Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 301717
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1217 PM CDT FRI SEP 30 2016

.SHORT TERM...(Today and tonight)
Issued at 415 AM CDT Fri Sep 30 2016

Dry and seasonal weather conditions will continue across our region
during the short term periods with ridging across the Central Plains
in between an upper low pressure system in TN and trough in the
Pacific northwest. Surface high pressure extended from MN southwest
through central Nebraska and Kansas. Have been monitoring
observations early this morning for fog development along the ridge
axis in our eastern zones, where temp/dp spreads are within a degree
or two of each other. The surface ridge axis will shift a little
farther east into eastern Nebraska thru tonight and models advect
some low cloud cover into eastern Nebraska. The brunt of the low
clouds should remain to our east but this will be something to keep
an eye heading into tonight as there could be some fog development
along the surface ridge axis and edge of the stratus near our
eastern counties.

.LONG TERM...(Saturday daytime through Thursday)
Issued at 415 AM CDT Fri Sep 30 2016

General overview of this 6-day period (next two paragraphs):
For those who follow things pretty closely, you will find very
little noticeable change between our latest and previous forecast
packages. In short, this means that predominantly dry weather
prevails through the Saturday-Monday time frame and then again by
next Thursday, while in between, rain/storm chances highlight the
Monday night-Wednesday time frame with the highest chances
focused Tues-Tues night. While at least parts (key word "parts")
of the CWA will probably see some respectable rain totals with
this system (perhaps 1+ inch?), this is far from a "guaranteed
soaker" for all areas and some areas could easily pick up little
to nothing. In other words, don`t get your hopes up too much (if
you want rain) or get overly concerned (if you don`t). As for
severe weather chances, we have noted that SPC has opted to
include our far southwestern zones in KS in a 15 percent severe
probability for Day 5 (Tues/Tues night). While we agree locally
that at least a limited severe threat cannot be ruled out, at
least at this point this does not look like an "obvious"/concerning
severe weather setup for our CWA with progged instability/CAPE
values from both the ECMWF/GFS still looking fairly modest despite
fairly strong forcing in play. As a result, at least for now, we
will continue refraining from any severe weather mention in local
products such as the Hazardous Weather Outlook (HWOGID) and
continue to evaluate as it gets closer.

In the nearer-term, although the official forecast remains "dry"
this weekend (meaning void of 15+ percent mentionable precip
chances/PoPs), please note that it is not necessarily "guaranteed
dry" everywhere especially Saturday evening/night, and would not
be shocked to see at least some rogue sprinkles/light showers
roaming parts of the CWA (more on this below). Temperature-wise,
only very minor generally 1-2 degree tweaks were made versus
previous forecast, and overall things are looking pretty typical
for early October. This means that high temperatures should mainly
average in the 70s Sat-Tues, with Monday still the candidate for
overall-warmest day with parts of the CWA (especially southwest
counties) aimed into the low 80s. Overnight lows Saturday night-
Tuesday night will average a bit milder than lately, mainly in the
50s, with some places possibly struggling to drop below 60 Monday
night. A modest cool-down is then expected behind the departing
system with highs easing back into the upper 60s/near-70 for
Wed- Thurs with lows mainly in the 40s.

With the main points covered above...those interested in
day-to-day details feel free to read on...

