Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/18/23
Area Forecast Discussion
National Weather Service La Crosse WI
1026 PM CDT Thu Aug 17 2023
.DISCUSSION...(Tonight through Thursday)
Issued at 215 PM CDT Thu Aug 17 2023
Key Messages:
- Air Quality Advisories for Wisconsin counties from
Canadian Wildfire Smoke Resulting in Increased
Particulate Matter.
- Period of hot weather builds in starting this weekend,
but may not be extreme or need heat related headlines.
Tonight and Friday: Weakening winds and smoke impacts
Almost a touch of fall in the air in wake of mid level trough today
with diurnal statacu field, blustery northwest winds, and even a few
sprinkles. This will all fade going into tonight as gradient relaxes
and skies clear.
Smoke concentrations do not seem as high as previously thought
perhaps due to better mixing in wake of trough. As winds relax
tonight could start to see some of that impact but confidence is
waining in surface restrictions. Both RAP/HRRR do hint at another
wave of elevated, thicker smoke tomorrow which could be noticable.
Those details might need to be worked out in near-term given
distance from source region.
Saturday through Thursday: Period of warm / hot weather
Period of warmer temperatures still on track starting this weekend.
Center of large upper high seems to be trending a bit south
southwest which might hold temperatures back a category and increase
possibility of at least convective debris clouds from time to time.
Nonetheless, still very warm to hot, with NAEFS standard anomalies
of +2 to +3 from Sunday on. Closer examination of 925mb temperatures
also suggests most areas seeing highs in the lower to mid 90s with a
reduced risk of needing heat related headlines. Day to day subtle
differences could still lead to a day or two pushing records with
heat indicies approaching 100. While spread widens in medium range
ensembles, various members hint at Tuesday being the warmest as of
17.00z and 17.12z solutions.
Assuming ridge is strong enough to keep convective threat well north
through most of the period, dry forecast will continue. Ridge begins
to break down or weaken in latter half of next week which would not
only cool things down /closer to normals/ but also increase
convective threats.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1026 PM CDT Thu Aug 17 2023
Mainly VFR conditions expected through the period with light
winds overnight increasing out of the south Friday at 10 to 15
kts. However, brief IFR fog or stratus remains possible at KLSE
early Friday. RAP soundings show winds just off the surface of 15
to 20 kts until near sunrise, so confidence for fog is low,
despite light surface winds, but a short period of IFR stratus
could not be ruled out. Otherwise, smoke from Canadian wildfires
will lead to a milky sky at times, although chances for any near
surface impacts appear low.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...Shea
AVIATION...JM
Area Forecast Discussion
National Weather Service Boston/Norton MA
1008 PM EDT Thu Aug 17 2023
.SYNOPSIS...
Showers and thunderstorms are on tap for Friday with a warm front in
the morning followed by cold front approaching from the west during
the afternoon. A few of the storms may become severe and also
produce brief torrential rainfall and localized flooding. Then
dry, less humid weather returns Saturday, along with some
sunshine. Turning warmer and more humid Sunday into Monday. The
next chance for showers and thunderstorms arrives sometime late
Monday into Monday night. Turning slightly cooler and drier
through the middle of next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
10 PM...
Warm front remains south of 40N per SSW winds and dew pt of 75
at buoy 44066. As the Great Lakes trough takes on a negative
tilt and increases cyclonic flow across NE and New England, this
will capture the warm front begin to lift this boundary
northward. Patchy dense fog currently at BID, MVY and GHG will
become more widespread overnight. This will likely impact the
morning commute to a certain extent.
Lines of convection currently across western-central PA/NY will
advect into western New England around daybreak per hi res
guidance. Brief torrential downpours and potentially a few
strong storms will impact the morning commute, especially the
latter half across CT into western-central MA. These storms will
traverse eastward into the I95 corridor of RI and eastern MA
around midday Friday. Previous forecast captures these details
nicely, thus no changes with this update. Earlier discussion
below.
4 PM Update...
Key Points...
* Cluster of showers may graze areas near the Cape/Islands into the
evening, just a few showers elsewhere
* Areas of fog tonight & it may become locally dense along the coast
Details...
The main issue late this afternoon and evening was a shortwave
lifting northeast off the mid-Atlantic coast. This was increasing
the forcing for ascent and a cluster of showers that may graze
areas near the Cape and Islands. The bulk of this activity
should occur by the mid evening with mainly dry weather thereafter.
Otherwise...a bit of marginal instability may result in a few
diurnally driven spot showers across the interior but those should
dissipate this evening. After any isolated diurnal activity across
the interior dissipates and any activity exits the Cape
Islands...mainly dry weather is anticipated for most of tonight.
However...the threat for showers & t-storms will increase near
daybreak as the forcing for ascent increases ahead of a cold front.
The other issue tonight will be the development of areas of
fog...some of which may become locally dense along the coast and the
high terrain of the Worcester Hills. High pressure over the eastern
Canadian Maritimes will continue to result in moist/light onshore
easterly flow level flow. Given dewpoints in the 60s and the cooling
boundary layer...areas of fog should expand during the evening and
overnight hours. And some of this fog may become locally dense, so
later shifts will have to keep a close eye on this potential.
