Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/10/24
Area Forecast Discussion...CORRECTED
National Weather Service Boise ID
857 PM MDT Fri Aug 9 2024
.DISCUSSION...A weak shortwave is moving over the Pacific NW
this evening and will track across WA, northern ID and into
western MT by Saturday afternoon. As this moves through, there
will be enough instability to trigger isolated thunderstorms
generally north of a line from Burns OR to Jerome ID on
Saturday. Updated the forecast to add mention of isolated
thunderstorms in these areas early Saturday morning into
Saturday afternoon. Gusty winds and lightning main threats with
these storms. Drier air will move into the area on Sunday,
before a trough over SW Canada begins to move south along the
WA coast. This trough shifts the flow to the southwest, allowing
monsoon moisture to move north into northern NV along the ID
border, with isolated thunderstorms south of the Snake Basin on
Sunday evening.
&&
.AVIATION...Mostly VFR with areas of MVFR and local IFR near
wildfires. Patchy mountain obscuration. Chance of showers and
afternoon/evening thunderstorms north of KBNO-KBOI-Fairfield
Saturday. Surface winds: variable 5- 10kt overnight. Gusty erratic
outflow winds possible from showers and storms. Winds aloft at
10kft MSL: SW 5-15 kt. High density altitude 18Z-03Z.
KBOI...VFR with potential for occasional MVFR from smoke. Surface
winds: variable around 5 kt through Sat/18Z. High density altitude
18Z-03Z each day.
Weekend Outlook...Mostly VFR with areas of MVFR and local IFR
near wildfires. Dry Sunday. High density altitude 18Z-03Z.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Sunday night...Near-surface
smoke retreated from the Treasure Valley this morning but
returned on north-northwest winds early this afternoon. HRRR
smoke model keeps smoke in through midnight but then retreats
again overnight and Saturday morning on southeast winds. The
process repeats Saturday but less smoky than today, and again
Saturday night but less smoky than tonight.
Model consensus continues a 30-40 percent coverage of showers
and isolated thunderstorms tonight along the eastern edge of
our CWA, then a 40-60 percent chance of showers and afternoon
thunderstorms in the same areas Saturday as an upper trough
passes by to the north. Clearing and drying Saturday night and
Sunday.
Tonight looks cooler than last night in central and southern
areas due to less cloud cover. Max temps Saturday and Sunday
will average 2-4 degrees above normal, with min temps close to
normal.
Winds will be light tonight and Saturday morning, then northwest
10-20 mph Saturday afternoon, with gusts to 30 mph in south-central
Idaho and south of the Snake Basin. Gusty winds also near
thunderstorms.
LONG TERM...Monday through Friday...Persistent low-amplitude
upper trough along the coast and ridge over the interior west
will keep temps warm (i.e., slightly above normal) in Idaho,
but near normal in Oregon. No rain is forecast with monsoon
moisture staying south of our CWA. Areas of smoke for at least
another week.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
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DISCUSSION...KA
AVIATION.....SP
SHORT TERM...LC
LONG TERM....LC
Area Forecast Discussion
National Weather Service Denver/Boulder CO
947 PM MDT Fri Aug 9 2024
.KEY MESSAGES...
- Scattered to numerous showers and thunderstorms are expected
each day through the weekend. The primary threat will be flash
flooding on the recent burn areas as stronger storms will
produce locally heavy rainfall.
- Much warmer on Sunday with lower precipitation chances.
- Slightly cooler Monday with better precipitation chances. The
main threat will be heavy rainfall with a couple strong to
severe storms possible.
- Gradual drying trend expected from Tuesday through the end of
the work week with near to slightly above normal temperatures.
&&
.UPDATE...
Issued at 944 PM MDT Fri Aug 9 2024
Area radars are showing scattered light rain showers decreasing
over some of the plains at this hour. There is another batch of
rain showers to get into Larimer and Weld Counties from Wyoming
in the next few minutes. Latest models are not showing much
convection over the CWA after 06z. Will alter the pop grids with
reality and the latest high resolution models and lower pops over
some of the plains. Will make some grid adjustments to sky and
wind grids based on current trends.
&&
.SHORT TERM /Through Saturday/...
Issued at 254 PM MDT Fri Aug 9 2024
Radar shows plenty of convection, but overall intensity has
decreased as the leading edge of showers and storms is moving
across more stable air on the plains. Satellite imagery has shown
some recovery behind today`s early convective disturbance, with
more development upstream into western Colorado and northern Utah.
However, instability is marginal since some of the energy has been
used up. We`ll likely see more of the same (relatively high
coverage but weaker convection) through this evening, as the
forecast area resides in the right entrance region of an upper
level jet. CAMs have been quite poor with the earlier development
of convection, but appears the 18Z HRRR and NAMNest are at least
initializing a little better than earlier runs today. With lift
and upward QG forcing into the late evening hours, we`d expect a
few of these showers and storms to linger into the midnight hour
if not into the wee morning hours Saturday. Skies should then
gradually clear, although some stratus and low clouds/fog still
expected over the eastern and northern plains.
On Saturday, we should see less stratus and an easier breakup with
more southerly low level flow. This will allow temperatures to
start a warming trend, with highs warming into the 80s at least
in/near the Denver metro area and points east and southeast. There
are still indications some cooler boundary layer air could hold
highs in the 70s closer to the Wyoming and Nebraska borders. With
additional heating though, and still rich low level moisture,
MLCAPE will build to 600-1400 J/kg - at least in the interface of
the warmer temperatures and higher boundary layer moisture. At
this time, we think that ends up closer to the I-25 Corridor than
the eastern plains. Given sufficient shear, a couple strong to
severe storms will be possible in that instability axis. Shower
and storm coverage should be fairly high once again in/near the
mountains, I-25 Corridor, Palmer Divide, and Cheyenne Ridge.
