Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/21/20
Area Forecast Discussion
National Weather Service La Crosse WI
1030 PM CDT Mon Jul 20 2020
.SHORT TERM...(This evening through Tuesday)
Issued at 221 PM CDT Mon Jul 20 2020
Some high clouds will continue to push off to the east this
afternoon, with some clearing possible overnight. This should allow
temperatures to drop back into the 50s and 60s. With decent
radiational cooling, will have to watch out for patchy fog across
mainly Wisconsin.
12Z CAMs have backed off on early morning showers for Tuesday and
have trended that way, but wouldn`t be totally surprised to see a
few scattered showers as warm air advection increases into our area
before higher chances for showers and storms in the afternoon.
The big question for Tuesday will be severe potential in the
afternoon/evening. Kind of an interesting set up, as models suggest
the area gets sandwiched between stronger upper level forcing to the
north near the main upper level trough, and to the south where a
stronger shortwave feature moves through. A cold front should also
be approaching from the west during the late afternoon. Latest trend
is for showers and perhaps a few storms to pop up by late
morning/early afternoon with initial shortwave forcing. 0-6 km shear
around 30-40 kts progged to be over our area much of the day, which
would be sufficient for storm organization and potentially some
strong to severe storms. The big question is how much instability
will build into the area. Instability looks rather marginal by the
time showers/storms move in during late morning/early afternoon,
with values around 500-1500 J/kg MUCAPE depending on the model, but
couldn`t totally rule out a stronger storm or two. Models then vary
quite a bit on how well instability can build back in ahead of the
approaching front for late afternoon. The RAP suggests MUCAPE
exceeds 2000 J/kg ahead of the front by late afternoon, while the
20.06Z NAM would suggest sub-1000 MUCAPE and minimal SBCAPE (the 12Z
run has a little more instability) - sort of the upper and lower
bounds of the possibilities. If cloud cover is extensive during the
afternoon, weaker daytime heating could limit instability, whereas
clearer skies would allow more instability to build and increase the
severe threat. Still lower confidence with all of these caveats, but
marginal low/mid-level lapse rates around 6-7 C/km suggest sporadic
wind/hail would be possible if stronger storms do develop. In
addition, while the storms look progressive overall, precipitable
water increasing to 1.5 inches and warm cloud depths approaching
4000m suggest locally heavy rainfall will be possible.
.LONG TERM...(Tuesday night through Monday)
Issued at 221 PM CDT Mon Jul 20 2020
With the short wave trough coming across the Upper Midwest, some
of the convection associated with it is expected to linger into
Tuesday night, especially for locations along and northeast of
Interstate 94. The potential will still exist for a few of these
storms to be on the strong side early in the evening, but it
appears that there will be very limited CAPE for them to work
with. ML CAPE values only look to be between 500 and 1000 J/kg
with 30 to 40 knots of 0-6 km shear. There is also some suggestion
that the shear may be out ahead of the CAPE pool with just a
narrow corridor of overlap between the two.
Once this system moves past the region, upper level ridging is
expected to build over the central part of the country. While
there is general agreement by the models on this, as usual, there
are enough differences that have consequences on the forecast. The
20.12Z GFS is not as robust with the upper level ridging as either
the 20.00Z ECMWF or 20.12Z GEM and as a result, short wave troughs
running up and over the ridge are shown to track closer to the
area with potential chances for showers and storms. For now, will
honor the GFS solution with at least some chances for rain
starting Wednesday night and continuing through next Monday. If
the stronger ridging as shown by the ECMWF and GEM ends up being
correct, many, if not most, of these days will end up being dry.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1030 PM CDT Mon Jul 20 2020
Cigs: increasing high clouds overnight, with bkn mid level cigs for
the morning and some potential to dip into MVFR for a few hours,
mostly during Tue afternoon. Should scatter out later Tue evening.
WX/vsby: looking at scattered shra/ts to move east across the area,
mostly tied to a cold front in the afternoon, but could see some in
the morning, remnants and/or lingering mcv from an ongoing cluster of
storms over SD/western MN. Coverage expected to be a bit more
widespread to the north and south, associated with pieces of upper
level energy. Going to hold with VCSH/VCTS for the moment - refining
expectations as scenario becomes a bit more clear.
Winds: mostly light southeast tonight, increasing from the south on
Tue.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Lee
LONG TERM...04
AVIATION...Rieck
Area Forecast Discussion
National Weather Service Columbia SC
1055 PM EDT Mon Jul 20 2020
.SYNOPSIS...
The upper ridge will continue to dominate the weather early this
week before weakening later in the week as an upper trough moves
into the Ohio Valley and Mid Atlantic region. Temperatures will
remain above normal and hot with heat indices over 100 degrees.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Convection has mostly dissipated with a few light showers
persisting in the northern Midlands and Pee Dee. These showers
will end in the next hour or so with debris cloudiness
diminishing through the early morning hours. By daybreak
expect partly cloudy to mostly clear skies with low temperatures
in the low to mid 70s.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
High pressure aloft will dominate the weather pattern during the
middle of this week. Subsidence underneath this feature will
limit thunderstorm activity to the afternoon and evening hours
with initiation in the favored areas of the higher terrain of
SC/NC and along the sea breeze front. The biggest concern will
continue be the heat stress with indices values between 101 and
106 degrees in the afternoons.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
A strong upper level trough moves through New England Thursday
Night through Friday with an associated cold front moving into
The Midlands and CSRA. This front will enhance shower and
thunderstorm activity during this time period.
The cold front may push south of the region this weekend which
would slightly a slightly drier and cooler airmass to filter
into the region with highs in the lower to mid 90s and lows in
the lower to mid 70s.
High pressure aloft rebuilds across the region early next week
with a return to hot and humid weather with diurnal scattered
showers and thunderstorms.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Predominantly VFR conditions expected through the TAF period.
With minimal convective activity expected this evening and
overnight, there is low risk of restrictions at the TAF sites
from showers or thunderstorms. Fog also appears unlikely given
the sites have only received, at most, light rain and there will
be a 10 to 20 kt LLJ tonight. The HRRR and MOS guidance also
support VFR conditions, adding confidence.
Tuesday, light southerly winds will pick up by the early
afternoon. Upper level ridging will generally suppress
convection in the afternoon and limit thunderstorm coverage to
isolated or widely scattered.
EXTENDED AVIATION OUTLOOK...Restrictions are possible during the
afternoon/evening showers and thunderstorms during the extended.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Heat Advisory from noon to 8 PM EDT Tuesday for SCZ115.
&&
$$
Area Forecast Discussion
National Weather Service Caribou ME
910 PM EDT Mon Jul 20 2020
.SYNOPSIS...
A cold front is pushing off the Downeast coast this evening.
High pressure will build across the region Tuesday. A weather
disturbance will begin to approach from the west on Wednesday
and across the region on Thursday. High pressure will build
toward the region Friday into Saturday.
&&
.NEAR TERM /THROUGH TUESDAY/...
9:10 pm update: A cold front is now pushing off the Downeast
coast. In the wake of the front, a much drier air mass will
follow. The dew points are mostly in the upper 50s across far
northern Maine, but still a very muggy 71F in Bar Harbor at 9
pm. The 00z Caribou sounding showed the significant drying with
the PWAT dropping from 1.88" early this morning to 1.21" this
evening. Aside from one lone shower near Grand Manan Island, NB
all of the showers have ended. There is a weak post-frontal
trough that will drop down into far northern Maine overnight
and could touch off a very isolated shower.
Previous discussion:
A Pre-frontal trof ahead of the cold front was making its way
into central areas attm. This boundary is shown by the latest
HRRR and RAP to hit the coast later this afternoon. A broken
line of tstms have fired up in Washington County where the best
CAPE(2000+ joules) and shear resides. Dewpoints in this region
were in the lower 70s. A tstm or 2 could contain strong wind
gusts and brief heavy rainfall. Otherwise, activity will be
winding down by early evening as the drier continues toward the
coast. The cold front moving toward nw area attm will continue
to press se into tonight. Some clouds associated w/the front as
seen on the latest visible satl imagery. Some weak convergence
along the front could allow a few showers as the front moves in,
but give the upper levels drying out, not expecting than a
brief occurrence. WSW winds 10-20 mph attm will be shifting to
the W by evening and then NW overnight. The winds are expected
to let up later at night as the gradient weakens behind the
front. Noticeably difference in the airmass by Tuesday morning
w/dewpoints in the low/mid 50s across the n and upper 50 to
lower 60s central and downeast areas. Some patchy fog is
expected overnight into early Tuesday morning especially in
areas where rainfall was observed.