Overnight lows should bottom out mainly in the 65 to 70 degree
range...but it will be muggy.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Key Points...
* Showers & t-storms Fri AM & afternoon a few of which may
become severe but not expecting a widespread outbreak
* Brief torrential rainfall may result in localized street flooding
* Any lingering showers & storms come to an end during the first half
of Friday evening with cooler/less humid weather Fri night
Details...
Friday...
The main concern will revolve around the potential for a few severe
thunderstorms Friday morning and afternoon with the main risk being
localized damaging wind gusts. We will break things down more below.
Showers & thunderstorms should overspread the region Friday morning
as a warm front increases the forcing for ascent. Another round of
scattered showers & thunderstorms are expected during the afternoon
in association with the actual pre-frontal trough/cold front. Given
the early start to the activity...diurnal heating will be limited
and with initially poor mid level lapse rates will be a hindrance
to widespread severe weather. That being said...surface dewpoints
rising into the upper 60s to the lower 70s will be enough to
generate 750 to 1500 J/KG of Cape. The most favorable parameter we
have is strong fall-like effective shear on the order of 40 to 50
knots. The majority of those wind fields are aloft as the GEFS
indicates a 500 mb jet 3-4 standard deviations above normal. Down at
the 850/925 mb layer it is more on the order of 20 to 30 knots. The
NAM/HREF and HRRR do show some modest updraft helicity swaths with
this activity. In addition...there are at least some low severe
weather probabilities indicated from the Colorado Machine Learning
Probs and the CIPS Analogs. The strong wind fields/forcing will
compensate some for the lack of instability...but thinking that the
and the timing will prevent this from being a widespread severe
weather event but more of an isolated/localized risk. The second
round of activity with the pre-frontal trough/cold front during the
afternoon will have somewhat better mid level lapse rates arriving
especially across the interior...so that will be our greatest time
of seeing hail with the activity. However...this will be a
relatively short window before too much dry air works into the
region.
In a nutshell...a few severe thunderstorms are possible Friday
morning and afternoon with the main risk being localized damaging
wind gusts and perhaps some hail with the second round given colder
temps aloft/steepening mid level lapse rates during the afternoon.
Low risk of a brief tornado if a secondary meso-low can induce a
triple point and enhance 0-1 KM helicity...mainly during the
morning/early afternoon hours.
The other concern will be the potential for brief torrential
rainfall and localized urban street flooding. Pwats between 1.5 and
2 inches coupled with very strong jet dynamics/forcing will bring
the potential for brief torrential rainfall and localized urban
street flooding. The fast moving nature of the activity may limit
this risk compared to other events that we have seen this
summer...but still needs to be watched.
High temps on Friday will mainly be in the upper 70s to the middle
80s...but it will be quite humid.
Friday night...
Any lingering scattered showers & t-storms should come to an end
during the first part of Friday evening as much drier air works into
the region from the west. Overnight low temps should bottom out in
the middle 50s to the lower 60s by daybreak Saturday with less
humidity.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Highlights...
* Drying out this weekend into early next week with continued
seasonable temperatures.
* Next chance for unsettled weather comes late Monday/Monday Night,
but confidence is low.
Details...
Deep mid level low over southeast Canada should move northeast and
get absorbed into the longwave flow this weekend. This will combine
with a building ridge across the southern 2/3 of the USA to generate
a nearly zonal flow over the USA/Canadian border early next week.
This flow then morphs again into a broad longwave trough over the
North Atlantic towards the middle of next week. Have greatest
confidence in the details through about Monday, with confidence
diminishing through the rest of next week.
At the surface, southern New England is largely under the influence
of high pressure most of this portion of the forecast. Thinking the
greatest risk for showers will be ahead of a cold front sometime
late Monday into Monday night. Otherwise, expecting mainly drier
weather.
Near to slightly below normal temperatures expected during this
time, except for a brief period of slightly above normal
temperatures Monday.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight...Moderate Confidence.
IFR-LIFR conditions expected to spread from E to W. expecting
LIFR across just about all of southern New England by midnight,
either from low ceilings or areas of fog. Fog may be locally
dense. A few showers and perhaps an embedded TSRA this evening
and areal coverage may increase toward daybreak. Light ESE
winds.
Friday...Moderate Confidence.
IFR-LIFR conditions in low clouds and fog early should improve
to mainly MVFR-VFR ceilings by early afternoon, outside of any
showers and t-storms. It appears we may have one round of
showers and t-storms in the morning, with potentially another
in the afternoon. But, still too much uncertainty to give more
details on the timing. SE winds of 5 to 15 knots should shift to
the SW. Gusts of 20+ knots across the southeast New England
coast.
Friday night...High Confidence.
Any lingering MVFR conditions across the southeast New England
coast will depart early in the evening. Otherwise, VFR
conditions with WSW winds 5 to 10 knots.
