Area Forecast Discussion
Issued by NWS Hastings, NE

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989
FXUS63 KGID 211156
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
556 AM CST Sat Jan 21 2017

.UPDATE...
Issued at 553 AM CST Sat Jan 21 2017

Updated the forecast to account for the end of dense fog in Thayer
County, finally. This allows the last county in our Dense Fog
Advisory to expire.

&&

.SHORT TERM...(Today and tonight)
Issued at 453 AM CST Sat Jan 21 2017

The biggest issues include pesky dense fog near Hebron and potential
for at least some patchy fog this morning. Then a close call with
some rain tonight.

The HRRR has done a pretty good job with the fog so far, and it
indicates that we could have some patchy fog stick around this
morning through about 9 am. Hebron continues to be a bit of an
enclave of lower visibility/low stratus that is connected to points
to the east as Beatrice is still reporting dense fog. Most sites
have lost their dense fog with the general switch to a west wind
component.

Shortwave ridging will give us a dry and warmer day, possibly
pushing 50 in the tri-cities with some sun expected to show up. Then
tonight, the expected Southern Plains system with the surface low
tracking through OK will move through. Most models have brought the
edge of rain very close to our border in the south, but I have left
this us completely dry for now as the system still looks a bit too
far south to affect us. Wind will be light tonight, with some patchy
fog not out of the question, but guidance does not indicate this and
wind will north/northwest, which is not all that favorable for fog.
However, this evening there could be a window where we need to stick
some fog in. The SREF indicates that this may be needed, but the
SREF has overdone fog in the past. Expect another relatively mild
night with some increasing sky cover compared to the afternoon, with
lows in the upper 20s to around 30.

.LONG TERM...(Sunday daytime through Friday)
Issued at 453 AM CST Sat Jan 21 2017

General overview of this 6-day period:
Overall, little notable change to the forecast versus 12 and even
24 hours ago. That means that the paramount focus remains on the
POTENTIALLY impactful (key word "potentially) winter storm system
slated to cross the Central Plains during the Tuesday-Wednesday
time frame. Both before and after this storm system, the forecast
looks precip-free and fairly uneventful. Temperature-wise, we are
still looking at a seasonably-mild stretch Sunday-Monday with
highs well into the 40s/low 50s before a cool-down to more
January-like levels becomes established by Wednesday-Friday with
highs well down into the 30s most areas and lows in the teens.
Tuesday is the temperature "transition day", and still looks to
feature a tricky gradient from colder 30s northwest to perhaps
near-50 far southeast, with falling afternoon temps a good bet.

Comments on the Monday night-Tuesday night system:
Well, even though we are one day closer to this event, it is
still solidly out in the Day 4-5 time range and quite frankly
uncertainty remains uncomfortably high in the details. In a way,
it`s fortunate that we do not generally advertise specific storm
total snow forecasts beyond 72 hours, as model agreement still
leaves something to be desired. IN a nutshell, while primary
models such as the ECMWF/GFS/Canadian all actually exhibit some
consistency in the track of the main mid level and surface low
pressure centers, there are some timing differences (GFS the
fastest) and more importantly, there are some definite differences
in how much precipitation actually falls over the CWA. The last
few GFS runs continue to insist that this will be a pretty minor
event for our CWA, with snow potential only ranging from perhaps a
few inches far north to essentially nothing in KS zones.
Meanwhile, the ECMWF remains more bullish with most of the CWA
primed for at least an "advisory-worthy" event and perhaps pushing
warning criteria especially in the far north. Even for 4-5 days
out, this is a considerably disparity. Both models DO however
agree that areas slightly north of our CWA (especially the
northern 1/3 of Nebraska into far southern SD) stand a good chance
of seeing the highest snow totals Hopefully this snow amount
potential starts coming into better focus over the next 24-36
hours. Despite the low confidence in snow potential, confidence in
increasing that much of Tuesday into at least Wednesday morning
will feature fairly strong northwest winds behind the surging cold
front. The current forecast is more than likely still not high
enough, but at least calls for sustained 20+ MPH speeds and gusts
of 30+ MPH (this could easily trend upward another 5-10 MPH with
time). Obviously with these wind speeds it would not take much
snow to start causing some visibility and at least minor drifting
issues (although it should be a fairly wet/sticky snow). On top of
all of these aforementioned concerns, it still appears that there
could be at least a brief opportunity for a messy wintry mix of
freezing rain and/or sleet during the day Tuesday before enough
cold air arrives to make snow the dominant precip type. This mixed
precip potential has been introduced with this forecast package,
but confidence is admittedly low whether it actually occurs and is
even lower that it will be a "big deal". All this being said, we
are still at least 24 hours away from being close enough in time
to even start advertising specific snowfall potential with any
degree of confidence, and we are probably at least 36 hours away
from any possible winter headlines. Thus for now, will continue to
advertise the potential but also the inherent uncertainty in
products such as the Hazardous Weather Outlook (HWOGID).

