Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 ktop 200517 
afdtop

Area forecast discussion
National Weather Service Topeka Kansas
1117 PM CST sun Feb 19 2017

..aviation update...

Short term...(this evening through monday)
issued at 121 PM CST sun Feb 19 2017

The primary issue in the very short term is the impact of an area
of low cloud cover on near term temperatures. This stratus deck
has been advancing northeast while also eroding from the sides. It
has not been particularly deep but has been deep enough to limit
sunshine and keep temperatures cooler. On the other hand, as it
continues to advance it will keep temperatures warmer overnight.

Precipitation chances become the focus after 9 PM as an elongated
neutral-tilt upper trough is moving across the plains. Upper flow
overhead is quite meridional with ample deep moisture advection
into the region. Several short wave troughs were moving toward the
north-northeast out of the main longer wave trough. One of particular interest
was evident over The Big Bend region of Texas in WV imagery. This
appears that it may be the first piece of lead energy to provide
focused ascent for precipitation locally. Model guidance has
generally increased the expectation for precipitation late this
evening into early Monday largely tied to the trajectory of this
energy. Hi-res guidance such as recent runs of the hrrr and rap
support the larger-scale model theme, and seem to focus the
optimal timing for precip in the local forecast area between
midnight and 8 am with a gradual SW to NE precip transition. There
is some potential to linger a bit longer in the far east as the
upper trough slowly moves east and another slight chance for
precip mainly in far northern Kansas late in the day as the surface
front eventually moves into the area.

Precipitable water values are forecast to flirt with record values for this time
of year with some forecast values approaching 1.3-1.5". There
should also be some modest elevated instability, and the
combination of the two features may allow for a few areas of
decent rainfall to materialize. Duration will not be very long
with the progressive waves of energy, but wouldn't be surprised to
see precip amounts range from very light in north central Kansas to
potentially a half inch or more where better convection develops.

Long term...(monday night through sunday)
issued at 121 PM CST sun Feb 19 2017

Conditions will dry out for Monday night through Thursday morning.
Expect quite a bit of sunshine through tues/Wed with dry air just
above the boundary layer likely to mix to the surface. Similar
conditions in recent days have led to warmer and drier than
expected conditions so at this time have been forecasting a bit
warmer and a bit drier but will want to monitor for any potential
to go warmer and drier yet. Luckily wind speeds are unlikely to
exceed 20 mph either day so explosive fire conditions are
unlikely although minrh could fall below 20% each day.

On Thursday, model agreement is still strong in a strong jet
streak crossing into Kansas with surface cyclogenesis in southeast
Colorado. Expect a strengthening frontal zone to extend across
northern Kansas by late Thursday with cold air being pulled into north
central Kansas by Thursday evening. Guidance remains split on how soon
and how impressive the intensification of the upper low will be
but the overall message remains generally the same. Expect windy
conditions with the strengthening surface low, and continue to
see decent potential for snow over mainly northern Kansas northwest
of a Minneapolis to Clay Center to Marysville line but this could
obviously change substantially between now and the end of next
week. If snow develops, some accumulation is possible but expect a
sharp gradient in accumulation and could very well end up nearly
snowless especially with the warm ground temperatures.

Colder air overtakes the entire region for the weekend, but even
while it is much colder than the current airmass it will still be
fairly close to normal values. Another very weak system will bring
precip chances for Sunday with rain or snow possible, and the
active weather pattern looks to continue into the following week.

&&

Aviation...(for the 06z tafs through 06z tuesday)
issued at 1117 PM CST sun Feb 19 2017

Aside from the lack of fog and MVFR ceilings moving in ahead of the
precip, the forecast appears to be on track. Models suggesting the
lower restrictions may follow the precip through the mid morning
hours. Think the lower visibility are likely to occur with the showers
due to moderate rainfall and confidence in IFR ceilings is marginal
since there should be continued mixing behind the line of storms.
So have limited any chances for IFR conditions to coincide with
the storms. The models continue to shift the deeper moisture axis
east of the area with surface winds coming around to the
southwest. The dry air advection should usher in VFR conditions
for the rest of the forecast period.

&&

Top watches/warnings/advisories...
none.
&&

$$

National Weather Service Glossary of Abbreviations