Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/27/18
Area Forecast Discussion
National Weather Service Bismarck ND
1031 PM CDT Sun Aug 26 2018
.UPDATE...
Issued at 1030 PM CDT Sun Aug 26 2018
Cancelled the Tornado Watch for this update. The severe threat has
ended for western and central North Dakota tonight as the upper
level wave has pushed off to the east.
UPDATE Issued at 740 PM CDT Sun Aug 26 2018
Main change for this update was the issuance of a Tornado Watch
for the southeast. Storms are developing along the warm front.
While there is a slight cap to deal with across the southeast,
there should be enough forcing with the upper level wave swinging
through to break through the cap and support robust convective
development over the next 1 to 4 hours. All severe threats are
possible with storms that develop along the front, including a
tornado, due to the impressive shear profile and modest
instability. The upper level wave is moving rather quickly across
the state and therefore all thunderstorm activity should move out
of the area by around 11 pm CDT.
UPDATE Issued at 535 PM CDT Sun Aug 26 2018
Storms have been slow to develop so far this evening, but we are
seeing more robust development within the past hour as the main
upper level wave enters western North Dakota. The warm front
remains across far southern North Dakota. This is where the main
axis of instability has set up. Further north instability quickly
diminishes. However, shear remains quite high across the entire
area. Presently, what we are seeing is elevated cells develop
further south, just north of I-94, along the gradient of
instability. These cells rapidly intensify as they push north into
higher shear, potentially producing penny to quarter hail and
gusty winds as they do so, then they tend to weaken as they leave
the deeper instability behind. We expect this trend to continue
through the evening. Short-term models are advertising the warm
front becoming more active after 7 pm CDT. Any storms that develop
along the warm front have a much higher potential for being
severe with higher end severe threats. At this time it would
appear Dickey and LaMoure Counties have the best chance at seeing
this development later this evening.
&&
.SHORT TERM...(Today and tonight)
Issued at 344 AM CDT Sun Aug 26 2018
The main forecast concerns are with chances of thunderstorms and the
risk of severe storms this afternoon and tonight.
Currently, a surface low was near Pierre SD with a warm front
northeast to around Aberdeen and then east southeast into west
central MN. Current RAP analysis and forecast shows the warm front
lifting into the southern James River Valley by around 23 UTC.
This area will exhibit the most favorable instability and low
level helicity, in addition to strong bulk shear.
As you go farther north and west from the southern James River
Valley, things become more uncertain. Low level stratus remains
over a good portion of the southwest and south central, and is now
also pushing into the north central this is currently having an
negative impact on the CAPE and low level lapse rates. RAP
forecast does show moderate ML CAPE of 1000-2000 J/KG lifting into
west central through south central ND, with low and mid level
lapse rates also trying to push northward into this region. Latest
CAMS are not real keen on producing discrete cells over the west
central into the south central portion of the state. This would be
the favored area for more discrete cells to form, compared to
farther north where bulk shear is more parallel to the boundary.
And this was depicted by the cams earlier this morning. Not saying
that we are not expecting severe weather at all now in the west
central to south central,(some of the Cams are going back and for
with convection developing here, but weaker than this morning) but
our confidence is less in this happening now.
Farther north, along and north of the Highway 200 corridor. Cams
are still generating significant precipitation here. And with the
strength of the shortwave trough approaching from MT, that seems
reasonable. The problem is that this area is currently
experiencing mid 60 to mid 70 temperatures and dew points in the
40s. Recent radar trends indicate storm tops are quickly being
sheared as storms develop. It remains to be seen if any
additional heating, and especially increased mid level forcing
with the approaching trough will be sufficient enough to generate
more upright convection. The threat for hail seems minimal across
the northwest and only a little better in the north central with
the greatest severe threat being strong winds, if we can get
convection strong enough to force the very strong flow aloft, down
to the surface. Again, confidence here is lower than this morning
for severe winds, but not zero due to the very strong bulk shear
and the strong approaching shortwave trough.
Convection exits most of the forecast area by midnight, but
lingering showers and isolated thunder could linger along the
International Border into Monday morning.
.LONG TERM...(Monday through Saturday)
Issued at 344 AM CDT Sun Aug 26 2018
Another round of showers and thunderstorms is expected to traverse
the state on Monday and Monday night. However with cooler
temperatures at the surface and aloft, instability will be lacking
and severe convection is not expected at this time.
Nearly zonal flow returns to North Dakota Tuesday night through
Friday, with a gradual warming trend beginning on Wednesday. The
latest blend of model guidance suggests temperatures will warm
back into the upper 70s to mid 80s for highs on Wednesday through
Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 535 PM CDT Sun Aug 26 2018
Storms continue across northwest and north central North Dakota
this evening, impacting KMOT. Storms will push eastward with time
and could potentially impact KBIS/KJMS. Any storms that do
develop will have the potential for strong gust winds and large
hail in addition to IFR-MVFR cigs and vsbys. Behind the
convection, flow turns north and widespread MVFR to IFR ceilings
are progged to develop, lasting through 18Z Monday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...AJ
SHORT TERM...JV
LONG TERM...JV
AVIATION...AJ
Area Forecast Discussion
National Weather Service Charleston SC
943 PM EDT Sun Aug 26 2018
.SYNOPSIS...
Atlantic high pressure will extend across the area through the
work week.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
High resolution guidance is beginning to narrow in on a
potential dense fog event for the morning commute. The 26/23z
run of the NARRE-TL pings a >60% chance for dense fog across
much of Southeast South Carolina away from the immediate coast
with the highest probabilities clustered in the KRBW-KCHS-KMKS
corridor. Per coordination with neighboring WFO`s, have opted
to hold off on the issuance of a Dense Fog Advisory in hopes the
overnight shift will be able to fine tune the fog forecast even
more before the morning rush. Only minor tweaks were made for
the late evening update.
High pressure will remain anchored to the region tonight.
Lingering showers near the Savannah Airport at 26/2230z will
quickly weaken through sunset with mainly dry conditions
prevailing through the overnight period. Could see some
nocturnal convection redevelop over the Atlantic after midnight,
but most of this activity should remain along the western wall
of the Gulf Stream.
