Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/11/21
Area Forecast Discussion
National Weather Service Grand Rapids MI
939 PM EST Wed Nov 10 2021
Issued at 939 PM EST Wed Nov 10 2021
Little change in thinking this evening for the wind and shower
event on Thursday (Veterans Day). While our 88D radar composite
shows patchy rain showers from near Holland and as far south as
central Indiana, no surface reporting station has had any rain
from these showers so far. As the previous shift suggested, the
area of showers, moving north with the warm front will do better
in terms of getting rain to reach the ground as the precipitation
area reaches northern Lower Michigan. We will leave our evening
forecast as is in that regard.
We did however slightly increase the wind speed and wind gusts in
our forecast for Veterans Day, based on the latest hi-res model
forecasts. Still it does seem the wind gusts will stay just below
advisory criteria. The midnight shift and revisit this issue.
It does look good for a 3 hour band of showers to cross the CWA in
the afternoon but there is little instability for thunderstorms.
The 00z RAP and HRRR do suggest 300 to 400 j/kg of cape over Lake
Michigan early Friday morning. It would not be out of the question
we could see a few thunderstorms over Lake Michigan and maybe as
far east as US-31 early Friday. The EQ reaches as high as 20000 ft
near South Haven at 4 am Friday.
.DISCUSSION...(This evening through next Wednesday)
Issued at 250 PM EST Wed Nov 10 2021
- Fall storm with wind/rain Thursday
Current radar and satellite imagery showing warm advection wing of
light showers developing across northern Illinois and this will
lift northeast into Lower Michigan this evening with little in the
way of QPF. The main batch of rain arrives Thursday morning with
the warm conveyer belt as moisture is drawn north into the
expanding circulation of the deepening low tracking north from
Wisconsin into the arrowhead of Minnesota.
Isallobaric wind component of deepening low results in 35 to 40
knot winds within a couple thousand feet of the surface on
Thursday morning, so it won`t take much to bring wind gusts over
40 mph to the surface. Fortunately, instability is quite limited
so we are not expecting any deep convection or widespread wind
damage, but scattered power outages are possible. The wind threat
continues in the cold advection pattern Thursday afternoon, with
forecast wind profiles showing 30 to 40 mph in the mixing layer
during the afternoon over much of the forecast area and gusts over
40 mph possible along Lake Michigan.
- Lake enhanced snow with light accumulations this weekend
There looks to be a break in the precip Thursday night as the dry
slot is over Lower Michigan, then lake-enhanced snow showers move
in on Friday as deeper moisture with the upper low moves in.
Southwest flow at this time suggests our northwest zones from
Muskegon County to Mason County and inland of there will see the
possibility of a coating of slush/wet snow as strong low level
convergence in this area could produce snow rates able to at least
partially overcome marginal surface temperatures and wet bulb
zero heights around 1500 feet AGL.
As the axis of low pressure shifts east Friday night, the flow
goes west and the better surface convergence shifts south along
the coast and stays that way into Saturday. We expect p-type to
be mostly snow except right along Lake Michigan where the residual
warmth of the water may be enough to keep a mix with rain and
An uptick in the snow is expected on Sunday as a clipper type low
or sharp upper shortwave trough axis moves through. This feature
now appears to stay separate from the circulation of the big
upper low and lake effect snow showers should continue on the
northwest flow that develops on the backside of the low on Monday.
Height rises on Monday night should bring and end to the snow
showers with warm advection rain showers developing ahead of a
northern stream low tracking across southern Canada on Wednesday.
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 643 PM EST Wed Nov 10 2021
I expect VFR conditions to prevail until around noon on Thursday.
We will see low level wind shear overnight as winds above 2000 ft
AGL increase to near 40 knots by midnight from the south
southwest. There is an outside chance of a few light rain showers
in the 04z to 09z time frame as the warm front pushes in this
direction. I expect only mid cloud with the warm front tonight and
any showers would be little more than sprinkles.
The frontal rain band moves into the area by 16z over the western
sections and reached the eastern TAF sites by 20z. That will bring
MVFR to locally IFR conditions with rain and low ceilings. At this
point the thunder threat is very low.
Winds will be rather gusty Thursday with winds gusting to between
25 and 35 knots fairly frequently by early afternoon. Once the
frontal rain band moves through I expect gusty winds and MVFR cigs
Issued at 250 PM EST Wed Nov 10 2021
No changes to the advisory and warning as we ramp up winds and
waves tonight with south to southwest gales expected Thursday.
