Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/09/16
Area Forecast Discussion
National Weather Service Wakefield VA
959 PM EST Thu Dec 8 2016
.SYNOPSIS...
Canadian high pressure builds into the Mid-Atlantic overnight
into Friday, and settles over the region Friday night into
Saturday. The high slides offshore Sunday. Low pressure will
push north of the area on Monday...with the associated cold
front crossing the region Monday night. Another strong cold
front impacts the region during the middle of next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Mid-evening GOES WV imagery continues to feature broad cyclonic
flow aloft over the east-central CONUS, in association w/a deep
cold upper low situated over ern Quebec. The surface cold front
is now oriented along the coast of SE VA back into eastern NC at
03z, and is primarily indicated by a sharp drop in dewpoints from
the low to mid 30s to the upper teens to low 20s back in the
piedmont (with dewpoints in the single digits to low teens just
upstream).
The primary CAA arrives late tonight as strong Canadian high
pressure spreads ewd through the Ohio Valley and into the Mid-
Atlantic. Temperatures have already dropped into the mid to upper
30s inland, upper 30s to low 40s Se coast. LAV and RAP have
handled temps well thus far and have leaned in its direction for
the overnight. Look for temps to eventually settle into the
mid/upper 20s late tonight/early Friday morning, with low 30s for
coastal se VA/ne NC.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A cold/brisk day is anticipated Friday as the Arctic high builds
from the Central Plains toward the southern Appalachians. 850mb
temps drop to around -10C (-2 st dev) Friday afternoon. Steady CAA
will prevent temperatures from reaching their full potential
Friday afternoon, even with a sunny sky. MOS guidance continues to
show highs generally in the low/mid 40s, but will trend toward
cooler thickness regressions. Some Piedmont locales may struggle
to get out of the 30s, with around 40/low 40s elsewhere. A brisk
northwest wind of 10-15 mph inland and 15 to 20 mph near the coast
is expected and will keep wind chill values in the low to mid 30s.
The high builds into the region Friday night into Saturday. By
this point the airmass will have modified enough to lose its
arctic characteristics. Still cold and well below normal
nonetheless, with lows Friday night in the upper teens to low 20s
inland, to the low/mid 20s for se coastal locations. Limited
mixing Saturday will keep highs in the upper 30s to low 40s
despite some warming at 850mb. Sunny with a light westerly wind.
Cold high pressure remains over the region Saturday night.
Meanwhile, a nrn stream trough dives into the Great Lakes region,
which could result in increasing high clouds late, especially
across the north. There should still be several hours of rather
ideal radiational cooling conditions and lows should once again
drop at least into the low/mid 20s. The initial wave pushes north
of the region Sunday with a secondary wave diving tracking into
the Ohio Valley, with the surface high sliding offshore. Clouds
should thicken and mixing will be limited, so highs will still be
below normal and moderate only into the mid 40s to low 50s se.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Sfc high pressure slides offshore by Sun aftn and winds become
more sly on Sun. The combination of a weak coastal trough
developing off the Carolina Coast Sun night and a warm front
lifting north through the area should bring rain up along the Mid
Atlantic coastal areas Sun night into Mon morning with a brief
period of drying during the day on Mon as the region becomes
warm-sectored. A cold front associated with low pressure tracking
along the St Lawrence River Valley is then expected to cross the
region Mon night and exit the coast by Tue morning. Winds
generally sw ahead of the front...becoming nly Tue. The cooler air
behind the cold front is much more modified and what would be
typical breezy conditions along the coast are not anticipated at
this time. Sfc high pressure returns Tue/Tue night...followed by
what could be a developing coastal low off the Southeast into Mid
Atlantic coasts on Wed.
A brief warm-up should be anticipated as the aforementioned warm
front lifts through the region Sun night into early Mon. Areas
north of the warm front should remain wedged and keep cooler air
in place prior to the initial onset of precip. This could result
in a rain/snow mix quickly transitioning to all rain overnight.
Precip should remain as rain through Monday. Temperatures
generally at to slightly below normal throughout the period.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Canadian high pressure will begin to build over the Mid Atlantic
States tonight. Patches of high clouds early Thursday evening
will clear overnight with the sky remaining mostly clear Friday.
Winds will remain from the northwest through the 00Z TAF period.
OUTLOOK...High pressure builds into the area through Saturday.
High pressure slides offshore Sunday. There will be a chance for
rain Monday as a cold front approaches from the west. Following
the passage of the cold front Monday night...dry weather returns
for Tuesday.
&&
.MARINE...
Have started all SCA flags for the waters with the aftn forecast
issuance since winds are expected to increase in the next 3-6 hrs.
A strong cold front will cross the waters this evening...followed
by a rapidly tightening pressure gradient, strong cold air
advection, and a strong 140-160kt jet streak impacting the waters
in the post-frontal environment. Overall wind forecast over the
waters is on track with w-nw winds increasing to 15-25kt this
evening with gusts around 30kt over the ocean/Ches Bay overnight.
Speeds stabilize Fri morning (still sustained 15-20kt), and a
brief lull in winds to 10-15kt can be anticipated on the rivers
during this time. This will be short-lived as a secondary surge in
colder air/wind speeds is expected to occur Fri evening...with
speeds/gusts increasing by roughly 5kt. Seas build to 4-6ft this
evening and overnight... hovering around 4-5ft through early Sat
morning. Waves will average 3-4ft during SCA and may also drop to
a solid 3ft during the brief lull in winds Fri morning.
The cold air finally begins to equalize and the pressure gradient
slowly relaxes after midnight Fri night into early Sat as sfc high
pressure builds across the OH/TN Valleys and inches closer to the
Mid Atlantic Region. The high slides overhead Sat night into Sun
morning with light and variable winds. The high then slides
offshore by Sun aftn and winds become more sly aob 15kt on Sun.
The combination of a weak coastal trough developing off the
Carolina coast Sun night and a warm front lifting north through
the area should bring rain up along the Mid Atlantic coast Sun
night into Mon morning with a brief period of drying during the
day on Mon. A cold front associated with low pressure tracking
along the St Lawrence River Valley is then expected to cross the
waters Mon night and exit the coast by Tue morning. Winds
generally sw aob 15kt ahead of the front...becoming nly Tue. The
cooler air behind the cold front is much more modified and SCA
conditions are not anticipated at this time. Seas average 2-3ft
Sat night through Mon and may build up to 5ft briefly on Tue.
Waves 1-2ft.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 10 PM EST Friday for ANZ635-636-638.
Small Craft Advisory until 4 AM EST Friday for ANZ637.
Small Craft Advisory until 7 AM EST Saturday for ANZ630>632-
634.
Small Craft Advisory until 4 AM EST Saturday for ANZ633-650-
652-654-656-658.
&&
$$
SYNOPSIS...AJZ/LSA
NEAR TERM...AJZ/MAM
SHORT TERM...AJZ/SAM
LONG TERM...BMD
AVIATION...LSA/JAO
MARINE...BMD
Area Forecast Discussion...Updated
National Weather Service Billings MT
814 PM MST Thu Dec 8 2016
.UPDATE...
Clear skies, light winds, snow cover and arctic high pressure
combining for plummeting temperatures over eastern zones this
evening. Already -14 in Baker and near to below zero in many other
locations. HRRR seems to have caught on to the areas of snow cover
this evening showing a good contrast between snow and no-snow
areas in the temperature field so trended temperature forecast
toward it. With increasing cloud cover spreading west to east
overnight expect the temperature drop to end shortly after
midnight with steady or slowly rising temperatures toward sunrise.
Isolated to scattered snow showers should develop around midnight
over western zones and shift eastward with mid level warm
advection increasing. Falling pressures west of the divide
inducing easterly low level flow east of the divide should enhance
lift in the foothills where the best pops are. No big changes to
the precipitation forecast this evening. Rest of the forecast is
in good shape. Chambers
&&
.SHORT TERM...valid for Fri and Sat...
Snow chances will increase over the next 24 hours to 36 hours. An
approaching shortwave, along with moisture associated with an
Atmospheric River, will move into the area. Tonight into Friday
morning, most of the snowfall will be over the mountains. Winds
across the area will be lighter tonight, so wind chill issues will
be very marginal. For now will not issue any highlights.
Friday will see the moisture, and therefore chances for snowfall,
slowly spread east and into lower elevations. This will result in
an extended period of light to moderate snowfall through Saturday.
The best chance for snowfall will be Saturday morning as the best
push of energy and moisture moves through. The complicating factor
for the snow amounts will be a push of westerly winds during the
day on Saturday. Not only will this reduce the snowfall with
downslope flow, it will also bring warmer temperatures. Given the
finer scale nature of where that boundary will be, there is still
some model discrepancies with the placement. For now will not have
an advisory, but this will continue to be monitored. Reimer
.LONG TERM...valid for Sun...Mon...Tue...Wed...Thu...
Sunday will feature the warmest day across the forecast area as
west and southwest flow aloft, and at the surface, move in. This
will help erode the arctic air mass in place and get temperatures
back into the 30s in all locations but extreme eastern zones near
Miles City, Baker, and Ekalaka where mid to upper 20s are
expected. A large upper level low will be on the US doorstep
early Sunday night so dont expect the warmup to last long. If this
low moves in earlier expect less erosion of the air mass and
cooler temperatures Sunday. Some snow showers are possible over
the higher terrain with isolated snow showers expected over the
plains.
The aforementioned upper level low dives southeast on Monday
morning...driving another strong arctic front through the region.
Models are fairly consistent in developing a band of snow that pushes
south along and behind the front so folks should be ready for a
quick shot of 1-3 inches of snow Monday. Some residual snow
showers could stick around in southern zones, and along the higher
terrain Tuesday, but model uncertainty is high with regards to
snow (some solutions keeping light snow showers around the region)
but are in agreement on cold temperatures in the single digits
and teens.
Cold temperatures continue Wednesday and Thursday but model
uncertainty increases towards Fri and next weekend. The trend at
this point seems to indicate another round of cold air and snow
returning late Thursday into Friday. Dobbs
&&
.AVIATION...
