Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 182326
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
526 PM CST Tue Nov 18 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Wednesday)
Issued at 301 PM CST TUE NOV 18 2014

Water vapor imagery showed the broad, expansive mid-level trough
stretched across much of the eastern two-thirds of the U.S. with the
trough axis centered over the Great Lakes region. At the surface,
high pressure prevailed across the southeastern U.S. with an area of
low pressure across the High Plains and Northern Plains. As this low
pressure dug southward across the High Plains, winds backed to the
southwest through the day. These southwesterly winds combined with
sunny skies resulting in temperatures moderating into the low/mid
30s where there was still snow cover to low/mid 40s where there was
no snow cover. Models show a weak cold front tracking eastward
across the area tonight through the overnight hours, however expect
conditions to remain dry with only some mid/high clouds developing
with the frontal passage. Winds will veer to the northwest behind
the front, resulting in similar or slightly cooler temperatures for
Wednesday with highs in the mid 30s to low 40s.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 301 PM CST TUE NOV 18 2014

The amplified longer wave length upper trough across the eastern
conus will begin to fill and shift farther east. Split upper flow
will develop across the western and central conus.

Zonal upper level flow will develop across the southern plains on
Thursday. a low-amplitude H5 trough along the AZ/NM border will move
into the TX PNHDL by 00Z FRI. A lee surface trough will develop
across eastern CO. The cold surface ridge will extended from IA,
southward into the lower MS river valley. Easterly surface winds
will keep Highs cooler on Thursday, with mid 30s across the far
northeast counties and lower 40s south of I-70.

Thursday night into Friday morning. The weak H5 trough will move
eastward across OK. Southwesterly 850mb winds will advect richer
moisture northeast over the a shallow cold airmass in place across
the CWA. The resulting isentropic lift may produce patchy freezing
drizzle across the area after midnight and into the morning hours
of Friday. Temperatures will slowly warm Friday morning and should
warm above freezing from south to north across the CWA between 700
AM and Noon. The GFS is most robust with the potential for freezing
drizzle across the CWA. The NAM and ECMWF forecast soundings show the
better chances for freezing drizzle south of I-70 with perhaps
enough ascent in the lowest 3,000 feet for freezing drizzle to
develop late Thursday night into Friday morning. In the next couple
forecast cycles, some of the mesoscale model solutions will become
available within this forecast period.

Friday, WAA and isentropic lift will continue the chances for some
freezing drizzle north of I-70 from 8 to 11 AM. Surface
temperatures south of I-70 should begin to warm above freezing
through the mid morning hours. Friday afternoon, everyone should change
over to drizzle or periods of light rain. highs on Friday will
reach the upper 30s to mid 40s.

Friday night through Sunday, a more amplified H5 trough will move
east from the southwestern US across the southern plains.
Temperatures at the surface and up to 850mb will remain above
freezing, so the stronger ascent will only result in rain chances
through he weekend across the area. Friday night some areas of
north central KS may be close to the freezing mark and if drizzle
redevelops, some of it could be freezing drizzle before temps warm
above freezing. Highs both Friday and Saturday will reach the upper
40s to mid 50s. Overnight lows will only drop off into the mid 30s
across north central KS with lower to mid 40s across east central KS.

Sunday night and Monday, As the upper trough begins to lift
northeast into the upper Midwest and mid MS river valley, colder air
will eventually be advect southward across the plains. Most of the
moisture will move the the east and northeast of the CWA. The ECMWF
has a stronger H5 trough digging southeast across NE into MO on
Monday which could provide a chance for light rain mixed with snow,
changing to light snow as vertical temperature profiles cool below 0
deg C due to advection and ascent. Too early to tell about
accumulations but the 12Z ECMWF does a band of light snow moving
southeast across the CWA during the day on Monday with QPF values
near 0.15". This could potentially give the CWA a couple inches of
snow. Monday will be colder with highs in the 30s

Tuesday, a surface ridge will move east across KS. Even with
insolation, highs will only warm into the mid 30s to lower 40s.

&&

.AVIATION...(For the 00Z TAFs through 00Z Wednesday Evening)
Issued at 526 PM CST TUE NOV 18 2014

VFR conditions should be the rule. Warm air moving in overhead in
the first several hours of the forecast leads to wind issues,
particularly wind shear. Given strong inversion and warm air
advection, have lowered the height/intensified the going LLWS
mention. Cold front passage around 06Z actually weakens wind
issues with gusts becoming common in daytime mixing after 14Z.
Shallow moisture could lead to some lower, near MVFR stratus in
this later period.

&&

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

$$

SHORT TERM...Hennecke
LONG TERM...Gargan
AVIATION...65





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