Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 252154
AREA FORECAST DISCUSSION
National Weather Service Topeka KS
354 PM CST WED NOV 25 2015
.SHORT TERM...(This Evening through Friday)
Issued at 352 PM CST WED NOV 25 2015
Last of several quiet days of weather today, with breezy south winds
and highs rising into the 60s. Upper low that impacts our weather
over the next several days continues to spin over Nevada, with
little eastward progress. Plume of moisture is streaming northward
out ahead of the system in south to southwesterly flow aloft.
Several waves noted embedded in the flow, from the Central Plains
all the way out to southern California. Meanwhile, upper longwave
trof moving over central Canada continues to aid in driving a cold
front quickly southward into the Central US. Temperatures in Great
Bend Kansas are in the middle 60s, but quickly become the 30s as
close as Norton Kansas as the front comes southward.
Through the noon hour tomorrow, moisture continues to move northward
over the area, with enough lift developing this evening and
overnight to bring periods of rain showers and drizzle. Overnight
lows hold well into the 50s over the southeastern counties while the
far northwestern ones drop into the 30s toward the morning hours as
the front comes through. Precipitation at this time is expected to
remain as rain for tonight into tomorrow morning.
By around the noon hour Thursday, broad area of frontogenesis
develops over north central Kansas and acts to increase rainfall
rates and amounts. Problems arise as the cold northern high slides
under the warmer air and precipitation that was initially falling as
rain, now falls into the cold dome at the surface over NC Kansas. As
the cold air gets deeper, ice is expected to start to accumulate
after noon, with this impact spreading to the southeast through the
day. Confident enough in a quarter inch of ice to upgrade the watch
to a warning for areas northwest of Manhattan. Warm nose aloft gets
quite strong and deep the farther southeast across the area, with a
changeover near Manhattan late afternoon, and perhaps not getting as
far southeast as the Topeka area until sunrise on Friday.
It becomes a race between the lift, the moisture, and how much falls
as rain first, before ice begins to accumulate on surfaces. Highest
confidence is where watch has been upgraded to a warning northwest
of an Abilene to Seneca line, and may end up needing advisories to
the southeast f this as the system moves eastward with time. Will
carry watch/warning from Noon Thursday through 6am Friday.
Friday may also be problematic depending on how much precipitation
actually falls. Dry cold air continues to deepen at the surface
while the southwesterly moisture plume continues over the top.
Accumulations are forecast to be light, but are also more likely to
be of a frozen variety. Again will need to monitor for updates and
In addition to the changeover to wintery mixed precipitation, the
system is preceeded by a generous amount of rainfall across about
the eastern half of our forecast area. Widespread 1 to possibly 2
inches of rainfall are possible, but expected to fall at a slow
enough rate to keep widespread flooding a concern. Plenty to cause
ponding on roadways on a busy travel day, however.
.LONG TERM...(Friday Night through Wednesday)
Issued at 352 PM CST WED NOV 25 2015
Main questions through the weekend into Monday are the timing of the
upper low`s movement east through the region, any shortwaves
rotating around it before it exits, and of course the lower to mid
level atmosphere over which any of these things occur. Confidence in
much of these items is rather low, but at least early on have better
confidence in the bulk of the precip in the southern areas or even
south of the local area. Northeast to east winds off the surface
bring at least somewhat drier air into northern areas Friday night
and Saturday so have lowest PoPs there. ECMWF and Canadian bring a
lead wave through Saturday, but better agreement on deeper forcing
comes Saturday night with at least early, modest isentropic upglide
just ahead of it. Wintry mix bag of precip still anticipated with at
least a modest warm nose to deal with and varying moisture depths
for unknown amounts of ice availability in the cloud. Models diverge
rather noticeably with the main low`s speed by Sunday. Have lowest
confidence in any measurable precip occurring Sunday with the area
likely behind the Saturday night wave but will keep chance pops
going Sunday night and Monday. Precip types obviously more of a
challenge at this range and have kept wording more broad. Staying
farthest from the cold/fast ECMWF brings a slow warming trend
however and less concern for impacting precip phases.
Upper low finally moves northeast of the area Monday night allowing
for dry conditions through the end of the period. A surface high
pressure will advance east into central Kansas by Tuesday afternoon.
High and low temps Monday night through Wednesday will be near
climatology topping out in the mid-40s with lows in the mid-20s.
.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1125 AM CST WED NOV 25 2015
Conditions initially MVFR and becoming IFR on or after 0z at
terminals as precip and deep moisture continue to spread northward
today and tonight. Widespread rain expected at terminals by early
morning hours, with changeover to frozen precipitation outside the
scope of this TAF period.
Winter Storm Warning from noon Thursday to 6 AM CST Friday for
Winter Storm Watch from Thursday afternoon through late Thursday
night for KSZ011-012-022>024-026-035>039.