Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/15/24
Area Forecast Discussion
National Weather Service Aberdeen SD
647 PM CDT Sat Sep 14 2024
.KEY MESSAGES...
- There is a Marginal Risk (level 1 of 5) for hail in excess of 1
inch in diameter and damaging winds over central SD this
evening.
- Several chances for precipitation next week. Greatest confidence
for widespread rainfall will be Tuesday night into Wednesday
with 50-70% chances.
&&
.UPDATE...
Issued at 647 PM CDT Sat Sep 14 2024
The overall trend with the ongoing storms over and east of the
Missouri River has been a diminishing one. There are a couple of
exceptions over Lyman County and west of Stanley/Jones County,
where we have been seeing strengthening storms over the last hour
that will need to be monitored for gusty winds of 50-60mph and
quarter sized hail with the strongest storms. To the east, the
outflow surged east and across Aberdeen-Redfield with gusts around
35 mph. Limited precipitation is expected east of this area
(Aberdeen-Redfield).
&&
.SHORT TERM /THIS EVENING THROUGH SUNDAY NIGHT/...
Issued at 316 PM CDT Sat Sep 14 2024
The region will be between ridging over the eastern part of the
country and a digging trough over the west coast through the near
term period. This will keep a southwesterly flow over the Northern
Plains, with some shortwave energy tracking across the CWA this
evening, then again across central South Dakota Sunday night.
At the surface, already seeing thunderstorms develop across parts of
southwestern South Dakota this afternoon. These storms are
developing along a boundary associated with low pressure over far
western South Dakota and in an area where MUCAPE values are in the
1000-1500 J/kg and bulk shear is around 30 knots. The stronger
instability looks to diminish through the afternoon, but will see
about 700-900 J/kg remain over central South Dakota this evening,
along with 35 to 45 knots of bulk shear. This will likely be enough
to keep convection going through 03Z or so. Weak high pressure will
bring quieter conditions overnight and through the day Sunday, then
another boundary will set up from southwestern to central South
Dakota. The best shear and instability will be over central South
Dakota, but will not really be aligned timewise. CAMs hinting at
some convective development, but the HRRR is currently the only one
that shows any decent areal coverage, so will stick with POPs in the
20 to 40 percent range for now.
Low temperatures tonight will range from the mid 50s across north
central South Dakota to the mid 60s across northeastern South
Dakota. High temperatures on Sunday will be in the mid 80s to the
lower 90s. Lows Sunday night will be in the mid 60s.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 316 PM CDT Sat Sep 14 2024
The long term starts out Monday morning with a low pressure system
to our west over MT. This low will move northeast and enter Canada
before reaching our area. However, its warm and cold fronts will
move more easterly and impact the area Wednesday afternoon through
at least Wednesday. Thursday and Friday we are stuck in a blocking
pattern with a low on the western side of the Rockies, a high over
the Great Lakes region, and another low over the Carolinas. The EC
ensemble shows a low moving west southwest across Canada on Saturday
will help to break this pattern and another cold front will move
across the area. The CMC ensemble and GEFS have some members showing
a low in Canada but mostly lean towards a surface low circulating in
the lee of the Rockies on Thursday and lasting through the end of
the period. There is still a lot of time for models to come into
agreement since this is at the far end of the period.
There are several waves of possible precipitation through the
period. The first starts early Tuesday with pretty light PoPs from
the NBM of 20-30%. These chances move out of the region by late
morning to early afternoon, leaving the rest of the day dry.
Starting early Wednesday morning, another band comes through with
much higher PoPs. Highest chances (70-75%) stay mainly south of I-90
with a band of 50-70% moving west to east across SD, decreasing to
30-45% as it moves into west central MN during the afternoon hours.
Probability of more than 0.25" is generally between 50 and 60%, with
slightly lower chances across north central SD. The next wave starts
early Friday morning with widespread 30-40% chances that will stick
around through the day Saturday. There is a lot of uncertainty with
this event which accounts for the lower PoP values.
Temperatures will be slowly decreasing through the period. Monday
and Tuesday will continue our current pattern of above normal
temperatures with highs in the mid 80s to around 90. Wednesday,
Thursday and Friday are expected to be slightly cooler with highs in
the upper 70s to low 80s. After a few days of clouds and rain
chances, along with some fairly strong CAA, Saturday looks to be
much more fall-like with highs in the mid 60s to low 70s. Afternoon
wind gusts Monday and Tuesday are expected to be between 30 and 40
mph, mainly over central SD on Monday, but spreading to all of
central and northeastern SD on Tuesday. Wednesday could see some
gusts about of similar strength in higher elevation areas, but are
expected to die out in the afternoon. The rest of the period is
expected to be less windy.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 647 PM CDT Sat Sep 14 2024
Terminals KABR,KATY,KPIR,KMBG
While mainly VFR conditions will continue, we are monitoring for
the potential of additional thunderstorms moving across MBG and
PIR by 02Z, weakening and ending by 04Z Sunday.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...KF
SHORT TERM...Parkin
LONG TERM...KK
AVIATION...KF
Area Forecast Discussion
National Weather Service Cheyenne WY
815 PM MDT Sat Sep 14 2024
.KEY MESSAGES...
