Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/05/21
Area Forecast Discussion
National Weather Service Aberdeen SD
837 PM CDT Wed Aug 4 2021
.UPDATE...
Issued at 837 PM CDT Wed Aug 4 2021
Some showers/storms moving into north central sd this evening
along with showers with the short wave trough in the east leaving
the region through the rest the evening. Made adjustments to the
weather and pops.
UPDATE Issued at 647 PM CDT Wed Aug 4 2021
00z aviation discussion updated below.
&&
.SHORT TERM...(This Evening through Thursday)
Issued at 242 PM CDT Wed Aug 4 2021
A line of scattered showers, associated with an upper level trough,
continues to track from west to east across the Northern Plains.
Very little shear and CAPE to work with, so only general thunder (if
any) is expected. Should see clearing skies and light winds through
the overnight hours.
A weak surface trough lingers across the eastern CWA Thursday. Upper
level support is generally lacking however. Models do indicate a
shortwave tracking across southern Canada and into parts of North
Dakota/Minnesota, but best forcing would remain off to the north.
That said, Bufkit soundings show steep low level lapse rates and a
few hundred J/KG of CAPE to work with. Additionally, CAMs continue
to hint at an isolated shower or thunderstorm across the far eastern
CWA. The overall POPs reflect this.
Temperatures again trended cooler than normal today, both due to
cloud cover and still some lingering high level smoke. HRRR
integrated smoke product suggests smoke will be streaming in from
the west again Thursday. Stuck with the blended guidance for now,
but if smoke is a player, it may need to be adjusted down a degree
or two.
.LONG TERM...(Thursday Night through Wednesday)
Issued at 242 PM CDT Wed Aug 4 2021
The long term period begins on Friday with an upper level ridge
sliding across the region ahead of a northern Rockies trough. As the
trough approaches the region Friday night, a LLJ should develop over
the CWA bringing a chance for showers and thunderstorms. The
convection should push northeast of the CWA during the morning hours
on Saturday with a period of dry conditions possible. During the
afternoon hours, the surface low and associated frontal boundary
will begin advancing eastward into a more unstable environment. The
surface low and upper level trough could be fairly strong, which
combined with some instability and shear could produce a few strong
to severe storms, mainly in eastern SD and western MN. The
convection should push into MN Sunday morning, with the rest of the
long term featuring mostly dry conditions. Some models are showing a
frontal boundary clipping north-central SD, with additional pcpn
possible early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 647 PM CDT Wed Aug 4 2021
Terminals KABR,KATY,KPIR,KMBG
VFR conditions are expected through tonight and Thursday at all
airports. P6SM light showers from a short wave trough will affect
the ATY area early this evening as it moves east.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Mohr
SHORT TERM...Serr
LONG TERM...SD
AVIATION...Mohr
Area Forecast Discussion
National Weather Service Denver/Boulder CO
947 PM MDT Wed Aug 4 2021
.UPDATE...
Issued at 925 PM MDT Wed Aug 4 2021
The lone storm that developed over Gilpin and Clear Creek counties
has dissipated and no more showers or storms will develop tonight.
The only change to the forecast was to expand the area of smoke.
The latest HRRR smoke run shows quite a bit of smoke over all of
our CWA so I figured it was best to put it in the forecast for
the entire area.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 232 PM MDT Wed Aug 4 2021
After a prolonged active weather pattern, we`re finally trending
back to a warmer, quieter pattern. The trough axis that brought
healthy rain totals to much of the state yesterday through the
early afternoon today has now exited the area, with subsident
northerly flow in its wake. There`s been just enough moisture and
instability across the plains... as evidenced by an earlier FNL
sounding... to develop some shallow cumulus clouds, but otherwise
there`s not much to write home about this afternoon. Fairly quiet
conditions are expected through the rest of the evening. There
could be an isolated storm or two across the high country and into
the southern Foothills/Palmer Divide, but confidence in that
panning out is pretty low.
Tomorrow`s weather should also be fairly quiet, with a ridge
trying to build into the Four Corners region, while a shortwave
trough approaches from Oregon. Mid-level temperatures should be
about 2-4C warmer than today, meaning highs will likely make a run
at 90F for the Denver metro, with low 90s likely for the far
eastern plains. The main impacts tomorrow will come from wildfire
smoke. HRRR smoke forecasts show increasing near surface and total
smoke starting late tonight, with thicker smoke likely by late
tomorrow morning. Based on the last time we had forecast near
surface smoke concentrations this high, there will likely be some
haze/reduced surface visibility to go along with the air quality
concerns.
.LONG TERM...(Thursday night through Wednesday)
Issued at 232 PM MDT Wed Aug 4 2021
Thursday evening will be dry and mostly clear under ridging
aloft. RAP-Smoke output suggests that high smoke concentrations
from fires across the western states, especially the Pacific
Northwest, will linger over northeast Colorado into Friday as
smoke builds up under the ridge. The ridge axis will move over
Colorado late Thursday and early Friday and northeast Colorado
will be on the back end of the ridge by Friday afternoon.
Continue to expect high temperatures on Friday back in the mid to
upper 90s across the plains, upper 70s to mid 80s in the foothills
and mountain valleys, and upper 60s and lower 70s in the
mountains.
Friday afternoon and evening, there should be an increasing and
more zonal flow aloft at the base of an approaching shortwave.
Models seem to be coming to a consensus on the track and timing of
the shortwave which would bring enough forcing over northeast
Colorado coincident with enough instability to support isolated to
scattered storms and showers Friday afternoon and evening. About
5 g/kg of specific humidity from the lower to mid levels should be
enough moisture for some light precipitation. Forecast soundings
are currently showing deep mixing up to around 600 to 550 mb which
suggests high based showers producing light precipitation and
gusty outflow winds. Aside from the possible convection,
increasing flow aloft and deep mixing should mean increasing winds
in the high country and some breezy conditions in the afternoon
and evening Friday, especially in the northern mountains and
North Park. Forecast winds seem to be trending slowly stronger
with each run, now with gusts up to the 30 to 40 mph range in
that area.
The shortwave will move over northeast Colorado late Friday and
early Saturday, and a weak front behind it should bring a few
degrees of cooling. Saturday afternoon and evening should see more
breezy conditions, but weaker afternoon winds than those Friday,
and mostly clear skies. Sunday looks like a return to drying,
clearing and warming as heights rise again between the exiting
shortwave and another coming on shore over the Pacific Northwest.
Models continue to show this wave passing farther north without
significant impacts for Colorado, and a general lack of moisture
and instability anyway. Right now it looks like just some more
isolated convection bringing light precipitation early next week,
focused on the high terrain.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 925 PM MDT Wed Aug 4 2021
Smoke will impact the terminals through the TAF period as the
thickness of smoke is only going to increase. DEN may drop below 6
miles of visibility during the day tomorrow with visibility in the
3 to 4 mile range possible. Winds will be light and will follow
normal drainage patterns. No other weather, ceilings or visibility
issues.
&&
.HYDROLOGY...
Issued at 232 PM MDT Wed Aug 4 2021
Low flash flooding threat for tonight and tomorrow. The area of
monsoon moisture has departed the area today, with drier air in
place through tomorrow. There could be a few weak thunderstorms
this evening and again Thursday afternoon. However, with limited
instability and moisture available, any precipitation amounts
will be very light.
The threat of burn area flash flooding should remain low through
early next week due to persistent warm and dry conditions.
Isolated to scattered showers in the afternoon and evening Friday
should produce light precipitation. The weekend will be mostly
clear and dry, followed by more isolated showers bringing light
precipitation and low impacts early next week.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Danielson
SHORT TERM...Hiris
LONG TERM...EJD
AVIATION...Danielson
HYDROLOGY...Hiris/EJD
Area Forecast Discussion
National Weather Service Dodge City KS
510 PM CDT Wed Aug 4 2021
...UPDATE TO AVIATION...