Wave heights 6 to 9 feet expected by Thursday afternoon continuing
into Friday. Lake levels have decreased enough since last year
that these wave heights should not result in major flooding or
erosion, but some minor flooding and beach erosion is possible by
the time the winds and waves begin to decrease late Friday into
LM...Small Craft Advisory until 7 AM EST Thursday for LMZ844>849.
Gale Warning from 7 AM to 7 PM EST Thursday for LMZ844>849.
Area Forecast Discussion
National Weather Service Hanford CA
334 PM PST Wed Nov 10 2021
.UPDATE...Updated air quality issues section.
Rounds of morning Tule fog look to persist for at least the next
few days as high pressure builds. High pressure will also lead to
a warming trend, with afternoon highs reaching back into the mid
70s Sunday/Monday. Slightly cooler by the middle of next week as a
dry trough of low pressure reaches the district.
Dense Tule Fog plagued the San Joaquin Valley this morning with
many areas seeing visibility less than 1/4 of a mile. Most of that
fog has mixed out and we are left with a stratus deck, which is
keeping temperatures suppressed so far this afternoon. Wouldn`t
be surprised to see many areas of the lower elevations of the
valley only reach into the 64-65 degree range for afternoon highs
due to lack of sunlight. High resolution model guidance does seem
to indicate fog could occur again tonight due to the ridging and
the recent rainfall that added moisture to the ground. 18z HRRR
guidance doesn`t seem to favor the entire SJ Valley for fog
tonight though, so will hold off on issuing any products in this
forecast cycle due to location uncertainty of fog.
Daily bouts of morning fog are likely to accompany the stagnant
ridge pattern that will last through this weekend. Afternoon highs
are forecast to bump up a couple degrees each day through Monday
as the ridge builds. Ensemble guidance continues to show a trough
pass through the Pacific Northwest late Monday/Tuesday morning,
flattening the ridge of high pressure. As a result, afternoon
highs Tuesday will drop off a few degrees from Monday`s highs. The
cooling trend may continue into Wednesday, as blended model
guidance is forecasting highs Wednesday to only reach the middle
60s. The only chance for precipitation in the next 7 days would be
light, upsloping showers in the higher elevations of Yosemite
National Park accompanying the Tuesday trough. The overall pattern
favors dry weather for at least the next week.
.AVIATION...IFR to LIFR visibility in dense fog across the San
Joaquin Valley after 06z Thursday. Otherwise, VFR conditions will
prevail elsewhere over the central California interior during the
next 24 hours.
.AIR QUALITY ISSUES...
On Thursday November 11 2021... Fireplace/Wood Stove Burning
Status is: No Burning Unless Registered in Fresno... Kern...
Madera and Tulare Counties.
Further information is available at Valleyair.org
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is high.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.
Area Forecast Discussion
National Weather Service Nashville TN
757 PM CST Wed Nov 10 2021
FOR EVENING DISCUSSION.
Latest surface obs show temperatures in the upper 40s to around
60 across the area, warmest in the west and coolest in the east.
Temps in our southern and eastern counties have already fallen
below forecast lows, so have lowered min temps several degrees in
those areas for tonight. However, LLJ is forecast to ramp up
significantly overnight to near 30 knots at 1k ft agl by 12Z, so
temps should bottom out this evening then steady out or slowly
rise near/after midnight as surface winds increase. Line of
showers with a few isolated storms still on track to move across
our entire area Thursday, reaching the Tennessee River around
12-13Z, I-65 by 16-17Z, and move onto the Plateau by 19-20Z.
Instability still appears minimal to non existent, so no strong
or severe storms are expected despite the favorably strong shear.
Made small adjustments to pops based on latest HRRR and CONSShort
models, but nothing too significant.
00Z TAF DISCUSSION.
VFR will continue thru the overnight with changes to come after
08z. A LLJ will develop with wind shear at all sites thru 14z-16z.
A southerly surface wind will increase also, 10-15 kts, gusting
to 25 kts at times thru the day Thurs.
Poor flying conditions are expected after 15z. CIGs will degrade
to MVFR-LIFR after 15z-16z from west to east as a line of rain
and a few storms moves into Middle TN. This activity, associated
with a cold front, will be primarily centered over CSV at the end
of the TAF, with improvements in CIGs following closely behind.
