Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/16/20
Area Forecast Discussion
National Weather Service Denver/Boulder CO
955 PM MDT Sat Aug 15 2020
.UPDATE...
Issued at 942 PM MDT Sat Aug 15 2020
Tonight`s forecast looks on track as the dryline convection has
dissipated and the Palmer Divide convergence dropped south. We
expect we`ll see a similar pattern to the smoke tonight. The
Williams Fork Fire has been burning really, really hot, so it will
probably mostly keep an elevated plume toward the south side of
the Denver metro area. Less clear cut for the Cameron Peak fire,
it`s pretty hot right now but is more likely to wind up with smoke
settling to the ground toward Ft Collins/Loveland/Greeley
overnight. The winds aloft will be trending more northerly and a
bit lighter, but we`ll have at least one more smoky day for the
Front Range cities as the plume from the Cameron Peak fire should
be pointed further southeast toward Denver on Sunday. Again, this
should mostly be elevated during the day, but could settle
overnight. The good news is that the winds continue to turn
more easterly Sunday night and by Monday the smoke is mostly going
south and west.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 345 PM MDT Sat Aug 15 2020
Current surface analysis shows MLCAPE of 2000-3000 j/kg across the
eastern plains, but enough CIN (near 50 j/kg) to keep things
capped off so far. There is some surface based cumulus beginning
to develop over the Palmer Divide and along a narrow north/south
shear zone near Akron are temps are closer to convective temps
there. It`ll still be a close call whether or not we get storms
going. If we do break the cap, very large hail will be possible
given sufficient shear, large MLCAPE, and dry northwest flow
aloft. There is one lone storm for now in the Nebraska panhandle,
and some chance this could sneak southward through late evening
despite the boundary layer not fully mixing over the northeast
corner of the state.
Otherwise, a dry night is expected under mostly clear skies and a
dry airmass from the I-25 Corridor westward through the mountains
and high valleys.
We`ll keep smoke in the forecast near the fires and along the
Front Range where the airmass stabilizes and smoke settles in
overnight. Most of Denver may become smoke free later in the night
with a light southerly drainage wind. Otherwise we`ll have
widespread haze. Used the HRRR Smoke model and vertically
integrated smoke product for the haze, and the near surface smoke
product to represent areas of smoke, thick enough to smell and
result in poor air quality.
On Sunday, we`ll see a deep easterly flow to around 10-11 thousand
feet develop across the plains and Front Range. We should see a
little better heating and mixing and thus convective temps being
met, so a few high based showers/storms still possible roughly
from the Park County area east and northeast across the plains.
High mountain valleys and northern Front Range will see a
continuation of very dry conditions with low humidity. High
temperatures on the plains will be a couple degrees warmer than
today.
.LONG TERM...(Sunday night through Saturday)
Issued at 345 PM MDT Sat Aug 15 2020
Little to no relief in site for the extreme fire behavior
conditions that are driving the fire growth of both forest fires
in our county warning area. A strong upper level ridge with warm
and dry air is forecast to remain in position over the western
United States through the upcoming week and beyond. Initially, the
moisture levels are very low, leading to warm daytime
temperatures and poor humidity recoveries overnight. The winds
aloft will continue to be light to moderate and out of the
northwest, allowing for smoke plumes to propagate downstream.
Through the upcoming week, the ECMWF and GFS are advertising an
increase in moisture levels aloft, but it will be moisture that
has to ride over the top of a moderately amplified ridge. The
other possible source of moisture would be low level moisture
coming into the state from the southern Great Plains. And even if
moisture does move in from the southeast, the thermal profile may
be too capped to allow for much afternoon convective development.
The forecast will mention a slight chance of thunderstorms during
the afternoons, but with little in the way of measurable
precipitation. If storms are able to develop, they may just be
high-based, with little rain and the possibility of dry lightning.
Each of these things will offer little assistance to firefighting
efforts. It looks like it could be a long week.
Temperature-wise, the string of 90 degree days will continue
across the plains. Sky cover will vary between cloud-free and
smoke filled as the fires continue burning through a lot of
timber, generating sizable smoke plumes. Until the upper ridge
breaks down, there is very little good news to pass along.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 942 PM MDT Sat Aug 15 2020
VFR through Sunday, but with smoke that could limit slant
visibility. Isolated thunderstorms are possible after 21z Sunday
that could produce a few wind shifts with gusts to 30 knots.
&&
.FIRE WEATHER...
Issued at 315 PM MDT Sat Aug 15 2020
Winds will become light and variable this evening. Only moderate
humidity recovery will occur tonight on the existing fires,
despite good radiational cooling and cool temperatures.
It will be hot and dry again across the area on Sunday. The
highest fire danger will remain over the high mountain valleys and
Front Range mountains where humidities will drop to 8-14%. There
should be just a slight bump in humidity on the eastern slope of
the Front Range where light but deep easterly flow develops.
Expect elevated fire danger for much of the upcoming week for
the mountains and foothills with continued very dry conditions
and little if any chance of storms. Storms that do develop will
be over the east slopes and plains. Overall, winds will be
marginal for red flag conditons with majority of the afternoon
breezes at or below 20 mph. Humidity recovery during the overnight
periods will also be poor, allowing fires to remain active
through the nighttime hours, instead of laying down.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Gimmestad
SHORT TERM...Barjenbruch
LONG TERM...Dankers
AVIATION...Gimmestad
FIRE WEATHER...Barjenbruch
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
635 PM CDT Sat Aug 15 2020
.SHORT TERM...(This evening through Sunday)
Issued at 345 PM CDT Sat Aug 15 2020
Well the next 36 hours or so look to be rather finicky and a minor
annoyance to try and forecast. So now the question is...where to
begin?. Starting with a quick overview (and then breaking it down),
there is some VERY modest potential for some precip (I hesitate
to even say storms) this evening/overnight for the far southwest
third of the CWA. Tomorrow, however, there is a better (but still
not great) chance for a few strong to marginally-severe storms to
pop up in the afternoon/evening along a weak cold frontal set up.
All that being said...still expect majority of the CWA to be dry
majority of the time.
Going into more detail starting with this evening/overnight:
Focusing in on the southwest portions of the CWA, mid-levels show a
a little bit of warm air advection pushing in from the southwest.
Though this feature is minor, it could produce enough forcing for a
few sprinkles or possibly a thunderstorm or two. Hi-res models seem
to be keying in on this slight possibility, and are generating a
little activity tonight... generally in the midnight to 5am time
frame. The NAMNest continues to be the most aggressive model (as it
is known to be) and develops a pretty good smattering of precip over
north central KS that then becomes a more organized cluster of
storms just before moving south out of our area. On the other end of
the spectrum we have the HRRR and the HRRRv4, both of which keep
things high and dry tonight. So I`ve decided to trend to the drier
side (more toward the hi-res solutions as a middle ground) since the
NAMNest doesn`t have a great track record recently, and the HRRR
looks to be initialized better. Subsequently, I only brought lows
down a touch (hardly at all) given that there may still be cloud
cover from any near by storms that may form just outside our CWA.
Severe threat (for any storm that does develop with some merit)
looks to be very minimal, in fact SPC has adjusted the marginal risk
for today and essentially removed it from our area. Though it should
still be said that this doesn`t exempt us from any glancing blows,
and a strong thunderstorm is still a possibility.
Tomorrow (Sunday):
Nudged highs up a tad given the likelihood of having plenty of
sunshine for most of the day. The problem is that there appears to
be a very minor short wave in the midlevels that has an associated
weak cold front. This set up looks similar to Friday, but is
significantly less pronounced and should not produce nearly the
strength of storms seen on Friday. In fact, this feature looks so
marginal in nature, that the prospect of convection being generated
along the front is very iffy. Models certainly haven`t had a good
handle on this, and still don`t. The hi-res models and the GFS are
rather splotchy, and the 18Z HRRR has more of a pronounced line
along the front (though still somewhat splotchy). As far as timing
goes, the best bet looks to be in the late afternoon/early evening
hours for the northeastern half of the CWA, and then the later
evening to early overnight hours for the southeastern half.
Regarding severe potential...with roughly 3,000 to 3,500 J/kg of
CAPE, and 30-40 kts of shear tomorrow afternoon/evening, strong and
even a few severe thunderstorms are possible. SPC has most of the
area in a marginal risk except for the far southeast since storms
are expected to weaken and die off more by the time the front gets
there.
.LONG TERM...(Monday through Saturday)
Issued at 345 PM CDT Sat Aug 15 2020
Given that most of the effort was spent in the short term, I`ll keep
this rather short and to the point.
