Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 281701
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
1201 PM CDT THU APR 28 2016

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 307 AM CDT THU APR 28 2016

08Z water vapor imagery shows a closed upper low over western IA
moving to the north while a second upper low moves towards the four
corners region. Surface observations show low pressure over the mid
MO river valley weakening as high pressure builds in from the
northwest.

Today is expected to remain dry with the area generally under the
influence of upper subsidence from the upper closed low to the
north. Models continue to show cool and dry air advecting in from
the northwest through the day. This should cause afternoon highs to
generally by near or slightly cooler than seasonal norms. Have highs
ranging from around 60 near the state line where low clouds may
limit insolation, to the mid 60s across east central KS.

Forcing for precip is expected to improve tonight as the upper low
over the southwest starts to move into the southern high plains.
This should cause cyclogenesis to occur over the TX panhandle. As it
does, models prog moisture to begin advecting north over the cool
high pressure over northeast KS. Additionally there may be some weak
vorticity advection into eastern KS as the upper patter becomes
southwesterly. The stronger forcing still looks to remain more to
the west of the forecast area where upper diffluence and better PVA
is progged. Nevertheless with the low level warm air advection
pattern, think precip chances will be on the increase from west to
east during the late evening and overnight hours. Instability over
the forecast area appears to be fairly limited. Although mid level
lapse rates suggest there could be a few thunderstorms across east
central KS. Surface winds from the north and northeast overnight
support the models weak cold air advection pattern, so lows Friday
morning should be brisk once again with readings from the mid 40s to
around 50.

.LONG TERM...(Friday through Wednesday)
Issued at 307 AM CDT THU APR 28 2016

Friday begins with the upper level low located over the Four Corners
region forecast to move northeast over eastern Colorado by late
Friday evening. Ahead of this system, an increase in deep layer
moisture will lead to overcast skies and chances for rain and
thunderstorms Friday. For this time range, models indicate the
best instability remains west and south of the area. The main
concern for stronger thunderstorms would be late Friday night and
Saturday as the main wave moves through. With CAPE values anywhere
from 500- 1500 J/kg and 0-6 km bulk shear in excess of 40kts,
strong to severe thunderstorms will be possible during this time
frame. The main hazards with any potential storms would be strong
winds and hail. The best precipitation chances shift north as the
surface low moves over east central Kansas by Saturday afternoon.
The surface low shifts over Missouri on Saturday night, as the
main upper level closed low is ingested into the open wave trough
over the northeast CONUS. Lingering rain showers may be seen on
Sunday before the system completely clears the area and moves
eastward. For Friday and the weekend, one to two more inches of
rain may be seen across the area, possibly leading to more
flooding problems due to the saturated grounds and already
cresting rivers.

From here, the overall pattern begins to differ between the GFS and
ECMWF.  The GFS keeps northeast Kansas dry from Monday through the
end of the period as surface high pressure builds in across the
central US. The ECMWF brings a shortwave over the area Monday
afternoon allowing a small chance for precipitation Monday
afternoon and evening before the surface high pressure allows for
dry conditions. Kept what superblend had loaded in for Monday
night with very small precipitation chances, mainly in east
central Kansas, due to model uncertainties.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 1158 AM CDT THU APR 28 2016

After a struggle to get out from under the MVFR deck this morning,
cigs going to sct at issuance. Expect this trend to continue and
have kept TAFs VFR at this time. Winds become north then
northeasterly through the period. Chance of showers after 06z but
not enough confidence to be in TAF at this time.

&&

.TOP Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Wolters
LONG TERM...Heller
AVIATION...67



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