The main concern for tonight centers on the potential for fog
and stratus. Atmospheric profiles look a bit more favorable for
fog/stratus to develop after midnight with depending low-level
moisture (courtesy of a southeast low-level flow) forecast to
pool beneath a sharpening nocturnal inversion and a clear sky
within a decoupled boundary layer. Model condensation pressure
deficits are forecast to be lowest roughly along/north of the
I-16 corridor in Southeast Georgia and along/inland of U.S. 17
in Southeast South Carolina and this is the region that will see
the best chances for significant fog development early Monday
morning. This is agreement with the latest SREF, H3R and RAP fog
prognostication. Similar to this morning, the fog could be
dense at time with visibilities 1/4 mile or less. A Dense Fog
Advisory could very well be needed for some locations overnight.
Will continue to hit the fog forecast fairly hard, maintaining
"areas of fog" and "patchy dense fog with vsbys 1/4 mile or
less" qualifiers. Might introduce some widespread fog wording
with the late evening update once the early morning hours come
into the NARRE-TL guidance`s temporal window.
Lows will range from the lower 70s inland to the upper 70s/near
80a the beaches. A few upper 60s will be possible across the
more sheltered areas well inland.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
A deep layer Atlantic ridge axis will extend over the northern half
of the forecast area through the period. Moisture will gradually
increase through mid week, with PWs rising from about 1.5 inches on
Monday to around 2 inches by Tuesday and Wednesday. Although the
proximity of the ridge will help to suppress convection, feel there
will be enough deep layer moisture, and combined with the afternoon
sea breeze each day, will warrant slight chance to chance PoPs.
Temperatures are expected to be slightly above normal, with highs
ranging from the lower 90s inland, to the mid to upper 80s closer to
the coast. Lows in the lower to mid 70s, except upper 70s near the
coast.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
An expansive deep layered ridge will remain over the western
Atlantic and far eastern United States through the extended
period. Isolated mainly diurnal convection is anticipated with
highs in the low 90s.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
KCHS: There are increasing probabilities for fog/stratus impacts
early Monday. It does appear the terminal will be on the eastern
fringe of the best fog/stratus parameters, but latest short term
guidance continues to trend lower with cigs and vsbys. Will
highlight fog reaching the terminal by 08z with prevailing
vsbys/cigs dropping to alternate minimums by 10z. Given what
occurred this morning, will also introduce TEMPO conditions of
1/2SM FG BKN002 10-12z, but hold off on showing conditions below
airfield minimums at this time since the terminal is forecast to
be right on the edge of the more favorable fog parameters. The
fog/stratus should quickly lift by 14z with VFR conditions
prevailing thereafter.
KSAV: Main concern centers on fog/stratus potential. Right now,
it appears the terminal will remain just east/south of the most
favorable fog parameters so will continue to favor a fairly
conservative forecast for the early morning hours. Will only
show a TEMPO for MVFR vsbys/cigs 10-12z, but if guidance starts
to shift the axis of better fog parameters south or east, lower
conditions may need to be introduced with the 06z TAF cycle.
Once fog/stratus lift, VFR conditions will prevail.
Extended Aviation Outlook: VFR conditions are expected to
prevail both sites through the week. However, a gradual increase
in deep layer moisture through the week is expected to lead to
isolated to scattered mainly afternoon showers and thunderstorms
each day, which could result in very brief flight restrictions.
&&
.MARINE...
Tonight: A coastal trough will continue to lose definition
with high pressure becoming the dominant feature. E to SE winds
around 10 kt will diminish and become more or less light and
variable. Seas will average around 2 ft. Will have to watch for
possible fog development in the Charleston Harbor early Monday,
which could drop vsbys below 2 NM at times.
Monday through Friday: No highlights are expected through the
period. Atlantic high pressure will prevail through the work
week, with mainly southeast winds of 15 knots or less and seas
of 2 to 3 feet. Isolated to scattered mainly late night and
morning showers and thunderstorms are possible.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
Previous forecast discussion... Very warm and humid conditions
will continue into Tuesday with temperatures running 5 to 10
degrees above normal. Dewpoints will be especially oppressive
with readings in the lower to mid 70s. This morning`s residual
convection and lingering low clouds help limit heating today
despite warm advection aloft. There is plenty of MLCAPE this
afternoon with little CIN but no apparent trigger is seen to
initiate convection. The HRRR model produces a few weak echoes
in the southern counties this evening but confidence is rather
low. Some showers and storms are possible on Lake Erie later
tonight as the more organized activity over the upper Midwest
tracks east across Michigan.
Monday will be several degrees warmer than today due to
increased sunshine and warmer temperatures aloft. Dewpoints will
still be oppressive and heat indices will reach from 95 to 100
west of I-71. Widely scattered showers and thunderstorms could
develop in the afternoon mainly over the southeast half of the
forecast area.
Monday night will be muggy with gradual cooling into the 70s
with little in the chance for rain as ridging aloft prevails.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Main focus of the short term forecast is a cold front that is
expected to move through the area Wednesday afternoon through
Thursday. Models have come in a bit slower with the frontal passage
with the 12Z runs, and have slowed down pops accordingly. The GFS is
still the fastest piece of guidance, while the NAM/GEM are
significantly slower. The ECMWF is a nice compromise for now, with
pops mirror the overall trend of the 12Z run. Either way, dry
conditions are expected Tuesday and Tuesday night with a strong
Bermuda high still influencing the eastern CONUS, with continued
return flow and above normal temps across the area. Have pops coming
into the area through the day on Wednesday, but held of likely pops
until the afternoon across the northwest and the evening/early
overnight elsewhere. With the slower trend of the front, have kept a
low chance/slight chance pop in for Thursday across most of the
area. For temperatures, went close to the warmest MOS guidance for
highs on Tuesday. Went a degree or two warmer for highs on Wednesday
with the slower front, with much cooler temps expected on Thursday
behind the front. Highs should remain in the mid/upper 70s Thursday.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
Very few changes made to the long term today. The period will start
out quiet with high pressure off to the north. Will try for dry
weather through midday Saturday and after that will need to keep
precip in the forecast. The long range models continue to show
differences but both the GFS and ECMWF hint at a cold front over the
western lakes on Saturday. This front will try to push across the
local area on Sunday. Given the uncertainties will keep the precip
mention in the chance category beginning late Saturday in the west
and continuing through Sunday all areas. It will hardly feel like
early fall with dewpoints well into the 60s during the period and
highs both Saturday and Sunday mainly in the middle 80s.
&&
.AVIATION /00Z Monday THROUGH Friday/...
The critical period over the next 6 hours should be completely
VFR, with some mid-upper level clouds moving across the area.
