12/29 Potential Snowstorm Update #1

12z

18z

00z

rb924119 wrote:

Frank_Wx wrote:

jake732 wrote:Frank, is it possible to explain the last model u just posted ? What is that showing different?

700mb critical thickness shows where the best banding is. Areas in white are likely dry slotted or the storm is finished for them. Darkest green = heaviest precip rates.

?? Critical thickness relates to temperature, not precip.

True, that map with how VV and CT are displayed threw me off. I did not even see the 540 CT line until zooming in.

To revise: the VV's (vertical velocities) and green shadings (relative humidity) show where precip is falling and at what rate / intensity.

Valid 21z Wednesday, 00z GFS is better than 18z.

Trough is sharper.

00z



18z

GFS

Wow - this is what the onset of bombogenesis looks like

Here is why the immediate coast and NYC are unlikely to see major snow. Surface temps too warm.

Euro from last night

NAM

GFS

Roidzilla for Maine

Frank_Wx wrote:Roidzilla for Maine

The usual scenario for a Miller B.My area has a 2 to 4 inch possibility looking at the current models.NWS took out the change to rain and now its all snow.

I'll have a snow map out late tonight. Thinking the SE flow due to the primary Cutting in Canada will keep coast too warm for any accumulation. N&W in line for a moderate event.

Frank is right. By the time the precipitation gets going here (and it won't ever really get going here as compared to what it may in New England) we're looking at temperatures near 40 degrees. Not gonna cut it for snow; even if a bit mixed in, wouldn't stick during daytime. I can see where our friends in the Hudson Valley north of NJ could get a bit of snow from this, but south of there not looking good.

docstox12 wrote:

Frank_Wx wrote:Roidzilla for Maine

The usual scenario for a Miller B.My area has a 2 to 4 inch possibility looking at the current models.NWS took out the change to rain and now its all snow.

I'm not sure how fast this moves or if it slows down at all but the positioning of the low as depicted here over SE NH usually works out for some pretty decent backend snow in the HV. Of course if the low is racing NE not so much.

Holy NAM

DOC and CP, I PM'd you guys. Take a look.

RGEM looks colder than NAM

If the nam and euro are correct then there's no way we don't flip to snow with a deepening low just south of Long Island. 850 and 925 look good just have to overcome the southeast wind at the start which will affect the low levels but that could be overcome if precipitation is heavy enough.

syosnow94 wrote:DOC and CP, I PM'd you guys.  Take a look.

Already answered

We'll flip to snow, but look at these 2M surface temps.

925mb - cold enough for snow (look at solid white line. If it's south of you, you are likely snowing).



But then surface temps...




Need a CCB or better dynamics to get the surface much colder if you want stickage.

Yes Frank the surface does look warm but models almost always are too high with surface temperature when precip is falling in a setup like this. If the low deepens quick enough to our South surface temperatures can be overcome. Like you said my main concern is how much precip will be left

Nothing too significant on the GFS aloft so far compared to 00z. The 00z GFS did not show anything spectacular for the area. 12z GFS should finish shortly.

GFS aloft valid 12z THURS now looks better than 00z GFS. May want to transfer to coast sooner. Trough has more of a tilt to it. Not surprise given other guidance.