Pittsburgh PA Winter 2016-2017

[colonel717]

[MikeB_01]

 

00Z GFS backing down on snow over the last few runs. NAM Para still showing a solid 4-5 though.

[north pgh]

Looking more like a 1-2 then slop by the time we wake up Saturday. I hate the overnight snows because you can't even see it.

[RitualOfTheTrout]

7 hours ago, north pgh said:

Looking more like a 1-2 then slop by the time we wake up Saturday. I hate the overnight snows because you can't even see it.

That's really the most you can hope for and really all this was likely going to be anyways given the synoptic setup. Freezing rain will likely be the bigger headline because even after we break 32 at the surface for air temps, surface of everything else will likely lag well behind that. Not saying a big ice storm, but it only takes a light glaze to make things nasty. By mid afternoon though everything should be in the process of melting / washing away so I'm not to heart broken over not getting much snow on the front end.

[colonel717]

The consistency of each model run for this Fri/Sat system is amazing.  If you click each earlier model run for the same hour there are only minute changes from the previous run and this goes back a couple of days.   Its not only 1 model, its each one.    Why can't we get this consistency for all storms....freaking cutters...  

[Mailman]

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE PITTSBURGH PA
227 PM EST THU DEC 15 2016

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ020-021-029-031-
073>076-WVZ001>004-012-021-509>514-160330-
/O.NEW.KPBZ.WS.A.0002.161217T0000Z-161217T1900Z/
/O.CON.KPBZ.WC.Y.0003.000000T0000Z-161216T1400Z/
GARRETT-TUSCARAWAS-CARROLL-COLUMBIANA-COSHOCTON-HARRISON-
JEFFERSON-MUSKINGUM-GUERNSEY-BELMONT-NOBLE-MONROE-BEAVER-
ALLEGHENY-WASHINGTON-GREENE-WESTMORELAND-WESTMORELAND RIDGES-
FAYETTE-FAYETTE RIDGES-HANCOCK-BROOKE-OHIO-MARSHALL-WETZEL-MARION-
MONONGALIA-RIDGES OF EASTERN MONONGALIA AND NORTHWESTERN PRESTON-
PRESTON-EASTERN PRESTON-WESTERN TUCKER-EASTERN TUCKER-
INCLUDING THE CITIES OF...MOUNTAIN LAKE PARK...OAKLAND MD...
GRANTSVILLE...NEW PHILADELPHIA...DOVER...CARROLLTON...MALVERN...
EAST LIVERPOOL...SALEM...COLUMBIANA...COSHOCTON...CADIZ...
STEUBENVILLE...ZANESVILLE...CAMBRIDGE...MARTINS FERRY...
ST. CLAIRSVILLE...CALDWELL...WOODSFIELD...ALIQUIPPA...
BEAVER FALLS...AMBRIDGE...MONACA...PITTSBURGH METRO AREA...
WASHINGTON...CANONSBURG...WAYNESBURG...MURRYSVILLE...GREENSBURG...
NEW KENSINGTON...LIGONIER...DONEGAL...UNIONTOWN...CHAMPION...
OHIOPYLE...WEIRTON...FOLLANSBEE...WELLSBURG...WHEELING...
MOUNDSVILLE...NEW MARTINSVILLE...FAIRMONT...MORGANTOWN...
COOPERS ROCK...KINGWOOD...BRUCETON MILLS...TERRA ALTA...
ROWLESBURG...HAZELTON...PARSONS...HENDRICKS...SAINT GEORGE...
DAVIS...THOMAS...CANAAN VALLEY
227 PM EST THU DEC 15 2016

...WIND CHILL ADVISORY REMAINS IN EFFECT UNTIL 9 AM EST FRIDAY...
...WINTER STORM WATCH IN EFFECT FROM FRIDAY EVENING THROUGH
SATURDAY AFTERNOON...

