Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/25/20
Area Forecast Discussion
National Weather Service Bismarck ND
1051 PM CDT Mon Aug 24 2020
.UPDATE...
Issued at 1051 PM CDT Mon Aug 24 2020
Limited changes needed to the late evening update. Many may have
noticed a hazy sunset this evening from western wildfire smoke.
With a westerly flow aloft expect smoke and hazy skies to continue
into at least tomorrow. Some attention was given to pops for
tonight into tomorrow. Weak vort max moving over a flattening
ridge may bring a few thunderstorms across the northwest late
tonight into tomorrow morning. From there a weak warm front sets
up for Tuesday bringing more warm conditions and perhaps a few
thunderstorms. A weak cold front then moves through later in the
day Tuesday through Tuesday night which may be the focus for more
thunderstorms. With ample shear and instability an isolated storm
through Tuesday may be strong to severe.
UPDATE Issued at 655 PM CDT Mon Aug 24 2020
Limited updates needed this evening. Increased some cloud cover
based on satellite trends. Wildfires across the west also continue
to bring some smoky haze to the area, and could continue tonight
into tomorrow. Chances for an isolated thunderstorm remains on
track across the northwest later tonight, with widespread chances
possible for much of the area tomorrow.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 239 PM CDT Mon Aug 24 2020
Surface high pressure centered across eastern North Dakota will
drift east tonight as a lee side surface low pressure forms in
eastern Montana. We expect skies to be mostly clear this evening.
Upper level water vapor imagery shows an impulse moving northeast
across Oregon and Idaho. This will move northeast and bring a
slight change for thunderstorms to northwest North Dakota before
sunrise and Tuesday. There should be sufficient cape and shear
for widely scattered thunderstorms in the morning.
By Tuesday afternoon, 40kt shear and cape as high as 1500 should
support scattered thunderstorms with a few possible severe across
much of west and central North Dakota.
Upper level water vapor imagery shows a weak impulse moving
northeast across eastern Oregon and Idaho. This will move
northeast and should bring a slight change for thunderstorms to
northwest North Dakota around Sunrise.
Return flow ahead of the surface trough will bring an h850 thermal
ridge into western North Dakota. This will support highs into the
mid 90s west to teh mid 80s east.
The HRRR integrated smoke model brings widespread smoke back into
the northern plains tonight and Tuesday. Most of the smoke is
expected to remain aloft.
.LONG TERM...(Tuesday night through Monday)
Issued at 239 PM CDT Mon Aug 24 2020
The chances for a significant cooling trend appear reasonable by
the end of the extended period as a pattern shift will bring a
cool h500 low into the picture across western and central Canada.
Midweek shortwave energy will flatten the h500 ridge over the
northern plains, with a general cooling trend back to near normal
temperatures by Wednesday and Thursday and into the weekend. Much
cooler weather is possible Monday.
For precipitation, it looks like the best chances will arrive
Wednesday night through Thursday night.
The threat for severe weather will be at least marginal for
Tuesday and Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued
at 1051 PM CDT Mon Aug 24 2020
High pressure will maintain VFR conditions across the region.
There is a small chance of a thunderstorm in the KXWA area after
25/06z. Confidence was too low to include in the TAF at this
point. More thunderstroms are then possible after 25/18z across
the entire forecast area.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Anglin
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...Anglin
Area Forecast Discussion
National Weather Service Cheyenne WY
518 PM MDT Mon Aug 24 2020
.SHORT TERM...(This evening through Tuesday night)
Issued at 235 PM MDT Mon Aug 24 2020
Temperatures across the region continue to soar after morning
cloud cover left a question mark on whether or not sites would be
able to reach forecast highs. Portions of the North Platte River
Valley will see the highest temperatures where Scottsbluff and
Torrington are siting at 99F at this hour. Numerous sites across
the CWA are approaching record highs. Tuesday afternoon will
present much of the same with upper-90s to triple digits in the
Nebraska Panhandle, mid-90s across the Wyoming High Plains, and
upper-80s west of the Laramie Range as 700mb temperatures sit
around 17-19C across the region.
