Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/07/22
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
250 PM PDT Sat Aug 6 2022
.SYNOPSIS...Dry, seasonable weather is expected to persist through
early this week. A deep marine layer will keep clouds along the
coast with slightly cooler than average temperatures within inland
valleys.
&&
.DISCUSSION...Overall seasonal summer weather prevails throughout
Northwest California. A very deep marine layer around 2800 feet
alongside areas of smoke has kept many interior valleys in the 80s
with only valleys further east reaching into the 90s. Persistent
marine stratus has kept the coast cool in the mid 60s.
The persistent cutoff low stuck offshore is expected to slowly
lumber northeast through Wednesday. This evolution should allow for
mostly stable weather. A persistent deep marine layer will allow for
strong nightly intrusions of stratus perhaps as far inland as Ukiah,
keeping interior temperatures slightly below average in the upper
80s to low 90s. Stubborn marine status is expected along the coast
with little more than broken clouds likely through Monday.
With little wind to speak of and only modest afternoon mixing,
wildfire smoke is expected to gradually accumulate in interior
valleys. HRRR smoke guidance shows smoke coverage broadening over
the next couple of days, mostly in valleys to the northeast of
Willow Creek during diurnal winds. Air quality monitors currently
show unhealthy air quality near Willow Creek with conditions likely
to worsen at nearby locations in the coming days.
In contrast to the last week, the low as expected to swing mostly
dry desert air aloft over the area with monsoon moisture mostly
moving the the northeast. While model sounding show up to 300 MUCAPE
each afternoon, very dry air aloft will inhibit any significant
thunderstorm development. Some thunderstorms may still be possible by
midweek if the current track of the low changes.
Depending on the exact track of the low, significant forecast
uncertainty exists late in the week. Most cluster ensemble members
show similar weather continuing all week. But by next Friday, about
20% show weak ridging and hot temperatures behind the low while
about 50% show low pressure redeveloping offshore. /JHW
&&
.AVIATION...Stratus lingers along most of the North Coast, as well
as between Cape Mendocino and Fort Bragg, as the marine layer
remains about 2500 feet deep. Low clouds extended all the way to
KUKI early this morning, but inland clouds dissipated quickly with
daytime heating. Additionally, smoke from several fires around the
Willow Creek area is spreading N and NW, and this may affect
visibility upon approach at both KCEC and KACV. The smoke will be
thicker near KACV, but it may also skirt by N of the airport. Expect
coastal stratus to expand and thicken as it spreads inland once
again tonight, with visibility reductions in fog. Fog is not
expected at this time at KUKI, but 1500 foot ceilings are forecast
by 12Z. Area winds will be light. /SEC
&&
.MARINE...Winds are forecast to become more uniformly southerly
tonight, but speeds are forecast to remain light. Winds may become
NW over the extreme S by Sunday night, but speeds should remain
light through mid-week. Northerlies may increase by Wednesday night
or Thursday as a nearly stationary low pressure system W of the
waters weakens. /SEC
&&
.FIRE WEATHER...Dry and calm weather is expected through at least
mid week. Dry air moving in aloft will bring an end to the
thunderstorms experienced over the last week. A deep marine layer
should penetrate far inland over the next couple of days. Alongside
smoke cover, interior temperatures will likely be kept in the upper
80s to low 90s. There will be a strong humidity gradient along
interior valleys with minimum RH in the low teens in eastern Trinity
and Lake counties increasing into the mid 30s closer to shore in
places like Willow Creek and Ukiah. Overnight recoveries will be
good generally above 75 percent. Winds will be gentle and diurnally
driven, generally below 10 mph. As low pressure approaches shore,
some isolated ridges could see enhanced winds above 15 mph in the
afternoons. /JHW
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
None.
&&
$$
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Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
859 PM CDT Sat Aug 6 2022
.UPDATE...
Issued at 859 PM CDT Sat Aug 6 2022
No significant changes to going forecast this evening.
Very warm and muggy low level air mass remains in place across the
forecast area this evening as evidenced by tempos still holding in
the low-mid 80s (near 90 in the heart of the urban core of the
Chicago area) and oppressive surface dew point temps in the mid-
upper 70s in many spots. While easing from peak afternoon values
above 100F, heat indices remain in the upper 80s to mid 90s as of 8
pm. Overnight lows will likely not dip below 75F in much of the
forecast area, and may hold above 80 in the city of Chicago
especially if convection or associated outflow were not to develop
as expected toward morning. An uncomfortable night for those without
air conditioning.
