Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/16/23

Area Forecast Discussion

National Weather Service La Crosse WI

629 PM CDT Tue Aug 15 2023

.DISCUSSION...(This evening through Tuesday)
Issued at 149 PM CDT Tue Aug 15 2023

Key Messages:

- Thunderstorms expected Wednesday night, with a small chance for
strong to severe storms (10-20% chance).

- Medium to high confidence in highs reaching the low to mid 90s
this weekend into the middle of next week. A few locations
could reach 100 during the warmest periods.

Through Wednesday night: Gusty Winds & Strong Storm Potential

Heights increase Tuesday into Wednesday afternoon, with sunny skies
and near normal temperatures expected. Models are in good agreement
on the passage of a cold front on Wednesday night, which will bring
a chance (50-70% north of I90/94 and 30-50% to the south) of showers
and thunderstorms. SPC retains a marginal risk across our forecast
area, predominately for a wind threat tied to the frontal passage.
With the instability waning as the sun goes down, there is still
some uncertainty if any storms will be able to produce strong/severe
winds; however, a strong low-level jet (~60kts) accompany this
frontal passage. The strongest winds will remain aloft, above the
boundary layer, but expect gusts around 30 to 40mph as the front
approaches and mixes some of these winds to the surface.
Precipitation will also be able to bring some of these strongest
winds down to the surface as well.

This Weekend into Next Week: Persistent Hot and Humid Conditions

Clustered ensemble guidance shows strong agreement for the return of
hot and humid conditions Saturday afternoon through the start of
next week. NAEFS and ECMWF ensembles show strong probabilities for
well-above normal temperatures, with standardized anomalies of 2-3+
for 850 and 700mb temps. These equate to the 99th, to near maximum,
percentile relative to a 3-week (centered on the weekend)
climatological mean. Deterministic NBM run shows temperatures in the
low 90s by Saturday and mid 90s for Sunday and Monday. A 100-model
ensemble (consisting of 50 EPS, 30 GEFS, and 20 CMCE) shows a
greater than 50% chance for high temperatures to climb above 90
degrees Sunday through Tuesday. Removing the high-bias from the
current GEFS, both EPS and CMCE ensembles retain these higher
chances. The 100 member ensemble suggests strongly that this ridge
will remain in place through Tuesday, but uncertainty begins to show
up on Wednesday. This looks like it will be the warmest stretch of
the year so far, with 3-4 days of temperatures above 90 degrees,
with the potential for a day or two of reaching 100F, especially

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 630 PM CDT Tue Aug 15 2023

VFR conditions are expected through the TAF period. As a cold front
passes through the region tomorrow, southwest winds at both TAF
sites will increase to 15-20 kts with gusts around 30 kts into the
evening, particularly at KRST. Some uncertainty remains exactly how
high the gusts will be able reach at the TAF sites with winds off
the surface of 50-60 kts in the 15.21 RAP forecast soundings. If
deeper mixing occurs tomorrow, gusts could overachieve.

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&

DISCUSSION...JAW
AVIATION...Naylor

Area Forecast Discussion

National Weather Service Binghamton NY

1043 PM EDT Tue Aug 15 2023

.SYNOPSIS...
Low pressure over Lake Erie will drift into central New York
overnight, pulling a warm front across the area. This will keep
cloudy conditions with spotty showers across the region, with
fog developing in places overnight. Spotty showers and partly
cloudy conditions are expected Wednesday as low pressure pulls
away from the area. Quiet weather for Thursday will precede
additional showers and thunderstorms Thursday night into Friday.

.NEAR TERM /THROUGH WEDNESDAY/...

1040 PM Update...

Scattered showers, isolated thunderstorms and areas of
fog/drizzle are lingering across CNY and NE PA late this
evening. The thunderstorms should dissipate by approximately
midnight, with just some lingering showers and clouds overnight.
Otherwise it will be humid with lows in the 60s areawide. Had a
few minor reports of flooding earlier this evening across
Steuben county as a period of briefly heavy rain moved across,
dropping around 1" per hour (or less time). Was able to cancel
the last flood advisory before this update. Will continue to
monitor for any locally heavy rain showers overnight, as the
area is rather sensitive to more rainfall considering the recent
bouts of precipitation.

620 PM Update...

A line of slow moving showers and isolated thunderstorms is
approaching from western NY and central PA early this evening.
Latest HRRR, 3km NAM and RAP show this slowly pivoting across
the forecast area into the overnight hours. There are a few
other areas of showers at this time as well, with one spoke
across Central NY, and another further north toward the I-90
corridor. Instability is lacking north of the occluded front,
but heading into the evening expect around 500 J/Kg of MLCAPE
with LIs down to -5 to work into the region from the southwest.
Deep moisture, warm cloud layer around 12,000 feet thick and
pwats around 1.5 to 1.6 inches will provide a sufficient
environment for locally heavy rainfall with any t`storms that do
develop. Storm movement is generally east-northeast around 25
mph...so as long as the thunderstorms continue to move then
flooding won`t be a concern. However, if any of the storms
stall, pivot or back build we`ll have to watch for pockets of
locally heavy rain and isolated flash-flooding. Parts of the
Finger Lakes remain under a marginal risk of flash-flooding,
with a marginal risk for an isolated severe storm extending east
to about the I-81 corridor.

225 PM Update...
Spotty showers have been most persistent across the Finger Lakes
region and along the Thruway corridor this afternoon, with
occasional drizzle and mist across the Twin Tiers. An
approaching warm front over central PA has led to the
development of a few thunderstorms arcing NW to SE across
Pennsylvania, and these will approach SW portions of the CWA
early this evening, with isolated thunder possible in the Finger
Lakes, down into Bradford and Luzerne Counties. While the odd
stronger thunderstorm can`t be ruled out, we`ll need to see some
breaks of sun sneak in from the southwest in order to build
some instability.

