[AZ-Observing] Major Solar Flare; Possible Aurora Tonight

From Spaceweather.com:
+++++++++++++++++++++++++
** ALERT -- EXCEPTIONAL X18 FLARE **

An exceptionally intense class X18 solar x-ray flare has been observed from 
Region 486. It has produced a prompt high-energy proton event in space and is 
associated with a strong full-halo coronal mass ejection (directed heavily 
Earthward). This solar flare ranks as one of the largest of this solar cycle. 
It will produce a potentially strong impact at the Earth within 48 hours or 
less. The predicted arrival time has not yet been computed. Additional data and 
analysis are first necessary. Please allow us several hours to update our CME 
impact prediction web page. 
+++++++++++++++++++++++++

...and here's the updated forecast:
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Event #49 - 28 October 2003
Issued: 16:30 UTC, 28 October 2003

SOURCE EVENT

Class X17.2 Flare in Region 486 at 11:10 UTC on 28 October 2003
Type II: 1250 km/sec
Estimated LASCO-derived Plane of Sky Velocity: 2125 km/sec

ESTIMATED TIME OF ARRIVAL OF SHOCK AT EARTH

Estimated Impact Window: 00:00 UTC on 29 October to 21:00 UTC on 29 October
Preferred Predicted Impact Time: 08:00 UTC, 29 October 2003 (3 am EST on 29 
October)
Estimated Shock Strength (0=Weakest, 9=Strongest): 9 

Predicted Behavior of IMF at Shock Impact

At Shock Impact, the Interplanetary Magnetic Field is predicted to initially 
turn:
SOUTHWARD

IMPORTANT TIME OF ARRIVAL NOTICE FOR NORTH AMERICANS
The preferred time of arrival is ***TONIGHT***, TUESDAY NIGHT (before you go to 
bed that night) near or after 3 am Eastern Standard Time).
That's 2 am Central Standard Time on TONIGHT.
That's 1 am Mountain Standard Time on TONIGHT.
That's MIDNIGHT Pacific Standard Time on TONIGHT.

EXPECT RESIDUAL ACTIVITY (LESS INTENSE) TOMMORROW NIGHT (WEDNESDAY, 29 OCT) AS 
WELL !

EVENT #49 NOTES: 

This is the most energetic Earthward-directed event of the solar cycle.

SEVERE to MAJOR geomagnetic storming is expected to abruptly commence following 
the arrival of the shock front from this flare.

This flare was associated with a Ground-Level Event. It was also associated 
with very high energy protons at greater than 100 MeV (which are still 
climbing, over 5 hours after the event began). A magnetic crochet was observed 
over the daylit sections of the ionosphere. An exceptionally intense shortwave 
fadeout and polar cap absorption event are in progress. There are reports this 
event was observed in white-light. Intense radio bursts were associated with 
this event across the spectrum. The type II shock velocity is not 
representative of the observed velocity of this CME. The observed velocity as 
determined by SOHO was 2125 km/sec.

This event has the potential to produce the strongest geomagnetic storm since 
1989. Auroral activity could become visible into the deep low latitude regions. 
This one is worth driving a good long distance over to find clear skies. It has 
better potential to produce low-latitude aurora than almost any other event 
observed in the past decade. Keep in mind that it is also possible the 
disturbance may not be nearly as geoeffective as many would like. It all 
depends on the character of the magnetic fields imbedded within the coronal 
mass ejection. However, we believe it will either be very large, or only 
modestly large in terms of its capacity to produce disturbed geomagnetic and 
auroral activity. We do not expect this disturbance to be small. 

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