Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 241125
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
525 AM CST Fri Feb 24 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 250 AM CST Fri Feb 24 2017

Early this morning the mid-level low and trough were tracking
eastward across NE/IA and far northern KS with the surface low
having already exited eastward into Missouri.  A tight pressure
gradient on the back-side of this low will result in breezy
northwesterly winds early this morning and through much of the day
with gusts of 25-30mph.  This strong northwesterly flow will support
decent cold-air advection through the day, with early morning low
temperatures near/below freezing across north central KS and into
the mid/upper 30s over east central KS.  Ongoing cold-air advection
through the day will result in a non-diurnal temperature trend with
highs only reaching into the low 30s to low/mid 40s by early
afternoon from northwest to southeast across the CWA before falling
through the remainder of the day.

While the better moisture and lift associated with the advancing mid-
level trough was situated over NE and IA, shallow low-level moisture
was extending into far northern KS early this morning, resulting in
some areas of drizzle.  Model soundings show this shallow moisture
layer up to around 850mb persisting through mid-morning before the
saturation depth increases.  With surface temperatures across north
central KS this morning near or below freezing and with no
saturation noted in model soundings within the dendritic growth
zone, areas of light freezing drizzle/mist were being reported early
this morning and this light freezing drizzle will remain possible
through mid-morning for locations generally along and northwest of a
Minneapolis to Manhattan to Seneca line.  The recent stretch of
unseasonably warm weather has helped to keep road temperatures well
above freezing, however bridge temperatures were in the 30s and may
drop to near freezing.  As a result, some bridges across north
central KS may become slick this morning as some light ice
accumulation will be possible.  As the moisture depth increases by
late morning into this afternoon, saturation will occur within the
dendritic growth zone.  This saturation combined with temperatures
falling into the low/mid 30s will result in precipitation
transitioning to light snow across north central to northeast KS.
With the warm ground temperatures, it will be difficult to
accumulate much snow, so expect any snow accumulations to remain
less than one-half inch.  Much of this precipitation should remain
generally along and north of I-70, and exiting from west to east
across the CWA late this afternoon into this evening with dry
conditions expected by late this evening.  With the cloud cover
expected to scatter out some overnight into Saturday morning and
with northwesterly winds persisting, expect low temperatures tonight
to plunge into the upper teens to low 20s.

.LONG TERM...(Saturday through Thursday)
Issued at 250 AM CST Fri Feb 24 2017

High pressure will dominate the region on Saturday in the wake of
the significant storm system of Thurs/Fri. Temperatures will be
cooler but really only a few degrees below normal with highs in
the low to mid 40s and generally light winds. Expect a bit of
southerly return flow by Saturday night with lows probably holding
in the mid to upper 20s amidst good boundary layer mixing and
expectations of increasing cloud cover after midnight.

A weak upper short wave trough will cross the area on Sunday with
modest moisture and isentropic ascent in the lower levels. This
may be sufficient to support an area of light precipitation but
the overall quality of moisture and lift appears quite meager so
have kept precip chances very low. If precip develops, it seems
likely that wet bulb effects would result in cooler temperatures
and a snow or rain/snow mix during any precip periods. In the
absence of precip, which is more likely, expect a bit of a
warming trend and could see highs approach 50.

For Monday through Wednesday, the fast WSW to ENE flow aloft with
several embedded weak short waves is agreed upon by model
guidance in a broad sense. However, the timing and strength of
individual waves as well as moisture quality (or lack thereof)
are significant question marks when evaluating any given model,
and particularly in trying to find any run-to-run or model-to-
model consistency. The end result is multiple periods with a
chance of rain or snow and a more-uncertain-than-normal
temperature forecast as the presence of clouds and/or precip would
keep daytime temperatures markedly lower. All told, believe there
is potential for 1-2 periods of light accumulating precip during
this 3 day stretch but the exact timing of those best chances is
uncertain and any precip would likely be light with minimal
impacts.

The weather pattern looks totally dry under northwest flow for the
second half of the week with above normal temperatures again
expected through the period...although with a caveat that one or
more short-lived colder snaps can be expected as the west edge of
cold fronts will impact the local area.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 525 AM CST Fri Feb 24 2017

MVFR ceilings are expected to persist through the afternoon, only
lifting after 00-02Z for all sites. Gusty northwest winds will
persist through most of the period as well, with gusts up to 28
kts expected. Have kept the chance for VCSH at sites, with any
precipitation expected to be light.

&&

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

$$

SHORT TERM...Hennecke
LONG TERM...Barjenbruch
AVIATION...Heller


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