Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/18/20
Area Forecast Discussion
National Weather Service La Crosse WI
1050 PM CDT Fri Jul 17 2020
.SHORT TERM...(This evening through Saturday)
Issued at 240 PM CDT Fri Jul 17 2020
Lots of active weather to discuss in the short term! Ridging
continues to amplify in the low levels with broad southerly flow
pumping increasing heat and humidity into the region. Quite a stark
contrast as you step outside this afternoon compared to yesterday
with dewpoints having jumped a good 10 to 15+ degrees in the last 24
hours, currently sitting in the lower 70s across the majority of the
forecast area. And thanks in part to that heat-loving, humidity-
breathing Midwest corn, the muggy-meter will continue to climb a bit
more over the next 24 hours. Air you can wear, soupy, yucky (however
you choose to describe it)...any similar descriptors will be
applicable heading into Saturday as dewpoints climb into the mid to
upper 70s.
Of course that sets the stage for occasional shower and storm
chances as the weekend gets underway. The increase in low level
moisture today has favored development of a pretty expansive cumulus
field across the area. A warm front lifting through northern Clark
and Taylor counties has an accompanying band of higher MLCAPEs up to
2500 J/kg per RAP analysis. Already seeing some agitated cu and some
weak radar echoes developing along this boundary thanks to
associated weak fgen. As a result, a broken line of showers and
storms will be possible through late afternoon in this area, but not
expecting this activity to get out of hand.
For tonight, all eyes will be on MCS already developing over North
Dakota at this hour. Still considerable uncertainty as to how this
storm complex will evolve heading into tonight as it matures into a
bowing line crossing into northern MN and eventually northern WI
late tonight. CAMs are still split as to whether this system stays
mainly over northern WI or if it expands further south and perhaps
dives a little more southeastward into our area. Earlier HRRR runs
trended a little more northward, and recent runs have consistently
taken this complex just by or clipping our far north. ESRL HRRR,
RAP, and ARW have the MCS clipping areas north of I-94. Meanwhile
17.12Z NAMnest, NMM, and NSSL WRF show a greater southward
development that cuts through a greater extent of our forecast area.
Needless to say, still quite a murky picture, but am inclined to
lean towards the more northern solutions as the favored outcome
given the HRRR`s earlier trend and hour-by-hour consistency. Yes,
greater instability will reside farther south, but there will also
be considerable capping developing over our area due to elevated
warm layer building into the region. So not convinced the southern
solutions will manifest, but would like to see more agreement among
the CAMs before writing this idea off completely. For now, retained
highest PoPs north of I-90 and particularly north of I-94. This will
also be an area with plenty of deep layer shear in the vicinity of
the MCS to sustain it. Damaging winds will be the main threat, but
can`t rule out some isolated hail and perhaps a brief tornado
(impressive 0-1km shear and hodograph curvature). Timing would be
late tonight towards daybreak Saturday, roughly between 3am-7am, but
this too will need to be refined as mesoscale details are resolved.
Saturday`s main story will be the heat and humidity. Very muggy
morning lows of around 70 to the mid 70s will give a head start to
the day`s building heat, with afternoon temperatures climbing into
the low to mid 90s across most of the area. Exactly how hot it gets
will depend on whether we have any lingering widespread cloud cover
from the morning MCS, but models have been trending optimistic for a
decent amount of sunshine and a toasty southwest breeze. Expecting
peak heat index of generally 100-105 degrees for most of the area,
with some of the typical hot spots perhaps in the 105-110 range for
a brief time. So heat advisory for majority of the area (minus
Taylor County where heat index will be 95-100) remains unchanged.
Looks like stout low level capping in place through the day, so not
expecting any convective activity until round 2 of storms in the
evening (read on below for details).
.LONG TERM...(Saturday night through Friday)
Issued at 240 PM CDT Fri Jul 17 2020
A cold front will approach the area Saturday night, bringing another
round of more widespread showers and storms to the area through the
overnight hours. Due to very humid conditions lingering into the
evening hours, CAPE values of 3000-4000+ J/kg will be likely ahead
of the front. Shear will also be plentiful, with around 50 kts
between 0-6 km, though the 17.12Z GFS keeps the better shear behind
the front. There are some differences still with exact timing that
storms will develop and move into the local area as the very warm
temperatures will keep the area capped off through late Saturday
night. The general consensus is that storms will develop over
central Minnesota sometime late Saturday afternoon into early
evening and progress east with the front, reaching parts of
southeast Minnesota and western into central Wisconsin sometime
between 03-06Z. Storm mode will initially be discrete before
becoming more linear in nature as it moves into the local area.
