Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 231237
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
637 AM CST Mon Jan 23 2017

.UPDATE...
Issued at 635 AM CST Mon Jan 23 2017

Updated the forecast this morning to include patchy dense fog this
morning in roughly our northeastern third of the CWA as Aurora
has dropped to 1/4SM and York is at 1/2SM.

&&

.SHORT TERM...(Today and tonight)
Issued at 359 AM CST Mon Jan 23 2017

Quiet conditions reign across the region early this morning. Upper
air and satellite data showing shortwave upper level ridging
extending through the Plains, set up between areas of low pressure
spinning over the southeastern CONUS and just off the Pac NW
coast. Skies are currently partly cloudy across much of the CWA,
thanks to upper level cirrus streaming in from the west, but a
large area of lower level stratus continues to inch in from the
north. At this time, it`s only into the far north-northeast corner
of the CWA, but models show it sliding further south over at least
the next few hours. At the surface, winds are light/variable
across the CWA, thanks to a high pressure ridge axis extending all
the way through the Plains. Short term/hi res models have been
insistent with the potential for some fog development mainly along
the edge of the stratus this morning. Had inserted a mention of
fog in the forecast late last evening for the TAF, and will keep
the mention going for now. At this point, there are some area obs
with visibilities in the 1-4 mi range. Not a lot of confidence in
how visibility will evolve, as some of the models suggest there
should be a solid swatch of dense fog right now, and that`s not
quite the case. Will be watching closely in the coming hours,
models favor the northeastern third or so of the CWA to see fog.
Temps across the CWA at 3 am range from the lower 20s near ODX to
the upper 20s in parts of NC KS.

Looking to the daytime hours today and into at least early this
evening, the forecast remains dry. Models are in good agreement
showing that upper level shortwave ridging remaining a player
across the region. Zonal flow through the day turns more
southwesterly this evening with the ridging sliding east of the
CWA this evening, as that upper level energy along the west coast
moves inland. Models in pretty good agreement showing the low
currently off the Pac NW coast filling with time, and a second low
developing in the ID/WY/UT border area later this evening. At the
surface, whatever fog does develop this morning would dissipate
mid-late morning, as southerly winds pick up in response to a
deepening surface low over northeastern CO. Confidence in cloud
cover through the day isn`t the highest, mainly with the evolution
of that lower level stratus /how far south does it get & when does
it let up/. Have at least partly cloudy skies across the CWA
today, with higher cloud cover longer into the day across the
north and eastern portions. Expecting another day with above
normal temps, with forecast highs ranging from the mid 40s to
lower 50s.

Later tonight, in the 06-12Z Tues time frame, precipitation
chances will start to work their way back into the CWA. Lift is
on the increase, but the better chances will be after 12Z Tues/the
end of this forecast period. Precipitation type is a little
uncertain, models show the potential for a warm nose aloft (just
above freezing) in the area, but most cool it back off below
freezing when more precip develops/moves in. Had inherited a
SN/Sleet mention across areas along/north of I-80, and decided to
also throw a mention of -FZDZ in there too. Possible for a few
spots along the southern fringe of the precip to be barely warm
enough to stay liquid, but confidence in that is not high at all.
At this point, precip prior to 12Z Tues looks to be fairly light.

.LONG TERM...(Tuesday through Sunday)
Issued at 502 AM CST Mon Jan 23 2017

The biggest challenge of this forecast will be determining the
chance of precipitation on Tuesday/Tuesday night and what
precipitation Type we will get during the day on Tuesday.

We kick off Tuesday with a new area of low pressure spilling into
the central Plains, within a larger synoptic trough.

I`m concerned about freezing drizzle potential on Tuesday morning as
a persistent dry layer in mid-levels along with warmer air riding
over cooler surface air as the low approaches. The NAM soundings are
of most concern with this.

There continues to be a wide range of solutions among numerical
models for this next system. The ARW/NMM WRF solutions are paltry,
but the ECMWF and Canadian put a healthy amount of snow over the
middle of the CWA. The NAM advertises the possibility of either a
frontogenetic band of snow developing over the CWA and/or a piece of
energy breaking off from the main low Tuesday afternoon. For now,
the NAM advertises this QPF in our central/southern CWA. This band
continues to shift positions with the NAM, but the NAM has been
consistent with producing this feature nonetheless. So, there could
be a narrow band of snow develop somewhere within our CWA borders,
but we`ll need to wait until we almost see the "white`s of its eyes"
before we could better handle POPs with this smaller-scale feature,
if it pans out at all.

Most models forecast the 700 mb low to track east across the middle
of Nebraska. This is not favorable for much snow or precip in
general, so our best chance of measurable snowfall/precip would be
a smaller scale phenomenon. POPs are trending lower, in general, as
well as snow amounts. For now, it appears that the tri-cities should
not see more than half an inch, but I have to add the caveat of the
longshot potential for a smaller scale feature to dump some
considerable snow amounts over us.

The forecast looks rather complicated with different precip types,
but this is more of a function of uncertainty rather than our
thinking that all of these precip types could occur together. Sleet
is quite shaky in the forecast, but max Tw/T aloft suggests that
this is a possibility for a short time, before the ambient
environment cools sufficiently for all snow. A lot of this hinges on
surface temperatures, which will bottom out very close to freezing
for a good chunk of the CWA, furthering the uncertainty. With the
general consensus of a more northern track of the low, POPs have
been lowered to reflect this trend.

It appears we dry out for the rest of the forecast. However, the
upper ridge does not seem that anxious to build east, and there
could be a small piece of energy that heads down the pike within
northwest flow, so the dry forecast is not exactly solid. However,
there does not appear to be any major cold outbreak, with close to
normal temperatures expected, and possibly a bit above normal toward
the end of the extended forecast.

&&

.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Tuesday morning)
Issued at 535 AM CST Mon Jan 23 2017

The very start and the end of the TAF period are the main forecast
concerns. This morning, a large area of low level stratus
continues to inch south, and may impact the KGRI terminal in the
upcoming few hours. Do have 1SM and sub-1000ft cigs in a tempo
group. Models are in general agreement keeping it out of KEAR, so
did the same, but will be watching obs closely. VFR conditions are
then expected through this afternoon and into tonight, but
conditions look to deteriorate as we get closer to the end of this
period. An upper level disturbance will bring increasing precip
chances and lowering ceilings. Held off on a precip mention for
now, but do have a 1000ft deck forecast, which will likely end up
being lower.


&&

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

$$

UPDATE...Heinlein
SHORT TERM...ADP
LONG TERM...Heinlein
AVIATION...ADP


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