A weak, ill-defined surface low will track from Lake Erie into
northern New York Wednesday, dragging a surface trough across
the area through the evening. Expect a mix of clouds and sun
Wednesday, with spotty showers or a thunderstorm possible along
the trough axis. High temperatures will climb back into the
middle to upper 70s, still lagging climatological normals by
3-6 degrees.

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
150 PM Update...

High pressure remains in place Thursday morning keeping conditions
sunny and pleasant for the first half of the day. Southerly winds
allow temperatures to climb into the mid to low 80s across the
region. A deepening upper level trough starts to slide in from the
midwest increasing moisture allowing some pop up afternoon
showers and thunderstorms to develop. In terms of instability,
there is approximately a 30 kt difference in the 0-6 km bulk
shear with CAPE values up to 400 J/kg. Therefore some modest
destabilzation is possible, but with these parameters severe
thunderstorms are not expected at this time. The showers and
storms will become more widespread thursday night into Friday
as the trough moves overhead. PWATs Thursday night rise to
approximately 1.50 inches, so localized heavy downpours are
possible. Temperatures are expected to fall into the 60s
Thursday night.

Cold front is expected to move through sometime Friday morning
shifting winds north west. As a result Fridays highs are expected to
be slightly cooler with temperatures in the low to mid 70s in the
afternoon. Model guidance shows the trough moving out slowly with
lingering showers behind the cold front extending into the
evening hours. Once the trough exists, high pressure returns
Friday night with clearing skies and cooler temperatures ranging
in the upper 40s to low 50s.

.LONG TERM /SATURDAY THROUGH TUESDAY/...
150 PM Update...

High pressure conditions continue for most of this period as a
strong ridge begins to build in across the central plains. This
supplies a prolonged period of dry weather from Saturday to Sunday
with a possible short wave attempting to break the pattern on
Monday. Confidence on the position of the wave is low, with the GFS
bringing this wave in early Monday morning, while the ECMWF keeps
the wave well to our north. The ECMWF`s resolution would keep
conditions drier for longer period of time while the GFS would
suggest showers early next week.

Despite riding on Saturday temperatures remain slightly cooler with
highs ranging in the 70s during the day and lows ranging in the 50s
at night. Temperatures are then expected to return to normal Sunday
and Monday with highs in the upper 70s to mid 80s and lows in the
upper 50s to lower 60s.

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
MVFR to VFR conditions will be in place early this evening
before ceilings fall later tonight to IFR or LIFR levels at all
terminals. Showers will be scattered about tonight as well,
mostly through about 05-6Z with the exceptions being RME and SYR
where showers can still be in the vicinity through early
Wednesday morning. There is the potential for an isolated
thunderstorm this evening, mainly through 02-03Z, with ELM and
AVP having the best chance, but confidence was too low to add to
the TAFs, so this will be monitored.

With weak high pressure building in at the surface late tonight
into Wednesday, winds will be light and with the very moist low
levels, there is pretty high confidence for fog to form, with
ITH and ELM expected to see the lowest visibility down to 1/2
SM, with a tempo in for ELM for VISBY as low as 1/4SM. Later
Wednesday morning into the afternoon visibility and ceilings
will improve, returning to VFR levels.

Outlook...

Wednesday night through Thursday...Mainly VFR.

Thursday night through Friday...Occasional restrictions possible
in scattered showers and thunderstorms.

Saturday...VFR, other than some early morning valley fog with
KELM being most likely.

Sunday...Mainly VFR.

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.

SYNOPSIS...MPH
NEAR TERM...MJM/MPH
SHORT TERM...ES
LONG TERM...ES
AVIATION...DK/MPH

Area Forecast Discussion

National Weather Service Des Moines IA

604 PM CDT Tue Aug 15 2023

...Updated for the 00z Aviation Discussion...

.SHORT TERM.../Tonight through Wednesday Night/
Issued at 256 PM CDT Tue Aug 15 2023

Forecast Impacts for the week:

...Quiet through Wed with storm chances northeast Wed Night
...Quick return of heat late Friday into Tuesday
...Stretch of summer heat from Saturday through Tuesday

Confidence Short Term: High

Cool start to the day with lows in the 50s and patchy fog over the
area. As high retreats to the south tonight, H850 temps will begin
to warm into the overnight hours and rise to +17C by 12z Wednesday.
The main weather maker remains far north near Lake Winnipeg Canada.
Subjective H850 analysis shows exiting H850 low over the Ohio River
Valley with near neutral advection over Iowa today. Impressive high
with hot dome centered over northern Texas with 159dm H850 heights
and 594dm high at H500 over the southwest US this morning. This will
eventually drift back into the Great Plains by weekend and bring the
heat back into our area. The initial push of warmer air in the next
36 hours will arrive with little consequence and no precipitation
anticipated with the warm frontal forcing well north into northern
MN by 12z Wed. Though there is little moisture over Iowa early today
beneath the ridge of high pressure, moisture return will begin late
tonight and increase along an approaching cold front into MN through
00z Thursday, but still remain north of the border. After another
cooler night with overnight lows in the 50s will give way to highs
in the mid to upper 80s over most of the region for Wednesday. As
the trough/cool front trailing the Winnipeg system enters northwest
Iowa around 00z Thursday, moisture pooling along the boundary will
bring PWATs up to 1.25 to 1.5 over the region as it slides into
central Iowa overnight. Initially, much of the region will be capped
at H700 with temperatures of +10 to +13C. After the column begins to
cool over the northeast, there will be a small chance for showers
and thunderstorms in the far north/northeast overnight. The HRRR and
06z GFS have retreated somewhat, on chances as the better
instability and surface moisture convergence will remain farther
northeast in MN and Wisconsin. The Euro deterministic/ens shows
still shows some thunder chances in the northeast. Have trimmed
chances a bit, but left the coverage roughly the same. Lows tomorrow
night will cool quickly behind the boundary as northwest winds pick
up behind the boundary. Overnight mins will fall to the upper 50s
north to the mid 60s central to southeast.

