Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 250513
AFDGID

AREA FORECAST DISCUSSION
National Weather Service Hastings NE
1213 AM CDT Sun Oct 25 2020

.DISCUSSION...(This evening through Saturday)
Issued at 438 PM CDT Sat Oct 24 2020

The largest problem of this forecast continues to be nailing down
snow amounts and perhaps some freezing drizzle potential at onset
of precip. Since this is an early snow event with the small
possibility of freezing drizzle at onset and unusually cold air
along with brisk wind, I favor a winter weather advisory for the
entire CWA.

Snow is already starting to fall in parts of Wyoming, northern
Nebraska and South Dakota and is heading our way as a severely
positively tilted upper trough swings toward us from the
northwest. Synoptic lift continues to be very unimpressive for the
entire event spanning from tonight into Monday.

Most models indicate the start time of the event will be
late tonight/Sunday. The NAM indicates some light snow right now,
and that does not appear to be happening, so I am not depending
too much on the NAM solution in the first period, which seems to
be the model that indicates the best shot at onset mixed/freezing
drizzle precip with the light qpf advertised late tonight/Sunday
morning. Boundary layer bulk shear does not seem to favor drizzle,
and if it does occur, I would not look for much if any glazing.
Since I cannot completely rule this out as the NAM has bee
consistently forecasting the dry mid-level pocket at onset, I will
keep it in.

I have expanded the timing of snow through the entire day Monday
and increased amounts compared to the previous forecast. Overall
deterministic models show a marked increase in mid-level
frontogenetic forcing that could beef up amounts. Also, the
dendritic growth zone is particularly deep on forecast soundings.
Wind gusts could help cut down on the amounts, though. Ensembles
seemed to be trending south and a bit heavier snow up through 18Z
Friday ECMWF ensemble run and 00Z Saturday GFS Ensemble run, but
both seemed to be backing off of this, although the latest GFS at
12Z hitting us a bit harder again. In fact, there is some
consensus developing a relatively low snow amount strip right
across our central/south central CWA before picking up a bit more
in our south again. This is a solution that was generally
indicated a few days ago by long term models. Overall the NAM is
really weak with snow totals. I suspect that we may get something
like this as we will be depending more on mid- level support, and
given the lack of synoptic level support. Confidence continues to
be "medium" for snow amounts, but it does still appear to be
generally higher amounts toward our north.

As the upper trough axis approaches southeast and a closed low
develops toward the base in the southern Rockies, we will actually
get some weak synoptic support during the day on Monday, and this
has been consistently forecast. I believe we could have light
snow or flurries falling for much of the day on Monday with
continued cold air advection. ECMWF wind gusts have been
consistently been forecast to hit 20 mph or so as well. With highs
confidently forecast in the 20s, this will be a very wintry day.

The good news is that ensembles and operational runs alike are
consistently forecast a climb out of the cold abyss through the week
and this looks quite reasonable. Going past the realm of the
official forecast...ensembles indicate a considerable streak of
warmer temperatures. GFS ensembles are warmer than the already warm
operational run as it stands. From October 31st through November
8th, GFS ensembles indicate that highs will be in the 60s for much
of the CWA through this period with low temperatures in the 40s for
each day. It`s still early, of course, but this is a strong signal
for a marked change heading into early November.

&&

.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Monday)
Issued at 1205 AM CDT Sun Oct 25 2020

Low ceilings, increasing snow chances and winds will be the
primary concerns for this TAF period. Currently there is
widespread low level stratus across the area, and expect little/if
any change. Current ceilings are right around 1500ft, guidance
suggest ceilings at/below 1000ft will be possible in a few hours.
Confidence in the timing of the onset/extent of snow early on is
not high, as high-res models suggest activity not holding together
well closer to sunrise. Have a mention of -SN starting at 10Z but
kept visibilities up. May be a bit of a lull in activity until
closer to midday-into this afternoon, and having visibilities
lowering with time. Current easterly winds will turn northerly
through the morning hours, with gusts near 30 MPH possible this
afternoon.

&&

.CLIMATE...
Issued at 605 AM CDT Sat Oct 24 2020

- Upcoming daily record possibilities/likelihoods for Grand
  Island/Hastings airports (our two primary climate data sites):

Oct. 25 coldest Max T (possibly reached early Sunday AM):
Grand Island: forecast 32 (current record 37 in 1997/1957)
Hastings: forecast 33 (current record 37 in 1957)

Oct. 25 coldest Min T (likely reached late Sunday evening):
Grand Island: forecast 20 (current record 15 in 1936) Hastings:
forecast 21 (current record 19 in 1975)

Oct. 26 coldest Max T (Monday):
Grand Island: forecast 24 (current record 28 in 1997)
Hastings: forecast 25 (current record 28 in 1997)

Oct. 26 coldest Min T (Monday):
Grand Island: forecast 13 (current record 13 in 1997)
Hastings: forecast 16 (current record 12 in 1997)

Oct. 27 coldest Min T (Tuesday):
Grand Island: forecast 10 (current record 9 in 1997)
Hastings: forecast 10 (current record 4 in 1997)

- ** Oct. 22-28 Projected To Be Overall-Coldest Week on Record
  This Early In The Fall Season! **

Based on our latest forecast (and observations from Thurs-Fri), the
7-day stretch Oct. 22-28 is currently projected to feature an
average daily temperature around 29 degrees at Grand
Island/Hastings (based on highs averaging near 36 and lows near
22). Should this verify, it would EASILY go down in the books as
the overall-coldest week on record for so early in the fall
season, eclipsing Oct. 22-28, 2002 which averaged around 35
degrees.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory from 7 AM this morning to 7 AM CDT
     Monday for NEZ072>077-082>087.

     Winter Weather Advisory until 7 AM CDT Monday for NEZ039>041-
     046>049-060>064.

KS...Winter Weather Advisory from 7 AM this morning to 7 AM CDT
     Monday for KSZ005>007-017>019.

&&

$$

DISCUSSION...Heinlein
AVIATION...ADP
CLIMATE...Pfannkuch


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