287
FXUS63 KEAX 181051
AFDEAX

Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
551 AM CDT Fri Oct 18 2024

.KEY MESSAGES...

- Elevated Fire Weather Concerns Friday

- Warm, Mostly Dry Through The Weekend

- Rain Chances Return Monday into Tuesday

&&

.DISCUSSION...
Issued at 356 AM CDT Fri Oct 18 2024

H5 ridge axis has shifted eastward into the Central Great Lakes
Region along with the associated surface anticyclone, now centered
east of the area. Deep trough is digging toward the Four Corners
Region this morning with stronger dCVA present over the Front Range.
Lee surface cyclogenesis has been ongoing. With this developing
west of the area, and the stronger surface anticyclone east, low-
level flow has turned southwesterly from the Central Plains into the
lower Missouri River Valley. This is promoting a WAA regime, and is
expected to increase temperatures Friday afternoon into the lower
and mid 70s. Amongst NBM members and other ensemble suites, the
inner-quartile range spread is fairly narrow with most points in the
lower to mid 70s. Only far northeast reaches of the forecast area
may only hit the upper 60s. Subtle height falls will start ahead of
the trough axis in the western CONUS but overall forcing and
kinematics will not be overly robust. The lack of moisture transport
will keep conditions dry today. Diurnal heating should lead to
stronger boundary layer mixing, that will help boost temperatures,
as well as maintain lower dewpoints with southwest flow brining in
drier plateau air. With air temperatures in the lower 70s, and
dewpoints expected to remain in the lower to mid 30s this afternoon,
relative humidity values between 20 and 30 percent are expected. In
our northwestern counties, winds at the top of the mixed layer may
be around 20-22 kts. There is some spread amongst various guidance
on the strength of winds. For southeast counties, winds at the top
of the mixed layer between 17-20 kts appear favorable in various
model soundings. Have went ahead and increased wind gusts slightly
from NBM guidance to account for stronger mixing this afternoon.
These warm and dry conditions will lead to elevated fire weather
concerns, but are not currently forecast to reach headline criteria
this afternoon. There are essentially two different regimes divided
geographically. Stronger winds in our northwest with slightly lower
dewpoints depressions (and thus slightly higher RHs), and then
larger dewpoint depressions (lower RHs) but weaker winds in our
southeast.

Saturday, jet streak begins to wrap around the trough axis over the
desert the southwest, and puts dCVA at a standstill across the Front
Range. Current expectation is for a closed-low in the mid to upper-
levels of the troposphere, while the associated surface cyclone is
unable to advance with lack of upper-level support moving
downstream. The surface anticyclone to the east remains in tact,
keeping the WAA regime in place that should provide another day of
temperatures in the mid 70s across most of the area. Most inner-
quartile ranges amongst ensemble suites are clustered around this
range. Current deterministic guidance depicts subtle backing of the
surface winds, which may help our area tap into slightly better
moisture transport. Dewpoints are currently progged to reach back
into the lower 40s by Saturday afternoon. However, will need to
continue to monitor boundary layer mixing potential again, as some
guidance seems to be too high with dewpoint output the past few
days. Even with the possibility of moisture transport, most of the
column remains very dry, therefore, precipitation chances are not
expected on Saturday, as all of the forcing and large scale ascent
are tied out west with a closed-low system. Ensemble suites hold
less than 10 percent probabilities for any measurable rainfall
through Saturday evening. Sunday, a weak short-wave off the west
coast is progged to get the closed-low system over the desert
southwest moving again but progress will be slow. Previous WAA
regime will actually build a secondary mid-level ridge axis early
Sunday that will have to move eastward before any substantial height
falls can start. This eventually does push east, and with another
area of dCVA promoting cyclogenesis over the Front Range and High
Plains, stronger southerly flow should increase WAA and boost
temperatures into the upper 70s across most of the forecast area.
While a few short-waves and vort maxima may try to ride through the
ridge, the lack of moisture will continue to limit precipitation
chances. Ensemble probabilities for measurable precipitation Sunday
are also below 10 percent for most of the forecast area. Like with
Saturday, will continue to monitor local boundary layer mixing and
dewpoint trends to determine if any kind of elevated fire weather
concerns will be present during this warm and dry spell.

Next rain chances return mid-day Monday and continue through Tuesday
as the mid-level system gets another kick and begins to lift out of
the desert southwest, dragging a surface cyclone across the Plains.
Mid-level height falls begin to take place Monday afternoon, and at
the surface should promote meridional flow that helps transport more
moisture back to the area. The strongest forcing remains west of the
area for most of Monday, but there may be enough convergence out
ahead of the main trough axis to promote some shower activity into
the western portion of the forecast area. Ensemble probabilities for
precipitation are generally around 50-60 percent, then decrease
eastward. The stronger mid-level kinematic support moves through
late Monday into Tuesday as the main lobe of vorticity passes
overhead, where Q-vector convergence is concentrated within the
vicinity of low convergence along a weak thermal boundary. 24 hour
precipitation total probabilities by the end of Tuesday are around
40 to 50 percent to exceed 0.10 inches, but very low for anything
0.50 inches and greater. While any rain would be welcomed, current
forecast amounts would only provide minimal relief to drought
conditions. Even the outlier members amongst ensemble guidance
struggle to reach much above one inch of rainfall. Instability is
not currently progged to be very robust as this feature moves
through the start of the next work week, therefore looking at the
favored mode of precipitation to be general showers. Perhaps if we
realize elevated instability, a few isolated thunderstorms could get
going, but current pattern evolution is only favoring general
showers. As for temperatures Monday and Tuesday of next week,
continued WAA will support ranges from the upper 70s to lower 80s.
Tuesday will have bit more uncertainty, as cloud cover will play
large role in controlling the insolation.

For the remainder of next week, the short-wave trough exits our
area, and a few mid-level perturbations are progged to move
southwestward out of Canada. This will promote generally northwest
flow through the end of the forecast period. There are some low end
ensemble probabilities for isolated rain showers through the middle
of next week as these weak disturbances move through the flow, but
generally are only around 15 to 20 percent for any measurable
rainfall (and not widespread across the forecast area either).
Temperatures will likely be cooler compared to the weekend. Ensemble
spread for temperatures through the middle of next week are larger,
and this looks to mainly be due to precipitation production and cloud
cover differences associated with the short-wave perturbations in the
northwesterly flow. Overall QPF projections are very low though,
most models clustering around just a few hundredths of an inch.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 552 AM CDT Fri Oct 18 2024

VFR conds are expected thru the TAF pd with clr skies. Winds
will be out of the south btn 7-12kts thru 15Z when winds will
increase to 10-15kts with gusts to 25kts. Winds are expected to
diminish aft 23Z becmg SSE btn 5-10kts.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...None.
KS...None.

&&

$$

DISCUSSION...Krull
AVIATION...73