Primary hazards will be damaging winds and large hail. However, with
0-1 km shear of 15-25 kts, an isolated tornado cannot be ruled out
in any discrete storms, though the shear appears to be more speed
driven with surface winds mostly out of the southwest.
Heavy rainfall is also a concern, especially across parts of central
Wisconsin where very heavy rain occurred earlier this week.
Precipitable water values look to be near the climatological max
nearing 2 inches or slightly above and very deep warm cloud depths
of 4 km will allow any stronger storms to drop a lot of rain very
quickly. Depending on how the MCS plays out tonight, will need to
keep an eye on the flooding potential ahead of the second round of
storms expected Saturday night, though storms overall look to be
relatively progressive. Little relief in temperatures Saturday
night, with values ranging from the upper 60s to 70s - much of the
area will stay in the 70s to 80s prior to midnight.
Continued warmth on Sunday with highs in the 80s, though it will not
feel nearly as warm as Saturday thanks to lower dewpoints arriving
behind the frontal passage. Surface high pressure builds in from the
west throughout the day on Sunday, keeping things mostly dry. Flow
aloft will be mostly zonal for the beginning of next week before
transitioning to more northwesterly by midweek as high pressure
ridging builds out west. Occasional chances for showers and storms
appear likely, with the most notable possibly being Tuesday night or
Wednesday as a more potent shortwave trough moves through. Pretty
good model agreement that ridging will move overhead by the end of
next week, which may bring another period of above normal
temperatures to the area.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1050 PM CDT Fri Jul 17 2020
Will be watching the evolution of a complex of storms across
central MN as it moves ESE overnight. For now, confidence in
storms impacting KRST/KLSE is low enough to omit from the TAFs
during the 07-12Z time frame, but trends will be monitored.
Otherwise, expect mainly VFR conditions although patchy MVFR
ceilings can`t be ruled out overnight. Southerly winds will gust
up to 25 kts at times on Saturday. Another round of storms is
possible Saturday night with a cold front passing through the
area.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Heat Advisory from 1 PM to 8 PM CDT Saturday for WIZ029-032>034-
041>044-053>055-061.
MN...Heat Advisory from 1 PM to 8 PM CDT Saturday for MNZ079-086>088-
094>096.
IA...Heat Advisory from 1 PM to 8 PM CDT Saturday for IAZ008>011-018-
019-029-030.
&&
$$
SHORT TERM...Kurz
LONG TERM...NMB
AVIATION...JM
Area Forecast Discussion
National Weather Service Denver/Boulder CO
809 PM MDT Fri Jul 17 2020
.UPDATE...
Issued at 757 PM MDT Fri Jul 17 2020
Subtropical moisture moving across the area, led to high based
showers and a few tstms, over the higher terrain and along
portions of the I-25 corridor. Meanwhile, outflow boundaries have
triggered additional activity further east, over the plains, but
most of this will end by 10 pm.
Otherwise, with lingering clouds overnight, lows will be very
mild.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 255 PM MDT Fri Jul 17 2020
So far this afternoon, convection has been spotty and weak in the
mountains and mainly dying as showers come off the foothills.
Dewpoints have dropped into the 30s with resultant very little
CAPE less than 600j/kg. Latest HRRR continues to show some weak
convection moving onto the plains this evening with main impact of
gusty winds with inverted type v soundings. Saturday will be
another hot one with readings around 100 on the plains. Could see
at least a tied record at Denver, with the old record of 99
degrees. Like today, any convection will be weak, high based with
mainly gusty winds with showers. There is expected cold front
which will be entering the far northeast corner towards supper
time Saturday evening. Could see a few stronger storms there with
convergence and higher influx of low level moisture.
.LONG TERM...(Saturday night through Friday)
Issued at 255 PM MDT Fri Jul 17 2020
A cold front will push down into the forecast area Saturday
evening, increasing precipitable water values and CAPE, with
upslope flow that may keep convection going through the evening.
Could see some stronger storms over the far northeastern plains
where CAPE values of 1400-2000 j/kg will have a bit of CIN to
overcome as the sun goes down.
Upslope flow will continue Sunday and PW values expected to
increase over an inch over the plains, while the mountains remain
around 0.5-0.7 inches. While temperatures will be 5 to 10 degrees
cooler (mainly over the plains), a shortwave trough moving east
across the Northern Rockies will aid in lift to increase storm
coverage. The added moisture over the plains and the sun`s heating
will aid in producing mixed layer CAPE values upwards of 3000 J/kg
over the far northeastern plains, along with 40 kts of bulk shear.
