Central PA Winter 2024/2025

[Superstorm]

GFS seems a bit norther through 12. 

Definitely more north


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[Bubbler86]

[Bubbler86]

No bowling ball/transfer issues but wagons north on precip shield/northern accums.

[Superstorm]

More north, but less precip overall, but we end up with more.


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[mitchnick]

1 minute ago, Superstorm said:

More north, but less precip overall, but we end up with more.


.

I'm going to need a calculator for this one.

[Blizzard of 93]

3 minutes ago, mitchnick said:

I'm going to need a calculator for this one.

Here’s another view 12z GFS Kuchera.

its about .5 more snow in the LSV over its 6z run.

[mitchnick]

Gem should be north too based on early 12 hour snowfall prediction maps.

[Festus]

21 minutes ago, Mount Joy Snowman said:

They certainly have. We were just hanging with some Hempfield teachers last night and they are fully planning on having a remote day Monday. I always assumed you were in Manheim Central? 

Just outside of East Petersburg.  Manheim address, East Hempfield Township.  Right on the edge of the district so we get plowed last .

[Superstorm]

Looks like Canadian is north too


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[Blizzard of 93]

We don’t need much of a bump to get back into a little bit better of the goods for the LSV.

[Superstorm]

We don’t need much of a bump to get back into a little bit better of the goods for the LSV.

Wish these north bumps started like this yesterday.


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[Superstorm]

HRDPS north also


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[mitchnick]

5 minutes ago, Superstorm said:

Wish these north bumps started like this yesterday.


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Me too, but as jumpy as the models are, it only takes 1 or 2 cycles to adjust considerably. 

[mitchnick]

Gem

[Storm Clouds]

If the southern counties can score 6 inches from this, I’d consider a win. 

[Storm Clouds]

If we continue the north bump through 00z tonight maybe we’ll get a surprise…

[Festus]

Warnings now hoisted for PA counties previously under Watches.  Stil no love for York or Lancaster.

[Subliminal87]

A bit worried about my flight at 5am on the 11th out of Harrisburg.  Really hoping i can fly.  

[Rd9108]

FYI reports out west are showing that precip is falling in places that NAM said there will be zero precip.

 

[pasnownut]

1 hour ago, Festus said:

I'm in Hempfield School District and they've made extensive use of the "virtual learning day" these past number of years.

yeah thats my point.  Any reason.....

 

[AccuChris]

FYI reports out west are showing that precip is falling in places that NAM said there will be zero precip.
 

It would seem the HRRR is more accurate in the real-time world…see if that continues to play out in its forecasts too..


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[pasnownut]

28 minutes ago, Superstorm said:

Wish these north bumps started like this yesterday.


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weve got 3 model runs of "ticks" left....

Inside 24, its nice to see N ticks still happening.  IF we can get 1 or 2 more northers, many LSV'rs are affected and snow weenies rejoice.  

[Festus]

2 minutes ago, pasnownut said:

yeah thats my point.  Any reason.....

 

It's easier nowadays to breakout the virtual learning day anytime there's even a minor weather threat as it still counts as a school day.  WAY back in my HS days, the calendar was loaded with Snow Days and still had days tacked on at the end of the year which royally sucked.  I do remember driving to school in some pretty sketchy stuff that no way would be the case today.

[Rd9108]

6 minutes ago, AccuChris said:

It would seem the HRRR is more accurate in the real-time world…see if that continues to play out in its forecasts too..


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That does seem to be the case. We need the primary to hang on longer and stay stronger if we want the HRRR to play out. Seems like some of the models are under doing the northern precip shield. Not expecting a complete bust, but we've seen weird thing with storms that cause some huge busts. 

[mitchnick]

Ukie north, but it was so far soith idk how much help it'll be north of me.

[MAG5035]

1 hour ago, AccuChris said:

CTP had an interesting take and write-up this morning about the ongoing disagreement within the models. They point to the more suppressed models focusing on a mid-level vort in northern New England enhancing drier advection from Canada versus the HRRR which cant even see that in its domain. Time will tell as always

“Still quite a bit of uncertainty with 18 hours or less until
first flakes. The ECMWF and Regional Canadian models are on the
lower end of the snowfall total spectrum. Part of the reason
for this might be that they both develop a stronger midlevel low
pressure system over northern New England late Monday from a
shortwave trough originating east of Hudson Bay at 00z Sunday.
This could act as a kicker to bring in drier air more quickly
and shorten the window for moisture advection early Monday
before the Mid Atl coastal system gets nudged offshore. This
shortwave trough is outside the domain of the hires models (HRRR
and 3km NAM) and will remain so until the 00z Monday runs.
Given that the HRRR and 3km NAM together make up about 1/3 of
the NBM weighting in this time period, IF this Hudson Bay
feature is indeed responsible for the lower snow totals in the
ECMWF and Canadian models, it`s certainly possible that we see a
shift south in snowfall totals over the next 24 hours. That
said, the HRRR does represent the worst case scenario, with
warning criteria (6+ inches) across much of central PA from I-80
southward, which can not completely be ruled out at this point.”


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Here’s what CTP is alluding to in their AFD on the 500mb prog with a GFS vs Euro comparison (using the 6z run). I x’ed the vort responsible for our storm and the one over northern New England. The arrows indicate the flow, and they converge (aka confluence).

I did notice this feature yesterday scrutinizing the 12z models. At that point track and precip expanse was similar on the Euro v GFS but the Euro wasn’t bringing the heavier precip up. That feature above New England was not nearly as prominent on the GFS as the Euro. And as you can see today, both models now have it (A Euro win). 