Beyond these first 36 hours, things go back to being fairly calm and
average for August. With amplified upper level ridging over the
western CONUS and broad troughing in the east, we end up in a
prominent northerly flow regime. This pattern looks like it will
stay put for at least the remainder of the 7-day forecast period and
possibly even further. Even though this means we would be subjected
to any ridge running short waves, the likelihood looks slim at
this point. The remainder of the 7-day period should be
overwhelmingly dry, with only a weak chance for some rain Tuesday
night and again Thursday night. Temperatures will be slightly on
the warm side, but not "hot" necessarily. Highs will be mainly in
the mid to upper 80s with modest dewpoints in the 50s and 60s.
This period will feel more like typical August weather and should
be more comfortable in terms of relative humidity.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday)
Issued at 628 PM CDT Sat Aug 15 2020
VFR conditions are forecast for this TAF period, with any sky
cover expected to remain in the mid-upper levels. Recent radar
returns showing some scattered activity off to the NW of the CWA,
but is not expected to linger far enough east to impact the
terminal areas. No notable change in winds is expected through the
period, starting off SSE this evening, becoming SSW by the end.
Speeds look to top out around 10-15 MPH Sunday afternoon.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT TERM...Shawkey
LONG TERM...Shawkey
AVIATION...ADP
Area Forecast Discussion
National Weather Service Goodland KS
519 PM MDT Sat Aug 15 2020
.SHORT TERM...(This evening through Sunday night)
Issued at 229 PM MDT Sat Aug 15 2020
Across the region this afternoon, skies continue to be a mix of
partly sunny to sunny as lingering morning cloud cover remains in
part over the area. Temperatures are ranging in the upper 70s
through the mid 80s. The wide range is a direct result of the
lingering veil of cloud over portions of the area. Winds are east-
southeasterly gusting over 20 mph at times.
For the remainder of the afternoon hours into the evening
timeframe, focus will remain on the potential for any convection
to initiate over NE Colorado and shift eastward into NE/KS. Late
breaks in areal cloud cover have allowed much of the CWA to remain
stable due to lack of direct diurnal heating, with only the last
hour or so locales are seeing temps warm nicely, along with dewpts
ranging from the 50s up into the mid 60s in spots.
SPC has lowered the risk outlook areas to a bit further south,
keeping only SW portions of the area under a Slight Risk with a
Marginal for the remainder. Better instability does reside south
and west of the CWA closer to the trough over central Colorado. If
storms do develop and begin an eastward trek, they would have to
overcome a stronger MLcin environment with a cap in place. Have
decided to keep a 20 pop for storms this afternoon/tonight with a
trend to exit east by/just after 06z Sunday, as latest HRRR and
RAP40 don`t show a promising aspect to any major storm action
working into the area, but can`t rule out entirely.
Upper ridge remains in place for the remainder of the weekend
with NW upper flow. Surface ridge east and low pressure over the
east central Rockies will provide another low chance for storms on
Sunday afternoon/evening. Instability with daytime heating has a
good portion of the CWA under a Marginal Risk. Due to the
uncertainty over the past couple days in terms of storm
timing/initiation, will keep a 20 pop over the area for now. Hail
and wind threats for both days outlooks this weekend. Any precip
Sunday evening should clear the area by 06z Monday.
For temps, lower 90s on Sunday for highs will be off of lows
tonight in a upper 50s to mid 60 range, with a repeat again on
Sunday night.
.LONG TERM...(Monday through Friday)
Issued at 150 PM MDT Sat Aug 15 2020
There are not too many changes to what is expected next week. The
upper level pattern will still be dominated by the upper high and
ridge in the Desert Southwest while a trough drapes across the
Eastern CONUS. The evolution of the upper pattern appears to have
the ridge slowly shifting east and deamplifying while the trough
digs further south and potentially turns into a closed low. This
will leave the Tri-State area with north to northwest flow aloft
that will allow shortwaves into the area. However, the upper high
looks to expand at the end of the week and weaken our flow aloft.
This could lower the upper level support for instability.
Given the near constant pattern aloft, what conditions set up in
the lower levels of the atmosphere will largely dictate the day.
Monday is looking rather weak for storm chances, in spite of a
stationary front near the Colorado border, as moisture in the
lower levels is going to be less than what it has been the past
few weeks. However, an isolated storm is still possible mainly in
Eastern Colorado given the presence of the stationary front and a
potential shortwave moving through.
Tuesday will see the stationary front move over more into Western
Kansas with surface dewpoints dropping for our western counties
down into the 40`s where as the eastern counties stay near 60.
With the moisture and frontal boundary further east, our eastern
counties (mainly along and east of highway 25) will have a higher
chance for precip and lower temperatures with highs reaching the
upper 80`s. The rest of the area will likely be in the low to mid
90`s.
Wednesday and Thursday are likely to be similar with high
temperatures near 90 and afternoon and evening storms. The main
things worth noting is that the upper level high begins to expand
slightly east and that lower level dewpoints in the area climb
back up a bit (surface mainly 50F+ and 850 10C+).
Friday is a bit trickier as the models are not in agreeance with
the upper pattern and the location of a potential front moving
through the Northern Plains. Friday currently appears to be
similar to Wednesday and Thursday in terms of expected conditions,
but that could change depending on what conditions actually set
up. There is some uncertainty as a whole for Wednesday on as the
general pattern appears the same but the details are not very
consistent from run to run.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 520 PM MDT Sat Aug 15 2020
VFR conditions are anticipated to rule through the TAF
period at both terminals. An isolated thunderstorm cannot be
entirely ruled out at the GLD terminal this evening -- mainly
between 00-04Z -- though probabilities are too low to warrant
mention with the 00Z TAF issuance. 7-13 knot SSE-SE winds will
veer to the S late this evening/overnight. Light S winds (perhaps
variable at times) will prevail through the duration of the TAF
period.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JN
LONG TERM...KAK
AVIATION...VINCENT
Area Forecast Discussion
National Weather Service Green Bay WI
1032 PM CDT Sat Aug 15 2020
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Sunday
Issued at 228 PM CDT Sat Aug 15 2020
The latest RAP analysis and satellite/radar imagery show a cold
front in the process of exiting east-central Wisconsin early this
afternoon. Shower activity expanded over east-central WI by late
in the morning, but most of the precip has exited over Lake
Michigan. The back edge of the cloud cover is heading southeast
across north-central Wisconsin. Should see this clearing continue
to spread southeast over the rest of the afternoon into early this
evening. Looking upstream, the next upper level disturbance is
spreading mid and high level clouds across North Dakota and Minnesota.
Spotty showers with this disturbance along with the potential for
showers/storms along a weak cold front on Sunday are the main
forecast concerns.
Tonight...After a period of clearing, mid and high cloud cover
will return this evening as a surface ridge axis slides across the
region. The short range models show scattered showers and storms
will be moving southeast within a trough axis and the left front
quadrant of a 115 kt jet streak over northeast Minnesota and into
northwest Wisconsin. This shower activity is expected to approach
north-central WI after midnight, but guidance generally shows
precip diminishing in the process. Will keep a slight chance in
the forecast, highest over Wood county. Low temps will be cooler,
and mainly in the 50s.
Sunday...Another upper trough will move into the region in the
afternoon, along with a weak surface trough. With heat of the day,
some surface based instability up to 1000 j/kg is forecast to
developed, which could lead to an isolated showers and storms
developing in the afternoon, primarily over northeast Wisconsin.
Temps will be slightly above normal and range from the middle 70s
to low 80s.
.LONG TERM...Sunday Night Through Saturday
Issued at 228 PM CDT Sat Aug 15 2020
Fairly quiet weather in the extended with seasonal temperatures
expected. A couple chances for showers and thunderstorms are
possible late Tuesday into Wednesday and again next weekend.
Sunday night into Tuesday: A weak surface trough is expected to
drift slowly east of the area Sunday evening, which may allow for a
few sprinkles or light rain showers in the early evening hours;
otherwise, much of the night will be dry as high pressure approaches
from the west. The surface ridge is expected linger/becoming
reinforced across the area through the remainder of this time
period, allowing for lighter winds and mainly dry conditions. Aloft,
northwest flow will linger across the area, allowing for somewhat
cooler conditions. High temperature will likely be in the 70s for
most locations through this time period. Overnight lows will drop
into the 40s to around 50.