An approaching disturbance from the west will bring some snow and
MVFR/IFR restrictions to KLVM after 06z. Expect these lower cigs
and vicinity snow showers to spread east to KBIL after 12z. KSHR
and KMLS should remain VFR with wave passage. Expect brief period
of VFR conditions to return after 18z at KBIL and KLVM and before
MVFR/IFR conditions potentially return after 00z Friday.
Dobbs/Chambers
&&
.PRELIMINARY POINT TEMP/POPS...
Fri Sat Sun Mon Tue Wed Thu
-----------------------------------------------------------
BIL 903/008 005/019 012/031 006/016 901/010 003/016 001/009
24/S 54/S 22/J 34/J 31/B 11/U 12/J
LVM 903/020 015/030 021/030 016/024 000/012 003/018 004/011
35/S 65/S 32/J 34/J 22/J 11/B 24/J
HDN 901/011 006/017 008/032 006/014 902/012 902/015 901/012
12/S 44/S 22/J 34/J 21/B 11/U 12/J
MLS 907/005 901/009 000/026 002/007 907/007 902/012 905/006
02/S 65/S 22/J 33/J 21/B 10/B 02/J
4BQ 907/009 002/016 006/030 005/014 904/009 000/015 902/010
01/E 33/S 21/B 23/J 21/B 00/B 02/J
BHK 918/003 905/007 903/020 902/003 907/004 903/008 906/004
01/E 45/S 22/J 22/J 21/B 00/B 02/J
SHR 910/014 008/024 012/030 013/017 905/007 901/015 000/012
01/B 24/S 22/J 23/J 20/B 10/U 12/J
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Caribou ME
1016 PM EST Thu Dec 8 2016
.SYNOPSIS...
A cold front will cross the area this evening. An Arctic cold
front will move through the region Friday afternoon. The first
Arctic air mass will settle over the area for the weekend. Low
pressure will approach Sunday night into Monday with the threat
of winter weather.
&&
.NEAR TERM /THROUGH FRIDAY/...
1020 PM Update: More scattered snow showers can be expected
overnight and the arctic front makes its move into the state. IR
satl imagery showed some enhancement setting up along the ME-
Quebec border. The latest RAP which was handling things fairly
well, shows another set of scattered snow showers w/periods of
heavy snow moving across the region by early Friday morning. There
is the potential for a snow squall as winds are forecast to pick
up w/the front. Temps will stay in the 20s overnight w/the cloud
cover.
Previous Discussion...
A low in central Quebec with an associated cold front extending
back across the great lakes. By early Friday morning the cold
front will push into northwestern Maine, then into central Maine
tomorrow morning. By tomorrow afternoon the front will be through
the state and into the coastal waters. An early high temperature
tomorrow then falling through the day. Winds are expected to pick
up becoming gusty tomorrow afternoon and will continue into
Saturday.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
Arctic air will advect into the area through the night accompanied
by strong gusty winds due to a steep low level lapse rate. Wind
chills will drop below zero for the entire area by daybreak
Saturday, but no wind chill advisories are anticipated. The Arctic
front itself will likely cause some snow squalls Friday
evening...mostly towards NE Aroostook County. Accumulations will
be under an inch, but could cause hazardous driving when combined
with the strong winds. The strong winds could cause drifting
issues into Saturday morning in the open terrain of NE Aroostook.
Used a combination of NAM12 and Regional GEMs guidance to locate
the Arctic front and its southward progression during the night.
Expect temperatures to drop to the low single digits in the Crown
of Maine by Saturday morning. Bangor and the Down East coast will
drop into the 10-15 degree range for lows. Temperatures won`t make
a lot of recovery on Saturday and have dropped highs for this
forecast cycle to low teens north and upper teens to lower 20s
south. These temperatures will be accompanied by gusty NW winds
that will keep wind chills below zero in the morning and in the
single digits for most locations even into the afternoon. Did
reduce cloud cover for most of the day...just keeping flurries
towards the Saint John Valley and western mountains. Temperatures
on Saturday night will be challenging. If winds die off and
decoupling occurs, below zero readings will be commonplace. For
now...will bet on the winds. These will produce lows in the zero
to 5F range north of Millinocket and Houlton. Single digits are
forecast for Bangor while low teens are anticipated at Machias and
Bar Harbor. On Sunday, a ridge of high pressure will cross the
area. This means less wind and temperatures that will rise a
couple of degrees higher. Overrunning high clouds will increase in
the afternoon ahead of the next system.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Winter storm possible early next week...
With Arctic air in place Sunday night, low pressure will move out
of the Midwestern US in a fast westerly flow towards New England.
Guidance from GFS, GEFS, GEMS, and ECMWF has come into better
agreement with today`s 12Z run, but there remains questions
concerning the amplitude of the shortwave trough. The amplitude of
this trough dictates the track of low and its speed across the
region. The 08/12Z GFS took a dramatic turn towards a more
impactful storm for the forecast area and now looks like the
07/12Z ECMWF. Meanwhile, the last two ECMWF runs look more like
the 07/12Z GFS. As a result of the flip-flopping, will continue
with a consensus blend of available models over the past 24 hours.
This results in likely pops for snow for Bangor and the Down East
region and just chance pops for snow north of Millinocket and
Houlton. The pops for this system now extend from Sunday evening
when an initial burst of overrunning snow may fall towards to the
coast until Tuesday morning when the last of the wraparound
moisture leaves the forecast area. Did move the rain/snow line
further south to the outer islands along the coast.
Regardless of the model, the storm leaves the area Tuesday with
colder air, but not Arctic, and a narrow ridge of high pressure.
Another Arctic front will approach Wednesday, but there`s a lot of
uncertainty on the evolution of this frontal passage too. GFS
suggests southern stream moisture is drawn north with the prospect
of significant snow later Wednesday into Wednesday night while the
GEMS and ECMWF suggest no more than snow showers with the front.
Guidance continues to agree on some very frigid temperatures again
on Thursday.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: MVFR conditions with scattered snow showers all sites. Snow
squalls are expected across northern Maine tomorrow afternoon,
affecting FVE, CAR, PQI, HUL. The squalls will be brief but
intense, bringing VSBY and CIGS down to LIFR during the squall,
then conditions will improve rapidly after. Winds will be gusty
tomorrow, with increased gusts during squalls.
SHORT TERM: MVFR tempo LIFR in snow squalls north of HUL on Friday
evening. Strong gusty winds reaching 35 mph are possible Friday
night. All sites will be predominately VFR Saturday and Sunday
with the most likely exception being FVE in snowshowers. IFR
conditions in snow are possible for BGR and BHB by Sunday evening.
The period Sunday evening into Tuesday currently features a strong
threat of IFR to LIFR in snow south of MLT and mostly MVFR cigs
north of MLT and HUL.
&&
.MARINE...
NEAR TERM: An SCA is in effect through tomorrow afternoon. A Gale watch is
also in effect through the end of the period with a Gale Warning
expected to be issued for tomorrow afternoon. A cold frontal
system will move into the Northern Gulf of Maine tomorrow
afternoon.
SHORT TERM: Will maintain the Gale watch for Friday evening as
gusts will likely be just above criteria and sporadic. A small
craft advisory will follow any gale until late Saturday evening.
Light freezing spray is possible Friday night into Saturday
morning. The next big event appears set for later Monday into
early Tuesday. It`s too early to tell if it`ll be an SCA or gale.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory until 4 PM EST Friday for ANZ050>052.
Gale Watch from Friday afternoon through Saturday morning for
ANZ050-051.
&&
$$
Near Term...Hewitt
Area Forecast Discussion
National Weather Service State College PA
1029 PM EST Thu Dec 8 2016
.SYNOPSIS...
A upper level trough over the Great Lakes will pivot eastward
across the region over the next couple of days. A prolonged
period of lake effect snowfall will bring significant snow
accumulations to northwest PA through Saturday. High pressure
will briefly build into Pennsylvania late Saturday, then a weak
low pressure system is likely to track west of Pennsylvania
through the Great Lakes Sunday into Monday. Unsettled weather will
persist next week with additional storm chances by both mid week
and again late next week.
&&
.NEAR TERM /UNTIL 8 AM FRIDAY MORNING/...
The big band broke up almost completely as expected and the snows
are re-orienting to more of a general area and should go to
short-fetch bands in a couple of hours. The connections to
upstream lakes should not form until late tonight or early Fri.
Interestingly, the newest NAM actually paints a picture of an
extremely long fetch band/qpf beginning in LS, then over LM, over
Saginaw Bay (part of LH), over far srn LH (pretty close to Lake
St Clair), and finally over LE into NW PA on Fri! Wow. If it can
really manage to pull moisture from 5 of the 6 Great Lakes (yes,
Lake St Clair counts) with one band, that would be impressive.
Prev...
The main band is hanging over wrn NY and piling it onto nrn/cent
Chaut and Catt Cos. Saw BUF had a report of 17" of new snow in
Perrysburg - only HiRes WRF- ARW seems to be doing really well at
placement of the band and surrounding lighter area of SHSN coming
off LE. It along with the HRRR make a decent 20-30 degree veering
to the mean llvl wind and quickly break the main band up before
midnight - if not by 10 PM. The shorter fetch keeps the smaller
and more numerous bands within 70mi of the lake shore for a bit
until a good LH/Georgian Bay connection(s) develop later tonight.
Have tried to draw this into the POPs for the next few hours.
Otherwise all is as expected.
Prev...
Mid cloud deck associated with sheared 5h trough exiting my
southeastern counties this afternoon. Meanwhile...colder air
overspreading western and central areas has promoted stratus
development and flurries reaching into the central mountains.
Organized intense lake effect snow banding remains north of the
PA/Ny border as expected...and HRRR continues to indicate a slow
southward drift in time tonight...with moderate snowfall and
accumulations dropping south of the PA/NY border tonight..
