716
FXUS63 KGID 221026
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
526 AM CDT Sun Sep 22 2024

.KEY MESSAGES...

- While this weekend`s "rain event" will surely end up being a
  disappointing dud for the vast majority of our coverage area
  (CWA) with MOST places unlikely to exceed 0.10-0.20" (instead
  of the widespread 1-3" potential it appeared to carry a few
  days ago!), there already has been one "surprising stripe"
  with embedded 0.25-0.75+" amounts overnight, so this thing
  can`t be totally written off yet for all.

- Once the last rain from this system departs tonight, the vast
  majority of the next 7 days appear dry, although there are
  hints of least spotty rain chances centered on Tuesday and
  perhaps toward next weekend (although the latter is of very
  low confidence).

- A few of our far northern/northwest counties (especially
  Valley/western Dawson) could actually flirt with brief/patchy
  frost potential very late tonight/early Mon AM as temps there
  could drop into the upper 30s, but current thinking it should
  remain JUST warm enough to keep frost at bay.

- Temperature-wise, this next week will feature what most folks
  will probably consider a pretty darn pleasant/comfortable
  stretch of early fall weather, with daily high temps mainly
  70s and overnight lows mainly 40s/50s.

- That being said, medium range models are currently exhibiting
  an unusually large spread (high uncertainty) in both the upper
  air/low level pattern for especially Thurs onward...with at
  least some chance that Thurs-Sat end up being warmer than
  currently forecast.

&&

.DISCUSSION...
Issued at 526 AM CDT Sun Sep 22 2024

-- PRIMARY CHANGES/UNCERTAINTIES/WEAKNESSES WITH THIS 7-DAY
 FORECAST VERSUS THE PREVIOUS ONE ISSUED SAT AFTERNOON:

- Unfortunately, expected cumulative weekend rainfall amounts
  (QPF) have continued to "free fall" after peaking as high as
  1-3" just a few days ago (this forecaster honestly can`t
  remember the last time a larger scale rain event fizzled this
  drastically). It now appears that MOST places will be lucky
  to pick up more than 0.10-0.20" (if hardly a drop in several
  counties especially north of I-80). That being said, as
  mentioned above we will likely continue to see some very
  narrow/localized bands that "overachieve" the dwindling
  expectations and give some lucky folks at least 0.25-0.75".

- Although not a "high impact" uncertainty it appears, by far
  the biggest uncertainty apparent over the next 7 days are
  temperature trends for Thurs-Sat. Will hit on this more below,
  but in short our official forecast falls more in line with the
  cooler ECMWF solution (highs in the 70s), while the GFS
  suggests a more marked warm-up with highs climbing back well
  into the 80s to maybe even around 90. These trends bear
  watching, as this is a pretty notable spread even by Day 5-7
  standards.

- A bit closer in time, one of the possible weaknesses with our
  going official forecast is a lack of at least a low-end rain
  chance in most areas for late Mon night into Tuesday daytime,
  and it`s possible that later forecasts will at least need to
  expand some small chances/PoPs.


-- 7-DAY FORECAST CHRONOLOGICAL DETAILS:

- CURRENT/RECENT WEATHER SCENE AS OF 4 AM:
In the big picture of the mid-upper levels, water vapor
satellite and short term model data clearly reveal a fairly
strong low pressure system centered over CO, with various
smaller pieces of energy streaming out ahead of this main low
and extending over our CWA and points east. Meanwhile at the
surface, the seasonably-strong cold front that passed through
yesterday is now well south of us into OK/TX, with breezy (but
not overly-strong) north winds in place over our CWA (sustained
speeds mainly 10-15 MPH/gusts 15-20+ MPH). While a good chunk of
our CWA (especially KS zones and also several counties north of
I-80) have had a dry/mostly dry night, in contrast many places
within counties especially along the I-80 and Hwy 6 corridors
(along with Polk County north of I-80) have seen the development
of scattered to numerous rain showers...with this generally
west-southeast to east-northeast oriented swath of precip
apparently tied to a zone of concentrated mid level
convergence/saturation (somewhat evident at 700 millibars). As
of this writing, the main "rain winners" overnight have been
within a roughly 10-15 mile band extending roughly from
Holdrege-Kearney-Grand Island-Osceola...with some personal
weather stations in this band (along with Grand Island airport)
reporting at least 0.25-0.75". Overnight low temps are on track
to bottom out somewhere in the 50s most all areas...ranging from
low 50s north to upper 50s southeast.


- TODAY (daylight hours):
Although amounts will not be nearly what was anticipated for
most areas, today still features decent chances for scattered to
numerous showers...particularly for counties south of I-80 and
into our KS zones. In the mid-upper levels, the aforementioned
"parent" upper low currently over CO will gradually slide
eastward to over the heart of our CWA by late afternoon/early
evening, but likely in a somewhat weakening phase at it "shears
out" somewhat (this weakening trend, along with the invasion of
drier air from the north with dewpoints mainly only 40s are the
basic/primary reasons for the overall "rain event" falling
short). Leaning on higher-res shorter term models such as
HRRR/NAMnest, it`s quite clear that the vast majority of
scattered to numerous rain showers today will focus within
counties south of I-80 down into KS...within the main mid level
convergence/lift zone associated with the upper wave. MOST
places will likely receive no more than 0.10-0.20" of rain, BUT
as evidenced by what`s already happened tonight there will
likely be localized/luckier exceptions that could continue to
sneak into at least 0.25-0.75" territory. Unfortunately for most
areas near/especially north of I-80 (except for those limited
places that already got some rain overnight), little to no rain
is anticipated. As for the rain itself, have characterized it as
simply "showers" in the official forecast, as while a very rogue
rumble or two of thunder is not out of the question, convective
instability appears quite meager and unworthy of a formal
thunder mention.

