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000
FXXX12 KWNP 201230
DAYDIS

:Product: Forecast Discussion
:Issued: 2013 May 20 1230 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
# Product description and SWPC contact on the Web
# http://www.swpc.noaa.gov/wwire.html
#
#             Forecast Discussion
#
Solar Activity

.24 hr Summary...
Solar activity was at moderate levels.  The largest flare of the period
was a M1 at 20/0525 UTC from a region just behind the northeast limb,
likely old Region 1731 (N09, L=189).  Slight decay was observed in the
leader and trailing spots of Region 1748 (N12W09, Eai/beta-gamma-delta),
however it appears to continue to maintain its delta in the leader
spots.  Region 1750 (S09W76, Dai/beta) is still in a growth phase with
further spot development within its intermediate area.  The rest of the
spotted regions were either stable or in slight decay.  No
Earth-directed coronal mass ejections (CMEs) were observed during the
period.

.Forecast...
Solar activity is likely to be moderate with a chance for X-class flares
for the forecast period (20-22 May).  The most likely sources for major
flare production are 1748, 1750, and old Region 1731.

Energetic Particle

.24 hr Summary...
The greater than 2 MeV electron flux at geosynchronous orbit was at
normal levels.  The greater than 10 MeV proton flux at geosynchronous
orbit continued its decline to background levels, however is still
enhanced near 3 pfu.

.Forecast...
The greater than 2 MeV electron flux at geosynchronous orbit is expected
to be at normal to moderate levels.  There is a chance for a greater
than 10 MeV proton event (S1-Minor) for the forecast period (20-22 May).

Solar Wind

.24 hr Summary...
Solar wind speed ranged from approximately 329 km/s to 375 km/s while
total field ranged from 1 nT to 6 nT through the majority of the period.
Phi angle was negative (towards) until 19/1458 UTC when it crossed into
a mostly positive (away) sector.  At 19/2221 UTC, a shock was observed
in ACE data associated with the 17 May CME.  Solar wind speed increased
from approximately 353 km/s to 493 km/s while the total field increased
from 5 nT to 14 nT.

.Forecast...
Solar wind speed is expected to be enhanced due to activity from the
17 May CME through day 1 (20 May).  By day 2 (21 May), a return to
nominal solar wind conditions is expected.  On day 3 (22 May), a
recurrent coronal hole high speed stream (CH HSS) is expected to become
geoeffective causing another enhancement in the solar wind speeds.
STEREO B Mag and Plastic data indicate possible wind speeds in the 400
to 500 km/s range associated with the high speed stream.

Geospace

.24 hr Summary...
The geomagnetic field was at quiet to active levels.  At 19/2306, a
geomagnetic sudden impulse (39 nT) was observed in the Boulder
magnetometer.  The geomagnetic field increased to active levels during
the 19/2100-2400 UTC period due to the arrival of the 17 May CME but has
since subsided to quiet to unsettled levels.

.Forecast...
The geomagnetic field is expected to be at quiet to unsettled levels on
day 1 (20 May) due to continued activity associated with the 17 May CME.
Conditions are expected to return to quiet to unsettled levels by day 2
(21 May).  On day 3 (22 may) a recurrent CH HSS is expected to move into
geoeffective position causing conditions to increase to quiet to active
levels.