573
FXUS63 KGID 152331
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
631 PM CDT Mon Jul 15 2024

.KEY MESSAGES...

- Heat Advisory remains in effect until 8 PM for all but the far
  north fringes of our coverage area (CWA). Although Tuesday
  will be "somewhat hot" especially in our KS counties, we can
  thankfully wave GOODBYE to truly dangerous/excessive heat for
  the foreseeable future (high temps mainly between upper 70s
  and mid 80s most places over next week).

- While our entire CWA is officially under either a
  Marginal/Slight risk for severe storms later this evening-
  overnight, we are getting overall MORE CONCERNED about Tuesday
  afternoon-evening severe storm potential as storms develop
  along a secondary cold front and move south-southeastward
  through the area.

- Beyond Tuesday: While it will certainly be dry more often than
  not, the Wed night-Monday time frame features
  several/intermittent (and mainly low-confidence)
  rain/thunderstorm chances for various parts of the CWA. At
  least for now, the overall-highest/most widespread chances
  (PoPs) are focused Fri night.

 &&

.DISCUSSION...
Issued at 459 PM CDT Mon Jul 15 2024

-- PRIMARY CHANGES TO THIS 7-DAY FORECAST "PACKAGE" VERSUS THE
 PREVIOUS ONE (issued early this AM):

- As already mentioned above, concern has increased somewhat for
  a potential severe storm threat Tuesday afternoon-evening, as
  latest models have come in a bit more aggressive with
  development along a secondary cold front dropping southward
  through the area. Agree with SPC in "upgrading" essentially
  our entire CWA from a Marginal Risk (level 1 of 5) to a level
  2 Slight Risk.


-- 7-DAY FORECAST OVERVIEW/HIGHLIGHTS:

- CURRENT/RECENT WEATHER SCENE AS OF 4 PM:
Today has pretty much played out as expected. We remain in the
grips of our LAST day of excessive heat, with actual high temps
on track to range from mid 90s for most Neb zones, to upper 90s
along the state line, to 100-108 in KS. Thanks to dewpoints
still well into the upper 60s-mid 70s range across the majority
of our Neb CWA, heat index values are still solidly into the
100-108 range across the majority of the CWA. Our Heat Advisory
continues as-posted until 8 PM...considered trimming off a few
northwestern counties where heat index is "coolest", but even
there heat index is still into the 90s so opted to just let it
ride.

In the big picture of the mid-upper levels, water vapor
satellite and short term model data confirm broad west-
northwesterly flow aloft, as we remain in between the center of
expansive ridging/high pressure centered over northwest NM, and
a large-scale trough centered over southeast Canada into the
Great Lakes region. On the smaller scale, a low-amplitude
disturbance is pushing southeastward into mainly IA, where
strong to severe storms have blossomed. At the surface, although
it obviously hasn`t cooled us off much yet, a MUCH-WELCOMED cold
front continues marching south across our CWA and has reached
far northern KS. In it`s wake, north-northeast breezes are
sustained generally 10-15 MPH/some gusts 20+ MPH.


- THIS EVENING-OVERNIGHT:
With weak forcing aloft to the west of the IA convection, along
with warm air aloft/capping in play, our CWA is expected to
remain well west of any convection developing to our east, and
at least for several more hours, should also remain well east of
any convection developing off the High Plains/Foothills of
CO/WY. However, mainly sometime AFTER 10 PM, higher-res short
term models (particularly HRRR), suggest that a broken line
and/or cluster/complex of convection will likely arrive into our
CWA from the west. Although have at least slight chances (20%)
across our entire CWA for the late evening-overnight hours, have
the highest chances (currently 50% but possibly not high enough)
focused within our far western and especially southern/KS zones.
Latest HRRR suggests that IF our CWA is subjected to any severe
storm threat tonight, it would mainly focus 11PM-3AM in
association with a possible storm complex/MCS rolling mainly
along/especially south of the NE-KS border. Main hazards would
likely be 60+ MPH winds, with a somewhat lesser threat for hail
to around quarter size. While the main batch of storms would
likely depart our far east-southeast zones by around 3-4 AM,
left small PoPs intact through the rest of tonight to account
for possible spotty "residual" weaker storms.

