Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/31/21
Area Forecast Discussion
National Weather Service Denver/Boulder CO
822 PM MDT Fri Jul 30 2021
.UPDATE...
Issued at 822 PM MDT Fri Jul 30 2021
...FLASH FLOOD THREAT REMAINS OVERNIGHT AND THROUGH SATURDAY...
Unfortunately, it looks like we`re just getting started with this
heavy rain event. We have to get through the next 24 hours before
things may improve with regard to flash flooding. One large batch
of convection with heavy rainfall already spread across the
Cameron Peak Burn area and then work southward across portions of
the I-25 Corridor. That area has generally weakened over the last
hour or so, but now more strong storms with heavy rain are moving
slowly north from the Palmer Divide area. There are various
solutions to this convective complex, and some are not good. The
atmosphere continues to juice up this evening with likely a
substantial increase in Precipitable Water. 00Z Denver sounding
was up to 1.09", and that was before the surge of deeper low level
moisture. We`re probably closer to 1.25-1.3" now, or near the 99th
percentile from historical perspectives.
Thus, with all the favorable ingredients for heavy rain in place
including a deepening warm cloud depth and more efficient/warm
rain process, we could see flash flooding remain a problem along
the Front Range overnight. That could even be enhanced by a
mesoscale convective vortex which is hinted at by some of the Hi
Res models like HRRR, while NAMNest produces some rather amazing
rainfall totals of several inches along the Front Range. This
gives us strong concerns for additional flooding. The one thing
that`s not as favorable for heavy rain is the current low level
northwest wind off the foothills. We still can`t be sure what
evolves overnight, but certainly there`s potential we`re getting
into a long-lived heavy rain event and dangerous flash flood
threat for the Front Range. Flash Flood Watches will remain in
effect for the Mountains, Foothills, and I-25 Front Range Urban
Corridor through the night, and all the way through Saturday
evening.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 300 PM MDT Fri Jul 30 2021
Main concern through tonight and all of tomorrow will be threat of
flash flooding. We`re seeing storms with heavy rainfall
unfortunately developing in the burn areas this afternoon and that
will continue into this evening. We`re currently loading up the
precipitable water across the mountains and Front Range, and that
will only increase through the evening with a surge of moist
north/northeast flow from a combination of convective outflows and
an embedded front pushing across the plains this evening. There is
still considerable uncertainty as to how this all unfolds and what
this means for heavy precipitation and flash flood threat.
Convective allowing models (CAMs) have been all over the place and
understandably so. There is not much forcing and CAMs really
struggle with these scenarios. Thus, an ingredients based approach
to this forecast is optimal. Regarding those ingredients, we`ll
have everything in place for locally heavy rainfall and a flash
flood threat, including; Precipitable water values reaching close
to the 99th percentile (around 1.30 inches for Denver), very slow
storm motions given lack of steering winds, warm cloud depth
growing to around 6000 feet (but could be more if we fully
saturate), and a push of weak but deepening upslope winds
tonight. Stronger storms are already putting down 1-2 inches of
rain in an hour, and intensities could get even higher with the
environment only becoming more favorable through late tonight and
tomorrow. One of the biggest questions surrounds the exact
evolution and when/if we get stronger convection on the adjacent
plains. Right now, we`re still capped from the upper level ridge
and drying/subsidence noted on water vapor imagery, but this could
very well change by late evening with a north/easterly low level
push. If that`s enough to spark convection, then the threat for
flash flooding would occur overnight in/near the Front Range.
Latest HRRR is trying to come around to this while Canadian has
been very consistent. Even the NAM/NAMNest are showing hints of
this potential.
If we don`t get heavier rainfall tonight, then we may end up more
likely to get heavy rain and local flash flooding Saturday as we
destabilize slightly. If we do get more rain tonight, then we
could very well stay too stable to fire things up again (at least
across the plains) on Saturday. From above, ingredients are even
better tomorrow, depending on tonight`s evolution. As a result,
the long duration Flash Flood Watch for this event from tonight
through Saturday evening seems appropriate.
.LONG TERM...(Saturday night through Friday)
Issued at 159 PM MDT Fri Jul 30 2021
Precipitation should be on the downswing Saturday night, with
just a few lingering showers expected during the overnight hours.
Our moisture does decrease a little bit during the day on Sunday,
with cooler and more stable air also expected. Still, PWATs are
still near or above an inch, and there`s just enough instability
across the high country for another day of slow moving
thunderstorms. Storm coverage should be a little lower than
today/tomorrow, especially across Larimer county.
Monday could see another round of potentially heavy rainfall
across most of our forecast area, with precipitable water amounts
well above normal. There is some question as to how much
instability will be available in the area, but heavy rain will be
a distinct possibility across the Foothills and mountains.
Tuesday appears to be our last chance for heavy rainfall before a
warming and drying trend begin. Mixing ratios are still 7g/kg and
PWATs above an inch, with models also suggesting better
instability in the afternoon. Storm motions may be a touch faster
overall, but there is certainly potential for additional heavy
rains.
Warmer temperatures are expected for Wednesday and beyond. At
least a little moisture is projected to remain trapped under the
upper level ridge. Expect temperatures to slowly make it into the
90s by next weekend, with slight chances or chances of afternoon
storms each afternoon over the higher terrain.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 822 PM MDT Fri Jul 30 2021
Main concern will be showers and thunderstorms with locally heavy
rain, variable gusty winds, and reduced visibility and lower
ceilings. Main threat of that would be from now through 06Z,
although some showers/isolated storms possible after that. If
showers persist, then lower ceilings will develop as well with a
moistening of the boundary layer and possible MVFR conditions.
Northwest winds should mostly prevail overnight before turning
more northeasterly Saturday.
&&
.HYDROLOGY...
Issued at 822 PM MDT Fri Jul 30 2021
The threat of flash flooding will continue overnight and through
much of Saturday. Storm coverage will remain relatively high with
increasing moisture, and intensity of storms will be strong with
increasing rainfall efficiency due to moistening low levels and
warm cloud depths (up to 6000 feet, but possibly up to 8000 feet
depending on low level saturation). Stronger storms are already
producing 1-2 inches of rain in an hour, and thus a considerable
flash flood threat. We may very well see locally heavy rain
continue overnight along the Front Range, focusing in/near the
foothills and I-25 Corridor. A very efficient warm rain process
is expected as showers and storms are persisting. This coincides
with precipitable water values increase to the 99th percentile
and a deep warm cloud depth/efficient rainfall process. We`ll
also develop a weak but deepening upslope overnight into Saturday
morning which would help precipitation production and anchoring to
the Front Range. More widespread flooding potential would develop
if a mesoscale convective vortex develops which is indeed possible
given the existing amount of convection.
That heavy rain and flash flood threat may very well last through
the day Saturday, as ingredients are even better tomorrow,
depending on tonight`s evolution. As a result, the long duration
Flash Flood Watch for this event from tonight through Saturday
evening seems appropriate.
The flash flood threat should remain limited for most of our burn
areas on Sunday, with less moisture and more stable air overhead.
Nonetheless, PWATs will still be above normal and there should be
enough instability around in the high country to see isolated to
scattered thunderstorms. Mean flow is still very weak, and slow
moving thunderstorms still could produce briefly heavy rain across
the burn areas through the afternoon.
Moisture increases again on Monday, with more robust thunderstorm
development possible during the day. Storm chances continue
Tuesday, with moisture decreasing only slightly. We`ll have to
watch both of these days closely as well, with mean winds still
fairly slow. As noted in previous discussions, the repeated heavy
rainfall over several days could lead to much more sensitive soils.
A warmer and drier pattern begins to take over by the
middle of the week, which should decrease the flash flooding
threat substantially.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Saturday evening for COZ030>041-043.
&&
$$
UPDATE...Barjenbruch
SHORT TERM...Barjenbruch
LONG TERM...Hiris
AVIATION...Barjenbruch
HYDROLOGY...Barjenbruch/Hiris
Area Forecast Discussion
National Weather Service Columbia SC
803 PM EDT Fri Jul 30 2021
.SYNOPSIS...
Hot temperatures in the upper 90s to around 100 F expected Friday
with some afternoon thunderstorms. A heat advisory is in effect
through 8pm. The weekend looks slightly cooler, but still above
average before a pattern shift starts Sunday. Heat indexes
above 100 F expected each afternoon for most of the forecast
area over the weekend with afternoon showers becoming more and
more likely. Below average temperatures expected next week with
a good chance of rain each day, Monday through Thursday.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Heat Advisory expired at 8pm. Highest heat indices in our FA
today were 107 at several locations. Limited atmospheric
moisture aloft over our forecast area. Latest soundings indicate
high LFC heights and convect temps, suppressing most convective
activity. Convergence and some additional moisture along a
frontal boundary to our north promoting some convection there.
More coverage noted from N GA westward where better atmospheric
moisture is available. As the boundary slips into our FA this
evening, some convection possible. Will maintain maintain slight
chance POPs in the near term. Otherwise, fair overnight.
Despite light winds, questionable cloud cover, above normal min
temps, latest guidance and climatology all not favoring fog.
Hazy skies due to wildfire smoke, mainly aloft.
Decided not to hoist another Heat Advisory for Saturday at this
time due to limited confidence. Recent guidance has been too
warm on max temps, perhaps due to limited insolation from
wildfire smoke aloft and still fairly moist soil conditions from
recent rains. Next shift can reevaluate with latest guidance.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
By Saturday morning, the surface boundary will have drifted
across southern South Carolina, becoming weaker throughout the
day. Despite the ridge to our west slowly weakening as a deep
trough begins to dig across the eastern US, the pattern aloft
will stay much the same for the area. So we continue with west-
northwest flow at mid- levels and as the boundary sinks south,
much of the area will see north or northwest surface winds. The
boundary passage will help increase our PoPs Saturday afternoon
and will do little to reduce the high temperatures. Highs
Saturday afternoon again expected to reach the upper 90s region-
wide. The subtle northerly flow and some weak downsloping
behind the boundary should help drop dew points enough to keep
the heat indexes below heat advisory criteria. Currently, heat
index values are expected to top out around 108 across our
southern counties, so a few degrees less than Friday. The
primary focus for showers and thunderstorms will be the coastal
plain where convergence will be most sufficient. Hi-res
soundings suggest modest instability but with more dry air
aloft, wind gusts could be a concern in the cells that develop.
Sunday is a transition day aloft as a trough begins to dig into
the Ohio Valley but the sensible weather will be similar to
Saturday. With the trough axis remaining west of the fa and
steady mid- level height falls, PoPs Sunday afternoon quickly
increase. The coverage will be more widespread than Saturday as
the forcing is broader but the weak boundary still present over
the south eastern fa will continue to enhance convergence. High
temperatures are again expected to reach the mid-upper 90s with
heat indexes near 105 F. Low temps will remain high both
Saturday and Sunday mornings, staying in the mid-upper 70s.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
Little change in the forecast for next week with below average
temperatures and likely or categorical PoPs each afternoon thanks to
a digging trough from the Ohio Valley to the Gulf coast. Ensemble
guidance is consistently showing a favorable synoptic scale setup
for widespread rainfall as the trough axis sits just west of the fa.
Combined with persistent south-southwest flow, PWATs are expected to
remain above 2 inches for much of the week and with the synoptic
forcing, widespread showers and thunderstorms are expected. Total
rainfall is expected to be between 1 and 3 inches, generally
increasing from west to east. With a deep moisture supply and
forcing, any instability that develops could lead to locally heavier
rainfall. So flooding is a possible long term concern that we are
monitoring. Temperatures are expected to stay in the 80s thanks
to cloud cover and precipitation each day. The trough setup
will decay slightly as we get later in the week, but no
substantially drier air is expected through Friday.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Surface trough across the area early this evening. There is a
weak cold front east-west across north central North Carolina.
