Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 210852
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
252 AM CST Wed Feb 21 2024

.KEY MESSAGES...

- Warm temperatures persist today, ahead of a cool down for
  Thursday.

- Precipitation chances tonight appear limited to Coffey and
  Anderson counties.

- Warm and dry conditions are forecast for the weekend and into
  early next week. Confidence in the forecast through the
  weekend is good with little spread in the model blend.

&&

.DISCUSSION...
Issued at 252 AM CST Wed Feb 21 2024

08Z water vapor imagery showed broad ridging over the central and
southern plains, but upstream there was an upper trough along the
west coast with shortwave energy approaching southern CA. At the
surface, obs indicated a relatively weak are of low pressure across
the middle MO river valley and central plains. With high pressure
ridging into the lower MS river valley, a southerly low level wind
favorable for moisture return had developed through east TX.

For tonight models are in general agreement with the low level jet
starting off the evening veered to the west-southwest. This is
progged to keep the better theta-e advection and deeper low level
moisture just south of the forecast area. Additionally the shortwave
near southern CA at 08Z, is progged to shear out and weaken as it
moves over the central plains. However mid level lapse rates are
forecast to be steep between 8 and 9 C/km with bulk sheer around
50kt. If the modest moisture return of dewpoints around 50 degrees
is able to advect far enough north, there could be enough
instability for an isolated thunderstorm or two. Forecast soundings
suggests storms would be elevated with perhaps a hail risk during
the late evening and early morning hours. The latest CAMs and even
the 06Z NAM have kept the convection to the south of the forecast
area, and the 00Z HREF keeps the chances for convection south of the
area. So the main change to the previous forecast has been to
sharpen up the gradient in the POPs to confine the 15 to 30 percent
chances to Coffey and Anderson Counties where the probability for
the low level moisture advection are a little better. North of these
counties, low level flow is likely going to be from the west and
quickly switch to the north as a frontal boundary moves south
limiting moisture and instability.

A modified Pacific airmass is forecast to trail tonight`s shortwave
causing low level cold air advection to occur through the day
Thursday and into Friday. This should cool temperatures keeping
highs in the lower and middle 60s (still 10 to 15 degrees above
normal). But before the cold front moves through late tonight,
another warm afternoon is forecast with highs in the lower and
middle 70s. There should be more high clouds streaming in from the
west today, but forecast soundings show good mixing of the boundary
layer and I expect this mixing to push highs into the lower 70s in
spite of the high clouds.

Northwest flow is expected to transition to more of a zonal pattern
this weekend and into next week. This should keep dry weather in
place with seasonally warm temperatures. The deterministic solutions
show an anomalously deep upper trough sweeping through the region
Tuesday night and Wednesday morning of next week. While there is
similarity in the GFS and ECMWF solutions, cluster analysis of the
ensemble 500MB heights show the deterministic solutions fall within
about 32 percent of the ensemble output. So there remains some
spread in potential outcomes for next week and this is reflected in
larger spreads within the NBM for temps and relatively low POPs.
Will stick with the blend at this point, but there could be a better
potential for precip as the trough moves through then the blend is
giving.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1031 PM CST Tue Feb 20 2024

VFR conditions prevail. Winds remain under 10kts through the
period, generally from the southeast.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Wolters
AVIATION...Flanagan


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