Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 131202
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
702 AM CDT Wed Mar 13 2024

...Aviation Update...

.KEY MESSAGES...

- Although likely impacting only a fairly limited portion of
  primarily the southern 1/3 of our coverage area (CWA),
  confidence is increasing that we will see our first strong to
  marginally severe storms of 2024, especially between 7 PM and
  midnight (large hail likely the primary threat).

- North of the main severe storm threat area, broader areas of
  rain/mainly weak storms are probable through the night and
  into the day Thursday, bringing beneficial but likely highly
  variable rainfall (if anything the probability of receiving at
  least 0.50" has trended down a bit for most places).

- Although we still probably cannot completely rule out the
  possibility of a few snowflakes occurring IF precipitation is
  able to linger into Friday morning, it is becoming
  increasingly-clear that this system will not offer any
  "surprise" measurable snows like we had last week (by far the
  main snow threat this time will remain well west into CO/WY).

- Temperature-wise: Our 7-day forecast is "bookended" by the two
  warmest days being right away today and then Tuesday (highs
  well into the 60s). Meanwhile, the five days in between
  (Thurs-Mon) will average cooler (mainly 50s), with some 40s
  likely especially Sunday/maybe Monday behind a reinforcing
  cold front.

&&

.DISCUSSION...
Issued at 510 AM CDT Wed Mar 13 2024

-- PRIMARY CHANGES TO THIS 7-DAY FORECAST PACKAGE VERSUS THE
 PREVIOUS ONE (issued Tues afternoon):

1) Although some spotty lighter showers/passing sprinkles are
certainly possible today (pre 7PM), chances (PoPs) for
measurable rainfall were lowered significantly across much of
the area, with higher chances not arriving until this evening
(post 7PM).

2) Not surprisingly, some of the greatest temperature
uncertainty resides out in the Day 6 range (Monday), as although
our high temp forecast trended up 2-4 degrees (now mainly upper
40s-low 50s), especially the latest ECMWF (and its ensemble
data) suggests it could end up being roughly 10 degrees warmer
than this (all depends how fast colder air this weekend
dislodges).


-- SOME "BIG PICTURE" AND LONGER-TERM FORECAST COMMENTS
 (including all further discussion of the Friday night-Tuesday
 periods):

- Overall, the latest ECMWF/GFS solutions are in pretty
  reasonable agreement regarding the large scale upper air and
  surface patterns/trends through the next week. Starting off,
  our more active weather pattern especially tonight-Thursday
  will be driven by the arrival of low amplitude disturbances
  ejecting out ahead of a larger scale upper low that will
  eventually dig into and cut itself off over the Desert
  Southwest Fri-Sat. By then, our main weather influence will
  transition to north-northwesterly flow aloft, as a trough
  dives south-southeast out of Canada and across the Great
  Lakes/Midwest this weekend, tossing a reinforcing cold front
  southward through our area. Finally, early next week this
  trough will gradually depart eastward, allowing our flow aloft
  to turn more west-east (zonal) and allowing milder air to
  move back in at the surface.

- Renewed fire weather concerns mainly Sunday onward:
Although not looking overly-concerning at this point, at least
near-critical fire weather conditions look to return especially
Sunday onward, initially driven by blustery north winds and
very dry air Sunday (although cooler temperatures should help
mitigate the threat somewhat) and then by breezy winds/warming
temps Mon-Tues. With these concerns still several days out, have
opted against a formal Hazardous Weather Outlook (HWOGID)
inclusion at this time...just something to watch going forward.


-- SHORTER TERM FORECAST DETAILS FOCUSED SOLELY ON THESE NEXT 60
 HOURS (through Friday daytime):

- CURRENT/RECENT WEATHER SCENE AS OF 4 AM:
As was fully expected, it`s been a dry and tranquil night across
our CWA, despite the renewed invasion of plentiful mid/high
level clouds (following quite a bit of sunshine yesterday
afternoon). In the mid-upper levels, water vapor satellite and
short term model data reveal a series of relatively low
amplitude disturbances approaching us from the west-southwest,
ejecting out ahead of a larger-scale low digging southward
through the Northern Rockies/Intermountain West. At the surface,
broad high pressure reigns over the Central Plains, promoting
very light/variable breezes over our CWA (most areas calm to 6
MPH). Obviously if not for the plentiful high clouds we`d likely
see temps drop a good 5-10 degrees farther this morning, but
overnight lows appear on track to bottom out no colder than
37-41 most places.