Looking to the northwest of the forecast area this evening, a couple
of clusters of strong thunderstorms have developed across parts of
northern IA/southern MN since late this afternoon, in association
with a low-amplitude mid-level short wave propagating ENE from SD/NE
into southwest MN/northwest IA. SPC RAP mesoanalysis indicates
strong instability within the very warm/humid air mass across the MS
valley (DVN 00Z RAOB sampled 3900 J/kg), and despite modest deep-
layer bulk shear a small bowing segment (with evident rear inflow
jet) has developed just west of La Crosse WI. These storms may
weaken somewhat with time as they continue to spread into southwest
WI late this evening, though some eventual southeastward development
into far northern IL is likely after midnight with development of a
cold pool/outflow and a gradual veering of the low level jet. CAM
suite still shows some spread with respect to timing of this
southeastward shift, but generally looks to range from as early as
130 AM for our far NW cwa along the WI border to perhaps closer to
dawn for the northern Chicago suburbs. Some weakening is likely with
southeastward extent, both due to gradual decrease in low level
instability overnight and also due to higher mid-level heights and
dry mid-level air within mid-level ridge axis farther south across
IL/IN. Nonetheless, showers and thunderstorms with some locally
heavy rainfall potential do look to affect the area Sunday morning.
Going forecast has all of the above handled nicely, so despite the
complexities of the overnight and early Sunday morning weather
scenario no significant changes appear warranted to the current
forecast.
Ratzer
&&
.SHORT TERM...
Issued at 310 PM CDT Sat Aug 6 2022
Through Sunday...
The primary forecast messages in the short term are:
* Markedly muggy through tonight into Sunday, with encouraged heat
preparedness and checking on those without air conditioning
* Showers with some embedded storms expected to move southeastward
into at least along/north of I-88/I-290 in northern Illinois
late tonight or Sunday morning with a fade in coverage into
early Sunday afternoon
* A locally heavy rainfall threat with activity through the day
Sunday, though low confidence on exact evolution during Sunday
An impressively humid low-level air mass over the area this
afternoon with multiple AWOS in central to north central Illinois
having reached 80F dew points. While this was likely aided by
mature crop evapotranspiration, it does speak for much of that
area given the land cover, and does also show the moisture depth
with no mixing of lower dew points this afternoon. With lower 90s
temperatures, heat index readings are upper 90s to a few degrees
over 105 from east to west across the CWA. Spotty showers have
popped with the convective temperatures being breached by a few
degrees (thanks to the high dew points) in subtle confluence
corridors. These showers should dissipate by 6-7 P.M. with a very
low lightning threat due to dry air entrainment of updrafts and
no sustained low-level focus to give updrafts extra oomph.
No changes planned to earlier issued Heat Advisory for north
central Illinois. Area-wide, temperatures tonight will really
struggle to drop given the high dew point air, southerly winds of
5-10 mph, and incoming thickening cirrus from upstream. Lows in
some part of the Chicago urban heat island may not dip below 80,
while mid to upper 70s elsewhere.
The stout upper level ridge with 594 dam heights centered over the
Central Plains and Mid-Missouri River Valley will gradually start
to dampen late tonight into Sunday as a 95+ kt upper jet streak
across the international border precedes a short wave upper
trough. A couple small scale impulses ahead of this noted on
satellite water vapor imagery over South Dakota and Nebraska are
expected to initiate robust convective growth in the Minnesota-
Iowa border region this evening. This will also have the focus of
a slow-moving low-level front, and regenerating convection is the
character forecast from that region into western and southwestern
Wisconsin. Steering flow and favorable low-level moist and
veering wind profiles for cold pool sustainability should support
some eventual southeastward movement of any convective clusters
or potential MCS. A rapid forward propagation is not anticipated
given the Corfidi forward vector magnitudes. Guidance varies on
when southeast progression would move things into far northern
Illinois, and some guidance such as the 12Z ECMWF and 12Z NAM
almost entirely dissipate the activity before it arrives. That
seems too weak given a veering 35-45 kt low-level jet across the
Central Plains into Iowa replenishing moisture into the upstream
region. But do think we may get through much of the night (through
3-4 A.M.) without much in the CWA at all, before either festering
convection on outflow or spotty elevated convection to the south
of any MCS does eventually meanders over far northern Illinois.
