Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 080950

Area Forecast Discussion
National Weather Service Hastings NE
350 AM CST Fri Dec 8 2017

.SHORT TERM...(Today and tonight)
Issued at 350 AM CST Fri Dec 8 2017

The two main stories/challenges of these next 24 hours
are...1) Although actual high temps will be roughly 10 degrees
warmer than yesterday, the return of breezy north-northwest winds
combined with overall less sun will probably make it feel less
comfortable to many...2) Just how stubborn/prominent will cloud
cover be today (especially in our east half), and what impact will
that have on high temps? It`s worth noting that highs were nudged
down generally 2-3 degrees from the previous forecast most areas.
Precip-wise, certainly not looking at anything measurable, but
did linger a generic "slight chance of flurries" into the first
part of the morning for mainly our southeast half.

Looking at the current/recent weather scene as of 09Z/3AM:
The night playing out pretty as expected. While radar depicts
quite a few mid-level returns, ceilings largely at-or-above 7
thousand ft. and a lack of any flurries being reported by
automated stations strongly suggests that the majority of these
radar returns are "scarier" than they look. It`s been a somewhat
interesting night most places bottomed out pre-
midnight and in some cases have risen 10-15 degrees since then,
due to a combo of increasing clouds and the passage of a weak
trough axis/warm front. Officially, overnight lows will go in the
books mainly 16-23 degrees, but around sunrise most spots should
check in a few degrees either side of 30. In the big picture of
the mid-upper levels, water vapor satellite and short term model
data depict sharp northerly flow over the Central Plains, with our
region well east of an expansive/high amplitude ridge dominating
the West Coast, and north/west of a trough extending from the
south central CONUS northeastward into eastern Canada (even snow
overnight in Deep South TX!). With our area positioned within the
exit region of a strong upper jet and with weak mid level
disturbances passing through, it`s not surprising we are seeing
the possible very light flurry activity here or there as suggested
by radar. Getting back to the surface, the aforementioned weak
trough/warm front basically bisects our coverage area (CWA) at
this point, with its leading edge marked by more of a
northwesterly versus southwesterly wind direction, although winds
speeds are pretty much around 10 MPH or less area-wide.

Now looking ahead forecast-wise through today/tonight...

Have already outlined the main themes/forecast issues in the
opener above. In the mid-upper levels, we remain in sharp
northerly flow, but with the slightest hint of height rises as the
main upper jet core slights slightly slowly eastward. Right off
the bat this morning, have opted to continue a low-confidence
"slight chance of flurries" for a few hours for mainly our
southeast half, just in case a few rogue flakes make it to the
surface. However, a rapid southward exit of mid-level
clouds/saturation should pretty much end any chance of this by
8-9AM at the latest. However, as the mid level clouds depart,
model relative humidity and time height progs are fairly insistent
on driving a batch of lower stratus clouds southward into our
area, some of which are already evident to the north over SD. Am
not yet sold on how expansive/widespread these lower clouds might
be, but have opted to trend this latest forecast package toward a
more pessimistic theme, with increased cloud cover (especially
this AM). Assuming these low clouds do materialize, they should
gradually exit/scatter out from west-to- east, meaning that our
western half stands a better chance of more sun today than our
east, but even the west may see another modest increase in mainly
high level clouds by mid-late afternoon, so "pristine" sun may be
hard to come by. So, all this being said, expect a generally
mostly cloudy day east and a generally partly cloudy day west, but
the dividing line between these basic regimes is a bit tough to
confidently grasp at this point. Compared to yesterday, probably
the most obvious difference to many will be increased winds, as
once daytime mixing kicks in by mid-morning expect several hours
of sustained north-northwest speeds at least 15-20 MPH/gusts 25-30
MPH before diurnally easing late afternoon. Last but certainly not
least, temperatures: Given the expectations of more cloud cover,
have toned back highs roughly 2-3 degrees from previous forecast,
aiming for a range from mid-upper 30s northeast to low- mid 40s
southwest. Personally, would not be disappointed if this forecast
ends up erring a bit too cloudy/cool, but would rather have folks
be pleasantly surprised if it ends up sunnier/slightly warmer than
vice versa.

This evening/tonight:
In the mid-upper levels, the sharp northerly flow continues, but
with subtle west-to-east height rises persisting as the main upper
jet core slides east. This, along with the fact that the primary
reinforcing disturbance riding down the backside of the large
eastern trough will focus well to our east down the MS River
Valley of eastern IA/IL etc., should keep our precip chance pretty
much zero with even rogue flurries very doubtful. As a result, the
official forecast remains precip-free. At the surface, while
breezy daytime winds slacken quite a bit a few hours either side
of sunset, by mid-late evening a modest uptick will again occur in
response to the aforementioned wave passing to our east, with
sustained northwest speeds averaging at least 10-15 MPH (with
slightly higher gusts) through most of the night. Cloud-wise,
expect the night to average between mostly clear-partly cloudy as
a whole, although the latest NAM tries suggesting that some lower
stratus could sneak back into our northeast late in the night
behind a weak back-door cold front. Even if it mostly clear does
prevail, the steady breezes will obviously preclude ideal
radiational cooling. Considering raising low temps a bit based on
this, but in the end decided to make almost no change to previous
forecast, aiming most areas into a fairly uniform 24-27 range.