&&
.LONG TERM /Saturday night through Friday/...
Issued at 254 PM MDT Fri Aug 9 2024
Saturday night, upper level high pressure will be centered over
Texas with a moderate west to northwesterly flow aloft over
Colorado. This pattern should result in scattered showers and
thunderstorms continuing into the evening across the forecast area.
Latest models are showing most of the activity focused from South
Park eastward across the Southern Foothills and Palmer Divide. With
ample moisture and instability, some of the storms could be strong
with hail, gusty winds and locally heavy rainfall.
On Sunday, the upper ridge begins building north across the Rocky
Mountain Region with continued northwesterly flow aloft over the
CWA. Model soundings are suggesting some downsloping flow east of
the mountains which should result in a decrease in low level
moisture, lower precipitation chances and much warmer temperatures
(upper 80s to lower 90s) across the Front Range Urban Corridor and
adjacent plains. Further east across the plains, the cooler moist
air may linger with much cooler temperatures, especially across the
far northeastern corner of the state. This area may be too stable to
see much convection. However, there may an zone of higher
instability between the cooler stable and warmer drier air masses
with the potential for a couple of strong to severe storms with
hail and locally heavy rainfall across portions of the plains.
Further west, the convection should be higher based with gusty
winds and mostly light to moderate rainfall expected.
On Monday, the upper level flow weakens and becomes more westerly as
the upper ridge shifts eastward into the Central Plains States. This
pattern may allow an increase in monsoonal moisture across Colorado.
In addition, models are showing increasing low level moisture across
the Northeastern Plains behind the passage of a weak cool front.
With PW`s ranging between 0.75" in the mountains to 1.25" on the
plains, some of the storms could produce heavy rainfall, especially
across the far eastern counties where the moisture will be highest.
In Addition, there could be enough shear and instability to produce
a few severe storms across the plains as well.
For the Tuesday through Friday period, moisture and precipitation
chances are expected to gradually decrease with near to slightly
above normal temperatures each day.
&&
.AVIATION /06Z TAFS through 06Z Sunday/...
Issued at 944 PM MDT Fri Aug 9 2024
Models keep the northerly wind in at DIA through about 09Z later
tonight. After that, weak normal drainage patterns are a good bet.
The low Stratus has pushed out of DIA and cross sections do not
show it to get back into DIA overnight. So no ceiling issues
after 06Z.
&&
.HYDROLOGY...
Issued at 254 PM MDT Fri Aug 9 2024
Overall storm intensity through the afternoon and evening should
be less than the initial convection given some of the instability
is already worked over. However, the airmass remains quite moist
and a couple stronger storms could still produce brief heavy rain
and thus a limited threat of flash flooding in the recent burn
areas til about the midnight hour.
Saturday will feature scattered to numerous showers and storms
again in the afternoon. More instability will be present, and thus
isolated to scattered stronger storms will be capable of producing
heavy rain, and at least a limited threat of flash flooding for
the burn areas. The most recent burn areas will be most
susceptible. They will be moving along fairly quickly at 20-25 mph
given the flow aloft, but stronger storms in the mountains and
foothills will still be capable of producing a quick one half
inch of rain in 15 minutes. Stronger storms on the plains could
produce a quick 1 to 1.5 inches in 30 minutes as they intensify in
a more unstable airmass.
The burn area flood threat each day next week will depend on the
timing of disturbances in the flow and the amount of sunshine.
While the atmosphere will remain moist, storms should be moving,
which should limit the threat to burn areas and reduce it there.
There will eventually be a drier environment by later in the week,
but this trend looks to be very slow.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......RJK
SHORT TERM...Barjenbruch
LONG TERM....JK
AVIATION.....RJK
HYDROLOGY....Barjenbruch
Area Forecast Discussion
National Weather Service Cheyenne WY
537 PM MDT Fri Aug 9 2024
.KEY MESSAGES...
- Areas of dense fog possible into Saturday morning, especially
over the Interstate 80 summit.
- Another nocturnal shower and thunderstorm event this evening,
starting west of the Laramie Range and possibly making it to
Cheyenne towards midnight.
- Expecting a gradual warmup through the weekend returning to
near normal temps and daily chances for afternoon and evening
showers and thunderstorms continuing.
&&
.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 230 PM MDT Fri Aug 9 2024
Surface boundary lays along a line from a low over south central
Colorado to near Craig Colorado into northern Utah. East to
southeast upslope low level winds with low clouds and fog along
with light drizzle in the upsloping flow east of the Laramie
Range. Getting breaks in clouds west of the Laramie Range.
Temperatures at Rawlins up near 80 degrees with Laramie near 70.
Current SBCAPE west of the Laramie Range up near 1200 J/KG and
radar showing convection starting to develop across northern
Carbon and Albany Counties.
HRRR and RAP simulated radar develops a line of thunderstorms in
Sweetwater County towards 00Z that moves through Carbon County
early this evening. Not too concerned with severe
thunderstorms...but if the HRRR solution comes true...could have
strong winds at Arlington and possibly Laramie. RAP SBCAPE up
near 1500 J/KG over Albany County 00Z to 03Z. 0-6km shear pretty
high with 40-50kts and DCAPE around 1000 J/KG. Could see a few
severe thunderstorm warnings after 00Z. Main hazard will be
strong downburst winds.
