Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/09/20
Area Forecast Discussion
National Weather Service La Crosse WI
1050 PM CDT Wed Jul 8 2020
.SHORT TERM...(This evening through Thursday)
Issued at 313 PM CDT Wed Jul 8 2020
Forecast concerns in the short term will be the heat advisory
into early this evening and any convection that manages to develop
above the cap or with heating...thunderstorm evolution overnight
and Thursday and potential for severe storms and heavy rainfall.
By 18Z...LSE did reach 92 degrees with a heat index around 100...so
that makes a 9 day stretch of 90 degree plus days in a row. That
ties for 10th place for the longest stretch.
By early afternoon, the surface map and satellite imagery
highlighted an outflow boundary that had made it to Faribault, MN.
Behind the outflow, temperatures had cooled into the 70s and
dewpoints dropped back into the 60s. There is a mix of cumulus,
cirrus and convection. On the edge of the mid-level warming and with
a weak shortwave, convection continued and affected Taylor and Clark
counties, areas along that boundary and spotty locations outside
the cap. Early afternoon SPC mesographics have the 10 deg C h7
temperatures near LaCrosse, with the axis of higher precipitable
water still to the north. The thermal axis is over southeast MN
with There is a weak cap and it is forecast to remain weak, with
the 700mb 10 deg C temps building into southwest WI. So will need
to monitor during the afternoon for any convection with heating as
there may be some along boundaries and on the edge of the cap
where the 850mb moisture is around 18 deg C. and above the cap.
Water vapor satellite imagery highlights the mesoscale convective
complex traversing across the Upper Peninsula of Michigan and
spotty convection farther south over northern IL. The closed 500mb
low pressure system was noted over Saskatchewan with shortwave
trough energy in the flow across parts of Nebraska into the
Dakotas. As the closed low pushes east into Manitoba, the cold
front farther south and shortwave trough energy will tap into
precipitable water values around 1.5 inches. The low level jet
around 25kt across Minnesota will strengthen to 35 or
40kt...meanwhile, a 40kt low level jet develops across Kansas and
Nebraska, moving into Iowa by 12Z. The RAP MLCAPE/instability by
00Z along the cold front is 2500 J/kg and in parts of our area
with MUCAPE 4-5000J/Kg. 0-6km shear is around 45-55kts over the
Plains to our west. The deep layer shear is forecast to remain to
our west overnight, increasing to around 30kts for parts of the
northern WI ARX CWA by 12z and 25-35kts Thursday afternoon from MN
into parts of WI. Outside of the isolated storms locally, the
main attention will be from Nebraska toward MN where the organized
convection is expected and the storm prediction center has a
slight risk and an enhanced over Nebraska. Some of the CAMs have
the convection across Minnesota and northern WI with one area of
shortwave trough energy...spreading southward and weakening while
the convection over Nebraska drops southward. This seems
reasonable that some of the convection will drop south into the
instability, however the coverage should weaken as it moves into
the warm air. A 700mb circulation is forecast to move into Iowa
Thursday and this combined with the cold front should result in
more organized convection locally. Included pops for scattered
thunderstorms pushing south tonight and across much of the area
Thursday. With the moisture, instability, and steep lapse rate
environment along with focused wind maxes, some severe storms
possible late tonight into Thursday. Heavy rain is possible with
any of the storms that form. Precipitable water of 1.5 to 2
inches, warm cloud depth over 4Km and training of storms enough of
a concern for WPC to include parts of our area in the day 2
outlook for excessive rainfall.
Temperatures Thursday are only forecast to be in the 80s...so that
should end our streak of 90s.
.LONG TERM...(Thursday night through Wednesday)
Issued at 313 PM CDT Wed Jul 8 2020
Friday is currently looking dry with northwest winds and cooler.
A shortwave is forecast to develop over the Dakotas and drop
southeast in the northwest flow aloft sometime Friday night into
Saturday. Spotty rain is possible Sunday. Ridging is forecast for
Monday with a shortwave trough breaking down the ridge Monday
night into Tuesday. So...while locations to the south of the area
will be more on the hot and dry side, we will see periodic rain
chances with highs mostly in the 80s and more comfortable lows in
the 50s. and 60s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1047 PM CDT Wed Jul 8 2020
Overall, it looks like the HRRR is handling the current convection
the best, so trended the TAF toward it for the timing of the
storms on Thursday. Overall, the best chances of storms look to be
during the afternoon and early evening. The deep shear continues
to look weak, so there remains uncertainty on severe chances.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Boyne
Area Forecast Discussion
National Weather Service Denver/Boulder CO
914 PM MDT Wed Jul 8 2020
.UPDATE...
Issued at 912 PM MDT Wed Jul 8 2020
The convection has exited the CWA. There was a pretty strong
boundary with northeasterly winds behind it pushing southwestward
across the CWA this evening. It is falling apart at this time.
There is still a bit of mid level cloudiness around. Models have
this dissipating after midnight. Made appropriate minor GFE
updates.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 314 PM MDT Wed Jul 8 2020
Just a few wrinkles to the forecast this afternoon as hot dry air
covers most of our area. An incoming jet streak will provide a
little forcing that may allow storms to break the cap out in the
less dry air from the Nebraska panhandle to northwest Kansas.
Models have been showing an isolated storm or two forming in this
area in the late afternoon or early evening. CAPEs will be less
than 1000 J/kg but it`s a good environment for downdraft winds so
we could see a few storms with 50-60 mph wind gusts as we have the
past couple of afternoons.
There have been hints of a weak, shallow surge of cooler air
behind these storms. The HRRR is bringing low clouds westward to
about Fort Morgan with dew points in the upper 50s in the morning,
with a little westward slosh of the intermediate air now over the
northeast plains into Denver. If this is a bit more solid, it
could result in slightly cooler temperatures on Thursday and
eventually a better chance of strong storms in northeast Colorado
by Thursday evening. At this point though, the current forecast
looks like a reasonable solution with just a little cooling and
another day with isolated late day storms. There would be
potential for a supercell storm to develop on the dry line in the
northeast corner of Colorado Thursday evening if the cap is
broken, but it may not quite be warm/moist enough and the models
mostly have this happening elsewhere.
Meanwhile, the western part of the area will stay warm and dry.
There will be a bit less wind Thursday.
.LONG TERM...(Thursday night through Wednesday)
Issued at 314 PM MDT Wed Jul 8 2020
A review of the latest medium range models and MOS guidance shows
little chance of any break in the ongoing heat wave. The strong
upper level ridge covering the southern half of the country shows
only signs of strengthening over the next few days. Unseasonably
warm temperatures at mid and upper levels are in place with no
sign of any upper troughs to disturb the pattern. The warm
temperatures and subsident effects of the upper ridge will
suppress most, if not all, afternoon convective development. The
ECMWF and GFS hint at a couple afternoons with minor short waves
generating afternoon showers on Sunday and Monday. However, these
are questionable as moisture will probably be lacking and mid-
level temperatures will be warm enough to keep afternoon
convection capped. The primary story will be the afternoon highs
in the mid to upper 90s on the plains each day. Thankfully,
surface pressure gradients should remain weak enough that
sustained winds will not become a problem for fire weather
concerns. Friday and Monday have indications that they will be a
couple degrees warmer than the other days. So Denver could see
some 100 degree readings on those days.
During the second half of next week it is possible that the center
of the upper ridge retreats to the east which may allow
subtropical moisture to move over Arizona and towards Colorado. If
this comes to bear, the latter half of the week may need the
mention of showers. Until then, be careful in dealing with the
heat. Stay hydrated and look out for friends and neighbors who may
need assistance.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 912 PM MDT Wed Jul 8 2020
A boundary has made it through DIA with decent east-northeast
winds now in place. Models never show normal drainage wind
patterns overnight. They bring in a surge of northerly winds
around 12Z. There should not be any ceiling issues overnight.
&&
.FIRE WEATHER...
