Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 201703

Area Forecast Discussion
National Weather Service Hastings NE
1203 PM CDT Thu Oct 20 2016

Issued at 650 AM CDT Thu Oct 20 2016

Looks like the fog that reduced visibility to a mile-and-less at
Ord earlier in the night was pretty fleeting, and no other
automated obs have shown much in the way of reduced visibility
since then. Will keep a generic patchy mention going for a few
more hours just in case, but reduced the area a bit to only
include counties west of Highway 281 in Neb.


.SHORT TERM...(Today and tonight)
Issued at 443 AM CDT Thu Oct 20 2016

Like "major" weather concerns through the first 24
hours, but still plenty of minor challenges including in roughly
chronological order: at least localized patchy fog this morning,
the potential for continued limited light shower/sprinkle
activity through the morning hours, and what appears to be
increasing prospects for stubborn cloud cover (mostly lower
stratus) hanging tough well into the afternoon hours across much
of the CWA, with obvious implications for high temps on what was
already expected to be the coolest day of the entire 7-day
forecast. Compared to the previous forecast, increased sky cover
percentages for today was probably the biggest overall change.

As for the current/recent weather situation as of 09z/4AM:
Overall, the evening/overnight hours have panned out largely as
expected 24 hours ago. For one, a couple bands of rain showers did
in fact traverse various portions of the CWA, largely dropping no
more than a few hundredths of an inch at most. However, a slightly
stronger narrow line affected mainly far southeast counties during
the evening (even featuring some limited lightning strikes),
producing slightly higher totals up around 0.20" in localized
areas such as Geneva (per a mesonet station). Since midnight, most
of the CWA has been dry except for some very light
showers/sprinkles mainly skirting the far east, although some
additional shower activity is gradually approaching from the
northwest. At this time, satellite imagery and surface obs
indicate fairly extensive low-mid level cloud cover over most of
the CWA, except for lingering clearing mainly in KS zones which
will probably fill in with more clouds over the next few hours. In
the mid-upper levels, water vapor imagery and model data confirm
that the heart of the gradually-amplifying mid level shortwave
trough is centered directly over the local region as it continues
its trek east-southeast, with pronounced ridging in its wake over
the western CONUS. At the surface, a somewhat loosely-defined cold
front continues sinking southward through the local area, with
high pressure centered to the west-northwest helping to promote
light-but-evident northerly winds of generally 5-10 MPH in most
areas. In spite of the clouds and light breezes, at least some
localized/patchy fog has materialized in the fairly low
temp/dewpoint depression environment. Based on limited airport
obs/webcams, the most noticeable fog has been mainly confined to
the Ord area. However, with short term model solutions such as
the HRRR/RAP showing that this hit-and-miss fog could affect other
portions of mainly the western half of the CWA through mid-
morning, opted to just introduce a generic "patchy fog" mention to
the official forecast. However, would be rather surprised if any
kind of widespread dense fog situation developed given the
aforementioned mitigating factors. Temp-wise, cloud cover trends
are again resulting in some tricky hourly trends, but from here on
out most of the CWA is expected to be in the 40-45 range for
morning lows.

Now looking ahead forecast-wise through roughly sunrise Friday...

Early this morning through this afternoon:
As stated at the top, the overall-biggest issue/change from
previous forecast is the likelihood of considerable, mainly lower
level cloud cover hanging tough over most of the CWA through much
of the day, as strongly suggested by both plan view/time heights
plots from models such as the RAP13/NAM. Very generally speaking,
basic forecast products reflect a "mostly cloudy morning becoming
partly cloudy this afternoon" message, but even this may be a bit
optimistic as some areas may not see much appreciable clearing/sun
until rather late in the afternoon. In the mid-upper levels, the
aforementioned wave slowly departs southeast of the CWA as the
day goes on, with its main vort max reaching the MO/AR border area
by sunset. However, the back/trailing edge of the trough will
linger locally essentially all day. At the surface, broad high
pressure will persist with a gradually-weakening pressure
gradient. As a result, north winds will average 5-15 MPH for the
most part through much of the day, before becoming very light/more
variable toward sunset. This environment with the lingering trough
and the weakening pressure gradient can often foster stubborn
lower cloud cover, so this shouldn`t be a big surprise if it in
fact plays out this way. Not be completely ignored, chances for
isolated light showers/sprinkles remain non-zero through at least
mid morning and possibly a bit longer, especially within the
western half or so of the CWA. Just to play it safe though, have
at least an "isolated sprinkle" potential mentioned all areas this
morning even where there is not an official 20 percent PoP. Last
but not least, high temps today carry at least a little
uncertainty depending on how much afternoon/late day-clearing
manages to occur. Ended up following a blend of various
guidance/model sets, which resulted in roughly a 2-3 degree
decrease from previous forecast, now aiming most of the CWA into
only the 55-59 range.

