Area Forecast Discussion
Issued by NWS Topeka, KS

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547
FXUS63 KTOP 202327
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
527 PM CST Tue Feb 20 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Wednesday)
Issued at 334 PM CST Tue Feb 20 2018

By mid-afternoon, the back-edge of the freezing rain was finally
exiting the outlook area as the system progressed into Missouri.
Surface high pressure was diving into the central U.S. behind this
exiting system, with visible satellite imagery showing clearing
skies extending into central KS as of 21Z.  This scattering cloud
cover will allow for decent radiational cooling overnight with lows
dropping into the teens.  These temperatures combined with northerly
winds continuing to gust 15 to 20 mph overnight will cause Wednesday
morning wind chill values to range from -5 to +5.  With these cold
conditions in place, there is the potential for some slick road
conditions overnight into Wednesday morning on any untreated
surfaces from today`s freezing rain/sleet event.

On Wednesday, focus shifts to an embedded shortwave that models show
near the Texas panhandle Wednesday morning and lifting northeastward
into the outlook area by late afternoon/early evening. This
advancing shortwave will cause mid-level clouds to stream over the
area through the day, thus limiting the amount of diurnal heating
with high temperatures only reaching into the low 30s.  While models
show much of the precipitation lifting northward into the outlook
area by Wednesday evening, there is a slight chance for some light
snow to move into portions of east central KS as early as late
Wednesday afternoon.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 334 PM CST Tue Feb 20 2018

Another messy weather pattern looks likely Wednesday night
through Friday morning with a mix of precipitation anticipated. By
Thursday evening, a main mid-level trough will be located over
the Central Great Basin while a lead shortwave moves across
northeast Kansas bringing a potential for snow, freezing rain, and
sleet. Soundings are consistent with a warm-nose setting up
across east central Kansas. With this nose, the NAM has
consistently been the warmest with 850mb temperatures near +7C,
while the GFS comes in slightly cooler with temperatures at +2C.
This will make a difference in whether freezing rain or more sleet
is seen in areas south and east of I-35. North of this line, the
NAM is still showing a slight warm nose making some mixed
precipition possible, while the GFS indicates all areas will be
cold enough for snow only. Late Wednesday night into early
Thursday mornings, soundings indicate a loss of ice in the cloud,
although isentropic upglide looks to continue across much of the
area leading to the potential for freezing drizzle across the area
much of Thursday morning. As for accumulations during this time,
models indicate a higher band of QPF setting up somewhere across
the area. For now, ice accumulations near a tenth of an inch or
slightly higher look most likely in areas of east central Kansas
through Thursday morning. With snow, a quick hit of an inch to two
inches is possible across areas north and west of I- 35. This
could be impacted significantly if more sleet or freezing rain is
seen than currently expected. Either way, difficult travel is
expected Wednesday night into Thursday morning.

Temperatures Thursday afternoon rise into upper 30s with the
exception of north central Kansas and areas near the Kansas Nebraska
boarder that linger near or below freezing.  Any freezing drizzle
will transition back to drizzle or rain by the afternoon as
another mid-level shortwave approaches the area with the exception
of colder areas mentioned earlier with freezing drizzle or
freezing rain may linger on through the day. Overnight, the GFS is
a bit warmer with temperatures than the NAM although they all
seems to lose ice in the cloud around 03Z. After this time, went
with either drizzle or freezing drizzle through the night on
Friday before the system finally clears. During this time, ice
accumulations look to be minor.

From here, models diverge slightly but another system looks to enter
the area Friday night, exiting by early Sunday morning.  The ECMWF
indicates a more broad trough while the GFS shows a compact
negatively tilted trough traversing the area. Dry conditions look
to remain the rest of the period with temperatures back up into
the 50s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 525 PM CST Tue Feb 20 2018

MVFR ceilings are expected at TOP/FOE until around 04z to 06z.
Otherwise VFR conditions expected.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 PM Wednesday to 6 AM CST Thursday
for KSZ054>056-058-059.

&&

$$

SHORT TERM...Hennecke
LONG TERM...Heller
AVIATION...Sanders



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