Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/22/17
Area Forecast Discussion
National Weather Service Gaylord MI
950 PM EST Tue Nov 21 2017
.UPDATE...
Issued at 949 PM EST Tue Nov 21 2017
In eastern upper MI...one dominant band has been slowly pushing
eastward across Luce and western Mackinac Co, and is now edging
into far western Chippewa. Surface winds are already going a bit
more northerly at the twin Saults, implying it will be struggle to
get better lake effect that far east. But that also implies that
convergence to the west could be further enhanced as drainage flow
increases as the pressure gradient relaxes. Will keep potential
snow amounts tonight in western Chip as high as 4 inches. Would
note that the HRRR has very isolated liquid QPF totals up to 0.50
inches from time to time in the Whitefish Bay area. Would also
note that the HRRR has been a little over-exuberant in lake effect
events so far this season.
In northern lower...after the late afternoon and early evening
featured nothing more than flurries, lake effect has intensified
since 8 pm. Dominant band (connecting up to the Superior band
mentioned above) punching into the GLR area presently, though is
still translating eastward. Another stronger band is trying to
organize further west, over northern Gd Trav Bay. Will kick snow
amounts a little higher in nw lower, with some very localized 2-4
inch accums in parts of Charlevoix/Antrim/Kalkaska/Otsego Cos.
None of the above quite rises to the level of an advisory,
especially given the slackening gradient and less blowing/drifting
with time.
&&
.NEAR TERM...(Tonight through Wednesday)
Issued at 309 PM EST Tue Nov 21 2017
High impact weather potential: Minimal.
Pattern synopsis and forecast:
A mid level trough axis was working into the region, with the
associated strong cold front now south and east of nrn Michigan.
Forcing with the trough was a bit better than expected with DPVA
working with RUC analyzed stronger upper divergence. This allowed
for some flurries to develop over nrn lower and some frontally
forced precipitation just scraping Gladwin and Arenac counties.
Otherwise the main show continues to organize itself. Strong cold
advection was allowing for temperatures to fall through this
afternoon, with NW flow lake effect snows already developed and
pushing into eastern upper Michigan. Over the next couple hours,
lake effect will get going over NW lower as the deeper, but not
impressive moisture arrives. High pressure and clear skies were seen
in the middle of the country.
Cold air continues to pour into the region tonight, maxing out
around daybreak Wednesday at -12C to -14C while gusty NW winds taper
down. Moisture is not deep within the convective BL, and inversion
heights vary amongst different data sets. Average inversion heights
are around 5kft or so, with the best of the snows looking to set up
closer to evening. This ought to be the better snow intensities, but
unidirectional flow and a tap from Lake Superior result in hi-res
data suggesting a couple of dominant bands again, while the rest
of the LES likely being quite light as moisture shallows some.
Through Wednesday, the higher pressure will work into the region
with low level winds backing more west then possibly a little
south of west. Continued shallowing moisture will make this more
of just a nuisance snow/flurries type deal with minimal
accumulations. For the remainder of this afternoon through
tonight, 1 to maybe 3 inches in the NW flow snowbelts of nrn
lower, and 1 to 4 inches across eastern upper.
&&
.SHORT TERM...(Wednesday night through Friday)
Issued at 306 PM EST Tue Nov 21 2017
...More Changeable Weather...
A weak short wave moving through the flow will lead to a chance for
a few light snow showers on Thanksgiving Day, otherwise quiet but
chilly holiday weather is expected. Low pressure then approaches
from the west Thursday night into Friday with strong warm air
advection out ahead of it. This will lead to increasing chances for
rain showers (mainly Friday afternoon). Temperatures will be near
normal through Thursday night then rise to a few degrees above on
Friday.
.LONG TERM...(Friday night through Tuesday)
Issued at 306 PM EST Tue Nov 21 2017
...A Continued Roller Coaster Ride...
The up and down weather pattern is expected to continue through at
least the beginning of next week. Colder air moving in behind low
pressure moving by to the north will likely change rain over to a
period of snow early Saturday. This will be followed by a shot of
colder air and lake effect snow showers Saturday into early Sunday.
Model trends are for less available moisture but am still concerned
that we could see icy spots developing early Saturday as
temperatures drop to near freezing followed by accumulating lake
effect snow and blowing snow Saturday into Saturday night as winds
become quite gusty. Lingering lake effect should diminish Sunday due
to increasing ridging aloft. Turning milder once again Monday into
Tuesday with another chance for rain Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 649 PM EST Tue Nov 21 2017
MVFR tonight at PLN, otherwise mostly VFR with light lake effect
snow.