.SHORT TERM...(This evening through Thursday)
Issued at 231 PM CDT Wed Aug 4 2021
GOES-16 water vapor channels have been showing a continued expansion
eastward and thickening of mid to high level cloud cover across the
western 2/3rd of our area this morning although still a few pockets
of diffuse insolation was apparent. This synoptic trough will
continue to shift across our region Today and Tonight. The only
areas where any sort of surface based convection will probably
remains to the north and west of our area (nw KS and NE CO), however
a few isolated more elevated storms can`t be ruled out as the trough
moves dead center over the DDC area in the evening bringing some
weak elevated MUCAPE with it. Nothing suggests severe weather,
however until sunset, gusty winds with a stronger storms in the west
would`t be ruled out given the steep low level lapse rates.
Additionally, as the CAPEs are not high there are decent PWAT values
around an inch or higher which may lend itself to a slightly more
elevated downdraft potential. As of 2 pm a line of weak
thunderstorms has rapidly unzipped just northwest of Syracuse and
the HRRR has the best handle of the timing and spatial attributes
and would have these initial storms to be unable expand very far
eastward as the convection much farther north in NW Kansas push
towards Scott City after 00Z.
Extensive mid level cloudiness will have an impact on the overnight
temperatures, especially across the lower plains eastern sections of
our forecast area (warmer lows in the mid to upper 60s). Cooler
air advection and longwave radiational cooling behind the trough
should ensure cooler temperatures by Thursday morning in the 50s
out west.
.LONG TERM...(Thursday night through Wednesday)
Issued at 239 PM CDT Wed Aug 4 2021
Statistically speaking the chances for rain from about Thursday
afternoon through about Tuesday are near zero. The influence of
the upper trough bring the hot summer conditions back with
downslope higher terrain air overspreading the High Plains region
from the Dakotas to the Texas panhandle. DDC ought to reach the
100 degree mark as early as about Saturday if not Friday
afternoon. The hot temperatures should plateau through the
weekend and persist in to early next week. By Tuesday/Wednesday
three major 3 global spectral models drive another synoptic scale
500 mb trough/low center across the Northern Rockies and Northern
Plains which should result in some surface response of a surface
and mid level front being driven equatorward. These model have
varying degrees of precipitation fields across the central Plains,
but all seem at least to weaken the intensity of the hot air.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 505 PM CDT Wed Aug 4 2021
VFR conditions will prevail in the vicinity of all TAF sites
through early Thursday afternoon. Showers and a few embedded
thunderstorms will continue to drift northeast across west central
and extreme southwest Kansas through late evening, resulting in
possible periodic gusty winds in vicinity of KGCK and KLBL.
Otherwise, south-southwest winds 10 to 20kt are expected to
subside somewhat after sunset this evening.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 64 91 65 98 / 20 0 0 0
GCK 59 90 61 98 / 20 0 0 0
EHA 57 90 61 98 / 20 0 0 0
LBL 59 91 62 99 / 10 0 0 0
HYS 64 91 65 98 / 10 10 0 0
P28 67 91 67 98 / 10 10 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...JJohnson
Area Forecast Discussion
National Weather Service Des Moines IA
635 PM CDT Wed Aug 4 2021
.DISCUSSION.../Tonight through Wednesday/
Issued at 407 PM CDT Wed Aug 4 2021
Forecast Highlights:
-- Scattered showers and a few non-severe thunderstorms Thursday.
-- Warming temperatures into the weekend and early next week.
-- Strong to severe storms possible Saturday, details below.
TODAY AND TOMORROW: Surface high pressure exited the state of Iowa
and pushed into Illinois this morning but high pressure conditions
continue today with another dry, mild, and quiet day. High
temperatures today will again be below normal for early August in
the low 80s. The HRRR smoke products suggest increased
concentrations of smoke will be in place aloft moving across western
into central Iowa today into tonight and into eastern Iowa
overnight. Concentrations at the surface look to be light over
northeast and far western Iowa late afternoon into this evening with
improvements overnight but increased concentrations aloft again late
Thursday into Friday.
Moisture returns to the area tonight in tandem with a shortwave
trough moving through the state. This will bring the threat for non-
severe scattered showers and a few thunderstorms across the area
overnight into tomorrow morning with another round of scattered
showers and thunderstorms on Thursday afternoon, most likely in
central and southern IA. These afternoon showers and thunderstorms
are the most likely to bring some measurable precipitation, though
not widespread due to the scattered nature of the storms, and still
with amounts near to below 0.25 in. Although MUCAPE values look to
be around 1500 J/kg tomorrow afternoon, forcing and shear still look
fairly weak so still not expecting any severe weather.
BEYOND THURSDAY: A thermal ridge builds into the area behind the
Thursday system with southerly surface winds ushering WAA into the
area and sending temperatures towards the 90s on Friday, Saturday,
and Sunday and into the 90s on Monday. Have backed off temperatures
slightly on Sunday with some hints of lingering clouds, and possibly
some additional showers overnight into Sunday morning in the west
and southwest, both of which would decrease high temperatures a bit
Sunday. Humidity will build into this weekend and early next week
with heat indices on Monday looking to be above 100 in southern Iowa
as of current trends. The warm and humid conditions look to persist
into early next week as well.
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. No
significant updates since the previous forecast as models still
differ on timing and location for the greatest threat of severe
weather, with timing in the models varying more in recent runs than
in previous runs. The best shear still appears to be post-frontal,
but all models do indicate sufficient instability, so we will
continue to monitor and provide updates in subsequent forecasts on
the shower and possible storm potential Saturday.
&&
.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 635 PM CDT Wed Aug 4 2021
Scattered SHRA/TSRA will affect the terminals at times during the
TAF period. The first and most likely period will come overnight
into Thursday morning...roughly between 06Z and 15Z depending on
the terminal...with periodic MVFR ceilings/visibility possible but
probability at any given time too low for more than VCTS in the
00Z TAFs. During the day Thursday additional SHRA/TSRA may occur,
but low confidence in location and short duration preclude TAF
mention at this range. Prevailing MVFR ceilings may also be
possible on Thursday, mainly at MCW/ALO. Expect details to be
refined in subsequent TAF issuances.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
DISCUSSION...KCM
AVIATION...Lee
Area Forecast Discussion
National Weather Service Grand Junction CO
525 PM MDT Wed Aug 4 2021
.SHORT TERM...(Tonight through Thursday night)
Issued at 239 PM MDT Wed Aug 4 2021
The current 500mb high is centered over the NV/CA/AZ triple point
with north-northwesterly winds covering the entire CWA. As such,
dry northwest flow rolling over top the ridge of high pressure has
eroded through what was just recently an exceptionally moist
atmospheric profile. Satellite imagery only conveys shallow
cumulus puffs atop mountain ranges with just a few isolated clouds
showing any vertical extent, near Monarch and Wolf Creek Pass.
High terrain along the central and southern Divide have the best
chance to wring out precipitation from said convection, while the
rest of the region maintains a drying trend. Also, accelerated
streamlines across the Western CONUS ridge certainly didn`t take
long to infiltrate smoke from PacNW fires across much of Western
Colorado and Eastern Utah`s skies. Unfortunately, recent
vertically integrated HRRR solutions maintain a thick plume of ppm
aloft through the short term period. This may inhibit radiational
cooling (especially for the northern half of the CWA), moderating
overnight lows.
The next low pressure system spinning ashore the NorCal coast
will nudge high pressure overhead on Thursday. This shift in ridge
axis places the CWA in between two upper level jets and
temporarily reduces winds aloft. Expect mostly clear skies across
the region, with high temperatures running back above normal.
Otherwise, the dry and warming trend continues on Thursday,
priming the environment for critical fire weather concerns to
resurface during the long term.
.LONG TERM...(Friday through Wednesday)
Issued at 239 PM MDT Wed Aug 4 2021
The high pressure over the Great Basin will start to flatten
Thursday evening as a shortwave trough approaches from the west.
