Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/16/17
Area Forecast Discussion
National Weather Service Duluth MN
542 PM CST Wed Nov 15 2017
.SHORT TERM...(This evening through Thursday)
Issued at 302 PM CST Wed Nov 15 2017
Colder air will settle across the Northland this evening and
overnight, which will support slick road conditions, especially on
secondary and untreated roadways. Strong cold air advection behind a
cold front that swept through the Northland earlier today will bring
in below freezing temperatures across the area. 925 mb temperatures
are progged to quickly fall into the 5 to 10 below zero range by 06z
tonight, only decreasing from there through Thursday morning.
Observed road temperatures across Minnesota are hovering around the
lower to middle 30s, so temperatures don`t have to drop far to allow
freezing precipitation on road surfaces. NAM and RAP model soundings
indicate there will be very little in the way of saturation in the
ice producing layer, so thinking that the predominant precipitation
type will be freezing drizzle as there is a shallow saturated layer
in the low-levels, although some light snow is possible over the
Minnesota Arrowhead. Overnight lows tonight should drop into the
lower to middle teens along the International Border into the lower
20s over northwest Wisconsin. Thanks to the colder air and
northwesterly flow off Lake Superior, there should also be some
light snow accumulation from the Bayfield Peninsula southeast over
north-central Wisconsin. The heaviest snowfall amounts should fall
along the Gogebic Range in Iron county, with new snow amounts
between 1" to 2" possible.
Thursday will be a drier day, with colder temperatures compared to
the last few days. Highs Thursday should range from the middle to
upper 20s over the Minnesota Arrowhead to the lower 30s over the
south. The only things of note for Thursday are winds turning more
on-shore/northeasterly in the morning, which some models are
progging some light precipitation from Duluth and points northeast
along the North Shore. However, it looks too dry in the 1000-850 mb
layer to support any lake effect showers. The better support for
precipitation will come in the afternoon and evening as 850-700 mb
layer warm air advection will bring increasing clouds and some small
chances of snow showers. Also, enhanced moisture advection will
increase precipitation chances Thursday night into Friday.
Southeasterly winds will also intensify in the afternoon due to a
tightening sfc pressure gradient, with gusts between 20 to 25 kts,
especially across our western counties.
.LONG TERM...(Thursday night through Wednesday)
Issued at 302 PM CST Wed Nov 15 2017
An area of low pressure will move through the central Canadian
Plains Thursday night and Friday. This will be accompanied by a mid
level trof and pieces of vorticity in the southwest flow aloft. There
will be enough warm air ahead of this system and its cold front to
result in a mix of winter p-types Thursday night, possibly
becoming all rain over the southern tier of the forecast area. The
mixed p-types will continue Friday morning before becoming all
rain over the south and a rain/snow mix over the north. Some
freezing drizzle/freezing rain is also possible over the higher
terrain of northeastern Minnesota. Some light snow accumulations
may occur along the Canadian border, especially Friday. The mixed
p-types will continue Friday night as the low moves east and
another area of low pressure moves from Iowa into the lower Great
Lakes by Saturday afternoon. Enough cold air is pulled into the
region Saturday afternoon to change the p-type to all snow. The
snow will also diminish over all but the elevated terrain of
northwest Wisconsin. High pressure moves over the region Saturday
night and Sunday. However, lake effect processes will persist
along the south shore of Lake Superior. A quasi-zonal flow aloft
with ridging at the surface will be in charge Sunday night and
Monday. Warm, dry air will be pulled into the area through Monday.
By Monday night, a strong area of low pressure will move through
the Canadian Plains and drag a cold front through the region. It
will take some time for enough moisture to saturate the atmosphere
and produce pcpn, but the cold air surging into the area will
lead to snow for the main ptype through Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 539 PM CST Wed Nov 15 2017
Low pressure will move off to the east across the region tonight,
as high pressure moves in from the west. Some of the clouds will
break up as the night wears on, although stubborn areas of clouds
will persist through the night and into Thursday. Another area of
low pressure will approach the region from the west on Thursday.
Strong WAA ahead of this system will bring an increase in mid and
high level clouds. IFR/MVFR conditions overnight will transition
to a mix of MVFR/VFR on Thursday.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 19 30 28 37 / 10 20 30 60
INL 14 28 27 35 / 10 20 40 60
BRD 21 33 31 40 / 0 10 10 20
HYR 23 33 31 38 / 20 10 30 70
ASX 26 33 30 40 / 50 20 30 70
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 4 AM CST Thursday for LSZ121-140-146-
147.