Cooler air continues to enter the region, behind a cold front
exiting the eastern Great Lakes. Lake effect clouds and snow
showers will be prevalent tonight, but will dwindle on Wednesday.
VFR conditions will be most common, but MVFR conditions may be
seen at times. MVFR conditions will actually be prevalent at PLN
tonight.
Nw winds will remain gusty this evening, then weaken while backing
to the sw thru Wed afternoon.
&&
.MARINE...
Issued at 306 PM EST Tue Nov 21 2017
After a strong cold front crossed the region earlier today, WNW
winds developed and remained quite gusty. For most areas across
Lake Michigan, gales were not being met based on area observations,
so will allow that headline to expire. Gales are likely to continue
through evening in Whitefish Bay and in and around the Presque Isle
Light area. Advisories through tonight all other areas. Higher
pressure and sub advisory winds expected with higher pressure
Wednesday, before winds ramp back up Wednesday night ahead of the
next cold front for potential new advisories.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 6 AM EST Wednesday for LHZ345-346-349.
GALE WARNING until 11 PM EST this evening for LHZ347-348.
LM...SMALL CRAFT ADVISORY until 6 AM EST Wednesday for LMZ323-341-342-
344>346.
LS...SMALL CRAFT ADVISORY until 6 AM EST Wednesday for LSZ322.
GALE WARNING until 11 PM EST this evening for LSZ321.
&&
$$
UPDATE...JZ
NEAR TERM...SMD
SHORT TERM...AS
LONG TERM...AS
AVIATION...JZ
MARINE...SMD
Area Forecast Discussion
National Weather Service Grand Rapids MI
944 PM EST Tue Nov 21 2017
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 300 PM EST Tue Nov 21 2017
Light lake effect snow showers and flurries will develop tonight
but with very little to no snow accumulation. A weakening clipper
system may also bring a few light snow showers and flurries mainly
north of Muskegon during the early morning hours of Thanksgiving
Day.
&&
.UPDATE...
Issued at 945 PM EST Tue Nov 21 2017
Really for the most part our on-going forecast is working out
nicely. We had and still have a 50% chance of snow showers along
the lake shore and we are seeing very light snow showers on the
radar and here at GRR we are getting flurries (10SM -SN in GRR
obs). Also the latest run and numerous previous runs of the HRRR
and for that matter the NAM3km and the RAP model, not to mention
the HiRes ARW and HiRes NMM all show light snow showers mostly
west of US-131 and really near US-31 most of the overnight. There
is decent lift seen near the lake shore in those models and while
the -12c does not get reached the -10/-11 does with RH values over
90%. Since we are already seeing snow, that is clearly close
enough to believe our on-going forecast is on track.
The one thing I did change is I added more cloud cover to
Wednesday forecast and that is based on the 1000mb to 900mb RH,
which is mostly above 90% to US-131 nearly all day. Typically that
sort of RH means nearly overcast. That being so I lowered the
highs about 2 degrees due to more cloud cover.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 300 PM EST Tue Nov 21 2017
A relatively tranquil wx pattern will continue through the short
term fcst period. A few light northwest flow lake effect snow
showers and flurries will develop tonight as h8 temps fall to -11
to -13 C yielding delta t/s in the upper teens.
However lake effect snow shower potential is mitigated by several
factors including lack of deeper moisture and low inversion heights
of only around 4-5 kft agl. Areas mainly near to west of US-131 will
have very light snow accumulations of under an inch. Very little to
no snow accumulation is fcst over our eastern fcst area.
Flurries or very light snow showers will linger near to west of US-
131 into early Wednesday morning before ending. Dry wx is forecast
Wednesday afternoon through Wednesday evening.
A weakening clipper system will bring a few light snow showers
and flurries to our northwest fcst area (mainly north of KMKG)
mainly between 06Z and 12Z Thursday with only a few tenths of an
inch of snow accumulation up there. Other than that tranquil and
dry wx is forecast for the Thanksgiving holiday and for Thursday
night.
.LONG TERM...(Friday through Tuesday)
Issued at 300 PM EST Tue Nov 21 2017
No major systems are expected in the long term but the pattern of a
cold front every few days will continue. No significant cold air
outbreaks will occur since the polar jet stays north most of the
time which also means minimal lake effect precipitation.
Out next cold front is progged to come through on Friday night and
out ahead of it guidance brings in H8 temps around 10C on Friday.
That should lead to high temps at or above 50 although breezy
conditions will make it feel colder.
Model consensus is for high pops for light rain showers with fropa
on Friday night, then a chance of mixed rain and snow showers in the
colder air behind the front Saturday. Little or snow accumulations.
