Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/14/21
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1039 PM EDT Fri Aug 13 2021
.SYNOPSIS...
A cold front will bring some scattered showers and
thunderstorms to the region overnight. The front will
move south of the region tomorrow with isolated to scattered showers
and thunderstorms ending as cooler and drier air moves in. Less
humid conditions and pleasant weather are expected Saturday night
through Sunday as high pressure builds in.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
UPDATE...As of 1030 PM EDT, remaining portions of severe
thunderstorm watch 437 has been cancelled.
Still some isolated showers/thunderstorms across portions of the
western Mohawk Valley/SW Adirondacks, with dissipating showers
across western New England.
For the overnight hours, expect a relative lull in
shower/thunderstorm coverage through around 3 AM, with best
chances for isolated coverage across the southern Adirondacks
and western Mohawk Valley.
After 3 AM, showers/thunderstorms across NW PA may expand
northeast into central NYS and the SW Adirondacks/Mohawk Valley
region, with increased forcing ahead of the approaching cold
front and also mid level height falls. Locally heavy rainfall
could occur.
Showers/thunderstorms may eventually increase in coverage into
northern/western portions of the Capital Region and Schoharie
Valley by sunrise.
Otherwise, remaining warm and humid overnight, with lows mainly
in the mid 60s to lower 70s. Some patchy fog may form,
especially in areas which received heavy rainfall earlier this
evening.
Previous discussion follows...
The Heat Advisory has expired and the Severe Thunderstorm Watch
was canceled north and west of Albany in eastern NY. A severe
thunderstorm produced the gambit of severe weather for portions
of Albany and the Capital Region. WFO ALY office was also rocked
by numerous close CG strikes, heavy rainfall, wind gusts
estimated to 45-50 mph, and M & M size hail. Voorheesville
reported 1" hail, and several wind damage reports have come in
with some flash flooding near Route 20 in Albany. Please see our
LSR for all the reports.
A few strong to potentially severe thunderstorms are moving
across the mid Hudson Valley. Moderate amounts of instability
remain southeast of the Capital Region with dewpts in the lower
70s. The instability will continue to wane as the prefrontal
trough moves through. The cold front is getting close to western
NY and the St Lawrence River Valley. Some isolated to scattered
showers and a few thunderstorms are possible overnight but they
are not expected to be severe after midnight. The latest 3-km
HRRR continues to show limited and isolated activity overnight
with the most coverage west of the majority of the forecast
area. We continued slight and low chance PoPs after 06Z.
Low temps will be in the 60s to around 70 though a few upper
50s are possible in the southern Dacks.
The cold front should be moving across the western Adirondacks,
northern NY and the Mohawk Valley in the morning.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Tomorrow...The cold front makes steady progress across the
region from northwest to southeast. A chance of showers or
isolated to scattered thunderstorms is possible from southern
VT, the Capital Region and northern Catskills. The limited
heating should preclude a severe threat but some stronger
thunderstorms with gusty winds may be possible close to I-84 in
the afternoon. Stronger cold advection should kick in during the
early afternoon from the Capital Region north and west and then
southeast. A distinct change in the air mass should be felt
with dewpoints falling into the 50s or lower north and west to
northwest winds. Again, this dewpoint boundary may not move
through the southern most zones until the late pm and early
evening. Highs will be in the upper 70s to lower 80s in the
valleys with a few mid 80s near KPOU. Expect upper 60s to
mid/upper 70s over the higher terrain.
Saturday night...Relief from the heat will be felt across the
entire area. Dewpoints will fall into the mid 40s to mid 50s
with northwest to north winds with high pressure building in
from the Great Lakes Region and southeast Canada. Lows will be
in the 50s with some 40s over the southern Greens, southern
Dacks, and eastern Catskills.
Sunday...A beautiful close to the weekend with the 1025 hPa or
so anticyclone building in over NY and New England with lots of
sunshine and fair weather. The strong subsidence from the sfc
high will yield mostly sunny or sunny skies with light winds.
Max temps will be near or slightly below normal for mid-August.
Highs will be in the 75-80F range in the valleys, and mid 60s to
mid 70s over the higher terrain.
Sunday night into Monday...The fair and pleasant weather
continues into early next week with a cool night with lows in
the mid 40s to mid 50s with perhaps some shallow radiational
mist over the river valleys with clear skies and light to calm
winds. High pressure remains over New England with mid and upper
level heights increasing along the East Coast. Temps increase
to seasonal levels with a slight increase in humidity levels but
still fairly comfortable for August with dewpoints in the 50s
to lower 60s.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
After a brief respite from very humid conditions, it looks like
humidity levels will climb through the middle/end of next week,
along with increasing chances for showers and thunderstorms, as
ridging rebuilds off the eastern seaboard.
Shower/thunderstorm coverage looks to be modulated mainly by diurnal
heating, however additional forcing from any remnant tropical entity
from the southeast states could enhance coverage of
showers/thunderstorms, with best chances looking to be sometime next
Wed-Thu.
Otherwise, Tuesday looks to be the transition day in terms of
increasing humidity levels, with dewpoints climbing into the
lower/mid 60s by afternoon. Dewpoints will likely rise into the
mid/upper 60s by Wednesday afternoon, with perhaps some upper 60s to
lower 70s in valley areas late Wednesday into Friday. Highs will
mainly be in the lower/mid 80s in valleys, and 75-80 across higher
terrain, with min temps generally in the lower/mid 60s, except 55-60
across higher elevations.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
A prefrontal trough will focus some showers and thunderstorms
tonight. The cold front will move across the region late
tomorrow morning into the afternoon. High pressure will build in
for Saturday night.
VFR conditions are expected ahead of showers and thunderstorms
with a pre frontal disturbance. The showers and thunderstorms
will impact KALB prior to 02Z/SAT, and potentially
KPOU/KGFL/KPSF between 02-06Z/SAT. Conditions will briefly lower
to MVFR/IFR levels with some gusty winds.
Expect some partial clearing and some stratus or patchy MVFR/IFR
mist or fog may form, especially at KGFL/KPSF. KALB may also
have some form due to the recent wet ground. Some showers
associated with the front may arrive shortly before or after
12Z/SAT. We tried to address these showers with VCSH or TEMPO
groups with reductions to the MVFR levels. The cigs and vsbys
may briefly increase to VFR levels at KGFL/KPSF before the
showers arrive. The threat showers decreases after 17Z/SAT for
KALB/KGFL, but may continue for KPSF and KPOU depending on the
placement of the boundary.There is a small chance for
thunderstorms and later TAF issuances can address it.
Any storms this evening could result in briefly strong wind
gusts and a sharp wind shift to the west. Winds then become
light and variable overnight before turning west to northwest
tomorrow morning into the afternoon increasing to 8 to 12 kts
with some gusts to around 20 kts at KALB/KPSF.
Outlook...
Saturday Night to Monday Night: No Operational Impact.
NO SIG WX.
Tuesday: Low Operational Impact. Isolated SHRA...TSRA.
Tuesday Night: Low Operational Impact. Isolated SHRA.
Wednesday: Moderate Operational Impact. Scattered SHRA...TSRA.
&&
.FIRE WEATHER...
A cold front and an upper level disturbance will bring
some strong to severe thunderstorms into tonight. The front will
move south of the region tomorrow with isolated to scattered showers
and thunderstorms ending as cooler and drier air moves in. Less
humid conditions and pleasant weather are expected Saturday night
through Sunday as high pressure builds in.
The RH values will increase to 90 to 100 percent in the
morning, and lower only to 40 to 60 percent Saturday afternoon.
