762
FXUS63 KGID 172131
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
431 PM CDT Tue Sep 17 2024

.KEY MESSAGES...

- Chances for showers/storms spread across the entire forecast
  area tonight (60-70 percent). Potential for some strong to
  marginally severe storms remains in place late this evening
  into the early overnight hours...mainly for areas along/west
  of Highway 183. Wind gusts near 60 MPH would be the main
  threat.

- After a dry Thursday, precipitation chance ramp back up for
  Friday on through early next week. At this time, the best
  overall chances look to be Friday night through Sunday night,
  with area-wide 50-60 percent chances at various points thorugh
  this period. Potential is there for a decent chunk of the area
  to pick up at least one inch of rain...however there are still
  several days to see how models trend and iron out the details.

- High temperatures in the 80s remain through Friday, with a
  downward trend following. The overall-coolest day is currently
  Sunday, as the main upper low passes through...with 60s-70s
  for Saturday, Monday, and Tuesday.

&&

.DISCUSSION...
Issued at 425 PM CDT Tue Sep 17 2024

Currently through tonight...

Fairly uniform conditions remain in place across the forecast
area this afternoon, with gusty southerly winds and mostly
clear skies. Looking aloft, upper air and satellite data show
southwesterly flow in place across the region, driven primarily
by a low pressure system working its way east near the UT/ID
border. At the surface, the pressure gradient across the area
has tightened as low pressure deepens along the central High
Plains...with south-southeasterly winds gusting anywhere from
25-35 MPH (the higher gusts have been across the western half of
the forecast area). No big surprises as far as temperatures go,
with mid-afternoon readings for most spots in the mid-upper
80s.

The rest of this afternoon, focus will be off to our west across
the High Plains, where thunderstorms are expected to expand in
coverage as energy from that upper level low swings northeast.
Models showing that low continuing on a northeastward track
through tonight...ending up around the MT/WY/ND/SD border area
by sunrise Wednesday. Models have been pretty consistent showing
a fairly solid line of storms moving into western NE/KS later
this afternoon/evening, with the big question being how well do
things hold together as it approaches our forecast area. Our
forecast here remains dry through at least the early evening
hours, did slow down the onset of preciptiation chances for our
area a few hours from the previous forecast...with hi-res models
having been pretty consistent showing it being closer to 03-04Z
before activity moves into our western edge. The better
parameters for strong/severe storms... instability, deeper layer
shear, and aid via daytime heating... remain mainly focused to
our west, but can`t totally rule out some of those storms moving
to western areas being a problem. SPC Day 1 outlook keeps the
Marginal Risk area over areas along/west of Highway 183...the
main concern being with straight-line winds. The further east
things push, models show that line potentially not being as
solid, but kept preciptiation chances pretty high area-wide in
that 06-12Z time frame (60-70 percent)...the overall threat for
severe weather is expected to wane. Precipitation chances
diminish from west to east as we get closer to 12Z, western
areas may be totally dry by that time.

Wednesday and Thursday...

Can`t rule out some lingering activity across eastern portions
of the forecast area to start the day on Wednesday...but
coverage should diminish with time. Have chances (anywhere from
20-40 percent) lingering through the first half the day for
areas along/east of Highway 281...but confidence in the exact
timing of precip ending is not high. In the upper levels, we
continue to sit under southwesterly flow...the main low driving
activity through tonight doesn`t look to make a lot of progress
during the day on Wednesday, with models showing it only to have
made it into the northern MT/ND border area by early evening.
Thinking there will be at least a brief lull in activity...with
the potential for at least isolated- scattered thunderstorms
developing mid-late afternoon. Some uncertainty remains with
exact location of sfc/lower-level boundaries that this activity
would be focused on...models show a surface dry line pushing
east across the area during the day, but there could also be a
boundary left from tonight`s activity/outflow meandering around.
Overall upper level lift is on the weaker side, with the main
low being well north of the area...looking to help keep things
more scattered in nature. At this point, the better chances for
these storms looks to be across eastern portions of the forecast
area...along/east of HWY 281/into north central KS...but a few
models show some isolated activity a touch further west than
that is not out of the question. Models showing the potential
for MLCAPE values near/exceeding 1500 j/kg across portions of
the area...with deeper layer shear generally around 30 kts.
Potential for some of this activity to be strong-severe remains,
and central/eastern portions of the forecast area are included
in the SPC Day 2 Marginal Risk area. Because activity is not
expected to be widespread, precip chances remain in the 20-30
percent range. Otherwise, generally partly cloudy skies are
expected, with afternoon highs forecast to again reach into the
mid-upper 80s.

