Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 221055
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
455 AM CST Sun Jan 22 2017

.SHORT TERM...(Today and tonight)
Issued at 454 AM CST Sun Jan 22 2017

The biggest issue with the short term will be wind today. Although
pressure gradient should relax somewhat this afternoon as a low
tracking across the southern Plains moves east, a jet max will
approach area and as mixing ensues by late morning into the
afternoon, we could get some decent northwest gusts of 25 to 30 mph.
With upper level ridging, there will be a significant amount of
subsidence behind the departing trough, so the chance of precip will
be zilch today and tonight. Another mild day is in store, but it
will feel a bit cooler due to the increased wind speed compared to
yesterday. No huge changes, as highs should reach the mid 40s to
around 50 and lows tonight will be in the upper 20s to lower 30s.

.LONG TERM...(Monday daytime through Saturday)
Issued at 454 AM CST Sun Jan 22 2017

General overview of this 6-day period:
It`s this forecaster`s third and final night handling the upcoming
storm system for Tuesday-Wednesday, and unfortunately, will
frankly admit that even with this system now into the Day 3-4
range, our confidence in snowfall potential/totals remains
solidly below-average. If anything, it "seems" to be trending
toward only being a minor event, but at least one often-reliable
model still holds out potential for this to yet turn into a
"bigger deal" (plenty more on this below). Otherwise, apart from
the forecast frustrations of Tuesday-Wednesday, the remainder of
the long term forecast (both before and after Tues-Wed) remains
remarkably quiet and likely precipitation-free. Temperature-wise,
Monday looks to be the last day of solidly above-normal warmth for
the foreseeable future (highs upper 40s/low 50s), with Tuesday
then a tricky "transition day" as a strong cold front blasts
through (more on this below), then followed by several days of
colder-but-not-unusually-cold temps with highs well down into the
30s most places Wed-Fri before perhaps rebounding more so into the
upper 30s to mid 40s by Saturday (day 7). On the low temperature
side of things, after a pretty remarkable stretch of relative
overnight "warmth", we will get back to several nights of dropping
well down into the 20s/teens.

Various general comments regarding the Tuesday-Wednesday storm
system:
It seems like we have been talking about this POTENTIALLY
(key word "potentially") impactful winter system for days now, and
we want to make it abundantly clear that no matter what you might
have heard over the past several days about what this storm might
be capable of, we still have a LONG WAYS to go in nailing down the
specifics. As touched on above, if anything, the current official
forecast (which just barely captures this system given that our
snow accumulation forecasts only go out 72 hours) is leaning
toward this being a fairly minor event with no more than 1-2" of
snow within the CWA, and highest amounts favored north of I-80.
The majority of precipitation is currently expected to fall from
Tuesday afternoon-Wednesday morning but could start a little
sooner and end a little later in some places. Of all primary
models, our official snow forecast mostly closely resembles the
GFS and is also largely in line with the 03z SREF mean and also
national WPC guidance. Also adding a bit of confidence to the
going forecast for a fairly minor event is the last few runs of
the NAM, which keep the vast majority of the CWA at-or-under 1".
Unfortunately, some of our continued uneasiness with this storm
stems from the sometimes- very-reliable ECMWF solution, which also
has some support from the Canadian. Despite seemingly fairly minor
differences in key large scale features, the ECMWF is just flat-
out markedly more robust with raw QPF/snow potential. Taking the
latest 00z ECMWF run literally, it paints at least 1-3" of snow
across the majority of the CWA, with perhaps as much as 6-8" north
of I-80...in other words, a fairly significant snow event. Again,
our official forecast currently leans much more conservative and
considers the ECMWF to be an outlier, but with a few days to go
before this event even starts one never can be too quick to
totally discount outliers. All this being said, we have done our
best to try to capture this above-average uncertainty in products
such as the latest Hazardous Weather Outlook (HWOGID).
Fortunately, confidence remains fairly high in other aspects of
the Tuesday-Wednesday forecast, including the likelihood of fairly
strong northwest winds especially Tuesday afternoon-Wednesday
morning. Although our official forecast wind speeds are likely
still not high enough, there seems to be a good chance of
sustained speeds around 25 MPH/gusts around 35 MPH, which would
obviously make for some legitimate travel impacts if it turns out
that the more aggressive ECMWF is onto something. All of this
being said, the bottom line is this: Although this system seems to
be getting into fairly close range, forecast-wise we probably
still have another 24-36 hours to go before hopefully we can start
toning down our uncertainty wording somewhat and really start
pinning down what`s really going to happen...in the meantime
thanks for your patience.

With the "big picture" thoughts/uncertainties clearly outlined,
will conclude with some fairly brief meteorological details for
those interested...

