IT WAS A CME-

My initial hunch was correct. Apparently a 'stealth CME' caused last nights G2 storm. I posted the SWPC forecast above and there was no mention of an incoming CME. SURPRISE!

SWPC has come to the same conclusion now. They're still expecting a coronal hole stream to arrive.

SWPC Forecast Discussion-

Solar Wind

.24 hr Summary...
Solar wind parameters became enhanced from approximately 28/2300-01/1530
UTC due to possible CME effects. Total field reached a maximum of 14 nT
at 01/0328 UTC while the Bz component reached a maximum southward
deflection of -13 nT. Solar wind speed increased briefly to a maximum of
538 km/s at 01/0902 UTC. Phi angle was variable throughout the period.

.Forecast...
Solar wind parameters are expected to become enhanced once again on 02
Mar as a negative polarity CH HSS moves into geoeffective position. HSS
conditions are expected to persist through 03 Mar and slowly taper off
on 04 Mar. Solar wind speeds are expected to be mostly in the 500-550
km/s range based on recurrent values.

Geospace

.24 hr Summary...
The geomagnetic field increased to G2 (Moderate) geomagnetic storm
levels, observed during the 01/0300-0600 synoptic period, in response to
sustained periods of southward Bz and a brief solar wind speed increase
to 538 km/s. Quiet to unsettled levels were observed during the second
half of the UTC day.

.Forecast...
The geomagnetic field is expected to increase to unsettled to G1 (Minor)
geomagnetic storm levels on 02 Mar in response to the arrival of a
negative polarity CH HSS. Unsettled to active levels are expected on 03
Mar as HSS conditions persist followed by quiet to unsettled levels on
04 Mar.

[link to www.swpc.noaa.gov (secure)]