- Critical fire weather conditions continue this afternoon,
mainly in Carbon, Albany, and Converse counties. A Red Flag
Warning is in effect.
- Chances for showers and thunderstorms will return Sunday
through Tuesday, followed by another chance for precipitation
and cooler temperatures late in the week.
&&
.UPDATE...
Issued at 813 PM MDT Sat Sep 14 2024
The Red Flag warning expired at 8pm this evening. Relative
humidity values increased above critical thresholds and winds
decreased as the sun went down. Decreased overnight lows a
degree or so due to clear overnight skies and cooler than
forecast temperatures as of 02Z. No other major changes were
made with this update.
&&
.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 305 PM MDT Sat Sep 14 2024
Latest GOES WV imagery showers primarily zonal flow across the
area in the wake of the vort max passing through earlier this
morning. A mid-level jet will continue to traverse central WY
today with elevated winds downsloping off the North Laramie
Range contributing to critical fire weather conditions today
(see fire weather discussion below for more details). Otherwise,
mostly clear skies across the CWA. With the earlier timing of
the vort max passage this morning, the dryline has quickly
passed into the NE panhandle through Chadron, but Alliance and
Sidney remain with winds out of the south and dew points in the
mid-50s. The latest HRRR and NAMNest now does initiate a storm
or two in Morrill/Cheyenne Co where latest GOES imagery shows
ongoing cumulus development. Will need to continue to monitor
observational trends through this afternoon for possible storm
development, but decided to continue with 15-20% PoPs in the
southern NE panhandle.
The dryline will begin to retreat westward overnight towards the
I-25 corridor as an upper level low begins to build into the
western CONUS. Moist southerly flow into the NE panhandle could
support patchy fog early Sunday morning. As larger scale lift
arrives with a leading shortwave passage in southwest flow,
showers and thunderstorms will be possible Sunday afternoon.
CI will be most likely between the dryline position and the
Laramie Range. Additional diurnal circulations (Chugwater
Cyclone) may lead to additional areas of convective initiation
around Platte/Goshen Co Sunday afternoon before storms begin to
propagate eastward. Large instability profiles for this time of
the year (~1500 J/kg MLCAPE) will support the possibility of
hail, but shear will be marginal limiting organization to
multicellular structures. A capping inversion will be in place
farther east that will likely limit any deep convection until
early in the evening across the NE panhandle. SPC has included
eastern portions of our CWA into a Marginal Risk for Sunday
afternoon.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 305 PM MDT Sat Sep 14 2024
The long term will feature a switch to a more active, wetter
pattern. With a first taste of more fall-like temperatures towards
the end of next week.
Next week will start off mild with the CWA sandwiched between a deep
trough coming on shore of the west coast, and a broad ridge over
much of eastern CONUS. This puts the CWA in south to southwest flow
which will advect both warmer air and Pacific moisture into the
region. This will lead to temperatures on Monday that are above
average, especially east of the Laramie Range. Expect highs east of
the Laramie Range to be in the 80s and 90s, and highs out west to be
in the 70s. With the increased moisture advection Monday, showers
and storms will likely develop. Models seem fairly consistent with
keeping the better mid-level moisture west of the Laramie Range, so
this area will be the most likely location of any precipitation that
develops. Showers and storms could develop by late afternoon and
continue into Monday night.
Good agreement between the GFS and ECMWF with bringing the west
coast trough into Wyoming by Tuesday afternoon. Moist southerly flow
ahead of the trough and lift from the trough will provide the set-up
for another, more widespread precipitation event Tuesday afternoon.
Showers and storms will linger into Tuesday night, but will quickly
clear out by Wednesday morning as the trough passes north of the
CWA. Wednesday will be dry, but cooler, as more seasonable 700 mb
air sits overhead.
Headed into the end of the work week, expect even more precipitation
chances and cooler temperatures. The GFS and ECMWF remain in good
agreement, bringing a potent positively tilted trough into the
Rockies by Thursday night. Mid-level moisture and frontogenesis from
a strong cold front will likely produce widespread precipitation
across the area. This cold front will also likely lead to some light
mountain snow accumulations in the Sierra Madre and Snowy Ranges.
