Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 300012
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
712 PM CDT SAT AUG 29 2015

...Update to aviation forecast discussion...

.SHORT TERM...(THIS EVENING THROUGH Sunday)
ISSUED AT 344 PM CDT SAT AUG 29 2015

Elongated upper trough axis is currently stretched this afternoon
from the Great Lakes region, southwest towards eastern OK. Weak
embedded impulses were filtering southward towards Missouri during
the day and tonight periods. Towards the sfc, the 850 mb front and
closed low are centering over the CWA this afternoon with shallow,
yet persistent stratus that has been unable to overcome the strong
inversion seen earlier this morning. Weak mixing through the day
will likely leave most of east central KS mostly cloudy to overcast.
Over north central KS, increasing subsidence is gradually eroding
cloud cover eastward. In addition to the cloud cover, weak lift
advecting through the area may develop light showers or an isolated
storm for areas just east and south of the CWA. Confidence in
showers impacting CWA are too low to mention pops at this time.

There is definite uncertainty with guidance on how far eastward
cloud cover clears by this evening. Based on current trends, have
kept partly to mostly cloudy skies through much of the evening as
the surface inversion and adequate BL moisture increase shortly
after sunset. Believe low level stratus and fog are once again
likely after midnight through sunrise Sunday. Setup suggests areas
of haze or fog, but there is some question of dense fog forming
based on the coverage of low stratus so will not issue any headlines
at this time. Lows tonight fall to the lower 60s.

On Sunday, 850 mb low shifts southward in response to incoming
trough builds into western KS. Frontal boundary in this layer
lingers over far east central areas where stratus may linger through
the afternoon. Temps therefore are in question, like today, where
highs may only reach the low or mid 80s for eastern areas.
Otherwise, mostly sunny skies for north central KS will peak highs
in the upper 80s.

.LONG TERM...(Sunday NIGHT THROUGH Saturday)
ISSUED AT 344 PM CDT SAT AUG 29 2015

Upper ridging will spread east with time during the Sun night
through Tues period with sfc-850mb response expected to be a gradual
southeast to south flow re-establishing. NAM is trying to generate
precip Sun night but given CAA at 850mb and lack of other focus and
building hts will keep conds dry.  Highs will gradually warm to
around 90 both Monday into Tuesday when a weak wave will move into
the northern plains and could bring some low chcs for storms to
north central Kansas late Tues more likely into Tues night.

By mid week, the western edge of the main ridge axis extending along
the Appliachains will continue to be flattened by a series of weak
shortwaves moving out of Colorado into Nebraska.  These will be the
main weather makers into at least Wednesday morning, but most
forcing appears to remain to the North of the forecast area.  So
small chance POPs have been kept over areas mainly North of I-70.
Meanwhile, a longwave trough will be digging into the Pacific
Northwest, which in turn will re-amplify the longwave ridge over
Southern MS Valley into the Great Lakes region.  Heights will
generally rise into the Saturday time frame.  As the previously
mentioned trough begins to deepen and lift into the Northern Rockies
and Central Canada, it wouldn`t be unreasonable that another series
of shortwaves could move out of the Rockies and into the Central
Plains helping to develop some isentropic lift early into mid-day
Saturday over North Central KS into Central and Eastern Nebraska.

Temps could push into the mid 90s by Thursday, especially over East
Central KS. Low temps will generally be in the upper 60s.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z Sunday EVENING)
ISSUED AT 704 PM CDT SAT AUG 29 2015

Clouds and areas of fog will be the main forecast challenge over
the next 12 to 15 hours. Moisture remains trapped below a strong
subsident inversion aloft at around the 5000ft level per 00z KTOP
sounding. Could be a few breaks in the cloud cover between now and
9-10z, which should help set the stage for potential fog
development or at least very low stratus at all terminals between
the 10z and 15z time frames. The potential to dip into the
IFR/LIFR categories seems reasonable given the moisture and the
expectation of winds to calm overnight. The good news will be that
after 15z, conditions are expected to improve and by the 18z time
frame skies should begin to trend toward VFR for the rest of the
forecast period.

&&

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

$$

SHORT TERM...Bowen
LONG TERM...Drake/Omitt
AVIATION...Drake


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