Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/13/21
Area Forecast Discussion
National Weather Service Binghamton NY
952 PM EDT Thu Aug 12 2021
.SYNOPSIS...
Lingering thunderstorms late this evening, then drying out
overnight. Hot and humid conditions and another round of
showers and thunderstorm are expected Friday. After a passing
cold front late Friday, the weekend will be seasonable and much
less humid.
&&
.NEAR TERM /THROUGH FRIDAY/...
950 PM Update...
Made some adjustments to raise PoPs where thunderstorms are
likely over the next several hours across most of NE PA. These
storms still have the potential to bring heavy downpours,
frequent cloud to ground lightning and isolated damaging winds,
through about midnight. Otherwise, just some minor adjustments
to overnight lows, cloud cover and winds...but overall the near
term forecast remains well on track.
730 PM Update...
The environment still has quite a bit of energy until the sun
sets, so it is possible that strong to severe storms may
continue into the late evening. Of most concern is a cluster of
thunderstorms in western PA which could clip the Wyoming valley
and Poconos late this evening. However, lapse rates are very
poor which has prevented more in the way of thunderstorms. The
HRRR overall has a better handle than the overdone NAM nest.
With this in mind the northern edge of the watch was trimmed
back at 7 pm with the rest of it expiring at 8 given the overall
decreasing threat. Temperatures fall to around 70 tonight, not
much relief from the heat.
Tomorrow will be a similar story with hot and humid conditions
and another chance for thunderstorms. Low-level cloud cover
present through the morning hours and even into the afternoon
could keep temperatures below the forecasted highs. Expected
highs will be in the mid to upper 80s across CNY and upper 80s
to lower 90s in NEPA. These forecasted highs are lower than the
previously forecast based on updated guidance. This was the
result even after blending in some of the 75th percentile from
the NBM. Due to this, heat indices are borderline advisory
criteria and a heat advisory was not issued at this time. It
does look like NEPA will not have the low-level cloud cover for
as long of a period tomorrow, so an advisory may be needed for
the southern counties of our forecast area. This will be re-
evaluated during the overnight update.
Another day of strong to severe storms are possible tomorrow.
Some scattered storms are possible tomorrow afternoon due to a
couple of weak waves passing through. Instability is not quite
as good as today as CAPE values are no more than 2000 J/kg and
shear values are 20-25kt. There is a little upper level support
as the jet dips down into our region and there is a slight fall
in 500mb heights.
Overnight lows will be in the 60s. A passing cold front late
Friday night and into early Saturday morning could bring some
additional scattered showers and thunderstorms, but likely
nothing severe. There is some uncertainty with how quickly this
frontal system will pass through so kept at least chance PoPs
through 06z Saturday before decreasing PoPs through the early
morning hours.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
245 PM Update...
A significant change in airmass is expected this weekend behind a
late night/early Saturday morning cold frontal passage. A
Continental Polar airmass will build in from Canada on Saturday with
much lower dewpoints in the 50s and high temperatures expected only
to reach the mid 70s. Morning clouds will give way to at least
partly sunny skies on Saturday followed by generally clear/sunny
skies for Sunday. Predominantly loaded the NBM forecast guidance,
although skewed it a bit with a blend of the cooler 10th
percentile guidance on Saturday night as there will be
significant radiational cooling prior to overnight fog/stratus
development. Upper 40s not out of the question in many parts of
CNY, although NEPA should hold out in the 50s.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
245 PM Update...
High pressure continues to influence the Northeast`s weather pattern
into early next week, although warming begins again on Monday
as we start to feel the influence of return southerly flow
aloft. This trend will continue through midweek with increasing
moisture resulting in better and better chances for thunderstorm
activity again toward Wednesday and Thursday. Confidence in the
forecast becomes less during the middle part of the week as we
keep an eye on what should be the remnants of tropical system
Fred moving through the Gulf States next week. Looks like enough
moisture return for showers and thunderstorms, anyway, but the
details of whether or not we`ll be dealing with tropical-like
downpours remains to be sorted out. Temperatures should be back
into the 80s for Wednesday and Thursday.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Conditions are gradually becoming less favorable for
thunderstorms this evening. Still radar shows a brief shower
approaching KITH right around 00Z tonight. This shower should
be a quick mover and if lightning ramps up a quick AMD may be
needed. KAVP also may see another cluster of storms move through
around 01-03Z but confidence is too low for TAF inclusion at
this time. main concern overnight is for fog at KELM from 09-13Z
with indications of IFR restrictions at times.
VFR late evening through most of Friday. Some showers and
perhaps thunderstorms should develop by mid to late afternoon.
Given coverage and timing uncertainities held off on anything
more than VFR showers with this TAF set.
Outlook...
Friday night through Saturday...Scattered afternoon- evening
thunderstorms/restrictions, especially Friday night.
Saturday night through Monday...Mainly VFR.
Tuesday...Mainly VFR; slight chance for thunderstorms and
restrictions.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.
&&
$$
SYNOPSIS...BTL
NEAR TERM...BTL/MJM/MWG
SHORT TERM...JAB
LONG TERM...JAB
AVIATION...MWG
Area Forecast Discussion
National Weather Service Denver/Boulder CO
835 PM MDT Thu Aug 12 2021
.UPDATE...
Issued at 834 PM MDT Thu Aug 12 2021
An area of slow moving showers and strong thunderstorms have
persisted over Southern and Central Lincoln as well a much of
Eastern Elbert County from late afternoon into the evening hours.
These storms have produced locally rainfall with rates up to 2
inches per hour and hail.
Additional storms may develop further north and west possibly
back into Denver later tonight as outflow boundaries propagate
outward from the storms. The latest KDNR sounding has a cape of
745 J/KG, a CIN of - 63 J/KG, and a descent inversion just above
700 MB which doesn`t look favorable for convection. However, if a
strong enough boundary moves into the area, the cap could be
broken and trigger a few storms.
The HRRR model suggests this with convection developing in the
Denver area around 11 pm and ending after midnight. However, many
of the other high resolution models only show a few light showers.
With increased low level moisture behind the boundary along with
PW`s rising to near an inch, there is the potential for brief
heavy rain if the storms do form.
&&
.SHORT TERM...(This evening through Friday)
Issued at 213 PM MDT Thu Aug 12 2021
Current radar shows isolated thunderstorms developing in southern
Lincoln county. With sufficient CAPE values reaching 1000J/kg and
CAMs showing favorable conditions, thunderstorms will likely
continue throughout the afternoon into the evening hours till 07Z.
This afternoon isolated thunderstorms will continue along the
Palmer Divide which may produce brief heavy rain, small hail and
wind gusts to 40 mph. Additionally, areas of the eastern plains
could receive a stray thunderstorm between 0Z and 06Z due to some
lingering instability but kept PoPs low. Tonight`s low
temperatures will range in the upper 50s to lower 60s east of
Interstate 25 and mid 40s to lower 50s west of Interstate 25.
In terms of smoke, wildfire smoke will continue through tonight
but with the assistance of upper level forcing majority of the
smoke at the surface will decrease and improving conditions on
Friday.
Tomorrow, temperatures will decrease slightly due to increasing
cloud coverage. Rising dewpoints and increase moisture content
will support thunderstorm growth potential. Isolated severe
thunderstorms are possible due to deep layer shear and CAPE values
reaching 1500J/kg. Scattered thunderstorms will develop west of
Interstate 25 which may bring flooding concerns for northwestern
portions of Cameron Peak. Storm motion will move southeasterly
with QPE values up to half an inch in isolated foothill areas.
