Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 051725
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1125 AM CST Tue Dec 5 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 347 AM CST Tue Dec 5 2017

The mid level shortwave responsible for the cold front has lifted
over the Great Lakes region. Upper level confluence and the
ageostrophic circulation associated with an upper level jet
stretched across the US is supporting a surface high pressure that
is moving southward through the high plains. Due to the positioning
of this high the forecast area will remain in a tight pressure
gradient although not as strong as directly following the front.
Wind gusts should be less frequent this morning as the nocturnal
inversion combined with cold air advection allows partial
decoupling. Temperatures are expected to reach the 20s by sunrise
with wind speeds causing wind chills to drop into the teens for a
short period. The 850 mb temperatures should briefly rise a few
degrees today and as a result the highs should reach the mid 40s.
Daytime mixing and a continued pressure gradient cause wind speeds
to increase today to around 20 mph with gusts up to 30 mph. Not much
change in the pattern tonight as a re-enforcing shortwave drops out
of Canada forcing the surface high into the southern plains. Wind
speeds should decrease again tonight although there is enough of a
gradient to prevent a strong inversion. Low temperatures are
forecasted to be around 30 degrees across the area.

.LONG TERM...(Wednesday through Monday)
Issued at 347 AM CST Tue Dec 5 2017

By Wednesday, an expansive mid-level trough will be stretched across
the eastern half of the CONUS, resulting in northwesterly flow aloft
over the central U.S.  Models show this strong mid-level trough
remaining anchored over the eastern U.S. through the weekend and
into next week with a few embedded shortwaves developing within the
northwesterly flow during that time. Despite multiple shortwaves
developing within this pattern and skimming near the forecast area,
the limited amount of available moisture with these waves continues
to deter the mention of PoPs through much of the forecast period.
The only exception is with a shortwave that clips the area on
Friday, in which some very light snow or perhaps just flurries may
skim across far northeast KS. As a result, have some slight chance
PoPs along the KS/NE border in far northeast KS for Friday morning.

This persistent northwesterly flow aloft will support reinforcing
CAA through the latter part of the week and into the weekend, so
have continued to trend a few degrees cooler than the model blend
for high temperatures Wednesday through Saturday.  The biggest push
of colder Canadian air comes Thursday as a decent shortwave trough
tracks southeastward over the area, with high temperatures likely
hovering near the freezing mark.  These high temperatures will
gradually moderate into the 40s Friday/Saturday and then into the
50s by Sunday/Monday as surface winds gain a bit more of a westerly
component.  Low temperatures through this period will generally be
in the 20s and even into the teens for some locations Wednesday
night through Friday night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1121 AM CST Tue Dec 5 2017

VFR prevails at KTOP/KFOE/KMHK with main concern being the
development of LLWS aft 03Z. Stout sfc inversion develops tonight
with a passing upper system increasing winds around 1000 feet
between 30 and 40 kts. Winds at this level also veer towards the
northwest with light southwesterly winds at the sfc.

&&


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

$$

SHORT TERM...Sanders
LONG TERM...Hennecke
AVIATION...Prieto



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