Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/26/17
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
320 PM AKST Sat Nov 25 2017
.SHORT TERM...Tonight through Monday...According to water vapor
satellite imagery, a weakening upper level trough extends over the
eastern gulf, and a deepening ridge extends over the western gulf,
with a strengthening shortwave digging east through the Aleutian
Islands. A strong jet can also be seen wrapping around the trough
over the eastern gulf, advecting moisture aloft from south of the
Haida Gwaii area. In addition, weak surface lows can be seen
rotating around each other in the associated upper level low, and
a strong high remains over British Columbia and extends into the
Yukon Territories. Due to this synoptic setup, outflow winds will
persist throughout most of the northern inner channels. We
upgraded Lynn Canal to Storm Warning this afternoon, as current
observations indicated as such. We expect the winds to remain this
strong through this evening and diminish through tonight. We also
have some lingering showers being reported across the panhandle.
This is due to the TROWAL associated with one of the lingering
surface lows lifting north that is supported by divergence aloft
from the left exit region of the jet that was mentioned
The main story for tonight and continuing into tomorrow is the
winds, as precipitation should be drying out through most
locations tonight. A shortwave will swing northeast into the
southern panhandle beginning tonight and lift northeast into
British Columbia tomorrow. This feature will help to tighten the
pressure gradient between the high that`s already over Canada.
We`ve been monitoring high resolution model guidance, in addition
to current observations, for our wind analysis. These models have
been struggling with wind values through the inner channels, so
most of the local effects for wind throughout the inside waters
have been added manually. The Storm Warning will remain for Lynn
Canal through early this evening, but expect winds to diminish
overnight. High res models and mountain wave guidance also hinted
at a strong wind event for the downtown Juneau and Douglas area.
Forecast soundings for Juneau, mainly the GFS, also indicated
possible favorable conditions, so we opted to follow HRRR guidance
for timing and strength of the wind downtown; we`re expecting
winds out of the northeast at 25 to 30 mph tonight and continuing
into tomorrow morning, with wind gusts to 45 mph.
On Monday, a weather front associated with a surface low
developing over the western gulf will lift northeast, increasing
winds along the offshore and eastern gulf marine zones. PoPs will
also increase along this front and bring more snow to the northern
two-thirds of the panhandle and rain over the far south once it
lifts north early Monday.
We opted to use a blend of GFS and EC for pressure adjustments and
opted for high res models and hand analysis for the winds over the
gulf and throughout the inner channels. A combination of the NAM,
GFS, and SREF was used for PoP updates.
Overall, forecast confidence in the short range is average,
trending below average due to model disagreement.
.LONG TERM...Rather different weather pattern for the Gulf of
Alaska and SE Alaska for the long range period compared to what we
have seen over the last few weeks. Mean 500 mb trough axis is
forecast to shift westward to be more over western Alaska and the
Bering Sea opening the door for warmer and wetter SW flow through
much of next week. Several shortwaves are embedded in the SW flow
pattern and promise to bring rather unsettled conditions through
late week at least.
Several new trends are apparent in the long range forecast today.
First off, the scenario of a weak low that was forecast yesterday
to advance on Cross Sound from the SW on Tue has been abandon in
favor of a stronger low crossing over Haida Gwaii late Mon night.
This has stabilized wind forecasts for the NE gulf and gulf coast
Tue with more general SW winds expected now, but has dropped
confidence on wind forecasts for the extreme southern panhandle
Mon night (due to some indications that guidance wants to put the
low even further SE and a wide spread on low strength). Used Nam
and some ECMWF to represent it as both had a decent track and
Second forecast trend is for a general increase in winds in many
areas Tue night into Wed. Several models are now suggesting a
rather vigorous front will travel east across the gulf at that
time with 20 kt (Canadian) to 35 kt (GFS) winds accompanying it.
Ended up increasing wind in the forecast with a wide area of 25 to
30 kt winds across the gulf. Winds also increased in the inner
channels to 15 to 25 kt especially for the southern panhandle.