- TODAY/DAYTIME (through around 7 PM):
As hit on above, the biggest change to the daytime forecast has
been a reduction in measurable rain chances (PoPs). In the mid-
upper levels, increasing lift from the incoming upper waves will
continue to promote widespread mid-upper clouds (skies mostly
cloudy to cloudy today). At least for now, have kept out any
official mention of precipitation before Noon, although elevated
radar returns to the west suggest a few rogue sprinkles probably
cannot be ruled out. Winds this morning will also remain very
light (mainly under 10 MPH), as direction gradually trends
easterly. This afternoon, although PoPs were again lowered, at
least painted a basic "slight chance of sprinkles" all areas,
while acknowledging slight chances (20%) for a few passing light
showers mainly north/west of the Tri Cities, while also
introducing low (20-30%) chances for thunderstorms in our KS
zones between 4-7 PM. That being said, much better chances for
storms should hold off until slightly beyond this time frame
(see below). Winds this afternoon will gradually pick up out of
the east-northeast in response to low pressure deepening over
southwest/south central KS (sustained speeds by late afternoon
at least 10-15 MPH/gusts 15-25 MPH). The high temp forecast is
slightly tricky, as it`s possible that plentiful clouds could
hold things down a bit more than expected, but for now kept
things very similar to previous forecast, with most areas aimed
64-69, and any low 70s most favored in far southeast zones
toward Hebron/Beloit.

- THIS EVENING-OVERNIGHT (after 7 PM...strong to severe storms):
This time frame is clearly the "highlight" of the entire 7-day
forecast at this time, as it`s looking increasingly probable
that our first strong to severe storms of the year will unfold.
Leaning heavily on higher-res models such as RAP/HRRR/NAMNest,
the general expectation is for a west-to-east corridor of
vigorous, likely slightly-elevated convection to blossom mainly
between 7-10 PM within counties along and south of the KS
border. The million dollar question continues to be: just how
effective will northward return of higher dewpoints/moisture and
resultant instability be by this time? Even in our far south-
southeast zones, we are only expecting dewpoints to reach the
upper 40s/perhaps 50 by early evening, as the primary surface
moisture axis should remain BARELY south-through-east of our
southern zones, focusing the more robust low-level/near-surface
based instability/CAPE more so into northeast/east-central KS.
For one thing, this should in theory render our tornado threat
quite low (albeit non-zero as acknowledged by SPC 2% tornado
probs mainly in our eastern KS counties). Of greater confidence
is that slightly elevated instability mainly in the 850-700
millibar layer will be released early this evening, with the RAP
suggestion of 1000-1500 J/kg most-unstable CAPE in the presence
of at least 40KT of deep-layer shear strongly supporting the
development of at least a few elevated supercells capable of
producing mainly large hail (at least ping pong ball size
possible), and perhaps spotty damaging winds. Again, this would
mainly be within counties along/south of the KS border.

With time (especially after roughly 10 PM), increasing coverage
of a broader zone of showers/weaker storms (but some with at
least small hail potential) will likely expand well north of the
state line into much more of our Nebraska zones, generally tied
to the elevated front noted up around 700 millibars. While the
primary severe storm threat in our southern zones should largely
weaken/depart eastward by midnight, potential for at least
small hail could linger well into Thursday morning along this
elevated frontal zone. As for actual evening-overnight rainfall
amounts, higher-res models are predictably all over the place.
While many places will likely receive at least meager amounts of
0.10-0.25" inch, a relatively narrow swath centered mainly 25
miles either side of a line centered from around Phillipsburg-
Nelson-Geneva appears most favored to pick up the greatest
concentration of 0.50-1.00" amounts (and localized higher
possible under the strongest storms). Although one can never
rule out spotty/isolated flooding especially early in the season
when vegetation is still largely inactive, recent dry
conditions have our flooding concern level fairly low with this
setup. In other departments this evening-overnight, our winds
will pick up another notch out as they turn more northerly in
response to the surface low tracking into southeast/eastern KS,
with overnight gusts commonly 20-30+ MPH. Widespread clouds/rain
and these strong winds will hold up overnight lows well into
the 40s most all areas.