Will see a chance of severe storms Sunday evening out near the NE
border.
Yet another shortwave trough over the Northern Rockies and a bit
of a northeasterly surge into the plains Monday will keep another
day of scattered to numerous showers and storms. Cooler
temperatures will lead to weaker CAPE, and the combination of
weaker shear will allow for weaker storms.
The upper high will begin to move from the Four Corners area
Tuesday, increasing heights over the state, yet another surface
northeasterly surge will keep a chance of storms across the area.
The upper high will then transition east to be positioned over the
southern and southeastern states through the rest of the week.
This will allow for southwesterly flow into the state, which will
bring a warming trend as well as subtropical moisture into the
area. A thermal trough over the plains will likely keep most of
the showers and storms over the high country, with isolated
activity over the plains.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 757 PM MDT Fri Jul 17 2020
High based showers will continue for the next hour or so with
brief gusts up to 30 mph. Winds will remain southwest to south
overnight.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...RPK
SHORT TERM...Entrekin
LONG TERM...Kriederman
AVIATION...RPK
Area Forecast Discussion
National Weather Service Dodge City KS
522 PM CDT Fri Jul 17 2020
...Updated Aviation...
.SHORT TERM...(This evening through Saturday)
Issued at 233 PM CDT Fri Jul 17 2020
A mid level trough was in place over eastern Colorado this afternoon.
ahead of the trough southerly winds were common across western KS.
Weal 850 mb moisture transport was still in place from around Garden
City eastward, and temperatures were looking slower to rise in many
areas likely due to the rainfall overnight and to a lesser extent
areas of cloudiness. Recent HRRR runs have explicitly developed
convection in a NE-SW oriented line southwest of Dodge City,
possible associated with an area of low level convergence and very
high theta-e. The NMM nits at it as well although the HiRES models
do seem to struggle with the same scenario. Given the state of the
atmosphere the last few nights we went ahead and added slight chance
precipitation TSRA over some southeast counties for he late
overnight hours. Any storms that pops up could easily produce a few
tenths of an inch of localized rain. In the closer term - the
western edge of the heat advisory may have trouble reaching the
criterion apparent T of 105, however the higher dew points in the
70s farther west will give it a shot. Have trimmed off the western
2/3rds of the advisory for this afternoon.
.LONG TERM...(Saturday night through Friday)
Issued at 233 PM CDT Fri Jul 17 2020
Saturday there will be a better setup for thunderstorms as a cold
front begins to push southward out of Nebraska and convection at
some point is likely to unzip near the cold front dryline interface
in northern Kansas...and southwest along the convergence axis toward
the Liberal area. With the possibility of a stalled front on Sunday,
the pops are even higher. No period of he extended appears
definitively dry although by Thursday and Friday it looks like we
will be under deeper southwest flow, dryer air and capping for
possible a stretch of days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 514 PM CDT Fri Jul 17 2020
VFR conditions are expected for all terminals this TAF period.
Strong SSW winds will combine with the nocturnal low level jet to
produce strong S to SW wind shear overnight at all terminals in
the 03-14Z time frame. After 14Z, the wind shear is expected to
relax, however, strong SSW winds will persist throughout the day
tomorrow.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 76 104 72 93 / 10 10 20 20
GCK 74 104 71 91 / 0 10 20 30
EHA 73 101 69 97 / 10 10 30 20
LBL 75 103 71 98 / 10 10 30 20
HYS 75 102 71 88 / 10 10 30 20
P28 76 103 74 97 / 20 10 10 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT this evening for KSZ090.
&&
$$
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Springer
Area Forecast Discussion
National Weather Service Grand Rapids MI
1152 PM EDT Fri Jul 17 2020
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 333 PM EDT Fri Jul 17 2020
-Rounds of storms possible over the weekend
-Some storms could be strong to severe, especially late Saturday
night into Sunday.
-Hot and humid weekend; less humid early next week
&&
.DISCUSSION...(This evening through next Friday)
Issued at 333 PM EDT Fri Jul 17 2020
-- Rounds of storms possible over the weekend --
Active thunderstorm/MCS pattern quite possible this weekend, with
the potential for damaging wind gusts, power outages, isolated
large hail, and heavy downpours.
Current thinking is that late Saturday night into early Sunday
will be the most active period since that`s when the cold front
will be coming through. However timing/location of events in MCS
patterns can be very challenging since each MCS can
influence/alter the downstream environment and future convective
development.