Areas in the northeastern plains starting after 00Z will receive
QPE values up to a half an inch as well.
.LONG TERM...(Friday night through Thursday)
Issued at 213 PM MDT Thu Aug 12 2021
Scattered thunderstorms will be tracking east across northeast
Colorado Friday evening to begin the extended period. The severe
threat should have shifted to the northeast plains as outflows
from storms help to stable areas along the Front Range. Storms
eventually end as they dissipate and move off to the east this
could be after midnight over the far northeast corner.
Northwest flow aloft will prevail Saturday around a high over the
Great Basin. Precipitable water values decrease a little to two-
thirds of an inch over the higher terrain to one inch over the
northeast plains. CAPE will be lower as well with 200-600 J/kg.
Should be enough for isolated thunderstorms Saturday afternoon with
the best chance being over the higher terrain.
The high retrogrades to the west Sunday and will be centered over
the Nevada/California border. This will lead to a stronger northwest
flow and cooling aloft. Instability increases a little with CAPES of
up to 1000 J/kg. Should see an increase in thunderstorms Sunday
afternoon and evening. How much more thunderstorm activity will
depend on the amount of moisture. Don`t see much of an increase
for Sunday.
For Monday and Tuesday, the ridge flattens and weakens as a trough
moves onto the Pacific Northwest coast. The ridge will track
across the Central Rockies. Moisture and instability will decrease
with only isolated convection expected. Temperatures look to be
near to slightly above normal.
The trough over the Pacific Northwest will track eastward across the
northern states. With the ridge off to the east, a southerly flow
will transport moisture into the area. Lift from the trough combined
with the moisture is expected to bring a good chance for showers and
thunderstorms Wednesday afternoon and evening. With precipitable
water values climbing over an inch, expect heavy rain to be the main
threat. Airmass will remain moisture Thursday. However, with the
loss of synoptic lift, fewer storms are expected. With this being a
week away, still a lot of uncertainty on how this will pan out,
but with a moisture airmass in place scattered to numerous
thunderstorms should occur Wednesday and Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 803 PM MDT Thu Aug 12 2021
An outflow boundary is expected to move into the Denver Metro area
around 03z with moist southeasterly winds developing behind it.
This boundary could trigger a few storms around 05Z. If storms
develop, they could produce brief heavy rain before ending after
midnight. In addition, some of the high resolution models are
showing low clouds developing over KDEN during the early morning
hours. Therefore, have decided to add scattered low clouds into
the Denver TAF. With more moisture and instability expected
tomorrow, have decided to add a PROB group for scattered
thunderstorms into the local airport TAF`s tomorrow afternoon.
&&
.HYDROLOGY...
Issued at 213 PM MDT Thu Aug 12 2021
There is a chance of isolated thunderstorms across northwestern
portions of Cameron Peak starting 21Z Friday afternoon which may
cause burn scar flooding concerns. Afternoon and evening showers
and thunderstorms are expected every day for the upcoming week. An
uptick in activity is expected for Sunday. A slight decrease in
storms should occur Monday and Tuesday. However on Wednesday, a
moist airmass may lead scattered to numerous thunderstorms with
heavy rain.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Kalina
SHORT TERM...AD
LONG TERM...Meier
AVIATION...|Kalina
HYDROLOGY...AD/Meier
Area Forecast Discussion
National Weather Service Dodge City KS
1043 PM CDT Thu Aug 12 2021
...UPDATE TO AVIATION...
.SYNOPSIS...
Issued at 1032 PM CDT Thu Aug 12 2021
WV imagery indicates a broad scale upper level trough of low
pressure stretching from the Dakotas eastward into the Great Lakes.
Near the surface, a weak frontal/outflow boundary is sinking
slowly southward across southwest and south central Kansas.
&&
.SHORT TERM...(This evening through Friday)
Issued at 220 PM CDT Thu Aug 12 2021
A stationary surface front was located just north of a line
extending from near Scott City to near Hays. Surface dew points
averaged in the upper 50s over the far southwest section of the
forecast area south of the boundary - to the mid/upper 60s over
the lower plains mainly east of highway 283. A generally similar
mesoscale environment exists Today as we saw yesterday, which
brought slow developing but deep convective updrafts with a
marginal severe wind risk. There are a few notable differences
with respect to how the convective allowing models evolve this
evening. The HRRR is different than the 4km NAM/ARW solutions
which quickly convect all along the front by 4 pm in that it only
convects this afternoon in the area of enhanced surface
convergence over the southwest counties (base of the surface
trough or weak low pressure). Looking beyond this evening`s
isolated severe risk, the potential exists for the eastern
periphery of the DDC forecast area to be along a possible central
KS overnight MCS. Similar challenges will be posed for Friday`s
forecast however the opportunity for severe risk will likely be
not as high as the threat area is more likely to be over the
southwest third or so of the forecast area as more of central
Kansas becomes under the influence of post frontal easterly
surface flow. Cooler afternoon highs also over portions of central
Kansas may not exceed the upper 80s.
.LONG TERM...(Friday night through Thursday)
Issued at 220 PM CDT Thu Aug 12 2021
The post frontal easterly upslope flow regime may remain in
place, providing thunderstorm chances to persist through much of
the weekend. Another benefit to the regime will again be not as
hot temperature each afternoon. The range of temperatures for
saturday and Sunday from the models and mos top out in the mid
90s at DDC, with many of the models supporting temperatures not
exceeding upper 80s. Much of that will depend of potential outflow
boundaries and afternoon cu/cloud cover however it is still near
or just cooler than climatology for late August. The period of the
first half of next week looks potential quite dry and lacking any
potential for widespread organized convection, probably through
about at least Wednesday, with a warming trend placing highs
squarely back in the 90s. The ECMWF/FV3,GFS/Canadian all develop
another well developed upper synoptic trough over the northern
Rockies which places sw Kansas in sort of a hot dry southerly wind
regime with incrementally warming temps - but we cannot still
rule out moisture advection though the panhandles in that pattern
however mesoscale features are impossible to resolve that far out.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1042 PM CDT Thu Aug 12 2021
Showers and thunderstorms will linger across portions of southwest
and central Kansas overnight before dissipating/moving out of the
area toward daybreak. Otherwise, mainly VFR conditions will prevail
in the vicinity of all TAF sites through Friday afternoon. Any gusty
north winds in wake of an outflow boundary moving southward across
southwest Kansas overnight are expected to give way to more light
and variable winds by sunrise. Light easterly winds will develop in
central Kansas north of a stalled frontal boundary bisecting southwest
Kansas while more south/southeasterly winds are likely farther south
closer to the Oklahoma border.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 67 90 65 88 / 40 40 30 40
GCK 63 89 63 88 / 40 40 30 30
EHA 64 90 62 89 / 10 30 20 20
LBL 65 91 64 89 / 20 30 20 30
HYS 66 85 63 85 / 80 40 40 40
P28 71 94 68 89 / 40 40 30 50
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...JJohnson
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...JJohnson
Area Forecast Discussion
National Weather Service Des Moines IA
630 PM CDT Thu Aug 12 2021
.DISCUSSION.../Tonight through Thursday/
Issued at 215 PM CDT Thu Aug 12 2021
Convective trends have been challenging to pin down so far today.