KBOS TAF...High confidence in trends. Moderate confidence in
timing.
KBDL TAF...High confidence in trends. Moderate confidence in
timing.
Outlook /Saturday through Tuesday/...
Saturday: Mainly VFR, with local MVFR possible. Breezy.
Saturday Night through Sunday Night: VFR. Breezy.
Monday through Monday Night: VFR. Slight chance SHRA.
Tuesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High Confidence.
Pressure gradient will remain weak enough tonight to keep
winds/seas below small craft advisory thresholds. Main issue
will be areas of fog continuing to develop some of which may
become locally dense. Showers and isolated t-storms will also
impact mainly our southeast waters this evening.
Friday and Friday night...High Confidence.
Long southerly fetch on Friday should result in marginal Small
Craft Advisory seas developing across our southern waters on
Friday, and persists into Friday night. Southerly winds Friday
should turn more westerly Friday night behind a cold front, but
marginal Small Craft Advisory seas may persist for much of the
night from the leftover swell. Areas of fog along with showers
and t-storms on Fri should exit the region Friday evening
behind a cold front.
Outlook /Saturday through Tuesday/...
Saturday: Winds less than 25 kt. Seas up to 5 ft.
Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.
Sunday through Sunday Night: Winds less than 25 kt.
Monday through Monday Night: Winds less than 25 kt. Slight
chance of rain showers.
Tuesday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from noon Friday to 4 AM EDT Saturday for
ANZ235-237.
Small Craft Advisory from 7 AM Friday to 8 AM EDT Saturday for
ANZ254>256.
&&
$$
SYNOPSIS...Belk/Frank
NEAR TERM...Belk/Frank/Nocera
SHORT TERM...Frank
LONG TERM...Belk
AVIATION...Belk/Frank
MARINE...Belk/Frank
Same sentiments as previous forecast discussions still apply.
UPDATE Issued at 645 PM CDT Thu Aug 17 2023
Adjusted sky coverage to account for next batch of smoke aloft
expected to move into the area this evening from wildfires within
the northwest CONUS. Latest guidance from RAP and HRRR keep smoke
aloft generally over the area throughout tomorrow within the mid
to upper flow of the building ridge aloft to our south/southeast.
Still thinking near surface smoke will start to mix and/or advect
out of our area as the surface ridge pushes east and daytime
mixing quickly commences.
Looking into wind potential tomorrow a bit more, the southern Red
River Valley may hold a locally higher chance at meeting wind
advisory criteria, mainly in the morning.
This is based on experience of terrain affects from the Red River
Valley aiding in locally higher winds within the southern Red
River Valley (including Fargo- Moorhead metro) via downsloping
and/or increased mixing. Many forecast soundings show low level
jet winds around 40 kt just above the morning inversion as daytime
heating/mixing commences generally starting around 7 am CDT. Any
subtle increase in mixing would easily tap into this low level
jet.
That being said, notable veering winds with height near the
inversion may interfere with transfer efficiency to the surface.
Thus the expectation in the southern Red River Valley is for
southerly winds to quickly become windy at around 25-35 mph in the
morning as early as 7 am CDT, with sporadic gusts to 40-45 mph
possible. Deeper daytime mixing toward midday and afternoon may
suppress wind gusts somewhat, more in the 35-40 mph range.
Other areas within the Red River Valley may also see local
enhancement of winds similar to the aforementioned magnitude,
again due to terrain influences. Confidence is less compared to
the southern Valley, however.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 314 PM CDT Thu Aug 17 2023
Smoke as well as how high the heat and winds will go tomorrow are
the primary issues for the period.
Northwesterly flow aloft will give way to ridging overnight. The
surface high will move to the southeast, with southerly winds
picking up late in the night. HRRR has the near surface smoke
currently along the Red River Valley into MN pushing eastward this
evening. By morning, think that much of the near surface smoke
will be mixed out by the southerly winds or pushed out of the
area. Air quality alert continues but MPCA has toned down the
levels a bit. Southerly winds will continue to pick up through
the day tomorrow as a surface trough over western ND develops.
BUFKIT soundings have the mixed layer getting into the 25 to 35 kt
range. Probabilities of getting above 22 kts from the NBM are high
(75 to 100 percent), but much less for over 34 kts for max winds.
Could flirt with wind advisory criteria in a few places, but for
now will keep it around or just below.
The strong southerly winds will also bring some warm air
advection. Temperatures are expected to rise back into the 80s
across most of the area, with dew points also increasing. Warm and
humid conditions will still be below our heat advisory criteria.
There are a couple of ridge riding shortwaves moving through
Canada during the period. No precip expected for us, but some
clouds could move in as a trough axis moves into the Central and
Eastern Plains.