Tuesday will be much drier and a bit cooler w/daytime temps near
seasonal norms. The NAM and GFS show an upper level disturbance
moving across the region and w/the center of high pres still w
of the region, there will be a NW wind kicking in by late
morning at 10-15 mph. No showers expected as the soundings show
it to be dry through the column.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Tuesday night will feature mainly clear skies as high pressure
builds across. Light winds and mainly clear skies will set the stage
for some radiational cooling. Lows Tuesday night will fall into the
mid to upper 40s in the Allagash and the normally colder valley
locations of far northern Maine.
High pressure slides east toward the Canadian Maritimes during
Wednesday. After a mainly sunny start to the day, increasing cloud
can be expected by afternoon as short waves embedded in the
mainly zonal flow aloft move toward the region. This leads to
the potential for some shower activity as we head into later
Wednesday evening and Wednesday night.
Thursday will potentially see a more significant short wave approach
the region, with more widespread shower activity. Will maintain
slight chance for thunderstorms with some surface based cape
forecasted.
Highs through the period will be near normal for this time of
year.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Short wave exits to the east Thursday evening, with any showers
or thunderstorms diminishing early Thursday evening. This
should set the stage for a couple of fairly quiet weather days
both Friday and Saturday. That being said, the upper trof will
be in place across the region with Northwest flow aloft. Thus,
we will likely see a fair amount of diurnal clouds developing
both afternoons, and a stray shower couldn`t totally be ruled
out. Another upper level disturbance heads toward the region
later in the weekend and early next week, with unsettled
weather conditions expected. Temperatures through the extended
period will be close to normal for this time of year through the
period.
&&
.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: VFR through Tuesday for all terminals. Some patchy
fog overnight could drop vsbys to MVFR for a brief time
especially at terminals that received rainfall. WSW winds 10-15
mph early this evening diminishing and shifting to the NW at
5-10 mph overnight. NW winds 10-15 mph for Tuesday.
SHORT TERM: Tue Night-Wed...VFR. Light Wind.
Wed Night-Thu night...VFR/MVFR in showers.
Fri-Sat...VFR.
&&
.MARINE...
NEAR TERM: No headlines expected. SW wind 10-15 kt becoming WNW
later tonight into Tuesday. Seas around 4 ft tonight subsiding
to 2-3 ft on Tuesday.
SHORT TERM: Winds/sea generally below SCA levels through the
period.
&&
.CLIMATE...
So far this meteorological summer is the warmest on record in
Caribou, but only ranks as the 24th warmest on record in Bangor.
Weather records began in Caribou in 1939, and in Bangor in
1926.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...CB/Hewitt
Short Term...Duda
Long Term...Duda
Aviation...CB/Hewitt/Duda
Marine...CB/Hewitt/Duda
Climate...CB
Area Forecast Discussion
National Weather Service Cheyenne WY
605 PM MDT Mon Jul 20 2020
.SHORT TERM...(This evening through Tuesday)
Issued at 206 PM MDT Mon Jul 20 2020
Latest GOES-E satellite imagery shows pockets of convection this
afternoon along the Laramie Range and portions of Converse County.
Blended much of the POP/QPF this afternoon towards the HRRR and
NAMNEST as model solutions appear to initialize well to the
current conditions. Expect further development of showers and
thunderstorms further eastward as an embedded elevated shortwave
moves through today. Some storms will be on the strong to severe
side with best chances out in NE. Wind shear remains a bit lacking
this afternoon as values generally between 20 and 35 kts leading
to limited storm growth and longevity that will likely limit our
severe warned storms till later this afternoon and evening to
just a few storms if that. MLCAPE values from 1000 J/kg across
Laramie Range to 3000 J/kg across portions of Cheyenne County NE.
Some CIN remains along the WY/NE border that may require the
outflow from the storm over central Laramie Range to provide the
initial lift prior to shortwave arrival.
Otherwise, a less heat-stricken day across the region with
temperatures falling into the slight-below-normal range as KCYS
and other sites are just now reaching past the 80 degree mark.
Another chance for showers and thunderstorms, strongest across
southeastern Wyoming on Tuesday as frontal boundary begins to
eject.
.LONG TERM...(Tuesday night through Monday)
Issued at 206 PM MDT Mon Jul 20 2020
Pockets of moisture advection as monsoonal flow begins to impact
the American West and Southwest with almost near daily chances of
precipitation. Some storms may be on the strong side given an
above-normal stretch of days ahead. Upper 80s and 90s daytime
temperatures expected by the beginning of the Dog Days of Summer
through the weekend though additional moisture may add a bit of
what we may try to consider a muggy-humid feeling for WY and NE.
Biggest concern still remains the passage of mid-layer shortwave
with a deeper digging by the GFS vs the EURO into CO that sets up
the deeper monsoonal rich atmospheric river into the CWA. 12z runs
are coming into some bit of agreement though QPF amounts have some
stark difference in terms of coverage and amount that will require
some tracking over model cycles as better sampling of system as it
comes onshore.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 541 PM MDT Mon Jul 20 2020
All sites from Wyoming to the Nebraska Panhandle remain in VFR. An
extreme moist layer will hover through the KCYS site which may
lower visibility temporary; overcast skies are included in the
KCYS TAF along with thunderstorms until 01Z. Isolated
thunderstorms will move across our area from the northwest but
will likely affect KBFF and KAIA until 01Z. Cloud ceilings for
most sites will trend between SCT and BKN under 5k ft. Next
discussion could indicate MVFR conditions for KCYS due to
overcast skies and low level moisture.
&&
.FIRE WEATHER...
Issued at 133 PM MDT Mon Jul 20 2020
Portions of Carbon County area of main concern for elevated fire
weather risk this week. Periods of light rain and gusty winds
possible with showers and thunderstorms. Possibility remains for
lightning fire starts in the western forecast area where min RH
values will remain from the low teens into low 20 percents this
week coupled with temps into the 80s and 90s. East of the Laramie
Range, fire weather concerns are lessen as min RH values will
generally remain above 20 percent.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...WM
LONG TERM...WM
AVIATION...AW
FIRE WEATHER...WM
Area Forecast Discussion
National Weather Service Dodge City KS
530 PM CDT Mon Jul 20 2020
...UPDATE TO AVIATION...
.SHORT TERM...(This evening through Tuesday)
Issued at 341 PM CDT Mon Jul 20 2020
Typical summer pattern through the Short-term period (Tonight
through Tuesday Night) with very weak mid-upper tropospheric flow
across southwest Kansas. Residual low level moisture and enhancement
from evapotranspiration from all the recent rains have helped keep
afternoon temperatures a few degrees below forecast. DDC was still
sitting at 86F as of 2015 UTC. There was a mid level weakness
rolling very slowly east across southern Kansas/northern Oklahoma as
was seen on RAP analysis and satellite today, and this feature had
already reinvigorated convection across the eastern TX Panhandle
through northwest OK. The latest thinking is that this feature and
associated thunderstorm activity will only clip our far southeast
CWA (Barber County in particular), so this is where we will keep
highest initial POPs (albeit still 40 percent or less). The other
area of semi-organized convective activity was starting to develop
across portions of eastern Colorado.
Latest short-term high resolution models suggest at least a small
MCS will develop out of this as it approaches far west
central/southwest Kansas later this evening. There should be enough
low level MCS maintenance parameters in place after sunset to
maintain at least a weak MCS, rolling south-southeast across the far
southwest through late tonight. Yet a third area we will be
monitoring will be what comes out of southern Nebraska later
tonight. A formidable MCS will likely develop up in that region as
well, which will move southeast into northern Kansas through the
night. This MCS is expected to perhaps clip our far northeastern
sections (Ellis County in particular), so that will also need to be
monitored. Somewhere in the middle (i.e. around Garden City-Dodge
City), there is much lower confidence in any measurable
precipitation, but given low level moisture in place and remnant
outflow boundaries, we cannot rule out rogue scattered storms
developing overnight and/or very early Tuesday morning.
On Tuesday, the summer subtropical ridge will continue to be
suppressed just enough such that we have to keep an eye out for
additional late day/evening thunderstorms just about anywhere,
especially in vicinity of remnant outflows. Another eastern Colorado
MCS will likely develop Tuesday evening and make a run on far
western Kansas. There may be just enough northwest mid-level (cloud-
bearing) flow to push an MCS into some of our counties Tuesday
Night, so that is something we will continue to monitor as well.
