Pittsburgh PA Winter 2016-2017

[blackngoldrules]

My temp has dropped to 32. Looks like I'm getting freezing rain right now. Hate these types of slop systems. 

[north pgh]

Been bouncing back and forth between 31 and 32 all night. Mostly light freezing rain and sleet as well. 

[Rd9108]

These models are all over the place. I think we have to wait a few days before they get a handle on the storm this weekend. Any chance we see any arctic squalls in the meantime?

[RitualOfTheTrout]

Got a couple of light events this week with LES and some little shortwaves then who knows this weekend. Looking like another front end snow to mix to rain deal.

Hopefully amidst all of this we can score a couple inches because in about 7-10 days the pattern looks awful, here is day 10 of the Euro, +EPO, -PNA +NAO +AO, and SE Ridge. All the opposite of what you want to see for cold and snow chances. Hopefully we can reshuffle the deck and get something better for the start of January if this actually happens or it turns out to just be more transient in nature.

 

 

 

[colonel717]

Changes for the NAM and GoodBye DGEX..

http://www.nws.noaa.gov/os/notification/tin16-41nam_updates.htm

Subject:  Upgrade to the North American Mesoscale (NAM) Forecast 

          System and Discontinuation of Downscaled GFS by NAM 

          Extension (DGEX) Forecast System Effective 

          February 1, 2017

 

Effective on or about February 1, 2017, beginning with the 

1200 Coordinated Universal Time (UTC) run, the National Centers 

for Environmental Prediction (NCEP) is proposing to implement 

Version 4 of North American Mesoscale (NAM) and discontinue the 

Downscaled GFS by NAM Extension (DGEX) Forecast System. Changed 

include the following:

 

- Discontinue all DGEX model output

- Remove legacy NAM products on NOAAPORT and NCEP/NWS servers

- Make resolution changes for NAM nests

- Make major changes to the NAM Data Assimilation System (NDAS) 

- Make model changes to convection, microphysics, land-surface 

upgrades; frequency of physics calls increased

 

FORECAST MODEL CHANGES

 

1) Resolution changes to the CONUS (from 4 km to 3 km), Alaska 

(from 6 km to 3 km), and CONUS fire weather (from 1.333 km to 

1.5 km) nests 

2) More frequent calls of physics (now every 2nd time step for 

all domains); change frequency of radiation updates for the NAM 

12 km parent domain from hourly to every 20 minutes

3) Advect specific humidity every dynamics time step

4) Changes to Betts-Miller-Janjic convective scheme to improve 

12 km parent QPF bias, especially during the cool season

5) Update Ferrier-Aligo microphysics to improve stratiform 

precipitation, better anvil reflectivity, reduce areas of 

light/noisy reflectivity over oceans

6) Improve effect of frozen soil on transpiration and soil 

evaporation, leading to reduced cold/moist bias during cool 

season

7) Radiation/microphysics changes to reduce incoming surface 

shortwave radiation; reduced warm-season 2-m temperature bias

 

 

DATA ASSIMILATION / ANALYSIS CHANGES

 

1) Replace 12-h NAM Data Assimilation System (NDAS) with 

3-h analysis updates for the 12 km parent domain with a 6-h data 

assimilation cycle with hourly analysis updates for the 12 km 

parent and the 3 km CONUS/Alaska nests. The Hawaii/Puerto 

Rico/Fire weather nests will be initialized from the 12-km first 

guess at the end of 6-h assimilation cycle. 

2) Use of lightning data (from NLDN and ENL networks) and radar 

reflectivity-derived temperature tendencies in the diabatic 

digital filter initialization.

3) Add execution of the diabatic digital filter initialization 

prior to the NAM forecast (was only run during NDAS in current 

ops NAM version 3).

4) Assimilate new observation types:

  - Aircraft data: Aeromexico, ADS-C, Air-Wisconsin

  - New satellite radiance data: NOAA NPP (ATMS, CRIS), 

    METEOSAT-10 SEVIRI, DMSP-F17 SSMIS; METOP-B AMSUA, MHS, 

    IASI

  - New GPS Radio Occultation data: METOP-B 3 (subtype)

  - New satellite winds: Himawari-B, METEOSAT-7, 10 Imager WV 

AMV, 

    NOAA-15, 18, 19 AVHRR IR AMV, METOP-A, B AVHRR AMV 

[Rd9108]

Gfs basically has a colder redux of this past storm. maybe this can trend colder. 

 

[Rd9108]

I'll be back for the 0z. work until then  

[colonel717]

Here is for Tue/Wed

[RitualOfTheTrout]

7 minutes ago, colonel717 said:

Here is for Tue/Wed

That is quite the uptick, looks like a solid 1-3 if correct.

[RitualOfTheTrout]

54 minutes ago, Ryd10 said:

Gfs basically has a colder redux of this past storm. maybe this can trend colder. 

 

Just looking at 12z GFS for this storm, and its still advertising snow to mix to rain, then as the front approaches we switch back to snow. That might go from moderate to heavy rain to moderate to heavy snow pretty quick before precip shuts off. Not ideal but will be fun to track if it stays interesting like that.

[olafminesaw]

The kuchera snow ratio is below 10:1 on  pivotalweather for the Tuesday storm, but the sounding looks good for high ratios, with the right temp for dendrites at about 700 mb. what gives? I would think it would be around 15:1 based on that, but I'm obviously no expert.

[colonel717]

16 minutes ago, RitualOfTheTrout said:

Just looking at 12z GFS for this storm, and its still advertising snow to mix to rain, then as the front approaches we switch back to snow. That might go from moderate to heavy rain to moderate to heavy snow pretty quick before precip shuts off. Not ideal but will be fun to track if it stays interesting like that.

