Saturday, January 24, 2015

Wait for ground truth

This time in Baltimore, 
wait for "ground truth."




Latest NOAA liquid projections show 0.50" or more for southern I-95 corridor, 
in excess of 1.00" for metro areas to New York City and into most of New England

6:30 AM 1/25 - UPDATED STATEMENT IN PROGRESS


With the NWS Advisory Map lighting up overnight straight to Maine, the "Boom" scenario is becoming more probable as a faster arrival of the clipper into the Mid-Atlantic with a faster development of the coastal Low puts the I-95 corridor under an increased risk of seeing 4 or more inches of snow. 

The projected surface map for 7 PM tonight displayed left shows the situation becoming a battle for control of the "Route 30" corridor between a southward pressing Arctic High and the Low developing underneath as it slides East.

A HYBRID CLIPPER AND A SCHEMING ARCTIC HIGH:




  • Unlike traditional clippers that just swing through unimpeded by a High pressure system to the north, this one has to battle for control of the map as it moves East.
  • This will enhance Easterly flow ahead of the system while the High delivers cold Arctic air, creating an ideal arrangement for snow,
  • The outcome will be a tale of two different storms. The west to east clipper will eventually deliver it's energy to, and form a secondary coastal Low that should turn the corner and head north, bringing heavy snow to the northeast corridor.
  • We think the cards are not yet all played, though. Southward pressing Highs like this can play a steady quiet hand through the round, then shoot the moon when you least expect it. Areas south of Baltimore and on the Eastern shore should stay alert for a changing forecast if this High tries to drop that Queen of Spades.

11:00 PM 1/24 - WSC TEAM ADVISOR'S STATEMENT 

Before everyone takes off into snowfall projection land for this next event, there is an important weather concern our Advisors and Senior Forecasters wish to bring forward. This message was also shared with our partners, clients and Powderhound Insider subscribers.

BOOM OR BUST? We believe there is both an increasing probability of a blockbuster event, AND an equally strong chance for a major bust. We have seen this kind of setup before, and we've seen the negative reaction from readers when a big forecast goes belly us. Here's the issue:
  • "Clipper to Coastal" type energy transfer forecasts are fraught with peril. Sometimes they come together like a charm, other times you are expecting 6"+ of snow, and get clouds.
  • A healthy and moisture laden clipper IS coming rapidly East from the northern Plains. A large coastal storm should develop on the heels of that clipper energy as it reaches the Atlantic.
  • However, the scenario concerning us is that the Baltimore-DC region will be whipped into a frenzy just like this last dud (which we also expected to be a significant snow/ice event too....). Winter Storm Warnings will fly, then the snow will come down in sheets. Then some school districts may may pre-emptively announce closures Sunday night thinking that being proactive is always better.
Then--- at 3 AM, it shuts off-- and, crickets. The supposed energy transfer from the clipper to the coastal occurs too late. The front end snow turns out to be much less than we thought (when does that ever happen?) and there's a 12 hour window which was supposed to be all snow, and ends up as all nothing. Crews begin cleaning up, and viola! By 6 or 7 AM, many lots and roads are improving. 

But Monday would be beyond salvaging. Businesses and schools would be already closed, when they could have squeaked out a 2-hour delay or modified hours. It is true several models are showing 0.60" or more for BWI airport, and that translates to 6-8" easily, but we've seen the models overproject on snow several times this winter.

This system is not a traditional coastal, nor is it a customary clipper. It's a clipper-to -hybrid-to-coastal, and it MIGHT become an example of our old rule: "Storms from the West don't bring extra rest." (If you work in or attend a school system.)  For now, the one lesson we want to convey to all essential staff whose decisions impact their organizations:
This is one time we suggest you wait for ground truth to prove the forecast. 
Don't pre-emptively close Sunday night just because it looks like a blizzard, even if there's a Winter Storm Warning. Just wait and see what conditions look like at 5 AM Monday. Maybe this time ground truth, or lack of it, is all the observations you will need to make the call.

31 comments:

samantha said...
This comment has been removed by the author.
samantha said...

When I stumbled across FF 6 or 7 years ago now, the forecasts were spot on, clearly written without a lot of fluff, but still filled with all the cool, simple scientific explanations for their predictions. For the last few years the site appears to be more of a sweatshirt ad filled with overdone movie quotes and 50/50 weather predictions. I've also noticed the updates on FF come up a day or two after my local news has already put out the weather warnings. Fingers crossed it's not too late for FF to return to its roots of high and college students writing brilliant forecasts. Can we get away from the flash and filler?

Andy, Southern York County Pa said...

It is clear we are on the edge of a major nor'easter in the greater Baltimore area. Phila, NJ, NYC and New England will have near or above 24 inches.

