Pittsburgh PA ❄️ Winter 2017-2018

[Longdong]

11 minutes ago, MikeB_01 said:

Mesonet still has that station reporting light rain and 34.

Yep there back to freezing rain .

[Rd9108]

Drains are clear and it's nowcast time. It's crazy how fast the cold air came in after being in the 50s. 

[MikeB_01]

Mike here it says light snow..if it’s mostly snow that change over is happening faster we’ll see I guess !

Very interesting. I’ll keep watching that station. Also something to note about the changeover. My dad who lives in Youngstown said she they are already sleeting. No freezing rain. Pretty much straight to sleet. Not as much warm air aloft as they thought?


.

[SteelCity08]

Cold def seems a bit ahead of schedule. Too early to know if it will make a difference but interesting nontheless. 

[cwc]

Stellar AFD by Bookbinder:

Area Forecast Discussion
National Weather Service Pittsburgh PA
216 PM EST Fri Jan 12 2018

...SIGNIFICANT FLOODING CONTINUES AS ARCTIC BLAST AND WINTER
STORM ARRIVES...

.SYNOPSIS...

Temperatures will fall sharply as arctic air pushed into the
region. Rain will change sleet and freezing rain late today and
this evening, then eventually snow tonight. Significant
accumulations of snow and ice are expected. Bitterly cold air
will remain in place for the weekend into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Powerful arctic front slamming through the CWA as of this
writing. Temperatures fall a whopping 25F (61 to 38F here at WFO
PBZ in 45 minutes) in the first hour post-FROPA, and then a
steadily decline thereafter!! This places the western CWA below
freezing by mid afternoon, I-79 corridor by 6PM, and the eastern
mountains by 9 PM.

Issue #1: Flash freeze. Any standing water from earlier/ongoing
rainfall will freeze as soon as the air temps reach ~30F. Any
ground thaw from the past 36 hours warmth reached a nominal
depth of an inch or two. Additionally, roads should be
considered untreated. Any chemicals have been washed away, and
treatment cannot be applied while rain continues. This will
result in base layer that`s slick and hazardous irrespective of
the incoming winter storm.

Issue #2: Freezing/frozen precipitation. Shallow arctic air
penetration will precede mid-level cooling by ~6 hours. This
yields a sharp inversion with a low static stability and warm
air aloft. Moderate precipitation will redevelop this afternoon
and evening with some convective elements. This rain, falling
into sub-freezing surface air should yield a several hour period
of freezing rain before warm-nose erodes sufficiently to change
over briefly to sleet and then snow. Ice accumulation forecast
is tricky to say the least. We could potentially yield 0.3 to
0.4" of liquid rainfall during the 3-4 hour period that
soundings support freezing rain. However, numerous studies have
shown that moderate or heavier precipitation rates are
counterproductive to ice accretion due to kinetic energy and
heat release from impact (a bit too technical perhaps). Still,
feel that ice accretion of up to a quarter inch thickness is
possible, especially over wrn PA/ern OH/WV panhandle. Coupled
with 15-25 mph wind gusts, this could lead to downed branches
and power lines.

Issue #3: Snow. Probably a worst-case scenario here with
accumulating snow on top of a sheet of ice. Snow amounts are
almost irrelevant in this type of an event, with major impacts
regardless of accumulation. Road temperatures will continue to
plummet as temperatures fall through the 20s and into the teens
overnight, with the ability to treat them a difficult challenge
at best. Thus, travel may be extremely difficult if not
impossible. Closed mid level low over the TN valley will begin
to open and slowly fill as it lifts negatively tilted toward the
area overnight. The elevated frontal zone will couple with an
ill-formed dry slot to yield a deformed band of moderate to
locally heavy snow overnight. Suite of model guidance is in
particularly good agreement over the placement of the axis of
snow overnight, likely resulting from better mass field handling
with the 12Z runs. The heaviest snow will develop from SE OH
northeastward into NW PA. Dendritic snow growth looks favorable
despite the increasingly frigid boundary layer. Modest QPF
within the cold air should yield an axis of 4 to 7 inches of
snow across ern OH into NW PA (highest north of I-80) tapering
off toward the south and east. The gradient in snow
accumulations may setup right over Pittsburgh, with a several
inch variance possible across the city depending on where the
primary band sets up (as low as 2" southeast to as much as 5-6"
NW suburbs). Snowfall should rapidly wane from SW to NE toward
daybreak, leaving a landscape that looks vastly different than
the one this morning.

