Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/30/23
trends. Forecast discussion below on track.
230 PM Update...
Concern has further increased for a coming wave of rainfall
overnight, some of which could be heavy with localized flash
flooding possible. A Flood Watch has been issued for Northeast
Pennsylvania, several bordering counties of New York, and up the
Interstate 88 Corridor.
Before that, a stationary frontal axis from Steuben County-
Finger Lakes to Syracuse has already had small clusters of
showers running along it. For this afternoon-early evening,
that will indeed continue to be the main zone of scattered
showers, which will edge into Elmira-Ithaca-Cortland-Norwich-
Utica areas with time. While thunder will be possible, it will
probably be quite isolated given the amount of drier air above
10 kft, and narrow Convective Available Potential Energy (CAPE).
Highs this afternoon will be mid 70s-lower 80s, yet with
dewpoints of mid-upper 60s keeping things humid with a mostly
cloudy sky.
For tonight, several ingredients come together well for the
potential of locally heavy rainfall, even though the areal
averages are not that high. Aligned cloud layer flow and low
level jet flow, as well as plume of high precipitable water
values 1.5 to 1.9 inches with tropical origins as a wave of low
pressure runs up along slow-moving frontal positions, will act
in concert with forced ascent of a right entrance region of
upper jet maximum. Rain will also be efficient given warm cloud
depths projected to be 11-12 kft. Convection Allowing Models
(CAMS) are starting to catch on, with the High Resolution
Ensemble Forecast (HREF) output not agreeing on an exact area;
yet having the common idea that a narrow stripe or two of 1-2
quick inches of rainfall or more. Too tough to narrow down
exactly which counties will receive it, but much of our area is
moist enough to where an abrupt rainfall of that much could
cause flooding problems. Generally speaking, Northeast PA and
Eastern-Southern Tier NY, extending up the I-88 corridor; have
the more increased potential for locally heavy rainfall/possible
flooding issues overnight. A Flood Watch has thus been issued
for those areas. Model areal averages are only about a half
inch to one inch, but the reality is that embedded within in
that will be higher amounts.
Though frontal positions will be slow or stuck during the
overnight period, once the southern stream wave of low pressure
actually passes, things will quiet down quickly by mid morning;
though hydrologic responses to the earlier rainfall may linger.
There will be a lull in the shower activity and perhaps even some
breaks of sun at times midday Wednesday, though with a northern
stream cold front squeezing through.
Behind that cold front, winds turn northwesterly with a moist
yet shallow layer of upsloping flow to most of the region.
Therefore, clouds will probably increase again Wednesday
afternoon from the Twin Tiers northward along with spotty
isolated to scattered lake enhanced showers courtesy of cooling
aloft. Highs will be mainly upper 60s-upper 70s, with initially
humid dewpoints of upper 50s-upper 60s backsliding into the 50s
by evening. Both dewpoints and even temperatures will backslide
into mainly upper 40s-lower 50s by dawn. Upslope tags of low
clouds/fog may still hang on for some of the terrain given the
moisture from earlier rains, but the overall trend will be for
north-northwest wind Wednesday night to clear things out with a
stirred-up boundary layer.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
310 PM Update...
High pressure will bring a much needed dry end to the work week.
Northerly flow will keep temperatures slightly below normal Thursday
with highs in the upper 60s to low 70s and low in the 40s to low
50s. Light winds, clear skies, and a sharp, shallow inversion will
likely lead to patchy fog overnight and into Friday morning. An
upper-level ridge will move in on Friday and will lead to a slight
warm up. Temperatures will max out in 70s across the region before
falling into the upper 40s and to mid 50s.&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
310 PM Update...
Surface high pressure will remain in control to start the weekend. A
weak upper-level trough will move through Saturday night into
Sunday, possibly kicking off some rain showers for a small portion
of the region. Then high pressure over the eastern half of CONUS
will expand eastward, resulting in a dry start to next week as well.
While we have had a taste of fall for awhile, summer will make a
return during the holiday weekend. Along with this 594dam high,
850mb temps will be over 20 deg Celsius. But with the heat will also
be humidity.
Surface temperatures will trend warmer from Saturday through
Tuesday, starting out in the upper 70s/low 80s and climbing to the
mid 80s/low 90s. Dewpoints during the warmest days will be in the
upper 60s to low 70s. The lows will be mild, starting out in the 50s
Saturday night but then staying in the 60s for the rest of this
period.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
Surface high pressure will remain in control to start the weekend. A
weak upper-level trough will move through Saturday night into
Sunday, possibly kicking off some rain showers for a small portion
of the region. Then high pressure over the eastern half of CONUS
will expand eastward, resulting in a dry start to next week as well.
While we have had a taste of fall for awhile, summer will make a
return during the holiday weekend. Along with this 594dam high,
850mb temps will be over 20 deg Celsius. But with the heat will also
be humidity.
Surface temperatures will trend warmer from Saturday through
Tuesday, starting out in the upper 70s/low 80s and climbing to the
mid 80s/low 90s. Dewpoints during the warmest days will be in the
upper 60s to low 70s. The lows will be mild, starting out in the 50s
Saturday night but then staying in the 60s for the rest of this
period.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Dry conditions are in place this evening with all terminals at
VFR. Overnight, showers and even an isolated thunderstorm or two
will move in from the southwest, and the rain can be locally
heavy in the area, especially between 06-10Z. Confidence in
where any spotty thunderstorm may be is low, so thunder was not
included in the TAFs overnight but will need to be monitored.
Besides the reduced visibility from the rain overnight, ceilings
will be lowering to IFR or worse at all terminals except for
SYR which is expected to drop to fuel-alternate levels. Locally
dense fog is possible for ELM and a TEMPO was added for
visibility and ceilings to fall below airport minimums between
08-12Z Wednesday. By late morning or early afternoon Wednesday,
all locations are expected to be back to VFR levels, but with a
northwesterly wind flowing over the Great Lakes, this can
enhance afternoon clouds and even lead to a couple of showers to
the north for RME and SYR and ceilings can fall back to MVFR.
Depending on how far south the clouds and spotty showers push,
this could lead to occasional Mvfr conditions for ITH, BGM and
ELM as well later in the afternoon.
Outlook...
Wednesday night through Sunday...Mainly VFR, but there can be
areas of fog Thursday night into early Friday.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch until 9 AM EDT Wednesday for PAZ038>040-043-044-
047-048-072.
NY...Flood Watch until 9 AM EDT Wednesday for NYZ024-045-046-
055>057-062.
&&
$$
SYNOPSIS...MDP
NEAR TERM...MDP/MWG
SHORT TERM...BTL
LONG TERM...BTL
AVIATION...DK/MDP
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
947 PM CDT Tue Aug 29 2023
.UPDATE...