Tuesday night through Wednesday: A nearly west to east oriented cold
front is expected to sag southward into much of northeast Wisconsin
late Tuesday afternoon. This front is currently progged to drop
slowly south through all of northeast Wisconsin before departing to
the south by late Wednesday afternoon. The front doesn`t have a lot
of moisture to work with as the Gulf is basically cut off through
much of the first part of the week. The main area of moisture
associated with this feature will drift into the area from the
northwest, across central Canada. With that in mind, models are
showing enough forcing and instability along the front to touch of
some showers and thunderstorms through this time period. For the
reasons previously mentioned, model only paint out around a tenth to
a quarter of an inch of QPF. Lows are expected to be in the 50s with
highs warming into the 70s to around 80. Of course, temperatures
could be held back a bit if cloud cover is extensive (it looks like
this could be the case) during the day.
Wednesday night through Thursday: Dry high pressure is expected to
quickly build back across the area Wednesday night and linger into
Thursday afternoon as it slowly drifts to the east. This is expected
to allow increased/southerly return flow by late Thursday afternoon.
Again, for the most part, this time period should be fairly quiet
with moderating temperatures as the upper-level flow flattens across
the area. Lows will be mainly in the 50s with highs warming into the
upper 70s to low 80s.
Rest of the extended: A surface low and upper-level trough is
expected to trek across Ontario Friday into Saturday while dragging
a cold front across much of Wisconsin. This will lead to increased
chances for showers and thunderstorms across the area along with
more widespread cloud cover. Considering this is toward the end of
the forecast period and there are timing/placement issues, will
stick with a blend of the models, bringing the aforementioned
chances of showers/storms to the area. Temperature are expected to
be near or slightly above normal.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1031 PM CDT Sat Aug 15 2020
A series of shortwaves will drop ESE across the area during the
next 24 hours. Clouds will be a mix of middle-level clouds and
diurnal clouds with VFR bases. Isolated showers are possible in
central Wisconsin late tonight, and mainly across far northeast
Wisconsin Sunday. Winds may become a little gusty tomorrow,
especially in central Wisconsin.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......Cooley
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Wilmington NC
940 PM EDT Sat Aug 15 2020
.SYNOPSIS...
Occasional showers and thunderstorms will continue through
Sunday, but will diminish Sunday night and Monday as slightly
drier air moves in behind a front. Unsettled weather will
return by mid to late week.
&&
.UPDATE...
POPS re-hashed for the remainder of the evening thru Sun
morning...based on latest 88D trends and 18Z model runs as well
the latest HRRR and RAP. Various model MOS guidance all over the
place with the respect to low stratus and fog occurrence but in
the end placed atleast a patchy fog possibility. NAM indicates a
couple weak vorts or embedded mid-level s/ws...all ahead of the
upper trof pushing to the Carolinas thru Sun. Weak sfc front
will make it`s way closer to the coast overnight with it`s
passage reaching the I-95 corridor, around daybreak. POPs will
remain in the fcst overnight, overall dropping to low chance
inland and increasing to moderate chance along the coast, or
ahead of the front. Tweaked tonights min temps a degree or 2
higher, mainly east of the sfc front, ie. closer to the coast.
Tweaked initial SW winds slightly hier for the remainder of the
evening, then dropping them back to 10-15 kt by daybreak Sun.
Seas will run 2 to 4 ft and primarily driven by wind driven
waves at 4 to 6 second periods. With an underlying 1 to 1.5 foot
SE swell at 9 to 10 second periods.
&&
.NEAR TERM /THROUGH SUNDAY NIGHT/...
Mid to upper trough pushing eastward across the Southeast
through Sunday will maintain a deep stream of moisture and
increased convective activity. Pcp water values will remain
above 2 inches through Sun aftn in a moderately unstable
atmosphere ahead of an approaching front. Overall expect
occasional shower and thunderstorm activity with the focus
shifting toward the coast by Sun aftn and then offshore by Sun
evening as front makes its way across the Coastal Carolinas.
Decent SW winds and steering flow will keep storms moving off to
the northeast with brief periods of very heavy rain and gusty
winds possible.
Should see drier air making its way in through the mid to upper
levels as trough aloft reaches the coast and lifts off to the
north through Sun night. Therefore convective activity will
diminish through Sun aftn from west to east as winds shift
around to the NW. The best convergence and chc of shwrs/tstms
Sun aftn will be near the coast where front comes against sea
breeze. Models seem to be showing a faster push offshore and may
see all pcp end by early evening on Sunday. A deep dry NW to N
flow Sun night will bring a change in air mass as pcp water
values drop below 1.5 inches and dewpoint temps drop several
degrees. This will bring overnight lows on Sun night closer to
70 instead of mid to upper 70s for tonight. Daytime highs on Sun
should once again reach into the mid 80s with variations due to
clouds and shwrs.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
A mid level trough will ease its way through the area
during the period pushing a persistent and quite active baroclinic
zone offshore. Some cooler and drier air infiltrates the region
briefly but moisture and pops quickly return for Tuesday. Highs will
be in the middle 80s or so with lows in the lower 70s. There could
be a reading or two below 70 but guidance is usually a bit low on
this type of situation.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Any respite of the unsettled nature of daily showers
and thunderstorms will be long past as the extended period
progresses. The inland trough will reappear as will Bermuda High
Pressure. In fact the mid level feature for the latter feature
seems to build south and westward with time increasing the
moisture feed into the area. Good chance to likely pops are the
story each day and with the nocturnal season in full swing
showers and thunderstorms are possible anytime of day.
Consistent temperature forecast with highs in the middle 80s or
so and lows in the lower to middle 70s.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Southeast NC and Northeast SC remain entrenched in PWS above
2 inches with a weak sfc front combined with an approaching
mid- level trof producing convection well into this evening and
again starting early Sun morning. The threat for VCSH and VCTS
will dominate the terminals with a highlight of the best time
for Sun convection using PROB30 6 hr groupings. Model MOS
Guidance indicate at threat for fog and low stratus between 06z
and 12z Sun...mainly across the inland terminals. The sfc front
will track slowly across the area during Sun with winds becoming
NW-N 5 to 10 kt in it`s wake. Ahead of it looking at SW-WSW
around 5 kt, slightly across the coastal terminals.
Extended Outlook...Scattered to numerous showers and tstorms
expected thru Sun evening. Drier air may work its way briefly
across the area late Sun into early next week with less
thunderstorm activity and coverage possible. Early morning
MVFR fog and/or IFR low stratus possible Mon and Tue mornings.
&&
.MARINE...
Slight increase in southerly winds up to 15 kts will drive seas
up to 3 to 4 ft through tonight. A longer period SE swell 1-2
feet every 8-9 seconds will mix with shorter period southerly
wind waves. SW winds Sun night will veer to the north by Mon
morning as front moves through the waters. Seas will begin a
downward trend at that time.
A few hours of northeast winds should be in place early
Monday as a brief push of drier air moves across. As would be
expected the weak surge is quickly dissolved and light and
variable winds develop. In time the synoptic direction goes
southeast then south/southwest. Speeds will struggle to make it
over ten knots but may have more success later in the period and
with smaller features such as the sea breeze. Synoptic seas
will be 2-3 feet.
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...RGZ
UPDATE...DCH
NEAR TERM...RGZ
SHORT TERM...SHK
LONG TERM...SHK
AVIATION...DCH
MARINE...DCH/RGZ/SHK
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
1031 PM EDT Sat Aug 15 2020
.SYNOPSIS...
A weak cold front will approach the region from the west
tonight. The cold front will then move east across the region
on Sunday. Another weak cold front will pass over the area on
Monday.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Isolated showers are lingering up in West Central Ohio. The HRRR
and RAP are showing them linger for a couple more hours before
dying out.
Skies will then be mostly clear for the first half of the night.
Fog is forecast to build northwest from West Virginia and some
low clouds could be associated with this for areas southeast of
I-71. Lows still look like they will range in the 60s from east
to west.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
The cold front is poised to move across our area on Sunday. The
front will be associated with an embedded s/wv aloft. Diurnal
heating will bring instability to the region, likely on the low
end moderate scale. And with just enough forcing and deep layer
shear between 25 and 30 knots, scattered showers/storms should
occur, peaking during the afternoon across the eastern two
thirds of the CWFA. There could be a few strong storms, possible
isolated severe, with strong or damaging winds being the
primary threat. Highs will warm into the upper 70s to the lower
80s.
For Sunday night, the cold front will be exiting to the east
during early evening. Convective coverage will decrease and also
shift east during the evening. By the overnight hours, much of
the region will see mostly clear skies. Lows will range from the
upper 50s to the lower 60s.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
This period characterized by persistent longwave troughing in the
Great Lakes - downstream from very strong western CONUS ridging.
