Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 291139

Area Forecast Discussion
National Weather Service Topeka KS
639 AM CDT Sat Apr 29 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 313 AM CDT Sat Apr 29 2017

Strong mid level low pressure was currently located over the four
corner region, while a surface front stretches from southwest TX
into southern MO. Mid level frontogenesis along the mid level frontal
zones is beginning to increase north of the surface front over NM
into southwest KS. The models are showing that this area of
frontogenesis will migrate northeastward this morning. Moisture
transport vectors become maximized over the area later this morning.
Widespread rain and embedded thunderstorms will spread across most
of the area mainly between predawn hours and mid day. Rainfall
amounts during this time frame could be as high as 1 to 1.5 inches
although the models are still struggling with exact where this axis
will set up. The consensus is east central and northeast KS, but a
few models are trending slightly westward. Regardless most locations
should receive over one quarter of an inch.

There may be a brief lull in the moderate rainfall rates this
afternoon with the exception of east central KS. As the main system
begins to lift out over the plains that surface front drifts
northward into southeast KS. Surface dew points along and south of
the front could approach the the lower 60s. During this time frame
the mid level moisture transport vectors remain maximized as the
lift continues along and just north of the surface front fueling the
convection. This will continue through the evening as the surface
low moves into southeast KS. The concern is that areas along and
southeast of I-35 could receive moderate to heavy rainfall rates and
training of storms through the afternoon and evening. The RAP is
suggesting that mucape gets over 1000 j/kg and the pwat values reach
1.75 inches in this region. There is a chance though that the
heaviest of precipitation remains just east of the area into MO. But
this area will need to be monitored for the potential for flash
flooding. A majority of the ensemble guidance both large scale and
high res support the fact that the highest rates remain just to the
southeast of the area although the mean totals are around 2 to 3
inches. Of course locally higher amounts could be possible with some
of the highest members show upwards 4 inches. Towards midnight a new
surface begins to deepen over central KS as the strong system tracks
over southern KS. The should end the heavy rain threat across
eastern KS.

Further west across central KS the mid level frontogenesis and large
scale lift continues over that region. Therefore a shield of rain
looks to persist through the evening and overnight. Luckily the
rates appear to remain relatively low therefore flash flooding is
not expected. The low level temperatures profile will remain too
warm to support snowfall across north central KS late tonight. Total
amounts in this region will be around 2 to 3 inches. Given the
forecasted rainfall totals a few of the area rivers will likely
reach flood. Therefore stay tuned to the latest forecast because
there may be changes to the amounts and locations.

.LONG TERM...(Sunday through Friday)
Issued at 313 AM CDT Sat Apr 29 2017

The intense upper low will continue to deepen as it moves across
the state on Sunday. The surface low is now forecast to move
northwest late Sat night and re-develop near Salina on Sunday
while deepening to around 992mb. The warm front/occlusion should
move north of the area leaving much of the CWA within the dry slot
by midday. Cold mid level temps may allow instability showers to
re- develop under the upper low Sunday afternoon but the more
widespread light rain or wet snow should hold off until after 00z
Monday across north central KS. At this time do not expect any
accums as the system is finally filling as it departs Sun night.

Conds should be dry on Monday however the next upper trough will
deepen across the region by Tues into Weds bringing another chance
for rain to the area. The current track of the sfc system and
orientation of the mid level trough suggest any severe threat may
stay south of the area but something to watch given time of year.
A very amplified pattern will then develop by late week but KS
should finally see ridging and dry weather into next weekend.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 635 AM CDT Sat Apr 29 2017

Widespread rain is expected across the area through the morning
and early afternoon. There may be some lulls in the rain or more
scattered coverage during the afternoon. The LIFR/IFR ceilings
look to continue through most of the period as well as the wind
speed and direction. The visibility may become lower in the more
moderate rainfall, but should stay MVFR most of the period. There
may be some isolated thunder especially at TOP/FOE through late




SHORT TERM...Sanders
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