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fxus61 kbtv 200124 
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Area forecast discussion 
National Weather Service Burlington Vermont 
924 PM EDT Friday Mar 19 2010 


Synopsis... 
the string of sunny and very warm days will be coming to an end as 
a cold front will move through the north country Saturday and 
then stall. Although no rain is expected with the front...there 
will be an increase in clouds. Rain and higher elevation snow 
showers will develop Sunday as the front begins to slowly lift 
northward. Cooler and unsettled weather will continue into at 
least Tuesday. 


&& 


Near term /until 6 am Saturday morning/... 
as of 325 PM EDT Friday...surface temperatures remain quite mild 
late this evening across the north country...especially in the St. 
Lawrence and Champlain valleys with temperatures generally 54-56f 
at 01z /9 PM/. The north country will remain southeast of an 
approaching cold front from the northwest overnight. This front 
will just be reaching the international border near Massena New York around 6-8 
am Saturday. Pressure gradient will maintain a south to southwest 
wind of 5-10 miles per hour except in the more sheltered valley locations. 
Low temperatures will range from the low 40s in the Champlain and 
St. Lawrence valleys to the middle 30s in the sheltered locations 
east of the Green Mountains and within the northern Adirondack region. Only 
change to the forecast was to adjust temperature and dewpoint 
trends to account for current conditions. Do not expect any 
precipitation overnight with dry low-level conditions south of the 
boundary and anafrontal nature of the boundary with most of the frontal 
ascent north and west of the surface frontal position. 


Three daily maximum temperature records were broken on Friday. 
These included btv /66f/...mpv /64f/...and mss /61f/. The old 
records were 60f...57f...and 60f...respectively. For further 
details...please see our record event statement. 


&& 


Short term /6 am Saturday morning through Sunday night/... 
as of 325 PM EDT Friday...confidence not all that high for this 
forecast period. 


12z guidance suite are in general agreement with overall 
scenario...but there are minor differences in the details. 
Unfortunately...those details play a significant role in the 
weather we will be seeing. For the details... 


Saturday...cold front will be oozing southward. Expect it to reach 
the St Lawrence Valley about 12z...the Champlain Valley about 
15z...and then into southern sections about 21z. As a 
result...temperatures will be very tricky. Highs will occur just 
before frontal passage with temperatures then slowly falling off. 
As a result...the Rutland/Springfield areas will be warmest 
(likely getting into the lower 60s)...the btv area should pop into 
the middle-upper 50s before cooler air gets in. Middle 40s should do it 
for Massena. The frontal passage will be a dry one...no precipitation...a 
subtle wind shift to the northwest and clouds. 


Saturday night...the front hangs up across the southern half of 
the region...thus southern half of region will be the warmer area. 
Clouds should hang tough. 850mb flow begins to turn southwest 
ahead of an approaching low in the Ohio Valley. This flow will 
lead to isentropic lift over the stalled front (which will be 
evolving into a northward moving warm front on sunday). That lift 
will lead to perhaps a few flurries developing across western New York 
and the 'dacks. 


Sunday...precipitation should become more widespread across the 
region as that isentropic lift intensifies. Not expecting heavy 
amounts of precipitation (less than 1/4")...but as warm air rides over 
the colder air we start to have to deal with precipitation-type issues. 
This is where those details are key...how cold/deep is that cold air? 
Exactly where does the front stall out? How quickly will warm air 
be moving northward? I think you get the picture. Think boundary 
layer temperatures during the day Sunday should keep precipitation all 
rain...however things are more tricky Sunday night. Have painted in 
some snow or rain/snow mix primarily for northern areas and at 
elevations generally above 1000ft. To be honest...some guidance 
indicates that a little sleet or freezing rain could be in the mix 
as well Sunday night. Too much uncertainty at this point to 
include such potential. Snow accumulations of an inch or two are possible. 
Gotta Love mother nature...gives US fine Spring weather in late 
winter...then winter weather in early Spring. Go figure. 


Given all this uncertainty...pretty much stayed close to guidance 
for temperatures. 


&& 


Long term /Monday through Friday/... 
as of 226 PM EDT Friday...a return to more typical late March 
weather is expected during much of next week. At the beginning of 
the period low pressure tracking south of the region will bring 
widespread light to moderate precipitation to the region Monday 
into early Tuesday. This morning's operational and supporting 
ensemble members in overall good agreement regarding surface track 
across the Middle-Atlantic States and eastward south of New England 
during the period. Temperatures/weather quite tricky despite real lack of 
colder air aloft...as tight gradient in the 925-850 mb 
thickness/thermal fields suggests at least a decent threat of 
mixed precipitation (mainly rain or snow) by later Monday/Monday night in a 
band across the dacks into the central greens where some minor wet 
accumulate possbl. That said...majority of p-type should be rain Monday 
afternoon as temperatures will be cool but well above the 32 degree mark. 


Surface low then shunts eastward by Tuesday afternoon with any 
lingering light rain or snow showers ending by evening and skies 
gradually clearing toward Wednesday morning. High pressure then provides 
generally quiet and seasonably mild conds during Wednesday with light 
winds and ample sunshine. Toward the end of the forecast period 
confidence is slowly increasing of a fairly strong modified-Arctic 
frontal passg by Thursday accompanied by gusty winds and scattered 
rain/snow shower activity. Indeed...if you believe this morning's 
GFS run verbatim 850 mb temperatures plummet from 02c at 18z Thursday to -22c by 
12z Friday morning under strong cold air advection. If that were to occur high 
temperatures on Friday would only struggle into the 20s...though with the 
gfs's general cold bias in these types of surges in the medium 
range...something closer to last night's milder Euro solution likely 
closer to reality. Still a decent frontal passg seeming more likely 
however with temperatures falling back to chillier readings by next 
Friday. 


&& 


Aviation /01z Saturday through Wednesday/... 
through 00z Sunday...a cold front...now to the north and 
extending across the Great Lake region...will be the main feature 
for the prd. As a result middle and high level clouds are moving in with 
generally light southwesterly winds ahead of the front. This feature is 
slow moving and relatively dry with no precipitation expected as it 
passes from north to south in the morning. Winds will veer west 
around 12z and northwest after 16z at the northern most site of kmss and 
21z at the southern most site of krut. Winds will likely become 
gusty after frontal passage. VFR conditions are expected with scattered low clouds as the 
front passes. 


Outlook 00z Sunday through Wednesday... a new low pressure center 
will form in the Midwest along the tail end of cold 
front...causing the front to become stationary across our region 
into next week. This will lead to the potential for -shra and 
occnl MVFR ceilings until the low center passes to the south Monday 
through later Tuesday when southern taf sites could see more 
persistent precipitation and MVFR/IFR cigs/vis. Wednesday conditions improve 
as the system moves away with VFR. 


&& 


Btv watches/warnings/advisories... 
Vermont...none. 
New York...none. 


&& 


$$ 
Synopsis...Nash 
near term...banacos 
short term...Nash 
long term...jmg 
aviation...jmg/NH 

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