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The 4 Seasons

Quick Hitter Coastal Threat, Feb 7-8th

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23 minutes ago, USCAPEWEATHERAF said:

the freaking NWS just issued the updated statement with the WSW for the Cape, they are now expecting mostly rain on the outer Cape with 1-3" of snow now expected.  What is the crap with this?  Why such a warm forecast?

...because they know the forecast will piss you off....

 

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Our first and hopefully only call for the super bowl storm. If we see a continued trend this evening and tonight we'll adjust accordingly. Expecting 4-6" for most with the higher end of the range in E and SE CT. 2-4" N & W of 84. 

02_06.21_jdj_snowfall_forecast.thumb.jpg.43ec9247aa0a3bc959c4302f1d24a1fc.jpg02_06.21_jdj_northeast_overview_2.thumb.jpg.14358f1727ef3fe809e34a9671795f68.jpg

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While we are confident in a plowable snow across most of southern
New England, the uncertainty exists on whether or not higher amounts
advertised by certain models will be realized. Also, the northwest
extent of the heavier amounts is also uncertain. There is a battle
amongst a lot of the global vs. high resolution model guidance. The
tendency is for a lot of the high resolution data to be heavier with
the snow amounts and also further northwest compared to the global
models. It is quite evident even comparing the 3 KM to 12 KM NAM
model.

Given the differences we somewhat blended the guidance together.
While we think some of the high resolution guidance may be too heavy
with the QPF & as well as being too far northwest; there are a few
things we need to consider. There are some indications of a band of
pretty intense 700 mb frontogenesis and good snow growth on the
northwest side of the storm. We also should mention there are
decent mid level lapse rates and a -EPV signature. This may result
in 1-2 inch per hour snowfall rates for a time especially late
Sunday morning and Sunday afternoon. In addition, a period of good
SLR/s would occur in this band especially if it is able to reach
northwest of I-95, where surface temperatures will be colder.
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5 minutes ago, SeanInWayland said:


That’s quite the description


.

In my crazy days 45-50 years ago it occasionally was apt.

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33 minutes ago, OceanStWx said:

It's my SE zones where I've had a harder time. I essentially issued a forecast I don't believe in to make the map work. :arrowhead:

You went 2-4!  Goin big...   I'd consider 3" a big win in this scenario.  I think we do better Tuesday and especially Friday.

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Reggie tickled NW. pretty close to NAM and Euro now. Still some very small differences. I’d not have any confidence in warning snows BOS-PVD northwestward. But it’s not going to take much for some banding to be NW of model progs to cause warning snows well into the interior. 

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4 minutes ago, mahk_webstah said:

You went 2-4!  Goin big...   I'd consider 3" a big win in this scenario.  I think we do better Tuesday and especially Friday.

Like I said, kind of got boxed into it. I could have said eff it and put out the map I wanted but that's generally not what HQ likes to see.

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2 minutes ago, OceanStWx said:

Like I said, kind of got boxed into it. I could have said eff it and put out the map I wanted but that's generally not what HQ likes to see.

no pun intended

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40 minutes ago, OceanStWx said:

It's my SE zones where I've had a harder time. I essentially issued a forecast I don't believe in to make the map work. :arrowhead:

I'd be absolutely thrilled with 3", but am feeling the under. 

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1 minute ago, moneypitmike said:

I'd sell on warning veriffying anywhere north of the pike/west of 128.

More likely north of the pike / west of 495.

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1 minute ago, The 4 Seasons said:

no pun intended

:ph34r:

I'm just having a hard time justifying QPF much over 0.25" for most of my area. It's going to be hard to crank out 4-5 inches of snow that way. 

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Just now, WinterWolf said:

James challenging the NWS....I hope you don’t rain James. 

Maybe the SE trends just keep going and he stays all snow. :o

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7 minutes ago, USCAPEWEATHERAF said:

Don't pay attention to it, no guidance has mixing pass ACK.

No 

rgem_mslp_pcpn_frzn_neus_26.png

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1 minute ago, Patfan1987 said:

NWS has lowell getting 6-8. I don’t buy it.

Read their AFD.

Very interesting thoughts from them.

