Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 131038
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
438 AM CST Sat Jan 13 2018

.SHORT TERM...(Today and tonight)
Issued at 437 AM CST Sat Jan 13 2018

The highlights of these next 24 hours are: 1) A potentially
organized swath of generally 1-2" of snow this evening/overnight
primarily within the northeast half of our coverage area
(CWA)...2) Another very cold day with highs 20-25 degrees below
mid-January norms, although a 1-day "warm-up" is still slated for
Sunday (see LONG TERM below for more on this).

Taking a look at the current/recent weather as of 330 AM:
Overall no big surprises overnight. The big question 24 hours ago
was whether there would at least be partial clearing, and in fact
a blanket of lower clouds mainly in the 2500-5000 ft layer has
remained very stubborn/persistent. On a positive note, this
blanket of clouds will keep overnight lows slightly "warmer" than
earlier expected, with most all areas holding up in the single
digits above zero instead of below zero. However, these clouds are
also in a favorable temperature range to yield "random flurry
flair-ups" so to speak, and just within the last hour radar and
area airports obs have revealed an uptick in pesky/non-
accumulating flurry activity in some areas. In the mid-upper
levels, water vapor imagery and short term model data confirms
pronounced northwesterly flow over the Central Plains, directed
between a Pacific coast ridge, and a broad/large scale trough
enveloping the central/eastern CONUS. At the surface, our local
area remains south of a strong, roughly 1045 millibar ridge
centered over the eastern Dakotas. North breezes are averaging
roughly 5 MPH lighter than last night, mainly in the 5-10 MPH
range. While this is still promoting cold wind chills as low as
around -10 in some areas, this is roughly 10 degrees "safe" from
Advisory criteria, thus am not carrying a formal mention in the
Hazardous Weather Outlook (HWOGID).

Now looking ahead forecast-wise through today and tonight...

Today:
While weakly-organized batches of flurries or light snow cannot be
ruled out at almost anytime or place (especially this afternoon),
have kept any mention of true accumulating snow out of the daytime
(pre-6PM) forecast. In the mid-upper levels, our next elongated
shortwave trough/upper jet streak will gradually approach from the
Northern Rockies, but organized forcing/lift does not really ramp
up until after dark. At the surface, the aforementioned ridge
axis will slip just east of our area as the day goes on, allowing
generally light/variable direction winds this morning to flip
around from the south this afternoon, but at speeds largely only
around 10 MPH or less. Thanks to continued abundant cloud cover,
high temperatures will again struggle, and have shaved 1-2 degrees
off the previous forecast, aiming from 12-14 degrees northeast to
perhaps 18-20 far southwest. That being said, please note that
many areas may not actually realize these "daytime" highs until
closer to sunset or even slightly after.

This evening/tonight:
All eyes on are are next quick-hitting snow event, which although
not "major" by any means, certainly appears to pack more light
accumulation potential than any chances over the past 24 hours
have. The instigator will be the aforementioned disturbance/upper
jet diving southeast across the Central Plains. This will promote
a somewhat-organized band of low-mid level frontogenesis and warm-
air advection. Although there is still room for some modest
adjustments, the vast majority of models are targeting roughly the
northeast 1/2 of our CWA with the greatest snow potential, and we
are officially calling for 1-2" in these areas, and snow chances
(PoPs) have been raised to as high as 80 percent. While at least a
light dusting up to around one-half inch can be expected in many
of our southern/western counties, certainly anything close to 2"
should focus mainly east of an Ord-Hastings-Superior line, barring
any "last-minute" shifts in the primary snow axis. The vast
majority of the CWA should see snow end/move out between 3-6 AM.
Given that south-southwest winds should only average 10-15 MPH
during this snow event, and that amounts should safely remain
below our traditional 3" Advisory criteria, there are no plans for
a formal Winter Weather Advisory at this time, but will continue
to emphasize overnight snow potential in the HWO. Temp-wise, it`s
a somewhat unique setup as the aforementioned warm-air advection
on south-southwest surface breezes overnight will actually result
in slightly-rising temps, with most of the CWA expected to average
in the 15-20 degree range by daybreak Sunday. In other words,
there will be little-to-no dropoff in temps tonight.

.LONG TERM...(Sunday daytime through Friday)
Issued at 437 AM CST Sat Jan 13 2018

General overview of this 6-day period:
The two main stories are: 1) One more quick-hitting round of
fairly light snow Sun night-early Monday morning, although this
one will have more wind at play than tonight`s round...2)
Fluctuating temperatures, as a one-day "warm-up" Sunday is
followed by another Arctic blast centered on Mon-Tues along with
likely Advisory-level wind chill concerns, before the latter half
of the work- week gradually recovers to back above normal. The
official forecast remains void of any precip chances beyond Monday
morning. Read on for details...

