The HRRR and RAP solutions regarding
instability on Monday have been
all the rage on social media since their domains reached that
period. Both are anomalously high on
dew point temperatures with
values in the low to mid 50s into central Iowa and both tend to over
mix the
boundary layer during
stratus events. Other solutions are
more conservative on both temperatures and
dew points and do not
overcome the warm wedge aloft.
Sounding wind profiles do have
direction
shear below 900
mb but whether that
shear is acting on
surface based
instability certainly is questionable. January
tornadoes have occurred on only one day in Iowa recorded history,
January 24, 1967 when 13 tornadoes occurred over the southeast
portion of the state. That event was followed up by a
blizzard
with record snow accumulations over the state, thus a very strong
system. It often takes a historical type system such as Dec 15,
2021 when nearly 80
kts of
flow was at 850
mb or below. The
majority of the time,
stratus wins which leads to non- events. As
always, will need to monitor trends and will have a great
opportunity to do that over the next 24
hrs as the low matures and
we can get a better handle on how much
moisture will reach the
state.