.LONG TERM.../Thursday through Tuesday/
Issued at 256 PM CDT Tue Aug 15 2023

Confidence: Medium to High

Cooler and breezy conditions are expected for Thursday as mixing
increases behind the front and H850 temperatures fall to near 12C
northeast to 13C southwest. This will help cap highs to the mid 70s
north to the upper 70s elsewhere. Bufkit soundings suggest wind
gusts approaching 25 to 30 mph again from the northwest during the
mid morning through afternoon hours. With little moisture through
the column and some weak subsidence following the boundary, few if
any clouds are anticipated for the day. With the jet stream and main
storm track generally north of the region into the weekend, warming
temperatures will return quickly aloft by Friday afternoon and build
into the weekend. While model differences remain with regard to
thermal profiles and the eventual breakdown of the upper level ridge
expected to build over the Great Plains from the weekend into early
next week. The operational GFS, with support of about half of the
ensemble members shows a brief, slightly cooler push of air around
Monday night as a Canadian ridge of high pressure builds southeast
into the Great Lakes. The Euro deterministic continues to hold onto
the heat into midweek despite a weakening and capped surface frontal
passage into southern Iowa Sunday afternoon. This is similar to
previous runs and prior to a weakening of the main upper level ridge
allowing for cooling sometime Wednesday into Thursday. Given the
uncertainty and forecast of a rather strong H500 ridge, will hold
onto the more stagnant pattern into next week. Despite a several day
heat episode, at this point it would be about the same length as our
late July hot spell.

Overall, the increase in H850 temps into the weekend is quite
impressive. The GFS operational model is likely overaggressive with
temperatures warming to 33C by 12z Sunday and remaining over 30C
through 00z Monday. The Euro deterministic model is rather close to
its ens mean with around 27 to 29C both Saturday and Sunday, which
leads to more confidence that the operational GFS is a bit of an
outlier. Needless to say, 27 to 29C H850 temps will bring afternoon
readings into at least the mid 90s with a range of 95 to 98 over the
region. Sunday appears a bit hotter with highs approaching 100;
especially in the southwest third. The remainder of the forecast
still features hot weather into Tuesday with highs generally topping
out in the lower to mid 90s. Lows will continue to hold in the upper
60s to lower 70s. Though the heat index each day doesn`t appear to
exceed by much, headline criteria at this point due to any pooling
surface moisture, the several days of hot weather and possibly
reaching a 4 day stretch may see headlines moving forward. The other
factor that will still need be monitored will be evapotranspiration.
If the low remains far enough from the region and a weak boundary
can pool surface moisture over the southern/southwest areas Sunday
afternoon, we may see heat indices nearing 105 to 110 there by afternoon,
similar to the midweek event of late July. Will continue to parse
through data the next several days.

.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 604 PM CDT Tue Aug 15 2023

High confidence in VFR conditions prevailing through the period
at all terminals. Winds will become from the southwest overnight
and then through the day Wednesday become gusty ahead of a cold
front. Gusts over 20 knots will be common north of a CSQ-DSM-GGI
to the Minnesota border in the afternoon hours.

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SHORT TERM...REV
LONG TERM...REV
AVIATION...Ansorge

Area Forecast Discussion

National Weather Service Grand Rapids MI

733 PM EDT Tue Aug 15 2023

LATEST UPDATE...
Aviation

.SHORT TERM...(This evening through Wednesday night)
Issued at 235 PM EDT Tue Aug 15 2023

-Patchy dense fog tonight into Tuesday Morning

Radar echos continue to decrease in intensity as light to moderate
rain pivots eastward. Latest satellite supports clearing skies
late this afternoon into this evening with only fair weather
cumulus int its wake.

Winds will shift other north behind the system as it exits. The
cooler daytime temperatures, followed by cool nighttime temps
should aid in the region decoupling. Looking at boundary layer
moisture, especially where the heavy rain fell, there will ample
moisture and calm enough winds for patchy dense fog to form
tonight into tomorrow morning.

-Fair weather Wednesday with gusty winds Wednesday evening

High pressure will dominate the weather pattern tomorrow with
highs in the upper 70s to low 80s. Winds will begin to increase
late in the day out ahead of an approaching upper level low.
The deepening trough with a strong pressure gradient associated
with it should bring southerly winds that could gust upwards of
20 to 30 mph, especially along the lakeshore.

.LONG TERM...(Thursday through Tuesday)
Issued at 343 PM EDT Tue Aug 15 2023

-Strong to Severe Storms Possible Thursday

A potent/amplifying northwest-flow shortwave and associated sfc cold
front will push through on Thursday. A narrow ribbon of PWATs near
1.75 inches is progged to precede the front, supporting a period of
widespread showers and scattered tstms with categorical pops.

SPC has added much of our area into the marginal risk of severe
storms in the day 3 outlook, and this will hinge on timing of the
cold front and whether or not we can destabilize before its passage.
Models do show nearly 50 kts of deep layer shear and RAP has
1000-1500 J/KG of cape so a line of organized storms with a few
healthy wind gusts seems plausible, mainly east of Hwy 131 and
especially east of U.S. 127. Excessive rainfall looks unlikely
though given the fast movement of the system.

-Above Normal Temps with Mainly Dry Weather Friday through Tuesday

A pattern change toward more summer-like weather is in store as our
active northwest flow aloft finally retreats and the upper ridge
over the wrn U.S. builds in our direction. A 600 dam upper level
high will be centered over Iowa Sunday through Tuesday with H8 temps
near or in excess of 20C over MI. Subsidence aloft associated with
the upper high and mid level capping/warmth should limit convection
threat, so will run with a dry forecast Friday through Tuesday with
temps moderating into the mid to upper 80s by Sunday. 90 degrees may
be topped for the early to middle part of next week.

