Central PA & The Fringes - February 2014 Pt. VI

[EasternUSWX]

6Z GFS much improved over 0Z. 

[EasternUSWX]

lol back to the goods of yesteryear.

 

[Blizz]

Seems to like PA.... When its supressed it can't seem to print out the high QPF for south of M/D besides the Euro. We'll see if this continues with 12z or it starts to lock in with minor wobbles. I think we still have a few more runs to go before a solution is 'locked in' whether it is north or south.

[EasternUSWX]

[Wmsptwx]

Lol I swear I've seen that map before.

[Voyager]

Lol I swear I've seen that map before.

 

For most of the storms this winter, CTP, and even all the FB pages, could have made one map back in December, and just used the same one the rest of the winter for each storm threat. While the accumulation numbers have changed, the general contours have pretty much been similar for each one. The NWS could have saved a bit of money....lol!

[Voyager]

All joking aside, the State College map and the Mount Holly map don't quite line up right. It seems as if State College likes a more northern track, bringing 8-10 inches up into Schuylkill County, then extrapolating it north eastward into the southern half of Carbon, and perhaps Monroe Counties. The Mount Holly map keeps the 8-10 contour farther south, coming out of Lancaster County, skirting the southern quarter of Berks, and then into Montgomery and Bucks. Per Mount Holly, only 4-6 would fall in Schuylkill and 6-8 in the Lehigh Valley.

 

I'm curious to see which office corrects. Usually as we get closer to "game time" they seem to coordinate better.

[NeffsvilleWx]

 

3:00pm Friday, February 28:

I always try to issue a responsible forecast that expresses both the most likely outcome AND the uncertainty of the situation....and so today I could probably write a book on the complexities of the upcoming storm. The southern impulse for our Sunday-Monday event is producing heavy rain and mountain snow in CA today, but the actual upper-level system won't come onshore until early Saturday. Currently, the upper-level system is closed off and moving very slowly--just when this system releases into the southwest states is critical to the outcome here...timing, precip type, and precip amounts. Computer models are a tool we use to help us suss out possible outcomes and veteran meteorologists use these tools with discerning and thought, rather than blindly hugging their choice model and letting it do the forecasting for you. The current situation--a closed low off the west coast--is one of the situations models struggle with...and so the wise meteorologist proceeds carefully in issuing targeted forecasts with sharp lines too early in the game. And so with this storm, while I'm confident that a wintry mess will impact the region Sunday night into Monday, it's really still a bit too early to give county-by-county specifics...or draw sharp lines on maps with inches of accumulation. Web sites interested in "hits" (traffic, clicks, and revenue dreams) often throw prudence and professionalism out the window and post sensational forecasts hoping for "shares", "likes", and fame. Of course, that's not how we play it here at MU--we strive to issue reasonable/responsible forecasts that give enough information for decision-makers, while trying to avoid grandiose forecasts filled with bad information and false sense of certainty.

Given the difficulty of the storm coming into Cali, I'm holding off on issuing a targeted accumulation map until early Saturday. The main event (here) isn't until Sunday night and Monday, so there's no reason to issue a bold forecast now--that may need revised a few times--when some of the key ingredients remain a bit nebulous. Instead, I'll issue a Storm Overview map (below) giving you plenty of info to begin adjusting plans for Sunday and Monday. Check back midday Saturday for a detailed Storm Outlook map.

Let me leave you with a few bullet points:

No record low this morning, as we only got down to 3 degrees. However today's daytime high of 20 shatters the record for "lowest max temp" (28) for this date.

Saturday into Sunday will turn a bit milder (it's all relative at this point!), and Sunday's high temps should rise just above freezing. The leading edge of light precip will arrive during the afternoon...probably as light rain or a light "icy mix". Arctic air will be pressing in from the north Sunday evening, so temps should be at or below freezing when the steadier precip arrives between 7pm and 11pm. My concern is for a few hours of freezing rain, followed by couple/few hours of sleet.

By later Sunday night into Monday, deeper Arctic air should have moved in, thus allowing for a period of all snow. Several inches of snow are quiet possible later Sunday night into Monday, before the storm exits during the afternoon.

Timing of the southern stream impulse (the Cali storm) is the key to the quickness of the changeover here--a rapid change to snow could leave us with 10 or 12 inches, whereas an extended period of plain rain and ice would leave us with just a couple inches. The most likely outcome is somewhere between these two extremes. Yet another possibility is that the Cali system flattens out as it moves east into the Arctic confluence zone...in which case it would be a weaker storm here with the best precip shearing out to our south. Obviously, this storm isn't even half-baked yet!

As for travel, the daylight hours Sunday shouldn't be too problematic unless you are traveling north and west into the mountains. Locally, it's Sunday evening through Monday afternoon that looks to be most treacherous. A hard freeze Monday night means the wintry mess will linger on some secondary roads into Tuesday.

