Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/01/18
Area Forecast Discussion
National Weather Service Taunton MA
1032 PM EST Wed Jan 31 2018
.SYNOPSIS...
A weak warm front may bring some light snow accumulations north
of the Massachusetts turnpike late tonight into Thursday
morning. A cold front then may bring a period of mixed precipitation
changing to snow Thursday night into Friday morning with some
light accumulations possible. A brief shot of arctic air Friday
night into Saturday with wind chills dropping to between zero
and 10 below zero. A storm system will likely bring rain and/or
snow to the region Sunday into Monday morning...but
precipitation types and amounts are highly uncertain. Another
storm system may bring more rain and/or snow to the region
sometime Wednesday into Thursday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Abundant low level dry air still in place, but it was slowly
eroding. Latest few runs of the HRRR appear to have a good
handle on the timing, so used it as the basis for updating the
timing of this forecast. Thinking the best window for any
accumulating snow will be between 2 AM and 6 AM. Not as
confident in the southern extent of snowfall, especially south
of the Mass Pike.
Minor tweaks to temperatures and dew points to reflect observed
trends.
645 pm update...
Mid level cloudiness continues to overspread the region. Temps
were mainly in the 20s early this evening and will generally
remain steady or slowly rise overnight...especially near the
south coast as southerly flow develops. Still looks like main
threat for snow will be along the east slopes of the Berks and
north of MA Turnpike...mainly after midnight and into Thursday
morning where some locations may receive an inch or two of snow.
Greatest risk will be across east slopes of Berks/northern
Worcester Hills and perhaps into Essex county. This may impact
the am rush hour given cold ground temperatures and previous
forecast handles this well.
Previous Discussion...
* Accumulating snowfall north of the Mass Pike for the Thursday
morning commute *
Zonal flow aloft with southwest flow in the mid-levels. This
southwest flow will yield to some warm advection across the region
and increase the moisture aloft. Cold surface temperatures/cold dome
over the region in combination of the WAA and isentropic lift will
result in snow showers for the area tonight. Light snow showers
will start after 03z but the area and intensity will increase
after 06-09z as LLJ begins to strengthen. NAM and GFS model
soundings also indicate some lift within the snowgrowth region
around 6-8 units of omega. Again, while not a lot, just enough to
produce snowfall for the northern half of the region. Locations
south of the Pike and east of I-84 will probably see just a flurry
or two. Still a lot of dry air in place for much of the overnight
and mid-morning hours.
While this won`t be a significant event, the timing of snowfall
appears to fall during the Thursday morning commute. Because of
the cold surface temperatures, snowfall will quickly stick to
area roadways, especially if untreated. Current thinking is
half of an inch or less for locations around the Mass Pike and
I-84. For 1-2 inch amounts, highest confidence will be across
Route 2 and areas north. The east slope of the Berks and the
west side of the Worcester Hills could also see 1-2 inches. This
is due the southwesterly flow resulting in some upslope along
the Worcester Hills.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
Thursday afternoon into Friday
Warm front to the north with cold front approaching from the west
for this time period. Mid and upper flow amplifies slightly
with a broad trough over much of the northern CONUS. Weak isentropic
still during the day which could erode the near-surface dry layer
(south of the Pike) and result in some scattered showers. P-type
should mainly be rain as the boundary layer warms through much
of the day. With continued warm air advection, high temperatures
are expected to be several degrees above normal in the upper
30s to mid 40s.
Upper level disturbance moving through the trough will push an
Arctic front from the west towards southern New England late
tonight into Friday. Any ongoing precip Thursday evening may
transition back to snow as thermals begin to fall below
freezing. Main focus for this time-frame is a little anafrontal
wave which will move into the region around Friday morning.
Models still show a good spread on when this could potential
occur. The EC is fastest keeping the bulk of the heaviest precip
confined to the immediate south coast, where as the NAM is the
slowest resulting in more precip and thus snowfall for a good
portions of the area. GFS is down the middle with Hi-res also
on the faster side. These waves are quiet tricky as it is all
about the timing of the wave and location of the front. Will
continue to blend the guidance resulting in 0.5 to 2 inches of
snowfall especially across the southeastern half of the region.