Issued at 947 PM CDT Tue Aug 29 2023
The forecast remains on track. A very slight improvement in
visibility has been observed at most areas, but the concentration
of near-surface smoke is once again forecast to increase across
the western half of the state later tonight into Wednesday
morning.
UPDATE Issued at 655 PM CDT Tue Aug 29 2023
No significant forecast changes are needed for this update.
Visibility continues to be reduced by smoke to around 4 to 6 miles
across much of western and central North Dakota. Recent HRRR
modeling suggests some improvement may occur this evening through
tonight, more so farther to the east.
&&
.SHORT TERM...(This Evening through Wednesday Night)
Issued at 255 PM CDT Tue Aug 29 2023
Areas of smoke look to be found tonight, with breezy to windy
conditions expected for Wednesday.
Main weather impact for tonight will be how long does smoke stick
around and for what locations. A surface high will push just to
the east of the CWA tonight switching winds to more of a east
southeast direction. This could clear up smoke across the east,
while pushing the smoke to the west and some central areas. HRRR
smoke model showing this as well and generally followed that trend
through the night. Light winds and near saturated conditions could
bring some patchy fog to the east tonight. Elevated winds in the
lower layers could hinder this formation, thus confidence was not
high enough to place in the forecast at this time. Lows tonight
closer to the low will be in the lower 50s east, to near 60 west.
Dry conditions are expected for tonight.
Wednesday, surface high moves east while a surface low develops
lee of the Northern Rockies. ND is in the middle of this with
breezy winds and a passing warm front. Look for highs in the 80s
to lower 90s to return. South southeast winds could also be breezy
to windy at times, with ECM EFI values near 0.8. Timing of the
strongest winds still doesn`t look to quite line up with peak
afternoon mixing, thus no highlights are expected at this time. By
later in the afternoon a cold front will approach the state. There
may be enough instability and ample shear for an isolated
thunderstorm. The shear is high enough for severe weather,
although the CAPE is on the lower end, and is relatively skinny in
the hail growth zone. Thus the threat for severe storms through
the day Wednesday still remains low. HRRR smoke also continues to
show smoke lingering from west to east Wednesday through Wednesday
night, and generally went along with this trend in the forecast.
There could also be some fire weather concerns for Wednesday,
although the lower RH and the highest winds do not line up at this
time, and fuels still appear to be green.
Wednesday night, a clipper like system moves a cold front through
at night. This will be the focus for showers and thunderstorms
through the night. Like previously mentioned shear parameters are
high, but instability is on the lower side. A strong low level jet
could help overcome some of this though, and could help for a
borderline severe wind threat. Given all this an isolated strong
to perhaps severe storm is possible during this time period
although confidence remains low. The mentioned LLJ could also
provide for some stronger winds Wednesday night. 50 knots could be
found at the 850 mb level, although looks to be hard to mix down
to the surface at night. Pressure rises are not particularly high
either Wednesday night. Thus confidence in advisory level winds
still remains low. Low temperatures Wednesday night look to be in
the 50s west to 60s east.
.LONG TERM...(Thursday through Tuesday)
Issued at 255 PM CDT Tue Aug 29 2023
Look for a warming trend through much of the upcoming Labor Day
weekend, with cooling conditions and perhaps some showers to start
next week.
Thursday looks to be somewhat of a post frontal type of day with
breezy winds and slightly cooler temperatures. Some showers and
thunderstorms may linger in the morning, then diminish in the
afternoon except across the northwest. Highs will generally be in
the 80s with some upper 70s. Winds then diminish Friday, with dry
conditions and highs in the 80s. The start of the Labor Day
Holiday weekend then sees warming temperatures through Sunday,
with highs in the 90s each day. Afternoon RH may lower into the
20s at times, although winds look to be relatively light under
building high pressure limiting any fire weather concerns.
Labor Day into early next week, another cold front associated with
a large trough could bring cooling temperatures and chances for
showers and thunderstorms. The signal for severe weather looks
limited at this time. This could bring breezy winds, especially
on Labor Day. Cooling temperatures in the 70s and some 80s should
improve RH values, also limiting fire concerns. Overnight lows
still also look to be in the 50s to 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 655 PM CDT Tue Aug 29 2023
Smoke will continue to reduce visibility to MVFR levels at times
through the forecast period. Otherwise, VFR conditions should
prevail. Strong south-southeast winds are expected on Wednesday,
sustained around 15-20 kts with gusts to 25-30 kts.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Hollan
SHORT TERM...Anglin
LONG TERM...Anglin
AVIATION...Hollan
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
610 PM CDT Tue Aug 29 2023
...New AVIATION...
.SHORT TERM...
(Tonight through Wednesday night)
Issued at 226 PM CDT Tue Aug 29 2023
Current BRO radar shows a line of showers and thunderstorms
associated with a weak cold front is making their way towards the
southeast over Starr, Hidalgo, and Cameron Counties. The HRRR model
continues to show some convection that will last into the late
afternoon period into the early evening over the southern parts of
Deep South Texas and the Rio Grande Valley. Some of thunderstorms
may have some gusty winds and contain heavy downpours.
By tonight, drier air due to subsidence from Hurricane Idalia is
expected to move in, which will squash rain chances for the rest of
the short term period. Winds are expected to be light and variable
tonight, with low temperatures in the range of upper 70s and lower
80s. A similar pattern is expected for Wednesday night as well, with
the only difference being that Wednesday night low temperatures will
have some places into the lower 70s.
The big story for tomorrow will be the heat. Temperatures are
expected to be in the 100s for most of the region, expect along the
coast which will be in the 90s. The subsidence from Hurricane Idalia
will push the ambient temperatures up a bit, on the bright side it
will also decrease the moisture in the atmosphere keeping Deep South
Texas and the Rio Grande Valley out of Heat Advisory criteria.
Another impact from Hurricane Idalia on the region will be that the
swell will result in a moderate risk of rip current for the beaches.
Currently no other coastal hazards are expected at this time for
Wednesday. There is some limited fire weather concern for tomorrow
because of the dry air over the region, however the 20-foot winds
are light during the short term period.
&&
.LONG TERM...
(Thursday through next Tuesday)
Issued at 226 PM CDT Tue Aug 29 2023
The mid-level ridge heads east through the Plains and into the
Ohio River Valley over the weekend before elongating back across
the Southwest mid next week. Low pressure across the western Gulf
generally hangs around over the weekend and into early next week
just under the ridge. The persistent onshore flow will increase
moisture into Labor Day and early next week, bringing back low
rain chances, mainly along the seabreeze each afternoon Saturday
through Tuesday. Triple digit heat continues for most inland
locations with a slight reprieve along the coastal counties and
lower to mid valley over the weekend due to increased cloud cover.