Given the very moist moist air mass that has settled over the
area, some patchy MVFR fog is expected to develop by 09Z and
dissipate just after sunrise with it completely gone by 14Z.
The GFS LAMP model guidance suggests that brief IFR fog could be
possible especially at KYNG and KCAK near sunrise between
11-13Z, so included a TEMPO for them.
OUTLOOK...Non-VFR possible in showers/thunderstorms possibly
late Tuesday night and Wednesday.
&&
.MARINE...
Quiet weather expected on the lake for the next few days as a large
area of high pressure centered over the Carolinas will bring
southwest winds over the region. Winds will generally be in the 5-15
kt range through Monday night, increasing to 20 kts on Tuesday. A
cold front will push across the lake Wednesday and Wednesday night,
with winds becoming northwest behind the front, likely bringing
small craft advisory conditions to at least the eastern half of the
lake for a period of time Wednesday afternoon/evening. High pressure
will build across the lake Thursday through Friday, with light north
winds slowly becoming southerly by the weekend.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
SYNOPSIS...LaPlante
NEAR TERM...Garnet
SHORT TERM...Greenawalt
LONG TERM...Kubina
AVIATION...Saunders
MARINE...Greenawalt
Area Forecast Discussion
National Weather Service Duluth MN
957 PM CDT Sun Aug 26 2018
.UPDATE...
Issued at 955 PM CDT Sun Aug 26 2018
A severe thunderstorm watch has been issued and is in effect
until 4 am CDT for Koochiching, Itasca, and Cass counties.
UPDATE Issued at 710 PM CDT Sun Aug 26 2018
Updated aviation discussion below.
&&
.SHORT TERM...(through Tonight)
Issued at 327 PM CDT Sun Aug 26 2018
The focus is on the potential for thunderstorms and severe
weather through tonight. There is a complex scenario today from
the Northern Plains to western Great Lakes which could lead to
multiple rounds of thunderstorms across the Northland through
tonight. The complexity is contributing to uncertainty in the
forecast.
As of the middle of the afternoon, there as an area of low
pressure in central South Dakota. A warm front extended from the
low across southern Minnesota into southern Wisconsin. A
stationary front extended from eastern South Dakota to northwest
and north-central Minnesota. Shortwaves were lifting northeast
through the region, including one across northeast Minnesota, and
another near west-central Wisconsin. These shortwaves were
triggering areas of thunderstorms.
The Northland will, at the least, be affected by the shortwaves
lifting through the region, and continue to see showers and storms
across northeast Minnesota and parts of northwest Wisconsin
through this afternoon. There is then a good chance of additional
thunderstorm development late this afternoon and this evening.
These storms would begin in areas of northwest Wisconsin to
central Minnesota and spread north and will be in relation to a
surge of humid air with the lifting warm front. The latest HRRR
and RAP runs have suggested the storms might not develop until
nearly as far north as the Grand Rapids to Duluth to Ashland area.
Wherever these storms develop, strong to severe thunderstorms are
possible. There will be an environment of up to 3000 J/kg of
MUCAPE, 30 to 40 knots of deep layer wind shear, and precipitable
water values of 1.5 to 2 inches. The primary concern will be large
hail, but strong wind gusts and heavy downpours are possible. The
flooding threat is limited because of the relatively dry soils
and progressive nature of the storms lifting northward. However,
ponding is possible in more urban areas.
Another round of storms is possible late this evening into the
wee hours of the morning. These storms will be related to an
approaching trough from the west. The latest convective-allowing
models suggesting a storms that develop earlier in the evening in
eastern North Dakota and northwest Minnesota could evolve into a
north-south orientated line of storms by late this evening that
would move into the Northland from the west. These storms could be
severe, with large hail and damaging winds. Brief heavy rain is
also possible. There be an environment of up to 3000 J/kg of
MUCAPE, 40 to 55 knots of deep layer wind shear, and precipitable
water values of about 1.5 inches.
Another round of storms is possible near Price County late
tonight. These storms will be tied to another shortwave lifting
northeast Isolated thunderstorms are possible over western Lake
Superior through this evening. through the area. The environment
will not favor severe weather, but some of the storms could be
strong with small hail, gusty winds, and very heavy rainfall
rates. There will be about 2000 J/kg of MUCAPE, 25 to 30 knots of
deep layer wind shear, and precipitable water values of 2 inches.
If the storms produce heavy rain over areas that get heavy rain
this afternoon, there could be a heightened risk of flooding.
Overall, it will a warm and humid night with chances of
thunderstorms. Overnight lows will be in the middle 60s. Areas of
fog are likely by dawn.
.LONG TERM...(Monday through Sunday)
Issued at 327 PM CDT Sun Aug 26 2018
A shortwave will lift northeastward into Ontario Monday morning,
while a ridge briefly builds in. This will bring an end to showers
and thunderstorms across much of the Northland Monday morning.
This will be brief as a trough slowly digs across the Northern
Plains into northern Minnesota on Tuesday. At the surface a quasi-
stationary front will be the focus for thunderstorm development.
MLCAPE values will increase to 1000-3000 J/kg and 0-6 km bulk
shear to 40-50 knots. This environment will be conducive for
organized convection with strong to severe storms possible.
Precipitable water values will increase to 1.5 to 2.0 inches,
which is at or above the 90th percentile for MPX sounding
climatology. The majority of the 12Z CAM guidance suggests that an
MCS will develop across central Minnesota and propagate eastward
through northwest Wisconsin. In this environment expect the main
threats of damaging wind gusts and heavy rain which may lead to
flash flooding. Expect the heaviest rainfall across northwest
Wisconsin where 1 to 2+ inches is possible. Despite the high
agreement with CAMS there is uncertainty with the evolution as
the convection that occurs late this afternoon and overnight will
impact how things develop on Monday. Expect the heaviest rainfall
late Monday with the highest totals over northwest Wisconsin.
Highs on Monday range from the upper 60s to the mid 80s.
The trough will continue lifting northeastward into Ontario on
Tuesday. This will gradually move the stationary/cold front
eastward through Wisconsin. In its wake a mid-level ridge will
build in from the Northern Plains. This will gradually end
precipitation from west to east. Flow aloft will become
northwesterly and advect in cooler air. High temperatures on
Tuesday range from the mid 50s over the Minnesota Arrowhead, to
the low 70s across southern portions of northwest Wisconsin.