While temperatures are not expected to be cold enough to snow in the
lower elevations and plains, expect chilly low temperatures Saturday
morning, followed by what will likely be seasonable to below average
temperatures during the day.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 520 PM MDT Sat Sep 14 2024
Southwest flow aloft will continue, while a weather disturbance
brings increasing chances for showers and thunderstorms Sunday
afternoon.
Mostly clear skies will prevail until late Sunday morning, then
scattered clouds near 9000 feet will develop. Winds will gust to
25 knots at all terminals except Scottsbluff this evening,
except Chadron through the entire TAF period, then will gust to
25 knots at all terminals after 16Z Sunday.
&&
.FIRE WEATHER...
Issued at 305 PM MDT Sat Sep 14 2024
Critical fire weather conditions continue this afternoon across
much of south-central Wyoming northeast through east-central
Wyoming, as a mid-level jet traverses the North Laramie Range.
Afternoon RHs have dropped near 10 percent with gusts up to 35
mph. Did have to expand the Red Flag Warning to FWZs 417, 423, and
425 based on observational trends early this afternoon. Expect
conditions to persist into early this evening before winds begin
to calm overnight, but could still see gusts around 15 mph around
the higher terrain. Additionally, poor recoveries up to 35 percent
are likely west of the dryline tonight. Chances for precipitation
return Sunday afternoon with thunderstorms possible along and
east of the Laramie Range into the Nebraska panhandle. Farther
west, dry conditions will lead to elevated fire weather concerns
with afternoon RHs around 10-15 percent, but winds are expected to
remain below critical thresholds. Active weather pattern with
chances for precipitation continue into early next week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...AM
SHORT TERM...MB
LONG TERM...SF
AVIATION...RUBIN
FIRE WEATHER...MB
Area Forecast Discussion
National Weather Service Grand Junction CO
517 PM MDT Sat Sep 14 2024
.KEY MESSAGES...
- Showers and thunderstorms return to the area on Sunday as the
leading elements of remnant moisture from TS Ileana moves into
the region.
- Conditions become favorable for strong, organized
thunderstorms Monday afternoon/evening which could result in
localized wind gusts in excess of 60 mph and hail approaching
an inch in diameter.
- Above normal temperatures persist through Monday before a cold
front moving through the region on Tuesday brings cooler than
normal readings for the latter part of the week.
- Aside from Wednesday, off and on showers can be expected
across eastern Utah and western Colorado next week.
&&
.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 303 PM MDT Sat Sep 14 2024
Per the previous discussion, 315K isentropic surface indicated
the leading edge of remnant moisture from TS Ileana will reach
the Four Corners region late tonight. A low amplitude mid-level
trough moving northeastward from southern California appeared to
provide sufficient lift to generate some high based showers
over portions of southeast Utah and southwest Colorado before
12Z/Sunday. The GFS solution was most bullish with showers and
the Canadian and HRRR models less so, while the NAM and ECMWF
were dry. Like the previous forecaster, suspect ACCAS and virga
are likely, but can`t rule out some sprinkles reaching the
ground. Therefore, blended equal parts of the previous forecast
with latest NBM along with 10 percent of the GFS`s output. The
remainder of the forecast will remain dry with high clouds
sweeping in after midnight.
Moisture continues to spread north and east during the day on
Sunday and begins to deepen as well. PWATs are expected to climb
to between 0.5 to 0.75" or roughly 120 to 303% of normal.
Meanwhile, the short wave trough sweeps overhead during the
warmer part of the day which when combined with difluent flow
aloft and increased moisture will bring scattered showers and
thunderstorms to the La Sal, Abajo and San Juan Mountains as
well as the central Colorado mountains. Moist convection, should
it form, will be more isolated over the northern mountains and
plateaus of eastern Utah and western Colorado. Despite increased
cloud cover and showers, highs are expected to continue to run a
few degrees above normal.