All eyes tonight will be on the bow echo expected to track through
nrn MN into nw WI, where the SPC has a MDT risk of svr wx. This
feature will need to be closely watched since it could easily
curve southeast and begin impacting west central Lwr MI after
daybreak Saturday.
While the mid level flow would suggest an easterly trajectory of
this feature across upr MI and far nrn Lwr MI, the deep layer
thickness/thermal progs very much suggest a southeast trajectory,
with areas north of I-96 possibly seeing a morning convective
event.
This conundrum is quite evident in the various CAMs and HRRR
ensembles, with various solutions of how upstream convection will
behave very late tonight into early Saturday. The solutions range
from 1) All convection remaining to our north, to 2) our nw/nrn
cwfa being impacted by a bowing segement, to 3) a few clusters of
storms developing southeast of the main MCS along the warm
advection wing in the early morning.
And to make matters worse, we have one model, the 12Z NAMNest,
indicating new clusters of storms developing directly overhead
late Saturday afternoon after 21Z, presumably from remnant outflow
from the early morning convection. This solution is an outlier,
and we tend to believe most of Saturday afternoon and evening
will be dry since we should be fully in the capped warm sector.
Highest pops and best potential for strong to severe storms
impacting a larger portion of our area is Saturday night and
Sunday morning. New strong to svr storms that form over nrn WI and
nrn LWR MI Sat evening are expected to eventually propagate
southward into our higher instability air with capes over 2500
J/KG.
If a large MCS impacts the area Saturday night/early Sunday, new
convection on Sunday will probably develop south and east of our
area. If that MCS doesn`t occur or is focused farther north and
west, then Sunday could be an active day especially south and
east of GRR.
-- Hot and humid weekend; less humid early next week --
While heat indices will be 95-100 this weekend, especially in
southern sections, the passage of a cold front late Sunday will
bring in less humid air to start next week. That front could
bounce back north Tue-Wed briefly and bring another round of
storms before returning south of the area again.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday)
Issued at 1145 PM EDT Fri Jul 17 2020
VFR conditions will continue at all the terminals
through late Saturday evening. South to southwest
winds will increase to 10-15 kts with gusts to around
20 kts Saturday and some higher gusts to near 25 kts possible at
KMKG.
Isolated storms are possible Saturday afternoon but
there is not enough potential to warrant mention in any
of the terminal forecasts. There is a chance for
thunderstorms by early Sunday morning but only after 06Z
Sunday.
&&
.MARINE...
Issued at 333 PM EDT Fri Jul 17 2020
Will be issuing a Small Craft Advisory and Beach Hazard Statement
for Grand Haven northward, to be in effect starting 8am Saturday.
This is for the increasing south-southwest flow (15-25 kts) that
develops after a warm front lifts north through the area.
The south side of south piers will be most dangerous such as at Pere
Marquette Park in Muskegon and Grand Haven State Park, however the
highest waves (near 5 feet) should be north of Whitehall.
Once any morning/midday clouds and shower/storms get out of the
way, beach populations will likely swell Saturday given the hot
and humid weather. Strong longshore and structural currents can
pull swimmers into deeper water and high waves can sweep people
off piers, so "steer clear of the pier"!
These marine headlines will be out through midnight Saturday, but
will probably need to be extended and expanded southward for Sunday
with the flow turning more westerly with time.
There is a good deal of uncertainty in how convective events will
play out over the weekend, but obviously thunderstorms will be a
hazard on Lake Michigan at times over the weekend - especially
late Saturday night.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 8 AM EDT Saturday through Saturday
evening for MIZ037-043-050.
LM...Small Craft Advisory from 8 AM Saturday to midnight EDT Saturday
night for LMZ847>849.
&&
$$
SYNOPSIS...Meade
DISCUSSION...Meade
AVIATION...Laurens
MARINE...Meade
Area Forecast Discussion
National Weather Service New Orleans LA
324 PM CDT Fri Jul 17 2020
.SHORT TERM...
Today and tomorrow, drier conditions will persist due to dominant
higher pressure over the area. Southeasterly surface winds will
act to enhance the moisture in the environment. Consequently, a
shower or two is possible, especially during peak heating hours
tomorrow, but chances are low. Cloud cover will be increasing as
we move into the weekend. MSW
.LONG TERM...
Overall, a typical summertime pattern will dominate Sunday
through the end of next week. Surface southeasterly and easterly
winds will help to enhance the moisture and warm air advection
into the area. Scattered showers and thunderstorms will be
possible daily, especially during the afternoon and early evening
hours. These storms could have locally heavy rainfall at times
where they do occur, especially if any training develops or if
storms build over one area for a long time. These storms also will
have the potential for frequent lightning and gusty winds in
their vicinity. Waterspouts could also be possible if these storms
form over the marine waters. MSW
&&
.AVIATION...
