Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/01/21
Area Forecast Discussion
National Weather Service La Crosse WI
656 PM CDT Sat Jul 31 2021
.SHORT TERM...(This evening through Sunday)
Issued at 133 PM CDT Sat Jul 31 2021
A cold front is dropping into our northern forecast area early
this afternoon with scattered convection developing along and ahead
of it. Under mostly sunny skies for most of the morning, this area
has built around 500-1000 J/kg of MLCAPE so far, perhaps up to
1200 J/kg at its peak this afternoon. Isolated convection has been
sparking along this boundary since late morning with modest low to
mid-level lapse rates. Convective initiation has been slightly
suppressed by a bit of CIN in the 800-700mb layer, but this is
quickly eroding with continued strong afternoon heating ahead of the
boundary. Indeed, coverage along the boundary is quickly increasing,
evidenced by a line of growing towering cu on satellite. CAPE
profiles in RAP forecast soundings fall into the tall/skinny
category, so with limited updraft momentum (and meager deep layer
shear for that matter) do expect storm longevity will be limited
overall. That said, there could be a few stronger, more prolonged
updrafts within this broken line of convection this afternoon that
may pose an isolated damaging wind and/or large hail threat into
early evening as the front drops south through the area. This fits
in line with SPC`s marginal risk for our area into early evening.
Waning instability past 7PM should lead to a rapid diminishing
trend in lingering convection across our south, with dry conditions
heading into the overnight.
As for hazy/smoky conditions, the HRRR shows near-surface smoke
concentrations at their peak through this afternoon, diminishing a
bit in the northerly flow behind the front tonight. There then looks
to be marked improvement in both near-surface and vertically-
integrated smoke through midday Sunday...at least momentarily.
A quieter day on tap for Sunday as surface high pressure builds into
the region with cooler conditions / highs in the 70s. Turning even
less humid with dewpoints falling into the 50s. With a return to
bluer skies, it should make for a very pleasant Sunday afternoon.
.LONG TERM...(Sunday night through Saturday)
Issued at 133 PM CDT Sat Jul 31 2021
Sunday night through Monday night will feature quiet and
seasonably cool conditions, as high pressure migrates from
the Northern Plains to the Upper Great Lakes. Will likely
continue to deal with smoke with northerly flow aloft, and
will have to monitor for more areas seeing impacts to
visibilities and air quality with increasing subsidence and
lighter winds. The Air Quality Alert continues for MN into Tuesday
afternoon.
Tuesday there remains a signal in some of the guidance for a
backdoor cold front nearing in the wake of passing mid level
shortwave. Considerable uncertainty though on extent/location,
thus have maintained the slight chance PoPs for some of our
northeast service area.
Wednesday through Saturday the general theme is a warming trend
to around normal, with generally 60s for lows and 80s for highs.
Moisture will gradually increase in time with a broad trough
developing in the Plains. This along with some ejecting impulses
will bring periodic chances for showers and storms, mainly heading
into the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 657 PM CDT Sat Jul 31 2021
Currently monitoring a broken line of showers and storms north of
KLSE. Timing at KLSE would be about 0130Z. However, at this time
the SHRA/TSRA look to be just east of KLSE and for now have left
it out of the TAF. The activity should also wane with sunset
hours. Will monitor for an update as needed.
Northerly flow should scour most/all of the wildfire smoke out of
the area by Sunday afternoon, thus MVFR smoke vsbys will be
improved at sunrise to VFR.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Kurz
LONG TERM...McClure
AVIATION...Baumgardt
Area Forecast Discussion
National Weather Service Bismarck ND
925 PM CDT Sat Jul 31 2021
.UPDATE...
Issued at 920 PM CDT Sat Jul 31 2021
For this update, decided to extend mention of smoke across the
east in the gridded forecast until 07z based on current
observations and trends. Otherwise, just blended in the latest
observations.
UPDATE Issued at 604 PM CDT Sat Jul 31 2021
Not much to report weather wise. Another quiet evening with less
smoke at the surface. However, smoke aloft will keep the sky hazy
at least through the night. For this update, just blended in the
latest observations to the going forecast.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 146 PM CDT Sat Jul 31 2021
Latest water vapor imagery shows high amplitude ridge in place over
the western CONUS with northwest flow over the Northern Plains
and drier air aloft continuing to push southward over ND. Surface
analysis shows cold front well south of the state with high
pressure nudging into ND from the north. Satellite also shows
smoke continuing to advect southward across parts of central and
eastern ND.
Winds will diminish this evening with lows in the 50s and even
some upper 40s north. RAP and HRRR smoke model guidance suggest
some improvement overnight, though shows a deeper area of smoke
moving from Canada into our northeast CWA, progressing
south/southeast. Models indicate this smoke will be mainly aloft,
not near the surface. Given the relatively limited impacts on
visibility this afternoon so far, will not carry smoke in the
forecast overnight.
.LONG TERM...(Sunday night through Saturday)
Issued at 146 PM CDT Sat Jul 31 2021
A similar pattern continues on Sunday with strong western ridge in
place and surface high drifting across the Northern Plains. Expect
another dry day with highs in the 80s and light winds.
Global models and ensemble products, including WPC cluster
analysis, continue to indicate the western ridge will deamplify
with some shortwave troughs moving through. This supports an upper
level low over the Pacific Northwest by next weekend and a more
zonal flow over our region. Current forecast reflects this with
chance pops Thu night into Friday with a more pronounced shortwave
crossing the region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 925 PM CDT Sat Jul 31 2021
VFR conditions are mostly expected through the period with
generally light winds. Surface smoke across the east will continue
through at least the first part of the night which could bring
reduced visibility at KJMS (MVFR categories at times).
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...ZH
SHORT TERM...JNS
LONG TERM...JNS
AVIATION...ZH
Area Forecast Discussion
National Weather Service Denver/Boulder CO
844 PM MDT Sat Jul 31 2021
.UPDATE...
Issued at 810 PM MDT Sat Jul 31 2021
Flash Flood Watches will be allowed to expire.
A few changes were made to the forecast. The biggest was to reduce
PoPs overnight tonight and through tomorrow. Basically any chance
of showers or storms will be west of the Continental Divide
tomorrow. East of the Divide will be too stable with an inversion
just above 700 mb likely being too strong to overcome considering
the drier air in place. The increased smoke tomorrow will aid in
keeping instability down as well. So the burn area flash flood
matrix will be moved to "none" over the Calwood and Cameron Peak
for Sunday.
The HRRR smoke model is showing a lot more smoke moving into the
area tomorrow. Smoke was clearly visible on satellite today and
surface visibility observations were as low as 3 miles in the
panhandle of Nebraska due to smoke. It should be noticeably
smokier tomorrow so smoke was added to the forecast.
Lastly, moist and hazy air will be in place across the eastern
plains tonight leading to the possibility of fog. The best chance
for fog will be in southern Weld, Fort Morgan, and Washington
counties so fog was added to the forecast there. Fog can`t be
ruled out elsewhere but the chance was too low to include it into
the forecast.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 231 PM MDT Sat Jul 31 2021
...FLASH FLOOD THREAT REMAINS IN PLACE ALONG THE FRONT RANGE THIS
EVENING...
Satellite and radar shows fairly widespread but not tremendously
intense convection across the mountains and foothills. While
maximum rainfall rates have been limited by marginal instability,
we have seen some breaks in the clouds and MLCAPE near 500 J/kg
now over the Denver metro area. There is also a push of stronger
northeast winds now arriving to the Front Range, as evidenced by
Cheyenne gusting to around 25 mph. Meanwhile, precipitable water
values have climbed to around 1.3 to 1.35 inches along the I-25
Corridor, or above the 99th percentile and approaching near
historical highs. Warm cloud depths are around 7000 feet, which is
quite impressive for the Front Range so despite the limited
instability and rainfall rates so far, we`re not done with this
event. Extended periods of moderate to heavy rain are still expected
in/near the Front Range this evening. The Palmer Divide may also
be setting up for heavy rainfall yet this evening, and that could
last as late as midnight. The only revision we`ve made so far is
to remove central Weld County from the Flash Flood Watch given the
increasing stability there and propensity of convection to push
back toward the immediate I-25 Corridor and Foothills. The Palmer
Divide and southern foothills could see the threat last until
midnight, but that depends on how this still evolves this evening
so will adjust the Flash Flood Watch there later if necessary.
Overall, the rain threat will shift southward through the course
of the evening, but perhaps a few showers may linger over the
southern portions of the forecast area into the early morning
hours.
Sunday will feature drier and more stable conditions. We`ll likely
stay capped off across the plains due to warm temps aloft and
still relatively cool boundary layer, but mountain areas will
still see enough elevated heating to potentially break the cap.
The flash flood threat will be decreased by only marginal
instability and a slightly drier airmass. High temperatures should
respond with a little more sunshine and push into the upper 70s
and lower 80s over most of the plains.
.LONG TERM...(Sunday night through Saturday)
Issued at 231 PM MDT Sat Jul 31 2021
A pronounced change in the weather pattern is forecast to take
place by mid-week, effectively splitting the long term forecast
period in half. Above normal moisture and heavy rain will be the
primary impacts through Tuesday night, with the latter half of the
week seeing a warming and drying trend.
We`ll start of the day Monday with PWATs near normal values...
roughly 0.6-0.8" for the area. However, there should be a gradual
moistening through the day. There is still some question as to how
unstable the higher terrain can get by the afternoon... but do
agree on at least some destabilization west of the divide. The
past couple of model cycles have shifted the brunt of the heavy
rain axis west a little, but the current forecast solution would
still favor heavy rain potential, especially over the East
Troublesome and Williams Fork fires. Moisture will continue to
slowly drift east on Tuesday, with heavy rain possible once again.
As is typical a few days away from an event, there is a fairly
large spread in model solutions, but in general there continues to
be good agreement in an elevated flash flood threat as well.
Moisture will decrease substantially across the area by
Wednesday, which will mark the end of a very wet period across our
forecast area. Mid-level temperatures will increase with low-
level southwesterlies also gradually increasing. This should lead
to much lower chances of precipitation (generally dry for I-25,
chance PoPs for the high terrain). Temperatures should climb into
the upper 80s Thursday and Friday, with low 90s possible for the
start of the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 810 PM MDT Sat Jul 31 2021
DEN will be in MVFR for ceilings until roughly around 10Z before
clouds disperse. Besides a bit of drizzle, rain is not expected
for the rest of the TAF period. There is a slight chance that fog
develops to the north of DEN during the early morning hours on
Sunday. It does not appear that the fog will move into DEN but
there is a non-zero chance it does. Smoke was added to the TAF for
tomorrow as a swath of thicker smoke will move in from the north.
This could impact slantwise visibility tomorrow.
&&
.HYDROLOGY...
Issued at 231 PM MDT Sat Jul 31 2021
Local flash flooding has returned this afternoon, with burn areas
most susceptible as peak rainfall rates were near 1 inch per hour.