Hi-res models struggled to resolve the persistent training
convection over southeast Iowa as well as the further development
over much of northern Missouri. This considerably hinders
forecast confidence going forward as additional storms are
possible along a sagging frontal boundary. As of 19z the front
generally stretched from southwest through east central Iowa. Northerly
winds and drier air behind the front has gradually dropped dew
points into the 60s and 50s. However a very humid and unstable
airmass is still in place south of the front with dew points in
the mid to upper 70s common. The extensive cloud debris and cool
outflow left over from the morning convection has locally limited
destabilization/enhanced inhibition, but 3000+ MLCAPE is analyzed
over parts of southwest and south central Iowa that has
experienced mostly full insolation so far today. RAP mesoanalysis
also shows moisture pooling just ahead of the front along with
increasing convergence along the boundary, so it remains plausible
that isolated to scattered convective initiation may occur later
this afternoon. More widespread thunderstorm activity is possible
over far southern Iowa late this evening through the overnight as
the LLJ and moisture transport intensifies. The deeply moist
airmass and strong instability will be supportive of severe storms
capable of hail and strong winds in addition to heavy rainfall.
Lagging deep shear may create messy, disorganized storm modes. A
Flash Flood Watch was hoisted for Appanoose and Davis Counties
which saw anywhere from 2 to 5 inches of rain from storms earlier
today. The severe threat should wane during the overnight hours as
instability weakens.
Quiet conditions return Friday as the humid airmass is scoured out
to the south. Expect a pleasant day as an area of surface high
pressure drifts through the region. Highs fall back into the low
to mid 80s and considerably lower humidity with dew points in the
40s and 50s. Going through the weekend the GFS remains aggressive
with moist return flow and generating precip on the backside of
the departing high. The Euro remains dry, consistent with all
previous runs. Looking to ensemble data for more clarification,
the deterministic GFS is on the wetter side of its ensemble spread
with the majority of members staying dry. ECENS is nearly
unanimous in a dry forecast and keep any precip west, so feel
confident sticking with the dry NBM output for now. Pattern stays
dry over the first half of next week as a shortwave ridge slowly
builds over the region. Models have trended a bit slower with the
progression a wave that will break down the ridge over the middle
of the week, but should still result in a next best shot for
precip as the wave pushes a front through the region Wednesday
night into Thursday.
&&
.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 630 PM CDT Thu Aug 12 2021
A few thunderstorms are still possible overnight in vicinity of
KOTM. Otherwise, a cold front is moving through Iowa and will
bring a switch to northerly wind. The wind may become light and
variable at times tonight. Breezy conditions are expected over
northern Iowa by Friday afternoon while conditions remain VFR.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Friday morning for IAZ096-097.
&&
$$
DISCUSSION...Martin
AVIATION...Donavon
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
348 PM PDT Thu Aug 12 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 Friday afternoon, otherwise
expect more dry weather.
&&
.DISCUSSION...Layers of smoke from various wildfires across the
region have expanded across northwest California today. Surface
and low-level smoke has been mostly restricted to Trinity County
and some adjacent portions of interior Humboldt, where Air Quality
Advisories are in effect, with an Alert for northern and eastern
Trinity County for truly hazardous air quality conditions. Air
quality along the coast remains very good, 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 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. As far as the layers of
smoke aloft go, we are going to probably see much of the same for
Friday and even into Saturday. 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 along the
coast as well, at least during the nights and mornings.
All the smoke around has really limited daytime heating, with area
temperatures running 5 to 10 degrees cooler than Wednesday
afternoon, on average. A few spots around Lake County still
managed to approach 100, but elsewhere across the interior, highs
are topping out in the 80s and 90s where smoke is thicker. We
should expect that to be the case once again tomorrow, and 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. With the diminished daytime
heating, instability has been minimized and we haven`t really
seen any cumulus development across our area. Left a slight chance
of thunderstorms in eastern/northern Trinity, but at this point do
not really expect anything. SREF/HREF probabilities and CAMs
suggest a better shot in northeast Trinity County for isolated
thunderstorms, but with the smoke probably limiting things once
again, do not expect more than a stray storm.
Another feature to keep an eye on will be a surge of tropical
moisture coming northward toward the coast later Friday night.
Precipitable water anomalies are remarkable with this surge, and
models are suggesting at least some elevated shower activity. That
said, forecast soundings point toward quite a bit of CIN to go
along with what meager (100-200 j/kg) CAPE there is to be found,
so at this point thinking elevated thunder is unlikely. Otherwise,
the rest of the forecast for our area is looking pretty dry
heading into next week, with at least a weak trough or two
clipping our area from the Pacific Northwest. That should allow
for slightly less hot interior temperatures next week. /AAD
&&
.AVIATION...Smoke aloft from inland forest fires has been spreading
over coastal terminals once again. Conditions have been VFR, however
brief MVFR in haze will be possible at the forecast terminals this
evening and overnight. The marine layer remains quite shallow and
perturbed. Any stratus and fog at the forecast terminals (KACV and
KCEC) that forms again tonight will be very localized and brief with
winds remaining light or calm. Other than smoke from the fires in
Trinity County, VFR with occasional mid and high clouds are expected
across the interior and at KUKI through the period. Isolated
thunderstorms are also possible over northeast Trinity county near
Siskiyou county this evening as well.
&&
.MARINE...Light winds and low seas are forecast to prevail through
Friday as surface gradients remain loose across the coastal waters.
A slight uptick in northerly winds is expected over the weekend
south of Cape Mendocino, with increasing probabilities for winds
around 20kt by Sunday. Probabilities for winds of 20kt or more
increase both north and south of Cape Mendocino Monday and Tuesday,
with larger steep seas building into early next as well. Probability
for localized regions (downwind of Cape Mendo and near Pt St George)
of gale force northerly winds will also increase around Tuesday.
&&
.FIRE WEATHER...Areas of thick smoke have really limited daytime
heating today, with temperatures this afternoon running a good 5
to 10 degrees cooler than yesterday. That has also kept the
atmosphere more stable, and probably ended our thunderstorm threat
for today. Still am leaving an outside shot at a stray storm
around northeast Trinity County, but that is looking pretty
unlikely at this point. Friday seems to offer slightly better
chances in that same area, but smoke will once again be a
limiting factor. For now will headline zone 283 for isolated
thunderstorms Friday afternoon, but 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,
especially 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.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...None.
&&
$$
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Area Forecast Discussion
National Weather Service Lincoln IL
901 PM CDT Thu Aug 12 2021
.SYNOPSIS...
Issued at 900 PM CDT Thu Aug 12 2021
Showers and isolated lightning will continue through tonight as a
cold front moves across Illinois. Some lingering showers or
storms are possible on Friday, but a trend to drier and cooler
weather will be underway, as high pressure builds in from the
northwest to start the weekend.
&&
.UPDATE...
Issued at 900 PM CDT Thu Aug 12 2021
Updates to PoPs and thunder chances sent in the wake of a
disorganized line of thunderstorms pushed generally south of the
area this afternoon and early evening. Still expecting chances for
showers overnight, although severe weather potential has greatly
diminished with overturning from previous thunderstorm activity.
Cold front, still north of the forecast area this evening, should
start to cross the forecast area a few hours after midnight.
&&
.SHORT TERM...(This evening through Friday)
ISSUED AT 329 PM CDT Thu Aug 12 2021
A back-building line of storms across our central counties has
finally started making forward progress to the south-southeast.