Radar imagery shows clear trend shore-hugging snow banding
along the Lake Erie shoreline for now...thanks to lee shore
troffing induced by warmer lakes. Consensus of hi res models drops
the main band southward towards PA tonight before event evolves
into a Lake Huron connection with NW to SE oriented bands
overnight into Friday morning.
Little change to forecast storm total snow amounts as 12"+
locally expected over western portions of Warren County by
Saturday. Mins tonight will range from the lower 20s northwest
to the upper 20s southeast.
&&
.SHORT TERM /8 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Long duration lake effect snow event continues on Friday as
anomalously cold cross-lake flow maintains multiband le snow event
across the northwest Pa. Model soundings showing a deep, moist
boundary layer with an inversion height around 700MB and although
the 850mb temps of around -11 to -14C sufficient to maintain
moderate to heavy banding from relatively warm lake waters of
around 50F.
The passage of a shortwave around midday Friday could briefly
support lake effect snow extending well downwind of the lakes,
with a quick coating likely in the ridge/valley region of Central
Pa and possibly even into parts of the Susq Valley.
The boundary layer flow is progged to remain close to 270 degrees
across Southern Pa, excluding the Laurel Highlands from a direst
link to lake moisture. However, persistent upslope flow should
yield occasional light snow with accumulations of 1-2 inches
between Friday and Sat morning.
Although not an exceptionally cold air mass for this time of the
year, this will be the coldest air mass so far this season with
temps 5-10F below normal Friday/Saturday. A gusty wind will make
it feel even colder.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Gradually improving conditions heading into Sat across the NW
Mtns as lake effect snow bands become more scattered and slowly
wind down. Still potential for a renegade snow band (with Lake
Huron connection) to stretch into the central mtns Fri night with
localized impacts though as trough lifts out. However, WSW fetch
off the lakes should continue to produce snow showers until Sat
evening across the N Mtns.
Breezy winds abate Fri night, with clearing skies across Southern
Pa late Friday night and Saturday as surface high pressure builds
in from the Ohio Valley.
High pressure will bring a brief period of tranquility Sat
evening. However, a developing overrunning scenario is expected
Sunday into Monday, as weak low pressure lifts into the Eastern
Grt Lks and high pressure remains lodged over northern New Eng.
Enough cold air is in place to support a light snowfall across
much of area by Monday AM, with GFS bringing light precip into the
area on Sunday earlier than the ECMWF. Model consensus low track
west of PA should bring in enough warm air to cause snow to
change to rain across Southern PA, and esp the Lower Susq Valley,
a before precip tapers off later Monday.
A bit cooler than normal temps indicated early next week, but
longer range models indicate a significant cold front passage
Wed with noticably below normal temps filtering in for the rest
of next week.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
03Z TAFS sent.
Starting to see stronger radar returns near BFD, as winds shift
more to the NW and bands of snow showers shift southward into
northern PA.
Earlier discussion below.
Shear axis moving across the region this evening. Westerly flow
will become more northwesterly overnight. Some snow showers may
get as far southeast as UNV and AOO. Main areas to see snow showers
will be BFD and JST.
Little change is expected before Saturday afternoon, when winds
shift more to the southwest. Warming aloft and the wind shift at
this point should allow the lake effect snow showers and upslope
snow showers to come to an end.
Outlook...
Sat...MVFR/IFR with snow showers in the morning. Improving
conditions in the aft.
Sun...Becoming MVFR/IFR with some snow. Rain may mix in at
times.
Mon...Additional rain and snow. MVFR/IFR conditions. Becoming
windy late.
Tue...Mainly dry with VFR conditions. MVFR/IFR still possible
acros the north and west with snow showers.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Lake Effect Snow Advisory until noon EST Saturday for PAZ005.
Lake Effect Snow Warning until noon EST Saturday for PAZ004.
&&
$$
SYNOPSIS...DeVoir
NEAR TERM...Dangelo/DeVoir
SHORT TERM...DeVoir
LONG TERM...Fitzgerald/RXR
AVIATION...Martin
afternoon forecast discussion, equilibrium level will remain in
the 7-8 kft range through the night which will make it possible
for elements from a Lake Superior to Lake Michigan band to reach
the Saginaw Valley. Surface analysis indicates a lake aggregate
pressure trough setting up favorably to support that trajectory.
About the only negative factors are the downslope from higher
terrain in the north and 0-1 km theta-e lapse rate dropping to
about 1 K/km by western Saginaw Bay. This actually may act to
limit activity from reaching Flint more than the Tri Cities, so
plan to maintain high chance/low likely POPs in that area. The
other trouble spot is central Lake Huron where lake effect has
been strong enough for a few lightning strikes near Goderich.
Expect mid lake bands to remain nearby but offshore of the Thumb
while the Lake Superior/Lake Michigan contribution to aggregate
troughing remains strong. As soon as it weakens, then the mid Lake
Huron surface trough will become more dominant and bands will
migrate farther from the Thumb into mid lake. Interestingly, not
much change in equilibrium level/convective depth is shown in
model soundings suggesting mid level subsidence will be weak and
not very effective at suppressing lake effect as the short wave
ridge builds overhead by morning. About the only forecast
adjustment being considered is an upward bump in POPs to
likely/numerous in the Saginaw Valley depending on how strong the
snow showers remain as the Lake Superior/Michigan band matures
during the rest of the evening.
&&
.PREV DISCUSSION...
Issued at 653 PM EST Thu Dec 8 2016
AVIATION...
A trough of low pressure will move in from northern Lower Michigan
during the evening with a brief flare up of snow showers possible
along and ahead of the boundary. There is also potential for bands
of lake effect to remain active in the northwest flow during the
night after the trough passage. This will be monitored for trends to
set up west of the terminal corridor. For now, the forecast will
lean toward low end VFR ceiling that usually accompanies northwest
flow and closely monitor both cloud and snow shower trends for later
updates. Assuming the favorable zone for lake effect does set up to
our west overnight, then a slight backing of the low level flow will
help shift activity eastward mid Friday morning through early
afternoon. MVFR in a combination of snow showers/flurries and
stratocu should then move quickly through SE Michigan by mid
afternoon. This will allow a period of VFR before continued backing
low level flow guides more lake clouds into the region Friday
evening.
FOR DTW... MVFR in patches of snow showers and stratocu remain
possible through the evening as a surface front/trough moves through
the region. There has been a flare up of lake effect between GRR and
RQB over toward MBS that will be monitored which could make it into
the JXN to DTW area during the evening. Broken VFR ceiling overnight
is expected to remain below 5000 feet through mid Friday morning.
//DTW Threshold Probabilities...
* High for ceiling 5000 ft or less through tonight.
* High for snow as precipitation type.
PREV DISCUSSION...
Issued at 325 PM EST Thu Dec 8 2016
DISCUSSION...
Snow squall activity around this afternoon will be
diminishing/decreasing in coverage as sharp shear axis/trough swings
south through the Central Great Lakes this evening, allowing for
wind shift to the northwest and general subsidence and a drying out
process (some breaks in cloud cover). However, there looks to be a
good chance for a dominate/narrow Lake Superior-Lake Michigan band
to set up overnight into Friday, as average 925-850 mb temps looks
to be lowering to favorable -10 to -12 C range. 12z Regional GEM
most aggressive with the band Impacting Tri-Cities into Flint
Vicinity, while the HRRR is farther west. 12z nam appears to be the
farthest east, with northern Thumb region being impacted on Friday.
Inversion heights look to be at or above 7 kft, which favors the
case for band(s) reaching southeast Michigan. Narrow nature of the
band and uncertainty with movement makes for difficult call on
amounts, but potential for localized amounts greater than 1 inch is
there as we get into the tail of the upper level pv lifting
northeast, providing some support during Friday, with near saturated
and cold 700 mb temps of -20 to -23 C. Backing flow in the afternoon
will also likely bring some snow shower activity back into the I-94
corridor as well.
Upper level northwest confluent flow Friday Night/Saturday, but
westerly flow and 850 mb temps still hovering in the negative mid
teens will continue to support flurries or light snow showers.
Warm advection/Fgen Saturday Night will bring increasing chance of
light snow by Sunday Morning. Favorable thermal profiles and 850 mb
specific humidity approaching 2 G/KG suggest a few inches possible.
A brief lull from snow will be possible throughout the late morning
to early afternoon hours. Any periods or little to no snow will be
short-lived as low pressure centered over northern Texas/Oklahoma
early Sunday will begin to push northeast into the Ohio Valley into
early Monday. The chance for snow will once again increase
throughout the late afternoon to early evening hours on Sunday, with
the chance for snow continuing into Monday morning. While we are
starting to narrow down on timing of the system as models converge,
uncertainty still exists regarding placement of the low. The GFS and
ECMWF models have flip-flopped over the past 24 hours, with the GFS
model bringing the low more north, clipping SE MI Monday morning and
afternoon. This allows SE winds to pool in warmer air into the
region, allowing 850 mb temperatures to straddle the 0 degree
isotherm during the morning, which has the potential to influence
precipitation type. Both the ECMWF and GEM models keep the low just
south, tracking across Ohio throughout Monday morning, keeping
conditions much cooler and allowing precipitation to remain as snow.
We will likely be a day off before issuing snowfall estimates for
Monday`s snow, as models continue to converge, however, it`s safe to
assume accumulation totals will impact travel Sunday through Monday.
Snow from this system will taper off late Monday, however, a shift
in winds from northeast to east will bring additional chances for
lake effect snow throughout the early part of the week. The second
main story for the extended will be the advent of polar air, which
looks to take daytime high from the lower 30s to upper 20s during
the early part of the week, to the upper 20s to lower teens by mid-
week.
MARINE...
Existing near gale conditions across the southern Lake Huron waters
will gradually ease early tonight as the become more northwesterly
with a frontal passage. This will maintain small craft advisory
conditions for all near shore waters into tonight. This will shift
to northwesterly will introduce a greater potential for snow squall
development tonight into Friday. Building high pressure south of
the Great Lakes will then allow moderate winds to take hold for the
end of the week before the arrival of the next low Sunday into
Monday.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 10 PM EST this evening FOR LHZ422.