A shortwave will move across the High Plains into the Mid
Mississippi River Valley on Wednesday bringing chances of
scattered shower. There is some uncertainty at this point as GFS
has high pressure building in overhead, while a ECMWF/GEM keep the
frontal boundary lingering across northwest Wisconsin. There is
more agreement in shower/storm chances late in the week heading
into next weekend. A trough will dig in from the Pacific Northwest
into central portions of Canada. This will bring southwesterly
return flow to the Upper Mississippi River Valley. Expect
temperatures to warm up to the low to mid 70s on Friday/Saturday
with shower and thunderstorms being possible.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 710 PM CDT Sun Aug 26 2018
A complicated setup befalls the Northland tonight. Storms forming
along a warm front moving northward through the region should linger
on and dissipate around midnight. Another round of storms coming
from the west will affect most sites around the late night and
early evening hours. MVFR or lower conditions are possible with
both rounds of storms. With the recent rainfall and winds becoming
relatively light overnight, patchy fog may develop. The
uncertainty with fog development lies in whether skies will clear
enough before and after the second round of storms. For now, did
not feel confident to put fog in the TAFs. VFR conditions return
late Monday morning. Another round of showers and storms come
through Monday afternoon/evening.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 64 76 56 60 / 50 40 50 40
INL 63 65 47 61 / 90 20 50 40
BRD 68 76 56 65 / 30 50 50 30
HYR 67 83 60 68 / 40 70 80 40
ASX 65 83 59 63 / 90 60 60 40
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
UPDATE...Wolfe
SHORT TERM...G2
LONG TERM...WL
AVIATION...KC
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
252 PM PDT Sun Aug 26 2018
.SYNOPSIS...Near normal temperatures are expected to continue
through the upcoming week as a series of upper-level disturbances
impact the West Coast. Additionally, areas of smoke and haze will
linger across some of the area for the next couple of days.
&&
.DISCUSSION...Upper-level troughiness is expected to continue
through early this week, with another upper-level disturbance
forecast to dig across the Pacific Northwest and northern
California late in the work week. These features will aid in
keeping temperatures near normal across northwestern California
through next weekend. No rain is expected across the forecast
area over the next seven days, though the GFS does portray
showers over eastern Del Norte county, but confidence is low.
Sunday afternoon visible satellite imagery shows marine stratus
has dissipated once again over most of the coastal waters. The
lone exception today is south of the Cape Mendocino, which
continues to see stratus offshore and along the immediate coast.
Smoke looks to be less widespread than yesterday, though wildfire
smoke from southwestern Oregon continues to drift southward.
Recent HRRR smoke guidance indicates smoke may continue to pass
across coastal waters and the immediate coast as the area drifts
southward. Sunnier conditions are expected this evening and Monday
evening, though some smoke layers may linger.
&&
.AVIATION ...Offshore flow helped to keep KCEC free from stratus
development early this morning while coastal locations from the
Humboldt Bay area southward to Point Arena experienced MVFR to IFR
conditions today. KACV will experience VFR into the early evening as
daytime mixing maintains mostly clear skies. Otherwise everywhere to
the south will be stuck under the clouds with brief scattering
possible late this afternoon. The forecast through tomorrow
afternoon will be close to persistence with stratus returning to
coastal airfields except for KCEC due to dry easterly flow.
Otherwise expect mostly VFR across the interior. /KML
&&
.MARINE...Fresh northerly winds will continue across the outer
coastal waters this afternoon and begin to diminish late Monday as a
weak front causes the pressure gradient to relax. Winds will overall
be lighter nearshore but gusts near 30 kt will be possible around
Point Saint George and Cape Mendocino through Monday afternoon.
Additionally, eddies in the wind flow will bring south winds to
parts of the Mendocino and Humboldt county coasts. Light to moderate
winds will then persist through most of the week ahead with more
widespread south winds forecast to develop off of the Mendocino
Coast on Tuesday. Models indicate a return of fresh northerly winds
by next weekend but there is still some uncertainty at this time.
Otherwise, steep seas will gradually subside this week and west-
northwesterly swell will impact the coastal waters. Expect the sea
state to fall around 5 ft later in the work week. The small craft
advisories remain in effect through Monday afternoon. /KML
&&
.FIRE WEATHER...Locally gusty east to northeast winds will be
possible tonight and Monday evening/night across the ridge tops
of interior Del Norte county as a weak upper-level trough
continues to move out of the western U.S. RH recoveries have been
pretty good the past few days and this trend is expected to
continue through Monday. Otherwise, onshore flow will yield near
normal temperatures area-wide through next week.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until noon PDT Monday for PZZ450.
Small Craft Advisory until 9 PM PDT Monday for PZZ470-475.
&&
$$
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For forecast zone information
see the forecast zone map online:
http://www.weather.gov/eureka/zonemap.png
Area Forecast Discussion
National Weather Service Grand Forks ND
1017 PM CDT Sun Aug 26 2018
.UPDATE...
Issued at 1016 PM CDT Sun Aug 26 2018
With a shortwave ejecting out into the Northern Plains and the low
level jet starting to ramp up, convection has been increasing in
coverage across much of the central and northern CWA. Storms have
been moving into the southern counties also but are more isolated
in coverage. MU CAPE is ranging from near 1500 J/kg in the north to
3000 in the south, and deep layer bulk shear is over 50 kts. A
severe thunderstorm watch has been issued to include the counties
to the north and east of the existing tornado watch as the storms
move eastward. CAM models have not been very consistent with
where they are taking the strongest cells, but have a general idea
of quite a bit of rain in the north and more hit and miss in the
south. Adjusted POPs accordingly.
&&
.SHORT TERM...(This evening through Monday)
Issued at 247 PM CDT Sun Aug 26 2018
Watching ongoing convection, so will keep the discussion brief.
Seeing intensifying activity over far southeast ND right now, with
satellite imagery correlating the growing clouds. SPC put out a
mesoscale discussion a short while ago, talking about a potential
watch for the southern third of our FA. This growing convection
may push this watch into a quick reality. Latest HRRR runs have
been showing other activity firing over the Red River Valley by 8
to 9 pm, and lasting until just past midnight. They no longer show
any activity pushing in from western ND. So will see how things
play out tonight.
.LONG TERM...(Monday night through Sunday)
Issued at 247 PM CDT Sun Aug 26 2018
Rain chances return Monday night into early Tuesday across the area
as a shortwave trough moves into the region and a low pressure
system skirts by to the south through the Central Plains. With
little instability present on the cool side of this system, suspect
this will be mainly shower activity with perhaps some embedded
thunder.