Issued at 314 PM MDT Wed Jul 8 2020
Winds will diminish this evening, but it will be another night of
warm temperatures and limited humidity recovery over the ridges,
foothills, and areas near the Front Range. Further east, higher
humidity air will move in from the east overnight. Over the
mountains Thursday, conditions will be similar to today but with
less wind. The plains will still be hot and dry, but humidities
will be higher than today.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.........RJK
SHORT TERM.....Gimmestad
LONG TERM......Dankers
AVIATION.......RJK
FIRE WEATHER...Dankers/Gimmestad
Area Forecast Discussion
National Weather Service Columbia SC
823 PM EDT Wed Jul 8 2020
.SYNOPSIS...
Relatively deep moisture will remain across the area over the
next couple of days then shift offshore. Low pressure along the
South Carolina coast will slowly move to the northeast. With
moderate instability and a weak trough across the area,
scattered mainly afternoon and evening showers and thunderstorms
are expected into the weekend. Temperatures are expected to be
at or above normal for the next few days.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Shower and isolated thunderstorm activity winding down with
loss of heating as expected. Surface low will continue to push
off to our NE. Overnight lows near 70.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Thursday and Thursday night...Low pressure along the North
Carolina coast will move slowly to the north. Upper trough
remains over the area and precipitable water remains about 125%
of normal (above 2 inches). Surface trough remains across the
area and instability moderate. There may be a weak short wave
trigger in the afternoon. So expect scattered afternoon and
early evening showers and thunderstorms with a focus in the
east. Temps near normal around 90 and lows in the low 70s.
Friday and Friday night...The low pressure area along the North
Carolina coast may evolve into a tropical cyclone but will be
moving away from the area. Long wave upper trough remains over
the area and expect the weak surface convergence associated with
persistent trough. Air mass remains moist and moderately
unstable and short waves rotating through upper trough may
trigger a few scattered afternoon and evening thunderstorms. The
temperatures may be a little warmer with more sun as the deeper
moisture shifts offshore and 850mb flow becoming more west with
resulting warm advection and downslope. Expect mainly diurnally
driven convection although the GFS appears to be faster than
ECMWF brining a short wave trough thru the area Friday night so
convection could linger into the evening. The blended guidance
suggests lower pops. Expect muggy conditions overnight.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Upper trough remains over the area through early next week
although the deeper moisture will be east of the area. Blended
guidance suggests higher pops for Saturday with short wave
trigger and lower pops Sunday. Temps slightly above normal.
Upper trough along the coast by Wednesday with upper ridge
building across the lower Mississippi Valley and southern
Plains. The air mass may be a little drier by Tuesday afternoon.
Expect scattered afternoon and evening thunderstorms with temps
above normal.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Isolated showers this evening should continue to diminish.
Chance of any shower impacting a taf site appears small, so have
kept mention of any rainfall out of all sites for the entire
forecast period. Models are split on the amount of clouds and
even with the category of the ceilings though. SREF prob
ceilings do not indicate any widespread restrictions, and
neither does the hrrr through morning. Deterministic GFS does
show mvfr ceilings developing late tonight, so there is a lot
more uncertainty overnight. Deepest moisture should be moving
off to the east with the exiting surface low, with some clearing
possible. For some consistency, have kept broken ceilings in
late tonight, but have trended ceilings higher into mvfr at all
sites except kogb. There moisture may still be deeper to bring a
period of ifr ceilings in late. Conditions should improve at
all sites by 14z-15z, with a return to vfr expected through the
day on Thursday. Isolated showers possible once again on
Thursday. Winds light and variable tonight, then out of the
northeast during the day.
.EXTENDED AVIATION OUTLOOK...The deepest moisture moves east
late in the week. A more seasonal pattern of mainly diurnal
convection and early morning fog will be in place for the weekend.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Cheyenne WY
527 PM MDT Wed Jul 8 2020
.SHORT TERM...(This evening through Thursday)
Issued at 300 PM MDT Wed Jul 8 2020
Forecast concerns deal primarily with fire weather conditions the
next several days.
Currently...Slow moving frontal boundary now lays along the
Colorado/Wyoming stateline this afternoon at 18Z. Temperatures
have cooled about 10 degrees over yesterday...but that`s about the
only good news with this front. Very dry air behind the front with
1PM humidity in the upper single digits and low teens across much
of southeast Wyoming. Gusty winds mixing down from 500mbs with 25
to 35 mph common. Laramie reporting a gust to 49 mph at 1PM.
Current Red Flag Warnings looking good and no changes planned. The
one zone of concern is FWZ 310 (east of Laramie range). Cheyenne
had a gust to 28 mph...but has since calmed down. Will continue to
monitor.
Not seeing too much on radar currently. But latest HRRR and Hires
guidance continues to show convection developing for a brief
window late this afternoon through 01Z. Latest RAP guidance shows
a pocket of instability over the northern Nebraska panhandle from
22Z to 01Z with strong storms developing in 2000 to 2200 J/KG of
SBCAPE. So far...not too concerned with severe storms. After
that...winds ease early this evening as cooling begins. Timing of
RFW cancellation looks good.
Less wind Thursday will ease fire weather concerns some. GFS
soundings only showing roughly 20kts mixing down Thursday...so we
should stay below critical levels.
.LONG TERM...(Thursday night through Wednesday)
Issued at 300 PM MDT Wed Jul 8 2020
Fire weather concerns return Friday as a low pressure system
tracks across Montana and flattens the upper ridge. This creates a
tightening gradients across southeast Wyoming with 700mb winds
increasing to 25 to 35kts. With afternoon humidity forecast in the
single digits again Friday...critical fire weather conditions
looking likely. Will likely need a watch from the night crew
tonight for Friday.
Dry and breezy through the weekend with additional fire weather
concerns. Next chance for showers/storms appears to be maybe
Tuesday next week as another clipper system moves through the
area. Not looking too good though as QPF very light on both the
GFS and ECMWF.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 524 PM MDT Wed Jul 8 2020
Wyoming TAFS...VFR. Wind gusts to 35 knots until 03Z, then to
24 knots after 15Z Thursday.
Nebraska TAFS...VFR, with occasional MVFR in thunderstorms with
wind gusts to 50 knots at Alliance and Sidney until 01Z. Wind
gusts to 23 knots at all terminals until 02Z, then to 20 knots
after 15Z Thursday.
&&
.FIRE WEATHER...
Issued at 300 PM MDT Wed Jul 8 2020
Hot and dry weather pattern continues as upper high pressure over
the Rockies continues through the week. For this afternoon...winds
are mixing down from higher elevations of the
atmosphere...creating wind gusts of 25 to 35 mph across our higher
terrain areas. Afternoon humidity in the single digits and low
teens. As a result...Red Flag Warnings are in effect for those
FWZs where fuels are reported critical. See a reprieve in winds
Thursday with gusts 20 to 25 mph...before stronger winds return
Friday. Likely critical fire weather conditions Friday. No chances
for showers or wetting rains til maybe Tuesday next week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning until 8 PM MDT this evening for WYZ301-302-305-
307-309.
NE...None.
&&
$$
SHORT TERM...GCC
LONG TERM...GCC
AVIATION...RUBIN
FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Dodge City KS
953 PM CDT Wed Jul 8 2020
.UPDATE...
Issued at 953 PM CDT Wed Jul 8 2020
After coordinating with SPC and WFO Wichita, opted to include
Trego/Ellis counties and the I-70 corridor in the severe
thunderstorm watch. Tough call if convection can build as far
south as the interstate. Highly organized complex currently in
Nebraska should take on more of a SEly trajectory soon, with moist
68 dewpoints and SE winds at Hays/Russell, a strong CAPE axis and
MCS maintenance per mesoanalysis near 90% for Trego/Ellis. Still,
700 mb temps are warm, near +14C, and this capping may deflect
convection out of the CWA, as the latest HRRR runs try to suggest.