The max RH values will be in the 80 to 100 percent range Sunday
morning.
The winds will be southwest to west at 5 to 15 mph tonight.
Expect the winds to shift toward the west and northwest at 5 to
15 mph on Saturday. Northwest winds of 5 to 10 mph will persist
Saturday night.
Winds gusts in excess of 30 mph will be possible with any
thunderstorms.
&&
.HYDROLOGY...
Some heavy downpours and localized hydro issues are possible
late this afternoon into Saturday morning with any
thunderstorms. Dry weather returns late Saturday into early next
week.
Any storms with high precipitable water values could bring
some minor flooding of urban, poor drainage and low lying areas
and isolated flash flooding. Some notable rises may occur on
the main stem rivers with heavy rainfall over them. However,
widespread main stem river flooding is not expected at this time.
Flows should lower over the weekend into early next week, as
high pressure ridges in.
The next chance of widespread rainfall will be on Wednesday.
For details on specific area rivers and lakes, including observed
and forecast river stages and lake elevations, please visit the
Advanced Hydrologic Prediction Service /AHPS/ graphs on our
website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...Wasula
NEAR TERM...KL/Wasula
SHORT TERM...Wasula
LONG TERM...KL
AVIATION...Speciale/Wasula
FIRE WEATHER...Wasula
HYDROLOGY...BGM/Wasula
Area Forecast Discussion
National Weather Service Charleston SC
952 PM EDT Fri Aug 13 2021
.SYNOPSIS...
High pressure will prevail across the area into the upcoming
weekend. A front will then stall northwest of the area late
this weekend and early next week while Tropical Cyclone Fred
moves onshore along the northeastern Gulf Coast. Fred will then
weaken as it moves north into the southern Appalachians into
mid week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As of 950 PM: Latest IR satellite detected several patches of
mid and high clouds across the forecast area, steadily expanding
across coastal GA. Based on the satellite trends, the forecast
update will feature greater sky cover through the rest of the
night. The increase sky cover should limit the fog potential
during the pre-dawn hours, we will keep a mention of patchy fog
across the region. Temperatures are on track to reach the low to
mid 70s inland and the upper 70s along the coast.
As of 720 PM: KCLX detected the sea breeze across Allendale
south to Candler County, pushing inland. Previous shower and
thunderstorm activity along the sea breeze has dissipated over
the past hour. Latest HRRR indicates that the rest of the
evening and overnight will remain dry. However, based on
guidance and the passage of the sea breeze, I will add a mention
of patchy fog during the pre-dawn hours.
Previous Discussion:
High pressure and subsidence have kept most of the area
rainfree with the exception of a few short-lived showers just
along the sea breeze. From the 18Z RAOB sounding, PWATs at KCHS
are around 1.70" with decent instability in place. Although, the
sounding also shows quite a bit of dry air aloft. Therefore,
for the rest of the afternoon, only isolated
showers/thunderstorms are expected, with most convection (if
any) forming along the seabreeze. A stray shower cannot be ruled
out elsewhere though. By this evening, any lingering showers
should diminish quickly with the loss of daytime heating.
Thereafter, a mostly quiet night is expected. By late tonight, a
few showers move into the coastal waters. Low temperatures will
be in the 70s.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
High pressure at the surface and aloft will remain in place across
the SE coast into the Atlantic to start the weekend, along with an
ill-defined sfc boundary/trough along the Appalachians down into the
Lower Mississippi River Valley. A little stronger SE flow and
moisture push off the Atlantic into the South Carolina and Georgia
coasts may bring slightly better shower/thunderstorm chances to the
forecast area Saturday afternoon...as compared to what we`ve seen
the last few days...particularly across SE Georgia where higher
dewpoints/better instability will reside. Severe weather potential
remains low. But any showers/storms could produce localized heavy
rainfall.
Sunday into Monday: Still anticipating Tropical Cyclone Fred to
slide up through the northeast Gulf into the Florida Panhandle by
early Monday morning, although forecast track and heavier QPF
forecasts have been trending westward. But with further increasing
moisture transport into the SE states and larger scale forcing, most
active weather period is anticipated through this time. As
mentioned, higher QPF forecasts have shifted slightly westward. But
the area remains within the WPC Day 3 marginal risk for excessive
rainfall through early Monday...and likely beyond.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Larger scale upper level ridging will remain the dominant pattern
from the SE states into the Atlantic through next week, keeping the
door open for a more active tropical weather. Region will likely
still be feeling the impacts from Fred during the early part of next
week, primarily in the form of decent moisture flow off the
Atlantic, resulting increased instability and shower/thunderstorm
chances that will largely follow the diurnal heating cycle.
Inherited forecast features some fairly high pops through Wednesday
before trending downward through the latter half of the week as what
remains of Fred dissipates over the SE. But main forecast challenge
and impacts will continue to revolve around localized heavy rainfall
possibilities. For the later half of the week and eventually into
next weekend, will have to see what happens with potential tropical
cyclone seven.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
The terminals are forecast to remain dry with VFR conditions
through late tonight. Patchy fog may develop inland of the
terminals during the pre-dawn hours. However, KSAV could see a
period of light fog between 9-12Z. A band of showers are
forecast to approach the coast during the mid-morning, pushing
onshore during the mid-day into the afternoon. 0Z TAFs will
feature VCSH at KSAV and KJZI on Saturday.
Extended Aviation Outlook: Forecast continues to hinge on Tropical
Cyclone Fred. But overall risk for flight restrictions/impacts
increases late this weekend through the early part of next week, as
Fred works into the SE part of the CONUS and brings increased
shower/thunderstorm possibilities to the region.
&&
.MARINE...
Rest of today and tonight: High pressure and a southerly flow will
prevail. Winds less than 15 knots and seas 2-3 feet are
expected.
Saturday through Wednesday: Atlantic high pressure persists through
the period. Tropical cyclone Fred is expected to work into the
eastern/northeastward Gulf bringing minimal impacts to the
coastal waters. No marine headlines anticipated at this time.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...NED
SHORT TERM...TBA
LONG TERM...TBA
AVIATION...NED
MARINE...RAD/TBA
Area Forecast Discussion
National Weather Service Cheyenne WY
514 PM MDT Fri Aug 13 2021
.SHORT TERM...(This evening through Saturday)
Issued at 136 PM MDT Fri Aug 13 2021
Latest satellite picking up on a growing cumulus field mainly over
the higher terrain across the Snowy and Sierra Madre Ranges in
addition to portions of the Rocky Mountains in CO as a few have
begun to be tall enough to return echoes on the KCYS radar.
Lingering broken cloud deck across the high plains have limited
early diurnal heating with KIBM, KCYS, and KSNY reaching only in
the middle 70s as of latest obs. High res CAMs are not all
favorable for widespread convection especially east of the Laramie
Range with the 17z HRRR run showing some additional convective
development across portions of the Laramie Range and then again
across portions of the North Platte River Valley in NE late
tonight as a LLJ begins to impact the region. Time frame for KLAR
this afternoon that is of concern for any potential for strong to
severe storms between 5 and 10 PM MDT.
Latest sounding from CSU PRECIP study shows a well capped
environment hence the lackluster thinking for severe convection
early on today as well as a fairly dry mid to upper level as lapse
rates remain less than ideal. Some decent inverted V on soundings
across the region to keep a wind threat alive even under 20 dBZ
echoes. SPC with latest update has removed the slight risk as
marginal risk of strong to severe thunderstorms remain as
stationary front continues its influence over us.