THE NATIONAL WEATHER SERVICE IN PITTSBURGH HAS ISSUED A WINTER
STORM WATCH...WHICH IS IN EFFECT FROM FRIDAY EVENING THROUGH
SATURDAY AFTERNOON.

* WIND CHILL...AS LOW AS 14 BELOW DUE TO TEMPERATURES 1 TO 14
  ABOVE...AND WINDS WEST 10 TO 20 MPH WITH GUSTS UP TO 30 MPH.

* ICE ACCUMULATIONS...AROUND A TENTH OF AN INCH OR MORE.

* SNOW ACCUMULATIONS...UP TO 1 INCH ORE MORE.

* IMPACTS...ICE ACCUMULATIONS WILL CREATE TREACHEROUS DRIVING
  CONDITIONS. THE WEIGHT OF THE ICE ON TREE LIMBS AND POWER LINES
  COULD PRODUCE NUMEROUS OUTAGES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND CHILL ADVISORY MEANS THAT COLD AIR AND STRONG WIND WILL
COMBINE TO GENERATE A LOW WIND CHILL INDEX. THIS COULD RESULT IN
FROST BITE AND HYPOTHERMIA IF PRECAUTIONS ARE NOT TAKEN.

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.

[jwilson]

12Z Model roundup (numbers are total through Sunday 00 Zulu):

NAM - no accumulating snow for the greater Pittsburgh area.  A few inches confined to the northern zones.  Slight potential for ice but even there the accumulations are under .10" from greater Allegheny and south.  There's some nasty potential not far to the north (we're talking almost half an inch of ice).  Precip does start as snow around 5 PM tomorrow, but it only lasts around 4 or 5 hours before changing to ice, for another 4 or 5 hours.  Then rain.  Not much backend snow, maybe an hour or two of it, nothing substantial.

Canadian - 2-3" of snow followed by .10" or more of ice (more as you move south and east of Pittsburgh, actually).  Looks like a terrible icing event for the mountains and perhaps some southern zones.  Precip starts around 8 or 9 PM as snow.  A good six to eight hours of snow before it changes to ZR.  By early Saturday afternoon it has changed to plain rain.  No backend snow shown so any accumulations are on the front end and likely washed away.

GFS - almost no snow, maybe an inch in the immediate Pittsburgh area (perhaps two inches extreme north Allegheny into Butler).  Another significant ice event for the mountains but much smaller amounts in and around Western PA.  Highest outside the mountains seems to be .09" of ice accumulation.  Starts much later with the precip than the NAM.  Brief period of ice or snow early Saturday morning (3 AM), however temps have risen almost above freezing before the precip even reaches the area, so it's a short-duration frozen p-type event.  The GFS does show a minor backend squall before precip departs late Sunday morning/early afternoon.

4K NAM - largely same as regular NAM with a bit less ice in certain areas.

 

As far as I can tell this has trended toward a non-event.  It seems we have a higher likelihood of an ice storm vs. snow at this point, but even that looks somewhat uncertain.  Clearly the quicker the precip moves in the better it would be for the area.  As GFS holds the precip back later, it tends to show almost zero snowfall.

Even though local NWS just issued Watches, I wouldn't be surprised to see those downgraded to Advisories or nothing before the event begins.  Slight chance that changes, but as the storm has kept creeping north overall, I doubt we get any big southern corrections at this point.

[jwilson]

18Z NAM largely same as 12Z.  Snow actually starts a bit earlier (around 4 PM) and lasts for six hours or so before a dry slot moves in from the south briefly, then a changeover.  Dry slot may not affect Pittsburgh, though.  Ice accumulations look even worse here, overall.  Places in Central PA would be looking at almost 3/4" of ice according to this run.  Very tight ice gradient in the Pittsburgh area (from .04 to >.30 at the Allegheny/Butler line).

There should be some snow accumulations with this sort of snow duration, I'm not sure why it shows a zero in the accumulating department.

[olafminesaw]

12z Euro has about half an inch of snow and a quarter inch of ice.