Earlier CAMs were more enthusiastic about storms reaching the
Hays vicinity, and given the environment, feel the watch is
warranted. Confident any convection will struggle/fail to progress
southward out of Trego/Ellis. At any rate, the primary threat from
thunderstorms through early morning is damaging outflow winds of
60-70 mph.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 307 PM CDT Wed Jul 8 2020
The main issues for this shift will revolve around convective
chances this evening and as late as around midnight. The WRF-NMM has
been the more robust and likely over convecting model the last
couple of days, developing dryline storms and connecting those
spatially to a southeast diving mcs from Nebraska into northern and
central Kansas by late Tonight. Other CAMs have been far less
aggressive, with both convective modes/locations. Still there is at
least a small chance for isolated dryline storms later this
afternoon and early evening. Owing to he large uncertainty is even
the ARW completely missing the Hays area late tonight with MCS.
With all this in account, have opted not to change up the
relatively small pops although light spatial adjustments made to
the grids for this evening. Overnight lows should range from mild
low 70s across south central Kansas to the low 60s over the higher
elevation locations around Syracuse.
.LONG TERM...(Thursday night through Wednesday)
Issued at 307 PM CDT Wed Jul 8 2020
Not as hot temperatures should be noticed across the northern
counties on Thursday as a result of the expected convective outflow
from the overnight before. From model sounding and plan views it
looks like there may be extensive clouds in the morning breaking
up in to scattered cu by the afternoon. Consensus was to remove
Pops from central KS for Thursday evening. Following this there
will be an extended period of likely dry weather through mid next
week. Models show a largely dry cold front on Saturday that may
provide a short respite to the temperatures and a small window of
opportunity for diurnally driven convection. The NBM ramps
temperatures back up into the 100s for Monday and Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 509 PM CDT Wed Jul 8 2020
VFR will continue through this TAF period, interrupted by
potential convective impacts at/near HYS tonight. A thunderstorm
complex will develop rapidly across Nebraska and NW Kansas this
evening (00-03z). The latest HRRR runs show the tail end of this
complex impacting the HYS terminal in the 05-07z Thu time frame,
and included a TEMPO group. Elsewhere, convective development will
be isolated at best, and too limited to include in the other
TAFs. SE surface winds will remain elevated overnight tonight, at
10-20 kts. Widespread low level wind shear was included in all
TAFs after 06z Thu, with the NAM developing a strong low level jet
(850 mb winds 45-50 kts). Models remain in good agreement that a
convective outflow boundary from tonight`s convection will remain
intact and sweep through the terminals with a NEly wind shift
around 12z Thu. NE wind gusts of 22-27 kts will be common, along
with a period of broken mid layer clouds, Thursday morning.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 72 95 69 99 / 20 10 10 0
GCK 68 93 67 99 / 10 0 0 0
EHA 67 96 67 100 / 10 0 0 0
LBL 68 97 68 101 / 20 0 0 0
HYS 70 89 68 94 / 40 10 10 0
P28 76 98 72 99 / 20 20 10 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Turner
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Turner
Area Forecast Discussion
National Weather Service Duluth MN
1044 PM CDT Wed Jul 8 2020
.UPDATE...
Issued at 933 PM CDT Wed Jul 8 2020
Will leave the Severe Thunderstorm Watch as is. SPC mesoscale
analysis and CAM trends through 02 UTC favor a strong to severe
thunderstorm threat into much of the night. Thunderstorms
developing across northeast South Dakota into west central
Minnesota are expected to continue to propagate northeast into the
night with sufficient instability and effective shear to support
at least a marginal severe threat. Precipitable water values near
1.8 inches with continued strong moisture transport via the low
level jet and training of storms supports an increasing flash
flood threat.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 305 PM CDT Wed Jul 8 2020
Severe weather is the focus in the short term, especially from late
afternoon into late evening. Latest satellite imagery was showing
cumulus growing over the western half of the Northland and radar
shows a few showers/storms have formed. These are elevated given
that substantial MLCIN remains across most of the area. However, the
RAP shows the MLCIN diminishing by late afternoon as most of the
cloud from the earlier convection has diminished and strong heating
was occurring. The surface cold and warm fronts in addition to
the low level jet of 25 to 35 knots, an upper wave, and jet
streak will all contribute to forcing and sustenance of the
storms. We should see thunderstorms increase in both coverage and
intensity between late this afternoon and early evening over
northern Minnesota and this evening over northern Wisconsin. All
modes of severe weather will be possible including large hail to
golfball size, damaging wind to 70 mph , flash flooding, and a
tornado or two. Plenty of instability will be present with MLCAPE
forecast to increase to 1500-3500 J/KG, deep layer shear from 25
to 35 knots will be supportive, as will steep mid level lapse
rates, and high PWAT values from 1.6 to 2.0 inches. Storm mode
should start out with some discreet cells but most of the CAMs
show coverage will transition to clusters or lines. Low level
hodographs show decent veering and the longer storms can remain
discreet the better the chance for a possible tornado. In addition
to the tornado, hail, and wind threat will be very heavy rain.
Several strong thunderstorm complexes may track over the same
areas leading to heavy rainfall. We tossed the idea around for a
Flash Flood Watch but opted to not issue at this time. Much of the
Northland has seen below normal precipitation over the past week
and in some areas of northern Minnesota, the past few weeks. That
said, localized flash flooding will be possible late today into
tonight. The storms are expected to diminish but not end entirely
late tonight.
Another round of storms will be possible on Thursday as the front is
moving through the region slowly. The best chance for strong to
severe storms will be over parts of northern Wisconsin which will
remain ahead of the front and should recover from overnight
convection. Elsewhere, we have POPs as far west as eastern Minnesota
and the Arrowhead which remain just ahead of the front. Highs will
be in the eighties but dewpoints will be lower than today, except in
northern Wisconsin where mid sixties to around seventy will occur
again.
.LONG TERM...(Friday through Wednesday)
Issued at 305 PM CDT Wed Jul 8 2020
The extended period will feature a building ridge over the west that
will last into the weekend as the northern portion of the ridge
moves east. An upper low will then move east and push the ridge east
backing the upper winds to more southwest late in the period as
troughing takes over.
Friday will be dry and warm with weak ridging. Highs will range from
around eighty to the mid eighties in northern Wisconsin. Dewpoints
will be lower though and be in the fifties. There will be a few
chances for showers/storms over the weekend as a couple shortwaves
move through the region. However, coverage of the showers/storms do
not look to be particularly high. Highs will again be from 77 to 85
with dewpoints from the mid fifties to lower sixties for most areas.
A brief lull in precipitation chances will occur Sunday night into
Monday across most of the Northland then we have POPs again Tuesday
and Wednesday as the upper trough moves closer to the Northland.
Highs from Monday through Wednesday will be from 78 to 85 for most
areas.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 638 PM CDT Wed Jul 8 2020
The main issue for this evenings terminals will be thunderstorm
chances. Several areas of thunderstorms have been occurring this
afternoon and evening so far. A weak MCV was moving through
northeast Minnesota and was at least partially responsible for the
storms over the Iron Range and far northern Wisconsin. Further
west and south, a cold and warm front were aiding in causing
showers/storms. The airmass over the region is quite moist and
unstable making it relatively easy to form storms. We still think
an increase in both coverage and intensity to the storms will
occur over the next 1 to 2 hours. The strongest storms may
produce large hail, damaging wind, frequent lightning, very heavy
rain, and possibly a tornado. Most of the storms will occur
through the late evening hours but it`s possible they may last
through much of the night in some form. Most of the guidance
agrees that coverage will decrease between 09-12Z. Some fog and
stratus will be possible later tonight and could reduce conditions
to IFR or LIFR. The cold front will still be over far eastern
Minnesota by early Thursday afternoon and more thunderstorms will
be possible along and ahead of it.
&&
.MARINE...