The most probable time and area of precipitation in the short term
period is Sunday morning for north of I-80, although still by no
means at all a slam dunk (hence why only 50-70 PoPs have been
placed into the forecast). While the convective footprint is well
agreed upon by CAM guidance to gradually shrink into the post-
daybreak Sunday morning hours, there looks to be enough low-level
support with elevated CAPE to have probable showers and
embedded/scattered storms moving into at least part of northern
Illinois. While some of the MUCAPE levels are >1,500 J/kg on
forecast guidance for Sunday morning, interrogation of soundings
show that the steepness of elevated lapse rates is fairly
marginal, so thunderstorms will probably not have as much coverage
as any showers. How far south activity makes it is uncertain and
may well depend on what type of cold pool push is provided. The
true boundary/focus though will remain north of the area, and that
is also why the focus for training activity for a flash flooding
threat through at least the daytime Sunday looks on the lower side
(risk level 1 of 5). A severe weather threat looks even lower,
with deep layer shear of 20 kt or lower. Conceivably could see
some gusts of up to 40 mph with any semi-organized convection on
more quicker propagating outflow.
For Sunday afternoon, temperatures will likely be hindered by
cloud cover from the morning that may struggle to dissipate during
the afternoon. Have lowered highs some in far northern Illinois,
though still humid conditions area-wide. In at least the far
southern and southwestern CWA, there may be some risk of reaching
Heat Advisory criteria in the afternoon. There may be some
diabatic heating boundary along the southwest side of this, as
well as a possible outflow boundary(ies) that could serve as a
source of scattered afternoon convection. Confidence is fairly low
though.
MTF
&&
.LONG TERM...
Issued at 310 PM CDT Sat Aug 6 2022
Sunday night through Friday...
An upper-level trough will be pushing eastward across the upper
Midwest into the northern Great Lakes at the start of the extended
period with surface low and associated cold front taking shape
across the central Plains and mid Mississippi River Valley. While
the trough itself is expected to remain well north of our forecast
area, the projected northeast track of the surface low will allow
the cold front to push southeastward across northeastern Illinois
and northwest Indiana overnight Sunday night and through the day on
Monday.
Ahead of the cold front a warm moist and somewhat unstable airmass
will be in place characterized by dew points in the low to mid 70s
and PWATs over 2.0 inches across the majority of the area which will
allow for the development of showers and thunderstorms. This moist
airmass should allow for any showers and storms to be rather
efficient rainfall producers which could lead to flash flooding
concerns if storms are able to train over the same area for extended
periods of time. However, guidance continues to struggle with the
timing of this cold front and the foot print of where the heaviest
rainfall will set up across the area. The majority of the ensemble
and deterministic guidance seems to favor areas closer to the IL-WI
state line which makes conceptual sense given the forecast track of
the aforementioned surface low and upper-level trough. The showers
and storms should push southeastward with the front during the day
on Monday and should be able to maintain their heavy rain potential
as they do so. Given the uncertainty I have maintained the likely
POP mention Sunday night through the day on Monday which seems
reasonable with the current expectation of the environment and the
frontal timing.
Rain chances are expected to gradually to come to an end Monday
night as the cold front pushes south of the area and high pressure
begins to build back into the area. While I do suspect that most
locations will be dry on Tuesday I did decide to keep a slight to
chance POP forecast mainly for areas south of a Pontiac, IL to Gary,
IN line to account for the uncertainty in the front`s speed as it
exits the area. Any lingering showers that do persist on Tuesday
will come to an end Tuesday night leaving the rest of the extended
period with a rain-free forecast. Temperatures and dew points will
also become much more comfortable behind the front with dew points
hanging out in the 60s and temperatures forecast to be in the 80s
through the rest of the upcoming week.
Yack
&&
.AVIATION...
For the 00Z TAFs...
Aviation Forecast Concerns:
* Timing of greatest shower/thunderstorm chances late tonight
through Sunday. Confidence is generally medium with thunder
timing and coverage.
* Brief IFR/MVFR vis and cigs in heavier shra/ts.
* Surface winds generally southwesterly through period, though
some low-confidence potential for an easterly component due to
convective outflow Sunday morning/early afternoon.
Isolated showers and thunderstorms which developed out of very
hot/humid low level air mass this afternoon have weakened and
decreased significantly in coverage as of 6 pm, as we begin move
away from our diurnal peak heating hours. Expect this trend to
continue, with quiet VFR aviation weather anticipated through the
evening hours.