By Friday, the ridge will have all but broken down, or at least
shifted to the south and east, causing flow to become more
southwesterly. Supporting the trough will be a 70kt jet streak and
as the trough passes, the gradient will tighten while deep mixing up
to 500mb will also bring some stronger winds to the surface.
Dewpoints look to decrease so this combination looks to bring some
critical fire weather conditions to the region as described below.
The best forcing looks to stay just to our north and also weaken
very quickly during the day Friday. Hardly any precip is expected
with trough passage with maybe a few sprinkles or quick rumble of
thunder along the Divide but that looks to be it. High temps will
drop a few degrees both Fri and Sat thanks to the cooler air moving
in from the north.
Previous model runs were indicating the possibility of another
monsoonal push next week but latest cluster guidance indicates
another trough dropping down from the northwest. While we won`t see
any precip because the trough will be too far north, it does like
the trough will suppress the high pressure. If this latest solution
pans out, the brunt of moisture will make its way into Arizona and
New Mexico from Monday through Wednesday and just barely nip our
southern zones. Confidence is sorta `meh` at the moment but with the
GEFS and EPS getting into better agreement, we`ll take and wait and
see approach for the next few runs. The long and short of it...much
drier over the next few days with temperatures generally increasing,
with a slight cooldown Friday and Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 524 PM MDT Wed Aug 4 2021
Clear sailing over the next 24 hours with mainly clear skies..well
except for the smoke layer which is creating hazy conditions but
for the most part vsby remains unlimited.
&&
.FIRE WEATHER...
Issued at 239 PM MDT Wed Aug 4 2021
A ridge of high pressure sliding overhead through Thursday will
result in a warming and drying period. By Friday, a disturbance
crossing the Northern Rocky Mountains will enhance winds across
much of Eastern Utah and Western Colorado, with a frontal passage
anticipated Friday afternoon. As such, widespread critical fire
weather conditions resurface. Uncertainty lies in fire weather
zones where fuels haven`t been updated since early May. Despite
recent monsoonal surge, used the last status entered to determine
areas included in Fire Weather Watch. Zones included in the Watch
may change if conditions have significantly improved from recent
rainfall. Otherwise, meteorological conditions will be met.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Fire Weather Watch from Friday afternoon through Friday evening
for COZ200-202-203.
UT...Fire Weather Watch from Friday afternoon through Friday evening
for UTZ490.
&&
$$
SHORT TERM...ERW
LONG TERM...TGR
AVIATION...TGJT
FIRE WEATHER...ERW
Area Forecast Discussion
National Weather Service Green Bay WI
1036 PM CDT Wed Aug 4 2021
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Thursday
Issued at 238 PM CDT Wed Aug 4 2021
Smoke from the wildfires out west continues to plague the forecast
area this afternoon, and is expected to impact the area through at
least Thursday morning. Cumulus clouds across northeast Wisconsin
have generally been fairly flat given the upper level ridging
across the western Great Lakes; therefore the weather should be
fairly quiet during the evening hours. Lows tonight are expected
to be fairly warm; ranging from around 60 across the north, with
lower to middle 60s across central and east-central Wisconsin.
A weak mid level trough and surface cold front will approach the
upper Mississippi Valley on Thursday, which could set off showers
and thunderstorms across central and north-central Wisconsin
during the afternoon hours. Given the main forcing will be west
of the area confidence is not high that we will see much in the
way of this activity. The arrival of the low pressure system will
turn winds to a southwesterly direction, which should help push
the aforementioned wildfire smoke out of the forecast area on
Thursday. Highs on Thursday are expected to range from the upper
70s across north-central Wisconsin to 80 to 85 across east-
central Wisconsin.
.LONG TERM...Thursday Night Through Wednesday
Issued at 238 PM CDT Wed Aug 4 2021
Active pattern is expected into early next week as several systems
will impact the area. Temperatures should run at or above normal
during the period.
For Thursday night, the first 500mb trough moves into the western
Great Lakes region. The ECMWF has the better forcing with the
upper level energy well north and south of the state. The ECMWF
has meager rainfall amounts across the forecast area, thus capped
rain chances for now in the high end chance category. The upper
trough will slide east across the area on Friday. Daytime heating
combined with a weak frontal boundary moving across the area will
be the focusing mechanism for thunderstorm development. The latest
bufkit soundings were a little more robust with CAPE values of
1,500 to 2,500 J/KG. Wetbulb zero heights were around 13,000 feet
with 0-6km shear values of 10 to 20 knots. With this in mind,
added a mention of stronger storms in the Hazardous Weather
Outlook (HWO) Friday afternoon into Friday evening for gusty
winds, hail and torrential rainfall. 700mb winds were only around
15 knots, thus storms will be relative slow movers. Could not rule
out an isolated severe storm with a wet microburst. July and
August are the prime months for these type of events.
The storms should end later Friday night. There will be a dry
period from late Friday into Saturday. The far northeast appears
to have the longest period of dry weather while central Wisconsin
will have the shortest due to the closer proximity of the warm
front. Convection is expected west of the area and some of this
activity could spill into north-central and central Wisconsin
before dissipating. The main show will be later Saturday night
into Sunday night where there is the potential for stronger
storms. There is some timing differences among the models when the
upper trough and best forcing with the upper level disturbance
moves across the region. Also, the amount of instability available
will depend on how much clearing takes places after the Sunday
morning showers and storms.
From Monday through Wednesday, low confidence in the chances of
showers and storms due low confidence in the placement and timing
of upper level features moving through the mean flow.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1032 PM CDT Wed Aug 4 2021
Quiet weather with generally good flight conditions is expected
overnight, but clouds will increase and lower from west to east
and showers and scattered thunderstorms will overspread the area
on Thursday. No big changes to the handling of the smoke as the
HRRR guidance has been consistent with that aspect of the
forecast and will continue to rely on it.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....Kurimski
LONG TERM......Eckberg
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Grand Rapids MI
738 PM EDT Wed Aug 4 2021
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 218 PM EDT Wed Aug 4 2021
- Isolated storm risk for late this afternoon
- Increased potential storms Friday and into early next week
- Warming up with some 90 degree reading possible next week
&&
.DISCUSSION...(This evening through next Wednesday)
Issued at 218 PM EDT Wed Aug 4 2021
- Isolated storm risk for late this afternoon
Based on SPC Mesoscale Analysis page...through 2 pm we have
developed 500 to 1000 J/kg of CAPE across the northern half of the
CWA. Visible satellite imagery suggest the smoke may be limiting
the convection around Southwest Lower MI. Some increased CU where
noted along the lake breeze slightly inland from Lake MI. Enough
CAPE is around to support an isolated storm or two...mainly north
of a Muskegon to Lansing line. The wind fields are relatively weak
so any storms should be slow moving and could lead to very
localized heavy rain.
- Increased potential storms Friday and into early next week
A mid to upper level trough tracks through the Great Lakes region
Friday into Friday night. An associated low level jet arrives as
well which will advect in abundant moisture and better
instability. Thus we will feature higher POPs to for this period
given the moisture...lift and instability that will be in place.
Deep layer shear is shown to be relatively weak so organized
severe weather looks unlikely.
Another mid to upper level wave arrives Sunday night into Monday.
This feature is shown to be losing amplitude...and should be
weakening. However plenty of moisture and instability will be
around to support showers and thunderstorms. A southwesterly 25
to 35 knot low level jet is shown as well which should help to
increase the low level lift.
A stronger mid level wave is shown to be tracking eastward
through the Canadian Prairies for the middle of next week. It is
possible that this system could send a stronger cold front in our
direction by the end of the week.