Subsidence behind the short wave trough combined with diurnal
cooling will bring a downturn in shower/thunderstorm coverage
Sunday evening. However, later Sunday night a deepening closed
mid-level low over the San Francisco Bay Area is expected to
accelerate the influx of subtropical moisture into the region at
the same time divergence associated with the cyclonically
curved 90+ Kt jet becomes focused over southwest Colorado. As a
result, showers are expected to become widespread over the San
Juan Mountains and abutting lower elevations to the south late
Sunday night. Lift and moisture appeared less impressive to the
north so chances are definitely more limited there. Due to
clouds, morning lows will become milder than normal.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 303 PM MDT Sat Sep 14 2024
Monday sees ridging dominating the eastern half of the CONUS,
while the western half is under the influence of a potent
Pacific trough. The cutoff low at the heart of this trough will
be located over Northern California, with diffluent
southwesterly flow aloft over eastern Utah and western
Colorado to kick off the work week. This flow will tap into
remnant tropical moisture from Tropical Storm Ileana as well as
general subtropical moisture from the Gulf of California,
bumping PWAT values into the 303-180% of normal range over much
of eastern Utah and western Colorado. The Four Corners region
and the southern mountains will see the best of the moisture,
therefore also the best shower and storm coverage. This amount
of moisture in combination with an expected 500-1000 J/kg of
CAPE would be enough to raise concerns about stronger storms
capable of producing gusty outflow winds in excess of 50 mph,
hail, lightning, and heavier rainfall. But, in addition to this,
we also have some decent wind shear moving in associated with a
90-100 knot 250 hPa jet. With this combination of factors,
currently the Storm Prediction Center has the Four Corners
region under a marginal risk for severe weather on Monday, with
their expected main threats being hail and strong, gusty winds.
Further north, the threat for severe weather lessens a bit, as
areas north of I-70 are generally on the edge of the moisture
plume and therefore also will have less instability available,
though the shear profile may be able to make up for that and
lead to a few stronger storms. Overall though, with the jet
aloft and the tightening pressure gradient ahead of a strong
cold front, Monday will be breezy. The warmer air advecting in
on the southwesterly flow will be balanced out somewhat by the
widespread clouds and showers, leading to near normal
temperatures.
Tuesday morning sees the region still under that strong
southwesterly flow, but the cold front will be on the doorstep.
The cutoff low is expected to have rotated up into the
Nevada/Idaho/Utah border region by this point, and will continue
lifting northward through the day. Above normal moisture will
linger through the morning, leading to one more round of shower
and thunderstorm activity, before the cold front sweeps through
and ushers in some much drier air for Tuesday night onward. Much
cooler air moves in behind the front, with highs on Tuesday
topping out 5-10 degrees below normal for much of the region.
With the moisture and cooler airmass in place Tuesday, there is
a high likelihood of a dusting of snow on the highest peaks of
the eastern Uintas and some of the peaks along the Divide. A
transient ridge moves in on Wednesday as the early week low
continues to lift northeastward. This ridge will bring some
warmer air aloft and increased sunshine to combine with the
drier airmass, allowing highs to rebound about 5 degrees over
Tuesday. That said, we will remain 5-10 degrees below normal.
While eastern Utah and western Colorado see a bit of break from
the wild weather, the next low will be dropping down the West
Coast. This will likely be our next weather maker during the
late week period, but model agreement remains relatively poor in
the forecast from Thursday onward. What is in decent agreement
is that this low will swing through the central Great Basin
during the late week period, with another round of strong
southwesterly flow for the Western Slope Thursday. Ensembles
were also indicating this system will be drier than the early
week storm. Hopefully, with subsequent model runs things will
become more clear. As it stands, we`re moving into a cooler and
more fall like pattern during the long term, with wetter and
unsettled conditions punctuated by brief periods of glorious
fall sunshine.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 515 PM MDT Sat Sep 14 2024
Some gustier southwest winds have kicked in across northwest
Colorado, bringing gusts up to 25 mph to KHDN. Otherwise, skies
area mostly clear, aside from a few mountain cumulus. Light and
terrain driven winds will prevail through tomorrow morning.
Clouds increase tomorrow ahead of a Pacific system, and winds
will become southwesterly and strengthen. VFR conditions will
prevail for the next 24 hours.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...NL
LONG TERM...BGB
AVIATION...TGJT
Area Forecast Discussion
National Weather Service Louisville KY
805 PM EDT Sat Sep 14 2024
.KEY MESSAGES...
* Widespread showers around Bowling Green tapering off by
midnight.
* Chances for rain (<40%) possible around midweek; otherwise,
mostly dry and warm through next weekend.
&&
.UPDATE...
Issued at 804 PM EDT Sat Sep 14 2024
Quick update to increase PoPs southwest through southeast of Bowling
Green as showers, and a couple rumbles of thunder, move up out of
middle Tennessee. IR satellite shows warming tops and radar
indicates that the convection is increasingly poorly organized and
outflow dominated as the sun sets. HRRR agrees with this trend, and
still has convection dissipating by midnight.
&&
.SHORT TERM /THROUGH SUNDAY/...
