coldThe good news is that it seems to be working now (the inside temp was below 60 a few hours ago, according to
starmalachite; it's now up to 62). Based on the pattern I observed last night (the pilot igniter came on, the gas jets lit for about 10 seconds, the gas jets quit, about 15 seconds later the pilot igniter came on again, lather-rinse-repeat, accompanied by occasional sounds suggesting strained air circulation), my guess is that the snow was blocking an outlet vent, triggering the safeties to shut off the burner when the exhaust wasn't escaping properly. If so, the problem may have solved itself when enough warm air got through to melt the blockage. I'll be monitoring the situation for now.