Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/04/21
Area Forecast Discussion
National Weather Service Aberdeen SD
843 PM CDT Tue Aug 3 2021
.UPDATE...
Issued at 843 PM CDT Tue Aug 3 2021
Current forecast looks good. No updates needed at this time.
UPDATE Issued at 639 PM CDT Tue Aug 3 2021
00z aviation discussion updated below.
&&
.SHORT TERM...(This Evening through Wednesday Night)
Issued at 350 PM CDT Tue Aug 3 2021
Filtered sunshine from mostly lofted smoke continues this
afternoon - visibilities are now up to 8 miles or better across much
of the region. While there are still some 4 to 6 mile visibilities
across northeastern ND and central/northern Minnesota, the HRRR
Smoke model`s near sfc smoke output keeps this more impactful smoke
away given the southerly winds. These winds are out ahead of an
incoming shortwave/sfc trough. This feature has just enough
instability and moisture to work with to yield a few showers and
storms beginning tonight across portions of central SD, and then
through the day from west to east across the rest of the forecast
area. The majority of the area won`t see any precipitation, but
everyone will at least see an increase in cloud cover and some ever
so slightly cooler temperatures with highs in the 80s. Winds will
shift from the southeast to a more westerly direction with the
passage of this system as well. Finally, it`s possible that
additional smoke from Western US wildfires works in on Wednesday.
Dry weather is anticipated across the area by Thursday morning, with
lows generally in the low 60s.
.LONG TERM...(Thursday through Tuesday)
Issued at 350 PM CDT Tue Aug 3 2021
The long term portion of the forecast begins on Thursday with an
upper level trough crossing the region with showers and
thunderstorms possible, mainly in the eastern CWA. Ridging aloft
should spread over the region on Friday, with a trough crossing the
northern Rockies. The trough should progress across the region
Friday night and into the weekend, with a couple of rounds of
convection possible. With some instability, and perhaps good deep
layer shear at times, a few strong to severe storms could be
possible. Of note, the 12Z ECMWF and the 12Z GFS both show a trough
crossing the region, but are vastly different in timing and
placement of convection. Temperatures throughout the period will
favor above average. Early next week, the GFS is showing a potential
cool down with 700 mb temps dropping into the single digits above
0C, and 850 mb temps in the upper teens/low 20s. The ECMWF on the
other hands keeps temps near to above normal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 639 PM CDT Tue Aug 3 2021
Terminals KABR,KATY,KPIR,KMBG
VFR conditions are expected through tonight and Wednesday at all
airports. A short wave trough moving in from the west tonight and
Wednesday is expected to bring scattered high based showers and
storms to the region on Wednesday. PIR and MBG may be affected by
these at or in the vicinity.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Mohr
SHORT TERM...Lueck
LONG TERM...SD
AVIATION...Mohr
Area Forecast Discussion
National Weather Service Denver/Boulder CO
937 PM MDT Tue Aug 3 2021
.UPDATE...
Issued at 937 PM MDT Tue Aug 3 2021
Area radars are indicating mostly light rain still falling over
the mountains and foothills with a few areas of moderate rainfall.
There are isolated light rain showers over the plains currently as
well. Some new model data and high resolution model data are
indicating a continued decrease in the rainfall. Models also
indicated a bit of an increase in QPF late tonight into Wednesday
morning. Current GFE grids do show that. I will let the Flash
Flood Watch expire at 10 PM based on real data. Will make a few
cosmetic changes to the sky, temperature and pops GFE grids this
update.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 300 PM MDT Tue Aug 3 2021
Radar continues to show relatively weak convection across the
area. As of 300PM... the most vigorous convective growth has been
across the southern Foothills and Palmer Divide, and a few of the
more robust storms have produced up to about one to two inches of
rain in an hour. Convection should increase in coverage and
strength across the higher terrain over the next hour or two.
Satellite shows some clearing across Grand and Larimer county
which should aid in destabilization. The subtle mid-level
vortex/upper trough axis moving slowly across the mountains should
be enough to provide forcing for widespread thunderstorms into
the evening hours. Though confidence is lower than normal, the
overall pattern setup suggests the potential for heavy rainfall
over the high country, and thus we`ll continue the Flash Flood
Watch through 10PM.
For the urban corridor, we still don`t have a good answer to the
question "what about my backyard?" The last 6 runs of the HRRR
have shown very little consistency for the Denver metro into
Boulder county. Convection is gradually converging from the west,
south and east, with outflow starting to push out from the
stronger convective cores. I would expect at least some coverage
of storms reaching the metro by about 4 or 5 PM, with a few stronger
storms capable of dropping a quick inch of rain. Still, the odds
of seeing rain are close to the odds of a coin flip.
The trough axis will slowly drift east overnight and into
tomorrow, with showers continuing across a good chunk of our
forecast area. Models are latching on to a better chance of
showers tomorrow morning for the I-25 corridor and points to the
east as the trough axis moves through, but rainfall amounts will
generally be light. There should be gradual clearing through the
rest of the day with a few showers and storms possible in the
afternoon. Highs will be in the low to mid 80s for most of the
plains and in the 60s to 70s for the high country.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 236 PM MDT Tue Aug 3 2021
Wednesday evening, northeast Colorado could see a few lingering
showers then skies should be mostly clear overnight with lows
cooling down to the mid to upper 50s across the plains and upper
30s to mid 40s in the high country. Thursday will be warmer and
drier with low instability and probably at most just some isolated
convection over the high terrain in the afternoon. There is still
significant uncertainty involving temperatures Wednesday and
Thursday, but expect the peak of warming on Friday with high
temperatures back in the mid to upper 90s across the plains, upper
70s and lower 80s in the foothills and mountain valleys, and
upper 60s and lower 70s in the mountains.
Models are still showing another shortwave moving over the
Rockies late Friday through Saturday, in more zonal and increasing
flow aloft as the ridge flattens out. The forecast track has
shifted to the south but not far enough yet for a really
significant increase in vorticity and ascent over northeast
Colorado. There may be enough to support another round of
scattered storms and showers late Friday and early Saturday, with
enough moisture for some light precipitation. The timing of the
event is also somewhat uncertain and will affect the impacts. If
the wave was to advance a little more quickly to better coincide
with the afternoon peak of instability then there could be more
precipitation. Aside from the possible precipitation, increasing
and more zonal flow aloft should mean increasing winds in the high
country and some breezy conditions in the afternoon and evening
Friday and Saturday.
Saturday and Sunday should then return to drying and clearing as
heights rise again between the exiting shortwave and another
coming on shore over the Pacific Northwest. Models are still
showing this shortwave passing farther north with little impact
for Colorado, though that track is also trending slowly southward.
While there actually seems to be good model consensus on the
overall synoptic situation there are significant disagreements in
the details which will mean major differences in how the situation
develops for northeast Colorado early next week.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 937 PM MDT Tue Aug 3 2021
Northwesterly surface winds are in place at DIA currently. Models
do eventually show normal drainage patterns to kick in. Some of
the models do have this until 08Z. Radar pictures show some very
light sprinkles around the Denver metro area at this time. Will go
with a "VCSH" in the DEN TAF until 07 or 08Z. We could see some
sky conditions in the SCT-BKN060-080 range overnight.
&&
.HYDROLOGY...