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 733 PM EDT Tue Aug 15 2023

VFR conditions will prevail this evening then some areas of MVFR
and IFR can be expected later tonight as areas of fog form in
clear skies and light winds with the ground still saturated from
the recent rains. Northwest winds this evening 10 knots or less
will go light to calm by midnight then turn west southwest on
Wednesday AOB 10 knots.

.MARINE...
Issued at 235 PM EDT Tue Aug 15 2023

winds and waves will subside as the afternoon and evening
continues. However waves will continue to be 2 to 5 feet through
this period so conditions hazardous to small craft and to swimmers
will continue through the first half of the evening.

A breezy period is expected from Wednesday evening through
Thursday evening. Southwest winds will increase ahead of the next
cold front Wednesday afternoon and winds should increase enough
for possible Gales from 03Z to at least 15Z Thursday. The Gales
should begin in the north and overspread the entire lake
potentially into Thursday afternoon. A Beach Hazards statement
will most likely be needed during this time frame too.

.HYDROLOGY...
Issued at 102 PM EDT Tue Aug 15 2023

Locally heavy rainfall over the last 24 hours has resulted in
rises on some of our area rivers, specifically over the Grand
River Watershed. None of the rivers are forecast to reach their
flood stage however several sites are forecast to reach
action/bankfull stage. Those include: The Grand at Ionia, Sycamore
Creek at Holt, the Looking Glass at Eagle, the Thornapple at
Hastings, and Buck Creek at Grandville (cresting now).

For more specific information and hydrographs, please go to:
https://water.weather.gov/ahps/index.php?wfo=grr

While most locations had 1-1.5" of rain, pockets of 2-4" fell in
a corridor from South Haven and Holland east to the Lansing area.
Interesting to note that a 10"+ bullseye fell over Lake Michigan
just offshore of Allegan County.

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 8 PM EDT this evening for MIZ056-
064-071.

LM...Small Craft Advisory until 8 PM EDT this evening for LMZ844>849.

Gale Watch from Wednesday evening through Thursday morning for
LMZ844>849.

SHORT TERM...Ceru
LONG TERM...Meade
AVIATION...Ostuno
HYDROLOGY...Meade
MARINE...Ceru

Area Forecast Discussion

National Weather Service Jackson MS

922 PM CDT Tue Aug 15 2023

...New MESOSCALE UPDATE...

.MESOSCALE UPDATE...
Issued at 922 PM CDT Tue Aug 15 2023

Rest of tonight...

A quiet, dry & cooler evening is on tap across the region. RAP
sfc analysis indicates frontal zone continues to sink to the
south, with drier air advecting in the wake. 00Z synoptic analysis
indicate center of the cold core is moving into the Great Lakes,
while troughing/northwest flow is bringing dry & subsident airmass
into the region. GOES East water vapor/total precipitable water &
00Z regional soundings indicate much drier air, with PWs falling
near or less than an inch, building in. Due to that, a quiet
evening is anticipated with dewpoints falling into the low 60s &
cooler lows, generally around 5-8 degrees below normal in the low
60s north to upper 60s south. Updates are out. /DC/

.DISCUSSION...
Issued at 308 PM CDT Tue Aug 15 2023

Tonight and Tomorrow:

Rain chances decrease through the evening into tonight as the
cold front moves out of the area. Generally light northerly winds
will allow cooler and drier air to filter in overnight. This mild
cold air advection regime will aid in clearing out cloud cover,
and temperatures should steadily fall overnight. By daybreak,
overnight lows will range from mid-60s for most to near 70 in the
Pine Belt. A few showers that do linger briefly into the period
across the Pine Belt could leave enough residual moisture to lead
to shallow, patchy fog for a short time around dawn.

On Wednesday, high pressure builds into the area with post frontal
dry air in place. Mostly clear to partly cloudy skies and full
August sun will allow temperatures to rise to lower 90s along and
south of I-20 and generally mid to upper 80s in the north. Low
humidity will keep heat indices in check and forecast products for
heat stress are not expected.

With substantial diurnal heating, relative humidity across the area
will likely fall below 35%. With winds occasionally breezy out of
the north combined with short term fuels that are very dry, a risk
for brush fires will continue. For this reason, fire weather
graphics and HWO will continue through the period. The areas most at
risk for fire weather concerns are generally along and south of I-20
where very little rain has fallen recently. /SW/

Thursday through Tuesday:

The upper-level pattern - which has had us locked into oppressive
heat - will remain more progressive through Thursday into Friday. A
shortwave moving into the Great Lakes region will reinforce the
trough over the East Coast, but the ridge is expected to re-
establish itself over the Southern Plains and strengthen as it
slides east toward the central CONUS this weekend. Forecasted 500mb
heights of 600 dam over KS/MO/IL would be near all-time max values
for those areas at this time of year, but the location would keep
the Gulf Coast under more of an easterly flow aloft. At the surface,
we will enjoy this slightly cooler and drier post-frontal air mass
for a few days. Even some chance for reinforcement of the drier air
is possible Friday into Saturday with a front entering northern
parts of the area. But in general, the return of some easterly flow
along the Gulf Coast and building ridge aloft will allow for some
degree of humidity to edge back into the area. Once again, this
means dangerous heat stress conditions for the ArkLaMiss region.
Peak heat index values in the 105 to 110 degree range are expected,
with increasing chances for max temps to hit the 100 degree mark
again by Friday. Models suggest an easterly wave moving across the
Gulf of Mexico could bring at least some chance for rain to areas
closer to the Gulf Coast, but most locations will likely remain dry
through at least this weekend. /NF/

