Jan 19th Snow on Snow: the this always works until it doesn't thread

[nj2va]

Hot off the press:

[LeesburgWx]

Just now, nj2va said:

Hot off the press:

Loudoun Special Boys

[Shad]

NAM juicier at hr 10

[Solution Man]

Just now, nj2va said:

Hot off the press:

We know where this is going

[SomeguyfromTakomaPark]

Looks like perhaps more interaction between the vorts early on the NAM run...maybe the trough a tad sharper too.

[adelphi_sky]

1 minute ago, nj2va said:

Hot off the press:

Just need that 3-4 to come down just 10 miles and I'm good. 

[WVsnowlover]

1 minute ago, nj2va said:

Hot off the press:

Love when they play catch up!

[stormy]

1 hour ago, LeesburgWx said:

You listed 5 models. So is the blend 4 or 5 models?

I did not include the ICON in the blend.

[Solution Man]

MAM more ampd trough 12, should be good

[deer]

3 minutes ago, nj2va said:

Hot off the press:

[yoda]

Long and well written afternoon AFD from LWX 

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
243 PM EST Thu Jan 18 2024

.SYNOPSIS...
A pair of low pressure systems over the Ohio River Valley and off
the Southeast Coast will affect the Mid-Atlantic through Friday.
Arctic high pressure will build in the wake of these lows this
weekend as they merge offshore. High pressure will then settle south
of the area early next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
High pressure has departed off the East Coast into the western
Atlantic Ocean as of mid afternoon. Low pressure was moving from the
mid Mississippi River Valley up the Ohio River Valley, with a second
area of low pressure off the coast of GA/SC moving northeastward.

Aloft, a ridge axis was moving eastward across the western CONUS
approaching Idaho, an upper-level low was moving offshore of
Newfoundland, and a trough with a few embedded vort maxes was in
between moving southeastward into the Midwest. This pattern is
typically favorable for accumulating snowfall over the Mid-Atlantic
given sufficiently cold temperatures (which are firmly in place).

The flow is progressive, and this lends to a quick-moving system,
with phasing/stronger deepening of low pressure not occurring until
the system is well offshore. Still, PVA from multiple shortwaves,
LFQ of a strong (150+ kt) upper jet, and modest WAA will result in a
period of snow across the region. Given the strong dynamics aloft,
an inverted trough axis will likely develop well to the NW of the
offshore low. With the cold airmass and a deepening DGZ to around
150 mb, snowfall in some areas may very well overperform beneath
wherever this trough axis sets up (could be as far north as central
NJ, or as far south as northern/central MD). Confidence remains low
in the exact placement of the heaviest QPF/snow, as these mesoscale
features typically have lower predictability.

In terms of sensible weather...
Flurries may develop as early as nightfall along and west of the
Allegheny Front, and by mid to late evening elsewhere as the column
gradually saturates with the lead wave pushing across. Accumulating
snow most likely holds off until just after midnight over the
Alleghenies, and the pre-dawn hours further east toward the metro
areas/I-95 corridor. This initial snow will be largely jet induced
as the LFQ dynamics move atop moistening low levels. The strongest
lift overlays the DGZ for a brief (1-3 hr) window east of the
mountains from just before dawn through the first half of the
morning commute. Given cold temperatures and moderate snowfall rates
which may briefly exceed 0.5 in/hr, this will likely lead to a very
slippery Friday morning commute.

From late morning into the early afternoon, the mid-level trough
axis sharpens and takes on a negative tilt overhead. This is a
period of greater uncertainty, as the exact placement of this trough
axis will dictate the placement of enhanced precipitation/snow. This
is also the period where the DGZ is at its deepest (per BUFKIT), and
the most likely time period for overperforming snowfall. Bands of
snow spawned by these types of features can be narrow but produce
much higher snowfall on a localized basis, so it bears close
monitoring. As confidence in the placement of this banding
increases, areas of northern/northeast MD may need to be upgraded to
a Winter Storm Warning. But confidence in the placement of higher
totals was a bit too low to upgrade with the Thursday afternoon
forecast package.

Lingering low-level moisture, increasing MUCAPE in the BL
(stretching up into a lowering DGZ), and lift via continued PVA
ahead of a trailing wave, could cause at least scattered snow shower
activity to linger through late Friday afternoon or later. These may
add another coating to an inch in isolated spots where snow showers
are heavier or more persistent.

Low temperatures tonight will range from around 20 over the higher
ridges of the Alleghenies, to around freezing over southern MD.
Temperatures will likely rise to or just above freezing along and
southeast of a line from near Baltimore and along the immediate
northern bay shore, across far northern VA, to the lower elevations
of the central Shenandoah Valley on Friday. Further north and west,
temperatures will hold between 25-30 degrees (20-25 mountains)

[LeesburgWx]

Are we getting NAM'd?

[Solution Man]

Moderate snow through 15 throughout 

[stormtracker]

[Solution Man]

Still snow light to moderate through 18

[yoda]

Just now, stormtracker said:

F....

[stormtracker]

Just now, yoda said:

F....

Nah.  just interesting.  It's probably gonna be a hold.  But the vort pass is still south

[yoda]

Just now, stormtracker said:

Nah.  just interesting.  It's probably gonna be a hold.  But the vort pass is still south

I didn't remember what the new terminology was for certain amounts 

[NorthArlington101]

Moderate snow through 15 throughout 

Sounds like it’ll still be better but WxBell has no snow at 15 minus western zones so I’m wondering if whatever you are looking at is virga

[Solution Man]

Still snowing light to moderate through 21

[yoda]

I like hour 21 on the soundings near DCA

[Solution Man]

Looks like it’ll be a bit better than the previous run

[stormtracker]

Looks like a slightly wetter run.  Nobody get pumped.  Should be the same general out come.  Vort is a bit souther

[LeesburgWx]

I'm all in. Wetter 

[stormtracker]

Yeah, vort is noticeably souther  maybe by 50-75 miles

[konksw]

The trend is wetter though. Man if we manage another winter storm warning mid storm that would sure be something. 

[Chris78]

Just now, stormtracker said:

Looks like a slightly wetter run.  Nobody get pumped.  Should be the same general out come.  Vort is a bit souther

Should PSU start working about the F word?

 

 

 

Fringed

[stormtracker]

It's going to be a better run

[Bob Chill]

Nam has a really nice IVT axis. Targets MD and that's def nice ratios 

[stormtracker]

Just now, Bob Chill said:

Nam has a really nice IVT axis. Targets MD and that's def nice ratios 

Booooo