This evening/tonight:
Barring any unexpected surprises, this still looks like a rather
straightforward/quiet forecast period. As the large-scale trough
continues departing into the eastern CONUS, our local region sees
somewhat pronounced mid-level height rises tonight as broad
ridging builds in from the west. At the surface, the ridge axis
which is centered very near the CWA at sunset will gradually
depart east, allowing light southerly breezes to gradually
overtake the entire area as the night wears on, possibly as strong
as 5-10 MPH by daybreak Friday. Cloud-wise, am counting on any
stubborn daytime stratus to have pretty much broken up/moved out
by sunset, paving the way for a mostly clear evening. However,
some limited mid-high clouds streaming in from the northwest
should bring in a few more clouds late in the night. As for low
temps, if not for the surface high moving east and allowing
southerly breezes/weak low-level warm air advection to kick in, we
could have been looking at a rather cold night. However, because
of these mitigating factors, would expect temps to drop fairly
quickly in the evening but then steady out and perhaps even rise a
couple degrees late in the night. Made little change from previous
forecast lows here, aiming most of the CWA into a fairly uniform
35-39 range. Although these readings could technically support
some patchy frost formation especially in low-lying areas, please
note the following: Because our entire CWA experienced at least
1-2 frost/freeze events earlier in the month, we will no longer be
issuing Frost/Freeze headlines this fall and will no longer be
placing frost in forecast products. However, some of our
neighboring KS offices will continue highlighting frost/freeze
potential for a while longer yet.

.LONG TERM...(Friday daytime through Wednesday)
Issued at 443 AM CDT Thu Oct 20 2016

Overview: Dry weather is expected Friday through Monday with an
upper level ridge across the southern and central plains. A weak
shortwave will undercut the upper ridge Tuesday into Tuesday night
bringing a chance for showers and thunderstorms with the higher
probability of appreciable precipitation once again to the east of
our forecast area. We should then dry back out on Wednesday behind
the departing shortwave. Normal highs are now only in the lower 60s
and we will see above and even much above normal temperatures
throughout the forecast period with highs in the upper 60s and 70s.

Friday through Monday...Warm and dry weather will be the story. The
primary forecast concern will center around the somewhat elevated
fire danger on Saturday as winds increase to around 15 to 20 mph and
RH values drop into the 20 to 25 percent range mainly west of hwy
281. Therefore, will need to keep an eye on the fire weather
forecast for Saturday as it could be close to headline level
conditions. Saturday should be the warmest day of the period with
highs ranging from the lower 70s around York, to the mid and upper
70s along and west of hwy 281.

Tuesday into Tuesday night...The 00Z ECMWF and GFS both favor far
eastern Nebraska and Iowa with the best chance of appreciable
showers and thunderstorms. If the timing of this shortwave remains
similar to what our forecast models are currently saying then we can
expect little if any precipitation across most of our forecast area.
However, if the wave slows down by even 6 hours we could see a
little better chance for measurable rainfall especially across
eastern areas.

Wednesday...The upper ridge will once again be the story with dry
and mild conditions.


.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Friday afternoon)
Issued at 1159 AM CDT Thu Oct 20 2016

Low cloud cover will vary at times the next several hours before
breaking up/departing toward evening, with cigs varying from VFR
to MVFR. Skies clear for a time tonight with high level cloud
cover expected to move in toward morning. Wind will remain light
tonight but will increase from the south Friday in return flow.
Wind gusts of 25kts are possible at times Friday as mixing





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