.AVIATION...
(00Z TAFS)
Issued at 643 PM CDT Tue Aug 15 2023

VFR conditions will prevail through the next 24 hours. With cold
front analyzed over the northern Gulf Coast, gusty northerly
winds at a few sites ongoing will wind down by 16/01Z & at most
around 10mph through the rest of the period. Other than some
scattered clouds/ceilings around 6-10kft, no flight restrictions
are anticipated. /DC/

.PRELIMINARY POINT TEMPS/POPS...
Jackson 66 90 66 96 / 0 0 0 0
Meridian 66 89 65 93 / 0 0 0 0
Vicksburg 66 90 66 96 / 0 0 0 0
Hattiesburg 71 94 69 98 / 10 0 0 0
Natchez 68 91 68 98 / 0 0 0 0
Greenville 63 85 63 91 / 0 0 0 0
Greenwood 63 87 63 91 / 0 0 0 0

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&

DC/NF/DC

Area Forecast Discussion

National Weather Service Spokane WA

741 PM PDT Tue Aug 15 2023

.SYNOPSIS...
Temperatures will continue to be hot through Thursday, reaching
the upper 90s and triple digits. A cool down, with a push of
breezy winds and possible showers, arrives by next weekend.

.DISCUSSION...

Evening update: Based on increased fire activity on fires today
along the East Slopes of the Cascades and southern British
Columbia, the 00z run of the HRRR smoke is showing more haze and
smoke over the region into Thursday morning, especially over
northern Washington including the Upper Columbia Basin and Spokane
area. Thus the forecast has been updated to reflect these latest
smoke developments. JW

...Excessive Heat Continues Through Thursday...

Tuesday, Wednesday, and Thursday:
The dog days of summer are upon us as we are in the midst of a
multi-day heat event in the Northwest. As of this writing, many
locations are climbing into the upper 90s and just passing that
triple digit mark. Clear skies outside of some smoke and haze will
continue for the next few days.

* Temperatures: Normal high temperatures for mid August are 83-90F
for many areas and normal low temperatures are in the mid to
upper 50s. Yes it`s summer and yes it`s supposed to be hot,
however our low temperatures will be about 10-15F above normal
as well as the daytime temperatures. This will lead to that
Moderate to Extreme Heat Risk that will impact nearly every
citizen and animal in this region, as little to no relief will
be felt. Many record high temperatures are in jeopardy today
and again Wednesday. Looking at our 12z KOTX sounding, the 850mb
temperature was 26C and it appears that the record for this
date was 25.8C, so even a record warm start to the day just
above the surface.

* Winds: Today, and namely this evening, the winds will increase
out of the west through the Cascade Gaps and onto the Waterville
Plateau. Wednesday morning north winds down the Okanogan Valley
will become breezy to windy with sustained winds advertised from
the National Blend of Models of 15-20 mph (similar story from
the UW-WRF). The plus side to these winds will be the strength
will not line up with the driest humidity for the day. By
Thursday afternoon wind speeds will increase with the passage of
a front. The Waterville Plateau, Columbia Basin and the
Okanogan Valley will have more than 90% chance of seeing
sustained 20 mph winds and a 50-70% chance (depending on
location) of seeing gusts over 30 mph. The winds Friday will
shift farther east and the dry conditions will persist.

* Dry: The precipitable water anomalies aren`t as impressive as a
few weeks ago when it was dry, and actually with the westerly
winds Wednesday we`ll drop to around 80% of normal. After that,
the Inland Northwest will remain around 120% of normal. This
will change come Friday into the weekend with the push of
moisture from the south. /Dewey

Friday through Tuesday: Though daytime temps will come down several
degrees on Friday, persistently dry conditions along with gusty
winds will lead to continuing fire weather concerns. **A Fire
Weather Watch is in effect for nearly of eastern WA and northern ID
thru Friday.** This will all occur as a trough pushes into and
across the Pacific and Inland Northwest. Daytime temperatures will
drop back into mid 80s-mid 90s Friday for most locations, before
dropping another 5 or so degrees for the weekend. In addition, some
well needed moisture may return by Saturday night into Sunday, with
chances for showers making an appearance across the region through
Monday. The best chances for showers with isolated embedded
thunderstorms will be over the Idaho Panhandle and over the northern
mountains of Eastern Washington. /KD

.AVIATION...
00Z TAFs: Satellite showing some high level smoke in the north
Cascades pushing east into Okanogan Valley and the northeast
mountains. Likely localized smoke near COE and SZT from nearby
fires, but overall the HREF guidance has less than 10% probability
for MVFR conditions. Smoke models have higher concentrations for
smoke from the north through Wednesday, so Okanogan Valley to
Spokane/Coeur d`Alene may have slim chances for 8-15k ft ceilings
and have included that in the TAF. Isolated locations will see
decreasing visibility due to haze/smoke. Winds will be diurnally
driven and mostly light, however Cascade gradient will support
breezy winds from EAT into the Waterville Plateau this evening
into Wednesday. /Dewey

.PREV DISCUSSION... /issued 358 PM PDT Tue Aug 15 2023/

SYNOPSIS...
Temperatures will continue to be hot through Thursday, reaching
the upper 90s and triple digits. A cool down, with a push of
breezy winds and possible showers, arrives by next weekend.Temperatures will continue to be hot through Thursday, reaching
the upper 90s and triple digits. A cool down, with a push of
breezy winds and possible showers, arrives by next weekend.

DISCUSSION...

...Excessive Heat Continues Through Thursday...