Potential coastal hazards locally from Idalia will still need to
be monitored into late week. Long period swell Thursday will
maintain elevated offshore seas and likely enhance rip currents
along the lower Texas coast. Coastal run-up and flooding may also
be in play during high tide cycles Thursday. Confidence is a
little low at this time on the extent of coastal impacts, due to
the limited run the cyclone has within Gulf waters before landfall
and the strength of the rapid intensification expected over the
next 12 to 24 hours.
Fire weather is also worth monitoring through the end of the week
with RH values generally less than 30 percent across most inland
areas and tanking into the teens across Zapata County Thursday and
Friday. At this time, 20 foot winds either remain just below
criteria or arrive as RH values recover into the evening hours.
Regardless, with crispy fuels and the summer wildfire season in
full swing, RH values this low are concerning.
And finally, with better moisture and humidity returns higher Heat
Indices Monday and Tuesday, potentially leading to another round
of Heat Advisories. Indices in this forecast package remain just
below advisory criteria.
&&
.AVIATION...
(00Z TAFS)
Issued at 605 PM CDT Tue Aug 29 2023
VFR conditions are expected to prevail through the TAf period
across all aerodromes. A few showers will continue in the vicinity
of HRL for the next hour or so before it clears out. Winds will
become light and variable overnight with north to northeasterly
wind picking up by midday Wednesday and becoming more moderate.
&&
.MARINE...
Issued at 226 PM CDT Tue Aug 29 2023
Tonight through Wednesday Night...Mostly favorable conditions are
expected tonight with light winds and wave height between 2 to 3
feet. However, by tomorrow swell from Hurricane Idalia could bring
wave heights up between 4 to 5 feet for the offshore Gulf waters,
so Small Craft Exercise Caution might be needed for tomorrow and
tomorrow night. Winds are expected to be light to moderate for
tomorrow and tomorrow night as well.
Thursday through Tuesday...A long period swell across the Gulf
from Idalia is possible through Thursday. Offshore waters persist
around 5 feet before more favorable marine conditions generally
return during the holiday weekend and early next week. Low
pressure across the western Gulf of Mexico will gradually build
rain chances into Tuesday, generally offshore overnight and
onshore each morning. Winds and seas will be higher near any
thunderstorms.
&&
.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE 79 100 75 100 / 10 0 0 0
HARLINGEN 75 100 71 101 / 10 0 0 0
MCALLEN 77 103 74 104 / 20 0 0 0
RIO GRANDE CITY 77 103 74 104 / 10 0 0 0
SOUTH PADRE ISLAND 81 91 79 91 / 0 0 0 0
BAYVIEW/PORT ISABEL 77 97 73 97 / 0 0 0 0
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
SHORT TERM...64
LONG TERM....56
AVIATION...68
Area Forecast Discussion
National Weather Service Duluth MN
629 PM CDT Tue Aug 29 2023
.DISCUSSION...(This evening through Monday)
Issued at 313 PM CDT Tue Aug 29 2023
Mostly quiet weather with a weak cold front Thursday. Temperatures
continue to warm with some much above normal temperatures possible
into and through the weekend.
This afternoon, some stratocumulus has popped up under northwest
flow, but so far has produced no precipitation, with none expected.
We`ll have a quiet couple of days tonight through most of Thursday.
Tonight, mostly clear skies and fairly calm winds should lead to
quickly dropping temperatures and fog development. Widespread dense
fog is possible for much of the Northland, which should burn off
after sunrise tomorrow. Some temperatures below 40 are possible as
well, especially over portions of Ashland, Iron, and Price Counties
which should stay under a CAA regime all night. Over portions of
northern Minnesota, some very weak WAA is expected to begin
overnight, which may limit just how low temperatures can go.
Precipitation wise, the main chance for any rainfall is with a weak
cold front moving from NW to SE Thursday evening into early Friday
morning. These chances are pretty minimal and thermal profiles
continue to look poor with a lot of dry air in the low levels. The
best chance (only about 30%) exists over the Minnesota Arrowhead.
Tomorrow, our warming trend begins and will continue through the
extended forecast. By Friday, widespread temperatures in the 80s are
expected, with temperatures into the 90s for portions of the region
through the Labor Day weekend. Some high temperature records could
be broken, and Duluth has the potential to hit its first 90 degree
day of the year this weekend. Any potential for relief in the form
of lake breeze circulations is unknown. For more details on this
heat, please see the climate section of this discussion.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 626 PM CDT Tue Aug 29 2023
VFR conditions to start the forecast period. Satellite shows diurnal
cumulus slowly eroding with the loss of heating this evening. Some
hazy skies are still prevalent with near surface impacts still
affecting BRD. The latest HRRR guidance suggests the haze will
push west of the terminal as the Lake breeze moves in later this
evening. Overnight, clearing skies may lead to fog development
across the Northland. This fog will erode shortly after sunrise
with sunny skies and surface high pressure over the region for
Wednesday.
&&
.MARINE...
Issued at 313 PM CDT Tue Aug 29 2023
A brief period of northeast winds continues into this evening, with
some stronger gusts 20-25 knots possible late this afternoon near
the Twin Ports. A small craft advisory is in effect from 5 to 9pm
for those higher winds, which should force waves of 1-4 feet between
Two Harbors and Port Wing. Winds become southerly overnight into
Wednesday. Tomorrow afternoon, some southwest wind gusts may be a
little stronger 15-20 knots near Grand Portage, but overall
conditions should be fairly benign. Wednesday late afternoon and
early evening, with mostly calm winds over the land, a slight lake
breeze circulation may develop around the Twin Ports and Apostle
Islands leading some winds to turn more onshore, but they should be
fairly light. Thursday and Friday winds become southerly and
increase in magnitude with gusts in excess of 20-25 knots possible.
A cold front Thursday night may bring some light showers to the
lake.
&&
.CLIMATE...
Issued at 313 PM CDT Tue Aug 29 2023
There is widespread agreement amongst global ensembles for an
amplified upper level pattern to settle in across the CONUS that is
expected to bring a period of above normal temperatures to much of
the Upper Midwest, including the Northland. Strong, broad high
pressure should settle in across the central and eastern portions of
the U.S., bringing a blossoming of warmer than average temperatures
into our region beginning this Labor Day weekend and progressing
into early September. Current Climate Prediction Center temperature
outlooks for the 6-10 period (September 3rd-7th) put most of the
Northland at around an 85% chance of above normal temperatures with
only a 10-15% chance of normal temperatures and a 3% chance of below
normal temperatures. Beyond this, in the 8-14 day period (September
5-11th), there is around a 70-75% chance for above normal
temperatures with a 25-30% chance of normal temperatures. Specific
to the Labor Day weekend timeframe, latest Euro Ensemble guidance
for maximum temperatures shows EFI values over 90% for a good
portion of the Northland Sunday with SOT values over 1, indicating
high confidence for extremely unusual maximum temperatures. EFI
values for minimum temperatures are also beginning to approach the
70-80% regime, indicated that some unusually warm overnight lows are
possible, minimizing nighttime relief. Normal temperatures this time
of year range from the low to mid 50s into the mid 70s. Forecasted
high temperatures may rise into the 80s and 90s with some
temperatures overnight not making it below the lower 60s. Record
afternoon high temperatures and high minimum temperatures are
possible.