I can only go back to 18z yesterday on the comparison, but here’s the 6z GFS (new 12z run is similar) vs yesterday’s 18z run. X’s again denote the shortwaves and arrows illustrating the confluence on the left. Now look at the right one in the circled area (yesterday’s 18z). No closed off low with that shortwave above New England. 

The flow speeds up in a confluent pattern, and thus as CTP mentioned would limit the window for moisture advection. As I mentioned yesterday, the WAA precip phase was going to be the primary part of the event for most in here outside of the far southern tier (which could catch the back end of the shield with the upper feature passage). So it’s not really an issue of north or south with the actual storm, models have been similar with expanse of precip. It comes down to simply being a more progressive event here, which lessens QPF. Honestly, a good catch and call by CTP IMO by factoring that in their accum forecasts (since high res won’t account for it til 0z) . Now that doesn’t mean we can’t get some north trend back to a degree, but that’s their reasoning for their headline placement… which is solid at this juncture. I think there’s still room to expand advisories a bit, and maybe the LSV advisories to low end warnings. This affects the heavy swath to the south too, as I think we’re back to the ceiling of a general 6-10” event (maybe some 12s) in the axis of heaviest. 

[dcfox1]

25 minutes ago, Festus said:

It's easier nowadays to breakout the virtual learning day anytime there's even a minor weather threat as it still counts as a school day.  WAY back in my HS days, the calendar was loaded with Snow Days and still had days tacked on at the end of the year which royally sucked.  I do remember driving to school in some pretty sketchy stuff that no way would be the case today.

I remember that and the chains on the busses in the 70's and early 80's at Eastern York. Lots of Hills. 

[Bubbler86]

4 hours ago, Bubbler86 said:

11 this AM

I guess I have to make a call.  HRRR holding its ground. 

 

KHGR-8

KTHV-6

KMDT/CXY-5

KLNS-4

KAOO-3

KIPT-1

 

 

Regardless of the euro I still like these numbers sans dropping mdt to 3-4 vs 5.

[canderson]

New CTP disco.  I’ve never heard if the “classic Colorado low” hah 

SHORT TERM /7 PM THIS EVENING THROUGH MONDAY NIGHT/...
A classic Colorado low storm type will bring a swath of
moderate to heavy snow across the Middle Atlantic late this
evening into the day on Monday. Snow arrives late this evening
across the southwest and overspreads east and north early Monday
into Monday afternoon. Snow ends from west to east by Tuesday
evening, so it will be a quick-hitting (less than 24 hour)
storm. Travel impacts are likely for the Monday morning and
Monday evening commutes, with the most significant impacts
favored along and south of the PA Turnpike.

Still quite a bit of uncertainty with 18 hours or less until
first flakes. The ECMWF and Regional Canadian models are on the
lower end of the snowfall total spectrum. Part of the reason
for this might be that they both develop a stronger midlevel low
pressure system over northern New England late Monday from a
shortwave trough originating east of Hudson Bay at 00z Sunday.
This could act as a kicker to bring in drier air more quickly
and shorten the window for moisture advection early Monday
before the Mid Atl coastal system gets nudged offshore. This
shortwave trough is outside the domain of the hires models (HRRR
and 3km NAM) and will remain so until the 00z Monday runs.
Given that the HRRR and 3km NAM together make up about 1/3 of
the NBM weighting in this time period, IF this Hudson Bay
feature is indeed responsible for the lower snow totals in the
ECMWF and Canadian models, it`s certainly possible that we see a
shift south in snowfall totals over the next 24 hours. That
said, the HRRR does represent the worst case scenario, with
warning criteria (6+ inches) across much of central PA from I-80
southward, which can not completely be ruled out at this point.

Regardless, the isentropic ascent and favorable upper jet
dynamics do look to be over central PA between midnight Sunday
night and at least early morning on Monday. The main period of
snow will start over the Laurels right around midnight Sun
night, and spread NE through sunrise, struggling to get too far
past I-80 as it encounters drier low-mid levels. By the
afternoon, the precip may be tapering off over the I-80
counties, and by sunset, many models have little or nothing
falling over the bulk of the CWA. The places that we continue
higher PoPs Mon night are the far NW where lake effect-
favorable flow returns and in the SW where the snow may not end
for another 2 days thanks to another shortwave trough coming
down Tue night - Wed.

No worries for p-type (all snow) even though the precip will be
falling during the daylight hours on Mon. Profiles show no warm
nose whatsoever, even along the MD border. SLRs will generally
range from 11:1 to 14:1. 1"+ per hour snowfall rates are
possible in the Laurel Highlands and extreme southern PA on
Monday morning. The most likely snow totals at this time range
from a coating to 2 inches along the I-80 corridor, little if
anything to the north, about 3-6 inches in the Lower Susq, and
4-8 inches in the Laurels.

Have issued Winter Storm Warnings for the southern stripe of
counties over to Adams and Winter Weather Advisories for the
rest of the Lower Susquehanna Valley along with Huntingdon,
Blair, and Cambria County. The 4" snowfall contour currently
runs along 22 in Cambria County and then extends east southeast
through southern Cumberland County, York city and just south of
Lancaster. We`ll be monitoring for shifts in the track of this
storm along with any suppression from the aforementioned
midlevel low over New England. Think we are in pretty good shape
if the suppressed solution verifies, but a northern shift would
likely require upgrades and/or expansion of products farther
north.

[paweather]

@AccuChris what are you thinking for Lebanon County?