Issued at 311 PM EDT Sat Sep 14 2024
Temperatures across the region have warmed well into the 80s this
afternoon, and the cu field has developed due to the sfc heating
taking place. Much more cloud cover is located just to our south,
with an axis of thick and agitated cloud cover stretching from
Georgia to far western Kentucky. This area is under more influence
from the remnants of Francine, with large scale forcing and a
corridor of 850mb jetting providing an increase in moisture
transport and convergence. Most of our region will remain dry
for the rest of the day, but some isolated to scattered showers
and storms are possible this afternoon and into the evening
hours for south-central Kentucky. The main corridor for
convection will be within the moisture transport axis, which
follows the 850mb core from northern Georgia/Alabama, through
middle Tennessee, and into far western Kentucky. A few cells are
already popping on the northern periphery of this corridor.
Steep low level lapse rates, along with some marginal
instability, will allow for some thunderstorms across the south
for the next few hours. However, wind profiles are very weak
this far north, so shear will be nearly nonexistent. Severe
storms are not expected, but some heavier rain rates may be
possible given PWATs over 1.5 inches. Precip activity will
diminish as we get later into the evening hours, and should have
dry conditions after midnight across the entire region.
Rex Block pattern for tomorrow will help push the tropical remnants
more southward, which will keep us dry again. Temperatures will warm
into the 80s again, and perhaps some spots closer to 90. Some
guidance suggests a low chance of an isolated shower again tomorrow
afternoon southwest of Bowling Green, but not too confident in this.
Will limit PoP to 20% for a few hours tomorrow afternoon for areas
west of I-165, but otherwise dry conditions and mostly sunny for the
rest of the area.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 311 PM EDT Sat Sep 14 2024
Much of next week will feature an unusual upper level pattern for
our region as broad upper ridging over the northeastern U.S.
interacts with a decayed tropical system (Francine) and one that
may develop early next week near the Carolina coastline in a weakly
sheared environment.
The remnants of Francine will likely be confined to our south as
upper ridging in the northeast and weak steering flows keep it from
wobbling into the Ohio Valley, so no rainfall is anticipated from
that early next week. What could briefly impact us is a potential
tropical system that may develop near the Carolinas and swing into
eastern Kentucky as early as Tuesday. There is still quite a bit of
uncertainty in the path and development of this system, though at
this time it appears the majority of precipitation associated with
this system will be well off to our east. Both NBM and a composite of
ECMWF/GFS/CMC ensembles highlight chances for measurable rainfall
(greater or equal than 0.01") around 30-40% near the I-75 corridor
in our eastern CWA, with lesser chances as you progress westward.
Outside of the potential glancing blow from this system, the
forecast looks quiet and dry in the weak upper level flow pattern.
Temps will be on the warm side of climo given the higher
thicknesses/heights due to the proximity of the broad upper ridge.
The coolest temps are expected mid-week due to mid/upper level
clouds from the potential tropical system limiting solar insolation.
A western CONUS trough will attempt to slide eastward through much
of this week, but may only make it as far as the central U.S. by
next weekend.
&&
.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 645 PM EDT Sat Sep 14 2024
A few showers will be possible in/around BWG this evening before
they dissipate entirely. Otherwise, surface high pressure stretching
from Maine to Missouri will keep skies mostly clear/partly cloudy
and winds coming in from the east. Winds could get a little gusty
tomorrow afternoon, especially at LEX.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...13
SHORT TERM...CJP
LONG TERM...DM
AVIATION...13
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
732 PM EDT Sat Sep 14 2024
.SYNOPSIS...
High pressure to the north will continue to impact the area
locally through the weekend and into early next week. An area
of low pressure is expected to form off the southeast U.S. Coast
this weekend before moving northwestward toward the coast
during the first half of next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Mostly dry conditions will continue tonight with lows in the
50s for most areas with low 60s possible near the waters. Cannot
rule out an isolated sprinkle or patchy drizzle across central
VA/southern MD as clouds move more into those areas heading into
Sunday morning.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
High pressure to the north will continue to build further south
Sunday into early next week, leading to dry conditions locally.
Overcast skies will build across central VA and southern MD as
an area of low pressure forms off the NC coastline.
By Monday night, high pressure shifts offshore, while at the
same time, coastal low pressure begins to move inland increasing
the onshore flow, bringing abundant cloud cover, initially high
level clouds, then lowering toward daybreak Tuesday. However,
any precipitation is likely to hold off until after daybreak
Tuesday.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
The key feature of interest next week is related to a region of
either subtropical or tropical development off the Carolina coast.
What remains of the surface and upper air circulation is expected to
slowly lift northward in time. Ensemble surface low plots indicate
there is still quite a bit of spread among the global ensemble
members. Some solutions carry the system toward the Appalachians
while others move east of the Delmarva Peninsula. Depending on the
track, quality of tropical moisture, and speed of the system, some
heavy rainfall signal may emerge. Given the current area of
interest is just a blob of disorganized convection near the Gulf
Stream offshore of the Carolinas, uncertainty is quite high at
this point. For now, expect a multi-day period of increasing
rain chances which may run through the remainder of the work
week.