.LONG TERM...(Saturday through Thursday)
Issued at 314 PM CDT Thu Aug 17 2023
Saturday through Monday...West to southwesterly flow aloft will see
heights rise as upper ridging builds over the Central Plains for the
end of the weekend into Monday. There is decent agreement on some
fairly toasty air out ahead of a cold front on Saturday, with a few
model solutions putting 925mb temps into the 30s C. Dew points will
also be pooling out ahead of the front, and muggy, hot conditions
will be probable. NBM probabilities of over 90 degrees are in the 50
to 80 percent range across our southern counties for Saturday. At
this point, think we will stay below heat advisory criteria but much
will depend on the exact timing of the front. Temps will be knocked
back quite a bit on Sunday behind the front, although there could be
some precipitation chances from a ridge riding shortwave, at least
in our northern counties. Another ridge rider lifts up into Ontario
on Monday, with a frontal boundary lifting back into the CWA. Some
precipitation chances for Sunday into Monday, although probabilities
of over a tenth of an inch are not high (less than 30 percent).
There is a wet signal in the ensembles, but both the GEFS and ECMWF
M-climate percentiles have it all north and west of our counties.
Tuesday through Thursday...Upper ridging amplifies a bit and the
heat returns to much of our area. However, there is still a lot of
spread in the ensembles with some solutions not bringing the heat as
far north as some of the others. A general warmer than average trend
that the NBM shows seems reasonable at this point. Precipitation
chances look even less impressive than the first part of the period.
There is signs for heights to come back down towards the end of the
week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 645 PM CDT Thu Aug 17 2023
VFR conditions are expected throughout the TAF period, however
there is hazardous weather in the forecast, mainly from smoke and
gusty southerly winds.
Near surface smoke will continue to create minor vsby reductions
through 12 UTC, especially within Minnesota. Additional,
potentially dense smoke from wildfires in the northwest United
States will stream into the Dakotas and Minnesota tonight through
Friday, although this is forecast to remain aloft.
Gusty southerly winds are likely to develop over the area starting
after 09 UTC Friday morning, lasting until around 00-03 UTC Friday
evening. Winds up to 20-35 kt are forecast at all sites, mainly
during the daytime, with highest winds in this range expected
within the Red River Valley including KFAR, KGFK, and KTVF. KFAR
and KGFK may see gusts exceed 40 kt at times, generally between
12-21 UTC Friday morning into afternoon.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...CJ
SHORT TERM...JR
LONG TERM...JR
AVIATION...CJ
Area Forecast Discussion
National Weather Service Flagstaff AZ
145 PM MST Thu Aug 17 2023
.SYNOPSIS...Deep tropical moisture will overspread western Arizona
Friday. This will lead to increased chances for heavy rain and flash
flooding, primarily west of I-17 and highway 89 from Flagstaff to
Page. As a result, a flood watch is in effect for most of Coconino
and Yavapai counties Friday afternoon and evening.
As Hurricane Hilary moves north along the Baja Peninsula Saturday,
Sunday, and Monday, the heavy rain should shift westward towards
Nevada and California. Arizona will still have chances for
afternoon thunderstorms during the weekend. A monsoonal pattern
will then develop over the southwestern United States Tuesday
through Thursday, with typical daily thunderstorm chances
returning to the forecast by mid-week.
&&
.DISCUSSION...A monsoonal pattern will continue across Arizona
through tonight. Diurnal convection across the Mogollon Rim, Chuska
Mountains, and Bradshaw Mountains should dissipate later this
evening with the loss of daytime heating. The main impact will be
localized flooding under the heaviest storms.
For tonight, the hi-res models were indicating a nocturnal MCS over
the desert valleys moving north into Yavapai and Coconino counties
after midnight. However, the latest HRRR and other CAMs no longer
prog this feature to develop. As a result, lowered PoPs a little
over the favored areas later tonight, but kept the mention in the
forecast for now.
Deep tropical moisture ahead of Hurricane Hilary should arrive over
northern Arizona Friday. Given the persistent monsoonal pattern in
place, think the deeper moisture will raise the likelihood for more
widespread thunderstorms Friday afternoon, increasing the threat for
flash flooding. The area of greatest moisture and instability will
be over Coconino and Yavapai counties. There, a flood watch has been
issued for the aforementioned area.
As Hurricane Hilary lifts north along the Baja Peninsula Saturday,
Sunday, and Monday, the threat for heavy rain and flash flooding
should shift farther west, primarily affecting the areas along the
Colorado River near Nevada and California. Drier air will also
filter into eastern Arizona during the same time as high pressure
strengthens over the Central Plains.
Tuesday through Thursday, a monsoonal pattern should quickly return
over the southwestern United States. This should lead to a more
typical diurnal thunderstorm pattern over northern Arizona by mid-
week next week.
&&
.AVIATION...For the 00z TAF Package...VFR conditions will generally
prevail over northern Arizona through the TAF period. Brief MVFR/IFR
conditions and erratic wind gusts up to 40 knots will be possible
near storms early this evening. Thunderstorms should diminish
tonight. However, additional precipitation could impact KPRC-
KSEZ-KFLG-KGCN between 06z-12z tonight. Thunderstorms, heavy
rain, and TEMPO MVFR/IFR conditions will be possible over KPGA-
KGCN-KFLG-KSEZ-KPRC Friday afternoon. Aviation discussion not
updated for TAF amendments.