Farther to our northwest, a cold frontal boundary from central NE
to the IA/MN border region and into northwest WI will be the focus
for repeated thunderstorm development tonight into Sunday morning,
with some of the southeastern periphery of this activity likely to
spill into far northern IL at least in a weakening fashion after
midnight tonight and into Sunday morning. Current suite of CAM
guidance suggests shra/tsra after 2-3 am for KRFD area, and after
4-5 am for the northern Chicago metro terminals. Initial activity
may be tied to outflow boundaries from larger footprint of
convection across central/southwest WI and actual TSRA coverage is
somewhat uncertain as this activity will be moving southeast into
somewhat less favorable conditions especially farther south of a
KRFD-KORD line. There appears to be some guidance agreement
however in greatest TSRA potential Sunday morning with an embedded
mid-level disturbance and have highlighted this period with tempo
mention of TSRA. By early afternoon, this disturbance looks to be
moving off to the east of the area, which along with somewhat
subdued surface-based instability due to morning clouds/precip
looks to limit thunderstorm coverage by afternoon. May still be
convective showers festering with modest but persistent warm
advection ascent above the surface-based outflows/cold pool, and
thus have maintained VCSH mention through the afternoon.
CAM guidance again depicts a reasonable uptick in convective
coverage and thunderstorm potential by mid-late Sunday evening as
another somewhat more-amplified mid-level disturbance approaches
from the west. Have indicated another period of prob30 for TSRA
for the latter part of the KORD/KMDW 30-hour forecasts after 02Z/9
pm Sunday evening.
Very moist low levels as well as robust column moisture will
likely support periods of MVFR/IFR vsbys with the heavier showers
and thunderstorms, as well as MVFR cigs. Winds through the period
are expected to be largely from the southwest, though convective
outflow may make for variable directions especially Sunday
morning/early afternoon. Confidence is low in details of this,
though it`s not out of the question that there could be a period
of easterly surface winds if Sunday morning`s convective cold pool
is substantial enough.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1059 PM CDT Sat Aug 6 2022
.UPDATED for the 06Z Aviation Discussion...
Issued at 1100 PM CDT Sat Aug 6 2022
&&
.DISCUSSION...(This evening through Saturday)
Issued at 301 PM CDT Sat Aug 6 2022
- Confidence increasing in heavy rain and potential for flash
flooding across southern MN, near the I-90 corridor tonight.
- Next week will bring us back to a mild and dry weather pattern.
An MCV moving across southern MN this morning gave us our first
round of rain this morning. It has left an outflow boundary down
near the IA border, with the main synoptic cold front slowly
dropping south to meet it. This looks to setup a classic heavy rain
environment down near the IA border. Within the 12z HREF, the
NSSLwrf, ARW, HRRR, and NAMnest all show a band of 4-7 inches of
rain falling somewhere within a couple of counties of either side of
the MN/IA border. Seeing these sorts of rainfall totals is supported
by heavy rainfall conceptual models for an overrunning heavy rain
event along a warm/stationary boundary. MUCAPE in the warm sector is
forecast to peak at over 3000 j/kg and this unstable atmosphere will
be forced up and over the boundary in a airmass characterized by
PWATs near 2.25" and freezing level depths up around 15k feet, so a
classic setup for a heavy rain event. Though location differ, most
CAMs show a training thunderstorm event developing tonight near the
MN/IA border. Given the signal we`ve seen with the 12z HREF, that
the HRRR carried into its 18z run, we have issued a Flash Flood
Watch for tonight down in our southern two tiers of counties.
We say all of this about the heavy rain and have passed up on the
severe risk. Well there`s good reason for that, this just isn`t a
significant severe environment with the main synoptic boundary
expected to be down in northern IA into far southeast MN. In
addition, the best shear will be up across northern MN where the
better mid/upper flow will reside. In addition, lapse rates are
weak, which is good for heavy rain, but not necessarily severe
weather. We may get a good downburst or two late this afternoon into
the evening, but widespread severe weather is not anticipated.
Sunday, storms are expected to dissipate in the morning as the LLJ
veers toward eastern WI and we should get a several hour long lull
in precipitation Sunday morning into the afternoon. However, by late
afternoon into the evening, we expect one more round of more
widespread showers as the main shortwave comes across South Dakota
and moves through southern MN. This looks to be a shower with a
thunderstorm or two type of setup, with additional rainfall amounts
generally expected to be a quarter of an inch or less.
Next week, we`ll see an upper ridge amplify over the Rockies early
in the week, that will work east through the week, with the ridge
axis setting up over the upper MS Valley by Thursday and Friday.
Over the weekend, this ridge will flatten some, which will open the
door for us to potentially see some weak fronts work back into the
area. We`ll start off the week with beautiful weather conditions on
Monday with highs in the mid/upper 70s under mostly sunny skies.