Unfortunately this will also occur during the Friday morning
commute, so a few slick spots are possible.
The rest of Friday appears blustery and frigid behind the front as
850 mb temps fall below -20C. Temps at the surface may remain steady
or fall during the day, as heating will be limited. Westerly winds
will increase to 25-30 MPH resulting in wind chill values in
the single digits.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Highlights...
* Dry but a brief shot of arctic air Fri night into Sat
* Storm expected Sun into Mon am but ptype highly uncertain
* Another storm system possible Wed and/or Thu
Details...
Friday night and Saturday....
A brief shot of arctic air Friday night into Saturday as 850T drop
below -20C. Low temps Friday night should drop mainly into the
single digits to lower teens along with gusty northwest winds.
Wind chill values should be on the order of zero to ten below zero.
High temps on Saturday will be held in the 20s.
Sunday into Monday morning..
Interesting and another difficult forecast Sunday into Monday
morning. Models indicate an initial wave of low pressure lifting
towards the Great Lakes on Sunday. This results in a burst of warm
air advection aloft and at the surface. Ptype would probably be
initially snow for much of the region...but might be a quick change
to rain on the coastal plain depending on strength of warm air
advection. Antecedent airmass is pretty cold...so will have to
factor that in as well.
Attention will then turn towards developing low pressure off the mid
Atlantic coast. While current track is uncertain most of the data
suggests something near the far southeast New England coast to
around the Benchmark. One would think this would be favorable track
for heavy snow given time of year/climatology. However...the initial
low that tracks towards the Great Lakes appears to warm the mid
levels considerably making it tough for a significant snow event
along the coastal plain given GFS/ECMWF solutions. This is
especially true with the lack of high pressure to our north. With
that said...The GGEM indicates a colder/snowier solution Sun into
Mon am as it is weaker with that initial low headed towards the
Great Lakes. This limits the mid level warm advection ahead of the
developing coastal storm.
In a nutshell...it is too early to rule anything out but greatest
risk for significant snowfall appears to be across the interior. A
snowier scenario would feature a weaker initial low tracking to our
west with a stronger coastal storm. A mainly rain solution would
feature the opposite.
Monday night and Tuesday...
Quieter weather follows Monday night into Tuesday, although can not
rule out a few rain/snow showers Tuesday but does not look like a
big deal at this point.
Wednesday into Thursday...
Low confidence in this time range...but guidance indicates the
potential for another storm. Ptype/timing highly uncertain given the
time range.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Friday/...High confidence.
Before midnight...
VFR with southwesterly flow.
Midnight til Thursday...VFR with occasional MVFR across the
higher terrain and north of the Pike. SHSN increasing after 06z
which could result in lower vsbys and accumulating snowfall.
Highest confidence is across terminals near route 2 and points
north. Snow accum around 1-2 inches possible.
Thursday 18z til Friday...
Mixture of MVFR/VFR late in the day falling to MVFR during the
overnight. A few spotty showers are possible but more widespread
precip could move in after midnight. IFR conditions are possible
towards the Friday morning push as any rain transition to snow
resulting in an inch or two snowfall.
Conditions improve to VFR by Friday afternoon. Blustery
westerly winds towards the evening with gusts near 25-30 knots
possible.
KBOS Terminal...High confidence in TAF. Low confidence in light snow
risk during the morning push...but odds favor bulk of it staying north
of the terminal.
KBDL Terminal...High confidence in TAF. Low confidence in light snow
risk during the morning push...but odds favor bulk of it staying north
of the terminal.
Outlook /Friday Night through Monday/...
Friday Night: VFR. Windy with gusts to 35 kt.
Saturday: VFR. Windy with local gusts to 30 kt.
Saturday Night: Mainly VFR, with local MVFR/IFR possible late.
Breezy. Chance SHSN.
Sunday: Mainly MVFR, with areas IFR possible. Breezy. RA
and SN likely.
Sunday Night: Mainly IFR, with local MVFR possible. Breezy. SN and RA
likely.