However, we still can`t rule out flash flood concerns in the lower
adjacent areas, although instability is limited to MLCAPE around
500 J/kg. That said, all the other parameters are still in place
so we`ll continue the Flash Flood Watch until 9 pm. There`s a
chance the Watch may need to be extended over the Palmer Divide
and southern Foothills. We have cancelled the Watch for Central
Weld County which appears to be stabilizing, and the frontal
surge should keep the highest coverage in/just west of the I-25
Corridor and Palmer Divide. Despite somewhat more limited rainfall
rates around 1 inch per hour with the strongest storms, the
persistent nature of the showers and storms will keep the flash
flood threat in place.
For Sunday, the airmass will dry and stabilize a little. This will
reduce the flash flood threat as well as convective coverage.
There`s still a small threat, however, given the above normal
amounts of moisture residing in the atmosphere.
Flash flooding concerns ramp up a bit on both Monday and Tuesday.
Better moisture returns to the area, particularly along and west
of the divide by Monday afternoon, with long skinny CAPE profiles
evident in BUFKIT soundings. WPC has much of our higher terrain in
a SLGT excessive rainfall outlook which at this point seems
fairly reasonable. Primary areas of concern would be the East
Troublesome/Williams Fork burn areas, with a lower threat on the
Calwood and Cameron Peak burn areas.
Models show the potential for another heavy rain day on Tuesday,
but confidence is below average at the moment. Given the amount of
moisture available along with very slow storm motions, it does
look like a favorable setup. We`ll have to watch the trend for
both days closely, especially since there`s been a substantial
amount of precipitation over the past few days.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 9 PM MDT this evening for COZ030>041.
&&
$$
UPDATE...Danielson
SHORT TERM...Barjenbruch
LONG TERM...Hiris
AVIATION...Danielson
HYDROLOGY...Barjenbruch/Hiris
Area Forecast Discussion
National Weather Service Cheyenne WY
544 PM MDT Sat Jul 31 2021
.SHORT TERM...(This evening through Sunday morning)
Issued at 200 PM MDT Sat Jul 31 2021
Challenges with this forecast package deals with rain
chances. Still a lot of guidance discrepancy for tonight into
Sunday.
Currently...Surface front that was on the Colorado Wyoming state
line yesterday has slipped well south into southern Colorado
today. MCV feature over northeastern Colorado through the morning
hours...continues to push southeast into western Kansas this
afternoon. Another cold front lays across southern South Dakota
into northeast Wyoming into south central Montana this afternoon.
MCV has really decreased our rain chances this afternoon. NAMNEST
short term guidance has begun to come more in line with the HRRR
this afternoon with decreasing chances for showers and storms. 18Z
NAM showing PWATS really falling across southeast WYoming and
Nebraska Panhandle after 00Z. So do think rain chances come
quickly to an end after 00Z. Based our PoP forecast on the HRRR
solution with showers coming to an end after 8PM tonight.
.LONG TERM...(Sunday through Friday)
Issued at 351 AM MDT Sat Jul 31 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.
Moisture advection ahead of main shortwave Tuesday will allow for
widespread precipitation chances on the Wy side mainly along and
west of the Laramie Range before spreading further Wednesday into
the high plains and the Panhandle. In its wake high pressure
builds again into the region drying us out and return back into
the 90s for the Panhandle Thursday into the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 538 PM MDT Sat Jul 31 2021
VFR conditions will continue for all TAF sites across
southeastern Wyoming. Wildfire smoke will lower visibility levels
for all western Nebraska Panhandle sites to MVFR conditions
through the TAF period Sunday 0Z. Light winds under 13kts overall
for all sites across the region as dry conditions are expected to
persist through Sunday morning. Clouds will trend from SCT to BKN
for the remainder of the TAF period.
&&
.FIRE WEATHER...
Issued at 200 PM MDT Sat Jul 31 2021
Minimal fire weather concerns through the rest of the weekend
through the middle of next week as monsoonal moisture remains over
the area. Expect afternoon humidity to stay in the low 20 percent
range with good overnight recoveries. Begin to dry out Thursday
as temperatures begin to warm up quite a bit. Could see critical
afternoon humidity west of the Laramie Range Thursday and Friday
next week. But winds are expected to be weak at this time.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...GCC
LONG TERM...WM
AVIATION...AW
FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Des Moines IA
637 PM CDT Sat Jul 31 2021
.SHORT TERM.../Tonight through Sunday Night/
Issued at 234 PM CDT Sat Jul 31 2021
Confidence: High
Clouds linger late this afternoon over the south with the departing
cool front and associated area of overnight convection. Subjective
surface analysis at 12z shows one front south of Iowa with another
weak boundary over central MN moving southeast, along with a third
cool front over northeast MN. Low pressure is stacked up over the
northern Great Lakes near Lake Superior while high pressure is now
beginning to enter the Northern Plains. Aloft, a large gyre at H850
over New England will be merging with a low currently over Hudson
Bay. High pressure continues across the west with ridging far north
into the Canadian provinces. Cooler temperatures will continue to be
slated for the eastern/northeast states while rather hot conditions
will rebuild over the west.
As the weak boundary over central MN heads south this evening, a few
showers and isolated thunderstorms are expected to develop with an
area of instability along the boundary. The activity will be
mainly diurnal and if it holds together this evening, likley not
making it any farther south than the US30 corridor in the northeast.
As well as a chance of showers and isolated thunderstorms north,
smoke is again showing up in the visible imagery over northwest
and north central Iowa. Hazy to smoky skies are reported from Ft.
Dodge north to Algona and Estherville and across southern MN as
well. Have already added smoke to grids over the north this
afternoon. Current HRRR modeling of the smoke has it tracking
south with the boundary overnight into southern Iowa by daybreak.
Lows tonight will cool most areas and drop into the mid 50s
northwest to the lower to mid 60s southeast. There may be only a
little break early Sunday, but another large plume of smoke in
northern MN now, tied to the third cold front identified this
morning, will likely also track south southeast which brings it
close to southeast MN by 12-15z tomorrow and should again clip our
northeast and eastern counties through at least the morning
tomorrow. With the broad area of high pressure and reinforcing
cooler H850 temperatures anticipated to arrive and continue for
several days, afternoon highs Sunday will cool a bit to the mid to
upper 70s with a few lower 80s over the region. Sunday night will
also be refreshingly cool with overnight lows in the lower to mid
50s north to the upper 50s southeast.
.LONG TERM.../Monday night through Saturday/
Issued at 234 PM CDT Sat Jul 31 2021
Confidence: Medium to High
A combination of several waves dropping nearly due south into the
large eastern North American trough at H500 and a cyclone in the
Gulf of Alaska/North Pacific off the BC Coast through Thursday will
result in a more amplified regime with much of the Great Lakes and
eastern plains seeing northwest flow aloft through Tuesday. With
H850 temperatures struggling to move much higher than the lower to
mid teens through Wednesday afternoon, afternoon highs over the
region will be rather pleasant in the upper 70s to lower 80s for the
first half of the week. Through Wednesday, generally dry conditions
can be expected with occasional clouds due to weak system passage
and diurnal heating considerations. By mid to late week and into the
weekend, the H500 pattern will begin to flatten with a wave approaching
the area from the west Thursday into Friday. With increasing warm
air advection and moisture, showers and thunderstorms will be on
the increase over the area. The precipitation will signal the
beginnings of another round of hotter conditions across our area.
Despite some significant differences between mid-range model
guidance, a conservative increase in H850 temperatures back to a
20 to 23C range by Friday into Saturday will have our area highs
pushing back into the upper 80s to lower 90s again. There are
hints in both the Euro and GFS solutions that another wave will
track through the region about this time, bringing some additional
chance for showers and storms. Though there is no real way to
predict levels of smoke across the region into late week, the
general pattern would suggest that some will still be lingering
due to the overall persistent northwest flow through Tuesday and
more westerly flow aloft Wed through Saturday. This may have some
impact on highs and visibility/haze from time to time.
&&
.AVIATION.../For the 00Z TAFS through 00Z Sunday evening/
Issued at 637 PM CDT Sat Jul 31 2021
The only non-VFR impact of concern will be smoke with periods of
MVFR conditions anticipated at all TAF sites, the most lengthy of
which will occur at KALO/KDSM/KOTM. Otherwise expect VFR
conditions with intermittent smoke aloft through the period,
along with little beyond patchy cumulus and generally light NW
winds.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...REV
LONG TERM...REV
AVIATION...Small
Area Forecast Discussion
National Weather Service Quad Cities IA IL
659 PM CDT Sat Jul 31 2021
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 207 PM CDT Sat Jul 31 2021
Partly to mostly cloudy skies covered much of eastern Iowa,
northwest Illinois and far northeast Missouri early this afternoon,
and were left over from a morning MCS. That system was well into
southern Illinois as of this writing, and other than some lingering
rain showers in west central Illinois conditions have been improving
through the late morning and early afternoon. Surface obs in
portions of our area extending north and west were also picking up
on hints of wildfire smoke, which was building south into the upper
Mississippi River Valley thanks to northwesterly flow. Visibilities
were reduced to 2 miles in portions of northwest Iowa, where
concentrations were more dense.
&&
.SHORT TERM...(This Evening through Sunday)
ISSUED AT 207 PM CDT Sat Jul 31 2021
[Key Messages]
*Chance of a shower or storm mainly north of Hwy 30 this evening
*Sunshine and haze/patchy smoke to close out the weekend
[Discussion]
Much of eastern Iowa, northwest Illinois and far northeast Missouri
will see a dry and quiet end to the weekend, as a renewed surge of
northerly flow from a passing cold front and high pressure build
into the area. This front will arrive in our northern CWA this
evening, and may be accompanied by scattered showers and storms that
will develop in response to steepening lapse rates and forcing along
the front. There is potential some storms could be strong thanks to
favored speed shear and dry air aloft, and steep low-level lapse
rates for momentum transfer. Damaging winds and large hail would be
the primary concern. Activity will diminish once the sun sets. The
Storm Prediction Center has a sliver of a Level 1 (marginal) risk
for severe storms north of Highway 20.
On Sunday, partly to mostly sunny skies will prevail as the high
pressure slowly builds south into the upper Mississippi River
Valley. Forecast soundings suggest deep mixing will be occurring in
the low-levels, which will have potential to mix a plume of wildfire
smoke aloft building south into the Mississippi River Valley down
to the surface. Analysis from the HRRR and RAP hint at periods of
high surface smoke concentrations during the late morning and
early afternoon, before gradually waning during the evening. Those
most sensitive to air pollution may be affected, but most will
likely experience periods of visibility issues from haze.
Below normal temperatures will prevail thanks to the northerly flow.
Lows tonight will drop into the upper 50s to low 60s, with PM highs
Sunday int the upper 70s to low 80s. A welcomed break from the past
week of heat and humidity!
.LONG TERM...(Sunday Night through Saturday)
ISSUED AT 207 PM CDT Sat Jul 31 2021
Northwest upper level flow between the deepening trough over the
eastern U.S. and persistent upper level ridge over the Rockies will
provide an extended period of mostly dry and cooler than normal
temperatures through at least the middle of next week. The continued
trajectory from smoke sources in Canada and the western U.S. will
likely provide continued hazy skies and possibly some additional
period of smoke or haze at the surface.