That line makes to to the Laramie Range around 10PM this evening
and moves through Cheyenne towards midnight. Definitely not
looking at severe storms east of the Laramie Range and storms
weaken considerably as they move into the southern Panhandle.
Convection gets going again Saturday afternoon as highs climb
into the low 80s. ECMWF/NAM/SREF and GFS all showing pretty good
QPF Saturday afternoon across much of southeast Wyoming that
eventually makes it into the Panhandle towards 00Z. Long/skinny
CAPE profiles and PWATS up near and exceeding 1 inch east of the
Laramie Range may produce a flash flood threat mid Saturday
afternoon into the evening hours.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 230 PM MDT Fri Aug 9 2024
An active weather pattern continues to be well advertised for the
extended forecast. We will see near to slightly above average
temperatures for mid August as well. Monday will bring daytime highs
in the 70s to mid 80s for the lower terrain, and we will be on the
periphery of a departing upper level ridge. Further upstream, we
will begin to see the influence of an approaching upper level
longwave trough from the Pacific NW. Since we will be wedged in
between these two weather features, rich monsoon moisture will trek
northward. PWATs of 1.0" to 1.5+" are forecast to surge north by
Monday evening. Atmospheric instability from daytime heating and
steep lapse rates will be combined to produce some much-needed
rainfall across our cwa. The GFS is the most aggressive with
widespread showers and thunderstorms. Should this consistent trend
persist over the weekend, moderate to high confidence of localized
heavy rainfall would be favored east of the I-25 corridor.
Additional shortwave disturbances are progged to advect east across
the CONUS through mid-week, keeping daytime highs minimized, and
chances for showers and thunderstorms maximized. Thursday and Friday
will bring the chances of the upper level ridge amplifying from the
Four Corners region of the desert SW towards our cwa. This will
begin to reduce the chances for showers and thunderstorms, and allow
daytime highs to begin their trend upwards to above normal
thresholds. Stay tuned for the extended forecast as the active
weather pattern continues to favor above normal chances of
precipitation for our cwa.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 521 PM MDT Fri Aug 9 2024
Northwest flow aloft will continue, while moist low level
upslope winds help produce light rain, fog and low clouds
tonight for areas along and east of Interstate 25.
Wyoming TAFS...For Rawlins, scattered to broken clouds from
9000 to 10000 will prevail, with thunderstorms in the vicinity
until 06Z. Winds will gust to 23 knots after 15Z Saturday.
For Laramie, ceilings will lower to 3500 to 5000 feet this
evening, then will improve to 10000 feet after 09Z.
Thunderstorms will be in the vicinity until 03Z, and from 05Z to
09Z. Winds will gust to 25 knots until 03Z.
For Cheyenne, light rain and fog will occur until 15Z, reducing
visibilities to 2 miles or less, along with ceilings under
1000 feet. Ceilings will improve to 3500 feet after
15Z Saturday.
Nebraska TAFS...For Chadron and Alliance, ceilings will range
from 1500 to 3500 feet until 06Z, with occasional light rain and
fog reducing visibilities to 3 to 5 miles and ceilings from
500 to 2500 feet. After 06Z, clouds will be scattered to broken
at 10000 feet.
For Scottsbluff, ceilings will range from 600 to 2000 feet until
16Z Saturday, with areas of fog reducing visibilities to 3 miles
until 03Z. After 16Z Saturday, clouds will be scattered at
10000 feet.
For Sidney, ceilings will range from 600 to 2000 feet until 12Z,
then ceilings will improve to 4000 feet. Areas of light rain and
fog, reducing visibilities to 2 to 6 miles, will occur until
12Z.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...GCC
LONG TERM...BW
AVIATION...RUBIN
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1028 PM EDT Fri Aug 9 2024
.SYNOPSIS...
A cold front will track across the region through this evening,
bringing the potential for a round of scattered showers and
thunderstorms. High pressure will build into the area this weekend,
lingering through the middle of next week, while the front stalls
over the Southeast and keeps daily shower and thunderstorm chances
in place, especially over the southern zones.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 1025 PM: Scattered convection continues to slowly move south
across the NW Piedmont into the Southern Piedmont this evening.
Isolated convection seen over the western Upstate. The HRRR slowly
moves this activity southeast with it dissipating before daybreak.
Have followed these trends in the PoP with this update. The severe
chances have fallen but isolated heavy rainfall remains possible in
the high PW and slow moving cells. Isolated flooding could also
develop. With the convection in place, there`s much more debris
clouds than expected earlier which could put a damper on the
radiational cooling. Still have some patchy fog in place, but the
chances of dense fog have diminished. The mountain valleys would
have the best chance. Lows overnight will remain a few degrees abv
normal with the warm airmass remaining unchanged. Sat will see
afternoon general tstms again, but the activity will be mostly
limited to ern zones near the stalled frontal zone as downslope
warming ensues west. Highs Sat will be similar to today with
readings in the low to mid 90s across the non/mtns and u80s over the
mtn valleys.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 141 PM EDT Friday: A closed upper low will slide across
the Great Lakes Sunday and into Quebec by Monday. It`ll be
distant enough that little if any DPVA forcing will develop
over the Carolinas during the short term. However, persistent
pockets of upper-level moisture will stream around the periphery
of this feature and across the Carolinas; following some brief
drying on Saturday night and the first part of Sunday, better
moisture will build back in aloft and keep skies partly cloudy
or worse. In association with one of the passing vort lobes,
a weak reinforcing cold front will make its way across the CWA on
Sunday, reinvigorating the stagnant boundary across the southern
tier of the forecast area.