- Warming up with some 90 degree reading possible next week
The steady south to southwest flow through the weekend and into
early next week will support warming temperatures. Some 90 degree
readings are starting to show up in the MOS guidance. Temps at 925
mb are shown to reach 26 deg C Sunday afternoon...with similar
values for Tuesday and Wednesday. These values will allow for
daytime high temps climbing into the upper 80s to near 90 degrees.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 738 PM EDT Wed Aug 4 2021
The smoke layer will prevail through this forecast period. Based
on the HRRR smoke model most of the smoke is below 15000. The
smoke seems thickest in the 3000 ft to 10000 ft layer.
Otherwise, expect VFR conditions with light winds through
Thursday. Like today, cumulus clouds will develop by early
afternoon. An isolated shower is not out of the question but
should so isolated that it should present little problem to VFR
flying Thursday.
I put VCSH in the GRR TAF since there is a shower currently near
Sand Lake. That shower should be gone by shortly after these TAFs
are valid.
&&
.MARINE...
Issued at 218 PM EDT Wed Aug 4 2021
One low level jet moves in for later Thursday night into Friday
night. Southwest winds from this feature will support building
waves...especially north of Grand Haven. We will need to monitor
the potential for small craft and beach hazard conditions. A
similar setup will exist for Sunday into Sunday night. Given the
warm waters and likely high beach populations...we will need to
assess the situation closely going forward. For now we will
feature 2 to 4 foot waves for these periods.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...WDM
MARINE...MJS
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1012 PM EDT Wed Aug 4 2021
.SYNOPSIS...
A stationary front will remain stalled along the southeast United
States coast through early Saturday before dissipating. Meanwhile,
the trough situated over the eastern United States will gradually
lift northeast. High pressure builds in briefly Friday across the
southeast before another trough tracks across the region. Diurnal
shower and thunderstorm chances will continue this week but will be
somewhat limited by lack of moisture. Friday night into Saturday
looks like the best chance for showers and thunderstorms as the
trough tracks east across the forecast area.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 10 pm EDT Wednesday: The most recent HRRR runs have finally
come around to idea that spotty showers will be possible across the
NC foothills through the overnight hours as a vorticity lobe in the
base of the upper trough lifts northeast through the region. There
will not be much instability to work with, so will generally cap
nocturnal PoPs in the isolated range, with any thunder confined to
the immediate Blue Ridge escarpment where upslope forcing will be
best. Otherwise, showers will dissipate overnight in the southern
sections that will be on the NVA side of the passing vort lobe
overnight. Considerable overnight clouds will continue with moisture
trapped beneath a mid-level inversion in area profiles, and mountain
valley low stratus and fog will be possible if enough breaks in the
clouds form to permit some measure of radiational cooling.
Otherwise, lingering surface high pressure to the north and
northeast will provide mostly northeasterly winds through Thursday.
This will result in even less moisture in profiles, a drier boundary
layer, and with upper support moving off to the east, any PoPs will
be limited to the western mountains during peak heating. Max
temperatures should rebound at least a category with a bit better
insolation.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SUNDAY/...
As of 200 PM EDT Wednesday: The stationary front along the SE CONUS
should dissipate early Saturday. Meanwhile, northeast Georgia and
the Carolinas will be sandwiched between troughs Thursday night into
Friday. A high pressure ridge in the western Atlantic should nudge
into the southeastern CONUS Friday. With this synoptic pattern in
place at the start of the short term period, moisture should be
limited across the CWA as PWAT values remain low Thursday night into
most of Friday. Therefore, have capped diurnal showers and
thunderstorms to a slight chance to chance during this time frame.
The ridge of high pressure extending into the area will be forced to
the south and east as a trough approaches from the west Friday
evening into Saturday. PWATs increase during this time frame as the
trough tracks east towards the forecast area. Both the GFS and ECMWF
have come into better agreement in regards of the timing and
behavior of the trough this weekend. At this time, Friday night into
Saturday looks like the best chance to see showers and thunderstorms
from this upper-level trough due to the increased moisture the
system brings. Capped PoPs from a high end chance to low end likely
across the CWA. Sunday this trough should lift northeast into the
northeastern CONUS allowing high pressure in the western Atlantic to
build in from the south. In response to this ridge building back
into the area, PWATs should slightly decline again Sunday. As a
result, capped PoPs across the CWA to a slight chance. Highs Friday
and Saturday should be near normal to a few degrees below normal.
Sunday highs return to above normal.
&&
.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
As of 200 PM EDT Wednesday: High pressure could continue to build in
across the Southeast Sunday night into Monday. The ECMWF shows this,
however the GFS hints at a small area of low pressure forming across
the Deep South and tracking into the Carolinas during this time
frame. Tuesday into Wednesday remains even more uncertain as models
continue to diverge on the overall synoptic pattern. The ECMWF keeps
the ridge in place for the second half of the extended period while
the GFS has the low dissipating early Tuesday with high pressure
retreating east as a trough digs from southern Canada into the
northern United States. With model disagreement throughout much of
the extended period, decided to keep diurnal shower and thunderstorm
chances in the forecast, but capped PoPs to a slight chance to
chance. Highs throughout the extended period should be above climo
and much warmer compared to what we are seeing now.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Surface high pressure northeast of the
region will maintain light easterly winds across the region. This
will permit winds at the foothill and Piedmont TAF sites to toggle
between ESE and ENE through the period. Winds will be light to calm
at KAVL, but mainly NW early and SE late. Showers have diminished
around KAVL this evening and expect all sites to remain dry for the
rest of the overnight hours despite the passage of an upper trough
axis. Thursday appears to have even less of a chance for showers or
thunderstorms, with drier air advecting in, dewpoints mixing out
further, and any upper support east of the terminals. Expect mainly
SCT to BKN VFR bases through much of the period at 5 to 7 kft with
moisture under a nighttime inversion, followed by daytime heating
through Thursday. Fog and low stratus will be possible in the fog-
prone mountain river valleys overnight, with brief daybreak IFR
possible at KAVL.
Outlook: More typical summertime diurnal convection will redevelop
over the area Friday into the weekend. Fog and low stratus will be
possible each morning, particularly for the mtn valleys and areas
primed by rainfall from the previous evening.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 90% High 100%
KAVL High 100% Low 56% High 100% High 100%
KHKY High 100% High 100% High 100% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 100% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...AP
NEAR TERM...HG
SHORT TERM...AP
LONG TERM...AP
AVIATION...HG
Area Forecast Discussion
National Weather Service Gray ME
949 PM EDT Wed Aug 4 2021
.SYNOPSIS...
Low pressure will track through southern New England later
tonight, before passing through the Gulf of Maine Thursday
morning possibly bringing some heavy rain to the coast. An upper
level trough will bring more clouds to the region Friday, with
high pressure building in at the surface through Saturday.
Scattered showers and thunderstorms are possible Saturday night
into Sunday as a frontal boundary crosses the region. Ridging
will continue to build early to mid next week, with a warmer
pattern becoming more established.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
945 PM Update... Radar and ASOS reports indicate that some light
rain shower activity has now reached portions of southern NH but
the main precipitation shield is still off to the east over the
waters. The latest few runs of the HRRR have trended downward in
total QPF as a result of keeping the steadiest and heaviest
rainfall both to our south and east with little to no measurable
rain reaching ME until around 09Z. As a result, PoPs and QPF
were adjusted to account for these trends in both radar imagery
and model guidance. Other than some minor tweaks to
temperatures, dew points, and sky cover the rest of the forecast
remains on track.
Previously... 530 PM...Some adjustments, mainly to timing of
arrival of rain, more chance pops later this evening in SE NH
and coastal, and pushing the heavy potential until after
midnight, and more likely, the heaviest will be around and after
daybreak. Also adjusted temps a bit, although overall mins a re
close to previous forecast, but most of the cooling happens
this evening, especially in the S, with temps closer to holding
steady later tonight. The HRRR continue to focus the heaviest
along or just inland of coastal front, which would keep the
heaviest of rain in SE NH and the ME coastal plain.
