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Area forecast discussion...updated 
National Weather Service Gray ME 
1116 am EDT Sat Mar 20 2010 


Synopsis... 
a cold front will approach the region this afternoon...then cross 
the area tonight. The cold front will stall just south of the 
region tonight through Monday. Low pressure over the Middle Atlantic 
States on Tuesday will then ride along the frontal boundary 
Tuesday night into early Wednesday. Low pressure located north of 
the Great Lakes later Thursday will move eastward and cross north 
of the region Thursday night. A trailing cold front will cross the 
region on Friday. High pressure will approach the region Friday 
night and cross the region on Saturday. 


&& 


Near term /until 7 PM this evening/... 
***update at 1115 am... 


Well...the question of whether Portland would break the record for 
today has been answered. It appears as though the gradient will 
remain west to southwest long enough to allow even the coast to 
reach well into the 60s. The full sun temperature off the 1200 UTC 
gyx sounding was 73 degrees. While this number tends to run couple 
of degrees high...did mention 70 for some interior areas of 
southwest Maine. 


In addition...starting to see some gustiness to the wind. While 
still not expecting to mix from the top of the inversion...did 
include gusts in all areas with warmer temperatures and better 
vertical mixing. 


Previous update... 
the gridded and text forecasts were updated this morning 
to account for trends in temperatures...clouds and to add wind 
gusts for this afternoon ahead of the cold front. 


Currently...the forecast area is in a general middle level zonal flow 
with a surface cold front draped over the St Lawrence River valley. 
The front is marked by a cloud band stretching from the Maritimes 
southwest through southeast Ontario. Canadian radar mosaics show 
some activity with the front. Across the forecast area...mainly 
just some middle and high cloudiness ahead of the front across the 
mountains. 


Not much change to the philosophy of the previous forecast. The 
surface cold front should cross the region during the middle to late 
afternoon. While there is some activity with the front now across 
northeast Ontario and southwest Quebec...the sub cloud layer is 
fairly dry...and the mention of showers was limited the the higher 
terrain. 


Further south...would expect sunshine until the cloud band with 
the front approaches. With this in mind...sky conditions were 
improved a bit for the southern most zones. 


With regard to temperatures...the gradient flow is southwest 
ahead of the surface cold front. Since the gradient does not 
tighten much ahead of the front...it is possible that southwest 
coastal areas could see a sea breeze circulation develop ahead of 
the front. As the frontal zone approaches...the gradient flow 
should kick in. 


This is important for high temperatures near the coast. With the 
expected southwest gradient this afternoon...would expect Portland 
to get close to the record high for today of 62 degrees set in 
1959. Elsewhere...1200 UTC soundings suggest highs in the 60s away 
from the coast. Went a bit below this in the mountains...where 
clouds and a faster cold frontal passage will limit heating. 


Finally...1200 UTC soundings showed 35 to 40 knots of wind just 
above the top of the inversion. Not sure the frontal zone will be 
able to tap these winds...but did add some gusts to the higher 
terrain to account for the possibility. 


&& 


Short term /7 PM this evening through 6 am Sunday/... 
have gone with a chance of precipitation over northern/mountain 
sections for tonight and kept southern/coastal sections dry. 
Could even see some snow showers over northern/mountain sections. 
Used a blend of mav/MOS/current forecast for temperatures/winds. 


&& 


Long term /Sunday through Friday/... 
complex situation setting up with models having a tough time 
deciphering exact track of upper low as it moves across the southeast 
U.S. On Sunday...expect some overrunning to begin. Atmosphere may 
be dry enough at the onset to allow for light snow over northern 
areas. Terrain will play a role in the ptype as well during the 
day. Over southern locales...showers will break out from west to 
east during the day. 


As atmosphere saturates...light precipitation will continue into the 
nighttime hours. However...any frozen precipitation by this Point May be 
confined well to the north...over the higher terrain. 


Stacked low inches closer...so by Monday rain should be falling 
across much of the region. Models then diverge Monday night. WRF 
solution is most aggressive building a surface high to our north. 
This allows for a cold drainage flow to develop. This would allow 
for the precipitation to change to freezing rain over a relatively large 
area. Other models are not as robust with this feature. GFS 
develops more dynamic surface coastal low which would make for 
more of a rain/snow line situation somewhere over central/southern 
interior sections. 


So the big question remains whether or not a sizeable portion of 
the quantitative precipitation forecast arriving late Monday night into Tuesday will be in the 
form of freezing rain. It is very late in the season...and with 
the record breaking warm weather...the ground temperatures are 
coming up fast. Question will be low level temperatures by 
Tuesday...for icing of trees. There is still quite a bit of time 
to digest this possibility. 


After the potential mix Tuesday/Tuesday night...the weather 
becomes more benign. A significant shot of cold air will arrive 
by next weekend. 


&& 


Aviation /15z Saturday through Wednesday/... 
short term...VFR conditions today. 


Short term /tonight/...local MVFR conditions tonight over 
northern/mountain sections in any chance rain/snow showers. VFR 
southern/coastal sections. 


Long term...conditions slowly deteriorate Sunday during the day with 
some rain and snow showers possible. Ceilings will continue to 
lower as well as visibilities on Monday...and more so on Tuesday. Icing 
may be problematic. Conditions improve by Wednesday. 


&& 


Marine... 
near term /today/...the southwest gradient is tightening a bit ahead 
of the surface front across the St Lawrence River valley. The gradient 
does not appear to support small craft winds...even in gusts. At this 
time...there are no wind gusts near 25 knots with the front. 


1200 UTC soundings show 35 to 40 knot winds between 5000 and 6000 
feet. While the depth of the mixed layer does not appear to support 
tapping this winds...made sure to carry over the gusts for the 
ocean waters should mixing occur. The warmer air over the colder 
ocean should effectively cut the mixing potential until just ahead 
of the front. 


Short term /tonight/...no flags tonight. 


Long term...gales are possible by Monday/Tuesday. 


&& 


Fire weather... 
could be a marginal fire weather day across the region where there 
is no snow cover and clouds do not become a factor until later this 
afternoon. The 1200 UTC soundings across New England and eastern 
Canada show quite a bit of dry air in the sub cloud (or potential 
sub cloud) layer. At the top of this layer...winds of 25 to 35 knots 
may be available for mixing just ahead of the surface front poised 
to move through the area this afternoon. 


Across the mountains...where there is still enough snow cover to 
mitigate conditions...problems are not expected. Still quite a bit 
of standing water across southern zones (especially just below the 
dry surface layer). Could be that portions of central Maine could 
get close to red flag conditions...as relative humidity values 
drop to near 30 percent. Wind gusts here may be just short. 


Bottom line...no red flag warnings are anticipated for today with 
marginal conditions. A change to wetter conditions Sunday into 
early next week should mitigate fire weather concerns. 


&& 


Gyx watches/warnings/advisories... 
ME...none. 
New Hampshire...none. 
Marine...none. 


&& 


$$ 

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