Scattered cumulus has been building over the Snowy and Sierra
Madre Ranges since midday as a few showers have developed. Limited
CAPE and weak shear should result in short-lived storms through
early evening. Main threat could be gusty outflow winds with the
strongest storms with limited boundary layer moisture. A few
storms could form off the Central Laramie Range pushing into the
Wyoming High Plains, however the NAMNest and HRRR are lacking any
agreement with the later being slightly more aggressive with
convection. Tuesday afternoon shows much of the same with
afternoon convection mainly being focused along the high terrain.
LCLs reach above the freezing level supporting the potential for
strong downburst winds. Heading into Tuesday night, 500 mb heights
begin to lower with the suppression of the upper level ridge
overhead which will bring a pattern chance across the region
heading into mid-to-late week.
.LONG TERM...(Wednesday through Sunday)
Issued at 315 AM MDT Mon Aug 24 2020
The anticipated change from hot/dry to cooler/unsettled weather pattern
commences Wednesday as the upper ridge is displaced to the south and
east with the passage of shortwave energy along the international
border. Southwest flow aloft will open the subtropical moisture tap
with precipitable water increasing to around an inch later this week.
Upper level disturbances riding northeast across the region will
provide the lift for scattered mainly afternoon/evening convection
into the first half of the weekend. Weak low level shear and MUCAPES
below 1000 j/kg will limit the severe threat. QPF amounts on the order
of a quarter to half inch will provide minor relief from the ongoing
drought. A cold front is progged to move through Friday, replacing
highs in the 80s and 90s Wednesday and Thursday with 70s and 80s
for the weekend. Models are hinting at a significantly cooler airmass
arriving late Sunday and early Monday, with 700mb temperatures dropping
to -2 to -4C. Scattered showers and thunderstorms will accompany the
front.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 518 PM MDT Mon Aug 24 2020
VFR prevailing at all terminals through the period though some light
amounts of smoke may lower visibilities to around 7 miles at times
in a few spots. A few showers and a brief tstm affecting the area
from about KLAR to KCYS early this evening. Otherwise mainly mid
level clouds over southeast Wy this evening.
&&
.FIRE WEATHER...
Issued at 235 PM MDT Mon Aug 24 2020
Hot and dry weather continues this week with afternoon
temperatures expected to be well above normal Monday and Tuesday.
Most of the Nebraska Panhandle could temperatures rise into the
triple digits keeping relative humidity fairly low around 15 to 20
percent. However, aside from shower and thunderstorm outflow
gusts, winds are expected to remain below critical thresholds.
Isolated showers and thunderstorms are possible Monday and Tuesday
afternoon initiating over the high terrain in southeast Wyoming.
Storms will be short- lived, but cloud-to-ground lightning is
definitely a concern with the dry soil conditions. More scattered
showers and thunderstorms will be possible Wednesday with better
chances for precipitation continuing later in the week. Long-range
guidance has begun indicating the possibility for a strong cold
frontal passage early next week that could bring relief to the hot
and dry conditions as of late with an extended period of below
normal temperatures.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...MB
LONG TERM...MAJ
AVIATION...RE
FIRE WEATHER...MB
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
332 PM PDT Mon Aug 24 2020
.SYNOPSIS...Isolated to scattered showers and a slight chance of
thunderstorms will remain in the forecast through Tuesday morning,
primarily for areas north of Cape Mendocino. Thunderstorm potential
will then be limited mainly to Trinity County from Tuesday afternoon
onward, with seasonably hot conditions inland and marine cloudiness
at the coast.
&&
.DISCUSSION...A plume of mid level moisture with origins in the
tropical Pacific continues to advect northward across NW California
this afternoon. This is generating isolated to scattered shower
activity north of Cape Mendocino, although these showers have
produced little rainfall. Elevated instability has remained a bit
too meager to support thunderstorm development so far today, but
cannot rule out a few lightning strikes through this evening if any
breaks of sunshine can contribute to further destabilization.