&&
.FIRE WEATHER...Friday and Saturday...Widespread thunderstorms with
heavy rain, gusty winds, and small hail is forecast Friday afternoon
and evening. The heaviest rain will be over Coconino and Yavapai
counties. The heavy rain chances will shift west on Saturday, with
drier conditions moving into Apache and Navajo counties.
Sunday through Tuesday...Thunderstorm chances will actually decrease
a bit over northern Arizona as Hurricane Hilary moves north along
the Baja Peninsula Sunday and Monday. Southerly wind gusts up to 35
mph will be possible Sunday, with 30 mph wind gusts on Monday. A
typical monsoon pattern (afternoon thunderstorms) returns to the
forecast by Tuesday.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Friday morning through Friday evening for
AZZ004>008-015-037-038.
&&
$$
PUBLIC...TM
AVIATION...TM
FIRE WEATHER...TM
For Northern Arizona weather information visit
weather.gov/flagstaff
Area Forecast Discussion
National Weather Service North Platte NE
644 PM CDT Thu Aug 17 2023
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 330 PM CDT Thu Aug 17 2023
Key Messages:
- Hot weather is likely Friday but a weak cold front will drift
into Nebraska Saturday and Sunday making temperature forecasts a
challenge.
- The forecast highs around 100F Monday through Wednesday continue
in place. A Heat Advisory may be needed in some areas during
this time.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 330 PM CDT Thu Aug 17 2023
The forecast Friday is leaning on the HRRR model for support; plus
the short term model blend for balance. The HRRR sharpens up the
dryline during the afternoon and fires off a cluster of
thunderstorms during the peak heating period.
The dryline should be near or just east of highway 83 late in the
afternoon. Highs in the low 100s are in place along and west of the
dryline; 90s to the east. Isolated thunderstorms are in place in the
super-mixed, super-heated air west of the dryline. The HRRR model is
probably overdone on coverage and POPs are limited to 20 percent for
this reason.
The RAP vertically integrated smoke product suggests very little
smoke aloft Friday and this suggests full sun and strong heating
will occur. The smoke, or haze, underway this afternoon should move
off east tonight.
A Heat Advisory is in place Friday afternoon and early Friday
evening across parts of swrn Nebraska and the Sandhills for heat
indices in the low 100s.
.LONG TERM...(Saturday through Thursday)
Issued at 330 PM CDT Thu Aug 17 2023
The NAM model shows a backdoor cold front dropping through nrn
Nebraska Saturday morning which reaches swrn Nebraska during the
afternoon. The attendant sfc low will be across scntl Nebraska and
this should focus the warmest temperatures across KS. Still, the
model suggest highs around 100F across ncntl and swrn Nebraska.
Later forecasts may include a Heat Advisory in these areas if dew
points warrant it.
This cold front is the result of fairly strong nrn stream dynamics
moving through Canada which set off convection across the nrn
Plains. If the model is correct, the front could be resting
stationary across the Sandhills Sunday afternoon and this would
limit highs across the north but 100F+ temperatures would continue
south of the front. The gist of all this model discussion is the
predictability of the heat wave this weekend and beyond will become
difficult if weak cold fronts drift into Nebraska. So, the location
of additional heat advisory or warning products Sunday and beyond is
uncertain.
Otherwise, there is little change in the extended forecast
philosophy. An upper level ridge of high pressure across the central
Rockies will build south tonight and then east into the srn Plains
Friday. The ridge will then build north and strengthen to near 600Dm
Sunday. The model consensus shows the ridge center near Kansas City
Monday and Tuesday followed by a slight drift south into the
Midsouth Wednesday and Thursday. The model consensus shows 15-17C
h700mb temperatures across wrn and ncntl Nebraska this weekend. This
supports highs in the 90s to low 100s. The GFS and ECM lower h700mb
temperatures to 15C Monday and hold them at 15C through Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 636 PM CDT Thu Aug 17 2023
VFR conditions will persist over the next 24 hours. There will be
some LLWS that moves in after midnight tonight with wind speeds
just off the surface around 40 kts. There will be some smoke aloft
which may result in some hazy skies, but smoke should not reach
the sfc and impact visibility.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 1 PM CDT /noon MDT/ to 8 PM CDT /7 PM MDT/
Friday for NEZ005-006-008-025-026-036-037-057>059-069>071.
&&
$$
SYNOPSIS...CDC
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Gomez
Area Forecast Discussion
National Weather Service Medford OR
858 PM PDT Thu Aug 17 2023
.DISCUSSION...The forecast was updated to cancel the Red Flag
Warning and Heat Advisory a few hours shy of their original
expiration. Also, the Air Quality Alert /PDXAQAMFR/ has been
updated to include Josephine and Jackson counties through 5 PM
Friday, and Klamath County through 8 PM Friday. Wildfire smoke
from a complex of fires in northwest California, including
western Siskiyou County, has spread into southern Oregon. Air
quality is expected to deteriorate in Klamath County overnight and
diminish in northern Lake County also. North to northwest winds
developing Friday afternoon are expected to bring improved air
quality, particularly in southwest Oregon.
