re: Tornado! Bama - State of Emergency - High Risk Portions of GA & SC

Uograde to High Risk being considered:




Mesoscale Discussion 0440
NWS Storm Prediction Center Norman OK
0943 AM CDT Wed Apr 05 2017

Areas affected...Portions of AL/GA/SC

Concerning...Outlook upgrade

Valid 051443Z - 051645Z

SUMMARY...Portions of the states of AL/GA/SC are being considered
for an Outlook upgrade -- though the details are still being
analyzed. A very notable dry bias is apparent in the latest model
guidance, and observational data and previous model runs are being
heavily referenced in Outlook preparation.

DISCUSSION...GPS PW data are exhibiting a low bias by at least 0.5
inch from parts of AL into GA, which has influenced initialization
of the latest numerical weather prediction guidance. Per
coordination with the Weather Prediction Center, it appears that
related initialization is causing substantial dry biases in model
guidance -- extended through the Day 1 forecast period. With an
inland influx of rich moisture feeding ongoing intense supercells in
southern AL (with dewpoints into the middle 70s), and the
around-16.6-g/kg mean mixing ratio per LIX 12Z sounding, and around
1.5-inch PW per Atlanta and Birmingham 12Z soundings, it is evident
that rich moisture and related strong buoyancy does indeed extend
inland. As such, observational data and previous model runs will
play a major role in the consideration for a High Risk upgrade, as
the dry bias has influenced the latest model guidance. While an
Outlook upgrade is possible, it is not certain.