Monday daytime:
This looks to be the overall-warmest day for at least a week or
so, so get out and enjoy if possible. Aloft, our flow starts
turning southwesterly but with the primary large scale upper
trough still hanging back well to our west there remains pretty
high confidence in this being a dry and partly cloudy day with
highs mainly 47-53. It will be a bit breezy, however, but this
time out of the south with sustained speeds at least 10-15
MPH/gusts 20+ MPH especially central/west.

Monday night:
Odds are reasonably good that the vast majority of the CWA gets
through the night precip-free, but there are some hints that at
least far northern zones could start seeing some light precip late
in the night. For now, will only advertise a slight chance of snow
far north late, but if precip actually does break out, it could
perhaps fall as light sleet (ice pellets) and perhaps even extend
a bit farther south toward I-80. There may also be some patchy fog
development post-midnight as winds lighten and start turning more
northerly/easterly but with with confidence still fairly low in
this scenario have left out for now.

Tuesday daytime-Wednesday daytime:
Obviously these 36 hours remain the "highlight" of the entire
7-day forecast, and the big-picture themes/scenarios have already
been discussed in length above. Meteorologically, primary models
such as the ECMWF/GFS are actually in pretty good agreement on
the track of the mid level vort max, taking it across
central/northern Neb during the day Tuesday before quickly
departing into IA/WI Tuesday night and into the Lower Great Lakes
region Wednesday. However, timing differences remain with the GFS
fastest/ECMWF slower and the Canadian even slower yet. The
associated fairly strong surface low of around 990-995 millibars
is slated to pass somewhere across/near the southern half of our
CWA per the ECMWF/GFS. As discussed previously, despite these
seemingly somewhat minor differences (especially by Day 3-4
standards), the amount of actual precipitation/QPF being generated
by models varies significantly, although all of them depict fairly
strong northwest winds on the backside of the low. Temp-wise, and
adding to the uncertainty, Tuesday looks to feature quite a range
in highs ranging from 30s northwest to near-50 southeast, meaning
that much of the initial precip could start out as rain, a
rain/snow mix or perhaps a brief period of freezing rain/sleet,
although the confidence in seeing the latter has decreased enough
that is is no longer in the official forecast (at least for now).
No matter how much or how little precip falls, the majority of it
should focus Tuesday afternoon-Wednesday morning, with only a
slight chance of snow lingering Wednesday afternoon before all
precip shuts down by sunset.

Thursday-Saturday:
In short, this remains a dry forecast through all 3 days in the
wake of the departing system, as the flow aloft initially turns
northwesterly and eventually more due-northerly as an expansive
ridge builds into the western CONUS. There may be a non-zero risk
for a few rogue flurries, but it`s far too soon to latch onto this
possibility for a formal mention. The main story will be a return
to cooler temps with highs mainly 30s and lows teens/near 20.

&&

.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Sunday night)
Issued at 1159 PM CST Sat Jan 21 2017

Biggest issues include a patch of fog heading south of KGRI. Just
recently the vis was in the IFR range, but has quickly improved.
Expect now that wind has gotten a bit strong from the northwest
that this will not be an issue. Expect wind speed to increase
Saturday afternoon with increased mixing and pressure gradient.

&&

.HYDROLOGY...
Issued at 454 AM CST Sun Jan 22 2017

Although we don`t currently have an abundance of "ground truth"
reports of actual flooding impacts, we continue a Flood Warning
for a stretch of the Platte River from near Grand Island
downstream along the Hamilton-Merrick County line. Over the past
12 hours or so, the official river stage at the Highway 34 bridge
gauge has largely maintained just barely above-to-below the minor
flood stage of 6.5 ft. Although certainly subject to change, the
current forecast from Missouri Basin River Forecast Center (MBRFC)
calls for a slow downward trend to several inches below minor
flood stage by later today into tomorrow. In other words, the
current expectation is that this Flood Warning should only be
warranted for no more than another 24 hours or so (in theory).

&&

.CLIMATE...
Issued at 454 AM CST Sun Jan 22 2017

Here are some notes regarding SEASON-TO-DATE SNOWFALL at Grand
Island airport (our primary long term data site for which we issue
records/statistics for)...

- While this winter has certainly not lacked precipitation
(solidly above normal), somewhat oddly, the vast majority of it
has fallen in the form of rain/freezing rain and NOT snow.

- So far this winter, Grand Island has only measured 3.5" of snow
(9.9" below normal). The last time Grand Island had less snow
through Jan. 22 was 15 years ago in 2002 (2.7"). Although what
happened the remainder of that winter is NOT INDICATIVE of what
will occur the rest of this winter, that winter of 2001-2002
actually ended up with near-normal snowfall of 26.7". In other
words, there is still plenty of time to pile up snow this winter
despite the slow start!

&&

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

$$

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



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