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On Mon, 23 Oct 2006 19:29:25 -0400, Scott Braaten <[log in to unmask]> wrote:

>Look for accumulating snow Tuesday evening through
>Wednesday but I don't think I'm going to be able to give a confident
>forecast on snowfall amounts.  Lots of factors to consider, especially 
>time of year (don't take Friday's snowfall to the valley as an indicator 
>since it was caused by extreme dynamics aloft with a very strong 500mb 
>vort max passing overhead).
>
>My best guess (it is a guess) stands at 4-8" from MRG/SB to Jay,
>respectively, though I fear that might be 2" too high <snip>

Going to stay the course with 4-8" and will need field reports (Kevin B. 
you are one of the best sources I have with reliable accounts from above 
2,000ft) from this afternoon through Wednesday.  My time-line forecast is 
at bottom of post along with thoughts regarding Lake Champlain enhancement 
into mtns of eastern Addison County.

From NWS at BTV:
BUFKIT SOUNDINGS INDICATE HIGHEST RH LAYERS ARE TOO WARM FOR
OPTIMUM SNOW CRYSTAL GROWTH SO NOT EXPECTING SIGNIFICANT
WIDESPREAD ACCUMULATIONS. NEVERTHELESS WILL NOT BE SURPRISED BY 1
OR TWO HIGH ELEVATION REPORTS OF 4-6 INCHES...BUT OVERALL SNOW
TOTALS IN ADIRONDACKS...AND NORTH CENTRAL/NORTHEAST VT SHOULD BE
1-4 INCH RANGE.

However, in a rare turn of events, GYX (Gray, ME) is actually more robust 
than BTV.  I don't think I've ever seen this, seriously.  Its something to 
consider but GYX's morning discussion repeats my thoughts from the past 
few days...daytime marginal for accumulating snow but the upslope signals 
are there.  Thus, there's a Snow Advisory for NH and ME but don't let that 
fool you.  GYX cites .40" QPF in upslope favored terrain in their region, 
while highest resolution NAM indicates an axis of .5-.75" along Mansfield 
to Jay and in the northern Adirondacks.  

FOR TONIGHT...THE FOCUS SWITCHES TO THE UPSLOPE POTENTIAL. THE
CLOSED MID LEVEL SYSTEM OVER THE UPPER GREAT LAKES DRIFT
EAST...MERGING WITH AND DEEPENING THE SYSTEM JUST TO THE EAST OF
THE AREA. THIS WILL MAKE THE FLOW EVEN MORE CYCLONIC...AS WELL AS
INCREASE THE FLOW. THIS SHOULD CREATE NEARLY IDEAL UPSLOPE
CONDITIONS FOR NORTHERN NEW HAMPSHIRE AND THE MOUNTAINS OF WESTERN
MAINE. 

WHILE THERE ARE SOME MITIGATING CIRCUMSTANCES (BORDERLINE
TEMPERATURES IN THE LOWER LEVELS AND DIURNAL EFFECTS)...THE QPF
FORECAST OF UP TO 0.40 INCHES OF LIQUID IN THE FAVORED UPSLOPE
LOCATIONS INDICATES AN ADVISORY TYPE EVENT FOR THESE LOCATIONS.
BASED ON THIS...WILL RAISE A SNOW ADVISORY FOR THE HIGHER TERRAIN
OF COOS...GRAFTON AND NORTHERN OXFORD COUNTIES FOR TONIGHT AND THE
FIRST HALF OF WEDNESDAY. 

THE BEST UPSLOPE SHOULD OCCUR TONIGHT AND EARLY WEDNESDAY...AHEAD
OF AN IMPULSE IN THE CYCLONIC FLOW. THE WARMING IN THE DAY TIME
AND THE PASSING OF THE IMPULSE SHOULD TEND TO BRING THE CHANCES
DOWN...AND CAUSE MAINLY RAIN IN THE AFTERNOON IN THE LOWER
ELEVATIONS. AT THIS TIME...EXPECTING BETWEEN 3 AND 6 INCHES OF
SNOW FOR THE FAVORED LOCATIONS. 

I am going to stay with 4-8" for the favored areas from MRG northward 
though have a feeling it might be more like 2-4" south of I-89 and 4-8" 
northward.  I've been toying with the idea that Lake Champlain is still 
warm with -6C air advected over top the warm dome, especially Wednesday 
afternoon when winds are NNW, my local knowledge wants to say 
MRG/SB/Eastern Addison County sees lake enhanced orographic snows (the 
best of both worlds) as a low level jet max swings through Wednesday 
afternoon.  Timing is between 2pm-8pm for best lake flow, which is max 
daytime heating time as well.  Will daytime instability with cold pool 
aloft coupled with lake moisture feed directly into General Stark Mtn 
overcome daytime heating to produce something special?  Don't know but it 
is something to pay attention to...especially considering the position of 
the Maritimes low is progged to be further east than the major NVT upslope 
events last year that sort of missed MRG/SB due to friction with the 
Adirondacks.  With this low position, the flow into ENE Addison County is 
crossing agricultural land in NY/CA then a long fetch of Champlain before 
turning SE into a 4K foot wall.  One Champlain Special coming up?

On another note, next weekend is going to be incredibly interesting and 
model solutions are all over the place.  What they all show is a major low 
moving out of the south and tracking either up the Apps (mix to rain here 
with snow on backside) or low tracking up the Apps then getting blocked by 
the low that will provide upslope precipitation tonight-tomorrow only to 
form a secondary low near Long Island or in the vicinity of eastern New 
England coastline.  The 6z GFS actually has the blocking low drilling low 
level cold air into northern New England while advecting warm, moist air 
over top: Ice.  I can't imagine anything like it would take place but a 
1.5" rainfall with temps at 30-31F at BTV would be interesting to say the 
least.  Another run yesterday had it in the Gulf of Maine with a thump 12" 
snowfall then the next one had a 40F rain.  EURO and Canadian all develop 
strong low and the EURO has been sticking with an inland track with a snow 
to sleet/freezing rain to rain then back to snow situation.  

Not many look at this but to me, what happens after the weekend when a sub 
990mb low cuts off north of the region means one helluva orographic 
snowfall and arctic blast.  What month is this?  The models all have 
better looks than they did last January for the next 10 days.

So much to tell, sorry for the length but that should wake the crowd up.

-Scott

 

   

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