Cancelled the Red Flag Warning across southern portions of Lake and
Mendocino Counties as what limited thunderstorm threat remains has
shifted north of those areas. Meanwhile, another subtle disturbance
to the south will move into the area tonight and has the potential
to bring one last round of nocturnal convection. This is supported
by an uptick in offshore lightning activity noted well to our
southwest this afternoon, but confidence remains low in how this
feature will evolve as it spreads northward overnight. Have
maintained a slight chance for thunderstorms through Tuesday
morning, with the best potential once again remaining over the
northern half of the area.
We should settle into a more benign pattern from Tuesday onward as
the area remains in southwest flow aloft on the periphery of a broad
eastern Pacific trough. Thunderstorm potential for Tuesday and
Wednesday afternoon looks to be confined to Trinity and possibly far
NE Mendocino County where surface destabilization will be maximized.
Inland temperatures will generally be in the 90s with marine
cloudiness continuing to moderate temperatures near the coast. /CB
&&
.AVIATION...By midday, the LIFR conditions remained stubborn, with
only brief windows of IFR. Light rain was reported at KACV, with
only trace accumulation. Scattering was eventually realized at KACV
into the early afternoon. A persistence forecast is in store through
the period, with more LIFR Cigs and Vis with fog. Southerly flow
throughout the column has once again advected smoke into KUKI with
significant reductions in visibility. HRRR Experimental Smoke
guidance depicts chances for improvement by tomorrow morning, but
with another return through the early afternoon. Chances for
isolated elevated thunderstorms/showers at the coastal terminals
will remain through the early morning hours of Tuesday, mainly for
Humboldt, Trinity and Del Norte counties.
Profiler data shows a somewhat more compact marine layer, as a upper
disturbance weakens on approach. The marine layer may deepen some
overnight in response, potentially allowing ceilings to lift
somewhat. A better defined trough will move into the area Wednesday
with better chances for marine layer deepening, with possibly
inhibited typical diurnal scattering. /JW
&&
.MARINE...Breezy northerly winds will continue across the outer
waters today, generating short period seas of around 8 to 10 feet.
Northerly winds will generally continue through the forecast
period, with the strongest winds continuing across the northern
outer waters. The inland thermal trough will occasionally venture
closer to the coast, providing lighter winds and occasionally
southerly flow reversals along the immediate coast, particularly S
of Cape Mendocino. Advisory level northerly winds and seas are
expected to continue for the outer waters for the foreseeable
future, slowly strengthening as the week progresses. /JW
&&
.FIRE WEATHER...Isolated thunderstorms remain a possibility this
afternoon and evening, primarily for areas north of Cape
Mendocino. Another weak disturbance approaching from the south
will maintain a slight chance of thunderstorms for these areas
overnight. Additional isolated thunderstorm development may occur
over portions of Trinity county during Tuesday and Wednesday
afternoon. /CB/Garner
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning until 11 PM PDT this evening for CAZ201-203-204-
211-212-277-283.
NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until
3 AM PDT Wednesday for PZZ470-475.
&&
$$
Visit us at https://www.weather.gov/eureka
Follow us on Facebook and Twitter at:
https://www.facebook.com/NWSEureka
https://www.twitter.com/NWSEureka
For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png
Area Forecast Discussion
National Weather Service Glasgow MT
854 PM MDT Mon Aug 24 2020
.DISCUSSION...
EVENING UPDATE:
Changes this evening were focused around updating hourly clouds
and wind fields to the latest model data. That being said most of
the hourly tweaks were minor and will likely not have a
significant affect on the forecast. GAH
AFTERNOON DISCUSSION:
A particularly hot and especially dry day today has sparked a
couple of small fires in the area. HRRR Smoke keeps smokes over NE
Montana for another couple days. A series of frontal passages is
in store for the rest of this week with varying degrees of
intensity. The first will arrive tonight with a very isolated
chance of a thunderstorm. The boundary layer is still quite dry,
therefore any thunderstorm may produce dry lightning and locally
gusty, erratic winds. SPC has placed NE MT in a general
thunderstorms category. The wind forecast has been especially
challenging today as gusts have been higher than models are
producing.