.LONG TERM...(Tuesday night through Monday)
Issued at 341 PM CDT Mon Jul 20 2020
As we head deeper into the week, the overall pattern will most
likely transition toward a drier one for southwest Kansas, as the
summer subtropical high expands its influence across our region.
Temperatures for the remainder of the week into the weekend will be
quite consistent with highs in the lower to mid 90s and lows in the
lower 70s. There does not appear to be much indication, as of today,
that excessive heat will occur (Heat Indices of 105+) as low level
trajectories will actually be more out of the southeastern Great
Plains/Gulf Coast region (not a "hot" low level trajectory for us in
southwest KS). Increasing subsidence and lack of low level wind
convergence will likely lead to gradually lower and lower dewpoints
each afternoon, which will also negate development of 105+ heat
indices. It is something we will continue to monitor, however, but
as of this forecast update, it looks like the rest of the week into
the weekend will be fairly tranquil with respect to what is normally
experienced the third week of July.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 530 PM CDT Mon Jul 20 2020
VFR conditions will prevail in the vicinity of all TAF sites through
Tuesday afternoon. South-southeast winds around 10 to 20kt will
persist through early Tuesday morning as a surface low remains
anchored in southeast Colorado.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 68 93 69 92 / 20 20 10 10
GCK 66 92 68 93 / 20 20 20 10
EHA 66 94 67 93 / 30 20 30 10
LBL 66 95 68 94 / 20 20 20 10
HYS 67 90 69 92 / 40 20 30 10
P28 71 92 71 92 / 40 40 10 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Umscheid
LONG TERM...Umscheid
AVIATION...JJohnson
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
1101 PM CDT Mon Jul 20 2020
.Discussion...
Issued at 254 PM CDT MON JUL 20 2020
Key message: Additional storms possible overnight into tomorrow
morning with more heavy rain and flash flooding potential.
This is a very uncertain forecast with a multitude of mesoscale
features, not handled particularly well by any guidance, affecting
the forecast. First, there are at least two distinct boundaries
noted via satellite imagery. One is across southern KS and MO and
progressing southward this afternoon. There is another boundary from
north central KS that may extend into west central MO. This showed
up well at 925mb, and helped initiate new convection in north
central KS, but has been weakening as the low-level flow focuses on
the southern boundary. The main synoptic front looks like it`s
across northern MO/ southern IA and slowly lifting northward. Any
of these boundaries could be a focus for some afternoon/ evening
storms. Additionally, there is an MCV along the KS/OK state line
that is slowly tracking to the east. With broad/ weak
northwesterly flow, there`s subtle shortwave troughs moving
through the flow into WY and NE. The morning MCS, residual cloud
cover, and new cloud cover from showers/ storms that developed on
the 925 boundary, are really inhibiting renewed instability this
afternoon, lowering chances for afternoon and evening storms.
Given this, the best chances look to be overnight into tomorrow
morning again. The RAP has had the best handle, though still not
very good, on the features mentioned above and feel that
incorporating that more into the forecast may offer the best
guidance. With that in mind, several areas of ascent develop
overnight that should become the focus for renewed convection. An
area of ascent noted on the 305K to 310K surfaces develops over
central to eastern KS around midnight that shifts into western MO
early in the morning. Another area of ascent, on the same theta
levels develops over Nebraska and builds mainly southward. Think
that showers and storms will develop over central to eastern KS,
possibly into western MO tonight, and persist into tomorrow
morning. With precipitable water values at or just over 2" over
the area, the main concern will be from heavy rainfall and flash
flooding. There could also be some gusty winds, especially areas
that begin to surge forward, similar to this morning where 40 to
50 mph winds were observed with the line that surged through the
KC metro
For the middle portion of this week through the weekend, the
pattern remains mostly unchanged. Ample moisture will continue to
be present with the upper ridge remaining suppressed to our south.
There`s also a weak boundary draped through the region. So it`s
hard to find a period of time that looks dry. Rather, there could
be afternoon, heat- of-the- day, showers/ storms as well as
overnight convective systems that track southeastward along
wherever the boundary may be that particular day. The upper ridge
builds back north by the end of the week but both the GFS and the
ECMWF keep a week boundary in place as high pressure moves into
the Great Lakes. This pattern keeps low chances of PoPs going
through the extended forecast, even with the upper ridge building
northward. The good thing with the potential rainfall and cloud
cover would that temperatures would be subdued some. Otherwise, it
looks hot and humid through early next week.
&&
.Aviation...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 1101 PM CDT MON JUL 20 2020
We are currently tracking a system in eastern Kansas that has the
potential to bring scattered rain showers to our terminals. The
last few sets of model runs have been giving little guidance to
whether these storms will fizzle out at the Kansas/Missouri border,
so we kept the chance for rain showers near our terminals in the
early morning hours. Off and on rain chances will continue for the
rest of the TAF period until the early afternoon, so it was
difficult to nail down a constant dry period before the next round
of rain showers. There is still uncertainty in the timing of the
late morning round of showers. We kept everything mostly the same
with showers arriving by mid-morning, though we did extend the
chance for rain farther into the afternoon. VFR conditions are
expected into the evening.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&
$$
Discussion...CDB
Aviation...Klaus
Area Forecast Discussion
National Weather Service El Paso TX/Santa Teresa NM
538 PM MDT Mon Jul 20 2020
.AVIATION...00Z TAF CYCLE
VFR conditions expected except during TSRA when MVFR (visibility)
may occur. Scattered showers and thunderstorms are expected this
evening over much of the area, decreasing overnight but with a few
showers lingering until dawn. Winds are expected to be light
except during thunderstorm outflows where wind gusts up to 35
knots could occur. Scattered thunderstorms will redevelop after
20Z Tuesday in the lowlands.
&&
01
.PREV DISCUSSION...235 PM MDT Mon Jul 20 2020...
.SYNOPSIS...
The typical monsoon pattern is expected to continue through the
weekend. Scattered to numerous showers and thunderstorms are
expected across the area with the additional moisture in the area.
There is also a possibility for locally heavy rainfall with some
of this storms. Strong gusty winds and small hail are expected
with the strongest storms during the afternoon and evening hours.
Temperatures continue to show a downward trend with near normal
values in the second half of the week.
&&
29
.DISCUSSION...
.SHORT TERM...Thru Tuesday...
We have the humidity. We have the terrain (lift), but
thunderstorms appear to be a bit slower to initiate today as
compared to yesterday, likely attributed to clouds and shower
activity from this morning. The Gila mountains have a few light
showers, but the only thunderstorms noted at 1PM were over the
Sacramento Mountains. With plenty of sun and dewpoints coming in
around 55, CAPE values over 1000 J/kg, and PW values 1-1.2",
thunderstorms should continue to develop this afternoon across
mountains before moving into the lowlands--very similar to what
has been seen the last several evenings though maybe a bit later.
Coverage may also be more robust. The NAM-Nest and HRRR are in
remarkable agreement (the HRRR has been aggressive lately, but the
NAM-Nest has performed well) that we could see scattered to
perhaps numerous coverage in storms across the Rio Grande Valley
and into much of the lowlands. I did not want to bring up chances
to reflect that given how coverage has come in under forecast that
past several nights by CAM models, but it could be an active
evening with many people getting rain. The main threats would be
locally heavy rainfall and maybe some small hail. Storms could
have some gusty outflow winds, but DCAPEs less than 1500 suggest a
very isolated threat for severe caliber gusts. Activity may last
well after dark but should weaken after midnight to just a few
scattered showers.
Tuesday`s weather looks to repeat today`s weather with little change
in the pattern expected. Highs may be a couple degrees cooler, but
once again, it appears we will see scattered to numerous mountain
storms with isolated to scattered lowland storms. Heavy rain, small
hail, and some strong gusty winds will remain the threat again.
&&
34
.LONG TERM...
Broad upper high prevails over most of southern US. This feature
keeps a southeasterly flow near the surface which advects moist
and warm air into the region. At the same time, an upper trough
over northern California will help to reinforce the southerly flow
in the area. Both the NAM and the GFS are showing slightly higher
PWs with values ranging from 1.25 to 1.6 inches, which is
slightly higher than in the previous model runs. Therefore, we are
expecting scattered to numerous showers and thunderstorms in the
mountains and scattered over the lowlands. The additional moisture
increases our chances for observing heavy rain, which will be
more predominant in area mountains.