However, that ridge moving in means we will quickly return to above
normal temperatures, with highs back in the mid to upper 80s
expected from Wednesday through next weekend. At this point, another
run of widespread highs in the 90s looks unlikely, though we may
start to see a few 90s show up on the map next weekend. As for rain,
there`s virtually no chance during the work week with the upper
ridge overhead, but we do see low chances return next weekend with
some of the guidance showing a weak boundary working across the
area, which it were to happen, would be a focus for thunderstorm
chances, but at this point, the rain chance signal for next weekend
isn`t all that strong.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1100 PM CDT Sat Aug 6 2022
Still expecting the development of additional showers and
thunderstorms in south central Minnesota later tonight. Chances for
this though are moving a little farther south and later in the night.
So MKT is now only on the edge of where this could happen. So overall
expecting VFR tonight with a chance for some high MVFR. Locations
closer to the possible activity like MKT will see some lower ceilings
as low as IFR. Another chance for rain will arrive on Sunday night.
KMSP... Additional rain showers unlikely and VFR is expected tonight
into tomorrow. Another chance for some SHRA and MVFR tomorrow night.
/OUTLOOK FOR KMSP/
MON...VFR. Wind N 5-10 kts.
TUE...VFR. Wind SW 5-10 kts.
WED...VFR. Wind NW 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Flood Watch until 10 AM CDT Sunday for Blue Earth-Faribault-
Freeborn-Martin-Steele-Waseca-Watonwan.
WI...None.
&&
$$
DISCUSSION...MPG
AVIATION...NDC
Area Forecast Discussion
National Weather Service Marquette MI
1204 AM EDT Sun Aug 7 2022
.SHORT TERM...(This evening through Tonight)
Issued at 317 PM EDT SAT AUG 6 2022
Water vapor imagery and RAP analysis show two main features of
interest. One is a vigorous shortwave along the Manitoba/Ontario
border near Hudson Bay which is progged to move east across northern
Ontario today as it propels a cold front across Upper Mi. The second
feature is a remnant MCV from a convective system over southern MN,
and its interaction with the passing cold front will likely play a
role in determining coverage/evolution of convection into Upper Mi
later this afternoon into tonight.
Other than isolated to scattered light showers over western counties
into early afternoon, the consensus of the CAMs indicate the initial
batch of convection initiating along the incoming cold front late
afternoon/early evening (22z-00z) into Baraga, Iron and western
Marquette and then sagging se into eastern Marquette, Alger and
Dickinson counties by evening. Daytime heating will support
convective initiation along the front, but with fcst soundings
showing skinny CAPE profiles of 500-700 j/kg MUCAPE and effective
shear values of barely 30 knots not expecting any severe storm
development. However, the skinny CAPE profiles, deep warm cloud
depths to around 12kft will enhance warm rain processes, and
precipitable water of around 2 inches or around 200pct of normal,
will support torrential downpours with some of the storms this
afternoon. Temporary ponding of water will be an issue in poor
drainage areas affected by heavy rain producing storms. It`s been
a very humid day today with dew points into the 65-70F range.
Warmest/most uncomfortable conditions have been in s central Upper
MI where temps have risen into the upper 80. Otherwise, low to
mid 80s have been the rule, except for mid 70s right along Lake Mi
in a southerly flow.
Consensus of latest CAMs are now trending that any convection that
forms early this evening along the incoming cold front over the
central counties may die out or dissipate by late evening as the
remnant MCV from last night`s convection over southern MN develops
another MCS over central/southern WI along the higher instability
gradient to the south with MUCAPE values of 2000 j/kg or more and
widespread dew points in the lower to mid 70s. Models seem to
suggest that this developing MCS could act to sap some of the
available moisture for convection over Upper Mi later tonight into
Sunday morning. As a result, my gut feeling is convection will be
more isolated to scattered and confined generally to south
central and eastern sections of Upper Mi overnight tonight into
early Sunday. Flooding threat is looks pretty minimal at this
point, but that said, with the anomalously high PWATs and high
freezing levels, any thunderstorms that do form later tonight will
probably produce heavy downpours and could cause ponding of
water.
.LONG TERM...(Sunday through Saturday)
Issued at 323 PM EDT SAT AUG 6 2022
Shower and thunderstorm activity becomes limited Sunday to only the
south central and east as a weak sfc high moves over Lake Nipigon.