Previously...Satellite imagery this afternoon continued to show
plumes of moisture developing off the Mid Atlantic coastline
with convection firing along and ahead of a surface area of low
pressure which was gradually forming just off the coastline.
Radar imagery depicts rainfall off the New England coast,
similar to most operational and mesoscale models near term
forecasts.
Most operational and ensemble model solutions continue to have a
significant model to model and run to run discontinuity. This is
particularly true with the timing and evolution in the
precipitation forecast. There has been an eastward shift in the
high precipitation and pop forecasts for tonight, with a couple
mesoscale models bucking the trend and keeping heavy rainfall
totals along the coast. This disparity remains relatively
significant. Out of all the model solutions however, the Euro
ensemble mean perhaps would lead to the most consistent
forecast.
In any case, the forecast remains highly uncertain as any
waiver in the track of the surface low and high PWAT axis could
shift the focus for heavy rainfall back to the coast and some
inland areas. This system appears to be similar to the August
13, 2013 event, however this event is displaced further to the east.
After coordination with adjacent offices, will hold off on
Flash Flood Watches for now as confidence is not sufficiently
high to warrant these headlines. However, short term trends
will need to be closely monitored during the overnight hours.
Precipitation should advance north during the late evening
hours.
Patchy fog is possible during the overnight hours as easterly
winds begin to bring enhanced moisture off the Gulf of Maine.
The cloud cover will make for relatively uniform temperatures
from north to south with mid to upper 50s for overnight lows in
most areas.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
12Z models and ensemble solutions suggest a second period of
shower activity on Thursday with showers continuing during the
morning hours as the upper level low and jet streak crosses the
region. Locally heavy rainfall may continue along and near the
coastline with the highest totals potentially in the Midcoast
region of Maine.
Surface dew points will continue to rise across the region as
tropical air will remain nearby over the Gulf of Maine. The
clouds and shower activity will limit daytime highs to the lower
70s in most areas.
The chance for showers will continue to diminish Thursday night
as the upper level trough pushes east. Nighttime lows will drop
into the mid 50s to lower 60s.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
General pattern in the extended will consist of a sprawling
Bermuda High along the Eastern Seaboard through Saturday night
before a progressive polar jet becomes reestablished bringing
mid-level shortwaves between periods of ridging next week.
Overall pattern will support above average temperatures and near
normal precipitation with rain chances on Sunday and Tuesday
night.
All rain ends by daybreak on Friday with zonal flow
aloft and ridging at the surface as the Bermuda high becomes
dominate along the eastern seaboard. SW return flow will become
established with a hot and humid airmass in place as dewpoints surge
into the upper 60s with heat index values reaching the mid to upper
80s. Still muggy on Saturday and mostly dry on the coastal plain
with chance for afternoon showers and thunderstorms across the
interior mountains. Weak surface cold front pushes through on
Saturday night into Sunday morning along with a 500mb shortwave
trough. This will bring in a slightly cooler airmass, but by no
means a big cool down. Shower activity will be more widespread
across interior areas. Warm and humid airmass returns for the
beginning of next week with the potential for instability
showers/thunderstorms. No significant widespread events on the
horizon at this time.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Short Term...VFR conditions early this evening will turn to
MVFR later this evening and IFR overnight as a moist airmass
moves into the region with the potential for a period of heavy
rain through Thursday morning. Conditions will improve later
Thursday afternoon.
Long Term...
High pressure is expected on Friday with no significant impacts to
aviation operations expected. Fog could be possible on Friday night
leading to IFR conditions. Isolated thunderstorms are possible on
Saturday afternoon, but threat is low at coastal aviation
terminals.
&&
.MARINE...
Short Term...Easterly winds will pick up tonight into Thursday
with a few gusts to 20 kt, just below Small Craft Advisory
criteria. Winds will switch to the north Thursday night. Seas
will gradually be on the increase with a few waves near 5 feet
along the outer waters Thursday night.
Long Term...
High pressure is expected over the coastal waters through this
period with predominate flow out of the southwest. Seas and winds
will stay below SCA conditions but gusts up to 20kts could be
possible this weekend. Pattern will also support the chance for fog
and low visibilities at times.
&&
.HYDROLOGY...
Much uncertainty continues from model to model and run to run in
terms of the QPF in the short term portion of the forecast.
There is a consensus that the highest rainfall totals will fall
along the coast where an inch or two of rain may fall in about
a 12 hour period which remains above flash flood guidance values.
These amounts will likely need to be adjusted and modified
however as radar and satellite signatures are identified during
the overnight hours. Therefore, conditions will still need to be
monitored for the possibility of a Flash Flood Watch.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM...Cempa/Tubbs
Area Forecast Discussion
National Weather Service Key West FL
956 PM EDT Wed Aug 4 2021
.DISCUSSION...
A ridge axis currently is extending across the Florida Keys and
South Florida, which is supporting gentle breezes across the
coastal waters and the island chain. Convection across South
Florida and the Keys has mostly dissipated, leaving us with partly
to mostly cloudy skies from the remnant upper-level cloud cover
that came off earlier convection. This cloud cover will continue
to deteriorate and leave us with partly cloudy skies. KBYX is
mostly echo-free, with only a few light showers in the Straits of
Florida that are rapidly falling apart. The 00Z KEY RAOB recorded
a layer of drier air beginning around 890 mb. This, combined with
an inversion around the same height, has helped keep any shower
activity shallow this evening. Temperatures across the island
chain are currently in the lower to mid 80s, with dewpoints in the
mid 70s. The ridge axis will shift northward overnight, allowing
for another wind surge like we experienced last night with breezes
becoming light to moderate. Have nudged PoPs down to a slight
chance for tonight, which is in line or even slightly above
guidance. Otherwise, the forecast looks to be on track and no
other changes are needed.
&&
.MARINE...
No watches, warnings, or advisories are in effect for the Florida
Keys coastal waters. From synopsis, A ridge axis in the vicinity
of the island chain will lift northward into Central Florida over
the next several days. East to southeast light breezes will tend
to freshen in the overnight to early morning periods, occasionally
becoming moderate. Breezes will freshen early next week as the
ridge axis broadens and lifts further northward. Near-normal rain
and thunder chances are expected tonight through at least Monday.
&&
.AVIATION...
Shower activity around airports has diminished in the past hour.
However, showers are likely to redevelop along the island chain
later this evening between 04-06Z per the HRRR model, and will
maintain VCSH at terminals overnight. Additional widely scattered
showers are also expected near airports much of the day tomorrow and
will continue VCSH, and cannot rule out brief periods of MVFR
cigs/vis. Light northeast winds this evening will veer to east then
southeast and increase to around 8-9 knots overnight into tomorrow.
&&
.CLIMATE...
On this day in 1894, both the daily record low temperature of 68F
and the daily record rainfall of 2.74" were recorded in Key West.
The low temperature of 68F is also tied for the coldest
temperature ever recorded in August. Rainfall records date back to
1871 and temperature records date back to 1872.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...NB
Aviation/Nowcasts....Shamburger
Data Acquisition.....JAM
Visit us on the web at weather.gov/key
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www.facebook.com/nwskeywest
www.twitter.com/nwskeywest
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
658 PM CDT Wed Aug 4 2021
.SHORT TERM...
249 PM CDT
Through Thursday...
With high pressure still in place, mostly quiet conditions are
expected to continue overnight into tomorrow. Skies remain hazy
from wildfire smoke aloft with scattered afternoon cumulus clouds.
A weak lake breeze pushed inland earlier this afternoon but has
since slowed its westward progression. Surface dewpoints have
remained a bit higher today west of this boundary which has aided
in a few spotty showers/sprinkles developing this afternoon. A
more persistent shower has since developed along the Cook and
Lake County IL border this afternoon along the lake breeze
boundary. Expect very spotty showers/sprinkles to be bubble up
and down through the afternoon. Any showers that are able to
sustain taller updrafts may be able to tap into some marginal
instability to produce a rogue lightning strike or two. Will also
note that model soundings depict a slightly less subsident
airmass than yesterday. Any remaining activity should diminish
quickly toward sunset with the loss of diurnal heating.
