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479
FXUS63 KGID 130556
AFDGID

AREA FORECAST DISCUSSION
National Weather Service Hastings NE
1156 PM CST Thu Dec 12 2019

.UPDATE...
Issued at 1150 PM CST Thu Dec 12 2019

Sent an update to include some fog and freezing fog across the NE
quadrant of the CWA the rest of tonight. The GOES nightime
microphysics RGB and sfc obs indicate low stratus from Greeley to
York, with sfc obs showing dense freezing fog at BVN. This fog
likely extends into far N/NE portions of Greeley, Nance and Polk
counties as well. Will need to monitor how far this fog tries to
expand S/W, but current expectations are that slowly veering winds
should keep the fog NE of ODX to GRI to AUH.

&&

.SHORT TERM...(This evening through Monday daytime)
Issued at 453 PM CST Thu Dec 12 2019

Am including the entire first 4 days of the forecast in this
"Short Term" section, as they include a multitude of tricky/pesky
chances for precipitation, some of which will likely be snow.
Unfortunately, most all of these chances also still carry an
above-average degree of forecast uncertainty, so while the
"general picture" will be outlined below, you can pretty much
count on at least minor changes over the next few days, so please
stay up to date with the latest. For a more concise/basic overview
of our concerns please check out our latest Hazardous Weather
Outlook (HWOGID), which has had plenty of detail added to it this
afternoon.

The highlights version/most important points of the next 3-4 days:
- We have at least 4 distinct chances for at least pesky/light
  precipitation between late tonight and Monday AM, one late
  tonight into Fri AM that is expected to be very minor (if it
  even occurs at all)...another Friday afternoon into Friday
  night that could drop a sneaky dusting of snow in some
  spots...more chances for light snow mainly in our western zones
  Sat-Saturday night...and then finally what COULD be a more
  significant chance for at least a few inches of snow mainly
  favoring our southern zones between Sunday daytime and Monday
  AM.

- In terms of travel impacts, it`s this last snow chance from
  Sunday into Monday AM that carries the greatest potential of
  causing some issues. But because this is still 3+ days away, it
  also carries PLENTY of uncertainty, especially with regard to
  "exact" accumulations. It was hoped that primary models such as
  the GFS/ECMWF should come into a bit better agreement today
  regarding snow potential, but unfortunately they still vary by a
  far degree. All we can really say for now is that the southern
  half of our coverage area (CWA) stands the BEST chance of
  perhaps seeing at least a few inches of snow (especially our KS
  zones), with our northern half (especially from near I-80 and
  northward) looking less favored for anything more than roughly 1
  inch. However, yet again, there is still time for this to
  change, shift north or south etc., so yet again, please keep
  checking back.

- Temperature-wise, Friday will most certainly be the overall-
  warmest of the next several days (perhaps of the entire next
  week). Then, a markedly colder airmass arrives for the weekend
  before a gradual moderation takes place next week (see Long Term
  section below for more on this.

Taking a step back and briefly looking at the current/recent
weather scene as of 4 PM: For at least the third day in a row,
daytime high temperatures have fallen at least a few degrees short
of original expectations. This was due to a combo of plentiful
high level cloud cover for several hours (although this is now
gradually moving out from west-to-east) and also a bit more
influence of colder air especially in the northeast half of our
CWA. More specifically, highs only reached the mid-upper 30s in or
north-northeast, low-mid 40s central, and the mildest mid-upper
40s southwest. Despite falling a bit short, light winds due to a
passing surface ridge axis made it feel halfway decent for mid-
December. In the mid-upper levels, water vapor satellite depicts
a fairly active west-northwest flow regime, thus why we will see
the passage of several/mainly low-amplitude disturbances over the
coming days.

Now looking ahead forecast wise between tonight and Monday, and
taking things in 12-24 "chunks":

This evening/tonight:
High confidence that the vast majority of the CWA gets through
sunrise dry, with only varying degrees of passing mid-high level
clouds. However, very late tonight (mainly after 3 AM), the next
disturbance approaching from the west-northwest looks like it
could try to generate some very light/pesky precipitation mainly
within some of our far northern/northeast counties (N-NE of Grand
Island). Did not have enough confidence in this to introduce a
"formal" 20+ percent PoP/chance, but did acknowledge the small
chance by including a "slight chance of sprinkles" just to hint
that it might not be completely dry. Should any precipitation
actually occur, it conceivably could take the form of very light
freezing rain and/or sleet, but with such a low probability of
occurrence opted not to cause any "undue concern" at this point.
Something for next few shifts to watch though. Temperature-wise,
not expecting a big drop tonight, with light south-southwest
breezes and increasing clouds expected to hold most places up in the
upper 20s to around 30 (any mid-20s most favored northeast.

