dallen7908

five-sigma corresponds to about 1 in 3.5 million assuming a normal distribution So if we hear discussion of another 4 or 5 sigma event we should consider the source and/or unfollow Kayleigh McEnany

Just over 10% of the EPS members look promising for XMAS. Here is an extreme example.

12/16 0.6 " (College Park)

Finished? with 0.7" here in College Park - changed from snow to sleet to rain within the last hour. Surface temperature 32.4

Yes it shifted from sleet to light snow about 10 minutes ago. 32.9 degrees

Been sleeting in College Park for the last 5-10 minutes

Slowly rising surface temperature here. 29.7 at 6:40, 30.6 at 7:30, and now 31.5F

Euro 6z: Verbatim (without looking at the soundings), Similar or very slight worse than 00 UT, for DC it shows snow beginning between 11 AM and noon changing to mixed precipitation between 2 and 3, surface temperature of 34 degrees. Snow maximum still in central PA - just under 2 feet

In case anyone is wondering GDPS on the pivotal weather plot is the acronym for the operational "Canadian" model.

Are the ensembles still based off of the old GFS? If yes, it's less staggering

For comparison purposes here is the EPS panel, superficially they look similar ... although SE ridge is much stronger here - 50 N low too far east to help us?

How about this ... the EPS shows a positive EPO for much of this period while the CPC 3-4 week outlook gives us a > 60% chance of above normal temperatures as La Nina reasserts itself.

Based on my limited knowledge of this ... Warmings have strong correlation with winter temperatures in Europe; not so much in the northeastern U.S.. We'll have to wait and see. In any case, probably not much of a factor until mid-December

Saint Martin's summer; would use the more familiar Indian summer - if my back yard had experienced a freeze

The NWS forecast discussions out of Sterling are about to get more interesting - for snow lovers https://www.weather.gov/lwx/GarrettCecilTransfer

From the NWS discussion: Day IAD high/high min BWI high/high min DCA high/high min 11/8: 77(1987)/57(1977) 80(1975)/62(1975) 81(1975)/63(1975) 11/9: 78(1994)/56(1987) 78(1994)/61(1945) 79(1994)/64(1895) 11/10: 75(1985)/60(1966) 75(1999)/62(1966) 76(1999)/60(1975) 11/11: 78(2006)/55(2002) 77(2006)/59(1970) 78(1949)/58(1970)

https://frontierweather.dtn.com/WinterClimateDrivers.pdf Just in case you need background as to what a rising QBO value MAY mean for our winter weather.

The high-bias in the forecast values reminds me of last winter. Could the bias be due to a poor coupling between the ocean model and the atmospheric model? On the positive side, the high-bias may allow some fantasy storms to come up the coast. On the negative side, reality will be much more mundane. Not that the AO forecast has much to say about it but I'm rooting for a warm November. My hunch is that the correlation between November temperatures and winter temperatures is negative - perhaps -0.02. I'll take any advantage I can get. A depressing truth; the "smartest" forecast might be to use the ensemble with the most positive AO value. Another depressing feature of the time series is that it goes negative about when the forecast skill goes to zero or at least to 0.16^2.

4.9" in my College Park rain gauge. Several neighbors are wet-vacuuming their cars - glad ours was up on our driveway

https://reichlab.io/covid19-forecast-hub Tool for ensemble fans "The ensemble forecast combines models unconditional on particular interventions being in place with those conditional on certain social distancing measures continuing. To ensure consistency, only models with 4 week-ahead forecasts ahead are included in the ensemble."

UKMET not as optimistic as GGEM wrt snow chances

Thanks for the ensembles. Perhaps going forward continue ending them at 18Z 31 March. Would be interesting to see if any of the perturbed members are more skillful. Of course, this would not be possible to determine this year when the least snowiest is almost always if not always the most accurate.

The climate change tangent got me thinking of nordic skiing and a sign I saw this past January. Hopefully "forever" won't end sooner than the Doucettes' hope

Low 40s and rain unless you head to Canaan Valley or Garrett County where accumulations of up to 6" are possible for the system according to the UMKMET through Saturday morning

Strictly speaking the maps give the percent of ensemble members showing at least a certain amount of snow/sleet. They are a tool not a forecast.