Any shift in either direction will impact ground truth for our area. I think a reasonable expectation is 4-8 inches from Baltimore north. South and south west of Baltimore 2-4 seems reasonable.

The models have struggled and this is a fluid situation. This will still likely be the largest snowfall of the season to date for most of us I don't trust the models with this set-up as it is very volatile and we are on the edge of something huge.

Here is to another day of crunching data, and to the most interesting storm we have seen in a long time!

Westsidehideaway said...

Hi Samantha and Fellow FF Followers.

I see Samantha's point regarding timing. I also agree about watching the wording of your headlines. Mr. Foot even asked for feedback on Friday evening on the use if Dynamite on that headline. It did have an "alarmist" feel to it when there was so much uncertainty to the event. So I suggest that you let us bloggers take the lead on being Weather Drama Kings and Queens. I love this site. I am a banker by day but love learning about (and Gossiping about) the Weather and this site lets me do that. And watching all of my fellow bloggers comments and banter makes for a really fun way to help get through the winter.

Westsidehideaway said...

Channel 11 is reporting 2-4in tonight and tomorrow for Bmore. Tuesday is the wildcard and they won't comment on totals until tomorrow. Hmmmmm

BioPat said...

Just got up to check the most recent posts and am a bit disappointed that we're not seeing the storm moving further west. I need to check out some more information and will work on that once my eyes can focus a bit better. I am sure we'll be seeing multiple snow events over the next several days.

genser95 said...

To me this is a "somewhat" classic case of the strong blizzard forming a few miles too far north/east for this area. It's happened many times before.

Adam Herb said...

Foot Team - I thought this morning's explanation (and title) of how it could go in a few different directions was good. Thanks for that. It will help me just go about my day, and I will just wait and see what happens, knowing it is uncertain. The detail in the post goes beyond what I hear in the news. Keep up the good work!

Syracuse1 said...

So I see the NWS is flip flopping with their watches and warnings today. having changed the Winter Storm Watch back to a Winter Weather Advisory.

Andy, Southern York County Pa said...

Statement as of 7:54 AM EST on January 25, 2015

... Winter Weather Advisory now in effect from 6 PM this evening
to 1 PM EST Monday...
... Winter Storm Watch in effect from Monday afternoon through
Tuesday morning...

The National Weather Service in State College has issued a Winter
Storm Watch... which is in effect from Monday afternoon through
Tuesday morning.

* Locations... the lower Susquehanna valley.

* Hazard types... snow.

* Accumulations... 3 to 5 inches tonight through midday Monday.
Additional significant accumulation is possible from a
secondary storm Monday afternoon through Tuesday morning.

* Timing... snow should arrive this evening and last through
Monday. However... most of the accumulation will likely occur
tonight. Additional significant snowfall will develop on the
western edge of a strong secondary storm Monday afternoon
through Tuesday morning... and several more inches of snow are
possible in the watch area at that time.

* Impacts... hazardous travel.

Precautionary/preparedness actions...

Hazardous winter weather conditions are expected or occurring.
Use caution if traveling. For the latest weather information... go
to weather.Gov/statecollege or monitor NOAA Weather Radio.

Report snow or ice accumulation to the National Weather Service
State College by sending an email to ctp.Stormreports@noaa.Gov...
posting to the NWS State College facebook Page... or tweet
@nwsstatecollege with the hashtag c... T... p... W... x.

NeedaSnowday said...

I just kicked the box with the snowblower still tightly packed in it..... :::: stomps off cursing NE again ::::::

Andy, Southern York County Pa said...

Statement as of 9:38 AM EST on January 25, 2015

... Winter Weather Advisory in effect from 10 PM this evening to
6 PM EST Monday...

The National Weather Service in Baltimore MD/Washington has
issued a Winter Weather Advisory for snow... which is in effect
from 10 PM this evening to 6 PM EST Monday. The Winter Storm Watch
is no longer in effect.

* Precipitation type... snow... possibly heavy at times.

* Accumulations... 2 to 4 inches.

* Timing... snow will begin late this evening and continue through
late Monday afternoon. The heaviest snowfall will occur
between midnight and late Monday morning.

* Temperatures... in the upper 20s.

* Winds... northeast 10 to 20 mph.

* Impacts... roads will be snow covered and slippery with
visibilities being reduced to near one-quarter mile at times.
The combination of snow covered roads and low visibility will
make traveling dangerous.

* Outlook... snow will continue Monday night into Tuesday... with additional
accumulations possible.

Precautionary/preparedness actions...

A Winter Weather Advisory for snow means that periods of snow
will cause primarily travel difficulties. Be prepared for snow
covered roads and limited visibilities... and use caution while
driving.

Andy, Southern York County Pa said...

