Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 051138
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
638 AM CDT Tue May 5 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 228 AM CDT TUE MAY 5 2015

The synoptic warm front was across eastern Nebraska early this
morning with an outflow boundary across eastern Kansas. Shower and
thunderstorm activity decreased significantly after midnight due
to the lack of overall forcing and stabilization of the atmosphere
due to convective overturning. The upper low over the desert
southwest early this morning is forecast by all the models to move
northeast today and tonight as another upper trough digs south in
the western CONUS. Eastern Kansas will be in warm sector today
with southerly flow and warm and humid sensible weather. The lack
forcing, or a trigger and only modest CAPE should result in dry
mostly weather today and the only day in the next several with low
precipitation chances.

As the upper wave moves through the region tonight, expect a band
of showers and thunderstorms to move through eastern Kansas. The 00
UTC models were in general agreement with this scenario with the
best chances for thunderstorms after midnight tonight and
Wednesday morning. Although the storms should be efficient
precipitation producers, they will be moving quickly which should
minimize their flash flood potential unless there is training.
Since there is no low-level boundary to focus redevelopment,
training storms is less likely tonight. Even so, will forecast
high POPs since the shortwave has abundant moisture and modest
instability to work with.

.LONG TERM...(Wednesday through Monday)
Issued at 228 AM CDT TUE MAY 5 2015

The overall synoptic pattern is very wet for the next several days
across eastern Kansas in the long term. No significant changes
were made to the previous forecast with moderate to high POPs
through Saturday night. The strong looking upper trough over the
Pacific Northwest this morning is forecast to curve out another
southwest US upper low by late this week. Both the 00 UTC
GFS/ECMWF bring a strong shortwave out of the desert southwest across
the plains this weekend. There will likely be severe weather
chances with this system due to it`s strong wind fields and
forcing intercepting the moist and unstable airmass across the
plains. The timing and location of the hazards are unclear at the
present time. The wave looks strong enough to push a stronger cold
front through and it should finally clear the warm and humid
airmass out of eastern Kansas sometime Saturday night or Sunday.

&&

.AVIATION...(For the 12Z TAFs through 12Z Wednesday Morning)
Issued at 633 AM CDT TUE MAY 5 2015

VFR prevails at terminals with light easterly winds becoming
southeasterly above 10 kts sustained during the afternoon. Next
cluster of TSRA will develop over central Kansas, potentially hindering
conditions as it tracks eastward overnight. Timing and duration
is still highly uncertain however appears to be after 03Z becoming
more likely after 06Z. Inserted rain shower mention with lower
confidence in TSRA impact.

&&

.HYDROLOGY...
Issued at 228 AM CDT TUE MAY 5 2015

Heavy rain across part of the forecast area, especially in the
Manhattan area, resulted in flash flood last evening. The airmass
across eastern Kansas tonight will be very moist with
precipitable water values of around 1.50 inches which is near the
90th percentile compared to climatology for May. Warm cloud depths
are large of around 10000 feet at TOP. This suggests that the
thunderstorms should be very efficient precipitation producers
with high rainfall rates. The good news is that the storms should
be fast moving and the lack of a focusing boundary should limit
the potential for redevelopment over the same area. We will need
to watch areas which were hit hard last evening tonight.

&&

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

$$

SHORT TERM...Johnson
LONG TERM...Johnson
AVIATION...Bowen
HYDROLOGY...Johnson





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