A blocky pattern persists across North America with a rex block
potentially setting up into next weekend. A meandering negative
height anomaly persists over the eastern U.S. while heights build to
its north. Where this ridge/trough couplet sets up will dictate the
degree of additional shower chances. As expected, uncertainty is
high through much of the period next week.
Overall temperatures stay near to slightly below average next week.
Clouds should be plentiful given the slug of tropical moisture
surging northward into the Mid-Atlantic region. As a result, this
will raise humidity levels for much of the week.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
The last few runs of the HRRR and GLAMP both have IFR/LIFR CIGs
at CHO/IAD 8Z-13Z Sunday. Will monitor. Other guidance tries to
bring in lower CIGs from the E/SE to DCA/BWI/MTN. MRB may be
susceptible to patchy fog early Sunday morning.
Otherwise, periods of MVFR/IFR CIGs are possible through 12Z
Monday, mainly at KCHO; elsewhere, mostly VFR conditions will
persist. Strengthening onshore flow late Monday night is likely
to result in more widespread CIG restrictions by 12Z Tuesday.
Enhanced onshore flow combined with increasing rain showers will
make for a lengthy period of restrictions from Tuesday through
Thursday. While some breaks are likely at times, expect sub-VFR
ceilings to dominate. Depending on the degree of instability, there
could be a few thunderstorms on Tuesday into Wednesday as the
coastal low tracks nearby. Otherwise, a breezy east to northeasterly
wind is expected to dominate.
&&
.MARINE...
SCA winds are likely later this evening, especially south of
North Beach MD. Winds gradually strengthen Sunday into Monday
with SCA conditions becoming increasingly likely. The strongest
winds are most likely late Monday into Tuesday.
The gradient formed by high pressure to the north and low pressure
approaching from the southeastern U.S. will lead to a breezy east to
northeasterly wind. Current forecast gusts on Tuesday into Wednesday
range from 20 to 25 knots, possibly increasing to around 30 knots
over the southern waters. There is an outside chance for gale force
wind gusts, but confidence is low given uncertainties in the low
track and strength.
&&
.TIDES/COASTAL FLOODING...
Light but persistent onshore flow will cause water levels to
gradually rise over the next several days. Onshore flow
strengthens further Monday night into Tuesday with minor coastal
flooding becoming increasingly likely by Tuesday. Depending on
the strength of onshore flow and the track of low pressure to
the south/southwest, near moderate flooding may be possible at
vulnerable shoreline locations late Monday through Tuesday.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory from noon Sunday to midnight EDT Sunday
night for MDZ008.
VA...None.
WV...None.
MARINE...Small Craft Advisory from noon Sunday to midnight EDT Sunday
night for ANZ530>532-535-536-538>542.
Small Craft Advisory until 6 AM EDT Monday for ANZ533-534-537-
543.
&&
$$
SYNOPSIS...DHOF/ADM
NEAR TERM...DHOF/ADM
SHORT TERM...DHOF/ADM
LONG TERM...BRO
AVIATION...BRO/DHOF/ADM
MARINE...BRO/DHOF/ADM
TIDES/COASTAL FLOODING...LWX
Area Forecast Discussion
National Weather Service San Francisco CA
525 PM PDT Sat Sep 14 2024
...New AVIATION, MARINE...
.SYNOPSIS...
Issued at 310 AM PDT Sat Sep 14 2024
Cooler temperatures persist, with rain chances arriving late
Sunday. Rainfall will be minimal, and ends Monday afternoon.
Another chance for rain arrives towards the midweek. Ridging and
warmer weather on the horizon for next weekend.
&&
.SHORT TERM...
(This evening through Sunday)
Issued at 1257 PM PDT Sat Sep 14 2024
Stratus persists at the immediate coastal regions, with some mixing
out possible through the afternoon although patches of stratus look
to persist through the day. A deep marine layer of around 1500-2000
feet deep will promote extensive inland stratus development tonight
into Sunday morning.
The weather pattern is dominated by a upper level trough developing
off the Pacific Northwest, which is expected to develop into an
upper level low that comes through the state on Sunday and Monday.
Breezy onshore winds pick up this afternoon, remaining rather strong
overnight into Sunday with the arrival of a cold front. The
strongest winds are expected Sunday afternoon, with gusts reaching
25-30 mph across the lower elevations, and 35-45 mph in the higher
elevations, through gaps, passes, and the Salinas Valley. Take some
time today to bring in anything that could easily blow away or over,
unless, as the previous forecaster noted, you want to recreate a
scene from Mary Poppins!