Issued at 1044 PM CDT Wed Jul 8 2020
Thunderstorms, some strong to severe, will impact the nearshore
waters tonight, particularly along the North Shore from Duluth to
Silver Bay and the entire South Shore. Winds will generally be
southerly, but expect rapid changes in both speed and direction at
times tonight as thunderstorms move through. In addition, hail
will be possible as well in stronger thunderstorms. Winds will
become west to southwesterly tomorrow as a cold front moves
through during the afternoon. Thunderstorms will continue to be
possible particularly along the South Shore during the day
Thursday. Light westerly winds Thursday night into Friday with
high pressure moving in.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 63 84 59 83 / 80 20 10 0
INL 62 83 58 79 / 10 10 0 0
BRD 65 84 59 84 / 80 10 0 0
HYR 65 85 60 84 / 60 40 20 0
ASX 65 87 62 86 / 80 40 10 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
UPDATE...PA
SHORT TERM...Melde
LONG TERM...Melde
AVIATION...Melde
MARINE...JDS
Area Forecast Discussion
National Weather Service Des Moines IA
706 PM CDT Wed Jul 8 2020
.DISCUSSION.../Tonight through Wednesday/
Issued at 326 PM CDT Wed Jul 8 2020
...Updated for 00Z Aviation...
Warm and humid conditions this afternoon with temperatures in the
low to mid 90s common with dew points in the low 70s. A cumulus
field has develop around 5 kft. A wave dropping south from early
morning Minnesota MCS has led to some agitated cumulus and even a
few showers as it passes by to overcome weak capping but these cells
have been short lived. The wave is now approaching the Highway
30/Interstate 80 corridor and into an area where weaker inhibition
will be as stronger daytime heating continues. That said, while an
isolated strong storm could develop and there remains a low chance
for a cell to become severe, though it should be short lived with
deep layer less than 20 kts. The main threat is microburst with any
of the stronger cells. Subsidence behind the wave should keep the
remainder of the evening relatively quiet.
Storms will develop today along a boundary across South Dakota into
Nebraska. The trends continue to suggest the activity will congeal
into an MCS across Nebraska and dive southeast along the ribbon of
higher instability through eastern Kansas into nw Missouri while the
northern activity dissipates prior to reaching the forecast area.
This scenario would leave much of central Iowa devoid of
precipitation through the night. The HRRR and other CAM solutions
continue to suggest a remnant MCV arriving Thursday morning and
moving slowly east across the state with thunderstorms igniting by
mid to late morning mainly along and north of Interstate 80 as
strong instability develops in that area. Deep layer shear will be
much more favorable for organized storms even an isolated supercell
or two. These type of situations can end up having an isolated
tornado threat with more shear and vorticity around than progged in
addition to a large hail and damaging wind threat.
Thursday night into Friday will be mostly quiet with thunderstorm
chances ending. Friday will be cooler and less humid with high
temperatures in the mid to upper 80s. Another MCS is expected to
develop Friday night into Saturday morning though the projected path
is currently lining up along the Missouri valley and will miss much
of the area. Will continue to monitor further once the current
system passes.
Next week is trending warmer again as the thermal trough leans into
Iowa by around Tuesday and Wednesday. A boundary does lean into Iowa
during this time but 850 mb temperatures in the mid 20s and 700 mb
temperatures in the mid teens would likely suppress any convective
chances. These temperatures are also much warmer than what was over
the area today. Should the area miss much of the rain this week, the
dry ground combined with very warm temperatures aloft could allow
surface temperatures to push into the upper 90s to near 100 next
week. That will be the forecast challenge following the convective
chances early this weekend.
&&
.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 700 PM CDT Wed Jul 8 2020
VFR conditions will continue through the evening and much of the
overnight hours. Scattered thunderstorm chances increase tomorrow
morning into midday and will be moving from west to east.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT this evening for IAZ004>007-015>017-
024>028-035>039-047>050-059>062-072>075-083>086-095>097.
&&
$$
DISCUSSION...Donavon
AVIATION...KCM
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Sioux Falls SD
601 PM CDT Wed Jul 8 2020
.SHORT TERM...(This Evening through Thursday)
Issued at 222 PM CDT Wed Jul 8 2020
Mid and upper level clouds across most of eastern SD with some
clearing in central SD. This has allowed for some heating in central
SD but temperatures still mostly upper 80s to lower 90s at 19z. The
surface front was just west of the area. Latest HRRR starting to
back off on the more widespread convection in the James Valley from
about 22-01z and starting development a little later and mostly in
south central SD. Thunderstorms do still expand northward after this
but more in the 1-3z window. This seems to make some sense as the
cap is fairly robust and the HRRR and RAP were both eroding the cap
by what appears to be some sort of diurnal mixing of moisture
upwards. This seems pretty likely, but not sure if the 6 to 10
degree C rises in dew point and a 2 degree C or so fall in
temperature near 700 mb is plausible. There is no mid level moisture
upstream at DDC or LBF. If the cap cannot break late this afternoon
there does appear to be a wave moving into the panhandle of NE that
could move into north central NE from roughly 0-3z and would kick
start the convection. One other concern is the surface low to the
northwest is steady state or filling a bit so the winds at the
surface are not back and converging on the surface front but
remaining southwest. Once the convection gets going suspect that
anything that can develop north of I-90 will move northeast and
dissipate shortly after sunset or become more organized north of our
area. The activity in NE has a better chance of holding together
into the later night hours and could bring a MCV into northwest IA
Thursday morning. This would bring a chance for some isolated strong
updrafts into IA on Thursday morning and early afternoon.
As for the environment, if storms get going in central SD late this
afternoon CAPE values are burly, around 2500 to 3000 J/kg with
decent unidirectional shear. This might support a splitting
supercell or two with left movers racing north northeast about 35
to 40 mph and right movers moving southeast about 15 to 20 mph. Low
level inflow oriented from the south and southwest so in all
likelihood storms will progress east and southeast for a time, then
start to drop a little more due south as the new updrafts form and a
possible cold pool starts to drive development. Later tonight it
would mainly be a wind threat and this would likely be close to the
Missouri River.
.LONG TERM...(Thursday Night through Wednesday)
Issued at 222 PM CDT Wed Jul 8 2020
On Thursday increased pops in northwest IA with concerns that the
MCV will drift northeast and bring some showers and thunderstorms.
The main concerns for this will likely be farther east but northwest
IA should still see some activity. And once again a few stronger
updrafts are possible with hail the main threat. Otherwise
temperatures and humidity will be a bit more seasonal with highs in
the 80s and dew points in the 60s.
Thursday night should be quiet as upper level ridging spreads across
the area. This will allow for quieter weather, lighter winds and
Friday morning lows in the lower to mid 60s.
Friday and especially Friday night have some red flags for severe
weather potential. A fairly strong wave is expected to move onto the
Western High Plains and into eastern SD, southwest MN and northwest
IA by evening. Models very agreeable in producing a westerly upper
level jet with winds averaging about 50 to 90 knots. This really
cranks up the low and mid level wind field and in turn of course
offers a significant increase in available shear. CAPE values appear
as though they will be a bit lower, likely 1500 to 2000 J/kg. Would
expect an environment like this to produce a larger scale bowing
segment if model timing is correct.
Saturday continues the trend of highs in the 80s as the main wave
associated with this strong jet streak drops southeast. Will likely
see some lingering showers and thunderstorms east of Interstate 29
but for now looks like a dry sounding so only small chances.
Saturday night through Sunday night looks quiet with dry northwest
flow aloft. There are hints that another fairly strong wave will
move into the area on Monday but Monday through Wednesday far enough
out to not really bite on anything other than what looks like a
continued busy weather pattern with highs in the 80s to lower 90s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 554 PM CDT Wed Jul 8 2020
Main impact this evening will be scattered thunderstorms
developing along a weak cold front, likely remaining east of
KHON/K9V9 and west of Interstate 29 early this evening. This
activity will affect locations near KHON initially, then trek
east overnight toward KFSD and KSUX with strong wind gusts, large
hail, and heavy rain possible with the strongest storms this
evening. Confidence is low as to whether storms will make it to
KFSD and KSUX; could see storms, just rain, or just lower VFR
ceilings, most likely from 04-08z near KFSD and 07z-11z at KSUX.
Outside of storms, VFR conditions are expected. Gusty south winds
should decrease after sunset, turning north behind the front
overnight. Expect VFR conditions to prevail early Thursday.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...08
LONG TERM...08
AVIATION...BP
Area Forecast Discussion
National Weather Service Goodland KS
857 PM MDT Wed Jul 8 2020
.UPDATE...