Area Forecast Discussion
National Weather Service Portland OR
242 PM PST Wed Nov 10 2021
.SYNOPSIS...A warm front this evening will bring increasing rainfall,
enhanced by an atmospheric river for periods of moderate to
heavy rain over the region through Friday. A brief break will arrive
Saturday before the northern areas see a return of rain Sunday. A
cold front will push down Monday to bring cool and wet weather for
the beginning of next week. An active pattern is expected to
continue through next week.
.SHORT TERM...Tonight through Saturday...The expected warm frontal
system is just about to push onshore with radar returns showing the
stratiform rain out ahead of it. Just offshore, an area of elevated
thunderstorms has stayed organized and will likely push onshore
within the next hour or two. Model soundings continue to show the
elevated potential across the marine areas, coast and into the
western part of the inland valley. Precipitable Water amounts will
increase to near 1.1-1.2 inches this evening and snow levels will
surge up to near 10,000 feet. Synoptic and dynamic lift with this
system will combine with the moisture for increasing rainfall through
the night, with some rainfall rates in the quarter to half an inch
per hour as PW values bump up slightly more to 1.25 inches.
Thunderstorms may be able to add additional rainfall to this for
localized areas of flooding concern, especially in steep terrain.
This area of heaviest rainfall is expected to spread in through the
central part of the forecast area. Moisture transport into the area
will then decrease slightly by early morning, as a shortwave off in
the southern Gulf of Alaska creates a pull to the north. Rainrates
should slow down and the main area of rain will start lifting north.
The shortwave to the north will then pull up additional subtropical
moisture Thursday and swing it into the Pacific Northwest by the
afternoon, with PW values increasing up to 1.4 inches. EURO and GFS
IVT plume forecasts for locations along the central/northern Oregon
coast and south Washington coast suggest 500-700 kg/ms IVT
magnitudes, peaking near 750 kg/ms, which suggests a moderate to
strong atmospheric river event. The synoptic and dynamic lift will
increase with this shortwave to act on the increased moisture. This
is when the concern for widespread impacts to rivers, as well as poor
drainage areas, flood-prone locations and landslides begin. With snow
levels rising above 9000 feet, the recent snowfall will have rain
fall on top, adding to the expected water flowing down the mountains
as the previous snow melts. All of this culminates in why the Flood
Watch has been issued for most of the area. The one exception will be
the central OR Cascades and foothills as well as the far southern
Willamette Valley where no major rivers will be impacted. The cold
front behind this atmospheric river is expected to slowly sink down
Friday afternoon and into the evening, with rainfall rates finally
receding by nighttime.
Please see the Hydrology section below for a detailed discussion
regarding potential impacts. /Kriederman
.LONG TERM...Saturday night through Wednesday...Uncertainty remains
regarding the potential of a brief drier period as Saturday ends and
transitions into Sunday. While a ridge of high pressure is expected
to continuing building in across the region, the position and
strength of this ridge will dictate what areas will be impacted by a
weak atmospheric river approaching the Pacific NW Sunday and into the
start of the upcoming week. Ensembles currently have the atmospheric
river pointed between the Olympic Peninsula and Haida Gwaii, there
are some outliers that have the atmospheric river dropping further
south towards our CWA.
Starting Sunday night and continuing through Wednesday, models and
their families start to diverge temporally as there is a 12 to 18
hour difference between the GFS, ECMWF and Canadian model families.
However, they are in relative agreement as to what the overall
pattern will look like. What guidance is showing that towards the
start of Monday, an upper level trough will dive southeast from
around the Alaska Panhandle, brining along a cold front,
precipitation and cool temperatures across the CWA. A portion of
this precipitation will likely come from the previously mentioned
atmospheric river. Also, while colder temperatures and lowering snow
levels are expected through the start of the upcoming week, the bulk
of the moisture will likely be east of the Cascades by the time the
colder -3C to -4C 850mb temperatures manifest. As a result of the
cooler air expect, snow levels look to drop from 9000 ft Sunday
towards 2500 to 3500 by Tuesday/Wednesday.
Overall, the expect a somewhat active weather pattern to continue
through the remainder of the weekend, with a more active pattern
expected for the start of the week. /42
.AVIATION...0Z TAFs: VFR conditions continue across NW Oregon
and SW Washington this afternoon, though incoming rain will lower
ceilings to low MVFR at the inland terminals. Brief periods of
IFR ceilings and especially visibilities in heavier bursts of
rain will be possible this evening through the night as well.
Along the coast, conditions will be worse due to sea haze and
rain-induced IFR stratus. KAST, being inland several miles, may
average slightly better flight conditions throughout the night
compared to KONP, which is expected to experience IFR conditions
between roughly 06Z and 15Z Thursday.
