Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 192110
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
310 PM CST Fri Jan 19 2018

.SHORT TERM...(This evening through Saturday)
Issued at 306 PM CST Fri Jan 19 2018

This period will be the calm before the storm. Upper level wind
becomes southwest as an amplified wave develops over the Great
Basin. A surface cold front will pass through tonight and by
Saturday, temperatures will be noticeably a bit colder with highs
in the 40s.

.LONG TERM...(Saturday night through Friday)
Issued at 306 PM CST Fri Jan 19 2018

Main focus will be on the winter storm Saturday night through Monday
morning.

As anticipated a closed low will develop east of the Rockies within
an amplified longwave trough that will be the main concern.

Initially, we will add to the troublesome weather with a fairly
strong signal in forecast sounding data that suggests at least a
good chunk of our CWA will experience some light icing late Saturday
night into Sunday morning from freezing drizzle occurring from
pronounced isentropic lift, a pronounced dry mid-layer, and an
inverted saturated low-level profile, along with obvious warm air
advection showing up in the wind profile. This has been consistently
indicated by more than one model, and could potentially add misery
to the already difficult conditions expected.

There is high confidence that a heavy snow producer in the works for
Sunday night into Monday morning as numerous numerical models have
consistently forecast a track of snow. Trends are clearly placing
the track farther southeast compared to previous model runs and
slowing things down a bit. The 700 mb track clips our southeast CWA,
placing us within the axis of heaviest snowfall Sunday night.
Divergent Q vectors in the 500-300 mb level indicate an overall
increase in large scale lift Sunday evening. This could be a heavy
snow event for a significant swath across our area Sunday night into
early morning Monday and very possibly very poor visibility
conditions for Monday morning on the backside of the low tracking to
the northeast. The ECMWF solution looks particularly troublesome for
potential blizzard conditions on Monday as it has slowed down the
exit of the low more than other model solutions. 850 mb and 700 mb
forecast tracks are extremely favorable for the band of heaviest
snow to track across our CWA. With warmer temperatures this time
around, this snow should be heavier than what we`ve experienced with
the past couple of snows. Unless some huge about face occurs, or if
the track of the low somehow inexplicably plunges farther south than
what models are trending toward, I do not see how at least some of
our area will not be clobbered by this system. The biggest question
is where the heaviest snowband will set up. High temperatures may
also need to be knocked down a few degrees. General trend is for
higher snow amounts farther to the south, so I extended the watch
farther south. Also, freezing drizzle may start earlier than 6 am
especially in our south.

Again, Monday morning winds will just howl, especially central and
east. No other way to put it. GFS 925 mb wind speeds are over 40 kts
at 12Z Monday and 850 mb wind speeds are forecast for 55 to 60 kts.
This translates 35 to 40 mph wind gusts for a good chunk of our CWA.
There will probably be at least some snow still flying at that time,
so visibility will probably be quite poor for at least some of our
area, especially east. Will be increasing wind speeds a good 5 mph
for Sunday night/Monday morning from the overnight forecast. High
temperatures may need to be knocked down a few degrees with strong
cold air advection and snow cover, but hardly the arctic outbreak
that we`ve experience in the recent past.

As for post-system, expect a rather seasonable temperature
situation, although I suspect that temps may need to be knocked down
due to expected snow cover.

Looking just beyond the extent of the long term, another winter
system may be in the offing for the weekend, but of course, it is
way too early for much speculation.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Saturday)
Issued at 1156 AM CST Fri Jan 19 2018

VFR conditions expected as a cold front passes through and shifts
light wind from southwest to north overnight, but should remain
light. Cirrus sky cover could continue to be thick into the night,
but this should not hinder VFR category. Some models indicate
lower visibility from perhaps daytime melting of snow, but this is
being discounted as strong enough subsidence should stop this from
happening.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Watch from Sunday morning through Monday morning
     for NEZ039>041-046>049-060>064-072>077-082>086.

KS...Winter Storm Watch from Sunday morning through Monday morning
     for KSZ005-006-017.

&&

$$

SHORT TERM...Heinlein
LONG TERM...Heinlein
AVIATION...Heinlein



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