This boundary is expected to move slowly south overnight and
possibly wash out across the area. Convection has developed
across north Ga but not in central SC or east central Ga where
mid level temps quite warm with some capping suggested by model
soundings. Mid level lapse rates weak. ML CAPE is moderate but
trigger lacking. So based on latest radar trends and HRRR
showers and thunderstorms will be quite limited (or non-
existent) in the region this evening. So no impacts to terminals
expected. Scattered cumulus into the evening perhaps strato-cu
overnight as weak boundary approaches. Ceilings likely high
level VFR. Fog not expected overnight with limited cooling.
Scattered showers and thunderstorms Saturday afternoon near the
boundary. Latest high resolution models pointing to the SC
coastal plain and lower CSRA. Still can`t rule out a storm near
the terminals into the evening.
EXTENDED AVIATION OUTLOOK...Scattered showers and thunderstorms
with associated restrictions Sunday mainly in the afternoon and
evening. Showers and thunderstorms may become more numerous
early next week.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Cheyenne WY
828 PM MDT Fri Jul 30 2021
.UPDATE...
Issued at 820 PM MDT Fri Jul 30 2021
An SPS for the entire Nebraska Panhandle is in effect for
degrading air quality due to wildfire smoke until Saturday 8 PM
MDT. Rain showers are moving into the Panhandle currently, but it
is possible for the smoke to continue to impact most TAF sites and
areas throughout the Panhandle.
Additionally, a rainfall report of 3.37 inches fell 3 miles south
of Chugwater which is a significant amount of rainfall through
this ongoing drought.
UPDATE Issued at 241 PM MDT Fri Jul 30 2021
Looking at latest HRRR simulated radar...looking at heavy rain
developing across northern Laramie County that extends to the
Nebraska state line. These storms slowly track across Goshen
County as well. Went ahead and expanded the watch further east to
cover these areas.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 215 PM MDT Fri Jul 30 2021
Forecast challenges deal with heavy rainfall potential over the
next 12 to 24 hours.
Currently...Frontal boundary from a surface low near Ogallala
Nebraska extends west along the Colorado/Wyoming state line to
Laramie to Casper this afternoon. East of the front...surface
based CAPE around 2500 J/KG in the southern Panhandle off SPCs
Mesoanalysis Page. To our north over Converse/Niobrara Counties
near 2000 J/KG and west of the front...near 500 J/KG. Sfc-6km
shear over extreme southeast Wyoming around 35kts. Radar showing
cells developing over northern Colorado already early this
afternoon. Starting to see some development over the northern
Laramie Range as well. Storms are stationary at this point. Mid
level water vapor imagery showing entire CWA covered in
moisture...setting the stage for widespread convection to develop
through the afternoon.
Using the latest HRRR simulated radar...which was great
yesterday...storms develop in the next hour or so and continue
pretty much where radar is showing development currently. Storms
become widespread around the 22-23Z timeframe across Albany County
and the south Laramie Range. Looks like Cheyenne stays under
convection through at least 02-03Z. Think I will add central
Laramie County to the Flash Flood Watch here in another hour or
so. 12Z NAM PWATs up near 1.5 inches over Laramie County with 1.7
inches in the Panhandle. These high PWATs continue through the
evening hours.
Looks like another wet day Saturday before the monsoon moisture
moves back south into Colorado. May need another Flash Flood
Watch for Saturday...maybe not as widespread over today.
.LONG TERM...(Sunday through Thursday)
Issued at 233 AM MDT Fri Jul 30 2021
Passage of cold front through the region early Sunday will usher
closer to near-normal temperatures along with limiting moisture
spread mainly to the southern elevated terrain in southeast Wyoming
in the afternoon. High pressure builds once more across the American
Southwest with continued influence over our region with pockets of
vorticity advection leading once more to afternoon showers on the
Wyoming side. GFS and EURO are bit off by some mileage in location
of showers and thunderstorms as moisture is advected into the
region. Temperatures to remain slightly above normal with highs
reaching into the upper 80s and low 90s east of Laramie Range and
from the middle 70s to middle 80s west of the Laramie Range for
majority of the extended forecast.
Shortwave passes through the region Wednesday with better chances of
precipitation across Nebraska with extended models having solutions
of upper level low near Montana limiting influence of high pressure
and return to zonal flow aloft. Drier conditions to prevail later in
the forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 539 PM MDT Fri Jul 30 2021
Scattered to numerous showers & thunderstorms should spread across
a large portion of southeast WY and the western NE Panhandle until
06z prior to decreasing in coverage & intensity. A few storms will
likely linger into the overnight, mainly along I-80 between KCYS &
KSNY. Brief MVFR ceilings & visibilities may accompany some of the
heavier storms, along with gusty/erratic surface winds. Smoke will
also impact the western Nebraska terminals through at least midday
Saturday, reducing visibilities to as low as 1 mile at KBFF / KCDR
and KAIA.
&&
.FIRE WEATHER...
Issued at 215 PM MDT Fri Jul 30 2021
Monsoon moisture overhead this afternoon will continue into Sunday
before shifting back to the south. This means widespread wetting
rains for most of southeast Wyoming and Nebraska
Panhandle. Look for no critical fire weather conditions through
the weekend into the first half of next week with afternoon
humidities staying well in the 20 percent range for most areas.
Could see drier weather for the end of next week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Flash Flood Watch until midnight MDT tonight for WYZ103-105>108-
110-114>119.
NE...None.
&&
$$
UPDATE...AW
SHORT TERM...GCC
LONG TERM...WM
AVIATION...CLH
FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
634 PM CDT Fri Jul 30 2021
.AVIATION...
Shower and thunderstorm activity has been much more isolated today
and mainly well east of the TAF sites. Will continue to keep the
forecast dry and VFR prevailing through the period as chances for any
restrictions and showers are too low to mention in the forecast at
this time. Otherwise, light south/southeasterly flow will also
prevail through the period.
&&
.PREV DISCUSSION... /ISSUED 223 PM CDT Fri Jul 30 2021/
SHORT TERM (Tonight through Saturday Night)...
A somewhat quieter day is ongoing to end the work week with nothing
on the radar as of 1830Z except along the Gulf Coast. Areas of
cumulus are depicted on visible satellite imagery. Water vapor
imagery and RAP analysis show a 597dm upper ridge centered over
eastern OK/KS, but at the surface the pressure gradient is weak and
winds are generally at or below 5mph out of the E/SE. The 12Z CAM
suite came in a bit drier than previous runs, but we likely will
still see a few very isolated showers and perhaps a thunderstorm
develop this afternoon over the east half of the area as moisture
remains elevated. Any activity will be lesser than the last couple
of days in both coverage and intensity, and again will die out with
the loss of insolation this evening. Temperatures are already in the
80s and lower 90s, and we expect highs to top out in the 91-99
degree range with maximum heat indices of 100-107 for much of the
region.
Saturday, more of the same. A low chance for a few isolated showers
and a thunderstorm or two in the afternoon, with otherwise partly
cloudy skies and warm, muggy conditions. In fact, temperatures may
warm a degree or two tomorrow from today`s values, and with dew
points remaining elevated we`ll see heat index values again rise
into the 100-108 range, potentially locally higher over the Coastal
Plains. At this time, not anticipating a need for a heat advisory
but it will still be worth taking precautions if spending extended
periods of time outdoors. Lows both tonight and tomorrow night will,
as usual, be in the 70s.
LONG TERM (Sunday through Friday)...
The ridge currently centered across Oklahoma and Kansas is forecast
to amplify through the Rockies over the weekend, with a deep long
wave trough carving out downstream into the eastern half of the
CONUS. This will open the door for better rain chances next week
across South Central Texas.
This could come as early as Sunday afternoon and night for northwest
portions of the CWA as models have been consistent with developing
scattered convection across the northern Hill Country, southern
Edwards Plateau, and back into the the Trans Pecos/northern Rio
Grande. Given the forecast inverted-V soundings a DCAPE values
approaching 1200-1500 J/kg in some areas, we will watch for the
potential for some stronger downdrafts in storms producing strong
wind gusts Sunday afternoon and evening.
However, the best coverage and chances of showers and storms Sunday
afternoon and night currently looks to remain north of the CWA,
closer to the frontal boundary. Eventually that boundary, along with
a better pool of moisture, works into portions of the area Monday.
Mesoscale boundary influences, which are difficult to predict this
far out, are likely to play a role in the position of the front and
better rain chances Sunday through Monday. At this time the PoPs for
Monday are favoring the northern half of the CWA, but this will need
to be watched should things overachieve to the north Sunday
afternoon and night.
In general the GFS and ECMWF are in good agreement with the axis of
moisture and low level convergence pushing farther south into the
remainder of the CWA Monday night through Wednesday. The details will
continue to be refined as we get closer, and for now we have
indicated high end scattered PoPs during this time.
High temperatures Sunday look to be near normal, however peak
afternoon heat index values could reach 105-108 degrees in some
areas, mainly along and east of the I-35 and I-37 corridors.
Beyond Sunday forecast high temperatures gradually trend back below
normal as the rain chances and cloud cover increase.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 76 98 77 97 77 / - 20 0 20 20
Austin Bergstrom Intl Airport 75 96 76 96 76 / - 20 0 20 20
New Braunfels Muni Airport 76 96 76 97 76 / - 20 0 20 10
Burnet Muni Airport 75 95 76 94 75 / - 10 0 40 30
Del Rio Intl Airport 78 100 79 101 78 / - - 0 20 30
Georgetown Muni Airport 76 96 76 96 76 / - 10 0 30 30
Hondo Muni Airport 75 95 76 96 76 / - 20 - 20 10
San Marcos Muni Airport 75 96 75 97 75 / - 20 0 20 10
La Grange - Fayette Regional 77 96 78 96 78 / - 20 0 20 10
San Antonio Intl Airport 76 95 77 95 76 / - 20 - 20 10
Stinson Muni Airport 77 96 78 97 78 / - 20 - 20 10
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term/Aviation...Hampshire
Long-Term...04
Area Forecast Discussion
National Weather Service Grand Forks ND
958 PM CDT Fri Jul 30 2021
.UPDATE...
Issued at 954 PM CDT Fri Jul 30 2021
Thick smoke remains well established within the lower levels
tonight across much of the area. A cold front is starting to clear
some of this smoke as it pushes in from the northwest. We are
seeing scattered thunderstorm activity develop along and just
ahead of the front. Temperatures are in the 70s across the area.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 352 PM CDT Fri Jul 30 2021
Main impacts continue to be from wildfire smoke into Saturday.
Thunderstorms will be possible late this afternoon into the evening
hours, and while a strong storm can`t be ruled out severe weather
is not anticipated.
Smoke has continued to linger with higher concentrations in the
south and better improvement along the International border where
stronger southwest flow flow is just ahead of the approaching cold
front, and it is still possible . A second round of smoke should
arrive later tonight behind the front and higher concentrations
should return based on HRRR smoke model. This could then get trapped
over our region once again with lingering impacts through the day
Saturday. Smoke complicates daytime heating/temps and stability/low
level lapse rates during peak heating.
CAMs still show a period of widely scattered showers/isolated
thunderstorms mainly during the evening period along the front as it
moves north to south out of Canada. SPC objective analysis shows MU
CAPE in southern Manitoba near or just over 1000 J/KG close to this
front where better low level lapse rates developed in clearing/less
smoke. In our north CAPE is generally 500 J/KG or less, and
ultimately it will likely fall in this range (500-1000 J/KG) with
inconsistent values. Effective shear may be enhances immediately
along the frontal zone as it passes, so if CAPE were on the higher
end of this range a strong cell with sub-severe hail/wind can`t be
ruled out before sunset. Confidence isn`t particularly high due
unfavorable mid level lapse rates and marginal nature of instability
in general.