.LONG TERM...(Saturday daytime through Thursday)
Issued at 350 AM CST Fri Dec 8 2017

Models are in good agreement at the start of the period Saturday
morning, showing well amplified northwesterly flow in place across
the Plains. Set up between ridging extending north along the West
Coast and troughing digging through the Great Lakes/Midwest, models
showing little change in this pattern through the upcoming weekend,
keeping the forecast dry. At the surface, not expecting much change
through much of Saturday, with winds remaining northwesterly,
topping out around 15 MPH. Late in the day, and more into the
evening/overnight hours, a frontal boundary swinging through the
region (associated with a sfc low moving through southern Canada)
will bring a more westerly component to the winds, with WNW winds
expected during the day Sunday. Winds on Sunday have the potential
to be a bit more breezy/gusts, as models show a corridor of stronger
winds aloft moving into the area. At this point, models suggest any
stronger winds would mainly be through midday, with speeds tapering
off mid-late afternoon. Warming temps still on track through the
weekend, with models showing increasing temps aloft building in from
the west (850mb temps are near 10C Sunday), aided by the downsloping
component to the winds. Sat highs are currently forecast to range
from the upper 30s in the far northeast to near 50 in the southwest.
Sunday still on tap to be the warmest day of the entire forecast
period, with highs in the mid 50s to lower 60s. Will see how models
trend, some guidance suggest it could be even a couple degrees

Something that will need to be monitored for Sunday is fire wx.
Current forecast highs combined with dewpoints in the mid
teens/lower 20s (some models are even lower than that) are resulting
in RH values falling into the mid teen-mid 20% range. Debated
putting a mention of near-critical conditions in the HWO, but with
winds currently forecast to be diminishing through the afternoon,
the strongest winds aren`t matching up with the lowest RH values. So
will keep the mention out of the HWO for now, but will be something
for upcoming shifts to watch.

A cold front swinging through the region will bring cooler
conditions as we get into the early-mid work week. Upper level flow
remains northwesterly, and a lack of notable systems keeps the
forecast dry. Models are in good agreement showing an upper level
shortwave disturbance sliding southeast out of central Canada,
through MN on its way to the Great Lakes/Midwest. The main push of
the front looks to come during the day on Monday, with winds turning
more NWrly by midday and the cooler airmass building in behind. It
doesn`t look to be a drastic change in temperatures, with Monday`s
highs in the mid 40s to mid 50s, but the windy conditions return,
with NW winds of 20-25 MPH. Not expecting any notable swings in
temps through Thursday, with highs generally in the 40s/lower 50s.


.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Saturday)
Issued at 1228 AM CST Fri Dec 8 2017

General overview:
Confidence is high in VFR visibility and precipitation-free
conditions through the period (except for the slightest chance of
some rogue flurries these first 6 hours) and confidence is high in
VFR ceiling the majority of the period, with the main exception
being MVFR focused during a 5-7 hour period during the day.
Sustained surface winds will average near-to-below 12kt the
majority of the time, except for higher speeds mainly focused
15-23Z. There could also be some marginal low level wind shear
(LLWS) during the final few of the period Friday evening. Read on
for more element-specific detail...

The biggest questions are how low in the MVFR range does a
ceiling get during the daytime hours and for how long. For now
have gone a touch lower and longer duration at KGRI (BKN020 from
15-22Z) compared to KEAR (BKN025 from 15-20Z), but this is
certainly subject to some adjustment.

Winds (including LLWS):
Surface winds will gradually swing from southwesterly to
northwesterly early this morning, and will then peak in speed from
15-23Z from the north-northwest with sustained speeds generally
15-20kt/gusts up to around 25kt. A brief decrease will occur
around sunset before picking up again slightly in the evening. As
for LLWS, there could be some very marginal values during these
first 6-9 hours, but have deemed this unworthy of a formal
inclusion. A more legitimate period of LLWS looks to begin late in
the period around 02Z, as winds within roughly the lowest 1,500
ft. increase to 40-45kt, setting up roughly 30kt of shear
magnitude between the surface and this level.




SHORT TERM...Pfannkuch
AVIATION...Pfannkuch is the U.S. government's official web portal to all federal, state and local government web resources and services.