All of this occurs with many areas under water from significant
rain, snow-melt and ice jam flooding. I do not want to minimize
this ongoing threat either. Runoff continues with as much as 3"
of rainfall, a complete melt of the existing snow pack, and ice
jams breaking loose. Some of the social media video we have
received today has been nothing short of impressive. Runoff
should come to an end this evening as temperatures plummet,
however ice formation will quickly resume over the coming days
as temperatures fail to escape the teens.

[Rd9108]

4 minutes ago, cwc said:

Stellar AFD by Bookbinder:

Area Forecast Discussion
National Weather Service Pittsburgh PA
216 PM EST Fri Jan 12 2018

...SIGNIFICANT FLOODING CONTINUES AS ARCTIC BLAST AND WINTER
STORM ARRIVES...

.SYNOPSIS...

Temperatures will fall sharply as arctic air pushed into the
region. Rain will change sleet and freezing rain late today and
this evening, then eventually snow tonight. Significant
accumulations of snow and ice are expected. Bitterly cold air
will remain in place for the weekend into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Powerful arctic front slamming through the CWA as of this
writing. Temperatures fall a whopping 25F (61 to 38F here at WFO
PBZ in 45 minutes) in the first hour post-FROPA, and then a
steadily decline thereafter!! This places the western CWA below
freezing by mid afternoon, I-79 corridor by 6PM, and the eastern
mountains by 9 PM.

Issue #1: Flash freeze. Any standing water from earlier/ongoing
rainfall will freeze as soon as the air temps reach ~30F. Any
ground thaw from the past 36 hours warmth reached a nominal
depth of an inch or two. Additionally, roads should be
considered untreated. Any chemicals have been washed away, and
treatment cannot be applied while rain continues. This will
result in base layer that`s slick and hazardous irrespective of
the incoming winter storm.

Issue #2: Freezing/frozen precipitation. Shallow arctic air
penetration will precede mid-level cooling by ~6 hours. This
yields a sharp inversion with a low static stability and warm
air aloft. Moderate precipitation will redevelop this afternoon
and evening with some convective elements. This rain, falling
into sub-freezing surface air should yield a several hour period
of freezing rain before warm-nose erodes sufficiently to change
over briefly to sleet and then snow. Ice accumulation forecast
is tricky to say the least. We could potentially yield 0.3 to
0.4" of liquid rainfall during the 3-4 hour period that
soundings support freezing rain. However, numerous studies have
shown that moderate or heavier precipitation rates are
counterproductive to ice accretion due to kinetic energy and
heat release from impact (a bit too technical perhaps). Still,
feel that ice accretion of up to a quarter inch thickness is
possible, especially over wrn PA/ern OH/WV panhandle. Coupled
with 15-25 mph wind gusts, this could lead to downed branches
and power lines.

Issue #3: Snow. Probably a worst-case scenario here with
accumulating snow on top of a sheet of ice. Snow amounts are
almost irrelevant in this type of an event, with major impacts
regardless of accumulation. Road temperatures will continue to
plummet as temperatures fall through the 20s and into the teens
overnight, with the ability to treat them a difficult challenge
at best. Thus, travel may be extremely difficult if not
impossible. Closed mid level low over the TN valley will begin
to open and slowly fill as it lifts negatively tilted toward the
area overnight. The elevated frontal zone will couple with an
ill-formed dry slot to yield a deformed band of moderate to
locally heavy snow overnight. Suite of model guidance is in
particularly good agreement over the placement of the axis of
snow overnight, likely resulting from better mass field handling
with the 12Z runs. The heaviest snow will develop from SE OH
northeastward into NW PA. Dendritic snow growth looks favorable
despite the increasingly frigid boundary layer. Modest QPF
within the cold air should yield an axis of 4 to 7 inches of
snow across ern OH into NW PA (highest north of I-80) tapering
off toward the south and east. The gradient in snow
accumulations may setup right over Pittsburgh, with a several
inch variance possible across the city depending on where the
primary band sets up (as low as 2" southeast to as much as 5-6"
NW suburbs). Snowfall should rapidly wane from SW to NE toward
daybreak, leaving a landscape that looks vastly different than
the one this morning.