For Tuesday through Thursday, expect quiet and dry weather.
Temperatures will be notably cooler Tuesday and Wednesday as the
upper trough axis swings through the Plains and dry northwest flow
aloft develops. A warming trend develops from Wednesday to Friday in
warm air advection ahead of a system moving through the Canadian
Plains.
After a breezy day Thursday amidst pressure gradient winds, chances
for showers and thunderstorms develop Thursday night through Friday
night as a shortwave trough aloft and surface front pass through the
Northern Plains.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 642 PM CDT Sun Aug 26 2018
Still tried to hit the 8 pm to just past midnight time frame as
the prime hours for storm development. Not much happening right
now, but expect storms to blossom over the area in the next couple
of hours. Pretty hard to say exactly where and when, so all TAF
sites still have a chance. Activity should begin to wane a few
hours after midnight. These storms could also drop some heavy rain
at times.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...JR
SHORT TERM...Godon
LONG TERM...BP
AVIATION...Godon
Area Forecast Discussion
National Weather Service Hastings NE
632 PM CDT Sun Aug 26 2018
.SHORT TERM...(This evening through Monday)
Issued at 312 PM CDT Sun Aug 26 2018
Aloft: WV imagery/RAP dynamic tropopause analyses/aircraft wind
data showed a large subtropical high over TX/OK. A longwave trof
extended from the Nrn Rckys down to Cntrl CA. This config has
resulted in SW flow over the Cntrl Plns. A weak/subtle shortwave
trof was currently over Neb/KS and was responsible for the spotty
light shwrs this AM. This trof will exit E of the CWA this eve.
Cyclonic flow will remain over the rgn in its wake thru tomorrow
as the Nrn Rckys trof deepens.
Surface: The CWA was in the warm sector. High pres was over the
SE USA while a cool front extended from Hudson Bay thru SD and
into the Nrn Rckys. Much of this front was stationary. Low pres
was along the front over SD. This low will strengthen and rapidly
move into SW Ontario tonight. With the SW flow aloft...the front
will struggle to move S but it is fcst to sag into Nrn Neb
tomorrow.
Rest of this afternoon: P-M/cldy. Lowered high temps where cloud
cvr has been most persistent.
Some HREF members suggest a couple tstms could fire over the SE
fringe of the CWA (Osborne-Hebron-York). HRRR and the HRRRX
ensemble say no...but have a low 20% POP to cover this potential.
SREF MLCAPE is fcst 1500-2500 J/kg with 0-6 km shear around 30 kt.
So a stg-svr tstm can`t be ruled out if something develops.
Tonight: if any tstms dvlp far SE...they will exit the CWA early.
Should see a temporary decrease in clds as the trof departs and
subsidence moves in...but then an increase in clds from distant
tstms over the high plns. There is a lot of uncertainty but have
introduced a low 20% POP W of Hwy 183 just in case some dying
remnants of high plns tstms move in from the W after 03Z. HREF
members suggest they will die before reaching the CWA...but the
HRRR and a minority of the HRRRX ensemble maintain a little tstm
activity could survive and move in.
There is a very low chance a few high-based tstms could also form
after midnight well N and W of the Tri-Cities.
Overall...another very warm and muggy night. Winds will remain
brzy over the SE 1/2 of the CWA.
Mon: Could see a few high-based tstms before noon well N and W of
the Tri-Cities. Decreasing clds and hot with widespread 90s.
Would not be surprised to see 100F in a couple spots from Furnas
into Phillips counties where the air will be driest. Even if the
temp doesn`t reach 100F...there will be a few spots where the Heat
Index reaches 100-103F over the SE 1/2 of the CWA. Mercifully...
that area will be the breeziest.
.LONG TERM...(Monday night through Sunday)
Issued at 312 PM CDT Sun Aug 26 2018
Aloft: Looking at spaghetti plots of the last 2 runs of the
EC/GFS/GEM/UKMET...the longwaves trof over the NW USA trof will
advance across the Nrn/Cntrl Plns Tue followed by rising heights
Wed with zonal flow continuing into Thu. The longwave trof over
the NW USA will reload during that time and it now looks like it
will progress thru the Nrn/Cntrl Plns Fri...somewhat ironically
like the 12Z/Sat GFS which I dismissed as an outlier. A lot of
spread dvlps Fri which is not surprising given that a blocking
subtropical high (currently btwn AK and HI) will persist thru the
wk. We should see a trof deepen over the Wrn USA with a ridge in
the E. Amplification is fcst...but how the mdls are treating
shortwave activity circulating around the top of the ridge results
in tremendous spread within the Wrn trof next wknd into the 1st
wk of Sep.
Surface: The cool front will finally drop S thru the CWA Mon
night into Tue. Cool high pres will cross the rgn Wed with return
flow dvlpg. Deep low pres will swing thru SW-Cntrl Canada Thu.
This will induce warm frontogenesis over Neb/KS and this front is
fcst to move thru Thu night. Warm sector Fri with passage of a
cool front Fri night. Thereafter there`s just too much uncertainty
to provide any other specifics. We`ll have to wait and see.
Temps: Breezy and much cooler Tue in CAA. Wed temps will be
cooler than normal as well. Then returning to near normal Thu.
Above normal Fri in the warm sector...then back to near normal
Sat-Sun behind the cool front.
Rain: No significant widespread rain is currently envisioned. As
is typical of summer...most of the time will be dry. Can`t rule
out a few isolated tstms in vicinity of the cool front Mon night
into Tue night...espcly as the RRQ of a strong 130 kt jet streak
moved thru ahead of the upr trof. Best chance will be S and E of
the Tri- Cities where instability will exist.
The next modest chance for a few tstms will be Thu night as the
nose of the low-lvl jet impinges upon the warm front.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday)
Issued at 630 PM CDT Sun Aug 26 2018
A few thunderstorms to the southwest of the KGRI terminal area and
could briefly affect the terminal in the next couple of hours.
They should be dissipating as the sun goes down. Ceilings should
remain VFR through the period. There could be some low level wind
shear late tonight then winds increase late tonight and Monday
during the day.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...JCB
Area Forecast Discussion
National Weather Service Goodland KS
450 PM MDT Sun Aug 26 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 328 PM MDT Sun Aug 26 2018
Forecast concerns will be chance of precipitation tonight along with
Monday night into Tuesday night, high temperatures Monday and
Tuesday, Fire weather on Monday, and the winds with the passage of
the cold front. Satellite showing an amplified flow from the Pacific
into western North America. This flow flattens out and is more
progressive over the central and eastern portion of the country.