Small Craft Advisory until noon CST Thursday for LSZ148.
&&
$$
SHORT TERM...JTS
LONG TERM...GSF
AVIATION...DAP
Area Forecast Discussion
National Weather Service Green Bay WI
511 PM CST Wed Nov 15 2017
Updated aviation portion for 00Z TAF issuance
.SHORT TERM...Tonight and Thursday
Issued at 158 PM CST Wed Nov 15 2017
The latest RAP analysis and satellite/radar imagery show low
pressure centered over the eastern Upper Peninsula and a cold
front extending south from the low across eastern Wisconsin early
this afternoon. A secondary cold front is moving across northwest
Wisconsin. With help from a shortwave, an area of showers is
moving northeast across the Fox Valley, while spotty drizzle
persists over north-central WI under a low overcast deck.
Temperatures are slowly falling over north-central WI, though
remain in the middle to upper 30s. As temps fall into the lower
30s late this afternoon, some potential for drizzle to start
freezing on roadways over north-central WI. But with road temps at
or slightly above freezing, any freezing drizzle probably will be
spotty in nature. Forecast concerns revolve around light precip
across north-central WI tonight, and cloud trends.
Tonight...While most shower activity will be exiting eastern WI
by mid afternoon, light precip will be ongoing over north-central
WI at the start of the evening. Lake effect processes will slowly
ramp up through the evening as delta T`s fall into the mid teens.
But marginal instability and lack of deep saturation, to go along
with temps (and road temps) falling below freezing, will likely
call for a mix of snow and freezing drizzle from early to mid
evening until lake effect bands become better developed. Not out
of the question that slippery roads could develop. A period of
lake effect snow should then ensue from late evening into the
overnight. Lake effect parameters are not ideal despite decent
wind trajectories. Incoming mid-level dry air and marginal temps
should keep accumulations in check, and will continue to go with
an inch or two over northern Vilas county. For the rest of the
area, delayed the clearing trend until late tonight, and even then
it is questionable whether it will occur. Low temps ranging from
the mid 20s in the north to low 30s near the lake.
Thursday...Even though lake effect snow showers will mostly likely
have retreated into the Upper Peninsula by early morning, its
looking more likely that scattered to overcast skies will stick
around for much of the morning. Some clearing should take place
from late morning into the afternoon, but just when cirrus invades
from the west. High temps will range from near 30 in the north to
the upper 30s south.
.LONG TERM...Thursday Night Through Wednesday
Issued at 158 PM CST Wed Nov 15 2017
The main focus for the long term will be Thursday night through
Friday for the wintry mix across the region as the next system
passes through to start off the weekend.
The kitchen sink remains for Thursday night into Friday morning.
Recent models hold precipitation start off until around midnight,
with enough cold air and possible saturation to start off with
some light snow near Vilas County. The main challenge for this
part of the forecast will the be the warm air advection around
800-600 mb and the development of an associated dry slot. Current
depth of the dry layer is expected to be around 5000 feet which
should be just enough to prevent seeder feeder mechanisms and keep
freezing drizzle in the region for a portion of the morning in
the north. Slick spots could therefore affect the morning commute
on Friday as road temperatures ahead of the system remain well in
the 20s. By around noon to the afternoon, saturation of much of
the column will coincide with temperatures pushing into the
middle 30s throughout, bringing light rain showers to most of the
region into Friday evening.
The next hurdle for the forecast will arrive early on Saturday as
colder air follows behind the now retreating system. A switch back
towards more frozen precipitation can be expected, especially in
the northern portions of the forecast area. Models differ once
again in the speed at which this system retreats, but a switch
back to snow will be possible into Saturday afternoon. Can`t rule
out another brief chance of sleet or freezing drizzle before this
system is done. The remainder of Saturday will just see some
chances of lake enhanced precipitation lingering in the far north
towards Vilas County.
Dry and calmer conditions follow on Sunday and Monday. The next
system is shaping up to arrive Tuesday night to Wednesday with
another chance for some rain or snow.
