Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 132343
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
543 PM CST Tue Feb 13 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Wednesday)
Issued at 315 PM CST Tue Feb 13 2018 At 20Z an elongated upper
trough stretched from the northern plains through central CA per
the water vapor imagery. This left southwest flow over the area
with the main westerlies along the northern tier of the country.
At the surface, a trough of low pressure has set up along the lee
of the Rockies as a surface ridge continues to move east of the MS
river.

For tonight and Wednesday, the main forecast question is with the
boundary layer and moisture. Models do not show any obvious
shortwave within the southwest flow aloft. So forcing for widespread
precip appears to be absent. However souther low level winds are
expected to bring higher dewpoints north late tonight and Wednesday
morning. Based on forecast soundings, moisture return appears to be
fairly shallow while winds at the top of the boundary layer remain
in the 10 to 20 KT range. So there may be some shallow fog develop
late tonight. Although there is some concern that the mixing of dry
air into the top of the boundary layer could inhibit saturation.
Additionally there may be some passing high clouds as satellite
indicates some mid level moisture heading this way from the
southwest. Have a mention of patchy fog for east central KS where
there is a better opportunity for low level moisture advection. But
later shifts will need to monitor dense fog potential or stratus
formation as the NAM (which is notorious for to easily saturating
the boundary layer) shows.

Temperatures overnight should see steady or slightly warming
readings through dawn as low level moisture and warm air move north.
Think temps could drop off into the lower and mid 30s for lows.
Highs in the middle and upper 60s still looks reasonable for most
areas with upper 50s across the far north were there is still snow
on the ground. The NAM is the exception which maintains a stout
inversion and refuses to mix the boundary layer with fog and stratus
over eastern KS. Even with some morning fog or stratus, the pressure
gradient and shallow nature of the moisture favor the boundary layer
mixing out.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 315 PM CST Tue Feb 13 2018

Models are still in agreement with the cold front moving through
northeast Kansas on Thursday. However, the cold air continues to lag
behind the front with the bulk of the cold air advection in
northeastern Kansas Thursday night. This will mean another day of
above normal with highs in the 50s and 60s with a few lower 70s
possible southeast of Interstate 35. Much of Thursday night looks
dry save a small chance of rain and snow southeast of I-35.

High pressure builds into the region on Friday brining temperatures
back below normal in the 30s. This cooler air will be short lived as
return flow quickly sets with the advance of a mid level trough
moving across the Rockies Friday night. Highs on Saturday will warm
back into the 40s and 50s. Precipitation chances return early next
week as a mid and upper level trough deepens over the western states
and Rockies, although there remains differences with the models on
the timing and strength of the trough. However will maintain a small
chance of precipitation, similar to prior forecast.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 539 PM CST Tue Feb 13 2018

There may be some moderate low-level windshear as a southerly
low-level jet increases to 30 KTS. Surface winds should remain 5
to 10 KTS through the night to keep the low-level wind shear in
the 25 to 30 KT range through the early morning hours. Several
models show stratus and light fog advecting northward across the
terminals with low MVFR to IFR ceilings possible 12Z through 16Z
WED.

&&

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

$$

SHORT TERM...Wolters
LONG TERM...53
AVIATION...Gargan



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