[MikeB_01]

30 minutes ago, jwilson said:

12Z Model roundup (numbers are total through Sunday 00 Zulu):

NAM - no accumulating snow for the greater Pittsburgh area.  A few inches confined to the northern zones.  Slight potential for ice but even there the accumulations are under .10" from greater Allegheny and south.  There's some nasty potential not far to the north (we're talking almost half an inch of ice).  Precip does start as snow around 5 PM tomorrow, but it only lasts around 4 or 5 hours before changing to ice, for another 4 or 5 hours.  Then rain.  Not much backend snow, maybe an hour or two of it, nothing substantial.

Canadian - 2-3" of snow followed by .10" or more of ice (more as you move south and east of Pittsburgh, actually).  Looks like a terrible icing event for the mountains and perhaps some southern zones.  Precip starts around 8 or 9 PM as snow.  A good six to eight hours of snow before it changes to ZR.  By early Saturday afternoon it has changed to plain rain.  No backend snow shown so any accumulations are on the front end and likely washed away.

GFS - almost no snow, maybe an inch in the immediate Pittsburgh area (perhaps two inches extreme north Allegheny into Butler).  Another significant ice event for the mountains but much smaller amounts in and around Western PA.  Highest outside the mountains seems to be .09" of ice accumulation.  Starts much later with the precip than the NAM.  Brief period of ice or snow early Saturday morning (3 AM), however temps have risen almost above freezing before the precip even reaches the area, so it's a short-duration frozen p-type event.  The GFS does show a minor backend squall before precip departs late Sunday morning/early afternoon.

4K NAM - largely same as regular NAM with a bit less ice in certain areas.

 

As far as I can tell this has trended toward a non-event.  It seems we have a higher likelihood of an ice storm vs. snow at this point, but even that looks somewhat uncertain.  Clearly the quicker the precip moves in the better it would be for the area.  As GFS holds the precip back later, it tends to show almost zero snowfall.

Even though local NWS just issued Watches, I wouldn't be surprised to see those downgraded to Advisories or nothing before the event begins.  Slight chance that changes, but as the storm has kept creeping north overall, I doubt we get any big southern corrections at this point.

I think the big concern for the NWS is the ground temperatures after this recent cold snap. After some brief snow, when the precip changes to liquid, the cold surface is going to make the roads dicey. 

From what the models are showing now, I think we get very little snow from this. I lean more in the direction of a period of pretty bad freezing rain. This could be a fun one to nowcast and watch friday night. Could be nasty out on the roads though.

[Rd9108]

I just want a white Christmas by some miracle and a 12 inch storm is that too much to ask?

[jwilson]

I'm seeing 2-3" on some other NAM products so perhaps I was getting visual misrepresentations on the other products I was using.  I'm also having internet issues so apologies there.  Those totals make sense given the duration of snowfall the NAM has been showing.  That pushes it more in line with the Canadian.  Precip shield faster and more expansive than the GFS.  As the NAM tends to overdo these I won't buy in just yet.

 

22 minutes ago, MikeB_01 said:

I think the big concern for the NWS is the ground temperatures after this recent cold snap. After some brief snow, when the precip changes to liquid, the cold surface is going to make the roads dicey. 

From what the models are showing now, I think we get very little snow from this. I lean more in the direction of a period of pretty bad freezing rain. This could be a fun one to nowcast and watch friday night. Could be nasty out on the roads though.

Fair enough.  For those that aren't aware, however, a Winter Storm Watch is issued when the NWS has >=50% confidence that the warning criteria will be met.  Warnings are issued at 80% confidence.  I clearly don't have the same confidence levels they have, of course I also don't know which data points they are integrating to get to that level of confidence at this time.  Personally I see trends away from "Warning" criteria event (which is 6" of snow in 12 hours or 8" of snow in 24 hours, or 1/4" of ice).  I think there's almost a 0% chance we see that much snow, so I'm going to assume they issued the watch based on the ice potential instead.