Issued at 849 PM MDT Wed Jul 8 2020
Continue to expect severe weather to be tied to the line of storms
moving easterly across the forecast area. Currently there are two
severe thunderstorm watches going. The older one will continue for
counties where storm activity will occur by 11 PM CT. The new
watch will be for counties that will have storm activity after 11
PM CT. Even though the new watch lasts until 5 AM CT, will be
ending it for the counties in our forecast area well before that
when storms exit Norton and Graham counties.
&&
.SHORT TERM...(This evening through Friday)
Issued at 255 PM MDT Wed Jul 8 2020
Tonight...strong to severe thunderstorms are expected, mainly
along and east of a line from Max Nebraska to Atwood and
Grainfield Kansas. Along and east of this line CAPE values
approaching 4000 J/KG with DCAPE values approaching 2000 J/KG.
Thunderstorms are expected to begin further west and more high
based/isolated near a dryline then increase in coverage across our
northeast and eastern zones in response to an approaching upper
disturbance within west-northwest flow aloft. Several runs of the
operational HRRR have suggested wind gusts to 90 mph across our
far northeast area turning to the right into Graham and Norton
counties by mid evening. Given the large DCAPE values and the 91
mph wind gust in Hill City last week its certainly possible.
Precipitable water values are in the 1.5 to 1.7 inch range across
the east as well supporting WPC outlook for excessive rainfall.
Surface winds will shift to an easterly direction overnight behind
the departing MCS. Post frontal low clouds are also possible. Low
temperatures are expected to range from the upper 50s to around 60
in far eastern Colorado to the low and mid 60s east of the CO/KS
border.
Thursday-Thursday night...lots of uncertainty regarding
temperatures and precipitation forecasts. NAM/GFS 700-500mb
forecasts show some moisture reaching our far eastern Colorado
counties in the late afternoon hours then dissipating some while
moving east across the rest of the area during the evening. Cant
rule out some isolated storms as a result. We`re currently
expecting high temperatures in the upper 80s to low 90s. If the
NAM verifies readings will be a little cooler. Low temperatures
are expected to be in the low to mid 60s.
Friday...dry weather is expected but will need to be watched as
another weak disturbance aided by an increase in 700-500mb
moisture moves into the northwest 1/2 of the area during the time
of peak heating. High temperatures are expected to be in the low
to upper 90s.
.LONG TERM...(Friday night through Wednesday)
Issued at 233 PM MDT Wed Jul 8 2020
The ridge will continue to build north with the area of high
pressure centered over New Mexico, Arizona, and western portions of
Texas Friday night. The area of high pressure will continue to
remain stationary over the southwest states through the extended;
however, the extent of the ridge around the high will be suppressed
starting Monday afternoon. On Monday afternoon, an upper level low
will move east across western Canada, suppressing the amplitude of
the ridge generating westerly zonal flow aloft over and north of the
Central Plains region through the forecast period. Looking towards
Wednesday, there is disagreement between the GFS and ECMWF over the
placement of the low in the Saskatchewan province. The GFS is
trending lower towards the center of the providence with a trough
digging south into central Colorado during the early morning hours.
In this scenario the trough would move east across the Tri-State
area Wednesday afternoon to evening, straightening the trough to a
more zonal flow aloft as it moves. The ECMWF is placing the low in
the northern part of Saskatchewan, maintaining westerly zonal flow
over the Plains.
Due to the pattern we are in, much of the extended period will be
hot and dry. Surface level winds will generally be from the south
Friday night into Saturday morning before the winds shift towards
the northeast then east. The winds will gradually become southerly
through the day Sunday remaining from that direction through Monday
night. There is a slight chance of showers and thunderstorms Sunday
evening due to a shortwave trough. There is some disagreement into
the timing and location of the precipitation occurring, but it
appears the western portion of the CWA along and west of Hwy 27 has
the greatest chance. Monday will be hot and dry. Tuesday, another
shortwave trough will move east across the Tri-State area bringing
another chance of showers and thunderstorms in the evening into
early Wednesday morning ahead of a cold front.
High temperatures across the Tri-State area will be in the mid to
upper 90s with some locations reaching the low 100s on Saturday,
Monday, and Tuesday. Wednesday will be "cooler" with high
temperatures in the low to mid 90s after the passing of the front.
Lows each day of the extended will be in the 60s to low 70s, warming
to the eastern counties of the CWA. Due to the hot and dry
conditions, near-elevated fire weather conditions are possible for
the western portion of the Tri-State area, especially along and west
of the Colorado state line. Model guidance indicates relative
humidity values dropping near and below 20% west of highway 27
Saturday, Monday, and Tuesday. Forecasted wind gusts are currently
expected to remain below the elevated fire weather criteria of 25
kts; however, the winds could gust close to the threshold for
eastern portions of Kit Carson and Cheyenne counties in Colorado.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 537 PM MDT Wed Jul 8 2020
VFR to possibly MVFR conditions are forecast for the TAFs. Main
focus is the impacts/timing of the storm activity this evening.
KMCK will receive the brunt of the storm activity this evening.
Isolated storms may form to the west of Hwy 83. However, am
thinking most of the storm activity will occur along and east of
Hwy 83 this evening. Straight-line winds will be the main threat,
with a secondary threat of large hail. Behind the storm activity
the ceilings may lower to MVFR for both sites. The question is
will there be enough cloud cover to create a broken vs. scattered
deck. The clouds should clear out by late morning from west to
east.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JTL
SHORT TERM...99
LONG TERM...KMK
AVIATION...JTL
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1045 PM EDT Wed Jul 8 2020
.SYNOPSIS...
A weak area of low pressure will continue to slowly drift along
the North Carolina coast on Thursday. The low will then track
northeast along the East Coast through the rest of the week. Rain
chances will be in store every day of the forecast period with drier
air trying to work into the area by Sunday. Better chances for rain
will be in store for the early part of next week.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 1040 pm EDT: Shower activity has all but come to an end with
just a few showers continuing along earlier outflow boundaries
across southern areas. The forecast is on track through tonight with
the main question mark being the potential for fog or low stratus
development across the lower Piedmont. The latest RAP surface
condensation pressure and soundings suggest its probable for the
central Carolina`s, but can`t rule it out across the lower Piedmont,
especially where we saw rain today. Fog and low clouds continue to
be forecast for mountain valleys.
Otherwise, the quasi-tropical circulation along the NC/SC coast this
afternoon will move slowly northward over the Outer Banks tonight
through Thursday. On the western periphery of this system, rich
precipitable water air and weak banding will produce scattered
showers and thunderstorms through mid-evening before the instability
wanes. Meanwhile, differential heating, terrain flow, and weak
convergence will fire ridge scattered to numerous top showers and
thunderstorms over the mountains. Steering flow will take the
mountain convection southwest, with the extreme southern
Appalachians seeing the highest PoPs through late afternoon/early
evening. SBCAPE values are already running around 1500+ J/kg and
spotty 2000+ values are likely, which could lead to a couple of
strong to severe storms especially in the southwest mountains. The
convection will wane quickly overnight, with patchy mountain valley
stratus and fog developing.
Thursday could look quite similar to today, but with just slightly
drier air wrapping in on northeast to north flow, and a shallow
ridge stretching along the Appalachians west of the slowly departing
coastal surface low. Expect another round of more numerous ridge top
convection and scattered piedmont activity in the deeper moisture
during peak heating. Maxes will rebound by at least a category.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 130 PM EDT Wednesday: The short term forecast begins Thursday
afternoon with upper troughing still in place over the eastern
CONUS. The upper low that brought unsettled weather to our area over
the past couple days will move off over the Outer Banks, and at this
point it seems likely that some sort of tropical system will result.