.LONG TERM...(Sunday through Friday)
Issued at 352 PM CDT Fri Jul 30 2021
Not much in the way of any impacts outside of the continuing smoke
keeping us cool. Ensemble guidance indicates high agreement between
members of continued enhanced ridging, shifting us to northerly
flow. This will allow temperatures to rise up into the 80s. Main
question will be if we can manage to cross into the 90s. The primary
limiting factor will be the question of smoke. Smoke issues are
expected to persist through the weekend and possibly well into next
week. This will limit temperatures and possibly keep us away from
the 90s. Unfortunately, this also means persistent air quality
issues could continue through the long term.
Outside of that, signals are there for potential shortwave troughs
late next week, although predictability is low.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 627 PM CDT Fri Jul 30 2021
MVFR to IFR conditions prevail across the area this afternoon as
thick smoke continues to impact visibility. This is expected to
continue through the evening hours ahead of a cold front that will
push through the region tonight. Expect some clearing once the
front passes; however, short term models continue to bring
additional smoke into the area over the next several days.
Visibility will range from 1 to 4 miles on average, but could vary
over short distances.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...Lynch
SHORT TERM...DJR
LONG TERM...Perroux
AVIATION...Lynch
Area Forecast Discussion
National Weather Service Glasgow MT
916 PM MDT Fri Jul 30 2021
.DISCUSSION...
AFTERNOON UPDATE:
Changes for this afternoon were first focused on smoke and haze.
HRRRSmoke model appears to be ignoring smoke where it exist on
visibility sensors around Baker, Beach, and Dickinson; and adding
smoke where it doesn`t across Roundup, Lewistown, and Havre.Becuas
of this have switched over to NBM/GLAMP to catch on to surface
observations for the remainder of the afternoon. HRRR does appear
to catch on to the light visibility decreases across southern
Saskatchewan and drag them south behind the cold front this
evening generating haze so switched back to it in the evening
hours.
Monday night to tuesday night, while further out in time there
does appear to be a bit of a pattern change coming up. The ridge
axis out west will reach our area by Monday night. Underneath this
will be a lee side thermal trough and plenty of monsoonal moisture
just above. While the trough will promote lift at the surface
during the afternoon and evening, the ridge will likely suppress
widespread development. Therefore, we are monitoring for evening
to nocturnal thunderstorms that could dump copious amounts of
rain, but still be extremely scattered to isolated.
Thursday onward, After the ridge exits a strong shortwave embeds
into the southwest flow and drags lift across Montana. The pattern
looks severe with a high chance of heavy thunderstorms and
showers in this group of periods, but the placement and timing are
uncertain by about half a state and half a day. These periods
will need to be monitored for future development. GAH
915AM UPDATE:
Change this morning was focused on the smoke plume to the
southeast over Beach, Baker, Dickinson. This plume is moving
northwest and could rise into the Yellowstone Valley before being
stalled out and pushed back by a slow front in the area. Model
winds show the front arriving in the next hour or two and stopping
this airmass around Wibaux, but they also projected the smoke
plume to be well further southeast of its current position, so
confidence is low with the poor initialization start involving
smoke. GAH
MORNING DISCUSSION:
Hot and Dry Continues (through Tuesday)...
The general pattern doesn`t really change much through the weekend
into the first half of next week, and that being the upper level
ridge remaining entrenched across Montana helping to keep the hot
and dry weather in place. A few spotty showers/storms may develop
underneath that ridging, but widespread precipitation still
remains elusive.
For today and tonight`s forecast, did add some low-end POPs using
the HRRR as guidance for their placement. There have been some
showers and thunderstorms in southern Saskatchewan overnight, but
their general trend has been to weaken as they drift southward.
For now, it looks like all we`ll get out of these--if anything--is
a few drops, and that`s it.
Ridge Breaks Down (Wednesday and beyond)...
There`s some hinting in the guidance that the ridge may begin to
actually break down mid to late week next week. Ensemble guidance
at least flattens the ridge out and begins to push some sort of
trough towards the Pacific Northwest late in the week next week;
operational guidance agrees in principle with this thought, but
don`t agree on the details (the trough / upper low would be
anywhere from the Pacific Northwest Coast to overhead here late
week, depending on the model, for example).
97
&&
.AVIATION...
FLIGHT CATEGORY: VFR
WINDS: NE-E 5-15 kts overnight through Saturday afternoon.
DISCUSSION: Upper level ridging will keep the area mainly dry the
next couple days although an isolated afternoon thunderstorm is
possible.
RMB
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
weather.gov/glasgow
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
711 PM CDT Fri Jul 30 2021
.DISCUSSION...(This evening through Friday)
Issued at 319 PM CDT Fri Jul 30 2021
Main focus for the forecast if focused on severe weather potential
tonight and smoke tonight through Saturday night.
Upper level ridge shows signs of retrograding west. Mid-level
short-wave will approach to help spark some thunderstorms north of
a nearly stalled boundary. This boundary has struggled to move as
far north as expected. Am tracking the weak boundary by
streamlines and moisture pooling. As of 3 pm or so, this boundary
stretches from north of Lexington to south of York and continues
to nudge and struggle north. If the boundary does not make it as
far north, storms may sneak in a bit farther south this evening
than earlier thought, and already nudged POPs a bit farther to the
south. There is definitely some deep layer shear on the north side
of the boundary and we do have a good amount of MLCAPE/MUCAPE
this afternoon/evening. 0-3 km SRH indicates possibly a quick
spinup this evening with some storms as well. Severe parameters
indicate that the time frame we are most concerned for severe
would be 6 pm to midnight-ish. Hail to the size of quarters and
wind gusts of 60 mph are possible. This may wind up being a bit
more of a wind threat for us considering the potential later
timing of thunderstorms this evening/night.
As for smoke, the HRRR smoke run indicates that thicker smoke will
mix behind the cold front coming in tonight into Saturday night,
with significant improvement by Sunday morning. An SPS has been
issued to message this. We will dry out by Saturday night through
Tuesday with much cooler and drier air coming in behind the cold
front. Although Saturday will be cooler, it will take a while for
the lower dew points to finally get here. Sunday will feel much
more comfortable, with a few days of cooler and drier air to make
it feel like late summer or early fall typically might.
Return flow brings more chances of thunderstorms by mid-week.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 655 PM CDT Fri Jul 30 2021
There are several aviation concerns. The primary concern will
center around possible thunderstorms moving in from the northwest
late this evening probably after 10 pm or more likely after
midnight. The better chance for thunderstorms will be north of
KEAR and KGRI tonight. We will continue to see a lot of smoke in
the air through tomorrow and it could result in minor visibility
reductions down to 4-5SM at times. We also expect low clouds with
MVFR ceilings around dawn and can not rule out a brief period of
IFR ceilings around that same time.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory until 9 PM CDT this evening for NEZ062>064-075>077-
085>087.
KS...Heat Advisory until 9 PM CDT this evening for KSZ006-007-018-019.
&&
$$
DISCUSSION...Heinlein
AVIATION...Wesely
Area Forecast Discussion
National Weather Service Green Bay WI
1047 PM CDT Fri Jul 30 2021
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Saturday
Issued at 253 PM CDT Fri Jul 30 2021
Main forecast issue will be extent/potential severity of
thunderstorms on Saturday.
The 19Z MSAS surface analysis showed an area of high pressure that
stretched from eastern Lake Superior southwest through eastern WI
into northwest IL. A cold front was located from southern Manitoba
through northwest ND. Visible satellite imagery indicated a large
band of clouds/scattered showers and storms from SD east-
southeast into the western Great Lakes region associated with a
weak system.
The high pressure will slowly shift east this evening, allowing
for the cold front to approach northern sections of the Great
Lakes toward daybreak. Accompanying the cold front will be an
embedded mid-level shortwave trough moving southeast within the
broad northwest flow aloft. Have kept a small chance pop over far
northern WI after midnight, otherwise partly cloudy skies and hazy
conditions to exist with smoke from western wildfires drifting
overhead. Min temperatures to mainly be in the middle 50s to
around 60 degrees.
The cold front and shortwave trough are forecast to push southeast
through the forecast area Saturday afternoon (early to mid-
afternoon north/late afternoon-early evening south). The air mass
over the region will be moderately unstable with SBCAPES of 1000-
1500 J/KG, 0-6km bulk shear of 30-40 knots and mid-level lapse
rates of 5.5 to 6.0 C/KM. Anticipate scattered showers and
thunderstorms to move across northern WI late Saturday morning
into Saturday afternoon, then spread across central and east-
central WI Saturday afternoon. Some of these storms may become
strong to locally severe across central/east-central WI where
stronger instability to be present. Marginally large hail and
gusty winds would be the primary threat. Max temperatures on
Saturday to be in the middle to upper 70s north/near Lake MI,
upper 70s to around 80 degrees south.
.LONG TERM...Saturday Night Through Friday
Issued at 253 PM CDT Fri Jul 30 2021
Northwest upper flow and surface high pressure will make for mainly
cool and dry weather Sunday through Tuesday. Temperatures should
be 5 to 10 degrees below normal with comfortable relative humidity.
A few weak upper troughs will move around the upper ridge over the
Rockies and Plains states during the middle of the week, with a
chance of afternoon showers or thunderstorms. Temperatures will be
close to normal.
Upper heights will rise towards the end of the week, as the upper
ridge slowly edges east. Southerly low level flow will bring
warmer and more humid air into the region, though warming mid
level temperatures may inhibit convection most of the time. Highs
will be 5 to 10 degrees above normal by Saturday.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1044 PM CDT Fri Jul 30 2021
No significant changes in forecast reasoning for the 06Z TAF
issuance. The primary aviation weather concern will be the impact
of a cold front dropping south across the area tomorrow. Opted to
keep the mention of thunder close to the front, and rather limited
in duration. Timing may still need to be adjusted with later
issuances. A secondary issue is the impact of smoke from western
wildfires. Based the forecast for his on HRRR output. Carried a
SCT skycon for the smoke aloft and a 4-6SM vsby restriction late
tonight into early Saturday for smoke/haze at the surface.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....Kallas
LONG TERM......RDM
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Grand Rapids MI
755 PM EDT Fri Jul 30 2021
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 257 PM EDT Fri Jul 30 2021
- Cold front brings scattered thunderstorms Saturday evening
- Upper Troughing and cooler than normal next week
&&
.DISCUSSION...(This evening through next Friday)
Issued at 524 PM EDT Fri Jul 30 2021
The 18z HRRR smoke model is indicating a higher concentration of
smoke aloft moving from Minnesota into Michigan by Saturday
afternoon and lasting into early Sunday. Upstream observations
across the northern Plains and Upper Midwest reveal rather
significant reductions in surface visibility to 2 miles or less in
smoke across the Dakotas and Minnesota. While we are not
expecting those kinds of reductions here, the sky will likely
become muted by smoke aloft and there could be some reductions
in surface visibility mainly across Central Lower Michigan. As
such, we added some areas of haze and smoke to the forecast for
tomorrow into early Sunday. It is also conceivable that any
showers or thunderstorms that develop ahead of the front could
be somewhat impacted by the smoke particles acting as cloud
condensation nuclei, perhaps adding a dirtier element to the water
droplets.
Previous discussion is below...
- Cold front brings scattered thunderstorms Saturday evening
Fair and cool night in store for Lower Michigan then return flow
moisture pooling ahead of a southward advancing cold front should
be sufficient for scattered showers and thunderstorms by late
afternoon into the evening on Saturday.