With the latest thoughts on next week`s story system established,
will conclude with some fairly brief day-to-day details...

Sunday daytime:
Although breezier than today will be, this looks like another
fairly pleasant and partly cloudy to mostly sunny day with
essentially zero risk of precipitation. We remain well to the
north of the departing, strong low pressure system zipping out of
the Southern Plains into the southeast CONUS. Right away in the
morning, a few model visibility progs hint at some limited
potential for patchy fog, but with northwest breezes on the
increase this looks pretty unlikely and will leave out. During the
heart of the day, northwest winds will average 15-20 MPH with some
gusts to 25+ MPH so breezy for sure. Temp-wise, little change was
made, still aiming for mid 40s most Neb zones and near-50 in KS.

Sunday night:
Still high confidence in a dry forecast as a brief period of
shortwave ridging moves in aloft. Breezes become light and mainly
westerly. Again some models/guidance suggest at least some patchy
fog potential especially far east, but with this being a few
nights away will forego a low-confidence mention. For the first
time in several nights, the entire CWA will drop solidly below
freezing, with lows mainly mid-20s.

Monday-Monday night:
While the vast majority of the CWA will probably stay precip-free
through these 24 hours, at least small chances for light snow may
brush into mainly far northwest zones late Monday night as forcing
increases in advance of a large-scale trough approaching from the
west. During the day, clouds start to increase and breezes turn
southerly in response to pressure falls centered to the west.
Assuming clouds aren`t overly thick, highs are still expected to
reach well into the 40s to low 50s.

Tuesday daytime-Wednesday daytime:
These 36 hours are now the main focus of next week, and the
potential wintry impacts already discussed at length above.
Although there are at least small differences, both the ECMWF/GFS
track the heart of the mid level vort max into the central NE area
during the day Tuesday while an associated strong surface low of
around 990 millibars tracks eastward somewhere near the NE/KS
border. Then Tuesday night, the mid level and surface system
departs eastward across IA/WI but with strong northwest winds
continuing over our area and likely at least light lingering snow.
One change from 24 hours ago is that at least small snow chances
are now advertised into the day Wednesday, but the "main event",
if there is one, should still focus Tuesday afternoon into Tuesday
night. In addition to the various factors already discussed, our
forecasted temps during the day Tuesday may very well prove to be
too warm, meaning that we could be hanging on to rain/snow mix
potential too long.

Thursday-Friday:
Although models hint that perhaps some rogue flurries may be
lurking in or near the CWA at some point during this Day 6-7 time
frame, the official forecast remains a dry one for now as the flow
aloft transitions to fairly moisture-starved and northwesterly. At
the surface, a noticably colder airmass compared to earlier in the
week will be established, with highs mainly only 30s and lows
teens.

&&

.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Sunday morning)
Issued at 553 AM CST Sat Jan 21 2017

I left some 6SM BR in the forecast for the first few hours to
account for the possibility of some patchy fog in the area with
light wind and small dew point depressions. VFR conditions are
forecast with shortwave ridging aloft for today and a weather
system too far south in the southern Plains to affect our weather
for tonight.

&&

.CLIMATE...
Issued at 453 AM CST Sat Jan 21 2017

A few interesting temperature notes regarding Grand Island and
Hastings airports (our two primary long term sites for which we
issue records/statistics for)...

- At both Grand Island and Hastings, the entire two-day stretch of
Jan. 19th-20th remained ABOVE the 32-degree freezing mark (in
fact Hastings set record warm low temperatures of 36 each day).

- Consecutive JANUARY days remaining above freezing are quite
rare! At Grand Island, it had been 20 YEARS since that last happened
(Jan. 2-3, 1997) and at Hastings it had been 15 YEARS (Jan. 8-9,
2002)

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Dense Fog Advisory until 6 AM CST early this morning for NEZ087.

KS...None.
&&

$$

UPDATE...Heinlein
SHORT TERM...Heinlein
LONG TERM...Pfannkuch
AVIATION...Heinlein
CLIMATE...Pfannkuch



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