Also arriving later on Sunday are chances for rain. While the
chances start arriving late on Sunday, it`s now looking more likely
that the bulk of the rainfall will arrive on Monday, see the long
term discussion for more information about the rainfall.
Highs today range from the lower 80s to the lower 90s across the
inland valleys, to the 70s across the Bayshore, and the low to mid
60s along the Pacific coast. With the cold front on Sunday, expect a
dramatic fall in temperatures with the inland valleys cooling to the
70s, the Bayshore seeing highs in the mid to upper 60s, and even the
warm spots in southern Monterey County topping out in the low 80s.
&&
.LONG TERM...
(Sunday night through next Friday)
Issued at 1257 PM PDT Sat Sep 14 2024
It`s now looking more likely that the bulk of the rain from the
approaching low will fall Monday morning and afternoon. Even then,
not much rain is expected. The latest forecast shows the higher
elevations (the Santa Cruz Mountains, the eastern Santa Clara County
mountains, and the northern Gabilan and Santa Lucia ranges) reaching
around a tenth to a quarter of an inch of rain, with some of the
favored peaks seeing up to a third of an inch. Most of the lower
elevations in the Bay Area and Central Coast will see a few
hundredths to a tenth of an inch of rain, and in the North Bay
valleys and southern Monterey County, you`d be lucky to see any rain
at all. Of note, the latest extended HRRR model run shows that the
rain may be more showery than stratiform; if this model situation
plays out, rainfall totals could be a lot more uncertain as
predicting where a shower will develop is very difficult. Something
to watch over the next few days.
The rain should come to an end Monday afternoon, with most of the
region seeing highs in the upper 50s to the 60s, and the inland
valleys struggling to reach the low 70s, barring the North Bay where
temperatures could reach the mid 70s. Tuesday should bring a slight
warming trend with the inland valleys returning to the mid to upper
70s, before a second low pressure system arrives on Wednesday.
Similar to Monday`s system, there`s not a lot of rain expected with
this one with rain totals a few hundredths of an inch at most.
The chances for rain end on Thursday, with ensemble models
suggesting a return to upper level ridging towards the following
weekend. CPC outlooks lean towards the return of temperatures
slightly above seasonal averages towards the last full week of
September.
&&
.AVIATION...
(00Z TAFS)
Issued at 525 PM PDT Sat Sep 14 2024
The marine layer is deepening, currently it`s varying from 1400
feet to 1800 feet deep. Stratus and fog /MVFR-IFR/ are embedded in
a coastal eddy and trough supported by juxtaposed northerly and
southerly pressure gradients and winds, ACV-SFO is 4.7 mb and
SMX-SFO is 2.3 mb; mesoscale models are slightly under-forecasting
the current strength of both gradients.
It`s cooler per 24 hour trends and there`s steady or higher
dewpoint temps (water vapor). Radiative cooling after sunset will
result in additional stratus and fog development tonight and Sunday
morning with onshore breezes ushering stratus and fog inland. A
few patches of drizzle may develop tonight and Sunday. Conditions
improving to MVFR-VFR by Sunday afternoon, the marine layer deepening
due to lower level cold air advection.
Vicinity of SFO...Low to moderate confidence VFR holds through
early to mid evening. Tempo IFR ceiling forecast to develop 06z-10z
then IFR prevailing 10z-1730z Sunday. West-northwest wind 15 knots
decreasing to near 10 knots mid-late evening then increasingly gusty
Sunday particularly Sunday afternoon and evening.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Stratus and fog /MVFR-IFR/ tonight and
Sunday morning. Conditions improving to MVFR-VFR Sunday afternoon.
A few patches of coastal drizzle possible tonight and Sunday.
Onshore winds 10 to 18 knots decreasing to light onshore winds
tonight and Sunday morning, onshore 10 to 15 knots Sunday
afternoon.
&&
.MARINE...
(Tonight through next Thursday)
Issued at 453 PM PDT Sat Sep 14 2024
A series of early season cold fronts will move through the
coastal waters this week with a persistent strong NW breeze and
near gale force gusts. Seas will remain rough outside of protected
waters through the forecast period. There a chance for
thunderstorms Monday and Wednesday, which would produce locally
stronger winds.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 AM Sunday to 3 AM PDT Monday for SF
Bay N of Bay Bridge.
Small Craft Advisory from 9 AM Sunday to 3 AM PDT Monday for Mry
Bay-Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras
Blancas 0-10 nm.
