Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 261116
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
616 AM CDT Wed Apr 26 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 318 AM CDT Wed Apr 26 2017

Cool northwesterly surface winds have moved in across the forecast
area as the cold front continues to move eastward across Missouri.
Upper trof that brought the front through has additional pieces of
energy rotating through its base, with the base essentially extended
into the panhandles at this hour.  This piece and what is the
effective trof axis moves to the east of our area slowly thorough
0z, and will therefore continue to carry some low end rain chances
across the eastern counties through the afternoon. Northwesterly
winds around 15 mph diminish into the evening, keeping high
temperatures today in the 50s.

As clearing skies set in over the western and into the northern
counties as the winds lighten up, the cold airmass in place will
drop temperatures into the middle 30s not long after midnight.  Have
therefore drawn up a frost advisory for generally the northern two
rows in our area, north of I-70 and from Nemaha county westward.
Patchy frost is possible farther to the southeast, but think best
chance for areas of frost lie to the north.

.LONG TERM...(Thursday through Tuesday)
Issued at 318 AM CDT Wed Apr 26 2017

Tomorrow a mid level shortwave trough is forecasted to lift out over
the plains. As it tracks over the area later in the day upper level
divergence and isentropic lift will increase. Also, moisture
increases in the mid levels within the enhanced return flow. The mid
level lapse rates will not be that steep therefore the instability
will be limited so do not expect much thunder. A few models are
indicating a few hundred j/kg so perhaps embedded thunder may be
possible. Given the large scale lift widespread rain should develop
especially in the evening hours and spread northeastward overnight.
The models seem to focus the highest rainfall totals where the lower
convergence and upper level divergence overlap. A strong low level
jet will help supply moisture into this region and contribute to the
convergence. This area of enhanced lift is forecasted to move over
north central and far northeast KS and locations in this area could
see rainfall amounts over half an inch. Elsewhere, the lift will
not be as strong so amounts may struggle to reach a quarter of an
inch.

There may be a brief lull in precipitation on Friday before a
stronger mid level shortwave begins to lift out. On Friday night
widespread rainfall develops over most of the forecast area. Rain
will continue into Saturday with the highest amounts across east
central KS, which will be closer to a frontal zone just southeast of
the area. Saturday  night and Sunday the main mid level low pressure
lifts directly over eastern KS. Trowal precipitation should develop
as a response to the strong system. There is still some model
discrepancy on the exact track of this low pressure, which will
dictate where the location of the rainfall. Amounts during this time
frame could be as high as a few inches. The main concern for any
localized flooding will be if the rain from this system occurs in
the same place as rain on Thursday night. Given the strength of this
system temperatures may be cold enough aloft to support snow Sunday
morning in north central KS. Now temperatures at the surface will
barely be borderline unless the forecast is too warm. Regardless if
snow occurs the impacts will likely be minimal and accumulations
confined to grassy surfaces if at all.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 615 AM CDT Wed Apr 26 2017

CIGS initially MVFR in the TAFs, with some gusts to the northwest
winds. CIGS lift through the morning hours and should be VFR by
afternoon. Winds then become light into the evening hours.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 2 AM to 8 AM CDT Thursday for KSZ008>011-
020>023.

&&

$$

SHORT TERM...67
LONG TERM...Sanders
AVIATION...67


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