The next trough will sweep west to east Tuesday afternoon through
Wednesday. Tropical moisture from the southwestern US will stream
over on upper southwesterly flow to the area and while there is
enough to allow convective initiation, the boundary layer will
once again be fairly dry and similar hazards of dry lightning and
winds. Storms may become more dry as it progresses east. SPC has
placed the area into a marginally severe category for Tuesday and
Wednesday.
Later in the week, confidence is remains low for the intensity of
the trough and associated winds. Models such as GFS and ECMWF have
a jet streak directly over NE MT, bringing a gusty system
Thursday night into Friday, however, NAM has the trough and
associated jet streak too far north to see much of the impacts.
NBM also shows a relatively weak system as well with more moisture
chances further SE. Temperatures will gradually cool down and by
the weekend, expect much cooler temperatures, especially with the
arrival of a deep Alaskan low will drop into Montana on Sunday.
CPC has higher probabilities of cooler and wetter weather in the
week to two week outlook, which will hopefully provide relief to
the recent abnormally dry weather and the heightened fire risks.
Roxy
&&
.AVIATION...
LAST UPDATED AT 03Z
FLIGHT CATEGORY: VFR
SYNOPSIS: A few isolated thunderstorms are possible during the
overnight hours in the area. Tuesday starts out dry with hazy
skies due to wildfire smoke from local and out of state fires.
Another chance of thunderstorms approaches from the west by the
late afternoon hours.
WINDS: SE 5-15 kts this evening, becoming NW 10-15 kts Tuesday
mid-morning. Veering to the north Tuesday evening.
RMB/GAH
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
weather.gov/glasgow
AREA FORECAST DISCUSSION...CORRECTED
National Weather Service Hastings NE
710 PM CDT Mon Aug 24 2020
.UPDATE...
Issued at 643 PM CDT Mon Aug 24 2020
Updated the forecast this evening to remove showers/t-storms
northwest. Relatively high based showers and mid-level inversion
along with weak wind shear producing little more than virga as
there is plenty of dry air below cloud base.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 129 PM CDT Mon Aug 24 2020
Expecting another hot one today thanks to high pressure aloft and a
relatively unchanging pattern. Today continues the trend of above
average highs with mid to upper 90s across the board. Breezy winds
will be a slight relief from the heat but not much, as they continue
to be warm southerly winds. Looking at satellite we have sunny but
hazy skies all across the area this afternoon. Smoke from wildfires
in California and Colorado is the cause of the haziness (and the
stunning sunrises and sunsets too!). Thankfully the smoke is mainly
in the upper levels (for now) for our area, and therefore has less
of an impact on air quality at the surface. However, that being
said...looking at the HRRR Near-Surface Smoke model, it looks like
areas northwest of a line from Beaver City to Ravenna to Greeley, NE
could see more smoke near the surface, but the air quality index
should still remain in the "good" category according to AirNow.
Tomorrow will look very similar to today (and the last several days)
with highs in the mid 90s, overnight lows in the mid to upper
60s, and more breezy winds.
.LONG TERM...(Wednesday through Monday)
Issued at 129 PM CDT Mon Aug 24 2020
As the main ridging aloft begins to broaden and spread out across
most of the central CONUS we will see the jet stream shift further
north to more over the Canadian border. This is not a good thing for
anyone hoping for a pattern change any time soon. With the jet
stream this far north, we are essentially cut off from any
significant changes in flow. This means conditions will remain
rather static until the high begins to break down and we re-enter
the mainstream flow. Highs are expected to remain in the 90s through
Thursday, which would make for 8 consecutive days in the 90s. This
would be the longest stretch of 90s since the beginning of June.