Sunday night through Wednesday: Surface high pressure will prevail,
providing light winds and low humidity, which will slowly increase
toward midweek. Isolated afternoon showers cannot be completely
ruled out,with steep low level lapse rates, especially Tuesday
afternoon under a weak mid level impulse. However, forecast
confidence is too low to mention. Temperatures will slowly moderate
with daytime highs going from the mid and upper 70s Monday to the
lower to mid 80s Wednesday, while the dry air and low dewpoints lead
to lows in the 50s to lower 60s.
Thursday through Saturday will see a return of at least slight
chances for showers and thunderstorms as the upper flow deamplifies
to a more zonal configuration with periodic shortwaves. Southerly
surface winds and rising heights will bring warmer temperatures,
back to near or above normal by the weekend. This will also result
in the return of ore typical summer humidity levels.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
ISSUED AT 659 PM CDT Sat Jul 31 2021
MVFR vsbys due to smoke will continue through most of the period.
There is some indication of IFR into tomorrow morning, but will
hold off on that at the current time. Otherwise light winds and no
cig restrictions expected.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...Speck
SHORT TERM...Speck
LONG TERM...Sheets
AVIATION...Gibbs
Area Forecast Discussion
National Weather Service Grand Forks ND
701 PM CDT Sat Jul 31 2021
.UPDATE...
Issued at 657 PM CDT Sat Jul 31 2021
Breezy north winds are tapering off this evening with temperatures
in the 70s. Smoke continues to loft into the region out of
Manitoba and Ontario, with only partial clearing to the east of
the Red River Valley. Looking upstream, another plume of wildfire
smoke will work towards the area through the evening and early
overnight period.
&&
.SHORT TERM...(This afternoon through Sunday night)
Issued at 246 PM CDT Sat Jul 31 2021
Periods of smoke continue to impact visibility and air quality across
our forecast area.
Northerly flow advected a plume of thick smoke into our forecast
area with some locations near or less than 1 mile visibility and AQI
values within the red category. This initial plume should transition
into our southern CWA, while additional smoke moving into the region
mainly aloft (some still being reported at the surface). HRRR smoke
model shows improving trends in surface smoke concentrations
tonight, however as surface winds go light this evening the forming
nocturnal inversion may act to trap any lingering smoke near the
surface. Smoke models keep most smoke aloft within northerly flow as
surface flow is much weaker, however at least some impacts at the
surface are possible.
Temperatures will tend to be near or even slightly lower based on
latest guidance in the upper 70s/lower 80s. Lows tonight may be the
coolest with some colder spots in our north-northeast in the upper
40s.
.LONG TERM...(Monday through Saturday)
Issued at 246 PM CDT Sat Jul 31 2021
Overview...
Stop us if you`ve heard this one before, but hot and dry weather is
expected across the majority of the long term period. Overall
minimally impactful weather is looking likely, although there is a
small signal for precipitation to return to the area by late week.
The week ahead...
An upper level ridge over the western CONUS and trough over the
eastern CONUS continue to dictate our weather pattern. The northern
Plains are stuck in between these features, and while this would
typically be an impetus for a more active weather pattern, the ridge
out west is amplified enough to really block any appreciable
shortwaves that try to pass through. In conjunction with surface
high pressure, weather is expected to remain quiet with
incrementally increasing temperatures as the week progresses.
Initial highs in the mid 80s on Monday will likely begin to creep up
toward the low 90s yet again by midweek.
The primary shift in the weather pattern is then expected to occur
later in the week as an upper trough over the Gulf of Alaska pushes
southward toward the Pacific Northwest. This should act to weaken
the upper ridge and catapult the Plains into a zonal to
southwesterly flow regime. General ensemble guidance and cluster
analysis are all in agreement on this solution, with slight
variances with respect to timing and magnitude of the weakening
ridge. Otherwise, a potential shift to a more active pattern may be
in the cards moving toward the latter half of the week and into the
weekend with increasing precipitation potential becoming evident
within guidance at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 626 PM CDT Sat Jul 31 2021
VFR to MVFR conditions prevail this evening with smoke remaining
in the region. The thickest smoke has moved to our south as north
winds persisted through much of the day. For tonight, low level
smoke should keep visibility in the 4 to 6 mile range; however,
mid to upper level smoke could build back into the area through
the overnight hours and into Sunday morning.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...Lynch
SHORT TERM...DJR
LONG TERM...Rick
AVIATION...Lynch
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1049 PM CDT Sat Jul 31 2021
.SHORT TERM...(This Evening through Sunday)
Issued at 235 PM CDT Sat Jul 31 2021
There are two concerns in the short term forecast. The first
concern is the near surface smoke which has been over the region
since Thursday. Satellite shows that the smoke rapidly dissipates
behind a surface front that is currently near I-90. This front is
expected to be south of Sioux City and Storm Lake by early
evening. While there will still be smoke aloft moving over the
area, the lack of near surface smoke will remove the hazy surface
conditions.
In addition to clearing smoke out, moisture is pooling along the
boundary with an area of cumulus forming near the Iowa and
Minnesota border. Soundings show that there is a warm layer around
600 mb and most soundings only have a 1-2 h window where the
parcels are warm and moist enough to overcome this warm layer.
Due to lapse rates of 6-6.5 C/km, the resultant MLCAPE is
generally 500-1000 J/kg. The HRRR depiction of a only a few cells
developing seems reasonable given the limited surface convergence
and weak upper level forcing. So have only 20-30 PoPs from mid
afternoon through sunset for the area.
Any storms that develop should dissipate shortly after sunset.
With decreasing winds and drier air moving in, lows overnight will
be in the 50s. On Sunday, northerly flow and dry air favor
efficient mixing. While sustained winds will only be around 10
kts, the boundary layer may mix deep enough to support wind gusts
of 20 to 25 mph during the early to mid afternoon. Also expect
this will help to warm temperatures to near normal with highs from
the upper 70s along the Buffalo Ridge in Minnesota to the mid 80s
west of I-29.
.LONG TERM...(Sunday Night through Saturday)
Issued at 235 PM CDT Sat Jul 31 2021
The early part of the week will continue to be dry and seasonable.
Upper level smoke will continue to be across the area. And there
is some indication surface smoke may return to the area sometime
Sunday night or Monday. Given that smoke is very dependent upon
the evolution of fires across portions of Canada, did not add any
smoke into the grids at this time. But if smoke moves back in, it
may be hard to get rid of until later into Tuesday or even
Wednesday when the low level flow turns to the south. So there is
the potential for degraded air quality into early next week.
Otherwise dry conditions are expected with temperatures generally
in the 80s for both days. With high pressure nearby, light winds
are expected.
For Wednesday through Saturday, both the ECMWF ensemble and NAEFS
predict a large scale ridge in the west and trough in the east to
begin the period. By next weekend, the ensemble mean goes to a
quasi-zonal flow with a low amplitude ridge over the area. While
there are strong signals for a gradual warm up late this week and
into the weekend, the degree of the warm up remains uncertain. The
GEFS is much warmer than the ECMWF and Canadian by late this
week. The warmer GEFS may be a result of the model
parameterization overestimating surface heating which has been an
issue over the plains the last 2-4 years so am favoring
temperatures closer to the ECMWF and Canadian solutions. The
ECMWF and Canadian ensembles have not been as extreme although
highs could reach the 90s west of the James River by Thursday and
across the remainder of the forecast area by Friday and Saturday.
As for precipitation, models show a low (20%) probability of
precipitation Wednesday night and Thursday. The 00Z deterministic
models showed more QPF than the 12Z deterministic models and most
ensemble members with several members remaining dry. As noted in
the previous discussion, shear is limited and the lapse rates
remain less than 7 C/km so if thunderstorms develop, severe storms
appear unlikely at this time. As the flow transitions to quasi-
zonal toward the weekend, predictability decreases as to the
timing of waves. While most ensemble members agree there will be
some rain over the weekend, the amount of the rain and timing is
uncertain. There is also some concern about mid-level capping
which could limit coverage of any thunderstorms.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1047 PM CDT Sat Jul 31 2021
Satellite imagery before dusk combined with sfc observations show
patchy smoke lingering in the region overnight. Generally expect
VFR conditions to prevail late tonight through at least early
Sunday with the bulk of the incoming smoke streaming through
aloft. North winds will weaken overnight as sfc high pressure
builds in.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...Schumacher
LONG TERM...Schumacher
AVIATION...BP
Area Forecast Discussion
National Weather Service Goodland KS
639 PM MDT Sat Jul 31 2021
.SHORT TERM...(This evening through Monday night)
Issued at 328 PM MDT Sat Jul 31 2021
The primary forecast concern is the continuation of the hazy
conditions due to smoke from tonight through Sunday, Sunday night
and into Monday morning.
The upper ridge continues to amplify over the Rockies and
Intermountain region tonight into Sunday before several short wave
troughs move slowly through the apex of the upper ridge between
Monday and Monday night. At the surface, high pressure over the
northern and central plains pushes deeper into the southern
plains. Expect any thunderstorms that may develop to stay outside
of the forecast area to the west and south in closer proximity to
the surface convergent areas near the remaining surface
boundaries and along the areas of higher terrain.
The Near Surface Smoke concentrations in the HRRR show a gradual
dissipation of the smoke through the next couple of days. As a
result, the heavy haze seen across the area today following the
passage of a cold front last night should be gradually dissipating
over the next few days. Expect some near surface re-concentration
as the overnight inversion sets up. However, once the surface
inversion breaks up with the heating of the day, expect the near
surface concentration of smoke to mix out through a larger depth.
Unfortunately, the vertically integrated smoke being depicted by
the HRRR is showing max concentrations through the day on Sunday
before pushing further to the south and west. This would tend to
support continued hazy conditions through the remainder of the
weekend and into the first part of next week, although near
surface smoke concentrations may stay low enough to not create air
quality issues for potentially susceptible individuals.
Expect temperatures to gradually through through Monday with highs
back up around 90 degrees on Monday.
.LONG TERM...(Tuesday through Saturday)
Issued at 156 PM MDT Sat Jul 31 2021
The extended forecast begins with a ridge over Eastern Montana and a
longwave trough extending west to east from the Dakotas to New
England and south to the Gulf Coast. Northwest flow aloft remains
in place over the Tri-State area. High pressure will be in place
over the Baja Peninsula. The pattern remains favorable for daily
chance for showers and thunderstorms as a few disturbances move
across the region. Given the dry conditions we`ve had in the area
for the last week and precipitable water values of 0.8-1.0" across
portions of the area, confidence in the potential for isolated flash
flooding remains low at this time. Any showers and thunderstorms
that do develop on Tuesday and Wednesday will have the potential to
produce some gusty winds and much needed rainfall.
Tuesday afternoon, the ridge begins to break down, shifting to the
east over the area. High temperatures will make it up into the 80s
with a few areas flirting with the 90 degree mark. Wednesday, the
ridge continues to break down with an embedded shortwave trough
moving into the area from the northwest. A few showers and
thunderstorms will be possible and high temperatures will once again
be in the 80s.