For completeness, a Winter Weather Advisory (>=80% of advisory criteria being met) calls for 3" of snow in 12 hours or any ice accumulation.  I see an Advisory level event as being the much higher likelihood outcome at this time.

[olafminesaw]

30 minutes ago, MikeB_01 said:

I think the big concern for the NWS is the ground temperatures after this recent cold snap. After some brief snow, when the precip changes to liquid, the cold surface is going to make the roads dicey. 

From what the models are showing now, I think we get very little snow from this. I lean more in the direction of a period of pretty bad freezing rain. This could be a fun one to nowcast and watch friday night. Could be nasty out on the roads though.

Especially once the temp rises to near freezing and if there's relatively heavy rain. The road will keep the ice frozen, but there will be a layer of water on top. Thankfully, it looks like temps will rise fairly rapidly through the day. Actually, if there was some snow before the ice, that would improve road conditions, since the ice would break once driven on.

[colonel717]

1 hour ago, Ryd10 said:

I just want a white Christmas by some miracle and a 12 inch storm is that too much to ask?

How about an 1 or 2 possibly on the 23rd... Will that work...

[meatwad]

Winter Storm Watch

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE PITTSBURGH PA
227 PM EST THU DEC 15 2016

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ020-021-029-031-
073>076-WVZ001>004-012-021-509>514-160330-
/O.NEW.KPBZ.WS.A.0002.161217T0000Z-161217T1900Z/
/O.CON.KPBZ.WC.Y.0003.000000T0000Z-161216T1400Z/
GARRETT-TUSCARAWAS-CARROLL-COLUMBIANA-COSHOCTON-HARRISON-
JEFFERSON-MUSKINGUM-GUERNSEY-BELMONT-NOBLE-MONROE-BEAVER-
ALLEGHENY-WASHINGTON-GREENE-WESTMORELAND-WESTMORELAND RIDGES-
FAYETTE-FAYETTE RIDGES-HANCOCK-BROOKE-OHIO-MARSHALL-WETZEL-MARION-
MONONGALIA-RIDGES OF EASTERN MONONGALIA AND NORTHWESTERN PRESTON-
PRESTON-EASTERN PRESTON-WESTERN TUCKER-EASTERN TUCKER-
INCLUDING THE CITIES OF...MOUNTAIN LAKE PARK...OAKLAND MD...
GRANTSVILLE...NEW PHILADELPHIA...DOVER...CARROLLTON...MALVERN...
EAST LIVERPOOL...SALEM...COLUMBIANA...COSHOCTON...CADIZ...
STEUBENVILLE...ZANESVILLE...CAMBRIDGE...MARTINS FERRY...
ST. CLAIRSVILLE...CALDWELL...WOODSFIELD...ALIQUIPPA...
BEAVER FALLS...AMBRIDGE...MONACA...PITTSBURGH METRO AREA...
WASHINGTON...CANONSBURG...WAYNESBURG...MURRYSVILLE...GREENSBURG...
NEW KENSINGTON...LIGONIER...DONEGAL...UNIONTOWN...CHAMPION...
OHIOPYLE...WEIRTON...FOLLANSBEE...WELLSBURG...WHEELING...
MOUNDSVILLE...NEW MARTINSVILLE...FAIRMONT...MORGANTOWN...
COOPERS ROCK...KINGWOOD...BRUCETON MILLS...TERRA ALTA...
ROWLESBURG...HAZELTON...PARSONS...HENDRICKS...SAINT GEORGE...
DAVIS...THOMAS...CANAAN VALLEY
227 PM EST THU DEC 15 2016

...WIND CHILL ADVISORY REMAINS IN EFFECT UNTIL 9 AM EST FRIDAY...
...WINTER STORM WATCH IN EFFECT FROM FRIDAY EVENING THROUGH
SATURDAY AFTERNOON...

THE NATIONAL WEATHER SERVICE IN PITTSBURGH HAS ISSUED A WINTER
STORM WATCH...WHICH IS IN EFFECT FROM FRIDAY EVENING THROUGH
SATURDAY AFTERNOON.