Wednesday a tropical disturbance looks to make landfall over the
Gulf Coast but is not expected to affect our area. The remnants of
Laura will then rejoin the main stream flow as the ridge collapses
thanks to an upper level trof that will then swing down from the
northwest. This trof will usher in a front on Friday and looks to
bring about a shift to more seasonal weather. However this is still
a ways out and much is likely to change between now and then.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 643 PM CDT Mon Aug 24 2020
Main issue tonight will be wind shear during the overnight hours
between mainly 06Z and 12Z. This is a fairly strong signal and I
have lowered the height of LLWS a bit from the previous forecast
to 800 ft.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
UPDATE...Heinlein
SHORT TERM...Shawkey
LONG TERM...Shawkey
AVIATION...Heinlein
Area Forecast Discussion
National Weather Service Hanford CA
438 PM PDT Mon Aug 24 2020
.UPDATE...Air quality section updated.
&&
.SYNOPSIS...
Continuation of smoke across the forecast area for the next few
days due to widespread fires throughout California. An isolated
thunderstorm or two is possible this afternoon over the Sierra
Crests as remnant moisture remains in place. After today, the
forecast is to remain dry with near normal afternoon highs.
&&
.DISCUSSION...
A few thunderstorms occurred overnight as moisture from the
remnants of Genevieve supported instability over the mountains and
foothills. However, this activity waned over the Southern Sierra
Nevada by early morning. Additional thunderstorms will be focused
mainly to the north of our forecast area this afternoon, but an
isolated storm or two will be possible over the Sierra Crests. In
terms of valley smoke today, the HRRR smoke model is still
depicting smoke spreading across the forecast area for the time
being as area fires continue to burn.
Afternoon highs across the San Joaquin Valley will remain a few
degrees above normal under the influence of the desert southwest
ridge, but will drop to near normal tomorrow as the ridge weakens.
A trough of low pressure will approach the California Coastline
by Wednesday night or Thursday morning. This may influence high
temperatures down a degree or two more for the latter portion of
this work week, and hopefully will remove some of the smoke that
has been plaguing the valley by Thursday or Friday. Through the
weekend and into early next week, only oscillations of a few
degrees are forecast for afternoon highs along with no
precipitation as dry flow aloft prevails.
&&
.AVIATION...
Areas of MVFR visibilities and ceilings can be expected in the
San Joaquin Valley for at least the next 24 hours due to smoke and
haze. Haze will reduce visibilities to as low as 1 mile in the
San Joaquin Valley at times. Isolated thunderstorms will be
possible over the Sierra Nevada crests through 02Z Tuesday.
&&
.AIR QUALITY ISSUES...
An Air Quality Alert remains in effect for the Central California.
For details, please see SFOAQAHNX.
On Tuesday August 25 2020... Unhealthy in Fresno... Kings...
Madera... Merced and Tulare Counties and Sequoia National Park and
Forest. Unhealthy for sensitive groups in Kern County. Further
information is available at Valleyair.org
&&
.CERTAINTY...
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.
&&
.HNX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
public...Bollenbacher
aviation....Bollenbacher
weather.gov/hanford
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
618 PM CDT Mon Aug 24 2020
.SYNOPSIS...
