Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 192309
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
609 PM CDT Sun Apr 19 2015

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Monday)
Issued at 335 PM CDT SUN APR 19 2015

Upper low was moving east across northern Oklahoma as it was phasing
with the northern stream shortwave over the northern Plains. Latest
surface analysis at 20Z was located just to the north of I-35 and is
expected to continue to push to the southeast as the upper trough
moves east through the rest of the afternoon. Expect scattered
showers and thunderstorms to continue along the front with scattered
showers behind it through 01Z. Some small hail is possible with
storms southeast of I-35 where mid level lapse rates were steeper
near the core of the upper low. The upper level trough will move
east into Missouri and Arkansas this evening bringing an end to the
showers. Skies clear through the evening and overnight, but winds
will remain gusty through the evening before decreasing overnight.
Cold advection will send temperatures into the mid to upper 30s
across much of the forecast area with lower 40s expected in east
central Kansas.

Cooler temperatures are expected on Monday as cold air advection
continues across the area in northwest flow. Soundings show deep
mixing to almost 700 mb and expect winds to increase by the
afternoon to 15 to 20 mph with gusts to around 30 mph. Highs on
Monday are expected to range from the upper 50s to lower 60s.

.LONG TERM...(Monday Night through Sunday) Issued at 335 PM CDT
SUN APR 19 2015

In the medium range (Monday night through Wednesday), broad
cyclonic flow remains over the eastern CONUS with the southern
stream from the desert southwest through the southern plains. A
few reinforcing shots of cool air should move through northeast
Kansas during this period as the cold air is pulled south in the
cyclonic upper flow. The 12UTC models are in good agreement with
the overall pattern, but there are subtle timing differences with
respect to shortwave energy, frontal passages and associated
precipitation chances and temperatures.

The immediate concern in the medium range is the potential for frost
Tuesday morning.  Both the 12UTC GFS/NAM are forecasting a weak
surface boundary over northeast Kansas Tuesday morning with some
weak forcing aloft and mid-level RH.  Although not enough to support
precipitation, the mid-level forcing should be enough to support
some cloudiness.  The 12UTC model temperature guidance was a little
warmer than the previous forecast and the min temperatures were
adjusted a little warmer.  Given the light surface winds, the could
be some light frost depending on the how much cloudiness there
is.

Another boundary moves through late Tuesday night or Wednesday
morning.  The GFS is faster than the NAM and both models produce
some light qpf in association with this boundary. Used a compromise
for the POPs/weather with the precipitation chances in the southern
part of the forecast area. The 12UTC ECMWF is even faster than the
GFS which supports keeping small precipitation chances south.

Concerning temperatures, they were adjusted down Wednesday and
Wednesday night due the degree of cool moving into the area
following the frontal passage early Wednesday morning or Wednesday
depending on the model solution.

In the extended (Wednesday Night through Sunday), dominant upper-
level closed low is situated over Ontario while another closed low
is located right off the coast of southern California. This leaves
split flow over the area until Friday when the low over California
pushes onshore and this shortwave dominates the rest of the
period. This wave is forecast to track over our area on Saturday,
leaving increased precipitation chances Friday night to Saturday.
From here, another slight chance of precipitation is seen Sunday
associated with a smaller shortwave. Overall, instability is
limited with these systems and expect mostly rain with possible
isolated thunder for the period. Highs Thursday through Sunday
remain in the low to mid 60s, slightly cooler than climatological
normals. Lows stay in the 40s.

&&

.AVIATION...(For the 00Z TAFs through 00Z Monday Evening)
Issued at 604 PM CDT SUN APR 19 2015

Upstream observations indicate ceilings will improve to VFR at
KTOP/KFOE shortly after 0Z with some lingering sct MVFR stratus
and the light rain showers. Shower activity is expected to exit by
03Z from terminals while northwest winds back towards the west
near 10 kts through the evening. Northwest winds increase above 12
kts once again in the afternoon with gusts above 20 kts.

&&

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

$$

SHORT TERM...53
LONG TERM...Johnson/Heller
AVIATION...Bowen






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