Sunday and Monday look dry with moderating temperatures as sfc high
pressure moves from the Plains to the mid Atlantic. Another cold
front approaches on Tuesday although timing is low confidence at
this time. ECMWF suggests highs in the 50s in the warm advection
ahead of this next front.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 638 PM EST Tue Nov 21 2017
With the cold front through we will see a shallow layer of lake
effect stratocumulus clouds with mostly VFR ceilings through most
of Wednesday. Winds will largely be northwest from 5 to 15 knots.
There will be some flurries around this evening into early
tonight, mostly at MKG so I put VCSH but even there whatever
occurs should be so light that visibilities should stay 10+
miles.
Some clearing is expected toward 00z Thursday but that can be a
feature in the next set of TAFs.
&&
.MARINE...
Issued at 300 PM EST Tue Nov 21 2017
A small craft advisory remains in effect through tonight into
early Wednesday morning. Wave models continue to suggest wave heights
will finally subside to below sca criteria after 13Z Wed. However
wave heights will ramp back up on Thanksgiving day when another
small craft advisory will likely be needed.
&&
.HYDROLOGY...
Issued at 100 PM EST Tue Nov 21 2017
Several rivers remain at advisory/action stage level as runoff
continues from rain that fell over the weekend. Water levels in
these and other rivers will remain fairly steady or slowly fall
through the end of the week. Rain and snow showers today and tonight
will only provide light amounts of precipitation, and will not have
an impact on water levels in rivers, creeks and streams. Additional
flooding is not expected.
A few more rounds of light rain/snow are expected through the end of
the week, but should not have a significant impacts on river levels.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 7 AM EST Wednesday for LMZ844>849.
&&
$$
UPDATE...WDM
SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Meade
AVIATION...WDM
HYDROLOGY...HLO
MARINE...Laurens
Area Forecast Discussion
National Weather Service Wilmington NC
647 PM EST Tue Nov 21 2017
.SYNOPSIS...
A coastal wave will move northward overnight, bringing a chance
of showers. A cold front will press southward across the
Carolinas on Wednesday. A few coastal showers are possible
Thanksgiving Day, as a low pressure wave passes offshore.
Seasonably cool and dry conditions will prevail into the weekend
and early next week, as a series cold fronts sweep off the
coast, and low pressure areas remain offshore. Strong Canadian
high pressure will pass across the area early next week.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 630 PM Tuesday...Isolated light showers moving ashore from
the south this evening. HRRR handling situation quite well so
far and has rain coverage expanding through the evening hours
from S to N, peaking around midnight or so with a focus on the
coast, then out of the area by around daybreak. This scenario is
close to what we already have in the forecast so if any changes
are made they will be minor tweaks to coverage and timing. Still
looks like a low QPF/stratiform event. Previous discussion from
this afternoon follows:
Coastal trough sitting offshore will attempt to move onshore
this evening and confidence is low on whether or not this will
happen. Should it move onshore the most noticeable difference
would be increased rainfall rates within showers east of the
trough as opposed to lighter rain on the west side. In the grand
scheme of things the increase in rainfall would not be
significant, a couple tenths of an inch at most as opposed to
around a tenth of an inch. Temperatures would also briefly spike
up as the trough moves onshore.
Regardless of where the trough ends up this evening it will be
lifted north and then pushed east later tonight. A shortwave
rounding the base of the high amplitude 5h trough over the
eastern CONUS will move northeast just off the Southeast coast.
Surface wave/low associated with the wave will lift northeast
along the coastal trough, helping move the feature out of the
region. Light rain will spread over the area this evening as
isentropic lift on the 295k surface increases and deeper
moisture arrives. Precipitable water increases from half an inch
around midday to around 1.3 inches overnight which should allow
for measurable rainfall across much of the area. Rainfall
amounts and coverage will be highest closer to the coast.
Isentropic lift starts to wind down around midnight with any
rainfall expected to come to an end shortly thereafter. Westerly
flow below 7k ft as the surface and mid-level wave exit help
dry the region out during the second half of the overnight
period. Lack of any significant cold advection, combined with
lingering cloud cover and mixing helps to keep lows above climo.