Monday: MVFR/IFR conditions possible. Windy with local gusts to
30 kt. Chance RA, chance SN, FZRA likely.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Friday/...High confidence.
Tonight into tomorrow...
S-SW winds increase overnight, reaching at least 30 kt across
the waters, although a few gusts could approach Gales, most
winds should remain below criteria. Therefore, will continue
small crafts, rather than gales at this time, but this will have
to be watched. Even though winds may diminish somewhat during
the day on Thu, seas will continue above 5 ft, so will maintain
the advisories through Thu.
Outlook /Friday Night through Monday/...
Friday Night: Moderate risk for gale force winds with gusts up
to 35 kt. Rough seas up to 10 ft. Freezing spray.
Saturday: High risk for Small Craft Advisory winds with gusts
up to 30 kt. Seas up to 5 ft.
Saturday Night: Risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas up to 5 ft. Slight chance of snow showers.
Local visibility 1 to 3 nm.
Sunday: Winds less than 25 kt. Local rough seas. Rain likely.
Local visibility 1 to 3 nm.
Sunday Night: Risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas. Rain.
Monday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Rough seas up to 13 ft. Rain likely.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 10 PM EST Thursday for ANZ231-232.
Small Craft Advisory until 7 PM EST Thursday for ANZ233-234-
236.
Small Craft Advisory until 7 AM EST Thursday for ANZ230.
Small Craft Advisory until 2 PM EST Friday for ANZ235-237-256.
Gale Warning until 7 AM EST Thursday for ANZ250.
Small Craft Advisory until 10 AM EST Thursday for ANZ251.
Small Craft Advisory until 4 AM EST Friday for ANZ254-255.
&&
$$
SYNOPSIS...Frank/Dunten
NEAR TERM...Belk/Frank/Dunten
SHORT TERM...Dunten
LONG TERM...Frank
AVIATION...Frank/Dunten
MARINE...Frank/Dunten
Area Forecast Discussion
National Weather Service Burlington VT
649 PM EST Wed Jan 31 2018
.SYNOPSIS...
A changeable weather pattern is in store for the remainder of
the week and into the weekend and early next week. An area of
low pressure will affect the region overnight into Thursday.
Expect some snow that will mix with light rain on Thursday as
southerly winds bring in warmer air. A cold front will bring
another round of cold weather to end the week. Another front is
expected to move through late Saturday with additional snow,
while yet another low pressure area on Monday gives us another
chance of snow.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 637 PM EST Wednesday...Massaged pops a bit through the
late evening hours to account for current radar/observational
trends as surface warm front lifts through the area. Most of the
snow has been on the light side (visibilities 1-5sm) and leaned
toward a blend of the latest BTV 4km WRF and HRRR output to
govern coverage during this time frame. There were no
adjustments to our minor snowfall forecast showing totals
generally less than in inch in most locations this evening.
Prior discussion...
Interesting developments on the radar the last few hours with
the development of a narrow band of moderate to heavy snow that
has developed in association with a burst of warm air advection
aloft. Looks like it will be moving across a good chunk of the
region by early evening, and could cause the evening commute to
be a little slower than normal. It won`t last too long, so
accumulations should remain under 1" for the most part. HRRR
also suggests the southern portion will be weakening as it moves
through.
For the rest of the overnight, it`s been a bit of a challenging
forecast. After this initial burst of snow, there really isn`t
much behind that. Radar mosaics show that, as do the hi-res
models. Did use a blend of the hi-res models for the PoPs, and
in general have most of the region with <25% chance of
precipitation by midnight. There`s really no strong forcing
overnight and the moisture depth decreases. So it`s not out of
the question we`ll just see some snizzle (very light snow with
very small flakes). Perhaps a touch of drizzle? If that happens,
we could have a few slick spots since temperatures will be below
freezing.
Temperatures however will be rising all night, so by daybreak
we`ll probably be pushing 30F or warmer from the Champlain
Valley westward. Southerly winds will also get a bit gusty in
the Champlain Valley as well (20-30 mph gusts).