So, by Sunday afternoon, the environment will be primed for
destabilization along and south of I-85, with sbCAPE values surging
to 1000-1500 J/kg. Subsident profiles elsewhere should keep
convection at bay, limiting initiation or preventing it entirely.
Even over the southernmost unstable reaches of the forecast area,
what CAMs extend out that far depict little if any convective
activity. Otherwise, temperatures botgh Sunday and Monday will stay
a category or so below climo, only hitting the mid- to upper-80s.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 207 PM EDT Friday: The upper jet will remain displaced just to
our north through the extended, allowing for alternating periods
of more and less active weather as shortwaves drop out of the
Midwest and into the Carolinas. The first of these will arrive
Monday night, ushering drier air aloft and and at the surface
as a high pressure system slides across the Upper Ohio Valley.
The second will arrive sometime Wednesday or Thursday, though
models begin to diverge on timing by this point in the forecast.
Instability generally looks anemic on Tuesday and Wednesday,
but should start to improve on Thursday. A 500mb speed max
will arrive on Thursday, affecting mainly the NC zones...so if
the elevated shear associated with this feature intersects the
improving instability currently depicted in operational guidance,
Thursday could be our next potential severe weather day. Otherwise,
temperatures will remain near or up to a category below normal
through the end of the week, as the ever-present upper trough
continues to exert its influence over the region.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: VFR conditions continue through the evening.
Isolated convection has developed and will move very close or over
KHKY soon so a short TEMPO starting now. It will also be near KAVL
and the SC sites so VCSH there. CAMs suggest the storms will
eventually move over KCLT, so have a later TEMPO there. Winds have
gone S to SW for all but KAVL where they remain NNW. Winds become
light and variable overnight with convection and clouds dissipating.
There may be mountain valley fog, so put some MVFR in at KAVL.
Otherwise, don`t expect any restrictions. There will be some
afternoon VFR cu Saturday, but looks like best chance for convection
will be to our southeast. Light NE wind in the morning becomes NW to
SW for the afternoon.
Outlook: Expect generally isolated to scattered diurnal convection
across the region each day through the middle of next week. Patchy
fog and low stratus will be possible each night in the mountain
valleys and in locations that receive rainfall.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...MPR
NEAR TERM...RWH/SBK
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...RWH
Area Forecast Discussion
National Weather Service Gray ME
1129 PM EDT Fri Aug 9 2024
.SYNOPSIS...
Debby passes west of the region tonight with a period of heavy
rain possible overnight...especially in the mountains. Clearing
skies arrive with warm temperatures Saturday...before seasonably
dry weather arrives to end the weekend Sunday. Fair weather
looks to persist through most of next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
1130 PM Update...
Quick update to lower the Flood Watches in the north as the
precip has exited the region. Also extended the rip risk along
the coast through to WFO CARs area. Otherwise, have dropped the
flood advisory in the North Conway area. The rest of the
forecast will remain unchanged.
1025 PM Update...
The precipitation continues to settle south of the mountains
which is in relatively good agreement with the latest HRRR
solution. This will bring the highest rainfall rates to southern
areas over the next few hours. Have adjusted pops accordingly.
Have introduced patchy fog for the late night hours. After a
brief surge of winds, the gradient will relax leading to pooling
of low level moisture.
May be able to lower the Flood Watches over northern areas over
the next few hours as precipitation clears the region.
Prev Update...
Line of showers and storms continues to progress east per latest
radar imagery. The latest HRRR has this precipitation moving out
of the region relatively quickly during the late night/early
morning hours. However, a weak wave may ride up this boundary,
temporarily stalling the precipitation over portions of southern
New Hampshire and Maine.
We continue to monitor for the potential for flash flooding
and/or severe weather. Greatest mixing has occurred in southern
New Hampshire and southwest Maine as surface dew points continue
to climb through the lower to mid 70s.
Fog will be persistent, especially over Maine until the
occlusion crossing the region.
Prev Disc...
Impacts:
* Heavy rainfall will pose a Flash Flood threat across the
area, but especially in the mountains due to rapid runoff.
* Strong to severe thunderstorms are possible this evening. The
primary threat is damaging wind gusts, but an isolated
tornado is not out of the question.
Visible satellite and radar shows the center of post-tropical
Storm Debby over central New York at this hour. It will continue
its northeastward movement through tonight while pushing in a
tropical airmass over our area. This combined with a trailing
cold front will bring the threat of flash flooding due to
excessive rainfall, and strong to severe thunderstorms.
Flash Flooding: Maintained the area of the Flood Watch as
northern New Hampshire is certainly the most vulnerable area
tonight as showers will be further enhanced by an upslope wind
component. However, anywhere in the CWA could see a flash flood
purely from the expected rainfall rates. The GYX 12z sounding
was already observing PWAT values just over 2 inches, with
models continuing to show peak values around 2.25 overnight.
This will allow storms to achieve rainfall rates in the ballpark
of 2"+. With this being said hi-res guidance continues to be
very progressive with this area of heavier showers, which means
flash flooding in the less vulnerable southern areas may only
occur with persistent or training storms. Either way expect at
least tropical downpours that could be hazardous to travel,
especially at night, as they would reduce visibility. The period
of heaviest rains is expected overnight. For additional details
on this threat, please see the hydrology section below.
Severe: Breaks in the moist conditions and warm air advection
are building up instability in southern and western New
Hampshire today. SPC mesoanalysis is already showing surface
based and mixed layer CAPE values around 500 j/kg. This is
expected to increase into the evening, as well as increasing
shear and helicity as Debby continues to move to the northeast.