Expect highs today to be on a touch cooler with upper 80s near
Chadron but low to middle 80s across the rest of the high plains
in WY and NE as well as west of the Laramie Range. Lows tonight
from the low 50s into the upper 50s for most.
.LONG TERM...(Saturday through Thursday)
Issued at 420 AM MDT Fri Aug 13 2021
Afternoon showers and possibly a few thunderstorms will again be
possible on Saturday, mainly focused over western Nebraska as
easterly upslope flow remains in place. On Sunday, a weak ripple
trough will pivot around the top of the broad ridge in place over
the southwestern CONUS. This feature will help increase convective
coverage on Sunday afternoon over both southeast Wyoming and
western Nebraska. Temperatures will run a bit warmer on both
Saturday and Sunday with afternoon highs around 5 to 8 degrees
above average. Weak ridging will return to the high plains on Monday
and Tuesday with dry weather likely. By the middle of next week
however, differences between the ECMWF and GFS emerge with regard
to our next weather event. A broad trough is expected to move
ashore over the Pacific Northwest. The GEFS favors a deeper
trough and higher precipitation chances over the high plains by
Wednesday and Thursday. The ECMWF and its recent ensemble runs
favor a slightly weaker system and a better chance of rain by
Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 507 PM MDT Fri Aug 13 2021
MVFR to VFR conditions across southeast Wyoming and the Nebraska
panhandle with some lower cigs and gusty winds to 35 knots.
Timing to showers and thunderstorms this afternoon for southeast
Wyoming is between 23Z and 5Z, then for the southern Nebraska
panhandle it is between 3Z and 10Z, and for the central Nebraska
panhandle between 6Z and 12Z. Gusty and erratic winds are likely
around these showers and thunderstorms, as well as frequent
lightning, hail, and briefly limited visibilities during heavy
rainfall. Skies should clear by tomorrow morning. Confidence is
fairly low at this time with any convection developing east of the
Laramie range, with the atmospheric dynamics being much less
impressive than earlier model runs. Nevertheless, there is some
convective development around Laramie with upwards to 35 knots and
some hail signatures. As a result, went ahead and left VCTS in
the TAFs.
&&
.FIRE WEATHER...
Issued at 140 PM MDT Fri Aug 13 2021
Afternoon shower and thunderstorm chances today have minimized
overall fire weather concerns for today outside of the exception
of lightning starts. Some low precipitation chances into the
weekend and early work week before dry conditions set in once
more under high pressure.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...WM
LONG TERM...MAC
AVIATION...LK/MD
FIRE WEATHER...WM
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
243 PM PDT Fri Aug 13 2021
.SYNOPSIS...Areas of smoke and haze along with hot interior
temperatures will continue into the weekend, with high pressure
aloft persisting. There will be a slight chance of thunderstorms
around portions of Trinity County this afternoon and evening,
otherwise expect dry weather is forecast to prevail.
&&
.DISCUSSION...We had one cloud-to-surface strike over the coastal
waters this morning with a brief 40dBz cell. Composite radar
imagery show another area of elevated returns offshore Central
California this afternoon. Convective allowing models brings this
area of returns aloft into NW California waters tonight. It
appears to be very high based and completely disconnected from the
surface. Based on current trends and recent observations, we
added a slight chance of thunderstorms over the coastal waters for
late tonight into early Saturday morning. Convective allowing
models keep the returns mostly offshore tonight, though a distant
rumble of thunder near the coast is certainly not out of the
realm of possibilities.
The heat risk will increase this weekend, however thick smoke in
Trinity and NE Humboldt Counties will likely reduce that threat.
The smoke aloft and hazy conditions in Mendocino and Lake
Counties has been less of a factor in blocking out solar
insolation. With heat risk forecast to reach high to very high
levels in portions of Lake and Mendocino Counties this weekend,
we hoisted a heat advisory. Highs may peak near 110F in Lake
and southern Mendocino Counties, though NBM indicates only a 50%
chance for 105F or more at Ukiah both days.
Otherwise layers of smoke from various wildfires across the
region will continue across regions of northwest California today
and tonight, however the most intense surface and low-level smoke
continues to be mostly restricted to Trinity County and some
adjacent portions of interior Humboldt. Air quality along most of
the the coast remains very good this morning, while some limited
smoke has brought some moderate air quality levels to interior
Mendocino. HRRR and Blue Sky smoke modeling along with larger
scale model wind fields continue to suggest that the coast will
remain mostly protected from any surface smoke, and if anything
areas of interior Humboldt to the west of the fires should see
some improvement due to some increase in westerly flow. That may
even help some areas near the fires with dispersion, but otherwise
expect areas to the east including Trinity County to stay pretty
socked in with smoke through the weekend. Later in the weekend and
especially early next week, increasing southwest to westerly flow
aloft should help make for more blue skies. That said, we will
probably tend to see a bit more marine layer cloudiness by then
along the coast as well, at least during the nights and mornings.
All the smoke around will likely continue to limit daytime heating,
as many interior valley temperatures have been running 5 to 10
degrees cooler than most guidance for the last couple days, on
average. We should expect this trend to continue into the weekend,
though if the smoke aloft thins out anywhere, heat risk may be
locally elevated enough to threaten advisory levels, particularly
around Lake County. Although the diminished daytime heating will
likely minimize instability, have decided to leave a slight chance
of thunderstorms along the eastern border of Del Norte, northern
Humboldt and eastern/northern Trinity this afternoon. SREF/HREF
probabilities and CAMs suggest the best shot in northeast Trinity
County for isolated thunderstorms, but with the smoke probably
limiting things once again, currently not expecting more than a
stray storm, and if any form they will likely track northeast
toward either Siskiyou or Shasta counties.
Extended forecast...850MB temperatures begins to wane early to
mid next week as a weak upper trough moves across the Pacific NW
and marine air pushes deeper into the coastal river valleys. The
heat risk will likely diminish early next week, however daytime
highs are still forecast to be above normal across portions of
interior Mendocino and Lake Counties. In Trinity County, the smoke
from the forest fires will continue to impact high temperatures
each day. Also, ensemble and deterministic guidance indicates
offshore flow developing next week, with potentially gusty
northerly and northeasterly winds over the ridges and warmer
coastal temperatures. That remains to be seen as 925mb and 850mb
winds from the deterministic and ensemble guidance are not looking
too strong at this point except over the King Range where
northerlies will howl. The potential for another round of heat
will increase into the latter portion of the week as an upper
ridge re-builds toward the West Coast and the trough departs.
&&
.AVIATION...The marine layer is ragged and shallow along the coast
today. It has mostly scattered out this afternoon to VFR with some
brief pulses of IFR conditions. As the clouds scatter, they have
given way to overcast smoke aloft from interior fires. The marine
layer should bring IFR conditions back late this evening. Gradually
warming interior temperatures will help keep the marine layer
shallow, but may also strengthen the inversion a tad over the weekend.
This may keep IFR conditions around a bit more consistently into the
morning tomorrow. In the interior, smoke continues to blanket the
area through tomorrow, though VFR conditions should remain for all
areas except those closest to and downwind of active fires.
&&
.MARINE...Light to gentle breezes are expected to prevail over the
coastal waters through this evening. Winds will slowly increase in a
fan south of Cape Mendocino this weekend and reach over 20 knots by
early Sunday in the southern outer waters. A small crafts advisory
has been issued starting tomorrow evening to reflect this.
Winds are forecast to quickly increase further to fresh to strong
breezes on Monday over the outer waters with gale force gusts. These
conditions will slowly weaken from south to north on Wednesday.