Issued at 937 PM MDT Tue Aug 3 2021
I will allow the Flash Flood Watch to expire at 10 PM this
evening as the rainfall in mainly light and slowly decreasing
across the CWA.
Elevated flash flood threat will continue this evening and
early overnight hours, especially over the high country, southern
Foothills, and Palmer Divide. Locally heavy rainfall could cause
flash flooding with slow moving storms and above normal moisture.
The threat should decrease overnight and tomorrow. A limited
threat of flash flooding will continue tomorrow with scattered
thunderstorms over the higher terrain, but moisture and storm
coverage will be much lower compared to today.
The threat of burn area flash flooding should remain low through
early next week due to warm and dry conditions. Isolated to
scattered showers in the afternoons and evenings should produce
light precipitation.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 10 PM MDT this evening for COZ030>034-
037.
&&
$$
UPDATE.......RJK
SHORT TERM...Hiris
LONG TERM....EJD
AVIATION.....RJK
HYDROLOGY....RJK/EJD/Hiris
Area Forecast Discussion
National Weather Service Columbia SC
758 PM EDT Tue Aug 3 2021
.SYNOPSIS...
Drier air will push in on Wednesday and Thursday, confining
greatest rain chances to our eastern counties. By the weekend, a
more summer-like pattern is expected to take shape with daily
chances of thunderstorms and highs in the 90s.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Amplified upper trough over the Ohio/Tennessee valley moving
little overnight. Stationary front along the coast with ridge
across western Carolina. Widespread clouds expected to remain in
place with moisture trapped beneath the inversion as stratus
clouds should overspread the region which will limit radiational
cooling. However, continued northerly flow should allow for
some weak cool and dry advection over the forecast area and
expect lows to drop into the 60s. Based on latest radar trends,
HRRR and Rap guidance, lowered pops significantly across the
region overnight despite short wave trough currently over
Alabama expected to move through overnight.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
The eastern US trough is replaced by weak ridging aloft during
the short term. Have continued the overall trend of decreasing
precipitation chances for the CWA during the period, especially
for northern and western areas. Wednesday morning looks mainly
dry with only a few spotty showers expected. Chances increase
somewhat in the afternoon and evening with isolated showers and
thunderstorms passing through the forecast area though many
locations stay dry. PWATs are generally in the 1.25-1.75 inch
range with the highest values closer to the coast where the best
chance for convection will be. High temperatures remain below
normal and are mostly in the lower eighties though values could
be higher if we can get significant breaks in the cloud cover.
Wednesday night will be partly to mostly cloudy with isolated
showers possible, especially in eastern counties.
The forecast for Thursday is tricky as there is some model
disagreement regarding the timing of an area of low pressure
forming in the Northern Gulf of Mexico and riding along a
stationary boundary draped across the southeastern US. While
the GFS shows this feature passing through the region Friday
night into Saturday, the latest NAMNest is a full day faster and
develops scattered to widespread convection in the region on
Thursday. The NAM is similar in timing but not nearly as
bullish on rain chances in the CWA on Thursday. For now, the
forecast is leaning closer to the GFS given the expected
development of weak ridging aloft. This solution is similar to
Wednesday meaning that the best chance of precipitation will be
in southern and eastern portions of the CWA. This means that
most areas will likely see fewer clouds and therefore warmer
temperatures. Highs are forecast to be 2-4 degrees warmer than
Wednesday and generally in the mid-eighties. Thursday night is
similar to Wednesday night in terms of temperatures. Rain risks
will be dependent on the timing of the GOMEX low but are on the
lighter side for now.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
The long term period looks will eventually become much more of a
typical August summer like pattern. The NAM is the fastest with
the next s/w and pattern transition with the ECMWF the slowest.
However, it be a gradual transition through the weekend into
early next week. Some weak s/w riding will develop across the
Southeast ahead of the next s/w moving into the lower/mid MS
Valley Thursday night into early Friday. However, by Friday
afternoon into Saturday the region will be under the influence
of the s/w passing across the Southeast. Ahead of this feature,
PW plume is expected to surge back into the region on Friday
and create a favorable moisture regime for showers and
thunderstorms that will continue into Friday night. With PW
values increasing to 2+ inches across the Midlands and CSRA,
expect locally heavy rainfall with showers and thunderstorms
that develop during the afternoon and evening hours.
Temperatures are expected to moderate given the middle to upper
80s. Saturday will be similar, and coverage may be about the
same as the primary trough approaches the region. The threat for
severe weather is low, but the threat of locally heavy rainfall
and lightning will be the primary threats through the period.
By the end of the timeframe (Sun-Tues), ensemble and individual
models indicate 500 hPa ridging gradually building in from the
Atlantic. The Bermuda high is expected to build in at the
surface as well, leading to seasonal PWs remaining in the area.
With rising heights expected, highs will moderate to near and
slightly above normal values again (90-94F) NAEFS even indicates
500 hPa heights nearing the 90th percentile for this time of
year by Monday and Tuesday, so I may be a bit low on forecast
highs. With decent PWs, it won`t be hard to get afternoon
thunderstorms in this pattern so that should be expected as
well. Lows throughout the period will gradually moderate from
the upper 60s Friday morning to the low and mid 70s again by the
end of the period.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Stationary front along the coast and ridge across western
Carolina. Most of the precipitation has moved to the northeast
of the region. A short wave trough will move through overnight
but guidance is indicating little in the way of precipitation
with weak surface low along the coast moving to the northeast.
Extensive low clouds with widespread MVFR ceilings overnight.
The guidance is suggesting IFR or LIFR possible but most likely
at the OGB terminal especially 06z-12z. Ceilings will slowly
rise during the morning as an upper trough to the west moves
slowly east and deep moisture shifts to the northeast. By 18z-
19z expect mainly VFR strato-cumulus. A few showers possible
mainly in the afternoon but not expected to impact terminals
significantly. Winds will remain northeast 5 to 10 knots.
EXTENDED AVIATION OUTLOOK...An unsettled weather pattern will
remain in place for much of the extended. Expect at least a
chance of showers and thunderstorms each day.
&&
.HYDROLOGY...
Rainfall totals from early this morning into the early afternoon
hours of 2 to 4 inches across a good portion of the middle to
upper portion of the basin for the North Fork of the Edisto. The
forecast and gages along the N. Fork of the Edisto to Orangeburg
will need to monitored over the next few days. The river gage,
N. Fork of the Edisto above North is a good one to monitor
(NFES1).
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Cheyenne WY
950 PM MDT Tue Aug 3 2021
.UPDATE...
Issued at 946 PM MDT Tue Aug 3 2021
Went ahead and cancelled our Flash Flood Watch as WSR-88D radar
reflectivities continue to decrease as well as the areal coverage
of the showers. Looking at the most recent HRRR run continues to
show most showers ending by midnight, with some redevelopment of
showers over far eastern Wyoming and western Nebraska late tonight
as the slow moving shortwave trough aloft traverses to the east.
Gridded forecasts have been updated with adjusted coverage of
showers and modifications to the wind based on the 00Z model runs.