Small Craft Advisory until 10 AM EST Friday FOR LHZ441>443.
Small Craft Advisory until 6 AM EST Friday FOR LHZ421.
Lake St Clair...Small Craft Advisory until 10 PM EST this evening FOR LCZ460.
Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EST this evening FOR LEZ444.
&&
$$
UPDATE.......BT
AVIATION.....BT
DISCUSSION...SF/AM
MARINE.......MR
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Goodland KS
420 PM MST Thu Dec 8 2016
.SHORT TERM...(This evening through Friday)
Issued at 244 PM MST Thu Dec 8 2016
Main forecast concerns will be temperatures and wind chills.
Northwest flow aloft is over the area as arctic high pressure has
settled over the area at the surface.
For tonight...keys to the forecast is how fast the winds can shift
back to the south and increase and how much/fast will the cloud
cover increase. Left front quadrant of the jet moves from southwest
to northeast across the area. Models do increase cloud cover at mid
and higher levels this afternoon into the night, although they look
a little fast in bringing it in.
Some hires model output is increasing boundary layer moisture. This
may be in response to the very cold temperatures. Sometimes the
models think there are clouds there when they are not. However there
are low clouds to our south. So not an easy temperature forecast.
Current temperatures are running colder than what the model output
expected. There will be a period the evening and probably beyond
midnight in the eastern counties where there will be little to no
wind.
The latest Rap seems to be catching the current temperature and wind
field well and is colder, especially in our northeast counties, than
any other output. If more clouds come in than expected then we will
not drop as much. At this time I am trending toward the colder
guidance. In regards to the wind chills, wind chills late this
evening into the overnight stay just above wind chill advisory
CRITERIA. My confidence level is not there as I think by the time
we get the winds the temperatures will start going up.
For Friday...Per the discussion above on wind chills, there looks to
be a brief period of wind chills getting to -13 to -14. Will brief
the overnight shift on this. There looks to be some kind of cloud
cover lingering around into the afternoon, especially in the
northeast half. That combined with the cold start and little mixing
with unfavorable surface winds will make for another cold day,
especially in the eastern portion of the area. Right now it looks
like the far western portion of my area will be the warmest and the
northeast portion the coldest. In the middle of those areas will be
interesting and closer to the Colorado border it could go either
way. So overall tended to go near to slightly below most of the
guidance.
.LONG TERM...(Friday night through Thursday)
Issued at 152 PM MST Thu Dec 8 2016
Dry conditions start off the long term period, followed by a couple
opportunities for some light snow for mainly the northern portion of
the forecast area.
Northwesterly flow aloft prevails at the start of the period. The
arctic air mass impacting the High Plains slides further east and
warmer air surges north into the region Friday night. This allows
for a decent warm up on Saturday ahead of our next shortwave.
A disturbance heads towards the area late Saturday as broad, upper
zonal flow develops. This shortwave generates chances for light snow
Saturday night into Sunday morning north of Interstate 70. Moisture
continues to look limited, so still am not anticipating much as this
wave moves through. Drier weather returns Sunday night, with
slightly warmer temperatures on Monday ahead of the next front
moving in.
A cold front traverses the High Plains Monday night and arctic air
spreads into the region, dropping temperatures once again through
midweek. Will need to monitor how cold the area will get as model
discrepancies are better resolved. There is another chance for light
snow Tuesday night, generally for the northern zones, with little
accumulation at this time. A trough moves through the westerly flow
into the western CONUS during the latter half of the week.
The warmest temperatures of the period will be on Saturday, with
highs in the 40s to low 50s, followed by a drop into the 30s and 40s
on Sunday and Monday. Tuesday through Thursday will be colder, with
highs currently forecast in the 20s and 30s. Lows should stay in the
teens to low 20s Friday through Monday nights before we see a dip
back down to around 10 degrees Tuesday night and Wednesday night
when the arctic air sets in.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 420 PM MST Thu Dec 8 2016
Conditions...VFR with SCT-BKN100-250 in a decreasing trend thru
the period.
Precip/Wx....None expected.
Winds........For KGLD...SE around 5 kts thru 05z Friday then S
around 10 kts. For KMCK...LGT/VRB thru 07z Friday...becoming ESE
around 10kts thru 17z Friday then SE around 10kts.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...BULLER
LONG TERM...JBH
AVIATION...JN
Area Forecast Discussion
National Weather Service Indianapolis IN
923 PM EST Thu Dec 8 2016
.UPDATE...
The Near Term and Aviation sections have been updated below.
&&
.SYNOPSIS...
Issued at 315 PM EST Thu Dec 8 2016
A pair of low pressure systems will bring chances for accumulating
snow late this weekend into Monday and again next Tuesday.
Temperatures will be below normal through the period.
&&
.NEAR TERM.../Tonight/
Issued at 923 PM EST Thu Dec 8 2016
Pesky flurries continue across the area, and have expanded a bit
further south. Have added flurries to the grids across the entire
area. With tail end of weak vort lobe unlikely to exit the area
until late, have gone ahead and taken the flurries out til morning.
Additionally, latest hourly numerical guidance and obs trends
suggest min temps will likely get down into the upper teens many
areas, and made adjustments accordingly. Previous discussions
follow.
Issued at 602 PM EST Thu Dec 8 2016
Upped cloud cover overnight in accordance with satellite trends and
HRRR low level moisture progs. Remainder of forecast in good shape.
Previous discussion follows.
Issued at 315 PM EST Thu Dec 8 2016
Models in good agreement that cold air advection will continue
tonight as northwest winds continue ahead of strong surface high
pressure over the Plains. However, thick cloud cover associated with
cyclonic flow aloft should keep temperatures from falling too much
overnight. Consshort handles this well with lows in the lower 20s.
Would not rule out a few flurries.
&&
.SHORT TERM.../Friday through Sunday/
Issued at 315 PM EST Thu Dec 8 2016
The main concern for the short term will be snow potential late in
the weekend associated with warm air advection and upper jet
dynamics. Models have some timing issues with subtle waves in thelow
amplitude fast upper flow, and differences in strength of
warmadvection on Sunday. With this in mind, low confidence
forecastespecially Sunday, when some areas should see the snow
change to ormix with rain or possibly some other mix. With this low
confidence,will go with a blend.
The early part of the weekend will be quiet with strong high
pressure expected to provide cold but dry weather through at least
most of Saturday. Then, things get interesting with 100 plus knot
jet stream over the area and warm air advection. Models were
agreeing on 2-4 g/kg specific humidity values on the 290 K level by
Saturday night. Critical thicknesses favor all snow Saturday
nightand a mix across roughly the southern half on Sunday
afternoon.Condensation pressure deficits suggest the snow will start
offacross our far northwestern area late Saturday afternoon and
notherntwo thirds Saturday night. Precipitation chances will
increase tolikely Sunday and occasional Sunday night as a surface
low liftsnortheast nearby. The 12 ECMWF was further south with the
track ofthis low, taking it across south central Indiana. The 12z
GFS wasstronger and took it across far northern Indiana. As it looks
now,there is a potential for several inches of snow across
ournorthernmost counties by Monday morning and lesser amounts
south.However, the exact track of the low will be the key. Any
change inthe track will have large implications on precipitation
type andsnow amounts.
MOS suggests below normal temperatures through the period. See
noreason to deviate from a blend. Did not use diurnal
temperaturecurve Sunday afternoon as warm air advection continues
ahead of aPlains low pressure center.
&&
.LONG TERM /Sunday Night through Thursday/...
Issued at 255 PM EST Thu Dec 8 2016
The period begins with a weak warm front lifting north across the
area. An upper trough begins to amplify over the western great
plains...particularly South Dakota and Nebraska. The GFS is stronger
and more amplified with this feature...leading to a stronger surface
low passing across Illinois and Indiana Sunday night/Monday morning.
This allows for more warm air into the forecast area on the front
end and a quicker return of cold air after the low passes. It also
allows for higher QPF across the area. Mid/long range models have
not been in good agreement as it pertains to this portion of the
forecast lately. Thus...confidence not high in timing...depth and
strength of the cold air in advance of and behind the passage of the
surface low...affecting precipitation type. Model initialization
went with a blend...which seems reasonable.
Tuesday night sees the passage of a strong cold front with model
differences in the amount of precipitation Tuesday and Tuesday
night...but both the GFS and ECMWF signal the coldest air of the
season pushing in behind the front...with temps at 850mb in the
teens Wednesday afternoon/evening as an example.
&&
.AVIATION (Discussion for the 09/03Z TAF update)...
Issued at 923 PM EST Thu Dec 8 2016
Wind gusts have been a bit more persistent than anticipated, and
have added them back in at IND for another few hours. Previous
discussion follows.
Issued at 602 PM EST Thu Dec 8 2016
MVFR ceilings will likely persist and may lower a bit through the
night into Friday morning. VFR conditions may return Friday
afternoon.
Widespread stratus in cyclonic flow aloft will persist overnight
into Friday.
A few flurries are occurring at IND and may occur off and on the
next few hours. This is likely to be low to no impact but will
include a -SHSN mention for a few hours.
No significant obstructions to visibility anticipated during the
period.
Winds will remain northwesterly through the period, generally around
8-12KT, but may gust a bit for the first hour or so of the period.
&&
.IND WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SYNOPSIS...MK
NEAR TERM...MK/NIELD
SHORT TERM...MK
LONG TERM...MRD
AVIATION...NIELD
Area Forecast Discussion
National Weather Service Northern Indiana
857 PM EST Thu Dec 8 2016
.SYNOPSIS...
Issued at 359 PM EST Thu Dec 8 2016
Lake effect snow showers will increase in intensity and coverage
this evening as cold air continues to overspread the region. The
most intense lake effect snow showers are expected from late this
evening through early Friday morning. Winter storm warnings and
advisories are in effect through Friday for southern lower
Michigan and far northern Indiana due to the combination of lake
effect snow and gusty winds causing blowing and drifting snow. In
addition to lake effect snow showers, very cold conditions will
persist into Friday with wind chills as cold as 5 above to 15
above zero.