They are being fueled by a persistent low level jet and moderate
instability. The line has started producing severe winds as an
outflow dominant system. Satellite and radar trends show the line
will likely continue to advance into our SE counties, producing
areas of strong to severe wind gusts. DCAPE ahead of the line is
near 1000 J/kg, with additional support for downbursts from the
LLJ. The 18z NAMNest indicates this is the last line of strong
storms for today, while the 18z HRRR shows another flare-up of a
line of storms across central IL from SW to NE. The complete
flip-flop of the NamNest tends to lower confidence, so will
continue to have some storm chances across our CWA later this eve,
until better agreement develops in the models on limited overnight
convection. Lingering showers and a few storms are still possible
Friday morning as the cold front makes progress away from our CWA
to the SE. By afternoon, all of our area should generally be dry.
Highs will be much more pleasant, in the lower 80s for the most
part.
The heat advisory was trimmed by a row of counties on the northern
edge, due to storms and much cooler conditions in that area. The
rest of the advisory will likely be able to be cancelled before 7
pm, due to the line of storms blasting into our southern counties.
.LONG TERM...(Friday night through Thursday)
ISSUED AT 329 PM CDT Thu Aug 12 2021
Canadian high pressure will slowly progress along the northern
CONUs states, reaching the Great Lakes area by Monday. Much cooler
and less humid conditions will prevail through Monday, with light
northerly winds and generally sunny days. Highs should mainly top
out in the lower 80s each day, with some northern areas possibly
only seeing upper 70s for highs on Sunday and Monday.
Winds will begin to shift around to the south on Tuesday and
continue southerly through Thursday. A warm front approaching the
area from the southwest will trigger warming conditions on
Wednesday and Thursday, along with chances of showers and storms.
Highs will climb back into the upper 80s by Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 622 PM CDT Thu Aug 12 2021
Most of the storms have passed south of the terminal sites. SPI
remains closest to the nearest MCS, but that complex is projected
to continue on its SE path. The CAMs still show varying solutions
for the rest of the night. The cold front is still well to our
west and progressing toward the area, so there is potential for
some redevelopment in the midnight to 6 am time frame. Therefore,
utilized VCTS for the overnight. Cigs could drop to MVFR later
tonight, plenty of moisture on the ground could even allow for
some fog to form. Confidence is too low to add fog with this
update. Winds will become variable as the front arrives tonight,
then shift out of the N-NW tomorrow.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...37
SYNOPSIS...37
SHORT TERM...Shimon
LONG TERM...Shimon
AVIATION...Shimon
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
939 PM EDT Thu Aug 12 2021
.UPDATE...
Issued at 935 PM EDT THU AUG 12 2021
Raised Pops along and north of I-64 for the next several hours.
Convection has developed over northern KY this evening, and the
CAMS continue to struggle catching on to this activity. While
overall the trend in convection should be weakening as the evening
progresses, can`t rule out some showers and storms reaching the
northern portions of the forecast area over the next few hours.
Updates sent to NDFD and web servers.
UPDATE Issued at 715 PM EDT THU AUG 12 2021
Minor adjustments to Pops along with T/Td to reflect the latest
trends. Few widely scattered storms developed over the past
several hours near the borders with VA and TN, but they have
largely dissipated at this hour. Will be monitoring showers/storms
to the NW over southern Indiana to see if they hold together
tonight. If so, may have to bump up Pops across the north with the
next update.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 414 PM EDT THU AUG 12 2021
Eastern Kentucky has been fairly quiet so far with only isolated
showers/storms along the southeast bordering Virginia this
afternoon. Anticipate these to dissipate with the loss of daytime
heating tonight. Temperatures thus far have been in the upper 80s to
around 90 with afternoon cu across much of the state. In the upper
levels, high pressure is positioned off the coast of the Carolinas,
while a longwave trough sits to our north and runs through Northern
Canada. At the surface, high pressure remains settled across the
Southern Appalachians. An upper level wave will be progressing
eastward through the trough into Friday, dragging a cold front with
it across the Ohio River Valley toward the end of the day/period. Hi-
Res guidance continues to agree on better convection ahead of the
front by Friday evening, but the lack of shear and jet dynamics
indicates a more broken/multi-cell storm type. With that said, CAPE
values of 2500+ J/KG sit across our north and western counties late
Friday afternoon and into the evening. With a more high instability/
low shear setup, localized strong to damaging winds will be
possible. This coincides with CIPS guidance, which indicates near
900 J/kg of DCAPE by 18z Friday and 500 J/kg through the
overnight. RAP and GFS analysis suggest PWATs increasing to near
2" for our northern counties by 00Z Saturday, which could also
lead to some localized flooding in areas of training storms.
River valley fog is expected to develop tonight, but given a drier
day overall, expect this to be mostly patchy. Lows will remain mild
in the low 70s to upper 60s for the more sheltered valleys. Friday
will continue to be warm and muggy with highs in the upper 80s for
most and low 90s for a few valleys. Heat indices will again be near
100 degrees CWA-wide for Friday. Increasing cloud cover the latter
half of the day from a cold front will lead to showers and storms
through the overnight and into the extended period. As a result
of the cloud cover and front, lows will be in the upper 60s into
Saturday morning.
.LONG TERM...(Saturday through Thursday)
Issued at 310 PM EDT THU AUG 12 2021
We will have a few primary weather makers in the extended. The
first two will be a large upper trough and its associated surface
cold front, while the third will be what`s left of tropical
cyclone Fred. The expected pattern will be for the upper trough to
move through the Great Lakes and into New England Saturday and
Sunday, while the cold front makes its way southward through the
Ohio Valley and into the Tennessee Valley. After that, the front
is progged to stall out for a bit, before moving back northward
and into the southern fringes of our forecast area, perhaps aided
by the north and then northeast progression of the remnants of
Fred. Long story short, we will see daily, mainly in the afternoon
and evening hours, chances for showers and storms. This will be
the result of the cold front moving through the area, stalling to
our south, and then moving back north towards us, perhaps aided by
the energy/moisture associated with TC Fred. Any dry air behind
the front will have trouble pushing very far south, as the front
itself will likely not move far enough south to allow a full
intrusion of dry air.
Temperatures look to be generally below normal each day and normal
to slightly below normal each night. The cooler daytime
temperatures will be the result of persistent cloud cover and
precipitation across eastern Kentucky. Daily highs should top out
in the low to mid 80s, with nightly lows in the mid 60s on tap. A
few locations may see upper 70s for highs depending on how much
cloud cover/rain they end up getting.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 715 PM EDT THU AUG 12 2021
VFR to start the 00Z TAF period. Some patchy river valley fog is
expected overnight, however may not impact any of the terminals.
For this issuance, kept the mention of fog out. Scattered showers
and thunderstorms are expected Friday ahead of an approaching
front from the north. Any of the stronger storms may result in
brief flight restrictions. Winds SW 5 kts or less tonight and
overnight, and 5-10 kts on Friday.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...CMF
SHORT TERM...BB
LONG TERM...AR
AVIATION...CMF
Area Forecast Discussion
National Weather Service North Platte NE
655 PM CDT Thu Aug 12 2021
.SHORT TERM...(This evening through Friday night)
Issued at 402 PM CDT Thu Aug 12 2021
The main forecast challenge to round out the week revolves around
thunderstorms. A surface boundary will remain draped along the
central High Plains, primarily just south of the forecast area. This
setup will provide seasonable temperatures and periodic
precipitation chances.