All of this occurs with many areas under water from significant
rain, snow-melt and ice jam flooding. I do not want to minimize
this ongoing threat either. Runoff continues with as much as 3"
of rainfall, a complete melt of the existing snow pack, and ice
jams breaking loose. Some of the social media video we have
received today has been nothing short of impressive. Runoff
should come to an end this evening as temperatures plummet,
however ice formation will quickly resume over the coming days
as temperatures fail to escape the teens.

I think the key point that regardless of how much snow we get, sleet then snow on top is a major event. 

[Longdong]

1 minute ago, Rd9108 said:

I think the key point that regardless of how much snow we get, sleet then snow on top is a major event. 

Yes all will agree to that>lets watch ohio and see how things are there.

[cwc]

NWS State College going with the 18z RAP.

They also point out the extended period of  FRZA 

The latest MESO discussion identifies E OH/NW PA as potentially experiencing very heavy snow between 4-8PM.

[Mailman]

Well... this should be an interesting evening/night, if anything.  

[MikeB_01]

16 minutes ago, cwc said:

Stellar AFD by Bookbinder:

Area Forecast Discussion
National Weather Service Pittsburgh PA
216 PM EST Fri Jan 12 2018

...SIGNIFICANT FLOODING CONTINUES AS ARCTIC BLAST AND WINTER
STORM ARRIVES...

.SYNOPSIS...

Temperatures will fall sharply as arctic air pushed into the
region. Rain will change sleet and freezing rain late today and
this evening, then eventually snow tonight. Significant
accumulations of snow and ice are expected. Bitterly cold air
will remain in place for the weekend into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Powerful arctic front slamming through the CWA as of this
writing. Temperatures fall a whopping 25F (61 to 38F here at WFO
PBZ in 45 minutes) in the first hour post-FROPA, and then a
steadily decline thereafter!! This places the western CWA below
freezing by mid afternoon, I-79 corridor by 6PM, and the eastern
mountains by 9 PM.

Issue #1: Flash freeze. Any standing water from earlier/ongoing
rainfall will freeze as soon as the air temps reach ~30F. Any
ground thaw from the past 36 hours warmth reached a nominal
depth of an inch or two. Additionally, roads should be
considered untreated. Any chemicals have been washed away, and
treatment cannot be applied while rain continues. This will
result in base layer that`s slick and hazardous irrespective of
the incoming winter storm.

Issue #2: Freezing/frozen precipitation. Shallow arctic air
penetration will precede mid-level cooling by ~6 hours. This
yields a sharp inversion with a low static stability and warm
air aloft. Moderate precipitation will redevelop this afternoon
and evening with some convective elements. This rain, falling
into sub-freezing surface air should yield a several hour period
of freezing rain before warm-nose erodes sufficiently to change
over briefly to sleet and then snow. Ice accumulation forecast
is tricky to say the least. We could potentially yield 0.3 to
0.4" of liquid rainfall during the 3-4 hour period that
soundings support freezing rain. However, numerous studies have
shown that moderate or heavier precipitation rates are
counterproductive to ice accretion due to kinetic energy and
heat release from impact (a bit too technical perhaps). Still,
feel that ice accretion of up to a quarter inch thickness is
possible, especially over wrn PA/ern OH/WV panhandle. Coupled
with 15-25 mph wind gusts, this could lead to downed branches
and power lines.