Small Craft Advisory until 3 AM PDT Monday for Pigeon Pt to Pt
Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt
Reyes 10-60 NM.
Small Craft Advisory from 9 PM this evening to 3 AM PDT Monday
for Pt Reyes to Pigeon Pt 0-10 nm.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Canepa
MARINE...Sarment
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea
Area Forecast Discussion
National Weather Service Reno NV
131 PM PDT Sat Sep 14 2024
.SYNOPSIS...
* Gusty SW winds Sunday, with choppy lakes and localized critical
fire weather conditions.
* Significantly colder Monday with increasing chances for rain and
high elevation snow, along with isolated thunderstorms.
* Another cold storm arrives late Tuesday into Wednesday with more
chances for rain and high elevation snow.
&&
.DISCUSSION...
* Hope you were able to get outside and take advantage of this (IMO)
beautiful mid-September day! We`ll see southwest winds increasing
once again Sunday ahead of a cold front, but the strength and
duration do not look quite as intense as what the region
experienced this past Wednesday. Still, it will bring choppy lake
conditions in addition to localized critical fire weather
concerns. See the fire weather section below for additional
details.
* The associated upper level trough shifts into the region Sunday
night into Monday, ushering in a significantly colder air mass
and increasing rain and high level snow chances. There remains a
rather significant spread in where the heaviest bands of
precipitation will occur, but the HREF is in the best agreement
in west-central Nevada. One stand out is the HRRR developing
convectively banded heavier precipitation before daybreak Monday
from the Tahoe Basin into NE CA. It is an outlier, but also
would be more impactful with snow levels possibly dipping to
near 6000` in the band and greater concerns for heavier rainfall
over recent burn scars (Bear and Davis). Per NBM probs, the
entire region has 60-70% chances to see wetting rains (0.10"+)
Monday. Temperatures will be ~20-25 degrees below normal Monday,
more similar to late October norms. The combination of
rain/snow, cold temps, and breezy NW winds will be quite the
shock to those who aren`t prepared, esp if recreating in the
backcountry. There are also thunderstorm chances (10-20%) under
the core of the low, in particular south of US-50 and areas
near and east of US-95.
* While some showers may linger in north-central Nevada into
Tuesday morning, the low quickly kicks east Tuesday with a bit
of warming and drier conditions. This is short-lived as the next
low pressure system follows right behind Tuesday night into
Wednesday. Interestingly, there is actually better agreement in
the placement of this cold low and associated precipitation
Wednesday than what ensembles are indicating on Monday. In any
event, this brings the return of colder temps, rain and high
elevation snow, and isolated thunderstorms as well.
* A gradual warming and drying trend will be on track as we head
into late week and next weekend with no major wind or rain
events on the horizon. -Dawn
&&
.AVIATION...
* Flying conditions will be favorable the remainder of today with
mostly clear skies and typical afternoon breezes through 03z.
* Winds will ramp up Sunday with SW FL100 winds sustained 30-40 kts,
leading to mountain wave turbulence along and downwind of the
Sierra. Terminals will see gusts of 25-30 kts from 19z-03z.
* Breezy NW winds to follow Monday behind a cold front, with
widespread rain and high elevation snow. While conditions
generally will remain VFR, localized IFR is certainly possibly
along with mountain top obscuration in the heavier showers. There
is also a 10-20% chance for thunderstorms, primarily south of US-
50 and near/east of US-95.
* While chances are only about 20% for snow at KTRK, KTVL, and
KMMH, if snow does fall, the warmer ground and mid-September sun
angle should help snow to rapidly melt on runways. -Dawn
&&
.FIRE WEATHER...
* Winds ramp up out of the southwest Sunday ahead of a cold front
slated to shift through the area Sunday night. While speeds do
not look as intense or widespread as the event that unfolded
this past Wednesday, it still bears watching with solid chances
for 30-40 mph gusts late morning through late afternoon,
especially along the Sierra Front, including the US-395/I-580
corridor. Sierra ridge gusts will be in the 60-80 mph range
ahead of the front.
* RH values are much higher than the last event as well, generally
25-40% in valley locations. Localized critical conditions are
expected, but no watches or warnings are planned at this time.
* Breezy NW winds with gusts of 20-25 mph to follow on Monday.
* Widespread wetting rains (0.10"+) are likely (60-70% chance)
Monday and again Wednesday as a pair of cold weather systems drop
into the region. These storms are cold enough to bring up to a few
inches of snow to high elevation terrain. -Dawn
&&
.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from 11 AM to 8 PM PDT Sunday NVZ002.
CA...Lake Wind Advisory from 11 AM to 8 PM PDT Sunday CAZ072.
&&
$$