VFR CAVOK condiitions expected at all terminals next 24-30 hours
with light and variable to SE wind. Isolated nature of any
convection too low to mention explicitly in TAFs at this time. RR
&&
.MARINE...
Winds will be calm (<15 knots) and southeastery to easterly
through the next week. Wave heights will correspond to the wind
speeds. MSW
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 74 92 74 92 / 10 20 10 30
BTR 74 93 75 92 / 10 20 10 40
ASD 74 93 75 92 / 10 20 10 50
MSY 78 91 78 90 / 10 20 10 60
GPT 76 89 77 89 / 10 20 10 30
PQL 73 93 74 92 / 10 20 10 30
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&
$$
Area Forecast Discussion
National Weather Service Lubbock TX
658 PM CDT Fri Jul 17 2020
.AVIATION...
VFR conditions will continue for all TAF sites for the next 24
hours. Storms currently in New Mexico are not expected to directly
affect TAF sites. Density altitude is currently around 6500ft.
&&
.PREV DISCUSSION... /issued 239 PM CDT Fri Jul 17 2020/
SHORT TERM...
Hot temperatures are once again in place across the region but not
quite as hot as previous days. Main forecast concern for tonight is
the possibility of isolated thunderstorms near or along the TX/NM
state line that could push into our western zones. Visible and
Water Vapor satellite imagery shows a slight northeast component to
the mid and upper-level flow which could favor steering any storms
that develop towards the area. However, models have backed off
considerably with generating precipitation in eastern New Mexico and
now only the RAP and HRRR are generating storms. Convective
parameter fields are looking pretty poor for convection with MLCAPE
values at or below 250 J/kg and a strong cap in place. With the
preponderance of models remaining dry and meager instability, will
keep PoPs out of the forecast for tonight.
Biggest question remains how strong the ridge will be tomorrow
across the area and how that may impact high temperatures. The
ridge will remain overhead but will start to weaken through the day.
Thickness values and H850 temps are pretty much unchanged from
today so it remains possible that we could see another day of highs
at the century mark for Lubbock and most of the forecast area but a
few pockets of 98-99 as well. Will keep things on the warmer side
of guidance as uncertainty about any cloud cover (looks like we
should remain clear to mostly clear) or changes in boundary layer
moisture favor going slightly warmer.
Jordan
LONG TERM...
More seasonable temperatures (mid to upper 90`s) are expected for
the majority of next week as upper level ridging weakens across the
area. Unfortunately, this weak ridging will remain in place
across much of the southern U.S. hence limiting the rainfall
potential across the area. Monsoonal moisture will continue to be
advected into NM during this time period which may set the stage
for a few bouts of activity across primarily the southwestern
Texas Panhandle. The best shot at precipitation appears to be
Sunday evening as a weak shortwave rounds the ridge to the north.
This feature should provide enough additional lift for widespread
convection to develop across NM which may then move into the
southwest Texas Panhandle into the northern South Plains. But each
evening through at least Tuesday there will be a chance at seeing activity
from NM drift east into our region. This activity will be
dissipating as it moves east, therefore it may not make it very
far into our forecast area. /WCI
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
14/58/10
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
702 PM CDT Fri Jul 17 2020
.UPDATE...
Issued at 701 PM CDT Fri Jul 17 2020
Updated for Aviation Discussion below.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 255 PM CDT Fri Jul 17 2020
Main concern is the potential for severe convection tonight,
particularly from late evening into the overnight hours north of
I-94, with some concern of excessive heat Saturday afternoon and
additional severe weather potential late Saturday afternoon into
Saturday night. Short term CAM guidance is in good agreement on a
forward propogating MCS impacting the region tonight, but there
remains disagreement on where it will track (and to a lesser
extent, the timing). The environment will definitely be supportive
of strong to severe convection, with heat and moisture surging
into the region, and current MLCAPE values AOA 3000 J/KG along and
south of I-94. Visible satellite does a nice job of highlighting
where the best instability is present in terms of the currently
observed cu field. Some convection has already fired in North
Dakota, and additional activity will develop to its south and
southwest as the shortwave trough in eastern Montana moves
eastard. In addition to the instability, wind fields will be
supportive of maintining a forward propogating system as it moves
into Minnesota tonight, with 0-3 km bulk shear forecast AOA 35 kt
across northern and central Minnesota. The main question/issue is
how far south activity will track. The HRRR has been one of the
more northern solutions, but has trended a bit south with each run
through the day. The NAMNest is a southern outlier, with the
various other CAMs generally falling in between. Would initially
expect things to track eastward with a bit of a dive (and/or
southward development) later this evening, with the southern end
of the strongest activity near I-94. Damaging wind gusts will be
the main concern across our area, with widespread damaging winds a
likelihood along the axis of where the primary bowing portion of
the MCS ultimately tracks.
