Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 011343
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
843 AM CDT SAT OCT 1 2016

.UPDATE...
Issued at 843 AM CDT Sat Oct 1 2016
ESTF: Sent a quick update to drop hourly temps/dwpts/winds as
fcst was running to high.

&&

.SHORT TERM...(Today and tonight)
Issued at 349 AM CDT Sat Oct 1 2016

The short term periods are still looking dry and seasonal in between
low pressure systems to the west in the Pacific Northwest and to the
east in the Ohio Valley region. At the surface, a high pressure ridge
extended from Minnesota south through eastern Nebraska and Kansas.
An area of stratus was working west of the Missouri River and the
low clouds and any fog potential is expected to remain east our
eastern zones this morning, aligning along the ridge axis. High
cloud cover is expected to linger through the first part of the day,
then scatter and increase again heading into tonight. A couple of
observations have reported some mid level clouds and KOGA had a
report of light rain or a sprinkle, but given the drier low levels
and the mid level cloud cover fairly isolated have maintained a dry
forecast the next 24 hours. The airmass does moderate slightly today
and expect afternoon highs to be a degree or two warmer than on
Friday. A couple of short term models try to generate some light
pcpn or a sprinkle tonight in the warm air advection, but confidence
is higher on clouds vs pcpn and plan to keep the dry forecast
attm.

.LONG TERM...(Sunday daytime through Friday)
Issued at 349 AM CDT Sat Oct 1 2016

General overview of this 6-day period (next three paragraphs):
For those of you "following along at home" the past few days, once
again there are no truly major changes in our forecast products
from the previous version, as we continue to advertise dry (but
not necessarily "guaranteed dry") and breezy/windy conditions
Sunday-Monday, followed by some respectable rain/thunderstorm
chances mainly in the Monday night-Tuesday night time frame,
followed by a return to dry and slightly cooler conditions by next
Thursday-Friday to round out the work week. Compared to 24 hours
ago, suppose if anything, confidence in the overall
evolution/timing details of the incoming large-scale trough has
waned a bit. Very generally, primary 00z models such as the
GFS/ECMWF seem to be tracking the heart of the mid level closed
low a bit farther north and departing it more quickly into Canada
in the Wednesday-Thursday time frame. However, as this occurs,
secondary/trailing disturbances in the base of the mean trough
will swing across our local Central Plains region, keeping decent
forcing in play. Probably the biggest uncertainty/impact on our
forecast involves the timing of the associated surface cold front
and how slowly/quickly it passes from west-to-east across our
area. This will have huge implications for not only overall-
rainfall potential and amounts but also whether or not Tuesday
might feature at least a marginal severe storm risk within the
CWA (SPC continues a 15% risk area for a small part of our CWA on
the Day 4 outlook). Although individual deterministic model runs
will undoubtedly continue to fluctuate somewhat over the next few
days, taking these latest runs literally suggests that the faster
frontal timing of the GFS (and also the Canadian) could greatly
limit rain chances within the western half of our CWA especially
Tues-Tues night, while the somewhat slower ECMWF still focuses the
greatest rain/storm potential in our eastern zones but also shows
decent chances over central counties (including Tri Cities) as
well, possibly even lingering well into Wednesday. However,
because our default model blend used to initialize the Day 4-7
time frame is geared more toward the faster GFS solution, the
majority of the CWA now features a dry forecast for Wednesday
(except for small lingering chances in far eastern zones).
Obviously rain chances for Wednesday could really change/increase
in later forecasts if things do in fact trend slower, so this will
need watched closely. So, in summary, if anything, rain chances
(PoPs) have been tweaked downward a bit in the central/western CWA
for the Tues-Tues night time frame, while low-end "likely" 60
percent chances continue at this time only for counties east of
the Highway 281 corridor. As stated here last night, parts of our
CWA (especially east) are likely going to see some decent rain
totals (perhaps 1+ inch) while others (especially western
counties) could really miss out.

Backing up to the nearer-term periods, the single-most impactful
weather element during the Sunday-Monday time frame will probably
be the downright-windy conditions Monday out of the south-
southeast, with sustained speeds averaging 20-30 MPH (highest
west) and gusts 30-40 MPH. This looks to be one of the overall-
windiest days we have experienced in several months. Otherwise,
although the official forecast for Sunday-Monday remains a dry one
at this time (meaning PoPs are less than 15 percent), rain chances
during this time are not truly "zero" either, as various models
suggest that there could be some rogue sprinkles/light showers
here or there, or even some weak isolated thunderstorms
(especially during the day Monday). So, do not be surprised/caught
off guard if some small rain chances end up making their way into
the Sunday/especially Monday time frame as it gets closer, but no
matter what, confidence is high that the majority of the CWA will
remain dry the majority of this time.