Rather strong and cold upper trough moving through southwest Canada
and northwest portion of the country. Satellite and upper air
analysis show a more moist air mass through mid levels than compared
to 24 hours ago.
For Tonight/Monday...Right rear quadrant of the jet is near or over
the far western portion of the area later this afternoon/early this
evening and then only moves a little further east through the rest
of the night. A couple of shortwave troughs move through during the
evening and overnight hours. There now appears to be some surface
covergence out west with a new surface trough.
Even though the instability is less further west, models appear to
be latching onto all the above and generating some thunderstorms
across the area through the night. The Rap is the most aggressive
with this. Considering that there is development out there already
will follow the above trend. At this time, the lift and greater
instability to our east, is just to the east of our forecast area.
Per all the above am keeping the thunderstorms out of the eastern
portion of the area.
Above mentioned right rear quadrant is slower/further west than what
was shown yesterday. It will continue to affect the southeast half
through the morning hours. There may be some lingering lift and
rainfall going on early in the morning so will keep a slight chance
there.
After any morning precipitation clearing should be rapid and
expect plenty of sunshine. There is a deep layer of dry air and
downslope winds. Trend in the 850 mb temperatures, 2 meter, and
Mos is to maintain or warm the air mass even more than today. That
makes sense with less cloud cover and more downslope. So raised
high temperatures in according with 850 mb temperature bias and
warmer 2 meter and Mos. This means temperatures will be near 100
in a lot of places tomorrow. Refer to the fire weather section for
discussion on this.
Monday night into Tuesday night...Will get into more detail on the
front below, but the front looks to be arriving later. Overnight
shift was thinking that some thunderstorms could develop along it.
700 mb temperatures ahead of the front would indicate air mass ahead
of it will be capped. Area is in subsidence from exiting jet.
Forecast soundings are also showing an extremely deep dry air mass
in place ahead of the front. Due to all that and collaborating, have
kept Monday night dry.
Models are now generating a lot of post frontal precipitation.
However, models are differing on how deep the moisture is. Forecast
builder now has pops in Tuesday and especially Tuesday night. A
complicated jet structure moving across and showing some differences
in how they want to move this across. First jet segment/right rear
quadrant moves across the area Tuesday afternoon with a second
segment and right rear quadrant moving across during the evening and
overnight hours.
Models showing a strong baroclinic zone at 700 mb beneath the jet
lift. Frontogenesis forecasts show weak to moderate forcing moving
across the area during this time. Midlevel theta-e lapse rates near
to slightly below zero so there should be a good response to the
lift. Models also showing some elevated Cape. May end up being more
embedded thunderstorms in the rain showers but decided not to get
too cute with this. So like the pops that are in there Tuesday and
especially Tuesday night. Potential is there for pops to be expanded
in time and space on Tuesday.
Cold front looks to be a little slower in arriving and looks now to
not move into the area until after midnight. It looks to be through
the northwest half by late in the night and through the entire area
by late morning. Very tight pressure gradient and 3 to 6 hour
pressure rises of 5 to 10 mb would indicate windy conditions to
follow behind the front. Per that and collaboration with neighbors,
loaded in Consmos for the winds for this period.
There is about a 20 degree difference in the high temperature
forecasts for Tuesday. The Nam/Met is by far the most aggressive
with the temperatures which they have mostly in the 60s. This is
due to a blanket of stratus and any ongoing precipitation. Believe
the Nam is on the right track, and with the last major cool down
it did best. I did cool down the blend temperatures to near the
mid point of the extremes from the Mos and 2 meter guidance.
However this may need to be reduced much more.
Wednesday...Precipitation looks to be done. Temperatures remain
cool, and depending on how Tuesday works out, still look reasonable.
.LONG TERM...(Wednesday night through Sunday)
Issued at 156 PM MDT Sun Aug 26 2018
High pressure over the southwest U.S. and upper level zonal flow dominate
through Friday leading to above normal temperatures. A dryline
sets up along the Kansas/Colorado border Wednesday night into
Thursday morning which could provide the necessary lift for the
formation of thunderstorms Wednesday night into Thursday morning.
The dryline then moves east by Friday taking above normal
precipitable water values with it. The lack of decent PWAT values
should hinder any chances for rain until moisture returns to the
region Saturday night.
The base of a trough moves across the central Plains Friday night bringing
a surface low that will lead to cooler temperatures Saturday. A
ridge moves over the Plains Saturday with the high pressure
centered over the far southwest U.S. An incoming trough over most
of the western U.S. pushes the ridge out quickly leading to only a
slight warming of temperatures Sunday. The east side of the
incoming trough extends into central Kansas leading to
precipitation chances Sunday evening.
The main takeaways are that the heat returns Thursday with some
cooling over the weekend and mostly dry conditions are expected
throughout most of this forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 445 PM MDT Sun Aug 26 2018
KGLD, vfr conditions expected through the period. Some
disagreement on the wind forecast from taf issuance through
sunrise Monday morning but general idea is for a south wind 10kts
or less with some erratic direction changes dependent on possible
convection near or over the terminal. At this point precipitation
coverage is very spotty and will leave out of the forecast but
will amend should an impact be expected. Main threat will be gusty
outflow winds. For the day Monday will see southwest winds veer to
the west 10kts or less then back to the southwest and increase a
bit with some gusts toward 20kts or so ahead of an approaching
weather system from the northwest.
KMCK, vfr conditions expected through the period. Am expecting
south winds under 10kts through 11z with southwest then west winds
around 6kts or so through 20z. After 21z winds back to the
southwest and approach 10kts with perhaps a few gusts as pressure
falls increase ahead of an approaching weather system from the
northwest. Similar to KGLD will leave out any mention of showers
and/or thunderstorms for now as coverage is very spotty.
Amendments will be issued should an impact to the terminal be
expected. Gusty outflow winds will be the primary concern.
&&
.FIRE WEATHER...
Issued at 328 PM MDT Sun Aug 26 2018
For Monday...Air mass looks a little drier than yesterday. Relative
humidities are 16 to 20 percent across all but the far eastern
portion of the area. The lowest humidities are along and west of the
Colorado border. Lapse rates look good and should mix that drier air
down and also some stronger winds. Per collaboration with neighbors,
I used Consmos, and still did not get winds of 25 mph or greater
where the lowest relative humidities will be. At this time where the
strongest winds will be is where the highest humidities will be.