AVIATION...
00Z TAFs: Satellite showing some high level smoke in the north
Cascades pushing east into Okanogan Valley and the northeast
mountains. Likely localized smoke near COE and SZT from nearby
fires, but overall the HREF guidance has less than 10% probability
for MVFR conditions. Smoke models have higher concentrations for
smoke from the north through Wednesday, so Okanogan Valley to
Spokane/Coeur d`Alene may have slim chances for 8-15k ft ceilings
and have included that in the TAF. Isolated locations will see
decreasing visibility due to haze/smoke. Winds will be diurnally
driven and mostly light, however Cascade gradient will support
breezy winds from EAT into the Waterville Plateau this evening
into Wednesday. /Dewey
00Z TAFs: Satellite showing some high level smoke in the north
Cascades pushing east into Okanogan Valley and the northeast
mountains. Likely localized smoke near COE and SZT from nearby
fires, but overall the HREF guidance has less than 10% probability
for MVFR conditions. Smoke models have higher concentrations for
smoke from the north through Wednesday, so Okanogan Valley to
Spokane/Coeur d`Alene may have slim chances for 8-15k ft ceilings
and have included that in the TAF. Isolated locations will see
decreasing visibility due to haze/smoke. Winds will be diurnally
driven and mostly light, however Cascade gradient will support
breezy winds from EAT into the Waterville Plateau this evening
into Wednesday. /Dewey

.PRELIMINARY POINT TEMPS/POPS...
Spokane 66 101 67 101 69 93 / 0 0 0 0 0 0
Coeur d`Alene 66 99 65 100 67 92 / 0 0 0 0 0 0
Pullman 63 96 61 97 64 88 / 0 0 0 0 10 0
Lewiston 74 107 72 106 74 99 / 0 0 0 0 10 0
Colville 58 101 57 101 57 93 / 0 0 0 0 0 0
Sandpoint 61 96 59 97 62 89 / 0 0 0 0 0 0
Kellogg 69 95 69 97 69 87 / 0 0 0 0 0 0
Moses Lake 66 103 67 103 68 93 / 0 0 0 0 0 0
Wenatchee 76 104 76 103 74 91 / 0 0 0 0 0 0
Omak 71 104 70 106 68 96 / 0 0 0 0 0 0

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Heat Advisory until 11 PM PDT Thursday for Central Panhandle
Mountains-Lewis and Southern Nez Perce Counties-Northern
Panhandle.

Fire Weather Watch from Thursday afternoon through Friday
evening for Northern and Central Idaho Panhandle (Zone 101).

Excessive Heat Warning until 11 PM PDT Thursday for Coeur
d`Alene Area-Idaho Palouse-Lewiston Area.

WA...Fire Weather Watch from Thursday afternoon through Friday
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).

Excessive Heat Warning until 11 PM PDT Thursday 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.

Area Forecast Discussion

National Weather Service Pendleton OR

813 PM PDT Tue Aug 15 2023

.EVENING UPDATE...Today was very hot with some new record high
temperatures being set. Also saw the return of smoke as light
westerly flow returned advecting the smoke over the Cascades into
central Oregon. Convection fired off this afternoon from Bend to
John Day and is in the process of coming to an end now as the sun
sets. Overall precipitation amounts were light generally less than a
tenth of an inch. However, a weather station on the south side of
Hamner Butte just south of Deschutes county reported 1.49 inches of
rain. Wednesday will see a repeat of very hot temperatures with
smoke and haze spreading across more of the forecast area. THere
will again be a slight chance of thunderstorms in central Oregon
Wednesday afternoon through evening.

.AVIATION...00Z TAFs...VFR conditions expected all sites. VCTS
continues for BDN through around 04Z when storms should weaken for
the day. Expecting storms to weaken before they reach RDM but
monitoring. Breezy winds continue DLS through 04Z, with light and
diurnal winds all sites overnight. SKC all sites except BDN/RDM
with high clouds 15-25k feet. Goatley/87

.PREV DISCUSSION... /issued 151 PM PDT Tue Aug 15 2023/

SHORT TERM...Tonight through Thursday night...There are a lot of
forecast challenges this week that will keep forecasters on our
toes--the heat, the smoke, the wind, and thunderstorms. Excessive
Heat Warnings and Heat Advisories are in effect for all of the
forecast area through Thursday. For most of the forecast area,
we are already in the heat. However, smoke arriving to Deschutes,
Crook and southern Grant Counties will play a role in temperatures
over the next 48 hours. Based on the HRRR near surface smoke,
temperatures tonight were bumped up a couple of degrees and toned
down about 3-5 degrees on Wednesday for areas south- southwest of
Madras and Prineville where a thick smoke layer is advertised by
the model. This area will remain under the Excessive Heat
Warning, as it will still remain quite hot. Deschutes County is
also under an Air Quality Advisory issued by OR DEQ in effect
until Thursday evening. Elsewhere, temperatures are currently in
the 90s to around 103-- about a 4-8 degree warmup from 24hrs ago.
The inverted surface thermal trough is shifting eastward, as shows
by the wind shift to the NW at DLS and RDM. There will be winds
gusting to around 25 mph through the eastern CR Gorge (80%
confidence) and through the Kittitas Valley (40% confidence) this
evening but winds will decrease overnight.

A Red Flag Warning is in effect this evening for fire zone 611
which is the southern Deschutes NF. Satellite shows cumulus
buildups over south central OR. Some of the buildups are over
southern Deschutes County. Water vapor shows no indication of any
waves to trigger storms at this point, but most of CAMS agree that
an embedded wave along the northern periphery of the CA low will
develop just south of Deschutes County by late afternoon with a
30% bullseye over northern Klamath County in the HREF Calibrated
Thunder.

Other than the air quality and heat-related statements, no other
highlights are anticipated on Wednesday. The weather pattern
changes little and we will remain under the surface thermal
trough. Will keep the slight chance of thunderstorms for the far
southern Deschutes and Crook Counties again but there will be less
instability and moisture to work with for anything more than
isolated convection. Most storms will be south of the forecast
area. Winds will also be locally breezy with gusts to 25 mph
through the eastern CR Gorge but relatively light elsewhere.

