Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 211139

539 AM CST Fri Nov 21 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 353 AM CST FRI NOV 21 2014

Early this morning the upper air maps showed split mid and upper
level flow across the western US and plains states. A weak upper
level trough was embedded within the subtropical jet across the TX
PNHDL. A more amplified upper level trough was located across
southern CA.

Ahead of the H5 trough across the TX PNHDL, southerly 850mb winds
were advecting moisture and warmer temperatures northward across OK.
Forecast soundings across the CWA were quite dry in the low-levels
early this morning. Temperatures were in the lower to mid 20s across
much of the area. As the richer moisture begins to advect northward
this morning the isentropic lift across southeast KS on the 285
theta surface will increase. The resulting isentropic lift will
cause low stratus to form and spread northward across the CWA after
12Z. The dry low-levels of the atmosphere will prevent drizzle from
south of I-35 until after 15Z at the earliest. All the mesoscale
models are showing temperatures warming through the mid 30s by the
time any drizzle does form south of I-35 by 16Z. Temperatures across
the remainder of the CWA will begin to warm into the mid to upper
30s by 18Z. Most numerical models show drizzle and perhaps periods
of light rain expanding northward across east central and northeast
KS during the afternoon hours due to increasing isentropic lift and
ascent ahead of the H5 trough lifting east-northeast across northern
OK and KS during the afternoon hours. The slightly deeper moisture
will probably not expand into north central KS as 850mb will veer
through the day to the south-southwest. Therefore, the best rain
chances this afternoon will be across east central and northeast KS.

High temperatures will gradually warm into the mid to upper 40s
across east central KS with lower 40s across the remainder of the

Tonight the best rain chances will remain across east central KS as
850mb trajectories will continue to transport deeper moisture
northeast from western OK, across south central KS, then northeast
into east central KS. The WAA will keep temperatures nearly steady
in the mid to upper 40s across the southeast counties of the CWA.
Lows across north central KS will drop into the mid 30s. The more
amplified upper level trough across southern CA this morning will
dig east-southeast into far west TX by 12Z SAT.

.LONG TERM...(Saturday through Thursday)
Issued at 353 AM CST FRI NOV 21 2014

Models consistent on the translation of strong shortwave trough from
the TX Big Bend area eastward into central TX thru the day on
Saturday before lifting negatively tilted into southern MO by midday
Sunday before phasing with the northern stream trough over the Great
Lakes region into Monday. As this occurs the sfc low will also lift
from OK into MO by Sunday then on into Lake Michigan Sunday night.
With the upper level forcing more in proximity to the front boundary
to the will keep the heavier rainfall amounts south and
east of the county warning area through the weekend. Although
precipitation will be extensive at times...the limited depth of the
moisture fields and forcing most precip to very light rain or
drizzle. The one exception may be south and east of I 35 Saturday
afternoon and night when deeper moisture and some elevated
instability may briefly surge northeastward across this area for a
period of higher rainfall amounts. Still...rainfall totals across
the area through the weekend will generally range from less than a
tenth of an inch in the northwest half of the cwa to a half to
locally three quarters of an inch south and east of I 35.

Highs for Saturday still look on track to be in the middle to upper
50s...but cooler in the low to middle 50s with the surging cold
front on Sunday. Although there may be a brief window for a
rain/snow mix Sunday accumulation is expected as the
drier air aloft and subsidence surges southeastward.

It should remain dry from Monday through Wednesday before a
northwest flow shortwave trough brings a chance for rain or snow
to the area Wednesday night into Thanksgiving Day. Following highs
in the 30s and lower 40s Monday...highs should be in the 40s for
Tuesday and Wednesday. Colder air will then overspread the area by
Thanksgiving with highs in the 30s.


.AVIATION...(For the 12Z TAFs through 12Z Saturday Morning)
Issued at 536 AM CST FRI NOV 21 2014

VFR conditions are expected to hold until 16Z, when MVFR stratus
will move into the area.  SHRA with drizzle will begin between
17-18Z, keeping ceilings between IFR/MVFR throughout the day with
MVFR visbys.  Have introduced MVFR visibilities after 06Z at all
terminals with the increased possibility of fog tomorrow morning.
Locally denser fog is not out of the question, but will keep this
out of the TAF until there is greater confidence.




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