Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 141256
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
656 AM CST Sun Jan 14 2018

.UPDATE...
Issued at 656 AM CST Sun Jan 14 2018

Quick update mainly to address tricky sky cover today:
Although there will still be plenty of at least mid-high level
cloud cover today (especially this afternoon), satellite trends
suggest that especially the western half of the CWA will see more
sunshine than earlier expected (especially this morning), as the
low level stratus is clearing more aggressively from west-to-
east. It is possible that this sunnier-than-expected theme could
progress into the eastern half of the CWA as well, but with more
stratus sinking southward from north central NE kept cloud
percentages higher there for now.

&&

.SHORT TERM...(Today and tonight)
Issued at 456 AM CST Sun Jan 14 2018

The main items to focus on during these next 24 hours include:
1) A brief, one day "warm-up" before the next blast of Arctic air
arrives for Monday...2) One more round of fairly light/albeit
pesky precipitation late this afternoon through tonight, with some
light snow accumulation likely, especially in north central KS.

Taking a look at current/recent weather as of 4 AM:
Obviously the "big story" overnight has been the currently-
winding-down batch of snow, which is poised to exit our
southeastern coverage area (CWA) by 6AM or so. Although the vast
majority of official snow reports will not start rolling in until
around 7AM, limited ground-truth suggest that the highest totals
in the 1-2" range fell in a swath across the heart of the CWA from
around the Tri Cities southeastward toward Hebron, with most
places in our northeastern and also southwestern zones averaging
under 1" (would be very surprised to hear of any truthful 3+"
amounts). Compared to expectations 24 hours ago, the most
concentrated swath of snow ended up shifting generally 30 miles
southwest (targeting central counties more so than northeastern).
As expected southerly winds only averaging 10-15 MPH have kept any
blowing/drifting to a minimum, and overall this should go down as
pretty low-impact event. In the mid-upper levels, water vapor
imagery and model data confirm the responsible shortwave trough
and associated upper jet streak tracking southeast across the
Central Plains at this time, with forcing for snow also aided by a
belt of low-mid level warm-air advection. At the surface, a
generally north-south oriented warm front is in the process of
working across NE/KS from west-to-east, with breezes starting to
turn a bit more southwesterly with time across our CWA. As
expected, temperatures have in fact warmed slightly overnight
across the area, and by sunrise readings should range from around
15 far east to around 25 far west (warmer than yesterday`s highs
in most places).

Now looking ahead into the daytime/overnight forecast periods...

Today:
For most of the day, the #1 story will be the warm-up, but this
forecaster continues to have some reservations about how
significant it will be, especially given: 1) Fresh light snow
cover in most areas and 2) plentiful cloud cover, initially of
mainly the low-level variety, but later in the afternoon more mid-
high level. There could be a window of opportunity for at least
partial sunshine around mid-day, but overall looking at a mostly
cloudy day. Nonetheless, a decent warm-up versus Saturday is
assured, thanks to the aforementioned warm front passing through,
signified at the surface breezes turning southwesterly-westerly at
5-15 MPH for most of the day. We have gradually been trimming high
temps for today over the past few days, and we may still need to
back off a little more, but will aim for a range from low 30s far
east to mid 40s far southwest. While most of the day will be
precip-free, already by late afternoon the next upper trough
currently diving due south out of Canada toward our region will
become a player. While most areas will probably make it to sunset
without seeing any precip, have sped up/added some low chances for
precip to especially the northern half of the CWA post-3PM, which
would most likely take the form of light rain or snow.

This evening/tonight:
The aforementioned southward-driving upper disturbance will drive
a very well-defined/noticeable Arctic cold front southward across
the CWA between sunset and midnight, with its passage marked by
increasing (but not overly-strong) north winds sustained at
generally 15-20 MPH and perhaps gusting to around 30 MPH. Precip-
wise, what could end up being a fairly narrow band that enters
northern zones late this afternoon will just continue developing
southward through the night, ending across most Neb zones by
midnight, but lingering later into the night in KS zones before
moving out by daybreak. As the colder air surges in, the majority
of this post-sunset precip should take the form of snow, but a
BRIEF/fleeting period of sleet/freezing rain probably cannot be
ruled out within the transition zone, with little to no icing
impact anticipated. Snowfall-wise, this should be an overall-less
impactful event than the one we just had, with most Nebraska zones
expected to see only a dusting to perhaps one-half inch. However,
parts of our KS zones (especially our southern-most 3 counties)
could see slightly higher amounts to around 1". Although the
increasing winds could result in a bit more blowing snow than we
had with the currently-ending event, the minimal amounts make the
need of a formal Winter Weather Advisory seem fairly unlikely.
Nonetheless, will continue to highlight in the Hazardous Weather
Outlook (HWOGID). Temp-wise, needless to say temps will steadily
fall behind the passing front, with overnight lows eventually
ending up in the single digits (above zero) most areas, and 10-15
in KS zones. Near-Advisory level wind chills of -15 to -19 degrees
will become common Monday morning especially north of Interstate
80, but unless things trend colder we should be able to get away
without needing a formal advisory until Monday night (see below).