An upper ridge moves in from the west on Thursday and Friday with a
gradual warming trend possible. Highs are expected to return to the
low to mid-90s for most of the region Friday afternoon. All eyes
turn to the west Friday as a shortwave trough ejects out of the PAC
NW, trekking across Montana and the Dakotas through the day. Models
are in slight disagreement with the ECMWF being more aggressive in
the forward movement of the trough at this time. Models also show
an upper low nearing the Olympic Peninsula late in the forecast
period. The system is still nearly a week from reaching shore, so
will want to continue to monitor the forecast over the coming
days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 627 PM MDT Sat Jul 31 2021
Reduced visibilities (3-6SM) associated with smoke emanating from
wildfires in the western CONUS will affect both terminals through
Sunday morning. Otherwise, VFR conditions will prevail. 5-10 knot
NNE winds will become variable overnight. Winds will remain light/
variable through the day on Sunday.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...LOCKHART
LONG TERM...AW
AVIATION...VINCENT
Area Forecast Discussion
National Weather Service North Platte NE
616 PM CDT Sat Jul 31 2021
.SHORT TERM...(This evening through Sunday night)
Issued at 347 PM CDT Sat Jul 31 202147
The HRRR near-surface smoke forecast indicates the smoke across
wrn and ncntl Nebraska will continue moving south tonight and
should be south of the region Sunday morning. Satellite and sfc
obs across ND and MN show areas of smoke but visibility is
generally 5 miles or greater according to the observations. This
smoke could be partially or mostly aloft so no areas of smoke are
included in the forecast across wrn and ncntl Nebraska Sunday.
A fairly broad area of Canadian sfc high pressure across Manitoba
and Saskatchewan this afternoon will build south and be located
across the upper Midwest by Monday morning. This high pressure
should back into wrn and ncntl Nebraska presenting cooler
temperatures and a continued decrease in humidity. By Sunday
morning, dew points could be in the upper 40s to mid 50s and they
will continue to remain steady or slowly fall Sunday and Sunday
night.
The temperature forecast leans on the cooler short term model blend
plus bias correction. This suggested lows in the 50s tonight and
Sunday night with highs in the 80s Sunday. This forecast factors in
the effects of smoke aloft which could keep high temperatures a few
degrees cooler than the very warm MET and MAV guidance which suggest
highs closer to 90. The official forecast is close to the cooler
ECM guidance.
The MCV and isolated shower activity across swrn Nebraska this
afternoon should move south into KS by late evening. Isolated
showers are in place along and south of Interstate 80 for a few
hours this evening.
.LONG TERM...(Monday through Saturday)
Issued at 329 PM CDT Sat Jul 31 2021
The models are in good agreement showing an upper level ridge of
high pressure across the Rockies this afternoon. The models will
carry the associated subtropical moisture west away from Nebraska
Sunday through Tuesday presenting dry weather conditions. The
moisture plume will return Wednesday with an attendant warm front.
This would probably be the best chance for thunderstorms next
week. By this time the upper level ridge has flattened and winds
aloft have become more zonal. A second wave of moisture will move
through Friday. Oddly, the blended model forecast, including WPC,
suggested little or no rainfall on these days or any of the next 7
days, for that matter. Later forecasts will need to be examined
to determine the rain chances next week.
Otherwise, highs in the 80s are in place Monday through Wednesday
and this is the result of Canadian high pressure across the Midwest.
An approaching long wave trof off the West Coast next week will
flatten the ridge and send warmer air across the Rockies and into
Nebraska Thursday through Saturday. Highs in the upper 80s and 90s
are in place during this time which is consistent with temperatures
at h700mb rising to 11C to 15C.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 614 PM CDT Sat Jul 31 2021
In the short term, MVFR conditions are expected due to smoke and
haze reducing VIS. Expecting this to clear and make way for VFR
conditions into the day tomorrow. Winds will be generally from the
northeast at the sfc, under 10 kts.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Sinclair
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
644 PM CDT Sat Jul 31 2021
.SHORT TERM...
206 PM CDT
Through Sunday...
Skies are a bit hazy this afternoon as some of the wildfire smoke
aloft is advected our way ahead of a cold front. Otherwise, the near
term attention grabber is an area of thunderstorms that have been
increasing in coverage across north-central Wisconsin this
afternoon. The storms are along and ahead of a cold front that is
working southeastward toward our area tonight. With some warming
ahead of the front and colder temperatures aloft in the northwest
flow aloft pattern, mixed layer CAPE approaching 1000 J/KG and some
lower end shear values should allow storms to continue this
afternoon.
By the time the front approaches, we will be past the heating of the
day which has had some influence on convective coverage to this
point. To that end, much of the near term guidance continues to
suggest that these storms will likely decrease in coverage this
evening and weaken or dissipate. Forecast soundings do depict skinny
CAPE values aloft hanging on into the evening hours. Current
thinking is there will be a few weakening showers or storms,
especially since guidance is a bit slow, and we may not decouple
if they arrive a bit quicker. Current timing is about 9 pm into
the Chicago area if they hold together. Afterwards, the front
should help clear out some of the hazy skies for Sunday.
Sunday will feature more sunshine, and we will have a reinforcing
shot of northeasterly winds and cooler dewpoint air. These winds
will again lead to a period of high swim risk conditions at southern
Lake Michigan beaches through Sunday evening. Highs will top out in
the 70s with afternoon wind gusts near 20 mph inland, making for a
somewhat seasonally cooler day.
KMD
&&
.LONG TERM...
243 PM CDT
Sunday Night through Saturday...
After the dangerous swimming conditions at the beaches on Sunday
night, there are no significant weather impact concerns through
next week. There`s just a few items of interest, starting off
with early season lake effect shower potential Sunday night into
Monday. Temperatures will start out below normal with comfortable
humidity levels and moderate back to around normal by mid week.
Signs are then pointing toward above normal warmth and higher
humidity returning next weekend.
850 mb temperatures over southern Lake Michigan will cool down to
9C or even slightly lower toward daybreak Monday. With lake
surface temperatures in the lower to mid 70s, this will yield a
respectable 850 to lake delta T of nearing 15C. Increasing lake
induced equilibrium levels (inversion heights) with several
hundred J/kg of CAPE and convergence should generate cloud cover
initially and then even some at least isolated to scattered shower
activity. Have some concern for isolated thunder, though well
above freezing level ELs are only brief and there`s a good amount
of mid-level dry air when parameters are maximized. The
convergence should shift to the southwest portion of the lake
overnight, with low PoPs added downwind into parts of northeast IL
and extreme northwest Indiana through Monday morning. Aside from
the lake effect, forecasting coolest overnight lows. in quite some
time of lower-mid 50s inland of lake effect clouds.
A short-wave pivoting in on the western flank of longwave
troughing over northeast North America will move overhead Monday
afternoon. As this occurs, the convergence axis from the lake
will be shifting inland. Expecting a fairly healthy Cu field due
to seasonably cool air mass aloft steepening lower level lapse
rates. Moisture profiles are fairly meager and ELs generally top
out near or below the freezing level, so while some
isolated/spotty showers are possible, think they would be on the
lighter side. Highs will be 5-10F below normal in primarily mid
70s (locally upper 70s) on Monday, with lower 70s lakeside due to
onshore flow.
Tuesday through Friday have dry forecasts in the official grids.
Can`t rule out some spotty shower/sprinkle activity at times.
However, think that splotchy afternoon-early evening QPF on some
of the guidance, especially from NCEP, is probably owing to
unrealistically high dew points (even when accounting for some
crop ET) and instability. Humidity levels will remain in check
likely through the work week as temperatures warm back to normal
low-mid 80s, so no dog days of August yet. Next week should
finally bring a return to very warm to hot and humid conditions,
with some variance on the magnitude of the warmth. Opening up of
moisture trajectories will allow for the aforementioned more humid
conditions and also potentially set the stage for a somewhat more
active stretch for the second half of next weekend into the
following work week. Low chances for showers/thunder return
Saturday-Saturday evening in the official forecast.
Castro
&&
.AVIATION...
For the 00Z TAFs...
Aviation Forecast Concerns:
* Isolated SHRA/TSRA over WI may spread into northern IL late this
evening, though low coverage/low probability for impact to any
particular terminal.
* Surface cold front moves through during the pre-dawn hours, with
wind shift to the north-northeast. Breezy northeast winds with
gusts 15-20 kt Sunday morning/midday.
* Hazy skies with smoke from western wildfires this
evening/tonight. Minor VFR vis restrictions possible.
Early evening surface map shows weak low pressure moving southeast
across Lake Huron, with a cold front west-southwest across north
central WI into northwest IA. Pool of mid-60s surface dew points
ahead of the front was producing some modest instability across WI
and northeast IA, where isolated to scattered TSRA have developed
this afternoon. While isolated SHRA/TSRA can`t completely be
ruled out for the forecast area later tonight as the front
approaches, the loss of diurnal heating/instability is expected to
result in decreasing coverage and intensity by the time the front
approaches late this evening/toward midnight (generally 03-06Z).
CAM guidance trends continue to favor a decreasing/weakening
scenario and thus will maintain dry TAFs, but will monitor for the
need to tactically add a VC mention later this evening.
The actual cold frontal boundary looks to move into northern IL
and across the terminals in the 07-10Z time frame, with a wind
shift to the north-northeast. Winds will likely become a bit gusty
(15-20 kts) after sunrise as cooler air pushes in with some patchy
MVFR cloud bases also possible. Winds should ease and lingering
cu/stratocu bases should rise to VFR in the afternoon.
Otherwise in the near term, GOES visible satellite imagery depicts
hazy conditions across the region associated with smoke from
western wildfires. HRRR near-surface smoke forecasts indicate this
will remain in the area into tonight, before north-northeasterly
winds clear things out tomorrow. A few sites upstream in eastern
IA were reporting some 4-6SM visibility restrictions, and its
possible the terminals may see some minor restrictions with low
level west winds ahead of the cold front this evening.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement...ILZ006-ILZ103-ILZ104...7 AM Sunday to
7 AM Monday.
IN...Beach Hazards Statement...INZ001-INZ002...7 AM Sunday to 7 AM
Monday.
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...7 AM Sunday to 7 AM Monday.
&&
$$
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Updated for 00Z Aviation Forecast Discussion below.
PREV DISCUSSION... /issued 348 PM CDT Sat Jul 31 2021/
DISCUSSION...
Another hot and humid day across the Mid-South. Temperatures are
mainly in the mid to upper 90s with dewpoints in the mid 70s.
Nearly every location in the Mid-South has a heat index of 105 or
greater at this hour, with a few locations at 110 or greater.
Current heat products look good with an expiration of 8PM this
evening.
Latest KNQA radar sweep shows a few isolated storms moving into
northern portions of our CWA. Storms have behaved themselves thus
far, with wind gusts mainly in the 35 to 45 mph range. These
storms are expected to weaken as they trek southeast into our area
over the next couple of hours. Behind this activity, there is a
cold front that will move into the area tonight. CAMs are
consistent with storms moving into our CWA around sundown and
persisting through the overnight hours. Activity will be confined
mainly to areas north of I-40.