&&
.UPDATE...
Issued at 857 PM EST Thu Dec 8 2016
Only minor changes to the going forecast this evening. Snow totals
so far have been fairly light but more dominant lake effect bands
beginning to develop and shift southward as expected given slowly
veering flow and increasing convergence due to lake aggregate
troughing. Previously forecasted snow amounts still appear to be
in good shape and expect a sharp increase in snow intensity
overnight as more organized bands drift south. Still some concern
that lake effect bands may reach further east, particular Branch,
Steuben, and Williams counties given latest RAP guidance, earlier
hi-res WRF-ARW and NMM runs, and quick peak at 00Z NAM12.
However, HRRR maintaining more westward placement of strongest
bands and this solution is better supported by latest surface obs
and radar mosaic. Will therefore hold off on any expansion/upgrade
this evening and continue to monitor band evolution overnight for
any final headline massaging. Lake effect will gradually wind
down during the day Friday as winds back and dry air advection and
subsidence increase.
&&
.SHORT TERM...(This Evening through Friday)
Issued at 359 PM EST Thu Dec 8 2016
Lake effect snow event will continue to be the primary forecast
concern for the short term. Broad cyclonic flow along with steep low
level lapse rates and weak embedded waves in upper flow have
sustained widespread light snow showers and flurries across the
region through the afternoon. Lake effect snow has had a difficult
time to this point with still some saturation issues at depths
sufficient enough for ice introduction. Mid level trough will drop
southeast across the southern Great Lakes tonight which will
augment depth of lake induced instability by the mid to late
evening hours, with better saturation into at least the lower
portions of the DGZ. In addition, lake aggregate troughing will
becoming sharpened tonight along eastern shoreline of southern
Lake Michigan that should focus lake effect snow bands in the 03Z-
12Z timeframe. Given fetch considerations, still believe the axis
of greatest snow accumulation tonight into Friday should extend
from northern Berrien county extending southeast across Cass/St.
Joseph counties, and possibly into Branch county. Did consider
going with a warning for Branch county, but not quite enough
confidence in this scenario to stray from current advisory. Snow
ratios/accumulation efficiency should start to diminish toward
midday Friday as mid levels begin to dry out and inversion heights
lower. Other than the addition of Hillsdale county to the advisory
this morning, no other changes to current lake effect snow
headlines are anticipated with the afternoon package. Have
maintained maximum axis of 4 to 8 inch accumulation with some
potential of localized higher amounts. Greater impacts now appear
to be more focused for the Friday morning commute as opposed to
early this evening. Wind chills will be the other story through
Friday morning with wind chills persisting in the 5 to 15 degree
above zero range.
&&
.LONG TERM...(Friday Night through Thursday)
Issued at 359 PM EST Thu Dec 8 2016
Lake effect snow showers will likely continue into Friday evening
but should become progressively more focused across southern lower
Michigan as low level flow slightly backs Friday afternoon.
A brief lull in the active pattern is expected late Friday night
through the day Saturday, but focus will shift to the Saturday
night-early Monday period for a possible two pronged event for our
area. Low level return flow will become established quickly
Saturday evening as flow deamplifies and becomes more progressive.
Strengthening low level flow and a strong baroclinic zone will
focus swath of warm advection snow Saturday night into early
Sunday. Still some uncertainty as to the southern extent of this
accumulation, but have hedged on even southern locations receiving
accumulating snow in this first phase. Overall it appears as
though a quick 1 to 3 inch type of accumulation would be possible
Saturday night/early Sunday.
A brief break in snow coverage/intensity is expected later Sunday
morning/early Sunday afternoon, but next progressive eastern Pacific
wave will be amplifying upstream across the central Plains inducing
another round of warm advection-forced snow. Higher chances of snow
should persist into Sunday night/early Monday as actual mid/upper
level wave tracks across the area. Consensus of model guidance has
trended toward the idea of a stronger wave somewhat like old EC
guidance was advertising. This stronger solution and more pronounced
thermal advection may very well also lead to some precip type
concerns and possible transition to rain across the south late
Sunday night, and across central portions of forecast area Monday
before diminishing. Still plenty of uncertainty how this will
unfold this weekend but 36 hour snowfall totals could add up to at
least advisory levels across portions of the area, with early
indications suggest northern half may be most favorable for higher
accumulation. This certainly will be a system to watch over the
next few days.
Medium range models suggest larger scale trough/strong cold air
intrusion may unfold toward middle of next week, with all
indications of much below normal temp pattern setting up middle to
late next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 620 PM EST Thu Dec 8 2016
Low MVFR/IFR conditions will persist through the overnight period
with abundant stratus and lake effect snow in CAA regime. Slow
veering of low level winds still expected to bring an increase in
snow intensity at KSBN (along with slightly lower ceilings) but
did delay the timing of that transition a bit more based on latest
obs and hi-res guidance. Left in prevailing half mile/LIFR visibilities
overnight but that may be too pessimistic and could remain in IFR
category with the heaviest bands just to the NE. For KFWA, still
expect fuel alternate ceilings overnight but may be slightly
delayed. Conditions will gradually improve at both TAF sites
during the day tomorrow as winds back and lake effect gradually
winds down.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Weather Advisory until 4 PM EST /3 PM CST/ Friday for
INZ003>007.
MI...Winter Weather Advisory until 4 PM EST Friday for MIZ080-081.
Winter Storm Warning until 4 PM EST Friday for MIZ077>079.
OH...NONE.
LM...Small Craft Advisory until 7 PM EST Friday for LMZ043-046.
&&
$$
UPDATE...AGD
SYNOPSIS...Marsili
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...AGD
Visit us at www.weather.gov/iwx
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Area Forecast Discussion
National Weather Service Miami FL
806 PM EST Thu Dec 8 2016
.UPDATE...
The 09/0000Z MFL sounding shows around 1500 J/KG of SB CAPE and
a near record PWAT of 2.10 inches. These values are rather
impressive for December and indicate an ample amount of both
moisture and instability in the atmospheric column. This evening,
radar had depicted moderate to heavy rain showers, which affected
eastern Broward and Miami-Dade counties. With the heaviest cells,
rain rates were as much as 2-3 inches per hour causing isolated
incidents of minor street flooding. Through tonight, as a
stationary front remains planted over the Florida Straits, the
threat for showers and slight chance for thunderstorms will
continue. Short term models, including the HRRR and Hi-Res WRF,
show this activity mainly affecting southern portions of the East
Coast metro and adjacent Atlantic waters. Have adjusted PoPs to
better reflect coverage. Otherwise, forecast appears on track.
&&
.PREV DISCUSSION... /issued 655 PM EST Thu Dec 8 2016/
AVIATION...Ongoing shra affecting east coast from KFLL southwards
with -DZ vcnty KPBI with next frontal boundary. Tempo for MVFR
vsbys and cigs at these sites through 03Z-04Z with potential for
IFR in heaviest activity. Prevailing VFR remainder of tonight, but
potential for occasional MVFR cigs will linger through remainder
of TAF cycle. Winds shift NNW this evening 6-9kts, then becoming
NE 11-16kts with gusts to 20kts for all sites after 15Z.
PREV DISCUSSION... /issued 444 PM EST Thu Dec 8 2016/
DISCUSSION...Latest surface analysis indicated a stationary
boundary sitting along the Florida Straits and a cold front draped
across the central Florida peninsula. Warm, moist, and unstable
air ahead of this front led to spotty shower coverage early today,
but no lightning activity was observed. Light flow near the
surface allowed for a waterspout to develop off the Miami beach
coastline at around 11:30 am this morning.
Current radar trends show scattered convection along a southwest to
northeast oriented line affecting portions of Inland Monroe County
to coastal Miami-Dade. According to the latest HRRR and Hi-Res
WRF runs, this activity will persist through tonight over the
aforementioned areas, as well as the local Atlantic coastal
waters. Enough instability is present to maintain a slight chance
for thunderstorms, but none are expected to become strong. On
Friday, as the cold front continues to push south over our region,
surface winds will shift to the north and northeast. In addition,
drier air will be advected in, allowing dewpoints to fall down
into the 50`s across Collier, Glandes, and Hendry counties, and
low to mid 60`s elsewhere. These values are more typical for this
time of year when compared to the last few days. Cooler air will
also spread across South Florida with Forecast high temperatures
around 10 degrees lower than todays. Similar conditions are
expected on Saturday with northeast flow, cooler weather, and an
enhanced chance of showers along the eastern portion of the
peninsula.
Sunday through early next week, long range models depict a surface
high moving off the coast of Virgina/North Carolina. This feature
will generate a period of east and southeast flow over South
Florida. Sufficient low level moisture will continue the daily
chances of showers, mainly affecting the east coast metro and
interior regions. Maximum temperatures early next week are
forecast in the low to mid-80s, around 5 degrees above normal for
this time of year.
MARINE...An approaching cold front will bring increasing
northerly flow later tonight and into Friday. Winds on Saturday
could reach over 20 knots at times with seas reaching the 7 to 10
feet range, especially over the Gulf Stream. Winds and seas should
decrease from Sunday through early next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach 64 72 67 75 / 30 50 50 50
Fort Lauderdale 67 74 65 75 / 50 40 50 50
Miami 67 75 66 77 / 50 40 50 50
Naples 60 69 58 78 / 20 30 10 10
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
GM...None.
&&
UPDATE...27/JT
DISCUSSION...27/JT
MARINE...27/JT
AVIATION...88/ALM
Area Forecast Discussion
National Weather Service Marquette MI
637 PM EST Thu Dec 8 2016
.SHORT TERM...(This evening through Friday)
Issued at 309 PM EST THU DEC 8 2016
WV loop shows deep troughing across eastern Canada and the Great
Lakes. Cold airmass continues to pour across Upper Great Lakes with
h85 temps of -13c to -16c lowering to -16c to -19c by Fri aftn. IR
satellite loop showed colder cloud tops this morning with shortwave
working through then that faded this aftn but more hints of larger
scale forcing is showing up this aftn north of Lk Superior so lake
effect late this aftn into tonight should get a boost from this
forcing. Lake effect thus far today has been cellular instead of
banded, likely due to some shear present in the lake convective
layer and lingering sfc based instability over the land areas.
