Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/22/20
Area Forecast Discussion
National Weather Service Birmingham AL
712 PM CDT Fri Aug 21 2020
.UPDATE...
For 00Z Aviation.
&&
.SHORT TERM...
/Updated at 0145 PM CDT Fri Aug 21 2020/
Through This Evening.
No major changes were made to the short term forecast this morning.
On visible satellite imagery, the closed upper low can be seen
rotating over Central MS. We had numerous light showers and low
clouds over the northern/northwestern portions of Central AL this
morning which did slow surface heating in those areas, but forecast
temperatures are largely on track as the cloud deck has broken
apart. Highs will range from near 80 north to mid 80s south.
Additional scattered to numerous showers/storms will develop this
afternoon as the PBL continues to destabilize. There is more
instability across our south where these areas did not see as much
rain and cloud cover earlier today. Therefore, will maintain the
afternoon Marginal Risk for a couple severe storms capable of
isolated, strong downbursts as SBCAPE values reach 2000-2500 J/kg
while a slot of dry mid-level air surges northeastward per RAP
mesoanalysis. The threat will be highly conditional as the drier air
might suppress development in the first place, and latest CAMs seem
to be indicating this. As a result, I lowered PoPs in our
southeastern quadrant with highest PoPs focused in the better
moisture pool across our north and northwest. However, any storms
that develop among this drier, unstable air will have the potential
to produce strong, gusty winds.
Tonight Through Saturday.
With the proximity of the upper low to Central Alabama tonight,
scattered showers and thunderstorms will linger well into the
evening hours. If storms do develop over southwest Alabama, outflow
boundaries will keep higher rain chances west of I-65. By sunrise
Saturday whats left of the upper low center will likely be over
northeast Mississippi. The low circulation appears to evolve into an
trof by afternoon, and overall forcing is weak throughout the day.
Better rain chances will reside over the far northern counties of
Central Alabama, closer to trof axis.
86/58
.LONG TERM...
/Updated at 0218 PM CDT Fri Aug 21 2020/
Features.
Sunday and Monday.
The upper trough will begin to lift northeast into the Ohio River
Valley region on Sunday. Residual weak troughing, however, looks
to remain from the Ohio River Valley region southwest over the
Mississippi River Vally and into Deep South Texas. Mid-level
ridging over the Southwest Atlantic Basin will build a bit further
west into the region from the southeast.
Tuesday through Thursday.
The upper level ridging to the southeast will continue to build a
bit more west while the mid to upper level weakness to our west
slides further west, becoming positioned over the Central Plains
states.
Expect the upper level ridging to continue to expand over the
Southeast into Thursday while an upper low is progged to develop
over the Central Plains by Thursday.
Tropical Considerations.
Overall, we are nearing the peak of the hurricane season and now
is a good time to ensure that residents have their hazardous
weather plans ready and their safety kits stocked and ready. There
will likely be continued fluctuations in the forecast until the
systems become well-established and the environments in and around
the storms become better sampled. Please continue to check back
for forecast updates through the weekend along with the latest
products from the National Hurricane Center.
There remains considerable uncertainty with the forecast for
Tropical Depression Thirteen in the Western Caribbean Sea and
recently formed Tropical Storm Laura near the Leeward Islands.
Model solutions are and will continue to vary and deviate from run
to run, due to the current weak intensity/loose organization of
the systems and limited observational information currently
available at this time. The ultimate track and development of
these systems will largely depend on the size, strength and
location of the deep-layer ridging over the Southwest Atlantic
Basin along with the position and depth of the remnant
trough/weakness aloft to our west during this time period. The
track of the systems will affect their intensification potential
and the intensity of the system will have an influence on its
track as well.
We are nearing the climatological peak of the Atlantic Hurricane
Season. The Gulf and Caribbean Sea are considered favorable for
development with more than sufficient water temperatures and wind
shear values expected to be relatively low as the deep trough over
us is forecast to lift well to the northeast of the area.
Forecast.
Isolated to scattered showers and thunderstorms are forecast with
the better coverage across the east and southeast on Sunday and
Monday. Shower and storm chances will increase from the southeast,
becoming scattered to numerous across the southeast counties on
Monday with the rest of the forecast area experiencing isolated to
scattered showers and storms. Scattered to numerous showers and
storms are expected Tuesday into Wednesday with the better chances
across the south and central counties. This trend looks to
continue into Thursday.
Expect High temperatures to range from the low to mid 80s to the
low 90s through the period with the lower temperatures expected
Wednesday and Thursday, coinciding with the higher rain and storm
chances. Overnight lows will range from the mid 60s north to the
low 70s south Sunday and Monday, followed by readings around 70
north to the low and mid 70s south Tuesday through Thursday.
05
&&
.AVIATION...
00Z TAF Discussion.
Some parts of Central Alabama will experienced thunderstorms the
next several days. The summer pattern will remain active. For
this terminal forecast period, convection continues and at this
writing was affecting areas near EET/TOI. There certainly remains
a chance that any terminal may experience a brief thunderstorm.
Reduced visibility, lightning , and wind gusts of 25kts would be
possible. Handled the forecast with VCTS and if trends hold up,
may introduce prevailing. Otherwise, the convection will slowly
lose some intensity and coverage this evening. Not anticipating
any restrictions overnight. We repeat the thunder chances again on
Saturday. Winds may temporarily have a south to southwest
component but overall light and variable.
75
&&
.FIRE WEATHER...
Scattered to numerous showers and thunderstorms are expected this
afternoon and evening with the better chances north and west.
Expect a similar trend tomorrow with the better chances across the
north tomorrow. Rain and storm chances will become maximized
across the south and southeast counties on Sunday and this trend
will persist through midweek next week as the airmass becomes more
tropical across the area. Minimum afternoon relative humidity
values will drop into the low to mid 50 percent range today and
tomorrow followed by minimums in the mid to upper 50 percent range
Sunday and into early next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 65 85 66 88 68 / 40 60 30 40 20
Anniston 66 86 67 88 70 / 40 60 30 40 20
Birmingham 67 85 69 88 71 / 40 50 20 30 20
Tuscaloosa 68 88 69 89 71 / 40 50 20 30 20
Calera 66 85 67 87 69 / 40 40 30 40 20
Auburn 67 86 68 84 70 / 40 50 30 60 20
Montgomery 68 89 70 88 71 / 40 40 30 60 20
Troy 68 88 69 86 71 / 40 40 30 60 20
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
758 PM MDT Fri Aug 21 2020
.UPDATE...
Issued at 758 PM MDT Fri Aug 21 2020
Smoke will persist through tonight, Saturday, and likely well
beyond. Latest HRRR smoke fields indicate smoke should get thicker
later tonight and Saturday morning. Yuck. Other than the smoke,
quiet weather conditions will prevail tonight. No changes to the
forecast are planned.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 350 PM MDT Fri Aug 21 2020
Satellite pictures are showing about 10% convective cloudiness
over the CWA at this time. The clouds are over the mountains,
foothills, Palmer ridge and Cheyenne ridge. The satellite pictures
are also showing a decent hot spot and smoke plume coming from
and off the Cameron Peak Fire in west central Larimer County.
Upstream, much of the western U.S. is covered by significant
smoke mainly from the vast California forest Fires. There is a
fairly uniform north-northeasterly wind field in place over the
plains of the CWA right now along with dew point readings in the
40s to lower 50s F. Models show the upper ridge center to push
northeastward overnight with its location right over the four
corners on Saturday. There is weak subsidence noted on the QG
Omega fields overnight and Saturday. The low level winds should be
weak drainage patterns tonight with north-northeasterlies on
Saturday. Moisture-wise, it stays pretty dry overnight and
Saturday with the precipitable water values ranging from 0.25
over the western CWA to 0.80 over the far eastern CWA both
periods. CAPE is pretty limited this evening with some over the
far east and a tad over the southern half of the high country.