So will keep the previous of only elevated fire weather danger. SPC
forecast reflects that as well. If however mixing will go even
higher than what I think, then the winds and humidities may need to
be lowered even more.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...BULLER
LONG TERM...NEWMAN
AVIATION...99
FIRE WEATHER...BULLER
Area Forecast Discussion
National Weather Service Grand Rapids MI
754 PM EDT Sun Aug 26 2018
LATEST UPDATE...
Update/Aviation
.SYNOPSIS...
Issued at 313 PM EDT Sun Aug 26 2018
Several rounds of nocturnal thunderstorms are possible starting
tonight lasting through Wednesday morning. Areas north of I-96 have
the best chance of seeing thunderstorms tonight and Monday night
with area wide activity possible Tuesday night and into Wednesday.
While localized severe weather is possible each night (damaging wind
gusts to 60 mph and 1" hail), very heavy rainfall and localized
flooding are the greatest concerns. Dry conditions are then expected
by the end of the workweek.
&&
.UPDATE...
Issued at 754 PM EDT Sun Aug 26 2018
I have increased the POP and QPF over our northern two rows of
counties tonight since run after run of the HRRR continues to
show an area of 2 to 4" of rain near and north of Route 10
tonight. There is good 1000/850 moisture transport into that area
and 1000/700 thickness pattern supports this idea. I am concerned
about that much rain but it has been dry in that area so at this
point I am not planning on issuing a flood advisory. Still this
will have to be watched as this area may see storm after storm go
over the same area. Areas near and south of I-96 should for the
most part stay dry tonight.
I am planning on letting the marine fog advisory end as
scheduled at 8 pm. Seems the fog is lifting out of that area.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 313 PM EDT Sun Aug 26 2018
As a shortwave trough embedded within broad southwesterly flow aloft
moves northeast into the Great Lakes, all eyes will be on convective
trends this afternoon across portions of Iowa, Minnesota, Wisconsin,
and perhaps as far south as northern Illinois. Several clusters are
already ongoing as of this writing but everything so far has been
relatively unorganized. Surprisingly, the 12Z suite of numerical
model guidance (e.g. HREF ensemble, SREF [derivative of the NAM],
various WRFs and iterations of the HRRR, etc.) all agree that
whatever develops upstream will move into northern Lower Michigan
overnight, specifically north of a line from Stony Lake to Mount
Pleasant. Frankly I have no reason to disagree. However, a slight
shift south is definitely in the realm of possibility. So, we`ll
say areas north of I-96 have the best shot of seeing activity
tonight.
Forecast MUCAPE >2000 J/kg and 0-6 km bulk shear suggests that the
storms will become increasingly organized upstream of our area this
evening with an east/northeastward propagation (e.g. 0-1 km shear
vectors will be orientated east/northeast). The linear nature of
expected convection suggests that strong to locally severe winds
are possible with a lesser threat of hail in individual "pulsey"
cores. If the clusters become somewhat staggered--that is, one
leads the pack--the interaction of the expected orientation and
magnitude of the low- level jet overnight with a potentially west-
to-east orientated outflow boundary will promote rearward off-
boundary development (e.g. training convection; see Peters and
Schumacher [2014] in MWR Vol. 142). Interestingly several
numerical models suggest such a scenario with a west-to-east swath
of very heavy rainfall (2-4"+) by midday Monday. In fact, the
HREF 24-hr ensemble localized probability-matched mean rainfall
shows a swath of 2-3" across northern Lower Michigan tonight,
demonstrating the agreement among various CAMS in the placement
and occurrence of heavy rain. So, we have high confidence that
there will be a narrow swath of very heavy rain tonight somewhere
in lower Michigan most likely north of a line from Stony Lake to
Mount Pleasant.
Elsewhere across lower Michigan, dry conditions are expected
overnight but patchy fog is possible. Surface winds at/above 5 kts
overnight should limit both the spatial extent and intensity of the
fog compared to this morning.
By late Monday morning, the expectation is for any remaining
convection to wane as the low-level jet weakens and veers west. A
period of dry weather is then expected in lower Michigan before we
do it all over again Monday night and into Tuesday. A similar
regime appears possible with one or two clusters of strong to
severe convection propagating into lower Michigan aided by a
southerly low- level jet. There does seem to be a signal that the
convection will be decaying this time around, but again areas
north of I-96 (and especially north of a line from Stony lake to
Mount Pleasant) are favored for repeated activity. Depending on
how much rain falls tonight, localized flooding may become an
issue north of I-96 especially if the same areas are hit (see the
hydrology discussion below).
Then, we get to do it -again- on Tuesday and Tuesday night.
However, development Tuesday seems like it`ll be tied to a
southward-drifting outflow boundary/effective warm front
originating from activity from the nights before. Indeed,
development may occur right overhead Tuesday afternoon/evening
with both severe weather and heavy rainfall possible. We`ll leave
it at that for now.
So, to summarize, repeated rounds of storms are expected starting
tonight and lasting through early Wednesday favoring areas north of
I-96 through early Tuesday. While locally strong winds and hail
are possible, the main threat is heavy rainfall and flooding where
the convective complexes train.
.LONG TERM...(Wednesday through Sunday)
Issued at 313 PM EDT Sun Aug 26 2018
Model guidance has started to hint at the development of a low
pressure system on Wednesday along the effective warm front draped
along our area. Given the dependency on convection basically
tonight through Wednesday and associated uncertainties, I have
very low confidence that a low will actually develop. However, it
is still worth noting that Wednesday may be wet. Thereafter, a high
pressure system is expected to slide into the Great Lakes by
Thursday and last into the first portion of the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 754 PM EDT Sun Aug 26 2018
Currently all TAF sites are VFR and more than likely will stay so
till at least 03z or so. There is an area of convection over
eastern WI moving toward Lake Michigan as I write this. All
indications are the storms will mostly stay north of our TAF
sites. However I am concerned about MKG so I did bring the storms
into that area in the 04z to 08z time frame. It is possible the
convection from the WI line would get there sooner, so I will
continue to watch this.
Otherwise it should stay largely VFR into Monday evening. Most of
the convection will be north of our TAF sites through Monday
evening. Low level wind shear is expected at the MKG and GRR taf
sites due to the position of the mid-level jet to those TAF sites.