Sensible weather should be rather benign/quiet in nature, with
temperatures averaging out slightly below normal for mid-late
August. While there are small/episodic chances for showers given
the persistent troughing aloft and cyclonic flow with weak
disturbances moving the Great Lakes, feel chances are low enough to
keep most days dry in most areas.
Probably the most concerning day in the entire extended period is
right off the bat on Monday as a weak shortwave trough rotates
through the longwave trough axis at peak heating. Most convectively
parameterized NWP models are generating scattered/light blobs of QPF
- a signal of weakly forced scatted showers and a few thunderstorms.
The NAM is has the strongest surface reflection of the shortwave
trough and has the most instability of any NWP evaluated in the
15.12Z cycle - which is a common theme - with other deterministic
CMC/ECMWF/GFS all having some semblance of weak convergence axis /
cold front slipping through the area but with dramatically less
instability and convergence along its length. The mid-upper level
flow through the ILN CWA on Monday will be cyclonic and of
sufficient magnitude to support an organized updraft or two through
peak heating, but forecast instability will be the key whether an
organized severe weather threat can develop or not. A lot of
uncertainty in this regard - not to mention the aforementioned
discrepancies in the lower level forcing signals. For now, have
included a 20-35% chance for storms in the aftn/eve with plenty of
time to refine threat assessment. If a stronger storm or two can
develop, deep unidirectional west-northwesterly flow and some lower
level linear forcing suggests a gusty line segment or multicell
cluster is possible.
In the wake of this trough, Tuesday and Wednesday look like the
driest/sunniest days of the week, although with relatively cool mid
level temperatures and associated steep/er/ lapse rates, can`t
completely rule out a shower either day somewhere in the CWA. But
enough confidence right now to just run dry forecast with nice
mornings in the 50s and highs around 80.
Thursday/Friday, with the southern portion of the longwave trough
over the Deep South showing hints of cutting off and deepening there
are hints and suggestions that heights will rise just a bit to the
east/northeast of the deepening negatively anomaly and will allow
moisture and warming to begin to increase in slow fashion from south
to north. Thus, small chances for showers and storms are in the
forecast for these days in northern Kentucky into the Scioto Valley,
along with warming temperatures into the lower and middle 80s, as
well as slowly increasing dewpoints.
Into next weekend, seemingly a better ensemble signal of more
trackable shortwave trough through the Great Lakes with a better
chance of showers and storms, as it interacts with more established
plume of moisture and instability which had been slowly building
over the previous days.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Isolated convection continues to pop from about the U.S. 68
corridor to the I-75 corridor. Latest guidance is still showing
that this dissipates over the next couple of hours.
Skies will be mostly clear over the tafs tonight, but models
develop an area of fog over West Virginia and build it up to the
northwest, reaching about I-71 by morning. This will bring
MVFR/IFR visibilities to all but CVG/DAY.
Fog should lift quickly after 12Z Sunday. Focus then is on a
front which is forecast to move into the area during the
afternoon. Ahead of the front, convection will develop in the
instability. It looks like the best window for the convection to
affect the tafs is between 15-21Z, with DAY on the early end of
the window and ILN/CMH/CMH on the later half. MVFR/IFR
conditions will be possible in the thunderstorms.
Winds will turn to the northwest and will increase with the
frontal passage in the afternoon. Gusts up around 20 kts will
be possible.
OUTLOOK...Thunderstorms are possible Monday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Hickman
NEAR TERM...Sites
SHORT TERM...Hickman
LONG TERM...Binau
AVIATION...Sites
Area Forecast Discussion
National Weather Service Lincoln IL
731 PM CDT Sat Aug 15 2020
.SYNOPSIS...
Issued at 259 PM CDT Sat Aug 15 2020
Scattered showers and thunderstorms will develop along a weak cold
front and move east across the area late this afternoon through
this evening. A few of the storms could be strong with gusty
winds and locally heavy downpours, east of the IL river. Quiet
and seasonably warm conditions are expected on Sunday, as high
pressure builds across the Midwest.
&&
.UPDATE...
Issued at 731 PM CDT Sat Aug 15 2020
Cold front continues to push southeast, centered roughly along the
Illinois River based on sharp dew point dropoff to the west. A
broken line of thunderstorms that began forming around mid
afternoon has fractured into two sections, one well south of
Springfield and the other just east of Bloomington. Some
convective activity expected to continue the remainder of the
evening across mainly east central Illinois, though the HRRR
suggests a few showers may linger past midnight.
Zones/grids have been updated for the latest rain and sky trends.
&&
.SHORT TERM...(This evening through Sunday)
ISSUED AT 259 PM CDT Sat Aug 15 2020
As a cold front slowly moves east across the area, scattered
thunderstorms are still expected to develop late this afternoon
through this evening and move east across central Illinois.
Airmass ahead of the front still remains unstable enough for
storms, but wind shear and convergence along the front remains
minimal. So, storms should remain scattered, but some could still
be strong with isolated damaging winds, small hail, and brief
heavy downpours. Any precip should be short-lived and it should be
out of the CWA around midnight. Then dry and warm weather is
expected tomorrow. Overnight lows will vary across the CWA with
middle to upper 50s behind the front in the north, to the middle
60s in the southeast. Highs tomorrow will once again rise into the
lower to middle 80s.
&&
.LONG TERM...(Sunday night through Saturday)
ISSUED AT 259 PM CDT Sat Aug 15 2020
A secondary cold front is expected to move through the Great Lakes
region Monday and bring cooler air into the region. Previous
forecast had some small chances of precip with this front, but
newest forecast suggests this front will come through dry with no
precip expected. The rest of the week should be dry with
seasonable temps in the lower to middle 80s, as high pressure
dominates the region. Then the extended models suggest a stronger
cold front will move into the area for Friday night and Sat with
a chance of precip across the northern part of the CWA. Temps may
also warm a tad toward the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 613 PM CDT Sat Aug 15 2020
Broken line of thunderstorms from KBMI-KSPI will continue to push
southeast early this evening. Brief IFR/LIFR visibilities
occurring with the heavier storms, but intensity should wane some
as we get closer to sunset. Timing-wise, will hold off on any VCTS
mention at KCMI until near 02Z, with most other sites with a
thunder mention through 03Z. Threat is east of KPIA and will go
with little cloud cover there through the period.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Geelhart
SYNOPSIS...Auten
SHORT TERM...Auten
LONG TERM...Auten
AVIATION...Geelhart
Area Forecast Discussion
National Weather Service North Platte NE
620 PM CDT Sat Aug 15 2020
.SHORT TERM...(This evening through Sunday night)
Issued at 310 PM CDT Sat Aug 15 2020
An inverted sfc trof associated with a warm front across wrn
Nebraska will continue moving slowly east tonight and then be
pressed back south with the arrival of a weak Canadian cold front
Sunday. Both the warm front and cold front may be the focus for
isolated showers and thunderstorms tonight and again Sunday
afternoon.
The severe weather potential this evening appears to be marginal,
given the lack of forcing aloft and relatively modest MLCAPE around
2500J/KG as shown by the RAP model. It is also possible the winds
aloft are too strong and the RAP model suggested Bulk Richardson
numbers of 45 or less which is on the low side considering the
actual live storm based CAPE will be lower. The better show will
likely be across KS and Colo where instability will be greater.
Still, the warm front, will be the focus for isolated strong or
severe storms across wrn Nebraska as suggested by the SREF model.
The HREF, HRRR, RAP and NAM are largely silent on any sort of
rain chance this evening. The thunderstorm forecast is guarded
with an isolated chance across a fairly broad area of western
Nebraska.
The temperature forecast leans on the short term model blend plus
bias correction for lows in the 50s and lower 60s and highs Sunday
in the upper 80s to lower 90s. This is in the middle of the guidance
blend.
.LONG TERM...(Monday through Saturday)
Issued at 310 PM CDT Sat Aug 15 2020
The models are in very good agreement holding a strong subtropical
ridge near the four corners region. The ridge will amplify north
a bit for couple of days and then settle south. Temperatures at
the h850mb level should warm about 5C from the upper 20s to lower
30s celsius and this should support highs in the upper 80s to mid
90s depending upon mixing.
Winds aloft will be north and strong at 20 to 40kts. The resulting
strong shear would normally be favorable for storm development but
subsidence around the northeast periphery of the h500mb ridge and
limited moisture with sfc dew points in the 50s to near 60 appear to
be limiting storm development. Just isolated thunderstorm chances
are in place Monday through Saturday.