On Thursday, the precipitation should re-develop, especially for
the southern half of the region thanks to frontogenesis across
that region. Should be mostly light snow, but boundary layer
temperatures at lower elevations should be warm enough for a
little mix of rain at times. Despite the relatively high chances
for precipitation, there won`t be a lot of moisture falling from
the sky. Snowfall accumulations will generally be no more than
1" for the lucky people. Have highs into the mid/upper 30s
across the Champlain Valley and much of northern NY, though some
guidance indicates highs into the lower 40s for some places.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 355 PM EST Wednesday...some interesting weather changes
during the period. First off will be the passage of an arctic
front Thursday evening into the early overnight hours. Some
differences in timing amongst all the models, but best guess is
that the front will come through the St Lawrence Valley about
00z Friday (7pm Thursday), reaching the Champlain Valley about
03-05z (10pm-midnight) and then into eastern Vermont by 09z
(4am). The snow squall index parameter does show some
respectable positive values Thursday evening, indicative of the
potential for snow squalls. There will also be a little bit of
surface based instability across the St Lawrence Valley. The BTV
4km WRF model does show a couple of linear features resembling
snow squalls in the radar reflectivity forecast output. On the
negative side, the timing with the lack of daytime heating is
not the best for maximizing the intensity of any snow squalls
(just like summer thunderstorms). At this point thinking it`s a
good bet that we`ll have some snow showers rolling through
during the evening in association with the strong cold front,
but not enough confidence to blanket a large area with a chance
of heavier squalls. Still uncertain if we`ll have the situation
to actually issue our first "Snow Squall Warning" product. Later
shifts will fine tune that aspect.
After the front, temperatures crash. 925mb temperatures by
Friday will be down to -20C near the Canadian border to -14C in
the south by mid afternoon. Thus surface temperatures are not
expected to move much during the day, and may actually slowly
fall. Plan for highs only in the teens. Still a fairly tight
pressure gradient, and good low level mixing, so we`ll have
breezy northwest winds gusting over 20 mph quite often. That
will produce wind chills much of the day in the -5 to -15F
range. Still a good amount of low level moisture around, so I`d
expect the mountains will squeeze out some light snows. Speaking
of the mountains, air temperatures at the higher elevations will
only be in single digits, with winds producing wind chills well
below zero (-20s to -30s, and pushing -45F at the highest
summits).
Friday night is looking cold, but we`ve seen much worse earlier
this winter. Lows should range between +3 to -8F. Some wind
will continue for much of the night, so wind chills will bottom
out between -10F to -25F. We may end up having some wind chill
advisory issuance requirements.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 232 PM EST Wednesday...Should see a cold start to the
weekend with 850mb temps of -22C to -25C in place across the
North Country and sfc ridge axis cresting across the region
during Saturday morning. Generally looking at high temperatures
of 15 to 20F Saturday afternoon with light westerly winds in
place. It appears a weak frontal system developing across the
Great Lakes will bring increasing clouds to the region later
Saturday into Saturday night from SW-NE. Should see some
developing light snow within the frontal zone, especially across
nrn NY where we`ve increased PoPs to around 60% for Saturday
night, and 40-50% across VT. Based on present indications, may
see light snow accumulations of 1-2" Sat night, with locally up
to 3" possible across nrn NY. The increasing clouds and light
S-SW winds developing Saturday night will keep temperatures a
bit warmer, with lows mainly in the low-mid teens.
Next potential coastal low pressure system we are monitoring
arrives Sunday night into Monday. Appears the 12Z GFS has
shifted a bit further north and west with the sfc low tracking
across Cape Cod/sern MA during Monday morning. The sfc low is
also a bit deeper at 990mb or so. On the other hand, the 12Z
ECMWF has shown little change with prior runs with 999mb sfc low
tracking just south and east of the 40N 70W benchmark at 12Z
Monday. Both operational runs indicate the system would be
rather quick moving, consistent with the open nature of the
associated 700-500mb shortwave trough. Appears best potential
for accumulating snow would be across central and eastern VT
Sunday night into Monday morning. The GFS solution would bring
potential moderate snowfall (4-8") across central/ern sections
of VT, and we`ll need to continue to monitor this potl. At this
point, have raised PoPs, to 60-70% across central/ern VT and
45-60% elsewhere (lowest in the St. Lawrence Valley). Highs on
Monday should be in the mid 20s.
