Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 221105
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
605 AM EST Wed Feb 22 2017

.SYNOPSIS...
A weak cold front over New England dissipates early this
morning. Unseasonably mild temperatures will remain across
southern New England through the end of the week as weak low
pressure systems pass west of the region. A strong cold front
will cross the region Saturday afternoon and evening bringing
showers. Near seasonable temperatures will return early next
week, with blustery conditions on Sunday and Monday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

600 AM Update...

Weak showers/sprinkles across southeast MA will continue to push
offshore resulting in a dry forecast for today. Biggest question
is the amount of sunshine the region may see. The more sunshine,
the better potential for temps to be a few degrees above current
forecast and vice versa. Only other change is the potential for
onshore flow during the afternoon hours across eastern MA. This
could keep temps a degree lower or two. Aside from a few minor
changes, the bulk of the forecast remains on track.

Previous Discussion...

Moisture lingers below 850 mb through the day. But deeper dry
air layer works in above that level. This should be enough to
generate partial clearing by the afternoon.

Southwest flow surface and aloft will bring a warming trend.
Mixing to 950 mb supports max sfc temps in the 50s. Mixing to
925 mb would support max temps around 60. Limited sun and warm
advection just off the deck would favor the shallower mixed
layer. The forecast for today will aim for the 50s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Tonight...

Dry weather with continued southwest flow. Guidance shows no
rising trend on dew points, but it does show developing fog and
low clouds. This seems a little contradictory, but may allow for
patches of fog especially on the South Coast and the interior.
Min temps will be near dew point, roughly 34 to 40.

Thursday...

High pressure remains offshore with southwest flow across
Southern New England. Shortwave moving through the Great Lakes
drives low pressure into Ontario and Quebec. Forcing with this
feature is primarily in Canada as well as adjacent parts of NY
and VT/NH. Will favor a dry forecast for Southern New England
during Thursday.

Southwest jet associated with this system brings 20-25 knot
low level winds to our area Thursday afternoon. Could be a few
gusts in this range during the afternoon especially across RI
and Eastern MA.
Thursday...High confidence. S-SW winds in place, gusting up to
around 20 kt during the afternoon. Gusts up to 25 kt and seas
building to around 5 ft on the outer waters Thu night. May see
patchy drizzle and fog develop Thu night along the S coast with
reduced visibilities.
Mixing depth will continue limited due to the differential warm
advection. But temps within the layer will have climbed a few
degrees, with values equiv to 850 temps of 1-3C which would
support max sfc temps of 59-63F. Noting the record high temps
listed in the Climate section, this would suggest values at or
near record high at PVD and ORH, while BOS and BDL records are
well above this.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Highlights...

* Temperature spread possible due to backdoor cold front on Friday
* Mild with widespread showers likely Sat into Sat night
* Blustery and cooler Sun/Mon
* More active pattern for next week

Pattern Overview...

00z guidance is in general agreement synoptically, still have some
mesoscale features to resolve. Ensemble guidance continues to
indicate mean ridging over the region on Friday as upper level
trough pushes across the Plains. This shortwave will become more
diffuse and stretched as it approaches the Northeast due to building
ridge. A cold front will sweep through the region late Saturday as
upper level trough moves through. Ensembles this indicate a more
zonal pattern beginning next week as a few shortwaves move through
the flow. Next system to watch is Wednesday/Thursday timeframe but
model sensitivity to this system is high.

Overall high confidence in above average temperatures Friday and
Saturday with more seasonable by Sunday. Also increasing confidence
in precipitation falling on Saturday/Saturday night. Lower
confidence on precipitation chances Friday into Sat morning and
again for middle of next week.

Details...

Friday...

Again a good check of Friday appears to be dry, but low level
moisture trapped within an inversion could result in a drizzle
potential for the area. Highest confidence is across the south
coast.

Guidance continues to show a back door cold front moving through
early Friday morning which could limit high temperatures. Still some
uncertainty on how far southward this front will sag. Highest
confidence in across Northeast MA. Believe the region could see a
large temperatures spread with 60s in southern CT and mid 40s in NE
MA. Bust potential is possible with this forecast and anticipate
a better handle with hi-res guidance.

A warm front will push through the region late Friday keeping
temperatures overnight well above average. Could see a few showers
associated with this warm front.

Saturday...

