Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 160533
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1133 PM CST Wed Nov 15 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday)
Issued at 305 PM CST Wed Nov 15 2017

Northwest flow aloft is currently supporting surface high pressure
that will slide across the forecast area. During this period skies
will be clear and winds generally light. Due to the drier air mass
and radiational cooling lows tonight dip into the lower 30s and
upper 20s. By tomorrow morning the southeast winds increase as the
high pressure progresses eastward. Zonal flow aloft and the lack of
any arctic air the highs reach the 50s. The pressure gradient
appears to be strong enough to support wind gusts upwards of 30 mph
especially across central KS. Relative humidity tomorrow afternoon
along with the wind speeds will contribute to high fire danger.

.LONG TERM...(Thursday night through Wednesday)
Issued at 305 PM CST Wed Nov 15 2017

The extended forecast period highlights (up to the day before
Thanksgiving) will be largely dry outside of small chances for
drizzle and rain on Friday with better chances for early morning
rain on Saturday.  Above normal temps should be in play Friday with
a return to near or below normal temps through the rest of the
period.

Model guidance is in overall good agreement early in the period with
surface high pressure sliding off to the east of the area with
return flow setting up over the area Friday with as a lee trough
tightens its grip over the area overnight Thursday into Friday.
Upper flow exhibits a low amplitude broad ridge over the Rockies
into the Central Plains.  This should allow for WAA regime to
strengthen in the lower levels over the area.  Isentropic lift
increases on the 295-305K surfaces with ample saturation to increase
drizzle chances over eastern portions of the area late Thursday
night.  As lift increases into Friday morning the expectation is for
drizzle to transition to rainshowers.  Total amounts likely remain
small though with fairly shallow moisture in place.  Clouds should
begin to breakup as isentropic ascent advects to the east and
downglide occurs.  WAA should allow temps to increase to well above
normal with highs around 70 common.  Not expecting record temps to
be eclipsed at this point.

Overnight Friday into Saturday, a cold front will push into the area
as a positively tilted shortwave quickly sweeps across the Northern
Plains into the Upper MS Valley.  Right now the low level front
should outrun the upper level jet streak before it advances over the
area. Thus, it is possible to have post frontal rainshowers work
into the area very early Saturday morning before the midlevel trough
translates through the area returning a northwest flow regime to the
Northern and Central Plains.  As H85 temps cool to around -1C, highs
on Saturday return to near normal in the low 50s with a stiff
northwest breeze.

Models really start to diverge in solutions by Wednesday before
Thanksgiving with the ECMWF and GFS becoming out of phase with the
EC developing a cutoff low over the Southern Plains region and the
GFS laying out a broad and deeper trough through the Central CONUS.
This will likely greatly impact temperatures and any weather systems
that do enter the picture during the very long term.  Ultimately,
the story for the Thanksgiving period is stay tuned.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1131 PM CST Wed Nov 15 2017

VFR conditions are expected for the remainder of the night and
during the daytime on Thursday, with MVFR to IFR stratus working
northward across eastern Kansas after 00Z. Light and variable
winds tonight will increase out of the S/SE at around 10 to 15 kts
during the day on Thursday.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Sanders
LONG TERM...Drake
AVIATION...Skow


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