Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 171740
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1240 PM CDT Tue Oct 17 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 1240 PM CDT Tue Oct 17 2017

Potentially Hazards Weather: None.

Aloft: Multiple ob platforms and RAP model inits indicated low
amplitude WNW flow over the CONUS with a modest anticyclonic
curvature over the W. A benign shrtwv trof was over WY and this
trof will cross the CWA tonight with nothing more than sct high/
cirroform clouds. Low amplitude WNW flow will cont tomorrow in
its wake.

Surface: Strong high pres was over the Ern USA with return flow
over the Plns. A strong cool front moved onshore into the Pac NW
this AM. The CWA will remain the warm sector until this front
moves thru tomorrow. Weak high pres will rapidly develop over the
rgn behind this front tomorrow afternoon.

More on the sensible wx details later...


.LONG TERM...(Wednesday daytime through Monday)
Issued at 420 AM CDT Tue Oct 17 2017

General overview of this 6-day period:
Overall, this forecast package is pretty similar to the last one,
albeit with lesser chances/coverage of rain Fri night-Saturday.
For most of this long term time frame though, we continue high
confidence of being dry and remaining seasonably-mild. For sure,
the majority of "excitement" and also inherent uncertainty resides
in that Friday night-Saturday daytime time frame as a potent upper
system/modestly-strong cold front enters/crosses the Central
Plains. For sure we can count on some fairly strong winds
(initially out of the south Fri-Fri night and then out of the
north-northwest Saturday), but it`s still highly uncertain whether
our particular CWA will see much in the way of rain/thunderstorm
activity. If anything, the latest models have trended drier.

The basic mid-upper air pattern through these 6 days:
While yesterdays`s 12Z runs of the primary ECMWF/GFS models
exhibited some noticeable differences mainly late in the longer
term, the latest 00Z solutions are again in pretty remarkable
agreement throughout the entire Day 2-7 range. Starting Wed-Thurs,
our region will reside under an area of broad ridging as the flow
aloft gradually turns southwesterly ahead of the primary upstream
trough just starting to approach the western CONUS. Then between
Friday daytime-Saturday night, the large-scale western trough
gradually moves toward us, amplifying/deepening as its central
axis passes overhead Saturday night. In its wake, Sunday should
feature at least brief shortwave ridging, but at least for now,
both the ECMWF/GFS show another, quick-moving disturbance diving
out of the Northern Plains across mainly IA/MO on Monday, with our
area along its southwestern fringes.

Precipitation/thunderstorm potential:
As already mentioned, the latest model blends that initialize our
long term forecasts have backed off on the likelihood/coverage of
rain chances Friday night-Saturday, and this appears reasonable.
Technically speaking, only a small part of our far
eastern/northern CWA carries any mention for Friday night now, as
even the GFS shows warm-sector convection mainly focusing to our
east and north. Then during the day Saturday, while the speed of
the invading cold front is obviously a critical factor, the latest
consensus is that this front will pass through most, potentially
all of our CWA mainly dry, before a more organized line of
convection (and probably some strong-severe thunderstorms)
blossoms generally along an axis from IA southwestward through
central KS and into the Southern Plains. For now though, we are at
least showing some limited rain chances (PoPs) mainly within the
eastern 1/4 of the CWA, as our domain could still be on the
western/northern edges of active weather, especially if timing
slows as it gets closer. Almost certainly, any rain that does
potentially fall in our area should be vacated south/east by
sunset Saturday.

Temperatures:
Little in the way of noticeable change here, although there
continue to be a few particular periods that probably could trend
warmer (such as Friday night) and cooler (such as Saturday night).
Focusing first on highs, Wednesday-Friday are clearly the warmest
of these 6 days with relatively consistent highs mainly mid-upper
70s. Saturday is then a bit of a tricky day with the cold front
slicing through, and our latest rendition has a modest gradient
from mid 60s northwest to low 70s southeast, but this is very
dependent on frontal timing. Temperature-wise, this does not look
to be a "major" front, however, and highs Sunday-Monday still are
aimed well into the 60s. That being said, if this latest model
depiction of another cold front passing through Monday occurs,
then some downward trending may be needed here. As for low temps,
it will be a bit of roller-coaster. Wednesday night will be
coolish with mainly low 40s, but then persistent southerly flow
and increasing dewpoints/moisture will give us very mild readings
on both Thursday and Friday nights, with at least mid-upper 50s
common, and suspect as it gets closer that it could trend up more
into the low 60s especially in our southeast half. These will
likely be at least near-record warm lows both nights (although the
Saturday morning lows may not survive the entire calendar day to
become official). Behind the cold front, Saturday night will feel
more like fall with mainly upper 30s/low 40s, and this could trend
colder depending on how light winds go around sunrise Sunday. Even
so, not expecting any sub-freezing temps at this point. Sunday
night is then preliminary aimed into the 40s area-wide.

Other weather concerns worth mentioning:
- Strong winds:
Have already touched on this, but Friday and Saturday will almost
surely be the windiest days of the next week. Fully expect that
our official forecast speeds will continue trending upward, as
based on the latest models Friday will probably feature sustained
southerly speeds at least 20-25 MPH/gusts 30+ MPH, with Saturday
then featuring a similar surge of strong north-northwest winds
behind the cold front. Speeds currently aren`t strong enough to
trigger a formal mention in our Hazardous Weather Outlook, but
eventually it may trend upward enough to get there.

- Near-critical fire weather conditions:
Now that we are considering vegetation (fuels) to be dry enough to
support active fire growth through the remainder of the fall, we
only need to consider meteorological factors such as wind/relative
humidity (RH) for fire danger. While no afternoons during the next
week currently look to feature a particularly-concerning combo of
strong wind AND low RH, at least in the nearer-term, we may have
to keep an eye on mainly the northwestern 1/3 of the CWA for some
near-critical conditions Wednesday afternoon. Considered
introducing this to the Hazardous Weather Outlook, but with it
being so marginal have held off for now and will let next few
forecasts take a closer look.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Wednesday)
Issued at 1240 PM CDT Tue Oct 17 2017

Significant Wx: WSHFT from SW-NW in 15Z-18Z timeframe tomorrow.

This Afternoon: VFR with no clds at or below 10K ft. Lgt/vrbl
winds become S around 5 kts. Confidence: High

Tonight: VFR with no clds AOB 10K ft. S winds 5-10 kts.
Confidence: High

Wed thru 18Z: VFR with no clds AOB 10K ft. SW winds 7-15 kts
shifting to NW with passage of weak cool front. Confidence: High

&&

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

$$

SHORT TERM...Kelley
LONG TERM...Pfannkuch
AVIATION...Kelley


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