However, mostly cloudy skies are still expected over the area (save
for clearer conditions in the Keweenaw and west) as the cold front
stalls out near Upper MI, in addition to a shortwave low lifting NE
towards the Upper Great Lakes from the Northern Plains. Therefore,
expect temps to range from the mid 60s to lower 70s, with the
coolest temps expected in the north central due to this area having
the most cloud cover behind the cold front. As the shortwave low
makes its way near the Mackinac Straits late Sunday night into
Monday morning, some CAM guidance has a band of stronger shower
activity moving across the UP from west to east. Locally heavy
rainfall rates could be seen in this band, with ponding of water
possible in spots. However, given that there looks to be no training
behind this band, any flooding that would occur should be limited to
areas that have already been inundated with rainfall late this
afternoon and tonight, should heavy rainfall occur late this
afternoon and tonight. As always though, please remember to have
your low-beam headlights on during rainfall (especially heavy
rainfall), as having high-beam headlights on in the rain could
reduce your vision; in addition, if there is ponding of water
locally, it`s best to avoid going through it, as it can be deeper
than one suspects.
Expect rainfall to end across the central and east throughout the
day Monday as the cold front and shortwave move away from Upper MI.
With cooler air still in place and clearing skies, expect highs to
be pretty similar to what we will see Sunday. Expect clear skies
Monday night to allow temps to drop to the mid 40s in the interior
west, with around 50 expected everywhere else.
WAA and ridging over the area Tuesday should bring temps closer to
normal. With another cold front dipping down from northern Ontario
Wednesday, there is a small chance that we could see some precip
along the front as it passes. However, given the relatively dry air
near the sfc (as seen on the GFS model soundings), don`t think much,
if anything will reach the sfc. That being said, I do believe that
there should be more cloud coverage over the area Wednesday given
the moist GFS model soundings aloft and ensemble guidance showing
around 1" of PWATs. However, given that the change would be from
mostly sunny to mostly cloudy conditions and not many, if any, other
changes would be needed at this time, decided to leave the NBM sky
grids on Wednesday alone for now (even though, again, I think the
cloud coverage is too little). Behind the cold front, expect temps
to be slightly below normal as ridging moves back in.
Moving into next weekend, we have another shot of seeing rainfall
via a warm front followed by a cold front. However, given the
divergence in model guidance, confidence is pretty shaky. We should
see temps become slightly above normal next weekend, though, as WAA
is expected.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1202 AM EDT SUN AUG 7 2022
Any lingering showers/isolated thunderstorms have become confined to
south central and eastern portions of the UP early this morning. So,
VFR will be the prevailing flight category at KIWD and KCMX for this
TAF period. However, will carry mention of rain for most of Sunday
morning at KSAW along with IFR fog and CIGS in the upslope northerly
flow. Winds will become primarily northeasterly at 5 to 10 kts.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 337 PM EDT SAT AUG 6 2022
Light winds of 20 knots or less are expected across Lake Superior
late this afternoon into the evening hours as a stable layer above
the lake sfc prevents mixing down of stronger winds from the passage
of a cold front. However, late tonight through Sunday, expect NE
winds of 20 to 25 knots across the western half of the lake as the
cold front stalls out over the UP and brings a tight pressure
gradient over Lake Superior. However, as the pressure gradient
weakens late Sunday afternoon, expect winds to become 20 knots or
less again, remaining that way to the end of the forecast period.
Thunderstorms could be seen mainly across the southeastern part of
the lake this evening into Sunday morning. Some patchy fog, locally
dense in spots, is possible across the eastern lake tonight.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...TAP
AVIATION...TDUD
MARINE...TAP
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 401 PM CDT Sat Aug 6 2022
A recent surface analysis this afternoon depicts a front draped from
south central Nebraska to Storm Lake, Iowa with very hot
temperatures and high dewpoints to the southeast of it. That heat is
the big ticket focus for the early forecast period, as heat indices
reach 105 to 110. The scattered cumulus across northeast Nebraska
should generally hold around the same are through the afternoon and
move perhaps a little bit to the southeast. Along the front, storms
have been struggling to sustain themselves in the lower-sheared
environment. These weak storms should continue to pulse up and down
over the course of the afternoon and evening with meager rainfall
totals where expected for any one location. Overnight, temperatures
will be able to fall to the 60s across far northeast Nebraska behind
the front while elsewhere 73 to 77 degrees will be the norm.
During the early morning hours Sunday, spotty shower and isolated
storm activity will be possible north of the front. By late morning,
the front will once again begin its slow movement to the southeast.
Just to the south of the front high dewpoints do most of the heavy
lifting to increase heat indices. Areas southeast of I-80 will see
heat index values reach 100 to 105 degrees while high temperatures
reach 93 to 97. The same kind of pulse storm activity is expected
once again tomorrow afternoon into the evening across much of
eastern Nebraska and western Iowa with a very low likelihood of
severe weather thanks to continued weak shear.