 
Low pressure developing off the Carolina coast early Sunday morning
will rapidly lift northeast and pass near the 70W/40N Benchmark
Sunday afternoon/early evening. Snow will rapidly overspread the
region from southwest to northeast Sunday morning and continue
Sunday afternoon. Precipitation type with this system should be
mainly snow away from the immediate coast. The Outer Cape and
Nantucket will likely see mainly rain, while rain/sleet mixing
should cut down the snow totals across Eastern MA coast,
including parts of Boston. Further west towards the East Slopes
and Hartford County, they will be on the northwest edge of the
heaviest precipitation, so have issued a Winter Weather Advisory
for these areas. Block Island is a tough call because they are
west enough to be removed from the strongest warm advection (as
opposed to Nantucket and Martha`s Vineyard) so have put them in
an Advisory as well.
Dynamics couldn`t be more perfect for heavy snow where mixing is
not an issue. Omega is maximized in the -12 to -18C Dendritic
Growth Zone (as low as -10C for the coastal area due to
abundance of salt nuclei) along with 700-925mb speed/directional
convergence will result in a 3 to 4 hour window of impressive
frontogenesis. This is a strong signal for convective snow and
where mixing is not an issue, could easily see 2 to maybe even 3
inches per hour snowfall rate. So even giving the progressive
nature of the system, snow could easily pile up and accumulate 7
to 10 inches in the most persistent mesoscale bands.

Key issue that we have been grappling with is where the rain/snow
line would set up. With such a robust system, the thinking is that
it will bring in quite a bit of warm air out ahead of it to preclude
snow for most of the time for the Outer Cape and Nantucket. The 00z
and 12z HREF have both been very bullish with intense snowfall rates
over the Cape and Islands. The global ensemble guidance is also very
bullish with the probability of 3 and even 6 inch plus snowfall over
the Cape and Islands. However, wet bulb temperature bottoms out
around 32-34F across the Cape and Islands even according to the
NAM. So thinking at best high-end Advisory/very low-end Warning
snowfall for the Inner Cape and possibly no more than a couple
inches for the Outer Cape and the Islands. The fact that the
snow is falling during the daytime hours also makes it harder to
accumulate. In addition, I did lower the snow totals over the
immediate Boston area and much of the Eastern MA coast. With the
winds initially out of the E and NE during precip onset, snow
ratios will be in the 5-7:1 range initially but gradually
increase to around 10:1 as winds back to the N by 20-21z. As for
the interior, higher SLRs are expected generally 12-15:1. QPF
wise, expect generally 0.3 to 0.5 inches west of Worcester and
0.5 to 1 inch over SE MA and RI. Overall, highest snowfall
totals should be from NE CT to Worcester to Metrowest Boston in
the order of 6 to 9 inches where the mesoscale banding coincides
with a thermal profile that minimizes mixing.

Temperatures wise, have used Hi-Res Ensemble Forecast (HREF) to
populate the hourly temperatures given that the most reasonable
way to get around uncertainty with the thermal profile is using
an ensemble approach. It should be noted here that the forecast
temps by the HREF does not correspond with the most likely
precip type (snow) across SE MA, which is a red flag against
forecasting too much snow especially over the Outer Cape and the
Islands.

https://forecast.weather.gov/product.php?site=BOX&issuedby=BOX&product=AFD&format=CI&version=1&glossary=1&highlight=off

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56 minutes ago, mahk_webstah said:

Just go 1-2 for our area.  If it is 3 nobody will notice.  cept the weenies

HEY neighbor, I represent that  

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This has bust written all over it for areas they expanded the warning to (Boston/NW).  I don’t even know why when most models show advisory snows at best for Boston.  It’s like who is calling the shots with 6-8 and even 8-12 right in SW burbs.  Insane and expect complete bustorama

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They don't think the Outer Cape will snow much because it occurs during the day, and the warmer ocean layer will allow stronger warm air advection out ahead of the storm will preclude snow accumulating and they believe the storm will be robust enough to bring in warm air.  I think the dynamics will offset the little warm layer at the boundary layer and instead the intense lift and best snow totals occur over the Cape.  ACK will mix.

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BOX discussion is a good read but not sure I buy the great snow growth for the ORH-BOS-PVD triangle. Esp on some of these solutions where the banding isn’t getting much NW of SE MA...PVD might be best spot in that triangle. The best omega is well above the SGZ on a lot of soundings I checked. However, very frequently we’ll see the fronto bands get a little NW of guidance so using that logic you could make a case. 

Still, I’m not all that enthusiastic about warning snows here. BOS-PVD may be in a decent spot but worried that we’ll be too far NW in the 495 belt and westward. 

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Keep in mind heavier bands may park themselves somewhere north of the south coast, possibly farther north than some expect, while some areas of the cape and south coast are struggling with BL issues. 

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1 minute ago, ORH_wxman said:

BOX discussion is a good read but not sure I buy the great snow growth for the ORH-BOS-PVD triangle. Esp on some of these solutions where the banding isn’t getting much NW of SE MA...PVD might be best spot in that triangle. The best omega is well above the SGZ on a lot of soundings I checked. However, very frequently we’ll see the fronto bands get a little NW of guidance so using that logic you could make a case. 

Still, I’m not all that enthusiastic about warning snows here. BOS-PVD may be in a decent spot but worried that we’ll be too far NW in the 495 belt and westward. 

I think TAN may be even too far NW for warning amounts....especially if we tic East another cycle 

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