This possibly extended period of above normal temperatures for the
Northland could have a spectrum of impacts. Hot temperatures both
during the day and overnight could lead to heat-induced health
impacts to people and pets. Hot temperatures and dry to normal
precipitation is likely to continue to exacerbate current drought
conditions across Minnesota and Wisconsin. Additionally, hot
temperatures with potentially dry conditions may lead to some fire
weather concerns, especially on any day that is accompanied by
stronger winds. What is unknown at this time is the potential for
any lake breeze circulation development on Lake Superior. Strong
southerly flow would likely prevent any circulation from getting
very far inland, but calmer wind days may allow a lake breeze to
push further inland providing some relief for coastal communities.
Those details will only be able to be forecasted a couple days in
advance at best.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 48 73 51 78 / 0 0 0 0
INL 47 74 53 78 / 0 0 0 10
BRD 50 76 57 81 / 0 0 0 0
HYR 43 73 49 78 / 0 0 0 0
ASX 43 73 48 80 / 0 0 0 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 9 PM CDT this evening for LSZ144-145.
&&
$$
DISCUSSION...Levens
AVIATION...Britt
CLIMATE...Levens
MARINE...Levens
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1027 PM CDT Tue Aug 29 2023
.SHORT TERM...(This Evening through Wednesday Night)
Issued at 245 PM CDT Tue Aug 29 2023
KEY MESSAGES:
1. Wildfire smoke will continue to reduce air quality and visibility
until at least Thursday morning.
2. Expect stronger south winds Thursday with peak gusts in the 40s.
3. Dry, hotter than normal conditions continue with a Labor Day
Weekend heat wave and highs peaking on Sunday 90-105 degrees.
TONIGHT: Due to incoming wildfire smoke from the north, visibility
has dropped to under 10 miles for much of the area near and north of
the Interstate 90 corridor and as low as 3 to 5 miles across
northeast South Dakota and much of North Dakota. Air quality is
moderate across most of the region and as low as Unhealthy for All
Groups across most of North Dakota. Light north winds combined with
diurnal mixing down smoke from aloft means a surface layer of smoke
will continue to stream south into the region, further reducing air
quality and visibility.
Other than smoke related impacts, weather conditions remain fairly
pleasant across the region this evening with near seasonal
temperatures, low humidity, and dry conditions as weak sfc high
pressure slides through.
WEDNESDAY: By early morning, strong sfc high pressure builds east
and upper level ridging builds in from the west. Expect a slightly
warmer day west of I-29 where warm air advection kicks in. Winds
swing southward, increasing through the day ahead of sfc troughing
digging into the western Dakotas.
Despite southerly sfc winds, there will be nothing to scour out
lingering smoke in the region so agree with RAP and HRRR guidance
that expect reduced air quality and visibility to continue through
Wednesday night and early Thursday. Experimental air quality
forecasts suggest Unhealthy (for all) air quality will continue
through at least early Thursday so it is recommended to reduce
physical activity and outdoor activity, especially if you begin to
experience symptoms.
.LONG TERM...(Thursday through Tuesday)
Issued at 245 PM CDT Tue Aug 29 2023
THURSDAY: South winds strengthen by Thursday morning as we lie
between a progressive, approaching sfc trough and stalled high
pressure over the Great Lakes. NBM wind guidance remains overly
strong compared to deterministic models, so decreased the wind
forecast again to be near a NBM 10th percentile/NBM Experimental
combo. This resulted in south winds still sustained in the teens and
20s with gusts in the 30s to lower 40s on Thursday. Especially
reduced the wind forecast for Wednesday and Thursday nights, though
gusts into the 30s or maybe 40s cannot be entirely ruled out with a
strong low level jet in the vicinity. Strong mid level warm air
advection will start a warming trend, yielding highs ranging from
the 80s (east of I-29) to low to mid 90s (west of I-29).
FRIDAY THROUGH NEXT WEEKEND: Main impact for the holiday weekend
will be hot summery, mostly dry weather. Confidence is high that
strong upper ridging remains stalled over the Central and Southern
Plains in response to departing Hurricane Idalia with temperatures
aloft in the top 10% (and at times exceeding the max) of values for
early September in relation to EPS climatology.
Ignoring outlier heat of the GFS/GEFS guidance with a greater focus
on the EPS/CMC ensembles suggests a >50% chance of highs exceeding
95 degrees west of the I-29 corridor on Sunday, when the peak heat
is expected. Several sites will see near record high temperatures on
Sunday with EPS/CMC ensembles suggesting a 10-40% chance of highs
exceeding 100 degrees near the James River Valley (respectively).
Fortunately lower humidity readings (with dew points in the 50s and
60s) and a south breeze should help temper impacts, capping heat
index readings near the air temperature.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
Issued at 1025 PM CDT Tue Aug 29 2023
Some surface based smoke will remain possible through the period
with visibilities as low as 3 miles. Generally visibilities will
be 6 miles or greater. Otherwise, outside of any smoke concerns
VFR conditions are expected.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
SHORT TERM...BP
LONG TERM...BP
AVIATION...08
Area Forecast Discussion
National Weather Service Gray ME
1021 PM EDT Tue Aug 29 2023
.SYNOPSIS...
A weak area of low pressure approaches from the west tomorrow
with widespread showers and thunderstorms. More humid air is
drawn northward into the system and leads to some localized
moderate to heavy rainfall. Hurricane Franklin passes well
offshore but sends increasing long period swells into the Gulf
of Maine through Thursday, bringing the risk for rip currents.
High pressure will then return Thursday and build through much
of the upcoming weekend and early next week, bringing with it a
warming trend.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
1025 PM Update...
Have updated the forecast to add drizzle across southern and
central portions of the region. Areas of fog will continue to
develop as well during the overnight hours. Made minor
adjustments to temperatures, dew points and winds for the near
term portion of the forecast.
Update...
The much anticipated stratus and fog continue to pour into the
coastline early this evening per latest satellite imagery,
surface observations and webcams. This trend will continue after
sunset as fog develops over the interior as well.
Mesoscale models do have some showers reaching the coastline by
around midnight. Some precipitation already shown on latest
KBOX radar imagery over southern New England will spread to the
north. Otherwise, very little in the way of changes to the near
term portion of the forecast with this latest update.
Prev Disc...