This evening and tonight... Low level northeast flow continues in
the wake of the cold front passage early this morning, coinciding
with modest CAA at H85. Mixed cloudiness and generally light winds
will be conducive for some boundary layer decoupling, mainly in the
Sandhills. Blended in some cooler guidance for min temps. New
forecast ranges from mid 50s in the north to near 60F in the south.
Did increase PoP in the south to account for a mid-level front in
the vicinity and the surface front that stalls in northern Kansas.
Broad isentropic upglide along with upslope flow near H85 will
provide some weak forcing. Moisture below H7 is somewhat limited,
which will likely keep any precip coverage scattered at best.
Regardless, guidance suggests weak instability (MUCAPE to around
200j/kg), decent mid-level lapse rates around 7.5 C/km, and modest
deep layer shear of 30kts. Should development occur, thunder is a
possibility but severe threat stays low.
Friday and Fri night... Winds near the surface and H85 transition to
south/southeast as the northern Plains high drifts east. Intensified
upslope flow combines with stronger isentropic upglide (most notable
at 315K) and some weak fgen forcing at H5-7. Kept chc PoP through
the day for most areas along/west of Hwy 83. Conditions are not
pointing to a washout, but rather hit-and-miss activity early in the
day with a growing threat of organized convection past peak heating.
A ribbon of better instability develops near the theta-E axis in the
panhandle while deep layer shear strengthens. A short window exists
around 00z for stronger convection in the panhandle, but a more
sustained threat occurs closer to 06z across the whole southwest.
Enough elevated instability exists to support large hail, and
relatively dry low levels earlier in the day will boost DCAPE values
for a wind threat. Went with a general blend of HREF and HRRR for
placement and timing of greatest thunder threat. Temperature-wise,
subdued temp advection will keep highs in check with most locations
staying in the mid 80s. One concern is the ensemble spread, which is
fairly large for a day 2 envelope. GFS and NAM are much more
aggressive with late day return flow/WAA, while ECM keeps the greater
warmth pushed to the south. The forecast hedges more closely to
mixed cloudiness and scattered daytime showers, but should more
sunshine occur, temps may need to be pushed up.
.LONG TERM...(Saturday through Thursday)
Issued at 402 PM CDT Thu Aug 12 2021
Nebraska remains caught between the Western US upper ridge and Great
Lakes through the weekend, then the synoptic pattern shifts to
include broad southwest or quasi-zonal flow into next week.
Temperatures gradually warm with peak heating due Sunday or Monday
as strong southwest flow at H85 push temps near 25C. Assuming deep
mixing and a good deal of sunshine, this should translate to highs
in the lower to mid 90s for western Neb. Drier conditions join the
warmup, then precip chances increase again by midweek as a cold
front approaches the central Plains.
&&
.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 655 PM CDT Thu Aug 12 2021
VFR conditions are expected at TAF sites through the valid period.
A surge of low level moisture will result in MVFR/IFR cigs that
will remain to the south of KLBF. Some modest low level forcing
across southern Nebraska may also produce some showers/thunder
late tonight up to about Interstate 81 though coverage looks
limited so will only use VCTS at KLBF. Next chance for convection
will hold off until toward the end of the valid period so will not
address with this issuance.
Winds will be a bit gusty for a couple of hours after issuance but
will gradually subside after sunset with loss of heating. Some low
end gusts through Friday morning after heating becomes
established.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Snively
LONG TERM...Snively
AVIATION...MBS
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
929 PM EDT Thu Aug 12 2021
.SYNOPSIS...
High pressure will remain offshore through Friday. A cold front
will move through the area on Saturday, before eventually
stalling out to our south Sunday through early next week.
Eventually the front will return back northward as a warm front
toward the middle of next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
After a lackluster day of convective activity across the region,
some threat still looms north of the Mason-Dixon Line. While
cloud tops continue to warm, there is still a healthy line of
thunderstorms dropping down out of southwestern Pennsylvania.
The thermodynamic environment downstream over western Maryland
and the eastern West Virginia panhandle shows some inhibition
based on the 23Z RAP objective analysis. However, plenty of
elevated CAPE exists which should support some residual
thunderstorm threat into tonight. They should weaken some
relative to their current severe-warned status.
Have maintained shower and thunderstorm chances through the
first half of the night, especially north of the DC Metro/I-66
corridor. Nighttime lows will stay in the 70s across most spots,
locally in the 60s at mountain locales, with humid conditions
persisting.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
High pressure both at the surface and aloft will remain in
place offshore through tomorrow. Meanwhile, a trough at mid-
upper levels will progress from the Upper Midwest toward the
Great Lakes. Large scale ascent in advance of the approaching
trough in conjunction with strong daytime heating will lead to
the development of thunderstorms tomorrow afternoon, with a
considerably higher areal coverage of storms compared to today.
The aforementioned trough will press eastward toward northern
New England on Saturday, driving a surface cold front southward
toward our area in its wake. Additional thunderstorms will
develop on Saturday along and south of this cold front. Strong
to severe storms may be possible within the hot and humid
airmass either day. The threat for flash flooding may begin to
increase on Saturday as moisture pools in advance of the
approaching cold front. Precipitable water values are expected
to increase to in excess of two inches, which will allow any
storms to produce heavy rainfall. Conditions will remain hot
tomorrow, with highs in the mid to upper 90s and heat indices in
the upper 90s to lower 100s. With heat indices locally reaching
105 degrees east of the Blue Ridge, a Heat Advisory is now in
effect from noon until 8 PM. Temperatures will start to cool
off on Saturday, with highs in the upper 80s and lower 90s.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
A cold front should stall south of the region Sunday as a 1020-1024
mb sfc high builds across New England. Sunday will be notably cooler
with temperatures struggling to get out of the upper 70s in
most locations (60s in the mountains) due to more cloud cover
and easterly flow off the Atlantic. Shower chances exist,
especially over the southern half of the CWA. The severe threat
should be limited given the stability on the northern side of
the front.
As an upper level ridge of high pressure builds across the SE-US
Monday, the aforementioned frontal boundary will move northward
across the Mid Atlantic. The front will linger nearby as a
stationary front through Wednesday providing the opportunity for
showers and thunderstorms. Temperatures will slowly moderate through
midweek.
Tropical Depression Fred (see hurricanes.gov for the latest official
forecast) could also impact the region next week. While the track of
Fred remains uncertain, should Fred track towards the local area,
the influx of tropical moisture combined with the stalled frontal
boundary could be hydrologically problematic. However, since most
locations west of the Blue Ridge are in the abnormally dry or
moderate drought category (see drought.gov for details), this rain
could be beneficial if it falls over the course of several days and
not in a short period of time.
&&
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
Prevailing VFR conditions are through tonight. While similar
conditions are likely on Friday and Saturday, terminal
restrictions are possible given scattered afternoon and evening
thunderstorms each day.
MVFR conditions are possible in any showers Sunday and Monday,
though VFR conditions should dominate. MVFR conditions are most
likely across southern terminals such as CHO. There could also be
brief reductions in vsbys due to low clouds/fog each morning.
&&
.MARINE...
Sub-SCA level winds are expected through Saturday. SMWs can`t
be ruled out each afternoon and evening in association with any
thunderstorms. Expect a large uptick in areal coverage of
thunderstorms both on Friday and Saturday.
Winds are expected to remain below SCA criteria Sunday into Monday
with a stalled front nearby.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory from noon to 8 PM EDT Friday for DCZ001.