Final trend is the general southerly flow and warm air advection
that will affect just about the entire panhandle. Warmest
temperatures appear mid week with many areas threatening to rise
above freezing by Wed. With these warmer temps snow level will be
rising above sea level and snow will be changing to rain for many
Main changes to the forecast were from Mon night through Wed with
changes in low position and strengthening fronts changing around
the wind forecast a bit. Main guidance was Nam with some ECMWF
followed by WPC guidance for later periods.
PUBLIC...Strong Wind from 9 PM AKST this evening through Sunday morning
MARINE...Heavy Freezing Spray Warning for PKZ012.
Storm Warning for PKZ012-013.
Gale Warning for PKZ022-032-035-043-051-052.
Small Craft Advisory for PKZ011-021-031-034-041-042-053.
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Area Forecast Discussion
National Weather Service Burlington VT
717 PM EST Sat Nov 25 2017
A cold front will sweep across the North Country this evening,
allowing rain to end as a period of snow showers across the
mountains. Temperatures will trend colder for Sunday with highs
only in the upper 20s to mid 30s with northwest winds. Skies
will remain mostly cloudy, and another weak upper level
disturbance approaching from the northern Great Lakes region
will bring additional snow showers to most areas during Sunday
Night. Should see temperatures trend milder on Tuesday and
through the remainder of next week.
.NEAR TERM /THROUGH SUNDAY NIGHT/...
As of 717 PM EST Saturday...The forecast remains largely on
track this evening as surface cold front, currently entering the
Adirondacks makes steady progress eastward. Did opt to adjust
precipitation chances slightly based off the latest BTV 4km WRF
and HRRR hourly output into the overnight hours which are
capturing current radar trends quite nicely. The overall theme
remains the same however, as scattered to numerous rain showers,
most focused across the northern high terrain, transition to
snow showers over time as front clears east and cold thermal
advective processes commence on northwesterly flow. Have a great
Overcast conditions prevail across the North Country this
afternoon in SW flow regime. Briefly reached 52F at BTV and 57F
at RUT during the late morning hrs, but pre-frontal trough and
associated -SHRA has generally cooled readings into the 40s, and
locally into the upper 30s in the nrn Adirondacks. Lingering
showers across central/nrn VT will result in <0.10" additional
rainfall thru mid-late aftn. Otherwise, just looking at cloudy
conditions with SW winds generally 5-10 mph thru early this
Trailing cold front across the Ottawa Valley at 19Z will bring
a northwesterly wind shift as it moves across northern NY and VT
between 00-06Z late this evening. Anticipate FROPA at BTV
around 03Z. Cooling low-level thermodynamic profiles will begin
to support snow around 01Z in the nrn Adirondacks and by 04Z or
so in the northern Green Mountains. So, will have some
upslope/orographic snow showers during the overnight hrs with up
to 1-2" across the higher summits, and a general coating to 1"
possible across the nrn Adirondacks region and central/nrn VT in
general by 12Z Sunday. Generally cloudy in valley locations with
a brief flurry or two. Daybreak lows will range from the low-mid
20s across the nrn Adirondacks and St. Lawrence Valley, to the
uppr 20s to lower 30s across central/nrn VT where low-level CAA
arrives a bit later. Highest PoPs (70-80%) confined to the
higher summit locations, with just 20-30% in the lower valleys.
Will see NW winds 10-15 mph with some gusts to 25 mph with steep
lapse rates (and downsloping in the CT River Valley) thru
Sunday morning, before sfc ridge axis briefly shifts into the
region with lighter winds expected late in the day. Any
lingering snow showers should end across the mtns during the
morning hrs before upslope winds diminish. Not looking for much
sunshine with trapped moisture and low- level inversion -- maybe
a few breaks in the afternoon before clouds advance ahead of
next shortwave trough from the nrn Great Lakes. Highs on Sunday
mainly 28-35F, warmest at BTV.