Shear values are in the 35 to 40 knot range although instability
is somewhat limited and decreases during the evening. Thermal
profiles still show potential for hail and strong downdrafts with
any storms that do form.
- Upper Troughing and cooler than normal next week
Fairly quiet weather with low humidity and cooler than normal
temperatures next week as upper troughing prevails across the
eastern CONUS. There will be a chance of showers on Tuesday as a
shortwave trough drops south and eventually closes off across the
Ohio Valley.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 750 PM EDT Fri Jul 30 2021
There is some indication from forecast guidance that some light
fog may develop from AZO to BTL and JXN for a few hours prior to
1200z. This likely would not reduce the visibility below 3sm, so
no IFR is expected at this time. Some smoke from Canadian
wildfires may slightly obscure visibility north of MKG/GRR
Saturday afternoon and evening. Some obscuration in visibility due
to smoke (likely not much below 5 or 6sm) may occur in MKG and
GRR Saturday evening into Saturday night.
&&
.MARINE...
Issued at 257 PM EDT Fri Jul 30 2021
Observations show that wind gusts have been below 20 knots since
morning and waves also been diminishing so the Small Craft
Advisory and Beach Hazard Statements have been cancelled for the
southern Lake Michigan zones. The next chance for higher winds and
waves will be behind the cold front on Sunday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
SYNOPSIS...Ostuno
DISCUSSION...Hoving
AVIATION...Hoving
MARINE...Ostuno
Area Forecast Discussion
National Weather Service Houston/Galveston TX
652 PM CDT Fri Jul 30 2021
.AVIATION [00Z TAF Issuance]...
The thunderstorm complex that developed over HOU earlier this
afternoon continues to track westward away from area TAF sites.
Winds become light and variable tonight with a few models hinting
at an inversion near the surface leading to brief MVFR cloud
ceilings from 11z-15z. Winds will pick up out of the southwest on
Saturday morning and gradually transition to become more southerly
by the afternoon hours. As far as convection goes for tomorrow,
I`ve leaned towards the HRRR since it handled today`s convection
very well. Showers/storms look to be much more sparse tomorrow,
especially for inland sites, so I do not have any mention of TS in
any of the TAFs. Morning showers along the coast look likely, so
the LBX and GLS have VCSH in their TAFs around 15z. Otherwise, VFR
conditions will prevail throughout the period.
Batiste
&&
.PREV DISCUSSION /Issued 322 PM CDT Fri Jul 30 2021/...
.SHORT TERM [Tonight Through Saturday Night]...
Another day, another flirtation with the heat advisory threshold.
We`ve been lucky again to see dewpoints mix down just enough to
keep the heat index in the 103-106 degree range so far. We`ve got
a couple hours of good sun left to push things to just shy of 108,
but it appears we`ll fall just short of the advisory criteria
again today. In the end, it`s mostly a function of paperwork. Like
a tropical storm making landfall at 70 mph, whether it becomes a
hurricane or not is kind of meaningless as the impacts aren`t
really going to be any different. Thus, we`ve been hitting the
heat safety message hard lately and will continue to do so this
weekend.
Beyond the heat, we do have some isolated showers kicking up, both
along the seabreeze and also further inland. There may be some sort
of subtle boundary in place, as today`s inland showers again seem to
be oriented on the same line between Caldwell and Lufkin that we saw
yesterday. These will likely be the preferred zones into the mid-
afternoon, but we may also see some isolated stuff thanks to outflow
interactions, localized heating differentials, and some such
elsewhere.
Speaking of the weekend, what does Saturday look like? Well...it`ll
be a lot more of the same summertime daily pattern. Overnight lows
will quite warm thanks to the humid conditions, and we`ll likely see
nocturnal Gulf convection crop up in the pre-dawn hours. As the
seabreeze forms up, it will become a new convergence zone and the
primary focus for isolated to scattered afternoon showers and
storms.
Oh, right, the heat. I`d like to be able to forget about the heat,
but the atmosphere will not play along. Saturday again becomes a
race between temperatures rising through the day, and dewpoints
mixing out as the boundary layer deepens. Who wins? Well, that
depends...I`m personally rooting for the NAM as it leans hard into
the mixing, with IAH even seeing the dewpoint briefly get to a
pretty nice 69 (?!?!) - I suspect this is probably overly
optimistic, and other guidance supports that theory. In all honesty,
my first guess model blend kept the humidity up just enough that a
heat advisory could be justified. Though winds at the upper end of
what will be the daytime boundary layer shifting may make some
marginal difference, I`m inclined to keep a forecast pretty close to
persistence, and undercut that consensus just a bit. This is
ultimately not too dissimilar from the NBM, though I cut things a
little closer to that 108 threshold.
Again...the differences here are essentially splitting hairs. We are
near the climatological peak of apparent temperature here in
Southeast Texas, and even climatologically typical levels of heat at
our peak can be dangerous to those unacclimated and/or unprepared.
The fact that the forecast heat is not necessarily anomalously high
does not imply that it`s safe to ignore things like proper breaks in
cool air and plenty of available water. It`s hot, y`all. Don`t push
it too hard and have a drink in the shade. Safe is smooth, and
smooth is fast.
Luchs
.LONG TERM [Sunday Through Friday]...
On Sunday rain chances will be enhanced by short wave...currently
shown on satellite as a cluster of showers and thunderstorms over
the NE Gulf...moving into coastal TX from the east on southern
flank of retreating upper ridge.
Meanwhile large scale flow pattern undergoes a change with broad
upper trough amplifying eastern half of U.S....and narrower upper
ridge amplifying over the interior West....especially along and in
the lee of the Rocky Mountains. At surface this corresponds to a
back door cold front dropping down from the north...stalling out
over the area by Tuesday and Wednesday. This front will act as a
focus for more showers and thunderstorms for at least the Monday
through Wednesday time frame. Potential for heavy downpours with
these rains. Model PWATs are up in the 2.25 to 2.5 inch range
during this period around that boundary. Some potential of a
little drier air sneaking in behind this front from the NE in the
Wednesday...Thursday time frame with best chances as usual in
northern and northeastern portions of the forecast area...lowest
chances SW zones. Still plenty of uncertainty in timing and
ultimate SW extent of this boundary as fighting climatology with
these fronts certainly rare this time of year.
Reilly
.MARINE...
Fairly modest winds and seas are expected through period with
mainly light south winds this weekend...becoming SW to W on
Tuesday...then variable Tuesday night and Wednesday as a weak
backdoor cold front becomes drops down from the N then becomes
nearly stationary. Exact timing and location of this front still
uncertain. With this front expect an increase in shower and
thunderstorm activity. Locally higher winds and seas are expected
in and near thunderstorms. Will likely see more typical onshore
flow set up late in the week as front washes out.
Reilly
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 76 96 77 96 77 / 10 10 10 20 20
Houston (IAH) 78 96 77 96 79 / 20 30 10 40 20
Galveston (GLS) 83 91 83 91 82 / 20 20 20 30 20
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
SHORT TERM...Luchs
LONG TERM...Reilly
AVIATION...Batiste
MARINE...Reilly
FIRE WEATHER...Luchs
Area Forecast Discussion
National Weather Service Lincoln IL
902 PM CDT Fri Jul 30 2021
.SYNOPSIS...
Issued at 304 PM CDT Fri Jul 30 2021
Cooler and less humid conditions will continue this evening.
However, showers and storms are expected to develop and move into
west central Illinois after midnight, and then spread across the
rest of central and southeast Illinois tomorrow. Overnight lows
should drop into the lower 60s with Saturday afternoon highs
reaching only into the lower to middle 70s.
&&
.UPDATE...
Issued at 902 PM CDT Fri Jul 30 2021
MCS has begun developing across eastern Nebraska and western
Iowa, with current placement a couple hours ahead of what was
depicted on the 00Z HRRR model. Projected track remains aimed for
west central Illinois late in the night, pushing southeast across
a large portion of the forecast area Saturday morning. Forecast
was updated go adjust some of the timing of the PoP`s, including
higher values into the afternoon over the southeast CWA.
&&
.SHORT TERM...(This evening through Saturday night)
ISSUED AT 304 PM CDT Fri Jul 30 2021
Cooler and less humid weather will continue this evening across
the area, but another weather system developing in the central
plains with become active with showers and thunderstorms later
this evening across the NE/IA/MO states. These showers and storms
will move east and then southeast, possibly reaching west central
Illinois after midnight and then progressing into central Illinois
by Saturday morning. The remnants of this complex of storms will
move further into the state during the day and should begin to
dissipate some as it does. The strongest area of the storms should
move southeast, more along the Mississippi river, keeping the
lower chances of precip to the north and northeast...mainly south
of I-74. Additional storms will be possible in the afternoon but
still more in the southwest third of the CWA, still south of I-74.
As any outflow boundary from these storms moves south, the threat
of storms will also move south. The chance of storms will linger
around southeast Illinois Sat night, but the remainder of the area
will be dry as high pressure begins to build into the CWA.
Temps will be cooler tonight through tomorrow night with
overnight lows in the lower 60s and Sat afternoon highs only
reaching the low to mid 70s due to rain and cloud cover.
&&
.LONG TERM...(Sunday through Friday)
ISSUED AT 304 PM CDT Fri Jul 30 2021
The extended forecast will be dominated by high pressure,
resulting in cooler, drier, and less humid conditions. Highs in
the lower 80s will be the rule with a couple of days of mid to
upper 70s possible. Lower to middle 80s will be possible toward
the end of the week when another system moves toward the area for
Friday. Models show differences that far out and allowing a
blended forecast is best.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 625 PM CDT Fri Jul 30 2021
Thick smoke layer around 8,000 feet per model cross-sections will
remain in place for an extended time, but cloud-related ceilings
will gradually lower overnight ahead of a thunderstorm complex
moving in from Nebraska. Greatest impacts expected to be around
KSPI where steady rain develops by sunrise and ceilings quickly
drop below 3,000 feet, and may be near IFR at times. Storms
expected to fade out as they get further east, so waning coverage
of thunder makes it difficult to go more than VCTS with just
prevailing showers. MVFR ceilings expected to spread east during
the morning, though areas near KPIA-KBMI may be just on the
periphery.
&&
.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
642 PM CDT Fri Jul 30 2021
.SHORT TERM...(This evening through Saturday night)
Issued at 324 PM CDT Fri Jul 30 2021
The 12z HRRR model near-surface smoke forecast suggests the thick
plume of trapped smoke across nrn Nebraska this afternoon will
drop south through swrn Nebraska tonight and continue moving south
into KS Saturday. This smoke will remain trapped in an inversion
below 700mb. Areas of smoke are in the forecast tonight and
Saturday for this event.
The severe weather forecast late this afternoon and tonight is
somewhat uncertain in regard to upper level forcing. Satellite
suggests the upper level disturbance which moved through SD last
night may have produced an area of high pressure in it`s wake. The
next obvious upper level disturbance appears to be moving across
the Black Hills. The models are taking this disturbance into ncntl
Nebraska this evening.
Another area of interest is the wrn Sandhills. Visible satellite
shows a circulation across the wrn Sandhills and this is probably
the best force for storm development. Yet another disturbance is
near SLC but this is probably to far away to affect Nebraska this
evening.
Since all of these disturbances are subtle, the models have trouble
depicting heights falls. The disturbance across the Sandhills would
appear to be the best support for storm development.
A cold front has dropped into the Sandhills and ncntl Nebraska for
focus, moisture is plentiful and winds aloft are fairly strong, 30-
35kt at h500-h300mb. The lapse rates are not particularly steep and
this is a result of warm air aloft. The warm sector is quite robust
and deep layer shear is about 40kts along the focus- a sfc front
which is expected to be located across the cntl Sandhills east along
highway 2 and highway 91 across ncntl Nebraska.