After Wednesday, northerlies will remain elevated over portions of
the northern outer waters through the rest of the work week.
Otherwise, a mid-period northwest swell will wane through Wednesday
and a south-southwest swell will linger throughout portions of the
waters during the next several days.
&&
.FIRE WEATHER...Areas of thick smoke will continue to limit daytime
heating today, keeping the atmosphere more stable and weakening
the thunderstorm threat for this afternoon. Best chances for storm
development remain in northeastern Trinity this afternoon. Will
continue to headline zone 283 for isolated thunderstorms, with the
caveat that if anything goes it will likely be restricted to
eastern or northeastern portions.
Otherwise, RH recoveries will remain rather poor through the weekend
into early next week outside of valleys and lower slopes.
Smoke will continue to limit daytime heating, particularly around
Trinity County, but some gradual uptick in westerly flow later in
the weekend may help with smoke dispersion, especially west of the
fires. Winds will remain fairly light outside of local terrain-driven
up-valley and west to northwest gap winds late each afternoon and
early evening into the weekend. Stronger diurnal westerlies in the
wind channeled gaps and valleys in the interior will be possible
late Sunday into Monday as an upper trough moves toward and
eventually across the area. Possible stronger E-NE ridge level
winds and poor overnight RH recoveries will be possible as we head
into mid next week. Yhere is considerable uncertainty regarding
the magnitude and duration of the offshore wind flow, however.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 1 PM Saturday to 8 PM PDT Sunday for CAZ110-
111-113>115.
NORTHWEST CALIFORNIA COASTAL WATERS... SMALL CRAFT ADVISORY IN
EFFECT FROM SATURDAY EVENING THROUGH SUNDAY EVENING FOR PZZ475.
&&
$$
Visit us at https://www.weather.gov/eureka
Follow us on Facebook and Twitter at:
https://www.facebook.com/NWSEureka
https://www.twitter.com/NWSEureka
For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png
Area Forecast Discussion
National Weather Service Grand Junction CO
544 PM MDT Fri Aug 13 2021
.SHORT TERM...(Tonight through Saturday night)
Issued at 223 PM MDT Fri Aug 13 2021
Radar and satellite tell the story as increased moisture and
daytime heating has allowed another round of convection to fire
this afternoon. As anticipated, this convection has spread
further northward with only showers noted north of I-70. The San
Juans look to be the big winners as a few thunderstorms move from
northeast to southwest, quite slowly. Skew-Ts do show moisture
increasing down south with V-profiles becoming less so, indicating
less of a wind threat and more rain possible. Even so, any
convection can produce some gusty outflow winds so that will
remain a concern with some of the storms bringing brief, heavy
rain. Most of this activity will end near and after sunset though
the HRRR does want to keep a few showers going over the San Juans
and southern foothills through midnight.
Tomorrow, more of the same though moisture will continue to slowly
increase. This is borne out as dewpoints will increase anywhere
from about 5F to nearly 10F for central portions of the CWA. Like
today, daytime heating and moisture will lend themselves to
convection firing in the afternoon with favored areas remaining
the same though the eastern Uintas may also see a bit more
activity.
Smoke has decreased noticeably across the region. This will
allow more shortwave radiation to reach the surface and thus, the
hotter temperatures we`re expecting over the next few days.
Fingers crossed it stays that way as guidance shows plenty of
smoke over the PacNW.
.LONG TERM...(Sunday through Friday)
Issued at 223 PM MDT Fri Aug 13 2021
An upper level trough is still projected to push inland across the
Pacific Northwest Sunday night, leading to a flattening of the high
over the Great Basin. However, the flow over western Colorado and
eastern Utah is not expected to shift much in response to this, so
moisture will continue to push into the area. Monday, flow becomes
more southerly to southwesterly due to the approaching trough,
allowing deep monsoonal moisture to begin pushing northward in
earnest, with PWATs expected to increase to at or slightly above
average for this time of year. An increase in coverage of showers
and storms is also expected, but without upper level support, these
storms are expected to be weak and tied to the higher terrain of the
San Juans and along the divide. As with afternoon convection in
previous days, a few heavy rainers will be possible, especially in
the San Juans. PWATs are expected to increase to near an inch for
much of the area from Tuesday onward, which is 150% of the average
PWAT for this time of year. Wednesday is looking to be the wettest
day, as the trough finally approaches eastern Utah and western
Colorado. From this point onward, though, forecast confidence
decreases rapidly. The EC continues to present a drier solution,
with the trough moved out of the area Thursday and northwesterly
flow on the back side shutting off the moisture. The GFS continues
to be wetter, although it has come a bit more into line with the EC.
Instead of the brief shift to northwesterly flow and then return to
southerly flow within 12 hours that previous runs had, the GFS now
indicates that the main trough will linger for an extra day, keeping
moisture and precipitation chances in the forecast for Thursday
before shifting to northwesterly flow Friday. Ensembles are evenly
split between these two solutions at this point as well. Either way,
cooler and unsettled conditions will be the story through at least
mid-week. If travelling next week, pay special attention to the I-70
corridor for any closures if/when heavy rains move back in.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 538 PM MDT Fri Aug 13 2021
VFR conditions will persist for the next 24 hours. Showers and
thunderstorms across the San Juans and along the Continental
Divide will dissipate after 03Z with the loss of daytime heating.
Until then, gusty outflow winds and perhaps brief downpours are
possible, mainly at KASE and KTEX, if anywhere. Otherwise, quiet
weather expected overnight with winds becoming light and terrain
driven. Similar weather expected on Saturday with another round of
showers and storms possible over the higher terrain and adjacent
valleys of southwest Colorado after 18Z. Gusty winds and downpours
are the primary threats once again.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...TGR
LONG TERM...BGB
AVIATION...MDM
Area Forecast Discussion
National Weather Service Goodland KS
831 PM MDT Fri Aug 13 2021
.UPDATE...
Issued at 831 PM MDT Fri Aug 13 2021
Based on the current radar coverage over Colorado/Wyoming, have
opted to remove mention of precipitation across the CWA thru 06z
Saturday. Any activity currently is very weak...slow moving and
not even close to affecting the forecast area over the next 3-4
hours. Will re-assess in a few hours for the 06z-12z timeframe.
Low chance of some development along the warm front draped over
the CWA, but can`t rule out entirely.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 205 PM MDT Fri Aug 13 2021
Satellite imagery and 500 mb RAP analysis showed high pressure
centered over Utah this afternoon, with a trough over the Great
Lakes region. This pattern placed the High Plains under northwest
flow. Meanwhile at the surface, the leftovers of a frontal boundary
were draped across the region. Cloud cover prevailed across much of
the area through the morning hours and has begun clearing early this
afternoon as east/southeast winds increase to 10 to 15 mph. At 2 PM
MT, skies were mostly to partly sunny, with temperatures mainly in
the upper 70s and low 80s.
Due to lingering cloud cover, instability appears much lower than
originally expected for today. Have lowered storm chances to 20
percent this afternoon and evening as a result, and even that may be
too optimistic. Additionally, severe thunderstorms are no longer
anticipated. That being said, a few storms could develop off of the
higher terrain in Colorado/Wyoming and travel towards the area.
Confidence in these storms making it into the CWA is low.
Temperatures fall into the mid 50s to low 60s tonight.
Guidance does suggest the potential for another shot at some
showers/storms early Saturday, mainly east of Highway 25. If
precipitation does develop, it will likely move out of the eastern
portion of the region by midday as temperatures climb into the upper
80s to low 90s.