Winds turn light and variable this evening into the overnight
hours then trending more southerly early Thursday morning as the
surface high shifts to the east. Winds begin to pick up out of the
southwest through the daytime hours ahead of our next weather
system with temperatures warming into the lower to mid 80s again.
Petr
&&
.LONG TERM...
249 PM CDT
Thursday Night through Wednesday...
The late week into weekend forecast features a pattern transition
back to a warmer, more humid, and unsettled pattern. While most
forecast periods have chances for precipitation given this
pattern, the chances for scattered thunderstorms are a little
higher Friday, then again Sunday and Sunday night (could be
widespread for a part of that time), before predictability
notably drops off early next week. The heat early next week could
build to the level of heat index readings exceeding 100F.
A slightly positively tilted short wave trough will be very
gradually easing its way into the Upper to Mid Mississippi Valley
Thursday night and then still lingering over the Lower Great
Lakes on Friday. There is little window for deep moisture return
on Thursday ahead of this, and instability also lags the elevated
warm advection that eases overhead Thursday night. So we just
inch in a chance of showers in the forecast Thursday night,
especially overnight. Cloud cover looks like it will impact the
degree of destabilization on Friday, but how much so is tough to
tell yet at this point. Model soundings from the NAM and GFS as
well as the end of the RAP support convective temperatures being
reached. Considering a slightly cooler pocket of air in the mid-
levels with the trough, it probably will not take much for
diurnally- assisted scattered thunderstorms. The severe threat
looks limited due to marginal deep layer shear and questions on
what degree of instability there will be.
Looking at the weekend, short wave ridging is forecast to spread
at least partially over the area on Saturday. Continued southwest
low-level flow will nudge our dew points to around 70, and at
least some if not quite a bit of sun will probably offer upper
80s. A few storms could pop on any subtle convergence zones, such
as a lake breeze predicted to hug the shore that afternoon.
Overall though, some capping is shown and the pattern is not
supportive of widespread or long lasting storms (low shear).
Sunday looks like the more active day, with a fairly strong
neutrally tilted short wave forecast to approach the area and pass
over it sometime late Sunday or Sunday night. While the mass
field agreement in our area is fairly good for Sunday given it is
a ~Day 4 forecast, there are some key disagreements upstream
Saturday night with convection and how it may evolve toward or
into our area on Sunday. This will be a day and/or night we will
have to keep an eye on as the parameter space advertised presently
would support a scattered/possibly organized severe threat.
Into next week, the confidence drops on convective timing due to
low amplitude short waves in quasi-zonal flow. Confidence is
higher though on the warm, humid pattern. Both the GFS and ECMWF
advertise mid 70s dew points knocking on the door Monday and then
into the area Tuesday. With 850 mb temperatures of 20-22C, there
is support for 92-94 high temperatures, however the pattern is
not favorable to deterministically forecast that especially this
many days out with potential for multiple rounds of regional
convection. Again forecast heat index readings could near
Advisory level (105 in our area) Monday and Tuesday afternoons.
MTF
&&
.AVIATION...
For the 00Z TAFs...
Some random pop-up and short lived showers will linger into the
first hour or so of the forecast period, but overall coverage,
which was never large to begin with, should continue to decrease
with the loss of peak heating. Variable winds near the outflow
boundaries will trend southerly through the remainder of the
period. There appears to be enough of a gradient tomorrow to keep
the lake breeze confined closer to the shore, so for now there
are no plans to reflect this at ORD or MDW.
Lenning
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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www.twitter.com/NWSChicago
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Please see the previous forecast discussion below for more details
on the cooldown and eventual return to hot conditions. Keene
&&
.AVIATION...For the 05/00Z TAF Cycle...Over the coastal waters,
along the coast, and in the coastal valleys...IFR/LIFR ceilings
are expected tonight into Thursday morning. Patchy drizzle or
intermittent light rain can also occur. MVFR ceilings could
occur inland into the Umpqua Valley, including Roseburg, along
with a chance of showers Thursday morning. Stratus should lift to
MVFR/VFR Thursday afternoon.
Over the remainder of the area...VFR conditions will mostly persist
tonight through Thursday. However, smoke and haze from area
wildfires will result in reduction of visibility to MVFR/local IFR
at Medford and Klamath Falls. IFR/LIFR visibility is also possible
very near the fires. A disturbance will cause isolated to scattered
thunderstorms from northern California to the east side Thursday
afternoon and evening. The best chances for these storms will be
north and east of Klamath Falls. But, any storms that do occur
will have the ability to produce strong wind gusts and hail.
-Spilde
&&
.MARINE...Updated 200 PM PDT Wednesday 4 August 2021...Gusty north
winds and areas of steep seas will persist through this evening with
high pressure offshore and a thermal trough inland. The strongest
winds are expected between Port Orford and Gold Beach. Winds will be
weaker in the inner waters north of Cape Blanco, but weakest near
shore south of Pistol River with a southerly wind reversal.
Steep seas linger south of Nesika Beach late tonight into early
Thursday morning as winds begin to diminish ahead of a front. Winds
and seas will continue to diminish into early Friday. A thermal
trough and stronger north winds will return this weekend into early
next week. -DW/Petrucelli
&&
.FIRE WEATHER...Updated 825 PM PDT Aug 4 2021...A challenging
weather scenario is expected over the next 24-36 hours. The region
will quickly transition from hot, very dry, windy with unstable
conditions through early Thursday afternoon, to cooler conditions
with improving humidities, strong shifting winds and thunderstorm
potential Thursday afternoon and evening. During this 24-36 hour
period, the weather pattern will shift from high pressure over the
Four Corners/Nevada Region with low pressure offshore today to
low pressure to the east and a more zonal flow pattern over the
region.
Increasing winds today were in response to an upper level trough
offshore approaching the region, tightening pressure gradients
and pushing the thermal trough farther inland. This upper trough
will move through the region on Thursday and will result in
another critical fire weather day, though critical for different
reasons compared to today. Afternoon temperatures will drop by 10
to 20 degrees compared to today`s readings and this will help
bring up humidities as well. However, there will be a transition
period during the early afternoon where strong winds/low RH result
in critical conditions across the East Side and Modoc before the
concern transitions to thunderstorms. We`ve upgraded the Fire
Weather Watch to a Red Flag Warning, and it`s sort a hybrid
product. The first few hours of the Red Flag Warning (it`s valid
from noon to 10 pm Thursday) will be for strong winds with low RH,
then transition to abundant lightning on dry fuels. This Warning
is for FWZ 624, 625 and 285, including the Bootleg Fire.
While each zone may not see both abundant lightning and/or strong
winds with low RH, there`s no arguing that tomorrow is a critical
fire weather day and the wind element is the most concerning. First
with the low humidities anticipated during the earlier portion of
the day, then with shift in wind direction anticipated during the
afternoon (from southwest to west/northwest), to strong gusty and
erratic outflow winds with any thunderstorms. Regarding the
thunderstorm potential, isolated thunderstorms are certainly
possible from the Cascades eastward and across northern California.
Scattered coverage seems most likely across FWZs 624 and 625, maybe
even into the northern portions of the Modoc. This is where the SREF
calibrated thunderstorm guidance highlights a 20-30% chance of
thunderstorms across the aforementioned areas, so we have added a
slight chance of thunderstorms for those areas. The SPC HREF is also
concentrating the strongest convection in these areas. Of course the
wildcard in all of this is the concentration of smoke across the
region. If thick enough, it can inhibit surface heating thus
limiting instability and we`ve also seen smoke be an inhibiting
factor in thunderstorm development. However, there are some strong
dynamics associated with this trough, and it difficult to ignore
this. Therefore, have gone ahead with the abundant lightning on dry
fuels for Thursday.
