Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 282142
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
442 PM CDT THU JUL 28 2016

.SHORT TERM...(This evening through Friday night)
Issued at 441 PM CDT Thu Jul 28 2016

Obviously the paramount focus of these next 3 forecast periods/36
hours is the ongoing threat of severe storms mainly within
counties near/south of the state line right away during these
next 3-6 hours. Severe Thunderstorm Watch 420 has been issued
through 11 PM for 9 counties in our southern CWA, but unless
additional activity develops behind the current strong/severe
cluster entering the western edges of our KS CWA at this time,
could foresee most if not all of this Watch being cancelled early
for our CWA.

Taking a quick look at current/recent trends:
It has been a challenge today trying to get a handle on the
ongoing severe threat in the south, and just rain/storm chances
(PoPs) for the CWA as a whole in general. We had one early-day
round of weakening convection brush into the far western CWA
before dying, and now this ongoing cluster is holding together
better but frankly seems to be several hours "ahead of schedule"
versus expectations from overnight/early morning model runs. In
the mid-upper levels, a low amplitude but evident disturbance is
evident in model data and water vapor satellite imagery passing
east-southeast across western Nebraska. If anything,
CAPE/instability values have gotten a touch higher than expected
across southern zones today possibly 1500+ J/kg which in tandem
with at least 30-40kt of deep layer shear is promoting the ongoing
severe storms near the state line which are mainly exhibiting a
severe wind threat. Under increasing afternoon clouds, high temps
will end up reaching somewhere in the 80s across most of the CWA,
but with cooler 70s west-central and near-90 far southeast.

Now looking ahead forecast-wise through these next 36 hours:

This evening/tonight:
Quite honestly, our precip chances/PoPs for this evening (post-
00z/7 PM) may be well-too high for especially our western/northern
zones UNLESS some additional activity manages to develop behind
the ongoing complex. As earlier mentioned, both the onset and
quite possibly the ending of the primary thunderstorm/severe
threat for the day seems to be at least a few hours "ahead of
schedule" from earlier expectations. That being said, cannot pull
the plug yet on additional evening activity posing a problem
either, but at this rate the main severe threat may be over with
closer to 7-8 PM than 10 PM-midnight. Stay tuned for potentially
noticeable updates to PoPs as the late afternoon/evening wears on,
but at least for now, will carry some pretty high chances
especially in southern areas this evening before tapering chances
down overnight in all areas but still at least hanging on to
slight chances. Low temps aimed into the low-mid 60s most areas.
Could also see some patchy fog late tonight into the first part of
Friday morning in a light wind regime with moist ground from rain,
so this has been added to the forecast.

Friday daytime:
This has the potential to be a rather cloudy, seasonably-coolish
day with at least isolated, hit and miss shower/storm activity
here and there. However, CAPE values appear to be lower than today
so the severe risk seems pretty minimal. Given low confidence in
PoPS, will only advertise blanket slight 20 percent chances for
now. For most of the CWA, this has a good chance of being the
overall-coolest day of the next several, with highs only near-80
in Neb zones and low-mid 80s in KS.

Friday night:
Low-confidence precip chances remain, and have blanketed low-end
20-30 PoPs across the CWA as various subtle mid level waves
continue to pass over the local area in northwest flow aloft.
Again, the severe threat appears rather low, but possibly not
"zero". Low temps aimed very similar to tonight with mainly low-
mid 60s.

.MID TERM...(Saturday daytime through Sunday daytime)
Issued at 441 PM CDT Thu Jul 28 2016

This section briefly addresses the 36-hour "mid term" time frame
from Saturday daytime through Sunday daytime:

These 3 day/night forecast periods continue an uncertain pattern
of mainly slight thunderstorm chances/PoPs, but possibly "somewhat
greater potential/coverage of storms focused on Saturday night. In
the mid-upper levels, the pattern remains one of continued mainly
west-northwest flow aloft, with various small-scale shortwave
disturbances traversing the local Central Plains area. Here are a
few details regarding each of these 3 periods:

Saturday daytime:
While most models suggest that most of the CWA is likely dry
/storm-free most of the day, there appears to be just enough
potential for "spotty" activity here or there to justify slight
chances CWA-wide. Otherwise, expect temps to climb roughly 5
degrees warmer than Friday with mid 80s most Neb zones and upper
80s in KS, in the presence of southeast breezes generally 10-15
MPH.

Saturday night:
With hints of a "slightly" stronger wave dropping through from the
northwest, along with some low level jet support, have went with
slightly higher 30-40 PoPs across the CWA. Although our area is
not yet advertised in any kind of SPC severe risk area, would not
be shocked to see later updates possibly include at least portions
of our CWA in a Marginal if things come together.

Sunday daytime:
Kept some small PoPs for the morning hours mainly in southern/far
eastern zones, but otherwise the vast majority of the CWA appears
to be looking at a warmer and dry day, and kept out any
mentionable precip chances from all areas during the afternoon.
High temps look to be roughly 5 degrees warmer than Saturday with
upper 80s/low 90s in Neb and mid 90s KS.

.LONG TERM...(Sunday night through Wednesday)
Issued at 441 PM CDT Thu Jul 28 2016

Looking at the Sunday night through Wednesday night time frame, main
concerns lie with continued thunderstorm chances and hotter
conditions for Monday and Tuesday.

In the upper levels, models aren`t in too bad of agreement. This
time frame starts off with generally zonal flow in place as broad
high pressure remains over the southern CONUS. Gradually, flow turns
more southwesterly with a trough digging into the west coast. Kept
the forecast for Sunday night into Monday dry, with periodic
shortwave disturbances after bringing thunderstorm chances back into
the forecast. Hard to have a lot of confidence in those chances, as
model differences with timing/location do exist.

As far as temperatures go, a warming trend is expected for the
early/mid week period, with highs climbing back into the lower/mid
90s CWA-wide. Heat index values Mon/Tue currently forecast to reach
near 100 degrees, so will continue mention in the HWO.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Friday afternoon)
Issued at 103 PM CDT Thu Jul 28 2016

Although confidence is high that the MAJORITY of the period will
feature VFR ceiling/visibility and rain/storm-free conditions,
there is plenty of uncertainty in the finer details...as there
could easily be at least brief periods of sub-VFR and also
passing showers/storms.

Going into some of these details:
Starting with precipitation/storm chances, have focused a generic
"vicinity thunderstorm" (VCTS) mention during the mid-afternoon
through mid-evening hours to capture the most favored time frame
for possible convection, but it`s not out of the question that
some activity could affect the terminals both slightly before and
also after this specified time. Confidence in timing is still too
low to go with any TEMPO groups so stay tuned for amendments if
these become necessary. Turning to ceiling, confidence is pretty
high in VFR especially the first 6-12 hours (unless convection
lowers briefly), but model guidance varies quite a bit on ceiling
potential during the latter half of the period. For now have went
with a low-end VFR ceiling late tonight into Friday morning.
Visibility should also be VFR most of the period, but with enough
hints of at least "light" fog possible late tonight/early Friday
have introduced an MVFR visibility from 10-13z. Lastly, unless
convection results in briefly higher/erratic speeds, surface winds
should otherwise remain fairly light through the period at speeds
largely under 10kt and generally from a north-northeast direction.

&&

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

$$

SHORT TERM...Pfannkuch
MID TERM...PFANNKUCH
LONG TERM...ADP
AVIATION...Pfannkuch



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