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1/27/12 SWFE Discussion


Baroclinic Zone

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Looks at 925mb temps (2,500ft) at K1V4 it stays below freezing throughout north of KLEB...850 does get above freezing for atleast 6 hrs..is that warm layer from about 720mb to 870mb thick enough to cause zr or would it be ip? The surface here at St. Johnsbury is at like 970mb FWIW and It warms the most at 800mb to 2C for a short time. The warmest surface temp is 32.8F at 18z. Thanks.

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Just looked at the NAM FOUS and even Concord NH stays at or below freezing for much of this. At least it is fast moving. I wonder if ice accumulates faster with a lighter rain than if it is pouring? I would think at 31/32F with moderate or heavy rain much just drips off rather than coating branches. Either way just crappy!

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Looks at 925mb temps (2,500ft) at K1V4 it stays below freezing throughout north of KLEB...850 does get above freezing for atleast 6 hrs..is that warm layer from about 720mb to 870mb thick enough to cause zr or would it be ip? The surface here at St. Johnsbury is at like 970mb FWIW and It warms the most at 800mb to 2C for a short time. The warmest surface temp is 32.8F at 18z. Thanks.

After doing some research, it seems like this may be a sleet, rather than freezing rain, sounding? The cold layer near the ground is almost 100mb thick and doesn't get crazy warm it seems. Is this correct?

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Just did a full analysis of the 0z NAM solution for St. Johnsbury,VT because I have the time tonight and we are discussing in my thermo class tomorrow...dont feel like writing everything out with explanations but overall this is what the conditions are like:

Snow 10pm Thurs-5am Fri

Sleet 5am-9am Fri Total Snow/Sleet accumulation 2-3"

Freezing rain 9am-1pm Fri at St. Johnsbury as temps get to 33F by 1pm Total Freezing Rain (700' ASL) accumulation 0.1-0.3" with 0.2"-0.4" above 1500' ASL where it stays completely below freezing throughout.

Rain 1pm-3pm

Snow 3pm to 10pm with wrap around moisture as temps crash aloft and at the surface. Total snow accumulation around 1" at 700' and 1-3" above 1500'

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...WINTER WEATHER ADVISORY IN EFFECT FROM 7 PM THIS EVENING TO 1 PM EST FRIDAY...

THE NATIONAL WEATHER SERVICE IN TAUNTON HAS ISSUED A WINTER

WEATHER ADVISORY FOR FREEZING RAIN AND SLEET...WHICH IS IN EFFECT FROM

7 PM THIS EVENING TO 1 PM EST FRIDAY.

* LOCATIONS...SOUTHERN NEW HAMPSHIRE AND INTERIOR MASSACHUSETTS.

* HAZARD TYPES...FREEZING RAIN...SLEET AND SNOW.

* ACCUMULATIONS...SNOW ACCUMULATION OF UP TO 1 INCH...ALONG WITH

UP TO ONE QUARTER OF AN INCH OF ICE.

* TIMING...A MIX OF RAIN AND SNOW WILL BEGIN LATE THIS AFTERNOON

WITH FREEZING RAIN BECOMING THE PRIMARY PRECIPITATION TYPE BY

THIS EVENING AS TEMPERATURES FALL BELOW FREEZING. FREEZING RAIN

WILL LAST THROUGH THE OVERNIGHT HOURS AND COULD PERSIST DURING

THE FRIDAY MORNING COMMUTE...ESPECIALLY NORTH OF I-90 IN WESTERN

MASSACHUSETTS AND ACROSS SOUTHERN NEW HAMPSHIRE.

* IMPACTS...SLIPPERY CONDITIONS ARE POSSIBLE ACROSS UNTREATED ROADS...SOME

TREE LIMBS AND POWER LINES DOWN WITH SCATTERED POWER OUTAGES

POSSIBLE.

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Well there is a slight chance of getting some very light snow into SNE later tonight as mid level WAA tries to move in aloft.

Otherwise, it looks like you could possible have a very brief period of SN, and then some ice before a cold rain.

Actually have a coating right now with very light snow.

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Seems like parts of SW NH..probably near or north of Socks and up into IZG area could have decent icing. IZG will have snow before, however.

Advisory notwithstanding, BOX's AFD throws the three w's (wet weenies wildly) to everyone in Mass. In it, they do question the impact in western MA, but really don't think freezing will be an issue of significance outside of NH. At least that's how I read it. Furthermore, 'trace' accretions of ice as mentioned in the zfp is about as boring a forecast as there is. Yawn.

27.9/24

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Seems like parts of SW NH..probably near or north of Socks and up into IZG area could have decent icing. IZG will have snow before, however.

That SWFE jackpot area of Conway/IZG might be the wrong ptype this time around.

A lot of the sounding analysis is concerning, especially if the low levels hang onto the cold. Most of the models eventually take things above freezing, but it's not by much.

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That SWFE jackpot area of Conway/IZG might be the wrong ptype this time around.

