Area Forecast Discussion
Issued by NWS Hastings, NE

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268
FXUS63 KGID 300521
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1221 AM CDT Sun Apr 30 2017

.SHORT TERM...(This evening through Monday daytime)
Issued at 507 PM CDT Sat Apr 29 2017

Apologize for being so late this afternoon, but the wealth of
complexities regarding this highly-unusual late April weather
pattern and associated snow amount forecasts/winter weather
headlines took considerably longer than average today and this
product was unfortunately pushed to the back-burner somewhat.

The bottom line:
While confidence in "official" snow totals is certainly running
below average (especially compared to a snow storm during a more
"normal" time of the winter/early spring), we have collaborated
with not only neighboring local NWS offices but also national
Weather Prediction Center (WPC) snow guidance to continue
increasing the likelihood for several hours of wet, sticky/heavy
and somewhat wind-blown snow, perhaps starting as early as late
tonight in western counties but with the "main event" clearly
centered on the daytime-overnight hours Sunday into Sunday night.
While there remains a chance that just a small/subtle increase in
expected temperatures anywhere from the surface to the mid-levels
could solidly "eat into" expected snow amounts, the strength of
forcing/dynamic cooling with this powerhouse low pressure system
is just too hard to ignore, and thus why we continue erring
solidly on the side of caution given the potential for not only
travel impacts, but also perhaps damage to trees/power
infrastructure from heavy/wet snow weighting things down.

No matter how actual snow totals ultimately turn out, we are
almost surely (high confidence in this aspect) looking at a sharp
west (higher) to east (lower) gradient in snow totals. Please
refer to our Warning/Advisory products for further details, but in
general we are aiming for 5-9" in most western counties, to as
little as less than one-half inch in most far eastern counties,
especially those along the Highway 81 corridor. The real headache
is in between, including the Highway 281 corridor, where a Winter
Weather Advisory now serves as the "buffer zone" between the
higher amounts west and little to no snow farther east. While
sustained wind speeds of 30+ MPH and gusts to around 50 MPH argue
that near-blizzard conditions are likely at times especially in
western areas, the very wet/heavy nature of expected snow brings
the horizontal blowing/reduced visibility aspect somewhat into
question, and thus why we are content with the going Winter Storm
Warning for now. As for the start times of the headlines, they are
probably plenty generous, as although the western counties
technically begin at 1 AM tonight they probably won`t see much
meaningful snow development into after daybreak. Same story with
the Advisory counties closer to Highway 281, as although that
headline technically starts at 7AM for now, the main impacts will
not likely occur until afternoon-evening.

Whether it snows considerably or largely remains as rain for some,
the ENTIRE CWA is looking to see a solid 1-2" of beneficial
moisture from this system, which is very much a good thing.

Will finish with a very brief look at the evolution/timing of this
storm:

Tonight:
Areas of primary rain (eventually mixing with and changing to snow
far west) will expand in coverage as the night goes on, with some
non-severe thunderstorms even possible especially in our southeast
1/3 to 1/2. The center of the main upper low/vort max will reach
the KS/OK border by sunrise. Low temps in the mid 30s most areas.

Sunday-Sunday night:
About as awful as weather can possibly get for April 30th, with
record cold highs in the mid-upper 30s looking quite likely, as
precipitation remains abundant (especially in the northwest half
of the CWA), although a dry slot in the southeast could perhaps
result in less coverage and maybe even a lull. Precipitation will
likely gradually transition to a rain-snow mix and eventually
all-snow from west to east, with eastern areas holding into rain
the longest. By day`s end, models are in good agreement that the
center of the main low is over northeast KS, then reaching central
IA by early Sunday morning. As the system starts pulling away, our
precip will gradually end with it as winds start to decrease a
little and turn more westerly.

Monday daytime:
Perhaps a little bit of very light snow and/or sprinkles linger
into the first part of the day northeast , but otherwise the vast
majority of the area should see a precip-free day with at least
partial sunshine and lighter, albeit still breezy west-northwest
winds. The high temps aimed into the mid-50s most areas could
easily be 5+ degrees too optimistic if there is in fact
appreciable snow cover, but no matter what, a rapid melt of the
very wet snow should take place.

.LONG TERM...(Monday night through Saturday)
Issued at 507 PM CDT Sat Apr 29 2017

For obvious reasons, am going to be keeping this section
addressing Days 3-7 much shorter than usual, but the bottom line
is that we are looking at a welcomed return to more typical/milder
spring weather, especially by the latter half of the week into
next weekend.

Precipitation-wise:
There are various chances for rain showers (NOT snow) littering
the Tuesday afternoon through Wednesday afternoon time frame as
the next shortwave trough moves in from the northwest and passes
through the Central Plains. There is probably non-zero chance for
a few non-severe thunderstorms during this time also, but will
leave out a formal mention of thunder for now. Beyond this, the
forecast dries out into next weekend, and there is actually
relatively-high confidence in this thanks to a large-scale ridge
building eastward into the central CONUS.

Temperature-wise:
A gradual warming trend back into spring is most certainly on the
table. High temps for Tuesday-Wednesday are aimed around 60 most
areas, likely held down somewhat by plenty of clouds and at least
spotty rain activity. Thursday then looks to feature highs closer
to 70 as precip chances wane, with highs Friday-Saturday then
solidly into the low-mid 70. Overnight lows follow a similar
pattern, climbing from the upper 30s/near 40 Tuesday and Wednesday
nights to more solidly into the 40s by week`s end. Even on the
colder nights earlier in the week, we are currently not
anticipating any frost issues, but this will need closely watched
in case temps trend down a few more degrees.

&&

.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Sunday night)
Issued at 1212 AM CDT Sun Apr 30 2017

It`s a complicated TAF period with widespread precipitation with
rain mixing with and changing over to snow at times as an upper
low pressure system lifts northeast from Oklahoma across southern
and eastern Kansas. The rain shield will be fairly widespread
through the overnight hours, with rain forecast to mix with snow
at KEAR around day break with more of a rain/snow mix for KGRI
through mid day. KEAR could see snow accumulations mainly during
the afternoon and evening with lesser amounts forecast to the east
at KGRI. Cloud ceilings will continue to deteriorate through the
overnight hours with cig heights expected to mainly be IFR to LIFR
for much of the TAF hours. North wind speeds will be intense,
with speeds around 25kts and gusts near 40kts. The combination of
the strong winds and falling precipitation will cause visibility
restrictions.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Warning until 6 AM CDT Monday for NEZ039-046-060-
     061-072>074-082-083.

     Winter Weather Advisory from 7 AM this morning to 6 AM CDT
     Monday for NEZ040-041-047-062-075-084-085.

KS...Winter Storm Warning until 6 AM CDT Monday for KSZ005-017.

     Winter Weather Advisory from 7 AM this morning to 6 AM CDT
     Monday for KSZ006.

&&

$$

SHORT TERM...Pfannkuch
LONG TERM...Pfannkuch
AVIATION...Fay



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