Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 261116
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
516 AM CST Sun Feb 26 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 250 AM CST Sun Feb 26 2017

Early this morning fairly zonal mid-level flow was in place across
the central U.S., with water vapor imagery showing a weak
disturbance over central/south central KS.  Regional radar imagery
was showing some light reflectivity returns over central KS with the
increasing mid-level moisture.  However, much of this precipitation
early this morning was likely struggling to reach the ground due to
the low-level dry air in place.  While there were still some model
discrepancies with regards to whether or not this mid-level moisture
will saturate low enough for precipitation to reach the ground,
enough models were showing this moisture overcoming the low-level
dry air.  As a result, have slight to chance PoPs in place by around
sunrise through the mid/late morning hours across east central KS
before this weak disturbance shifts east of the area.  Temperatures
this morning will continue to hover near the freezing mark before
moderating into the upper 30s/low 40s by mid/late morning.  As a
result, any initial light precipitation that develops would likely
be in the form of snow before transitioning to rain.  Do not expect
much QPF from this passing wave, so little to no snow accumulation
is expected.

As this wave shifts to the east by this afternoon, the cloud cover
will begin to scatter out.  This scattering cloud cover combined
with west/southwesterly winds this afternoon will allow temperatures
to quickly rise into the low 50s across much of the CWA.  With
mostly clear skies across the region by tonight, expect enough
radiational cooling to drop low temperatures into the mid 20s to low
30s.

.LONG TERM...(Monday through Saturday)
Issued at 250 AM CST Sun Feb 26 2017

Monday will feature substantial warm advection into the area as a
surface low tracks from northeast CO along the NE/KS border
through Monday night, and expect highs around 60 although some
potential to go warmer or colder based on presence of low cloud
cover. Will also have a chance for rain showers with a focus in
eastern KS as the warm front lifts north through the area with a
zone of focused isentropic ascent shifting north along with the
front. South winds overnight will keep lows mainly in the 40s and
have mentioned potential for patchy fog in the NW part of the
forecast area as locations along/north of the sfc low track have a
decent setup for fog development. The passage of the low will push
a cool front into the area with a stronger surface low developing
over northwest OK on Tuesday. This should result in a pretty good
temperature gradient across the area on Tuesday with highs in the
warm sector in the 70s and 50s on the cool side.

On Tuesday evening, model guidance is coming into stronger
agreement in the development of a band of light to moderate
precipitation extending SW to NE across the forecast area. The
forcing mechanisms for this precip are pretty impressive with
moderate to strong mid level frontogenesis, moderate pressure
advection on the 1.5 PVU surface, a bit of isentropic ascent, and
presence of CSI and even some CI. Mid and upper level moisture
content is good, but the low levels are very dry. Current believe,
supported by virtually all model guidance, is that precipitation
efficiency will be sufficient to overcome dry air and reach the
surface, especially in the band of greatest vertical motion. Any
precip should begin as rain given warm temperatures but wet bulb
profiles still suggest a transition to snow. The main question is
how quickly this will occur. At this time have not gone aggressive
with snow in the forecast, but there remains a slightly less
probable scenario where a relatively narrow band of moderate
accumulating snow could develop owing simply to rapid wet-bulb
effects and potential for quality snowfall rates to out-pace
melting rates from the warm ground. The primary time frame for
snow potential seems to be from around 9 PM to 3 AM.

Cooler (but still near-normal) temperatures arrive behind this
system on Wednesday, but then expect another warming trend through
the remainder of the forecast with highs once again well into the
60s for next weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 516 AM CST Sun Feb 26 2017

Light snow is expected to impact MHK at the beginning of the period,
and TOP/FOE shortly thereafter at 13Z.  There may be brief MVFR
conditions as this precipitation passes.  After 16Z, VFR conditions
are expected for the rest of the period.  Winds will be light and
variable after 00Z at all sites.

&&

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

$$

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


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