We should see the bulk of any lingering cloud cover from tonight`s
system exit the area Saturday morning, allowing for temperatures
to climb into the 90s while dewpoints remain in the 70s. This will
result in heat indices from 100-110 across much of the area, and
wet bulb globe temperatures maxing out in the mid 80s. Excessive
heat warnings and watches cover much of the area (generally near
and south of where the frontal boundary is expected to be by mid
afternoon). We will see convection develop along the boundary
during the mid to late afternoon hours then shift east through the
evening as the upper trough moves in and helps push the front east
into Wisconsin. Damaging wind gusts and large hail would appear to
be the primary concerns given what looks to be a lack of good low
level directional and speed shear in the forecast profiles.
.LONG TERM...(Sunday through Friday)
Issued at 255 PM CDT Fri Jul 17 2020
With significant weather in the short term, stuck pretty close to
the consensus NBM guidance for the remainder of the forecast
period. Low amplitude troughing looks to remain in place through
the first part of the week, with ridging developing over the
center of the CONUS once again during the latter half of the week.
The upper jet axis will loiter nearby and just north for much of
the week, with the baroclinic zone lifting northward through the
area during the Thursday/Friday time frame. Several weak
shortwaves will move through the region over the course of the
week, and after some initial subsidence and dry air Sunday into
Monday it looks like we`ll have sufficient moisture and
instability for some PoPs through much of the remainder of the
week. Given some disagreement in the model guidance, this results
in chance PoPs across much of the area from Tuesday through
Friday, and at this point there isn`t enough confidence to go dry
for many specific periods of time over that span.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 701 PM CDT Fri Jul 17 2020
Incoming storms tonight is the concern, and winds could be very
strong. Timing looks to be a bit earlier than previously thought
based on short term models and current trends. Storms do appear
to be taking somewhat of a turn to the southeast, so only KRWF may
escape the storms. Have added low level wind shear in the
southwest since storms may avoid that area. After that, a quiet
day before more storms fire up later Saturday afternoon ahead of
and along the front.
KMSP...
Will bring in storms a little earlier than before, now about 06Z,
and it could even wind up being 05Z. At this point it looks like
storms will sweep across MSP, with potential for 40-50 knots or
more. Then another round of storms developing after 22z.
/OUTLOOK FOR KMSP/
Sunday...VFR. NW wind 10 to 15 kts.
Monday...VFR. W wind 5 kts.
Tuesday...MVFR possible. Chc TSRA. SE wind 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Heat Advisory from 11 AM to 9 PM CDT Saturday for Chippewa-Dunn-
Eau Claire-Pepin-Pierce-St. Croix.
MN...Excessive Heat Warning from 11 AM to 9 PM CDT Saturday for Blue
Earth-Brown-Carver-Dakota-Hennepin-Le Sueur-Martin-McLeod-
Nicollet-Ramsey-Redwood-Renville-Rice-Scott-Sibley-Waseca-
Watonwan.
Heat Advisory from 11 AM to 9 PM CDT Saturday for Anoka-Chippewa-
Chisago-Faribault-Freeborn-Goodhue-Isanti-Kandiyohi-Lac Qui
Parle-Meeker-Sherburne-Steele-Washington-Wright-Yellow
Medicine.
&&
$$
UPDATE...TDK
SHORT TERM...
LONG TERM...
AVIATION...TDK
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Morristown TN
913 PM EDT Fri Jul 17 2020
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
Isolated to widely scattered showers and thunderstorms early this
evening with the greatest coverage over northeast Tennessee.
Airmass will slowly stabilize with loss of daytime heating.
Isolated storms will be possible through around midnight,
otherwise, patchy fog is expected again early Saturday morning.
Made some minor adjustments to hourly temperatures.
Have a great night.
&&
.AVIATION...
00Z TAF DISCUSSION.
Isolated showers and thunderstorms are developing near/over the
TAF sites early this evening. With the loss of daytime heating
these storms will dissipate soon after sunset.
For Tonight, MVFR fog is possible at TRI between 08-13Z with
potential of IFR ceilings due to low cloud development. Otherwise,
VFR conditions anticipated.