&&
.PREV DISCUSSION... /Issued 516 PM PDT Wed Aug 4 2021/
DISCUSSION...
Thick smoke from multiple wildfires continue to cover the region
with unhealthy air quality. Because of the thick smoke and
unhealthy air quality, the Oregon Department of Environmental
Quality has issued and air quality advisory for southern Oregon.
The general flow pattern won`t change over the next 24 hours with
upper level winds pushing the smoke in from California and low
level winds bringing smoke in from the Skyline Ridge Complex into
valleys west of the Cascades. With all the thick smoke, expect
temperatures 3 to 5 degrees below most model guidance. This was
what was observed yesterday across multiple observation stations.
By Thursday, an upper level low will traverse the forecast area
bringing thunderstorms and a general change of the weather
pattern. Convective available potential energy(CAPE) will be
around 800 to 1000 J/kg east of the Cascades. With CAPE around
these values, we have the potential to see some stronger storms.
In addition, the storm prediction center has the east side under a
marginal risk for severe weather Thursday afternoon and evening.
This is likely due to the potential for some strong wind gusts as
storms seem to be over riding a fairly dry airmass. Some of the
convective allowing models also show the potential for severe wind
gusts east of the Cascades Thursday afternoon.
In addition, we feel pretty confident that scattered
thunderstorms will develop Thursday afternoon. Some of this is
based on the model ensemble probabilities showing a 50% chance of
thunder around northern Lake and Klamath Counties. Also, the upper
level pattern suggests strong upper level divergence on the
eastward flank of the low. The only uncertainty here is how much
the smoke will play a role in limiting instability and
thunderstorm coverage. We dismissed the role of smoke here since
we felt the upper level dynamics will be quite strong. In
addition, the smoke appeared thinner over locations east of the
Cascades.
By morning Friday, it appears a warm front will push into the
coast of Oregon. It`s denoted by slightly warmer temperatures and
a lot of moisture between 1000 to 500 mb. Some models are
predicting spotty precipitation along the coast Thursday night
into Friday morning. Even with more warmth and moisture moving in,
high temperatures will be in the upper 80`s with some locations
hitting the lower 90`s in northern California.
With deep north westerly flow from Friday onwards, the antecedent
smoke should clear out. However, fresh smoke from the wildfires
will then pour in from the north west as deep northerly to
northwest flow develops. Temperatures appear to warm up briefly on
Saturday before cooling down quickly on Sunday as a cold front
moves through. This will help keep temperatures in the 80`s on
Sunday into early next week. By Tuesday and Wednesday,
temperatures begin to warm up again.
-Smith
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning until 10 PM PDT this evening for ORZ623-624.
Red Flag Warning from noon to 10 PM PDT Thursday for
ORZ616-624-625.
CA...Red Flag Warning from noon to 10 PM PDT Thursday for CAZ285.
Red Flag Warning until 10 PM PDT this evening for CAZ280>282.
Red Flag Warning until 10 PM PDT this evening for CAZ284-285.
Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Thursday for PZZ356-376.
$$
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
740 PM EDT Wed Aug 4 2021
.UPDATE...
FOR 00Z AVIATION.
&&
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
Isolated to scattered showers will dissipate shortly after sunset.
Most locations will remain dry overnight. No significant changes
were made to the forecast for tonight during the evening update.
&&
.AVIATION...
00Z TAF DISCUSSION.
Isolated showers near CHA will dissipate shortly after sunset.
Scattered showers near TRI may linger to around or after midnight.
Tomorrow, showers will be confined to the higher elevations in and
near the Smoky Mountains. Patchy fog is possible in the early
morning hours but confidence is too low to include in TAF. VFR
conditions are expected this TAF cycle.
McD
&&
.PREV DISCUSSION...
/ISSUED 311 PM EDT Wed Aug 4 2021/
SHORT TERM...(Tonight and Thursday)
Key Messages:
1. Showers/thunderstorms diminish in coverage this evening,
drying out tonight.
2. Warmer and drier Thurs with only very isolated afternoon
storms in the far E TN mountains.
Discussion:
Late Afternoon/Evening...
The inverted surface trough that caused the persistent showers in
NE TN and SW VA all morning is finally lifting out. Clouds and
temps mainly in the low 70`s in these areas has kept instability
limited, but farther south, breaks of sunshine have warmed temps
into the upper 70`s/low 80`s and led to scattered convection
blossoming across much of the S Plateau and SE TN where latest RAP
soundings and SPC Mesoanalysis depict SBCAPE of 1000-2000 J/Kg
and 1000-1200 joules of MLCAPE. This along with abundant low-level
moisture in place, large scale lift beneath a deep eastern CONUS
mid/upper trough, and relatively steep mid-level lapse rates
around 6 C/Km will continue to support this diurnal convection
through the evening. Deep layer shear remains weak at under 25
kts, but the instability and some precip loading owing to
seasonably high PWATs of 1.20 to 1.40 inches will support gusty
winds and locally torrential rainfall within the strongest cores.
Expect the convection to quickly wane after 00Z.
Tonight and Thursday...
The weather pattern will begin to transition away from the cooler,
pleasant conditions of late during this period. The eastern CONUS
mid/upper trough will shift toward the east coast tonight with the
S Appalachians region becoming increasingly under upper level
convergence associated with the left entrance region of a 60 kt H3
jet streak. This downward motion combined with drier air and
additional subsidence from a surface high dropping through the
Midwest will allow the area to dry out overnight. Skies should go
mostly clear over most of the region, but lingering moisture will
lead to some cloud cover persisting near the mountains and across
NE TN into SW VA. The wet ground and small T/Td depressions will
lead to patchy fog, but northeastern areas may not see as much
due to the lingering clouds. Lows tonight will dip into the low
60`s with some upper 50`s from the N Plateau into parts of SW VA.
For Thurs, a mid/upper shortwave ridge will build into the TN and
OH Valleys with the aforementioned surface high moving over the
Appalachians. The large scale subsidence and dry air will allow
any lingering clouds in eastern areas to quickly diminish in the
morning allowing for mostly sunny skies areawide. H85 temps will
surge to 15-17 C as the shortwave ridge builds in, and this
combined with the sunshine and good mixing will boost highs into
the mid/upper 80`s (near normal). Increasing southeasterly low-
level flow during the afternoon as an upstream shortwave trough
approaches from the MS Valley and the surface high begins to shift
E could develop isolated convection in favored upslope areas of
the Blue Ridge in western NC, and this could spill into the far E
TN mountains, but the rest of the area will stay dry, and any
coverage in the mountains will be sparse as dry air mostly wins
out.
Garuckas
LONG TERM...(Thursday Night through Wednesday)
Key Messages:
1. Best chance of showers and thunderstorms through the extended
will occur Saturday.
2. Near normal temperatures through Saturday. Above normal
temperatures by Sunday with continued warming through Tuesday.
Discussion:
-Thursday Night through Saturday-
To start the long term period, an upper level trough will be exiting
the area to the east-northeast as very brief ridging moves in behind
it. The longwave trough will be positioned so that upper level
convergence will cover the majority of the CWA. As a result,
locations should remain dry late Thursday evening and overnight with
the passing of peak heating. Compared to 12Z model runs from
yesterday, the weak amplitude ridging expected Friday looks to move
through slightly quicker due to the more progressive manor and
higher amplitude of the shortwave energy just upstream of it. With
the large scale subsidence not looking to be quite as prominent as
before, pulse convection will have a little less dynamics working
against it, thus, a slight chance of showers and thunderstorms will
be possible late Friday afternoon and evening. However, the higher
coverage of showers and thunderstorms still looks to be Saturday as
better vorticity will be in place associated with the shortwave
moving through the region. The precipitation will continue to keep
temperatures in the seasonal normal range on Saturday.