Should see continued seasonably cold temperatures into Tue/Wed
of next week, with highs generally in the low-mid 20s. The 12Z
GFS suggests another potential shortwave trough and sfc low near
sern New England by Wednesday, but fast nature of the mid-level
flow pattern suggests timing of any features out at day 7 will
be of relatively low skill at this point.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Through 00Z Friday...Some light snow is moving through the area
this evening as a warm front pushes in. Ceilings are generally
low VFR, temporarily becoming MVFR/IFR as bands of snow move
through. Current radar shows two fairly focused bands of light
snow- one falling apart as it moves eastward over the Green
Mountains and a smaller band to the west over MSS/SLK pushing
east. Will see another hour or so of MVFR conditions over
MSS/SLK while the western band pushes through, elsewhere expect
just some flurries and lingering low VFR clouds through the
night. Gusty southwesterly winds will develop overnight/Thursday
morning at MSS/SLK, while BTV/PBG will continue to see southerly
winds channeled up through the Champlain Valley.
Outlook...
Thursday Night: Mainly VFR, with local MVFR possible. Chance
SHSN.
Friday: VFR. Slight chance SHSN.
Friday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Saturday: VFR. Slight chance SHSN.
Saturday Night: MVFR/IFR conditions possible. Chance SHSN.
Sunday: Mainly MVFR, with areas IFR possible. Chance SHSN.
Sunday Night: Mainly IFR, with areas MVFR possible. Likely SN.
Monday: Mainly IFR, with areas MVFR possible. Chance SN, Chance
SHSN.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Nash
NEAR TERM...JMG/Nash
SHORT TERM...Nash
LONG TERM...Banacos
AVIATION...RSD
Area Forecast Discussion
National Weather Service Caribou ME
1036 PM EST Wed Jan 31 2018
.SYNOPSIS...
A warm front will cross the region overnight into Thursday. A
strong Arctic cold front will approach the region from the west
late Thursday night and cross the region on Friday.
&&
.NEAR TERM /THROUGH THURSDAY/...
1030 PM Update...
The radar loop showed things filling in w/most of the returns
being aloft. The high reflectivity across the swrn areas
indicative of some light snow moving into western Piscataquis
County. The activity is expected to push ne overnight as shown
by the latest Canadian GEM and RAP. The latest run of the HRRR
aligning closer to the obs and what the radar depicted. Pushed
back the timing of steadier snowfall til around midnight. Latest
indications given are that the snow will push through fairly
quickly due to the 925mb jet moving across the region. Precip
shield pushes to the coast and becomes aligned w/the upper flow
into midday Thursday. Stayed close to the daycrew`s assessment
of going with 1-2 inches of snowfall into early Thursday.
Temps look like they have leveled off and are now beginning to
rise. Daycrew did a fine job in showing this trend overnight.
Previous Discussion...
A weakening warm front that will morph into a warm occlusion
overnight. A weak shortwave associated with the front will move
quickly through the area later tonight. This impetus will be
sufficient to generate up to an inch of snow within a few hours.
The front pushes through northern zones by late tonight, but
the occlusion will tend to stall towards the coast into Thursday
morning as it becomes parallel to the flow and a weak
baroclinic zone emerges. This means up to 2-3 inches of total
snow for Bangor, southern Penobscot County and much of Hancock
County by midday Thursday. There`s still a lot of NWP
uncertainty as to the exactly where the front stalls and how
much precip falls, but would tend to favor a position closer to
the coast and the greater thermal gradients. Towards the coast,
strong warm advection will create some boundary layer P-type
issues during the morning and allow mixing with rain. This warm
air will be drawn northward Thursday afternoon. Temperatures
will reach the lower 40s on the coast and nearly 30F all the way
to the Saint John Valley. The remnants of the precipitation
shield will tend to lift back to the north by late morning with
the warm advection, but no further accumulations are
anticipated. One item to watch as this precip does move back to
the north will be freezing drizzle.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
Sfc low wl be to our north by the start of the short term with a
trailing cdfnt down acrs the international brdr. Expect that
sctd snow showers wl be ongoing on Fri evng ahd of boundary. By
Fri morning expect that cdfnt wl bisect CWA with temps falling
throughout the day. Maxes wl lkly be similar to ovrngt lows
Cannot rule out a snow squall along the bndry drg the mrng hrs
as fropa occurs. As the time gets closer and bcms more certain
wl be able to add in blowing snow to fcst.