For Saturday, widely scattered afternoon/evening storms are
expected generally after 18Z.
Outside of storms, ridging will keep winds light and less than
10kts throughout the forecast.
&&
.PREV DISCUSSION...
/ISSUED 258 PM EDT Fri Jul 17 2020/
SHORT TERM (This Afternoon through Saturday)...
Most locations as of 2 pm are already in the low to mid 90s with
heat indices around 100 degrees for a good portion of the southern
Tennessee Valley. Seeing these higher heat indices due to the
elevated surface dewpoints in the upper 60s to low 70s for most
locations. These warm temperatures are from the ridge aloft with 500
mb heights in the 594-596 dm range. Current water vapor imagery and
RAP upper air analysis does indicate a weak shortwave trough to the
north across KY/IN/OH. At the surface, there is a E-W stalled
frontal boundary across KY. This boundary is more of a wind shift
with little to no difference in surface temperature or dewpoint along
the boundary. Convection has develop along this boundary this
afternoon. Satellite imagery indicates convective initiation from KY
to the west into N AR and MO. Water vapor imagery depicts dry air in
the mid-levels across the forecast area. Mid-level lapse rates are
weak with high heights and warm air aloft. Could see some minor
heights falls later this afternoon and evening with the shortwave
from KY but these will not be that impressive. Overall, expect the
best chances for showers and storms will be for locations north of I-
40 and in the higher elevations. These locations will have slightly
better convergence and some very weak synoptic lift. SBCAPE values
will range from around 500-1500 J/Kg with 0-6 km deep layer shear of
less than 10 kts. Therefore, do not expect any strong to severe
storms. Expect any ongoing convection will come to an end near
sunset with the loss of daytime heating. There could be some areas
of patchy fog near sunrise, especially for areas that experience
rainfall later this afternoon and evening.
The upper level ridge will be centered over the Tennessee River
Valley on Saturday. Temperatures are forecast to be a degree or two
warmer than today with most locations climbing into the low to mid
90s. Heat indices for the southern and central Tennessee Valley
will range from 100-105 degrees. PW values will range from around
1.5-1.8 inches. These values are near the 75th percentile for mid-
July. However, with the ridge overhead, there will not be any
synoptic support but could see a few isolated to scattered afternoon
showers/storms with best chances across the higher elevations.
Again, not expect any strong or severe storms with warm temperatures
aloft and weak mid-level lapse rates. The main concern in the short-
term forecast period will be the continued heat.
MA
LONG TERM (Saturday Night through Friday)...
Key Messages:
1. Very hot and humid through early next week with only isolated
afternoon/evening thunderstorms.
2. Slightly cooler mid to late week with greater coverage of
thunderstorms.
Discussion:
Saturday night through Monday Night...
Generally quiet weather is expected this period with very hot and
humid conditions as an elongated mid/upper ridge stretches from the
4 corners through the SE CONUS with 592-595 H5 heights centered over
the TN Valley and southern Appalachians. A large Bermuda surface
high will maintain southerly low-level flow under the mid/upper
ridge continuing to pump high Td air into the region. This low-level
moisture combined with strong boundary layer heating each afternoon
will yield 2000-2500 J/Kg MLCAPE, but mid level capping from the
ridge overhead should keep diurnal convection isolated to higher
elevations. Used chance PoPs over the plateau and eastern mountains
Sunday and Monday afternoons with slight chance in the valley.
Convection will quickly wane after sunset. Went slightly above NBM
guidance due to the antecedent dry soils with highs in the mid/upper
90`s S and low/mid 90`s N, which will give heat indices near
advisory criteria (105) over the S Plateau and S/central valley.
Tuesday and Tuesday Night...
Heights slowly begin to fall during this period as a mid/upper
shortwave trough moves across the upper Midwest into the Great Lakes
causing some suppression of the S CONUS ridge. This will cause a
quasi-stationary front in the lower Great Lakes to begin to slowly
push southward. This front will be active with convection as ripples
of energy in the zonal flow traverse the boundary. Virtually all of
the forcing is N of our region during this time, but moisture
beginning to pool ahead of the boundary, continued southerly flow,
strong diurnal heating, and possible outflow boundaries reaching the
region will allow for better coverage of afternoon/evening
convection. The highest coverage will continue to be in the plateau
and eastern mountains where chance to likely PoPs were utilized with
chance elsewhere. The increased convection will temper highs
slightly with low/mid 90`s S and generally low 90`s N. Given the
high Td`s, heat indices will still approach 105 in the S Plateau and
S valley. The convection will again dissipate after sunset with just
slight chance PoPs retained in the mountains.
