A weak disturbance approaches from Canada today. After a dry
start to the day, a period of clouds and scattered light showers
will develop late morning and afternoon, then dissipate early
tonight. Midwest high pressure then brings drier weather to
Southern New England tonight. Clouds return on Tuesday. Not a
washout but a chance of scattered showers and thunderstorms
midweek followed by drier but warm weather Thursday, this
occurring behind a departing weak cold front. Scattered showers
and thunderstorms may return Fri and Sat ahead of the next cold
front. Dry, less humid and cooler weather likely follows Sunday
behind the departing front.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Shortwave trough sweeps across New England today, bringing with
it a cold pool aloft that destabilizes the airmass. (500-mb
temperatures will be -25C to -28C. Model cross-sections
continue to show a layer of moist air between 850-mb and 700-mb.
PW values through the layer will be 0.6 inches or less...mostly
less. So not a lot of moisture. But daytime solar heating near
the ground and cold advection aloft will combine to bring lift
to the airmass, and this may convert some of that moisture over
to scattered showers.
The mixed layer will be deep again, like yesterday, reaching
near 775 mb. Temps at that level will be equiv to 2-5C at 850
mb, supporting max temps in the 60s...a few upper 50s possible.
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
340 AM update ...
Highlights...
* Late Wed aftn/eve - not a washout but possible Showers/T-storm
* Thursday - could be the pick of the week, warm but dry
* Fri/Sat - not a washout but possible showers/T-storms
* Sunday - Dry, less humid & cooler weather likely
Synoptic Overview ... fast/progressive northern stream will result
in some weather impacts/changes every 1-2 days and given fast upper
air pattern low predictability on precise timing of fronts and
associated timing of rain/thunder chances. Also given NW flow aloft
lots of uncertainty on eastward propagation of upstream convection
and associated warm sector into SNE. Given this will lean heavily on
ensembles and less on deterministic guidance. Upper air pattern then
becomes more amplified this weekend leading to increased forecast
confidence.
Tue night ... deamplifying short wave and weak associated surface
low in the NW flow aloft yields lots of clouds for SNE but likely
not much if any shower activity given dry air over SNE. Clouds and
SW winds will result in seasonable temperatures with lows in the
50s.
Wed/Wed night ... should be a period of dry weather the first half
of the day behind departing short wave from Tue night. However
fast/progressive flow aloft has next northern stream short wave
approaching SNE late in the day. Model consensus suggest NW flow
precludes warm sector from advecting into our region. Thus chance of
scattered showers and elevated convection. PWATs climb to 1.5 to 2"
depending on model guidance. Therefore brief heavy downpours
possible. Given NW flow aloft some uncertainty how far east elevated
convection and heavy rain potential will track. True warm sector
airmass appears to remain to our southwest, this will limit highs to
75-80 and dew pts 55-60.
Thursday ... should be the pick of the week with dry post frontal
airmass overspreading the region. Warm with +13C at 850 mb but model
soundings indicating mixing to 800 mb along with downsloping west
winds up to 25 mph. Given these parameters sided with the warmer
guidance with highs 80-85, few upper 80s possible. Westerly winds
will dry out the blyr keeping dew pts in the 50s and humidity levels
tolerable.
Friday ... northern stream short wave and associated cold front
approach the region from the west. Southern stream moisture may be
pulled/captured northward into SNE increasing deep layer moisture
and chances of convection. 850 mb temps climbing to about +15C so
with partial sunshine 80-85 should be attainable. Not as comfortable
as Thu as dew pts climb toward 60.
Next Weekend ... chance of scattered showers and T-storms Sat
depending on exact departure time of the cold front. Should be post
frontal by Sunday with drier, cooler and less humid weather.