[psuhoffman]

I didn't think the move back north would start until at least 12z but maybe even 0z tonight. With the gfs nam and rgem I think we may have seen the bounce back begin at 6z. The best news is all of them came north the right way, by putting less emphasis on the first wave and amplifying the second more.

[heavy_wx]

Comparing today's 06z GFS with yesterday's 06z run, it appears as if the biggest difference is the strength of the ridge over the Pacific northwest. I chose yesterday's 06z run because that was the last run to give the entire state of PA a significant snowfall. You can see it here on the 24 hr forecast from today's run.

 

 

 

The 48 hr forecast from yesterday's 06z run has a weak trough over the Pacific northwest.

 

 

Looking at this morning's water vapor image over the north Pacific region, you can see there is a clear plume of moisture offshore around the latitude of central CA and longitude of ~140W. This feature may be responsible for building the Pacific NW ridge over top the 500 mb trough responsible for the storm in southern California.

 

 

The main result of the Pacific NW ridge development is that it forces more troughing downstream underneath where the PV lobe will be positioned. This serves to bring the height gradient associated with that PV lobe farther south, along with the frontal boundary crucial for track of this next system. It also allows for freer rotation of the enhanced vorticity maxima and associated shortwaves around the main lobe. One of these shortwaves positions itself over southern ON/QC around Monday morning, pushing the boundary farther south.

 

As this pacific moisture becomes better sampled over the west coast, I suspect we'll see some further strengthening of this ridge. However, I also think there will still be some amplification of the ridge ahead of the shortwave currently moving onshore in CA. This will probably occur as the Gulf convection begins to develop Sunday into Monday. We'll also have to see how the shortwave rotating around the PV lobe falls into place. If it swings through faster than modelled, we could see the 500 mb gradient weaker and the boundary farther north. There's no indication right now that will happen, but it is something to watch.

[Eskimo Joe]

OMG lol this response to the guy that came on my page and posted the S & S map is an instant classic.

 

greg.jpg

Isn't that Greg guy from CTP?

[canderson]

So, MDT might see > 12" or lucky to get 3"? Nice.

[Eskimo Joe]

OT, but NWS is proposing changes to the icons for the point & click forecasts.  I'm excited about the changes:  http://www.weather.gov/forecast-icons

 

Scroll down the page to see the changes.

[pawatch]

This from the NWS forecast discussion. Could someone explain what they are talking about....Thanks

 

THE 06Z NAM HAS INJECTED A VERY INTERESTING
TWIST TO THIS UPCOMING EVENT BY DISPLAYING A WELL-DEFINED...AND
RATHER INTENSE RIBBON OF 850-700 MB FGEN BETWEEN THE RT22/322
CORRIDOR AND I-80 LATE SUNDAY THROUGH THE MID MORNING HOURS MONDAY.

 

http://forecast.weather.gov/product.php?site=NWS&issuedby=CTP&product=AFD&format=CI&version=1&glossary=1&highlight=off

[NeffsvilleWx]

This from the NWS forecast discussion. Could someone explain what they are talking about....Thanks

 

THE 06Z NAM HAS INJECTED A VERY INTERESTING

TWIST TO THIS UPCOMING EVENT BY DISPLAYING A WELL-DEFINED...AND

RATHER INTENSE RIBBON OF 850-700 MB FGEN BETWEEN THE RT22/322

CORRIDOR AND I-80 LATE SUNDAY THROUGH THE MID MORNING HOURS MONDAY.

 

http://forecast.weather.gov/product.php?site=NWS&issuedby=CTP&product=AFD&format=CI&version=1&glossary=1&highlight=off

 

frontogenesis, I believe. I think they're mentioning banding potential between RT22/322 and I-80 during the mentioned time period.

 

Check out presentation on frontogenesis by the NWS: http://www.crh.noaa.gov/lmk/soo/presentations/frontogenesis_lmk2.pdf

[Eskimo Joe]

FYI:

 

 

 

 

Sat Mar 1 13:35:42 2014 GMTNOUS42 KWNO 011335
ADMNFD
SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE
NWS NCEP CENTRAL OPERATIONS COLLEGE PARK MD
1334Z SAT MAR 01 2014
THE 12Z NAM HAS STARTED ON-TIME...WITH 14 ALASKAN...29
CANADIAN...70 CONUS...9 MEXICAN AND 8 CARIBBEAN RAOB REPORTS AVBL
FOR INGEST.
12Z NAM RAOB RECAP...
78073/NAS - PURGED TEMP/RH 854-847 MB...WET BULB EFFECT
71082/YLT - PURGED TEMP/RH 851-847 MB...SUPER-ADIABATIC
78866/SXM - PURGED WINDS 400-398 MB...BAD SPD
76654/MZL - 10142...GROUND EQUIPMENT FAILURE
76692/HYY - 10158...FLIGHT EQUIPMENT FAILURE
CRITICAL WEATHER DAY STATUS...
A REGIONAL CRITICAL WEATHER DAY...CWD...IS IN EFFECT FROM 1200Z
SAT MAR 01 2014 THROUGH 0000Z TUE MAR 04 2014. THE FOLLOWING NWS
REGIONS ARE IMPACTED BY THIS CWD...SOUTHERN/EASTERN/CENTRAL.
NCEP/NWSTG AND THE NCF ARE ALSO PARTICIPATING IN THIS CWD TO
ENSURE A RELIABLE FLOW OF WEATHER DATA.
OREILLY/SDM/NCO/NCEP