Question is how much does Baltimore Metro receive from the coastal? If there is any tick west the Baltimore area would also likely be under a watch after the advisory. State College took that 2 part approach of Advisory and Watch. If 12z follows west track then LWX would likely hit Baltimore with a Watch also.

Andy, Southern York County Pa said...

BOOM! AS EXPECTED WINTER STORM WATCH FOR CENTRAL MD

Statement as of 10:40 AM EST on January 25, 2015

... Winter Weather Advisory remains in effect from 10 PM this
evening to 6 PM EST Monday...
... Winter Storm Watch in effect from Monday evening through
Tuesday afternoon...

The National Weather Service in Baltimore MD/Washington has
issued a Winter Storm Watch... which is in effect from Monday
evening through Tuesday afternoon. The Winter Weather Advisory
remains in effect tonight through Monday.

* Precipitation type... snow... possibly heavy at times.

* Accumulations... 2 to 4 inches expected tonight through
Monday... with an additional 3 to 5 inches possible Monday night
through Tuesday.

* Timing... snow will begin late tonight and continue through
Tuesday. The heaviest snowfall will occur between early Monday
morning and Monday afternoon... with another round of heavy snow
possible Monday night.

* Temperatures... in the upper 20s.

* Winds... north 10 to 20 mph with gusts up to 30 mph Monday night
and Tuesday.

* Impacts... roads will be snow covered and slippery with
visibilities being reduced to near one-quarter mile at times.
The combination of snow covered roads and low visibility will
make traveling dangerous.

Precautionary/preparedness actions...

A Winter Weather Advisory for snow means that periods of snow
will cause primarily travel difficulties. Be prepared for snow
covered roads and limited visibilities... and use caution while
driving.

A Winter Storm Watch means there is a potential for significant
snow... sleet... or ice accumulations that may impact travel.
Continue to monitor the latest forecasts.

NeedaSnowday said...

Watch.... Advisory.... Watch....

Getting whiplash.... should I kick the snowblower box again?

Andy, Southern York County Pa said...

6-10 inches by Tuesday morning for the Baltimore metro area seems like a good early estimate. Blowing a drifting could be a problem by Tuesday.

Andy, Southern York County Pa said...

Needy two separate impacts from the same event. First is advisory level front end Clipper snow, second is potential warning level 5 plus inches from the coastal after clipper bombs out.

Wisconsin Native said...

I'm wondering if these projections Andy has are just the boom or what he really thinks is going to happen. I thought I read the comments earlier from the week expecting no more than 1-3 inches. Obviously as we get closer to the actual event things get a little more accurate. I could really use a day off from work tomorrow to get ahead on some schoolwork and snowmen (probably not enough for an igloo).

Shawn B. said...

First time poster, but longtime reader/follower of Foot and Andy's take on storms.
I have to say kudos/thanks from years back on that Jan 26, 2011 that you pegged and NWS was late to the game issuing warnings. The dynamic cooling of that storm was just amazing watching, and remembered your warnings on that. Saved me and my coworkers a nasty commute.

So curious your take on this one, is this storm currently performing to the models. Looking at the latest radar. It looks more juicy to me. Is it a bit stronger than was modeled? I know models will be off to a degree. Curious of the south and westward slide. See Mike Masco seems pretty Gung Ho on 6-10 from Baltimore up.
By the way, I am in the Inner Harbor area just for geographic sake.

Andy, Southern York County Pa said...

SPECIAL STATEMENT
Statement as of 11:56 AM EST on January 25, 2015

... Complex winter weather coming to Baltimore/Washington region
tonight through Tuesday...

A complex winter storm scenario will develop tonight and continue
through Tuesday for the greater Baltimore/Washington region.

Low pressure will cross the Ohio Valley tonight... then redevelop
offshore of Cape Hatteras as a strong coastal storm during the
day Monday. This will give the greater Baltimore and Washington
region two separate bouts of winter weather.

The first round of precipitation will start early this evening in
western Maryland... extreme northern Virginia... and the eastern
Panhandle of West Virginia and continue through Monday. In these
areas... the precipitation may start as a period of mixed rain and
snow before changing over to all snow by daybreak Monday. The
snow will continue through the day on Monday... making travel
difficult particularly north of Interstate 66 and west of the Blue
Ridge. Winter storm warnings have been posted for this region.

Tonight... as the precipitation progresses eastward towards the
Interstate 95 corridor... rain will mix with snow in the immediate
Baltimore and Washington DC metropolitan areas as it spreads
eastward. However... by daybreak Monday... precipitation should
change over to all snow across the entire region with the
exception of southern Maryland. Some models suggest that
precipitation on Monday will stay all rain in areas south and
east of Washington DC... so there remains considerable uncertainty
for areas of Maryland south of Route 50. Winter weather
advisories have been issued for the greater Baltimore and
Washington metropolitan areas.

