Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 162340
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
540 PM CST Sat Dec 16 2017

.SHORT TERM...(This evening through Sunday)
Issued at 240 PM CST Sat Dec 16 2017

The warm weather from the past two days will be coming to an end
tonight, with cloudy/cooler conditions forecast for Sunday. Zonal
flow aloft today will give way to a troughy regime with an upper low
in west Texas lifting out across Kansas tonight/early Sunday while a
northern stream shortwave trough sends a cold front south across our
region. That southern low pressure system will bring some
precipitation chances to eastern Kansas, east of our area and have
kept our forecast dry despite the NAM suggesting a light drizzle
potential for our northwest counties. The NAM stands alone with its
light qpf amounts overnight/early Sunday and have kept the forecast
dry.

Low clouds and colder air move in tonight and there could be some
patchy fog along the edge of the stratus. SREF probs and most
guidance do not support dense fog and suggest visibilities may lower
to the 3 to 5 mile range, however the RAP is pretty aggressive
indicating the potential for dense fog across our southern and
eastern zones late tonight into Sunday morning. Wind speeds look to
remain steady enough near 10 mph which should limit dense fog
development and confidence is not high enough to mention fog in
the forecast.

Sunday is shaping up to be a rather cloudy day with noticeably
cooler temperatures trending near seasonal normals. Surface high
pressure settles onto the plains behind the cold front,
reinforcing the cooler airmass. The cloud cover and cooler air
will hold temperatures primarily in the 30s for highs.

.LONG TERM...(Sunday night through Saturday)
Issued at 240 PM CST Sat Dec 16 2017

Heading into next week, we warm back up with temperatures averaging
above normal again Monday through Wednesday, then markedly colder
air arrives by Thursday, just in time for the official start of
winter on December 21st. Thursday will also see the potential for
snowfall, and that frigid airmass which moves in early Thursday looks
to hold through Christmas.

Sunday night, the surface ridge axis departs to the south and a mid
level trough axis exits to the east allowing for rising heights and
a moderating airmass on Monday. Temperatures are expected to recover
nicely, returning to the 50s for highs. A trough translating through
the Upper Midwest region backs in cooler air on Tuesday, dropping
temperatures a few degrees compared to Monday.

Wednesday will feature one more warm but windy day ahead of the
approaching cold frontal boundary. Look for winds to be steady/gusty
from the south with daytime highs in the 50s.

The pattern change takes place Wednesday night and Thursday as an
upper trough dives south from Canada, crossing the northern and
central plains and sending a strong cold front south, bringing an
abrupt end to our above normal temperatures. Current timing of the
front has the boundary entering our NW zones after 06Z Thursday with
the boundary through our cwa by 12Z Thursday. The front will be
noticeable, accompanied by strong north winds and markedly colder
temperatures. H85 temperatures drop a solid 15C to 20C from
Wednesday to Thursday. Temperatures will struggle in the cold air
and high temperatures for the calendar day Thursday will likely be
at midnight, with readings leveling off or falling during the
day. The cold air combined with the strong winds will produce wind
chill readings in the single digits.

Precipitation wise, there is a small chance for light
precipitation (rain/snow) Wednesday night in our southeast zones
along the frontal boundary which is more in line with the latest
GFS. Better chances for snow exist Thursday into Thursday evening
in frontogenetic forcing and upper dynamics as the upper trough
moves through. It`s a fast moving wave, so overall snow amounts
are expected to be light with current models indicating snowfall
of around two inches possible for our northern zones with a half
inch or less in the south, but this will be refined as we get
closer to this event.

The forecast dries out by Friday and remains dry through Saturday
morning, then just small chances for light snow return to our
western zones Saturday afternoon. The cold weather looks to stay
through at least Christmas as a broad trough encompasses the
interior CONUS.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 521 PM CST Sat Dec 16 2017

TAFs could be challenging tonight as the models are trying to
bring in some fog and low ceilings to the TAF sites. Don`t have
high confidence in fog so left it out as the overnight winds will
be around 10kts. Went with MVFR ceilings for the 9z to 17z
period. Some of the models are hinting at some IFR also, but felt
the stronger signal was with the MVFR ceiling. Expect MVFR ceilings
to linger Sunday as mid and high clouds plus the short winter days
will hinder day time heating scattering out the layer.

&&

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

$$

SHORT TERM...Fay
LONG TERM...Fay
AVIATION...Beda



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