The primary threat with these storms will be wind as convection
and heavy rain could mix down damaging wind gusts from a 70KT
low level jet moving overhead. The increased shear and helicity
means an isolated tornado is not of the question. The severe
weather threat runs from now till around midnight, then it
should quickly taper off. Maine has stayed mostly stable today
with drizzle and patchy fog persisting, so would expect the
severe threat to be limited here.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/...
Impacts:
* Long period wind swell will pose a rip current threat
Saturday.
Hi-res guidance continues to be very progressive with the band
of rain Saturday morning, suggesting the bulk of it could be
done by 10 AM. This means Saturday is shaping up to be warm, a
bit humid, and clear. High temperatures will climb into the mid
80s south of the mountains, with slightly cooler upper 70s to
the north. If folks find themselves heading to the beach, they
should be aware that wind swell whipped up by the departing
system will pose a high rip current risk. Clear skies will allow
low temperatures to drop into the 50s Saturday night.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The 500 MB pattern across NOAM and its environs show ridging
over the E half of the continent shifting poleward and spreading
east into central Canada, while weak toughing settles over NB
and the maritimes and across the NE CONUS. With sfc ridging
pushing in from the W. This is very weak ridging and the flow
will become quite stagnant by midweek. There is not a lot of
forcing so for the most part it should be dry, but any weak
waves that rotate around the weaken trough to our NE will set
off some the stagnant flow will cause a chance for SHRA/TSRA.
Right now the best chance looks like Wed/Thu. Temps through the
extended should run fairly close to normal, depending on flow
direction as usual.
On Sunday, weak ridging behind the exiting tropical system and
the next trough diving SE through S ON will make for a mainly a
dry and seasonably warm day, with highs from the mid 70s in the
mtns to the low 80s in the S, and there should be enough
gradient WSW flow to keep the sea breeze at bay through most of
the day. Could see a few showers move into the mtns late, but
the chance there will be Sunday night. The forcing associated
with that 500 MB trough will weaken as it moves through, so
while showers in the mtns are possible, they will generally be
light where they do occur. Lows range from the mid 50s N to the
low 60s S.
On Monday afternoon another weak wave moves into the base of the
500 MB trough nearby, and the 12Z Euro has backed off showers
some, while the GFS has not, although the Euro still has some
very light QPF. The best chance will be in the N, and that is
where the chc POPs are. Partly sunny covers the sky forecast and
highs are mostly in the 70s to around 80 in the S. For the most
part the Euro stays dry on Tue, and have leaned in that
direction. Highs on Tuesday rebound a few degrees from Monday,
generally in the mid 70s to low 80s. Wed looks similar to
Tuesday, although there is a possibility of a few showers.
Thursday, POPS increase to Chc, as a wave move around the upper
level trough to our NE, which means a better chance of showers
across much of the CWA, with more clouds, and highs a few
degrees lower than Wednesday.
&&
.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
Short Term...IFR/LIFR will continue into early tomorrow
morning, with a band of heavy rain and thunderstorms moving
through overnight. Wind gusts 25-30 kts are possible within this
band as well. Conditions will quickly improve to VFR Saturday
morning as a front swings through with wind gusts tapering off
as well.
Long Term...Mainly VFR expected Sun-Wed. There is a good chance
of valley fog Sunday night, and could see a few showers Monday
aft/eve. I think there will be enough clouds around Mon night to
preclude valley but may see it again Tuesday night with stagnant
flow in place.
&&
.MARINE...
Short Term...SCA conditions will continue through at least
Saturday night as winds southwesterly winds will be gusting
upwards of 30 kts, with a few gusts to 34 kts possible, into
Saturday morning. Afterwards, seas will remain elevated, 5-7 ft,
through Saturday night.
Long Term...Winds/seas continue to subside on Sunday and then
stay stay below SCA conditions through Wed.
&&
.HYDROLOGY...
The precipitation will continue to shift to southern areas
overnight. However, with heavier rain from earlier, will
continue to monitor the Pemi and Saco Rivers across the
mountains of central NH.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...High Risk for Rip Currents from 8 AM EDT Saturday through Saturday
evening for MEZ023>028.
NH...High Risk for Rip Currents from 8 AM EDT Saturday through Saturday
evening for NHZ014.
MARINE...Small Craft Advisory until 11 PM EDT Saturday for ANZ150-152-
154.
Small Craft Advisory until 11 AM EDT Saturday for ANZ151-153.
&&
$$
Cannon
Area Forecast Discussion
National Weather Service Marquette MI
742 PM EDT Fri Aug 9 2024
.KEY MESSAGES...
- Scattered to numerous rain showers and breezy winds near 30 mph
today and tonight. Strongest winds expected near western lakeshores
and in the Keweenaw.
- Scattered showers and breezy conditions continue Saturday before
quiet and dry weather returns Sunday.
- A beach hazard statement remains in effect for today`s anticipated
dangerous swimming conditions for Alger County beaches.
- Warm, dry weather expected early next week thru at least the
midweek period.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 232 PM EDT Fri Aug 9 2024
GOES-16 Day Cloud Phase imagery shows a scattered to broken field of
banded low cu with some mixed phase clouds over the central UP. RAP
analysis shows a stacked closed low slowly approaching James Bay
with a 1007mb surface pressure. At 500mb, the closed low has a lobe
that is rotating around the parent low with the axis currently over
the Minnesota arrowhead. This will rotate over the UP today, and the
PVA from that lobe will support the already ongoing lake effect rain
showers that are apparent on satellite and radar imagery.
