Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 231734
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1234 PM CDT Sat May 23 2015

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 304 AM CDT SAT MAY 23 2015

Scattered rain showers moving over much of the eastern half of the
forecast area at this hour.  Stronger convection noted over eastern
New Mexico. Temperatures holding generally in the 50s as clouds
continue to increase.

Isolated to scattered showers expected through the morning hours.
Wave out over eastern NM progged to lift northeast, with short range
models bringing an area of showers and thunderstorms across eastern
KS in the afternoon.  Convection ramps up considerably in the
evening as moisture in the column increases, as does lift associated
with the incoming upper trof.  As lift continues to deepen in the
saturated layer, rain processes expected to become more efficient,
and will keep start of flash flood watch as is for Saturday
evening.  PoP chances also rise in the evening and overnight hours.
Some instability in the sounding so that thunder is possible but
keeping isolated at this time.  Highs Saturday forecast in the upper
60s, before more widespread rain comes in for the evening and
overnight, with lows in the upper 50s to low 60s.

.LONG TERM...(Sunday through Friday)
Issued at 304 AM CDT SAT MAY 23 2015

On Sunday the mid/upper level low will still be located over
northern CO and southeastern WY, while waves of energy lift
northeastward over the southern and central plains. These waves
will provide additional rounds of lift and reinforce the moist
southerly flow from the gulf. The precipitable water values are
forecast to be around 1.5 to 1.75, which is nearly record numbers
for this time of year. Models show that an area of maximized
850-700 mb moisture convergence will track over eastern KS with
each wave. The moderate to heavy rainfall that is expected
Saturday night into Sunday morning could cause the ground to
become well saturated in some locations. The next shortwave that
is forecast to track over eastern KS Sunday appears to keep the
threat for moderate to heavy rainfall around most of the daytime
hours. The mostly likely areas for heavy rainfall Sunday will be
east of a line from Council Grove to Hiawatha. Rainfall totals in
these areas could range from 2 to 4 inches. By Sunday evening the
more pronounced wave will lift northward into the upper Midwest.
This should end the flash flood threat, although river flooding
will likely begin to ramp up fairly quickly Sunday evening into
Monday.

The flow aloft behind that wave becomes more southwesterly bringing
drier air into the region. This should allow for a mostly dry period
Sunday night into Monday morning. On Monday models depict another
more pronounced wave rotating around the parent low that may lift
over NE and KS. The drier southwest flow aloft will allow the lapse
rates to steepen, while the increasing surface flow pumps higher dew
points northward ahead of a boundary in central KS/NE. This will
cause cape to increase significantly if dew points can reach the mid
to upper 60s. Deep layer shear also increases, but hodographs do
show a weakness in the mid level winds, which could disrupt storm
maintenance. The main concerns though will be if the cap can erode
either due to surface heating and or the wave lifting over the area,
and strength of the low level convergence along the boundary.
Therefore did not increase pops, but there is still a chance for
isolated to scattered storms, a few maybe strong to severe, could
develop along the boundary Monday afternoon or evening and move
eastward. The most likely areas to be affected by storms will be
north central KS. How these storms evolve and become supported
overnight is uncertain. West to southwest flow aloft persists into
the late week with at least some chance for additional thunderstorms
for most periods. A few shortwaves lift out of the Rockies late
week, which could bring better chances for precip next weekend.

&&

.AVIATION...(For the 18Z TAFs through 18Z Sunday Afternoon)
Issued at 1227 PM CDT SAT MAY 23 2015

The next 24 hours is a very tricky forecast period. Bottom line is
all terminals will experience IFR GIGS at times generally
beginning mid-afternoon today. IFR VIS is not out of the question
as precipitation picks up later tonight. Don`t think an extended
period of rainfall is out of the question, which is why showers
stay in the forecast. The possibility of a period of thunderstorms
in the local areas does set up this evening with the better window
for instability. Very late in the forecast period, the conditions
should begin to show some improvement, but have chosen to not add
another line in for now as this will be the very tail end of the
forecast period and will need further evaluation at the next
forecast update.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH from 7 PM CDT this evening through Monday
morning FOR KSZ012-024-026-037>040-054>056-058-059.

&&

$$

SHORT TERM...67
LONG TERM...Sanders
AVIATION...Drake






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