There is even less CAPE progged on Saturday with just a tad over
the eastern border areas. The QPF fields show no measurable
rainfall over the CWA tonight or Saturday. Will leave any pops out
for now. The ESRL HRRR does have smoke over the CWA overnight and
into Saturday. Satellite pictures concur. Will make sure the GFE
grids have smoke in them for sure. For temperatures, DIA is one
degree F cooler then at this same time yesterday. The ubiquitous
smoke through much of the column may be taking some degrees off
the temperatures. For Saturday, guidance values show readings to
be 1-2 C warmer than today`s. Tomorrow looks pretty smokey so
will adjust accordingly.
.LONG TERM...(Saturday night through Friday)
Issued at 350 PM MDT Fri Aug 21 2020
A hot ridge will remain over Colorado through the coming week.
Only slight model trends today toward holding the strength of the
ridge a little bit longer, with a shortwave Wed/Thu now up in
southern Canada. There`s still a little erosion of the ridge
starting with that shortwave passing and a surge of less hot and
dry air down the east slopes behind it.
There is a little...emphasis on little...moisture coming up around
the backside of the ridge over Utah. This seepage should continue
along with the daily mixing to gradually moisten up the ridge as
the week goes on. This will mean more afternoon clouds over the
mountains Saturday and maybe an isolated shower/weak storm over
the central mountains. Sunday will see a little more, but still
isolated and mainly dry thunderstorm coverage over the mountains
and maybe some clouds coming onto the plains mid to late
afternoon.
For Monday through Wednesday, it just looks like a continued
gradual increase in weak thunderstorm activity. By Wednesday we`ll
have the climatological scattered afternoon storms over the
mountains. With the air aloft not cooling at all, it will still be
hard to maintain convection on the plains but low chances are in
order mainly for storms slowly drifting off the mountains late in
the day.
The air dropping down the plains behind the shortwave for Thursday
and Friday should provide increased thunderstorm activity from the
Front Range eastward and a more favorable environment for storms
to survive on the plains. We`ll still be fighting that warm air
aloft though. Temperatures should cool, possibly even down into
the 80s though the trend of a weaker shortwave might mean less
cooling.
It should be emphasized that while we`re showing higher rain
chances later this week, for the most part we`re expecting weak
storms that won`t produce much rain. There may be some dry
lightning over the mountains, but coverage will be limited this
weekend and by midweek the storms will be a bit wetter. There
could be a bad transition day on Monday or Tuesday.
Finally, the smoke from the California fires should still be bad
across most of the area Saturday night, and perhaps quite a bit
longer. The building ridge might shift the brunt of it mainly into
Wyoming by Sunday or Monday. We`ll still have our local smoke
plumes which should have more of a west to east component, so we
won`t clear out, but hopefully there will be some improvement.
This west to east flow from both the California and local fires
will keep quite a bit of smoke around through the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 758 PM MDT Fri Aug 21 2020
Smoky skies are expected to persist through tonight and Saturday.
Visibility should remain restricted and may worsen late tonight and
Saturday morning as the HRRR shows. Otherwise, just a few clouds and
light winds are expected through Saturday.
&&
.FIRE WEATHER...
Issued at 350 PM MDT Fri Aug 21 2020
The fire danger will be somewhat elevated on Saturday with the
above normal temperatures and low relative humidities. However
winds are expected to be weak on Saturday.
There will be a very gradual increase in moisture through the
week. For Sunday and Monday, isolated storms are expected over the
mountains. By midweek, scattered mountain storms are expected,
with a chance of storms on the plains. Initially there will be a
dry lightning threat. Coverage should be very limited on Sunday,
but there could be more dry lightning on Monday and Tuesday. After
that the storms will mostly be rain producing. A cold front about
Thursday will bring more moisture from the Front Range eastward
with some cooling.
Strong winds are not expected during the period, though there
could be a little increase in ridgetop winds and afternoon upslope
breezes as a weak westerly flow aloft develops. A further increase
in the westerly flow aloft is likely next weekend, and while this
could result in some increase in surface winds, they do not look
particularly strong at this time.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Meier
SHORT TERM.......RJK
LONG TERM........Gimmestad
AVIATION...Meier
FIRE WEATHER.....RJK/Gimmestad
Area Forecast Discussion
National Weather Service Cheyenne WY
810 PM MDT Fri Aug 21 2020
.UPDATE...
Issued at 809 PM MDT Fri Aug 21 2020
Winds have eased and evening humidity is slowly recovering with
sunset. Allowed the Red Flag Warning to expire on time at 8 PM as
critical fire weather conditions are no longer expected overnight.
Updates have been sent.
UPDATE Issued at 400 PM MDT Fri Aug 21 2020
Hitting RFW criteria across Carbon County and western Albany
County this afternoon. Looks like winds will continue through
sunset today. Decided to issue a short fused RFW for FWZs 303
through 308 today. Updates sent.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 225 PM MDT Fri Aug 21 2020
GOES-16 GeoColor RGB highlights the large area across the western
CONUS engulfed by wildfire smoke from California advecting along
the north side of the upper level ridge. Plenty of smoke still
looks to be ejecting from their source regions so far this
afternoon and staying south of a stationary boundary analyzed from
eastern MT through central ID. So far, numerous ASOS sites across
the CWA have reported marginal reductions in visibility due to
the smoke. Most notably, Laramie and Rawlins are currently sitting
at 5 SM.
Height increases continue across the region today and Saturday as
warmer temperatures and drier weather settles in. An outside
chance for showers are possible across the Nebraska Panhandle and
extreme southeastern Wyoming associated with increased
convergence from a lee side trough. Best chance for any
precipitation or thunder will be between 3-6 PM MDT today and any
storms that do develop will be short-lived with limited
instability and weak shear. With little to no precipitation
expected, the main impact heading into the weekend will be
widespread smoke across the region. Recent HRRR Smoke forecasts
indicate that higher near-surface smoke concentrations will
continue to spread southeastward across the CWA through Saturday
morning. With the continued west-southwesterly mid-level flow the
next few days, expect smoke/haze to continue to fill the skies
through the weekend. Went on the cooler side of models for
Saturday and Sunday afternoon due to the potential hazy skies, but
forecast temperatures remain well above normal in the mid-90s
across the NE Panhandle and Wyoming High Plains.
.LONG TERM...(Sunday Night - Thursday)
Issued at 322 AM MDT Fri Aug 21 2020
No changes to the previous long term/extended forecast with all
models still showing a transition from hot and dry to a more
unsettled and rainy pattern by mid to late next week. The stubborn
upper level high will remain near the Wyoming/Colorado/Utah border
through Monday afternoon. The additional midlevel subsidence
associated with the upper level high will result in little or no
thunderstorm coverage through Monday afternoon. However, can`t rule
out a few thunder showers near/in the mountains due to upslope
convergence along the Laramie Range. Kept low POP, but did mention
of thunder along and west of I-25. Hot temperatures will continue
Sunday and Monday with highs around 90 (west), and mid to upper 90s
to around 100 degrees further east. Record highs are likely across
portions of the area both days.
Subtropical moisture and an increase in thunderstorm activity is
still expected beginning Tuesday and continuing through middle of
next week. Models show Pacific energy finally coming onshore late
Monday and Tuesday, which will flatten the upper level ridge axis
and nudge the stubborn strong high further south into the southern
Colorado/New Mexico/western Texas area. This will allow low to
midlevel moisture advection around the western fringe of the upper
level high. Kept the trend of increasing chances of thunderstorms
(30 to 50 percent) each day through Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 532 PM MDT Fri Aug 21 2020
VFR. Areas of haze with visibility of 6 miles. Wind gusts to
24 knots at Wyoming terminals until 04Z, then gusts to 20 knots
at Rawlins after 15Z Saturday.
