Area Forecast Discussion
Issued by NWS Topeka, KS

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549
FXUS63 KTOP 251152
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
652 AM CDT Sun Jun 25 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 259 AM CDT Sun Jun 25 2017

Early this morning a longer wave-length trough was nearly stationary
across the east central conus. On the west side of the upper trough
axis the central plains were under northwesterly mid and upper level
flow.

Embedded shortwave troughs within the northwest flow aloft will move
southeast across the plains through Tonight. A weak cold front across
eastern NE will move southward across northeast Kansas during the
morning hours and become stationary across southeast KS and extend
northwest into west central KS late this afternoon. At 850mb deeper
moisture will advect northward into western KS then northeast across
eastern KS tonight.

Today, one minor H5 trough was moving southeast across eastern KS
early this morning There was enough ascent along and north of weak
boundary that was stationary across central and east central KS for
a few showers to develop. There has been occasional lighting
strikes early this morning across the southwest counties of the CWA.
Most numerical models show another short wave trough across western
NE early this morning digging southeast across eastern KS this
afternoon and Tonight. The NAM model forecasts the greatest QPF and
develops scattered showers and thunderstorms across north central KS
around noon and moves these showers and thunderstorms southeast
across the western and southern counties of the CWA through the
afternoon hours and into the evening. Some of higher spatial
resolution models, such as the WRF model solutions show only
isolated showers and thunderstorms developing across the southwest
counties this afternoon. The HRRR shows more shower and thunderstorm
coverage across the southwest and southern counties of the CWA
during the late afternoon hours, generally south of a Concordia, to
Manhattan to Ottawa line.

Tonight the 850mb winds will veer to the southwest and west which
may cause more in the way of isentropic lift northeast of the
surface boundary. The approach of the H5 trough from the northwest
may also increase ascent. Most numerical models forecast showers and
thunderstorms developing farther northeast across the CWA through
the night.

The instability looks rather weak with less than 50 J/kg of MUCAPE
this afternoon. This may increase slightly Tonight to reach the 100-
200 J/KG range. It will probably be enough instability for
thunderstorms.

Increasing cloud cover will probably keep highs in the mid to upper
70s north of the advancing cold front. There may be some lower 80
temps across the southern counties. Tonight lows will drop into the
upper 50s.

.LONG TERM...(Monday through Saturday)
Issued at 259 AM CDT Sun Jun 25 2017

On Monday morning there will likely be ongoing showers and storms
across the area in response to isentropic lift and frontogenesis.
Later in the day a shortwave digs over the Great Lakes region
pushing another weak front in from the north. Also, a vort max
within the trough axis tracks over far northeast KS, which should
provide additional lift along with the front. Showers and storms
should develop along this boundary although the main question will
be how much instability can be realized given the near moist
adiabatic lapse rates in the mid levels. The other inhibiting factor
will be the lingering cloud cover and precipitation which could
limit surface heating. The one concern is that the deep layer shear
is forecasted to be sufficient for organized convection. As of now
the GFS and NAM are showing mucape upwards of 1500 j/kg Monday
afternoon. So if these conditions come together strong storms can
not be completely ruled out. By late Monday evening the storms push
south of the area as 50 dew points filter in behind the front.

On Tuesday the flow aloft becomes more zonal and a mid level trough
axis extending from MT to CO will initiate convection off the front
range. This convection is expected to move eastward Tuesday
afternoon and evening. Return flow should supply plenty of moisture
sufficient for sustaining this convection across the plains. It
appears the models bring several storm clusters into northwest KS
and central NE. These storms will be supported by a strong low level
jet, mid level shear, and possibly the main shortwave trough. Either
way the models show that by midnight those storms and or the
resulting outflow reach our area. So storms appear to linger through
Wednesday over a good portion of the area. By Wednesday afternoon
and evening the main cold front begins to push into the area, which
becomes the focus for overnight convection. Thursday has the
potential for an interesting set up for storms. There could be a
surface low pressure located over central KS and a left over outflow
boundary in the area with plenty of cape and shear present. On
Thursday night the cold front finally pushes southward so widespread
storms will be likely. The weekend looks less certain with quasizonal
flow aloft and several shortwaves tracking over the region.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 649 AM CDT Sun Jun 25 2017

Expect VFR conditions for the next 24 hours. There may be an
isolated shower or thunderstorm at the terminals this afternoon
and tonight. The more widespread showers and isolated thunderstorm
will probably develop north of the terminals later Tonight.

&&

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

$$

SHORT TERM...Gargan
LONG TERM...Sanders
AVIATION...Gargan



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