Sunday night-Monday AM snow details:
With this next round of snow still 36-48 hours away, there is
modest uncertainty in the details, but we are currently expecting
accumulations to only average one-half inch to 1 inch most areas,
with perhaps slightly higher amounts concentrating in counties
southeast of the Tri Cities. As always, stay tuned for
adjustments, but like tonight`s system, this does not appear to be
a "major deal". That being said, this one will have more wind at
play, as northerly gusts to at least 30 MPH charge in behind a
strong Arctic cold front, likely resulting in at least minor
blowing/drifting. Certainly, the vast majority of this snow will
fall during the night, and by sunrise Monday all but perhaps the
extreme southern CWA in KS should be snow-free, and even there it
should be gone by mid-morning at the latest. Although the majority
of Sunday night precip should fall as snow, it could be just warm
enough aloft to promote a brief wintry mix of sleet/freezing rain
along the leading edges of the cold air. Have refrained from
including any of these mixed types in the official forecast for
now, but this may need considered in later issuances.

Sunday-Tuesday details (except for the precip details already
discussed):
Those wanting a BRIEF reprieve from our current and upcoming cold
blast will want to try to enjoy Sunday as warmer low-level air
arrives on generally westerly breezes around 10 MPH. While there
is no doubt that high temps will be at least 20+ degrees warmer
than today, this forecaster is a little skeptical that we will
realize full warming potential given: 1) Fresh light snow cover
especially in our northeast half and 2) The potential for a decent
amount of mainly high-level clouds. As a result of these concerns,
have nudged down highs slightly from previous forecast, but still
aiming for a range from mid-30s east to mid-40s southwest. But
just as soon as this milder air moves in, it is quickly blasted
back southward by the aforementioned Arctic front on Sunday night.
This will give us two more very cold days on Monday-Tuesday, with
similar daytime highs generally ranging 10-20 degrees, and Monday
night lows currently expected to drop into the zero to -10 range
(and this may not actually be cold enough). Adding to the cold
Monday will be steady north winds at least 15-20 MPH with higher
gusts. While near-Advisory wind chills will already invade
northern zones Monday morning, nearly the entire CWA is expected
to see wind chills of -15 to -25 degrees Monday night into
Tuesday morning. A Wind Chill Advisory will likely be needed for
this night as it gets closer, but for now will continue to
emphasize the dangerous wind chill in the HWO.

Wednesday-Friday overview:
The big story of these 3 days will be a gradual warm-up, with
temps each day climbing anywhere from 5-15 degrees higher than the
day before. The latest ECMWF/GFS models are in pretty good
agreement keeping our local area precip-free, although a mid-
level trough translating from the Intermountain West southeastward
toward TX and the Gulf Coast region will need watched, as any
northeastward shift could bring pesky precip chances at least
somewhat close to our southwestern zones. Again though, the big
story will be moderating temps. High temps were changed very
little from the previous forecast, with Wednesday aimed mainly
25-35, Thursday 35-45 and Friday 40-50.

&&

.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Saturday)
Issued at 1147 PM CST Fri Jan 12 2018

General overview:
Confidence is high the majority of the period (especially the
first 12 hours) will feature prevailing VFR conditions, albeit
with at least a low-end VFR ceiling. VFR could easily continue
into the afternoon as well, but by evening ceiling should be more
solidly MVFR with light snow breaking out, especially late
evening, perhaps reducing visibility to at least IFR. Surface
winds will continue to remain relatively light, with sustained
speeds largely at-or-below 11kt, with direction starting out
northerly, then becoming light/variable for a time Saturday
morning before becoming steadier southerly during the afternoon-
evening. Read on for more details...

Ceiling/visibility/snow potential:
Have maintained a low-end VFR ceiling through the first 18 hours,
but an occasional dip into MVFR cannot be ruled out. Also kept the
first 18 hours void of any formal snow mention, but rogue flurries
are not out of the question. For sure, the most likely time frame
for sub-VFR ceiling and also light snow is during the last 6 (and
especially last 3 hours) Saturday evening, and have taken a best-
stab with prevailing MVFR ceiling/IFR visibility during this time.
However, the overall-best snow potential may ultimately occur
just beyond this valid period, especially for KGRI.

&&

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

$$

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


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