The thunderstorm forecast leans on the short term model blend which
is fairly quiet until 7 pm CDT. Isolated storm development is
expected across the wrn Sandhills which becomes scattered to
numerous eastward into ncntl Nebraska this evening.
The primary severe weather hazards are wind damage across the
Sandhills and ncntl Nebraska with the potential for isolated tornado
development across ncntl Nebraska where moisture will be robust and
mixing heights will be lower. All of this storm activity should be
south of the region by Saturday morning. No other thunderstorm
development is expected through Saturday night.
.LONG TERM...(Sunday through Friday)
Issued at 324 PM CDT Fri Jul 30 2021
There is little change in the extended forecast philosophy. The
subtropical high pressure ridge centered over Oklahoma will
retreat west through the Rockies and amplify. At the same time, an
upper level low will form across eastern Canada. This pattern
will set up a northwest flow across Nebraska. A fairly expansive
area of sfc high pressure will build down through Canada and into
the Midwest. The latest model blend suggested highs in the 80s to
near 90 with dew points in the 50s to lower 60s. This comfortable
weather will last Sunday through Wednesday. A modest warm up to
the upper 80s and lower 90s is predicted Thursday and Friday. This
is the result of an approaching long wave trof off the West Coast
sending a surge of hot desert air into the Rockies.
Rain chances are generally isolated; the result of weak disturbances
moving south-southeast off the Black Hills, the Big Horns and
Laramie ranges. WPC suggested total rainfall of less than 1/4 inch
Monday night through Friday. A dry forecast is in place Sunday and
Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 641 PM CDT Fri Jul 30 2021
MVFR ceilings and visibility are possible for both the KLBF and
KVTN terminals, however at KLBF, visibility should be noticeably
higher. Smoke from wildfires across Canada and the western US are
the reason for the reductions. Otherwise, guidance is mixed on the
lower ceiling and thunderstorm potential, but generally point to
isolated thunderstorms this evening that may impact KLBF. Will go
with a VCTS, but update if needed. Ceiling are forecast to lower
overnight for both terminals with periods of MVFR through early
morning. Overall confidence is low on location of storms, but
better than average for impacts due to smoke and lower ceilings.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Jacobs
Area Forecast Discussion
National Weather Service Louisville KY
1011 PM EDT Fri Jul 30 2021
.Forecast Update...
Issued at 1010 PM EDT Fri Jul 30 2021
Quiet but hazy evening across the region as 00z sfc analysis reveals
the sfc cold front draped across TN and extending up into central
MO. Temperatures at 02z are in the low-mid 70s in rural areas and
mid-upper 70s in urban settings. Expect morning minimum temps to be
split by the I-64 corridor, with the counties to the north expected
to reach the low 60s, and the counties to the south staying in the
mid 60s.
Winds generally from the north will go calm tonight as a sfc high
over northern IL builds across the Great Lakes. Combined with mostly
clear skies, could have some patchy fog develop across our southern
CWA, especially for the Lake Cumberland region and in river valleys.
Some guidance is trending towards more widespread or dense fog
tomorrow morning, but with relatively drier air in place, not
entirely confident at this time that areas of dense fog will happen.
Will stay with patchy fog wording in forecast and highlight our
counties along the Cumberland Pkwy with this update.
Webcams across the CWA also confirm that smoke/hazy conditions have
returned, which the HRRR appears to have a good handle on. HRRR
suggests near-sfc smoke will shift southward into tonight, which
will likely lead to improved conditions at Louisville and Lexington
by 07-09z tomorrow morning. Bowling Green will likely have increased
near-sfc smoke through the overnight and into tomorrow.
Otherwise, forecast is in good shape. Tuned up near term grids with
latest hi-res blend and will send updated products.
&&
.Short Term...(This evening through Saturday)
Issued at 316 PM EDT Fri Jul 30 2021
Earlier cloudiness has scoured out across the region with partly to
mostly sunny skies being reported. Temperatures varied across the
region as a frontal boundary bisected the region. The front was
located from near Owensboro southeastward to near Somerset and was
sinking southward slowly. North of the front, temperatures were in
the upper 70s to around 80. On the south side of the front,
temperatures were in the upper 80s to near 90 along the KY/TN border
area. In the short term, no significant weather is expected and
temperatures will fall back into the 70s across the north and back
into the lower 80s across the south this evening. Some drier air
will work into the region from the north and northeast. However
dewpoints across the region will remain in the upper 60s to around
70 north of the front, and in the low-mid 70s south of it. In
reality, not much relief will be seen this evening as the drier air
still remains well to the north of the area along the I-70 corridor.
Moving into tonight, some of the drier air across Indiana and Ohio
will push into southern Indiana and portions of northern KY as the
aforementioned front works southward and stalls out across southern
KY. Upstream, MCS development is expected later this evening and
overnight across the Mid-Missouri Valley. This activity will drop
southeastward with time and probably will stay west of our area
overnight. So for now, plan on going with a dry forecast. Lows
tonight will drop into the lower-mid 60s across southern Indiana and
over portions of northern Kentucky. South of the Parkways, lows
will probably drop into the mid-upper 60s.
For Saturday, surface frontal boundary is forecast to remain stalled
out to our south and southwest. Overnight MCS activity is expected
to diminish while moving into our region. Model soundings continue
to show a bit of dry air which may result in this system swinging
through without much rainfall in the morning. However, I would
expect plenty of convective cloud debris to spread across the
region. With some heating in the afternoon, some scattered showers
and storms will be possible, mainly southwest of a line from
Owensboro to Somerset.
Highs on the day will be cooler than what we`ve seen of late.
Current thinking is for highs to top out in the upper 70s across
southern Indiana and in northern Kentucky. A few spots near the I-
64 corridor could top 80. South of the WK/BG Parkways, highs of 83-
88 are likely with the warmest readings down along the KY/TN border
region.
.Long Term...(Saturday night through Friday)
Issued at 2:50 PM EDT Fri Jul 30 2021
Weather pattern for the bulk of the long term continues to feature
strong upper level ridging over the western US with a deepening
trough over the Great Lakes and eastern US.
The forecast period starts off with a mid-level disturbance swinging
through the trough across the Great Lakes Saturday night into Sunday
morning. Bulk of the rain looks to fall across western and southern
KY as a complex of showers/storms pushes through overnight into
Sunday morning. Showers will diminish during the day Sunday as drier
air filters in from the northwest as a weak, moisture starved cold
front drops in from the north. Sunday will be a touch warmer than
Saturday as highs warm into the low/mid 80s.
At the surface, high pressure builds in over the region and keeps
the bulk of the forecast mainly dry through the period. By the
middle of the week, a cut-off upper level low develops over the Ohio
Valley. This will keep us unseasonably cool for most of the week.
Highs Monday through Wednesday will be nearly 10 degrees below
normal in the low 80s with some locations seeing highs in the upper
70s. Mornings will feel down right chilly for early August, ranging
from the mid 50s to near 60.
While mostly dry, a stormy weather pattern sets up over the
southeastern US and up into the Mid-Atlantic for the second half of
the week. This could bring a slight chances of showers and storms
across the eastern part of our CWA Wednesday into Friday.
Temperatures will also slowly begin to moderate upwards with highs
getting back into the mid/upper 80s for the end of the week.
&&
.Aviation...(00Z TAF Issuance)
Issued at 745 PM EDT Fri Jul 30 2021
Sfc frontal boundary is now located south of our region, which has
allowed drier air and smoke from wildfires to filter into the
region. Satellite imagery reveals smoke across the region, and with
sfc obs at BWG reporting HZ, will keep HZ in TAFs for a few hours
this evening as it continues to mix down to the sfc.
Guidance was also hinting as some patchy fog development tomorrow
morning, especially for BWG and HNB, so did include a few hours of BR
and low end VFR flight cats due to limited confidence. Winds remain
primarily from the north through tomorrow morning, but could see VRB
as winds calm overnight.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...CJP
Short Term...MJ
Long Term....BTN
Aviation...CJP
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
855 PM CDT Fri Jul 30 2021
.UPDATE...
855 PM CDT
Had updated late this afternoon to include mention of light
rain/sprinkles across much of the forecast area. This is the only
significant update to the forecast for this evening, other than some
minor tweaks for temp/dew point trends through midnight.
Evening surface analysis depicts a stationary front stretching from
western NE, southeast across southwest MO and northeast AR. North of
this boundary, a fairly strong (by late July standards) 925-850 mb
baroclinic zone extended as far north as central IA into southern
IL. A mid-level short wave trough was noted tracking southeast along
the northern periphery of this baroclinic zone across southern MN/WI
and northern IL, with an area of associated light rain into the WFO
LOT cwa. 00Z RAOB from DVN depicts saturation generally above 700
mb, with relatively dry air below. Dry low levels become more
substantial in soundings to the north and east, with light
rain/sprinkles occurring across our forecast area generally falling
from cloud bases in the 10-12 thousand foot range. Forcing (notably
frontogenesis in the 700-600 mb layer and upper level divergence
beneath the right entrance region to a 95 kt upper level jet streak
across the Lakes) is expected to weaken with time through midnight,
as the mid-level short wave tracks east-southeast and shears and
weakens. Thus, light rain/sprinkles should gradually diminish in
coverage (already evident upstream in regional radar imagery) and
end as the mid-level wave passes very late this evening.
Later tonight, another area of rain (and thunderstorms farther west
across IA/MO) may clip the far southwestern parts of the cwa toward
morning. Going forecast has this depicted nicely, and no changes
were made beyond evening light rain and temp/dew point trends based
on surface obs.
Ratzer
&&
.SHORT TERM...
246 PM CDT
Through Saturday night...
A mid-level WNW-ESE mid-level fgen band extending from a wave
over southern Minnesota is generating plenty of mid-level cloud
cover over northern Illinois this afternoon. Precip from this
cloud deck is, for the most part, evaporating before reaching the
ground. However, some pockets of isolated sprinkles are possible
through mid- evening. Meanwhile, winds continue to diminish this
afternoon. Waves are correspondingly subsiding, with the current
00Z/7pm ending time of the Beach Hazard Statement looking on
track.
The high pressure ridge to the north will drift over the CWA
tonight, allowing light/calm winds late this evening into the
overnight. The upstream mid-level wave will somewhat phase with a
stronger wave farther west tonight. Associated low-level moisture
transport along the strengthening baroclinic zone from eastern
Nebraska into southern Illinois will support a fairly pronounced
shield of rain with embedded thunder to the SW of the CWA
overnight through Saturday morning. This shield may brush areas of
the CWA southwest of a line from La Salle to Watseka to Fowler,
but an expected sharp precip gradient should remain just southwest
of the area.
Dry conditions will prevail across much of the area on Saturday.
A return to low-level westerly winds will advect a layer of
western wildfire smoke back over the area through the day.
Afternoon mixing heights will likely become high enough to mix
into the lowest layers of the smoke around 5kft and produce some
haze. Additional mixing behind a cold front late Saturday evening
will maintain the potential for haze through Saturday night.
A narrow axis of low-level moisture ahead of the approaching cold
front Saturday evening should be sufficient for isolated to
scattered showers and possibly a thunderstorm or two along the
immediate front mid-evening Saturday into the early morning hours
Sunday. An associated broad mid-level trough and potentially minor
influence from the upper jet entrance support slightly coverage
in what would be considered a generally poor thermodynamic
environment this far southwest.
Kluber
&&
.LONG TERM...
246 PM CDT
Sunday through Friday...