Issue #3: Snow. Probably a worst-case scenario here with
accumulating snow on top of a sheet of ice. Snow amounts are
almost irrelevant in this type of an event, with major impacts
regardless of accumulation. Road temperatures will continue to
plummet as temperatures fall through the 20s and into the teens
overnight, with the ability to treat them a difficult challenge
at best. Thus, travel may be extremely difficult if not
impossible. Closed mid level low over the TN valley will begin
to open and slowly fill as it lifts negatively tilted toward the
area overnight. The elevated frontal zone will couple with an
ill-formed dry slot to yield a deformed band of moderate to
locally heavy snow overnight. Suite of model guidance is in
particularly good agreement over the placement of the axis of
snow overnight, likely resulting from better mass field handling
with the 12Z runs. The heaviest snow will develop from SE OH
northeastward into NW PA. Dendritic snow growth looks favorable
despite the increasingly frigid boundary layer. Modest QPF
within the cold air should yield an axis of 4 to 7 inches of
snow across ern OH into NW PA (highest north of I-80) tapering
off toward the south and east. The gradient in snow
accumulations may setup right over Pittsburgh, with a several
inch variance possible across the city depending on where the
primary band sets up (as low as 2" southeast to as much as 5-6"
NW suburbs). Snowfall should rapidly wane from SW to NE toward
daybreak, leaving a landscape that looks vastly different than
the one this morning.

All of this occurs with many areas under water from significant
rain, snow-melt and ice jam flooding. I do not want to minimize
this ongoing threat either. Runoff continues with as much as 3"
of rainfall, a complete melt of the existing snow pack, and ice
jams breaking loose. Some of the social media video we have
received today has been nothing short of impressive. Runoff
should come to an end this evening as temperatures plummet,
however ice formation will quickly resume over the coming days
as temperatures fail to escape the teens.

this was excellently worded.

[Mailman]

Nothing like a 23 degree temperature drop in 45 minutes.  Went from 65 (at 3pm) to 42 now.

[MAG5035]

Seeing some mPing reports of mixed precip (ice pellets and freezing rain) on the I-79 corridor near New Castle/Grove City and also near Beaver Falls by the I-76/79 junction. 

Did see that CTP's discussion noted a few hours ago that the front was progressing faster than earlier forecast by models. The key to snowfall is not going to so much be how fast the cold air gets there at the surface (which looks to be very rapidly), but rather how long this transitional period takes with getting things turned over to snow. It's a scenario that you don't see too much with these wintry mix events... the reverse rain to ice to snow scenario. I don't think it'll take long to get the cold layer deep enough (surface to 925mb or so) to get sleet and some freezing rain but it's going to be how fast that 850-700mb layer cools off. Latest mesoanalysis is still slightly above 0ºC all the way up at 700mb in most of western PA and 850mb temps are still quite warm as they're lagging the surface temps. Models have been indicating the lingering warmth up there which is why they've been cranking out a lot of sleet, especially in the case of the NAM. There's a pretty good chance of seeing a somewhat extended period of that which will take away from snow amounts. Might not be a big total event but if you get an inch or so of sleet with 3-4" of snow and some zr that might as well be a 15" snowfall in terms of shovelling/plowing. On the other hand if things change over to snow more quickly there might be more 6+ totals. 

[Longdong]

8 minutes ago, Mailman said:

Nothing like a 23 degree temperature drop in 45 minutes.  Went from 65 (at 3pm) to 42 now.

Undertaker from accu just said new castle turned to snow already and is the first station in pa to change to snow.

[ChalkHillSnowNut]

17 minutes ago, MAG5035 said:

Seeing some mPing reports of mixed precip (ice pellets and freezing rain) on the I-79 corridor near New Castle/Grove City and also near Beaver Falls by the I-76/79 junction. 