&&
.FIRE WEATHER...
Issued at 225 PM MDT Fri Aug 21 2020
Elevated fire weather conditions currently ongoing across Carbon
and Albany Counties with humidities and wind gusts hovering just
below critical levels. Warm and dry conditions continue into the
weekend. Relative humidities will drop down near critical levels,
especially west of the Laramie Range. However, as the upper level
ridge continues to build overhead winds will remain relatively
light with gusts only around 15 MPH Saturday and Sunday afternoon.
Additionally, smoke from wildfires across Colorado and California
will continue to advect across the region the next several days.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...GCC
SHORT TERM...MB
LONG TERM...TJT
AVIATION...RUBIN
FIRE WEATHER...MB
Area Forecast Discussion
National Weather Service El Paso TX/Santa Teresa NM
534 PM MDT Fri Aug 21 2020
.AVIATION...00Z TAF CYCLE
TSRA confined mainly to area mtns this afternoon, will drift
south through the evening with VCTS continuing across KDMN, KTCS.
Gusty outflow winds the main concern, with a TEMPO33020G35KT at
KDMN. Will be a chance for VCSH/VCTS at KLRU/KELP this
evening/early overnight, but current satellite imagery suggests
this threat will be small. Another round of TSRA Saturday in the
mountains with isolated TSRA/SHRA/gusty outflow spilling into the
lowlands by evening, mainly west of the Rio Grande.
&&
.PREV DISCUSSION...315 PM MDT Fri Aug 21 2020...
.SYNOPSIS...
After another hot day on Saturday, temperatures will cool down a
few degrees, but still remain above average. Scattered mountain
and isolated lowland thunderstorms will remain possible through
Sunday, but a drying trend will commence on Monday. By Tuesday,
rain chances will mainly be confined to the Gila Mountains.
&&
.DISCUSSION...
.SHORT TERM...This afternoon through Saturday...
The subtropical ridge remained centered over northern Arizona this
afternoon, with north to northeasterly flow aloft remaining in place
across New Mexico. Moisture remains limited. A special 18Z RAOB
(intended for testing equipment after the failed 12Z launch)
revealed PW of just 0.88 inches... and very strong CIN due to warm
air around 700 mb.
Low level moisture is lacking as well, especially across the Mesilla
Valley, where dewpoints have mixed out into the upper-30s. 50s
dewpoints are hanging on in Hidalgo County, leftover from outflow
from a strong MCS over Arizona last night. A strong Gulf Surge
continues to feed moisture into Arizona from the Gulf of California,
with light westerly winds pulling some of this moisture into SW New
Mexico. As such, this remains the most favored area for late
afternoon and evening thunderstorms, as convection over the higher
elevations of the Gila Region drops to the south and southwest. CAMS
runs have been flaky, with many of the 12Z HREF members and recent
HRRR runs backing off on lowland thunderstorms. 12Z GFS suggests
that while 700 mb temps are slightly cooler over SW New Mexico, CIN
nevertheless remains fairly strong. Still decided to keep slightly
higher PoPs in the Bootheel than most other lowland areas through
tonight. CAMS also suggest that after dark, some isolated showers
and perhaps a thunderstorm could develop in the lower Mesilla Valley
(including around ELP) as outflow convergence occurs. Given the
overall poor moisture and strong CIN, this doesn`t seem to deserve
much more than a 10-PoP.
&&
25
.LONG TERM...
The UL high over the Four Corners will not move much for the next
several days. Through Sunday, some recycled low-caliber monsoonal
moisture will continue to rotate around the high from the north,
keeping PWAT values near or just below 1.00". This will keep rain
chances in the picture with scattered afternoon thunderstorms in
the mountains and isolated storms in the evening. With northerly
flow in place, a few weak disturbances could give us some
enhancement to our convection, but given the sub-par moisture, it
wouldn`t be much. Temperatures will at least trend downwards, but
remain well above average.
On Monday, flow aloft becomes more oriented east-to-west, which
will pull in some dry, continental air into the CWA. Enough
moisture may hold on for Monday to keep rain chances alive,
especially west of the divide, but rain chances drop off by
Tuesday as too much dry air enters the forecast area. We may also
see some subsidence related to now TD 14 (expected to become
Marco) as it moves up the I-35 corridor in TX (keeping east of
our CWA), further reducing our storm chances. From Tuesday
onwards, storm chances will be mainly across the Gila where better
moisture will remain. Everyone else will likely stay dry though
an isolated storm cannot be ruled out over the Sacs during this
time either.
Forecast guidance begins to diverge beyond Wednesday into the
weekend. The ECMWF moves the high directly over NM and keeps
conditions very dry and very hot. The GFS depicts a much weaker
high and even forces a weak inverted trough into our area.
Moisture remains scant even in this scenario, but higher than its
European counterpart as some of now TS Laura`s moisture gets
pulled southwest into the Borderland. Either way, the GFS depicts
0 QPF, but its temperatures are not as hot as the Euro. The 6z run
of the GFS too has a weaker high, but instead of letting some of
Laura`s moisture get pulled southwest into our forecast area, it
forces the inverted trough into the heart of TX as a weak closed
low, reinforcing the dry air and subsidence across NM. Given the
uncertainties and no real signal to increase precip chances
otherwise, I kept the low to nil POPs from the NBM as we head
into the weekend with most lowland locations staying dry.
&&
&&
25
.FIRE WEATHER...
High temperatures will remain around 10 degrees above normal through
the weekend, dropping just a few degrees for much of next week.
Thunderstorms will mainly be focused on the higher terrain, with
below normal coverage, and secondary focus on the lowlands in
southwestern New Mexico. Overall thunderstorm chances will be even
lower next week. Afternoon minimum RH values will generally be in
the 25 to 35 percent range in the higher terrain, and dropping into
the 10s across the lowlands.
&&
25
&&
.PRELIMINARY POINT TEMPS/POPS...
El Paso 75 103 75 101 / 20 0 20 0
Sierra Blanca 70 95 68 95 / 20 20 0 0
Las Cruces 70 101 70 99 / 20 0 20 0
Alamogordo 69 102 71 101 / 10 10 10 10
Cloudcroft 54 78 52 77 / 20 30 20 40
Truth or Consequences 71 100 71 99 / 10 10 20 20
Silver City 64 94 66 93 / 30 40 30 30
Deming 70 102 70 101 / 20 10 30 0
Lordsburg 70 98 70 99 / 30 30 30 10
West El Paso Metro 75 104 77 103 / 20 0 20 0
Dell City 70 102 70 101 / 20 0 10 0
Fort Hancock 74 102 73 102 / 20 10 10 0
Loma Linda 70 95 71 95 / 20 10 10 0
Fabens 75 102 75 101 / 20 0 10 0
Santa Teresa 73 102 73 101 / 20 0 20 0
White Sands HQ 71 101 73 101 / 20 0 20 0
Jornada Range 69 100 71 99 / 20 0 20 0
Hatch 70 101 71 101 / 10 0 20 0
Columbus 73 103 73 101 / 20 10 30 0
Orogrande 71 101 71 101 / 20 0 10 0
Mayhill 59 87 59 87 / 20 20 10 40
Mescalero 58 89 57 87 / 20 30 20 40
Timberon 58 86 57 85 / 20 20 10 30
Winston 59 93 58 92 / 20 30 20 40
Hillsboro 66 100 66 98 / 20 20 20 20
Spaceport 69 100 69 99 / 10 0 20 10
Lake Roberts 58 94 58 93 / 20 40 30 40
Hurley 65 96 65 96 / 40 30 30 20
Cliff 65 99 64 98 / 40 40 30 30
Mule Creek 65 95 66 95 / 40 40 30 40
Faywood 66 97 67 96 / 30 30 30 20
Animas 69 99 68 101 / 30 30 40 0
Hachita 68 98 67 100 / 20 20 40 0
Antelope Wells 68 97 67 98 / 30 30 50 0
Cloverdale 65 92 66 93 / 30 30 40 10
&&
.EPZ WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...Heat Advisory until 9 PM MDT this evening for TXZ418-419-423-424.