Temperatures through the period will slip through the 30s Friday
and Saturday with highs in the 20s on Sunday before returning to
more seasonal conditions by next week.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 511 PM CST Wed Nov 15 2017
Conditions expected to change little this evening with mainly
MVFR cigs over east central Wisconsin to IFR conditions across
north central and parts of central Wisconsin. A band of showers
have departed east of far eastern Wisconsin late Wednesday
afternoon, leaving mainly drizzle over areas south of highway 29
and a light mix of snow showers and light freezing drizzle over
the north. Blustery west to northwest winds will continue
overnight into early Thursday before subsiding later Thursday as a
ridge of high pressure slides over. Cigs to gradually improve
later tonight from west to east and then move to vfr conditions
Thursday as the ridge builds in. Scattered snow showers will be
on the increase over north central Wisconsin this evening as
colder air on northwest winds pour over Lake Superior, then
subside Thursday morning.
&&
.MARINE...
Issued at 158 PM CST Wed Nov 15 2017
Northwest winds behind a low pressure system remain on track to
strengthen and become gusty by early this evening. Winds have been
slow to ramp up this afternoon, and may struggle to reach 35 kt
gales until later in the evening. On the other hand, the latest
guidance suggest that the gale warning may need to be extended
into Thu morning, but will let evening shifts first see how winds
respond tonight.
Another low pressure system could bring additional chances for
gale force winds, first from the southwest on Friday ahead of the
system, then from the northwest behind the system on Saturday.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......Uhlmann
AVIATION.......TDH
MARINE.........MPC
Area Forecast Discussion
National Weather Service Jacksonville FL
809 PM EST Wed Nov 15 2017
.UPDATE...This evening GOES 16 shows extensive stratus deck along
the First Coast into North Central Florida with clear skies across
most of SE GA and interior NE Florida. Satellite shows some
erosion of this layer across the western two thirds of Clay
County, with HRRR showing further significant erosion of the
layer from north to south between 10 pm and 1 am as coastal trof
along NE FL slips further south along to the east central Florida
coast. The inverted trough over the coastal waters will keep an
enhanced pressure gradient through this evening, with winds
diminishing slightly overnight as coastal trof starts to slip
southward overnight. During the overnight hours, higher level
cirroform clouds are expected to into the region associated with
the passage of the upper level short wave trof moves through the
region overnight. The cirrus is expected first to move through SE
GA between midnight and 4 am and then advect southward into NE FL
between 3 am and 7 am. Cirrus will exit NE FL during the early
daylight hours as short wave trof moves into the adjacent
Atlantic.
&&
.AVIATION...MFR Cigs will continue to provide restrictions through
04z then erode from north to south after midnight. Improving VFR
conditions are expected overnight with cirrus high clouds moving
in then advecting offshore Wednesday with mostly clear skies for
the rest of the day.
&&
.MARINE...
The combination of winds and seas will keep SCA conds over all
the waters through early Thursday morning then with winds
forecast to subside slightly during the day Thursday to 10 to
15 knots remaining out of the north. Northeast winds at 10 to 15
knots anticipated Friday. The high will move to the East on
Saturday while a cold front moves into the Mid South turning winds
to a southerly direction late morning /early afternoon and then
south-southwest Saturday mid to late afternoon. This front will
cross area waters Sunday.
Rip Currents: Moderate risk on Thursday and Friday.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 42 70 44 71 / 0 0 0 0
SSI 52 69 53 68 / 0 0 0 0
JAX 46 70 48 73 / 0 0 0 0
SGJ 54 67 55 72 / 0 0 0 0
GNV 47 72 47 76 / 0 0 0 0
OCF 50 74 49 77 / 0 0 0 0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...Small Craft Advisory until 6 AM EST Thursday for Coastal waters
from Altamaha Sound to Fernandina Beach FL out 20 NM-
Coastal waters from Fernandina Beach to St. Augustine FL
out 20 NM-Coastal waters from St. Augustine to Flagler
Beach FL out 20 NM-Waters from Altamaha Sound GA to
Fernandina Beach FL from 20 to 60 NM-Waters from Fernandina
Beach to St. Augustine FL from 20 to 60 NM-Waters from St.
Augustine to Flagler Beach FL from 20 to 60 NM.
&&
$$
Cordero/Kennedy/McGinnis
Area Forecast Discussion
National Weather Service Reno NV
744 PM PST Wed Nov 15 2017
.UPDATE...
The previous trends from an earlier update continue to hold. Snow
levels are lower where the pcpn intensity is higher...not so much
where pcpn is lighter. This is a common occurrence. But there is
one anomaly right now. Light snow continues falling in far
western Lassen County near Bogard. That area is seeing less pcpn
intensity now...but it is likely that warm air advection has not
returned to the area and driven snow levels up yet. There is
another area of heavier pcpn well to the west that should impact
western Lassen later tonight. Ahead of this...warmer air may
briefly push snow levels above 7000 feet...but then they should
fall again.