The front will get hung up and stall near the Tennessee and
Mississippi border tomorrow afternoon. There will finally be a
generous push southward tomorrow afternoon, as an upper low drops
into the Ohio Valley and northwest flow develops across the region.
However, ahead of the front, heat will once again be a concern
for portions of north Mississippi. Went ahead and issued another
advisory for a row of counties in north Mississippi. Elsewhere,
high temperatures are only expected to climb into the low to mid
80s as north winds persist.
The front will finally push south tomorrow night. A few strong
storms are possible, especially over north Mississippi where the
highest instability is. Gusty winds are the main threat. Monday
will see a few lingering showers over north Mississippi, but most
the region will remain dry. Expect highs in the low to mid 80s and
comfortable humidity.
Tuesday through Thursday looks to be a beautiful stretch of
weather for the region, as an upper low remains overhead. Expect
highs in the mid 80s, low humidity, no rain, and north winds. A
few mornings could get chilly, yes I said it, with readings in the
upper 50s across rural parts of west Tennessee on Tuesday and
Wednesday. The rest of the region will see lows in the low to mid
50s.
Return flow and upper level ridging return to the region next
weekend. This will bring the return of summer conditions. Expect
increasing humidity and highs in the 90s.
AC3
&&
.AVIATION...
00Z TAFs
Surface cold front remains on track to drop into the Midsouth
overnight, most likely 09Z at MEM. Scattered SHRA/TSRA are
expected ahead of the cold front - which remains the primary
forecast challenge.
Just prior to 00Z, Isolated SHRA/TSRA were already noted on radar
60N of JBR, ahead of any of the CAM output. Storm chances at JBR
through 03Z- 04Z will depend on convective cold pool organization
ahead of the cold front over southeast MO. If this cold pool /
convective gust front can become organized, there will be TSRA
potential at MEM around 04Z. Otherwise, main TSRA window for MEM
will be associated with closer to cold frontal passage after 09Z.
PWB
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...Heat Advisory from 10 AM to 8 PM CDT Sunday for Calhoun-
Chickasaw-Coahoma-Monroe-Quitman-Tallahatchie-Yalobusha.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
735 PM EDT Sat Jul 31 2021
.SHORT TERM...(This evening through Sunday)
Issued at 224 PM EDT SAT JUL 31 2021
NW flow aloft continues today with a W to NW wind at the sfc across
Upper Michigan. There has been some haze and smoke across the Upper
Midwest today, including the wern half of the UP, which has limited
daytime highs a little bit. Temps are generally in the low to mid
70s across the west and half and 60s across the east where some
morning convection has kept cloud cover. Diurnal cu continues to
develop as daytime heating continues.
Heading into this evening, the latest RAP analysis shows a sfc trof
draped across the southern UP into northern WI as enhanced conv has
kicked off some thunderstorms west of Shawano. MLCAPE across the
central UP is around 500-1000J/kg and mostly confined to the central
UP with sfc Tds in the low 50s across the interior west. CAMs
continue to suggest some thunderstorm development along this sfc
trof into the evening hours, before drifting further south out of
the cwa by sunset. While a storm could latch on to this boundary, or
a subtle lake breeze boundary in Marquette County locally enhancing
the shear, bulk shear values remain around 35 knots, which isn`t too
conducive for severe storms. While I am not expecting any severe
storms this evening, any storms that do develop will have just a
slight chance of bcmg feisty.
The chance for any storms will wane quickly after 00Z as reinforcing
colder air behind a secondary cold front will shift south across the
UP. This will bring some light upslope showers and lower clouds
across the northern portion of Upper Michigan. By tomorrow morning,
daytime heating should lift out these clouds and cut off any
remaining showers early on. By the afternoon, stronger low-level
lapse rates behind the front will bring a chance for a few diurnal
showers across the central interior portions of the UP, but they
would be rather transient in nature. Left this chance out of the
fcst for now.
.LONG TERM...(Sunday night through Saturday)
Issued at 300 PM EDT SAT JUL 31 2021
A mostly quiet long-term period is expected. The large scale pattern
will initially continue to be dominated by western U.S. ridging and
eastern U.S. troughing. However by the middle of next week, a more
potent and more equatorward mid-level short wave will move onshore
into the West Coast and begin chipping away at the western CONUS
ridge. This means a transition to a more zonal pattern across Canada
and the northern tier of the CONUS, albeit with weak flow and
perforated by multiple short waves in the flow. There is a good
model consensus that one of these waves will reach the Upper Great
Lakes late Thursday. Its associated cold front may spark off some
showers and thunderstorms, although right now the QPF signal in the
GEFS and EPS is somewhat muted. The next wave to impact our area
looks like it will be the one that began breaking down the amplified
pattern over the West Coast. That one should reach the area by next
Saturday or Sunday. Although it`s still far out in time, there is
decent model consensus on the timing of this wave and front, and a
somewhat more robust QPF signal in the ensemble guidance.
We`ll start off the week cool with 850 mb temps only around 7-8 C
Sunday night and Monday morning. Therefore, look for lows in the 40s
interior and 50s along the lakeshores Sunday night. However by
Monday afternoon warmer air will be moving in aloft. Therefore,
we`ll be in a warming trend Monday through Thursday, with highs in
the upper 70s Monday and then in the low 80s Tuesday and mid 80s
Wednesday. On Tuesday, the models all suggest enough moisture and
instability returning for lake breeze showers and thunderstorms in
the afternoon over the central and south central U.P., albeit with
northerly shear that is very weak at generally only 15 kts or less.
Thursday looks like the warmest day of the week with GEFS and EPS
mean 850 mb temps climbing to around 17 C and 15 C, respectively. A
southwesterly LLJ out ahead of the wave will make for a breezy day
with additional downslope warming in the favored downslope areas and
no Lake Superior lake breeze. Look for highs in the mid to perhaps
upper 80s. As for precip chances with the front, that remains a
question. The 06z and 12z deterministic GFS runs both have precip
only making it into the western U.P. before drying up, and the
deterministic EC is similarly bearish. With the front in the area,
however, it`s probably best to hold onto the chance POPs the NBM
populated with.
There will hardly be any cooldown behind the front, with temps on
Friday still expected to be in the low 80s. On Saturday, as that
stronger wave approaches from the west, the LLJ ahead of it will
pump moisture northward into the area leading to a hot and sticky
feel with highs in the mid 80s and dew points in the low to mid 60s.
When the wave and cold front reach the area, most likely Saturday
night, that heat and moisture could set the stage for thunderstorms
for much of the area. However with it still being 7 days out there`s
still plenty of time for things to change, so won`t get too caught
up in the details at this point.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 735 PM EDT SAT JUL 31 2021
Mainly VFR conditions will continue though the evening hours. A cold
front is passing through the area early this evening accompanied by
isolated showers and thunderstorms, mainly south of the TAF sites.
By morning upslope flow proceeding the front will result in MVFR
CIGs from KSAW to KIWD along with a few showers around KSAW.
Ceilings should lift by mid-afternoon with daytime heating tomorrow.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 224 PM EDT SAT JUL 31 2021
Reinforcing colder air behind a cold front tonight will bring an
increase in winds from the N to NW across Lake Superior. A few gusts
could approach 30 knots across the central portions of the lake,
otherwise most locations will see winds gusting around 25 knots.
Winds will remain generally light through the rest of the fcst
period, with brief SW winds across the west/central approaching 20
knots Monday night.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JAW
LONG TERM...RJC
AVIATION...NL
MARINE...JAW
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Morristown TN
944 PM EDT Sat Jul 31 2021
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
The main change for the update will be to increase PoPs for
central areas overnight.
A cluster of thunderstorms has developed quickly over northern
Middle TN, tracking E-SE. Projecting its speed forward, it should
arrive at our Plateau counties around midnight. Although it will
be encountering a less favorable environment with lower MUCAPE, the
HRRR shows that should hold together enough to warrant high
chance to likely PoPs in the 05-11Z time frame. A threat of gusty
winds and hail cannot be ruled out due to decent 0-6 km shear,
but with low CAPE that threat appears marginal at best.
DGS
&&
.AVIATION...
00Z TAF DISCUSSION.
Over the next few hours, haze will be an issue at TYS, reducing
vis to around 6SM. Later tonight, an area of showers and
thunderstorms is expected to move into the area. Best estimate of
timing is between 09-15Z at all sites, and will mention as a
PROB30 as there is some uncertainty about whether it will hold
together or fall apart before arriving. MVFR conditions will
accompany storms, and cigs in that range may linger for a few
hours after that. VFR conditions should return by the afternoon.
DGS
&&
.PREV DISCUSSION...
/ISSUED 303 PM EDT Sat Jul 31 2021/
SHORT TERM...(Today through Sunday)...
Key Messages:
1. Warm and dry today, with rain chances increasing tonight and on
Sunday.
Discussion:
Deep nwly flow prevails this afternoon across East TN and southwest
VA/NC as broad longwave troughing highlights the upper pattern for
much of the central/east CONUS, while at the surface and old frontal
axis slows/stalls across central AL/GA, stretching westward into
West TN and the Lower OH Valley. With that, expected MCS
development is underway with convection tracking southeast across
the OH River into western KY over the next few hours, which will
eventually make its way as a decaying MCS into the TN Valley region
overnight. However, today the weather will remain rain free for all
areas with the primary highlights being hazy conditions consequent
of the fires out west, as well as rather warm temperatures (upper
80s to lower 90s) and mostly full insolation amidst light nwly flow.
Moving into tonight, the OH Valley MCS looks to advect southeast
across KY into the Middle/East TN after midnight. Guidance favors
some MLCAPE in the region (< 750j/kg) along/north of I40 where the
bulk of the CAMs take the remnant convection. However, instability
will be a bit high in the southern valley/plateau thus any western
flanking cells could survive or strengthen as the entire complex
dives southward. With that, will keep pops elevated after midnight,
highest chances north of 40, yet holding modest chances southward.
As for hazards, all in all shear is rather unimpressive (20-25kts 0-
6km) thus not expecting much in the way of organized convection,
other than along any cold pool propagation. Still though, won`t
rule out a few strong storms with the possibilty of gusty winds and
moderate/heavy rain at times.
As for Sunday, the day will kick off amidst the approach of a weak
frontal boundary from the north and remnant debris cu/stratocu from
the overnight convection across the TN Valley. This should slow
warming trends a bit into the afternoon hours with highs only
topping out in the low/mid 80s northward, upr 80s southward.
Meanwhile, broad ascent is favorable as the right entrance region of
the H3 jetmax shifts east across the Central Appalachians, which
should combine with the aforementioned frontal intrusion to foster
additional convection in the afternoon hours, mainly east of
interstate 75. Therefore pops reflect such with low chances
westward, high chances to low likely pops eastward. As is the case
overnight tonight, flow on Sunday will be rather unidirectional
through the profile, however slightly stronger. This combined with
more favorable diurnal timing suggests the possibility for deeper
updrafts, however still thinking widespread organized strong/severe
convection chances are low.