.LONG TERM...(Monday daytime through Saturday)
Issued at 456 AM CST Sun Jan 14 2018

General overview of this 6-day period:
There are essentially four stories to focus on:
1) Very cold temperatures and wind chills Monday-Tuesday, with a
Wind Chill Advisory (maybe even a Warning?) all but guaranteed for
Monday night-Tues AM as it gets a bit closer in time.

2) A steady (and likely very-welcomed) warming-trend Wednesday-
Friday, with all areas expected to make it into the 40s by week`s
end.

3) Fairly high confidence in the going precipitation-free forecast
for the entire Monday daytime-Friday night time frame (although
there are hints of a weak disturbance passing through around
Thursday that could eventually necessitate a light rain/sprinkle
mention).

4) Although the details are FAR, far from set, our next
organized/larger scale low pressure system and precipitation
chance is currently set to arrive perhaps as early as Saturday
afternoon, but more so Saturday night, which is technically just
beyond the current official forecast period. This has the
potential to bring a quick round of wind-driven snow mainly
Saturday night, so this will obviously bear watching as it
gradually creeps closer.

With the 4 main points covered, will finish with a few more day-
to-day details...

Monday-Tuesday:
By far the coldest 2 days of the week, with highs each day mainly
in the 8-18 range. Monday will be the breezier of the 2 days, with
north-northwest winds averaging 15-25 MPH and gusting to around 30
MPH, making for a very unpleasant day despite plentiful sun.
Monday night lows are trending slightly colder, and now have most
of the CWA down into the -15 to -12 range for actual air
temperatures. Although winds will be lighter than the daytime
hours, dangerous wind chills will develop Monday night-Tuesday AM,
ranging from around -20 south to -30 (or slightly worse) north. In
coordination with neighboring WFOs, have held off an any formal
Advisories or Warnings for now, but they will likely be issued
within the next 24 hours. Tuesday night will not be quite as cold,
and although near-Advisory wind chills of -15 to -20 are likely
especially in Nebraska zones, we probably will not need another
formal headline.

Wednesday-Friday:
As mentioned, confidence is fairly high in the dry forecast, with
the gradual warm-up by far the biggest story. High temps are
expected to climb anywhere from 5-15 degrees from each day to the
next, with Wednesday generally 25-30 most areas, Thursday 35-45
and Friday 40-50.

Saturday:
See point #4 above. The majority of the CWA is expected to remain
precip-free through the daytime hours, but some low chances for
rain/snow could enter especially western counties in the
afternoon. Better precip chances (likely in the form of snow)
could enter the picture for Sat night, but this is still just
beyond the scope of the current official forecast. Plenty of
uncertainty in high temps, but currently aimed into the upper
30s-mid 40s range.

&&

.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Monday)
Issued at 637 AM CST Sun Jan 14 2018

General overview:
By far the biggest issue and also biggest uncertainty involves
ceiling trends. Although MVFR is currently expected to prevail
both right away this morning, and again much of this evening,
there could be a longer-than-previously expected period of VFR
conditions during the daytime hours. Precipitation-wise, a fairly
brief period of a rain/snow/sleet mix could occur this evening,
otherwise the vast majority of the period will remain precip-free.
Read on for more element-specific details.

Ceiling/visibility/precipitation trends:
If anything, uncertainty has increased somewhat regarding ceiling
trends, as satellite trends show that the daytime hours could
feature a bit more VFR than expected. At any rate, things will
start out MVFR, likely go VFR for a time (potentially anywhere
from 6-10 hours), and then an MVFR ceiling will likely return for
much of the evening behind a passing cold front. This next round
of MVFR may not last as long as currently advertised, but
officially have VFR again returning by 09Z. Precipitation-wise,
have continued to indicate a generic VCSH between 00-03Z to
capture the best window of opportunity for a passing area of rain,
sleet or snow (could be a little of each). Later issuances/updates
can obviously fine tune this, but any snow accumulation should be
very minimal (perhaps a few tenths of an inch).

Winds:
Surface winds through the first half of the period will average
near-to-below 11kt from a southwesterly-westerly direction.
However, a fairly strong cold front will slice southward this
evening and overnight, resulting in north-northwest winds
sustained 15-20kt and gusting to around 25kt. There are still
hints that some marginal low level wind shear (LLWS) could occur a
few hours either side of 00Z, but at this time it does not appear
strong enough to warrant a formal inclusion.

&&

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

$$

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


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