&&
.SHORT TERM...(This afternoon and evening)
Issued at 220 PM MDT Tue Aug 3 2021
Showers and thunderstorms that began late this morning continue to
develop early this afternoon over higher terrain of southeast
Wyoming. This monsoonal moisture sitting out ahead of a vort max
propagating through central CO is keeping anomalously high PW
values through tonight. 18z research sounding from Fort Collins
has PW exceeding 1 inch with a very moist profile conducive of
efficient rain processes. Additionally, winds do not exceed 10 kts
below the 200mb level which will contribute to slow moving storms
with long durations over select locations. With all these
considerations, the Flash Flood Watch which includes the Mullen
Burn Scar area remains in effect through midnight. Latest HRRR
guidance continues storm activity through late tonight including
multiple 1 hour periods with around 0.5 inch of QPF. Will
continue to monitor radar trends through the night for brief
periods of heavy rainfall along with slow moving thunderstorms.
.LONG TERM...(Wednesday through Monday)
Issued at 315 AM MDT Tue Aug 3 2021
Monsoon plume shifts further east Wednesday with good chances for
showers and storms east of the Laramie Range. That should be it
for a while as we turn drier after Wednesday. Monsoon moisture
drops south with upper ridging building in across western Wyoming.
Could be looking at critical fire weather conditions Thursday and
Friday as afternoon humidity drops to 15 percent or less. GFS
700mb winds increase above 25kts Friday afternoon across Carbon
County. so will likely need fire weather headlines out there
Friday. Still a little too early for any headlines at this time.
Really windy Saturday as GFS 700mb winds up to 50kts near
Arlington and over the south Laramie Range. We need to keep an eye
on this as wind headlines may be needed.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 628 PM MDT Tue Aug 3 2021
Wyoming TAFS...VFR. Occasional thunderstorms with gusts to
30 knots at Cheyenne until 01Z. Thunderstorms in the vicinity at
all terminals until 04Z. Wind gusts to 25 knots until 04Z, and to
23 knots at Rawlins and Cheyenne after 15Z Wednesday.
Nebraska TAFS...VFR. Areas of haze until 11Z. Thunderstorms in the
vicinity at Scottsbluff until 02Z. Wind gusts to 20 knots at
Scottsbluff and Sidney until 06Z.
&&
.FIRE WEATHER...
Issued at 220 PM MDT Tue Aug 3 2021
Minimal fire weather concerns mid-week with seasonable
temperatures and chances for wetting rain this afternoon and
evening. Warmer and drier weather will arrive late this week into
this weekend along with stronger winds along and west of the
Laramie Range. RHs will drop into the teens Friday continuing
through the weekend. Winds look to be strongest on Friday
afternoon with gusts to 40 MPH possible across much of Carbon Co.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...RUBIN
SHORT TERM...MB
LONG TERM...GCC
AVIATION...RUBIN
FIRE WEATHER...MB
Area Forecast Discussion
National Weather Service Des Moines IA
627 PM CDT Tue Aug 3 2021
.DISCUSSION.../Tonight through Tuesday/
Issued at 337 PM CDT Tue Aug 3 2021
Forecast Highlights:
-- Quiet, mild, and dry conditions continue through tomorrow.
-- Scattered showers and a few thunderstorms Thursday.
-- Warming temperatures into the weekend.
-- Better storm chances Saturday, but still some caveats to storm
potential.
TODAY AND TOMORROW:
Surface high pressure overhead today keeps the
quiet, dry and mild conditions in place over the area. As this high
will only gradually move eastward on Wednesday, similar conditions
with little threat for precipitation will persist through tomorrow
as well. High temperatures today and tomorrow will be below normal
for early August in the upper 70s to low 80s. The only other weather
phenomena of note for today and tomorrow is the continuation of
smoke transport into the area from western and Canadian wildfires.
The HRRR smoke products suggest patchy smoke will be in place aloft
over much of the area today and tomorrow with light concentrations
at the surface more likely over western Iowa today and northeastern
and northern Iowa into tomorrow, which could lead to some areas of
haze at the surface in those locations before conditions look to
improve into Thursday.
THURSDAY AND BEYOND:
Moisture returns to the area on Thursday in
tandem with a shortwave trough moving through the state. This will
bring the threat for scattered showers and a few thunderstorms
across the area on Thursday. Some recent model runs suggest stronger
CAPE values will be present on Thursday than previous runs, but
shear still appears to be weak and the system will be initially
fighting dry air.
A thermal ridge builds into the area behind the system with
southerly surface winds ushering WAA into the area and sending
temperatures towards the 90s on Friday and Saturday and into the 90s
on Sunday. Humidity will also be building into this weekend with
heat index values near to just above 100 on Sunday and again on
Monday as these warm and humid conditions look to persist into early
next week.
Along with the return of the heat into this weekend, storm chances
also increase again on Saturday. A surface low pressure will move
through Nebraska on Saturday with a surface boundary along the
leading edge. As this approaches the state on Saturday, it will be
riding a mid-level ridge, in combination with the surface boundary,
providing the forcing for strong to severe storms on Saturday.
Models still differ on timing and location for the greatest threat
of severe weather, but with deep shear over 35 knots and MLCAPE
values in the 1500 to 2000 J/kg range, we will definitely need to
keep an eye on Saturday as trends evolve. One possible caveat to the
threat of severe weather on Saturday would be the best shear appears
to be post-frontal, or not aligning with the warm, moist sector.
There also appears to be some potential for capping keeping an
additional question mark on the possibility for any surface-based
convection to form. We will continue to monitor and provide updates
in subsequent forecasts on this possible severe threat Saturday.
&&
.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 627 PM CDT Tue Aug 3 2021
With very light winds and mostly clear skies, no notable aviation
impacts are anticipated through the TAF period and beyond.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
DISCUSSION...KCM
AVIATION...Lee
Area Forecast Discussion
National Weather Service Grand Forks ND
1034 PM CDT Tue Aug 3 2021
.UPDATE...
Issued at 1034 PM CDT Tue Aug 3 2021
Weak showers/virga showers have been developing in western ND
over the last hour. Moisture transport vectors are rather weak
pointing into the area of development and not much of a LLJ
until after midnight. Latest HRRR does bring activity into
western zones by 08Z to 09Z. Will add slight chance west of Devils
Lake as dewpoints remain in the low 60s. Chances improve tomorrow
as instability increases ahead of the front.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 342 PM CDT Tue Aug 3 2021
Near term concerns are with lingering smoke and air quality
issues tonight into Wednesday. Then the short term transitions
into increasing convection from midday Wednesday into Wednesday
night.
Surface high pressure continues to push southeastward through IA
and away from the FA, with light south-southwesterly blayer flow
in its wake, leading to a recirculation of the trapped near
surface smoke layer. And aloft, a western NOAM H5 ridge has
leaned well into the Sask/Man border area bring a near northerly
flow aloft, and layered mid-level smoke.
The H5 ridge should begin to flatten overnight under the influence
of an approaching shortwave trof, while near surface southerly
flow will increase Wednesday morning into the afternoon as
surface low pressure digs into the central Dakotas. The overall
increasing southwesterly blayer flow and cooling air aloft should
help destabilize the airmass and both nudge our smoke layers
eastward and usher in scattered thunderstorm activity from
Wednesday afternoon into the evening hours. Scattered and brief
periods of light to moderate rain appear most likely with moderate
midafternoon CAPE values pushing into the 1000-1500 j/kg range,
though higher PWAT air expected over the southern RRV could result
in spotty /emphasis on spotty/ heavier rainfall areas.