NW flow conts thru the end of the short term with hipres
building off of the mid-Atlantic coast by 00z Sun. Coldest temps
look to be on Sat mrng with lows blo -10F and in the single
digits in Downeast. Winds wl still rmn high under strong
pressure gradient and wind chills are expected to drop blo -20F
north of Katahdin by midnight and into mid-morning Sat.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Hipres wl shift east offshore Sat night as cyclogenesis occurs
acrs the lwr MS Vly with overrunning pcpn dvlpng aft midnight
Sat night and contg thru Sun along wmfnt. All med range guidance
is in good agreement that lopres wl mv up the ern seaboard on
Mon tho differ slightly on location and timing. GFS ensemble
mean places coastal low just south of Penobscot Bay in the Gulf
of Maine which is about 300 miles northwest of operational GFS,
with latest EC and CMC sw of Cape Cod by 12z Mon. Either way it
appears that this wl be our next potential significant storm to
effect CWA.
NW flow mvs in its wake of system for Mon night with hipres
briefly building in Tue morning with another potential system
for mid-week.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
NEAR TERM: VFR conditions prevail until shortly before midnight.
At that point a burst of snow lasting several hours will create
IFR conditions at all terminals until later tonight. The snow
will move out of locations north of HUL...but may stall into
Thursday morning and continue to provide IFR vis at locations
such as BGR and BHB into late morning. By afternoon, all sites
will be varying between MVFR and VFR due to cigs.
SHORT TERM: MVFR/IFR expected into Fri morning at all terminals.
Will see improvement to VFR Fri evening in wake of frontal
passage, though expect brief IFR in blowing snow along cold
front. VFR expected through the day Saturday with conditions
lowering to MVFR/IFR late Sat night through the end of the
period.
&&
.MARINE...
NEAR TERM: Winds will pick up ahead of a frontal system tonight
with a few gusts reaching 35 kts, but did not feel that winds
would exceed that threshold consistently for any extended period
of time and continued with the SCA through Thursday.
SHORT TERM: SCA conditions expected with seas and winds expected
thru Fri with marginal gale force conditions Fri night. SCA
conditions expected to continue through the weekend.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory until 4 PM EST Thursday for ANZ050>052.
&&
$$
Near Term...Hewitt
Area Forecast Discussion
National Weather Service Gray ME
959 PM EST Wed Jan 31 2018
.SYNOPSIS...
A warm front will move in from the west tonight with some light
snow ahead of it continuing into Thursday. A cold front moves
through from the northwest Thursday night with a return to much
colder temperatures behind it through the end of the week.
Low pressure may affect the region Sunday into Monday with high
pressure building in thereafter.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
955 PM...Minor ESTF update to ingest the current mesonet into
near term grids.
Prev Disc...
720 PM...For this ESTF update I scaled back pops over the next
few hours as the initial surge of warm air advection snow has
largely dried up as it moved into the forecast area.
Temperatures were adjusted downward a bit...especially over
northern and eastern sections where thicker cloud cover has yet
to arrive and put a damper on radiational cooling. I adjusted
near term grids to reflect latest satellite and radar trends as
well as the current mesonet.
Prev Disc...
A short wave trough and attendant burst of WAA moving eastward
across Upstate NY as of this Wednesday afternoon will continue
moving eastward this evening. Regional radar mosaic shows
relatively narrow band of light to moderate snow from KART-KBGM
as of 1945z. This band will progress eastward and move into
portions of central and southern NH early on this evening, then
progress across the rest of our northern (and perhaps central)
zones through the evening hours. A little bit uncertain at this
time about how well the southern end of this band will hold
together, but could see an hour or two burst of snow this
evening across even portions of southwestern NH. Will keep an
eye on that. Either way, highest PoPs will be across the north.