Temperatures will continue to gradually trend lower into early
next week. Isolated to locally scattered thunderstorms (mainly in
the afternoon and evening) will continue each day into early next
week. Storms will gradually trend wetter, especially Monday and
Tuesday with the remnants of Hurricane Hilary possibly in the
region.
&&
.AVIATION...17/18Z TAFs...Complex TAF cycle coming up, but generally
speaking not the best flying conditions across the region; however,
categorically speaking, North Bend (KOTH) is the only site currently
in IFR. In fact, KOTH may go the entire cycle in IFR for low
ceilings given the added moisture in region today. Added moisture
will also aid in mid to high clouds dominating much of this cycle
with thunderstorm activity further complicating things. As it
stands, Klamath Falls (KLMT) has the best chance at seeing
thunderstorm activity this cycle. Light rain has been observed this
morning at KLMT, but later this afternoon thunderstorms will be in
the vicinity; at the very least. Similar story for Medford (KMFR)
but slightly lesser chances. Confidence was not high enough due to
uncertainty to include thunderstorms actually impacting either KMFR
or KLMT, but convection will be close to both terminals today. Both
sites have about a 20 to 30 percent chance at seeing thunderstorms
through this cycle.
-Guerrero
&&
.MARINE...Updated 830 PM PDT Thursday, August 17, 2023...Moderate
to strong north winds are expected through this weekend for a
majority of the region, especially south and southwest of Port
Orford Friday and Saturday. Confidence is moderate to high for Gale
Force Winds/Hazardous Seas to develop during the Friday/Saturday
time frame given the probabilities for strong gusts. These strong
winds will lead to Small Craft Adviosry conditions elsewhere. In
other words, our southern waters (zones 356 and 376) will be under
Gale Warning and Hazarouds Seas Warning, while our norther waters
(zones 350 and 370) will see Small Crafy Advisory conditions.
A look at probabilities from the National Blend of Models (NBM)
continues to indicate moderate to strong north winds Friday and
Saturday. For areas south and southwest of Cape Blanco, here are
some exceedance probabilities from the NBM:
* Sustained Winds:
- 60%-80% chance to exceed 34 knots
* Gusts:
- 95+% chance to exceed 41 knots
- 70%-90% chance to exceed 48 knots
- 10%-20% chance to exceed 56 knots
-Guerrero/Sven
&&
.PREV DISCUSSION... /Issued 234 PM PDT Thu Aug 17 2023/
DISCUSSION...Clouds continue to move over the area from the south,
bringing isolated showers across the east side and generally just
drifting over the west. However, terrain-generated cumulus continues
to develop in areas where the existing clouds have passed,
indicating that there is still moisture in the air. Moderate chances
(30-40%) for precipitation and thunderstorms will remain over
northern California and east of the Cascades through the afternoon
and evening before decreasing overnight. Lesser chances (10-20%)
creep past the cascades into eastern Douglas and Jackson counties,
but any activity that does pop up is expected to be pulse-type
isolated showers. Chances for lightning and localized gusty winds
are the main concerns from any activity.
Temperatures are at expected levels, with high 70s to low 80s east
of the Cascades and in northern California while the Oregon coast is
staying near 70 degrees. Temperatures in the mid 90s in west side
valleys still represent a hazard to vulnerable populations, and a
Heat Advisory for these areas will remain in place through 11 PM
tonight to communicate these conditions.
Looking towards Friday and the weekend, an upper trough will fully
develop over the area through the day Friday. This pattern will
allow temperatures to stay closer to seasonal levels. Slight chances
(15-25%) for isolated evening thunderstorms and precipitation will
continue Friday evening and through the weekend. Any activity is
most likely to be isolated and short-lived. Smoke from fires in
western Siskiyou County may start to affect southern Oregon on
Friday evening, as HRRR model outcomes for show increased near-level
accumulation moving northeast across Modoc, Jackson, Klamath, and
Lake counties Friday afternoon and into the evening.
The upper trough is currently expected to remain in place through
the middle of next week, with temperatures likely to stay at near-
seasonal levels. NBM probabilistic guidance shows only 10-20%
chances for daily temperatures to reach 100 degrees in Medford. One
feature of interest for the area will be Hurricane Hilary`s
progress. While nothing resembling a strong storm is expected to
reach this part of the country, the moisture associated with the
storm could be influential. GFS outcomes expect the storm to
dissipate fully near San Francisco, while ECMWF outcomes show
moisture from the storm supporting activity on Tuesday evening. The
effects are not expected to be impactful or hazardous, but will be
watched closely over the weekend for any changes. -TAD
FIRE WEATHER...Updated 200 PM PDT Thursday, August 17,
2023...Heat and thunderstorms remain the main concerns for today.
Overall, temperatures will trend slightly cooler today, but will
still remain above normal for this time of year.
