Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 120439
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1139 PM CDT Fri Jul 11 2014

...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Saturday)
Issued at 251 PM CDT FRI JUL 11 2014

Recent water vapor imagery and 12Z upper air data put the center
of the upper high over western Kansas. Thermal gradient at 700MB
had weakened considerably from recent days but warm air advection
remained with nearby dewpoints at this level around 8C. 315K theta
modeled isentropic surfaces showing end of the lift taking shape
over the next few hours and expect any remaining isolated showers
to end by late afternoon. Recent surface obs and objective
analysis put a cold front from southwest to northeast across South
Dakota.

Cold front, likely aided by outflow from late afternoon and
nighttime convection, should be entering northern locations late in
the afternoon Saturday. A relatively dry lower and middle
troposphere will be in place ahead of the boundary, keeping
instability less than 1000 J/kg and at least minor CIN in place.
Will keep PoPs small at this point. Beforehand, moderate south to
southwest winds will keep a very warm airmass in place. Expect lows
to be a bit warmer than this morning with somewhat stronger winds,
and highs very similar to today. Dewpoints will again support heat
index values slightly above highs, around 100F.

.LONG TERM...(Saturday Night through Friday)
Issued at 251 PM CDT FRI JUL 11 2014

Since models continue to show disorganized forcing for convection
at best with much of the low level moisture pooling behind the
initial front, precip chances could be tied pretty closely to the
lift provided by the fronts as they move through the area. Based
on model consensus, the initial front looks to move into the area
by Saturday evening while the main push of cold air moves through
on Monday, and this is where the POPs are relatively higher.
Instability and shear continue to look marginal for organized
severe storms Saturday evening. For Monday, deep layer shear
increases as the closed mid level low propagates south into WI
strengthening the flow over the plains. However instability appears
to be limited with no real chance for the boundary layer to
recover from the fist front. Therefore a widespread severe weather
threat looks unlikely at this time. However Monday looks like it
might be the best chance for precip across the forecast area as
the NAM and GFS show some Q vector convergence along the frontal
zone and some vorticity advection ahead of a subtle trough axis
rotating around the southwest flank of the closed upper low. Still
not convinced everyone will see rain so have POPs on Monday at 50
percent for now.

Sunday should see a slight cool down behind the first front but
think there will be enough insolation for highs to make it into
the mid and upper 80s. The cool down for next week still looks on
track, if not a little quicker than previously forecast. Trimmed a
couple degrees off highs for Monday with models bringing strong
cold air advection into northern KS by Monday afternoon. Then The
unseasonably cold air arrives for Tuesday and Wednesday. The
forecast seems to be in good shape relative to the new runs, so
have not made any significant chances to the temps forecast. By
the end of the week, the airmass should modify with highs warming
into the 80s once again. Continued with a dry forecast for Tuesday
through Friday with the surface high pressure system over eastern
KS. Not sure moisture return within the upslope regime across
western KS will be very strong, but there are signs of weak
impulses within the northwest flow aloft. For now any of this
activity looks to remain to the west and southwest of the area.

&&

.AVIATION...(For the 06Z TAFs through 06Z Saturday Night)
Issued at 1117 PM CDT FRI JUL 11 2014

VFR conditions expected at terminals as south winds below 10 kts
increase and become gusty from the south southwest aft 15Z. A cold
front will enter northeast Kansas with scattered TSRA near the
Nebraska border between 00Z and 06Z. TSRA may have an impact on
KMHK/KTOP/KFOE just after forecast period between 06Z and 12Z.

&&

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

$$

SHORT TERM...65
LONG TERM...Wolters
AVIATION...Bowen





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