FXUS63 KEAX 200815

National Weather Service Kansas City/Pleasant Hill MO
315 AM CDT Sun Oct 20 2019

Issued at 315 AM CDT SUN OCT 20 2019

Widespread dense fog will persist in the eastern half of the
forecast area through several hours after sunrise. This is right
under the surface high pressure area. Further west, where the
pressure gradient increases slightly to allow some light winds, fog
looks more confined to river valleys/ protected areas. However,
weak advection may bring some dense fog to parts of the KC metro
not in valleys/ protected areas. So will expand the dense fog
advisory into the metro area, despite it not being as widespread.
Will also extend the time to later in the morning. This mainly
applies to the eastern portions of the advisory where fog is
thickest. Western portions may end up being cancelled early
depending on how quick winds pick up and mix the boundary layer.

This evening and tonight, a cold front will approach the area. As
the upper shortwave deepens and moves into the Central Plains and
Upper Midwest, strong low-level flow will spread over the region.
Strong moisture advection ahead of the front will get dewpoints into
the middle 50s in much of the forecast area. As an upper-level jet
rotates around the base of the upper trough, strong deep-layer shear
will develop. Instability will be the limiting factor for potential
severe weather. Models are all over the place as well with this
parameter. The NAM and NAM 3-KM are the most aggressive with
instability and show 1000-1500 J/kg MUCAPE. Forecast soundings show
this to be mostly elevated in nature. This is fortunate as surface
winds ahead of potential storms are from the southeast resulting in
very high helicity values. If we were dealing with well mixed
boundary layer with even modest to steep low-level lapse rates, the
potential for more widespread severe storms would increase. But for
now, with the strongest storms looking to be late in the evening and
overnight, low-level lapse rates are weak due to a small inversion.
So storms should be elevated in nature, limiting tornado potential
and keeping the main impact to isolated hail and possibly gusty

Quiet weather is expected through the middle of the week. By the end
of the week and into the weekend, several upper shortwave troughs
will move across the middle of the country. The system moving
through Thursday may be cold enough that some areas could see some
snow mix in with any rain. This is still uncertain at this time as
temperatures and precipitation timing vary amongst the models. If
snow were to mix in, at this time it would be most likely across
the northern half of the forecast area.


.Aviation...(For the 06Z TAFS through 06Z Sunday Night)
Issued at 1140 PM CDT SAT OCT 19 2019

Fog and visibility will be the main challenge for aviation
forecasts over Missouri and eastern Kansas. Clouds have cleared
out and visibilities are currently IFR to LIFR over central
Missouri. The main uncertainty in the fog forecast along the KS/MO
border will be with the winds speeds. Guidance has a southerly
wind of 5-7kts picks up over the KS/MO border area in the next
couple hours which may be just enough wind to inhibit dense fog,
but will still allow for some MVFR visibilities towards sunrise.
Sites near a river (KSTJ and KMKC) may see the possibility for
dense fog and IFR to LIFR visibilities and will need to be
monitored as we go into the overnight hours to see where these
winds set up. If they remain calm then IFR to LIFR visibilities
will likely be added to all of the TAFs. A cold front will push
through tomorrow evening around 2-3Z with rain showers and
isolated thunder expected.


KS...Dense Fog Advisory until 11 AM CDT this morning for KSZ057-060.

MO...Dense Fog Advisory until 11 AM CDT this morning for MOZ007-008-




NWS EAX Office Area Forecast Discussion