Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 151133

Area Forecast Discussion
National Weather Service Topeka KS
533 AM CST Fri Dec 15 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 324 AM CST Fri Dec 15 2017

A positive tilt upper level trough extended from the Great Lakes
states southwest across MO into eastern OK and TX. The upper trough
will shift eastward across the eastern US and off the atlantic coast
by 12Z SAT. The southern stream portion of the upper trough will
close off into an upper level low across northern Mexico. Initially
the mid to upper level flow across the central plains will be from
the northwest but as the upper trough shifts eastward across the
easterly US, weak downstream ridging will develop across the central
and northern high plains Sunday nigh, ahead of an upper level trough
that will dig southeast over the west coast.

A surface ridge of high pressure across west TX into OK will shift
east across central TX and extend northeast into southern MO. West-
northwest surface winds this morning will gradually back to the west
and southwest through the mid morning hours and into the afternoon
hours. Deeper mixing across the western counties will cause wind
speeds to increase into the 10 to 20 MPH with some gusts of 15 to 25
MPH. The slightly deeper mixing across the western counties should
help high temperatures across north central Kansas to reach the mid
50s. The remainder of the CWA should see highs in the upper 40s to
around 50.

.LONG TERM...(Saturday through Thursday)
Issued at 324 AM CST Fri Dec 15 2017

Saturday will see the return of warmer than normal temps and
elevated fire weather conditions (see fire weather discussion
below) as southwest flow aloft is in place over the central and
southern Plains. Most guidance in agreement that H85 temps
generally could be warmer than about 10C.

Into the Sunday morning time frame, a western CONUS elongated
semi permanent trough continues to dig into the Desert Southwest
and Baja region. This will allow a low amplitude open wave to
translate into the region by early morning time frame. Chances for
precip increase into the morning with broad scale ascent
generally greater over eastern and southeastern portions of the
forecast area. Concerns for a mixed bag of precip could set up
along the KS/NE border, but due to general spread in the solutions
for temperature and depth of surface dry air in place, have only
gone with rain chances across the area. If temps do dip below
freezing at the surface and precip can actually make it to the
surface along the KS/NE border then the window for any mixed or
freezing precip remains small.

By Monday morning there may be another short window for some very
light rain in the morning as the southwest flow remains in place and
another minor wave works through the pattern.  Isentropic lift over
the area could be strong enough for some showers to develop.  The
middle part of the week should remain dry under the return of
northwest flow aloft before another positively tilted lobe of energy
digs into the northern Plains and central Plains by Thursday mid to
late day time frame.  Looks like much of the area will probably be
under the influence of a developing dry slot, so any precip should
be limited to the KS/NE border region.  As more significant cold air
works in behind the southern extent of the deformation zone could
bring some snow back into the forecast albeit briefly into the
afternoon and evening on Thursday.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 529 AM CST Fri Dec 15 2017

Expect VFR conditions at all terminals through the next 24 hours.
Moderate low-level shear may develop Tonight but may depend on the
degree in which the boundary layer decouples and if surface winds
become light. Though most numerical models show 6 to 12 KTS
south-southwest sfc winds through the night.


Issued at 324 AM CST Fri Dec 15 2017

Today, deeper mixing across Cloud and Ottawa Counties will allow the
minimum relative humidity to drop down to near 25 percent. Southwest
winds will increase to around 15 MPH with some gusts near 25 MPH.
The lower relative humidity combined with southwest winds of 15 MPH
and gusts to 25 MPH, along with dry fuels will cause a very high
fire danger across Cloud and Ottawa counties this afternoon.

Saturday will see strong gusty winds over southern portions of
the forecast area into east central KS, therefore have some
concerns for high to very high fire danger to develop. Have winds
gusting to near 30 mph in the afternoon especially south of I-70.
Minimum RH values could dip into the upper 20 percent range.




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