Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 221709
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1209 PM CDT Sat Apr 22 2017

.SHORT TERM...(Today and Tonight)
Issued at 335 AM CDT Sat Apr 22 2017

After a seasonably cool start to the day, expect clearing skies,
light winds, and a seasonable airmass to make for a pleasant late
April afternoon.

For today, expect an area of surface high pressure to sink
southward throughout the day, with generally light northerly
winds expected to prevail. In addition, skies should gradually
clear from north to south across the region, with mostly sunny
skies expected for just above everyone...locally...by mid
afternoon. With these sunny skies and a seasonable airmass in
place, expect a very pleasant afternoon, with high temperatures
climbing into the mid to upper 60s,

For tonight, with mostly clear skies in place along with light
winds, expect another cool evening/overnight period across the
local area. Thanks to relatively elevated dewpoints as well,
expect to see some frost formation across portions of the region
early Sunday morning. While the current forecast temperatures
along with light southerly winds are not conducive to widespread
frost formation, expect at least patchy frost formation across
the region with the best chance for more widespread frost
anticipated across sheltered and low lying areas.

.LONG TERM...(Sunday daytime through Friday)
Issued at 459 AM CDT Sat Apr 22 2017

First go-around dealing with this 6-day period for this
particular forecaster, so not a lot of personal history with
recent model trends, but here are some first impressions/key
points:

1) The biggest thing that stands out are a number of rain chances,
with every single day/night period from Monday night onward featuring
at least a small chance somewhere in our coverage area (CWA), and
with halfway decent/more widespread chances centered around
Tuesday and especially Thursday-Thursday night. In fact, taking
the latest Weather Prediction Center (WPC) 7-day cumulative
precipitation forecast literally, the majority of the CWA has a
shot at seeing 2+" of rainfall during the next week (most of which
occurring late next week). Of course, while this may in fact come
to fruition for parts of the area, we have recently seen some
seemingly-decent longer range rain chances fizzle as they neared,
so as always don`t get your hopes up too much yet if you`re really
hoping for a "big soaker", although the potential is certaintly
there.

2) Despite the aforementioned rain chances next week, at least
this latest round of deterministic medium range models (namely the
00z runs of the GFS/ECMWF) seem to have trended a little cooler
and thus more stable perhaps compared to previous runs. As a
result, for the majority of the Monday night-Friday time frame it
appears that thunderstorm activity may be hard to come by, let
alone a "big-time" severe weather threat, with most precipitation
simply taking the form of generic rain/showers. Going solely by
the latest deterministic runs, the consensus seems to be that both
Thursday and/or Friday could in fact feature a higher-end severe
weather event mainly to the south of our local area, primarily
from southern KS southward to around the Red River. This being
said, we have noted that SPC has opted to technically brush the
far southeast edges of our CWA with a 15% severe risk area on its
latest Day 6 outlook for Thursday, which likely has a lot to do
with accounting for the inherent uncertainty in the model world
at this extended time range, and cannot be completely discounted.
However, from our local office forecast perspective, we want to
make it clear that we are not currently advertising a formal
severe weather risk at this time in products such as the Hazardous
Weather Outlook (HWOGID), unless/until later model runs bring
more appreciable convective instability northward into our CWA. In
fact, this latest forecast package has actually trended back on
the areal coverage of generic thunderstorm mention for next week
versus previous forecast products.

3) Temperature-wise, confidence is fairly high that Sunday-Monday
will be the overall-warmest of these 6 days with highs into the
70s (perhaps near-80 Monday far south), before a halfway-decent
cooling trend kicks in for the remainder of the week with highs
trending back into the 50s-60s (especially Wednesday-Friday).
Although no truly "major" changes were made to temperatures in
this latest forecast packages, highs for days such as Tuesday,
Thursday and Friday were nudged down 2-3 degrees and potentially
not enough. As evidence of this, raw 00Z GFS/ECMWF model guidance
shaved a solid 5-10 degrees off highs for Thursday-Friday versus
its preceding 12Z runs. As for overnight lows, they follow suit
with highs, with the mildest night looking like Sunday
night/Monday night (holding well up into the 40s/near 50) before
cooler lows mainly between the upper 30s-mid 40s arrive
thereafter. At least for now, there are no "obvious" risks for
frost and/or sub-freezing temps beyond Sunday morning, but with
reasonable confidence in the cooler temperature regime for the
latter half of next week this bears close watching.

4) Other than at least limited thunderstorm potential (mainly
around Thursday) and a chance for limited, lingering frost right
away the first few hours of Sunday morning, the only other item
currently worthy of mention in our latest HWO is the likelihood of
"near-critical" fire weather conditions for Sunday afternoon (and
perhaps also Monday afternoon as well). For all further mention of
fire weather concerns please refer to the separate "Fire Weather"
section below.

With the main points now covered, will finish with some attempted
day-to-day details for those interested, while keeping in mind
the usual caveat that confidence in the finer forecast details
really degrade especially beyond Day 4 in active upper air
patterns such as this...