&&
$$
99/99/99
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
658 PM CDT Fri Aug 21 2020
.SHORT TERM...(This evening through Saturday)
Issued at 252 PM CDT Fri Aug 21 2020
Still a rather quiet forecast, but with a few interesting changes
to note (mainly regarding tonight). There has been a bit of back
and forth regarding the possibility of precip tonight. A couple
days ago models started picking up on a possible short wave with
an associated weak sfc boundary. This feature was generating some
QPF signals for portions of the area for this evening/tonight.
Even last night several of the hi-res models still showed this as
a possibility, but this morning`s 12Z runs have changed course and
gone completely dry for this evening/tonight. While this could
very well end up being the case...there are a few additional
considerations that make me hesitate. For starters there is the
recent history of nightly convection...5 out of the last 7 nights
actually. There is also the fact that we are not expecting much of
a pattern change aloft. However, even with that all being said, I
ultimately decided to err on the drier side for tonight (though
not 100% dry). Tomorrow looks to be more of the same (as tends to
be the case with very little pattern change). Highs will be above
average in the lower to mid 90s.
.LONG TERM...(Saturday night through Friday)
Issued at 252 PM CDT Fri Aug 21 2020
No significant changes have been made to the long term as there
is relatively very little pattern change aloft. This means we will
continue to remain in north and northwesterly flow aloft (till
about Mon) and the primary concern is the potential for ridge
runners. After Monday models are indicating that the eastern trof
becomes significantly less amplified. This will lead to the ridge
spreading out broadly over the majority of the CONUS, and rather
zonal flow over the northern CONUS. This would also subsequently
push the jet stream further north and effectively cut us off from
the main flow...effectively leading to rather static conditions
for several days. This week highs are expected to be above average
for late August, in the 90s, and dry.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 650 PM CDT Fri Aug 21 2020
Significant wx: None.
Tonight: VFR. Will see a temp incr in high clds this eve,
otherwise should be mostly clr. Smoke from fires across W CONUS
has noticeably increased this aftn and will continue into
overnight. Don`t have vsby restrictions attm as it is pretty high
based. Winds will be SSE-S less than 10kt. Confidence: High.
Saturday: VFR. Will probably see even more smoke Sat per HRRR
smoke model. Will have to watch vsby trends to the W, but don`t
think it`ll be thick/low enough to include in TAFs attm. Just
know vsby may not be perfect/10sm. Actual cld cover looks pretty
limited until perhaps mid to late aftn when a few tstms may
dev. Confidence on coverage/timing to low to include this far
out. Winds will be SE- SW at less than 10kt. Confidence: Medium
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT TERM...Shawkey
LONG TERM...Shawkey
AVIATION...Thies
Area Forecast Discussion
National Weather Service Elko NV
225 PM PDT Fri Aug 21 2020
.SYNOPSIS...Areas of smoke and haze continue to affect most of
northern and central NV today, and likely linger through the
weekend as large fires continue to burn in California.
Thunderstorms return to some areas on Sunday, and likely spread to
most of northern and central NV Monday and Tuesday. Temperatures
start to cool down after the weekend, but theyll remain
above average.
&&
SHORT TERM...Today through Sunday. Dry and mostly storm-free
conditions are expected across all zones through Saturday with
the exception of a stray isolated high-based dry thunderstorm
over White Pine county late tomorrow afternoon. Model guidance is
consistent with the idea that as more moisture streams north into
central and northeastern Nevada with a predominate southerly upper
flow, the risk for isolated thunderstorms will become an
increasing concern by Sunday and continue into next week.
Isolated dry thunderstorms should dominate the northern forecast
zones as a mix of wet/dry storms prevail over White Pine and
northern Nye counties.
Dense layers of smoke advecting into northern Nevada from the
large fires burning in California will likely lead to reduced
visibilities at times through tomorrow along with reduced air
quality over the region. HRRR model guidance shows a general
pooling of dense smoke layers over northern Nevada through at
least Saturday morning.
Heat risk factors could still be a concern going into Sunday as
daytime highs remain well above normal touching the high 90s over
some locations. Near record setting high temperatures are
forecasted for the Elko area on Sunday.
.LONG TERM...Sunday night through Friday.
Model agreement is consistent on the upper level ridge shifting
to settled over the Four Corners region producing southerly flow.
However, the handling of the remnants of Tropical Storm Genevieve
and the short waves associated with it are a little less
consistent. GFS has a stronger eastward push of the remnants than
the ECMWF. Instability is still expected throughout the beginning
of the period, with possible dry thunderstorms moving to include
showers as moisture builds over the week. Monday and Tuesday have
the best potential for showers and thunderstorms across the
region, while Tuesday afternoon also presents concerns for fire
weather conditions in south-central Nevada. However, confidence
remains low for fire weather and accumulation amounts for
locations are still uncertain. Temperatures continue to stay above
average, but should cool down a bit into the upper 80s and 90s as
the week progresses.
&&
AVIATION...Smoke from California and western Nevada fires will
continue to blanket most of the state. KWMC and KBAM will likely
be the most impacted with visibilities dropping as low as 1 SM
during the period.
&&
FIRE WEATHER...Drier and more stable air will continue across the
region through Saturday with a slight risk of isolated dry
thunderstorm activity over White Pine county. A moderately moist
monsoonal airmass will spread north into central NV through
Saturday evening and continue to influence thunderstorm
development into early next week. The expected combination of weak
instability over portions of central and possibly northern NV by
Sunday afternoon will result in a mix of isolated wet and dry
thunderstorms. Any storms that do develop on Sunday will likely
lean toward the dry side over the northern fire zones. As the
northward push of monsoonal moistens central and northern NV
through Monday, a transition to mostly wet thunderstorm should
occur.
&&
CLIMATE...Well above normal temperatures persist through the
weekend, with high temperatures running 10 to 15 degrees above
normal. Slightly cooler early next week with high temperatures
generally 7 to 10 degrees above normal.
&&
.LKN WATCHES/WARNINGS/ADVISORIES...
Dense Smoke Advisory until 9 AM PDT Saturday for Humboldt County-
Northeastern Nye County-Northern Elko County-Northern Lander
County and Northern Eureka County-Northwestern Nye County-Ruby
Mountains and East Humboldt Range-South Central Elko County-
Southeastern Elko County-Southern Lander County and Southern
Eureka County-Southwest Elko County-White Pine County.
&&
$$
97/94/86/97
Area Forecast Discussion
National Weather Service Lubbock TX
911 PM CDT Fri Aug 21 2020
.UPDATE...
Have updated forecast to reflect a decrease in precipitaion
chances area wide. The southeastern Rolling Plains may still see
a few isolated weak thunderstorms, but in general drier
continental air has begun to enter the area limiting storm
coverage.
&&
.PREV DISCUSSION... /issued 609 PM CDT Fri Aug 21 2020/
AVIATION...
VFR will likely continue for all TAF sites for the next 24 hours.
Isolated to scattered thunderstorms will be possible this evening
and overnight but coverage and timing is too low to mention in
the TAF.
