Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 182326
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
526 PM CST Thu Jan 18 2018

.SHORT TERM...(This evening through Friday)
Issued at 334 PM CST Thu Jan 18 2018

Hazardous Weather: None.

Aloft: NW flow was over the rgn with a moderate-amplitude ridge
extending from Srn CA to the Canadian Prairies. A trof was over
the E Pac. The ridge will deamplify further and flatten as it
crests over the rgn tomorrow. The base of the Pac trof will
approach CA by 00Z/Sat and it will be a player here this wkend.

Surface: High pres was over the Gulf Coast states with return
flow over the Cntrl Plns. A deep low was just offshore of BC. Its
cool front was advancing thru the Wrn USA. The CWA will remain in
the warm sector. The Nrn portion of the Wrn cool front will move
faster than the Srn portion...and it will be on our doorstep by
00Z/Sat.

Now: Extensive thick cirrostratus has invaded from the N and put a
cap on how warm it might have been today. Even still...the mesonet
site in Logan KS is 61F at 230 PM.

Tonight: P-M/cloudy. This will be a relatively mild night with
lows in the 20s. We`ve only seen 4 nights with low temps 20F or
above since Dec 21st (using GRI as a proxy for the entire CWA).

Fri: P/cloudy but we may be underplaying it...especially over S-
cntrl Neb where it could be m/cloudy at times or even much of the
day.

Mild/warm but with significant temp uncertainty over remaining
crusty snowpack. Fcstg warm temps over snowcover is always very
tough. Spread between the warmest and coldest temp guidance is
substantial (40s vs 60s). Used a model blend which has mostly 50s
except low 60s over the Wrn/Srn portions of the CWA.

.LONG TERM...(Friday night through Thursday)
Issued at 334 PM CST Thu Jan 18 2018

Potentially Hazardous Weather: Winter storm looming Sun-Mon.

Aloft: The trof that moves into CA/NV Sat night will progress thru
the Desert SW and deepen as it lifts NE across KS Sun into Sun
night...then across SE Neb into IA/MO Mon. This is still 3 days
away so while confidence is high that this low is coming at us...
we are still dealing with what we always deal with at these time
ranges: amts and location of those amts along with minor diff`s in
timing.

How we see this now: low-lvl stratus will invade and in the
presence of large-scale lift...this could result in pockets of
frzg drzl Sun AM. There could be a break or it could change to
non-frzg drzl before deeper mstr moves in and a band of def zone
snowfall sweeps thru parts of the CWA.

Snowfall: too early to talk specifics. Tonight`s shift will have
the first crack at amts/ranges. So expect the first details to be
available first this tomorrow AM. We have fairly high confidence
that warning-level snowfall will occur in part of our CWA (that is
6" in 12 hrs). The greatest risk of this occurring will be N of
Hwy 6 in S-cntrl Neb.

As is typical...not everyone will see that kind of accum.

Wind: we are concerned with some of the potential wind speeds we
are seeing in the guidance. The "B" word is on the table.
Sustained winds of 25-30 mph with gusts of 40-45 are possible.

Significant blowing/drifting snow will be an issue and make
measuring extremely difficult.

Caveat: This is preliminary info. Adjustments will occur to these
expectations as details come better into focus and the models
converge on what will actually occur. Cannot stress enough that
everyone should monitor fcsts throughout the coming 3 days. It`s
easy to disengage from important news/wx info on the weekend.

We have ramped up our messaging on this shift with the 1st
issuance of Situation Report (available on our website). An SPS
was issued at 310 PM and graphics via social media will cont.

Quiet wx is expected after Mon. New snowfall will impact fcst
temps and we probably don`t have a full grasp on this yet since
the snow hasn`t occurred yet. Overall...we are done with the
bitterly cold arctic air for a while.

For those who look beyond this 7 day time frame...the pattern is
transitioning to a -PNA (Wrn trof/Ern ridge). Most of our more
substantial winter precip events come in this pattern and we are
seeing its effects for this weekend. There is more potential for
meaningful precip before the end of the month.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 521 PM CST Thu Jan 18 2018

Dry weather with VFR conditions forecast for this TAF period.
Cloud cover expected to remain in the upper levels, above 15k ft.
Not looking at any significant changes in the winds through the
period, which will remain southwesterly, with speeds topping out
around 10 MPH.

&&

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

$$

SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...ADP



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