Finally... as the coastal storm starts to rapidly develop late Monday
afternoon off the North Carolina coast... a second round of winter
weather may further impact the region... this time primarily east
of Interstate 95. Snow bands along with gusty northeast winds up
to 40 mph are expected to develop around the powerful storm system
Monday night and Tuesday as it moves northeast towards Cape
Cod. An additional 5 inches or more of snow is possible in the
counties along Maryland's portion of the Chesapeake Bay. Blowing
snow is also possible... reducing visibilities to below one-quarter
of a mile at times. Winter storm watches have been issued for the
Maryland counties directly adjacent to the Chesapeake Bay.

Stay tuned to your favorite media outlet and NOAA Weather Radio
for further updates on this developing winter storm system.

weed said...

I read through all the comments and I still don't know if it's a BOOM or a BUST.....at what point will someone make a COMMITMENT to the forecast.....I realize it's difficult to do BUT There has to be a tipping point right????

Andy, Southern York County Pa said...

I am looking at this as a 6-10 inch type event for the Baltimore Metro region. It is a dynamic system and the details continue to evolve as the storm tracks toward our latitude. No one knows for certain how this will evolve so giving a certain forecast in a highly volatile low confidence environment would be reckless. Those numbers are my general expectation of where we are heading, but I would not bet the barn on it just yet.

Mike Cheuvront said...

Weed and all others agonizing over this situation listen up---When you see Barometric pressures falling off the coast of North Carolina. When you see precip moving our way. When you see how far off shore the Low goes and the intensity of it. When you see if it hugs the coast or goes too far off to effect us. THAT IS WHEN YOU WILL KNOW FOR SURE. It's really that simple. The big storm has not even been born yet my friend. Look at the radar. There is nothing there coming up from the south or forming at the coast yet. All this is conjecture based on COMPUTER MODELS and the way they are seeing things play out. No one really knows. Andy has said he feels 6-10". Awesome! But we get shafted if the storm is too far off the coast. Many times we get shafted here in Maryland, you all know these things! Calm down and back away from the computer and wait and see what happens. Be prepared for the worst or in our case the best scenerio but expect the lesser amount and be happy and maybe surprised. Be centered in reality. No one really knows for sure about this complex situation until it starts to unfold and show us it's hand.

Tara said...

What about between Baltimore and Frederick? By the sound of all the articles Baltimore and east, and western Maryland will be hit but not so much in the middle?

Morpheus said...

Being south and east of DC - This looks like a bust for us low lander, south of route 50 folks, if things play out as currently modeled. Here is hoping for a southern shift in clipper track...Man raises fists in the air and yells RAIN!!!!

Wisconsin Native said...

There is nothing more depressing than a cloudy rainy Monday in mid/late January. Bring on the powder and I'll be happy. Great analysis from you guys. I'll be paying attention as new analysis gets posted. Maybe the Canadians will let us borrow some cold so I can chill beers in the snow instead of my over packed fridge.

weed said...

thank you Mike...I understand better now......and Andy of course....I'm running to the store now to stock up on essentials....I Have a well so if we lose power I'm SOL....I'll be filling the tubs up in the bathroom just in case....I will check back when I return from the store to see if there are any updates....I love science even if I don't understand 99% of it:)

Mike Cheuvront said...

For what it's worth. observation.

Wind Direction (WDIR): N ( 350 deg true )
Wind Speed (WSPD): 4.1 kts
Wind Gust (GST): 6.0 kts
Atmospheric Pressure (PRES): 29.95 in
Pressure Tendency (PTDY): -0.04 in ( Falling )
Air Temperature (ATMP): 45.9 °F
Water Temperature (WTMP): 52.5 °F
***********************************
Station HCGN7 - 8654467 - USCG Hatteras, NC *****The Pressure off North Carolina is 29.95 and tending to fall. The energy is down there waiting to be ignited.

Westsidehideaway said...

So this year I have to be a Powderhound Insider to get frequent updates from the Foots team? Is this correct?

Tom Ley said...

First time to post. I need a glossary. Does one exist on the site? For example, Andy said: "Question is how much does Baltimore Metro receive from the coastal? If there is any tick west the Baltimore area would also likely be under a watch after the advisory. State College took that 2 part approach of Advisory and Watch. If 12z follows west track then LWX would likely hit Baltimore with a Watch also."
What does the term 12Z represent?
Thanks
Tom

genser95 said...

Tom,
Computer models are run at certain times of day, and those times are identified in Greenwich Mean Time. So 12Z simply means 12:00 GMT, which in our case is 7:00 AM because we are five hours behind GMT.