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000
FXUS63 KTOP 031200
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
600 AM CST Tue Dec 3 2013

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 342 AM CST TUE DEC 3 2013

Stratus/fog continues to develop early this morning again across the
southeast county warning area. Main moisture axis and better
advection will be south and east of I-35...so have issued a dense
fog advisory for this area until 9 am for visibilities commonly at or
below a quarter mile. Areas just north and west of this line will
need to be monitored as well thru sunrise as a couple models hinting
at shallow llvl moisture advecting further north and northwest
through sunrise which would warrant an extension. Will just go with
the southeast 3 counties for now. High clouds and some mixing will
complicate the fog trends/visibilities this morning. Models continue
to slow the front until this evening and overnight. Therefore should
not see any affects on temperatures until tonight. Clouds expected
to thin enough along with increasing south winds to push highs into
the lower 60s. Forcing remains weak and moisture shallow and dry mid
levels...so will continue with a dry forecast today. Tonight, again
expect any precip to remain north and east of the CWA as the front
pushes southeast across the area. Post frontal stratus will thicken
however from northwest to southeast. Raised lows slightly with the
slower arrival of front and colder air. Temperatures by sunrise
should range from the mid 20s north central to mid 30s in the
Garnett area.

.LONG TERM...(Wednesday through Monday)
Issued at 342 AM CST TUE DEC 3 2013

For Wednesday through Saturday, the models show little reason to
make any major changes to the forecast. If anything confidence is
increasing as all the solutions are much similar with the smaller
scale features. The main question is whether we can get enough
saturation with any weak disturbance in the flow aloft to get much
snow. And aside from the far southeastern parts of the CWA, models
have been trending dryer. Think this is primarily due to the
solutions agreeing on the arctic airmass pushing the front into
the lower MS river valley by Thursday with little or no moisture
being lifted over the cold air this far north.

Think that Wednesday is more likely to remain dry, but there
remains some doubt since there should be good frontogenesis. The
models have been reluctant to bring much deep layer moisture along
with the front, but the ECMWF is hinting at some light QPF. Don`t
have much confidence since none of the other models are generating
any QPF, but I suppose a sprinkle or flurry isn`t totally out of
the question. By Wednesday night there does appear to be more mid
level moisture coming in from the west but large scale forcing
remains relatively weak so have some slight chance pops mentioned
across northern KS where models show this moisture heading.

There appears to be a couple weak disturbances lifting from the
southern Rockies into the middle MS river valley Thursday through
Friday morning with the models bringing some mid level moisture
into southeastern KS. Therefore have maintained some chances for
light snow through this period with the better chances across far
southern parts of the forecast area in closer proximity to the
deeper moisture. However have a dry forecast along highway 36
thinking there will not be enough moisture to saturate the column
for snow. At this point Anderson County may be able to pick up an
inch of snow over 36 hours, in part due to high snow to water
ratios of 17 to 1 forecast by the GFS. Think the limited
moisture north of I-35 will keep snow accumulations from a dusting
to around a half inch. The mid level moisture appears to get
shunted southeast by Friday afternoon as a subtle upper trough
axis passes through the plains. This should bring an end to precip
chances through Saturday. Cold air advection through the period
should ensure temps remain below freezing.

Saturday night and Sunday may be the better chances for snow to
impact central and eastern KS as the ECMWF and GFS bring a better
defined shortwave across the state. The one kink in the works is
the ECMWF wanting to develop some cyclogenesis in the lee of the
southern Rockies Sunday afternoon. By doing this the ECMWF
develops some return flow across eastern KS with low level warm
air advection while the GFS maintains cold air advection. However
the ECMWF does not appear to be more aggressive with its
precipitation. This difference introduces some uncertainty in
specific details, but the overall pattern looks supportive for at
least some chance pops. And the ECMWF still looks cold enough for
snow even with the southerly winds.

Chances for snow should diminish Sunday night and Monday as the
shortwave passes to the east of the forecast area. Temps should
gradually moderate, but a lack of strong warm air advection argues
for temps to remain cold into Monday.

&&

.AVIATION...(For the 12Z TAFs through 12Z Wednesday Morning)
Issued at 548 AM CST TUE DEC 3 2013

MVFR/IFR Vsbys in fog will likely continue at KTOP/KFOE until
14z before gradually improving. Only mvfr vsbys in fog at KMHK.
Otherwise...vfr conditions by the 16-17z timeframe all terminals
which will persist until 06z-07z when post frontal mvfr stratus
around 1500 ft spreads southward into all sites with gusty north
winds to 22kts.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY until 9 AM CST this morning FOR KSZ040-
054>056-058-059.

&&

$$

SHORT TERM...63
LONG TERM...Wolters
AVIATION...63