Cold front trailing northern stream low moving into eastern
Canada late tonight moves across the area Wed. The front is
starved of moisture by the time it reaches the area and it will
pass dry while helping to clear out any lingering clouds. Some
modest cold advection behind the front but the air arrives too
late to have any real impact on highs, which will end up a
couple degrees above climo. Winds will become breezy following
the passage of the front in the afternoon, especially as
sunshine increases and stronger winds aloft start mixing to the
surface.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 230 PM Tuesday...H5 ridge across the Desert SW and a
trough will be positioned across the Eastern U.S. through the
short term period. At the surface, high pressure will prevail as
it builds across the Carolinas, possibly supplanting the areas
of low pressure far enough offshore to limit rainfall chances
during Thanksgiving. Isentropic lift is shown to be lacking as
well. Currently, we will maintain the highest POPs across the
coastal zones during Thanksgiving and keep QPF low unless the
low can evolve farther west. Maintained a blend of MET/MAV
temperatures through the period.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 230 PM Tuesday...A progressive yet overall dry extended
forecast prevails with seasonably cool temperatures, and dry
largely in part, because the atmosphere remains dry above 8000
feet. A moderately strong cold front Saturday night may bring a
few clouds but column moisture appears too scarce for rain. The
dynamics aloft will be running strong, so a brief shower over SE
NC cannot be ruled out but no QPF expectations at this time.
Sunday should bring brisk north wind, as high pressure builds
from the west. The core of the high, and clear skies will team
up overhead daybreak on Monday, and may greet some inland areas
with sub-freezing air.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 23Z...Latest radar and satellite pics showing area of light to
some patches of moderate rain off the GA coast moving to the NNE.
Developing low pressure system near Florida will track up the coast
this evening, bringing the chance for rain. The rain will mainly be
at the coastal terminals at least in the prevailing group and in the
tempo group across the inland terminals. After the low passes to the
northeast, winds will swing around to northwest, there will be a
brief window of IFR ceilings/vis expected. Conditions are expected
to improve within a few hours after daybreak as a cold front pushes
across the region and helps to clear out the fog and low ceilings.
Extended Outlook...VFR conditions expected by Wednesday afternoon.
VFR Thursday. Low confidence for MVFR to IFR conditions near the
coast late Thursday through Friday night in low clouds and rain.
&&
.MARINE...
NEAR TERM /THROUGH WEDNESDAY/...
As of 630 PM Tuesday...Winds are in the 10 to 15 kt range this
evening with a variable direction due to the proximity of the
coastal trough. Seas range right around 3 ft. May update the
forecast again for wind direction once we get a better sense as
to the progression, or lack thereof, of the coastal trough.
Given low wind speeds though, any changes will prove to be
minor. We do expect increasing rain coverage through the evening
hours, with the rain being mainly on the light, drizzly side.
Previous discussion from this afternoon follows:
Coastal trough continues to linger in the region with light
southeast winds over the eastern waters and northeast along the
coast. The trough will try to move onshore, and may briefly do
so this evening. This would result in east to southeast winds
across all of the waters but the weak gradient will keep speeds
10 kt or less. Surface wave moves northeast along the trough
tonight, with winds backing to southwest and then west as night
turns into day. Offshore flow following the wave/trough is not
particularly strong, 10 to 15 kt, but a dry cold front will
cross the waters late in the day. This feature is likely to be
followed by a stronger surge of cold air, albeit after the end
of the period. Seas will steadily build through the period with
2 to 3 ft this afternoon increasing to 2 to 4 ft this evening.
Seas continue to build as the wave approaches and then, with the
switch to southwest and then west, keep increasing, peaking at
3 to 5 ft during Wed.
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 230 PM Tuesday...High pressure building across the waters
from the north Wednesday night will maintain a northeasterly
fetch and choppy seas. During Thursday, the area of high
pressure will likely suppress areas of low pressure farther off
the Southeast U.S. coast. This pattern will shift the stronger
pressure gradient offshore by Thursday night allowing winds to
gradually diminish across the coastal waters. At this time think
seas will remain just below Small Craft thresholds across the
outer waters but will need to monitor.
LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 230 PM Tuesday...An easing trend in NE winds Friday will
begin to back to the NW and increase on Saturday as deepening
low pressure passes well offshore. The low will pull well away
to the NE Sunday, with moderate N-NNW winds as high pressure
builds from the west. An exercise caution period is possible
Sunday for N wind, and elevated seas offshore. No 0-20 NM TSTMS
this period but a few showers possible late SAT/early SUN as a
cold front moves through.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...99
NEAR TERM...REK/III
SHORT TERM...SRP
LONG TERM...MJC
AVIATION...MAC
MARINE...MJC/REK/III/SRP
Area Forecast Discussion
National Weather Service Jacksonville FL
845 PM EST Tue Nov 21 2017
...Departing Rainfall this Evening then Dense Inland Fog After
Midnight...
.UPDATE...