700mb shortwave trough in NW flow and weak sfc reflection move
in for Sunday night from the northern Great Lakes region.
Limited moisture with PW values 0.2-0.3" but sufficient synoptic
ascent and upslope enhancement for some light snow or snow
shower activity, especially 03-09Z. Went with high PoPs (70-90%)
for a low QPF event...liquid equiv. 0.05-0.15", highest in the
mtns. Everyone should see at least a light period of snow, with
1-3" in the mtns, and a dusting to an inch possible in valley
locations by 12Z Monday. Sunday night lows generally 22-28F.
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 315 PM EST Saturday...Monday will start out with a NW
flow at all levels, cold advection, and some leftover upslope
snow showers or flurries. As weak high pressure and rising
heights/temps aloft move in any snow showers will be winding
down some breaks of sun may develop from southwest to northeast.
and 925mb temps will range from -10 near KMSS to -4 at VSF in
downslope flow resulting in highs ranging from upper 20s north
to upper 30s south.
A ridge of high pressure will crest over the region Monday
night but warm advection aloft in advance of a warm front in the
Great Lakes will bring increasing high clouds overnight. Low
temps expected in the teens and 20s, but should level out after
midnight. Coolest readings in the northeast kingdom of VT.
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 315 PM EST Saturday...The long term feature of interest
will continue to be the progressive, near zonal synoptic flow
pattern across the northern tier of the nation. This west to
east flow will result in a roller coaster of temperatures, but
generally on the milder and drier side of average for this time
of year. Confidence is about average with models in general
agreement, though details get fuzzier toward the end of the
Tuesday is looking milder as a strong WSW flow of air (>50 kt
at 850mb) returns with high temps pushing into the 40s to around
50 warmest west of the Greens, cooler east as 925mb temps rise
to about 5-8 degC and 1000-500 thickness to about 552dm.
The next potential round of light precipitation still looks to occur
on Tuesday night, exiting during Wed morning. Most of that looks
to be of the light rain shower variety as it stays fairly mild
in the 30s to around 40 but could be a little mix in the cool
The rest of Wed into Thu look to be dry as high pressure and
ridging aloft builds into the area. Max temps will continue on
the mild side with highs in the 40s while lows will be closer to
average in the 20s.
GFS has joined the EC with the forecast of a more significant
weather maker late in the week as a trof digs and cuts off near
the mid-Atlantic coast along with it`s surface low nearby.
However, there is really no cold air in place in advance of the
low so right now looks to be more wet than white but it`s way
too early to get too caught up in the details. Raw model temp
guidance is much warmer than the statistical but have trended
toward that warmer solution for now with a mild SE flow of air
into New England, but stay tuned.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Through 00Z Monday...It appears ceilings will generally trend
downward into the MVFR category after 00Z with HIR TRRN OBSCD
and localized IFR at KSLK. Will see some upslope/mountain snow
showers overnight, mainly affecting KSLK with occasional
flurries or light snow showers during the overnight hrs. Will
see an increase in NW winds on Sunday, with gusts 18-22kts. Will
maintain mix of MVFR/VFR ceilings, mainly 2000-4000ft across
the region Sunday 12-18Z.
Sunday Night: Mainly VFR, with areas MVFR possible. Chance SHSN.
Monday: Mainly VFR, with local MVFR possible. Chance SHSN.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: Mainly VFR, with local MVFR possible. Chance SHRA,
Wednesday: Mainly VFR, with local MVFR possible. Slight chance
SHRA, Slight chance SHSN.
Wednesday Night: VFR. NO SIG WX.
Thursday: VFR. Slight chance SHRA, Slight chance SHSN.
Area Forecast Discussion
National Weather Service Wilmington NC
927 PM EST Sat Nov 25 2017
A dry cold front will cross the coast late tonight, followed by
dry and cool high pressure early next week. A gradual warming
trend will come by Wednesday as the area of high pressure moves
offshore. Another cold front should bring a few showers Friday,
with a cooling trend into next weekend.