Did see that CTP's discussion noted a few hours ago that the front was progressing faster than earlier forecast by models. The key to snowfall is not going to so much be how fast the cold air gets there at the surface (which looks to be very rapidly), but rather how long this transitional period takes with getting things turned over to snow. It's a scenario that you don't see too much with these wintry mix events... the reverse rain to ice to snow scenario. I don't think it'll take long to get the cold layer deep enough (surface to 925mb or so) to get sleet and some freezing rain but it's going to be how fast that 850-700mb layer cools off. Latest mesoanalysis is still slightly above 0ºC all the way up at 700mb in most of western PA and 850mb temps are still quite warm as they're lagging the surface temps. Models have been indicating the lingering warmth up there which is why they've been cranking out a lot of sleet, especially in the case of the NAM. There's a pretty good chance of seeing a somewhat extended period of that which will take away from snow amounts. Might not be a big total event but if you get an inch or so of sleet with 3-4" of snow and some zr that might as well be a 15" snowfall in terms of shovelling/plowing. On the other hand if things change over to snow more quickly there might be more 6+ totals. 

MAG thanks for chiming in here-we appreciate you taking the time to give us your input!  We need more of your expertise!

[CranberryWX]

33 and heavy rain, about as miserable as it can get

[Rd9108]

6 minutes ago, TeaysValleyWV said:

33 and heavy rain, about as miserable as it can get

That is some heavy rain out there. 

[SteelCity08]

8 minutes ago, ChalkHillSnowNut said:

MAG thanks for chiming in here-we appreciate you taking the time to give us your input!  We need more of your expertise!

Yes thank you. Always love hearing your thoughts on our neck of the woods. Much appreciated!

[north pgh]

Just had some really heavy rain go thru here. Power went out for a minute. Like a squall line. Thought I heard some thunder but I don't see any lightning strikes. 34 degrees.

[MikeB_01]

33 and heavy rain, about as miserable as it can get

36 and pouring in the south hills.


.

[PghPirates27]

35 in cranberry pouring 

[ChalkHillSnowNut]

36 and steady rain in chalk hill

[MikeB_01]

KPIT down to 30. Anyone seeing any freezing rain?

[north pgh]

I think everyone was so concerned about the winter storm that they missed the boat on the flooding. The rain was over 2 inches last night and also with the snow melt caused substantial flooding. I was out this afternoon and there is a lot of standing water and ponds that will surely freeze tonight. 

[SteelCity08]

I'm a few miles away from airport. I'll go check. Do find it interesting that nws updated their forecast for a steady temp of 35 while the airport 2 miles away is reporting 30. 

[SteelCity08]

7 minutes ago, SteelCity08 said:

I'm a few miles away from airport. I'll go check. Do find it interesting that nws updated their forecast for a steady temp of 35 while the airport 2 miles away is reporting 30. 

Still plain rain here as far as I can tell. 

[blackngoldrules]

I think everyone was so concerned about the winter storm that they missed the boat on the flooding. The rain was over 2 inches last night and also with the snow melt caused substantial flooding. I was out this afternoon and there is a lot of standing water and ponds that will surely freeze tonight. 

I think I mentioned on here about a week ago that flooding could become a problem eventually. We knew there was going to be a big warm-up after the frigid conditions we experienced and obviously snow melt and ice jams come with that. Combine that with heavy rain and you can have major flooding problems. Now, we're going to have major ice problems with all this water freezing quickly along with rain adding to that before the changeover.

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[Rd9108]

8 minutes ago, north pgh said:

I think everyone was so concerned about the winter storm that they missed the boat on the flooding. The rain was over 2 inches last night and also with the snow melt caused substantial flooding. I was out this afternoon and there is a lot of standing water and ponds that will surely freeze tonight. 

If anyone is familiar with spring garden in the city of pgh it was flooded to the point of being shut down. 

[north pgh]

My daughter goes to Pitt Bradford and they canceled classes today because of flooding in the town and on campus. They had the heavy rain last night and just recently they had close to 10 inches of snow on the ground.

[DanTheMan]

I can report firsthand that road conditions northwest of Pittsburgh are very poor. Heavy sleet and basically untreated roads, 76 is a skating rink. I saw at least 10 cars that had gone off into ditches, emergency vehicles driving up and down to try and meet the demand for the accidents. I strongly reccomend staying off the roads tonight if you planned on traveling north.  

 

[blackngoldrules]

Just to add my observation, it's 34 and I'd say a moderate rain coming down in Bethel right now.

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