Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 281346

Area Forecast Discussion
National Weather Service Hastings NE
846 AM CDT Fri Apr 28 2017

Issued at 846 AM CDT Fri Apr 28 2017

A rather substantial short-term fcst update has just published and
will show up on the point-and-click fcsts by the top of the hour.

We received a couple reports of snow falling from ODX-BVN and live
webcams show it. Also have lowered temps for the rest of the day
over S-cntrl Neb...espcly N of I-80 as the consensus of short-term
guidance keeps temps in the 30s there all day under thicker cloud

Attm with the warm ground am not expecting much more than a
coating on grassy surfaces. Any accum should be under and inch.

12Z RAP guidance shows lift in the DGZ (snow growth zone)
diminishing rapidly over the next 3 hrs...and then drying out as
the def zone lifts N. GOES-16 vis imagery shows the Srn edge of
the deepest/coldest cloud tops lifting N...confirming this trend.
So the snow will end by midday.

Isentropic ascent within the dry slot is still resulting in shwrs
between I-80 and the KS state line from remaining instability. But
that instability will wane and shwr activity will decrease.
However...the lift will cont into the drzl should
develop and be rather persistent. It should end from S-N mid-late


.SHORT TERM...(Today and tonight)
Issued at 318 AM CDT Fri Apr 28 2017

Ongoing rainfall and precipitation redevelopment tonight are
the features of the forecast.

Steady rain band is working its way north across the forecast area
early today, mostly as advertised. Couple things stand out as
difference from expectations. One is the speed at which the rain
band is lifting north. Much quicker than anticipated with most of
the steady rain today clear of Kansas by 7 AM. Have pushed the
rain chances along quicker as a result. Secondly, the rain amounts
appear quite a bit less than expected. As of this writing,
Holdrege has 0.44", probably about 1/2 of model advertising,
including the most recent runs of the HRRR and other models. Still
a nice rain, but have lowered expected rain amounts all areas. Not
seeing any cold advection to suggest snow is a big issue today.
Winds will continue to increase from the northeast. Far southern
forecast area may actually have a decent morning with break from
the rain and temperatures reaching the 50s for a time, before they
fall in the afternoon. The general trend in the precipitation area
should be a steady decline in coverage/intensity by this

Tonight, we wait for the upper low to spread precipitation
northeast. The low will be some distance away in northwest New
Mexico by Saturday morning. For that reason, forecast may be too
quick in spreading higher rain chances north. Tried to lay back a
bit and overall expected light precipitation at best tonight with
an increase in coverage across northern Kansas toward dawn. Models
remain persistent in some mix/changeover to snow in western areas
with weak cold advection and surface temperatures in the 30s.
Models also trying to do the same this morning, but that isn`t
happening. Any snow issues tonight are quite minor with no
accumulation and more likely west of Highway 281.

.LONG TERM...(Saturday through Thursday)
Issued at 318 AM CDT Fri Apr 28 2017

Primary forecast concern through the long term lies with rain/snow
chances during the Saturday through Sunday night time frame.

At the start of the period, 12Z Saturday, models are in good
agreement showing sharp southwesterly flow in place aloft, with the
main low pressure system in the 4 corners region. Through the day,
larger scale lift continues to increase as the system continues
moving east, but by 00Z Sun is shows by models to have only moved
into eastern portions of NM. The better chances for precipitation
will remain across south-southeastern portions of the CWA, with some
concern about just how far north precip will get. Not helping
northern areas is the north wind that are expected to be in place,
with the sfc low well south of the CWA and the main front boundary
only as close as far SErn KS. Expecting a breezy/windy day, with
speeds in the 20-25 MPH range not out of the question. As far as
precipitation type goes during the day on Saturday, while the
morning may start out with some RA/SN or just SN in western portions
of the CWA, highs are forecast to climb into the lower 40s, so ptype
is expected to switch over to all RA.

As we get into Saturday night, and moreso into Sunday, models remain
in good agreement showing the upper level low starting to take more
of a northeastward track. By 12Z Sunday the system is located in the
TX panhandle area, and through the daytime hours Sunday we start to
see some slight differences arise between models with timing and
location. By 00Z Mon model location of the upper low ranges from far
northeastern KS to south central KS, but come back into better
agreement by Monday morning over south central IA. The general story
hasn`t changed significantly for our area, with the model track
bringing the better deformation zone/frontogenetical forcing on the
backside of the system right across the CWA on Sunday. The million
dollar question continues to lie with temperatures, mainly sfc
temps. Models have been showing that when the heavier precip is
moving through, 850mb temps have at least at times been below 0C,
albeit not by much, generally 1-3 degrees. These same models have
been showing temps below that, at 925MB and sfc, being above
freezing, with Sunday highs in the upper 30s/near 40. At this point
am taking model temps with more than just a grain of salt, but as it
stands it`d be difficult to get significant accumulations through
the passage of this system Saturday night through Sunday night.
Current forecast totals showing 1-1.5" of wet snow Sat night/Sun
morning, and another 0.5" or so Sun night, with the higher totals
west of HW 281. The northerly winds from Saturday continue on
through Sunday, with speeds expected to be higher, sustained speeds
of 20-30 MPH are forecast to accompany any falling RA/SN. Plenty of
details yet to be ironed out, so folks need to stay updated to the
latest forecasts, there will be adjustments.

Looking ahead to Monday, do have some lingering PoPs through the
first half of the day, with the afternoon dry...but confidence in
that isn`t the highest. As we go through the first half of the work
week Mon-Wed, while the main storm system is moving further away,
another broad upper level trough axis looks to swing through the
Plains, so will have to watch for periodic precipitation chances. At
this point, hard to have any confidence in timing/location.
Expecting high temperatures to rebound back into the lower 60s by

Upper level ridging building in behind the early/mid week trough
axis is looking to keep Thur/Fri dry. Highs currently forecast to
reach back into the upper 60s/near 70 by Friday.


.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Saturday)
Issued at 617 AM CDT Fri Apr 28 2017

Heavier rain band working through KEAR and KGRI now and should be
pulling north soon. Still likely to see scattered showers for a
few hours this morning and some drizzle or light showers this
afternoon. IFR ceilings are expected most of the day even if the
rain stops. Winds are edging their way from the east to the
northeast and will gust over 20kts later today.




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