 

[Eskimo Joe]

frontogenesis, I believe.

 

Check out this link: http://www.crh.noaa.gov/lmk/soo/presentations/frontogenesis_lmk2.pdf

 

 

This from the NWS forecast discussion. Could someone explain what they are talking about....Thanks

 

THE 06Z NAM HAS INJECTED A VERY INTERESTING

TWIST TO THIS UPCOMING EVENT BY DISPLAYING A WELL-DEFINED...AND

RATHER INTENSE RIBBON OF 850-700 MB FGEN BETWEEN THE RT22/322

CORRIDOR AND I-80 LATE SUNDAY THROUGH THE MID MORNING HOURS MONDAY.

 

http://forecast.weather.gov/product.php?site=NWS&issuedby=CTP&product=AFD&format=CI&version=1&glossary=1&highlight=off

CTP is discussing a phenomena called fronteogenetic forcing.  This presentation I'm linking is a great teaching tool, technical but descriptive.  Pay close attention to Slide #37:

 

http://www.comet.ucar.edu/class/WDTB_WinterWx/03-2/docs/frontogenesis_talk_020918.ppt

[Superstorm]

Many of the snows in the Midwest is from frontogenic forcing.

Sent from my iPhone using Tapatalk

[pawatch]

Thank You guys! "awesome links"  Looks like I got some reading to do.

[KPITSnow]

Nam with another 200 mile shift.

[Eskimo Joe]

NAM is in line with EURO/GFS/Canadian.  Rt. 22 and points south storm.

[Voyager]

NAM is in line with EURO/GFS/Canadian.  Rt. 22 and points south storm.

 

Yup. I think the models are honing in on what will be close to the final solution. A few wobbles here and there, but generally another southern tier/Mason Dixon line special.

[MillvilleWx]

This is actually a formidable storm for the southern tier counties. NAM shows heaviest precip displaced in that area a bit east towards Lancaster and further east. Qpf values range from 1" in LNS and falls rapidly once north into Lebanon and I80 pretty much cut off of precip. These types of storms will be indicative of a tight N/S gradient so someone in the region will get fringed and others will be good to go. I keep saying this over and over, but snow breeds snow. The jackpot areas this winter will once again reap the rewards most likely. I do think the NAM is too far south overall in the situation since it's been crazy with its shifts in this time frame, but it should start honing in on a solution next few runs. My jackpot area of Adams over to Chester for PA still stands as called. 

[NortheastPAWx]

Just amazing how this one fell apart completely in 24 hours...a statewide crusher...instead now just the south.

 

I think the BlizzardMobile will need to be parked. March big one isn't coming folks...and if it does, you know it will be a southern event.

[canderson]

First guess:

MDT 3-5"

LNS: 6-9"

York: 8-10"

UNV: 1-3"

[MillvilleWx]

http://www.nynjpaweather.com/2014/03/01/final-forecast-for-storm-impacts-on-march-2-3rd-2014/

 

Here's Steve D's thoughts if anyone is interested. Pretty much my forecast for hardest hit areas. I don't have the high end of southern tier accumulation at 15" but rather 12". 8-12" to me is a good call for southern Pa counties. I think Northern MD will end up doing very well

[MillvilleWx]

First guess:

MDT 3-5"

LNS: 6-9"

York: 8-10"

UNV: 1-3"

 

I think that's a very reasonable call you go there. I83 Blizzard should get 12-15" 

[Itstrainingtime]

Just amazing how this one fell apart completely in 24 hours...a statewide crusher...instead now just the south.

I think the BlizzardMobile will need to be parked. March big one isn't coming folks...and if it does, you know it will be a southern event.

Pretty bold statement to make on March 1st. As time goes on and warmer air gradually progresses further north, it's quite possible that storms target areas north of where they have hit all winter. Who knows?...

You set yourself up to look really foolish making absolute statements like that. Their are a whole lot of weather extremes to come over the next several weeks.

[NortheastPAWx]

I think that's a very reasonable call you go there. I83 Blizzard should get 12-15" 

Nah, he's 18"+...

[MillvilleWx]

Nah, he's 18"+...

 

Touche