In other departments overnight, made little change to low
temps...aimed from mid-upper 60s north to low 70s far southeast.
With light winds late in the night, suppose some mainly
patchy/light fog cannot be ruled out, but kept out of forecast
as current expectation is for cloud cover to be a mitigating
factor.


- TUESDAY DAYTIME-OVERNIGHT:
While most places are likely to be dry in the morning through at
least early afternoon, have some low PoPs in to account for at
least isolated, non-severe storm activity. However, at some
point in the 4-7 PM time frame, things are expected to get
active along a secondary cold front arriving from the north. For
only being 24 hours out, models still show a fair amount of
uncertainty in the "exact" arrival of this front and associated
threat (HRRR closer to 4 PM...NAMNest closer to 7 PM). Either
way, once storm do develop, the environment will be favorable
for initial, at least briefly isolated/maybe supercellular
storms, that would then grow upscale into at least a broken
line/cluster as they track south-southeast. Fully agree with SPC
on the upgrade to Slight Risk (level 2), as healthy mixed-
layer CAPE of 2500-3500 J/kg in the presence of 35-40KT of deep
layer shear should be enough to stir up some trouble...mainly in
the form of hail to at least ping pong ball size/gusts to at
least 60 MPH. Based on current timing, the main severe threat
should exit our southern zones by around 11 PM-Midnight, with
most areas then likely storm-free the rest of the night.

In other Tuesday departments, although it WILL BE COOLER than
today, it won`t exactly be refreshing either. In fact, high
temps have trended up a few degrees...currently aimed mid 80s
most Neb zones, upper 80s-low 90s near the state line and mid
90s far southeast (esp Osborne/Mitchell counties). So better,
but not exactly cool by any means.


- WEDNESDAY-THURSDAY:
As cooler/drier (more stable) air arrives from the north-
northeast, things should certainly turn less active. In fact,
the Wednesday daytime -evening forecast is currently dry, with
only some "iffy" slight PoPs in far western zones late Wed
night. Winds Wed will be out of the northeast generally 10-15
MPH, and it will be the overall-coolest day we`ll have seen in
over a week with highs aimed mainly upper 70s-low 80s (a few mid
80s possible mainly KS).

Like Wed, Thurs-Thurs night will likely be mainly dry as well as
we remain under uneventful northwesterly flow aloft, but there
are some small PoPs mainly west. Highs again mainly upper
70s-low 80s, but more mid 80s south-southwest.


- FRIDAY-SATURDAY:
Although still several days out and far from a "sure thing",
latest ECMWF/GFS agree that a shortwave trough will drop
southward into our region...thus sparking our overall-highest
(widespread 50-60%) rain/thunderstorm chances of the week for
Friday evening-overnight. Lower chances continue into Saturday,
which should be mostly dry. Temp-wise, Friday warms up a touch
with more widespread 80s (pushing 90 far southwest), but then
cool down again Saturday (mainly upper 70s-mid 80s).


- SUNDAY-MONDAY:
Various, low-end/low-confidence PoPs continue, as there are
signs of at least weak disturbances in the area (more so GFS
versus ECMWF). As usual that far out, confidence is higher in
temps. At least for now, our official forecast MIGHT be a bit
too cool advertising highs mainly mid-upper 70s, but even if it
trends up a bit with time...should not be any warmer than low-
mid 80s.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 612 PM CDT Mon Jul 15 2024

For KGRI/KEAR Airports:

Prevailing VFR conditions expected through the period with a
small chance for a thunderstorm or two possible after midnight.
The developing line of TSRAs to our west is expected to weaken
as they approach our western fringe (Dawson county) late this
evening, with a VCTS possible aft 16/05Z as this line pushes
east southeastward. Behind this line, expect a mid level cloud
deck near 10KFT to persist through the overnight hours...and
with light winds and elevated dewpoints, could see a bit of
light BR...although would prefer less mid level clouds to have
anything more significant. Mid level clouds are forecast to
linger across the local area through much of the day Tuesday,
with more breaks during the afternoon hours, before another
front brings an additional chance for TSRAs to the terminals
Tuesday evening.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory until 8 PM CDT this evening for NEZ048-049-
     060>064-072>077-082>087.
KS...Heat Advisory until 8 PM CDT this evening for KSZ005>007-
     017>019.

&&

$$

DISCUSSION...Pfannkuch
AVIATION...Rossi