Saturday daytime/night:
As mentioned above, despite the official forecast being void of
mentionable rain chances, am not completely comfortable with this
especially for the late afternoon and night hours. In all honesty,
some of our forecasts 24+ hours ago contained small chances for
showers/storms in parts of the CWA Saturday night, but these
chances were just removed with the previous forecast package and
partly because of this was not very excited to immediately "flip
flop" them back in. If nothing else, future shifts may need to
consider adding at least a sprinkle/isolated shower chance back
in, but given this is still 3-4 forecast periods away there is
time yet to do so. So, the main message here is that rain chances
are low during these 24 hours but are not necessarily "zero"
either. in the mid-upper levels, the flow aloft over us will be
from the west-northwest, as we remain in between the stubborn
closed low over the eastern CONUS and the large-scale trough over
the Pacific Northwest. Although not strong by any means, a small-
scale shortwave trough will pass southeastward across our local
area, promoting some modest low-mid level isentropic lift. At the
very least, this lift should promote some enhanced mid level
clouds. Going strictly by model QPF fields, the GFS keeps things
largely dry, the ECMWF shows some shower potential mainly in far
southwest/southern zones and the latest NAM gives much of the CWA
a shot of at least sprinkles and perhaps an isolated shower/weak
thunderstorm. Despite harping on these caveats to our currently-
dry forecast, no matter what, this will "mainly" be a dry 24 hours
for the majority of the CWA. In other departments, considered
adding a generic "patchy fog" mention to far eastern zones right
away around sunrise where winds will be lightest, but coordinated
with short-termer handling Friday night to leave this mention out
for now, especially considering that fog formation has not really
been occurring these past few nights. No matter, the better fog
potential (should it occur) looks to focus slightly east of our
CWA. Later in the day, although not windy by any means, a steady
5-15 MPH breeze (highest in western zones) will prevail. High
temps are aimed low-mid 70s.

Sunday/Sunday night:
Not going to repeat all the same factors described in the previous
paragraph, but per models such as the latest NAM, especially the
daytime morning hours may need watched for some lingering
sprinkles/light shower potential before the modest forcing from
the aforementioned weak disturbance departs our local area. For
now though, the official forecast continues as a dry one, with
high temps climbing a few degrees into the mid-upper 70s.
Compared to Saturday, Sunday looks to feature a touch more
humidity (dewpoints climbing back up into the low-mid 50s) and a
bit more wind, with south-southeast breezes averaging at least
10-15 MPH with some higher gusts. A brief period of ridging aloft
lends pretty high confidence in the going dry forecast for the
night hours.

Monday/Monday night:
While the aforementioned brief ridging should keep the daytime
hours dry, modest 20-30 PoPs for showers/storms arrive Monday
night as the leading edges of forcing associated with a large
trough approaching from the west reaches the Central Plains,
including a steady transition to strengthening south-southwest
flow aloft. Prior to the rain chances, Monday is looking like a
seasonably-warm and breezy day, with highs temps upper 70s/low 80s
and sustained south-southeast winds at least 15-20 MPH with higher
gusts.

Tuesday daytime-Wednesday night:
Although it`s still far out to pinpoint much detail, these 48
hours contain the increasingly well-advertised passage of a large
scale mid-upper trough and its associated surface cold front
through the Central Plains. For being 5-6 days out, the latest
ECMWF/GFS runs are in pretty decent agreement on the large-scale
pattern, as the heart of the 500 millibar low shifts from the WY
area Tuesday to the eastern Dakotas area by daybreak Thursday.
Meanwhile, the main surface front looks to cross our CWA Tuesday
afternoon-night. Not surprisingly, Tues-Tues night contain our
highest PoPs, with widespread 40-50 percentages and even some 60s
in eastern zones for Tuesday night. Would normally not be
comfortable already advertising these "likely" chances this far
out in time, but previous forecast already introduced them so
maintained for now. Very generally speaking, rain chances do look
higher over our eastern counties than our western ones. As already
discussed above, it`s still a bit too early to pinpoint whether
severe storms might be an issue. Although most of the CWA
technically has a slight chance of lingering convection during the
day Wednesday, the latest models (especially GFS) shift the vast
majority of precip potential east of our CWA by this time, so
unless the overall-system slows (which is possible), this could
trend toward being a dry daytime forecast. Confidence is currently
fairly high in the going dry forecast for Wednesday night.

Thursday:
Not much to say at this Day 7 range other than dry and a bit
cooler behind the departing system. Things would have to slow
down/shift pretty dramatically from current projections for this
day to end up with any rain chances.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Saturday afternoon)
Issued at 1215 PM CDT Fri Sep 30 2016

Cirrus has moved into the terminals. At times it may be more
broken than scattered, but should be mainly thin. Winds will turn
more toward the south as the high pressure moves off to the east.

&&

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

$$

SHORT TERM...Fay
LONG TERM...Pfannkuch
AVIATION...JCB


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