* WIND CHILL...AS LOW AS 14 BELOW DUE TO TEMPERATURES 1 TO 14
  ABOVE...AND WINDS WEST 10 TO 20 MPH WITH GUSTS UP TO 30 MPH.

* ICE ACCUMULATIONS...AROUND A TENTH OF AN INCH OR MORE.

* SNOW ACCUMULATIONS...UP TO 1 INCH ORE MORE.

* IMPACTS...ICE ACCUMULATIONS WILL CREATE TREACHEROUS DRIVING
  CONDITIONS. THE WEIGHT OF THE ICE ON TREE LIMBS AND POWER LINES
  COULD PRODUCE NUMEROUS OUTAGES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND CHILL ADVISORY MEANS THAT COLD AIR AND STRONG WIND WILL
COMBINE TO GENERATE A LOW WIND CHILL INDEX. THIS COULD RESULT IN
FROST BITE AND HYPOTHERMIA IF PRECAUTIONS ARE NOT TAKEN.

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.

&&

$$

[Rd9108]

26 minutes ago, colonel717 said:

How about an 1 or 2 possibly on the 23rd... Will that work...

Yeah that will work. I meant I want a big storm doesn't have to be before Christmas necessarily. 

[RitualOfTheTrout]

NWS:
Surface low pressure will track from the Plains to the lower
Great Lakes Friday night and Saturday as an upper trough begins to
advance from the Upper Midwest. Latest model runs show reasonable
continuity and critical thicknesses indicate snow changing to a
wintry mix and eventually all rain Saturday afternoon.

Increased confidence has led to the issuance of a winter storm
watch with the main concern being a long duration of sleet and
mostly freezing rain after a period of anomalously cold
temperatures followed by strong warm air advection and moisture
transport. Further details can be hashed out as confidence
increases for proper headlines leading up to the event.

[MikeB_01]

 

Newest NAM has us taking a brutal hit from freezing rain... Not sure I believe it will pan out quite like this.

[MikeB_01]

 

4K is in on the action too.

[jwilson]

Compared to just about every other model, including the short-range HRRR and WRF, the NAM looks way overdone on the precip shield.  The short range models show a dry slot affecting the Pittsburgh area overnight, for at least a couple hours, which would ultimately cut down on snow totals moreso than anything else.

Generally speaking the NAM overdoes precip totals, but even cutting those ice forecasts in half, that's a somewhat significant amount of ice.  A .25" isn't impossible, perhaps improbable.

[MikeB_01]

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE PITTSBURGH PA
852 AM EST FRI DEC 16 2016


PAZ020-021-073-162200-
/O.CON.KPBZ.WS.W.0004.161217T0300Z-161217T1800Z/
BEAVER-ALLEGHENY-WESTMORELAND-
INCLUDING THE CITIES OF...ALIQUIPPA...BEAVER FALLS...AMBRIDGE...
MONACA...PITTSBURGH METRO AREA...MURRYSVILLE...GREENSBURG...
NEW KENSINGTON
852 AM EST FRI DEC 16 2016

...WINTER STORM WARNING REMAINS IN EFFECT FROM 10 PM THIS EVENING
TO 1 PM EST SATURDAY...

* ICE ACCUMULATIONS...ONE QUARTER OF AN INCH OR GREATER.

* SNOW ACCUMULATIONS...UP TO 1 INCH.

* TIMING...SNOW WILL OVERSPREAD THE AREA THIS EVENING. SNOW WILL
  MIX WITH AND CHANGE TO FREEZING RAIN LATE TONIGHT.

* IMPACTS...ICE AND SNOW ACCUMULATIONS WILL CREATE TREACHEROUS
  DRIVING CONDITIONS. THE WEIGHT OF THE ICE AND SNOW ON TREE
  LIMBS AND POWER LINES COULD PRODUCE NUMEROUS OUTAGES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WARNING MEANS SIGNIFICANT AMOUNTS OF SNOW...
SLEET...AND ICE ARE EXPECTED OR OCCURRING. THIS WILL MAKE TRAVEL
VERY HAZARDOUS OR IMPOSSIBLE.