The temperature forecast is somewhat problematic. The guidance blend
and temperatures at the h850mb level suggests highs a bit warmer
than the model blended forecast which is the basis for official
forecast. The ECM guidance is a few degrees cooler than the GFS
guidance. The blended forecast is similar to the ECM guidance and
the temperature forecast some days might need to be marked up a
couple of degrees.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 620 PM CDT Sat Aug 15 2020
VFR is primarily anticipated through the forecast period, aside
from brief visby and/or cig drops invof thunderstorms. Isolated to
scattered thunderstorms will affect parts of western Nebraska
through late this evening. Overnight, lower level clouds should
clear out and southerly winds become light and variable. A wind
shift to northwest takes place during the morning, with winds
becoming gusty at times in the afternoon.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Snively
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
943 PM EDT Sat Aug 15 2020
.SYNOPSIS...
Low pressure over the Ohio River Valley will track eastward
along a stalled front over Virginia this weekend. A second cold
front will follow Monday. High pressure then returns through the
middle of next week. Unsettled weather may return during the
second half of next week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Upper level trough and associated boundary are approaching the
western slopes of the Appalachians this evening. Secondary low
pressure is beginning to develop along a surface boundary well
to the south over the Carolinas. This low will lift northeast
across southeastern Virginia through Sunday morning.
The combination of the approaching trough, upper jet dynamics,
and isentropic lift over the frontal zone amongst 1.7-2.2 inch
precipitable water has led to fairly widespread shower
development. Rainfall has been light to occasionally moderate,
with some dry air to overcome due to high pressure to the north.
There will likely be some gaps in the showers during the late
evening/early overnight hours this initial shot of forcing
wanes.
As the low approaches later tonight, frontogenetical forcing
will increase in the 925-850 mb layer, with these boundary
located somewhere near the southeastern quadrant of our area.
Except perhaps far southern Maryland, instability is expected to
be at a minimum, so very high rain rates and true flash
flooding appear less likely. However, within the bands, rainfall
rates could be around 0.8" per hour or even briefly higher,
though the heaviest rain may be somewhat transient. Some of the
18Z model guidance indicated potential for 2+ inches of rain in
such a band from the central Blue Ridge toward the DC metro,
which could cause some localized flooding given the various
areas which have seen heavy rain lately. More recent runs of the
RAP and HRRR have shifted the highest QPF back toward southern
Maryland, which is where all the parameters line up better for
heavier rain totals. Therefore, will be considering a Watch for
this area. Elsewhere, will keep the isolated flooding threat
relegated to the HWO at this point, though sensitive parties
should be alert for any warnings or short-fuse watch
issuances... with the biggest threat of such generally south of
US 50 and along/east of the Blue Ridge. (hat tip to WPC for
their assistance in assessing rainfall rate potential)
With saturation, the temperature forecast will follow the dew
points... near 60 in the Shenandoah Valley/Potomac Highlands and
mid 60s to near 70s elsewhere (with possible nondiurnal rises
late tonight in the southeast).
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
The upper-level trough will pass through Sunday morning before
moving offshore Sunday afternoon through Sunday night. More
showers are expected Sunday morning. Locally heavy rain is
possible Sunday morning, especially near the 925-850mb boundary
over the VA Piedmont and southern Maryland.
Showers will gradually dissipate in coverage from west to east
Sunday afternoon into Sunday evening as the upper-level trough
and its associated surface low moves to our east. However,
plenty of clouds will hang around and it will turn out
unseasonably cool conditions for this time of year.
Weak high pressure will briefly build overhead Sunday night into
early Monday morning, bringing drier conditions. However, low
clouds and areas of dense fog are possible as moisture gets
trapped underneath the nocturnal inversion.
Another shortwave will carve out a low amplitude upper-level
trough over the area for Monday, but a west to northwest flow
aloft will allow for drier conditions compared to recent days.
The drier air will cause more sunshine, so it will turn out
seasonable with highs in the 80s for most areas. An isolated
shower or thunderstorm is possible during the afternoon and
evening hours. Dry and seasonable conditions are expected
overnight Monday.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
Overall good agreement concerning the extended period. A strong
upper level ridge over the western CONUS will result in a
prolonged trough pattern for the Eastern US. Therefore,
opportunities for afternoon showers and thunderstorms are likely
to continue.
Tuesday appears to remain mostly dry as weak high pressure
reigns over the region. Meanwhile, a developing shortwave will
enter the Ohio Valley Tuesday afternoon/evening. As a result, a
stationary front will linger over Central VA as shortwave
energy traverses along the stalled boundary. Given the increase
in moisture and plentiful instability, supports the idea of
scattered afternoon/evening showers and thunderstorms.
Thursday through Saturday looks somewhat uncertain at this time.
Question becomes how the Bermuda high strengthens offshore. If
the high develops closer to the East Coast, then it will keep
the trough stationary over the Ohio Valley; resulting in
continued unsettled conditions. However, if the high remains
centered over Bermuda, then the aforementioned trough will be
able to swing through the region, decreasing PoPs for Friday and
Saturday. At this time, seems more likely that we will remain
wedged in-between the trough to the west and the high offshore.
This will keep moisture and instability over the CWA, resulting
in continued chances for afternoon/evening showers and
thunderstorms.
Overall, temperatures will remain seasonable next week; ranging in
the low to mid 80s.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
Numerous showers are crossing the area this evening. In general
conditions should be VFR, although brief MVFR conditions are
possible. Since the rain has been a little steadier than
previous forecast, some areas may drop to MVFR ceilings a little
faster than indicated in the 00Z TAFs. Cigs will continue to
lower through tonight due to an onshore flow. The exact timing
is a little uncertain, but the best chance for IFR conditions
will be after 06Z (and possibly toward daybreak at BWI/MTN)
through Sunday morning. Rainfall could be moderate at times. Cigs
may improve a little Sunday afternoon as the showers taper off
(though likely remaining sub-VFR), but more low clouds and fog
are possible Sunday night into Monday morning.
Drier conditions are expected Monday and Monday night, but an
isolated thunderstorm is possible during the afternoon and
evening.
Mainly VFR conditions are expected both Tuesday and Wednesday
next week. However, instances of sub-VFR conditions cannot be
ruled out, especially with patchy morning fog and chances for
showers and thunderstorms during the late afternoon/early
evening. Sub-VFR conditions look more present Wednesday
afternoon/evening where chances for convection look to be the
highest.
&&
.MARINE...
An onshore flow will gradually increase through this evening. A
Small Craft Advisory is in effect tonight through Sunday
afternoon for most of the waters. As low pressure passes to the
southeast late tonight into Sunday morning, winds will peak,
and have added the upper Potomac to the advisory for 6AM-3PM.
Moderate rain expected late tonight into early Sunday, and a
stray thunderstorm can`t be ruled out.
The Small Craft Advisory may need to be extended for central
portions of the Bay into Sunday night before winds lighten on
Monday.
Light winds continue through Wednesday.
&&
.TIDES/COASTAL FLOODING...
An onshore flow will continue to cause anomalies to increase
through tonight into Sunday morning. A Coastal Flood Advisory is
in effect for the tide cycle late this evening into Sunday
morning for Anne Arundel and St Marys Counties. Additional
advisories may be needed for the high tide late tonight into
Sunday morning. Anomalies should fall later Sunday/Sunday night
as the flow turns offshore.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory from 1 AM to 7 AM EDT Sunday for MDZ014.
Coastal Flood Advisory until 2 AM EDT Sunday for MDZ017.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 PM EDT Sunday for ANZ530>534-
536>543.
Small Craft Advisory from 6 AM to 3 PM EDT Sunday for ANZ535.
&&
$$
SYNOPSIS...BJL
NEAR TERM...BJL/ADS
SHORT TERM...BJL
LONG TERM...MSS
AVIATION...BJL/ADS/MSS
MARINE...BJL/ADS/MSS
TIDES/COASTAL FLOODING...BJL
Area Forecast Discussion
National Weather Service Medford OR
854 PM PDT Sat Aug 15 2020
.DISCUSSION...There is some impactful weather to discuss this evening,
including heat, thunderstorms, and south winds that are
transporting smoke to the area. First, heat. Please see
weather.gov/medford for graphics that depict the record high
temperatures. In short, Medford reached 108 degrees, and this ties
a daily record for Aug 15, and Roseburg smashed the old record of
98 degrees set in 1933 with a high temperature today of 108
degrees! It...was...hot. Temperatures tomorrow will "cool" by a
few degrees, but it will still be hot. The Excessive Heat Warning
continues through Sunday to highlight the dangerous heat. We`re
considering extending this into Monday because of the little
relief expected early next week. We`ll see how the evening model
guidance trends.
