This is from 1025pm (waiting on the update)
Friday, a cold front riddled with convection will work through the
CWA from west to east. I have high confidence that everyone will see
rain, starting in the northwestern counties during the morning, then
reaching the eastern areas by afternoon. We are still 2 days away
from the event, so there could be some adjustments needed to the
timing.
As far as the severe threat is concerned, the current slight risk
from SPC looks like the most reasonable course of action this far in
advance. However, it would not surprise to see the enhanced risk
expanded westward by at least a couple of tiers of counties when the
new Friday forecast from SPC comes out overnight. Shear looks to be
very strong Friday, with the area in the favorable quadrant 100+
knot jet at 500 mb. Instability will be modest because mid lapse
lapse rates will only be seasonable, but it won`t take a ton of CAPE
to cause problems given the expected bulk shear. The biggest area of
uncertainty lies with the convective evolution, as well as the
mesoscale high/low couplet that should form with forcing this
strong. The GFS is not picking up well on this, whereas the 00Z/06Z
ECMWF and the 12Z hi res guidance do have a reflection of this
evolution. If the ECMWF/NAM solution is correct with the mesolow
moving north northeastward bisecting the CWA on Friday, areas along
and east of the mesolow track will have an enhanced risk of severe
weather, including tornadoes, due to increased low level helicity,
increased surface convergence, and the potential for stronger rear
inflow jets behind any bow echos that form. Unfortunately, our
models are simply not good enough yet to forecast the exact
evolution of these features 48 hours in advance, so we just have to
mention the possibility in our discussions and hope we can refine
things more as we get closer to the event.
There will also be some heavy rain with the front as PWs increase to
1.5+ inches under strong divergence aloft. At this time, excessive
amounts do not seem likely due to the quick speed of the front, but
local issues may arise that could require flood advisories, or
possibly a warning or two in our flashy areas.
One other issue Friday will be the winds ahead of the front. Given
the strong winds expected at 850 mb, we will likely have strong
enough winds mixing down to warrant at least a Lake Wind Advisory, if
not a full on Wind Advisory.