We`re coming down to the wire with a complex interaction of
jets, fronts, and tropical moisture as uncertainty remains
unusually high relative to the 12 to 24 hour thereabouts time
range we find ourselves in this afternoon. As has been discussed
for the last several days... the Eastern Seaboard is poised to
take impacts from distant Hurricane Franklin, mostly in the form
of a long period swell but also with locally heavy rainfall in
some locations. More on expected impacts from the incoming swell
is detailed in the dedicated section below.
This afternoon, two frontal zones flank our area, one well to
the northwest and another to the southeast. The northern one is
associated with a digging trough of low pressure over the upper
Great Lakes region and attendant developing low pressure near
Sudbury, ON... with a broad baroclinic zone extending through
the Saint Lawrence Valley and into our northern zones. This has
been associated with scattered rounds of light rain showers
across the north, is currently just north of the international
border, and will eventually cross the region on Wednesday.
Further south, latest RAP analysis shows a stalled boundary
extending along the southern periphery of the GoME. Further
south yet is Hurricane Franklin, which is sending deep, tropical
moisture north into the latter boundary. Favorable RRQ jet
dynamics on the downwind side of the incoming trough, ramping up
tonight and tomorrow as the trough swings from a positive to a
negative tilt, are expected to at least partially align with
deep moisture for our conditional heavy rainfall threat.
Model guidance continues to waffle on locations with greatest
rainfall potential. In general however there is growing
confidence across both ensemble and deterministic model suites
that deepest moisture with PWATs exceeding 2 inches is not
likely to align with significant forcing over our area,
delivering a glancing blow at best along the coast overnight but
likely falling mostly over SE New England and the GoME. The
likely result overnight is widespread low clouds, fog, and
perhaps a few lighter rain showers scraping along the coast and
into the southern interior. Northern zones will be blocked from
maritime humidity by the mountains so they can expect a drier
overnight.
There is however growing confidence that an initial front
crossing the region later in the morning through the afternoon
will introduce enough forcing to capitalize on deep moisture.
Although the front brings drier air, it also brings steepening
lapse rates and increasing shear which will provide more
convective support to realize deep moisture even as it begins to
wane. Latest GEFS/EPS guidance shows low probabilities for 24
hour amounts AOA 1" however some stripes in excess of 1-2 inches
are present on CAMs which is likely the higher end of what we
may see tomorrow. A secondary front dropping down from the north
later in the day likely reinvigorates convective activity,
potentially in the form of a fine line, however the primary
impact here would be gusty winds as mixing and NWerly flow
increases. Froude numbers even indicate a downsloping wind, so
gusty winds in the higher terrain and SE downslopes can be
expected along with warmer temperatures and clearing skies
toward the west.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Precipitation chances and cloud cover quickly diminish
Wednesday night as dry air filters in through the mid- and low
levels. The exception is in the northwest upslope areas where
cyclonic flow becomes blocked, pooling humidity and prolonging
stratocu/light shower chances. A belt of northwesterly 30-35 kt
850 mb flow shifts overhead behind the departing trough axis
which should keep steady CAA through the overnight. Between this
and lingering upslope clouds, I don`t expect many places to
decouple except perhaps in the most sheltered valleys southeast
of the mountains (looking at you, Fryeburg). Thus, leaned on raw
guidance for the temperature forecast with lows ranging from
the upper 40s in the north to near 60 along the coast.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Overview...
An extended period of warm and dry conditions sets up for the
holiday weekend and next week as a ridge builds across the
Northeast. An increased swell from Hurricane Franklin is felt
along the coast late this week and into the weekend, with some
lingering increased waves possible next week as Idalia meanders
around the Atlantic.
Details...
Just in time for the unofficial end of summer, a combination of
the driest, warmest, and brightest stretch of weather we`ve
seen in months sets up for Labor Day weekend and into next week.
Temperatures on Thursday are expected to be seasonably cool
behind the cold front, mainly in the mid 60s to mid 70s, but
then the warming trend will be underway as the ridge builds.
Temps climb into the 70s on Friday, and push the low 80s in
spots on Saturday. Widespread 80s are expected Sunday, and then
mid to upper 80s build in for Labor Day and next Tuesday.
This ridge will build in from the southwest, and while it won`t
bring with it the stifling heat the southern part of the
country has seen this summer, it could bring some of the warmest
readings we`ve seen so far this year early next week. Portland
is yet to hit 90 degrees so far this year, and while it`s still
too early to tell if they`ll make it next week, this stretch
would likely be the last chance to do so.
While this ridge is building into our area, what remains of
Hurricane Idalia is expected to be trapped under the ridge and
meandering around the Atlantic late this weekend and early next
week. An extended period of increased surf and rip currents are
the primary concern from this system as it interacts with the
high to the north.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Short Term...VFR conditions early this afternoon trend to IFR or
worse tonight outside of the mountains with lowered CIGs and low
VSBY in BR/FG. Fog is expected to be most dense, most
persistent, and come in earliest along the coast. SHRA should be
lurking just offshore overnight, but RA/isolated TSRA will
become more widespread Wednesday morning. Winds back to the
west, then northwest on Wednesday as a cold front crosses and
may be gusty... especially in SHRA/TSRA. Terminals trend back
toward VFR Wednesday afternoon and evening, though MVFR may
linger at KHIE for part of Wednesday night.
Long Term...VFR conditions are expected during the daytime from
Thursday through early next week. Nighttime valley fog will be
likely each night at most terminals, but especially HIE and LEB.
&&
.MARINE...
Short Term...Weak waves of low pressure are forecast to move
through the Gulf of Maine tonight and tomorrow with increasing
fog, drizzle, and rain chances. Some pockets of rain, especially
overnight, will be torrential and contribute to poor
visibility. A cold front crosses the waters tomorrow afternoon
with potential for gusty northwesterly winds and a perhaps a
thunderstorm or two. Northwesterly flow continues through
Wednesday night and may approach 25 kts. Meanwhile a southerly
to southeasterly swell will continue to build into the GoME
tonight through tomorrow, with periodicity increasing into the
12-14 sec range... potentially necessitating a SCA due to
increasing wave heights by Wednesday night as winds pick up.
Long Term...A southerly swell generated by Hurricane Franklin
may bring long period waves greater than 5 ft across the eastern
waters through the day on Thursday. High pressure builds across
the waters and brings fair conditions from Thursday through
early next week, aside from any elevated southerly swell.
&&
.TIDES/COASTAL FLOODING...
A southerly swell generated by Hurricane Franklin continues to build
through tomorrow night and on Thursday. Strong rip currents increase
during the daytime tomorrow as the swell builds through the day
tomorrow, with this threat continuing into at least Friday.
Large waves also pose the risk of sweeping people into the sea
from rocks should they venture too close to the water,
especially along the MidCoast.