The main concerns are the potential for haze from low level
wildfire smoke to linger into or through Sunday morning and the
likelihood of dangerous swimming conditions at Lake Michigan
beaches Sunday through Sunday night. Otherwise, an extended period
of quiet weather is in the offing.
Surface cold front driven southward by shortwave rounding western
portion of longwave troughing over northeast North America will be
passing through the southern CWA early Sunday morning. A few light
showers or sprinkles are possible, mainly into parts of northwest
Indiana, with an otherwise dry and partly cloudy to mostly sunny
day (though still a milkier sky due to wildfire smoke) in the mid
to upper 70s. Brisk northerly winds behind the cold front gusting
up to 25 mph near and over the lake will continue into Sunday
before slowly easing. Confidence is high that another Beach
Hazards Statement will be needed for all beaches due to high wave
action and strong currents. The HRRR surface smoke forecast does
show relatively high concentrations at 12z Sunday, with the
thinking that the north-northeasterly flow from the lake behind
the front will scour out the lower-level smoke/haze by mid day.
Looking ahead to the workweek, can`t rule out some spotty
sprinkles at times Monday and Tuesday as weak short-waves traverse
the region, though blocked off moisture trajectories will keep
things mostly dry and have no mentionable PoPs. Below normal but
comfortable temperatures on Monday will moderate back to normal
(low-mid 80s) for early August by the mid to late week. Continued
blocked moisture trajectories will keep dew points and humidity
levels in check each day, especially considering what can occur
this time of year when crops are maturing. Most indicators point
toward primarily dry conditions prevailing through Friday, though
some GFS suite members resulted in slight chance PoPs.
Castro
&&
.AVIATION...
For the 00Z TAFs...
Concerns:
- VFR sprinkles through mid evening
- Visibility reduction in haze from wildfire smoke Saturday later
afternoon and evening
- Potential for showers or storms toward the tail end (or just
past) the 30 hr ORD/MDW TAFs
A band of very light rain, more so sprinkles, is falling out of a
9-12kft cloud deck. These will likely impact a line from RFD to
GYY, which will include MDW and close to ORD. No visibility
reduction will occur. These will end later this evening. Winds
will shift to light northwest or west overnight (more likely
variable) and then remain with a westerly component on Saturday.
The lake breeze appears this point to remain east of ORD/MDW, and
may not even push into GYY, but it will be closer there.
Haze from the wildfires upstream has had IFR/MVFR vis reductions
in MN and portions of IA for the last few days. The wind direction
aloft tomorrow is favorable for some of this to spread back across
the terminals in the afternoon and evening. We will let the next
shift assess how far east the vis reductions get before deciding
if we need anything in the TAF.
There could be some decaying showers Saturday night, maybe later
evening or a slightly better chance for a shower or storm
overnight, but confidence is too low for any formal inclusion in
the TAF.
KMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1003 PM EDT Fri Jul 30 2021
.SYNOPSIS...
A cold front will cross part of the area tonight before
stalling. A weak area of low pressure will then develop along
the coast tomorrow. The boundary will then more or less remained
stalled over the area early to mid next week as several waves
of low pressure develop along it.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As of 10 PM Friday...Last of convection impacting the northern
Outer Banks at late evening, otherwise dry at late evening
across eastern NC. Latest runs of the HRRR and 3km NAM show
limited precipitation chances overnight, but kept isolated
showers/storms near the coast where some good instability
lingers. A very muggy night upcoming after a hot day as
dewpoints are in the mid to upper 70s area-wide. This will lead
to overnight lows in the mid 70s inland and around 80 beaches.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
As of 215 PM Fri...The latest trends for tomorrow show a more
active day as the cold front is not expected push south of the
region, but will instead stall across the southern coast and a
weak wave of low pressure will develop along it across the
Pamlico Sound or just offshore of Hatteras Island. This will
lead to an increased chance of convection across the eastern
half of the area, while locations farther west will see more
widely scattered storms. Better dynamics co-locate with the
convection tomorrow near the NC coast, however cooler surface
temps will limit instability to less than 1000 J/kg.
As mentioned above highs are expected to remain in the low to
mid 80s across the Outer and Inner Banks, but farther to the
west, where more sun will be seen, and where low level heights
remain very high, temps will reach the upper 80s to low 90s.
With dewpoints expected in the mid to upper 70s, heat indices
across the southwestern portion of the CWA will likely reach
100 to 105 tomorrow afternoon and evening.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
As of 235 PM Fri...A persistent upper level trough will linger
across the Eastern US, resulting in a very active pattern
emerging over the weekend and continuing at least into next
week.
Saturday Night and Sunday...Heights aloft will begin to fall as
troughing digs across the Ohio Valley toward the southern
Appalachians, and the first in what will be several waves of low
pressure will develop over the Southeast along the stalled
boundary. This wave will bring the next round of storms Sunday
as the boundary slides back over the area, where it will remain
for the better part of next week. Developing deep layer moisture
transport on the east side of the unseasonably high- amplitude
trough will bring the potential for heavy rainfall, with the
severe threat dependent on the timing and strength of the wave
as it crosses the area Sunday.
Monday through Thursday...Unsettled weather continues early to
middle of next week as the surface boundary remains stalled
over/near the area with a relatively high amplitude upper trough
over the southern Appalachians. The second significant wave
traversing the boundary looks to impact the area late Monday
into Tuesday, but timing is uncertain at this point. Numerous
lows are then expected to form in succession along this stalled
boundary during the week, prolonging our very active pattern.
Overall, expect a wet period with persistent deep moisture
advection brining flooding rainfall concerns, and periods of
severe weather concerns possible as well. Temps will be near to
below normal owing to cloud cover and periods of rainfall.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
SHORT TERM /Through 00Z Sunday/...
As of 730 PM Friday...With a relative lack of convection this
afternoon and early evening, TAFs are all VFR and should
continue that way into the early morning hours. Numerical
guidance indicates some threat of MVFR ceilings at KPGV and
KISO, which both had rain in the area today, and will trend the
forecast that way, with VFR continuing overnight at KEWN and
KOAJ. Any lower ceilings should improve by mid-morning Saturday
with VFR conditions. There could some widely scattered afternoon
and early evening showers and thunderstorms again on Saturday
producing brief reductions in ceilings and vsby.
LONG TERM /Saturday Night through Wednesday/...
As of 250 PM Fri...Very active weather pattern expected this
weekend and into next week. Heavy rainfall and variable wind
gusts will be possible in and around thunderstorms. Periods of
sub-VFR conditions can be expected.
&&
.MARINE...
SHORT TERM /Tonight and Tomorrow/...
As of 1000 PM Friday...With approach a front from the north,
gradient has weakened a bit over the past few hours and earlier
dropped all SCA`s for area waters. Winds continue SE/E over the
far northern tier and SW elsewhere at 5-15 knots with a few
gusts near 20 knots over the central outer waters. Expect a
continued decrease in winds through the night as the cold front
moves slowly toward the South Coast. Tomorrow the front will
stall along the southern NC coast, with winds to the south SW
around 10 kts, and NE 10-15 kts to the north. Through the day a
weak area of low pressure will form near Cape Hatteras, and
winds are expected to become NE for most of the area at 10-15
kts, with southerly flow remaining west of Cape Lookout at 10-15
kts. Seas will be 3-4 ft.
LONG TERM /Saturday Night through Wednesday/...
As of 315 PM Fri...Stronger low develops further west Sun,
turning winds Srly early morning and ramping them up through the
day. Expecting SWrly winds around 15-20 kts with gusts up to 25
kts by late aftn/early evening. Seas inc to 4-6 ft during this
timeframe, likely bringing conditions to SCA criteria. Strong
storms may bring erratic, gusty winds.
Marine conditions will briefly subside Sun night and into Mon
with Wrly winds around 10-15 kts and seas returning to 3-4 ft
before deteriorating again Mon night into Tue. Yet another
stronger low forms along the stalled boundary, ramping SWrly
winds up again 15-20 kts and seas 4-6 ft by Tue aftn. Strong
storms may bring erratic, gusty winds.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...MHX
NEAR TERM...CTC
SHORT TERM...SGK/ML
LONG TERM...ML
AVIATION...CTC/SGK/ML
MARINE...CTC/SGK/ML
Area Forecast Discussion
National Weather Service Nashville TN
635 PM CDT Fri Jul 30 2021
.UPDATE...
FOR 00Z AVIATION DISCUSSION.
&&
.DISCUSSION...
This afternoon isn`t quite as bad as the last couple, but it is
almost unbearable out there. Other than the Plateau (where I wish I
was right now), most everybody has been in the 90-94 degree range
with dew points in the 70s. Pulaski came in with the most
ridiculous 91/79 at noon CDT. `Sauna` doesn`t begin to describe
that. So, the Heat Advisory goes on until 6 pm for our southwest
counties. As far as storm chances, I still think there`s an
outside chance we start to see some convection, but it should
remain pretty isolated. Latest HRRR continues to show almost no
development. A healthy 5000+ J/Kg of CAPE does reside across the
south, so any convection that can fire up will have a good amount
of energy to feed off of, but without any shear, a gust to 40 mph
will likely be the best we can muster.
Saturday afternoon is kind of a question mark regarding rain
chances, but because I`m leaning towards our weekend rains holding
off until Saturday evening/night, temperatures tomorrow will be
quite similar to today. I wasn`t going to, but it does look like
we`re going to meet Heat Advisory criteria again tomorrow in a few
counties in the far southwest. Will prep this to match up with
the neighbors and issue with this package.
Our best chance for rain in the next 7 days looks to move into
Middle TN Saturday night. Models have been fairly consistent in
dropping a boundary through the state and hopefully giving
everyone`s yard a break from the dry conditions. I think we can
expect at least scattered showers and thunderstorms before daybreak
Sunday, then a continuation into the day Sunday. Looking over
forecast soundings, I do see some evidence of deep layer shear
(albeit only 25 kts), so a few strong storms will be possible by
the early afternoon, but I think we`ll be in good shape regarding
any severity this weekend.
On the plus side, this boundary coming in here for the last half of
the weekend will push the heat out of TN. Temperatures should fall
into the 80s for several days and there should only be small rain
chances each day next week as an upper level low lingers off to
our northeast.
&&
.AVIATION...
00Z TAF DISCUSSION.
VFR conditions currently with some brief MVFR HZ at MQY. Expect
MVFR to IFR conditions to develop overnight at all terminals as
vis will drop mainly after 08Z at CSV and 11Z at BNA/MQY/CKV.
Should begin to see conditions improving between 12Z and 13Z.
Winds will remain from the north/northwest throughout the TAF
period.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon to 6 PM CDT Saturday for Giles-Hickman-
Lawrence-Lewis-Maury-Perry-Wayne.
&&
$$
DISCUSSION......Unger
AVIATION........Adcock
Area Forecast Discussion
National Weather Service Spokane WA
754 PM PDT Fri Jul 30 2021
.SYNOPSIS...
Saturday will be hot and locally smoky with most communities
across the Inland Northwest in the triple digits. Chances for
showers and thunderstorms will increase Saturday evening. Sunday
and Monday are expected to be mostly cloudy with scattered
showers and thunderstorms and near average temperatures.
&&
.DISCUSSION...
A large upper level ridge centered over the Great Basin is
starting to pump monsoon moisture into the Pacific Northwest. This
is evident by the high and mid-level clouds moving into WA and ID
and increased precipitable water over the Northwest. The increase
in moisture has also helped to develop a pyrocumulus over the
Cedar/Cub Creek fires where numerous clouds-to-cloud flashes have
been observed along with at least one cloud-to-ground strike.