HREF mean 850mb temperatures throughout today and tonight will be
around 4 C over Lake Superior. With lake temperatures still between
13 and 21 C, there`s plenty of lake-induced instability to generate
rain showers into Saturday morning and with the slow movement of the
stacked low to the northeast, the low levels will remain cyclonic
enough to support shower development. Mean accumulated precip from
8AM this morning to 8AM Saturday morning only peaks at around 0.6
inches in the west, so impacts should be minimal from the rainfall.
Of more impact will be the winds, with the HREF showing widespread
wind gust potential up to 30 mph especially along the Lake Superior
shorelines. Temperatures today under cloudy skies and showers will
only peak in the 60s, with lows falling to the 40s.
&&
.LONG TERM /SATURDAY THROUGH FRIDAY/...
Issued at 341 PM EDT Fri Aug 9 2024
With the midlevel low and associated cool airmass situated over the
area through the weekend, and additional shortwave energy rotating
around it, expect showery weather to continue Saturday through
Saturday night. In addition, with 850mb temps falling to around 5C
per multi ensemble mean and with Lake Superior sfc water temps
ranging generally from 17 to 21C, there will be some lake
enhancement to the showers. As a moderating airmass moves in
Saturday night while the main low moves out, showers slowly taper
off across the western UP but linger to the east overnight. Highs
Saturday will be in the upper 50s to upper 60s F, then expect lows
ranging in the mid 40s to mid 50s (coolest interior-west). NW winds
remain breezy through Saturday, gusting to 20-30mph. Dangerous
swimming conditions are expected for the Lake Superior beaches of
Marquette and Alger counties on Saturday due to the wave action from
20-30kt winds over Lake Superior.
With departure of the last shortwave and with the mid-level low
exiting farther to the east, showers across the eastern UP into
early Sunday wrap up by the afternoon. Under a mix of clouds and
sun, temps will rise into the upper 60s to mid 70s F.
Tranquil weather is expected into next week as strong positive
height anomalies across central Canada induce ridging over the Great
Lakes. Diurnal instability will be on the limited side, so potential
of any afternoon convection is very low. If any diurnal convection
does happen to develop, it would be isolated in coverage at most.
The better chance for any shower activity (only 20-30% chance) would
be in the late Wed/Thu time frame with loose model agreement for a
weak shortwave ejecting out of the Plains to reach Upper MI at that
time. However, with ridging nearby, this feature may be suppressed
too far to our south for any impacts over the UP.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 742 PM EDT Fri Aug 9 2024
Borderline VFR/MVFR conditions will deteriorate to MFVR overnight as
the parent lower pressure over northern Ontario dips southeast over
Lake Superior tonight, lowering cigs and spreading more scattered to
numerous light rain showers across Upper Michigan, particularly at
IWD and CMX. Conditions improve back to VFR tomorrow morning, but
scattered lake-effect showers and clouds could keep cigs borderline
MVFR once again. Gusty northwest winds upwards of 25 mph continue
overnight through tomorrow, especially at IWD and CMX where gusts
could push upwards of 30-35 in the afternoon.
&&
.MARINE...
Issued at 341 PM EDT Fri Aug 9 2024
An early fall-like low pressure system will affect Lake Superior
into the weekend. Cooler air moving across the still warming waters
of Lake Superior (sfc water temps now generally 63-70F) will lead to
increasing instability and deeper mixing, allowing for stronger
winds to reach the lake sfc. W to NW winds of 20-30kts have become
common, and should continue through Saturday. Some gale force gusts
are possible today over western Lake Superior with probability at 10-
30pct, greatest toward the nearshore waters of Upper MI. Tonight
thru early Sat aftn, potential of gale gusts will shift to areas
from n of the Keweenaw down to btwn Marquette and Grand Marais.
Probability of gale gusts in that area is 10-40pct, greatest from
around Stannard Rock to Marquette and Grand Marais where water is
warmest. Winds then diminish Sat night to 10-20kt w half and to 15-
25kt e half. On Sun, expect W to NW winds gusting to around 20kt.
High pres building over the Great Lakes region will then lead to
winds mostly under 15kt Mon-Wed.
In addition to period of stronger winds into the weekend,
waterspouts are possible across Lake Superior. The potential of
waterspouts will diminish from w to e on Sat.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Beach Hazards Statement until 10 PM EDT this evening for
MIZ006.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...GS
LONG TERM...LC
AVIATION...BW
MARINE...LC
Similar to previous forecast discussions, the ridge continues to
weaken, making way for deeper marine layer, breezy onshore
conditions during the afternoon and evenings, and slightly cooler
temperatures as the trough continues to build. With the deepening of
the marine layer, expect a rinse and repeat for low clouds tonight
into Saturday morning along the coast and extending further inland
and into the valleys. Temperatures tonight will be relatively the
same as last night with temperatures in the 50s to low 60s over
most of the region, with higher terrains and isolated spots seeing
70s. The gradual, slight cooling will be reflected for Saturday
maximum temperatures, with a 1-3 degree difference than today.
Highs will be in the 80s to 90s inland, with some 100s in the
mountain ranges. The coastal areas will repeat its` usual and
seasonal temperatures of high 50s to 60s.
&&
.LONG TERM...