&&
.MARINE...
Issued at 313 PM EDT Sun Aug 26 2018
Areas of dense fog will continue this afternoon across portions of
Lake Michigan. Southerly winds are then expected to increase to 20-
25 kts tonight and to 25-30 kts Monday night. A few gusts to 30 kts
are possible on Monday night. Waves will accordingly increase to 3-5
ft toward daybreak tomorrow, and then 4-7 ft overnight into Tuesday.
While waves will start to relax during the day on Tuesday, an
increase in wave heights is possible on Wednesday in the wake of a
front.
All in all, very hazardous boating and swimming conditions are
expected through midweek. Remember...
- Stay dry when waves are high!
- Stay clear of the pier (including on walkways as waves can
still knock you off)!
&&
.HYDROLOGY...
Issued at 313 PM EDT Sun Aug 26 2018
A favorable pattern for heavy rainfall is setting up through Tuesday
night that will likely lead to rises on area rivers and streams
particularly near and north of I-96. Antecedent conditions are drier
across this region (mainly near/west of US 131, where a Moderate
Drought is in place) as compared to other regions across central and
southern Lower Michigan. As a result, rainfall will initially get
soaked into the soil pretty rapidly. However, successive rounds of
primarily nocturnal convection could saturate soils enough to lead
to significant rises on smaller rivers and streams.
Main stem rivers like the Muskegon River have plenty of capacity for
runoff at this point, with Evart currently sitting around the 20th
percentile for streamflow. The Pere Marquette is currently near
normal, with flows only around a foot at Scottville, which is a site
that requires a significant amount of rain to flood. Similarly, the
White River at Whitehall has a wide capacity to take on significant
rain at this point with flows around the 55th percentile.
If any of these sites get a few inches of rainfall through Monday
morning and then were to get significant additional rain Monday
night into Tuesday morning and beyond, it is conceivable that
flooding would be a problem. Shy of this happening, the rivers will
likely still rise (possibly quite a bit) but hold below flood
stage.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 4 AM EDT Monday through Tuesday
morning for MIZ037-043-050-056-064-071.
LM...Small Craft Advisory from 4 AM Monday to 8 AM EDT Tuesday for
LMZ844>849.
Dense Fog Advisory until 8 PM EDT this evening for LMZ846>848.
&&
$$
UPDATE...WDM
SYNOPSIS...Borchardt
SHORT TERM...Borchardt
LONG TERM...Borchardt
AVIATION...WDM
HYDROLOGY...Hoving
MARINE...Borchardt
Area Forecast Discussion
National Weather Service San Francisco Bay Area
831 PM PDT Sun Aug 26 2018
.SYNOPSIS...Cooler than normal temperatures are forecast to
continue, especially inland, through midweek as a trough of low
pressure remains over California. A brief warming trend is
possible later in the week as a weak ridge of high pressure
temporarily builds over the area.
&&
.DISCUSSION...As of 8:30 PM PDT Sunday...A slight increase in both
the depth of the marine layer and strength of onshore flow was
enough to bring about cooling across much of the North and East
Bay today. Otherwise little change was observed.
A longwave trough is currently located over the Pacific Northwest
and northern Rockies. A weak shortwave embedded in the flow on
the upstream side of the trough is dropping south along the coast
of Oregon. The models agree that this shortwave will pinch off
from the main flow and form a weak upper low near Point Arena by
Tuesday morning. This is expected to result in slight deepening
of an already deep marine layer. Thus, we can expect continued
cooler than normal conditions across our region through midweek.
The weak low is forecast to fill by Wednesday.
A second weak upper low several hundred miles west of the
California coast is forecast to approach the coast later in the
week. As the low approaches, a shortwave ridge is forecast to
develop upstream of the low and over California by late Thursday
and Friday. This should result in modest warming late in the week,
primarily inland. Even with this warming, temperatures are
expected to remain a bit cooler than normal.
Both the GFS and ECMWF forecast the upper low to track across
northern California sometime around Saturday. The low may produce
scattered showers over the higher mountains to our north and
northeast, but dry conditions are expected to prevail across our
area. The primary impact of this low will be to cool temperatures
during the first part of next weekend.
&&
.AVIATION...as of 6:38 PM PDT Sunday...It`s VFR except along the
immediate coast stratus is causing areas MVFR ceilings. A general
increase in stratus is forecast tonight and Monday morning due to
onshore winds, and little change in depth of the marine layer is
forecast for the period.
Today`s 18z High-Resolution Rapid Refresh (HRRR) output indicates
wildfire smoke from the Mendocino Complex remaining over the North
Bay while a combination of this wildfire`s smoke and additional
smoke from far northern California will spread into the Bay Area
mid evening to Monday morning; however, a 4 pm report from the
Farallon Islands showed good visibility at 10 miles while the 18z
HRRR forecast for this location showed light amount of smoke thus
the HRRR may in spots be overforecasting smoke coverage. Going
back to last Tuesday evening into Wednesday lower level cool air
advection within the marine layer appeared to have at least initially
helped slow or limit the arrival of then forecasted surface based
smoke on W-NW winds. Lower level cool air advection is forecast
tonight through late Monday thus there may once again be sufficient
mixing to keep surface based visibilities generally good while
slant range visibilities aloft may tend to lower to moderate to
poor over the Bay Area valleys above the marine temperature inversion
by early Monday morning.
Vicinity of KSFO...VFR, however westerly wind near 15 knots possibly
ushers in a stratus cloud based MVFR ceiling tempo MVFR 04z-06z then
it`s prevailing MVFR to 18z Monday. VFR returns late Monday morning
through the afternoon.
SFO Bridge Approach...Similar to KSFO. Slant range visibility may
tend to lower to moderate to poor by early Monday morning.
Monterey Bay Terminals...MVFR ceilings developing early evening,
transitioning to IFR tonight. IFR mixes out by late Monday morning,
VFR forecast Monday afternoon and early evening until stratus likely
returns early Monday evening. Slant range visibility may become
moderate Monday.
&&
.MARINE...as of 5:00 PM PDT Sunday...Breezy conditions will
continue tonight over the outer waters north of Pigeon Point as
northwesterly winds prevail. Generally light northwest swell
around 3 to 6 feet is expected through the forecast period.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm
&&
$$
PUBLIC FORECAST: Dykema
AVIATION: Canepa
MARINE: Sims
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