Fire Weather Watches will be issued for areas in and around the
Columbia Basin on Thursday for gusty winds and low humidity. On
Thursday, there will be a stronger marine surge as the thermal
trough tracks to the east and a westerly flow over WA state
increases. Friday`s winds will actually be stronger (for details,
refer to the long term discussion), but the combination of
increasing winds and critically low RHs warrant the fire weather
watch with a 60% confidence of red flag conditions on Thursday.
Meanwhile, eastern OR will observe an increasing southerly flow
with a 20-30% chance of showers and thunderstorms in south central
and southeast Oregon and as far north as the southern Blues and
Wallowa County. Since most storms will be south of the forecast
area, no fire weather highlights are planned for Thursday`s
storms. Wister/85

LONG TERM...Friday through Tuesday...Relatively active period in
store for the forecast area as multiple weather systems bring a
myriad of impacts to the interior NW. These systems will relieve us
from the heat, but breezy conditions and chances for showers and
thunderstorms will take its place, making for elevated fire weather
risks through the weekend and heading into next week. The Thursday
/Friday period looks to be especially problematic as a cold front
sweeping through the region will beget gusty winds immediately
following a warm and dry period. EPS wind gust ensembles already
showing a majority of members (50-60%) with gusts over 30 mph in the
Basin Friday afternoon, with gusts closer to 40 mph for the Cascade
Gaps, including the Gorge and Kittitas Valley. Winds look to be
closer to around 25 mph in central OR, but both the EPS and GEFS
have the vast majority of ensemble members (>80%) depicting RHs well
down into the teens across the forecast area.

Even after these dry and windy conditions subside, a cutoff low off
the coast of SoCal looks to pump moisture northward into the
forecast area over the weekend. Looking at PWATs, ensembles are in
fairly good agreement in unseasonable moisture across the CWA on
Saturday, with a majority of members pointing towards values around
the 0.8 range over the Basin, but model agreement drops off
substantially Sunday onward. Ensemble clustering suggests that this
lack of consensus may stem from how this SoCal low interacts with
another oncoming upper-level low from the Gulf of Alaska. Overall
picture looks to be that of SW/S flow over the interior NW through
the weekend heading into early next week, but whether or not this
SoCal low merges with the Gulf of Alaska low, or simply lifts
through the region on its own, will greatly impact the precip
forecast, as the latter scenario would make for a much more moisture-
laden forecast. The eastern mountains certainly look prime for
thunderstorm activity across this 3-day period, but confidence is on
the lower end (20-30%) on just how wet these storms may be. Will
gauge chances of showers/thunderstorms across our mountain zones at
around 40-50% Saturday through Monday, with lower PoPs of 20-30%
across the rest of the forecast area.

What lies beyond these two systems heading into the middle of next
week is uncertain, but ensemble clustering suggests that strong high
pressure may be in place over the south central CONUS by then,
resulting in continued SW flow through our area, albeit weaker than
what we`re expecting this weekend. End result should be relatively
seasonable temps, with perhaps a slight chance of elevated
thunderstorms across our high mountain zones around the tail end of
the period. Evans/74

FIRE WEATHER...Two separate highlights for fire weather. A Red
Flag Warning is currently in effect until 11 PM for fire zone
611--the southern Deschutes NF--for thunderstorms producing
abundant lightning. Confidence is 80% for the development of
thunderstorms. There was discussion about smoke from Bedrock that
may stabilize conditions, but this has not been the case. The
upper level flow is from the east in this area, as winds are
circulating around a large low over CA. A Fire Weather Watch will
soon be issued for fire zones WA690, WA691, OR639 and OR641 for
gusty winds and low humidity Thursday afternoon through Friday
evening. Other zones may need to be added to the watch for Friday
upon further review. Confidence is about 60% for Thursday and 70%
for Friday that conditions will meet criteria, particularly the
winds. Friday will have the strongest winds associated with a dry
cold front. Another fire weather concern will be the
thunderstorms over the weekend, but many of these will have deep
enough moisture with high PWATs that dry thunderstorm potential is
very low. Wister/85

.PRELIMINARY POINT TEMPS/POPS...
PDT 67 100 69 101 / 0 0 0 0
ALW 69 103 73 104 / 0 0 0 0
PSC 71 105 72 106 / 0 0 0 0
YKM 67 104 69 104 / 0 0 0 0
HRI 70 106 73 106 / 0 0 0 0
ELN 64 103 69 101 / 0 0 0 0
RDM 62 97 65 97 / 20 0 0 10
LGD 63 101 65 101 / 0 0 0 0
GCD 63 102 66 99 / 20 0 0 10
DLS 69 106 72 102 / 0 0 0 0

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 11 PM PDT Thursday for ORZ041-044-
503-505-507-508-510-511.

Fire Weather Watch from Thursday afternoon through Friday
evening for ORZ639-641.

Heat Advisory until 11 PM PDT Thursday for ORZ049-050-502-506-
509.

Red Flag Warning until 11 PM PDT this evening for ORZ611.

WA...Excessive Heat Warning until 11 PM PDT Thursday for WAZ024-
026>029-521-523.

Fire Weather Watch from Thursday afternoon through Friday
evening for WAZ690-691.

Heat Advisory until 11 PM PDT Thursday for WAZ030-522.

SHORT TERM...85
LONG TERM....74
AVIATION...87

Area Forecast Discussion

National Weather Service Phoenix AZ

500 PM MST Tue Aug 15 2023

.UPDATE...Updated 00z Aviation Discussion.

.SYNOPSIS...
Scattered showers and thunderstorms will be possible this afternoon
and evening across south central AZ. Any thunderstorm that develops
may produce gusty winds, frequent lightning, and brief heavy rainfall.
An Excessive Heat Warning remains in effect on Wednesday and Thursday
for the lower desert areas of central/southwest AZ and southeast
CA where temperatures will be near record levels. Increasing
moisture from a tropical disturbance near the Baja Peninsula will
result in much cooler temperatures and better chances for widespread
rainfall across the entire forecast area this weekend.