In other departments today, temperature-wise there is ZERO doubt
that this will be coolest day of these next 7, BUT high temps
continue to nudge slightly upward given the expectation of rain
showers to diminish in coverage through the mid-late afternoon
hours, along with possibly some limited/filtered sunshine
breaking through especially in our far northern counties. The
net result is highs aimed mainly low-mid 60s south to more
solidly mid 60s north. North winds will gradually/slowly ease as
the day wears on, but most of the day will generally feature
10-15 MPH with occasional gusts 15-20.


-THIS EVENING-OVERNIGHT (sunset onward):
It will take most of the night to actually get the heart of the
upper level low east of our CWA as it slowly passes overhead.
That being said, mid level saturation/lift will be on a steady
decrease. Although most models suggest it will be an almost
totally dry night (especially post-midnight), especially the
ECMWF hints at some "sneaky" lingering showers (at least
sprinkles if not spotty measurable rain) especially in some of
our eastern counties overnight, and thus have lingered
longer/expanded in area some slight Pops (20% chances) well into
the night.

Really, the biggest question mark overnight involves how
efficiently/quickly clouds clear and thus how chilly temps can
manage to get. While would not be surprised to see clouds linger
a bit stubbornly especially in our southern/eastern zones with
the upper wave still passing overhead, most models are fairly
insistent that especially our northwest half will clear pretty
efficiently post-midnight. This clearing, in the presence of
very light winds thanks to dominant surface high pressure, will
likely set the stage for the coolest night our CWA has seen so
far this late summer/early fall. Currently have lows for most of
the CWA aimed from low-mid 40s northwest to mid-upper 40s
southeast. HOWEVER, especially parts of
Valley/Greeley/Sherman/western Dawson counties could perhaps
drop into the upper 30s (currently have as cold as 37-39). This
puts these areas perilously close to possible frost formation,
but current thinking is that they will remain "safe" by a few
degrees, especially given the expected very limited time
duration of temps under 40. Something to watch though.


- MONDAY-MON NIGHT:
The daytime hours appear very seasonably-pleasant, as skies will
be sunny/mostly sunny as we reside "in between" the
aforementioned departing system and another one dropping in from
the north through the Dakotas. Breezes will start out very
light, but gradually pick up a bit from the south in the
afternoon, albeit only around 10 MPH and gusts mainly under 15
MPH. High temps were raised a decent 3-4 degrees from previous
forecast, as despite the chilly start to the morning afternoon
readings are aimed mainly 71-73.

Monday night, high confidence that most of the night and most of
our area stays dry. However, especially the latest NAM/ECMWF
suggest that we may need to add a chance for light
showers/sprinkles to the late-night hours as the aforementioned
disturbance drops down from the north. Temp-wise, it will not be
quite as chilly as tonight, with lows aimed mainly 46-49.


- TUESDAY-TUES NIGHT:
In suit with the preceding Monday night paragraph, it`s starting
to look like later forecasts very well might need to
increase/expand at least slight rain chances into especially
Tues AM, as the upper wave dropping down from the north appears
to be fairly potent. Amounts would likely be minimal (no more
than a few hundredths), but again potential seemingly
increasing. This wave will also send another weak cold front
across the area, flipping breezes to northerly. That being said,
temps are actually expected to be slightly warmer than
Monday...most of the CWA aimed 74-77. Lows Tues night again
mainly mid-upper 40s.


- WEDNESDAY-WED NIGHT:
High confidence in our going dry forecast here, as the Tuesday
disturbance departs to our southeast/east. Thus another
seasonably-pleasant day with highs mid-upper 70s and lows upper
40s to around 50.


- THURSDAY-SATURDAY:
Honestly, this is where things get unusually uncertain in the
model world. While confidence is reasonably high that most of
our CWA will remain dry most of this time (especially Thurs),
our official forecast features some small rain chances mainly in
our eastern counties Fri-Sat, which is a nod toward the latest
ECMWF solution. In short, the 00Z ECMWF solution shows a quasi-
stationary/cutoff upper low generally centered over MO/AR
throughout this time frame, with our CWA perhaps catching some
showers along its western periphery Fri-Sat. The ECMWF also
supports our going forecast high temps in the mid-upper 70s.
However, in start contrast, the 00Z GFS solution does NOT cut
off an upper low just to our east, but instead moves it well
east and allows widespread ridging to dominate the
Central/Southern Plains. Although not reflected in our currently
forecast, IF this scenario plays out, then Thurs-Sat could
easily trend 10-15 degrees warmer than currently advertised
(more 80s to possibly near-90). So much uncertainty here on the
large-scale pattern here and the ultimate evolution of any
larger scale trough/low over the central/eastern United
States...perhaps also influence by possible tropical development
in the Gulf.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1257 AM CDT Sun Sep 22 2024

For KGRI/KEAR Airports:
- Ceiling/visibility/precipitation:
High confidence in VFR ceiling/visibility throughout, with the
only possible "catch" being the possibility of brief MVFR
visibility IF a steadier rain shower happens to pass through.
Speaking of which, the area will be prone to at least scattered
(mainly light) showers through Sunday afternoon, so have opted
to "blanket" this time frame with a vicinity shower (VCSH)
mention (the probability of thunder is far too low to include).
As for ceiling, the majority of the period will likely feature a
mid-level VFR ceiling mainly in the 7-10K ft. range, with some
scattering/clearing possible late in the period Sunday evening.

- Winds:
The majority of the period will feature a fairly consistent
northerly direction, before a variable direction/light speed
regime sets in Sunday evening. The strongest speeds will focus
between now and 21Z, with sustained 10-15KT/gusts 15-20KT
common.

&&

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

&&

$$

DISCUSSION...Pfannkuch
AVIATION...Pfannkuch