Upper level short wave trough axis was pushing across the local
forecast area this hour, with a cluster of thunderstorms moving
from the JAX westside across the JAX Northside and Nassau and
Camden counties. This cluster of storms formed along a lifting
warm front/inland moving coastal trough axis, with upper level
dynamical support enhancing updraft formation this
afternoon/evening across inland NE FL. As the upper level trough
departs offshore over the next couple of hours, deepest convection
will press farther offshore as well, with just trailing showers
which will tapper off over inland areas through midnight. Low
level moisture will linger through the night, with the low level
trough axis meandering across north Florida. Moisture pooling
along this boundary and light winds favors low stratus setting as
dense ground fog overnight...with model consensus suggesting the
most widespread and persistent potential for dense fog across the
Suwannee River Valley between 06-09Z, with expansion farther
north and east through 12Z. A dense fog advisory will likely be
needed for some portion of the forecast area later tonight into
mid- morning Wednesday. Temperatures will be mild tonight with
lows only falling into the mid 50s to low 60s.
&&
.AVIATION...
Restrictions of down to LIFR in heavy rainfall and TS activity at
JAX this evening...elsewhere prevailing VFR to MVFR ceilings
through midnight possible as rainfall pushes offshore. After
midnight, MOS guidance, NAM12, SREF and HRRR still all in favor of
bringing restrictions to at least IFR due to dense fog and low
stratus. Highest probabilities of occurrence were across the
Suwannee River Valley including over GNV developing between 06-09Z
with expansion farther north and east through sunrise. Expect a
slow lift of ceilings Wed morning with VFR conditions not until
late morning or early afternoon as northerly winds increase.
&&
.MARINE...
Will continue with SCEC headline for the outer waters tonight
winds seas up to 6 ft offshore. SE winds 10-15 kts prevailed over
the waters this evening, with a wind shift to the NNE after
midnight toward daybreak working southward over the waters as the
surface front draped across the area gradually settles farther
south of NE FL.
Rip Currents: Moderate risk Wednesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 55 70 52 60 / 70 20 50 50
SSI 59 68 59 63 / 90 10 70 80
JAX 59 73 58 66 / 80 20 70 70
SGJ 61 73 60 69 / 60 30 60 70
GNV 58 75 58 69 / 50 40 70 60
OCF 58 77 59 73 / 20 30 60 60
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
$$
Enyedi/Zibura/Corless
Area Forecast Discussion
National Weather Service Marquette MI
646 PM EST Tue Nov 21 2017
.SHORT TERM...(This evening through Wednesday)
Issued at 407 PM EST TUE NOV 21 2017
WV imagery and RAP analysis indicated an amplified pattern with a
mid/upper level trough from Hudson Bay through the western Great
Lakes into the mid MS valley. 700-300mb Qvector div and subsidence
developed over Upper Michigan in the wake of a shrotwave trough to
the east of Lake Superior. However, another weaker shrtwv was
sliding into nrn Ontario (north of KINL). At the surface, gusty nw
winds prevailed over the region bewteen a 990 mb low se of James Bay
and 1033mb high pres building into the nrn plains. Radar indicated
that multiple wind parallel LES bands have gradually diminished this
afternoon as inversion heights drop to 4k-5k ft.
Tonight, 850 mb temps around -14C will provide enough instability
for continued LES even as 850-700 mb moisture moves out this
evening. The shrtwv moving through may provide a brief boost to the
LES. Winds backing to wnw overnight will shift the best chance for
additional accumulations from Munising eastward. Expect additional
accumulations of 1 to 3 inches in the favored nw flow locations.
Otherwise, only a few flurries or light dusting will be possible.
Wednesday, backing winds push the remaining LES bands in the east
offshore by afternoon. Mid/high clouds will increase in the aftrnoon
ahead of the next clipper shrtwv. Even with WAA, temps will only
climb into the mid to upper 20s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 217 PM EST TUE NOV 21 2017
...Temps on roller coaster with lake effect snow at times...
Upper air pattern heading into Thanksgiving features trough over
northeast Pacific to western Canada and another trough over Hudson
Bay. Appears that polar jet stream/arctic air intrusion stays just
north of Lk Superior for Thanksgiving. Weaker shortwave working
through may bring lgt snow/flurries even inland on Wed night then
could see some light lake effect snow or rain/snow from Keweenaw to
eastern forecast area on Thanksgiving Day. Possible there may not be
enough moisture around at times for ice so there could also be
drizzle or freezing drizzle. Not a big risk right now so just kept
ptype snow.
Attn Thu night into Fri turns to H25 130 kt jet streak pushing over
Pacific Northwest which will push upper troughing eastward toward
central Canada and northern Plains. Associated sfc low deepens to
lower than 980mb as it reaches central Manitoba on Fri morning. Warm
air moving in ahead of the low along with some mid-level moisture
could support some light mixed precipitation (light snow changing to
sleet and freezing rain) late Thu night into Fri morning, especially
northwest where sufficient saturation for precip looks like better
bet.