Along with the building surf, the highest astronomical tides of
the year continue to increase over the next few nights. Up to a
foot of surge from onshore flow helps push tides to around
minor flood stage tonight and tomorrow night. Depending how much
residual elevated water remains, we may also have to watch
Thursday night, but impacts are expected to remain minor.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...High Rip Current Risk from 8 AM EDT Wednesday through Thursday
evening for MEZ023>028.
NH...High Rip Current Risk from 8 AM EDT Wednesday through Thursday
evening for NHZ014.
MARINE...None.
&&
$$
Cannon/Clair
Area Forecast Discussion
National Weather Service Huntsville AL
756 PM CDT Tue Aug 29 2023
...New NEAR TERM...
.NEAR TERM...
(Tonight)
Issued at 756 PM CDT Tue Aug 29 2023
A couple of isolated showers continue over Morgan and DeKalb
Counties. HRRR runs have suggested some potential for
redevelopment along the weak convergence zone in this area this
evening. Will maintain a low PoP in this area this evening as a
result. But most areas will remain dry as north winds begin to
advect slightly drier air into the area. Dew points have dipped
into the middle to upper 60s in northwest AL into southern middle
TN. Stripes of mid and high level clouds will persist at times
over the southeast half of the forecast area (mainly southeast of
BGF-HSV. Overnight lows are still projected to be in the lower to
middle 60s.
&&
.SHORT TERM...
(Wednesday through Friday)
Issued at 206 PM CDT Tue Aug 29 2023
The short term period will contain very pleasant weather
conditions. With the passage of the frontal boundary in the
near term, PoP`s throughout the short term are limited to below
30% with highest covering being in the southeast counties of our
forecast area. Temperatures each day will be in the mid 80s, with
lows making it down to lower 60s and even upper 50s in our
Tennessee counties.
Two bigger factors in the short term will be our dewpoints and
winds. With the frontal boundary through our area, a much drier
air mass is being filtered in behind. This is seen in our dew
points dropping from the mid 70s to the 50s on Wednesday, and into
the upper 40s on Thursday. Relative humidity during this time
period looks to remain above 50%. Gusty conditions are also
possible on Wednesday as winds pick up due to closer proximity of
Hurricane Idalia that looks to make landfall in the FL Big Bend
Wednesday morning. The track for Idalia once she makes landfall is
directly northeast and is not expected to pose any threats to
North AL nor Tennessee. This can be seen in our near 0 PoP`s for
Wednesday and Thursday. The only byproduct of Idalia that we will
see are elevated winds of around 10-15 MPH, with gusts up to 25
MPH on Wednesday and Thursday.
Given lower RH and gusty winds, slight fire weather concerns have
been brought up, however with recent rainfall and with the
forecast currently keeping conditions well above red flag
criteria, no action is needed at this time.
&&
.LONG TERM...
(Friday through Monday)
Issued at 206 PM CDT Tue Aug 29 2023
Models are in decent agreement that an upper level ridge will
largely dominate the region for the long term period. Additionally,
surface high pressure is anticipated over the Appalachians through
early next week as well. Overall, with this pattern, not expecting
much in terms of showers and storms. NBM guidance indicates that
temperatures will remain near seasonal norms through early next week,
with highs in the upper 80s to lower 90s and lows in the mid to
upper 60s. However, some ensemble guidance hints that temperatures
may be warmer early next week, with highs perhaps in the lower to mid
90s and lows around 70 degrees instead. There may be some validity
to this, as the upper ridge looks to shift east early next week, with
the center axis over the Tennessee and Ohio valleys. For now, stuck
close with the blended guidance, but will keep an eye on temperature
trends to see if they should be a few degrees warmer than currently
forecast next week.
&&
.AVIATION...
(00Z TAFS)
Issued at 448 CDT Tue Aug 29 2023
VFR flight weather conditions are forecast.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...None.
TN...None.
&&
$$
NEAR TERM...17
SHORT TERM....RAD
LONG TERM....26
AVIATION...17
Area Forecast Discussion
National Weather Service North Platte NE
628 PM CDT Tue Aug 29 2023
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 247 PM CDT Tue Aug 29 2023
Key Messages:
- Near-surface smoke from Canadian wildfires are anticipated to continue
to impact the region into Thursday. The Air Quality Alert (AQA)
has been extended until 12 PM CT Thursday for portions of north
central.
- Another round of anomalously hot temperatures commences on
Thursday, continuing into early next week.
- No precipitation is in sight across western and north central Nebraska
through the weekend.
Recent GOES-16 WV and RAP 500-mb analysis showed high pressure
centered across southern California with high amplitude ridging
extending north-northwest into the Great Basin and Desert Southwest.
A negatively-tilted shortwave embedded within the mean flow aloft
was noted across far northern Montana. Northwest of this feature, a
negatively-tilted upper-level trough was apparent off the coast of
British Columbia extending southeast across the Pacific
Northwest. A broad upper-level trough was situated near the Hudson
Bay extending southwest across the Ohio River Basin and the Upper
Mississippi River Basin. All of these features combined has
resulted in northerly flow aloft across western and north central
Nebraska. At the surface, high pressure encompassed the region
resulting in a quiet day across the local area. Smoke from area
wildfires in Canada has pushed south across the region, producing
haze across much of western and north central Nebraska with thick
low-level smoke noted across South Dakota, North Dakota, and
Montana where surface visibilities has dropped 4SM or lower. At 3
PM CT, temperatures ranged from 82 degrees at Ainsworth to 89
degrees at Imperial.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 247 PM CDT Tue Aug 29 2023
The focus in the short-term surrounds smoke from area wildfires in
Canada impacting the local area. HRRR and RAP Near-Surface Smoke
model continues to highlight portions of north central Nebraska
seeing impacts from the smoke. Some visibility reductions are
possible, though of increased concern surrounds expected poor air
quality across the area. The smoke has also resulted in poor air
quality today across portions of north central Nebraska and is
anticipated to continue into Thursday. Given this, the Air Quality
Alert (AQA) has been extended until 12 PM CT Thursday for portions
of north central. Those who are sensitive to wildfire smoke or in a
sensitive group should limit time spent outdoors.
Heading into Wednesday and Thursday we will start to see
temperatures trending back into the above normal range as the
upper-level ridge begins to shift further east. Highs in the 90s
will be common across western and north central Nebraska. At the
same time, a strong (50+ kt) low-level jet (LLJ) develops across
the area in addition to a tightening surface pressure gradient
(SPG) will result in strengthening southerly winds encompassing
western and north central Nebraska. At this time, wind gusts of
25 to 35 mph will be common across the area with localized gusts
up to 40 mph possible. These gusty winds combined with hot
temperatures and dry conditions will promote afternoon relative
humidity values falling into the 25 to 20 percent range for areas
west of Highway 83, leading to elevated fire weather concerns on
both days.
