674 
fxus61 kgyx 211934 
afdgyx 


Area forecast discussion 
National Weather Service Gray ME 
334 PM EDT sun Mar 21 2010 


Synopsis... 
high pressure over Quebec will drift east tonight. A stalled front 
south of the area will drift north tonight and Monday night...spreading 
precipitation into the region Monday night and Tuesday. Low pressure 
riding northeast on the front could bring heavy rain to portions 
of the region Tuesday and Tuesday night...before exiting Wednesday. 
An Arctic cold front will approach the region Thursday...then cross 
the area Thursday night. This will bring much colder conditions to 
northern New England for the end of next week and the weekend. 


&& 


Near term /until 6 am Monday morning/... 
watching the last of the significant warm air advection precipitation 
moving across the mountains this afternoon. Despite temperatures 
just above the freezing mark...snow was the predominate precipitation 
type in the mountains. Also watching what appears to be mainly middle 
level precipitation across the southern zones. The low level seem 
to be too dry to allow precipitation to reach the ground. 


Lots of thin spots in the clouds across southern zones...and would 
expect this to continue tonight. In fact...after convectively driven 
clouds dry up this evening...could just be some cirrus for these 
areas. Further north...more in the way of clouds as the warm air 
advection starts to wrap up. 


Will have to carry a mention of snow in the mountains these evening 
as the last of the warm air advection crosses Vermont into these 
areas. With the warm temperatures of the last few days...would 
expect to see less than 2 inches of new snow. 


Based on the thin clouds at least to start down south...leaned 
toward the cooler NAM MOS numbers for lows. Further north...used a 
blend of MOS numbers for lows. 


&& 


Short term /6 am Monday morning through Monday night/... 
warm air advection commences again Monday morning...this time 
ahead of the closed middle level system moving east from the lower 
Mississippi Valley. The 1200 UTC model suite was close with 
timing...and a blend was used for timing. Very dry air across the 
northern zones Monday morning will slow the northward progression 
of the precipitation line. 


This also raises the potential for the precipitation to start as 
light snow...since the column may be dry and cold enough for this. 
Right now...as the precipitation will be fighting the dry air...not 
expecting much snow accumulation (if any). With clouds in place 
all zones...used a blend of MOS numbers for highs Monday. 


The best inflow begins Monday night...as the low level flow has 
its origins north of the Bahamas. Precipitable water values rise 
to near 1 inch Monday night...and this is pointing at southeast 
New Hampshire and southwest Maine. Since the best frontogenetic 
lift north of the closed low lags the increase in moisture...it 
would appear as though the heaviest rain will hold off until 
Tuesday. Based on this...did not raise a Flood Watch for these 
areas yet. Low were based on a MOS blend. 




&& 


Long term /Tuesday through Sunday/... 
heavy rain returns to New England early this week. Recent June-like 
weather is replaced with February-like temperatures later in the 
week. 


As low pressure moves up the coast and through the Gulf of Maine... 
moisture will stream in from the south into New England on Tuesday. 
The origins of this moisture will be the tropical Caribbean...thus 
there will be plenty of moisture available to produce heavy 
rainfall. But the system will be more progressive than last weeks 
storm with the heavy rain not lasting as long before shifting 
east. Lighter rain will continue through at least Tuesday night. 
The progressive nature will limit overall rainfall totals...but still 
could see a quick 1 to 3 inches of rain...most of that falling on 
Tuesday. The most likely areas for heavy rain will be along the 
middle coast of Maine from Portland to Rockland. However...areas 
further south remain vulnerable to flooding as rivers are still 
receding from the recent heavy precipitation. Therefore will have 
to monitor the potential for additional flooding and may need a 
Flood Watch at some point. 


For the most part this storm will be a rain event for the whole 
area. Although some snow is expected in the higher terrain of 
northwest Maine and northern New Hampshire. May see rain change to 
snow across a broader area on Wednesday...but do not expect 
excessive accumulations at this point aside from mountain peaks. 


As the low moves up into the Canadian Maritimes...a cold front will 
pass through the area Wednesday night. This will bring some colder 
air into New England...though it will only be a taste of what is to 
come. 


Brief ridging returns on Thursday with a slight warm up. But a much 
stronger cold front with Arctic air behind it will push across the 
area Thursday night. By Friday New England will be back to winter 
with temperatures falling into the 20s and 30s for highs on Friday 
and Saturday. Overnight lows will generally be in the teens with 
single digits expected in the north. 


&& 


Aviation /19z Sunday through Friday/... 
near term /tonight/...outside of snow and rain activity...conditions 
have remained VFR at the terminals this afternoon. With the best lift 
in the waning warm air advection staying across the mountains...would 
expect VFR conditions through at least 0900 UTC Monday. After this... 
moisture getting trapped under the lowering inversion could bring 
MVFR conditions to kleb. 


Short term /Monday and Monday night/...dry air trying to hang in 
there should slow the progression of the moisture under the inversion 
Monday...generally from west to east. Thus...would expect to see 
kaug remain VFR through at least 1800 UTC Monday. After conditions 
will worsen to MVFR and possibly IFR by 0000 UTC Tuesday as the 
rain arrives. 


Elsewhere...conditions should transition through MVFR to IFR 
between 1200 UTC and 1800 UTC Monday. As the rain shield covers 
the region...would expect an extended period of IFR conditions 
through late Monday night. 


Long term...will likely see MVFR to IFR conditions continue 
through Wednesday morning before improving to VFR. 


&& 


Marine... 
near term /tonight/...as the surface high shifts to the east...the 
gradient has become easterly...and there could be a few gusts to 
20 knot this evening on the ocean waters. After this...the gradient 
collapses and winds could become light and variable late tonight. 


Short term Monday and Monday night/...the stalled front to the 
south of the waters starts to creep north Monday as low pressure 
forms on the end of the front over the middle Atlantic. The gradient 
will start to tighten later in the day...but for the most part 
winds should remain below 15 knots Monday. The increased fetch 
will result in building seas...but again during the daylight hours 
seas should remain below 5 feet. 


The gradient tightens more Monday night as the low moves northeast. 
Right now...the gradient appears to support winds getting into the 
small craft range...especially on the ocean waters after 0600 UTC 
Tuesday. Mixing is limited...so it appears as winds will remain 
below 25 knots through daybreak Tuesday. 


The east to northeast fetch will probably build seas higher than 
the wave watch model shows. Because of this...seas on the ocean 
were increased about 2 feet above guidance...especially after 0600 
UTC Tuesday. 


Long term...as the main system approaches the Gulf of Maine on 
Tuesday...could see easterly winds strengthen to near gale force 
especially across the eastern waters. Waves will also pick up to 
near 10 feet with the easterly fetch. 


A cold front on Wednesday night will bring northwest winds close 
to gale force again. After a brief break on Thursday...another 
stronger front on Thursday night will also bring northwest winds 
near gale force. 


&& 


Hydrology... 
there is a potential for heavy rains to return to the area Monday 
night through Tuesday night. Moisture streaming in all the way 
from the Caribbean will allow heavy rainfall rates...but the quick 
progression of the system will limit the duration of heavy rains. 
With southern areas still recovering from last weeks heavy rains 
and flooding...they are potentially vulnerable to seeing more 
river rises on Tuesday. For now have decided to hold off on a 
watch as the heaviest precipitation is still two days away. But a 
Flood Watch may be needed at some point in the future to account 
for the expected rains. 


&& 


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


&& 


$$ 

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