Fri will be breezy with temperatures rising above normal (well into
the 40s some areas) as Upper Lakes is within warm sector of the deep
sfc low crossing into northern Ontario. Shortwave driving in from
northwest through the day will eventually spread precip back over
the forecast area in the aftn. Ptype should stay rain through Fri
evening, then as sfc temps fall blo freezing late Fri night expect
any rain to change to snow. Upper level trough deepens over Great
Lakes on Sat with colder air (H85 temps as low as -14c) moving
across the region. After the warmer temps on Fri, high temps on Sat
will be in the 20s west to low 30s east. Temps may fall through the
day in some areas. WNW-NW winds will result in lake effect snow.
Snow showers could be heavy at times early Sat as cold air first
charges in, but lake effect should diminish later in the day as
synoptic moisture exits and inversions fall with arrival of
anticyclonic flow as high pressure builds from central Canada to
the Upper Great Lakes and middle Mississippi River Valley.
Differences show up by Sun in how quick cold air departs. ECMWF
keeps cold air locked in longer and at stronger intensity compared
to GFS on Sun (H85 temps at 12z on Sun range from -15c on 00z ECMWF
to -3c on GFS). 12z ECMWF has now moderated somewhat. GEM provides
slight compromise. NAEFS and ECMWF ensembles, though not as cold,
look more like ECMWF compared to GFS. Overall, think operational GFS
may be too aggressive in getting rid of the cold and will lean
toward colder ECMWF idea with highs mainly in the 20s and some lake
effect snow continuing into the aftn. Warming will eventually win
out by early next week as upper ridging builds across much of the
eastern Conus. Sfc low over the plains will also support warming
with S to SW return flow. Eventually though the cold returns middle
of next week as the temperature roller coaster continues.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 646 PM EST TUE NOV 21 2017
MVFR conditions and lake effect -shsn/flurries will continue at
KIWD/KCMX until winds back to the sw as high pres ridge passes Wed
morning. VFR conditions will then continue thru the aftn. At KSAW,
downslope nature of the nw wind may allow VFR conditions to develop
by late evening with -shsn/flurries ending.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 407 PM EST TUE NOV 21 2017
NW gales across much of Lake Superior will end by late evening.
Winds will diminish to under 25 knots while becoming westerly
through Wednesday morning, before backing to SW winds of 20 to 30
knots Wednesday night. Westerly winds of 20 to 30 knots Thursday
will back to the south on Friday. Another strong low pressure system
will then bring the potential for northwest gales of 35 to 40 knots
Friday night into Saturday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Lakeshore Flood Advisory until 9 PM EST this evening for MIZ006.
Lake Superior...
Gale Warning until 10 PM EST this evening for LSZ243>245-248>251-
264>267.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...JLA
AVIATION...Rolfson
MARINE...JLB
Area Forecast Discussion
National Weather Service Spokane WA
645 PM PST Tue Nov 21 2017
.SYNOPSIS...
Expect wet and mild weather through the week as a series of storm
systems brings several rounds of precipitation to the Inland NW. Snow
levels will be quite high through Thursday allowing motorists to
travel over mountain passes on wet pavement. Snow levels will
begin to lower just as travelers are heading home Friday into the
weekend. Windy conditions are expected Thursday across the
exposed areas of the basin and into the Spokane Area and Palouse.
&&
.DISCUSSION...
Evening update: A winter weather advisory has been issued for the
East Slopes of the Cascades through 4 am. This is for freezing
rain around Loup Loup Pass and the Methow Valley. Web cameras at
Loup Loup Pass and the ski resort showed ice accumulating on trees
this afternoon with WADOT reporting ice in places with air
temperatures and road temperatures around 32F. With temperatures
around freezing in the Methow Valley could see pockets of freezing
rain here as well tonight. Soundings show the cold layer becoming
more shallow overnight so impacts from freezing rain may be at
their greatest this evening but this will depend on how much
temperatures warm overnight. With light winds would not be
surprised if temperatures hovered near freezing in the Methow
Valley through the night. JW
&&
.AVIATION...
00Z TAFS: Rain band will remain over the region through the
period with light winds. Cigs and vsbys will be fluctuating with
more intense showers or increased fog as the rain decreases.
Expect predominantly MVFR conditions with areas of IFR. The HRRR
shows a decrease in rain between 08z-13z for KMWH and KEAT. Rain
will persist at KPUW and KLWS into Wednesday morning, before
shifting northward in the afternoon. /rfox.