Yea, looks like all models showing snow transitioning to rain by Sat evening.  GFS has 3-6 before the switch to rain then another c-2in on Sunday.  Then next Tue. GFS has a few inches.  CMC has a much more potent one for next Tue.

I am just hoping we have snow on the ground for Christmas.  Have a projected warm storm late next week so anything we get could be wiped away.

 

[RitualOfTheTrout]

1 hour ago, olafminesaw said:

The kuchera snow ratio is below 10:1 on  pivotalweather for the Tuesday storm, but the sounding looks good for high ratios, with the right temp for dendrites at about 700 mb. what gives? I would think it would be around 15:1 based on that, but I'm obviously no expert.

I honestly don't know. I will admit I'm not that good at figuring out ratios, so much goes into it, temps, moisture, dgz, winds etc... If anyone else knows I'd be curious to know as well.

[RitualOfTheTrout]

55 minutes ago, colonel717 said:

Yea, looks like all models showing snow transitioning to rain by Sat evening.  GFS has 3-6 before the switch to rain then another c-2in on Sunday.  Then next Tue. GFS has a few inches.  CMC has a much more potent one for next Tue.

I am just hoping we have snow on the ground for Christmas.  Have a projected warm storm late next week so anything we get could be wiped away.

 

I would love to have snow on the ground for Christmas. My definition of a white Christmas is just that, snow on the ground, doesn't have to actually snow that day.

[jwilson]

I'll be in Pittsburgh this weekend, so maybe being further north will help in terms of seeing better snow.  As Ritual said, none of the teleconnections are very favorable right now.  There just aren't southern or east coast storms in this pattern.  I've recognized in the past that heavy snow for Eastern Wisconsin is usually bad news for those along the Mason-Dixon.  If the pattern can change before February we'll have a shot with the cold around.  Many are predicting a warmer end to winter, though, so late season chances may be few and far between.

I will say this December is more interesting than last.  At least we have things to track even if they are almost guaranteed to be busts.  50s and 60s around the holiday season just doesn't feel right to me.

[Juliancolton]

1 hour ago, olafminesaw said:

The kuchera snow ratio is below 10:1 on  pivotalweather for the Tuesday storm, but the sounding looks good for high ratios, with the right temp for dendrites at about 700 mb. what gives? I would think it would be around 15:1 based on that, but I'm obviously no expert.

Dendrites grow most efficiently between about -10C and -20C (the DGZ). It's not so much about the "right" temperature for any given height level, as it is getting as much moisture and vertical ascent as possible in the slice of the atmosphere occupying the aforementioned temp range. You can potentially get high-ratio snows no matter where the DGZ is situated.

Here's one product that I like to look at when trying to guesstimate ratios. It overlays vertical movement (cool colors = up, warm colors = down) against the DGZ in a sort of (over)simplified way. There are obviously other important factors, like column saturation and low-level winds, but it's often a good place to start. I've hotlinked it so you can change the location in the url as desired:

[olafminesaw]

17 minutes ago, Juliancolton said:

Dendrites grow most efficiently between about -10C and -20C (the DGZ). It's not so much about the "right" temperature for any given height level, as it is getting as much moisture and vertical ascent as possible in the slice of the atmosphere occupying the aforementioned temp range. You can potentially get high-ratio snows no matter where the DGZ is situated.

Here's one product that I like to look at when trying to guesstimate ratios. It overlays vertical movement (cool colors = up, warm colors = down) against the DGZ in a sort of (over)simplified way. There are obviously other important factors, like column saturation and low-level winds, but it's often a good place to start. I've hotlinked it so you can change the location in the url as desired:

Thanks, I've seen that tool before and lost the link, it's super handy, and that clarification is quite helpful.

The Euro has subzero lows for the city Thursday night. Its probably overdoing the effect of snowcover a bit, but impressive nonetheless.  https://www.windytv.com/?temp,2016-12-16-12,40.183,-79.360,9

[colonel717]

[colonel717]

[CranberryWX]

Last chance before Christmas is next Tuesday/Wednesday, the 20/21st according to the 12z GFS.  After that we get another cold dump that hopefully stays until Christmas Day.

[Mailman]

18z GFS has 1-3" area wide tomorrow.  Hopefully it ends up at the high end of that range.

[colonel717]

38 minutes ago, Mailman said:

18z GFS has 1-3" area wide tomorrow.  Hopefully it ends up at the high end of that range.

Yep looking good for higher end of 1-3

 

[colonel717]

[colonel717]

Could see some nice squalls on Thursday along the cold front

[Mailman]

PBZ not very bullish.

[olafminesaw]

47 minutes ago, Mailman said:

PBZ not very bullish.

A rapidly progressing shortwave will impact the region on
Tuesday via a period of snow. The progression with limited ascent
and specific humidity are expected to inhibit accumulation to
about an inch, and that mainly north of I 70.

[north pgh]

[RitualOfTheTrout]

9 hours ago, Mailman said:

PBZ not very bullish.

Updated  map seems more inline, plus I the less bullish was before they analyzed the 00z runs. Gotta keep in mind too that boundary layer temps are going to be marginal, so we may get some melting. Should be interesting to see how it plays out. If we can lay down 1-2 inches before the arctic air moves in some areas might be able to push 0 for a low.

[colonel717]

Short term models seem to be focusing more north of AGC

 

HRRR

 

[CranberryWX]

28 minutes ago, RitualOfTheTrout said:

Updated  map seems more inline, plus I the less bullish was before they analyzed the 00z runs. Gotta keep in mind too that boundary layer temps are going to be marginal, so we may get some melting. Should be interesting to see how it plays out. If we can lay down 1-2 inches before the arctic air moves in some areas might be able to push 0 for a low.

The latest runs show a strip of higher precip right across the Pittsburgh area today.

The color coding doesn't match the scale colors on that map...lol.