CDG
LONG TERM...(Sunday night through Saturday)...
Key Messages:
1. Near to below normal temperatures expected Monday through
Thursday with chances of showers and thunderstorms mainly confined
to far eastern portions of the forecast area.
2. Slight warming trend Friday and Saturday with temperatures back
to near normal.
Discussion:
Ensemble and deterministic guidance sources are still in great
agreement through much of the extended in showing a mid-upper level
trough remaining over the eastern CONUS. At the surface, we will be
between high pressure to our north and west and lower pressure
riding along the gulf coast. We will remain locked in the base of
this troughing through the latter portions of the week with several
impulses diving out of the midwest reinforcing the cooler weather
expected. Lower pressure to the south will generally keep low-level
flow out of the north and east through mid/late week keeping low-
level temperatures cooler (850mb T`s in the middle teens),
translating to high temperatures in the low to mid 80`s. High
pressure begins to lift into the Northeast allowing flow to veer
toward the south. Increasing thickness in response to warm air
advection will begin a slight warming trend on Friday lasting
through the weekend with temperatures rebounding to near normal.
While the region will remain in the base of deep layer troughing
through the period, low pressure to the south and a northerly low-
level wind will keep drier air across the area. Precipitation
chances will be confined to the eastern portions of the forecast
area. Wednesday and Thursday may provide the better chances of
coverage of showers and thunderstorms with a stronger impulse moving
across the Tennessee Valley. Yet still, the lack of deeper moisture
will keep PoPs capped at chance.
Diegan
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 73 89 68 86 66 / 50 50 20 20 10
Knoxville McGhee Tyson Airport, TN 69 84 66 86 64 / 60 50 10 10 10
Oak Ridge, TN 69 84 65 84 63 / 60 40 10 10 10
Tri Cities Airport, TN 66 82 61 83 62 / 60 50 10 10 20
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
Area Forecast Discussion
National Weather Service Reno NV
126 PM PDT Sat Jul 31 2021
.SYNOPSIS...
Daily thunderstorm chances are in the forecast through this weekend
with locally heavy rain. Winds generally light across the region,
except gusty in and around thunderstorms. A drier southwest flow
will bring decreasing storm chances and a return to typical
afternoon breezes next week. Other than the milder weather this
weekend, temperatures will remain around average.
&&
.SHORT TERM...
Some showers and thunderstorms could continue across the Surprise
Valley into northwest NV as a weak mid-level trough and weak
cyclonic circulation swings into southeast Oregon. The most recent
round of GOES-West imagery shows extensive cloud cover north of Lake
Tahoe generally moving northward over northeastern CA/northern NV.
South of Lake Tahoe a break in the overall cloud cover extends along
the central Sierra to another large batch of mid-level monsoonal
moisture working its way northwest into the southern Sierra Front
from SOCAL/southern NV. The continued moistening of the mid and
high-layer regions will maintain PWAT mostly 0.90" to 1.0 plus over
the region as storm development takes advantage of local heating and
heightened energy. Stronger more moisture laden storms should remain
for the most part south of US 50 this afternoon. But this line will
advance north to I80 and east to US95 going into the evening as
storm cells move off complex terrain of the eastern Sierra into
basin areas of western NV.
Stronger storm cells capable of much higher rainfall rates
sufficient for localized flash flooding could cause debris flows on
area burn scars and rock/mud slides in areas of steep terrain. The
highest probability for flash floods still appear to be from Mono
County to southern Lyon-Mineral Counties, so the current flash flood
watch has been expanded to cover the Numbers and Tamarack burn scars
in that area. Storm coverage for the northern Sierra (Plumas to Lake
Tahoe) and northern Sierra Front should be more isolated as Hi-Res
CAM guidance predicts a bit drier-stable conditions in the wake
of the mid-level shortwave that just exited to the north into OR.
So flood concerns will remain in those southern areas.
For Sunday, plenty of moisture remains over the region for storm
production with instability enhanced by increased boundary layer
heating that partners with the reduction of cloud coverage over the
region. Another upper trough digging into the west coast will shoot
energy into the increased upper flow and further elevate forcing,
instability, and shear over the region. Added to this mix is a weak
zephyr churning up to the lee of the Sierra that could enhance low
level convergence/focus. These combined elements could produce more
robust storm cores capable of strong outflow winds(40+ mph), small
hail, and heavier rain rates. As storms initiate along the eastern
Sierra in the afternoon, they will push off into the desert basin
areas of western NV and continue into the evening.
By Monday, other than a slight chance of thunderstorms near the
Oregon border and Mono-Mineral Counties in the afternoon, the
atmosphere will be much drier and too stable for widespread storms
as the upper flow increases from the southwest. A few shallow
buildups may occur along a weak zephyr developing later in the
afternoon. Monday will be greeted much clearer skies and abundant
daytime sunshine. Afternoon temperatures will quickly rebound to
more normal summertime heat as the cooler temps this weekend become
a brief footnote in history. -Amanda
.LONG TERM...Tuesday through Friday.
Tuesday will usher in the return of a drier-more stable summer like
weather pattern. High pressure up to now mostly centered over the
southern Rockies/Four-Corners region will retrograde west and settle
over the southwestern deserts (SOCAL/SRN NV/WRN AZ) An upper ridge
axis will extend north-south over the Great Region and increase a
southwest upper flow over CA-NV. Ensemble model guidance shows this
upper pattern persisting into next week as the upper ridge axis
tilts more positive in response to a deepening long-wave trough over
the eastern Pacific. Monsoonal moisture will once again be confined
mostly over the Four-Corners through this forecast period. Except
for the eastward directed shot of energy escorted by an upper trough
lifting into northern CA and western NV Wed-Thurs, the region should
remain mostly dry with near to slightly above average temperatures
through the extended period. This will yield more typical summertime
temperatures in the mid-90s for the valleys and a return to our
typical zephyr wind pattern.
But lets talk a bit about the nuisance shot of energy moving across
the region mid-week of the extended period. A shortwave trough will
approach CA Wednesday and lift northeast across the northern Sierra
and northwest NV later that evening. Forecast soundings show little
decoupling of the winds with the surface layer going into the
overnight hours. Higher elevation areas north of Lake Tahoe across
Lassen and Washoe counties could see gusty conditions lasting into
the early morning hours Thursday. Higher uncertainty follows this
scenario this far out into the extended forecast period. Therefore
new fire starts remain a reasonable possibility as elevated fire
weather concerns increase by the middle of next week. A more in-
depth discussion is included in the Fire WX section. -Amanda
&&
.AVIATION...
Showers and thunderstorms will be the primary impact through the
weekend as monsoon moisture remains across the Sierra and western
Nevada. There will be more cloud cover today as well as showers
along with embedded thunderstorms for the afternoon into the
evening. Best chances for showers and thunderstorms will be in
Mono/Mineral counties (KHTH-KMMH), with a few isolated storms
possible in far NW Nevada near the Oregon border. Terminals in far
wester Nevada will see a bit of a west wind kick up this afternoon
with 15 - 20 kt gusts possible, which may help to limit the
potential for showers/thunderstorms, especially at KRNO. For Sunday,
clearer skies in the morning along with enhanced mid-level shear
could result in a few stronger thunderstorms.
Main aviation hazards today will be periods of moderate to heavy
rain with reduced CIGS/VIS, terrain obscuration, and gusty erratic
winds. For Sunday, the hazards will also include small to moderate
sized hail and a higher potential for strong gusty outflow winds.
-Edan
&&
.FIRE WEATHER...
Thunderstorms with heavy rain and gusty outflow winds for the
afternoons and evenings are in the forecast through Sunday. There is
still some potential for widespread showers today with minimal
lightning activity. HRRR simulations are showing decent potential
for thunderstorms to initiate along the Sierra for the afternoon.
Areas north of Interstate 80 are still cloud-covered, so convection
in those areas may be hard to come by. Areas of most concern will be
recent burn scars, especially south of Highway 50. The Tamarack did
have some debris flows and runoff yesterday after the heavy rains.
As soils become more saturated from rainfall through the weekend,
mud and debris may more readily come loose and impact roadways and
fire operations. Plan on another round of wet storms for today as
well as Sunday, especially from the eastern Sierra into western NV
as low pressure nears the California coast.
The stable and drier southwest flow will push into western NV and
the Sierra late by Monday with our more typical afternoon and
evening breezes of 25-30 mph returning to kick off the week.
Simulations continue to highlight gusty winds for Wednesday as a low
pressure approaches the west coast. Latest simulations continue to
highlight the peak ridge winds arriving Wednesday night into early
Thursday morning. Plan on breezier than usual conditions starting
Wednesday afternoon and persisting into Thursday with the potential
for any holdover fires to become active. -Edan
&&
.REV Watches/Warnings/Advisories...
NV...Flash Flood Watch until 11 PM PDT this evening NVZ001>003.
CA...Flash Flood Watch until 11 PM PDT this evening CAZ072-073.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Riverton WY
952 PM MDT Sat Jul 31 2021
.UPDATE...
Issued at 816 PM MDT Sat Jul 31 2021
The flash flood watch has been cancelled based on radar trends,
and high resolution models showing little if any significant
convection over the next few hours. Did have some flooding in the
Kemmerer and Diamondville area earlier this evening.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 316 PM MDT Sat Jul 31 2021
Satellite shows the smoke plume that has been over the area for
several days to be in a northwest to southeast orientation across
the central portions of the state. This should continue to keep
hazy conditions across much of the state today.
Look for monsoonal moisture to continue for the afternoon with
dewpoints into the 50s and 60s. Current radar shows storms focused
over southwestern Wyoming, and this is where most lightning will
be this afternoon. SPC Mesoanalysis shows an area of 1 inch of PW
centered over central portions of the area with the rest of the
area from about 0.7 inches to 1 inch. MUCAPE values range in the
400-600 range as of 21z. There is a sharp cutoff over the eastern
and northern parts of the state due to drier air entering here.
Strong to severe storms with large hail or damaging winds does
not look to be an issue as there is very little shear through the
atmospheric column. With steering winds being rather light,
storms look to be slow moving, making heavy rain and flash
flooding the primary concern through this evening, mainly west of
the Divide.
For tonight storms look to diminish, but the HRRR shows
precipitation lingering along the western and southern borders
until around 04Z.
For tomorrow (Sunday), an elongated ridge axis will be over
Wyoming. This allows for southerly winds to transport monsoonal
moisture to areas west of the Divide. Far southwestern Wyoming
and the Salt and Wyoming Ranges appear to be the locations most
likely to receive additional rain with afternoon thunderstorms.
Areas east of the Divide should be significantly drier. Dewpoints
are expected to be about 10 degrees lower than yesterday for much
of the area with readings in the upper 30s for the central basins
to lower 50s in western valleys. The combination of the lower
dewpoints and drier air should aid in bringing temperatures up a
few degrees tomorrow afternoon.