The good news is that regardless of development, no direct impact
from this system is expected in our area as it lifts up towards the
northeast. Friday afternoon, an upper shortwave and weak surface
boundary will approach the area from the west, encouraging diurnal
convection especially in the mountains as normal summertime levels
of destabilization occur by the afternoon hours. It seems the front
may hang up before it`s able to reach too far into the forecast area
(though with latest model runs this has come into question), so
convection will favor the mountains. As always during the summer, an
isolated severe storm is possible, though nothing about the setup on
Friday looks particularly favorable for numerous instances of severe
weather. Saturday, model guidance has split...there is a decent
chance the frontal boundary will advance through the area before
peak diurnal heating on Saturday and result in very little
convective coverage in the afternoon, but some chance also remains
that the front will be hung up over our area at that point and work
as a focusing mechanism for storms. Either way, chances for severe
weather Saturday look low.
Finally, heat indices may become a concern Friday and Saturday with
a very muggy airmass hanging around the area and heights recovering
enough that max temps increase to a few degrees above climo.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 200 PM EDT Wednesday: Model guidance indicates a potential
blocking pattern over the extended forecast period. An immense
upper ridge will set up shop over the southwestern CONUS over the
weekend and promote upper troughing to dig into the eastern third
of the country. A shortwave trough should develop over the Upper
Great Lakes and Ohio Valley by late Sunday into Monday which could
allow for sparse convective development over the region during that
time frame. With the upper trough only gradually pulling away from
the East Coast, drier air should filter in on the backside of the
trough as a persistent northwest flow drives into the area during
the early part of the new work week. Both the ECMWF and GFS are
consistent on the overall large-scale pattern with upper troughing
staying confined to the area through Monday. The latest 12Z run of
the GFS still differs from the ECMWF with the trough deepening and
lifting much slower than the ECWMF starting Tuesday. The ECMWF on
the other hand, extends higher heights into the area by Tuesday
and the middle part of next week. The ECWMF has the upper ridge
in the Southwest stretching to the east and lifts the trough to
the north and east. The timing is inconsistent between the models
this far out, but temperatures should remain slightly above climo
for much of the forecast period with lowering PoPs as we go into
the first half of next week.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: High confidence in prevailing VFR at most
Piedmont sites except near KCLT where brief MVFR cigs are possible
between 09Z and 16Z and across mountain valleys where IFR cigs/vsbys
are likely sometime between 06Z and 12Z, especially for areas that
saw rain today like KAVL. Isolated (Piedmont) to scattered
(mountains) showers and thunderstorms are expected again Thursday
afternoon into the evening.
Outlook: Afternoon and evening showers and thunderstorms are
expected each day through the weekend. Morning cig/visibility
restrictions will also be possible each day, especially in river
valleys.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 100% High 98% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% Low 40% 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...DEO
NEAR TERM...HG/65
SHORT TERM...17
LONG TERM...CAC
AVIATION...65
Area Forecast Discussion
National Weather Service Wilmington NC
713 PM EDT Wed Jul 8 2020
.SYNOPSIS...
Showers and thunderstorms will continue tomorrow as low pressure
exits the region. This low could acquire some tropical
characteristics as it slides offshore. A stalled front will lead to
continued unsettled weather this weekend with much warmer
temperatures expected.
&&
.UPDATE...
Showers and thunderstorms continue over the area as of 6PM EDT,
but rapidly diminishing land-based instability should allow
lingering showers and thunderstorms to quickly collapse in the
next couple of hours. Latest surface analysis and hi-res models
show the center of offshore low pressure moving northeastward
and mostly out of the forecast area. A few isolated showers are
possible as onshore flow continues this evening and instability
over the coastal waters assists with vertical development,
mainly in portions of New Hanover and Pender County.
&&
.NEAR TERM /THROUGH THURSDAY NIGHT/...
The surface low that has been the weather story for the past few
days is slowly tracking to the northeast and is just off the coast
along the South Carolina and North Carolina border. With the low`s
position, the best forcing and deepest moisture are shunted to the
east over the Atlantic.
A more non-organized pattern of convection has developed once the
convective temperature was reached. Generally, this occurred where
there were breaks in the clouds, CAPEs are running 1500+ J/Kg, and
PW still in the 2.0"-2.4" range. The 18 UTC HRRR continues to show
this coverage of the convection to decrease after sunset.
As the slow-moving low-pressure center moves northeast to north-
northeast the threat of widespread flooding decreases, and the
chance of convection will fall to the 40 to 50% range in the
afternoon. Precipitable water is not expected to significantly drop
below 2", and with the weak winds aloft, there will be a possibility
of brief heavy downpours.
Highs will warm into the middle to upper 80s with the warmest
temperatures inland and in coastal areas south of Myrtle Beach. Lows
will be in the lower to middle 70s tonight and the middle 70s on
Thursday night.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Low pressure will lift northward toward the Northeast US on Friday.
The disturbance will bring a weak frontal boundary into the region
which will stall over the area this weekend. On Friday, this
boundary will be the focus for thunderstorm activity despite some
upper-level dry air and poor shear profiles limiting our widespread
coverage. Temperatures will be slightly above normal with heat
indices approaching the low 100s; heat issues will likely be the big
weather headline of the weekend. A similar day is expected on
Saturday with slightly increased coverage of thunderstorms during
the afternoon and heat indices approaching 105 in a few spots.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The stalled frontal boundary will remain in the area through the
weekend and into the early portions of next week. Afternoon showers
and thunderstorms will continue as a result. As an upper-level
trough approaches the area on Sunday evening and early next week,
shower chances will remain scattered through Tuesday. Along with the
shower chances, we will continue to see highs in the low 90s and
heat indices around 100. The upper-trough and stationary front
finally move east of the area on Wednesday. Thunderstorm chances
will decrease slightly as high pressure attempts to build into the
area by mid-week.
&&
.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
Popup showers continue to develop near the center of a tropical-like
low pressure system positioned just off the northern SC coast. The
main focus of the shower activity will be along a stationary
boundary which is draped along the coast. Weak instability and
saturation throughout a deep column will lead to continued sub-VFR
conditions and periodic fluctuations as low clouds move over our
various airports. Most of the variations will be just after sunset
as the boundary layer slowly collapses. Cooling temperatures and low-
level saturation will lead to widespread IFR with a few areas of
LIFR along the coast this evening. Stratus will stay with us for
much of the morning before clearing for a similar afternoon as today
with periodic drops to sub-VFR conditions during the afternoon due
to low tropical-like cloud bases.
Extended Outlook...Low pressure will exit the South Carolina coast
tonight, possibly acquiring tropical characteristics while offshore
Thursday and Friday. Diurnal convection will continue, especially
near the coast, with brief MVFR to IFR conditions expected through
the weekend.
&&
.MARINE...
The elongated low-pressure area along the coast seems to have
consolidated into a concentric shaped low just off the coast of the
North and South Carolina border. This low will slowly track to the
north-northeast through the remainder of the week.
Winds will be very light; that is, at or below 10 knots through
Thursday night. The wind direction will become more offshore on
Thursday. Seas will remain in the 2 to 3 feet range. The latest
WaveWatch III is showing an east-southeast swell continuing through
late Thursday before slowly dampening out.
Low pressure will move away from the coast on Thursday with
southerly winds at 10-15 knots returning to the coastal waters and a
continued chance of showers and thunderstorms. On Saturday, a weak
front will approach the area and increase the local gradient winds.
By Sunday winds will become 15-20 knots out of the south. With
multiple days of continued southerly winds, the fetch will generate
energetic wind waves at 3-5 feet. Small Craft Conditions could
become possible late Sunday and early Monday. Winds begin to relax
on Tuesday as the stationary front moves away from the area,
bringing an end to the prolonged unsettled weather and weakening
winds.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...21
UPDATE...21
NEAR TERM...RH
SHORT TERM...21
LONG TERM...21
AVIATION...21
MARINE...21/RH
Area Forecast Discussion
National Weather Service Louisville KY
914 PM EDT Wed Jul 8 2020
.Forecast Update...
Issued at 915 PM EDT Wed Jul 8 2020
Showers and storms have decreased in coverage this evening, and
after reviewing some of the latest guidance and trends, it appears
that we should remain dry through the overnight hours with loss of
surface heating. Forecast grids have been updated to account for
these changes.
