839
FXUS63 KGID 210542
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1242 AM CDT Tue May 21 2024

.KEY MESSAGES...

- BY FAR the main issue is the likelihood for at least a few (if
  not several?) severe storms this evening and overnight,
  followed by one final round of strong to potentially severe
  storms mainly during the first half of Tuesday daytime
  (particularly 9 AM-1 PM time frame). Large hail, damaging wind
  the main hazards, but a tornado or two is not out of the
  question especially if any isolated supercells can get
  established near/after sunset.

- Although not as big of a concern overall compared to severe
  storm hazards noted above, there is at least "some" concern
  for rainfall being abundant enough/heavy enough in narrow
  corridors to promote localized flooding/flash flooding tonight
  into Tues daytime, and a Flash Flood Watch has been issued
  for most of our Nebraska coverage area (CWA). Please see
  separate HYDROLOGY section below for more details.

- Once any strong/possible severe storms vacate our CWA to the
  east late Tues AM-early afternoon, we`ll have a fairly quiet
  and mostly dry 48+ hours (especially Wed) with little to no
  severe storm threat.

- From especially Thursday night onward, our forecast is again
  "littered" with various/intermittent chances for
  rain/thunderstorms, as a very active upper air pattern
  continues. At least for now, there are no "obvious" severe
  storm threats during this time (and we are not outlooked by
  SPC), but early signs do point to at least a marginal severe
  environment returning already Thurs evening and/or overnight.

- Temp-wise: Nothing unusual at all for late-May, with highs on
  most days between the upper 60s to around 80, and lows on most
  nights mainly 40s-50s.

&&

.DISCUSSION...
Issued at 507 PM CDT Mon May 20 2024

-- 7-DAY FORECAST OVERVIEW/HIGHLIGHTS (heavily focused on these
 first 24 hours):

- CURRENT/RECENT WEATHER SCENE AS OF 430 PM:
As expected, the vast majority of our CWA (save for some limited
shower activity mainly over Webster County this morning) has
remained dry and storm-free today thus far. Under what has
become partly to mostly cloudy skies, high temps have or soon
will top out in the 74-82 range most areas (coolest north/west
and warmest south/east. In the mid-upper levels, the main
player(s) tonight will be a series of subtle waves embedded in
west-southwesterly flow aloft, downstream from the main wave
still out over the Desert Southwest that will track directly
overhead the first half of the day Tuesday and take any severe
storm/flooding out with it. At the surface, nearly our entire
CWA currently resides just north of a developing/somewhat
diffuse warm front stretched across northern KS, with breezes
most areas currently out of the east-northeast 5-15 MPH. Surface
dewpoints are seasonably-moist...mainly low-mid 60s.

- THIS EVENING-OVERNIGHT:
Most of our CWA should remain storm-free until around 7 PM.
However, after that, and especially after 9-10 PM, all bets are
off as scattered to numerous/widespread thunderstorms are
expected to blossom over mainly our Nebraska CWA (along and
north of the warm front) as weak upper forcing arrives from the
southwest, and the low level jet (evident at 850 millibars)
begins to ramp up. Closely leaning on higher-res models such as
HRRR, a series of individual storms (possibly supercellular)
along with clusters and perhaps broken, mainly west east
oriented lines of convection will traverse our area overnight,
with a sharp south edge likely somewhere between Highway 6 and
the KS border (very little activity expected in KS). The later
storms form, there is some question as to how truly surface-
based they might be, but at the very least the environment is
primed for a large hail and/or damaging wind threat, given
mixed-layer CAPE at least 1500-2500 J/kg and deep layer shear
40-50 KT. This is a somewhat concerning environment as it is,
and if any storms are able to remain at least semi-
discrete/supercellular and tap into increasing low-level shear
mainly near/after sunset, then at least a brief/transient
tornado threat could be on the table as well, not to mention
some hydro concerns (see separate section below).

- TUESDAY DAYTIME:
Following what could be a relative lull in activity around
sunrise, the main upper wave and associated surface cold front
will cross overhead by late-morning/early afternoon. As this
occurs, one final round of more north-south oriented strong to
severe storms is expected to cross much of our mainly Nebraska
CWA from west to east between 9 AM-1 PM, perhaps offering up
more potential for large hail/damaging winds and localized
flooding. Once this activity clears, our severe storm and
flooding threat should end, as the severe threat focuses farther
east of our CWA through the afternoon and evening. Behind the
front, it will be very breezy/somewhat windy on Tuesday, with
northwest winds sustained 15-25 MPH/gusts 25-35 MPH. High temps
will depend on "exact" frontal timing, cloud cover etc. but we
are calling for roughly a 15-degree gradient from mid 60s far
north/west to upper 70s far southeast.

- TUESDAY EVENING-OVERNIGHT:
Most areas will likely remain dry, but isolated to scattered
showers and maybe a few WEAK storms could affect some counties
mainly south of I-80 into KS through the night. Winds will die
down, and this will be one of the cooler nights coming up with
lows mainly 44-51 most places.

- WED DAYTIME-THURS DAYTIME:
This is mainly a DRY/storm-free period in between upper
disturbances. High temps low-mid 70s Wed and upper 70s-low 80s
Thurs as south winds increase.

- THURS NIGHT-SATURDAY:
Intermittent shower/thunderstorm chances return as various upper
waves move through again. We`ll have to watch Thursday
evening/overnight for MAYBE our next, at least limited severe
storm chance.

-SUNDAY-MONDAY (Memorial Day):
The parade of low-confidence rain chances/PoPs continue as both
the ECMWF/GFS bring another disturbance somewhere across the
Northern/Central Plains. Although still several days out, at
least an early glance suggests instability levels fairly muted
by late-May standards and thus a lower severe threat.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1234 AM CDT Tue May 21 2024

Showers and thunderstorms are expected to be in the vicinity of
and impact the terminals overnight. Low ceilings are expected to
continue through the overnight period and into the morning
hours. Ceilings will improve some by 18z and will either be low
end VFR or high end MVFR for the early afternoon hours. VFR
conditions are expected by 00z Wednesday. Winds will be somewhat
variable, especially in and near convection, but are expected to
become elevated and gusty out of the north to northwest around
15z.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Flood Watch through this afternoon for NEZ039>041-046>049-
     060>064-072>077-082>084.
KS...None.

&&

$$

DISCUSSION...Pfannkuch
AVIATION...Schuldt