The upper high will center itself over the southern plains towards
the end of the week. This action shifts the deep moisture plume to
the west into Arizona, and western New Mexico. Thus, POPs remain
decent through the period in the western portions of our CWA,
including the area mountains. In turn, areas east of the Rio
Grande will have less chances for precipitation. However, this
doesn`t mean that we are not going to see any precip, as isolated
chances for storms are still possible through the rest of the week.
Over the weekend, an inverted trough will move along the fringes
of the upper high from the Gulf of Mexico. This system may be
reaching the area by Sunday or Monday, but there is still quite a
bit of uncertainty between the GFS and the ECMWF about its
trajectory. Regardless, of its final route storm chances remain in
the forecast through early next week.
Temperatures will continue their slow downward trend. Near
seasonal temperatures are expected for the second half of the
week and into the weekend.
&&
29
.FIRE WEATHER...
Thunderstorm activity will shift into the lowlands this evening from
the mountains with some shower activity possibly persisting into the
early morning hours tomorrow, though coverage would be very
isolated. Most of today`s activity should end by midnight. Min RH
values of 20-25 percent will be common in the lowlands with seasonal
highs. Winds will remain light except near thunderstorm outflows.
The light winds will keep vent categories within a category of fair.
Wednesday will see very similar conditions except that highs will
cool a degree or two, bringing slight improvements to min RH values.
Otherwise, expect afternoon and evening thunderstorms. Winds will be
again be light except around thunderstorms. Moisture may increase
further as the week continues, increasing rain and storm chances
with modest, daily improvements in min RH values.
&&
34
&&
.PRELIMINARY POINT TEMPS/POPS...
El Paso 77 97 75 95 / 40 40 40 20
Sierra Blanca 69 92 69 90 / 30 30 30 30
Las Cruces 71 94 69 92 / 30 50 50 30
Alamogordo 73 96 71 95 / 40 50 50 40
Cloudcroft 52 71 52 69 / 40 50 50 70
Truth or Consequences 72 94 71 91 / 40 60 60 50
Silver City 65 89 65 85 / 20 40 40 60
Deming 68 96 68 92 / 30 50 50 30
Lordsburg 69 95 69 92 / 20 30 30 40
West El Paso Metro 77 98 75 95 / 40 40 40 20
Dell City 70 98 70 96 / 20 20 20 20
Fort Hancock 76 98 74 97 / 30 30 30 30
Loma Linda 72 91 71 88 / 30 40 40 30
Fabens 77 97 76 95 / 30 30 30 20
Santa Teresa 73 97 71 94 / 40 40 40 20
White Sands HQ 77 95 75 93 / 40 50 50 30
Jornada Range 71 94 70 92 / 40 50 60 30
Hatch 71 95 70 93 / 40 50 60 40
Columbus 72 97 71 93 / 30 40 50 30
Orogrande 74 96 72 94 / 40 40 50 30
Mayhill 58 83 58 81 / 40 50 40 70
Mescalero 56 82 56 80 / 40 50 50 70
Timberon 55 81 55 80 / 40 40 40 60
Winston 58 86 57 82 / 30 60 60 70
Hillsboro 65 94 65 90 / 30 50 60 60
Spaceport 69 94 68 91 / 40 60 60 50
Lake Roberts 58 88 57 85 / 30 40 50 60
Hurley 63 91 63 88 / 30 40 40 50
Cliff 60 95 60 91 / 20 30 30 50
Mule Creek 67 91 66 88 / 20 30 30 50
Faywood 66 91 65 88 / 30 50 50 50
Animas 68 96 69 92 / 20 30 30 40
Hachita 66 95 66 91 / 30 40 40 30
Antelope Wells 68 94 67 91 / 30 40 50 50
Cloverdale 65 89 66 86 / 20 30 30 60
&&
.EPZ WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...None.
&&
$$
34-Brown/29-Crespo/01-Fausett
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
732 PM CDT Mon Jul 20 2020
.UPDATE...
Issued at 725 PM CDT Mon Jul 20 2020
Short term hi-res models have been all over the place this aftn w/
regards to tstm potential/evolution this eve into the overnight.
However, it appears as though the last couple of runs of the HRRR
are initializing better (wasn`t doing great early aftn) and doing
better with current trends. As such, it`s becoming more and more
likely that the tstms near North Platte will become forward
propagating over next hr or so, and drop S, mainly W of the CWA.
It could be close to Gosper and Furnas Counties 8-11pm, but MCK
and points W look more likely for the most intense tstms.
That leaves our primary threat for strong to severe tstms
dependent on activity currently moving SE through Cherry County.
My latest thinking as that this activity may struggle to maintain
severity after about 04Z for a few reasons:
1) developing LLJ this eve and into overnight will probably focus
further S closer to and ahead of the activity currently near LBF.
This would keep the primary WAA and convergence well S of the
northern cluster/MCS.
2) Main instability axis currently runs from W KS northward into
central and western Sandhills. Without a significant influence
from LLJ, will be tough to nudge this axis to the E and more
significantly impact/overlap the CWA.
3) Last 30 min or so of radar data suggests more of a Srly vs
SErly track, similar to the activity near LBF. If this holds, this
second round too would track mainly W of the area.
All of this would suggest the severe threat for local CWA is
pretty marginal and that going likely POPs for areas along/N of
I-80 is overdone. However, not wanting to completely buy into any
one solution just yet given very limited capping, weak forcing,
and not completely insignificant combination of CAPE and shear.
Will continue to monitor trends, but some significant updates may
be needed later this eve.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 224 PM CDT Mon Jul 20 2020
Showers and storms last night produced widespread rainfall, with
the heaviest rain falling in both the northern and southern parts
of our area with Ord seeing 2.22" of rain...with even higher
amounts of 2-4 inches falling along the Nebraska/Kansas state
line with Hebron tallying 4.06".
While we could see a hit or miss shower or storm this aftn in weak
warm air advection, better chances for precip arrive later
tonight and into the overnight hours. Convection is expected to
develop to our west in the Dakotas and western Nebraska in
increasing lift in upslope flow...and along a cold frontal
boundary associated with a shortwave trough translating across the
northern/central plains.
High resolution models have trended a few hours slower with this
next round of convection later tonight, with timing favored
primarily after dark and through the overnight hours with storms
organizing to our northwest and rolling through overnight. Model
instability progs continue to indicate instability around
2000-3000 j/kg with shear around 30kts and the potential remains
for strong to severe storms with the storm threats being damaging
winds of 60-70 mph and large hail of quarter size or larger...and
our region is outlooked in the SPC Day 1 Slight Risk for severe
weather.
Rainfall...after heavy rainfall of 2-4" in spots last night, locally
heavy rainfall is possible once again tonight in storms given sfc
dps either side of 70F and precipitable water values of 1.5-2.0".
Another round of heavy rain for areas which already saw several
inches of rain could result in some hydro/flooding issues.
Fog...models are in decent agreement with the potential for low
clouds tonight and SREF probs indicate some potential for reduced
vsbys. How much of this is associated with precip or actual fog is
more uncertain...but cannot rule out the potential for these low
clouds and some fog given moisture/light wind setup and will at
least include patchy fog to the forecast.
Tuesday...Precip from overnight is expected to depart by Tuesday
morning or shortly thereafter...but low clouds look to hold thru at
least the first part of the day especially in our eastern zones.
Will need to monitor trends of where the front stalls Tuesday...with
models placing boundary across northern KS attm. Once the low clouds
depart, the daytime on Tuesday is shaping up to be a fairly nice
summer day with fairly light winds. Temps north of the front are
expected to be in the upper 70s to around 80F...and south of the
boundary hotter temps in the upper 80s to near 90F are forecast.
.LONG TERM...(Tuesday night through Monday)
Issued at 224 PM CDT Mon Jul 20 2020
The stalled boundary will be the focus for another round of
convection Tuesday night aided by a weak low level jet, with
additional development possible along the high plains in eastern
CO/western KS which could organize and move into our region
overnight. Our southern zones are currently outlooked in a marginal
risk for severe weather which looks reasonable attm.