.LONG TERM...(Monday through Saturday)
Issued at 316 PM MDT Sat Jul 31 2021
An amplified but narrow longwave ridge sits over the Intermountain
West Monday. Within this larger feature a shortwave trough is
expected to slide eastward through the ridge, with its axis
remaining west of Wyoming. Models have been consistent in depicting
this feature over the past several runs. Lift from this mesoscale
feature aids in shower and afternoon thunderstorm development over
and near the terrain features on the western edge of the state. The
drier air in place east of the Divide allows high temperatures to
increase to near seasonal normals.
On Tuesday the slow-moving shortwave moves far enough east to
encourage afternoon convective development east of the Divide. More
widespread clouds, showers, and thunderstorms are forecast Tuesday
afternoon, and this will keep highs 5 to 8 degrees below average.
Surface winds remain light, but in the vicinity of thunderstorms
gusts 30 to 40 mph are still possible.
A drier period begins Wednesday as the upper level ridge reasserts
itself. Heights rise and monsoonal moisture is shunted off to the
southeast. After the cooler Tuesday, Wednesday afternoon highs again
rise to near normal. A well-defined shortwave trough pushes into the
western CONUS Thursday into Friday, and forcing from this wave puts
scattered afternoon thunderstorms in the forecast again. In addition
to storms, the pressure gradient will tighten ahead of the cold
front associated with this wave, so expect breezier conditions
for the end of the workweek.
&&
.AVIATION...06Z Issuance
Showers and thunderstorms should end overnight. VFR conditions
should prevail for the most part through the period. With monsoonal
moisture retreating to the west chances of showers and thunderstorms
should be confined to the western TAF sites, especially KJAC.
However, even here coverage will be much more isolated then the past
couple of days. There is a chance that VCFG may form in areas that
saw rain, but not enough confidence to include in the forecast.
&&
.FIRE WEATHER...
Issued AT 1145 AM MDT Sat Jul 31 2021
Monsoonal moisture is expected to be over the area today, but
showers and thunderstorms do not look to be as widespread as
recent days, mainly staying west of the Divide. The best
possibility for precipitation tomorrow (Sunday) is also west of
the Divide. Shower and thunderstorm chances increase area-wide
Monday as a weak weather system moves through.
Relative humidity levels are expected to stay well above critical
thresholds throughout early next week. Today looks to have the
highest values due to high dew points in the surface layer. For
tomorrow, humidity is highest west of the Divide. Winds look to
stay mainly under 10 to 15 mph through early next week, with
higher gusts of 25 to 35 mph near showers or thunderstorms.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
UPDATE...Murrell
SHORT TERM...Clayton
LONG TERM...VandenBoogart
AVIATION...Hattings
FIRE WEATHER...Clayton
Area Forecast Discussion
National Weather Service Blacksburg VA
1102 PM EDT Sat Jul 31 2021
.SYNOPSIS...
Low pressure and a wavy cold front will remain over the Carolinas
through Sunday leading to showers and thunderstorms for the region
late tonight and Sunday morning. After a dry day on Monday,
rain returns Tuesday along with cooler temperatures as the front
stalls from eastern Virginia through Georgia.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 1100 PM EDT Saturday...
...Limited Threat for Showers/Thunderstorms Late Tonight/Early
Sunday, Otherwise Chance for Showers Tonight/Sunday...
Made some more adjustments to the pops overnight to reflect
current and model trends. HRRR seems to be doing better than
NAMNest at the current time, but trended more toward NAMNest
later tonight. SPC has removed the severe threat from all except
the extreme eastern parts of the CWA and shifted the general
thunder mainly east of a LYH-DAN line as well. I am in agreement
with this. As noted earlier, think main threat for
thunder/severe is east of our CWA closer to the I-95 corridor.
Earlier Near Term Discussion from 750 PM EDT...
What is left of an MCS earlier in KY is nothing now but an area
of mid/high clouds and a few sprinkles/light showers tracking
across the northern parts of our CWA and expanding into
central/northern VA. P6SM -RA noted at LWB and here at our
office BCB/RNK within the last few hours. Removed thunder from
grids for this evening as the air mass is very stable and latest
analysis shows very limited CAPE and downslope westerly winds
across the region this evening. Extensive mid/high clouds from
dissipating MCS have left the CWA with even more stable
conditions and little to no CU observed across the region this
evening.
For the overnight hours, personally am not impressed with the
threat for severe weather in our CWA. With the exception of the
NAMNest, significant convection developing late tonight/early
Sunday generally starts up after 12Z and is just east of our
CWA. Granted helicity/shear is impressive for August 1st, but
timing is very poor and CAPE is little to none at that hour
absent of a low level jet, which is not evident in the wind
field at all. In low-level winds are either light and variable
or southwest to west, not favorable at all. It is noted that the
NAMNest wants to develop stronger convection further west in the
08Z-12Z time frame and often this model is correct, so will need
to watch, but leaning toward the less agressive solutions of the
other models at this point given the lack of instability and
low-level wind field as noted above.
Severe threat ramps up quickly toward the I-95 corridor during
the late morning/early afternoon so there will likely be severe
weather in those areas and as noted a threat for a tornado or
two there, but again this should in all probability remain east
of the RNK CWA. By afternoon, we are left with
downslope/increasing westerly flow and little to no
precipitation.
Previous Near Term Discussion...
As of 230 PM EDT Saturday
Potential for severe thunderstorms in the far east late
tonight/early Sunday morning
Mid level speed max helping to spawn showers and thunderstorms across
the Ohio Valley is expected to drift across our forecast area late
tonight, increasing the upper level divergence over the region.
Meanwhile at the surface, surface winds across the VA/NC Piedmonts
have veered to the east/northeast and already starting to note an
increase in dew points in this area.
The short range deterministic models are in relatively good
agreement that a wave of low pressure along the frontal boundary to
our south lifts northeast across southeast VA between 09z-12Z Sunday
morning. This helps push higher CAPE values into far southeastern
portion of our forecast area, and with sfc winds from the southeast
in advance of this feature, SREF output is showing over 70% chance
of 0-1KM SR Helicity values exceeding 100 m/s2.
All of this suggests the potential for damaging winds and even
isolated tornadoes in the far east late tonight and the HWO was
updated to reflect this.
Otherwise, leaned toward the warmer guidance for lows tonight with
the increased cloud cover.
On Sunday, we transition to a deep west/northwest flow and early in
the day the best conditions for severe weather shift east of our
area. Upslope clouds will linger across the western slopes, but
skies should clear along and east of the Blue Ridge and as a result,
pushed up highs a couple of degrees on Sunday. Some widely scattered
showers and isolated thunderstorms are still possible with height
falls, with the highest POPS placed in the south, closer to the
stalled sfc front.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 200 PM EDT Saturday...
Cooler Than Normal Temps With Best Shower Threat Tuesday...
Models showing the front pushing southward Sunday night with things
drying out. Could see some lingering showers across the mountains
early Sunday evening.
High pressure at the surface builds east across the Mid-Atlantic by
Tuesday, while upper trough deepens. Another wave across the South
moves along the front Tuesday, and with upper trough sharpening,
moisture looks to build back north.
Latest models showing a slower trend to ramping pops up til Tuesday,
but even then models are in different camps on higher pop placement.
The 12z GFS is keeping deeper moisture south across southern and
eastern Carolinas, and the NAM is not too far off on this solution
but shows a better low level convergence axis over the mountains
south of WV. The 00z Euro has a moisture convergent axis extending
across southside VA into the Alleghanys, then all models pivot the
best threat over the southern and central Appalachians and eastern
NC in the afternoon. Have decided to curtail pops a bit, and lowered
them to low likely Tuesday afternoon over the far SW CWA with chance
pops elsewhere. Confidence is not high enough on where the higher
pops will be.
Thinking more cloud cover will keep temps a little cooler Tuesday,
so kept close to the previous forecast thinking with highs running
about 10 degrees below normal.
This should limit thunderstorm activity, and not expecting any
severe weather this period. Once wave accelerates east late Tuesday
should see decreasing pops.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 1224 PM EDT Saturday...
Daily Threat of Showers/Storms But Not Widespread...
Keeping chance of showers/storms through the period as upper trough
cannot move east far enough due to a strong ridge in the western
Atlantic. Appears the best zone for convection will stay southeast
of us along a front, but southwest flow at the mid levels should
allow for moisture to remain around, and with any subtle shortwaves
a daily threat for showers and storms will occur.
Did cut back on the what National Blend of Models had, and went with
a more diurnal max/min for pops with highest chances in the
afternoon/lowest in the mornings. The synoptic models are in similar
camps to this idea, so overall pops will be less than 50 percent,
with lower coverage/driest days looking like Thu-Fri.
Temperatures through the period should be just below normal, but
heights rising toward Saturday should push temps back to normal,
with above normal lows given moisture in the low levels.
Forecast confidence in the overall pattern is high, but in where it
rains is low.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
As of 755 PM EDT Saturday...
VFR Conditions Expected Through Most of the TAF Valid
Period...
Limited Threat for Showers/Thunderstorms Late Tonight/Sunday
Morning...
Extensive mid/high clouds spreading across the CWA at this hour
from a dissipating MCS that was in KY earlier today. Nothing
left of this MCS but BKN-OVC clouds with ceilings in the 080-150
range and a few sprinkles generally north of U.S. 460. VFR
conditions should continue throughout the evening at all TAF
sites. Low-level air mass is marginally moist with dewpoints
mostly in the upper 50s to lower 60s. Fog will not be an issue
this evening.
Overnight, a strong short wave will round the base of a
deepening eastern U.S. trough. Timing of this system brings it
through the CWA in the 07Z-15Z time frame from west to east.
Scattered showers will likely accompany the trough, but limited
deep moisture, downslope westerly flow ahead of and behind the
trough, and best dynamics remaining just east of the CWA do not
support widespread/definite SHRA/TSRA at the TAF sites at this
point. Will readdress later, but for now have only indicated
VCSH for LWB and BLF. As noted in the near term section above,
threat for thunderstorms and severe weather further east in our
CWA late tonight/early Sunday appears limited and have removed
mention of VCTS in the LYH and DAN TAFs. Not enough confidence
for such at 07-09Z in the morning to include at this point. Will
monitor closely for amendments as needed, but main threat for
TSRA should be further east toward a DCA-RIC-RDU line.
Once the trough moves through, look for west to west-northwest
winds at speeds of 6-12kts with low end gusts to 20kts west of
the Blue Ridge after daybreak Sunday. SCT-BKN CU/SC in the
030-040 range will likely persist, especially west of the Blue
Ridge until at least mid-afternoon Sunday.
/Confidence Levels in Forecast Parameters/
- Moderate to High Confidence in Ceilings,
- High Confidence in Visibilities,
- Moderate to High Confidence in Wind Direction and Speed,
- Low Confidence in Thunderstorm Potential.
Extended Aviation Discussion...
A secondary frontal; system arrives Sunday evening/night,
bringing a period of sub-VFR conditions mainly to western areas.
Monday will be dry with mostly VFR conditions. During the
remainder of the week, the region becomes sandwiched between a
plume of tropical moisture anchored just to our east and along
the coastal areas and a broad upper trough just to our west.
