dallen7908

Saturday the 12th's newspaper emerged from a snow bank this morning; was out of town for last weekend's storm. 

Had more back end snow/sleet (occasional flurries around 11 this morning) than front end on this weekend's storm. 

A bit of snow left in "unsubmerged" shady spots.   Otherwise only the piles remain. 

1 hour ago, Danajames said:

It was 37 when I got up and I live in southern part of Harford County.   As soon as I saw that, I knew this one was a done deal.  

Not necessarily ...

grab your cell phone ...

purchase a sling psychrometer ...

have it delivered by a drone ... 

open the package ...

read the directions ...

take it outside ...

measure the wet bulb temperature ...

estimate the RH from the wet bulb temperature using https://www.sailangle.com/articles/details/id/10  ...

Go to http://www.sciencebits.com/SnowProbCalc?calc=yes ; plug in the RH and T

Estimate your chances 

I'm back after a week at the AMS meeting in Phoenix and a few days vacation in the Tucson area.  Did I miss anything?  

Ironically, I also missed last March's storm due to a trip to spring training, the St. Patrick's Day storm in 2014 due to business trip,   Commutageddon in 2011 due to AMS, ...

My next out of town trip -- February 14 - 20

CPC on board for transition to colder than average pattern and wintry precipitation for mid-Atlantic (week 3-4 discussion lead by S. Baxter)

http://www.cpc.ncep.noaa.gov/products/predictions/WK34/

I wouldn't call 1989-1990 a horrible winter.  Although my memory may be faulty,

I recall snow on Thanksgiving eve and being very cold watching Macy's parade in NYC. 

I also recall snow in early December; much of which sublimated. 

I recall ice skating on local ponds 

I also remember an abrupt end to winter between XMAS and New Years.  

I suspect he is saying that the 2nd half of the winter is unlikely to be mild and snowless but based on 89/90 alone he could be saying that the transition will not be as abrupt as 89/90

1 hour ago, Ralph Wiggum said:

Again, not getting too far out like mid month, but important changes consistently showing now within around 10 days. One important feature I've been watching is the ridge N of HI finally breaking down. Actually takes an interesting progression and moves into the EPO area building heights there like a flip of a switch. This scenario has repeatedly been hinted at and while still a long way out is now within about 10 day which is *fairly* reasonable for key pattern features being shown. 

Thanks for stepping up and taking over as bannerman for a mid-month pattern change ... may the odds be ever in your favor

How long does it take for a "perfect" pattern at 85000 feet to translate into a snow storm at the surface (for us)? Can I just add 20-30 days to the 16 day forecast? 

Likely, wrong but over the next 10 days the EURO for my backyard has more days with highs in the 60s (4) than below 50 (3) ... and two of those below 50 highs are 49. 

Looks like the next rain event on the Euro ends just as the New Year begins --- a good sign??

Is that wraparound snow the Euro is showing early morning to the NW of DC on the 5th; the Low appears to be well past us. 

Is the January 8/9th storm still forming or is it that clipper moving across New England? 

6 minutes ago, peribonca said:

Just slight differences between 12z and 6z GFS at 102h. Has the model lost its mind? When are we finally upgrading?

That's a good question.  I wonder if the upgrade will be delayed due to the partial government shutdown. 

7 minutes ago, frd said:

Two days in a row of overall better trends here with the - AO

Yes does look encouraging; however, note the increasing low-bias in the model forecast with time.  This bias is one reason why on average models' 7-14 day climatologies are colder and stormier than reality. 

The 12UT Dec 23 and 00 UT Dec 24 EPS give College Park a 30% chance of >1" of snow during the day 8-11 time period.  However, the chance for >3" of snow during this period has decreased from 18% for the 12UT run to 8% for the most recent run. 

Interestingly, the chance of >1" increases by ~2% (1 ensemble member) per 12-hour period between days 10 and 15 reaching 46% by day 15.  As expected as this range, the models have no clue which shortwave to focus on. 

Week 3-4 Forecast Discussion Valid Sat Jan 05 2019-Fri Jan 18 2019 
 

http://www.cpc.ncep.noaa.gov/products/predictions/WK34/

"While we do not issue explicit forecasts of winter weather potential at this lead, it would seem prudent to note that the forecast circulation pattern would favor an enhanced chance of winter storm events east of the Appalachians, including the major population centers of the Mid-Atlantic and Northeast, especially later in the period." 

EPS gives DCA a 34% chance of >3" of snow between days 10 and 15. 40-50% chance in northern Maryland

6 hours ago, frd said:

Wonder what the accuracy of the Euro is to the GFS in this area of the strat.

I would simply assume that the superior physics of the Euro would equate to a better, more accurate forecast. 

 

I  am not sure about the outcomes here for our areas versus a split or no split. Seems the Euro and the Canadian have it and the GFS no . 

Judah says too difficult to tell at this time.

I know a couple days ago the GFS ensembles vs the op were not even on the same page.  

Alexey Karpechko gave a talk on SSW predictability. He found that last year's event was hinted at by EPS members 12-13 days out, predicted by 30% of ensembles 11 days out, predicted by 100% of ensembles 4 days out. 

 

Climate Prediction Center Week 3-4 Outlook (Dec 29 - Jan 11) calls for above normal 500 hPa heights, temperatures (60+% chance), and precipitation (50-55% chance).  Next Friday's guidance will get us past January 15th, the date when some believe a back-loaded winter begins.  

"Dynamical model guidance from the various models is broadly consistent, depicting a trough over the Aleutian Islands into the North Pacific. Dynamical model ensembles from the CFS and ECMWF for Week 3-4 depict near or below normal 500-hPa height anomalies over Alaska and the U.S. West coast, while above normal 500-hPa height anomalies are forecast over much of the remainder of the forecast domain. The CFS, ECMWF, and JMA indicates above-normal 500-hPa heights over Hawaii. 

The Week 3-4 temperature outlook indicates increased probabilities of above-normal temperatures over southeastern Alaska, along with the northern and eastern half of the CONUS, with the highest probabilities across the Ohio Valley and Tennessee Valleys, and the Middle Atlantic area, supported by dynamical model forecasts. Below-normal temperatures are most likely for southeastern New Mexico and parts of the Southern Plains, consistent with the SubX guidance. 

The Week 3-4 precipitation outlook indicates increased probabilities of above-median precipitation for much of the East Coast, the Gulf Coast region, the southeastern Alaska, and the Alaska Panhandle, consistent with the SubX guidance." 

http://www.cpc.ncep.noaa.gov/products/predictions/WK34/

What city and since 1883-84 what percentage of winters have ended up with above average snow totals?

I know most of you know this ... but as most of the recent plots show composite reflectivity

Keep in mind that composite reflectivity shows the maximum reflectivity in the vertical column (i.e., the extent of virga).  It should not be confused with base reflectivity, which is a truer representation of where it may snow.

EPS now gives BWI (Andrews AFB) a 14% (26%) chance of > 1"

BWI chances of >1, 3, 6, and 12" according to EPS

While the EPS chance for > 1 inch at BWI is still 0, the chances for DC increased from 2 to 6%. 

% of EPS ensembles giving BWI > 1, 3, 6, and 12" of snow/sleet through early next week.  2% of the ensembles (i.e., one) give DC > 1" 

Percent chance of at least 1, 3, 6, and 12" of snow through early next week at BWI according to the EPS

EPS Percent chances that BWI exceeds 1, 3, 6, and 12" through early next week