Monday and Tuesday are shaping up to be the nicest days of the
forecast period as mid/upper heights reach their lowest. Highs in
the lower 80s are set for Monday that see a slight hike to the
upper 80s Tuesday. Another ridge of high pressure is set to move
in from the west as Wednesday marks the beginning of yet another
warming trend after our brief relief from the heat. Highs return
to the 90s and make their way to the upper 90s Friday with no
meaningful chances for rainfall on the horizon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 608 PM CDT Sat Aug 6 2022
A surface front over northeast NE has moved through KOFK, but
should remain north of KOMA and KLNK until tomorrow afternoon.
MVFR ceilings have developed behind the front with the leading
edge very near KOFK as of 6 PM. Latest model guidance suggest that
KOFK could bounce in and out of MVFR ceilings this evening before
becoming more solidly entrenched overnight. Further, those data
indicate an increased probability of IFR ceiling in the 08-15z
timeframe, which we will include in the forecast. The low clouds
are currently expected to remain to the north of the KOMA and
KLNK.
Shower and storm potential at the terminal sites remains highly
uncertain. Radar and satellite indicate a couple of disturbances
moving across western and central NE with some associated light
precipitation. Latest HRRR output suggests an increasing
probability of TSRA at KOFK in the 06-11z timeframe, and closer to
21-23z at KOMA and KLNK. For now, we will not include a
precipitation mention in the forecasts, but will be closely
monitoring observations.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Excessive Heat Warning until 9 PM CDT this evening for NEZ044-
045-050>053-065>068-078.
Heat Advisory until 9 PM CDT this evening for NEZ012-015-017-018-
030>034-042-043-088>093.
Heat Advisory from noon to 8 PM CDT Sunday for NEZ066>068-
089>093.
IA...Excessive Heat Warning until 9 PM CDT this evening for IAZ055-
069-079.
Heat Advisory until 9 PM CDT this evening for IAZ043-056-080-090-
091.
Heat Advisory from noon to 8 PM CDT Sunday for IAZ079-080-090-
091.
&&
$$
DISCUSSION...Petersen
AVIATION...Mead
Area Forecast Discussion...UPDATED
National Weather Service Portland OR
851 PM PDT Sat Aug 6 2022
Updated Aviation, Marine and Fire Sections
.SYNOPSIS...Ridging will build north across the Pacific NW over the
weekend and into Monday bringing hot temperatures across much of the
inland areas. Temperatures are expected to cool Tuesday as low
pressure makes its way across the area. This will bring showers and
thunderstorms for select areas.
&&
.DISCUSSION...Tonight through Friday...Clear skies across the region
as high pressure builds into the Pacific NW from the Desert SW.
Temperatures are about 5-10 degrees warmer today relative to this
same time [2 PM] yesterday. North, northeasterly winds have
established over the area as the surface thermal low moves east.
Drier, warmer air will move west of the Cascades through Monday. High
temperatures today will climb into the upper 80s to low 90s.
Satellite imagery shows smoke from the Cedar Creek fire pushing west
as east winds pick up across the Cascade crest. Much of Lane and the
southern parts of Linn County will likely see smoke and it may hinder
temperatures by a few degrees.
Overnight, the thermal trough will shift slightly more west over
towards the coast creating more offshore flow across the CWA. Gusty
east winds and lowered dewpoints over the high terrain will keep the
airmass dry and quite warm through the overnight hours.
Heights continue to rise over the area Sunday. With morning lows
starting out in the upper 50s, to low 60s, max temperatures on Sunday
will likely climb into the upper 90s. Some places may see temps as
high as 102. HRRR vertically integrated smoke continues
to show smoke from the Cedar Creek flow north aloft over much of the
area. At lower to mid levels however, northerly winds may start
allowing smoke from the fires across eastern Washington to spread
across the area. This may lower temperatures depending on the
thickness of the smoke.
A slightly stronger shortwave moving out ahead of the cutoff low
offshore from CA may lead to some elevated convection across the Lane
county Cascades Sunday. Sunday night, a flow reversal offshore will
move north along the coast, with marine stratus expected to move
inland into the Coast Range, cooling the coast off again. Some of
this stratus looks move up the Siuslaw drainage and into the western
part of the the southern Willamette Valley.
Models are trending for a cooler Monday as the upper level low that
has been locked in place offshore for over a week makes its way
toward the Oregon coast. Much of the area will cool into the low 90s
but the Portland/Vancouver metro, Columbia River Gorge, and the Upper
Hood River Valley continue to see temperatures in the mid to upper
90s. Therefore, the current Heat Advisory expiration time has not
been adjusted. If models continue the cooling trend the Heat Advisory
may be cancelled early.