Issued at 300 PM CDT Mon Aug 24 2020
H5 analysis this morning had a broad area of high
pressure located over the Four Corners. Ridging extended north of
the high into central portions of Alberta and Saskatchewan. West of
this high, a trough of low pressure extended from northern British
Columbia southwest to a point approximately 700 miles west of
northern California. East of the high, a low amplitude trough was
located from the eastern Great Lakes, southwest into the lower Ohio
Valley. High pressure was east of this trough, located north of the
Bahamas. Visible satellite imagery this morning has the center of TS
Marco approximately 100 miles southeast of New Orleans. Across
western and north central Nebraska this afternoon, skies were clear
east of highway 83. West of this route, skies were partly to mostly
cloudy. Temperatures as of 2 PM CDT ranged from 85 at Gordon, to
99 at Valentine.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 300 PM CDT Mon Aug 24 2020
The main forecast
challenges over the next 36 hours are temperatures and the tiny
threat for thunderstorms tonight and again on Tuesday night. For
tonight: The short range model solutions diverge quite a bit with
respect to convective development later today/tonight. A stationary
boundary will remain anchored from the northwestern Nebraska into
southern South Dakota. Convection will attempt to initiate INVOF
this boundary later this afternoon, then drift to the east and
southeast into northern portions of the forecast area. There is no
agreement between the short range models on this coming to
fruition. The NAM12 and NAMNest solns this morning are dry for this
afternoon/evening, while the GFS and 12z HRRR develop some
convection in the northwestern forecast area around 21z this
afternoon. It quickly dissipates by early evening as it tracks
southeast into the ridge. One note about the HRRR over the past
couple of days: It hinted at convection firing early on, then backed
off as the late morning and early afternoon runs came in. That being
said, will hedge toward a dry forecast for this evening. If any
storms do develop, the severe threat appears fairly minimal given
the 15 to 25 KT deep layer shear forecast. The stationary front will
drift north further into South Dakota on Tuesday. By late afternoon,
isolated thunderstorms will develop over the Black Hills and try to
drift to the southeast into the forecast area. They will have a hard
time making it into the NW forecast area as they approach the H5
ridge. For now, decided to leave this period dry. As for
temperatures, with the front being farther north Tuesday,
temperatures to the south of the front will reach the century mark.
Decided to trend the forecast in northern Nebraska toward 2 meter
temps as they tend to do well just to the south of a frontal
boundary. This will lead to highs around 100 degrees tomorrow over
portions of north central and NW Nebraska. Even with the century
mark temps, slightly drier air will push into the area tomorrow,
resulting in apparent T`s which are just below 100 degrees Tuesday
afternoon. That being said, will forgo heat headlines for Tuesday.
.LONG TERM...(Wednesday through Monday)
Issued at 300 PM CDT Mon Aug 24 2020
The before mentioned frontal boundary will sag south into the
central forecast area Wednesday morning. There will be a limited
threat for thunderstorms during the afternoon/evening along and
north of the frontal boundary. Immediately south of the boundary,
temperatures will surge into the upper 90s to near 100. In fact,
given the latest 21z Wednesday-NAM12 and GFS forecast frontal
position, locations along a line from Ogallala to Broken Bow will
have the potential to reach 100 degrees as they will be located
just south of the front. NBM seems to have this handled decent
right now as it has highs in the upper 90s. On Thursday, the front
lift north into South Dakota. Highs will reach into the mid to
upper 90s with mainly dry conditions expected. Precipitation
chances will then increase Thursday night into Friday as the front
tracks south into the forecast area. Aided by a strong northern
stream trough aloft, the front will push into northern Kansas on
Friday. With the frontal passage on Friday, highs will reach into
the mid to upper 80s. There will also be an increased threat for
thunderstorms. A warm front will push through the area Saturday,
followed by a strong cold front late Sunday night into Monday.
After highs in the mid 80s to lower 90s Sunday, highs will reach
the 70s for Monday. There will also be a chance for thunderstorms
Saturday into Sunday night associated with each front.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 618 PM CDT Mon Aug 24 2020
Widespread VFR is expected across wrn and ncntl Nebraska tonight
and Tuesday.
An upper level disturbance across ncntl Nebraska this evening will
move east. Sprinkles are possible for a few hours this evening.
Otherwise, an upper level ridge of high pressure will remain
stationary across the Four Corners region of the western U.S.. Dry
and stable weather should continue across wrn and ncntl Nebraska
tonight and Tuesday.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT /7 PM MDT/ this evening for
NEZ005>010-094.