PREV DISCUSSION... /issued 200 PM CDT Fri Aug 21 2020/
SHORT TERM...
Small PoP chances will manifest themselves this evening and
overnight into early Saturday morning. An upper ridge will remain
anchored over Arizona tonight with the center of the ridge shifting
to the 4-corners on Saturday.
For today, a weak surface trough was oriented from the northwestern
Texas Panhandle into southeastern New Mexico which is where isolated
to scattered convection is expected to develop. A minor speed max at
250mb will punch down into the area this evening from the north.
Although this looks to exclusively boost the large scale lift in the
Rolling Plains which will be under the left exit region of this jet.
Additionally, a short wave was seen on water vapor imagery moving
south across the Texas Panhandle this afternoon. The RAP model was
even showing a small amount of positive PVU advection with this
short wave confirming its existence. Higher levels of low-level
theta-e exist within the surface trough and will result in increased
instability. A notable drop off in instability will occur outside of
the surface trough axis with the smallest values across the Rolling
Plains. Any storms that do make it into the FA this evening and
overnight do not have a high chance of producing severe wind gusts.
Precipitation chances will be lower on Saturday with a drier layer
of air moving overhead at the mid levels of the atmosphere.
LONG TERM...
Currently, the upper-level ridge remains to the west over the
southwestern CONUS, and a trough is currently over the southeastern
CONUS. In the long-term, models seem to be split on how they want to
handle the trough to the east and tropical cyclone #14 located
southeast of the Yucatan peninsula. A majority of the models want to
stretch the trough to the southwest, creating a closed low near
southeastern Texas. The upper high will build to the northeast into
Canada. This amplification in the upper-level ridge will shift the
flow aloft more northeasterly by late Saturday, advecting drier air
into the mid-levels. The low will most likely open, becoming an
inverted trough, and move to the southwest early in the week. By mid
to late Tuesday, tropical cyclone #14 will make landfall, most
likely on the east coast of Texas. Models are currently weakening
the tropical cyclone as it makes landfall and advecting the latent
heat and vorticity into the inverted trough over south Texas. The
PVA and addition of the latent heat will amplify the inverted trough
which may cause it to close off again. The closed low will move
north towards the Texas Panhandle Wednesday, shifting the winds
aloft more easterly and then back to the north-northeast as it
slides east of the area. We should remain on the subsidence side of
the low, keeping precipitation chances to the east. By the end of
next week, the low near the area will move off to the northeast, and
a trough over British Columbia will dig to the south. This will
shift the high over the western CONUS east towards the forecast
area, shifting the winds more northerly aloft. With the upper high
remaining near the area, expect mostly dry conditions and above
normal temperatures next week.
Kendrick
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
28/28
Area Forecast Discussion
National Weather Service Midland/Odessa TX
637 PM CDT Fri Aug 21 2020
.DISCUSSION...
See 00z aviation discussion below.
&&
.AVIATION...
VFR conditions are expected for the next 24 hours. Winds will
generally be out of the southeast to east but may become northerly
tonight with a chance of SHRA.
&&
.PREV DISCUSSION... /issued 245 PM CDT Fri Aug 21 2020/
DISCUSSION...
Persistence rules. WV imagery shows the upper ridge has not moved
much over the past 24 hours, and is still centered over ern AZ,
maintaining meridional flow over West Texas and Southeast New
Mexico. Of immediate concern is a shortwave over south central KS
that will move down the ern periphery of the ridge this afternoon
and tonight. For the past few days, models have brought this
feature thru the ern zones, especially the SREF yesterday, and the
GFS today. However, the 12Z GFS appears to have the shortwave too
far west than what WV imagery shows The HRRR solution looks more
representative, in which case convection from this disturbance will
stay east of the CWA altogether. That said, models do hint at
developing convection in NE NM this afternoon, as they have the past
couple of days, and bringing it south into SE NM. In addition, once
the cap erodes, the Davis Mtns look to develop convection, as well.
The ridge is still forecast to move up to the Four Corners by 00Z
Sun, where it will remain the rest of the weekend. Models advertise
plenty of perturbations moving south into the area Sat/Sun, for
general isolated convective activity, mainly over SE NM and areas
east.
Next week, the ridge is forecast to link up w/its counterpart over
the SE CONUS, but the two tropical systems set to invade the Gulf
coast states look to keep this from happening, and keep the ridge
roughly over the Four Corners area. Much will depend on the
evolution of two tropical systems, but for now, grids look pretty
dry after Sunday.
Regarding temperatures, temps still look to drop below triple digits
for most areas after today, and bottom out in the mid 90s for most
of West Texas and Southeast New Mexico Mon afternoon. However,
w/the two tropical systems keeping the ridge over the Four Corners,
thicknesses begin increasing Tue thru the extended, and temps most
locations could very well be back in the triple digits by next
weekend. For now, most areas should stay at or below the century
mark.
&&
.PRELIMINARY POINT TEMPS/POPS...
Big Spring 72 98 71 98 / 10 10 10 10
Carlsbad 71 99 71 100 / 20 0 10 10
Dryden 74 100 71 98 / 10 10 0 10
Fort Stockton 72 99 71 97 / 10 0 0 10
Guadalupe Pass 68 92 69 91 / 30 10 0 20
Hobbs 69 97 69 96 / 20 0 10 20
Marfa 64 94 61 92 / 30 20 10 10
Midland Intl Airport 72 99 71 98 / 10 10 10 10
Odessa 73 99 71 99 / 10 0 10 10
Wink 74 102 72 101 / 20 0 10 10
&&
.MAF WATCHES/WARNINGS/ADVISORIES...
NM...Heat Advisory until 8 PM MDT this evening for Guadalupe
Mountains of Eddy County.
TX...Heat Advisory until 9 PM CDT /8 PM MDT/ this evening for Central
Brewster County-Chinati Mountains-Chisos Basin-Davis
Mountains-Davis Mountains Foothills-Guadalupe and Delaware
Mountains-Lower Brewster County-Marfa Plateau.
&&
$$
99/99/99
Area Forecast Discussion
National Weather Service Marquette MI
652 PM EDT Fri Aug 21 2020
.SHORT TERM...(This evening through Saturday)
Issued at 652 PM EDT FRI AUG 21 2020
Water vapor imagery and RAP analysis show wnw flow today across the
Great Lakes btwn troffing over se Canada and ridging over the
Rockies. Within this flow, a shortwave trof is noted from southern
Saskatchewan to the Dakotas with another shortwave over northern
Ontario btwn Lake Superior and James Bay. Otherwise, there are no
apparent shortwaves immediately upstream. Fog/low clouds were slow
to lift/break up today from the Keweenaw se into the eastern U.P.
To the sw, it`s been a partly to mostly sunny, warm/humid day with
temps rising into the lower 80s and dwpts in the 60s. The
differential heating boundary btwn the areas that cleared out early
today and the areas that have seen more clouds resulted in shra/tsra
developing around 18z from Ontonagon County e to the sw half of
Marquette County. With MLCAPE around 2000j/kg and around 30kt of
deep layer shear, several storms have been well organized and have
produce large hail/damaging winds.
As has been the case over the last couple of days, forecasting
when/where convection will occur tonight/Sat will be a challenge. At
least in the near term, shra/tsra will continue to expand along the
differential heating boundary over the next few hrs. Outflow
boundaries and advancing lake breezes will provide additional low-
level forcing. There will continue to be a svr risk with these
storms. Any of the storms will be capable of producing torrential
rainfall. What happens later this evening/overnight already becomes
more uncertain. Although approaching shortwave trof should support
an increasing low-level jet during the night, guidance does not show
anything more than 20-25kt at the higher end, but that may be
sufficient to develop some convection thru the night across the fcst
area.