MD...Heat Advisory from noon to 8 PM EDT Friday for MDZ004>006-008-
011-013-014-016>018-503>508.
VA...Heat Advisory from noon to 8 PM EDT Friday for VAZ052>057-506.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...KJP
NEAR TERM...BRO/KJP
SHORT TERM...KJP
LONG TERM...CPB
AVIATION...BRO/KJP/CPB
MARINE...BRO/KJP/CPB
Area Forecast Discussion
National Weather Service Memphis TN
1044 PM CDT Thu Aug 12 2021
.UPDATE... /issued 800 PM CDT Thu Aug 12 2021/
We saw another hot/humid day across the Mid-South with high
temperatures topping out in the mid 90s. Heat indices have fallen
below 105F across the Mid-South and the Heat Advisory will be
allowed to expire as scheduled. A portion of the Mid-South may
again need a Heat Advisory on Friday, but outflow and anticipated
convective activity will be a fly in the ointment so we`ll let the
next shift make that call.
Scattered thunderstorms developed across north MS this afternoon
and will continue to diminish over the next hour or two. This
will result in dry weather south of I-40 overnight. Some patchy
fog will be possible, mainly in areas that picked up rainfall
today. Looking up to our north, widespread convection is ongoing
across MO/IL and will continue to sink south this evening. The
HRRR has finally picked up on this the past few runs and does
bring this activity as far south as I-40 just after midnight.
Mesoanalysis of the convective environment suggests that
instability will remain fairly substantial this evening despite
some surface cooling. While CIN will increase, we do anticipate
this convection holding together long enough to warrant PoPs
through the early morning hours. That said, this activity will be
weakening and the severe weather threat is limited within the
CWA.
Outflow from any overnight convection and convergence along a weak
surface trough will support scattered showers and thunderstorms
Friday. Convection will likely redevelop during the mid/late-
morning hours and spread south during the afternoon. Ample
instability will be in place tomorrow, but deep-layer shear will
remain weak. An uptick in bulk shear during the evening hours
could promote a bit more organization, but a marginal risk appears
quite sufficient. Given the weak shear, downburst winds will be
the primary concern with tomorrow`s convection.
MJ
&&
.DISCUSSION... /issued 306 PM CDT Thu Aug 12 2021/
Temperatures are currently in the mid 90s with heat indices into
the mid 100s. Heat Advisory remains in effect until 8PM tonight.
Temperatures will cool slightly into the low to mid 70s overnight.
Showers and storms are beginning to pop up all over northeast
Mississippi. These should die off with sunset.
A cold front that is currently draped across the Great Lakes though
the Midwest will slowly start to drop into our area tomorrow, which
will be the focus of our weather. We are in a marginal risk for
severe storms tomorrow mostly for west Tennessee, Missouri Bootheel
and northeast Arkansas. It will still be a hot day across most of
the area. Heat indices will be in the low 100s. A heat advisory may
be needed for some portions of northern Mississippi however
confidence is not high enough to issue one at this time.
The cold front should be out of here by early Sunday morning. We
then return to the typical summertime pattern for the rest of the
week, with one notable exception, the temperatures. Temperatures
will be in the upper 80s and low 90s with no heat advisory concerns
for the better part of next week. Diurnal showers and thunderstorms
are possible each day.
SMW
&&
.AVIATION...
06Z TAF Set
Convection continues to move south through Southern Missouri.
Expect KJBR to be impacted over the next couple of hours. KMEM and
KMKL could as well, but will depend on how long the line holds
together. Converted VCSH to VCTS at both KMKL and KJBR and added
a TEMPO group as well for KJBR for the convection. Winds will
definitely switch around to the NNW behind a gust front coming off
of the convection. Added a tempo for the temporary switch in
northerly winds at KJBR, KMEM, and KMKL. Convection will redevelop
during the day along old outflow boundaries. Moved up timing of
VCTS at all TAF sites, but still too much uncertainty in regards
to timing to introduce any TEMPO groups. Expect another brief wind
switch to the north behind the convection during the afternoon
but left mention out of TAFs for now. Winds will become light and
variable after 00Z. Fog development could begin to occur near the
end of TAF period, but left mention out for now.
KRM
&&
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Melbourne FL
1019 PM EDT Thu Aug 12 2021
.UPDATE...
Wet weather along the Treasure Coast from increased moisture
advecting up from the Bahamas largely hasn`t materialized as of
around 10pm. However, the HRRR still holds out hope for increased
shower and thunderstorm activity occurring just offshore/along
the coast overnight, so have maintained a chance of showers and a
slight chance of thunderstorms through the early morning hours
there. Otherwise, expecting mostly dry conditions across much of
the area, as activity continues offshore. Lows overnight in the
mid 70s, with coastal areas remaining in the upper 70s thanks to
easterly flow.
Friday-Saturday (previous)...Rain chances will increase tomorrow
into the weekend as Tropical Depression Fred heads towards
Florida. Deep tropical moisture associated with the system will
move into South FL on Friday, then spread across Central FL over
the weekend. Rain chances will increase significantly tomorrow,
and remain high into Sunday. Widespread showers and scattered
lightning storms are forecast each afternoon, with activity
diminishing a bit overnight. Temperatures will stay warm with
highs in the mid 80s to low 90s and lows in the mid 70s.
Heavy rainfall leading to localized flooding will be the main
threat in east-central FL from Tropical Cyclone Fred, from Friday
afternoon through early Monday. The heaviest rainfall is forecast
along the Treasure Coast and Okeechobee County where widespread
amounts of 4-6 inches are possible, with isolated higher amounts.
Further north, widespread amounts of 2-3 inches are possible,
with isolated higher amounts. Volusia County is likely to see the
least amount of rain, with widespread amounts of 1-2 inches
possible. A Flood Watch may need to be issued for parts of the
area this weekend, most likely for the southern areas. Residents
and visitors should stay informed on the latest information from
the National Hurricane Center and NWS Melbourne.
&&
.AVIATION...
VFR conditions expected outside of convective activity through the
TAF period. Showers and isolated thunderstorms will continue
overnight offshore and may drift onshore, especially during the
early morning hours. Highest chances are along the Treasure Coast;
However, have included VCSH overnight for coastal terminals from
TIX southward. Then, scattered to numerous showers and
thunderstorms expected on Friday afternoon. But, persistent
easterly flow will keep a majority of activity on the western half
of the peninsula.
&&
.MARINE...
Scattered showers and isolated thunderstorms continuing through
the overnight hours, especially along the Treasure Coast, some of
which may affect the Intracoastal waters. Main threats with any
storm will be frequent lightning, gusty winds, and heavy rainfall.
Otherwise, easterly flow continuing at around 8-12kts overnight.
Seas 2-4ft.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 77 89 77 88 / 10 40 40 80
MCO 76 91 77 89 / 10 60 30 80
MLB 78 88 77 88 / 20 50 50 80
VRB 77 89 75 85 / 30 50 60 80
LEE 76 93 77 90 / 10 60 20 80
SFB 76 90 76 89 / 10 50 30 80
ORL 77 90 77 89 / 10 60 30 80
FPR 76 88 75 86 / 40 60 60 80
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Leahy/Negron
Area Forecast Discussion
National Weather Service Portland OR
223 PM PDT Thu Aug 12 2021
.SYNOPSIS...High pressure over the region will lead to a continuation
of the excessive heat and dry conditions through Saturday.