Earlier enhanced snow over the Keweenaw has shifted more over scntrl
Lk Superior and ncntrl Upper Michigan since 19z/2 pm ET while what
looks like convergence band off Lk Nipigon is quickly developing
ncntrl Lk Superior. Seems the combination of the subsidence to west
of the enhanced snow showers moving over ncntrl Upper Michigan and
lack of larger scale forcing for a time has put crimp on lake effect
over western Upper Michigan with vis sateliite showing less vertical
extent to the clouds there. Overall this event thus far at least
during the day is behaving much more like a fall or spring hybrid
type instead of a more typical setup with multiband and embedded
dominant bands.
RAP and HRRR do show winds becoming unidirectional late this aftn
into early evening and the ambient cape diminishing. Overall expect
the organization of the lake effect to increase through the evening.
Instability into later tonight and Fri remains very favorable with
inversions to at least 8kft/lake induced capes over 500j/kg and much
of the dgz within the lake convective layer. Decent agreement that
enhanced snow will continue to swing across ncntrl Upper Michigan
mainly Alger county late aftn then additional snow showers will
orient toward eastern Marquette into western half of Alger county
this evening. Elsewhere inversions to 5kft and some shear within
convective layer will limit lake effect to moderate instensity.
Stronger convergence will be over far west near IWD.
Later this evening stronger convergence band with origin off Lk
Nipigon and tip of Keweenaw peninsula should setup vcnty of far
eastern Marquette county into western half of Alger county. This
band of snow will be helped along by increasing sfc convergence with
W winds over cntrl Upper Michigan and NNW winds over scntrl Lk
Superior. Expect very fluffy lake effect snow to result with several
inches of accumulation with snowfall rates at least to 2 inches per
hour if not more. This heavy band of snow should persist over
western Alger county on Fri morning before shifting to the east
through the day. Elsewhere on Friday, expect similar setup to the
lake effect with inversions to 5kft and most of that convective
layer within the dgz. Thus, expect additonal fluffy accumulations to
continue. Winds diminish near Lk Superior so blowing snow so become
less of an issue as the day goes on. Since the dominant band is
expected to persist over western Alger county later tonight into Fri
morning, put a lake effect snow warning out earlier today for Alger
county into Friday and Friday night. Otherwise, will let all other
headlines continue as planned at this time.
.LONG TERM...(Friday night through Thursday)
Issued at 309 PM EST THU DEC 8 2016
A flow of arctic air wl dominate the medium/extended range fcst
period, resulting in sustained blo to well blo normal temps. While
no sgnft synoptic scale storms are likely to impact the area during
this time, persistent les thru the period wl likely result in some
sgnft accums over time in areas that see the most persistent snow
showers. The coldest air wl invade the area beginning next Tue, with
wind chills much of the second half of the week at least falling
near advy thresholds away fm the moderating influence of Lk Sup.
Fri ngt/Sat...A cold wnw llvl flow ahead of slowly aprchg sfc hi
pres rdg moving into MN on Sat wl advect h85 temps as lo as -18C to
-20C into the Upr Lks and bring persistent les in the favored sn
belts and aob normal temps. As the rdg shifts slowly to the e on Sat
and the llvl flow becomes more acyc and backs toward the wsw, much of
the les may end expect over the Keweenaw and the far e toward
Whitefish Pt. But a lk induced trof and enhanced llvl cnvgc
accentuated by a land breeze flow may result in some persistent mdt
sn fall in these areas despite the negative larger scale trends.
Presence of the dgz within the llvl moist lyr wl support hi sn/water
ratios 20-30:1 and greater albeit fluffy sn accums. Wl cont with
going les headlines in the favored wnw winds sn belts on Fri ngt over
the w and to the e of Marquette. Future shifts may need to consider
extending the les headlines over the Keweenaw and the far e on Sat.
Sat ngt/Sun...Most of the medium range models, except the 12Z NAM,
continue to track a shrtwv passing thru the ncentral Plains on Sat
toward the Lower Lks by 12Z Sun, with accompanying dynamic forcing
and deep mstr remaining to the s and brushing just the scentral with
some sn Sat ngt into Sun mrng before the shrtwv exits to the e. The
12Z NAM shows a farther n track with widespread lgt pcpn impacting
the entire cwa, including some lk enhanced sn over the e in the
stronger sly flow ahead of the aprchg farther to the n shrtwv. But
considering the persistent wnw flow aloft that would tend to shear
out this shrtwv and force a more srn track, suspect the NAM is on the
wrong track. The other models hint some les may linger near Lk Sup
with a relatively flat synoptic scale pres gradient/lgt llvl winds in
the presence of h85 temps slowly moderating toward -12 to -14C
allowing a lk induced trof to persist and focus this pcpn. The
locations most likely to be impacted by this les would be the
Keweenaw and far ern cwa near Lk Sup. Temps wl remain blo normal. If
the shrtwv tracks farther to the s and accompanying mid/hi clds on
its nrn flank are thinner on Sat ngt, min temps could fall sharply in
some areas.
Sun ngt/Mon...The medium range guidance indicates another shrtwv wl
track thru the Lower Lks during this period, with the sn on its nrn
flank impacting mainly the scentral cwa under the ely flow off Lk MI
to the n of accompanying sfc lo track near Chicago that could allow
for some lk enhancement. While a general acyc h925 flow and h85
temps moderating to arnd -10C wl suppress the pcpn farther to the n,
some lgt les wl probably linger near Lk Sup even as temps ease back
closer to normal on Mon.
Extended...The longer range models show a deepening upr trof over
central and ern NAmerica downstream of a bldg rdg along the w coast
during this period, which wl allow a very cold arctic airmass/well
below normal temps to invade and dominate the Upr Lks. The cold fnt
that wl introduce this very cold air into the area is progged to pass
on Mon ngt, accompanied by only sct-nmrs sn showers in the absence of
meaningful mstr inflow. As h85 temps fall toward -25 to -30C under a
steady w-nw flow on Tue thru Fri behind the fropa, expect wdsprd les
in the favored sn belts and wind chills to at least fall toward advy
thresholds away fm lk moderation.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 634 PM EST THU DEC 8 2016
Lake effect snow continues. Some blowing snow as well but with winds
less than 20 kts, main vsby reduction is from the snow. Overall
expect the snow showers to produce IFR vsby with MVFR cigs. Vsby
may trend toward VFR later tonight at SAW and MVFR to VFR later
tonight into Fri at IWD as winds back more nw or wnw. &&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 309 PM EST THU DEC 8 2016
NW winds will reach 30 kts through Fri with gale gusts to 35 kts
still possible over central and eastern sections, especially in the
vcnty of stronger lake effect snow showers over cntrl sections.
Winds diminish to less than 20 kts Sat through Mon. W to NW winds
increase to 30 kts by later Tue with gales possible Tue night into
Wed as bitter cold air arrives. There is a good chance of heavy
freezing spray by the middle of next week.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Lake Effect Snow Warning until 7 AM EST /6 AM CST/ Saturday for
MIZ001>003-006-009.
Lake Effect Snow Advisory until 7 AM EST Saturday for MIZ007-084-
085.
Lake Effect Snow Warning until 7 PM EST Friday for MIZ004-005.
Lake Effect Snow Advisory until 7 PM EST Friday for MIZ013.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLA
LONG TERM...KC
AVIATION...Voss
MARINE...JLA
Area Forecast Discussion
National Weather Service Pittsburgh PA
940 PM EST Thu Dec 8 2016
.SYNOPSIS...
Periodic snow showers are expected into the weekend, especially
north of Pittsburgh. All locations are likely to receive
accumulating snow on Sunday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
850mb flow veering northwest overnight on the backside of upper
trough crossing the northeast will result in continued scattered
snow showers across the forecast area overnight. However, without
good wind alignment vertically, inversions remaining below 5000
ft, the best lift outside of the dendritic growth zone, and
surface dewpoint depressions holding around 10 degrees on average,
confidence remains high that accumulations overnight should not be
much more than an inch or two north of Interstate 80 and lesser
totals to the south.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Surface winds finally take on a northerly component on Friday,
particularly during the late morning and early afternoon. This is
expected to be the period when snow accumulations would be the
highest. Continuing the trend of the previous forecast shift, only
minor changes were made to snowfall accumulations. While there
will be an extended period of snowfall, there is no period with
especially high snowfall expected. Although accumulations across
northern portions of Mercer, Venango, and Forest counties could
reach advisory levels of three inches per 12 hours on Friday, do
not think that county averages will be high enough to justify any
advisories. Perhaps the one exception might be in Forest county,
with the 18Z RAP suggesting that a dominant band may develop to
the east and move into the county by 15Z, a forecast that is also
suggested by the 12Z GFS. This will bear watching by future
shifts. With the arrival of today`s trough, an extended period of
below normal temperatures has begun, with temperatures about ten
degrees below normal.