Models continue to show some energy moving out ahead of the cutoff
low as it starts to finally lift northeast to eventually move inland
near Vancouver Island in the Thursday-Friday time frame. Divergence
aloft ahead of it, combined with moisture within divergent southerly
flow across the mid levels will increase chances for thunderstorms
across the area. The progression of the low continues to be quite
slow, therefore the chances of thunderstorms will remain Monday
through Wednesday. Convection chances may occur at night as well as
the energy remain aloft. Temperatures look to drop to their coolest
of the week on Wednesday, when readings are just about at normal for
early August.
Current guidance shows the cutoff low remaining off of Vancouver
Island Wednesday through the end of the week. This will maintain
onshore flow and seasonable conditions during the second half of the
week. However, this cutoff low has been quite unpredictable so not
much confidence remains beyond Wednesday. -BMuhlestein/Kriederman
&&
.FIRE...An upper level ridge and low-level offshore flow
will bring very dry and hot conditions to the district this
weekend. While wind speeds will decrease tonight over the
Willamette Valley, east winds over the Cascades will actually
increase a bit as a surface thermal trough pushes further west
and offshore flow strengthens. This will be especially true over
the high Cascades and along exposed ridgetops, where wind gusts
are expected to reach 25 mph or so tonight. Poor humidity
recoveries are also a concern over the Cascades tonight, in
addition to unstable conditions with mid-level Haines values of 6.
West of the Coast Range, a moist marine airmass will spread
northward up the coast and likely into the southern Willamette
Valley tonight. While Sunday afternoon will be even hotter and
drier than Saturday afternoon, winds should be weaker and not at
critical thresholds. That said, conditions will remain unstable
over the Cascades (mainly the Mt. Hood N.F. and Gifford Pinchot
N.F.) through the day on Sunday, hence the reason the Red Flag
Warning goes through 8 PM PDT Sunday for fire weather zones 605,
607, 660. Conditions may remain unstable for these zones through
Sunday night as well, however overnight humidities should start
to improve.
An upper low off the northern California coast will slowly lift
northeastward Monday through Wednesday, resulting in a prolonged
period of southerly flow aloft over the district. This will bring
daily chances for showers and thunderstorms Monday through
Wednesday morning, mainly over the Cascades during the afternoon
and evening hours. Tuesday appears to be the highest chance for
thunderstorms as moisture and instability will be on the increase.
-TK
&&
.AVIATION...06Z TAFs: VFR SKC inland through 06Z Monday. However,
expect areas of high-level smoke to spread south to north. This
should not be much of a flight impact, other than to reduce
slant-wise visibility at times, especially over the south half of
the area. Coastal areas to remain VFR SKC, but LIFR stratus/fog
will likely reach K6S2 a little before 12Z Sunday, and possibly to
KONP mid to late Sunday afternoon.
For detailed Pac NW aviation weather information, go online to:
https://weather.gov/zse
KPDX AND APPROACHES...VFR SKC at the terminal and vicinity through
06Z Monday. High-level smoke can be expected to spread over the
area tonight and continue to do so through Sunday. Smoke/haze mixture
Sunday could impact slant visibilities at the terminal and
surrounding airports. Weishaar
&&
.MARINE...No changes to the the current marine forecast. North
wind gusts to 20 kt will continue over the waters through around
07Z Sunday and then decrease. Model guidance suggests a southerly
wind reversal will develop over the southern zones around mid-
afternoon Sunday, but not reach the south Washington waters until
late Sunday night. The southerly wind reversal is usually
accompanied by a shallow stratus layer or fog which can result in
rapidly deteriorating visibility. Will need to closely monitor for
the dense fog potential.
Seas will remain around 4 to 7 ft at 7 to 9 seconds with a
dominant northwesterly swell. Weishaar
For information about upcoming marine zone changes, go online to:
https://www.weather.gov/pqr/marinezone
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 8 PM PDT Sunday for Mt. Hood National
Forest West of Cascade Crest-North Oregon Cascade Foothills.
Heat Advisory from noon Sunday to 8 PM PDT Monday for Central
Columbia River Gorge-Greater Portland Metro Area-Upper Hood
River Valley-Western Columbia River Gorge.
WA...Red Flag Warning until 8 PM PDT Sunday for Extreme South
Washington Cascades and Foothills.
Heat Advisory from noon Sunday to 8 PM PDT Monday for Central
Columbia River Gorge-Greater Vancouver Area-Western
Columbia River Gorge.
PZ...None.
&&
$$
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