Area Forecast Discussion
Issued by NWS Topeka, KS

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996
FXUS63 KTOP 161731
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1131 AM CST Thu Nov 16 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 311 AM CST Thu Nov 16 2017

High pressure continues to move eastward across the area allowing
for dry conditions for northeast Kansas today and early this
evening.  Winds continue to veer through the morning due to return
flow setup, with southeasterly winds seen by the afternoon. This
will help enhance moisture advection through the day, setting up the
stage for some possible drizzle later in the evening.  The pressure
gradient increases through the day as a lee cyclone continues to
strengthen in eastern Colorado allowing for some wind gusts up to 30
mph today, especially near north central Kansas. Highs today are
expected to reach into the mid 50s, with only some high clouds
present in the afternoon. Later tonight, the ample low-level
moisture mentioned previously, plus isentropic lift over the area
will bring chances for some precipitation to east and east central
Kansas.  Soundings indicate saturation will remain shallow enough
that only drizzle is mentioned at this time for the overnight
period.  With clouds overspreading the area shortly after midnight,
low temperatures only fall into the mid to upper 40s.

.LONG TERM...(Friday through Wednesday)
Issued at 311 AM CST Thu Nov 16 2017

Friday through Saturday, A positive tilt upper level trough will
translate eastward across the plains Friday night and Saturday.
Ahead of the upper trough a lee surface trough across the central
and southern high plains will continue south-southwesterly low-level
flow across the southern plains into eastern KS. The 295K theta
surface shows sufficient isentropic lift occurring Friday morning
across the eastern half of the CWA, for patchy to areas of
drizzle continuing through the morning hours across the eastern
half of the CWA. The 850mb and surface winds will veer to the west
and southwest respectfully through the late morning hours of
Friday and shift the deeper residual moisture east of the CWA.
During the afternoon hours of Friday skies may clear from west to
east, and WAA at 850mb along with deeper mixing will allow high
temperatures to reach the mid to upper 60s across the eastern
counties with upper 60s and lower 70s across the western counties.
If the low clouds remain in place across the eastern counties,
then temperatures may be 5 to 7 degrees cooler.

The positive tilt upper level trough will move east into the
northern plains and southern high plains. The resulting strong
CAA across the northern and central plains will cause a surface
front to move southward across the CWA during the evening hours of
Friday. The better frontogenetical forcing ahead of the upper
trough will be across eastern NE into IA. The greater chance for
post frontal rainshowers will be across the northern and northeast
counties of the CWA. After 6Z some of these showers may spread
southeast into east central KS. The rainshowers will linger into
the morning hours but should end before noon as the H5 trough axis
moves east across the CWA and the stronger ascent shifts east
across IA and MO. Th precip should remain in the form of rain
since forecast sounding across northeast KS show a deep layer from
the surface up to 860 mb that will remain above freezing, Thus
any snow flakes aloft will melt on their way down to the surface.
Lows will be in the upper 30s along the NE border to the mid 40s
across the southeast counties.

Skies should should clear from west to east across the CWA Saturday
afternoon as stronger isentropic downglide develops. The CAA  will
keep highs on Saturday in the upper 40s to lower 50s. As a surface
ridge builds southward across the high plains and a surface trough
deepens from the southern Great Lakes States into the lower MS river
valley will result in the tightening of the pressure gradient at
the surface and 850mb. Therefore, expect a windy day on Saturday
with sustained northwest winds of 15 to 25 MPH and some gusts to
40 MPH possible during the afternoon hours.

Saturday night through Thanksgiving, Both the ECMWF and GFS show a
longer wave length trough across the eastern US with an upper level
ridge across the western US. This will keep eastern KS in
northwesterly mid and upper level flow through the period. Expect
dry weather next week. Highs will be in the 50s from Sunday
through Tuesday.

A shorter wave length upper trough will round the upper ridge axis
across western Canada and dig southeast and amplify across the
Great Lakes states into the mid Atlantic and New England by
Wednesday. A surface ridge of high pressure will build southward
across the eastern plains and Midwest. The coldest airmass will
remain east of the CWA but high temperatures on Wednesday will
drop into the mid to upper 40s. The ECMWF is a bit more amplified
with the upper trough digging southeast across New England, so
the airmass moving southward across the Midwest and eastern
plains may be a bit colder and highs on Wednesday may only reach
the lower to mid 40s.

On Thanksgiving day the colder surface ridge will move east and
southerly winds will warm high temperatures back into the 50s. Most
of the central US will remain dry. There could be some lake
effect snow showers across the Eastern Great Lakes.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1125 AM CST Thu Nov 16 2017

VFR prevails through the daytime hours. Main forecast challenge
is the stratus deck noted in Oklahoma and progged to lift
northward across terminals aft 03Z. Increasing moisture advection
will quickly transition VFR stratus down to IFR by 12Z with some
uncertainties on exact timing of each category based on models.
Southerly winds remain just below 10 kts, mitigating any
widespread low visibilities overnight. Towards the end of the
forecast period, light drizzle may impact KTOP/KFOE sites.

&&

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

$$

SHORT TERM...Heller
LONG TERM...Gargan
AVIATION...Prieto



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