(Saturday night through next Thursday)
Issued at 1108 AM PDT Fri Aug 9 2024
Ensembles and clusters analysis continues to show agreement that
the upper level trough will continue the cool down in temperatures
starting Sunday with temperatures dropping to mostly 70s and 80s
inland and some isolated spots in the 90s. Coastal areas will
remain consistent of 50s to 60s. Going into early next week, the
temperatures continue to drop a few degrees each day. Chances for
above normal seasonal temperatures are looking less likely as
Climate Prediction Center 6-10 day outlook continues to suggest
near normal to below seasonal temperatures.
&&
.AVIATION...
(00Z TAFS)
Issued at 545 PM PDT Fri Aug 9 2024
Satellite and observations show coastal stratus and fog /LIFR-IFR/
otherwise it`s VFR. Lower level dry air on gusty northwest winds has
recently mixed into the boundary layer dissipating stratus coverage
over the coastal waters, but now more recently seeing a return of
saturated air (clouds) vs unsaturated air (cloud free). During the
early evening timeframe dry air above the marine layer may still mix
into the boundary layer along the immediate coastline, otherwise
nocturnal cooling will take over resulting in increasing areal
coverage of stratus and fog. The marine layer depth is 1200 feet
per recent Bodega Bay and Fort Ord profiler data.
The onshore SFO-SAC 4.4 mb pressure gradient currently predominates
while the ACV-SFO gradient is 3.2 mb. Onshore winds will usher
stratus and fog at least locally inland tonight and Saturday
morning. Conditions improving to MVFR-VFR near the coast by late
morning Saturday.
Vicinity of SFO...Low to moderate confidence VFR holds through
the evening, if the marine layer depth holds unchanged this may
help keep VFR going a while longer. Stratus was mixing out, but
now is rapidly filling back in again just upstream from SFO
Airport per recent satellite imagery. RAP model is showing IFR by
mid evening. For now, the 00z TAF shows IFR 11z-15z Saturday, will
closely monitor observations and amend as needed. Onshore wind
continuing with periodic gusts to around 25 knots in the afternoon
and evening.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Stratus, fog, patchy light drizzle /LIFR-IFR/
moving inland this evening and overnight while an eddy circulation
is forecast to develop over the northern Monterey Bay during the
evening. Stratus, fog and patchy light drizzle improving to MVFR-
VFR by late Saturday morning. Mainly onshore winds 5 to 15 knots.
&&
.MARINE...
(Tonight through next Thursday)
Issued at 511 PM PDT Fri Aug 9 2024
Gusty northwest winds will continue over the coastal waters
through the middle of next week. This will cause rough seas over
the outer waters, including rough seas to expand across the inner
waters at the end of the weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory until 3 PM PDT Sunday 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-Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory from 9 AM Saturday to 3 AM PDT Sunday for
Pt Reyes to Pigeon Pt 0-10 nm.
Small Craft Advisory from 3 PM to 9 PM PDT Saturday for Pigeon
Pt to Pt Pinos 0-10 nm.
&&
$$
SHORT TERM...SO
LONG TERM....SO
AVIATION...Canepa
MARINE...Murdock
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Area Forecast Discussion
National Weather Service Reno NV
127 PM PDT Fri Aug 9 2024
.SYNOPSIS...
* Smoke and haze will continue to impact portions of northeast
California and northwest Nevada through the weekend.
* Outside of a 10-15% chance for storms in Southern Mono/Mineral
Co this afternoon, the forecast largely remains dry.
* Breezy winds Friday-Monday will bring enhanced fire weather
concerns along with choppy lakes. This will usher in cooler temps
for next week.
&&
.DISCUSSION...
* Smoke and haze from the Park and Crozier wildfires will continue
to impact portions of northeast CA and northwest Nevada, but
exact impacts will depend on fire activity. The current wind
pattern remains largely the same through the weekend, so
anticipate similar impacts unless the fires are to burn more
actively. HRRR model simulations show a similar footprint,
although slight fluctuations north/south could bring impacts to
parts of Reno, especially the south end of the Truckee Meadows,
in addition to the Tahoe Basin. You can find information on
current air quality at fire.airnow.gov.
* A series of troughs brushing just north of the region will bring
increased afternoon breezes through Monday, with the greatest
risk (50-80% chance, location dependent) of gusts exceeding 30
mph on Sunday and Monday. The strongest winds aloft come in
Sunday night with an upper trough passage, so anticipate the
midslopes and ridges will remain rather breezy through the
night. The fact that the peak upper level winds do not align
with peak mixing on Monday will be the saving grace from seeing
a longer duration critical fire weather event. Still, there are
enhanced concerns and a 1-4 hour window of critical conditions
is possible in localized areas. Areas of greatest concern will
be along the Sierra Front and portions of northern Nevada. Area
lakes will also be choppy. If the trough slows further and the
two align, winds have the potential to be stronger on Monday.
* These troughs will also usher in a cooler airmass, which will be
a welcome change after the hot summer the region has experienced
so far. By Monday and through next week, temps will be near to
below normal for this time of the year. The cooler airmass also
means we`ll start to see some improvements to RH recovery
overnight as lows dip into the 50s to near 60 for warmer
valleys and into the 30s and 40s for colder Sierra valleys.
Longer range pattern in the ensemble cluster analysis is in good
agreement we`ll maintain a troughy pattern, meaning near to
below normal temps and breezy afternoons. -Dawn
&&
.AVIATION...
* For KRNO: Latest smoke models keep the smoke impacts just south
of the region, more Washoe Valley into north Carson. Light haze
isn`t out of the question, but visibility shouldn`t be impacted.