Temperatures will begin to cool over the weekend before a weak storm
system will brush the region Monday bringing with it much cooler
temperatures areawide early next week and a chance for light rain
across the north.
&&
.SHORT TERM...Tonight through Sunday...Water vapor satellite imagery
this afternoon reveals an elongated area of high pressure over the
northeast Pacific stretching east-southeastward into the Pacific
Northwest. Models are in good agreement this area of high pressure
will shift more squarely over the Pacific Northwest today before
gradually consolidating over the Great Basin Friday into Saturday.
This will result in near record high temperatures today and Friday in
the Willamette Valley. Expect high temperatures to once again top out
in the 100-105F range today and Friday.
Lowering 500mb heights over the weekend will allow marine air to
filter into more of northwest Oregon and southwest Washington. This
should result in temperatures cooling, but temperatures will still
remain hot in the Willamette Valley and Columbia River Gorge.
Fortunately, they will not be record setting and should end up much
closer to the 90F mark by Sunday vs. the 100F.
As the flow aloft turns more southerly over the next 48 hours with
high pressure consolidating over the Great Basin, we will see more
moisture and instability ride northward up the Cascades. At this
point, it generally appears the best instability and moisture will
remain well east of the Cascade crest. Have maintained a slight
chance mention of showers and thunderstorms near Willamette Pass
Friday afternoon and evening, but the latest global and high
resolution model guidance suggests storms will remain south and east
of the Willamette NF, but cannot completely rule it out given the
pattern. Shower and thunderstorm chances have diminished Saturday as
compared to 24 hours ago.
Finally, the HRRR smoke model does suggest some smoke near the
surface will make it into the Columbia River Gorge and the Portland
metro late this afternoon. The actual smoke does seem to be lagging a
bit behind what the HRRR smoke model suggests. Nonetheless, smoke has
clearly made it the area between The Dalles and Arlington based on
web cameras. With easterly winds being observed at Middle Mountain
and Three Corner Rock RAWS, some of this smoke is still on track to
spread into at least the Columbia River Gorge and possibly the
eastern portion of the Portland Metro late this afternoon and
evening. Between at least some of this near surface smoke filtering
into the region and smoke aloft spreading across the area, we are
likely to see one of our hazier, if not our haziest evening of the
summer.
Smoke has also pushed into the Eugene/Springfield area today from the
nearby wildfires burning in eastern Lane and Douglas Counties.
Originally thought northwesterly winds this afternoon would help to
clear out the smoke at least temporarily in the Willamette Valley,
but this has yet to happen and time is running out quickly. As a
result, not expecting a noticeable improvement in smoke across the
southern Willamette Valley. In fact, conditions may deteriorate
further later on tonight into Friday as additional smoke drifts down
the Willamette and McKenzie River Valleys into the southern
Willamette Valley. /Neuman
&&
.LONG TERM...Sunday night through Thursday...Models are in good
agreement the area will see major relief from the heat no later than
Monday as a weak upper level trough moves across the Pacific
Northwest. This will result in a weak front dropping southeastward
into southwest Washington and northwest Oregon Sunday night or
Monday. This appears likely to bring at least some light rain to the
south Washington and far north Oregon coast some time late Sunday or
Monday, but timing differences in exactly when it will arrive are
keeping 6 hour PoPs relatively low at this point. With even more
marine air spreading into the area during this time, smoke should
become increasingly confined to the immediate vicinity of ongoing
wildfires.
With onshore flow expected to continue into Tuesday, expect
temperatures to remain near to slightly below average. Thereafter,
more uncertainty begins to creep into the forecast. Most model and
ensemble guidance suggests shortwave ridging will begin to build back
over the northeast Pacific and Pacific Northwest. This would result
in a more pronounced warming trend while a smaller subset of the
model and ensemble guidance suggests weak upper level troughing will
persist over the region and keep temperatures near average for the
date. A blend of the model guidance results in the official forecast
leaning towards a warmer scenario. /Neuman
&&
.AVIATION...VFR flight conditions will continue across the area
through 00Z Saturday, aside from marine stratus returning to the
central OR coast this evening before potentially expanding up
the north OR coast between 06-12Z tonight. Sinking motion
associated with strong high pressure aloft should keep the marine
layer quite shallow with cigs/visibilities in the LIFR to IFR
range. The inland extend of the marine stratus deck will be very
limited tonight and skies will remain clear for all of the inland
TAF sites.
The exception to this is increasing wildfire smoke across
northwest OR and southwest WA from wildfires burning in the
region. At 21Z Thursday, near-surface smoke had moved
northwestward into the central and southern Willamette Valley,
reducing visibilities down to 4 SM at KEUG and 6 SM at KSLE. The
most dense smoke was occurring over the Lane County Cascades and
Foothills where fires continue to burn. Elsewhere, hazy skies
were being observed due to smoke at upper levels of the
atmosphere. Satellite observations at 21Z also showed an area of
surface smoke being produced by a fire burning to the east of
Mount Rainier, moving southward into the Columbia Basin. If east
winds kick in through the Columbia Gorge, then some of this smoke
would be able to push into Clark County and the northern
Willamette Valley. That said, it appears winds will remain
onshore and keep near-surface smoke out of the north valley
through tonight and into tomorrow. Forecast confidence is not
high in regards to the overall smoke forecast and how much
visibilities will be impacted at the surface.
For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse
KPDX AND APPROACHES...VFR flight conditions will prevail through
00Z Saturday. Visibility reductions down to 6 SM will be possible as
near-surface smoke pooling in the Columbia Basin attempts approaching
the KPDX terminal this evening, but it appears winds will remain
onshore and keep surface smoke out of the north valley for now.
-TK
&&
.MARINE...Weak surface low pressure will remain offshore through
this weekend, bringing a southerly flow regime to the coastal
waters. Southerly winds should remain relatively light with
sustained winds speeds generally around 10 kt or less through
this weekend. A weak front is expected to push across the waters
early Monday morning, 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 waters with conditions a bit less breezy for the
northern waters. Small craft winds up to 25 kt will be possible
over the central waters Tuesday through Thursday during the
afternoon and evening hours each day.
Aside from winds, a northwesterly swell around 7 to 8 ft at 11
seconds will continue through tonight before decreasing to 5 to 6
ft tomorrow. This trend should then continue through the weekend
before building back to 7 to 8 ft late Monday into Tuesday. -TK
&&
.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 from 11 AM to 10 PM PDT Friday for Mt. Hood
National Forest West of Cascade Crest-North Oregon Coast
Range.
Red Flag Warning until 10 PM PDT Friday 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 from 11 AM to 10 PM PDT Friday for Eastern
Gifford Pinchot National Forest Mt Adams Ranger District-
Extreme South Washington Cascades and Foothills.
PZ...Small Craft Advisory until 10 AM PDT this morning for Columbia
River Bar.
&&
$$
Area Forecast Discussion
National Weather Service Riverton WY
515 PM MDT Thu Aug 12 2021
.SHORT TERM...This evening through Friday night
Issued at 235 PM MDT Thu Aug 12 2021
The short-term forecast is quiet for the most part. Northwest flow
continues to dominate the pattern through tomorrow night, with not
much to discuss in terms of disturbances along the flow. Today will
be cooler than yesterday by 5 to 10 degrees. Unfortunately, the
relief from the heat will only be a brief tease that will last today
and tomorrow. Temperatures will increase for the weekend once
again, as the ridge slowly shifts eastward and settles more over
the region. More on this in the extended forecast.