.LONG TERM...(Thursday night through Tuesday)
Issued at 247 PM CDT Tue Aug 29 2023
The return of warm and dry conditions will be the main story in the
long term period for the region. The aforementioned upper-level
ridge builds further east across the southern Plains, encompassing
the central CONUS. This round of anomalously hot temperatures is
not anticipated to be on the same magnitude of what we experienced
last week. However, the signal for another round of hot days to
close out the month of August and begin September is supported by
both the NAEFS and ECMWF ensemble guidance which is suggesting
that the mean temperature at H85-5 will meet or exceed the 90th
climatological percentile Friday into Sunday. Furthermore, the EFI
(Extreme Forecast Index) is continuing to suggest increased
confidence of another anomalous event, such that the SoT (Shift of
Tails) is greater than 1 across portions of southwest and central
Nebraska. High temperatures through the weekend will climb into
the upper 90s with some locations seeing 100 degrees. The forecast
temperatures are approaching or reaching daily maximum
temperatures records at all climate sites (LBF, VTN, IML, and
BBW). All of this is in agreement with the CPC 6-10/8-14 Day
Temperature and Precipitation Outlooks favoring above normal
temperatures for the and below normal precipitation for the
region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 622 PM CDT Tue Aug 29 2023
Some smoke will reduce visibilities across portions of north
central Nebraska, including KVTN terminal this evening into the
overnight and Wednesday morning. There is also the chance for some
patchy areas of fog/smoke across north central Nebraska and even
some areas of the river valleys overnight into Wed. morning as the
particulates from the smoke may help to enhance fog potential.
Winds will become light and variable overnight then increase out
of the south Wednesday afternoon. Strongest winds will be across
portions of the northern Sandhills into north central Nebraska,
with gust of 25 to 30 kts possible.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...Viken
SHORT TERM...Viken
LONG TERM...Viken
AVIATION...Gomez
Area Forecast Discussion
National Weather Service Pendleton OR
842 PM PDT Tue Aug 29 2023
.EVENING UPDATE...No major changes to the forecast reasoning this
evening outside of minor temperatures adjustments. Winds have been
largely on track and have kept them as the afternoon package had
them. On that note, a few stronger gusts still ongoing this
evening, so no reason to cut short the wind advisory early as
locations like the Kittitas Valley as well as up on our hill here
in Pendleton continue to gust around 40-50 mph. Will continue to
monitor these winds as we approach 11 PM in case an extension is
necessary, but conditions have been gradually dying down and this
seems unlikely. Main thunderstorm concerns have also departed the
region with lingering areas of rainfall and some lightning noted
but our chances at stronger storms have become nil. Goatley/87
&&
.PREV DISCUSSION... /issued 434 PM PDT Tue Aug 29 2023/
AVIATION...00Z TAFs...Mostly VFR conditions expected. PDT has
seen some haze and dust cause a decrease in visibilities, but
expected this to get cleared out over the next few hours.
Otherwise the HRRR smoke indicates the winds should help to clear
out significant haze, so have brought visibilities up around
BDN/RDM in response over the next few hours. Winds remain breezy
overnight all sites and should continue to be breezy into
tomorrow, though lower with gusts generally around 20-30 knots.
Ceilings should be lifting as well with storms moving out of the
region, with high clouds expected 10-25k feet. Goatley/87
PREV DISCUSSION... /issued 250 PM PDT Tue Aug 29 2023/
SHORT TERM...Today through Thursday...Current radar and visible
satellite imagery showing light to moderate showers with a couple
embedded storm cells moving south to north across the Lower Columbia
Basin and through the Northern Blue Mountains and Elkhorns this
afternoon. Rain chances (25-55%) will continue through the afternoon
before pushing north later this evening, with most of the region
drying out by 11 PM with the exception of a slight chance (15-25%)
of showers and isolated storms along the east slopes of the Cascades
and around the Dayton area overnight into Wednesday morning. The
main concerns reside with frequent lightning, small hail, and gusty
conditions near any developing storm cells. Rain amounts are only
expected to amount to a couple hundredths of an inch, but amounts of
up to 0.25 inch is possible within developed storm cells. The other
weather concern today is associated with breezy to windy conditions
through the Lower Columbia Basin, Eastern Gorge, Blue Mountain
Foothills, and the Kittitas Valley as a Wind Advisory is in effect
until 11 PM tonight. Sustained westerly winds of 25 to 35 mph with
gusts of up to 55 mph will be possible through the evening as this
system passes through our area. Confidence in these wind values is
high (85-95%), as Ellensburg has already experienced a couple 55 mph
gusts earlier today, modeled pressure gradients between Portland
and Spokane stay between 10-15mb through 8 PM this evening
(indicative of advisory-level winds), and the NBM highlights an
80- 95% chance of wind gusts reaching 55 mph or above over the
aforementioned areas. These winds will become more locally breezy
into Wednesday and will continue to decrease through the morning
and afternoon hours.
These conditions are in response to a negatively tilted trough that
is passing through the Pacific Northwest today, poised to depart to
our east late tonight. High temperatures will only peak in the upper-
70s to low-80s through the Lower Columbia Basin today, which is
around 20 degrees cooler than on Monday and 10 degrees below normal
for this time of year. Minimum afternoon humidities have also
improved 20-30% from yesterday, dropping to only 30-50% across the
area. These cooler and more moist conditions will persist through
Thursday as westerly flow aloft sets up Wednesday before another
system drops from the Gulf of Alaska and digs along the Washington
coast on Thursday. The westerly flow will keep shower chances (15-
25%) along the Washington Cascades with some cells potentially
sneaking along the east slopes during the early afternoon.
Temperatures will be 2 to 4 degrees cooler on Wednesday as highs
will again break into the upper 70s to low 80s across the Lower
Columbia Basin. The upper level trough begins to dig along the
British Columbia coast overnight into Thursday morning before
continuing to dig along the Washington and Oregon coasts through the
day. Flow aloft will go from northwest Wednesday to westerly
overnight and from the southwest by Thursday morning, which is due
to this dropping trough feature. This southwest flow will help to
provide widespread rain chances (30-60%) along the east slopes of
the Cascades, north-central Oregon, and south-central Washington
Thursday morning before including our entire area in rain chances
(40-70%) through the afternoon. Rain amounts of 0.25 will be
possible west of the Tri-Cities, Hermiston, and John-Day areas, with
only 0.02-0.10 inch over these areas and east for areas of lower
elevations. In areas of higher elevations, like over the Northern
Blue Mountains, rain amounts of 0.10-0.25 inch will be possible
through the day on Thursday. High temperatures will again cool
another 5 degrees on Thursday, with afternoon temperatures reaching
into the low to mid-70s across the Lower Columbia Basin. This active
pattern looks to continue into the extended period. 75
LONG TERM...Friday through Tuesday...Overall the extended period
remains characterized by showery and unsettled conditions primarily
focused over the mountainous terrain across the region through the
weekend into early next week - model uncertainty grows substantially
late Sunday onward. To start the period on Friday, both
deterministic and ensemble guidance are in fairly good agreement
resolving the overall large scale pattern depicting a newly formed
closed upper-level low centered directly over top the Pacific
Northwest having progressed southward from British Columbia. The
overall setup certainly favors widespread shower activity,
especially the east slopes of the Oregon Cascades through Central
Oregon and the Eastern Mountains where terrain forcing relative to
the location of upper-low will be conducive to shower development.