Only other concern will be breezy WSW afternoon winds each day
from approximately 21z-03z with gusts of 20-25 kts. Similar
winds can be expected across the region, with winds remaining
elevated Sunday night as a trough swings through the region.
* Smoke from the Park and Crozier Fires may bring narrow bands of
MVFR conditions late day into the morning hours to KCXP/KMEV/KSVE,
but primarily that would impact slantwise visibility. Exact
impacts and extent of smoke will be dependent on fire activity.
* A 10% chance for showers and isolated thunderstorms this
afternoon for the Eastern Sierra of Mono Co (including KMMH)
eastward towards KHTH. Storms may produce reduced cigs/vis, but
it will be localized, along with gusty and erratic outflow
winds. -Dawn
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
Area Forecast Discussion
National Weather Service Las Vegas NV
859 PM PDT Fri Aug 9 2024
.SYNOPSIS...Chances for afternoon and evening showers and
thunderstorms will continue each day through the weekend for areas
near and east of a line from Yucca Valley to Mount Charleston to
Rachel as monsoonal moisture remains in place. Above normal
temperatures will continue as high pressure persists over the
southwestern states. Drier air is forecast to push into the region
next week, reducing thunderstorm chances and bringing slightly
cooler temperatures to the region.
&&
.UPDATE...Convection was dissipating early this evening altough an
isolated thunderstorm recently developed in far northeast Moahve
County near Colorado City. The latest high res models support mostly
tranquil weather across the region tonight. Saturday afternoon
should be more active over Clark County. The 00Z HRRR indicates that
thunderstorms that develop over the Spring Mountains will move
slowly toward the southeast which would take them over the Las Vegas
Valley. A moist and moderately unstable air mass will remain in
place as shown in this afternoon`s sounding...Pwat values near 1.4
inches and surface CAPE values around 1400 J/kg. The forecast was
updated with the 01Z NBM and a slight blend from CAM PoPs which
increased PoP values to 20-30 percent across the Las Vegas Valley
Saturday afternoon.
&&
.PREV DISCUSSION...
138 PM PDT Fri Aug 9 2024
.SHORT TERM...through Sunday night. Early afternoon satellite loop
showed thunderstorms initiating over the Spring Mountains and
towering cumulus over the Sierra Nevada, the Nevada National
Security Site, and the higher terrain of northern Mohave County.
Debris clouds from the overnight and early morning MCV-driven rain
had evaporated, and lifted indices had dropped to -4 in Clark and
San Bernardino counties. Convective inhibition was also decreasing.
Thus, expect isolated to scattered storms again this afternoon and
evening along and southeast of I-15. A second area of concern is
Lincoln County. Thunderstorms had already initiated just north of
our CWA, and high res models show them propagating farther south as
the afternoon wears on, which is supported by ongoing satellite
trends. The NBM captured this idea, and suggests activity will
persist well after sunset. Saturday and Sunday, Mohave County should
see the highest thunderstorm chances under east to southeast flow
around an easterly wave meandering around the Baja, with more widely
separated storms developing over the higher terrain in Clark and San
Bernardino counties. Overall, expect temperatures not to change
much, perhaps going up a degree or two from today to Saturday and
falling a degree or two from Saturday to Sunday, but point
temperatures could vary a lot depending on exact location and timing
of thunderstorms.
.LONG TERM...Monday through Thursday.
The upper level trough will continue to push into the West Coast
next week. This will scour out the moisture and bring an end to the
scattered showers and thunderstorm activity. Anomalously high PWATs
will be will be confined to eastern Lincoln and Mohave counties
Monday afternoon, then by Tuesday afternoon normal to below normal
PWATs will be in place for most areas. This dry air will remain over
the region through the rest of the forecast as the probability for
PWATs over 1 inch drops to 30% or less in the GEFS by Wednesday
morning. The chance for afternoon showers and thunderstorms will
decrease and shift east each afternoon next week, with a potentially
dry forecast for all areas by Wednesday or Thursday.
With the trough sitting nearby and decent southwesterly flow aloft,
breezy afternoon winds can be expected. The risk for impactful winds
over 40 MPH is low to none (20% or less probability), so most likely
it would be typical afternoon breezes of 25 to 35 MPH, especially
Monday. However. Will need to watch where the better winds will set
up and how fuels have changed with the recent rains and drier air
could increase fire danger. Temperatures will remain right around
normal through next week.
&&
.AVIATION...For Harry Reid...East to southeast winds are expected
for the remainder of the afternoon with speeds generally less than
10 knots. There is some potential of seeing a gust to around 12
knots this afternoon, but gusts overall should remain short-lived.
Thunderstorm chances are around 30-35% over the higher terrain and
only around 15-20% in the valley. There is also a slight possibility
of outflow winds originating off the Spring Mountains could impact
the airport after 23z with gusts up to 30 mph, but confidence does
remain low. FEW-SCT clouds at or above 12kft.
For the rest of southern Nevada, northwest Arizona and southeast
California...East-southeast breezes are expected over most areas
through this afternoon, while southerly winds take hold in the
Colorado River Valley. Speeds in both locations will largely remain
less than 10 knots. At KBIH and KDAG, expecting typical diurnal wind
patterns. Significant thunderstorm impacts appear unlikely (15%
chance or less) at the area TAF sites today though there is
potential for outflow winds gusting to 20 knots. Instead, VFR
conditions prevail as FEW-SCT clouds at or above 12kft persist.
Thunderstorm chances will increase Saturday for the Las Vegas valley
TAF sites along with EED and IFP.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Adair
SHORT TERM...Morgan
LONG TERM...Nickerson
AVIATION...Gorelow
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