The frontal boundary lifts north as a warm front on Wednesday, with
chances for showers/storms continuing in the vicinity of the
boundary mainly across portions of south central Neb. Temps trend
up by the latter part of the week as the front continues to lift
north, with highs returning near or into the 90s by Thursday, with
the hot temps continuing thru the weekend and into early next
week with a building upper ridge axis. As we heat back up, precip
chances taper off mid week on with mainly hot/dry/humid weather
expected for several days in the outer periods.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 648 PM CDT Mon Jul 20 2020
Difficult forecast due to uncertainty on tstm
potential/coverage/timing, and whether or not any low clds develop
behind convection/frontal boundary.
Tonight: Should be mainly VFR for several hrs this eve. Tstms
near LBF will likely drop S well W of the terminals, but this
may take the LLJ focus further S for late overnight, which casts
some doubt on if activity near NE/SD will hold together long
enough to make it here. If it does, looks like timing would be
around or after midnight, w/ lingering shwrs ending around dawn.
Just not enough confidence on tstm evolution to go with a
prevailing group at this time. Also uncertain is if low clds will
become an issue, as this likely depends on how tstms evolve. Given
the uncertainty, didn`t make too many changes other than to
shorten the time of IFR cigs given latest trends towards not
happening at all. Winds will be SE this eve, but will shift to the
N late overnight but remain lgt outside of tstms. Confidence: Low.
Tuesday: Continued low confidence forecast in the morning owing to
uncertainties in low cld cover evolution mentioned above. If low
clds form, should gradually lift and scattered out by late
morning, leaving some VFR CU for the aftn. Lgt and vrbl winds
during the morning may take on more of a prevailing NE wind, but
remain lgt, for the aftn. Confidence: Low.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
UPDATE...Thies
SHORT TERM...Fay
LONG TERM...Fay
AVIATION...Thies
Area Forecast Discussion
National Weather Service Goodland KS
951 PM MDT Mon Jul 20 2020
.MESOSCALE DISCUSSION...
Issued at 944 PM MDT Mon Jul 20 2020
Storms are continuing to move south behind an outflow boundary.
MLCIN/MLCAPE are still supportive of storm develop. However the
environment is more unstable over the eastern part of the forecast
area. Effective wind shear remains consistent at 40 kts over the
forecast area, which should cause the storms to maintain their
intensity. DCAPE is also still high ahead of the line. However as
the evening progresses the environment will become more stable and
limit the amount of wind reaching the ground. Have already noticed
a decrease in the wind speeds where radar has shown winds of 60+
MPH overhead.
As the outflow boundary continues to slowly move further from the
storm, the storms should weaken due to the lift from the boundary
becoming further ahead of the storms themselves. The question is
how far south will the storms move before dying out. Based on
current guidance, wouldn`t be surprised if they last well into
Southwest Kansas.
&&
.UPDATE...
Issued at 719 PM MDT Mon Jul 20 2020
A severe thunderstorm watch has been issued for the northern half
of the forecast area through 11 PM MT. Main threats are large hail
and damaging wind gusts.
UPDATE Issued at 608 PM MDT Mon Jul 20 2020
Updated the forecast given the current trends on radar and
satellite. Main activity continues to be the storms over Cheyenne
County CO. These may spread southeast over the next hour or two.
To the north another area of severe thunderstorms is moving
southeast toward the forecast area. ETA of storm arrival is
roughly two hours away. Behind that round another round of storms
may move through the forecast area later on closer to midnight.
Not sure how strong these storms will be with the incoming round
of storm activity approaching.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 206 PM MDT Mon Jul 20 2020
Satellite imagery and 500 mb RAP analysis showed a broad trough
across the northern half of the country this morning. A shortwave
exiting the central Plains sparked convection over eastern Kansas
and western Missouri. Behind this disturbance, northwest flow
prevailed over the region, with areas of high pressure across the
desert southwest and southeastern CONUS. At 2:00 PM MT, a cold front
was draped from west to east across the center of the region with
mostly sunny skies. Temperatures were in the upper 80s to low 90s
with east to southeast winds at 10 to 15 mph. A few small storms had
developed in western Kit Carson county.
The cold front is expected to help trigger thunderstorms this
afternoon and evening, as an upper wave passes through the northwest
flow. Showers and storms should develop in eastern Colorado this
afternoon, and spread east into western Kansas and southwestern
Nebraska this evening. There will be enough shear and instability
for a few severe thunderstorms. Main threats with these storms are
damaging winds, large hail, and locally heavy rainfall.
Another area of storms are forecast to form in central Nebraska this
afternoon and evening, congeal into an MCS, and track southeast
tonight. Depending on how this plays out, we could see another round
of thunderstorms across the eastern part of the region during the
late evening/overnight hours. However, confidence is low at this
time on where this cluster of storms will track. If the line grazes
the region, damaging winds and locally heavy rainfall would be the
main threats.
Otherwise, increased cloud cover is expected tonight, with lows in
the upper 50s to mid 60s. Will need to monitor for the potential of
stratus developing (and perhaps fog) around sunrise.
The region will see a brief break from storm chances Tuesday
morning. Temperatures should be slightly cooler behind the front,
with highs in the upper 80s to low 90s. Thunderstorms are forecast
to develop off of the Front Range and spread into the area in the
afternoon and evening. A few strong to severe storms will be
possible once again, with threats of damaging winds, large hail, and
locally heavy rainfall. Temperatures fall into the upper 50s to
upper 60s overnight.
.LONG TERM...(Wednesday through Monday)
Issued at 149 PM MDT Mon Jul 20 2020
For the extended period the models are showing an upper-level ridge
extending from the southern Plains over the Rockies dominating the
week with above normal temperatures (middle 90s). Thunderstorms may
develop around the periphery of the ridge each day, along the Front
Range, and move into northeastern Colorado during the late
afternoon/evening hours. Heading into the weekend, the ridge looks
to move eastward into the northern Plains region, which may allow
some storms to move into northwest Kansas/southwest Nebraska area.
Given the weak flow aloft in proximity to the ridge, the chance for
severe storms will be low.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 533 PM MDT Mon Jul 20 2020
VFR conditions are forecast for the TAFs. Confidence of storms
occurring near KGLD is too low to include in the TAFs. Confidence
is higher that KMCK will see storms this evening based on the ETA
of storms moving south in Nebraska.
Otherwise, KMCK may have ceilings fall close to MVFR around 12z.
Latest data seems to have raised the ceiling some from the last
TAF issuance, so have the ceiling remaining VFR for now.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
MESOSCALE...JTL
UPDATE...JTL
SHORT TERM...JBH
LONG TERM...BW
AVIATION...JTL
Area Forecast Discussion
National Weather Service Indianapolis IN
1136 PM EDT Mon Jul 20 2020
.UPDATE...
The AVIATION Section has been updated below.
&&
.SYNOPSIS...
Issued at 308 PM EDT Mon Jul 20 2020
A few areas of scattered showers and thunderstorms are possible
this evening and tonight, but mostly should be south of the
forecast area. Going into the day tomorrow, isolated to scattered
thunderstorms are likely during the afternoon hours with the
potential for a more organized cluster of storms late tomorrow
into the overnight hours. This pattern of isolated to scattered
storms will continue later into the week before becoming more dry
and hot this weekend into early next week.
&&
.NEAR TERM /Overnight/...
Issued at 950 PM EDT Mon Jul 20 2020
Surface analysis this evening shows high pressure in place over
the Great lakes. Another high pressure system was found over the
southeastern states. In between...a weak front boundary was draped
across southern Indiana. Radar this evening shows a isolated
showers and even more isolated thunderstorms across the southern
parts of the forecast area dissipating quickly and drifting
northeast. GOES16 show plentiful cloud cover arriving across
Central Indiana from Illinois...associated with earlier
convection. Dew points remained humid near 70.
HRRR suggests ongoing convection will dissipate with the loss of
heating. Confidence in this is high as radar trends reflect this.
HRRR also suggests additional very isolated showers overnight as
the front slowly lifts north. Confidence in that is rather
low...but it cannot be ruled out given our very moist air mass in
place. Thus have trended pops toward dry by midnight...but then
kept a low chc pops across the southern parts of the forecast
area overnight. Again confidence in that is quite low.
Given the increasing clouds along with the arrival of a warm
front...have trended overnight lows warmer then the NBM...going at
or above persistence.
&&
.SHORT TERM /Tuesday through Thursday/...