Wednesday through Friday...
This period will finally see a bit of a pattern change as the
aforementioned shortwave energy carves out a broad but fairly
shallow trough over the NE U.S, at least temporarily. This will push
the frontal boundary southward while stalling in the vicinity of the
lower OH valley. The lower heights above a continued moist and
unstable boundary layer, along with the surface front just to our N,
will allow for fairly widespread convection each afternoon, so have
chance to likely PoPs with the highest over the higher elevations.
Of these three days, I have the greatest coverage Thursday since the
deterministic GFS suggests that the front could push through the S
Appalachians, however, the GEFS, CMCE, and EPS ensemble means and
the deterministic ECMWF have a shallower trough keeping the boundary
just N. Nevertheless, there is an increasingly strong signal that
this front will begin to retreat back N Friday as southern CONUS
ridging rebuilds ahead of renewed western CONUS troughing. Highs
will be cooler Wed through Fri with upper 80`s/low 90`s.
RG
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 75 97 75 97 75 / 20 20 10 20 10
Knoxville McGhee Tyson Airport, TN 73 95 74 96 73 / 20 30 10 20 10
Oak Ridge, TN 73 96 73 96 73 / 20 30 10 20 10
Tri Cities Airport, TN 69 91 70 93 70 / 20 50 10 30 10
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
Area Forecast Discussion
National Weather Service Riverton WY
532 PM MDT Fri Jul 17 2020
.SHORT TERM...This evening through Saturday night
Issued at 250 PM MDT Fri Jul 17 2020
19Z radar, satellite and HRRR output indicates that a weak short
wave was moving east-southeast through southern Wyoming, with widely
scattered showers/storms developing across mainly Sweetwater county.
Expect precip to continue to develop to the northeast toward Natrona
county, weaken and dissipate by around 00Z this evening. Due to the
pressure gradient between the mid level ridge and short wave, winds
have picked up at most locations and will continue with red flag
warnings that will remain in effect for much of central Wyoming
until 02Z tonight.
The short term models continue to indicate that a weak frontal
boundary will shift southeast into the forecast area after 06Z
tonight. This system will filter in some slightly cooler air
especially into northern and into central sections by 12Z Saturday.
RH values will be slightly higher on Saturday across the area, but
still expect enough potential for critical values to be met across
portions of central Wyoming. Borderline red flag fire weather
conditions will be prevalent in Fremont county and will likely need
to update for Saturday by this evening. Dry conditions will continue
through Saturday night with temps expected to fall about five
degrees cooler by Sunday morning.
.LONG TERM...Sunday through Friday
Issued at 250 PM MDT Fri Jul 17 2020
Sunday will see another shortwave transit the more zonal flow with
convection possible mainly for the Bighorns and Johnson County, and
maybe into Natrona County. That will repeat on Monday and again
Tuesday, although with less coverage of showers each day. The zonal
flow will continue through mid week with the models all indicating
transitory shortwaves, mainly across the north, dropping across
eastern portions of the forecast area. Wednesday through Friday the
models are showing increased mid and high level moisture, however,
they are not in very good agreement on the timing or amplitude of
these waves. We will keep PoPs on the lower side. Temperatures are
not going to fluctuate much from day to day through the long term,
with humidity also hitting at low levels.
&&
.AVIATION...For the 00Z TAFS through 00Z Sunday
A line of showers and thunderstorms near KJAC will gradually end
by 02Z. Additional virga showers along the Sweetwater/Fremont
County line will end by this time as well. Otherwise, VFR
conditions will continue across the area through the end of the
forecast period. A cold front will make its way through northern
Wyoming after 06Z tonight and into central Wyoming by around 12Z
Saturday. Winds will increase again after 15Z Saturday for most
areas. Conditions will remain dry across the area Saturday.
&&
.FIRE WEATHER...
Issued at 250 PM MDT Fri Jul 17 2020
A weak cold front will move south into the region by Saturday
morning, with a gusty north to northwest breeze expected in portions
of central and southern Wyoming. This, combined with low humidity
will continue to bring elevated to critical fire weather to portions
of central and into southern Wyoming. Mixing and smoke dispersal
will be generally good to excellent. Otherwise, fire weather
concerns should ease on Saturday following the cold front passage
with somewhat cooler temperatures and higher humidity.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for WYZ280-281-285-
288-289-300.
Red Flag Warning until 8 PM MDT Saturday for WYZ283.
&&
$$
SHORT TERM...Troutman
LONG TERM...Swanson
AVIATION...Troutman/LaVoie
FIRE WEATHER...Troutman