Sunday, February 14, 2016

Flurries No Worries

Fear not, any flurries you see do not mean the storm has "started". No accumulation expected until after Midnight for majority of Piedmont.

 Worst case a heavier snow shower - while unlikely - could lead to a dusting at most. 

Still plenty of time to go buy bread and milk, even though you don't need it...

HRRR  simulated radar for the next 15 hours courtesy of Weatherbell Analytics

Saturday, February 13, 2016

Presidents Day Storm 2016 Update

Main change to forecast thinking is onset time of precipitation should be about 12 hours sooner. Generally speaking snow should start falling approx midnight - 2AM.

Models still struggling with some of the finer details so expect mixed messages from the NWS and local TV Mets. 

Reason being the low pressure track(s) which dictates timing of the warming is basically all over the place depending on which model one puts their faith in - as you can see in NWS map below which depicts potential low pressure locations and the big "L" is the official NWS guidance. Could be in Indiana or Alabama initially before going to the coast....but it doesn't really matter.
Storms in NC chasing departing cold air rarely come out on the winter weather side. Rain will be the bulk of the precipitation for most areas except far NW Piedmont.


So my model of choice is Penn Blanton's experience and I'll keep forecast as is for now and update tomorrow if there is need to.

Only other note at the moment is that total accumulation could go up in Davie and points N and West a bit and ice (freezing rain) is still the main concern in the NW Piedmont.   

Just not seeing Rowan and points south having to deal with much more than I posted yesterday. All to be wiped away by rain in the end regardless. School is still out folks and work for most looks less likely given earlier start time of snow.

Winter Storm Watches are posted for all counties and you can find text  here: NWS Home



Presidents' Day Storm 2016


I'll jump right to the point folks - we are looking at a "winter warm-up" storm to start the week with snowfall area wide beginning Monday AM, transitioning to sleet, then freezing rain, and ultimately all rain (temps above 32F) for everyone in the N.C. Piedmont.

Yes, your typical "slop" of a storm, however, by Monday evening most locales shouldn't even have any travel problems or snow on the ground. Using (in my mind...) a Cabarrus-Rowan-Davie South to North axis as far as accumulations.

When/What/Where/Why/School?: 

Snowfall should begin approx 6-9 AM Monday all areas. Exact time TBD.

Snow/Sleet, accumulating 1-3" South to North mixing with and changing to sleet around 10AM in southern areas as warm air moves north.

12-2PM most areas should transition to freezing rain. Expect a glaze around Concord increasing to approx .20 inches in N. Davie County 

4PM Rain, temps above freezing, except Davie County which might be a few hours later, hence higher amounts of ice.

Rain continues through Tuesday AM as temps warm overnight. Your high temperature on Monday will occur at 11:59 PM...

No school Monday. Work, eh, depends on what you do and exact time snow starts.

Fact = all snow that falls will stick as surface temps will be cold from the 48 hours of sub-freezing weather Friday night - Monday.


Nerd alert...
Storm Setup - Left Over Cold Air
As warm air moves in aloft the precip types will change as described above. We lack a parent high pressure system to the North for a classic cold air damming scenario, instead an "in-situ" damming event will occur. An in-situ wedge simply means the very dry (cold) air left from this weekend is our "source". It will take time to saturate and warm the air near the ground from about 10K feet down because at the start of storm the surface dew-point will be 10-15° F (AKA cold/dry) across the Piedmont.
Monday PM
Images above found here: https://climate.ncsu.edu/climate/winter_wx/Patterns.php


I'll put a map out sometime this weekend with an update if needed. Ciao.




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...)