Issued at 308 PM EDT Mon Jul 20 2020
Much of the same weather is expected in the short term period
with isolated to scattered thunderstorms likely, especially during
the evening and early overnight hours. Confidence in thunderstorm
activity is low at any given point due to uncertainty down to the
mesoscale level and the impacts of any previous thunderstorm
activity. Having said that, upper level forcing does appear to be
in place tomorrow evening which should bring a more organized
complex of storms to the area late tomorrow into the early
overnight hours. A few strong wind gusts will be possible and the
potential for flash flooding is there, especially across the
areas that received heavy rain last night.
Scattered thunderstorms will continue Wednesday and Thursday as
upper level vort maxes interact with a nearly stationary surface
front. Confidence in the axis of heaviest rain remains low, but
areas of 1 to 2 inches of rain look likely between now and
Thursday night.
Highs will climb into the mid to upper 80s Tuesday and Wednesday.
Lows will fall into the upper 60s to low 70s Tuesday and
Wednesday nights.
&&
.LONG TERM /Thursday night through Monday/...
Issued at 231 PM EDT Mon Jul 20 2020
Some chances for thunderstorms will continue through the day on
Friday as a stalled frontal boundary continues to provide a little
additional lift and focus for convection. By Friday night, though,
the center of the upper ridge that spends most of the week to our
west will move into central Indiana. This will serve to increase
temperatures and humidity, as well as provide subsidence to make the
weather mostly dry. An isolated storm may be possible Saturday
afternoon or Sunday afternoon just from the amount of instability,
but again, the subsidence from the high should keep coverage from
getting any more than isolated. High temperatures should again be in
the 90s for the weekend, with heat index values getting into the low
100s, and this should continue into Monday. Monday the upper ridge
appears to buckle a bit, and this could allow for more organized
convection with better coverage.
&&
.AVIATION /Discussion for the 210600Z Tafs/...
Issued at 1137 PM EDT Mon Jul 20 2020
Mainly VFR conditions are expected this taf period. Frontal
boundary near the Ohio River is expected to lift north across
Central Indiana overnight as a tropical plume of moisture over
TX- OK-MO-and NRN IL is expected to sag across Indiana over the
next 24 hours. GOES16 shows convective debris clouds over Indiana
and Illinois.
Isolated showers this evening have continued to dissipate as radar
is nearly quiet. Additional showers will be possible as the front
lifts north. This is suggested by the HRRR...but confidence for
specific timing and any coverage at all is quite low. Thus did not
include a mention of that at this time.
On Tuesday...forecast soundings are favorable for convection in
the afternoon with CAPE over 2000 J/kg along with Pwats over 1.9
inches. Thus expect afternoon tsra development and have opened a
large window during peak heating hours to account for this.
Confidence for specific locations and timing remains too low for a
prevailing mention at this time. Any TSRA that does strike a TAF
site on Tuesday may produce brief MVFR to IFR conditions.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...White
NEAR TERM...Puma
SHORT TERM...White
LONG TERM....CP
AVIATION...JP
Area Forecast Discussion
National Weather Service Mobile AL
1044 PM CDT Mon Jul 20 2020
.NEAR TERM /Now Through Tuesday night/...Same song different day
with this pesky upper level ridge anchored over the eastern US.
Luckily this appears the last day for the standard summertime
pattern as a weak tropical disturbance moves into the gulf by
Tuesday night. Unfortunately, my period only covers up to that
point which means same old same old with the seabreeze being the
driving factor for showers and thunderstorms during the late
afternoon and early evening hours. Like most days, ample cape will
be present but with PWATS of 1.7 to 1.9 and not much change
overall from today I would not expect much change from Mondays
forecast. Convective allowing models don`t have a lot of coverage
tomorrow except for the HRRR which typically has too many storms
as it did today. I was contemplating keeping isolated storms in
the forecast but stuck with scattered over the eastern half of the
area. It`s a bold strategy, but we will see how it works out. Per
normal, what storms that do develop will have the potential for
gusty winds as they spread inland into the evening.
Temperatures will be in the low to mid 90s across the area with a
few spots possibly getting into the upper 90s. Lows will be in the
mid to upper 70s with dewpoints remaining high. A moderate risk of
rip currents will continue through tomorrow before increasing
later in the week. BB/03
&&
.PREV DISCUSSION... /issued 634 PM CDT Mon Jul 20 2020/
NEAR TERM UPDATE /Now Through Tuesday night/...Just a little
update this afternoon as storms have struggled with dry air across
the area this afternoon. Due to this, I trimmed back pops for only
isolated storms tonight mainly around the Highway 84 corridor.
The good news is that current visible satellite looks good for
potential comet Neowise viewing conditions tonight. Be sure to
head out about an hour after sunset and look near the big dipper.
It might be tough to see in city areas due to light pollution but
you should be able to see it with binoculars or a telescope.
Temperatures will begin to slowly fall into the mid to upper 70s
tonight. BB/03
AVIATION...
00Z issuance...VFR conditions will once again persist through the
evening with only an isolated shower along the highway 84
corridor. Winds will become light and variable after sunset
tonight. Conditions will persist into the early afternoon with
the potential for isolated to possibly scattered thunderstorms
developing during the afternoon. BB/03
PREV DISCUSSION... /issued 347 PM CDT Mon Jul 20 2020/
NEAR TERM UPDATE /Now Through Tuesday/...A deep layer ridge of
high pressure continues to extend from the western Atlantic
through the Tennessee Valley and adjacent southeastern states this
afternoon. A light southeasterly flow continues across our region
with this pattern. Seasonably hot and humid conditions persist
with temperatures in the lower to mid 90s over interior portions
of the region and in the upper 80s to around 90 degrees near the
coast. Dewpoints in the lower to mid 70s are resulting in heat
indices in the 101 to 106 degree range over most places, and even
very locally as high as 109 at Mobile Brookley Field.
Radar is finally indicating the development of isolated showers and
storms along the seabreeze as of 2 PM CDT. With precipitable water
values between 1.7 and 1.9 inches and a weak impulse rounding the
area on the periphery of the ridge axis, we anticipate that
additional isolated to scattered showers and storms will continue to
develop through the afternoon and into the evening, with coverage
becoming more pronounced over interior portions of the CWA. The hot
temperatures and dewpoints in the 70s continue to promote pockets
of MLCAPE values between 2000-3000 J/KG, so there is potential
for a storm or two to produce very localized strong downburst
winds, in addition to frequent lightning and locally heavy
rainfall this afternoon into early this evening. Convection should
diminish by late this evening and will maintain a dry forecast
after midnight.
A similar weather pattern will continue across the region on
Tuesday. The deep layer ridge will continue to nose west-
southwest from the western Atlantic/eastern seaboard through
AL/MS. This pattern will continue to support the typical heat and
humidity, with highs once again forecast to range in the lower to
mid 90s over our interior areas and around 90 degrees near the
immediate coast and beaches. Max heat indices are forecast to
range between 102-107 degrees over much of the area. Isolated
showers/storms should be mostly confined to the marine area early
Tuesday morning, and perhaps also dotting portions of interior
southwest/south central AL, but more scattered coverage should
develop again by Tuesday afternoon, particularly over interior
areas. Instability should remain strong enough (2000-3000 J/KG)
for there to be concern for locally strong wind gusts and frequent
lightning with the stronger storm cells that develop Tuesday.
Swell has diminished to 1-2 feet, with periods decreasing to 5-6
seconds, so will allow the HIGH risk of rip currents to expire this
afternoon. The combination of 1-2 ft swell and high tidal ranges
will support a MODERATE rip current risk through Tuesday night.
/21
SHORT TERM /Tuesday night Through Thursday night/...An upper level
ridge generally remains to the north of the local area through the
week. This ridge briefly weakens as an upper level trough in the
northern stream swings across the far northern Plains and across the
Great Lakes region on its way toward the East Coast. Low level and
surface ridging from the Western Atlantic continues to spill into
the Southeast through the week, which will allow winds to be
southerly through the day and easterly at night. Looking to our
south, a tropical wave cruises to the west-northwest across the
central Gulf on Wednesday and reaches the northwestern Gulf later on
Thursday. Regardless if the tropical wave strengthens or not as it
traverses into a conducive environment in the Gulf, it is forecast
to remain south of our area, which will increase the risk for rip
currents and higher tides through the short term. We will continue
to monitor this tropical wave over the next few days.