Overnight low temperatures tonight should settle into the 60s,
while Wednesdays highs will rise into the mid to upper 80s.
.LONG TERM...(Thursday through Tuesday)
Issued at 342 PM CDT Tue Aug 3 2021
Overview...
An increasingly active pattern is progged to overtake the region
during the long term period. Increasing rain chances and slightly
above normal temperatures look to be the main impacts, with the best
opportunities for rain arriving over the weekend.
Thursday and Friday...
The end of the week should feature mostly quiet weather until the
next shortwave arrives late Friday into Saturday. An upper trough
will continue its southward journey from the Gulf of Alaska and work
to flatten the ridge aloft over the western CONUS. As a result, near
normal temperatures are expected for Thursday, along with the chance
to see a few spotty showers. Friday looks to remain relatively quiet
as well with slightly warmer highs. The aforementioned shortwave will
then introduce the next opportunity for rain late Friday into
Saturday.
The weekend into next week...
Moving into the weekend, the more active weather pattern looks to
ramp up as the upper trough will begin to trek eastward. A weak,
leading shortwave will initially introduce a chance for showers and
thunderstorms early Saturday. After this shortwave passes, modest
return flow should introduce more moisture to the area ahead of the
next wave, which is expected to move into the area Saturday evening
into Sunday. This should help to spark another round of showers and
thunderstorms during this time frame. Warm, above normal
temperatures are expected ahead of this second wave as well.
Finally, the main upper level trough is expected to traverse the
northern Plains on Sunday and will introduce yet another opportunity
for rain late Sunday into Monday. Moving into next week then, cooler
near normal temperatures look to settle into the area following the
shortwave parade.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1034 PM CDT Tue Aug 3 2021
GFK visibility has increased to 6SM and would not see any reason
for it to go back down other than this FU has been difficult to
forecast. Will keep 6SM as SW winds do set up and increase after
sunrise. CAVOK all other sites. DVL may see evening SHRA/TSRA
however not enough confidence in timing/location at this point to
add at DVL or the valley.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...Speicher
SHORT TERM...Gust
LONG TERM...Rick
AVIATION...Speicher
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1025 PM CDT Tue Aug 3 2021
.SHORT TERM...(This Evening through Wednesday)
Issued at 306 PM CDT Tue Aug 3 2021
Primary concern through Wednesday will be continued hazy skies due
to Canadian wildfire smoke. Surface visibility this afternoon has
improved to above 6SM in most areas and latest HRRR surface smoke
shows some additional improvement into tonight with lower
concentrations overall on Wednesday. For this reason, do not
anticipate many impacts at the surface through tomorrow, outside
of hazy skies from smoke aloft.
Surface pressure gradient on Wednesday will tighten in advance of
an approaching trough, allowing southerly winds to increase
somewhat with some afternoon gusts up to 25 mph. Overall,
temperatures will be similar to today...perhaps a degree or two
warmer, especially west of the I-29 corridor.
.LONG TERM...(Wednesday Night through Tuesday)
Issued at 306 PM CDT Tue Aug 3 2021
A weak short-wave in northwest flow aloft will drop across the
forecast area Wednesday night. Should be enough lift along the
surface trough to result in some scattered showers and
thunderstorms. Not a ton of moisture to work with, so rainfall
amounts not likely to exceed a quarter inch in any one area. Not
expecting severe weather with limited/skinny CAPE and weak shear.
Some lingering activity possible Thursday morning east of I-29,
but otherwise should see a gradual drying trend from west to east
through the day. Clearing skies and light westerly winds will
allow temperatures to rise into the mid 80s with some areas along
and west of the James River Valley reaching the lower 90s.
Short-wave 500 hPa ridging Friday will result in dry partly sunny
conditions. Temperatures will continue their upward trend with
afternoon highs peaking in the lower to mid 90s mainly along and
west of a line from Huron to Sioux Falls to Storm Lake.
The next threat for showers and thunderstorms will be late Friday
night into Saturday as Friday`s ridging gives way to a more potent
eastern Pacific wave. A bit too early to determine severe
potential, but an initial look at medium-range soundings suggest
modest CAPE, but still relatively weak shear. Something to keep an
eye on over the coming days.
500 hPa synoptic pattern diverges markedly Sunday and beyond between
12Z GFS/ECMWF with the potential for multiple waves within a more
trough-dominated regime. Difference in timing and strength of
waves leads to a low confidence forecast, but a blended solution
still favors more dry than wet conditions. Seasonably warm
temperatures appear to be the rule with daily highs in the mid 80s
to mid 90s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1024 PM CDT Tue Aug 3 2021
VFR through the period. Some patchy smoke is still expected around
the area. Scattered showers and isolated thunderstorms will be
possible after 0z/04 Wednesday evening.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...Rogers
LONG TERM...Rogers
AVIATION...08
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
638 PM CDT Tue Aug 3 2021
...Aviation Update...
.DISCUSSION...(This evening through Tuesday)
Issued at 403 PM CDT Tue Aug 3 2021
We`re gonna break things down into separate Short Term (first 36
hours) and Long Term (Thursday-Tuesday) sections here, but before
doing so here is a quick run-down of the two main stories of the
entire 7-day:
1) Another round of heat this weekend-early next week:
We`re still looking at 4-5 day stretch of solidly above normal
temps and at least moderately-high humidity (perhaps not as bad as
our last recent round), centered from Friday-Monday, but with
Sun-Mon currently looking like the overall "worst" two days in
terms of potential for (and greatest areal coverage of) heat index
100+ degrees. More on this in Long Term below.
2) Intermittent chances for thunderstorms:
Really four main windows of opportunity for convection in various
parts of the coverage area (CWA), starting as early as Wed
afternoon-evening and with other chances mainly focused Thursday
afternoon, Friday evening-Saturday night and finally Monday
evening-Tuesday (these latter chances way out in the Day 6-7 range
unsurprisingly being the most "iffy" of all. Although the risk for
severe storms appears relatively low with the Wed-Thurs chances
(not necessarily zero), there are at least early signs starting to
point toward Sat afternoon-evening perhaps being our "main"
threat for strong to potentially severe storms in the next week.
- SHORT TERM...this evening through Wed night/early Thurs AM:
Been another dry day across the area today, with upper air and
satellite data showing a continued well amplified pattern across the
CONUS. Flow over the region remains NNWrly, set up between low
pressure shifting through the Midwest/Great Lakes region and high
pressure anchored over the Desert SW. With little change in the
pattern, still seeing plenty of smoke aloft streaming south through
the region, keeping the hazy look to the sky even with
little/nothing in the way of clouds across our CWA. At the surface,
southeasterly winds remain, speeds have generally been around 10-15
MPH, but there have been occasional gusts of 20-25 MPH. Temps today
have worked out pretty well, 3 PM obs range from the lower-mid 80s
for most of south central NE to right around 90 in our far SW
corner.