An inch or two of snow may fall this evening across northern and
some central zones with this feature.
After midnight, jet dynamics increase a bit and mid level
frontogenesis strengthens - mainly from central NH eastward to
southern ME and then northeastward to the Midcoast. Again, we
are somewhat uncertain how strong the forcing for ascent will be
with this but it should be enough for light snow to break out in
these areas especially given the modest omega in a saturated
dendritic snow growth zone predicted by several deterministic
models. The best chance of accumulating snowfall will likely
remain north of the ASH/MHT (and possibly CON) but we are still
going with at least high chance to low likely PoPs there due to
the uncertainty in positioning of narrow zone of ample forcing.
Will be good to watch hourly trends in the HRRR as the evening
wears on. In any event it appears that the morning commute could
be a slippery one across mainly central NH eastward to southern
ME and the Mid coast.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Band of mainly light but accumulating snow should be ongoing at
the beginning of the period early Thursday morning across
central and southern zones with a relatively narrow band of
frontogenetical forcing. Therefore, as mentioned in the
paragraph above, the morning commute could be slippery in
these areas. This band should lift northward as the day
progresses with temperatures rising to above freezing across
southern zones as well as along the coast. A cold front
approaches from the west Thursday evening and crosses the region
during the night. Snow squalls may accompany this front -
especially across NH.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Overview: Looking ahead to the end of the week and the weekend
the overall pattern remains fairly constant through the start of
next week. Aloft, a broad trough remains over the eastern
portion of the CONUS with a high over low block in the Gulf of
Alaska. This is once again setting it up for the cold polar air
to funnel southward across the Canadian prairies and into our
area over the weekend. This airmass is slightly warmer than what
we saw at the beginning of January but will still bring a
return to below freezing temperatures.
As we move into the end of the weekend the long wave trough will set
up allowing for a storm track to move up the east coast drawing
good moisture out of the southeast US. The first waves drops
around this trough late Sunday initiating cyclogensis for
Monday along the eastern seaboard with additional waves bringing
more snow potential later in the week.
Friday:
A cold front will cross the area Friday morning ushering cold air
advection and gusty winds for the remainder of the day. A few snow
squalls are possible in the morning along the frontal boundary,
especially over southern New Hampshire.
By Friday night cold air is firmly in place as 500mb temperatures
fall to around -25C. Overnight low temperatures will be back below
zero in the north with single digits all the way to the coast. With
the strong pressure gradient in place expect winds to continue
through the overnight hours. While this will limit radiational
cooling and likely keep temperatures a bit warmer, the combination
of wind and cold temperatures will likely necessitate a wind chill
advisory across the northern portion of the area.
Saturday- Sunday: Saturday will be clear and cold as high pressure
crests over the region. That high pressure will shift east overnight
Saturday starting the return southwesterly flow and increasing
temperatures for Sunday.
Monday: Confidence is increasing for a coastal low to impact the
area on Monday. Ensemble members and deterministic guidance all
have cyclogensis occuring somewhere near Delmarva and moving
northeast up the coast through the day in a classic nor`easter
track. As with any coastal storm, the exact track will be
paramount to determining the precipitation type along the coast.
While some mixing is certainly possible, have leaned a bit
colder with the surface temperatures with this forecast package
keeping the rain/snow line just offshore as models tend to be
aggressive in bringing warm air inland.
Another wave moves in with additional snow possible Wednesday
into Thursday.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Short Term...VFR conditions early on this evening will
deteriorate to MVFR or lower at most terminals as the evening
progresses into the overnight hours as light snow develops.
These conditions should remain in place during the day on
Thursday for most areas - however MHT and CON may escape with
low-end VFR.
Long Term...Brief chance for snow squalls MHT and CON Friday
morning and the front moves into the region. Thereafter cold air
advection will bring gusty northwesterly winds with VFR
conditions. Winds will diminish late Friday night with VFR
returning through the weekend. A coastal low impacts the area on
Monday bringing widespread snow and IFR.