The big forecast challenge for tonight will be for the wildfire
smoke. Currently, the HRRR smoke indicates that much of the ID
panhandle and eastern WA will be envelop by smoke overnight. 24
hour trends show that not only will the smoke be more dense than
what we saw Friday morning, but also more widespread. This is all
due to the northeasterly flow at the surface which is able to
effectively channel wildfire smoke from the ID and Canadian
wildfires into eastern WA. It is likely that by Saturday morning,
many locations will be looking at reduced visibilities (< 6 miles)
simply due to the smoke. Wilson
&&
.PREVIOUS DISCUSSION...
...ANOTHER DAY OF TRIPLE DIGIT TEMPERATURES SATURDAY...
Tonight: Many communities across the Inland Northwest will remain
above 90 degrees until 8 or 9 PM, and most of our larger cities
will remain in the low to mid 70s through the night. Wenatchee may
not dip below 80 tonight. Folks without air conditioning will be
challenged to cool their homes tonight before tomorrow brings
another day of very hot temperatures.
Saturday: Triple digit heat is expected again across the majority
of the Inland Northwest again tomorrow. Increasing amounts of
smoke and the potential for clouds may keep temperatures from
surging above 105 in some locations, but most communities will
likely top 100 degrees.
We will be keeping a close eye on an upper level disturbance
expected to develop over the Desert Southwest tonight and move
northward during the day Saturday. Clusters of showers and
thunderstorms will develop over southern Idaho and eastern Oregon
Saturday. Depending on the track and strength of this disturbance,
parts of our forecast area may be dealing with late day
thunderstorms. At this time, several of the high resolution models
suggest Kamiah, Craigmont, Asotin, Lewiston, and possibly the
Palouse may experience thunderstorms or decaying storms late
Saturday afternoon into Saturday evening. With temperatures in the
upper 90s and low 100s, the potential for strong outflow winds are
a possibility. We have seen gusts of 50mph or more in the past
with thunderstorms or decaying showers and triple digit heat, but
everything has to come together just right. If convection arrives
in the mid to late evening, the gust potential may be reduced as
the evening inversion develops and limits our downward mixing
potential.
Saturday Night into Sunday: There has been a good deal of model
run to run variability with the placement and amount of
precipitation with the upper level disturbance moving across north
Idaho and eastern Washington. Our region will experience a strong
surge of deep atmospheric moisture (high precipitable water), but
it remains unclear how widespread our precipitation will be. The
potential for locally heavy rain exists, but it is doubtful
everyone will get the much needed rain we all want. /GKoch
Monday: A break from precip is expected Monday morning despite
the moisture still in place, but there is a little bit of support
for convective development over the northern Panhandle in the
early morning. Then, in the afternoon, things look to pick up
with where they left off Sunday, with most of the showers and
thunderstorms in Northeast Washington and the Idaho Panhandle.
Wetting rain may be possible, especially in the northern
Panhandle where the mean steering flow be relatively slow. There
is also some flash flooding potential in that area.
Tuesday: In the afternoon, some more convection is possible in the
Panhandle and Northeast Washington, but recent model runs have
been trending towards little to no development. Amounts will be
lighter than Monday due to lower precipitable water values and
faster steering flow, which means the cells will not linger over
one area for as long.
Wednesday and Thursday: As the long wave trough approaches from
the west, it appears there could be a small wave with an overlap
of favorable parameters for precipitation chances in central
Washington Wednesday morning. However, confidence is very low
because models have not been convinced enough to put in much
mention of PoPs for that time frame. Chances are good, however,
for nocturnal thunderstorms Wednesday night continuing into
Thursday morning. Current thinking is this would include the
Cascade Crest and Lewis, Nezperce, Garfield, and Asotin counties.
Later Thursday morning into the afternoon, convective parameters
don`t seem to be too excited, but some models suggesting an
uptick in thunderstorm activity along the Canadian border Thursday
afternoon due to potentially favorable synoptic forcing. RC
&&
.AVIATION...
00Z TAFS: The big impact to aviation the next 24 hours will be
wildfire smoke. Northeast flow overnight will likely allow smoke
from the ID wildfires to once again filter down into LWS and PUW.
There is even a chance GEG-SFF-COE could see reduced visibilities
and have indicated this in the TAFs with 6SM and HZ. Smoke may
also impact the lower Columbia Basin (MWH-EAT) but confidence is
much lower. Gusty outflow winds from thunderstorms will be
possible at LWS and PUW Saturday evening but not currently in the
TAFs as it is just outside our 24 hour TAF window. Wilson
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 70 102 73 87 66 88 / 0 0 20 40 30 20
Coeur d`Alene 67 102 72 87 63 86 / 0 0 20 40 40 20
Pullman 65 100 64 82 58 85 / 0 10 30 50 20 20
Lewiston 75 104 76 90 70 94 / 0 10 40 50 20 20
Colville 59 105 64 90 57 88 / 0 0 20 40 40 20
Sandpoint 62 99 67 85 61 82 / 0 0 10 40 50 30
Kellogg 71 99 75 88 67 81 / 0 0 20 50 40 30
Moses Lake 73 104 74 89 66 92 / 0 10 30 40 10 10
Wenatchee 81 103 78 90 73 94 / 0 10 30 30 10 10
Omak 74 103 77 92 69 95 / 0 0 20 50 20 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Excessive Heat Warning until 8 PM PDT Saturday for Central
Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-Lewis
and Southern Nez Perce Counties-Lewiston Area-Northern
Panhandle.
WA...Excessive Heat Warning until 8 PM PDT Saturday for East Slopes
Northern Cascades-Lower Garfield and Asotin Counties-Moses
Lake Area-Northeast Blue Mountains-Northeast Mountains-
Okanogan Highlands-Okanogan Valley-Spokane Area-Upper
Columbia Basin-Washington Palouse-Waterville Plateau-
Wenatchee Area.
&&
$$
Area Forecast Discussion
National Weather Service Portland OR
230 PM PDT Fri Jul 30 2021
.SYNOPSIS...Hot weather continues this evening with a warm night to
follow. Temperatures cool several degrees Saturday and a few more
Sunday, but highs are expected to remain slightly above normal
through the middle of next week. Thunderstorms in the Cascades should
redevelop this afternoon and spread north-northwestward, possibly
into the Willamette Valley by late evening. Off and on chances for
showers look to continue for the Cascades through early next week.
&&
.SHORT TERM...This evening through Monday...Recent visible satellite
imagery reveals convective clouds overspreading the Willamette Valley
from south-southeast to north-northwest. Radar has been showing an
increase in coverage of scattered, light precipitation echoes over
eastern Lane, Linn, and even Clackamas counties. Some of this is
probably virga, but we have gotten reports of sprinkles and even
thunder in places. Thus, the precipitation forecast is on track, with
chances for rain increasing from southeast to northwest across the
Cascades and Willamette Valley through the evening as convection
continues to develop along the instability axis extending along the
Cascade crest.
Hot weather continues this afternoon, with many Willamette Valley
locations in the 90s as of 3 p.m. Temperatures in many locations,
however, have been stabilized by the aforementioned clouds. Tomorrow
is still expected to be slightly cooler than today for most locations
(depending on cloud cover), with max temps in the upper 80s to mid
90s despite warm overnight lows in the upper 60s to low 70s. Since
temperatures will be so warm overnight tonight - especially in
densely-populated areas where the urban heat island effect will be
most pronounced - the Heat Advisory remains in effect through 11 a.m.
tomorrow morning.
Convection is a concern for much of the area this afternoon through
early Saturday morning. NAM forecast soundings suggest robust
instability across the Cascades and even much of the Willamette
Valley. The forecast sounding for an arbitrarily chosen sample point
just south of Tombstone Summit in the central OR Cascades suggests
around 1000J/kg of MLCAPE during peak heating late this afternoon. In
addition, it is forecasting steep ~8.5C/km 700-500mb lapse rates,
which should advect into our area from the drier airmass to our
southeast in central/southern Oregon. It also suggests sufficient
(though not overly impressive) shear, with bulk (i.e., 0-6km) shear
values at around 25kts. Most of this is speed shear, both with
veering low to mid-level flow and some directional shear
(southeasterly at 700mb to southerly at 500mb) as well. In addition,
forecast soundings suggest DCAPE will exceed 1000 J/kg in places,
which would suggest gusty wind potential stemming from efficient
evaporational cooling with any of these showers. However, we suspect
this won`t be much of an issue, given the boundary layer has
moistened substantially since yesterday with a ~10 degree increase in
surface dewpoints area-wide.
Short-term, high-resolution models are still in disagreement, both
with one another and reality (according to radar and satellite
observations). The HRRR, which had been doing well in its convection
forecasts the past several days, was depicting reflectivities where
the radar was showing none just a few hours ago. The RAP and FV3 were
not doing so great either, but were a little closer to reality. The
two models initializing the best were the UW-WRF and the NAMNest, so
these were the most closely followed when making the precipitation
forecast for the upcoming couple days. These models both suggested
convection to move north-northwestward across the Willamette Valley
and into the northern Oregon/southern Washington Coast Range later
this evening, so chances have been added to the forecast for those
areas. A slight (20%) chance of thunder was brought as far west as
the PDX Metro area, near the edge of the elevated instability axis
and where the SREF was suggesting 15+% thunder chances. Given this
risk is only slight, the chances are around 5 times higher that there
will not be thunder, but it is good for folks to know that it is
possible.
Increasing onshore flow Saturday into Sunday, along with lowering
upper heights, will lead to a noticeably cooler Sunday. However,
temperatures will remain above seasonal averages with a chance of
thundershowers along the Cascades both days. The chances appear to be
highest tomorrow evening ahead of a negatively-tiled shortwave trough
which will pass north across the area through Sunday night.
Bumgardner
.LONG TERM...Monday night through Thursday...Cluster analysis shows
agreement in the upper pattern at the start of the long-term period,
with Oregon and Washington remaining under southerly 500mb flow
between the stationary trough in the Gulf of Alaska and the longwave
ridge extending across much of the eastern 2/3 of the country. A
small-scale perturbation depicted by all three long range models (GFS,
CMC, ECMWF) is expected to pass into our area at some point next
week, but its exact timing and placement are somewhat uncertain given
the time range of its forecast arrival. This looks promising to bring
a chance for showers to much of our CWA during the Wednesday through
Thursday timeframe, but again it is still far out in time to put
anything appreciable in the forecast. For now, we have gone with
NBM`s forecast, which has a chance of showers north and a slight
chance south during this time period. The NBM also suggests it will
be cooler - near to slightly above normal - during this period with
only around a 25% chance for exceeding 90F at PDX by Thursday.
-Bumgardner
&&
.AVIATION...VFR conditions expected to dominate for inland
locations through tonight. However, expect IFR/LIFR conditions
to return around 04Z Saturday as shallow marine stratus returns
to the coast. Scattered showers and thunderstorms are slowly
developing along the Cascades and spreading north and west .
Expect these showers and thunderstorms to be high-based with
overall conditions remaining VFR. There is the possibility that
periods of MVFR/IFR conditions could develop if these
showers/thunderstorms linger near TAF locations. Confidence is
low on the exact timing and location of these showers and
thunderstorms. Thunderstorm chances diminish after 09Z Saturday
but, showers will likely linger through 18Z Saturday.
For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse
KPDX AND APPROACHES...VFR through the TAF period. Light N/NW sfc
winds in the morning will increase to around 10 kt later this
afternoon. Isolated high-based showers and thunderstorms are
possible through 09Z Saturday, with showers lingering through 18Z
Saturday. Confidence is low on the exact timing and location of
these showers and thunderstorms. /42
&&
.MARINE...The typical summertime N-NW wind pattern continues
across the coastal waters, will continue through the middle of
the upcoming week. Expect north/northwest winds, which will
become gusty during the afternoon and evening hours. There is the
potential during each afternoon and evening for some isolated
gusts up to 25 kt in all zones. However, a low pressure from the
Gulf of Alaska looks to be the harbinger of a potential pattern
change for the marine waters by Tuesday/Wednesday. This low looks
to bring some stronger north/northwest winds as well as a fresh
northwest swell around 2 to 4 ft. Will continue to keep an eye on
this system as it could lead to some solid small craft advisory
wind conditions.
