640
FXUS63 KGID 181146
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
646 AM CDT Tue Aug 18 2026

.KEY MESSAGES...

- A Severe Thunderstorm Watch is in effect for portions of south
  central Nebraska until 4 AM this morning.

- Showers and storms will continue across portions of the area
  through much, if not all, of the morning daylight hours.

- Strong to severe storms may develop across mainly southern
  portions of the forecast area later today but there is uncertainty
  in location and timing.

- Large hail and damaging winds will be the main threats with
  any storm later today.

- Some locations in north central Kansas may experience heat
  index values today around 100 to 104 degrees.

&&

.UPDATE...
Issued at 237 AM CDT Tue Aug 18 2026

Currently watching storms move southeastward across the forecast
area. A cluster of severe storms previously across eastern
portions of the forecast area are now east of the forecast
area. A Severe Thunderstorm Watch is in effect for areas in
Nebraska along and east of Highway 281 and along and south of
Highway 30 until 4 AM. Other storms are developing along the
outflow boundary to the west of the previously mentioned storms.
Additional storms are developing to the northwest of the
forecast area and are expected to move into northern portions of
the area around 3 or 4 AM. These storms will continue to
develop and move off to the southeast for the remainder of the
overnight period and into the daytime period. There is some
uncertainty as to how strong these additional storms will be
when they move into and through the area. Not expecting
widespread severe weather with the additional storms but
isolated strong to severe storms are possible (20% to 30%
chance). Low temperatures overnight are expected to be in the
60s and low 70s.

Most, if not all, of the storms should be out of the area by this
afternoon. A cold front will move into/through the area this
afternoon resulting in high temperatures today ranging from near 80
degrees across northern portions of the area to near 100 degrees
across portions of north central Kansas. Heat index values today for
portions of north central Kansas may get up to 100 to 104 degrees.
Storms are expected to develop this afternoon/evening along/near the
frontal boundary. These storms may become strong to severe with
large hail and damaging winds. There is some uncertainty as to where
these storms will develop. It will depend on how far south the cold
front gets and where outflow boundaries are from morning convection.
Areas in north central Kansas and in Nebraska near the Kansas border
will be at most risk for severe weather later today. It is also
possible that the storms will develop south of the forecast area.
Some models are showing the convection developing late this evening
into tonight along/near the Nebraska/Kansas border as a shortwave
moves overhead. High temperatures behind the front on Wednesday are
expected to be in the mid/upper 70s to the mid 80s. Showers and
storms may develop (20% to 40% chance) Wednesday into Wednesday
night. There is quite a bit of uncertainty as to where this
convection would develop (if it does at all).

&&

.DISCUSSION...
Issued at 500 PM CDT Mon Aug 17 2026

-- FORECAST CHANGES OF NOTE/BIG PICTURE COMMENTS:

- Certainly no truly "major" changes of note versus previous
  7-day "forecast package). As hopefully made clear in the Key
  Messages above, the varied thunderstorm chances these next ~
  60 hours (through Wed evening) without a doubt carry above-
  average uncertainty...not just regarding likelihood/areal
  coverage, but also severe potential (cannot really fault SPC
  for assigning Slight Risk to our entire CWA for Tuesday, but
  taking consensus of latest higher-res models (CAMs) at face
  value...it arguably could warrant more of a Marginal
  designation.

- Big picture overview of the upper air pattern through the next
  7 days: Latest ECMWF/GFS agree that we will reside under
  either west-northwesterly or more "true" northwesterly
  flow...as we continue being positioned along the broad
  interface between dominant upper level ridging/high pressure
  off to our south or southwest...and broad low
  pressure/troughing off to our north or northeast. Given that
  we`ll reside within this interface, we`ll be prone to
  continued/intermittent rain/thunderstorm chances, and
  experience temperatures that are fairly typical/normal for
  mid-late August...with no noteworthy heat or coolness.


-- 7-DAY FORECAST CHRONOLOGICAL DETAILS (through Mon. Aug. 24)
- CURRENT/RECENT WEATHER SITUATION AS OF 4 PM:
Other than high temps ending up a few degrees warmer than our
initial early-AM forecast (most of our CWA on track to top out
85-90), today is turning out very much as expected. Under sunny
to mostly sunny skies, breezes are predominantly southerly and
not overly-strong...sustained speeds mainly 6-13 MPH with
occasional stronger gusts (especially north and west).

In the mid-upper levels, water vapor satellite imagery and short
term model data confirm that we reside under west-northwesterly
flow, with the next low-amplitude shortwave disturbance
migrating out of WY into western NE.


- THIS EVENING-OVERNIGHT:
Let the rain/thunderstorm chances and severe storm potential
uncertainties begin! Leaning heavily on latest HRRR runs (this
model performed quite well when this forecaster was on shift
last week) along with 12Z RRFS, our entire CWA likely remains
storm-free until at least 7-8 PM. Then, between then and roughly
midnight, mainly isolated/spotty storms could work into mainly
the northwestern 1/3rd of our CWA out of western NE (counties
mainly north and/or west of the Tri Cities). Should storms get
in, severe is certainly possible, with miexed-layer CAPE
(instability) of at least 1500-2500 J/kg and sufficient deep-
layer shear of 35-40KT suggestive of supercells with hail
potential to around ping pong ball size/wind gusts to around 60
MPH.