Rain showers will continue for much of the day tomorrow, with
MVFR ceilings expected to continue through the end of the TAF
For detailed regional Pac NW aviation weather
information, go online to: https://weather.gov/zse
KPDX AND APPROACHES...VFR conditions should come to an end in the
next few hours as warm frontal rain moves in from the southwest.
With its arrival, MVFR ceilings will overspread the terminal.
Brief visibility drops into the IFR category will possible with
heavier bursts of rain tonight as well. High IFR or low MVFR
will become predominant by around 14Z Thursday and should
continue through the morning, with only gradual improvement into
high MVFR for ceilings expected by the end of the TAF period.
.MARINE...Brisk southerly winds gusting to around 30 knots will
continue across the waters Wednesday evening through Thursday
night, maintaining Small Craft conditions through that time
period. Seas have decreased substantially since this morning, but
a west to northwest swell of 7 to 8 feet at 10 to 12 seconds
will continue through tonight, with combined seas staying up at
around 8 to 10 feet through Thursday morning. The next chance for
Small Craft conditions appears to be late Saturday night into
Sunday, when southerly winds increase to 15 to 20 knots again
ahead of another storm system.
There will be a chance for thunderstorms Wednesday evening
through Thursday night as well. Some of these thunder showers
could produce briefly stronger wind gusts to around 35 knots.
.HYDROLOGY...Rainfall will be becoming more widespread and heavier
this evening as a warm front pushes onshore. Rainfall rates of a
quarter to a half an inch are expected, though some isolated 0.75-1
inch may occur as orographic effects take hold or some embedded
thunderstorms move overhead. At this time, this first rain event
shouldn`t cause too much of a threat of flooding of creeks and rivers
in the forecast area. However, after this event, the area of
precipitation will decrease and move north Thursday, then another
influx of moisture and lift will increase rainfall rates again
Thursday afternoon into Friday. This is when the rainfall from both
events will likely be sufficient to cause flooding of creeks and
rivers in southwest Washington and northwest Oregon, especially
creeks and rivers draining the north Coast Range and Cascades. At
this time, the best chance for river flooding appears to be along the
Grays River near Rosburg, the Wilson River near Tillamook, the Trask
River near Tillamook, and the Nehalem River near Foss. Creeks and
smaller rivers in the Willamette and coastal tributaries may also be
impacted. Flooding potential is low along the mainstem rivers. Minor
flooding will also be possible in low lying urban areas.
There is also potential for debris flows over and near the burned
areas in the Cascades. This includes the Lionshead, Beachie Creek,
and Riverside burn areas. The latest iteration of the HRRR
has backed off on its higher hourly rain rates, and is now suggesting
rates as high as 0.4-0.7 inches directly
over the Lionshead and Beachie Creek burn areas for several hours
tonight. These rates would lower the potential of debris flows over
the burn areas, but they`d still be non-zero. If higher rain rates
materialize right over the burn areas, then the potential for debris
flows would be fairly high. Debris flow potential is lowest over the
Holiday Farm burn area, as the axis of heaviest rain looks to occur
to the north of this burn area. Landslides near steep terrain cannot
be ruled out either, especially in the Columbia River Gorge.
Precipitation should finally wind down Friday night as surface high
pressure develops over the Pacific Northwest, but some rivers will
still likely be running high into Saturday. -TK/Kriederman
OR...Flood Watch from Thursday afternoon through late Friday night
for Central Coast Range of Western Oregon-Central Columbia
River Gorge-Central Oregon Coast-Central Willamette Valley-
Coast Range of Northwest Oregon-Greater Portland Metro
Area-Lower Columbia-North Oregon Coast-Northern Oregon
Cascade Foothills-Northern Oregon Cascades-Upper Hood
River Valley-Western Columbia River Gorge.
WA...Flood Watch from Thursday afternoon through late Friday night
for Central Columbia River Gorge-Greater Vancouver Area-I-
5 Corridor in Cowlitz County-South Washington Cascade
Foothills-South Washington Cascades-South Washington Coast-
Western Columbia River Gorge-Willapa Hills.
PZ...Small Craft Advisory until 3 AM PST Friday for coastal waters
from Cape Shoalwater WA to Cascade Head OR out 60 nm.
Small Craft Advisory until 6 AM PST Friday for coastal waters
from Cascade Head OR to Florence OR out 60 nm.
Small Craft Advisory until 6 PM PST Thursday for Columbia River
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