For tonight, overall no notable changes were made the forecast,
which remains dry. Confidence in that dry forecast isn`t the
highest, mainly as we get closer to sunrise Wednesday for areas
roughly along the HWY 14 and HWY 81 corridors. Some of the hi-res
models showing enough subtle lift to result in the development of
some isolated/scattered sprinkles/showers. Not all models show this,
and it`s not out of the question it`d be little other than some
ACCAS...so decided not to put in the forecast, but it`ll be
something for the evening/mid crews to keep an eye on. Otherwise,
HRRR showing potential for another night with some lowered
visibilities late tonight/early Wed morning thanks to the smoke/haze
in the area, kept that mention going. Low temperatures are forecast
to drop into the low-mid 60s, with little change in the SSErly winds.
Looking to Wed-Wed night, chances for thunderstorms returns to the
forecast. Models aren`t in too bad of agreement, showing an mid-
upper level shortwave disturbance (currently working east through
the Rockies) emerging out onto the Plains early in the day.
Gradually pushes east through the day, moving into western portions
of our CWA late in the afternoon-evening. An accompanying weak sfc
boundary accompanies this disturbance, and at 00Z the general model
placement has it draped through the WNW third of the CWA. This
boundary is expected to serve as a focus for late afternoon
thunderstorm development, with chances pushing east during the
evening-overnight hours. Models vary some with just how widespread
activity is and how well things hold together through the overnight
hours, so overall PoPs remain in the 20-30% range, and do have them
CWA-wide. There is a pretty wide spread in some of the models with
the amount of instability along the front (NAM too high-GFS too
low)...thinking modest amounts around 1000-1500 j/kg are possible.
Agreement is much better that deeper layer shear will be low,
perhaps 20 kts. At this point thinking is that some strong storms
will be possible, but the threat for severe weather is low.
For elements outside of the precip chances, no notable changes were
made. Should see increasing cloud cover (skies likely to still be
hazy from smoke aloft), with gusty southerly winds ahead of this
approaching boundary (20-25 MPH). May be a couple degrees warmer in
a few spots, but overall highs still in the mid-80s across Neb and
upper 80s-near 90 across KS.
- LONG TERM...Thursday daytime through Tuesday:
Overview:
The vast majority of the main concerns of this 6-day period were
already touched on in the opening paragraphs above so will not
fully repeat here, but again they are: 1) Heat concerns mainly
Fri-Mon and currently expected to peak Sun-Mon (although there are
early signs that Tuesday may eventually need to be included as
well)...2) Three windows of opportunity for at least limited
thunderstorm activity (Thurs afternoon/Friday evening-Saturday
night/Monday evening-Tuesday). Although still far enough out in
time that uncertainty is very much in play, Saturday afternoon-
evening probably bears the most watching for a possible severe
threat.
Now going into a bit more detail and taking things in 24-hour
blocks, with greatest detail focused on Thurs-Fri...
Thursday daytime-night (small PM storm chances a "new twist"):
Right off the bat Thurs morning, our current forecast "assumes"
that any late Wednesday night convection will already be departed
east of our CWA by daybreak. However, this is not a sure thing
(NAM suggest it will be, latest 18Z HRRR still has it lingering in
eastern zones for a few more hours), so this will bear watching
although this activity would be very weak/non-severe. The overall
greater concern though is the possibility for at least isolated
storms to develop along a weak surface trough axis arriving into
our northern zones during the afternoon/peak heating period. This
is far from a "sure thing", but there is enough of a hint of it in
the 12z NAMNest (and to a lesser extent ECMWF) that this forecast
has introduced slight chances (PoPs) to much of the eastern half
of the CWA (primarily Neb counties) for the afternoon. Should
storms develop, this looks like a non-zero severe risk given
perhaps as much as around 2000 J/kg mixed-layer CAPE in play, but
somewhat modest deep layer shear around 30KT and fairly limited
large-scale forcing behind the Wed night shortwave trough could be
a limiting factor. Certainly a period to watch, especially
considering that our previous forecasts for Thurs were completely
dry. At least for now, left the evening-overnight periods void of
PoPs, but any late afternoon activity could linger into the first
part of the evening. Temperature-wise, little change in highs from
previous, with upper 80s most areas and some low-mid 90s mainly
far west-southwest. Lows Thursday night mainly mid 60s area-wide.
Friday-Fri night:
Odds are actually increasing that the vast majority of these 24
hours will be dry/storm-free (especially the daytime-evening
hours) as our area remains "in between" forcing in a shortwave
ridging regime. However, have some small PoPs across most of the
CWA for the late night hours to account for possible convection.
However, the main story Friday will be our first day of the
upcoming hotter stretch, with most areas aimed into the low-mid
90s and some upper 90s far southwest. Fortunately, heat index
values are currently expected to hold below 100 degrees.
Saturday-Sat night:
As mentioned a few times already, we will probably need to keep a
wary eye on the afternoon-evening hours for MAYBE a threat for at
least a few severe storms. For being 4+ days out, the latest
ECMWF/GFS are in decent agreement on swinging a modestly-strong
(for August anyway) shortwave trough across the Central Plains,
with at least a weak surface trough in play at the surface. Decent
instability should not be a problem given temps solidly in the
low-mid 90s (similar to Friday), although somewhat modest deep
layer shear only around 30KT may be a limiting factor to a more
robust/widespread threat. At the very least, a period to keep an
eye on, as although our PoPs remain pretty low at this time, they
were at least expanded to include more of the CWA than previous
forecast.
Sunday-Sun night:
For being 5 days out, we have fairly high confidence in the
continued dry forecast here, as our area resides under low-
amplitude ridging behind the departing Saturday disturbance. That
leaves building heat as the main concern. That being said, high
temps did trend down a few degrees from previous forecast, but
still widespread mid 90s most areas with upper 90s to low 100s far
southwest. Will need to keep an eye on trends for possible Heat
Advisory, but at least for now have max heat index values "only"
100-103 and highest values in far southern/southeast zones.
Monday-Mon night:
Forecast remains dry for the daytime hours, but some "iffy" small
Pops are in the overnight forecast (mainly per GFS). Opposite of
Sunday, this day has actually trended a few degrees warmer than
previous forecast and now has very similar temperature/heat index
expectations. Again, technically just short of Advisory criteria,
but plenty of time for this to change over the coming days.
Tuesday:
Some very "iffy" slight PoPs for the afternoon (again mainly per
GFS), but would not be a bit surprised to see it stay dry and for
heat to trend upward from our current, very preliminary forecast
that "only" has highs in the low 90s most areas. In fact, latest
ECMWF ensemble data suggests another day of widespread mid 90s.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday)
Issued at 625 PM CDT Tue Aug 3 2021
Other than smoke, skies are mostly clear across the area this
evening. Midlevel clouds and possibly a few sprinkles are expected
to develop early Wednesday morning, with additional showers and
weak thunderstorms pushing in from the west late Wednesday
afternoon.
Only threat to VFR conditions will be possible haze developing
again Wednesday morning with visibilities dipping to around 5SM.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
DISCUSSION...ADP/Pfannkuch
AVIATION...Mangels
Area Forecast Discussion
National Weather Service Green Bay WI
1041 PM CDT Tue Aug 3 2021
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Wednesday
Issued at 227 PM CDT Tue Aug 3 2021
Quiet weather continued into the afternoon hours across our
region, as smoke once more spread across northeast Wisconsin. The
shortwave trough continued across the region through the late
morning and early afternoon as well, but shower activity remained
limited, mainly due to the cooler than previously forecast
temperatures.