Farther south into the Tahoe Basin...the northern part of the
basin is seeing heavier pcpn at this point. Snow levels have
dipped below 7000 feet as evidenced by snow over Donner Summit and
a little lower on the western slope where lift and dynamic cooling
are able to overcome warm air advection. We still feel that
decreasing pcpn intensity will briefly allow snow levels to rise
after about 9 pm for a short period of time before heavier pcpn
moves back into the region after midnight. That should drop snow
levels again or...at most...hold them steady. This is a struggle
between advection of warm air and lift causing cooling. At times
we see this manifest as an isothermal airmass that teeters
between rain and snow. It all depends on the pcpn intensity. Model
soundings still look too warm based on current trends so we have
had to go cooler tonight and early Thursday.
Winds remain an issue as well. The strongest wind gusts have
decreased this evening...but that has more to do with moisture and
spill over pcpn moving into western Nevada. This increased
moisture and some instability help to dampen the winds. Winds are
still rather strong into the southern portions of the basin and
range country where moisture is not increasing as yet. That will
happen later tomorrow. So we will continue to see periods of
decreased winds overnight when pcpn does occur...but when the
intensity or spill over decreases the winds will increase at the
surface again.
Bottom line: Snow level variations could result in higher totals
in Lassen/Plumas counties down to 5500 feet and the Tahoe basin
down to 6500 feet by the time the snow ends Friday morning.
Periodic strong winds east of the Sierra support maintaining the
warnings and advisories into Thursday. Updates out soon.
&&
.PREVIOUS DISCUSSION... /Issued 514 PM PST Wed Nov 15 2017/
UPDATE...
Recent web cam images show snow falling and accumulating at
Bogard Rest Area in far western Lassen County. Snow is also
falling at Donner Summit in the Tahoe Basin and near Chester in
Plumas County. This is a little lower than we had originally
forecast. But...this may be just a temporary condition owing more
to precipitation intensity than an overall lowering of snow levels
due to encroaching colder air. In fact...forecast soundings would
have one believe that snow levels should be steady or rising from
late afternoon into the early evening. Now...the models often
struggle with snow levels...so this is not a unique case. Radar
imagery indicates a lessening of precipitation intensity this
evening. This is likely to allow snow levels to rise again.
The latest HRRR shows an increase in precipitation again later
tonight. We will show a drop in snow levels early this evening
followed be rises after about 7-8 pm. Then we will indicate falls
again later tonight. This will change snow accumulations a little
across parts of Lassen and Plumas counties...but not enough to
change the winter storm warning as yet. Some of the lowest areas
with snow (below 6000 feet) may see little accumulation.
PREVIOUS DISCUSSION... /Issued 109 PM PST Wed Nov 15 2017/
SYNOPSIS...
A strong atmospheric river storm will impact the region through
Thursday. Strong and damaging winds are expected this afternoon
across western Nevada along with high wildfire danger before
precipitation arrives. Precipitation will continue to intensify
this afternoon through Thursday. A cold front will drop snow
levels Thursday and will provide heavy spillover rainfall for
western Nevada.
SHORT TERM...
The first significant atmospheric river event of the season is
just starting to move into the west. Light rain and high elevation
snow is falling throughout northeast California, the Sierra and
western Nevada. Precipitation will only intensify over the next 36
hours with snow levels a bit slower to fall. Winds are slowly
starting to pick up, with the strongest winds anticipated this
afternoon through Thursday afternoon.
Here is what has changed:
* Increased QPF (liquid precipitation) totals along the Sierra
crest. NCAR ensemble guidance is showing a 70% chance for
localized areas of 10" of liquid over a 48 hour period along the
central Sierra crest. In addition, model guidance continued to
trend upward in liquid totals.
* An areal flood watch was issued for portions of northeast
California, the Sierra, and the western Nevada Sierra Front.
While mainstem river flooding is not expected, significant rises
are likely. Small creeks and streams along with poor drainage
areas in urban areas and recent burn scars may see minor
flooding. While not in the watch, Hardscrabble Creek will also
bear monitoring.
* Extended the strong winds through Thursday night. Winds will be
periodically be dampened out by the heavier precipitation, but are
expected to continue to be gusty. The High Wind Warnings will be
extended by 12 hours through Thursday afternoon.
What we have confidence in:
* Strong, potentially damaging winds for the Sierra Front and along
the I-590/Hwy 395 corridor. The strongest winds are anticipated
this afternoon through Thursday afternoon, though gusty winds
will continue through Thursday night.
