Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 221107

607 AM CDT Fri May 22 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 246 AM CDT FRI MAY 22 2015

A cool start to the day today as overnight lows have fallen into the
lower 50s for much of the area.  Eastern Kansas sees a return to
southerly winds today as surface high moves to the east and next
upper shortwave trof is on approach.  Wave noted in WV imagery over
Western Oklahoma progged to aid in increased rain chances as the day
goes on.  Observed sounding from last night and forecast soundings
off the NAM are relatively dry through the column, with PW values
around half an inch.  Much of the morning will be spent increasing
mid level moisture through the atmosphere, and spreading from west
to east and saturating from the top down with time as lift from the
wave increases. CAPE values remains low, and have kept precip
chances as rain at this time, and will monitor for any additional
wording for thunder.  Highs anticipated in the low 60s, with rain
continuing through the mid morning into the evening and overnight,
although expect breaks at times especially between the two shortwave
systems in the late evening.

.LONG TERM...(Saturday through Thursday)
Issued at 246 AM CDT FRI MAY 22 2015

On Saturday waves of energy begin to eject out of the southwest US
as the main trough lifts northeastward over the central Rockies.
Moisture surges northward as the low level flow becomes more
southerly out ahead of the system. Scattered showers and
thunderstorms appear possible most of the day Saturday, although
the severe potential remains low since the instability will be
limited. Forcing increases late Saturday as most of the models
depict a complex of precip moving up from the southwest. This will
set the stage for a round of moderate to heavy rainfall during the
overnight hours. Pwats look to increase above 1.5 inches while the
850-700 mb moisture transport vectors maximize over eastern KS. The
models begin to struggle with how long this area of precip sticks
around on Sunday. The main problem seems to be the slow eastward
progression of the main mid/upper level low pressure as the upper
level jet continues to build the downstream ridge aloft. Although,
parts of central KS look to clear out during the day Sunday and end
up with the lowest amounts. The NAM depicts a freezing level around
12 kft with a warm cloud depth of around 11.5 kft. This means that
warm rain processes will be more efficient in squeezing this high
moisture content out of the air. Rainfall amounts today through
Sunday night appear to be between 1-4 inches with the highest
amounts in east central and southeast KS. With saturated ground and
elevated river levels, flooding continues to be the main concern.
There is a less potential for flash flooding, but it still remains
possible especially Saturday night into Sunday if storms can train
over the same areas.

On Monday the mid/upper level system tracks over the northern
plains and drags a boundary into central KS. Models are
indicating that instability will increase ahead of this boundary
as the cin decreases and more shortwaves lift northeastward over
the region. Deep layer shear becomes marginal during this time
frame so some severe storms could be possible. Ongoing morning
convection and the evolution of the shortwaves make it difficult
to pin down any specifics. Models then continue with the west to
southwest flow aloft through the week with several waves
progressing over the region. Some instability hangs around with a
weak cap in place although deep layer shear is basically non
existent, so do not expect any widespread severe storms.


.AVIATION...(For the 12Z TAFs through 12Z Saturday Morning)
Issued at 605 AM CDT FRI MAY 22 2015

Made only slight adjustments to previous TAF issuance. Brought
rain in an hour sooner and added VCSh ahead of its arrival, and
along with the rain are some lower clouds and have added a sct
group for that. Still difficult to pinpoint highest focus for
precip chances beyond the first 6 hours or so and should be able
to refine overnight chances as timing draws closer..




LONG TERM...Sanders
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