As we progress into the afternoon hours, the shortwave will
continue across the area, exiting sometime in the early evening.
Although the cooler start will greatly limit any shower and
thunder potential, low pops were kept in the far northeast and
lakeshore counties for any lake breeze interactions with the
shortwave as we approach peak heating. After the shortwave exits
however, the window for any active weather today will likely be
shut.
An upper ridge will then build into the region tonight and remain
in place through tomorrow, which will keep the area quiet and free
from active weather. Backed off on the temperatures for tomorrow
with the smoke still around, but only be a couple of degrees.
Highs are still expected to be in the 80s.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 227 PM CDT Tue Aug 3 2021
It appears an active pattern is shaping up as several upper level
disturbances and associated weak cold fronts will move across the
region into early next week. Temperatures should be close to
normal at the beginning of the period, then trend above normal
this weekend into early next week.
Dry conditions are expected Wednesday night into Thursday morning.
The next system approaches from the west Thursday afternoon. Model
trends continue to show a slower arrival of the showers and
storms. Trended toward the ECMWF model with bringing chances into
central and north-central Wisconsin. The chances of showers and
storms will spread eastward across the area Thursday night.
Instability and mid-level lapse rates not impressive, thus the
risk of severe storms is low. The 500mb trough will move across
the western Great Lakes region on Friday, bringing additional
chances of showers and thunderstorms.
Once the showers and storms end Friday night, there will be a
break in the rainfall Friday night into Saturday morning. There
is a great deal of uncertainty when precipitation chances arrive
this weekend. Storms are expected to form west of the area Friday
night and then weak and dissipate as they head towards the area.
More storms are expected to form Saturday afternoon and Saturday
night across Minnesota and western Wisconsin with the showers and
storms moving into the area late Saturday night into Sunday
morning. The ECMWF has a 500mb trough and associated shortwave
moving across the forecast area Sunday afternoon and Sunday night.
The risk of severe weather will be dependent on how much clearing
takes places from the morning storms, but the ECMWF has a robust
shortwave moving across the area that could trigger strong to
severe storms if we get some heating. 0-6km shear values increase
to 30 to 35 knots to support stronger storms if there is enough
instability. Did not make any changes beyond Sunday night.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1038 PM CDT Tue Aug 3 2021
Generally good flying conditions are expected throughout the TAF
period. The main weather concern continues to be smoke from
wildfires. Will continue to lean on the HRRR smoke forecast for
that. Conditions look a little less favorable for afternoon
Cu/Showers than today, so will maintain the dry forecast.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....Uhlmann
LONG TERM......Eckberg
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Grand Rapids MI
958 PM EDT Tue Aug 3 2021
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 228 PM EDT Tue Aug 3 2021
- Isolated showers and thunderstorms early this evening
- Risk for storms Friday into Monday
- Warming up for the weekend into early next week
&&
.UPDATE...
Issued at 957 PM EDT Tue Aug 3 2021
As expected the showers and thunderstorms, some with heavy
rainfall (over 1 inch in an hour) have dissipated with the setting
sun. So I have once again updated the forecast to reflect that.
I also added showers and thunderstorms to our forecast for
Wednesday afternoon in about the same place they happened today.
This idea is well supported by the SPC SREF which has a 20 percent
chance of thunderstorms north of route 20 after 21z Wednesday. The
HRRR 00z run also likes this. Model sounding loops show moisture
moving in the 700 to 500 mb layer (the 850 to 700 rh is already
fairly moist). Still there is not much forcing so I do have low
pops but it would seem showers and isolated storms would be
possible there Wednesday afternoon.
&&
.DISCUSSION...(This evening through next Tuesday)
Issued at 228 PM EDT Tue Aug 3 2021
- Isolated showers and thunderstorms early this evening
ML Cape values have risen up to around 250 to 500 J/kg mainly
north of a Grand Rapids to Mt Pleasant line. A few thunderstorms
have developed along and east of the lake breeze in this region.
They have been pulse in nature and will likely remain that way
given the low deep layer shear values. As we approach sunset the
convection will slowly diminish. We will continue to hold on the
low POPs for that region through the early evening hours.
- Risk for storms Friday into Monday
One low level jet moves in Thursday night into Friday. Elevated
instability starts showing up Friday. Meanwhile a series of weak
upper level troughs move through through this period. As the
moisture and instability increases through the period...so will
the risk for storms. The first trough arrives Friday and could
lead to a few storms. A second trough migrates through for later
Sunday into Monday. Diurnally driven showers and storms are
possible Saturday into Sunday...but the added lift from the second
trough may bump up the potential for Monday. Deep layer shear is
shown to remain relatively low so organized severe weather does
not look likely at this time.
- Warming up for the weekend into early next week
With a general west to southwest flow prevailing into early next
week...this will support climbing temperatures. Temps at 925/850
mb climb steadily Saturday into Tuesday. Above normal surface
temperatures are expected for this period. Based on the 925/850 mb
temps we should see highs in the mid 80s Saturday and upper 80s
for Sunday into Tuesday. There could even be a few values reaching
90. There are some indications that it will be even warmer for
the middle part of next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 707 PM EDT Tue Aug 3 2021
The storms that remain are weakening and mostly away from our TAF
sites. There is a chance the storm complex near Alma could reach
our LAN TAF site by 00z but I am fairly sure the storms will have
fallen apart by then. Likely there will be wind shift to the north
for an hour or so at LAN as the storm`s outflow reaches the LAN
TAF site but winds will remain under 10 knots so I did not show
the wind shift in their TAF.
Otherwise high pressure will remain over this area through
Wednesday. So expect skies to clear and winds to become light and
variable or calm by 02z or so.
On Wednesday winds will remain light and variable with a tendency
for a southwest wind around 5 knots the afternoon. Cumulus
clouds will develop tomorrow but they will not be able to develop
as nicely since since the air is drier above 800 mb tomorrow.
Still an isolated shower is not out of the question.
&&
.MARINE...
Issued at 228 PM EDT Tue Aug 3 2021
A low level jet moves in for Friday and that will cause the waves
to build. Right now we have values under criteria for
headlines...but this will need to be monitored closely. Then for
the second half of the weekend...another low level jet moves in
and could support waves building close to headline criteria.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...WDM
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...WDM
MARINE...MJS
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1201 AM EDT Wed Aug 4 2021
.UPDATE...
Issued at 1201 PM EDT TUE AUG 3 2021
A corridor of gradually weakening showers with embedded rumbles of
thunder continue to pass SSW-NNE across far eastern Kentucky.
Latest model suite generally shows this remaining nearly
stationary or propagating very slowly westward while diminishing
in coverage overnight. The RAP shows several hundred J/kg of
MUCAPE lingering through the night and have thus continued thunder
chances for the remainder of the night. Incorporated the latest
T, Td, Sky, and PoPs obs/trends into the grids.
UPDATE Issued at 852 PM EDT TUE AUG 3 2021
Slow-moving showers and storms have brought splotches of heavy
rainfall to far eastern Kentucky this afternoon and early evening.