Potent shortwave will move through the flow and approach southern
New England on Saturday. This wave will drag a cold front across the
region ending the chances for above average temperatures.

Ahead of the front, anomalous southerly flow with LLJ increasing to
35-45 kts as 925 mb temps warm to 12C. This will result in above
average temperatures for the region as well as gusty winds. PWAT
values also increase near 2 STD above normal as southern stream
moisture is fed into the system. Along the front, a secondary low
will develop but the 22.00z guidance develops it just far enough
offshore to keep southern New England out of the heavy qpf. This
appears to be inconjunction with the GEFS as well as the EC
Ensembles which has just a 20 percent prob of qpf over 0.5 inch.
This is quite different then 24 hours ago. Will need to continue to
watch this secondary low and see where it will eventually develop
during this system.

Otherwise appears that the bulk of the precip will be across upstate
NY and VT including the east slope of the Berks. This area is where
the better dynamics will be as well as enhancement due to upslope.
May need to watch river levels after this system because of the
heavy rainfall potential and snow melt up north. Right now ensembles
are pointing towards a few sites near action stage.

Low confidence on thunder potential as EC ensemble mean indicates
some instability.

FROPA will be quick as temperatures plummet behind the front. Could
see some wet flakes on the backside depending on how much moisture
is left as front moves through.

Sunday into Tuesday...

Chilly and blustery NW flow will take over the region by Sunday into
Monday. Temperatures difference between Saturday and Sunday could be
close to 20F. Wind gusts could also increase close to 30 MPH as the
region mixes well above 850mb.

A weak wave appears to move through the flow on Tuesday which could
result in some rain/snow showers for the region.  Low confidence on
timing, but it is moving quickly and bringing in another round of
cold air.

Wednesday and beyond...

Large spread in the guidance for this period as the GFS is more
progressive versus the more amplifies EC. Right now a quick warm up
is possible on Wednesday as mean level ridge begins to take hold.
Another low pressure system will develop dragging a cold front
through the region. Low confidence on when this will occur, either
Wed or Thursday. This timing will impact temperatures, dewpoints
etc.

&&

.AVIATION /11Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Short Term /through Thursday/...

Today...High confidence.

Generally VFR. Patchy MVFR cigs possible this morning. There is
the potential for sea breeze development for eastern terminals.


Tonight...Moderate confidence.

VFR through midnight. Areas of MVFR/IFR cigs and vsbys develop
with patchy fog.

Thursday...Moderate confidence.

Lingering MVFR/IFR cigs and vsbys in the morning, but trending
to VFR by late morning and through the afternoon.

KBOS TAF...High confidence in TAF. Moderate probability in weak
sea breeze after 19z.

KBDL TAF...High confidence in TAF.

Outlook /Thursday Night through Sunday/...

Friday...Low confidence. A mix of MVFR/VFR is possible across the
region depending on low cloud development as well as position of
back door cold front. This front will also dictate surface wind
direction.

Saturday...Moderate confidence. Potential for widespread MVFR/IFR
conditions with rain overspreading the region.

Sunday...Moderate confidence. Improving conditions with blustery NW
wind gusts near 30 kts.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Short Term /through Thursday/...High confidence.

Persistent SW flow through the period. Wind speeds today and
tonight remain light. Speeds Thursday increase as winds
strengthen aloft. This may be enough to bring gusts 20-25 kt
Thursday. Seas remain light today and tonight, but may approach
5 feet on the outer waters Thursday afternoon/evening.

Outlook /Thursday Night through Sunday/...

Friday...Low confidence. Southerly flow will switch to a more
northeast to east flow during the day. Vsbys restriction possible in
fog and drizzle especially across the southern waters.

Saturday...Moderate confidence. Increasing southerly flow with the
potential for SCA gusts. Waves will also increase in response. Vsbys
reduced in developing rain and fog.

Sunday...High confidence. Northwest winds will keep seas up and
increase wind gusts near 30 kts. Low probability for gales across
the outer waters.

&&

.CLIMATE...
Record Highs for Thu Feb 23

BOS...65/1990
BDL...68/1990
PVD...60/1990
ORH...61/1990

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...WTB/Dunten
NEAR TERM...WTB/Dunten
SHORT TERM...WTB
LONG TERM...Dunten
AVIATION...WTB/Dunten
MARINE...WTB/Dunten
CLIMATE...


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