With weakening shortwave trof moving across the area on Sat,
shra/tsra will be possible at any time during the day. However, will
probably end up with fog/stratus developing tonight, so that would
lead to the better potential of shra/tsra in the later aftn. In
addition, lake breeze will again push inland, providing a low-level
focus in the aftn hrs.
.LONG TERM...(Saturday night through Friday)
Issued at 357 PM EDT FRI AUG 21 2020
Long term pattern over the United States will continue to feature
upper-level ridging over southwestern CONUS that extends northward
into the Rocky Mountains and at times, into the northern Plains.
Initially in the period, Bermuda High over the western Atlantic will
allow the flow pattern over the Upper Great Lakes to flatten out
following the exit of Saturday into Sunday`s frontal passage. As
this high over the Atlantic shifts south early next week, long-wave
troughing will briefly establish itself over eastern North America
by midweek, ushering in another period of NW flow over the forecast
area. Beyond this, there are some discrepancies in the amplitude
and duration of the following ridge and subsequent timing of the
next shortwave trough over the region. Overall, this pattern looks
to usher in a few opportunities of showers due to embedded
shortwaves within the NW flow and near normal to above normal
temps with the potential for a brief cool period.
Beginning Saturday night into Sunday, frontal boundary over the
region with continued theta-e advection will keep showers possible
overnight into early Sunday. The west and central could see a break
in the precip begin overnight into Sunday morning, as the main
forcings shift eastward. As instability increases during the
afternoon, another round of scattered showers and thunderstorms look
possible in the west and central. In the east, expect the outgoing
shortwave to keep showers in the area overnight Saturday into early
Sunday, with the possibility of a break by mid-morning. I`m less
certain about this given the guidance spread. Regardless of this
break in the east, guidance is consistent with afternoon showers and
thunderstorms. Temps on Sunday should largely mirror Saturday`s
given the persistent airmass over the region.
Another shortwave may move into the region Monday afternoon into the
evening, but models vary on the evolution and location of the better
forcing. Ridging will extend into the Northern Plains as surface
high builds eastward over Ontario on Tuesday. This looks to be the
best shot of a dry day over the region, but a shower or storm can`t
be ruled out, mainly west and south. As upper level troughing digs
into the northeast, models vary on the southern and western extent
of the cooler temps. The 12z GFS is now trending more in line with
the Canadian and Euro with this evolution, and temps in the low-
mid 70s by the lakeshores and upper 70s is expected inland.
Beyond Tuesday, the next better shot for precip looks to be on
Wednesday afternoon or evening into Thursday, but guidance varies on
the timing and location of this feature.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 628 PM EDT FRI AUG 21 2020
Stalled frontal boundary over the area will support sct shra/tsra at
times across Upper MI thru Sat. This will make a challenging
forecast based on the fact that the models do not handle convective
pcpn very well, so confidence with this forecast is low. Expect low
clouds/fog to redevelop tonight, leading to MVFR conditions at KIWD
and IFR to LIFR at KCMX/KSAW. Conditions later Sat afternoon will be
VFR at all sites.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 652 PM EDT FRI AUG 21 2020
Weak pres gradient will prevail across the area for the next several
days. As a result, expect winds mostly under 20kt. With a more humid
air mass over the area and with some showers and storms moving
across the lake at times, some fog patches are expected. The fog
could be locally dense.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Dense Fog Advisory until 8 PM EDT /7 PM CDT/ this evening for
LSZ162-240-263.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...JP
AVIATION...07
MARINE...Rolfson
Area Forecast Discussion
National Weather Service San Francisco Bay Area
840 PM PDT Fri Aug 21 2020
.SYNOPSIS...Marine layer returns tonight. Winds weaken and back
towards the west to southwest through tomorrow. All eyes then on
the arrival of potential elevated thunderstorms late in the
weekend through early next week. A fire weather watch has been
issued as a result of these potential thunderstorms.
&&
.DISCUSSION...as of 08:39 PM PDT Friday...Thin high clouds have
been rolling into the Central Coast and parts of interior San
Benito County this evening. These are associated with post-
tropical cyclone Genevieve, whose moisture has been advecting into
SoCal this evening while also increasing instability in that
area. Please refer to the previous discussion for a more in-
depth analysis for this weekend`s setup, as the entrainment of its
moisture is progged to come in the form of pulses through the
weekend and into the early part of next week.
As for tonight, the LNU lightning complex is 15 percent contained
as of 8pm, while other fires in the region, including the SCU
lightning complex, are also around the same ballpark. Please refer
to CALFIRE for the latest on the containment of all the active
incidents in the region. Smoke is expected to continue blanketing
most of the Central Coast, East and North Bays, and the interior,
with slightly better conditions over the SF Peninsula. Recoveries
from last night`s marine layer played a large part in helping
firefighting efforts along the coast and in lower-elevation
locations across the CWA. The Fort Ord Profiler has steadily
approached 1000 ft while the 00Z sounding at OAK showed a similar
depth for the Bay Area. As such, looking for a marine layer depth
similar to what was observed last night in the 1000-1200 ft range,
which will help greatly in tomorrow`s humidity recoveries. Higher
terrain locations immediately above the ceiling will
Unfortunately not receive the same moisture benefits but winds
have been trending towards being lighter than what`s been observed
this week, which is good news for those locations.
&&
.PREV DISCUSSION...as of 02:00 PM PDT Friday...The Bay Area remains
situated between a 550dm H5 trough centered over the Gulf of
Alaska to the northwest and a 594dm H5 ridge to the southeast. The
ridge influence waned yesterday as the trough nudged slightly
moreso over the region, bringing cooler, moister air to the area
from the northwest and allowing the marine layer to deepen to
approximately 800-1200 feet (depending on location) last night
into this morning. This marine layer brought much improved
overnight humidity recoveries to fires burning in coastal counties
except the higher ridges and even helped ease the extremely dry
conditions for the LNU complex and River/Carmel fires farther
inland by bringing fair recoveries there as well. The two fires
that received the least aid were the SCU complex due to it being
deeper inland and well above the marine layer and the Dolan Fire
along the Big Sur coast, similarly due to the higher terrain there
above the marine layer. As we`ve previously discussed, some of
the warmest/driest conditions during the overnight period exist
just above the marine layer, in this case appeared to be roughly
1500 feet and above. The marine layer also made some pushes
inland, pushing into the Sonoma, Napa, Salinas valleys and forming
an "otter eddy" in the Monterey Bay that eventually drove moister
air into Santa Cruz and up high way 17/9s in the Santa Cruz
mountains under light southeast flow this morning.
So far today, the atmosphere is warmer and more humid when
compared to the same time yesterday. Temperatures are roughly 2 to
6 degrees warmer (as a lobe of the high pressure nudges westward)
while humidity values are 5 to 20% higher (due to lingering
impacts of the marine layer push and trough to the northwest).
While today should mostly play out similarly to yesterday through
the afternoon, there will be some subtle changes as we move into
the early evening and overnight period as a lobe of monsoonal
ridge air advects westward over the region. Due to the ridge
rebuilding in from the east later today, winds will begin to show
minor shifts, particularly late in the afternoon to evening,
shifts from predominately NW-WNW inland towards W to WSW (aka
backing winds), though due to our complex terrain there will be
many other minor variations. Winds are forecast to weaken and
shift increasingly more towards the WSW to SW across the broader
area on Saturday, which should be a net positive for fire fighting
efforts but could add some notable fire behavior complications
due to shift in wind directions driving fire movement (primarily
more E to ENE or even NE), though it is important to note-- at a
much slower pace due to the lower wind speed expected. The marine
layer is expected to redevelop along the coast again late today
and behave similar to last nights 1000 foot marine layer. That
said, some notable marine layer difference tonight include that it
will a) favor more WNW to W flow, b) show some signs of
suppression from the expanding ridge from the east, c) expanding
ridge may intensify the warm/dry air mass presence linger just
above the marine layer.