Radar estimates suggest that a few locations have received 2.0 -
2.50 inches, relieving dry conditions for some. The lingering
activity is expected to gradually propagate further west toward
the center portions of the CWA later this evening but should
continue to diminish in coverage and intensity with the loss of
daytime heating. Those locations which saw rainfall today will see
quicker fog formation this evening and tonight. Freshened grids
with latest CAM trends and observations.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 330 PM EDT TUE AUG 3 2021
Latest analysis shows an upper level trough across the area with one
short wave moving across the area this afternoon into tonight, and
another wave is expected to move across the area Wednesday into
Wednesday night. At the surface, a stationary front remains over the
SE and deep south states, with multiple areas of low pressure along
the front. Areas of high pressure continue to our N/NW. It`s a
beautiful day across much of eastern KY this afternoon with partly
cloudy skies and temps in the upper 70s to around 80. There are
however some scattered showers and thunderstorms this afternoon over
far SE KY near the VA line. A surface boundary in the area, along
with higher dew points and PWATS will continue to allow scattered
storms to develop through this evening, especially over far E/SE KY.
Locally heavy rain is possible with some of these storms. This part
of KY has been the driest over the past couple weeks, so unless
multiple storms move over the same area in a short period of time or
a storm becomes anchored over an area for an extended period,
flooding is not anticipated. Pops diminish late tonight with just
isolated showers expected overnight into Wednesday morning. Forecast
soundings and hi-res guidance shows some low stratus forming over
far eastern KY for several hours Wednesday morning, otherwise partly
to mostly cloudy tonight with some patchy river valley fog
developing towards morning. Low temps tonight in the upper 50s to
lower 60s.
Additional scattered showers and storms are expected Wednesday,
especially during the afternoon and evening as the second shortwave
moves across the area. Surface boundary will drift a bit further
west, so expect a greater coverage area of storms compared to today.
Storms diminish after sunset and then partly cloudy and drier
conditions expected overnight into Thursday morning with some
typical river valley fog possible. High temps will continue to be
below normal on Wednesday ranging from the upper 70s to lower 80s.
Low temps Wednesday night in the upper 50s to lower 60s.
.LONG TERM...(Thursday through Tuesday)
Issued at 310 PM EDT TUE AUG 3 2021
We will see alternating periods of dry weather and small rain
chances through out the extended, as a series of ridges and
troughs progress across the region. Any rain chances we see will
still likely be meager at best, as the weather systems moving
through will not be all that strong. Isolated to scattered showers
and thunderstorms will be possible around the area from time to
time from late Friday through the first of next week, with periods
of dry weather expected Thursday through Friday morning, Sunday
night, and Monday night. As for temperatures in the extended, a
gradual warming trend is on tap. We will start things off with
highs in the low to mid 80s Thursday and Friday, and should see
highs ranging from the mid 80s to lower 90s from Saturday onward.
Nightly lows will be in the 60s, with the same warming trend
expected each night. We should see lows only falling into the
upper 60s by the end of the period, after starting off in the low
to mid 60s. Winds should be generally out of the south and fairly
light through out the extended.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 852 PM EDT TUE AUG 3 2021
With exception of far eastern KY, VFR conditions were observed at
the start of the 0Z TAF period. Scattered showers and storms have
impacted far eastern KY earlier this afternoon and evening,
resulting in patchy MVFR fog at KPBX and KSJS. Lingering
shower/storm activity is expected to very slowly propagate
westward and diminish overnight. Cloud cover will be variable
through the night, but there should enough cloud thinning/breaks
for river valley fog formation. More widespread fog and/or patchy
low stratus will occur in those locations which saw rainfall
earlier today. Expect MVFR conditions toward dawn at KSME, KJKL,
and KLOZ with IFR or lower at KSJS. Winds will be light and
variable through the night. Low stratus and fog will dissipate by
around 14Z and all locations should be VFR for the remainder of
the period outside of any heavier thunderstorms. Winds on
Wednesday will continue to be N/NE and light around 5 kts or less.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEERTSON
SHORT TERM...CMF
LONG TERM...AR
AVIATION...GEERTSON/CMF
Area Forecast Discussion
National Weather Service Key West FL
1000 PM EDT Tue Aug 3 2021
.DISCUSSION...
Radar is more active this evening versus yesterday with widely
scattered showers and thunderstorms north of the Keys across the
Gulf waters eastward to the southern part of the peninsula. This
activity has been developing along southward-moving outflow
boundaries from earlier storms across the eastern Gulf and central
Florida. Based on latest radar scans, have nudged up pops across
the Gulf waters and upper Keys slightly, and may need to bump them
up further over the upper Keys if current activity over Miami-
Dade County continues southward. However, atmosphere across the
lower and middle Keys is much drier than further north with a
PWAT of only 1.71 inches per latest KKEY sounding (versus 1.93
inches at KMIA) and substantial dry air aloft between 925-400mb.
Thus current convection should gradually diminish with time and
the further south it gets overnight, much like latest HRRR model
runs suggest. Temperatures remain quite warm at this hour and
range from the mid 80s to around 90, but lows in the low to mid
80s are still on track. Lows could be a tad cooler across the far
upper Keys if current shower and thunderstorm activity continues
moving southward into that area.
&&
.MARINE...
Special marine warnings are currently in effect for strong
thunderstorms over Florida Bay and the adjacent Gulf of Mexico
waters near Flamingo through 1015pm EDT. However, shower and
thunderstorm chances will remain less than normal, but increase
over the weekend into early next week. A surface ridge axis in
the vicinity of the Florida Keys will maintain light to
occasionally moderate breezes with low seas through next week.
&&
.AVIATION...
VFR conditions will prevail at EYW and MTH through tomorrow. A
passing shower isn`t out of the question, however, confidence is
too low to include VCSH at this time. Surface winds will be
variable at near 5 knots, becoming southeast at 7 to 10 knots by
tomorrow morning.
&&
.CLIMATE...
On this day in 1890, the daily record cold high temperature of
81F was recorded in Key West. This is also tied for the coldest
high temperature ever recorded in August.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...Shamburger
Aviation/Nowcasts....NB
Data Acquisition.....JAM
Visit us on the web at weather.gov/key
Follow us on Facebook and Twitter at:
www.facebook.com/nwskeywest
www.twitter.com/nwskeywest
Area Forecast Discussion
National Weather Service Miami FL
812 PM EDT Tue Aug 3 2021
.AVIATION(00Z TAFS)...
Numerous showers and thunderstorms continue to push through the
east coast terminals this evening. Periods of MVFR or even IFR
will continue over the next several hours. Winds across the
region will become light and variable later this evening and into
the overnight hours before increasing out of the south southeast
by Wednesday morning. At KAPF, winds will shift around to the
southwest on Wednesday afternoon as the Gulf breeze develops.
&&
.UPDATE...
Numerous showers and thunderstorms continue across South Florida
this evening. While there may be a lull in the activity at
some point later this evening and into the overnight hours,
additional showers and thunderstorms could develop especially over
the Atlantic and Gulf waters. With the mid level trough remaining
in place, Wednesday will be another active day featuring scattered
to numerous showers and thunderstorms especially in the afternoon
and evening hours. With additional heavy downpours likely, the
potential for localized flooding remains in place in the low lying
and poor drainage areas. A few strong thunderstorms cannot be
ruled out as well during the afternoon containing gusty winds,
funnel clouds, and frequent lightning. High temperatures will
remain on the warm side once again as they will rise to around 90
across the east coast metro areas and into the lower 90s over the
interior sections.