&&
.Short Term...(This evening through Thursday)
Issued at 249 PM EDT Wed Jul 8 2020
With no real change in the stagnant air mass sitting over our
region, we can expect another warm and muggy night tonight. While
the majority of the afternoon convection will dwindle with the
setting of the sun, remaining instability, numerous left-over
boundaries, plenty of moisture, and a possible slight uptick in
850mb winds suggest holding on to a small chance of storms through
the night. This is supported by RAP and NAM guidance.
Tomorrow we`ll once again see scattered afternoon storms in the
humid, unstable atmosphere. The strongest instability should be west
of I-65, but all areas are fair game for convection. There will be
very little shear once again. A cold front will approach from the
west late in the day, but its influence should hold off until after
the short term.
.Long Term...(Thursday night through Wednesday)
Issued at 313 PM EDT Wed Jul 8 2020
The long term is going to see some change in overall flow as an
upper trough begins stretching from Iowa southeast towards North
Carolina. This will cover the Ohio Valley, but major changes won`t
be felt at the ground. Highs in the 90s with chances for isolated to
scattered thunderstorms remain.
On Friday, a quick moving cold front will move through central
Kentucky. This feature is extending from a low pressure system over
the Great Lakes, but due to the timing of the front, believe chances
of thunderstorms will increase from western Kentucky earlier in the
day to eastern Kentucky later in the day. Following the front, high
pressure will fill in over the area. Believe this will keep things
mostly dry on Saturday.
Saturday night into Sunday, a shortwave embedded in the northwest
flow will strengthen a surface low over northern Indiana and drag a
cold front through the Lower Ohio Valley. Expect this to elevate
chances for thunderstorms to move across region during the day.
Monday, surface high pressure behind the front will help to lower
rain chances and precede a surging upper ridge that continues moving
eastward for the next couple of days. Currently, it looks like this
ridge and high pressure at the surface could hold on through at
least the end of next week. This would drive conditions drier and
warmer.
&&
.Aviation...(00Z TAF Issuance)
Issued at 730 PM EDT Wed Jul 8 2020
Radar is currently showing a few lingering showers and storms
over central KY, but these are not impacting any TAF sites.
Showers and isolated storms should diminish later on this evening
and tonight, but muggy conditions will continue. There is
potential for patchy fog to develop during the pre-dawn hours at
HNB and BWG, so decided to drop them to MVFR for a few hours in
this TAF package. HNB has been consistent at reporting AM fog, so
confidence is higher for HNB than BWG.
Otherwise, same story different day for the Ohio Valley. Expect
scattered showers and storms tomorrow afternoon as daytime heating
ramps up again.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...DM
Short Term...13
Long Term...KDW
Aviation...CJP
Area Forecast Discussion
National Weather Service Melbourne FL
856 PM EDT Wed Jul 8 2020
.DISCUSSION...
Current-Overnight...Some ISOLD-SCT convection in the NWRLY flow
aloft traveling across Volusia and the adjacent coastal waters with
ample moisture and subtle impulses embedded in the flow, though
diurnal heating is ending and expect only an ISOLD threat into late
evening for Volusia and perhaps north Brevard. The local HRRR is a
bit optimistic for some additional coverage across the coastal
waters into late tonight. Remaining mostly dry everywhere else over
land. Cloud cover will diminish through the night. Winds light and
variable under 5 mph. Temperatures overnight will settle into the L-
M 70s.
Thursday...Previous...Weak low pressure will be along the North
Carolina coast with the Atlantic subtropical ridge axis remaining
across south FL. These two features will maintain a west to
southwest flow pattern across central FL. The stout west flow will
at least delay the east coast sea breeze formation and produce
slightly above normal temperatures in the low to mid 90s. The
deepest moisture is forecast to shift east of the area but
precipitable water values remain high, close to 2 inches. Rain
chances are 40-50 percent across the area, which is around
climatological average for early July.
Temperatures aloft look warm with -5C to -6C at 500 mb and
unimpressive lapse rates. However, forecast model soundings show
some drier air aloft which should promote additional gustiness. A
few strong storms will be possible especially where boundary
collisions occur (outflow and sea/lake breezes). Lightning
strikes will be the primary threat. Heavy rainfall will occur but
westerly steering flow around 20 knots should keep storms moving
so accumulations should remain low.
&&
.AVIATION...Diminishing convection but will need to watch KDAB, KTIX
thru the evening. Thinning clouds overnight. Winds light/variable to
near calm. SCT shra/tsra again on Thu, especially in the afternoon.
Tempo MVFR (ISOLD IFR) in storms.
&&
.MARINE...Overnight...Models hint at enough instability, moisture,
and upper-level features around to keep SCT showers/storms in the
forecast for much of the evening/overnight. WRLY flow (WSW-WNW) AOB
15 kts. Seas 1-2 ft near shore and 2-3 ft offshore. Winds/seas
locally higher invof storms.
Thu...Atlantic ridge axis will remain south of the local waters,
across south FL, with W/SW wind flow dominating. Onshore flow should
develop near the coast in the afternoon behind the sea breeze but
formation could be quite late and even not at all if the offshore
flow is too strong. Wind speeds forecast to remain 15 knots or less
with seas 1-2 ft near shore and 2-3 ft offshore.
Main threat to boaters will continue to be scattered to numerous
offshore moving storms producing frequent lightning strikes and
gusty winds, mainly from mid afternoon through early evening.
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Sedlock/Cristaldi
Area Forecast Discussion
National Weather Service Marquette MI
625 PM EDT Wed Jul 8 2020
.SHORT TERM...(This evening through Thursday)
Issued at 356 PM EDT WED JUL 8 2020
Well, so far not quite as warm as was forecast thanks to some cirrus
convective contamination from storms across MN this morning. Didn`t
cut them back too much, but took a couple degrees off across the
board to go with the trend through the day. A few thunderstorms made
their way into western UP this afternoon, but diminished quite
quickly as they propagated into an unfavorable convective
environment. Through the rest of the afternoon and into the evening,
temps may climb a few more degrees, but otherwise expecting more of
a filtered sun through the cirrostratus across the west and central
and status quo across the east.
Tonight, things become interesting fairly early on this evening as
CAMs suggest thunderstorms to develop across central MN and
propagate eastward. CAMs suggest upscale growth to occur earlyish on
as any isolated storms congeal into a MCS as they move over Lake
Superior into the UP circa 00UTC. Latest HRRR is suggesting a little
later closer to 02-04UTC. Either way, models suggest upwards of 2500
to 3000 J/kg of sfc CAPE, with bulk shear near 30kts and 0-3km
200m2/s2 helicity. The better shear remains just behind the CAPE
gradient, which should help keep the svr threat lower, but there is
some potential for strong to svr winds across western UP as the
storms move into the CWA. AS they continue to propagate eastward,
they move into a less favorable environment and as such, the CAMs
show a diminishing trend rather quickly, struggling to make it any
further than Marquette/Menominee counties.
Tomorrow, residual low-level moisture may lead to some morning fog
for some before skies become partly cloudy by mid morning/early
afternoon. Another hot and muggy day expected with highs a little
cooler in the west(mid to upper 80s), but near 90 across the central
and east where a little more sunshine is possible. With Tds in the
mid to upper 60s, the "feels like" temperatures will push in to the
low 90s for most. As a shortwave lifts north through WI tomorrow,
CAMs suggest another round of developing thunderstorms in the
afternoon/evening across the central, but better forcing remains
behind the instability and have cut back and slowed PoPs from the
going forecast. Seems like ARW core models are much faster to bring
these storms in with NMMB models keeping conv tightly tied to the
shortwave and developing weak sfc low.
.LONG TERM...(Thursday night through Wednesday)
Issued at 310 PM EDT WED JUL 8 2020
Generally progressive pattern will persist across the northern Lakes
through next week. Upper low moving into far northwestern Ontario
will push a weak cold front through the Upper Great Lakes and U.P.