While the overall pattern remains largely the same, a weak shortwave
looks to pass through the northwest flow over the High Plains during
the afternoon and evening hours on Saturday. As temperatures warm
and instability increases, thunderstorms should develop over western
Nebraska and track southeast into the region. Moderate shear and
instability could result in a few strong to severe storms along and
north of the Nebraska border during the late afternoon and evening.
The main threats will be large hail and damaging winds. Otherwise,
precipitation chances shift south and east overnight (exiting by
morning) as temperatures fall into the upper 50s to low 60s once
again.
.LONG TERM...(Sunday through Friday)
Issued at 143 PM MDT Fri Aug 13 2021
H5 Ridge will give way to a series of short wave
troughs as ridge center retreats to the west. Medium range models in
reasonable agreement through the first half of the period, although
significant differences appear towards the start of next weekend
with the development of closed low. While Canadian,ECMWF and GFS
all agree this system develops, the Canadian is much more
aggressive at moving system into the plains while the GFS/ECMWF
offer a slower solution. GEFS mean seems to support the slower
solution, with highest variability seemingly tied to how fast
trough kicks out, suggesting even slower solutions in the ensemble
space.
While the increase in uncertainty will make pinning down the details
a bit tricky, there are a few signals in the data that can provide
some guidance for the week ahead. Appears chance for diurnally
driven precipitation (i.e. late afternoon/early evening) will be
present through much of the period, with chances for more organized
precipitation and thunderstorms increasing after Wednesday as
closed low system mentioned earlier takes shape. While chance for
precipitation will be higher and strengthening shear profiles
will provide a better overall pattern for severe weather. That
being said, the overall pattern may be one where the warm/dry
sector expands eastward rapidly, limiting the actual areas seeing
storms develop. Temperatures will be closer to normal than this
recent week with highs in the upper 80s to low 90s in general.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 457 PM MDT Fri Aug 13 2021
Both terminals will see VFR conditions through the forecast
period with a mix of scattered mid/high clouds. Low chance for
VCTS near KMCK after 06z Saturday, but with uncertainty on
timing/placement will leave out for now. Winds for KGLD,
southeast around 10kts, with gusts to 20kts after 17z Saturday.
Winds for KMCK, meandering from east-southeast to southeast
around 10kts.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JN
SHORT TERM...JBH
LONG TERM...JRM
AVIATION...JN
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1002 PM EDT Fri Aug 13 2021
.UPDATE...
Issued at 1000 PM EDT FRI AUG 13 2021
SPC has removed the slight and marginal risk across eastern KY,
although there will still be some widely scattered showers and
storms through the rest of the evening. Made minor adjustments to
Pops, Sky, and T/Td. Updates sent to NDFD and web servers.
UPDATE Issued at 720 PM EDT FRI AUG 13 2021
Cold front is currently over central IN/OH and will slowly moving
south through the evening. Most of the strongest convection has
been in the surrounding CWA`s so far this evening where the
instability has been better. Despite the widely scattered coverage
thus far over eastern KY, didn`t mess with Pops too much overnight
as chances for showers/storms will continue overnight as the front
gets closer to the area. Still can`t discount an isolated stronger
storm, with wind gusts in excess of 40 mph. Updates have been sent
to NDFD and web servers.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 432 PM EDT FRI AUG 13 2021
Scattered showers & storms developed late this morning and through
the early afternoon across the northern fringes of the CWA and into
the higher terrain bordering the Virginias. A few isolated
showers/storms have continued to pop up across the heart of the CWA
as well. As a result, have bumped up Pops through the midday to
better reflect the trends and latest runs in guidance. An upper
level wave will continue to traverse through the broad trough
that runs across the Ohio River Valley and into Canada. This
feature will include a cold front, currently running through
Central Illinois and Northern Indiana and is expected to push
southeast across the CWA tonight and through Saturday. Guidance
has continued to struggle with convection across the region this
afternoon, but has shown some improvement in the more recent runs.
Shear remains minimal, so storms will likely stay more
multicellular/broken and unorganized. Soundings suggest a bed of
instability in the 2000-3000 J/kg range through early this
evening. This is best along our north and western counties and
into Central Kentucky. The GFS and NAM indicate a very moist
profile, while other higher-res guidance (namely, the NEST, HRRR
and the FV3) suggest a fairly shallow layer of mid-level dry air.
With sufficient low-level lapse rates (~7.5C/km), 500 J/kg of
DCAPE, and some mid-level dry air, strong to damaging winds will
be the main concern through this evening. Additionally, a moisture
rich airmass will increase PWATs into the 1.75-2.00+" range,
where localized flash flooding can`t be ruled out in training
storms. Activity will lesson with the onset of nightfall as
instability decreases, but a few chance showers/storms can`t be
ruled out as the front progresses south. Some redevelopment,
particularly along the higher terrain of the SE will be possible
tomorrow afternoon before things dry out overnight Saturday.
Showers and thunderstorms can be expected through this evening
before activity decreases to chance PoPs overnight. River valley fog
and possibly low stratus can be expected to develop with lows in
the mid and upper 60s. Highs will be around the norm Saturday with
the passage of the front, ranging in the low to mid 80s.
Similarly, lows into Sunday morning will be cooler, in the low to
mid 60s.
.LONG TERM...(Sunday through Friday)
Issued at 325 PM EDT FRI AUG 13 2021
The trends in the extended remain pretty much the same; Daily and
nightly chances of showers and storms, with the highest
precipitation probabilities during the afternoon and evening
hours, along with below normal daytime highs and normal to
slightly below normal nightly lows. The triggers for any rain we
receive around eastern Kentucky will be a surface front associated
with an upper level trough, and the remnants of tropical cyclone
Fred. Their is still some uncertainty as to exactly what the track
of Fred`s remnants will be, but the models continue to bring Fred
northward into the eastern Tennessee Valley Monday night and
Tuesday. This would do two things. First, Fred`s moisture would
flood into the region and would add additional instability and
lift to fuel shower and storm development. Fred`s northward
movement would also act to slow down a southward moving cold
front, and even push that boundary back northward and closer to
our forecast area. All that being said, we will repeated chances
for showers and storms through out the upcoming work week. Daily
highs should top out in the low to mid 80s on average, with a few
spots perhaps only reaching the upper 70s during the middle of the
week. The latest long range temperatures looked were a bit cooler
than the latest NBM numbers, but considering the clouds and
precip forecast we are putting out, the slightly warmer, but still
lower than normal, NBM min/max temps seemed a bit better than the
latest long range MOS, so the NBM was favored.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 725 PM EDT FRI AUG 13 2021
VFR to start the 00Z TAF period. Scattered showers/storms tonight
and overnight may result in brief flight restrictions. Patchy fog
is expected overnight but there is great uncertainty in coverage,
but areas that see rain tonight will have the greater chances for
seeing dense fog. Cold front crosses the area overnight into
Saturday morning, and ceilings may drop to MVFR along and just
ahead of the frontal passage. Ceilings improve by late Saturday
morning and all locations should return to VFR. Additional
afternoon/evening showers and storms may result in brief flight
restrictions. Winds will be light and variable this evening and
then northerly around 5 kts after the frontal passage on Saturday.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...CMF
SHORT TERM...BB
LONG TERM...AR
AVIATION...CMF
Area Forecast Discussion
National Weather Service Portland OR
251 PM PDT Fri Aug 13 2021
.SYNOPSIS...High pressure over the region will lead to a continuation
of the excessive heat and dry conditions through at least Saturday.
Temperatures will begin to cool slightly over the weekend before a
weak storm system brushes the region Monday bringing with it much
cooler temperatures early next week.
