Friday, January 22, 2016

3PM UPDATE

QUICK NOTE - AREA OF NO PRECIP SHOULD FILL BACK IN QUICKLY AND LAST SEVERAL HOURS BEFORE BULK OF STORM DEPARTS AREA AROUND 10PM. THIS IS SIMULATED RADAR FOR THE HRRR (RAPID REFRESH) MODEL. DON'T LIVE BY IT BUT NOT BAD IN TERMS OF GENERAL IDEA. SLEET AND SNOW SHOULD BE PREDOMINATE P-TYPE. HOPEFULLY A NICE THUMP OF SNOW AT THE END.




Blizzard Turns to Slizzard of 2016

It is fairly obvious that snow accumulations originally forecast can be cut by about 2/3rds in most location and add about 4x amount of sleet. (Slizzard...) The changeover to sleet has irreverently, irreversibly, and irrevocably busted my forecast.

Another thing that concerns me regarding total accumulations is the "dry slot" currently working its way in/over is. 

What is that exactly? Here is the NWS definition: http://forecast.weather.gov/glossary.php?word=dry%20slot. As the primary low pressure energy/system becomes the coastal low, precipitation is more or less sucked dry over the areas due west of the developing low due to the energy transfer.

Now I'm not saying it's over, just that accumulations (total moisture) will be slimmed down as well. 

So here are current and probably final thoughts:

Davie/Forsyth/Yadkin:
About 2-3" of snow and .5" of sleet so far... Should see more sleet and even some brief freezing rain before a little more snow later evening and into AM.

Total Snow = 3-7" South to NorthWest.
Sleet= 1" generally, which is a lot. 
Freezing Rain= .10"

Rowan/Cabarrus (Joe H.)
More sleet and freezing rain (especially the further south you go) with some snow at the end.

Total Snow = 1- 4" South to NorthWest.
Sleet= approx .75"  
Freezing Rain= .25" - .40" (North to S) 

Other Notes and Asides:
Please post any accumulations and location on blog or FB comments. Time/Place/What ya got etc. 

While a busted forecast in my book, it is very hard to determine where sleet warm noses will set up. Just takes a few degrees difference at 5000-7000' off the ground to change it all.

Problem with sleet is it will take a lot of snow an compact it into nothing so hard to measure total snowfall.

On the flip-side it does give cars and feet more traction (initially) and it's not freezing rain and a threat to power lines. 

With that said I'm going to the corner to cry a little inside and then I'll man up and  keep an eye on things. Keep it reals.   

Wednesday, January 20, 2016

WINTER 2016: "BLIZZARD OF '16" FORECAST

*Edited for brevity and clarity - no change to forecast thinking. I will point out the obvious - the further north you are, the snowier side of the scale applies, the further south one is, the opposite...

Stay safe and enjoy the weather. It'll melt before too long anyways (h/t snow-haters). 

TPB 


This has been a disappointing winter in terms of snow and cold so far - unless you are someone who would prefer to take up residence in Bermuda. If this includes you, read no further and go sit by the fire because what follows is my first (might be tweaked) and likely final forecast for the snowstorm beginning Friday AM and ending Saturday.

NEED TO KNOW / FORECAST FORMULATION:
  • THE FURTHER NORTH AND WEST YOU LIVE IN THE PIEDMONT = MORE SNOW, LESS ICE AND FREEZING RAIN. 
  • NO "PLAIN" RAIN EXPECTED 
  • EVERYONE WILL SEE SOME SNOW 
  • NOT EXPECTING POWER OUTAGES TO BE A MAJOR  ISSUE WITH THE EXCEPTION OF EXTREME S/SE ROWAN. IN OTHER WORDS CABARRUS AND POINTS SOUTH (CLT METRO) COULD BE DEALING WITH SEVERE ICING OF .50"+
Easy way to break down this storm for total accumulations is to look at total precip that I think will fall (APPROX 2") and then the expected thermal fields (air at different levels off the ground) and divvy that up by precip type. 

Only 3 possible categories for precipitation: freezing rain (ice), sleet, and snow. No rain expected.
  • Freezing Rain and sleet are the same in terms of liquid equivalence, i.e. .25" of sleet/freezing rain is .25" of water.  
  • Snow is trickier. Depending on the depth and temp of cold air (and a host of other factors) each snowstorm has a generally definable snow to liquid ratio. I expect about 8:1
    • Standard” is 10:1 (1 inch of snow = .1 inch liquid)
    • So .1" of liquid = .8" of snow OR 1 inch of rain = 8" of snow
Generally about 1.8" - 2.0” of liquid (precipitation) expected across the N.C. Piedmont, locally higher in spots if banding occurs, especially on Saturday if snow wraps-around.

Without Further Adieu or Map For Now,

Penn’s Storm Total Forecast
JANUARY 24TH – 25TH, 2016

DAVIE/ YADKIN / FORSYTH COUNTIES
12" - 14" SNOW
.25" SLEET
.10” (Glaze) of Freezing Rain

ROWAN CO.  (SALISBURY) & DAVIDSON 
 6" - 9" SNOW
.3” - .5” SLEET
                  .25” - .35” FREEZING RAIN       

That's all I got. Might make map later, might not, depending on my wife's tolerance of my weather obsession (very high so far, but also the first storm of the year...)       


Sunday, March 1, 2015

Freezing Rain This Morning


Winter Wx Advisories have been hoisted for the overnight hours from 3AM - 5PM tomorrow for about a tenth of an inch of freezing rain and minor sleet accumulation.

Davie and Rowan counties under WWA's - either the same or Freezing Rain Advisories out for the majority of NC. Only difference being the NWS thinks it is possible some sleet/snow mixes in at the beginning in WWA counties and just freezing rain in others - talking very minimal before turns to freezing rain, which will also be minimal.

However, if enough precip falls it could make bridges/roads icy so be careful in the morning. Most likely just a tree branch / elevated surfaces ice glaze expected.

The NWS forecast for Rowan/Davie (GSP) has issued the following accumulation / forecast map, which lists Farmington as the top ice winner with expected .11" and Salisbury close but a mere hundredth off... Right...


So mainly nuisance type event with temps rising above freezing and therefore erasing any ice by the mid-afternoon if not sooner.

Current temps are below 32ยบ now most places or will be per wet bulb temps. 


Here is the WPC Winter Weather Statement and map concerning the chances of having .25: of ice or greater - not much.  Only expect .1-.2" freezing rain overnight and tomorrow morning mainly.

DESPITE THE RETREATING HIGH AND NOT VERY STRONG WARM NOSE WITH  FLAT SYSTEM... ARCTIC/SHALLOW AIR MASS IS EXPECTED TO HOLD STRONG AND COULD REPRESENT THE THREAT OF ICING FROM THE WRN CAROLINAS INTO THE NRN MID-ATL STATES. ITS THE CORRIDOR WEST OF I95 THATS MOST WORRISOME ESPECIALLY FROM WRN NC THROUGH SWRN VA INTO THE DC/BAL AREAS AND POSSIBLY EXTENDING INTO SERN PA. WPC GENERALLY FOLLOWED THE GFS HERE ON QPF AND A BLEND OF 12Z THERMAL PROFILES FOR A .10 TO .25 ACCUMULATIONS FROM CLT TO PHL

Finally, the NWS Advisory Text if you click to read more. Out here. Be safe.