Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 201724
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
1124 AM CST Thu Nov 20 2014
...Update to aviation forecast discussion...
.SHORT TERM...(Today and Tonight)
Issued at 331 AM CST THU NOV 20 2014
Surface high pressure ridge currently extending across Nebraska
into northeast Kansas has kept winds light and variable across
most of the county warning area. As the high pressure gradually
translates eastward through the day...winds will become east to
southeast across the entire but mainly under 10 mph. The last few
frames of yesterdays visible satellite imagery at late afternoon
showed that residual snowcover across portions of the northern and
far southeast county warning area continued to melt leaving very
little on the ground. Therefore snowcover is no longer expected to
be a significant factor in temperatures across the area today.
Have continued the trend of highs ranging from the middle 30s with
the colder start and weakest mixing in the far north/northeast
counties to the middle south of I 70 under mostly sunny skies.
East to southeast winds will persist tonight helping to keep lows
generally in the 20s. Mostly clear skies early this evening will
give way to some mid and high clouds before midnight. As deeper low
level moisture then surges northward towards the county warning area
later in the night...warm air advection and some isentropic lift
will aid in the northward development of a lower cloud deck.
Although lift is weak and model trends are slower...cannot rule
out the potential for some very light drizzle to develop across the
far southern portions of the county warning area before sunrise and
have kept a slight chance for this potential south of Interstate 35.
Otherwise will keep the remainder of the CWA dry overnight with
.LONG TERM...(Friday through Wednesday)
Issued at 331 AM CST THU NOV 20 2014
Models continue to show low level moisture advection and
isentropic assent within the cloud Friday morning. Initially
temps may be at or just below freezing, so have continued with a
mention of freezing drizzle early in the day. Am starting to think
that drizzle may be the predominant precip type even into Friday
night as NAM and GFS forecast soundings show the moisture
generally below 800 MB with only weak forcing and little vertical
motion. In general Friday is shaping up to be a cloudy dreary day.
Because of this I do not expect temps to warm much due to overcast
skies. Forecast soundings show very little mixing of the boundary
layer with the bulk of the warm air advection above the surface.
Because of this have highs Friday in the upper 30s and lower 40s.
Saturday through Sunday will be the period where better forcing
moves across the southern plains. Models have shown reasonable
consistency in digging a shortwave into TX and then lifting it
through MO early Sunday. This track of the wave keeps the best
forcing and deeper moisture to the south and east of the forecast
area. Although think far eastern KS stands a good chance for some
light rain so have some likely POPs the for Saturday night into
Sunday. With persistent warm air and moisture advecting at the
surface, temps will eventually warm up in spite of limited mixing
of the boundary layer. With this in mind have maintained highs in
the 50s for Saturday and Sunday with relatively mild lows of upper
30s and 40s. May even be a touch to cool for lows Saturday and
Sunday morning if skies remain overcast through the period while
dewpoints potentially rise into the lower 50.
By late in the day Sunday, a Pacific cold front is forecast to
move through the forecast area with dry air advecting in from the
northwest. The GFS and ECMWF have continued to keep shortwave
energy from the northern stream to the north as a closed low
develops over the upper Midwest. Because of this the models have
been gradually backing of the precip chances for Sunday night and
Monday, and the forecast follows this trend by lowering POPs
Sunday night and keeping a dry forecast for Monday. Some modest
cold air advection is anticipated for Monday, but with the airmass
originating from the Pacific temperatures should not be as cold as
we`ve recently experiences. Highs Monday are forecast to be in the
40s. Persistent mixing of the boundary layer is expected to help
prevent temps from bottoming out Monday morning and the forecast
has lows in the lower 30s.
Dry northwest flow is progged by the models for Tuesday and
Wednesday. There does not appear to be a great deal of warm air
making it back into the area, so lows are expected to be in the
20s while highs remain in the 40s.
.AVIATION...(For the 18Z TAFs through 18Z Friday Afternoon)
Issued at 1121 AM CST THU NOV 20 2014
Forecast challenges begin tomorrow morning as freezing drizzle and
IFR cigs move into the area. TOP/FOE look to start around 14 or
15z while coverage farther west is less certain and have started
with a prob30 group. Expect to change over to drizzle by noon hour
for TAF sites.