&&
$$
SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC
Area Forecast Discussion
National Weather Service Marquette MI
635 PM EDT Mon Aug 24 2020
.SHORT TERM...(This evening through Tuesday)
Issued at 418 PM EDT MON AUG 24 2020
WV imagery and RAP analysis indicated a mid/upper level ridge over
the southern/central Rockies into the western Plains and a trough
from Hudson Bay into northern Ontario resulting in wnw flow through
the northern Great Lakes. A shortwave trough and sfc low south of
James Bay was dragging a cold front through Lake Superior and
central Upper Michigan. Mid/high clouds associated with the remnants
of a MCS/MCV were sliding through eastern Upper Michigan. Although
drier air with dewpoints into the upper 50s to lower 50s had spread
through northeast MN, dewpoints behind the front in western Upper
Michigan remained in the mid 60s. So far, capping has remained
strong enough to prevent shra/tsra from developing over Upper
Michigan even though MLCAPE values have climbed to 1000-1500 J/Kg.
Thunderstorms have remained well to the north near the sfc
low/shrtwv and over western WI.
Rest of this afternoon into tonight, the CAMS still suggest that
shra/tsra may develop over central Upper Michigan near the front,
especially downstream of the Lake Superior breeze boundary. So, at
least isold shra/tsra remain in the forecast into this evening. The
convection will diminish later this evening with the loss of daytime
heating. Additional tsra that strengthen over WI associated with
increasing 850 theta-e advection and the 850-700 front may brush the
far south near KMNM by late this evening. Clearing from the north
late evening/overnight behind the front could again lead to patchy
fog later on tonight as temps drop below the crossover dew point
temps. Lows should bottom out in the 50s away from the lakeshores,
but remain closer to 60F near the Great Lakes.
Tuesday, expect dry conditions with plenty of sunshine. Mixing
through 850 mb temps around 15C inland will support max readings
into the lower 80s south while ene flow over the north keeps
readings in the 70s.
.LONG TERM...(Tuesday night through Monday)
Issued at 342 PM EDT MON AUG 24 2020
Outside of a few breaks in the precip chances throughout the
long-term forecast period, it remains unsettled. Similar to the
ongoing pattern, it won`t be a situation of continuous rain/storm
chances, but rather periodic and episodic in nature. That said,
there are a few time frames of interest that should be monitored
as they inch closer.
The first round looks to occur late tomorrow night into Wednesday.
There are some spatial and temporal differences that create just
enough uncertainty in the forecast, but have attempted to account
for these scenarios in the issued forecast; highlighted change
includes a bit of a slower progression of main area of precip.
Essentially, it`s a combination of a WAA regime colliding with a
mid- to upper-level perturbation riding along the U.S./Canadian
border, yielding non-diurnally driven convection to potentially
impact a good portion of the U.P. at some point Wednesday. Strong
storms containing gusty winds and moderate to potentially locally
heavy rain can`t be ruled out, thanks to decent shear advecting
in, along with ample PWATs.
As advertised, a smattering of precip chances remains until the
next focused time period: Friday into Friday night (CMC depicts a
slower progression, which would keep convection in the forecast
area through early Saturday). Low crossing Manitoba into Ontario
with a frontal boundary being drug along with it will trigger
storm chances, with convection possible well ahead of this line as
yet another perturbation rides out ahead of the main trough axis.
However, confidence remains low on the finer details as this
system interacts with the northward march of TC Laura. Stay tuned.
A break in precip chances should occur later in the weekend,
looking to leave Sunday dry until the approach of the next
disturbance early next week. Temperatures are anticipated to
remain near seasonable for late August, with a slight cooldown
behind the aforementioned fropa this weekend. Otherwise, 70s
dominate through much of the forecast period, with some 80s still
popping up this week, and perhaps only some 60s this weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 635 PM EDT MON AUG 24 2020
Looks like enough drier air will occur in the low levels to maintain
VFR conditions through the period at all sites.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 418 PM EDT MON AUG 24 2020
Winds across Lake Superior will remain mostly under 20kt through
late this week. However, with high pressure building into the area
and funneling of the northeast flow over the west, winds to
around 20 knots are expected over the west end Tuesday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...lg
AVIATION...07
MARINE...JLB