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 40 53 46 55 36 45 / 80 90 50 90 30 10
Coeur d`Alene 40 53 45 55 36 45 / 100 90 50 100 40 10
Pullman 45 57 46 57 37 48 / 90 70 30 90 70 0
Lewiston 45 58 48 61 40 52 / 90 80 20 50 60 0
Colville 35 46 40 53 33 44 / 40 70 70 70 20 10
Sandpoint 37 47 41 51 35 42 / 100 90 80 100 40 20
Kellogg 40 49 42 51 34 41 / 100 90 50 90 80 40
Moses Lake 37 52 43 59 35 50 / 40 40 30 30 10 0
Wenatchee 37 49 41 54 35 47 / 50 50 40 40 10 10
Omak 38 48 41 54 34 45 / 50 30 50 50 10 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Winter Weather Advisory until 4 AM PST Wednesday for East Slopes
Northern Cascades.
&&
$$
Area Forecast Discussion
National Weather Service Blacksburg VA
1041 PM EST Tue Nov 21 2017
.SYNOPSIS...
A cold front will approach and cross the region tonight, all while
an area of low pressure heads north along the east coast of the
United States. High pressure builds back into the area by
Thanksgiving Day. Another cold front will cross the area this
weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 1030 PM EST Tuesday...
Increased pops across the NC Piedmont and into Southside VA
where light rain is developing on the back side of the larger
coastal system noted off the SC/GA coast. This region is within
the right entrance region of the upper jet with notable
convergence at both 850 and 700mb levels. In addition, another
band of light rain will approach the western portion of the
CWA, especially the WV counties during the next few hours. Have
used the HRRR as radar/pop guidance for the next several hours
as it seems to have a good handle on the current situation.
Only minor changes were needed to the T and Td grids.
As of 747 PM EST Tuesday...
Made some minor adjustments in temperatures utilizing the
surface obs, their trends and leaned towards the GLAMP for
this evening into tonight. With the latest HRRR showing a
little more qpf in the east, decided to expand the light pops in
the east a little further west towards the Blue ridge. The
Southeast regional WSR-88d images are showing some light rain
spreading north from South Carolina into North Carolina. We will
monitor for additional changes this evening. Have a good
tonight!
As of 245 PM EST Tuesday...
A broad upper trough was positioned from Hudson Bay southwest into
the lower Mississippi Valley. An associated cold front was extended
from the thumb of Michigan southwest into central Missouri. An area
of low pressure was developing near the GA/FL coast and was heading
north along the U.S. east coast. Surface high pressure was oriented
over our region. As we progress into and through the overnight
hours, the southeast U.S. low will continue its progression north
along the coast. Light rain on the western edge of this system is
expected to skirt the eastern section of the forecast area starting
this evening. The cold front to our west will approach this evening,
and is expected to cross the area late tonight into early Sunday.
Precipitation in the east will gradually shift eastward with the
approach of the front. Precipitation associated with the cold front
will be limited to scattered rain/snow showers across mainly
southeast West Virginia, south into the Northern Mountains of North
Carolina.
During the day Sunday, dry conditions are forecast for most of the
region. The isolated/scattered rain/snow showers across southeast
West Virginia will gradually dissipate through the morning hours,
with dry conditions expected during the afternoon.
Winds will turn gusty behind the front with gusts of 25 to 35 mph
common at the higher ridge tops, and 15 to 25 mph gusts common in
the mountain valleys and the Piedmont region.
Low temperatures tonight will range from the mid to upper 30s across
the mountains to readings around 40 to the lower 40s across the
Piedmont. High temperatures on Wednesday will range from the mid 40s
to around 50 across the mountains to the upper 50s to lower 60s
across the Piedmont.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 200 PM EST Tuesday...
An overall quiet holiday period in store with the area basically
under weak high pressure within an upper split flow regime through
the end of the week. With high pressure overhead under clear skies
expect a cold Wednesday night with lows mostly in the 20s, including
perhaps a few upper teens deeper valleys. This should lead into a
cool Thanksgiving under passing mid/high clouds as another weak
northern stream shortwave trough boots across from the northwest.
This along with the lingering 850 mb cool pool should interact with
only light mixing to result in chilly highs in the 40s, to possibly
a few warmer 50s east per weak downsloping and pending the degree of
insolation given proximity of the wave off the southeast coast.
Trough lifts out Thursday night into Friday with more zonal flow
developing allowing surface high pressure to slide offshore. However
guidance usually too fast to exit ridging in this setup at night
which should result in another rather cold overnight under mainly
clear skies as a weak extension of the parent ridge remains
overhead. Thus went with lows on the cold end of Mos, mainly 20s,
although may rise late along the ridges as warm advection starts to
increase. Quick warmup then looks to ensue on Friday in response to
increasing southwest flow behind the departing ridge and ahead of
the next upstream 500 mb trough. Latest thickness values under
sunshine support highs mostly in the 50s with values possibly
reaching 60 southeast.