Deep layer moisture streams into the area on Wednesday and Thursday
as the area receives return flow from the surface ridge and the
aforementioned tropical wave passes well south of the area. Forecast
soundings generally show PWATs of 1.6-1.9 inches on Wednesday
increasing to 2+ inches by Thursday afternoon across the southern
portion of the area. A diurnal pattern is anticipated for convection
each day with storms ramping up across the Gulf waters during the
late night and early morning hours before transitioning to the
land areas during the late morning hours and concentrating inland
through the remainder of the afternoon and early evening. The bulk
of the convection during the daytime will remain across the
southern portion of the area, generally south of the Hwy 84
corridor, as that is where the deep layer moisture resides.
Afternoon highs will top out in the mid to low 90s each afternoon
with upper 80s at the beaches. A few spots in southeast Mississippi
may struggle to reach 90 on Thursday afternoon due to an increase
in cloud cover and rain coverage. Heat index will generally range
from 100-105 each day. Lows continue to sound like a broken record
as they fall into the low 70s inland each night with upper 70s to
near 80 at the beaches.
Rip current risk increases to a HIGH Wednesday through at least
Thursday night. 07/mb
EXTENDED TERM /Friday Through Monday/...The pattern does not
change too much through the period as the upper level ridge expands
further into the Southeast and Central Plains while the surface
ridge remains draped across the Southeast. The local area remains on
the southern periphery of the upper level ridge with prevailing
easterly flow aloft. A subtle shortwave moves around the eastern
edge of the ridge and zips through the area later in the weekend.
This feature has the potential to enhance thunderstorm coverage in
the afternoons this weekend, but given some timing differences in
the operational guidance, we opted not to adjust POPs up just
yet. Outside of this feature aloft, light southeasterly flow at
the surface will continue with a diurnal convection pattern each
day. Subsidence associated with the ridge aloft will likely limit
the thunderstorm coverage somewhat.
Afternoon highs will generally rise into the mid to low 90s each day
with upper 80s at the beaches. Heat index will be slightly higher
this weekend with values of 102-107. Low temperatures only
fall into 70s each night. 07/mb
MARINE...No significant marine impacts forecast through Tuesday
night except higher winds and waves near isolated to scattered
thunderstorms. Small craft may need to exercise caution Wednesday
and Thursday due to increased winds and seas. /21
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Morristown TN
926 PM EDT Mon Jul 20 2020
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
Convection has been able to persist longer into the evening than
that last few nights, likely due to the presence of a mid/upper
level shortwave trough moving across KY. The 00Z OHX sounding also
shows a midlevel layer of steep lapse rates. The forecast will be
updated to extend PoPs until around midnight. The widespread
coverage of showers this evening makes it more likely that fog
will form in many locations, so a mention of this will be added.
DGS
&&
.AVIATION...
00Z TAF DISCUSSION.
With very little change in the overall weather pattern, the next
24 hours will be very much like the past 24, with scattered
afternoon showers and thunderstorms, and a potential for MVFR fog
at TRI for a brief period around sunrise.
DGS
&&
.PREV DISCUSSION...
/ISSUED 256 PM EDT Mon Jul 20 2020/
SHORT TERM (This Afternoon through Tuesday)...
Current water vapor imagery and RAP upper air analysis indicates a
trough moving to the east across IA/IL/WI. Closer to home, the upper
ridge continues to be the main feature but it is a bit weaker today
with the trough to the northwest. Temperatures are still elevated
across the forecast area with most locations in the upper 80s to mid
90s as of 2 pm. Convective initiation across the region has been
sparse so far as updrafts struggle to break through the cap. Continued
heating over the next hour or 2 should lead to a bit better
coverage. The latest HRRR indicates best coverage across the
northern Cumberland Plateau into southwest Virginia. Current radar
imagery indicates a decent cluster of storms back to the northwest
near the Ohio River. These storms are in the vicinity of a surface
front that stretches across the Ohio River Valley. SBCAPE values
this afternoon and evening will be in the 1000-2000 J/Kg range with
0-6 km bulk shear values of less than 10 kts. DCAPE values are
impressive in the 800-1200 J/Kg range but there is a cap and dry air
to overcome. Overall, any storm that does manage to form could
produce an isolated damaging wind gusts. Most storms should
remain well below severe criteria. Convection should come to an end
overnight but a stray shower/storm could linger, especially for
areas north of I-40 as the trough passes to the north tonight. Lows
will range from the upper 60s to mid 70s. Patchy fog will also be
possible again mainly for northeast Tennessee and southwest
Virginia, where the slightly higher rain chances will
feature this afternoon/evening.
The surface boundary currently to the north will nudge just a bit
further southward throughout the short-term forecast period. The
shortwave trough will move off to the northeast on Tuesday. PW
values will actually nudge upward just a bit and the upper level
heights may increase slightly as the ridge holds on. Model soundings
do not look much different than today except for the slightly higher
moisture. Overall, confidence in precipitation coverage may be a bit
higher tomorrow than today. SBCAPE values and deep layer shear will
be similar to today. Once again, could not rule out a strong to
marginally severe storm with an isolated damaging wind gusts but
most storms will stay well below severe criteria. High temperatures
will once again be in the low to mid 90s with heat indices of 100-
105 in the central and southern Tennessee Valley.
MA
LONG TERM (Tuesday Night through Monday)...
Key Messages:
1. Slightly cooler with fairly widespread afternoon
showers/thunderstorms Wednesday through Friday.
2. Hotter and drier trend again this weekend through early next week.
Discussion:
Tuesday Night Through Wednesday Night...
The elongated mid/upper ridge across the S CONUS will undergo its
long advertised break down during this period as a significant
shortwave trough progresses from the upper Midwest through the Great
Lakes with an associated surface low moving into Ontario and
dragging a cold front into the lower OH Valley by Wed night. This
will lower heights across the TN Valley and S Appalachians with a
broad but shallow trough taking shape across the northern tier
states. Mid level cooling should leave the region uncapped Wed, and
with abundant low-level moisture in place, afternoon instability,
and some upper support on the southern periphery of the shortwave,
expect convection to develop quickly through the morning and
afternoon, so have PoPs increasing to likely during the afternoon.
SPC has a marginal risk for severe weather in SW VA in closer
proximity to the upper support. This is dependent on how much
sunshine we see as clouds will be quite widespread, but at least
marginal instability, seasonably high PWATs, and modest deep layer
shear could support a few wet microbursts. Decreased PoPs to
chance/slight chance Wed night with the loss of heating, but with at
least weak upper support and the front reaching the OH Valley, did
not want to go dry. Highs will be tempered by the increased clouds
and precip with upper 80`s/low 90`s, which is seasonable but better
than the heat of recent days. Lows both Tue and Wed nights will
remain warm in the upper 60`s/low 70`s.
Thursday through Friday Night...
Guidance has finally come into agreement that as the aforementioned
shortwave moves across the NE U.S. Thursday, the front will
temporarily stall across the lower OH Valley and central
Appalachians before a stronger shortwave drops through the NE U.S.
Thurs night and Fri and pushes the front slowly southward through
our CWA. Small timing differences still exist, but consensus is for
the front to slowly cross from late Thurs through Fri morning,
moving S of the region Fri afternoon. Continued low-level moisture,
lower heights aloft, and afternoon instability combined with upper
support as the front slowly drops through will yield widespread
convection again, with peak coverage in the afternoon and evening.
Have likely PoPs all areas Thursday afternoon, but kept likely
wording confined to the eastern mountains and SE TN with high chance
elsewhere Fri afternoon since the boundary should be moving S.
Tapered PoPs to chance/slight chance during the overnights. Flow
aloft will still be weak, so generally not expecting severe weather,
but continued seasonably high PWATs and sufficient DCAPE as the
atmosphere destabilizes could cause an isolated wet microburst and
locally heavy rain. Highs Thurs and Fri will continue to trend
slightly lower in the mid 80`s to low 90`s, but the warm overnight
lows in the upper 60`s/low 70`s will continue.
Saturday through Monday...
A strong mid/upper ridge is still on track to develop over the
central CONUS at the end of the week with a 595-596 DM closed H5
high centering over MO or southern IL this weekend into early next
week. This will cause the heat dome to gradually edge back over the
region with warming mid level temps reducing convection to mainly
widely scattered, diurnal activity over the higher terrain. However,
kept chance PoPs each day across the entire area because guidance
continues to differ on how far east the core of the ridge builds,
which could potentially open the door to weak perturbations dropping
around the eastern periphery and periodically enhancing the diurnal
convection. Highs will trend back into the middle 90`s.
