HSV
There is where we get to the most complex and lower confidence part
of the forecast. Depending on the vertical temperature profile, it`s
possible we actually start seeing some wintry precipitation across
portions of northwest Alabama by the late afternoon on Wednesday and
north central Alabama into southern Middle Tennessee by the evening
and overnight period. We could see this start off as a light snow or
sleet and eventually mixing with or changing over to freezing rain
or rain depending on what the surface temperatures look like for a
given location. In this scenario, precipitation type is going to be
very messy and impacts will be very dependent on what surface
temperatures look like (which will range from a couple degree below
freezing to a couple degrees above freezing). Complicating things
further is that we do expect fluctuations in temperatures through the
night and into the day on Thursday as a secondary low
likely tracks
across central Alabama early Thursday -- meaning a mixed bag will be
in cards for much of the area.
As far as any potential accumulations/impacts go, that`s complicated
as well. If surface temperatures are near or above freezing, ice
impacts will be lessened and snow/sleet would mostly stay confined
to grassy/elevated surfaces. If we`re colder than expected, that`s a
different ballgame. While we will continue to advertise lower end
accumulations for this package (due to low forecast confidence), it`s
important to note that that both the
GFS and
ECMWF ensembles are
hinting at near Advisory level accumulations across at least portions
of northwest Alabama and southern middle Tennessee. In fact, over 40
out of 50
ensembles at at
MSL feature snow/sleet accumulations of 1
inch or greater. And it`s fairly similar for sites at Fayetteville
and Winchester. Again, storm total accumulations and impacts (which
are dependent on surface temperatures and other factors) are
different things and that`s important to note. We`ll keep a close eye
on this with the forecast update later today. For today`s forecast
package we nudged up snow/ice accumulations slightly (which mainly
occur in the Wednesday night to early Thursday period).