PLEASE REPORT SNOW AND ICE BY CALLING 412-262-1988... POSTING TO
THE NWS PITTSBURGH FACEBOOK PAGE... OR USING TWITTER
@NWSPITTSBURGH

[olafminesaw]

45 minutes ago, jwilson said:

Compared to just about every other model, including the short-range HRRR and WRF, the NAM looks way overdone on the precip shield.  The short range models show a dry slot affecting the Pittsburgh area overnight, for at least a couple hours, which would ultimately cut down on snow totals moreso than anything else.

Generally speaking the NAM overdoes precip totals, but even cutting those ice forecasts in half, that's a somewhat significant amount of ice.  A .25" isn't impossible, perhaps improbable.

The tropicaltidbits sim reflectivity is really off. It shows extended periods of moderate snow but there's actually no precip in that period. As for the ice threat, I'd trust the Nam with respect to temps and the gfs with precip.

[RitualOfTheTrout]

15 minutes ago, olafminesaw said:

The tropicaltidbits sim reflectivity is really off. It shows extended periods of moderate snow but there's actually no precip in that period. As for the ice threat, I'd trust the Nam with respect to temps and the gfs with precip.

NAM really does have precip getting in sooner, but I agree its probably not right. I'll be curious to see how long the low level cold air hangs on.

[colonel717]

1 hour ago, jwilson said:

Compared to just about every other model, including the short-range HRRR and WRF, the NAM looks way overdone on the precip shield.  The short range models show a dry slot affecting the Pittsburgh area overnight, for at least a couple hours, which would ultimately cut down on snow totals moreso than anything else.

Generally speaking the NAM overdoes precip totals, but even cutting those ice forecasts in half, that's a somewhat significant amount of ice.  A .25" isn't impossible, perhaps improbable.

Big differences among the 4 NAM models. Looking at 12z NAM both the 3KM and 32KM have no snow. Freezing rain starts near 6am Sat and turns to all rain by noon. The NAM 4KM and 12KM have 1-3 inches of snow turning to heavy freezing rain then to all rain by noon.

[RitualOfTheTrout]

Just reading around various threads \ twitter everyone is really down on the incoming pattern next week. It does look lousy, pretty much every thing is wrong. Definitely better the further NW you are in the country that is for sure, but as of right now it doesn't look like an all out shutout for snow. If we do end up wasting the next 3-4 weeks that will be a shame. Just once I'd like to get a solid pattern to establish itself through December 15-Jan-15th.

[RitualOfTheTrout]

3 minutes ago, colonel717 said:

Big differences among the 4 NAM models. Looking at 12z NAM both the 3KM and 32KM have no snow. Freezing rain starts near 6am Sat and turns to all rain by noon. The NAM 4KM and 12KM have 1-3 inches of snow turning to heavy freezing rain then to all rain by noon.

What is the difference between the 4, just resolution but all use the same physics?

[colonel717]

2 minutes ago, RitualOfTheTrout said:

What is the difference between the 4, just resolution but all use the same physics?

What is weird is you watch the precip/frozen and 3km shows no snow but when you click on total snow it shows 1-3 or so like the others.

[colonel717]

The 12KM shows 1-3 on the backside.

[olafminesaw]

20 minutes ago, colonel717 said:

What is weird is you watch the precip/frozen and 3km shows no snow but when you click on total snow it shows 1-3 or so like the others.

I think all of them are counting ZR as snow. None of them are counting the initial period of what will likely be all virga as snow.

Here's the sounding for the NAM as the precip shield is moving in. As you can see there is a very deep layer of dry air, but is saturated up above this. It doesn't saturate to the surface until the first dry slot. 

 

 

[colonel717]