As winds begin to develop a southerly component once again Friday
night, snowfall accumulations should begin to diminish. As high
pressure builds in from the southwest Saturday, coverage of snow
showers should really decrease, with any minor accumulations limited
to locations north of Interstate 80. The break in precipitation will
be short lived as more precipitation will lift across the region
Saturday night into Sunday. This is expected to bring snow to all
locations, although models are still differing in how far south
precipitation will extend. So far it appears that snowfall totals
would be highest in the north, with minimal snowfall accumulations
to the south where rain may mix in. Below normal temperatures
will continue through this period.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
12Z GFS/ECMWF are in relatively good agreement that a warm front
will lift across the region Sunday night into Monday, and until
the entire region is in the warm sector, a period of freezing rain
could be possible before snow changes over to rain. Did not have
enough confidence in this to include freezing rain in the forecast
at this time. The surge of warm air should bring temperatures back
towards normal on Monday. Model agreement drops after the cold
front moves through Monday night, and while models both show high
pressure developing in the Plains and a storm system moving up the
East Coast, the differences in where those systems track result in
little agreement on precipitation, and have stayed close to the
SuperBlend with chance pops through much of the rest of the
forecast. After Monday`s near normal temperatures, temperatures
will drop back below normal, with another reinforcing shot of cold
air likely to drop many locations into the single digits Wednesday
night and keep some locations in the teens on Thursday.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
MVFR to low VFR stratocu ceilings are expected through Friday
under broad upper troughing and cold W-NW flow. MVFR to local IFR
snow showers are expected overnight and Friday as a weak surface
trough crosses. This trough should veer boundary layer winds to
the WNW, resulting in some lake enhancement and localized IFR
restrictions for ports N of I 80.
A tight pressure gradient should result in gusty west winds
through the period.
.OUTLOOK...
Restrictions are likely through early Saturday under upper
troughing, and again Sunday and Monday with crossing low pressure.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...None.
WV...None.
&&
$$
Area Forecast Discussion
National Weather Service Mount Holly NJ
918 PM EST Thu Dec 8 2016
.SYNOPSIS...
An area of low pressure will continue to slowly drift across eastern
Canada through Friday, and offshore by Saturday. With high
pressure to our west, strong west to northwest flow will remain
through Saturday. A warm front is expected to lift across the area
Sunday night, before an area of low pressure moves north of the
region around Monday. This system will pull a cold front across
the area Monday, then another quick moving frontal boundary may
move across the area around Tuesday night.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Note: tonight`s low temp fcst at PHL will be the coldest of the
season so far at PHL and remember last winter, it didn`t drop
into the 20s until January 4th 2016!
Tonight...A light west-northwest breeze except PHL may gust 18-20
kt all night as well as adjacent all bodies of water as boundary
layer temps show increasing land-sst differential and resultant
enhanced land breeze effect, near the water. Clouds across
southern New Jersey and Delaware are likely to slowly erode over
the next few hours. Radiational cooling slightly delayed in those
locations.
Exception to the mostly clear skies: near the Poconos where lake
effect clouds arrive and then flurries should eventually develop
there sometime tonight.
Fcst was a 50 50 blend of the 12z GFS/NAM mos guidance.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Cold air advection and lake effect streamers of moisture, flurries
and snow showers from the Great Lakes combined with the cold
trough aloft increase the snow squall probabilities tomorrow and
so at least sct flurries to near I-95 (not expecting flurries or
sprinkles along the coast) and suspect small accumulation in
parts of Poconos Friday afternoon. A snow map will post shortly
followed by snow probs around 5PM for this first little terrain
related accumulation event.
Otherwise...mostly sunny skies to start (mo cloudy Poconos) becomes
considerable cloudiness everywhere during the afternoon. Breezy
with west northwest wind gusts 25 to possibly 30 mph.
Forecast basis was a 50 50 blend of the 12z gfs/nam MOS and added
a degree to the max T per the 12z/8 EC 2m temps.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Strong nwly flow will continue Fri night into Saturday a large
area of high pres builds to the w and a departing low moves away
to the e. This will keep things relatively dry but cold and
breezy. There could be a passing flurry or snow shower but that
should be the extent of any precip.
The high then moves over us Sat night and the wind will decrease.
We should be in for a cold night, before the high moves ewd.
As the high moves away, low pres will take shape over the plains
and head toward the Oh vly on Sun and drag a wmfnt thru the
region Sun night. Precip will begin acrs the area later Sun into
Sun night. There are still some disagreements in the mdls as to
the timing and path of the low, which will ultimately impact what
type of precip falls and where. However, it does appear that the
bulk of the precip will fall Sunday night into early Monday.
Temps will be cold enough Sunday night n and w for pretty much all
snow and a plowable event which would impact the Monday mrng
commute. Further s, there may be some low accumulations before a
changeover to rain on Monday. Acrs srn and ern areas, we shud
expect mainly rain.
The cdfnt assocd with the low will move thru on Mon and end the
precip. Then, dry wx is expected for later Mon into Tue.
Then, twd the end of the pd, there is the potential for another
mixed precip event. The GFS is faster bringing this sys in as
early as Wednesday morning, while the ECMWF holds off until later
Wed. Again, temps will be warm enough s and e for mainly rain,
while n and w it would likely be wintry precip. Again, the timing
and track of the sys will determine ultimately who gets what and
it is a week away but clearly we are entering a more active wx
patn.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Tonight: VFR, high scattered deck eroding for the southern
terminals of KMIV and KACY. West-northwest winds around 10 knots
with a few higher gusts. A mid VFR deck will likely encroach
toward KABE and KRDG, will look into inclusion with 06Z TAFS at
these sites.
Friday...Generally VFR sct-bkn aoa 4000 ft, although CIGS may
briefly lower to MVFR in scattered snow showers e PA higher terrain.
An afternoon flurry or sprinkle is possible southeastward to ILG-
PHL-TTN. Gusty west to northwest winds 22-30 knots.
OUTLOOK...
Fri night - Sat...Generally VFR, although cigs may occasionally
lower to MVFR. Scattered showers or flurries/sprinkles are
possible during the daytime of each day which may temporarily
lower conditions. Gusty w to nw wind 15-25 kts. High confidence.
Sun...VFR early, possibly lowering to MVFR by the afternoon. Rain
or snow psbl late in the day. Moderate confidence.
Sun night-Mon...Conds lower to MVFR then IFR. RA and SN becoming
likely, best chc for SN n. Most of DE and MD will stay all rain.
Any SN over srn NJ and sern PA will change to RA durg Mon.
Accumulating snow over nrn and wrn areas. Mdt confidence.
&&
.MARINE...
Based on the latest data is it looking more questionable that we
will see gale gusts. Soundings from the HRRR and RAP show the
potential for the highest wind gusts around 30 knots. these so far
have appeared slightly underdone tonight with both Ship John and
Cape May gusting slightly over 30 knots. However, a few 35 knot
gusts can not be ruled out so will leave the gale warning up.
For Friday...the winds should ease 3 kts or so on DE bay but some
of the guidance is suggesting increasing wind NJ coast, especially
NNJ later in the day. Therefore the gale watch.
OUTLOOK...
Fri night-Sat...Gale watch much of NJ coast early Fri night. SCA
in effect upper De Bay through Friday night, which may need to be
extended into Saturday. Atlc De and Cape May Atlc waters will
probably be SCA Fri night.
Saturday night...Winds expected to drop below SCA levels, but
pick up again late Sunday.
Sunday-Sunday night...Winds may increase and approach SCA levels.
Monday...SCA conds psbl.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Gale Watch from 6 AM EST Friday through late Friday night for
ANZ450>452.
Small Craft Advisory until 6 AM EST Friday for ANZ450>452.
Gale Warning until 6 AM EST Friday for ANZ431-453>455.
Small Craft Advisory until 6 AM EST Saturday for ANZ430.
&&
$$
Synopsis...Nierenberg
Near Term...Drag/Gaines
Short Term...Drag
Long Term...Nierenberg
Aviation...Drag/Gaines/Nierenberg
Marine...Drag/Gaines/Nierenberg
Area Forecast Discussion
National Weather Service Seattle WA
322 PM PST Thu Dec 8 2016
.SYNOPSIS...A front will move through Western Washington tonight.
Snow will turn to rain on the coast this evening and the snow
will change over to rain for most of the interior lowlands overnight.
The Bellingham area could see a mix of winter precip through Friday
morning as Fraser outflow decreases. Rainy milder weather will
persist
for the remainder of Friday through the weekend. Cold air over
British Columbia will likely drop south again around Monday.
&&
.SHORT TERM...The first band of snow is pretty narrow so far but
the precip will march north through evening and the front seems
to be in a good region relative to the jetstream and the upstream
upper trough. The satellite picture looks more impressive than
the radar and I think the front will develop a bit through evening
and the forecast for much of the lowlands is for 1-3" of snow. The
Hood Canal area is the only forecast zone with a winter storm
warning and up to six inches is expected in that area. Most of
Western Washington has a winter weather advisory, and that goes
for the mountains too where windy conditions will make for poor
visibility.
The models have been consistent in warming the air up through Friday
and whether you look at 850mb temps or 1000-850mb thickness the
lowlands of Western Washington will be back into rainy showery
maritime air for the weekend. The stretched out nature of the front
is a little unusual and snow lovers can imagine the front stops its
northward progression, but the global models clearly show the broad
upper trough offshore amplify a little and sweep in over the region
--so moist and milder air is unavoidable. The exception will be the
Bellingham area which can flirt with freezing temps in even shallow
Fraser outflow. 19
.LONG TERM...An upper level trough and cold front will cross Western
Washington on Monday maintaining a cool and unstable air mass.
There is a chance of showers across the region with snow showers
possible in the north interior and in the East Puget Sound
Lowlands where snow levels will remain low. Snow accumulations
look light at this point as the precip will be fading out. Strong
high pressure over interior B.C. will bring another blast of
Fraser river outflow to western Whatcom county.
Dry but cool weather will prevail through the rest of the period
as we remain in an offshore flow pattern. Temperatures will remain
below normal with highs only in the 30s and lows mainly in the
20s. 33
&&
.AVIATION...Warm front will lift northward through western
Washington this evening, with precip spreading northward through
the region. Precip will start as a few hours of snow, then change
to rain late this evening and overnight. In a few pockets where
surface temperatures remain at or below freezing, a little
freezing rain is possible overnight. The TAF for Olympia is the
only one reflecting this. An upper level impulse will enhance
rainfall around mid-day on Friday.