Models continue to be on the dry side in terms of convective
activity across the region through the next two days. Decreased PoPs
for today with one caveat, which is a signal in several CAMs
including the HRRR for a possible brief shower forming off the
southern Bighorns and moving across Natrona County after midnight
tonight. Models are also hinting at possible weak convection over
the Wind Rivers, Absarokas, and Bighorns beginning this afternoon
and continuing overnight. Overall though, these will be very weak
and brief if they do form and will stay over the mountains.
Tomorrow, will be a very similar situation, with low PoPs to account
for the possibility of some weak convective development during the
afternoon and evening. With the ridge ever so slowly pushing
eastward, Friday will see perhaps better chances of showers, again
focused over the mountains, but it would be only marginally better
than today.
Fire weather concerns will be mostly kept to a minimum due to light
winds and seasonal temperatures and little to no chance of lightning
despite continued dry weather and near critical relative humidity
especially across the south.
.LONG TERM...Saturday through Thursday
Issued at 235 PM MDT Thu Aug 12 2021
Northwest flow aloft transitions to low-amplitude ridging this
weekend. Increasing heights allow toasty afternoon temperatures,
with highs about 5 to 7 degrees above average. The jet stream is not
far removed to the north during the weekend, so a few transient
vorticity maxima could aid in providing the lift necessary for
isolated to scattered showers and thunderstorms. These would mainly
be confined to the terrain, as models don`t currently show any
organizing feature.
Monday will be a transition day as a deep longwave trough moves over
the Pacific Northwest. Temperatures remain mid-summer-like east
of the Divide, with low to mid 90s expected. Slightly cooler
conditions are forecast west of the Divide where geopotential
heights begin to fall. In addition, thunderstorm chances increase,
especially for the western mountain ranges of Wyoming. Deep
mixing and higher wind speeds in the middle atmosphere could make
the afternoon a bit more breezy (gusts 20 to 30 mph). This could
increase fire danger; however, humidities currently look to remain
in the upper teens to lower 20 percent range, and this may be a
mitigating factor.
As the trough continues to march eastward, temperatures cool down
significantly Tuesday into the middle of the week. Highs in the
60s are likely for Yellowstone, with 70s in most other valleys and
basins. Winds and humidity continue to increase with an
increasing pressure gradient and more widespread cloud cover. Many
locations, including basins, have a better chance for rain
showers due to widespread synoptic lift associated with the
trough.
&&
.AVIATION...For the 00Z TAFS through 00Z Saturday
VFR conditions and mostly clear skies are expected over the next
24 hours. Other than afternoon gusts in the 15 to 20 kt range,
winds remain light and mainly terrain-driven (upslope during the
afternoon and downslope overnight). Very isolated thunderstorms
are possible over the terrain this evening, but a vast majority of
locations remain dry.
&&
.FIRE WEATHER...
Issued AT 235 PM MDT Thu Aug 12 2021
Slightly cooler air has filtered into the region from the north
last night, leading to higher RH values this afternoon. Winds
this evening into Friday morning remain light with decent humidity
recovery. Friday into the weekend will see temperatures warm and
humidities fall. Winds are not forecast to be overly strong, as a
ridge of high pressure keeps the pressure gradient weak, but
afternoon RHs will drop into the low teens for lower elevations,
especially on Sunday. Terrain-focused thunderstorms remain very
isolated through Saturday, eventually becoming slightly more
widespread on Sunday afternoon. Rain chances, winds, and
humidities increase throughout the first half of next week, when a
large trough moves across the Rockies.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Fisher
LONG TERM...VandenBoogart
AVIATION...VandenBoogart/LaVoie
FIRE WEATHER...VandenBoogart
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
821 PM EDT Thu Aug 12 2021
.UPDATE...
It has turned out to be a rather stormy evening with several Severe
Thunderstorm and Special Marine Warnings issued. Heavy rainfall has
also been occurring with some of the stronger, slow moving storms
with some areas receiving over 2 inches so far. Most of the activity
has moved over the eastern gulf and will continue to taper down over
the next few hours. Made some tweaks to POPs to reflect current
radar trends and HRRR guidance.
Tropical Depression Fred remains off the northeast coast of Cuba
moving slowly to the west-northwest. TD Fred is still very
disorganized this evening with most of the convection displaced to
the south and east of the center. The National Hurricane Center is
still forecasting the storm to move just north of Cuba later tonight
into Friday, then into the eastern Gulf of Mexico on Saturday and
Sunday. Continue to follow the latest updates from the National
Hurricane Center on this storm.
&&
.AVIATION...
Some strong storms rolled through the terminals this afternoon and
evening producing gusty winds and heavy rainfall. Most of the storms
have cleared out so will hold VCTS only through 01Z and VCSH through
04Z, then VFR expected overnight. Similar conditions expected
tomorrow with continued easterly flow. Will hold VCTS once again
tomorrow starting between 17-19Z.
&&
.MARINE...
High pressure ridging over Florida and into the Gulf of Mexico will
keep a predominant easterly wind flow around 10-15 knots over the
eastern gulf through early Saturday morning. At that time, Tropical
Depression is expected to strengthen back to Tropical Storm strength
and move north-northwestward through the eastern Gulf of Mexico.
Conditions will rapidly deteriorate from south to north late
Saturday and Saturday night with Tropical Storm conditions possible
until late Sunday night or early Monday. Mariners are urged to check
the latest forecasts from the National Hurricane Center before
heading out this weekend.
&&
.Preliminary Point Temps/PoPs...
TPA 78 93 78 91 / 50 60 20 80
FMY 76 93 77 88 / 30 70 30 80
GIF 76 91 76 88 / 20 60 20 90
SRQ 76 91 76 89 / 60 60 30 80
BKV 71 92 73 90 / 50 50 20 90
SPG 79 91 79 89 / 60 50 20 80
&&
Sea Breeze Thunderstorm Regime For Today: 3
Sea Breeze Thunderstorm Regime For Tomorrow: 3
For Additional Information On Sea Breeze Regimes go to the link below
https://www.weather.gov/tbw/ThunderstormClimatology
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.
&&
$$
UPDATE/AVIATION/MARINE...74/Wynn
UPPER AIR...19/Hurt
DECISION SUPPORT...18/Fleming
Area Forecast Discussion
National Weather Service Tulsa OK
922 PM CDT Thu Aug 12 2021
...UPDATE...
.DISCUSSION...
Scattered convection continues across far southwest MO into
southeast KS. Based on current movement and recent HRRR output,
have introduced low PoPs into parts of far northern OK and
northwest AR a bit earlier than previously forecast.
&&
.PRELIMINARY POINT TEMPS/POPS...
TUL 77 96 72 89 / 20 30 40 60
FSM 77 97 74 90 / 0 30 30 60
MLC 76 96 72 90 / 0 20 20 60
BVO 73 93 70 87 / 20 40 40 50
FYV 73 93 68 86 / 20 40 40 60
BYV 74 93 70 86 / 20 50 50 50
MKO 76 96 72 88 / 10 30 30 60
MIO 73 92 70 88 / 20 50 50 40
F10 75 97 71 90 / 0 30 30 60
HHW 75 96 74 93 / 0 10 20 50
&&
.TSA WATCHES/WARNINGS/ADVISORIES...
OK...None.
AR...None.
&&
$$
SHORT TERM...18