There were about 120 cloud to ground (CG) lightning flashes this
afternoon and evening. A few more showers are ongoing. The lightning
was concentrated in Lake County with 103 CG flashes there.
Tomorrow`s thunderstorm activity will be more significant and is
expected to stretch west of the Cascades. Significant triggers will
move up from the south to help initiate thunderstorms in our area
tomorrow, acting in concert with significant moisture (Precipitable
Water values 1in+) and instability. Evening with evening model data
coming in, there`s still some uncertainty in how the situation
exactly plays out tomorrow, especially for areas west of the
Cascades. Enough data, however, points to lightning west of the
Cascades that Red Flag Warnings continue for much of the forecast
area tomorrow, including portions of Jackson and Douglas Counties.
Lots of moisture and some strong winds aloft suggest these storms
will produce brief periods of heavy rain along with the potential
for strong winds.
Lastly, smoke moving up from Northern California into Southern
Oregon. The Red Salmon wildfire in Western Siskiyou County pumped
out a lot of smoke this afternoon, and it`s moved into the Jackson
and Josephine Counties. Air Quality readings suggest we`re in the
Unhealthy for Sensitive Groups range, and that could remain that way
through the evening per latest HRRR smoke model output. Expect some
improvement tomorrow morning, but south flow will bring more smoke
to the area tomorrow evening. We`ve updated the forecast with the
latest HRRR smoke model output, which seems to be matching current
observations nicely.
Please see the previous discussions below for more details on the
thunderstorm potential and heat.
&&
.AVIATION...For the 16/00Z TAFs...VFR and clear skies are expected
to continue for most areas through the TAF period. One exception is
smoke from the Red Salmon Fire, which will reduce visibilities in
much of western Siskiyou County, with haze potentially spreading to
the north and northeast. Due to heat, density altitude could be a
concern today. Another concern is the possibility of isolated
thunderstorms this afternoon and evening, mainly over the high
terrain of the Cascades, Sikiyou, and Klamath mountains, and across
the East Side. Tonight, areas of IFR/LIFR conditions may affect the
coast and the coastal waters as a southerly surge brings low clouds
north. All other areas should remain VFR. -BPN/BR-y
&&
.MARINE...Updated 800 PM PDT Saturday 15 August 2020...South winds
will persist through Monday morning with low clouds and fog likely
returning sometime Sunday morning into the afternoon. Winds turn
northerly again by Monday afternoon but conditions will remain
relatively calm with light winds and seas through at least mid-week
when the thermal trough is expected to return. This event appears to
be trending to the weaker side, so while conditions may become
hazardous again by mid-week, it doesn`t appear to become as
hazardous as the most recent event. Stay tuned as details become
more clear. /BR-y
&&
.FIRE WEATHER...Updated 200 PM PDT Saturday 15 August 2020...
We`ll remain under the influence of a strong upper ridge, centered
over the Great Basin, the rest of this weekend into early next week.
This is bringing the hottest weather of the season thus far at
climatologically the driest time of the year. We`re not
anticipating widespread lightning this afternoon, but a couple
of isolated cells could pop up near the Siskiyous and also the east
side mountains through this evening (and move off to the NNE
before dissipating later in the evening).
Meanwhile, a closed low is off the California coast. Deep southerly
flow will transport subtropical moisture northward, especially
in the mid and upper levels, through California tonight and
into our area on Sunday. Multiple disturbances will move northward
during this time and likely generate isolated to scattered
thunderstorms beginning as early as Sunday morning. With the
initial surge of moisture Sunday morning, convection is likely
to be elevated, and thus, dry. What we have seen a few times in the
past is that these events end up being a large canopy of mid and
high level cloud cover w/showers leading to very little in the way
of lightning. This is a concern, but given the extreme dryness
preceding this event and the potential for numerous new fire
ignitions with any lightning, we have decided to upgrade the Fire
Weather Watches to Red Flag Warnings with a start time of 15z
(8 am).
The focus of the best instability is shown on the models to be on
the NW periphery of this potential convective area Sunday
afternoon/evening. This is from northern and eastern Jackson
County up across the Umpqua Divide and eastward to the Cascades with
another area across northern Klamath/Lake Counties. While all
locations within the Red Flag Warning could see new fire starts, it
is these areas that stand the highest chance of lightning-caused
ignitions. Even though PWs increase to 1.00 or greater and rainfall
will accompany storm cores, rainfall may be brief due to fast mid-
level flow and storm motions of 25-35 kt. And, it should be noted
that since the mid-level flow is strong, any of the stronger cells
will have the ability to produce gusty outflows of up to 55 mph.
Guidance shows most of the activity ending by around 03z (8pm), but
have maintained the end time of 06z (11 pm) as a buffer. Activity
should wane or end overnight.
Another shortwave will rotate north-northeastward Monday. There
should be another round of scattered thunderstorms across portions
of the east side, so have hoisted a Fire Weather Watch for Fire
Zones 624 and 625 in Oregon and 285 in California.
We`ll remain in S-SW flow aloft through at least Tuesday, so the hot
weather looks to continue, albeit not quite as hot as over the
weekend. Isolated thunder chances continue in north Cascades and
over far eastern sections Tuesday afternoon. Temperatures should
ease back but remain above normal Wed-Fri next week with little or
no chance of thunderstorms. -Spilde
&&
.PREV DISCUSSION... /Issued 300 PM PDT Sat Aug 15 2020/
DISCUSSION...Temperatures are within a couple of degrees of daily
record highs as of 2 PM PDT this afternoon. Therefore, confidence
is high that we`re going to see a number of records fall today.
Roseburg has already tied their record of 98 and North Bend is
within a degree of a 101 year old record of 84. Please keep in
mind that you need to make extra effort to remain hydrated today
due to the very hot and dry air mass in place.
Cumulus fields are developing in the areas that we`ve been
expecting them. We`ve also already seen a few significant cumulus
build-ups across the Modoc that are showing up on radar in the
last hour. However, there have been no CG flashes yet, nor has
there been any in-cloud lightning detected. Models and our going
forecast continue to indicate a slight chance of thunderstorms
developing this afternoon and evening from the Marble Mountains
to the western edge of the Shasta Valley northward into the
Siskiyous and Jackson County to north and northeast of Crater Lake
NP and across northern Klamath County, Lake, and Modoc counties.
If a storm does form, it will produce little or no rainfall.
Current convective cloud development has been coincident with
where the coolest air is at 500MB. While that coolest air is
currently east of the Cascades, models suggest it will shift to
areas along and near the Cascades through this evening.
Red Flag Warnings have been issued along with the pre-existing
Excessive Heat Warnings and Heat Advisories for Sunday. The Red
Flag Warnings are for expected lightning on very dry vegetation
along with gusty outflow winds. It will be generally breezy Sunday
and thunderstorms across the area will be capable of producing
gusty outflow winds of 40 to 60 mph. While increasing precipitable
water values of 1 to 1.5 inches by Sunday afternoon means that
these thunderstorms will be capable of producing moderate to heavy
rain rates, storm motions of 20 to 40 mph means that storms are
unlikely to be over any particular area for very long before
moving off. Therefore, if you will be outside Sunday between 8am
and 11 pm PDT where we`re forecasting thunderstorms, be ready to
take shelter should it become necessary to do so. While we have
moderate confidence in our going forecast for thunderstorm
coverage, there continues to be a high amount of spread in
possible solutions from the models due to the highly convective
and, therefore, chaotic nature of this weather event. Some of the
Convective Allowing Models (CAMs) suggest cloud cover and rain
with embedded thunder moving through Sunday morning with isolated
thunderstorms in the afternoon while others suggest thunderstorms
with little rain in the morning followed by severe thunderstorms
in the RFW warning area (to include on the west side in Jackson
and Douglas counties) in the afternoon to early evening.
While the heat and thunderstorm threat goes down with time, the
forecast has generally trended to keep thunderstorms in the
forecast a bit longer further west for Monday and Tuesday. The
NAM12 continues to be farthest west with the lingering threat,
while the GFS20 is further east. Collectively, the models have
generally trended toward the thunderstorm threat being from the
Cascades eastward for Monday and Tuesday. High PWATs of 1 to 1.4
inches Monday and Tuesday mean that thunderstorms could be quite
wet where they do occur. ~BTL
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 8 AM to 11 PM PDT Sunday for
ORZ617-621>625.
