Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 021132
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
532 AM CST Fri Dec 2 2016

.SHORT TERM...(Today and tonight)
Issued at 316 AM CST Fri Dec 2 2016

Generally nice late fall/early winter weather is anticipated
across the local area again today. Other than some passing mid
level clouds...skies will be mostly sunny...winds will be
light...and temperatures will be near...if not a degree or two
above...early December normals.

As evident in satellite imagery this morning...expect some broken
mid level cloud cover to stream across the northern and eastern
portions of Nebraska this morning...before mostly sunny skies
become dominant as a weak ridge of high pressure aloft temporarily
builds across the local area. With a weak surface pressure
gradient under this ridge and very little change in 850 mb temps
from yesterday...expect another nice afternoon with temperatures
near or just above yesterdays readings. In addition...winds will
remain light as an area of surface high pressure slowly
transitions into the Missouri river valley over the next 24 hours.

Also evident in satellite...some high level clouds are encroaching
from the desert southwest...and should eventually get pulled
northeast and towards the local are during the late afternoon or
evening hours today. While it will take a while for the atmosphere
to saturate...could see a few light snow showers develop before
dawn across north central Kansas overnight tonight...as weak lift
ahead of the upper level low across northern Mexico is realized
locally...and introduced some very small pops to cover this
potential. Any precipitation that does form overnight...
however...should be very light and primarily limited to our north
central Kansas counties.

.LONG TERM...(Saturday through Thursday)
Issued at 316 AM CST Fri Dec 2 2016

Chances for precipitation and a blast of very cold air remain the
primary concerns through the long term.

The period starts off Saturday morning with models not in too bad of
agreement looking aloft, with southwesterly flow across the area. A
cutoff low pressure system spins over northwestern Mexico, while a
northern stream shortwave trough is sliding through the High Plains.
Lift increases ahead of the disturbance, and models also showing the
potential for portions of the area to be influenced by the entrance
region of a strong upper level jet. Precip chances look to spread
north-northeast through the daytime hours Sat, clipping the east-
southeastern third or so of the CWA. PoPs are only in the 20-30%
range, as there is some spread between models with the coverage of
any precip and QPF. The NAM is the most aggressive, actually trying
to drop a few inches of snow across the southern half of the CWA,
while a few others have very little QPF. Overall through the event,
precip type may end up being a mix of both RA/SN, so snow accum may
be hard to come by. At this point do have a few tenths of an inch of
snow across SErn areas, but if things trend closer to the NAM,
adjustments will be needed. Confidence in precip/precip-type for Sat
is not the highest. Current forecast highs are in the upper 30s-
lower 40s, but if it pans out more like the NAM, that may be too
warm.

What precip that does affect the CWA on Saturday is expected to
shift off to the east during the evening hours. Upper level zonal
flow looks to build in across the area in the wake of this system
for Sunday, and the forecast remains dry. Though the continued dry
forecast, upper level flow turns more southwesterly as we get into
Monday, as the next round of troughing moves further into the
Rockies. Sun-Mon will bring our last shot of near/slightly above
normal temps, with forecast highs in the mid-upper 40s both days.
Westerly winds during the day on Sunday looks to transition to the
south on Monday, ahead of deepening surface low pressure/approaching
cold front.

That brings us to the Tuesday through Thursday period. At one point
in just the past few days, models had shown the possibility of a
potent closed upper level low pressure system swinging through the
Plains, bringing along the chance for quite a bit of snow. In the
past couple of model runs, and continued in the 00Z run, models have
trended more toward the area being affected by troughing associated
with a closed low over central Canada, with embedded pieces of
shortwave energy...more progressive flow. Models showing the chance
for the first, weaker wave to bring light precip Monday night into
Tuesday. The system bringing the better chance for precip still
looks to push through the area Tuesday night into Wednesday, not a
big change timing-wise from previous model runs. Still looking to be
an all snow event, with accumulating snow possible for the CWA, but
too many uncertainties/details yet to be ironed out before we can
confidently start throwing out amounts.

One thing that has not changed with several model runs now is the
significant air mass change, ushering in much colder temperatures.
The timing of passage of the cold front hasn`t changed
significantly, with it expected to have pushed through the entire
CWA by 12Z Tuesday. Colder air starts pushing in from the north,
getting an reinforcing shot with the passage of the main system
Tuesday night into Wednesday. Breezy NW winds can be expected both
Tues and Wed. A 15-20 degree drop in highs is currently forecast
from Mon to Tues, into the mid 20s to near 30 degrees. Wind chill
values through the afternoon hours on Tuesday are forecast to fall
into the teens, perhaps some single digits in the northwest.

The ECMWF has the brunt of the precip going on during the daytime
hours on Wednesday, the GFS is a touch quicker (mainly Tue
night/early Wed), GEM in between. Any solution, Wed not looking to
be the nicest of days. Highs are expected to only reach the mid
teens to mid 20s, after starting the morning in the lower-mid teens.
Wind chill values in the single digits either side of zero are
currently in the forecast for Wed morning, and then again Thurs
morning, with only a slight rise during the day.

Though Thursday is forecast to be dry in the wake of this system,
the cold air mass is solidly in place. Current forecast highs range
from the upper teens to mid 20s, starting the day with low sin the
single digits for a good chunk of the CWA. Wouldn`t be too surprised
to see forecast highs for both Wed-Thurs trend down more, if current
model trends hold. We`ll see what the coming model runs bring.

&&

.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Saturday morning)
Issued at 527 AM CST Fri Dec 2 2016

VFR conditions will continue through the period with increasing
mid/high level clouds late in the day and through the overnight
hours...as moisture associated with an upper level low pressure
system across northern Mexico continues to advect towards the
region. Otherwise...a weak pressure gradient will remain in place
across the local area...with light and occasionally variable
winds through the period.

&&

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

$$

SHORT TERM...Rossi
LONG TERM...ADP
AVIATION...Rossi



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