196
FXUS63 KGID 291158
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
658 AM CDT Wed May 29 2024

.KEY MESSAGES...

- A warm front will push through the area today and provide for
  slightly higher temperatures/humidity and breezy SE winds, but
  not much for precipitation chances (20% or less).

- Higher shower and thunderstorm chances arrive late tonight
  (30-60%), then become likely Thursday into Thursday night
  (60-80%) with the arrival of a weak cold front.

- Friday should trend drier through the day, but off and on
  shower and thunderstorm chances persist each day through the
  weekend - mainly during the evening/night hours.

- Severe weather potential next several days is low by late May
  standards, but not zero, so would expect periodic at least
  marginally severe weather. Locally heavy rain will also be
  possible, but confidence on details (amounts/location) is low.

- Ensembles have trended cooler for next week thanks to deeper
  troughing over the Great Lakes. This implies periodic cold
  fronts/precipitation chances continuing into next week.

&&

.DISCUSSION...
Issued at 450 AM CDT Wed May 29 2024

Today - Tonight:
AM surface analysis reveals a stationary front situated from the
Neb. Panhandle SEward towards the KC Metro with T/Tds in the
50s/40s N of the boundary, and 60s/50s to the S. There hasn`t
been a whole lot in terms of elevated convection early this
morning, and latest HRRR/RAP trends don`t offer much potential
for our area through the daytime hrs, despite the frontal zone
transitioning northward as a warm front. Instead, expect mainly
dry conditions and both air temperatures and dew points slightly
higher than yesterday on breezy SE winds gusting 25-30 MPH. No
significant changes to the forecast thoughts for tonight as
scattered convection is still forecast to develop within a broad
N-S zone along the Front Range/High Plains this afternoon, then
gradually shift E this eve/night. Think the brunt of our
potential will come after midnight and on a weakening and sub-
severe basis owing to lackluster instability and deep layer
wind shear. This general scenario is depicted well in recent 06Z
runs of the HRRR/NAMNest.

Thursday - Friday:
Remnant isolated-scattered showers/weak storms will remain
possible (40-60% chance) through Thursday AM, perhaps aided by
combination of veering low level jet and embedded MCV(s). A cold
front is forecast to enter far N/W portions of the forecast
area, generally Ord to Lexington, by the late afternoon hrs.
Assuming we clear out for a few hrs around midday, should have a
narrow zone of at moderate instability, weak capping, and
convergence along to boundary to generate new scattered storms
20-23Z. Exactly how robust this activity is will depend on how
much clearing we see during the afternoon, as well as lingering
subsidence from a potential departing MCV. If the moderate
instability materializes (aided by gradually moistening boundary
layer), then strong to marginally severe storms would be
possible given effective shear values of 30-35kt. Highest
chances for severe (relatively speaking) could favor areas W
through S of the Tri-Cities per 03Z SREF calibrated severe
probs, but the entire area is outlooked in a Marginal Risk
(level 1 of 5) per SPC Day 2 outlook. Large hail and locally
severe wind gusts would be main threats, but will need to watch
for potential outflow boundary from AM activity to possibly
return N and intersect cold front. This would also pose an
isolated tornado threat.

Convection could continue on at least an iso-scat basis into the
overnight, though exact evolution and coverage remains uncertain
due to vastly varies solutions regarding strength/placement of
LLJ. Some guidance has almost no LLJ, whereas others have
40-45kt Srly flow overriding the gradually southward sinking
cold front/outflow. Personally, I think upscale growth for at
least north central KS is quite plausible given the general
synoptic pattern and increasing instability to the S. Low end
PoPs continue into Friday, though to be honest, I`m not seeing a
lot for sfc/upper support. Sfc boundary should also be well S
of the area by the aftn/eve hrs. It`s only a weak front, though,
and expect highs will make it to at least low to mid 70s.

Weekend:
Models are in general agreement in primarily zonal upper flow
for the weekend, but disagree with timing, placement, and
magnitude of several embedded shortwaves. In the absence of a
coherent/apparent frontal zone, am inclined to think that our
chances will tend to be highest during the mid to late evening
into the overnight from convection that develops over the High
Plains in moist SErly upslope flow, then shifts E/SE. For
Saturday night, nearby mid level thermal gradient (H7 temps
ranging from 6-8C Neb zones to 10-11C just SW of the area per
00Z EC) and likely increasing LLJ would suggest a favorable
pattern for a NW to SE moving nocturnal MCS, somewhere over NE
and/or KS. There would probably be some risk of large hail
transitioning to damaging wind with any MCS, though due to the
nebulous sfc forcing and model differences, the predictability
of such evolution/detail is too low this far out. Instability
will increase on Sun with continued Srly flow, but so will mid-
level temperatures and capping. Some guidance suggests a repeat
scenario of Saturday, which seems plausible given potential
arrival of next cold front. However, with the higher mid level
temperatures would probably need a sufficiently strong and well-
timed shortwave, too. IF convection develops, then severe would
be possible given strong instability and area residing within
southern fringes of W to E belt of 40-50kt effective shear. LLJ
could also help sustain activity into Sunday night.

The next several days carries a lot of "IFs" and "possible",
but IF the repeated rounds of convection come to fruition, then
locally heavy rain and flooding could be an issue, as well. 00Z
EPS places periodic bouts of PWATs 125-150% of normal over the
area Thu through the weekend, and 90th percentile QPF is near
3", in spots, which could go up if member agreement increases.

Next Week:
Looks like more of the same off and on precip chances continue
into early next week before a potentially stronger shortwave
swings through Tuesday-ish. Ensemble guidance is quite varied
with the amplitude of this shortwave - which then impacts the
potential for a more notable longwave pattern shift towards
Great Lakes troughing and western CONUS ridging. EPS favors a
deeper shortwave on Day 7, and has trended W w/ deeper Great
Lakes trough and stronger NW flow for second half of next week.
This would cut back on the potential for 90s due to periodic
cold fronts/precipitation chances in active NW upper flow. GEFS
is weaker/flatter - but even still, it is not quite as warm/dry
as runs a few days ago. Just some trends to keep an eye on.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 655 AM CDT Wed May 29 2024

Today: VFR with only some passing mid to high clouds. ESE to SE
winds 10-15kt, gusts 20-25kt. Confidence: High.

Tonight: Expect increasing mid to high clouds this evening ahead
of isolated to scattered showers and weakening storms. Appears
this activity will arrive around or after 06Z, but kept it as
VCSH for now given uncertainty in coverage and strength by the
time they arrive. Model guidance suggests sub-VFR CIGs beginning
late overnight, generally after 08-09Z. Since this was at the
very end of the forecast period, opted to keep it as a SCT group
for now. Winds will continue out of the SE at 10-18kt.
Confidence: Medium

&&

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

&&

$$

DISCUSSION...Thies
AVIATION...Thies