Friday daytime:
Like tonight, most places will probably get through most of the
daylight hours dry. However, right away in the morning, have
lingered a small chance sprinkles in eastern zones to account for
tonight`s departing wave. Then, following a lull through much of
the day, more chances for sprinkles/light rain showers arrive
later in the afternoon as the next disturbance arrives. These
afternoon chances would mainly affect the NW half of our CWA, and
are a change from the previous fcst (which was dry). High
temperatures are a bit tricky, as would not be surprised to see
them yet AGAIN fall at least slightly short of expectations. Did
in fact nudge them down slightly (1-3 degrees), but still calling
for decent readings ranging from mid 40s northeast/upper 40s
central to low-mid 50s southwest. Daytime breezes will generally
average 10-15 MPH from the west-northwest, but some higher gusts
are likely especially west and especially late in the day as the
cold front starts pushing through.

Friday night:
Although not expected to be a "big deal", especially the evening
(pre-midnight) hours could feature a quick burst of passing
precipitation, transitioning from rain to snow as colder air takes
hold. Officially, we are calling for no more than a dusting in
most places, but given some decent forcing aloft, this looks like
the kind of setup that produce one or two "sneaky" bands of
slightly greater accumulation. Even so, would be quite surprised
to see any location see more than one-half inch to 1 inch tops.
Colder air definitely moves in, with lows falling into the teens-
low 20s range most areas.

Saturday-Saturday night:
Overall, this is not looking to be a terribly troublesome 24
hours, but for sure, at least some flurries/light snow
accumulation looks to occur, especially Saturday evening into
Saturday night and especially within the western half of our CWA.
If the latest ECMWF is onto anything, perhaps portions of our west
could see up to around 1 inch of snow, but our official forecast
remains less than this. For sure, the big story for all areas will
be a notably colder day than Friday, with highs only aimed from
mid 20s northeast to (maybe) mid 30s southwest. Then Saturday
night, lows fall into the teens all areas.

Sunday daytime-Monday daytime:
As earlier described, this will probably end up being the most
troublesome 24-30 hours of the entire next week, with potential
for perhaps up to at least a few inches of snow mainly within our
southern half. However, just as a testament to the lingering
uncertainty in this forecast, the GFS continues to hit our
central/northern zones harder than the ECMWF, so we cannot
completely discount at least an inch or two even north of
Interstate 80. No matter how much (or how little) snow falls
during this time, timing confidence is still fairly high that it
should be over by mid-day Monday. As is almost always the case,
confidence is higher in temps than precip/snow amounts, with
Sunday looking like the overall-coldest day of the next week with
highs only mid-upper 20s most areas. Monday is currently calling
for a modest rebound into the low-mid 30s, but a lot of this will
depend on exactly how much snow is on the ground by then.

.LONG TERM...(Monday night through Thursday)
Issued at 453 PM CST Thu Dec 12 2019

General overview of this 3-day period:
Not gonna say a whole lot here, as this is truly looks to be the
calmest/quietest portion of the 7-day forecast, and carries pretty
high confidence in remaining so.

Honestly, the biggest question mark involves how quickly our
temperatures moderate from Tuesday-Thursday. If not for the
potential for at least light/lingering snow cover from the Sunday-
Monday system, this forecaster would feel pretty strongly that we
are probably UNDER-forecasting the temperature recovery. For now
though, am alright with aiming perhaps a bit on the
cool/conservative side. Officially, we are calling for highs
slowly edging upward from the mid 30s Tuesday, to the upper 30s-
mid 40s Wed-Thurs. However, if snow cover is minimal and/or melts
before mid-week, then it`s very possible that highs Wed-Thurs could
rise well into the mid-upper 40s.

&&

.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Friday)
Issued at 1150 PM CST Thu Dec 12 2019

Significant wx: TEMPO IFR poss at GRI early this morning.

Tonight thru 12Z: Mainly VFR, but have introduced at TEMPO BKN005
group at GRI from 09Z to 11Z to account for slowly expanding
stratus deck as seen on satellite as well as sfc obs. Its poss
this deck could stall just a few miles NE of the terminal, but
it`ll be close. Think the fog should remain further NE. Otherwise,
will see some high clouds. Winds start off SSE but will veer to W
around dawn and remain less than 10kt. Confidence: Medium

Fri to 06Z Sat: VFR, MVFR poss late, esp. at EAR. Much of the
morning hrs should be mainly clr, but will see incr high clds
during aftn. CIGs will gradually lower late aftn-eve, and may
approach MVFR levels late in the period, best chc at EAR, as a
shortwave trough and associated rn/sn approach from the W.
Confidence too low attm to carry prevailing -SN and reduction in
VSBY, but its poss after 03Z. Winds will veer from W to NW and
incr in the eve. Confidence: Medium.

&&

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

$$

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