01z F 29 Apr 2011 Forecast Discussion

Very interesting forecast challenge for Friday night into Saturday....this is a classic example of what makes forecasting such a challenge around here!

The next system aloft is crossing the west coast at this writing, with a good surface low and cold front into Nevada. Some critical information is still offshore, mostly unobserved. So, the question remains, snow (or rain) or blow on Friday night. I think this will be obvious by late morning tomorrow, but probably not much before.

At present the most likely scenario is for variable amounts of cloudiness daytime Friday, but with enough daytime heating to allow strong winds from the S to WSW to develop on the plains, particularly E of I-25.

On the flats, I anticipate variable shifting winds, but predominantly from the SW - W, during daytime hours on Friday. Then, sometime in early evening this will be followed by a well marked frontal passage from the N, followed by good winds out of the N for a few hours and with pcpn beginning soon after frontal passage.

The alternative scenario also includes the daytime gusty winds mentioned above, but rather than these terminating with a frontal passage from the N, they would end with a frontal passage from the W, likely also in early evening, and accompanied by a brief shower and short period of strong W wind. Following the frontal passage would come a period of 0.5 to 2h of weaker wind, followed later by strong winds from the W - NW, likely persisting much of the night. I put the likelihood of this scenario about 1 in 3.

What happens beyond Friday night is also not real clear at this point, but the prospects for W to NW wind seem fairly low, and the threat of rainy or snowy periods continuing through Sunday to be fairly high.

John B.