Another influx of moisture from the south will produce an increased
risk for isolated to scattered thunderstorms this afternoon, as
additional moisture moves into the area from the south. Models
continue to support convection developing from the Cascades east
with moderate confidence for isolated to scattered thunderstorms
developing into areas west of the Cascades, including eastern
Douglas, eastern and southern Jackson, far southeast Josephine and
western/central Siksyou County. With a deeper moist layer, expect
storms to trend wetter, but lightning strikes outside of the wet
cores are still likely. Thunderstorm and shower activity may become
more isolated after sunset as the area of moisture lifts north. A
red flag warning is in effect for fire weather zones 617, 621, 622,
623, 624, 625, 280, 281, 282, 284 and 285 this afternoon and evening
for abundant lighting on dry fuels.
The increased cloud cover and smoke in the area may reduce the
ability for thunderstorms to develop this afternoon, but we are
still continuing the Red Flag Warning given the overall unstable
conditions.
Friday and Saturday, the low offshore of California, that has
acted to push moisture into the region, will slowly push
southeast. This will limit moisture inflow to portions of our
area, and thunderstorm chances will gradually retreat to the
Southeast as well. Above normal temperatures will continue
through at least Saturday, then will begin to trend lower Sunday
into Monday. There are some indications that tropical moisture
may stream into the area early next week, as the remnants of a
tropical storm push north into southern California. Confidence is
low, but should this occur, more substantial rainfall and
cooler/cloudy conditions are possible for at least some portions of
our area, most likely to the east of the Cascades. We will keep
an eye on this over the next several forecast cycles. -BPN/CC
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.
PACIFIC COASTAL WATERS...Small Craft Advisory until 8 AM PDT Friday
for PZZ356-376.
Hazardous Seas Warning from 8 AM Friday to 11 PM PDT Saturday
for PZZ356-376.
Small Craft Advisory until 11 PM PDT Saturday for PZZ350-370.
Gale Warning from 8 AM Friday to 11 PM PDT Saturday for PZZ356-
376.
&&
$$
Area Forecast Discussion
National Weather Service Spokane WA
448 PM PDT Thu Aug 17 2023
.SYNOPSIS...
Breezy dry conditions are expected into Friday raising fire
weather concerns. A cool down, with a push of breezy winds and
possible showers, arrives by the weekend.
&&
.DISCUSSION...
...CRITICAL FIRE WEATHER CONDITIONS THROUGH FRIDAY...
Tonight and Friday: The ridge of high pressure responsible
for our current heat wave will begin to breakdown allowing
excessive heat warnings and heat advisories to come to an end this
evening. The breakdown of the ridge is coming with increasing
winds this afternoon with numerous sites already gusting 20-25
mph. This is creating critical fire weather conditions this
afternoon as temperatures remain in the 90s-100s along with
humidity values between 15-20%. The last few days of hot and dry
conditions has allowed area wildfires to perk up. Active fires in
the Northwest and southern BC are putting a lot more smoke into
our airshed resulting in areas of poor air quality. In
coordination with our local air quality partners, several air
quality alerts have been relayed on the NWS site.
We are monitoring mid and high level moisture coming into the region
from Central Oregon. This moisture is associated with the
remnants of TS Eugene but has produced some light showers over the
Oregon Cascades earlier today. This moisture will get picked up
in the increasing southwest flow and stream across Eastern WA and
North Idaho. Probabilities for measurable precipitation are very
low (less than 10%) but several models do show a few speckles of
0.01" or so and we have added a 10-15% chance for showers. The
cloud cover from this moisture will help keep temperatures
elevated overnight.
A cold front will swing into the region Friday. As the front interacts
with the moisture over far SE WA and NC Idaho, there will be a
15-20% chance for brief organized bands of showers and possibly a
stray lightning strike. Otherwise, the main impact from the front
will be cool air advection and windy conditions. Temperatures will
cool 10 or more degrees back into the 80s and low 90s. The air
mass will become quite dry behind the front with dewpoints falling
from the 40-50s back into the 30s so despite the cooling,
humidity levels will dry back out into the teens. Winds will pack
much more of punch of Friday given a sharper pressure gradient and
cold air advection delivering our second round of critical fire
weather conditions. Sustained winds speeds on Friday look to be
more on the order of 15-25 mph with gusts of 30-40 mph. There will
also be a more pronounced shift from southwest to west to
northwest through the afternoon. Winds will subside Friday night;
clear skies and dry conditions will allow for cool overnight lows
within our sheltered northern mountains. /sb
Saturday through Thursday: At this point in the forecast a broad
but not well defined trof influences Eastern Washington and North
Idaho. Over the weekend there is some potential for weak
disturbances to move across the region from west to east as there
are hints of persistent, but weak, southwest to northeast flow
however at times over the weekend and over the early portion of
the next workweek the flow up from the south becomes more dominant
with hint of bits of moisture and energy, including remnants of
Hurricane Hilary in addition to remnants of an old cold core low,
moving up from the south. Therefore some mention of showers and
thunderstorms is in place over the weekend and continues on at
times into the following workweek. By about Wednesday on most of
the ensemble clusters hint of the presence of an upper level (cold
core) within the vicinity of the Southern BC and Washington Coast
which hinting at more of a favored southwest flow. Looking closer
at some of the deterministic models that far out solutions may
include having bits of energy rotating around the low and or
portions of the low itself ejecting into the area via the provided
southwest flow so pops for convection, including mentions of
thunderstorms at times, remain in place. Temperatures are still
likely to remain a bit on the warm side of climo with hints temps
may bottom out Saturday then either gradually rise and/or remain
nearly steady. Smoke and haze looks likely to linger on through
the weekend and into the early part of the next workweek. Less
wildfire smoke from Southern British Columbia wildfires looks
likely as the flow becomes more southwesterly on about Wednesday
but this flow could favor bringing in wildfire smoke from fires in
Southwest Oregon, the big question is how active those fire will
be at that time. /Pelatti
&&
.AVIATION...