-Sunday through Wednesday-
By Sunday, the aforementioned shortwave pulse will be moving
eastward as ridging starts to build and surface high pressure
settles along the TN/NC border. With southerly flow becoming more
present at the lower levels, some considerable warm air advection
will take place and temperatures will begin to rise a few degrees
above normal by Monday and Tuesday. With little synoptic support in
the region (i.e. no upper/lower jets, no surface boundaries) the
chance of diurnal showers and thunderstorms will largely rely on the
strength of the high pressure and overall subsidence within the
region. NBM loaded with high end chance PoPs on Tuesday and even
some low end likely on Wednesday but knocked them down to low/mid-
range chance as the confidence that far out with little to no
synoptic support is just not there.
KS
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 65 87 69 88 70 / 10 10 10 30 20
Knoxville McGhee Tyson Airport, TN 64 87 67 88 69 / 20 10 0 20 40
Oak Ridge, TN 62 86 66 87 68 / 10 0 0 20 30
Tri Cities Airport, TN 61 84 62 87 66 / 20 10 0 10 30
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
Area Forecast Discussion
National Weather Service New York NY
1106 PM EDT Wed Aug 4 2021
.SYNOPSIS...
Multiple waves of low pressure along a frontal boundary just
offshore will impact mainly eastern Long Island and southeast
Connecticut overnight. The front will then slowly work east on
Thursday as weak high pressure begins to build in from the west.
A broad area of high pressure will set up over the area on
Friday. A frontal system may pass Saturday night. A warming
trend is likely next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Rain chances have been adjusted due to current radar, with much
of the rain contained to southeast Connecticut and the Twin
Forks of Long Island. Western areas such portions of the Lower
Hudson Valley and northeast New Jersey will continue to be dry
through late tonight.
The combination of a longwave trough from the Great Lakes south
to the Gulf coast states will send a series of frontal waves
near or just south and east of Long Island and eastern CT
tonight into Thursday morning. This combined with a subtropical
feed of moisture up the eastern seaboard and PW values near 2
inches raises the concern for heavy showers along with embedded
thunderstorms, mainly from late tonight through around
daybreak. The best potential for the heavy rain will be across
far eastern LI and SE CT, where a Flash Flood Watch has been
issued.
Global models have come into much better agreement with the 12Z
cycle generally focus the axis of heavy rainfall across the
watch area. However, the GGEM keeps the axis to the east. The
CAM`s have been struggling with the frontal wave location, with
the 12Z NAMNest the farthest west and most aggressive with the
rainfall, with 2 to 5 inches of rainfall extending as far west
as New Haven and western Suffolk Counties. The FV3 is more in
line with the watch area, and the HRRR has been varying west to
east with the last several runs. While there is not a whole lot
of instability, moist adiabatic lapse rates and jet exit region
dynamics may be all it takes at this time of year to produce
heavy rainfall. Feel fairly confident of 1 to 2 inches in the
watch area, but the potential is there for more. At the very
lest, expect some minor nuisance, poor drainage flooding.
Elsewhere, chances of showers will drop appreciably as one goes
west, especially NYC and SW CT.
Overcast conditions and easterly winds will keep lows in the
60s, a few degrees below normal.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Widespread morning showers will exit around or shortly after
daybreak Thursday. However, with the upper trough lifting out
across the area, a few lingering showers will be possible into
the afternoon, especially across far easter LI and SE CT.
Weak high pressure builds in late Thursday into Thursday night
with gradually clearing skies late into the day and through
Thursday night.
Trended toward the cooler side of the guidance based on
Wednesday`s highs and the anticipated cloud cover. Highs will
be in the 70s, approaching around 80 across the NY/NJ metro.
Lows will be in the lower to mid 60s Thursday night with a few
spots around the metro around 70.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
The models were in good agreement in the extended, so the NBM was
closely followed with local adjustments.
Rising heights will end pcpn chances on Fri so a dry day has been
fcst. WAA from the west will produce more August-like wx, with temps
warmer than those experienced in over a week. The warmer wx however
appears to be locked in for a while now, with generally at or
slightly abv normal temps over the weekend. There are chances for
shwrs and tstms each aftn/eve over the weekend with the passage of a
weak h5 trof.
The heat really builds next week as the subtropical ridge expands
over the CONUS. The modeling has been really consistent on this. A
warm front comes thru on Mon, with perhaps some shwrs and tstms
invof the boundary. The NBM may be a bit too cool with highs due to
the front being close, but this far out decided not to stray from
the blended approach. It would not be surprising to see highs about
5 degrees warmer than currently fcst on Mon based on h85 temps
approaching 18C. This pattern will set the stage for air mass tstms
Tue and Wed with aftn/eve timing favored. The ECMWF suggests an upr
low will provide a brief round of relief towards the end of next
week, but the GFS disagrees. This is beyond the actual fcst period
anyway, so until then a hot and humid Tue-Wed can be expected.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
A frontal boundary will remain offshore with several waves of
low pressure passing along it.
VFR for NYC terminals and points north and west through 05Z.
For eastern terminals such as KISP, KBDR, KGON; MVFR conditions
will continue through the overnight hours. However, there may be
some improvement at times through 03Z. Thereafter, moderate to
heavy rain may affect KGON which may limit visibilities to 3 to
5 SM at times, mainly from 03Z-07Z.
E Winds will shift to the NE after 03Z, and then N around
daybreak Thursday. Winds speeds will be 10 kt or less for the
most part. There may be occasional gusts to 15 kt for coastal
terminals, mainly from 06Z-12Z. Sea breezes could then affect
coastal terminals late in the day Thursday.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments likely for changing flight categories.
.OUTLOOK FOR 00Z FRIDAY THROUGH SUNDAY...
.Thu night-Fri...VFR.
.Sat-Sun...Mainly VFR. Chance of afternoon showers and
thunderstorms.
.Monday...VFR
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Building seas ahead of an waves of low pressure along an
offshore frontal boundary will bring SCA conditions to the
ocean tonight. Seas look to range from 4 to 7 ft. These
elevated seas should linger into Thursday night. The Small Craft
Advisory is now in effect through 6am Friday. A few wind gusts
up to 25 kt cannot be ruled out on the ocean tonight as well,
although winds may stay closer to 20 kt or less. Elevated ocean
seas may linger into Thursday night.
Seas on the ocean will gradually subside thru the day on Fri,
with all waters falling blw sca lvls by Sat mrng. Winds on the
protected waters will be blw 25kt. Winds and seas will mainly be
blw sca lvls over the weekend, although waves could flirt with
5 ft at times on the ocean. Winds and seas are expected to
remain blw sca lvls Mon and Tue.
&&
.HYDROLOGY...
Rainfall amounts of 1 to 3 inches with locally higher amounts are
forecast late tonight into Thursday morning across eastern Long
Island and southeast Connecticut. Minor urban and poor drainage
flooding is possible with a localized risk of flash flooding.
Amounts should drop off significantly to the west with only
light amounts along and west of the Hudson River corridor.
No hydrologic impacts are expected Fri-Wed.
&&
.TIDES/COASTAL FLOODING...
There is a high rip current risk for all beaches on Thu, and a
moderate risk for Fri. Even though there is no wind component on
Thu, 5 ft waves are expected at all beaches, resulting in the
high risk.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Flash Flood Watch through Thursday morning for CTZ008-012.
NY...Flash Flood Watch through Thursday morning for NYZ079-081.
High Rip Current Risk from 6 AM EDT Thursday through Thursday
evening for NYZ075-080-081-178-179.
NJ...None.
MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ350-353-355.
&&
$$
SYNOPSIS...DJ/DW
NEAR TERM...JP
SHORT TERM...DW
LONG TERM...JMC
AVIATION...JP
MARINE...JMC/DW
HYDROLOGY...JMC/DW
TIDES/COASTAL FLOODING...