A lot of the sounding analysis is concerning, especially if the low levels hang onto the cold. Most of the models eventually take things above freezing, but it's not by much.

Probably the one thing preventing this from being a lot worse is the high location...its kind of cruddy to offset the latent heat release. Might be the type of situation where a lot of spots see a pretty nasty 6-8 hour period of icing but then creep up to 32-33F and rain eventually.

Though if the sfc ridging can hang on long enough N of Maine, then it could end up a tad colder than models show. Or even a little mesolow that forms on the east side of the CAD can help sometimes too. Duration also prevents it from too terrible, but we had a pretty nasty ice event on 3/2/07 here that was only about a 6 hour duration...we had like 3/8ths accretion which can start causing problems.

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Probably the one thing preventing this from being a lot worse is the high location...its kind of cruddy to offset the latent heat release. Might be the type of situation where a lot of spots see a pretty nasty 6-8 hour period of icing but then creep up to 32-33F and rain eventually.

Though if the sfc ridging can hang on long enough N of Maine, then it could end up a tad colder than models show. Or even a little mesolow that forms on the east side of the CAD can help sometimes too. Duration also prevents it from too terrible, but we had a pretty nasty ice event on 3/2/07 here that was only about a 6 hour duration...we had like 3/8ths accretion which can start causing problems.

I mentioned that in the AFD this morning. The duration will definitely be a limiting factor along with the latent heat release. Considering the thump of forcing, we should have pretty high precip rates, and like you said about the high pressure, if there isn't that steady cold (and dry) drainage places may hover near freezing. That 1500-3000 ft elevation looks like they'll get hit pretty hard though, soundings nicely showing that cold wedge hanging tough just off the deck for a time.

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I am assuming 90% of what falls here will be liquid

I have a meeting in Worcester this afternoon and will be making the trek back to the Pit at about 4:00pm or so. Perhaps I can pick up a few flake sightings as I head up 122 through Rutland/Barre/Petersham and the heading west along Rt 2.

I hope my snow can withstand the upcoming system. Afterall, the rain will be cold.........

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I am assuming 90% of what falls here will be liquid

I think more than 10% of your precip will be frozen. Might get an inch of snow before the flip if lucky. But there could def be a good 4-6 hour period of icing with decent rates for you...we'll probably go to cold rain eventually some time between 6z and 9z...esp if the sfc low tracks over interior SNE...but there's a chance the icing could be a bit longer duration if the sfc reflection gets squeezed more along the coastal plain and out E of BOS.

But its worth noting that over a half inch of qpf has fallen by 09z, so if it hangs onto ice until then, it could get pretty nasty for a time. Monadnocks will almost certainly hold onto ice until then.

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I think more than 10% of your precip will be frozen. Might get an inch of snow before the flip if lucky. But there could def be a good 4-6 hour period of icing with decent rates for you...we'll probably go to cold rain eventually some time between 6z and 9z...esp if the sfc low tracks over interior SNE...but there's a chance the icing could be a bit longer duration if the sfc reflection gets squeezed more along the coastal plain and out E of BOS.

But its worth noting that over a half inch of qpf has fallen by 09z, so if it hangs onto ice until then, it could get pretty nasty for a time. Monadnocks will almost certainly hold onto ice until then.

Mike (Oceanstate) indicated his thinking was els above 1500' for the GYX area being the level where freezing would hold on. That would translate nicely to MP3, but meh for home and essentially all of the SNE posters.

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Mike (Oceanstate) indicated his thinking was els above 1500' for the GYX area being the level where freezing would hold on. That would translate nicely to MP3, but meh for home and essentially all of the SNE posters.

Mike was sleeping soundly while I (Chris) was preparing this forecast. ;)

Will brought up the scenarios that could turn this really nasty. Going to be a lot of nowcasting the surface low and resulting temperatures. Just the amount of QPF really spits out some big ice totals for my area even with an eventual changeover to rain.

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Mike was sleeping soundly while I (Chris) was preparing this forecast. ;)

Will brought up the scenarios that could turn this really nasty. Going to be a lot of nowcasting the surface low and resulting temperatures. Just the amount of QPF really spits out some big ice totals for my area even with an eventual changeover to rain.

Chris nice to have you on here regularly...thanks for that. I'm in northern Merrimack County, on the town line of Webster and Salisbury...about 675 ft. You guys have had a good winter in terms of forecasts for winter events! Hopefully your skills get challenged in a good way over the next couple months. This one doesn't have the feel of an overperformer unfortunately but this is only my 4th winter up here. Are you on the afternoon shift today? Happy to post obs. We are only 15 miles nw of CON but often hang onto cold a good bit longer

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Mike was sleeping soundly while I (Chris) was preparing this forecast. ;)

Will brought up the scenarios that could turn this really nasty. Going to be a lot of nowcasting the surface low and resulting temperatures. Just the amount of QPF really spits out some big ice totals for my area even with an eventual changeover to rain.

Sorry, Chris--I thought you were Mike. My bad.

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