Fire Weather Watch from Monday afternoon through Monday evening
for ORZ624-625.
Blowing Dust Advisory until 9 PM PDT this evening for ORZ031.
Heat Advisory until 11 PM PDT Sunday for ORZ027>029.
Excessive Heat Warning until 11 PM PDT Sunday for ORZ024-026.
Heat Advisory until 11 PM PDT this evening for ORZ021-022.
Excessive Heat Warning until 11 PM PDT Sunday for ORZ023-025.
CA...Red Flag Warning from 8 AM to 11 PM PDT Sunday for
CAZ280>282-284-285.
Fire Weather Watch from Monday afternoon through Monday evening
for CAZ285.
Heat Advisory until 11 PM PDT Sunday for CAZ082>084.
Excessive Heat Warning until 11 PM PDT Sunday for CAZ080-081.
Pacific Coastal Waters...None.
$$
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
658 PM CDT Sat Aug 15 2020
.UPDATE...
Issued at 658 PM CDT Sat Aug 15 2020
Storms are really struggling up in northern MN. Instability has
come in a bit lower than expected and covergence along the
boundary hasn`t been enough to get more widespread convection
going in northern MN (convergence is slightly better in Canada,
where storms have remained). As a result, it looks unlikely we`ll
see severe weather in our northeast CWA through tonight. Still
looks like we`ll see scattered showers in western WI between 6z
and 10z in conjunction with a strengthening LLJ as shown by the
RAP (which is why the HRRR develops showers in this window), but
instability does not look robust enough to support severe
convection.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 230 PM CDT Sat Aug 15 2020
A shortwave moving through southern SK will support thunderstorm
development across northern Minnesota this afternoon. Lingering
convection may reach our northeastern CWA tonight where the SPC
upgraded a stripe into the Marginal risk category with the primary
hazard of large hail. While some severe storms are possible this
afternoon north, recent trends in guidance suggest the severe
threat remains north of our CWA with convection moving in after
sunset. That being said I can`t rule out the potential for some
small hail and heavy rain across northern Mille Lacs, Kanabec,
Polk, Barron, and Rusk counties tonight.
Another weak wave embedded in the northwest flow could generate a
few isolated thunderstorms across portions of southern Minnesota on
Sunday afternoon/evening. SPC continues a marginal risk over
southern MN on Day 2. More aggressive guidance has initiation
occurring on a steeper instability gradient with values of CAPE
as high as 2000 J/Kg on the WRF-ARW while 15z RAP has meager
instability with the gradient south of the CWA across northern
Iowa.
.LONG TERM...(Monday through Saturday)
Issued at 230 PM CDT Sat Aug 15 2020
Not much has changed in the long term period. An intense 600 dm ridge
centered over the southwest this weekend won`t move much at all
for the next 10 days. This will result in persistent northwest
flow into the end of next week. The longwave trough will be
confined to the eastern Great Lakes and east coast. Most of the
disturbances and upper energy should remain north and east of the
Upper Midwest until mid week when the pattern begins to deamplify
a bit and becomes slightly more zonal. This should introduce more
thunderstorm chances, but parent disturbances don`t appear
impressive enough for PoPs greater than slight chance at this
range.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 658 PM CDT Sat Aug 15 2020
Some threat for a brief shower between 6z and 10z at RNH/EAU,
otherwise, not much more expected this period than sct to bkn mid
level clouds as weak disturbances slide through in the northwest
flow.
KMSP...No additional concerns.
/OUTLOOK FOR KMSP/
Mon...VFR. Wind NW 10 kts.
Tue...VFR. Chc -TSRA late. Wind SW 10 kts.
Wed...VFR. Wind NE 5 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
UPDATE...MPG
SHORT TERM...BPH
LONG TERM...BPH
AVIATION...MPG
Area Forecast Discussion
National Weather Service Portland OR
849 PM PDT Sat Aug 15 2020
SYNOPSIS...Strong high pressure over western USA maintaining hot air
mass over Pac NW through Monday. At same time, southerly flow aloft
will bring a chance of a few thunderstorms for the Cascades during
the afternoons and evenings. Then, a slow cool down this week, but
still dry. Next chance of showers not until late Thursday.
&&
.SHORT TERM...Tonight through Tuesday...South winds around 6-10k feet
above the surface has been carrying smoke from a large wildfire in
north California northward into NW Oregon this evening resulting in
hazy skies. This smoke was initialized well in the HRRR smoke model
which shows that it will continue to move north and expand into SW
Washington by Sunday morning. Have therefore added haze to the
weather forecast for tonight and Sunday. South wind will develop
closer to the surface late tonight, and some of the smoke may advect
northward from lower in the atmosphere for potentially a thicker haze
layer in parts of the central and south Willamette Valley. This layer
of haze may be thick enough to limit radiation cooling overnight, and
have have raised the minimum temperatures in these areas a few
degrees. ~TJ
The rest of the discussion is from the previous issuance sent at 310
PM Saturday...The heat is on, as strong high pressure over the Great
Basin has pushed a very warm and dry air mass into the Pacific NW. It
will be warm inland this evening, with many areas slow to cool.
Generally, overnight lows in the upper 50s to middle 60s, with some
spots such as the mid-slopes of the Cascades foothills and the inner
urban areas of Portland and Vancouver only cooling to the upper 60s
to around 70 deg tonight.
Tonight, the thermal trough will slowly shift inland. By daybreak
Sunday, it will be located from about Eugene to Forest Grove to near
Hoquiam daybreak Sunday. With this position, will see low level
onshore flow kick up a notch, enough to bring some marine air into
the valleys of the Coast mtns, and possibly to Corvallis and Eugene.
Will not see clouds inland, but this marine air will be enough to
provide some minor relief for areas south of Salem on Sunday. Will
trend temperatures down for those areas, with highs at Salem around
97 and 90 to 95 towards Corvallis and Eugene. Still, it remains hot
on Sunday for much of the interior. So, will maintain the current
heat advisories and excessive heat warnings through Sunday evening.
There is a chance of thunderstorms arrives Sunday afternoon, as the
next disturbance lifts north across region. Will boost PoPs for 20 to
30 pct for the Cascades, but flow such that will be hard to get much
of anything farther west. So for now, will not put any thunderstorm
potential for areas west of the Cascade foothills. Air mass is quite
dry, so will see mix bag of rainfall. Generally less than 0.10 inch
expected, but a few spots that are lucky enough to have a storm core
pass overhead may get 0.10 to 0.25 inch in the afternoon/evening.
That disturbance will lift north across south WA Cascades Sun night.
Upper ridges will shift eastward a bit more on Monday, allowing the
thermal trough to shift east of the Cascades. So, will see a bit more
in way of onshore flow, enough to keep temperatures in the 60s on the
coast under lot more low clouds, and only 80s to lower 90s for
interior under partly to mostly sunny skies. Flow aloft turns a bit
more southwesterly. This will keep thunderstorm potential arcing from
southwest Oregon over east Lane County and then into eastern Oregon.
So, will add a 20 pct PoP for thunderstorms in eastern Lane County to
reflect this trend. /Rockey
.LONG TERM...No Changes. Previous discussion follows...Tuesday night
through Friday...The ridge over the western USA will gradually weaken
its hold over the Pac NW through rest of the week. In its place will
be a slowly approaching low pressure trough. As such, will see slow
cooling, with temperatures returning to more seasonal levels by Thu
and Fri. As the trough draws closer to the region, will see uptick in
a few showers, mainly over Washington and far northwest Oregon for
Thu and Fri. Models providing some potential for lot more in way of
clouds and cooler temperatures for Friday, as they highlight a front
arriving. But for now, will not bite on that idea, and will keep
with generally partly cloudy skies with better chance of showers.
/Rockey
&&
.FIRE WEATHER...The elongated OR/CA thermally induced trough is
shifting inland from the coast tonight for improving fire weather
conditions for the coast and the coast range. South winds are
observed along the central Oregon coast this evening indicating that
the OR/CA trough is beginning to move inland. This has increased
confidence for ending the red flag warning along the coast and coast
range tonight. Mid-level haines 6 conditions will persist for the
Willamette Valley and the Cascades through Sunday evening and warrant
continuing the Red Flag Warning for these areas. The main fire
concern with these conditions is for rapid growth of any existing or
new fires.