Sunday daytime:
This is the only true "guaranteed dry" day of the long term. Right
away for an hour or two after sunrise, at least some
limited/patchy frost remains possible, lingering out of the
Saturday night period (see short term section above for more on
this). Otherwise, by far the biggest story Sunday will be
strengthening south winds in response to steadily falling surface
pressures along a lee trough to our west. Especially by afternoon,
sustained speeds/gusts will average 15-25 MPH/25-35 MPH,
respectively, and highest in western counties. It should be mostly
sunny, but would not be surprised to see a little more high cirrus
spill over the area than currently depicted in the official sky
cover grids.

Sunday night:
The official forecast remains dry, but a few post-midnight
sprinkles may not be completely out of the question especially
west/north.

Monday-Monday night:
Let the more active weather pattern begin. While the daytime
forecast remains dry for now, various models hint that a few
passing sprinkles/light showers may be possible, and this light
precip mention may be needed as it gets closer. Monday night then
features a slightly more organized looking chance of showers as
the next wave moves in from the west. A few rumbles of thunder
cannot be ruled out, but just cannot justify a formal
thunderstorm chance at this time given an overall-lack of
instability in most models.

Tuesday-Tuesday night:
Modest rain chances continue as the disturbance that moves in
Monday night continues passing through. Amounts do not appear
"heavy" by any means during this time. Again, kept out/removed any
formal mention of thunder, as more appreciable instability looks
to reside 100+ miles south of our CWA.

Wednesday-Wednesday night:
Especially if the latest ECMWF is onto anything, the vast majority
of these 24 hours could be dry as we potentially catch a brief
break "in between" systems, but the GFS is more aggressive
spreading back widespread rain shower potential for Wednesday
night. As for the daytime hours, would not be surprised if later
forecasts might actually remove even the existing slight chance of
rain that most areas currently have.

Thursday-Friday:
Not worth attempting to break down many details for this Day 6-7
time frame, but the bottom line is that we are looking at a pretty
decent chance for a widespread, somewhat chilly rain (measurable
chances/PoPs as high as 60 percent already) mainly for Thursday-
Thursday night, with lower chances for Friday as in theory this
system starts/continues moving out. As covered in the main points
above, barring a noticeable northward shift in convective
instability, the primary regional severe weather threat should
focus at least slightly to our south. Peeking just beyond the
official forecast into next Saturday, there is a TON of
uncertainty as the faster GFS suggests a dry day while the slower
ECMWF suggests another round of rain associated with primary upper
low within the mean large-scale trough.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Sunday afternoon)
Issued at 1207 PM CDT Sat Apr 22 2017

Quiet weather with VFR conditions expected through this TAF
period. Will have a few clouds both in the lower (~4-5k ft) and
upper levels passing through this afternoon, but clear skies are
expected this evening/tonight. Surface high pressure will keep
winds on the light side through all but the final few hours of the
period, variable this afternoon/evening before turning more
southerly. Winds will increase/become more gusty mid/late morning
tomorrow.

&&

.FIRE WEATHER...
Issued at 459 AM CDT Sat Apr 22 2017

Regarding potential for at least "near-critical" conditions
especially Sunday afternoon but perhaps Monday as well:

General overview:
Despite recent/continued seasonal green-up of vegetation, we are
not quite to the point yet where we can declare fire concerns to be
truly "over with" for the rest of the spring (especially given an
overall-lack of appreciable rain in most of our CWA over the past
week or longer).

Sunday afternoon:
Although vegetation is not quite as primed for fire growth/spread
as it was a month ago, from a purely meteorological perspective
this is shaping up to be a solid near-critical event for the
majority of the CWA. Relative humidity (RH) values are progged to
drop into the 20-25 percent range most areas for at least a few
hours. Probably more importantly, southerly wind speeds continue
trending upward if anything, with sustained speeds solidly 15-25
MPH/gusts 25-35 MPH (higher end of these ranges in western
counties). With wind speeds being a "slam dunk" for higher-end
fire weather concerns, later shifts will want to keep a close eye
on RH trends to make sure things don`t slip into critical
territory. For now, will maintain a near-critical mention in our
latest Hazardous Weather Outlook (HWOGID).

Monday afternoon:
Although not currently looking quite as concerning as Sunday in
the official forecast grids, models such as the 00z GFS and now
the latest 06z NAM are becoming increasingly-suggestive that at
least a marginal overlap of near-critical conditions could occur
in mainly some of our far western counties behind a passing
surface trough, primarily west of the Highway 183 corridor. More
specifically, parts of this area are trending toward seeing 20-25
percent RH and west-northwest winds gusting to at least 20 MPH.
Because this is still Day 3 and there is still time to refine
details, will hold off for now on formally mentioning Monday fire
weather in the HWO.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&

$$

SHORT TERM...Rossi
LONG TERM...Pfannkuch
AVIATION...ADP
FIRE WEATHER...Pfannkuch


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