.NEAR TERM /THROUGH SUNDAY/...
As of 930 PM Saturday...A 500 mb shortwave is moving across the
eastern Carolinas now, outlined by a region of 600-300 mb
moisture and clouds. This cloud cover will clear off the coast
in just a few more hours with clear skies developing across the
area late tonight into Sunday.
A surface cold front extending from the upstate of South
Carolina into the western Piedmont of North Carolina will move
eastward and approach I-95 between midnight and 1 AM. The front
should reach the coast a couple hours later, with northerly
winds developing behind the boundary. Most models with the
exception of the NAM and HRRR are running a little fast with
their depiction of the front, but there should be little real
impact on sensible weather across the area. Forecast lows range
from around 40 in the Lumberton area to the mid 40s at the
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 248 PM Saturday...The forecast will remain only a
temperature one as a mostly zonal flow aloft prevails through
the period. The pattern does shift a little by early Tuesday
setting the stage for a decent warmup by the middle of the week.
At the surface, high pressure will move slowly from the
Tennessee Valley basically overhead by the end of the period.
Temperatures will be below normal through the period with lower
to middle 30s for lows (a little warmer Tuesday morning) and
highs mostly in the lower to middle 60s Monday afternoon.
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 248 PM Saturday...Pleasant late Autumn weather on tap
this period with temperatures and sunshine minutes both poised
to run above normal. Phasing of a dampening southern stream
short-wave and a progressive, northern stream upper trough, will
bring an air mass change to more `expected` seasonal
temperature levels for very early December, Friday into the
weekend. GFS/Ecmwf both resolve this upper feature in relative
good agreement for days 6/7, and the high amplification of the
upper trough will support a chance of showers or a TSTM Thursday
night or early Friday. Low-level winds appear moderately strong
ahead of the upper trough and a spike in column moisture, may
allow a `non- zero` chance of a brief line of severe storms late
week. We will see if models hold onto to the high trough
amplification, or not, in future runs.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 00 UTC...A weak cold front moving across the Appalachians
will cross the TAF sites later tonight and shift off the coast
around 06 utc. VFR conditions are expected with only mid and
high level clouds ahead of the front. Winds will be light
overnight and a windshift from the west-southwest to the north
will occur through the period. Wind speeds will increase to 8 to
10 knots by Sunday afternoon as high pressure builds in from
NEAR TERM /THROUGH SUNDAY/...
As of 930 PM Saturday...Westerly winds currently range from 10
knots at the beaches to 15-17 knots out at 20 miles distance
from shore. A cold front still across the western portions of
North and South Carolina should reach the beaches and will move
offshore late tonight, shifting wind direction northerly with an
increase to 15-20 knots. Gusts, especially across the waters
north of Myrtle Beach, could reach 25 knots after 4-5 AM. This
is very close to our previous forecast and no substantial
changes have been made to wind speed/direction forecasts.
Currently wave heights range from 2 to 2.5 feet nearshore to 3.5
feet out at Frying Pan Shoals. This necessitates another
decrease to wave height forecasts, but only for the next several
hours as waves should begin to increase late tonight behind the
SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 248 PM Saturday...Surface high pressure to the west will
move slowly eastward through the period. Winds will be from
the north through most of the period at ten knots or less. By
late Monday into early Tuesday the flow will turn more northeast
with similar wind speeds. Significant seas will be 2-3 feet.
LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 248 PM Saturday...This appears to be a favorable marine
period shaping up as high pressure over the waters migrates
slowly offshore, resulting in a light veering wind Tuesday.
A weak cold front will bring a wind shift to the north on
Wednesday, but speeds to remain well below advisory levels.
Light N-NE winds Thursday, will veer to south in the afternoon
as high pressure releases its grip, and low pressure moves into
the Ohio Valley. Light wind chop, and weak ESE swell will
describes seas this period, and no TSTMS expected on the 0-20
NM waters through mid-week.