of seemingly "non-stop" precipitation chances/PoPs. Literally each
and every day/night forecast period contains at least a slight
chance of showers/storms. Although anybody reading this knows
darn well it will not rain everywhere each day and night, there is
enough limited evidence of at least isolated, hit-and-miss
activity within or near the area that it is almost impossible to
rule out at least a baseline "slight chance" (meaning 15+ percent
PoP). For those who have been following the forecast closely the
past few days, you might have noticed that technically our
overall-highest PoPs (40-50 percent range) are focused on Tuesday
night. However, a word of caution: These latest round of models
suggest that other nights next week could have just as a good of a
chance of rain/storms as Tuesday night, so don`t be surprised to
see PoPs trend upward in some periods/down in others as things are
gradually refined.

A few comments on rain/storm chances:
From a large-scale, broad perspective, the mid-upper level weather
pattern reverts back to what we spent much of the first part of
the month in, tricky-to-forecast quasi-zonal (west to east) to
outright-northwesterly flow, containing a parade of mostly fairly
subtle disturbances passing through, any one of which could spark
primarily late-day/overnight storm chances that could easily
linger into the following morning. Although deep-layer shear looks
to be fairly typical/modest on most days/nights by late July
standards, this pattern could easily yield at least some isolated
severe storm activity, and would not be surprised to see at least
a few days eventually assigned at least a Marginal Risk from SPC
as they get closer:

A few comments on temperatures/heat index:
As mentioned in the opener, it cools down somewhat, but it is by
no means truly cool. If anything, high temps on most days next
week were nudged up very slightly from previous forecast. As it
currently stands, the first half of the week looks a touch warmer
than the latter half. As a whole, highs in Nebraska zones should
generally range from mid-80s to low 90s while KS zones are more-so
upper 80s to mid-90s. Although no days appear to feature
widespread 105+ heat index that might require headline issuance,
have added Tuesday afternoon in particular to the Hazardous
Weather Outlook given that our KS zones look to have a decent
coverage of 100+.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday evening)
Issued at 651 PM CDT Sat Jul 23 2016

VFR conditions are forecast. Wind will switch to a north component
as a cold front comes through. In previous numerical model runs,
there was some indication of flirting with low-level wind shear
with wind direction from the north, behind the cold front, but now
it appears that this will not be as big of an issue.


&&

.GID Watches/Warnings/Advisories...
NE...None.
KS...None.
&&

$$

UPDATE...Heinlein
SHORT TERM...Pfannkuch
LONG TERM...Pfannkuch
AVIATION...Heinlein



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