&&
.SHORT TERM...Tonight through Monday...Water vapor satellite imagery
this afternoon reveals a shortwave ridge over the Great Basin
extending northwestward into the Pacific Northwest. An upper level
low pressure can be seen spinning well of the California coast. This
has resulted in mid to upper level southeasterly flow spreading
across northwest Oregon today. An area of mid level instability and
lift allowed a few light showers and thunderstorms to fire across
southwest Oregon this morning. This area of unsettled weather has
now shifted northward into Lane County in the form of primarily just
debris clouds and possibly a few sprinkles. Expect this activity to
continue to weaken this evening as it shifts northward. Farther
south, some surface based instability will lead to a few additional
thunderstorms firing over Klamath County late this afternoon. There
is still a 15-20% chance of one of these storms impacting far
eastern Lane County this evening.
Similar to the past couple of KSLE soundings, the 12z KSLE sounding
measured an 850mb temperature of ~24C. With little change in the
airmass from yesterday was expecting temperatures to eclipse the
100F mark. However, there is enough smoke, particularly aloft, that
solar insolation has been reduced enough to hold temperatures down
considerably today. We are currently running 3-8F cooler across the
Willamette Valley than this time yesterday so high temperatures
today appear likely to top out in the mid to upper 90s instead of
the low 100s. Given low temperatures should remain unusually warm
tonight, and another hot day is expected tomorrow, will keep the
Excessive Heat Warning going for now even though we will now be in
more marginal conditions for the continuation of it.
Additional moisture and instability will likely ride up the Cascades
Saturday. However, it appears the west side of the Cascades will
largely remain capped based on model soundings. Even if an isolated
storm were to fire Saturday afternoon or evening, deep layer westerly
flow should result in any storm trying to form to the west of the
Cascade crest shifting east of the Cascade crest quickly.
As a shortwave trough approaches the region late in the weekend,
500mb heights and cooler air aloft will slowly filter into the region
Saturday night into Sunday. This should result in temperatures
lowering another several degrees for Sunday afternoon. It will still
remain hot, though, with high temperatures topping out in the low
90s.
Models are in good agreement the area will see relief from the heat
no later than Monday as a weak upper level trough moves across the
Pacific Northwest. This will result in a weakening front dropping
southeastward into southwest Washington and northwest Oregon Monday.
This could possibly bring some light rain to the south Washington
and far north Oregon coast some time late Sunday or Monday. NBM PoPs
have actually decreased during this time period over the past 24
hours and are now below mentionable thresholds. This appears to be
in response to the operational and ensemble data suggesting less and
less QPF. Nonetheless, nearly every member of the EC ensemble data
suggests light QPF will fall at KAST on Monday so opted to raise
PoPs into at least the slight chance category for Monday for the far
north Oregon and south Washington coast. Expect temperatures to drop
down well into the 80s in the Willamette Valley and Columbia River
Gorge on Monday.
Finally, smoke from wildfires across the Pacific Northwest is
impacting much of northwest Oregon and southwest Washington. The
thickest smoke continues to reside in the central Columbia River
Gorge around Hood River and across the Cascades stretching from Mt
Hood to Oakridge and Willamette Pass where unhealthy air quality
values are being observed this afternoon. Elsewhere, visibilities
are generally 6 miles or more and should remain at similar levels
into tonight. As onshore flow slowly increases over the weekend,
expect smoke to gradually shift out of the region. Smoke tends to
clear out a bit slower than modeled, but even the latest smoke model
guidance suggests significant improvement by either late Saturday or
Sunday. Either way, the weather pattern going into Monday will be
even more favorable to scoop out any remaining smoke lingering
across southwest Washington and northwest Oregon and push it well
east of the Cascades. /Neuman
&&
.LONG TERM...Monday night through Friday...A secondary shortwave
trough will slide down the backside of the upper level trough Tuesday
and keep temperatures near average for the date. Thereafter, models
and their ensemble members provide two scenarios for the second half
of the week. The first scenario which includes approximately 20-30%
of the available model guidance keeps a weak upper level trough over
or close enough to the Pacific Northwest that temperatures would
remain near to slightly above average for the remainder of the week.
The second scenario that approximately 70-80% of the model guidance
supports is that shortwave ridging will build more squarely over the
northeast Pacific before slowly shifting eastward towards the
Pacific Northwest. This would result in a more dramatic warm up and
result in another round of hot temperatures towards the end of next
week. NBM guidance suggests ~20-30% chance of 100F temperatures
returning to the region by next Friday or Saturday and around a 50%
chance of 95F. /Neuman
&&
.AVIATION...Shallow marine layer remains over the coastal waters,
with patchy IFR/LIFR along the coast. Stratus pulled back from
the coast in some areas this morning, but is already starting to
return as light to moderate westerly develops this afternoon.
Smoke from nearby fires covers the forecast area and is expected
to linger through Saturday, but based on the 18z run of the HRRR
smoke model conditions should mostly remain VFR at the surface.
Some 1-3 SM vsbys or lower possible within 5-10 SM downwind of
ongoing fires. Slant-range vsbys on approaches may be impacted
by the smoke, and some mountain obscurations are possible within
the smoke layer.
For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse
KPDX AND APPROACHES...VFR flight conditions expected to prevail
next 24 hours. Smoke layer is expected to remain over the region
through Saturday, but surface vsbys should remain 6 SM or better.
That said, slant-range vsbys may be impacted on approach due to
the smoke. Weagle
&&
.MARINE...Pressure gradients remain weak over the coastal waters
this afternoon, thus winds remain generally light. High pressure
is expected to strengthen enough offshore the OR/CA border to
turn winds more northwesterly along the Oregon coast Saturday
afternoon, adding a bit of breeziness south of Newport. This will
be short-lived as a weak front approaches from the northwest Sat
night/Sun morning, with weak southwesterly flow expected to
develop ahead of the front Sunday. Cold front will move across
the waters Sunday night/early Monday, bringing a quick
transition to northerly winds behind the front. Model guidance
continues to suggest a typical summertime northerly flow regime
will continue thereafter, most likely through the end of the
week. Thermally induced low pressure will reside over northwest
CA and far southwest OR during that time, bringing the breeziest
conditions to the central Oregon waters with conditions a bit
less breezy further to the north. Small craft advisory winds
gusting up to 25 kt will be possible over the central Oregon
waters Tuesday through Thursday each afternoon and evening.
Aside from winds, a west-northwesterly of 3 to 5 ft will prevail
through the weekend, before building back to 7 to 8 ft late
Monday into Tuesday. Weagle
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 10 PM PDT Saturday for Cascade
Foothills in Lane County-Cascades in Lane County-Central
Coast Range of Western Oregon-Central Columbia River Gorge-
Central Willamette Valley-Coast Range of Northwest Oregon-
Greater Portland Metro Area-Lower Columbia-Northern Oregon
Cascade Foothills-Northern Oregon Cascades-South
Willamette Valley-Upper Hood River Valley-Western Columbia
River Gorge.
Red Flag Warning until 10 PM PDT this evening for Mt. Hood
National Forest West of Cascade Crest-North Oregon Coast
Range.
Red Flag Warning until 10 PM PDT this evening for Central
Oregon Cascade Foothills-East Slopes of the Central Oregon
Coast Range-Willamette National Forest.
WA...Excessive Heat Warning until 10 PM PDT Saturday for Central
Columbia River Gorge-Greater Vancouver Area-I-5 Corridor
in Cowlitz County-South Washington Cascade Foothills-South
Washington Cascades-Western Columbia River Gorge.