.DISCUSSION...
Latest mid-lvl wv imagery shows a cutoff low positioned off the
coast of CA while a ridge of high pressure sits over the
Intermountain West. South Central AZ is positioned between both of
these features with deep south-southeasterly flow as indicated by
the 12Z KPSR RAOB. PWAT values are noticeably higher across the
region this afternoon at just over 1.5". MLCAPE is also higher
than yesterday with latest RAP 12 analysis indicating 500-800 J/kg
across southern and central Maricopa County. We are beginning to
see storms firing up over the higher terrain of SE AZ and this
activity will drift nwd this evening, potentially impacting
portions of Pinal and Maricopa Counties. Chances for seeing rain
in the valley is only around 20-30% however through this evening
and the rest of tonight. Any lingering thunderstorm activity
should begin to diminish around midnight with temperatures
settling into the mid 80s to low 90s across the region.

Heading into the middle of this week, high pressure aloft will begin
to sink further south and expand across AZ and NM. This will result
in temperatures increasing to near record levels both Wednesday and
Thursday. Latest deterministic NBM still shows highs across the
lower deserts ranging from 108-113F on Wednesday and 110-116F on
Thursday, resulting in a return of Major HeatRisk. Overnight low
temperatures will also be around 8 to 10 degrees above normal,
especially in the Phoenix Metro area. The Excessive Heat Warning
will remain in effect for both Wednesday and Thursday across the
lower deserts of Maricopa/NW Pinal Counties, the lower Colorado
River area, and portions of Imperial and Riverside Counties in CA.
Please be mindful of this heat and limit time spent outdoors.
Isolated to scattered showers and thunderstorms will be possible
both days, however moisture looks more marginal and thus coverage
will be lower across the desert areas with chances remaining 20-30%.

Friday will be a transition day as high pressure aloft begins to
move off to the east and a 500 mb trough strengthens over SoCal.
This pattern change will result in decreasing heights aloft and
cooler temperatures with highs across the lower deserts staying
below 110F. Therefore, HeatRisk will fall to the Moderate
category. Subtropical moisture will begin to increase across the
state on Friday afternoon as deep southerly flow resumes,
resulting in an overall uptick in precipitation chances. Rain
chances will increase to around 30-40% across the desert areas
and 50-60% over the higher terrain of south central AZ.

By this weekend, a tropical system which is now called Invest 90E is
forecast to strengthen into a potential tropical storm and track up
the west coast of MX, reaching the Baja Peninsula on Sunday. As it
does so, abundant moisture will begin advecting nwd through MX and
into AZ. Consequently, PWATs are expected to increase to around
1.8"- 2.0" or 1-2 sd above normal across south central AZ and
potentially over 2.0" in SE CA. This surge of moisture will not
only result in abundant cloud cover and much cooler temperatures,
but we will see a drastic increase in rain chances for most of the
forecast area. Rain chances will begin to increase over 60% by
Saturday, and 60-70% on Sunday for the lower deserts which is the
highest chances these areas have seen since early Spring. There is
still a lot of uncertainty regarding the evolution and track of
Invest 90E and this will have a lot of baring on where the axis of
heaviest precipitation will occur across our region. Latest mean
of the GEFS and EPS ensemble members show the storm tracking nwd
up the coast of Baja del Norte, eventually weakening off the coast
of SoCal. This will favor the western half of the forecast area
(mainly SE CA) where rainfall amounts could exceed 2.00". Stay
tuned for updates.

.AVIATION...Updated at 0000Z

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Convective activity in the vicinity of terminal locations along
with abrupt wind changes will be the main aviation concerns. Winds
will generally be out of the E and SE through most of the period.
Convective activity will move through the region this evening,
likely ending by early tonight. However, showers and storms are
not expected to move directly over any metro terminals at this
time. Terminal locations have the potential (30-50%) of seeing
outflow winds form nearby convective activity. These outflows have
the potential to generate gusty winds around 20-25 kts. Quieter
conditions are anticipated during the overnight hours. SCT-BKN
mid- and high-level clouds will be present over the region through
the forecast period.

Southeast California/Southwest Arizona including KIPL and KBLH:
Showers and thunderstorms in the vicinity of KBLH early this
evening will be the main aviation concern. Most convective
activity is expected to wind down over the next few hours. Winds
at KBLH will be out of the E this evening, with a switch to the N
expected early tonight. At KIPL, winds will be light and favor a
NW direction through this evening before becoming more variable
during the overnight hours. FEW-SCT mid- and high-level clouds
will increase in coverage as we go through the forecast period.

.FIRE WEATHER...
Scattered showers and thunderstorms will be possible this afternoon
and evening. Any storm that develops may produce gusty, erratic
winds, and frequent lightning. Overall rain chances will decrease
midweek as high pressure builds aloft. Well above normal temperatures
are anticipated on Wednesday and Thursday. Minimum humidities
will fall into the upper teens to around 25 percent each afternoon
through Thursday with overnight recoveries ranging from poor to
fair. Abundant moisture and much cooler temperatures will arrive
by this weekend, resulting in increasing humidity and better
chances for wetting rainfall across the lower deserts. Winds
should follow typical diurnal upslope/downvalley trends and remain
generally at or below 15 mph.

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning from 10 AM Wednesday to 8 PM MST Thursday
for AZZ530-532-534-537>544-546-548>551-553>555-559.

CA...Excessive Heat Warning from 10 AM Wednesday to 8 PM PDT Thursday
for CAZ562-563-566-567-569-570.

DISCUSSION...Salerno
AVIATION...RW
FIRE WEATHER...Salerno