Finally, a fire weather watch has been issued for the entire
San Francisco Bay Area and Central coast from 11am Sunday through
11am Tuesday. This is due to the remnants of former Hurricane (and
current Tropical Storm) Genevieve moving northward during this
time frame and merging with some ambient monsoonal
moisture/instability while being enhanced by a deepening trough
off the coast. Medium term models that better resolve convection
show strong indications that intermittent periods of elevated
convection will occur as this tropical moisture merges with
subtropical forcing. At this time, there are three time periods we
are watching closely. The first is actually not covered by the
fire weather watch as that watch is issued primarily for long
duration fire events and may distract from the second/third pulses
that will be considered the "main" event. However, we should not
gloss over it. So, an initial weak push of elevated instability
and moisture will move into the region from north to south,
primarily along the immediate coast and potentially into the North
Bay Saturday PM into Sunday AM. The tropical fuel with this
initial surge looks somewhat limited versus the second and third
surges, and will have little to no upper level support from the
adjacent trough. Expect to see some altocumulus clouds at a
minimum with the potential for a few isolated thunderstorms
developing in this timeframe, mainly just off the coast but
potentially just inland. Again, not to distract from the main
period of concern, this potential event is outside the fire
weather watch, but should be watched closely in case future
forecast model runs look more inviting during this time frame.
Confidence continues to increase that the ingredients will begin
to come together during the time frame of the fire weather watch,
or midday Sunday through midday Tuesday. There are two time
periods we are watching closely during this extent, however, just
the first of these two was sufficient in issuing the fire weather
watch, during the late Sunday into early Monday time frame. We are
also watching, though with much less confidence, a second
potential surge of elevated moisture/instability in the late
Monday to early Tuesday time frame as the last of the offshore
moisture/instability moves over the region. That said, this set
up does not look as extreme as the recent historic event that
brought thousands of lightning strikes and numerous fires to the
region. The "fuel" with this upcoming event looks similar to the
last event, however the "engine" that will dictate the performance
of the "fuel" is not as impressive. It is important to note
however that with our recent historic lightning event that we did
not see the true magnitude of the impact until it was only 24 to
36 hours out, which is not unusual given the poor data off the
coast and difficulties the resolving the break down of a
hurricane, and it is entirely possible that the forecast will
trend towards a stronger event. Even if so, there are some key
difference between the upcoming event and the previous event.
These differences include that the high pressure system to the
east will be weaker, meaning lower temperatures, higher
humidities, less marine layer suppression (though some will
exist), and finally much less monsoonal moisture/instability
merging into the remnant tropical moisture that we saw with the
last event. Additionally, numerous wildfires with a history of
extreme growth are already present on the ground and the bigger
factor from these thunderstorms may not even be the potential for
dry lightning, but instead the potential for erratic gusty outflow
winds ahead and with the thunderstorms and weaker breezy inflow
winds in the wake of the thunderstorms. Erratic gusty winds are
extremely difficult to manage on fire lines. These erratic gusty
winds are typically only associated with the strongest
thunderstorms in our region which are extremely rare however last
weekends event shows it can indeed occur here. A reminder, that
last cluster of strong thunderstorms which prompted an extremely
rare severe thunderstorm warning for the region was issued due to
these winds, of which brought peak gusts in the 50-75mph range,
especially over the higher and favorable terrain where many of
these wildfires are burning strongest at this time.
Current thinking is that the fire weather watch will remain the
active product through the next 24 hours, with high likelihood of
moving towards a more concentrated Red Flag Warning after Saturday
mornings fire weather conference calls and the arrival of the
latest forecast data from the 12Z runs. This situation will
continue to rapidly evolve, especially over the next 24-48 hours,
so please keep an eye on the weather conditions and latest updates
from us, your local CALFIRE unit (North Bay is LNU, East/South
Bay is SCU, San Mateo/Santa Cruz is CZU, Central Coast is BEU),
local city/county, county emergency managers, and sheriffs
departments for the latest information available for your local
area regarding the current ongoing wildfires and any necessary
evacuations.
Looking beyond the lightning, the forecast remains complicated.
The aforementioned low pressure trough off the coast is expected
to transition from offshore to along the coast and just inland
just beyond any burst of elevated convection, potentially
promoting a period of breezy to gusty onshore WSW to SW winds.
Otherwise, smoke will continue to impact the region to varying
degrees as long as the fires are burning, so be sure to follow
updates on spare the air days from the regional air quality
districts or from the latest HRRR smoke output shared by our
office on social media.
&&
.AVIATION....As of 5:58 PM PDT Friday...for 00z TAFs...A widespread
influx of higher humidity /water vapor/ has occurred per higher
dew point temperatures in the upper 50s to lower 60s per metar
surface observations at the airports. This influx is ahead of a
very weak cool front approx 100 miles NW of the coastal North Bay;
the front is seen as an isolated thin cloud band on visible
satellite. Coastal stratus is otherwise mixing with wildfire
smoke, the marine layer depth is near 1,000 feet. Wildfire smoke
continues to produce poor slant range and surface visibilities
/LIFR-IFR/ otherwise it`s VFR- MVFR. Cirrus clouds far in advance
of post tropical cyclone Genevieve will move up from the south
tonight and Saturday.
The 00z TAFs carry previous idea that wildfire smoke will mix with
a stratus push overnight; chilly sea surface temps 51 to 56 per buoy
data interacting with dew point temps at or above current sea surface
temps resulting in additional spontaneous saturation to stratus/fog
within the marine layer tonight and Saturday morning. Late night
and early morning air mass stability again causing poorest conditions
with VLIFR to IFR. Model forecasts hint that a slow, steady intrusion
of cooler air arrives Saturday afternoon and night. This influx
combining with diurnal mixing should lift stratus/fog and may help
a little with lifting wildfire smoke, not from a deepening marine
layer rather an influx of fresh sea breezes.
Vicinity of KSFO...VFR, west wind to 30 to 35 knots until mid evening.
May need to issue an airport weather warning for winds if sustained
or gusts continue longer at the terminal. Forecast is IFR ceiling
forming by 12z Saturday morning with a return clearing by 17z.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...Poor slant range and surface visibilities
due to NW wind advecting wildfire smoke downwind over the Monterey
Bay from the CZU August Lightning Complex. Expect VLIFR-IFR ceilings
and visibilities tonight and Saturday morning, improving somewhat
during the day due to diurnal surface warming and mixing and fresher
afternoon sea breezes undercutting wildfire smoke with a cooler air
intrusion from the northwest; similar improvement may continue into
Saturday evening just beyond the current 00z taf cycle.
&&
.MARINE...as of 4:53 PM PDT Friday...Moderate to locally gusty
northwest winds will continue across the coastal waters through
Saturday night. Winds will then begin to diminish on Sunday as
high pressure over the eastern Pacific weakens. Remnants of
Tropical Storm Genevieve will bring a chance of thunderstorms on
Sunday and potentially into early next week. Increased long period
southerly swell is possible over the outer waters through this
weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...Pt Reyes to Pigeon Pt 0-10 nm until 3 AM
SCA...Pigeon Pt to Pt Pinos 0-10 nm until 3 AM
GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Mry Bay until 9 PM
&&
$$
PUBLIC FORECAST: Diaz/AS/DRP
AVIATION: Canepa
MARINE: W Pi
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...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 250 PM CDT Fri Aug 21 2020
The main concern in the short term is the chance for thunderstorms
tonight into Saturday, then attention will turn toward temperature
forecasts through the mid part of next week.