Thursday night into Friday. Well defined MCV will eject out of the
Plains into the lower Lakes later Thursday into Friday. The end
result will be better upper forcing passing to the north and south
of the U.P. with the weak front the main forcing mechanism for
scattered showers and thunderstorms lingering across the area
Thursday night and moving eastward through Friday morning.
Dewpoints behind the front will fall off into the 50s especially
across the west by Friday afternoon. 85H temps will fall back into
the 10-12C range for the weekend allowing for more seasonable
temperatures through the weekend. 2 weak shortwaves in the west
northwesterly upper flow passing through later Saturday and on
Sunday may be enough to trigger a diurnal shower or tsra but
coverage of any precipitation will be small.
With ridging overhead on Monday expect a dry, seasonable day. Beyond
Monday the Upper Great Lakes will be on the northern fringe of a
nearly 600dam 500H ridge across the Ohio Valley. Shortwaves embedded
in the westerly flow may trigger some more organized shower and
thunderstorm activity by later next Tuesday into Wednesday.
Temperatures will return to their significantly above normal levels
by that time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 625 PM EDT WED JUL 8 2020
VFR conditions are expected to continue through at least tonight
before a line of thunderstorms develops this evening across north-
central MN and propagates eastward. The best chance of thunderstorms
look to impact IWD and CMX before they begin to diminish on their
way to SAW. With these thunderstorms, MVFR to potentially IFR vsbys
are expected in the heaviest rain axis. Have kept TSRA in for SAW as
there is still a decent chance they persist this far eastward.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 356 PM EDT WED JUL 8 2020
Patchy fog, locally dense at times, will continue through this
forecast period given the warm and moist airmass over the region.
This evening, thunderstorms are expected to move into the western
portions of Lake Superior. Some storms could be strong, capable of
producing gusty winds and heavy rain fall, capable of reducing
visibilities quickly. Expect fog to develop in locations that
receive the rainfall. Another small chance of thunderstorms are
possible across the east half tomorrow night. With the exception of
any gusty winds in these storms, winds are expected to be below 20
knots through the forecast period.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JAW
LONG TERM...MZ
AVIATION...07
MARINE...JAW
Area Forecast Discussion
National Weather Service Nashville TN
745 PM CDT Wed Jul 8 2020
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Scattered storms are ongoing south of I-40 as we head into the
evening. The existing cells are generally slow-moving and have
been producing some impressive rainfall totals. The evening
sounding from OHX shows deep instability and plenty of moisture
(LI -8, SBCAPE 2,693 J/kg, PWAT 1.74"). So the environment is ripe
for the kind of convection we`ve been seeing. The HRRR erodes
these cells by late evening, so we should be rain-free during the
overnight period. Radiation fog is somewhat of a concern after
06Z, especially along the Cumberland Plateau. We`ll need to keep
an eye on VSBY`s as dew point spreads shrink and winds diminish.
At this time, the hourly grids are holding up well, so we aren`t
planning any significant forecast changes for now.
&&
.AVIATION...
00Z TAF DISCUSSION.
BNA/MQY/CKV/CSV...Scattered storms continue to affect Middle
Tennessee mainly south of I-40, including the MQY terminal. Storms
are slowly moving southward and HRRR suggests the current
convection will weaken during the next couple of hours. Expect
radiation fog overnight, and it may be especially dense at CSV
where they received copious rainfall earlier today. Scattered
showers & storms will develop once again tomorrow afternoon. Will
handle this with VCSH remarks for now.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......08
AVIATION........08
Area Forecast Discussion
National Weather Service Blacksburg VA
738 PM EDT Wed Jul 8 2020
.SYNOPSIS...
A tropical low pressure area along the South Carolina coast
will gradually lift north and northeast along the coastline,
reaching Virginia Beach by Friday morning. Scattered to numerous
thunderstorms will continue through Friday. Saturday and
Sunday, a weak cold front will move into the region from the
west bringing a chance for more widespread showers and
thunderstorms.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 725 PM EDT Wednesday...
Showers/few thunderstorms clustered across southside VA into
the NC piedmont. Models had not picked up on it, so mainly going
with radar trends/mesoanalysis which overall favors a
decreasing trend this evening and can see that on radar at
720pm.
A few showers further west should also subside by 9pm. Appears
mainly dry overnight with low clouds and fog another possibility
especially east of the Blue Ridge.
Previous discussion from early afternoon...
Low pressure off the South Carolina coast will move slowly northeast
along the coastline. This will result in deep easterly winds tonight
which become northeast on Thursday. This upslope combined with the
persistent moist, unstable air mass and a weak short wave aloft with
trigger isolated to scattered thunderstorms along and west of the
Blue Ridge this afternoon. HiRes models, including the SPC HRRR show
a majority of the thunderstorms weakening then dissipating shortly
after 00Z/8PM tonight. Thursday the same pattern of afternoon
thunderstorms will continue in the mountains.
In the foothills and piedmont the deepest moisture and best coverage
of showers and thunderstorms will remain just southeast of Danville
this evening and east of a Lynchburg to Danville line on Thursday.
Have oriented probability of precipitation to align highest pops in
the east.
Used combination of persistence and NBM for lows tonight and highs
on Thursday. MOS and other guidance showed minimal change in surface
dew points tonight and Thursday which will keep the air mass humid
and the minimum temperature mild. More cloud cover in central and
eastern Virginia and North Carolina Thursday will cut high
temperatures a few degrees.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 100 PM EDT Wednesday...
The tropical low just offshore in the Atlantic will move north and
into New England by Saturday. An upper trough will follow close
behind, arriving from the west and lining up the trough axis over
our area Saturday afternoon. So up until the weekend, the tropical
system to our east will feed moisture into the area and cause
afternoon showers. With the tropical exit, troughing overhead will
combine with daytime heating to spawn afternoon showers and storms
over the weekend. These will likely be concentrated along and west
of the Blue Ridge, as the northwest flow afforded by the trough will
create some subsidence on the lee side of the Appalachians, and
orographic support will contribute to the formation of convection.
Temperatures are back on the rise as highs in the Piedmont and
Southside will consistently reach the 90s, and mountain areas will
be in the 80s. In short, its going to feel like summer.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 100 PM EDT Wednesday...
Several shortwaves will ride along the trough over the eastern
seaboard Monday and Tuesday, before the upper trough axis begins to
head offshore and is replaced by ridging. This ought to calm the
daily showers and storms of late and make Wednesday and Thursday a
bit clearer than the earlier parts of the forecast period. With that
clearing we may see another small nudge upwards in afternoon highs,
but overall expect highs in the upper 80s/lower 90s in this period,
with lows in the 60s.
&&
.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
As of 725 PM EDT Wednesday...
Keeping showers in at DAN til 01z, with VCSH at LYH. Otherwise,
looks mainly VFR through this evening, with models showing some
lower cigs arriving east of the Blue Ridge late tonight, and
plan on keeping IFR or lower at LYH/DAN after 08z. Not confident
Roanoke will see any sub-VFR conditions.
Further west, less cloud cover appears likely with fog an issue
at LWB/BCB, and possibly BLF. LWB should see LIFR again, with
IFR at BCB and MVFR BLF.
Low pressure will be over eastern NC Thursday which will bring
winds around to the northeast. At this time, mainly dry weather
is expected, though a few showers/storms are possible in the
piedmont, but not enough to have in the tafs.
Any low clouds/fog will be gone after 14z Thursday with mainly
VFR through the day.
Forecast confidence is above average for sub-VFR late tonight,
but average on condition after 14z Thursday.
Extended Aviation Discussion...
Thursday night moisture is trapped under the developing
nocturnal inversion resulting in widespread low clouds, fog, and
drizzle with high dewpoints.
Additional showers and storms are possible Friday through
Sunday thanks to a series of northwest flow shortwave troughs
crossing the area and a weak frontal system moving into the area
from the west Saturday. Coverage of convection will likely be
greatest across the mountains. Ceilings have a greater potential
of being sub-VFR across the mountains as compared to the
Piedmont region.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...AMS/WP
NEAR TERM...AMS/WP
SHORT TERM...VFJ
LONG TERM...VFJ
AVIATION...AMS/RAB/WP