Going through Saturday, confidence is high(80-99%) this cut-off low
slowly meanders southward, eventually parking over northern
California leaving us in prominently southerly flow aloft. During
this period thunderstorm chances remain at least a little ambiguous
as CAPE values projected by deterministic/ensemble models at this
time scale are fairly unimpressive(100-300j/kg). Still, given the
low to mid level moisture availability, terrain forcing, and decent
diurnal heating slight chances(15-24%) for thunderstorms are
expected both Friday and Saturday afternoon over central and eastern
Oregon. The NBM probability of thunder is similar in this region as
well, around 10-30% each afternoon.
Model uncertainty begins to magnify into early next week as the
aforementioned closed low to our south transitions into more of a
open wave, weakening and progressing eastward into Nevada and Utah
Sunday night into Monday morning. As the axis of this trough pushes
across the CWA expect breezy Cascade gap winds to develop Sunday
afternoon and evening with nearly 30-40% of the total EPS ensemble
members projecting gusts at or above 40mph for spots like the
Kittitas Valley. While guidance does a good job resolving the
aforementioned feature, the primary point of contention is the
development and progression of a compact upper-level low in the Gulf
of Alaska which deterministic guidance like the GFS, ECMWF, and
Canadian all show albeit with differing timing and placement.
Unfortunately due to the smaller size of the upper-level low, it’s
largely “washed out” when exploring ensemble guidance. Should it
swing into eastern Washington as shown by the GFS a burst of
increased shower activity and breezy to gusty winds would follow
Sunday night into Monday, although the ECMWF takes is much further
north comparatively with little additional impacts. At the very
least, all guidance indicates the return of drier zonal by Tuesday
and Wednesday of next week. Schuldt/99
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 54 75 54 68 / 20 0 0 40
ALW 57 77 57 72 / 40 10 0 40
PSC 61 81 62 72 / 30 10 0 50
YKM 52 79 55 73 / 20 10 10 70
HRI 59 79 59 72 / 10 0 0 50
ELN 55 72 54 73 / 30 10 10 50
RDM 44 75 47 66 / 10 0 0 40
LGD 51 73 51 68 / 20 0 0 30
GCD 47 74 48 70 / 0 0 0 30
DLS 59 78 61 71 / 20 20 10 60
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 11 PM PDT this evening for ORZ041-044-507-
508-510.
WA...Wind Advisory until 11 PM PDT this evening for WAZ024-026.
&&
$$
EVENING UPDATE...87
SHORT TERM...75
LONG TERM....99
AVIATION...87
Area Forecast Discussion
National Weather Service Sacramento CA
1229 PM PDT Tue Aug 29 2023
.SYNOPSIS...
A Red Flag Warning has been issued for critical fire weather
conditions expected 11 PM tonight through 8 PM Wednesday for gusty
north winds and low relative humidity across the Northern and
Central Sacramento Valley. Afterwards, a cooling trend begins
Saturday into early next week with increased chance for showers
and isolated thunderstorms.
&&
.DISCUSSION..
Quiet weather this afternoon with warm afternoon highs in the 90s
across the Valley and 80s and 90s in the foothills. Northwest
winds persists across northwest Sacramento Valley that will
continue smoke intrusion, as low as 2 to 4 statute miles for
Redding to Red Bluff areas. HRRR smoke shows chances for heaviest
smoke intrusion this evening and lessening through Wednesday
morning, tracking southward as far south as the Northern San
Joaquin Valley. Temperatures slightly increase tomorrow resulting
in some localized areas of moderate HeatRisk across the Valley and
portions of the Delta.
Models continue to swing an upper-level trough through the Pacific
Northwest, closing off in Northern Idaho early Wednesday morning.
Offshore pressure gradients will tighten with northerly winds
increasing across Northern, Central, and Western Sacramento
Valley late this evening, peaking early morning Wednesday and
dropping off Wednesday evening. Winds will be generally 15-25 mph
with the latest HREF showing a 40-80% chance of winds gusts above
35 mph across the Valley. This combined with relative humidity
values in the single digits to teens by Wednesday morning will
result in critical fire weather conditions across the West side of
the Sacramento Valley, mainly along and west of Interstate 5.
Accordingly, a Red Flag Warning has been issued from 11 PM tonight
through 8 PM Wednesday. Avoid outdoor activities that could cause
sparks and outdoor burning is not recommended.
Our weather pattern is expected to change as a strong upper-level
low moves into northern California early Friday morning from the
Pacific Northwest. This will bring in cooler temperatures Friday
into next week with even the possibility of afternoon highs in the
upper 70s Friday and Saturday before gradually increasing into the
80s next week. Additionally, shower chances increase for the
Northern Coastal Range and Sacramento Valley, Southern Cascade
Range, and Northern Sierra Friday (30-60% probability). There is a
lesser chance for thunderstorm development as cloud cover may
inhibit convection (20-30% probability) but further analysis will
be needed as we get closer end of the week and CAMs are available.
&&
.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...
Saturday looks to decrease in shower and thunderstorm areal extent
and potential as the upper-level low sinks south and moves chances
to the Coastal Range, Central and Southern Sierra. The NBM shows a
10-20% probability of thunderstorm development and decreasing
further into the weekend and early next week. Heights begin to
flatten out and increase early next week, resulting in increasing
temperatures into the 80s and drier weather. Cluster analysis
looks to keep Central and Northern CA in a general troughing
pattern however, supporting below to normal temps through the
extended.
&&
.AVIATION...
VFR conditions, with areas of MVFR visibilities from FU/HZ
increasing tonight into Wednesday, mainly in the northern
Sacramento Valley spreading southward. In the Central Valley,
surface winds mainly below 12 kts thru approximately 06Z, then
northerly surface winds up to 20 kts with local gusts up to 30
kts.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 PM this evening to 8 PM PDT Wednesday
for Central Sacramento Valley in Glenn, Colusa, Yuba, Northern
Sutter, and Butte County Below 1000 Ft-Eastern Mendocino NF-
Eastern Portion of Shasta/Trinity NF-Northern Sacramento Valley
to Southern Tehama County Line Below 1000 Ft-Southeast Edge
Shasta-Trinity NF and Western Portions of Tehama-Glenn Unit-
Southern Sacramento Valley in Yolo-Sacramento Far Western
Placer, southern Sutter and Solano County Below 1000 Ft.
&&
$$