279
FXUS63 KGID 281138
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
638 AM CDT Tue May 28 2024

.KEY MESSAGES...

- Low end (20-30%), light precipitation chances mainly SW of the
  Tri-Cities next couple of days. Otherwise, quiet and mild.

- Better chances (30-60%) arrive late Wednesday night, and
  especially Thursday into Thursday night (50-80%) with the
  arrival of a weak front.

- Off and on thunderstorm chances (generally 20-50%) continue
  through the weekend owing to "dirty" zonal flow and perhaps a
  couple sfc boundaries in the area.

- Overall severe weather threat days 4-7 remains uncertain,
  though probably not completely zero. Locally heavy rain could
  also be an issue, particularly Thursday-Friday.

- Ensemble guidance is in general agreement for stronger upper
  ridging and warmer and drier weather arriving next week.

&&

.DISCUSSION...
Issued at 445 AM CDT Tue May 28 2024

Today - Wednesday:
Not much change to the general forecast thoughts for the next
couple of days - mainly dry and seasonably warm. Areas mainly SW
of the Tri-Cities will be on the fringes of better mid level
warm air advection and isentropic ascent over the next 24-36
hrs, but models remain consistent in keeping the highest
chances/amounts from E CO into SW KS. Areas along and SW of a
line from Arapahoe to Beloit have fairly persistent 20-30%
chances of rain to account for this, with a mention of sprinkles
to the north for a buffer. Temperatures look to remain very
consistent (and pleasant) in the upper 70s to lower 80s. Winds
will be lgt today, then incr out of the SE for Wednesday.

Late Wednesday Night through Friday:
Also not much change to the forecast thoughts from the past few
days for Wednesday night. Still expect a swath of scattered
thunderstorms to develop N-S along the Front Range/High Plains
region Wednesday afternoon, then gradually shift E during the
evening and overnight. Mid to upper flow is modest, so the E
movement will be slow, but aided to some extent by broad and
increasing low level jet. Some of this activity to make it to W
zones after midnight, then further E towards Hwy 281 corridor
around dawn Thu AM. Shear looks to be too weak, and primary
instability axis remains W/SW of the area, so not expecting
anything severe.

What exactly happens the rest of the day and into Thursday
night remains something of a mystery, but general consensus is
that convection will redevelop at some point during the
aftn/eve, either along lingering outflow boundaries, or along an
advancing front from the NW in what otherwise looks to be an
increasingly moist and uncapped environment. There will likely
be at least a slight uptick in shear (locally enhanced by
outflow boundaries) to around 30kt sfc-6km, but the primary
plume of steep lapse rates remains over W/S KS, so instability
will still be weak by late May standards. Severe weather threat
is probably not completely zero, but looks to be more of a
Marginal (level 1 of 5) type threat at this time, thus below the
15% minimum threshold for a day 4+ outlook. Of potential
greater concern could be locally heavy rain given aforementioned
weak flow and slow storm motion vectors. PWATs, while not
tremendously high, will incr to around 1.5 sigma per latest EPS,
and "tall/skinny" CAPE profiles will incr efficiency. It`s
nearly impossible to pin down location of heaviest rainfall, but
some of the most recent deterministic guidance gives localized
2-3+", which seems reasonable. Suspect this will be supported by
hi-res CAMs once we get within their forecast range. Friday
could see some lingering activity in the morning, but should
generally trend drier through the day. Official forecast
continues some 20-40% PoPs into Friday afternoon and night, but
slowly rising heights and lack of coherent ascent mechanism
makes me think this is overdone.

Model guidance spread increases over the weekend with respect to
handling of a few low amplitude shortwave troughs, but agree
that general upper flow will be zonal or slightly SWrly. Am
confident there will be off and on thunderstorms rolling through
the region over the weekend, but there`s simply too much
uncertainty and weak forcing to discuss possible specific
outcomes. Severe risk could be greater than Thu-Fri given
slightly higher mid level flow/shear and instability, but again,
a lot will depend on features that are too unpredictable this
far out. Temperatures should remain in the 70s or 80s, depending
on cloud cover and rain coverage.

Ensemble guidance is in better agreement that ridging will
strengthen over the W 2/3rds of the CONUS by middle of next
week, which should support and increasingly drier and hotter
pattern locally. Core of highest temperatures anomalies should
tend to focus W of the area, but latest EPS still gives better
than 50/50 chances for highs breaching 90 deg for portions of
the forecast area several days next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 637 AM CDT Tue May 28 2024

VFR through the period. Expect off and on bouts of SCT clds
around 9-12K ft, some of which may produce a few sprinkles. Lgt
and vrbl winds this morning will become NW-N this afternoon,
with perhaps some minor gusts at GRI. Winds will continue to
back to NE-E tonight at around 6-9kt. Confidence: High.

&&

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

&&

$$

DISCUSSION...Thies
AVIATION...Thies