The result for our region will be unsettled conditions with
scattered largely diurnally driven showers and thunderstorms
increasing through midweek, decreasing somewhat by next weekend.
Periods of sub-VFR conditions can be expected and late
night/early morning fog will be on the increase as well.
However, there will still be substantial periods during the
daytime of VFR conditions.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...AMS/WP
NEAR TERM...PH/RAB
SHORT TERM...WP
LONG TERM...WP
AVIATION...RAB
Area Forecast Discussion
National Weather Service San Angelo TX
657 PM CDT Sat Jul 31 2021
...New AVIATION...
.SHORT TERM...
(This evening through Sunday)
Issued at 201 PM CDT Sat Jul 31 2021
At this hour, West Central Texas remains under an upper level ridge,
providing one last opportunity for relatively benign weather this
afternoon. Overnight, skies should remain clear with low
temperatures only in the mid 70s. By tomorrow morning, a shortwave
trough will rotate southward around the base of the main trough over
the Great Lakes. This should help to push a surface cold front into
our region by midday. While a few small showers are possible across
the Big Country in the morning, it appears the cap will erode by
early afternoon. This, along with some help from upper-level
dynamics moving into the area, should help to ignite more widespread
thunderstorms by late afternoon to early evening, which is supported
by both the HRRR and the NAMNest models. The main hazards for this
activity will be heavy rainfall and frequent lightning. Otherwise,
clouds should increase by early afternoon, with high temperatures
generally reaching the upper 80s to low 90s.
&&
.LONG TERM...
(Sunday night through next Saturday)
Issued at 245 PM CDT Sat Jul 31 2021
The upper level ridge which breaks down over our area will redevelop
over the southwestern CONUS in the first half of next week. An upper
trough will deepen over much of the eastern half of the country.
Associated cold front will continue to sag south across our area
Sunday night into Monday. Showers and thunderstorms will be likely
along and behind this front, with the more conentrated convective
activity closer to the front. With weak steering flow and a moist
airmass (precipitable water values 1.5 to 2 inches), heavy
rainfall will be possible with a threat for localized ponding of
water on roads/minor flooding. With increased cloud cover,
temperatures will be cooler Monday with highs expected to be in
the mid to upper 80s in most areas.
For Tuesday into Wednesday, the higher rain chances will be across
the southern part of our area along the I-10 corridor. That area
will be closer to a diffuse leftover surface boundary. Diurnally
driven isolated or widely scattered showers and thunderstorms will
be possible farther north across the central part of our area and
south of I-20. Daytime temperatures look to remain below normal with
highs Tuesday through Thursday in the upper 80s to lower 90s.
A weakness in the height field aloft will remain over our area late
in the week. Should have a continued possibility for isolated to
scattered diurnally driven showers and thunderstorms, over the
area mainly south of I-20. Indications are for temperatures to
increase by Friday and Saturday, with highs back into the 90s.
&&
.AVIATION...
(00Z TAFS)
Issued at 634 PM CDT Sat Jul 31 2021
VFR conditions will continue this evening and overnight across the
terminals. A cold front will move into the area on Sunday. Showers
and thunderstorms are possible along the front especially after
18Z. Have added VCTS to the TAFS to account for this possibility.
&&
.PRELIMINARY POINT TEMPS/POPS...
Abilene 77 90 70 88 / 10 60 70 50
San Angelo 75 95 70 87 / 10 60 70 60
Junction 74 96 71 90 / 5 60 60 70
Brownwood 75 95 71 89 / 5 60 70 60
Sweetwater 75 89 69 86 / 10 60 70 50
Ozona 75 94 71 86 / 5 60 60 60
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...SK
LONG TERM....19
AVIATION...42
Area Forecast Discussion
National Weather Service Tucson AZ
227 PM MST Sat Jul 31 2021
.SYNOPSIS...Isolated to scattered showers and thunderstorms continue
into this evening. The overall trend in thunderstorm coverage will
be less for most of next week and focused south and east of Tucson.
High temperatures will trend up to near or slightly above normal by
midweek. Better coverage of showers and thunderstorms is possible by
next weekend.
&&
.DISCUSSION...A few showers and thunderstorms have managed to
develop across the area early this afternoon, mainly over the higher
terrain. Some of the cu field, however, looks to be struggling for
any meaningful vertical development. This could be due to some
weaker mid-level lapse rates as noted via the SPC Mesoanalysis.
Otherwise, there seems to be plenty of instability to work with, as
SBCAPE values are in excess of 1500 J/kg for most of the area. What
seems to be generating these values are temperatures within a degree
or two compared to this time Friday, and dewpoints 2-6 degrees
higher. Satellite PWAT estimates continue to be sufficient, on the
order of 1.2" near the AZ/NM border up to around 1.8" across western
Pima and Pinal Counties. The storms that have formed are not moving
very quickly due to weak steering flow, and anvils seemed to be
getting sheared off above H3.
Convection should increase slightly through the afternoon, though
the latest HRRR run isn`t terribly excited and the U of A WRFs keep
activity mainly east of Tucson. However the NAMNest and other HREF
members are a bit more robust with precip continuing through the
evening and ending by about 01/03Z or 04Z. Threats remain the same
as they have in the past several days, with pockets of heavy
rainfall and gusty erratic winds associated with the strongest
storms. Additionally, the threat for flash flooding remains due to
soil saturation, so expect washes to be quick to react under the
heavier cores.
For Sunday, the upper ridge slides eastward a bit shunting moisture
into NM, resulting in thunderstorms remaining east of Tucson and
over the higher terrain. To start the new work week, high pressure
tries to establish itself to our south, gradually building and
migrating north/northwest through mid-week. We`ll see an increase in
daytime temperatures as this occurs, with the low-grade monsoon
conditions continuing. Later in the week into next weekend, there is
fairly good deterministic and ensemble model agreement that high
pressure reorients itself near the Four Corners as low pressure
rides over the top through the northern tier of the CONUS. Look for
deeper easterly flow to return to southeast AZ, and with it an
uptick in shower and thunderstorm coverage as our above-average
monsoon season continues.
&&
.AVIATION...Valid through 02/00Z.
SCT clouds at 8k-12k ft MSL (locally BKN) and SCT-BKN clouds AOA 18k
ft MSL thru 01/05Z, then decreasing clouds. FEW-SCT clouds at 9k-13k
ft MSL developing aft 01/17Z thru the end of the forecast period.
ISOLD-SCT SHRA/TSRA thru 01/05Z and then again aft 01/19Z. Strong,
gusty and erratic wind gusts with TSRA to 40 kts, heavy downpours,
and temporary MVFR CIGS/VSBYS. Outside of TSRA outflows, SFC wind
will generally remain less than 12 kts. Aviation discussion not
updated for TAF amendments.
&&
.FIRE WEATHER...Isolated to scattered showers and thunderstorms
are expected through Sunday, with a downward trend in storm activity
Monday through Wednesday when storm chances will mainly be east of
Tucson. An upswing in thunderstorm activity is expected going into
next weekend. Any thunderstorms that develop will be capable of
producing strong, gusty and erratic winds along with locally heavy
rainfall. RH values will remain well above critical thresholds the
next 7 days. After today, temperatures will be near normal through
at least Thursday. 20-foot winds will generally be less than 15 mph
when not influenced by thunderstorms.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None
&&
$$
Carpenter/Zell
Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Area Forecast Discussion
National Weather Service Las Vegas NV
1215 PM PDT Sat Jul 31 2021
.SYNOPSIS...Another round of thunderstorms in a high monsoonal
moisture environment is expected today, with a Flash Flood Watch
still in effect for much of the region through Sunday morning. After
another round of thunderstorms over eastern areas of the region on
Sunday, drier conditions are expected to move in the beginning of
next week and result in several days of drier and warmer conditions
through the week. &&
.SHORT TERM...Today and Tomorrow.
Convection has begun a little earlier today compared to yesterday
due to better morning clearing and extra support from a northward
progressing shortwave disturbance, both at the meso and synoptic
scales. This morning`s showers may have played a role in both
moistening and providing mid level vorticity to help kick things off
this morning as opposed to early in the afternoon. Additionally,
some UL divergence over the northern 2/3 of the CWA is kicking in
some lifting as well. This feature pushes north through the day with
an increasing UL jet positioned over the CO River Valley leaving the
region in a favorable location for UL support throughout the rest of
the day. Combine this added lifting feature with the very moist
environment still in place, topographic lifting, and thin but deep
instability, and another day of flash flooding continues for most
areas.
12Z HREF and latest runs of the HRRR show this activity waning by
nightfall, similar to the last several days of convection. Not sure
if this will indeed be the case with the aforementioned lifting
still in place by this evening, but we will indeed lose diurnal
heating and instability. Additionally, we will begin the downward
motion of PWAT as the Pacific shortwave comes onshore and advects
mid and upper level dry air into the western zones.
As previously mentioned, tomorrow will indeed see lesser overall
coverage of storms, favoring the eastern-most zones and areas, but
where enough moisture lingers for CI tomorrow, the added mid-level
dry air and cooling should enhance lapse rates, mid level dry air
entrainment into whatever updrafts develop, and more potential for
stronger downdrafts, maybe even hail. While the flash flood threat
stays more isolated in nature. Main areas of concern for these
threats will be along and east of a line from Hiko, NV to Wikieup,
AZ or mainly east of the HWY 93 corridor.
.LONG TERM...Next Week.
Not much change in the long term expectations. A lull in monsoonal
moisture is expected for much of the week and only a meager return
in PWAT values is expected by late week and the weekend. That being
said, trends continue to be on the drier side in the long range
ensembles and NBM as PoPs have decreased for Mohave county and are
now nil for the rest of the CWA over the weekend. Yesterday, cluster
analysis hinted at this possibility and looks like confidence is
gradually increasing that a more significant return of monsoonal
moisture may not occur over the next 8-14 days. CPC forecasts
indicate a slight favoring for below average precip during this time
frame as well.
What this drier forecast means is an uptick in potential high
temperatures and as such, heat risk values indeed increase mid week
briefly before moderating by late week. So above average
temperatures look to be the main story impact wise through next week
and possibly into the weekend should the drier forecast prevail.
&&
.AVIATION...For McCarran...SCT-BKN clouds mainly above 10kft AGL are
expected through the morning hours with thunderstorm activity on the
increase in the afternoon hours. Storms in the airport vicinity can
be expected mainly after 19z, with gusty and erratic winds likely
and brief heavy rainfall possible along with locally reduced CIGS to
near 8kft. Storm activity will gradually wane in the evening hours
with sct-bkn clouds lingering near 10kft AGL.
For the rest of southern Nevada, northwest Arizona and southeast
California...A few light morning showers can be expected across the
Mojave Desert with bkn-ovc skies around 10kft AGL near KDAG and KEED
through around 18z. Scattered thunderstorm activity will be on the
increase in the afternoon with storms first favoring the higher
terrain then gradually drifting into the adjacent valleys. Pockets
of sudden convective turbulence are likely along with locally gusty
surface winds. Storms will wane in the evening with SCT-BKN clouds
lingering between 8-12kft AGL.&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSIONS...TB3
AVIATION...Outler
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