Red Flag Warning until 10 PM PDT this evening for Eastern
Gifford Pinchot National Forest Mt Adams Ranger District-
Extreme South Washington Cascades and Foothills.
PZ...None.
&&
$$
Area Forecast Discussion
National Weather Service Reno NV
119 PM PDT Fri Aug 13 2021
.SYNOPSIS...
Hot afternoon temperatures prevail through early next week before
some cooling ensues. Isolated afternoon and evening thunderstorms
are expected in eastern CA and far western NV through the weekend
with a few lingering storms in Mono and Mineral counties Monday.
Wildfire smoke will continue to degrade air quality in many areas.
Increased afternoon breezes are forecast for Monday and Tuesday.
&&
.DISCUSSION...
An upper disturbance continues to move north across far northern
California and northwest Nevada. Last night into early this morning,
the disturbance and sufficient mid-level instability initiated
nocturnal thunderstorms across Churchill, Pershing, northern Washoe,
and far northeastern Lassen counties. As for smoke, denser smoke
from the Dixie Fire stuck mostly in northeast CA last night with
only a few hour block of worsening air quality for many spots into
western NV.
Turning to the future, the highlights through the middle of next
week are of course smoke but also isolated thunderstorms and hot
afternoons through Monday. One other item of note will be an uptick
in winds Monday and Tuesday as low pressure moves into the Pacific
Northwest. Let`s break it down into individual elements...
* SMOKE: Not just one broken record this summer but a whole store
of broken records. Anyway, idioms aside, as mentioned the
heavier smoke from the Dixie Fire remained in northeastern CA
last night with generally moderate air quality readings in
western NV. HRRR smoke runs from this morning indicate the
heaviest smoke spreading east to Doyle-Pyramid Lake-western
Churchill County before midnight before it sags south into Reno
and Sparks towards morning. Be prepared for a downturn in air
quality tonight and early Saturday; however, not all areas are
going to be equally degraded air quality-wise so check with
fire.airnow.gov for the latest readings in your area.
* THUNDERSTORMS: Isolated afternoon and early evening storms are
on tap today for eastern CA and far western NV. However, unlike
last night when there was forcing, storms should dissipate by
around sunset as daytime heating begins to dissipate.
Thunderstorms look to move VERY SLOWLY with little flow aloft
so localized moderate to heavy rainfall is likely. This is of
major concern for portions of the Tamarack Fire burn scar,
especially along and west of Highway 89 in Alpine County and
across far southern Douglas County near Highway 395. Those
areas could see increased risk of debris flows and flooding
from as little as 0.20" of intense rainfall.
Saturday, there is widespread simulation support for a
reduction in thunderstorm coverage as upper ridging becomes
stronger and brings subsidence to discourage deep convection.
Still, above normal heat is likely to bring some bubbling up
with a few showers or storms possible, mainly in the Sierra
south of Highway 50. On Sunday, chances spread back north into
northeast CA and far western NV with possible support from a
late day zephyr. Monday, drier and more stable air aloft is
expected for areas north of Highway 50 with a few residual
storms possible south of there before drier air invades by
Tuesday.
* TEMPERATURES: Remaining hot/above average through the weekend
with mid 90s to low 100s for lower valleys before next week`s
trough brings a cooldown closer to normal temperatures. This
brings good confidence that we will exceed the record number of
100+ for the Reno climate station (20, we are at 19 through
yesterday).
* WINDS: Generally on the lighter side through the weekend with
afternoon thunderstorm outflow being the dominate force for
gusty winds (perhaps up to ~45 mph). The impetus for winds
becomes more synoptic early next week as low pressure pushes
into the Pacific Northwest. This is expected to bring an uptick
in winds Monday afternoon/evening, peaking Tuesday afternoon and
evening before winds settle back down to typical breezes mid to
late next week. The winds will bring fire weather concerns...see
below for more information. -Snyder
&&
.AVIATION...
Smoke and haze remain widespread over the region due to active
wildfires. Slantwise visibility has been heavily reduced in addition
to terrain obscuration. Surface visibility is better today than the
past few days, but high resolution smoke models indicate smoke
potentially worsening overnight both tonight and again Saturday
night. Areas immediately downwind of wildfires will see IFR
conditions.
Thunderstorms will continue this afternoon into the evening, with
the greatest chances along the Sierra and eastern Sierra Front.
There is a 15-20% chance of a storm within 10 miles of western NV
terminals and 20-30% for Sierra terminals. Main threats from storms
will be erratic outflow wind gusts over 35 kts in addition to brief
heavy rain. Storms may also impact smoke, with improving conditions
in some areas and worsening conditions in others depending on outflow
speeds and direction.
High pressure settling over the region this weekend will limit
thunderstorm development. A few spotty storms remain possible,
mainly along the Sierra and CA/NV state line south of Tahoe. -Dawn
&&
.FIRE WEATHER...
Hot and unstable conditions will lead to a favorable environment for
plume dominated fires for the next few days. Increasing moisture may
boost pyrocumulus development for the Dixie Fire and open the door
for pyrocumulonimbus clouds.
Thunderstorms are most likely today and have already initiated along
the Sierra. There is a bit more moisture/instability today so expect
a better chance of wetting rains and possibly some spot flooding
if a slow moving storm passes over a burn scar. Dry strikes outside
of rain cores and gusty outflow winds over 40 mph are possible.
Thunderstorm potential for Saturday-Sunday may be squashed a bit
as high pressure is forecast to center itself over western NV.
Best confidence in weekend storms is along the Sierra and CA/NV
state line south of Tahoe with coverage rather spotty in nature.
Signs are pointing toward increasing winds Monday and/or Tuesday as
low pressure moves into the Pacific Northwest. For now the potential
for widespread critical fire conditions is low Tuesday with gusts
likely to be in the 25-35 mph range. There is starting to be signals
for stronger winds on Tuesday, but confidence is lower at this point
and will depend on whether or not a trough is able to overcome the
ridge and move into the area. Ensembles are hinting at a 40% chance
for winds to exceed 40 mph. Increasing winds next week could wake up
holdovers from this week`s lightning and the dry breezy conditions
may be critical for ongoing wildfires. -Dawn/Brong
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Shreveport LA
1010 PM CDT Fri Aug 13 2021
.UPDATE...
Raised pops mainly for I-30 overnight and then also spreading
better coverage across I-20 early in the daylight hours.
&&
.SHORT TERM.../Tonight through Saturday/
Warm night for most of us with a range of 80s most everywhere. 77
in El Dorado is our coolest as they had a shower. The warmest
around is the triple digit winner today at Texarkana with 87 at
10pm. Winds are very light on the surface and lower levels with no
desirable low level jet to feed on, just leftover instability
with still 3500 J/Kg along and south of I-30. We have likely pops
as radar is showing some improvement organization wise. The HRRR
takes aim at NW LA by daybreak, but falls apart on arrival. The
new NAM is encouraging and is similar to HRRR and does hold
together better in NW LA by 12Z. It also has better coverage
areawide and thus this update of increase extends into our
Saturday. /24/
&&
.PREV DISCUSSION... /issued 724 PM CDT Fri Aug 13 2021/
AVIATION...