&&
.PREV DISCUSSION... (Issued 336 PM EDT Tue Aug 3 2021)
..Strong Storms and Flooding Possible this Afternoon...
..Wet Weather Continues through Mid-Week...
SHORT TERM (Rest of Today through Wednesday)...
Another active start earlier this morning across the local waters,
especially the Atlantic waters and over the Gulf Stream where
clusters of strong thunderstorms have been developing and lingering.
Similar to past days, waterspout risk will continue, though more in
the favor of tornadic waterspouts as opposed to the fair weather
type. The good news is that wind magnitude is on the stronger side
today which will also help to dissuade fair weather development.
Mid-upper troughiness over the eastern CONUS will continue to
suppress high pressure over the region. This will allow moist S
surface flow across the region, with SW mid-level steering flow.
Forecast PW`s can reach as high as 2.4 to 2.5 inches along
inland/eastern counties this afternoon, allowing for widespread
showers and thunderstorms, high rainfall rates, and flooding to be a
concern. Did cap PoPs at 70 percent for today.
Looking at MFL`s 03/12Z sounding, a saturated column is evident,
with a measured PW of 1.93 inches, which is 1.9 standard deviations
above the climatological mean for this time of year (or in the 99th
percentile). Not too impressed with lapse rates but would not be
surprised to see some gradual steepening over the course of the day.
With that said, a fairly cold 500 mb temp of -8.1 C, a lowering
freezing level of ~14,600 ft, increasing SRH near 50 m2/s2, DCAPE
close to 1000 J/kg, and CAPE already exceeding 3,000 J/kg are a sign
for what is forecast to come for the rest of today, including:
-Strong, perhaps damaging wind gusts in excess of 45 mph
-Heavy rainfall and localized flooding
-Hail
-Funnel clouds, or perhaps a weak tornado due to increasing SRH
values along with S/SE surface winds behind the Atlantic sea breeze
and prevailing low-level S/SW flow that can further enhance low-
level wind shear and SRH values
-Frequent cloud to ground lightning strikes
After RAOB analysis, DCAPE values are projected to reach ~1200 J/kg
and CAPE values look to exceed 4000 J/kg. Despite an increase in
cloud coverage today, enough sun and heating are expected. This in
combination with the aforementioned forecast parameters will lead to
possible strong to low-end severe storms later this afternoon,
especially if deep and prolonged updrafts were to be sustained.
SSCRAM and HRRR also suggest decent strong wind gust probabilities
over the course of the day as well.
There is good news and bad news for today. The bad news is that for
the east coast a westerly steering flow continues, pushing showers
and storms that develop inland this afternoon eastward and towards
the metro areas while also allowing the Gulf breeze to be the most
dominant of the sea breezes. The good news is that steering flow has
strengthened compared to previous days, with storm motion in the 15-
20 mph range. This will keep convection on the move and allow it to
not congregate and squat over one area for a prolonged period of
time. With that said, training/back building is still possible,
especially if the Atlantic sea breeze boundary were to prop itself
against the east coast. Multiple boundary collisions and erratic
cell movement with mergers/collisions are likely and this activity
may become enhanced by the sea breezes. This activity should
gradually push offshore during the evening hours and linger offshore
overnight.
Mid-upper level troughing will remain over the SE CONUS on Wednesday
with a stalled frontal boundary over the FL/GA border. Deep moisture
will continue, with PW`s forecast to stay over 2 inches. Another day
of widespread showers and thunderstorms with the main threat being
heavy rainfall, flooding, strong wind gusts, and lightning. SW
steering flow again which will focus high PoPs across interior and
eastern sections tomorrow afternoon.
High temperatures through the short term in the low 90s, however if
cloud cover is thicker or more widespread than anticipated, then
high temperatures will struggle to reach the upper-80s. Heat indices
still in the lower 100s.
LONG TERM (Wednesday Night through Tuesday)...
The mid level trough will begin to lift northeastward on Thursday
as an area of high pressure starts to build in from the western
Atlantic. This ridge of high pressure will continue to build into
the area throughout the upcoming weekend. This will gradually
shift the winds around to an east to southeasterly direction
during this time frame. As the east and west coast sea breezes
develop and push inland, there will continue to be enough moisture
in place to support chances of shower and thunderstorm
development along the sea breezes as they push inland. However,
with high pressure moving into the region and strengthening, the
chances of showers and thunderstorms will not be as high as they
have been earlier in the week and they will resemble more of a
typical summertime pattern during this time frame. With the east
to southeasterly flow in place, the greatest chances of showers
and thunderstorms will focus across the interior and western
sections during the afternoon and evening. A strong thunderstorm
or two containing gusty winds and heavy downpours over the
interior and west coast cannot be ruled out. High temperatures
through the end of the week and into the weekend will generally
range from around 90 across the east coast metro areas to the
lower 90s across the interior sections.
Towards the end of the forecast period into early next week, this
ridge of high pressure will continue to strengthen over the area
allowing for the east to southeasterly flow to continue. With
plenty of moisture remaining in place, the chances of showers and
thunderstorms will continue during this time frame. The greatest
chances will remain across the interior and west coast each
afternoon and evening where the sea breezes will collide and
interact with each other. High temperatures will generally range
from around 90 across the east coast to the mid 90s across the
interior sections.
AVIATION(18Z TAFS)...
Intermittent MVFR conditions likely through about 01-03Z across
the region with thunderstorms in vicinity of most TAF sites.
SCT/NMRS convection may yield temporary IFR/LIFR conditions mainly
due to reductions in CIGs/VIS. Also cannot rule out isolated
strong to severe wind gusts. Convection should wane after around
00-02Z and winds become VRB overnight. Tomorrow, winds generally
SSE in the morning, then becoming SSW by afternoon. TSRA and
associated impacts may affect terminals as early as 14-16Z
tomorrow.
MARINE...
Weak high pressure over the region will keep mostly southerly winds
across all South FL local waters through mid-week before shifting
from a more east direction towards the end of the work week.
Increasing winds today will lead to periods of SCEC conditions
across portions of the Atlantic waters. Otherwise, benign conditons
should return mid-week aside from locally gusty winds and rough seas
around showers and thunderstorms. Scattered to numerous showers and
thunderstorms will remain in place through mid-week with seas
generally 3 feet or less.
&&
.PRELIMINARY POINT TEMPS/POPS...
Miami 79 91 79 91 / 40 70 20 60
West Kendall 78 90 78 91 / 30 70 20 60
Opa-Locka 78 90 79 91 / 40 70 20 60
Homestead 77 91 78 91 / 30 50 20 60
Fort Lauderdale 78 89 79 90 / 40 70 20 60
N Ft Lauderdale 78 90 78 90 / 50 70 20 60
Pembroke Pines 79 90 78 91 / 40 70 20 60
West Palm Beach 77 91 76 91 / 50 70 20 50
Boca Raton 78 90 78 91 / 50 70 20 50
Naples 79 91 77 91 / 50 50 20 50
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
GM...None.
&&
$$
Update/Aviation...CWC
Tonight/Wednesday and Marine...Fell
Wednesday Night through Tuesday...CWC
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