Weak leftover subsidence region between the approaching upstream
cold front and low pressure off the Carolinas will continue to get
squeezed out Friday night despite lack of any phasing aloft. This
should allow for some increase in clouds, espcly southern and
northwest sections but still dry. However continued mixing/warm
advection should at least act to keep lows a bit milder with most
seeing overall 30s with only the deeper valleys below freezing early
on.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 130 PM EST Tuesday...
Fast split upper flow will again show more amplification to start
the period with the translation of another deep 5h trough across the
region next weekend. This should swing the next rather strong cold
front across the area Saturday night and offshore on Sunday.
Boundary again lacking moisture given low pressure off the Carolinas
so mainly looking at perhaps a band of rain showers west late
Saturday and increasing clouds elsewhere. This then to be followed
by a few snow showers/flurries northwest mountains overnight into
early Sunday as much colder air arrives. Flow should quickly flatten
into early next week allowing for dry/sunny weather under moderating
temperatures as surface high pressure slides overhead Monday and
offshore into Tuesday. Mild high temps ahead of front with some 60s
possible Saturday to dive back into the 30s/40s Sunday before slowly
recovering to more seasonal levels by day7.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
As of 638 PM EST Tuesday...
VFR conditions will continue this evening into tonight.
SCT to BKN MVFR clouds should gradually work there way into
more of the region, and some patch light rain is possible with
MVFR ceilings especially across southern and eastern portions
of the forecast area.
Overnight, a cold front will approach and sweep across the area.
Concurrently, an area of low pressure will head north along the
U.S. east coast with the western edge of its associated
precipitation skirting the eastern sections of the forecast
area. MVFR/IFR ceilings will become more common as the night
progresses. Rapid improvement to VFR is expected east of the
crest of the Blue Ridge by Wednesday morning behind the front.
Sub-VFR ceilings will continue through at least mid-day along
and near a KBLF-KLWB line given the influence of lingering low
level moisture and a northwest flow regime. VFR conditions
should return Wednesday afternoon in the west.
Medium to high confidence in ceilings, visibilities and winds
during the taf period.
Extended Discussion...
High pressure will provide for primarily VFR conditions
Wednesday evening through Friday.
A cold front will cross the area over the weekend. While
primarily VFR conditions are still expected, some brief sub-VFR
conditions are expected in the vicinity of the front. Dry
weather return Sunday night into Monday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...DS
NEAR TERM...DS/KK/RAB
SHORT TERM...JH
LONG TERM...JH
AVIATION...DS/KK
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
424 PM MST Tue Nov 21 2017
.DISCUSSION...(This Evening Through Tuesday)
Issued at 111 PM MST Tue Nov 21 2017
Upper level flow will remain amplified, but progressive in the
period, bringing unseasonably warm weather with periodic ridge
topping/flattening impulses in the flow. Staunch WAA ongoing and
will intensify tonight as fast moving lead impulse progresses
through the region Wed. This system will support a mild but breezy
day Wed, with temps in the 50s and 60s, possibly near 70 east of
the Black Hills. Gusty NW winds can be expected on the NW SD
plains. Have increased winds, but remained in the 50 percentile
per numbers, with even breezier conds possible there. WAA will re-
initiate quickly behind Wed/s system with very warm air moving in
aloft. This will support very warm conds Thur, esp on the plains
east of the Black Hills, where record temps will be possible at
downtown Rapid and the airport. Current records at Downtown Rapid
City and at KRAP are 67 and 69 respectively, with current forecast
numbers above those values. Vigorous mid level impulse will push
into the region Thur night int Fri, supporting a cold front and
some precip chances over the western 1/3. Adv to warning wind
speeds will be possible across much of the SD plains Friday given
linked flow and expected decent mixing in a CAA regime. Beyond
Friday, mild weather will continue as another period of WAA and
ridging can be expected into early next week before an expected
longwave trough pushes into the region, supporting rain/snow
chances and a cool down mid next week. ECMWF/GFS/CMC are in pretty
good agreement with the large scale pattern by mid next week, the
differences lie in the low level details per sfc low development,
which continues to differ with each model run with MSLP GEFS
ensemble spread remaining quite high.
&&
.AVIATION...(For the 00Z TAFS Through 00Z Wednesday Evening)
Issued At 424 PM MST Tue Nov 21 2017
VFR conditions are expected through the TAF period. Winds will
pick up overnight across northeastern WY and tomorrow over
western SD as a low pressure system slides off to our northeast.
Northwesterly gusts at RAP late tomorrow morning through the
afternoon will be the primary concern of the period.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
DISCUSSION...JC
AVIATION...Sherburn