KSEA...Radar shows the leading edge of snow between OLM and TIW
advancing north. The 22z HRRR shrivels up the first round of snow
just as it tries to reach SEA around 430 pm. A few flakes are
possible, but will likely have to wait for another surge of precip
around 03z-05z to bring accumulating snow to the terminal. Snow
will last for a few hours before transitioning to rain overnight.
Not expecting freezing rain at the terminal as temperatures
overnight will be slowly rising into the mid 30s (Fahrenheit).
Otherwise, easterly winds are expected with gusts near 25 knots,
but speeds will ease a bit as the direction takes on an increasing
southerly component. Occasional rain will prevail Friday with
prevailing cigs from 020-030.Haner
&&
.MARINE...Strong offshore flow will ease late tonight as a warm
front lifts northward through the waters. Following the warm
front, winds will become more southerly. A weakening 1000 mb low
will pass eastward across southern Vancouver Island on Saturday
afternoon. It will be preceded by increased southerlies, then
followed by a surge of westerlies down the Strait on Saturday
night. Weak gradients will prevail during the day Sunday. Another
round of Fraser Outflow winds will bring a marked increase in NE
wind over the waters on Sunday night and Monday.Haner
&&
.HYDROLOGY...no flooding is expected over the next week.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 8 AM PST Friday for Admiralty
Inlet Area-Bellevue and Vicinity-Bremerton and Vicinity- East
Puget Sound Lowlands-Eastern Strait of Juan de Fuca- Everett and
Vicinity-Lower Chehalis Valley Area-San Juan County-Seattle and
Vicinity-Southwest Interior-Tacoma Area- Western Skagit County-
Western Strait of Juan De Fuca.
Winter Weather Advisory until 3 AM PST Saturday for Cascades of
Pierce and Lewis Counties-Cascades of Snohomish and King
Counties-Cascades of Whatcom and Skagit Counties-Olympics.
Winter Storm Warning until 8 AM PST Friday for Hood Canal Area.
Winter Weather Advisory until noon PST Friday for Western
Whatcom County.
Wind Advisory until 8 PM PST this evening for Western Whatcom
County.
Wind Advisory until midnight PST tonight for East Puget Sound
Lowlands-North Coast-Western Strait of Juan De Fuca.
Wind Advisory until 7 PM PST this evening for Central Coast.
PZ...Gale Warning until 3 AM PST Friday for Central U.S. Waters
Strait Of Juan De Fuca-Coastal Waters From Cape Flattery To
James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To
James Island Out 10 Nm-Coastal Waters From James Island To
Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville
To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point
Grenville To Cape Shoalwater Out 10 Nm-West Entrance U.S.
Waters Strait Of Juan De Fuca.
Small Craft Advisory until 6 AM PST Friday for Coastal Waters
From James Island To Point Grenville Out 10 Nm.
Small Craft Advisory until 9 PM PST Friday for East Entrance
U.S. Waters Strait Of Juan De Fuca.
Gale Warning until 10 PM PST this evening for Northern Inland
Waters Including The San Juan Islands.
Small Craft Advisory from 6 PM this evening to 9 PM PST Friday
for Admiralty Inlet.
Small Craft Advisory from noon to 9 PM PST Friday for Puget
Sound and Hood Canal.
&&
$$
www.weather.gov/seattle
You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.html
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
713 PM EST Thu Dec 8 2016
.UPDATE...
00Z water vapor and H4 RAP analysis showing a rather unamplified
upper level pattern across the CONUS this evening with broad
longwave ridging over the western States...followed by broad
downstream troughing through the central and eastern portions of
the country. Sharpest troughing is pivoting through the Northeast
States this evening...delivering a shot of winter-time air to the
north-central and northeast part of the country. The base of this
eastern trough will pivot through the southeastern States and
Florida peninsula overnight and Friday morning. The weak influence
of this passing trough and associated mid/upper jet dynamics are
helping to bring general weak lift to the central and eastern Gulf
of Mexico. Have seen cooling and expanding clouds in satellite
imagery the past several hours...as the weak large-scale synoptic
lift is coupled with weak mid-level upglide over the Gulf. All
this...will add up to keep the clouds rolling overhead the next
12-24 hours...mainly above 7-10KFT. Most of the NWP guidance
members are producing just enough synoptic lift with the passing
upper trough/diffluent flow later tonight and Friday morning to
squeeze out scattered light showers. Most spots will likely see a
shower or two...especially from the I-4 corridor
southward...however...qpf totals are going to be very low.
Underneath all of this mid/upper level "action"...a cold front
will be slipping southward through the Florida peninsula during
the overnight. This front will not be delivering the degree or
cold air being experienced to our north...but it will be a good
shot of cool air for Florida. We will all notice the cooler air
settling in tomorrow...especially Friday night/Saturday morning.
All we talked about above slowly exits out of the region during
the second half of Friday...allowing high pressure and dry
conditions to dominate our forecast for Friday Night through the
upcoming weekend. Although it will be a good shot of cooler air
behind this front...the warmup will begin quickly during Saturday
afternoon and continue into the second half of the weekend.
Have a great rest of your evening everyone! Remember...you will
likely need to bundle up a bit if headed out early Saturday
morning. Plan accordingly.
&&
.AVIATION...
Despite plenty of mid-upper level clouds in the forecast through
the TAF period...no significant restrictions are expected.
Forecast for all terminals will be prevailing VFR through Friday.
As mentioned...plenty of clouds aloft...with a few light showers
overnight into the first half of Friday...but no heavy rainfall
expected. Winds steady from the north and northeast through the
period and becoming gusty between 10-15 knots later tonight
through Friday.
&&
.Prev Discussion... /issued 204 PM EST Thu Dec 8 2016/
SHORT TERM (Tonight - Friday)...
A closed upper low sits over central Quebec with troughing extending
through the Great Lakes region. The trough moves slowly eastward by
Friday afternoon and deepens over northern Florida. On the surface,
a disturbance develops along a stationary frontal boundary extending
over southern Florida and into the Gulf of Mexico. This will bring
our highest rain chances through the period with 20-30 POPs from
Tampa northward and 30-40 POPs south of Tampa. This boundary moves
south of Florida by late Friday as a 1036 MB high pressure center
over the central U.S. moves eastward and takes control of the
weather over Florida. The gradient between the boundary over
southern Florida and strong high pressure up north will produce
Small Craft Advisory winds and seas over the coastal waters by
starting Thursday evening and lasting through Saturday afternoon.
This will also allow for some of the coolest air we`ve seen this
season to advect into the region. The high and low temps on Friday
and Saturday will be 6-10 degrees below average for this time of
year.
LONG TERM (Friday Night through Thursday)...
Broad cyclonic flow will engulf much of the eastern half of the
CONUS at the start of the medium range period, with a substantially
cold area of high pressure across much of the north central and
eastern U.S. Meanwhile...fast zonal flow will develop across the
northern and central Rockies...setting the stage for a number of
compact storm systems over the coming days.
Friday night will feature rather chilly overnight temperatures, as
high pressure settles into the southeastern states. While it will
certainly be cold, much of the coldest air will remain well to the
north of the Florida Peninsula, affecting mainly the Panhandle and
Georgia/Florida border regions. Temperatures over interior sections
of the Nature Coast and interior north Florida may fall to near
freezing or perhaps a degree or two below for a brief time Saturday
morning, but it currently looks that widespread freezing conditions
are unlikely. Further south, expect lows to only fall into the low
to mid 40s...with 50s south of I-4.
Within a progressive upper level flow pattern, we look to modify
rather quickly with temperatures rebounding into the 60s and low 70s
Saturday afternoon. The warming trend will continue into early next
week, as low to mid 70s return Sunday, and low 80s make a comeback
Monday and Tuesday. This will all occur as surface high pressure
slips eastward, and a return of moist east to southeast winds occurs
ahead of another cold front set to approach the region mid to late
next week.
AVIATION...
VFR conditions will prevail through 06Z. At that time, cloudiness
will increase with a BKN deck around 3000 feet developing. Will also
bring in VCSH at the northern terminals after 06Z and the southern
terminals around 08Z. Winds will remain out of the north northeast
in the 5 to 10 knot range. No other aviation impacts expected.
MARINE...
A tightening gradient between a frontal boundary over southern
Florida and strong high pressure over the central U.S. will create
some hazardous boating conditions over the coastal waters starting
later this evening. Gusty north-northeast winds has prompted the
issuance of a Small Craft Advisory beginning later this evening and
continuing through Saturday afternoon. The gradient slackens at that
time, but will likely still remain at cautionary level for the outer
coastal waters through Sunday morning. As the high slips east off
the mid Atlantic coast, the winds will shift to the east southeast
and remain around 10-15 knots through the beginning of next week.
FIRE WEATHER...
Drier air will filter into the northern half of the Florida
Peninsula by Friday afternoon. Relative humidity percentages will
drop into the mid 30s for a few hours over parts of the Nature
Coast, and into the mid to upper 40`s as far south as the Tampa Bay.
Elsewhere, relative humidity will only bottom out in the 50s and
60s. Relative humidity will then increase through the weekend with
no fire weather impacts expected.
&&
.Preliminary Point Temps/PoPs...
TPA 53 63 50 71 / 30 30 0 0
FMY 55 67 57 76 / 20 30 10 10
GIF 52 62 49 70 / 20 30 0 0
SRQ 56 65 52 74 / 30 30 0 0
BKV 48 60 43 68 / 20 20 0 0
SPG 54 62 52 69 / 30 30 0 0
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...Small Craft Advisory from 10 PM this evening to 1 PM EST
Saturday for Coastal waters from Bonita Beach to
Englewood FL out 20 NM-Coastal waters from Englewood
to Tarpon Springs FL out 20 NM-Coastal waters from
Tarpon Springs to Suwannee River FL out 20 NM-Waters
from Bonita Beach to Englewood FL out 20 to 60 NM-
Waters from Englewood to Tarpon Springs FL out 20 to
60 NM-Waters from Tarpon Springs to Suwannee River FL
out 20 to 60 NM.
&&
$$
UPDATE/AVIATION...Mroczka
Previous Discussion...Wynn/Austin