General seas will continue to be around 3 to 4 ft through the
middle of the week but, with the influx of the aforementioned
fresh swell, will likely cause seas to build towards 4 to 6 ft
towards the end of next week. /42
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until midnight PDT tonight for Central Oregon
Cascade Foothills-Mt. Hood National Forest West of Cascade
Crest-North Oregon Cascade Foothills-Willamette National
Forest.
Heat Advisory until 11 AM PDT Saturday for Cascade Foothills in
Lane County-Central Columbia River Gorge-Central
Willamette Valley-Greater Portland Metro Area-Lower
Columbia-Northern Oregon Cascade Foothills-South
Willamette Valley-Upper Hood River Valley-Western Columbia
River Gorge.
WA...Heat Advisory until 11 AM PDT Saturday for Central Columbia
River Gorge-Greater Vancouver Area-I-5 Corridor in Cowlitz
County-South Washington Cascade Foothills-Western Columbia
River Gorge.
PZ...None.
&&
$$
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Area Forecast Discussion
National Weather Service Phoenix AZ
506 PM MST Fri Jul 30 2021
.UPDATE...Updated Aviation Discussion.
&&
.SYNOPSIS...
Shower and thunderstorm chances will continue through at least
Saturday with the main storm threats being strong winds and locally
heavy rainfall. Drier air moving into the region beginning Sunday
will quickly diminish rain chances with chances mainly shifting over
the high terrain Sunday into early next week. An extended dry period
looks likely for most of next week which will also allow for warming
temperatures, and most likely reaching a few degrees above normal by
the middle of next week.
&&
.DISCUSSION...
Much of the region continues to fall under deep southeasterly flow
with the upper level inverted trough now positioned across Sonora
Mexico into southern portions of our region. Fairly deep moisture
has overspread much of SW AZ and SE CA this afternoon. Broad
ascent from difluent flow aloft remains in place over much of
Arizona, but with the inverted trough weakening and shearing out
today it will play less of a role than yesterday. However,
vertical ascent fields will remain stronger across southern
California into western Arizona supported by a south to north
oriented upper level jet positioned along the West Coast to just
west of Baja.
Latest HREF and HRRR output is focusing storms development across
the high terrain north and east of Phoenix and across Pima Pinal
Counties, out ahead of the remains of an MCV which is now moving
into SE AZ. They are also showing current storm development over
the Baja CA coastal ranges, with outflows from these storms
helping to develop more storms over Imperial and eventually
across Riverside County. The moist southeasterly low-level flow
likely will also favor convective development/heavier rainfall
totals along southeast-facing slopes of mountain ranges across SE
CA, including Joshua Tree NP this afternoon/evening. Thus, the
Flash Flood Watch that was earlier issued for parts of SE CA/SW AZ
has been expanded to include Joshua Tree NP. Moisture levels and
instability will likely be maximized this afternoon across the
Lower CO River Valley, where the HREF depicts fairly widespread
storms possible late this afternoon into early this evening. Yuma
forecast soundings also show a mostly uncapped profile and over
1500 J/KG of CAPE, so a few strong to severe storms will be
possible, on top of the heavy rainfall and flash flood threat. For
south- central Arizona into the high terrain east of Phoenix,
isolated to scattered storm activity will be likely, but drier air
working westward out of New Mexico should decrease instability
and likely storm limit coverage.
For Saturday, flow aloft shifts out of the south with the deeper
moisture shifting back across all of southern Arizona. HREF shows
higher MUCAPEs across south-central Arizona for Saturday afternoon
as moisture increases, but more limited storm activity due to a
southerly steering flow and likely weak subsidence aloft. The threat
for more widespread storms is definitely still there for Saturday,
but the latest guidance seems to be backing off on coverage. There
is also indications of storm development again Saturday afternoon
across Joshua Tree NP as a weak shortwave rotates northward across
the region ahead of an upper-level trof that is sitting off the
southern CA coast. Flow aloft should then shift out of the
southwest Saturday night into Sunday in response to the
afomentioned trough that will be moving northward across southern
California resulting in considerable drying to begin. The drying
on Sunday should mostly limit storm potential to the high terrain
north and east of Phoenix with even less potential into early next
week as PWATs likely lower to between 1.00-1.25". Temperatures
will also warm up Sunday through the first half of next week with
the subtropical high rebuilding over Arizona and likely persisting
for several days. NBM high temperatures are shown to warm to
110-113 degrees over the western deserts to 106-108 degrees across
the south- central Arizona deserts. The upper end of guidance
shows some potential for excessive heat, but so far the
probabilities for those temperatures remain fairly low.
&&
.AVIATION...Updated at 00Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Winds will favor southerly component SE-SW crosswinds early this
evening. Isolated thunderstorms may approach and enter the Phoenix
metro through 04-05Z. Confidence is low that a storm will directly
impact any terminal with higher probabilities (50-70%) of periods
of E-SE-SW thunderstorm outflow boundaries impacting the terminals
through 06Z. Wind gusts 20-30kt are possible with the stronger
outflows. Overall confidence is low regarding timing and location
of any specific feature.
While storms should lessen in coverage late tonight, outflow and
deep moisture may support a few isolated overnight showers.
Chances are less than 30%, but could create odd wind shifts and
isolated lightning strikes. Regardless, cigs should remain above
8K ft; and outside of thunderstorms, light east winds should
resume later tonight and Saturday morning around 09-11Z.
Southeast California/Southwest Arizona including KIPL and KBLH:
Thunderstorms continue to occupy the region incurring erratic and
occasionally gusty outflow winds and increasing cigs. Showers and
storms will continue to develop through SW AZ/SE CA into the
evening. Regardless, HREF members show better than a 30% of storms
with the chances potentially higher at KIPL. Have kept mention of
greater thunderstorm impacts in this TAF package, though trends
may allow removal in future updates. Thicker mid/high clouds
likely to persist through the overnight and Saturday morning as
SE winds resume following variability created by nearby
thunderstorms.
&&
.FIRE WEATHER...
Monday through Friday:
Drier air spreading across the region is expected to greatly
reduce for showers and storms with only isolated storms possible
across eastern Arizona. A warming trend is expected through early
next week with slightly above normal temperatures expected by the
middle/end of next week. Minimum afternoon humidity values will
range from 20-30% on Monday before falling to 15-25% by Tuesday.
Overnight recovery will be mostly good to excellent in a 40-80%
range through Monday before lowering to 25-60% later in the
period. Apart from thunderstorms, winds will favor typical daily
upslope/drainage patterns.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flash Flood Watch through late tonight for AZZ530>533-535-536-
538-539-559.
CA...Flash Flood Watch through late tonight for CAZ560-561-568>570.
&&
$$
DISCUSSION...Percha/Kuhlman
AVIATION...Sawtelle/18
FIRE WEATHER...Percha/Kuhlman
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
1020 PM EDT Fri Jul 30 2021
.SYNOPSIS...
Beneath occasionally perturbed northwesterly flow aloft, a pre-
frontal trough and surface cold front will move southeast across
central NC tonight. The front will then stall and waver over the
Carolinas through the weekend into the middle of next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 1020 PM Friday...
The weakening cold front continues to slowly move across Central NC
overnight. A few showers are still present in the NW Piedmont, but
diminishing slowly. Latest runs of the HRRR and NAM show limited
chances of rain overnight, but an isolated shower or two cannot be
ruled out, best chance being in the Sandhills and very SE Coastal
Plain. Expect lows tonight in the low 70s in the NW and mid/upper
70s US1 and east.
&&
.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 400 PM Friday...
The cold front will stall just south of the region tomorrow. Thus it
will feel much more comfortable across the northern Piedmont with
60s dew points and mid-to-upper-80s for high temperatures. But in
the far south it will only be marginally better, with highs still in
the lower-90s and dew points in the lower-to-mid-70s, resulting in
heat indices still in the upper-90s to 100. There may be enough low-
level moisture for isolated showers/storms in the far SE, but
otherwise no precipitation is expected with dry NW flow aloft.
The front will then lift north through central NC as a warm front on
Saturday night. Models are pretty consistent in showing a wave of
surface low pressure riding along the front. This combined with
isentropic lift will result in a better chance of showers especially
along and north of the boundary. A few storms can`t be ruled out,
but lack of instability that time of night will be a limiting
factor. Lows Saturday night will be in the lower-to-mid-70s.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 330 PM Friday...
In the upper-levels, a trough will dig across the Ohio Valley and
Northeast Sunday into Monday with a shortwave moving across North
Carolina early Sunday, then a deeper trough will dig into the
Mississippi Valley and develop a closed low across the region
through the middle of next week. By the end of the week, the low
will eject northeast towards the Great Lakes Region. At the surface,
a stalled surface front near the NC/SC border will lift north in the
morning, then a cold front will push southeast across the region
later in the day and stall along the coast through most of the week,
with high pressure building into the Midwest and eventually into the
Mid-Atlantic.
The aforementioned pattern will yield active weather through most of
the long term as multiple fronts and upper-waves move across the
region. Precipitable water values will lower near the Appalachians
to below 1 inch behind Sunday`s front, then values creep back to
near 1.5 inches early to mid next week as moisture advection
returns. Areas near the Coastal Plain will have higher values,
between 1.75 and 2 inches through the period. Confidence is high
that most areas will receive multiple rounds of rain next week, with
up to 1 inch of rain possible along the foothills to possibly a few
inches near the Coastal Plain through the end of the workweek. A few
strong to severe storms are possible Sunday as the cold front
approaches a more favorable environment for development near the
Coastal Plain. SPC currently has the eastern half of the region in a
Marginal Risk for severe storms on Sunday.
Sunday should be the warmest day in the period, with highs in the
mid 80s N to the mid 90s S. Southern areas could have heat index
values in the lower 100s again Sunday, but the heat will only be
temporary ahead of the front. Colder air behind the front, in
addition to increased cloud cover and precipitation, will help limit
highs to the 80s on Monday with even lower highs in the mid 70s to
low 80s expected on Tue/Wed. Highs slightly rebound Thu and Fri,
with most areas in the low to mid 80s.
&&
.AVIATION /00z SATURDAY THROUGH WEDNESDAY/...
As of 750 PM Friday...
A cold front will sag slowly south into the area late this evening
and overnight, where it is then forecast to stall out across
southern NC on Saturday. Until the passage of the front, cannot
rule-out an isolated shower or storm at any TAF site, but given the
low probability of occurrence, will preclude any mention at this time.
NELY flow behind the cold front will bring a chance for some MVFR
ceilings from stratus between 08 to 12z, mainly across the coastal
plain counties, INVOF KRWI. Any sub-VFR conditions in low clouds
will lift and scatter out after daybreak, with predominately VFR
conditions through Saturday afternoon with rain chances remaining
very low and confined to the SE counties.
Looking beyond 00z Sunday: The stalled front will lift back north
over the area Saturday night and will remain nearly stationary
across the Carolinas through much of the upcoming pattern. This will
lead to a very wet and unsettled weather pattern, especially across
central and eastern NC, with periods of sub-VFR conditions possible
each day in showers and storms. Sub-VFR conditions in fog and
low stratus will also be possible each morning.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...MWS
NEAR TERM...CA
SHORT TERM...Danco
LONG TERM...JJT
AVIATION...CBL