- THURSDAY DAYTIME:
For only being 24-36 hours out, models still leave something to
be desired regarding the coverage/likelihood of continued
measurable rain showers during the day. That being said,
especially the NAM and to a bit lesser degree HRRR continue to
support at least scattered, chilly rain especially within our
Nebraska zones, while the GFS really leans toward a largely dry
day. As a result of this uncertainty, PoPs were tempered a bit
but still well into the 40-60% range. What is for sure is that
it will be a cool, blustery and cloudy/mostly cloudy day. High
temps were kept similar (most areas upper 40s-low 50s, but
perhaps upper 50s far southeast). North winds will be sustained
around 25 MPH/gusting 25-35+ MPH, adding to the chillier feel.
Although confidence is not very high that we will see continued
non-severe/weak storms into this period, did linger a slight
chance of thunder through mid-day mainly in counties along/east
of Highway 281 for now.

- THURSDAY EVENING-OVERNIGHT:
Most models (except for mainly the NAM) shut down
lingering/light rain showers pretty quickly Thursday evening as
lift diminishes and weak ridging aloft starts nosing in, as we
reside in between energy departing to the east, and become
increasingly-removed from the larger upper low by now over the
Desert Southwest. At least for now, we have no official PoPs
beyond midnight, but IF the NAM ends up being onto something
later shifts may need to linger low PoPs into the post-midnight
hours, including the possibility for some flurries or even a
LIGHT dusting of snow especially far west before precip ends (a
very low probability at this time). Otherwise, breezy north
winds will continue into the night but slowly diminish, with
gusts mainly down into the 15-25 MPH range by sunrise Friday.
Low temps a good 10 degrees colder than Wed night, with most
areas well down into the low-mid 30s.

- FRIDAY DAYTIME:
Although the aforementioned NAM suggests pesky light precip
could hang on even into the first part of the day, our forecast
follows the ECMWF/GFS consensus of a dry day with sunshine
making a return. North winds diminish with time (even sustained
speeds easing under 10 MPH by mid-late afternoon). High temps
again very similar to previous...most areas aimed 52-56.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 701 AM CDT Wed Mar 13 2024

- General overview for KGRI/KEAR:
High confidence in VFR ceiling/visibility through at least the
first 15-18 hours of the period, and high confidence in
precipitation-free conditions (other than perhaps a few
sprinkles) through at least 02Z. However, the latter hours of
the period will bring increasing chances for showers/thunderstorms
(likely non-severe) and quite possibly MVFR ceiling. Winds will
start out very light this morning, but will gradually increase
out of the east-northeast this afternoon (gusts 20+KT by late
afternoon) and further increase out of the north this evening-
overnight (gusts up to around 25KT).

- Ceiling/precipitation trends:
Although spotty sprinkles/isolated light rain showers cannot be
ruled out during the first 6-12 hours, by far the main chance
for heavier showers/non-severe thunderstorms arrives after 02Z,
with at least spotty activity remaining possible through the end
of the period. Because these chances for convection are still
beyond the first 12 hours, and because there are still some
question remarks regarding likelihood/coverage at KGRI/KEAR
(much greater chances/coverage will likely focus 25+ miles
south), have only gone with a generic "vicinity thunderstorm"
(VCTS) for now.

As for ceiling/visibility trends, although any heavier
convection could create brief sub-VFR conditions already this
evening, better chances for a more persistent MVFR ceiling
should hold off until at least 06Z. Confidence is only medium
that ceiling will actually go prevailing MVFR as models/guidance
are a mixed bag, but have opted to lean on the pessimistic side
and introduce MVFR starting 06Z

- Winds:
By far the lightest winds of the period will be right away these
first 6 hours (mainly at-or-below 6KT/variable directions). This
afternoon, winds will become established out of the east
northeast and increase with sustained speeds by late
afternoon/early evening generally around 15KT/gusts 20-25KT.
Later this evening-overnight, direction will turn more northerly
and speeds will remain sustained around 15+KT/gusts 20-25KT.

&&

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

&&

$$

DISCUSSION...Pfannkuch
AVIATION...Pfannkuch


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