&&
.MARINE...
Short Term...Gales have been posted for a relatively short
period of time tonight (midnight to 7 am) for the ocean waters
as southerly flow with gusts around 35 kt occurs. These winds
should diminish early Thu morning but SCA conditions are still
likely.
Long Term...A cold front will cross the waters on Friday. Behind
the front cold air advection will lead to gust northwesterly
winds. A gale warning will likely be needed, but due to the
existing Gale headline for tonight no watch was issued at this
time. Winds will subside on Saturday as high pressure moves over
the waters for the weekend.
Onshore flow develops Monday night with increasing wind and
waves ahead of the next system.
&&
.TIDES/COASTAL FLOODING...
Will continue to monitor water levels through the remainder of
the week as astronomically high tides continue through Saturday.
Very light winds should preclude any issues tonight...but a
southerly component to the flow suggests at least a low risk for
minor flooding with both the Thursday and Friday morning high
tides.
Astronomical tides peak on Thursday (11.6 feet at 1120 am in
Portland Harbor).
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until noon EST Thursday for ANZ151-153.
Gale Warning until 7 AM EST Thursday for ANZ150-152-154.
&&
$$
ES
Area Forecast Discussion
National Weather Service Topeka KS
936 PM CST Wed Jan 31 2018
.UPDATE...
Issued at 936 PM CST Wed Jan 31 2018
The last couple runs of the RAP and the 00Z NAM show pretty good
cold air advection through the day tomorrow with mostly cloudy or
overcast skies at least through the morning. Looking at OBS
upstream and there is a much colder airmass across the Dakotas
poised to advect into the area. Because of this have lowered highs
for Thursday and only show a slight diurnal warmup in the
afternoon when clouds should thin. If mid clouds hold in through
the afternoon, this may be a little optimistic.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 335 PM CST Wed Jan 31 2018
As of 21Z Wednesday afternoon the stubborn northwest mid level
flow continues across the Plains states. Mid level Pacific
moisture continues to stream across central US, yielding scattered
mid and high level clouds. A surface cold front traversed the CWA
through the morning hours and now resides across far southeastern
KS. Little CAA behind the front has allowed temperatures to reach
the low 50s this afternoon.
Tonight - Tomorrow: Surface ridge axis will traverse the CWA
overnight, ushering in the initial push Canadian air. Low
temperatures will reach mid 20s to near 30. Northerly winds will
increase behind the surface ridge to 10-15kts with gusts upwards
of 20-25kts. The continued CAA will only allow high temperatures
to reach the upper 20s to mid 30s Thursday afternoon.
.LONG TERM...(Thursday night through Wednesday)
Issued at 335 PM CST Wed Jan 31 2018
Transitioning into the extended period, the pesky northwest mid
level flow will remain across the central Plains. The
aforementioned surface ridge axis will position overhead Thursday
night/Friday morning, allowing temperatures to bottom out in the
low teens. Surface high pressure will move into the mid-
Mississippi valley Friday allowing southerly surface flow to
return to the central Plains. Continued southerly flow will allow
high temperatures to reach the 40s and 50s Saturday afternoon! A
mid level shortwave trough and associated surface trough are
progged to traverse the central and northern Plains Saturday
night/Sunday. EC/GFS/Canadian solutions all bring a few hundredths
of QPF to the entire CWA, which would fall as all snow. The active
northwest flow looks to continue into next week with a secondary
shortwave trough traversing the area Monday night/Tuesday. Great
uncertainty exists amongst guidance regarding QPF amounts,
although any precipitation would fall as all snow. Otherwise,
temperatures look to remain in the 30s for Tuesday and Wednesday
of next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday)
Issued at 502 PM CST Wed Jan 31 2018
Models are trying to develop some light QPF across central KS with
the FROPA Thursday morning. However forecast soundings do not
really moisten up. So even flurries appear improbable. Still
would anticipate VFR conditions prevailing even if there is some
light precip.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Wolters
SHORT TERM...Baerg
LONG TERM...Baerg
AVIATION...Wolters