For the ArkLaTex terminals, we have increasing chances for
convection with a weak cool front on approach that will become
stationary in our vicinity late tomorrow. VCTS attm is winding
down already, but some nocturnal chances remain possible with
activity on models during the overnight and through about
daybreak, then a break until heating resumes. Variable winds will
become N/NE5-10KT by this time tomorrow. We will be watching and
amending with tempos throughout this weekend. /24/
PREV DISCUSSION... /issued 219 PM CDT Fri Aug 13 2021/
SHORT TERM.../Tonight through Saturday Night/
The good news is, better chances for rain are in store for the
Four-States region over this short-term period. The bad news is,
showers and thunderstorms may interrupt some weekend plans. I
personally welcome the idea of some rain cooled air, but I
certainly hope no one`s weekend plans are affected. At the upper-
level, a small disturbance is moving out ahead of a frontal
boundary moving south through the plains. This disturbance will
begin to increase shower and thunderstorm chances by this
afternoon, a trend that will continue through the weekend. At this
time, this activity looks to vary from scattered in nature, to
rather organized as the front approaches. Frontal passage appears
to occur right at the hand off of the long and short-term desk,
which means the best chances for widespread precipitation will
occur towards the end of my period, and into the long-term.
Unfortunately, we likely won`t see any reprieve from the afternoon
high temperatures this short-term. On the other side of that coin,
afternoon dew points have not been getting as high as previously
anticipated. This means that the Heat Advisory that was previously
in place has been canceled, and plans for another one are not in
place at this time. Highs tomorrow will range in the low to
upper-90s, with overnight lows both tonight and tomorrow ranging
in the low to mid-70s. /44/
LONG TERM.../Sunday through Friday Night/
As we move into the second half of the weekend, sfc ridging will
continue to retrograde westward into deep southwest Texas due to a
broad upper trough located across the Central and Southern Plains,
moving into the Ohio and Tenn Valleys. This trough should be enough
to pick up Tropical Storm Fred which should be in the NE Gulf of
Mexico by Sunday Night and steer him well to our east. Upper forcing
due to the vicinity of the trough axis and plentiful low and mid
level moisture should result in another period of scattered
convection areawide on Sunday, diminishing to isolated to low end
chance pop coverage Sunday Night.
The trough axis remains virtually unchanged Monday into Tuesday of
next week per the 12z ECMWF which again will result in primarily
diurnally driven convection each day with the higher pop coverage
likely across our eastern half, especially on Monday. The trough
finally begins to fill and lifts out during the day Wed with upper
ridging beginning to build into our region from the southeast U.S.
which will likely result in an downward trend in pop coverage and an
uptick in temperatures by the end of the upcoming work week. /13/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 76 96 74 90 / 30 50 40 50
MLU 76 95 74 90 / 20 70 40 50
DEQ 72 92 72 87 / 50 40 40 50
TXK 74 93 74 88 / 40 40 40 50
ELD 72 92 71 87 / 30 50 40 50
TYR 75 94 74 89 / 20 50 30 50
GGG 74 94 74 89 / 30 50 30 50
LFK 75 96 74 91 / 10 50 20 50
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
24/44/13
Area Forecast Discussion
National Weather Service Las Vegas NV
745 PM PDT Fri Aug 13 2021
.SYNOPSIS...A strong area of high pressure over the Great Basin and
Mojave Desert will lead to above normal temperatures this weekend.
Disturbances moving along the southern periphery of the high will
interact with monsoon moisture leading to chances for thunderstorms
through Saturday. Another disturbance will lead to an upswing in
storms Tuesday and Wednesday of next week.
&&
.UPDATE...As of 730 pm, most of the active convection from earlier
today, focused across San Bernardino County, has diminished with the
loss of daytime heating. Meanwhile, attention shifts eastward with
approaching convection moving in from Coconino and Yavapai counties.
It`s somewhat unclear how convection will evolve through the
remainder of the night. Most CAM guidance and the most recent HRRR
runs suggest ongoing storms entering Mohave county will quickly
weaken with the loss of daylight. However, the SPC mesoanalysis page
suggests 500-1000 j/kg of CAPe remaining in place for a few more
hours, and the 00z VEF sounding also showed pretty substancial
instability in play. Given the observations, and keeping in mind
what occured last night, suspect convection will be slow to wane
until late in the evening.
I suspect the current activity will likely continue to propagate
west, driven by a strong cold pool and develop into at least the
eastern half of Mohave county before slowly decaying. Given the
instability shown in the VEF sounding this evening, can`t completely
rule out storms making a run for the river or even a little further
west. Will continue to monitor trends and get a quick evening update
out to the forecast grids to account for the latest trends.
-Outler-
.AVIATION...For McCarran...Southerly winds with gusts to around 15
knots are likely through early evening before diminishing. More of a
typical diurnal pattern is expected tomorrow with lesser storm
impact potential compared to today.
For the rest of southern Nevada, northwest Arizona and southeast
California...Best chances for terminal impacts look like KEED/KIFP
and this evening, though confidence is low. Another complex of
thunderstorms is expected out of western Arizona that could push
gusty outflow winds from the east towards the Colorado River Valley,
shifting winds to the east late tonight and resulting in gusts over
30 kts. Continued the PROB30 groups from the earlier issuance for
these terminals.
&&
.SHORT TERM...through Sunday.
Thunderstorms that have started developing over the Clark County
mountains will tend to move slowly to the west or northwest due to
the influence of the circulation that could be seen on satellite
loops moving overhead this afternoon. However, individual cells
should have difficulty sustaining themselves as they move off the
mountains. Recent mesoanalysis showed mixed layer convective
inhibition persisting over the lower elevations through the
afternoon around Clark County and Mohave counties. The The main area
to watch will be central and southern Mohave County late this
afternoon and evening as multiple runs of the HRRR indicate late day
thunderstorms over the rim country west of Flagstaff will move
toward the west and expand into a complex impacting areas from Peach
Springs down to Kingman and the Hualapai mountains. A potentially
large cold pool associated with the complex should be enough to
overcome the CIN and the storms will propagate fairly quickly to the
west limiting the potential for excessive rain over any specific
site. Strong winds up to 50 mph will be possible with these storms,
but DCAPE values generally less than 1000 J/kg do not indicate
extensive severe storm potential.
The overall synoptic setup remains fairly similar for Saturday
though the circulation overhead will have moved toward the SoCal
Coast. The easterly flow in the base of the high centered over
Nevada and surrounding states will continue to support westward
movement of storms developing over the Mogollon Rim in the afternoon
and early evening hours. The HRRR indicates a similar threat of
storm impacts for Mohave County late Saturday afternoon and evening.
High pressure strengthens and expands southward Sunday which will
produce a drier north to northeast flow across our region and should
suppress storm development somewhat. Temperatures will continue
rising under the influence of the high pressure and the Excessive
Heat Watch for Inyo and western San Bernardino counties has been
upgraded to an Excessive Heat Warning which for Sunday into Monday.
.LONG TERM...Monday through Friday.
A pattern transition begins Monday as a broad trough begins to push
down from the Pacific Northwest which will push the high over toward
the Four Corners and lead to a southerly flow across which will
likely bring a moisture influx into our region by Tuesday. The
moisture should remain over southern Nevada and surrounding areas
through Wednesday. Increasing shear associated with the trough may
combine with the deeper moisture to produce more organized
thunderstorms. So, Tuesday and Wednesday should be fairly active
convective days.
A drying trend is indicated Thursday and Friday as the trough
progresses over the Rockies. However, there is not a clear
indication that moisture will scour out and sufficient moisture may
remain for chances of thunderstorms over the mountains of southeast
Nevada and northwest Arizona.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT TERM/LONG TERM...Adair
AVIATION...TB3
For more forecast information...see us on our webpage:
https://weather.gov/lasvegas or follow us on Facebook and Twitter