00Z TAFs: Smoke that collected in central Washington overnight
will be pushed eastward as gusty west winds develop behind a cold
front. The Spokane and Pullman TAFs include visibility reductions
through 03z for smoke. A large fire burning in British Columbia
just northwest of Oroville Washington will be the largest source
of additional smoke through the night into Friday morning. Smoke
fields from the HRRR predict significant visibility reductions for
Republic, Kettle Falls, Metaline and Bonners Ferry through the
night and into Friday morning. Bands of sprinkles and virga will
be detected by radar this evening and through the night leading to
bumpy conditions below our 10-12 thousand foot cloud base as
precipitation evaporates into a warm and dry air mass. By 18z
Friday, hot and dry west winds of 15 to 20 mph redevelop. /GKoch
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 70 89 54 87 55 87 / 10 0 0 0 0 10
Coeur d`Alene 69 89 52 87 56 86 / 10 0 0 0 10 10
Pullman 71 85 47 84 53 84 / 20 10 0 0 10 10
Lewiston 75 96 61 93 65 91 / 20 20 0 0 10 20
Colville 64 89 45 86 45 87 / 10 0 0 0 0 10
Sandpoint 67 87 48 85 52 83 / 10 0 0 0 10 10
Kellogg 68 84 56 85 59 82 / 20 10 0 0 20 20
Moses Lake 70 90 55 87 57 89 / 10 0 0 0 0 0
Wenatchee 67 87 60 86 62 88 / 10 0 0 0 0 0
Omak 65 91 57 89 58 91 / 0 0 0 0 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning until 9 PM PDT this evening for Northern and
Central Idaho Panhandle (Zone 101).
Red Flag Warning from 10 AM to 9 PM PDT Friday for Northern and
Central Idaho Panhandle (Zone 101).
Heat Advisory until 11 PM PDT this evening for Central Panhandle
Mountains-Lewis and Southern Nez Perce Counties-Northern
Panhandle.
Excessive Heat Warning until 11 PM PDT this evening for Coeur
d`Alene Area-Idaho Palouse-Lewiston Area.
WA...Red Flag Warning until 9 PM PDT this evening for Colville
Reservation (Zone 702)-East Portion of North Cascades
National Park/Lake Chelan National Recreation Area (Zone
697)-East Washington Central Cascades (Zone 696)-East
Washington North Cascades (Zone 698)-Eastern Columbia Basin
-Palouse -Spokane Area (Zone 708)-Foothills of Central
Washington Cascades (Zone 705)-Foothills of Northeast
Washington (Zone 701)-Lower Palouse -Snake River (Zone
709)-Methow Valley (Zone 704)-Okanogan Highlands and Kettle
Mountains (Zone 699)-Okanogan Valley (Zone 703)-Selkirk
Mountains of Northeast Washington (Zone 700)-Waterville
Plateau (Zone 706)-Western Columbia Basin (Zone 707).
Red Flag Warning from 10 AM to 9 PM PDT Friday for Colville
Reservation (Zone 702)-East Portion of North Cascades
National Park/Lake Chelan National Recreation Area (Zone
697)-East Washington Central Cascades (Zone 696)-East
Washington North Cascades (Zone 698)-Eastern Columbia Basin
-Palouse -Spokane Area (Zone 708)-Foothills of Central
Washington Cascades (Zone 705)-Foothills of Northeast
Washington (Zone 701)-Lower Palouse -Snake River (Zone
709)-Methow Valley (Zone 704)-Okanogan Highlands and Kettle
Mountains (Zone 699)-Okanogan Valley (Zone 703)-Selkirk
Mountains of Northeast Washington (Zone 700)-Waterville
Plateau (Zone 706)-Western Columbia Basin (Zone 707).
Excessive Heat Warning until 11 PM PDT this evening for Central
Chelan County-Lower Garfield and Asotin Counties-Moses Lake
Area-Northeast Blue Mountains-Northeast Mountains-Okanogan
Highlands-Okanogan Valley-Spokane Area-Upper Columbia Basin-
Washington Palouse-Waterville Plateau-Wenatchee Area-
Western Chelan County-Western Okanogan County.
&&
$$