A weak upper level disturbance will move near the Cascades Sunday
afternoon and support the chance for isolated to scattered
thunderstorms across the Oregon Cascades Sunday afternoon and evening
and across the south Washington Cascades Sunday night. The air mass
is still quite dry, so will see mix bag of rainfall. Generally less
than 0.10 inch expected, but a few spots that are lucky enough to
have a storm core pass overhead may get 0.10 to 0.25 inch in the
afternoon/evening. No Red Flag anticipated for this lightning.
TJ/Ahue
&&
.AVIATION...VFR with mostly clear skies through Sunday morning
for inland locations. This evening, expect a southerly wind
shift to happen as a low pressure along the California coast
travels northward. Currently, this wind shift can be seen in the
observations at KONP. As the wind shift occurs expect LIFR/IFR
conditions along the coast to develop tonight. These conditions
are expected to dissipate by 19Z Sunday.
Along with this wind shift, a level of smoke/haze from nearby
fires is likely to develop during the overnight hours, with a
thicker layer towards KEUG and becoming less pronounced as it
propagates northward towards KPDX. Currently, not expecting this
layer to impact flight conditions.
Sunday afternoon some mid level moisture will be drawn over the
region ahead of a weak upper level shortwave. This increase in
instability along with the south/southwesterly flow will provide
the opportunity for a slight chance of thunderstorm development
over the central OR Cascades.
METAR note: KTTD ASOS has several missing elements and will
likely not be repaired until Monday.
Refer to http://weather.gov/zse for detailed regional aviation
weather and hazard information.
KPDX and APPROACHES...VFR conditions through Sunday morning.
There is a very slight chance for some smoke/haze to filter in
near the terminal due to nearby fires. However, confidence is
very low and even if it does move into the area, should have
little impact on flight conditions. /42
&&
.MARINE...High pressure remains anchored over the northern Pacific
with a thermally induced low pressure trough along the Oregon
coast stretching from CA to southern WA driving gusty northerly
winds over the waters. Seas during this time are expected to be
northwesterly at 4 to 6 ft with a 7 to 8 second period.
Late Sat into early Sun, weak low pressure will advance
northward causing a southerly wind shift. The southerly winds
with gusts up to 20 kt will peak Sun night and persist through
Mon. As high pressure once again builds across the Pacific NW by
Tue, winds will become mostly northerly with onshore flow likely
prevailing. Northwesterly seas during this time will likely
remain around 3 to 5 ft with a 10 second period. Later in the
week models suggest a stronger low in the Gulf of Alaska may
drive in increasing westerly swell with seas increasing to 10
feet by late Friday. DDH/Muessle
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Excessive Heat Warning until 9 PM PDT Sunday for Cascade
Foothills in Lane County-Central Columbia River Gorge-
Central Willamette Valley-Greater Portland Metro Area-
Northern Oregon Cascade Foothills-South Willamette Valley-
Upper Hood River Valley-Western Columbia River Gorge.
Red Flag Warning until 11 PM PDT Sunday for Central Oregon
Cascade Foothills-Mt. Hood National Forest West of Cascade
Crest-North Oregon Cascade Foothills-Willamette National
Forest-Willamette Valley.
Heat Advisory until 9 PM PDT Sunday for Cascades in Lane County-
Central Coast Range of Western Oregon-Coast Range of
Northwest Oregon-Lower Columbia-Northern Oregon Cascades.
WA...Excessive Heat Warning until 9 PM PDT Sunday for Central
Columbia River Gorge-Greater Vancouver Area-Western
Columbia River Gorge.
Red Flag Warning until 11 PM PDT Sunday for Clark County
Lowlands-Eastern Gifford Pinchot National Forest Mt Adams
Ranger District-Extreme South Washington Cascades and
Foothills.
Heat Advisory until 9 PM PDT Sunday for I-5 Corridor in Cowlitz
County-South Washington Cascade Foothills-South Washington
Cascades.
PZ...None.
&&
$$
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Area Forecast Discussion
National Weather Service Pueblo CO
854 PM MDT Sat Aug 15 2020
.UPDATE...
Issued at 847 PM MDT Sat Aug 15 2020
Updated the precipitation chances for the next couple of hours
across the region. CAM guidance has isolated to scattered showers
and thunderstorms from near Monarch Pass, southeast over the
Eastern Mountains to the Spring Burn Scar. At this time, the
strongest storms are near the Decker Burn Scar, but have been
fizzling out. This trend should continue, with all precipitation
coming to an end by 10 pm. On the Plains, dry conditions are
likely to prevail. A stray shower or thunderstorm may be possible
through midnight, but confidence in this occurring is low at this
time. After midnight, expected dry conditions to prevail into
Sunday morning. Mozley
&&
.SHORT TERM...(This evening through Sunday)
Issued at 249 PM MDT Sat Aug 15 2020
Thunderstorms continue to percolate across the southern Sangre De
Cristo range and Raton Mesa region this afternoon where a couple
of strong to near severe storms have developed. Given light flow
aloft within the ridge, deep layer shears are likely weaker for
southern portions of our area. Still awaiting erosion of the cap
across the plains though HRRR suggests convective development will
occur along the Palmer and Raton Mesa late this afternoon into
the evening. Stout MLCAPE of 1500 J/kg along the I-25 corridor
increases to 2500+ J/kg near the eastern border this afternoon
which would be supportive of a severe thunderstorm or two with
large hail up to the size of golf balls and damaging winds. Deep
layer shears should be a little stronger for northern and eastern
portions of the plains with values around 25-35 kts. This area is
also where thunderstorm develop may be more conditional. So still
lots of uncertainty on how this will play out. Lots of potential
but high res models continue to show storm coverage will be more
isolated with lack of strong forcing. If storms can maintain, they
may form a cluster or two as they move into KS this evening and
encounter a strengthening low level jet. For now have maintained
isolated to scattered pops across the southern mountains and
southeast plains.
For Sunday, another round thunderstorms will develop across the
southeast mountains and plains. Dew points look a little lower,
though cap may be more easily broken given more surface based
heating. One or two strong to severe storms will be possible and
will have to watch the burn scars in the southeast mountains for
another round of potential flash flooding.
As for smokey hazy skies...experimental HRRR keeps the haze and
smoke around for another day and have included this in the grids.
-KT
.LONG TERM...(Sunday night through Saturday)
Issued at 249 PM MDT Sat Aug 15 2020
There are only minor changes from the previous forecasts as the
upper-level ridge of high pressure is expected to stay centered over
the Great Basin region through the upcoming week.
Sunday night...Isolated to scattered showers and thunderstorms are
expected to be ongoing over the region into the overnight hours,
with some guidance indicating that precipitation could linger into
early Monday morning near the Kansas border. A strong to marginally
severe thunderstorm remains possible over the far eastern plains
into the evening hours, but that risk diminishes after sunset.
Monday through Saturday...The ridge of high pressure over the Great
Basin remains relatively in the same location through the period,
keeping us in north to northwest flow aloft. However, the ridge is
expected to edge slightly southward midweek. Guidance then has the
ridge potentially flattening somewhat late week, but there is some
uncertainty in how much the ridge flattens if at all, which is the
main change in the latest guidance for the long-term forecast. This
flattening will depend on whether a trough moving through southern
Canada ends up being far enough south to affect the ridge over the
western U.S. For sensible weather, daily chances for isolated to
scattered PM showers and thunderstorms are anticipated through the
forecast period. The higher terrain has the better chance to see
precipitation each day with mainly isolated storms over the lower
elevations. However, Monday does look to be mainly dry across the
plains. If the Canadian trough does take a little more of a
southerly track, the plains will likely have a better chance of
precipitation Thursday afternoon and evening than the rest of the
forecast period. High temperatures are expected to remain relatively
similar through the week with the plains seeing highs in the upper
80s to mid 90s and mid 80s to around 90 in the high valleys.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 249 PM MDT Sat Aug 15 2020
Isolated thunderstorms will be possible at the TAF sites though very
spotty coverage will keep mention of VCTS out of KPUB and KALS. KCOS
stands the best chance for VCTS. If storms do develop, large hail
and erratic gusty winds will be possible. Thunderstorms will
diminish or move east of the TAF sites by 02z with light winds
and hazy skies overnight. Some patchy MVFR clouds may develop over
KCOS and KPUB but northerly winds off the Palmer Divide may keep
a firm ceiling from developing. Another round of thunderstorms
will develop over the mountains and drift off into the adjacent
plains on Sunday. Winds will generally be diurnally driven with
speeds under 15 kts except near afternoon thunderstorms. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...MOZLEY
SHORT TERM...KT
LONG TERM...CARLBERG
AVIATION...KT