Turning to beyond 12-1 AM, while any earlier activity south of
I-80 should mostly fade away, attention turns to especially our
northern/northeast counties (mainly north of I-80), as those
counties are most favored to PERHAPS be clipped by the
southern/southwestern fringes of a small convective cluster (or
two) that should MAINLY track just off to our north-through-
northeast. However, should any of this activity affect our area,
at least marginally severe hail/wind is again possible.

In other departments overnight, low temps aimed mid 60s most
areas (more so upper 60s in KS), with fairly light-but-steady
southerly to southeasterly breezes persisting UNLESS an outflow
boundary surges through and abruptly turns winds
northerly/easterly.


- TUESDAY DAYTIME (through around 7 PM):
Overall high-confidence in the "big picture"...as aloft a series
of disturbances will track overhead...while at the surface a
cold front will gradually pass through from north-to-
south...turning winds more north-northeasterly in its wake.

Unfortunately, confidence in the "finer details" is admittedly
fairly low. Right off the bat in the morning, the first question
is whether a potentially strong (maybe even marginally-severe?)
cluster of storms is might be tracking south-southeastward
through mainly our northeastern/eastern counties? If this
occurs, it should exit our CWA off to the southeast by mid-
morning, with plenty of question marks whether any additional
strong/severe activity is able to form during the afternoon.
Again, latest higher-res models (namely HRRR/RRFS, but with
support from 18Z NAM) show very little afternoon activity within
our CWA...possibly due to residual weak capping as we reside
"in between" disturbances.

Otherwise, high temps were changed little, as we call for a
halfway decent gradient ranging from low 80s far north-
northeast, to mid 80s central...to low-mid 90s mainly in KS (and
even upper 90s in especially southern Rooks/Osborne). In fact,
parts of our far southern KS counties (Rooks/Osborne/Mitchell)
could see heat index climb to at least 100-102 degrees (but
should hold slightly short of Advisory criteria).


- TUESDAY EVENING-OVERNIGHT (mainly after 7 PM):
The big question right away in the evening is whether
potentially strong/severe storms erupt along/near the cold front
mainly in/near our far southern CWA. Leaning on the same higher-
res models, the short answer is that MOST of our CWA appears to
be spared...with the MAIN zone of severe potential focusing at
least slightly off to our south-through southeast along the main
frontal convergence zone. Of course, should this cold front slow
down in later model runs, severe potential could increase into
our area accordingly. Again, this is best described as a
CONDITIONAL severe threat for our CWA...as IF storms can get
going a few supercells with large hail/damaging winds cannot be
ruled out.

For the post-midnight hours, we`ll have to watch to see if any
activity rolling in from the west (headed primarily toward
counties along/south of the state line) has much intensity or
instead remains fairly weak. Low temps aimed from low 60s far
north to upper 60s far south-southeast (most places mid 60s).


- WEDNESDAY-WED NIGHT:
Once again, the big question is whether we see any potentially
severe convection? While instability looks to be a bit lower
than Tuesday, deep-layer shear is still seasonably-strong
(40-50KT)...plenty sufficient for supercells. There will also be
decent forcing/lift aloft, as a somewhat stronger (compared to
Tuesday) shortwave trough passes through. Taking 12Z RRFS
"literally", at least a few/spotty severe storms (possibly
supercells) could pass south-southeastward through our CWA at
any point mainly late-morning through mid-evening...and thus
cannot argue against SPC expanding a Marginal Risk to our entire
CWA.

Temperature-wise, high temps were bumped up slightly, with most
places ranging upper 70s-low 80s except mid 80s far southwest.


- THURSDAY-FRIDAY:
Very briefly/in general...most of these 48 hours (especially
Thurs-Thurs night) look drier/quieter, as upper ridging edges a
bit farther eastward into our region from the southwest. In
turn, temperatures slowly warm...with highs mainly mid 80s
Thursday and mid-80s to low-90s Friday.


- SATURDAY-MONDAY:
Much the same continues...with mainly low/highly uncertain
rain/thunderstorm chances on an occasional basis. High temps are
currently expected to be quite similar each of these
days...ranging low-mid 80s northeast, to mainly mid-80s to
low-90s southwest.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 637 AM CDT Tue Aug 18 2026

For KGRI/KEAR Airports:

Showers and storms are expected from 12z to 14z with mainly
showers from 14z to 18z. Winds will become north to northeast
around 18z to 21z and will strengthen from 21z to 00z to 10 to
15 knots. MVFR ceilings will improve by this afternoon but may
return late this evening into the overnight hours.

&&

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

&&

$$

UPDATE...Schuldt
DISCUSSION...Pfannkuch
AVIATION...Schuldt