* Period of moderate to heavy rain with significant snowfall for
areas above 8000 feet. The peak intensity will be tonight through
Thursday evening.
* Liquid totals of 7-8" look likely along the Sierra crest with 2-4"
through the Tahoe Basin. 1-3" is possible for the western Nevada
Sierra Front and the Highway 395 corridor in Mono County. 0.25"-
0.50" is possible across the Basin and Range including areas such
as Lovelock and Fallon.
* Snow totals above 8000 feet could easily reach 2-4 feet with local
amounts over 5 feet possible. The character of the snow will be
heavy and wet.
Possible forecast problems:
* How quickly snow levels will fall. Guidance has been slower in
bringing the cold front through, however the heavier precipitation
rates may drag snow levels down faster. Snow totals below 8000
feet have a big boom or bust potential. Some ensemble guidance in
the 6000-7000 foot elevation range shows anywhere from a few
inches upwards of 3 feet of snow being possible depending on snow
level timing.
* While no mainstem river flooding is expected at this time,
significant rises are likely. This will be the first true test of
the hydrologic system this season. If snow levels stay up longer
and liquid totals are higher than forecast it is possible there
may be additional hydrologic concerns. -Dawn
LONG TERM...Saturday through next week
A quiet weekend will be followed by another storm early next week.
There is still quite a bit of variability with this storm for next
week, but there is potential for another round of valley rain and
mountain snows. Lower forecast confidence for how travel will be pre
and post Thanksgiving for next week as well.
The Monday-Tuesday storm continues to have variable snow level
scenarios, ranging from near 6000 feet to above 9000 feet. We are
still leaning toward the warmer side of the guidance range (snow
levels likely above 8000 feet) as the downstream longwave pattern
continues to favor a deeper trough over the eastern US, which
typically keeps the west milder. The strength of this system and
precipitation amounts also vary with the guidance sources, as the
warmer scenarios may tap into a deeper source of subtropical
moisture and produce a period of enhanced rainfall, especially north
of I-80.
After this storm pushes through, the overall trend favors a few dry
days leading into Thanksgiving as high pressure ridge builds from
the southwest US into the Great Basin. While there are still some
uncertainties with next week`s weather pattern, at this time there
do not appear to be significant weather impacts for the early part
of the Thanksgiving holiday peak travel period. ELW/MJD
AVIATION...
Winds will continue to increase this afternoon, with winds lasting
through Thursday night. LLWS will be likely as southerly winds
develop across valleys and southwest ridge level winds increase to
55-70 kts with gusts approaching 90kt. The critical period for winds
will be through 00z Friday (late Thursday afternoon), especially for
the eastern Sierra along the Highway 395 corridor extending out to
Hwy 95. Sustained winds 25-35 kts with gusts to 50 kts will be
widespread and there could even be a period of stronger winds from
Reno south toward KMMH this afternoon and evening.
Rain and high elevation snow will continue to intensify this evening
through Thursday. As this rain band shifts southward overnight,
surface winds will ease although they will remain fairly steady.
Also ridge level winds are going to remain strong and turbulence
will persist. Moderate to occasionally heavy rain in the Tahoe Basin
will push CIGS/VSBY down to MVFR levels tonight into Thursday
morning. This band of rain will shift southward into the eastern
Sierra of Mono County for Thursday with lowering CIGS/VSBY at KMMH.
As far as snowfall, accumulation is going to be limited to later
Thursday and Thursday night as snow levels will be a bit slower to
fall tonight and early Thursday than previously thought. A couple
inches are possible at KTRK/KTVL Thursday night with lesser
confidence in an inch or two at KMMH. -Dawn/Hohmann
&&
.REV Watches/Warnings/Advisories...
NV...Flood Watch through Thursday evening NVZ002-003.
High Wind Warning until 4 PM PST Thursday NVZ003-005.
Winter Storm Warning until 4 AM PST Friday above 7000 feet in
NVZ002.
Wind Advisory until 4 PM PST Thursday NVZ001-004.
CA...Flood Watch through Thursday evening CAZ071>073.
Winter Storm Warning until 4 AM PST Friday above 6000 feet in
CAZ071.
High Wind Warning until 4 PM PST Thursday CAZ070.
Winter Storm Warning until 4 AM PST Friday above 8000 feet in
CAZ073.
Winter Storm Warning until 4 AM PST Friday above 7000 feet in
CAZ072.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno