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Area forecast discussion 
National Weather Service Taunton Massachusetts 
359 am EST Friday Nov 21 2008 


Synopsis... 
dry and unseasonably cold weather will continue through this 
weekend. A storm system will affect southern New England Monday night 
into Tuesday. The atmosphere looks to warm up enough by then to bring 
mainly rain to the area...but some snow may occur over the higher 
elevations. Drier weather along with a return to colder than normal 
temperatures will arrive Wednesday and Thursday. 


&& 


Near term /until 6 PM this evening/... 
unseasonably cold weather will continue today and into the weekend. 
An upper trough will continue to approach southern New England today. 
This trough will aid in the development of strong low pressure well 
south of Nantucket. The low will form far enough out to sea so that 
it/S precipitation shield remains well to our south. A few rain or 
snow showers may briefly graze Nantucket. 


What this low will do however is help draw very cold air southward 
tonight. For today...a good amount of sun will be seen although there 
will likely be periods of broken cloud cover. Went a few degrees 
lower than MOS guidance for maxes today. It/ll be a chilly one...with 
highs in the 30s pretty much everywhere...about 15 degrees below 
normal. 


&& 


Short term /6 PM this evening through 6 PM Saturday/...low pressure 
strengthens rapidly as it rockets toward Nova Scotia tonight. This 
will help draw bitter cold air /for Nov standards/ southward into 
southern New England on gusty winds. Wind chill values by late 
tonight will probably reach the lower teens to single digits at most 
locations. Looks dry...but can/T rule out a few flurries in the 
cyclonic flow. 


500-505dm thicknesses in the 1000-500mb layer with 850mb temperatures around 
-16c are on tap for Saturday...which is downright cold and very 
January-like. It/S actually tough to get the thicknesses that low 
down here even in January. This will result in maxes nearly 20 
degrees below normal in spots. Undercut MOS guidance a bit which 
results in highs in the upper 20s to lower 30s. We/ll add strong 
winds on top of that /20-25 miles per hour with gusts 30 to 35 mph/. This will 
result in daytime wind chill values in the teens. It looks as though 
winds will fall short of advisory criteria...but we/ll have to keep 
an eye on the higher elevations as well as the cape and islands. 
Skies will be variably cloudy...with a few flurries possible. 


Although wind direction doesn/T appear optimal...some ocean effect 
snow showers may graze Cape Cod. 


&& 


Long term /Saturday night through Thursday/... 
blustery and very cold conditions expected Sat night as strong northwest 
gradient remains in place. Winds may gust to 30-35 miles per hour Sat evening 
before slowly diminishing. With northwest flow...ocean effect snow showers 
should remain largely offshore but may clip Outer Cape Sat evening 
so we will carry low chance probability of precipitation here. Otherwise...evening clouds 
should give way to clearing skies. Mins will be in the teens to 
lower 20s but gusty northwest winds will make it feel in the single numbers 
and lower teens. 


Surface high moves to the south on Sunday which keeps modest westerly 
gradient over southern New England. Airmass still quite cold Sun morning with 850 
temperatures -14 to -15c which will recover to -10c late sun. Temperatures will 
remain several degrees below normal with maxes ranging from lower 
30s higher terrain to upper 30s coastal plain. Developing warm air advection 
pattern will result in increasing middle/high clouds during Sun 
afternoon from west to east. 


Mostly cloudy and not as cold Sun night as SW flow develops well 
ahead of next system moving into the Great Lakes. 


Model suite in agreement with strong middle level low diving into the 
Great Lakes Monday then reaching new eng vicinity Tuesday. Primary low will move 
into the lakes region Monday but strong height fall center moving over 
existing baroclininc zone along the coast will likely result in 
development of coastal low near NE coast Monday night moving into new 
eng on Tuesday. 


Weak isentropic lift ahead of primary low may bring a few showers to 
west zones late Monday...but think bulk of precipitation will hold off until Monday 
night. Temperatures Monday should moderate into the 40s. 


Best chance of precipitation will be Monday night into early Tuesday and we will 
have likely probability of precipitation. Based on warming low level thicknesses and wet 
bulb temperatures...ptype should be mainly rain but some snow possible 
higher elevations in Berkshires and Monadnocks closer to deeper cold 
air. Southerly low level jet ahead of low may focus heavier precipitation late Monday 
night across eastern new eng or just offshore with lighter precipitation 
further west. Any snow accumulate should be light unless coastal storm 
ends up further east. Latest guidance suggests inland low track. 


Surface low expected to lift to the north on Tuesday with focus for precipitation 
also shifting north. But upper low over new negative will result in scattered 
rain/snow showers Tuesday afternoon with any snow mainly confined to 
higher elevations. Temperatures may briefly surge to 50 degrees in the 
coastal plain Tuesday morning before cooling...otherwise maxes will be 
in the uper 30s to lower 40s in the interior. 


Upper trough forecast to remain across the NE Wednesday/Thursday although GFS 
keeps upper low much further south across new eng which will result 
in a greater probability of diurnal rain/snow showers. European model (ecmwf) further north 
and drier. For now...we have slight chance probability of precipitation in the grids but no 
mention of probability of precipitation in the forecast text. Temperatures cooling to below normal 
Wed/Thu. 


&& 


Aviation /08z Friday through Tuesday/... 
today through tonight...VFR conditions expected...although a period 
of MVFR conds possible cape and islands tonight. 


Saturday...VFR for most along with northwesterly wind gusts around 30 knots. 
MVFR ceilings/visibilities possible on Cape Cod in ocean effect snow showers 
that could potentially graze the area. 


Outlook...Saturday night through Tuesday... 


Sat night and sun...VFR with gusts to 30 kts possible Sat evening. 


Monday...mainly VFR during the day...but lowering to MVFR/IFR in 
developing rain/snow Monday night. 


Tuesday...MVFR/IFR possible with gradual improving conditions in the 
afternoon. 


&& 


Marine... 
low pressure will develop well south of Nantucket by late 
today...then quickly move to Nova Scotia by late tonight. The 
gradient over the local waters will begin to tighten later 
today...and likely result Small Craft Advisory gusts on the south coastal waters by 
late this afternoon. Winds will only increase through Saturday. 
Hoisted a gale watch for all waters starting 12z Saturday as strong 
cold air advection and tight pressure gradient potentially allows for widespread 35 
knots gusts. 


Outlook...Saturday night through Tuesday... 


Sat night...gale force northwest winds expected Sat evening then winds will 
slowly diminish overnight. 


Sun...high pressure slides south of New England but westerly gradient 
will result in Small Craft Advisory winds. 


Monday...SW winds ahead of low pressure moving into the lakes with gusts to 
25 knots possible. 


Low level jet ahead of low pressure may bring a brief period of S to southeast gales to 
eastern waters late Monday night or Tuesday morning...otherwise winds 
becoming west with gusts 25-30 knots as low pressure moves to the north. 


&& 


Box watches/warnings/advisories... 
CT...none. 
Massachusetts...none. 
New Hampshire...none. 
Rhode Island...none. 
Marine...gale watch from Saturday morning through Saturday evening for 
anz230>237-250-254-255. 
Small Craft Advisory from 1 PM this afternoon to 7 am EST 
Saturday for anz232>235-237-254-255. 
Small Craft Advisory from 7 PM this evening to 7 am EST 
Saturday for anz230-231-236-250. 


&& 


$$ 
Synopsis...kjc/ekster 
near term...ekster 
short term...ekster 
long term...kjc 
aviation...kjc/ekster 
marine...kjc/ekster 

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