Large scale mid tropospheric pattern is similar to yesterday, with
a ridge extending from AZ up into Alberta and Saskatchewan. A
trough stretches from MI down to the western part of the Gulf of
Mexico. There was a weak closed low in the trough near the border
of MS and AL. Water vapor imagery early this afternoon showed a
shortwave trough moving across southern Canada and the Dakotas.
The tail end of this wave extended down into north central NE. A
few showers were noted in south central SD with that feature.
Surface analysis at 2 pm had a weak trough from eastern ND down
into western NE. Temperatures in eastern NE and western IA were in
the upper 80s and lower 90s with dewpoints in the mid and upper
60s and southerly winds.
Tonight into Saturday night...
The majority of the convection allowing models (CAMs) including
the HRRR, ESRL HRRR and RAP13 suggest the early evening hours
will be dry in our area. There is a fairly decent signal later
tonight and Saturday morning with some of the other CAMs that
isolated to widely scattered thunderstorms could occur mainly from
west central IA back into northeast NE. For now, will hold POPs
at 20 percent or less in the forecast area, generally north of
Omaha and Lincoln. Lows tonight should be in the 60s.
Spotty storms could linger until late morning Saturday, then we
expect the rest of the day to be dry. Temperatures should peak in
the upper 80s and lower 90s. It appears another weak shortwave
may move in from the northwest for Saturday night in some of the
model guidance, especially the GFS. There could also be some lift
from a weak low level jet. Will keep some low POPs for southwest
IA and far southeast NE.
Sunday through Wednesday evening....
This period is expected to be mainly dry. The 500 mb ridge to our
west will expand into the central US, with heights increasing to
591 decameters or more. With the mid level warming, we should be
mostly capped with precipitation chances dropping to less than 15
percent. High temperatures through this period should be mostly in
the lower and mid 90s, with some upper 90s possible mainly Monday
and Tuesday. Lows should be in the 60s to lower 70s. Heat index
values could reach near 100 each day for a few hours.
Late Wednesday night into Friday and next weekend...
There is fairly good model agreement that the ridge will start to
flatten by Thursday, with the flow across the central US becoming
more zonal by late week and then turning toward the southwest.
This would be a more favorable pattern for precipitation in our
area, especially at night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 648 PM CDT Fri Aug 21 2020
For the most part, VFR conditions should prevail across the region
through Saturday. This will include FEW-SCT clouds between 5,000
and 15,000 ft AGL and unrestricted visibility. We will be watching
for a few stray thunderstorms between 05Z Saturday and 00Z
Sunday, with the best storm potential between 21Z Saturday and
00Z Sunday. Any of the TAF sites (KOMA, KOFK or KLNK) may be
affected by a stray storm, but those impacts should be brief. For
the time being confidence is to low to include any mention of
thunderstorms in the TAFs.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Miller
AVIATION...Albright
Area Forecast Discussion
National Weather Service Nashville TN
921 PM CDT Fri Aug 21 2020
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Upper low continues to spin over the region late this evening,
and moisture remains deep. While a weak SFC boundary remains
well south, there is an H85 boundary over the mid-state, and
along with this upper low, will provide sufficient vertical
motion to keep showers and isolated storms going most of the
night. The heavier showers/clusters are likely to continue slow
northwest movement, and have adjusted pops to reflect this trend.
Overall the threat for flooding or strong/severe storms very low
rest of the night. Temps need no adjustment at this time.
&&
.AVIATION...
00Z TAF DISCUSSION.
BNA/MQY/CKV/CSV...An upper low is circulating to our south, with
widespread showers and a few storms occurring across Middle
Tennessee as a result. The HRRR suggests that some shower activity
will continue overnight, but the primary risk to aviation will be
radiation fog and possible low stratus, mainly after midnight and
lasting into the early morning tomorrow. Expect conditions to
improve after 12Z, but look for thunderstorms across the mid state
Saturday afternoon.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......07
AVIATION........08
Area Forecast Discussion
National Weather Service San Diego CA
123 PM PDT Fri Aug 21 2020
.SYNOPSIS...
Hot weather will continue today, except at the coast and in the
higher elevations. Temperatures will cool a bit this weekend
before slowly warming up next week. Scattered thunderstorms are
forecast to develop over the mountains each afternoon through
Monday. Mostly dry weather is anticipated Tuesday through the
remainder of the week as the upper ridge axis slides just south
of the International Border.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Latest GOES satellite at 1 PM shows thin high clouds streaming in
from the south from Tropical Storm Genevieve. Showers and
thunderstorms were beginning to develop over the mountains, and
will continue throughout the afternoon. The potential exists for a
few showers, and perhaps a thunderstorm or two, developing west of
the mountains this afternoon. The latest 19Z HRRR has backed off a
bit from this morning on development west of the mountains this
afternoon. Confidence is rather low, but the potential is there.
Another hot day is in store for inland areas, especially the
Inland Empire and the High Desert, where an Excessive Heat Warning
continues through this evening. The lower deserts, San Diego
Valleys and Inland Orange County will be a few degrees cooler
today compared to yesterday, but with the humidity, it will
continue to feel hot and muggy out there.
Increased moisture from Tropical Storm Genevieve and sufficient
instability will result in scattered thunderstorm activity over
the mountains this afternoon and again Saturday afternoon.
Moisture and instability look similar between today and Saturday,
with PWs around 1.1" to 1.3" over the mountains, and CAPE values
over 1000 J/kg. Given similar moisture and instability, there
should be similar activity on Saturday as today, mainly
concentrated over the mountains. Moisture largely moves out of the
region on Sunday, so thunderstorm chances decrease, although some
isolated convection over the mountains is not out of the question
on Sunday afternoon and Monday afternoon.
Over the weekend, cooler temperatures are in store for inland
areas as the strong high pressure further weakens. Temperatures
will be near to slightly below seasonal normals for Saturday and
Sunday.
Temperatures will warm up slightly on Monday as the high
pressure begins to strengthen again. The high pressure becomes
more northeast to southwest oriented on Tuesday, and will continue
to strengthen throughout the week. As the upper ridge axis becomes
positioned across the International Border, this will effectively
shut off the monsoonal flow for the middle to end of next week.
Temperatures will gradually warm-up throughout the week as the
high strengthens. At this time, the warm up is not looking as
significant as we saw this week, but still about 5 to 7 degrees
above normal for most areas.
&&
.AVIATION...
212000Z...Coast/Valleys...Expect stratus with bases of 1000-1500 ft
MSL to develop late tonight near the coast. Expect prevailing SCT
conditions, but may see periods of BKN ceilings 13-17Z Saturday at
KSAN/KCRQ/KSNA. The potential exists for isolated SHRA over the
coast/valleys through Saturday, mainly during the afternoon hours.
Confidence is too low on timing/coverage to mention in the TAFs.
Mountains/Deserts...SCT TSRA persist through 00Z with bases near
10,000 ft MSL and tops to 40,000 ft. Strong, gusty and erratic winds
and lightning will occur in vcnty of TSRA. The activity will
dissipate 00-02Z. Development can be expected again Saturday
afternoon 18-00Z, with scattered coverage over the mountains
expected. Otherwise, unrestricted vis prevailing through the period
with mainly high clouds.
&&
.MARINE...
No hazardous marine conditions are expected through Tuesday.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 10 PM PDT this evening for Apple
and Lucerne Valleys-San Bernardino and Riverside County
Valleys-The Inland Empire.
PZ...NONE.
&&
$$
PUBLIC...Connolly
AVIATION/MARINE...Moreland