Temperature-wise, not looking at anything all that "newsworthy"
by early October standards. Sunday-Monday carry high confidence
as being the overall-warmest days with highs generally mid-70s to
low-80s, followed by a slight cool-down to highs more so upper-60s
to mid-70s the remainder of the week. Overnight lows follow
similarly, with above-average readings in the 50s to near-60 on
Sunday and Monday nights, followed by primarily lows in the 40s
the rest of the week. At least for now (key words "for now"), we
are not officially advertising any readings cold enough to support
frost late in the week. That being said, only a small downward
nudge to forecasted lows could bring mid-30s into play for
counties mainly north and west of the Tri Cities on both Wednesday
and Thursday nights, so these trends will need monitored given
that we are getting into the heart of the "first frost/freeze
season" especially for the northwestern half of the CWA.

With the main points covered in the preceding "general overview",
will finish with the usual attempt at day-to-day details (for any
temperature info see preceding paragraph)...

Sunday/Sunday night:
As earlier stated, the vast majority of the CWA should remain dry
thanks to ridging aloft being the primary feature over the Central
Plains, but would not be surprised to see at least some spotty
sprinkles thanks to fairly subtle warm air/moisture advection in
the low-mid levels. Right away to start off the morning, suppose
some patchy fog could be flirting with our extreme eastern CWA,
but given that most models have largely been over-doing fog
potential the past few nights have coordinated with the short-
termer handling Saturday night to leave any fog mention out for
now. Otherwise, as surface pressure falls get underway across the
region, a modest increase in south-southeast breezes will occur,
with sustained speeds generally 10-16 MPH and gusts to 20+ MPH
especially west.

Monday daytime-night:
As earlier stated, will have to watch the daytime hours for some
spotty shower/thunderstorm activity well ahead of the main
incoming system, but with confidence low and still being a few
days away have left the day dry for now before bringing in modest
storm chances for Monday night to the entire CWA as large-scale
lift kicks in to the southeast of the parent mid level closed low
now expected to be over eastern MT by daybreak Tuesday.
Technically, the SPC Day 3 outlook barely clips our extreme west-
central CWA with a Marginal Risk of severe storms Monday night,
but at this point would expect the vast majority of storms in our
CWA to remain sub-severe with only small hail/gusty wind
potential.

Tuesday daytime-night:
These 24 hours still contain the overall-highest rain chances
(especially within the eastern CWA) as the crux of the upper level
forcing and low level frontal convergence impact the CWA. The
potential exists for at least a marginal severe storm threat and
heavy rainfall threat especially during the afternoon/evening
hours and especially if the ECMWF solution is correct, but there
is still too much uncertainty in the details to say anything more
yet. For now, cannot disagree with SPC keeping a small part of
the CWA in a Day 4 severe risk area (15 percent probability).

Wednesday daytime-night:
While the main surface front should already be through the CWA by
this time and scouring out any appreciable convective instability
with it, the main large-scale trough axis will still be swinging
through the CWA during this time. In theory, and especially per
the GFS, this is mainly a dry 24 hours, but if the slower ECMWF is
onto anything then especially the daytime hours may need rain
chances increased in area/magnitude.

Thursday-Friday:
For being 6-7 days out, the latest GFS/ECMWF are in pretty good
agreement in finally shoving the entire large-scale trough axis
off to our east and bringing in at least a brief period of
shortwave ridging. Confidence is reasonably high in the going dry
forecast, but especially the GFS suggests that a few passing
showers may not be out of the question during the day Thursday as
one last disturbance passes through in the base of the trough.

&&

.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Sunday morning)
Issued at 541 AM CDT Sat Oct 1 2016

VFR conditions are forecast through the taf period. Look for
varying high to mid level cloud cover with winds fairly light from
the southeast on the back side of a surface ridge axis migrating
east toward the Missouri River.


&&

.GID Watches/Warnings/Advisories...
NE...None.
KS...None.
&&

$$

UPDATE...Kelley
SHORT TERM...Fay
LONG TERM...Pfannkuch
AVIATION...Fay



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