NWS Open House on Saturday; weekend warmth portends generally milder pattern ahead after chilly start to November
Remember the National Weather Service Open House is Saturday at Blacksburg, from 10 a.m. to 3 p.m. If you’re there 11 a.m. to 2 p.m. or so, holler at me at the Virginia Tech Storm Chasers display.
Once we had the second-warmest winter on record, and the hottest March on record, and the hottest spring on record, and the hottest July on record, I presumed that 2012 was just about a lock to be Roanoke’s hottest year on record. But, locally, the year has fallen off that hot pace significantly. June, August and September were each within two-tenths of a degree of normal, and October was more than half a degree below normal. That leaves the last two months of 2012 needing to average 1.7 degrees above normal for 2012 to tie the record annual average temperature of 59.6, set in 1931. Now that November has started nearly 8 degrees below normal through the first 8 days , that seems to be an unlikely prospect. (Friday’s temperature averaged normal at Roanoke — 67 high, 33 low averaged to 50 — breaking an 11-day streak of below-normal temperatures, the longest since 20 in December 2010.) Still, if November and December are merely normal, or even just a little below normal, 2012 will become only the fifth year in Roanoke’s 101-year recorded weather history to average at least 59 degrees (1931 at 59.6 degrees, 1921 and 2007 at 59.4 degrees and 1991 at 59.1 degrees are the others.) The first 60-degree year, which seemed likely at midsummer, is just about out of reach now, barring an extreme blowtorch in the remaining 7 1/2 weeks of the year.
No “blowtorch” warmth appears to be in the offing, but it does look as if we are switching into a much milder pattern for at least the next couple of weeks, maybe beyond. The climatic indicators of PNA (Pacific-North America pattern) negative (signaling low pressure in West, high pressure in East, funneling milder air into our region), NAO (North Atlantic Oscillation) positive (no Greenland blocking high, so no forcing of jet stream southward to deliver Arctic air into East) and Arctic Oscillation positive (low-pressure over North Pole, keeping Arctic air pulled in tighter rather than expanding southward) all line up well for the expected period of milder weather ahead. Weekend highs may top 70 degrees from Roanoke south and east — Roanoke wasn’t far off that pace at 67 on Friday — but a cold front arriving Tuesday will temporarily pull temperatures back to near or below normal for a two or three days (50s highs, 30s lows, mostly). There may also be some showers and even a few thunderstorms with the front’s arrival, perhaps as early as Monday. Temperatures will slowly moderate upward after the front, but probably not into extreme warmth. There are many questions and mixed signals lingering for Thanksgiving week, including the European model already backing off considerably from a potential strong southern-stream storm crossing the nation during the preceding weekend that I mentioned in my last blog post. We’ll see if any of these details become clearer next week when Kathryn Prociv fills in for me Monday to Wednesday.