Models are in pretty good agreement keeping the best chances in
the 00-06Z time frame, and current forecast has the rest of
the overnight hours dry. That dry forecast remains in place as
we get into Thursday and Thursday night...with models showing
the area set up under upper level shortwave ridging, between one
low continuing its northeastward trek into central Canada and
another digging into central/southern CA. Forecast calls for
mostly sunny skies through the day, with mainly northwesterly
winds on the lighter side, around 10-15 MPH...and another day
with highs in the mid-upper 80s for most locations.

Friday on into early next week...

For the latter half of this forecast period, primary focus is on
that upper level low over the western CONUS and the more
widespread precipitation chances it is currently expected to
bring.

Looking at late Thursday night into the day on Friday, models
are in generally good agreement in the big picture...showing
the upper low shifting through southern CA toward the NV/AZ
border area. Over the past few days, overall the forecast has
trended drier due to the lack of better upper level lift being
outside of the area...but do continue to have some small chances
(20-30 percent) in the forecast...but if models continue on
that trend, could see those chances lowered. Friday night, lift
is increasing across the area, and could see a lead shortwave
disturbance ejected out ahead of the main upper low (which moves
into the Four Corners region). Precipitation chances increase
into the 50-60 percent range area- wide late Friday night into
Saturday.

Plenty of uncertainties remain in this portion of the
forecast...with one being how the rest of Saturday evolves. At
this point, preciptiation chances are broad in nature through
the day and remain elevated (40-60 percent)...but there will be
a period in there where the area could be between bouts of
better lift, sitting behind the shortwave disturbance driving
the increasing chances Friday night continue to move east...and
ahead of the arrival of the main upper low itself. Models show
the upper low sliding through the Central Plains Saturday night
into Sunday...with some differences whether there is any
weakening as it does so (which could taper back how much
accumulation there is). With it still several days away yet,
hard to argue with the broad nature of chances from the NBM...it
will be interesting to see how models trend in the coming days.

By the time the end of the weekend arrives...there is the
potential for a widespread appreciable rain across the
area...latest EPS and GFS ensemble runs show 50-70 percent
probabilities of an inch or more of rain over a decent-sized
chunk of our south central NE counties, though vary on where
it`s centered. Not totally out of the question given the
convective nature potential that there could be spots with a
couple of inches of rain...will just have to see how things
trend.

Have some low chances (20-30 percent) of precipitation
continuing on into the Monday-Tuesday time frame...but
confidence in those chances that far out are really low at this
point.

As far as temperatures go...currently have highs on Friday again
in the 80s, as the area sits out well ahead of the main system
and best preciptiation chances, with the rest of the period
cooling off. Have mainly mid-upper 70s for Saturday, with the
overall coolest day currently on Sunday, as that is the day
expected to have the main upper low passing through. Monday and
Tuesday currently sit in the mid 60s to mid 70s.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1237 PM CDT Tue Sep 17 2024

For KGRI/KEAR Airports:

For the rest of this afternoon, expecting little in the way of
cloud cover, and continued gusty southerly winds. Gusts around
30-35 MPH are not out of the question this afternoon. Winds
diminish a touch this evening, but remain gusty out of the SSE.
Main concern turns to mid-later evening into the overnight
hours, as a line of showers/storms passes from west to east
across the forecast area. At this time, the timing for the best
chances at the terminal areas is roughly in the 06-10Z time
frame...will be able to better refine that as activity develops
out west and moves east early this evening. Kept a VCSH mention
going through the early morning hours...confidence in just how
much activity lingers is not high at this point...with the rest
of this period expected to be dry. Kept this period VFR, but if
sub-VFR conditions were to develop, it`d likely be in that time
frame when precipitation is moving through/just
after...confidence not high to drop it below VFR at this point.
Gusty southerly winds look to redevelop mid-late morning
tomorrow.

&&

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

&&

$$

DISCUSSION...ADP
AVIATION...ADP