Garuckas
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 75 95 74 93 74 / 10 40 20 70 20
Knoxville McGhee Tyson Airport, TN 74 94 73 93 73 / 20 50 20 70 30
Oak Ridge, TN 73 94 73 93 72 / 20 50 10 70 30
Tri Cities Airport, TN 70 91 70 91 69 / 30 60 20 70 30
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
Area Forecast Discussion
National Weather Service Shreveport LA
920 PM CDT Mon Jul 20 2020
.UPDATE...
Convection has diminished for the remainder of the evening and
therefore, had to clean up pops a bit in the grids. Latest 00z NAM
and HRRR output suggests we could see isolated convection once
again spread north and west across Deep East Texas into West
Central Louisiana sometime during the predawn hours so for this
reason, have kept slight chance pops across our extreme southern
zones which is south of the I-20 Corridor. Areas that saw rainfall
earlier are within 5 degrees or so of forecast mins but these
areas should stabilize while rain free areas will continue to fall
as expected. Therefore, did not make any changes concerning
overnight lows.
We will continue to see this weak disturbance aloft and
increasing PWATs across our region on Tuesday which will result
in scattered to numerous showers and thunderstorms that will once
again become tied to daytime heating. The forecast for Tue has a
pretty good handle on this thinking so no additional changes were
necessary.
Update out shortly...13.
&&
.PREV DISCUSSION... /issued 723 PM CDT Mon Jul 20 2020/
AVIATION...
Convection is quickly dissipating across our airspace this evening
but for the 00z TAF package, did carry VCTS across most terminals
through 02z or so with TEMPO TSRA given coverage to begin the
package. Otherwise, VFR conditions should prevail through the
remainder of the evening and overnight hours.
Did start VCTS mention a little earlier on Tuesday (by late
morning) at our NE TX terminals only given the position of the
weakness aloft across our western half which again should be tight
to late morning, afternoon heating, elsewhere, kept VCTS tied to
the afternoon hours on Tue.
13
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 76 92 76 93 / 10 40 20 20
MLU 75 95 76 95 / 10 20 20 20
DEQ 73 92 73 91 / 10 20 20 20
TXK 74 91 74 91 / 10 20 20 20
ELD 74 94 74 94 / 10 20 20 20
TYR 74 89 74 91 / 10 60 20 30
GGG 74 90 73 92 / 10 50 20 20
LFK 75 89 75 92 / 20 60 20 40
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
13/13
Area Forecast Discussion
National Weather Service Tucson AZ
320 PM MST Mon Jul 20 2020
.SYNOPSIS...Above average heat and below average thunderstorm
chances to start the week. A more favorable pattern with
increasing moisture will set up, with increasing thunderstorm
chances the rest of the week. Strongest thunderstorm days are
expected to be Thursday and/or Friday. Some storms will generate
heavy rain and strong winds.
&&
.DISCUSSION...Isolated showers likely producing virga, sprinkles, or
perhaps a few hundredths of an inch of rainfall continued in a north-
to-south oriented band across western Pima County at this time.
Isolated showers/tstms were also noted across the White Mountains.
Otherwise, clouds have decreased markedly during the past 1-3 hours
from Tucson eastward, but mostly cloudy to cloudy skies continued
across western sections.
Several HRRR solutions suggest that the showers across western
sections will decrease in coverage during the next few hours.
Isolated showers/tstms should also continue mainly near the White
Mtns into early this evening, then isolated showers producing very
light rainfall should prevail tonight. Expect isolated to perhaps
scattered coverage of showers/tstms Tuesday afternoon/evening mainly
east to south of Tucson. Most models suggest that much of the Tucson
metro area would not receive measurable rainfall Tuesday afternoon/
evening, although the Catalina/Rincon Mountains may be the most
susceptible to measurable albeit light rainfall.
The various 20/12Z high-res and global models still support the
inherited official forecast scenario of an upswing in rainfall
chances starting Wednesday afternoon, when scattered showers/tstms
are expected across much of this forecast area. As of this writing,
the period for the highest rainfall chances/coverage of showers/
tstms appears to exist Thursday through Friday, although Saturday
and Sunday during the afternoon/evening hours also favor scattered
coverage mainly from Tucson eastward.
With increased rainfall chances, there is an increased potential for
locally heavy rainfall and gusty winds at times due to thunderstorm
outflows. The various models suggest that late night/morning hours
Sunday and Monday will likely have minimal if any measurable
rainfall across much of the area. Expect scattered showers/tstms
mainly from Tucson eastward and southward Monday afternoon.
High temperatures Tuesday and Wednesday will be generally a few
degrees above normal, then high temps especially Friday and Saturday
ranging a few to perhaps several degrees below normal. Daytime temps
by early next week should trend closer to normal for late July.
&&
.AVIATION...Valid through 22/00Z.
Isolated -SHRA west of KTUS this afternoon, with isolated -TSRA
across the White Mountains and the SE portion of Cochise County.
Isolated -SHRA may occur across southeast AZ 06Z-15Z then ending
late in valid period. Scattered -TSRA/-SHRA east to south of KTUS
Tuesday afternoon. Otherwise, FEW-SCT clouds 10-15k ft MSL and SCT-
BKN clouds above 15k ft MSL, which will continue through much of the
forecast period. SFC winds WLY/NWLY 8-12 kts this afternoon, with
higher speeds of 12-18 kts and gusts to 25 kts near KSAD. Winds
become light and variable during the evening, returning WLY/NWLY 8-
12 kts tomorrow afternoon. Aviation discussion not updated for TAF
amendments.
&&
.FIRE WEATHER...Isolated showers and thunderstorms are expected
today and tomorrow, favoring the White Mountains and the higher
terrain southeast of Tucson. By Wednesday, thunderstorm activity
increases area wide. This regime of enhanced precipitation chances
will continue each day into the weekend. 20-ft winds are breezy
across the Upper Gila River Valley this afternoon, but otherwise
less than 15 mph through the period. Thunderstorm gusts of 45 mph or
higher will also be possible around the stronger storms. Daytime
humidities reach 15 to 30 percent through Tuesday, then generally
above 25 percent Wednesday onward.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
DISCUSSION...Francis
AVIATION...Howlett
FIRE WEATHER...Howlett
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Area Forecast Discussion
National Weather Service Las Vegas NV
834 PM PDT Mon Jul 20 2020
.SYNOPSIS...Limited mid level moisture moving up from southern
Arizona will bring scattered clouds and a few showers and isolated
thunderstorms to the area today and Tuesday. This could result in
some additional fire starts in the area due to lightning as well as
gusty outflow winds. More significant monsoonal moisture may begin
to creep into the region toward the end of the work week resulting
in thunderstorm chances for at least northwest Arizona and slight
chances for southern Nevada. Temperatures should also begin to
slowly decline towards the end of the week.
&&
.UPDATE...Have not seen a cloud flash or CG detected by the
lightning network in about an hour. However, satellite shows partly
to mostly cloudy skies across southern Nevada, as well as Inyo and
Mohave County. There has been some IR cloud top cooling across parts
of Esmeralda and Lincoln County where a light rain shower or brief
thunderstorm could yet occur this evening.
Area will remain under the influence of this broad weak cyclonic
circulation with several vorticity lobes pivoting around the
circulation. Most clearly identifiable circulation early in the day
was over southwest Lincoln County which has since moved southwest
over southern Nye County. With these features around tonight can not
rule out seeing an isolated shower or thunderstorm popping up
anywhere over Inyo County, southern Nevada, lower Colorado River
Valley or northwest Arizona overnight.
Due to the lack of decent instability, Tuesday looks to be a repeat
of today with best thunderstorm coverage over the higher terrain.
Due to the lack of low level moisture primary concern will be gusty
wind and dry lightning. Our Red Flag Warning continues through
Tuesday evening.
Touched up the POPs/Weather Grids the rest of tonight and Tuesday.
&&
.AVIATION...For McCarran...Most of the overnight period is expected
to be quiet with mainly southwest winds around 6 kts and Few to Sct
clouds around 15k feet. There is some potential of showers
reentering the valley between 10-13z Tuesday morning bringing light
rain along with gusty winds, however confidence is low. There will
be another chance of seeing isolated thunderstorms Tuesday afternoon
along with the potential of gusty outflow winds. Best time for this
to occur will be between 18z-02z.
For the rest of southern Nevada, northwest Arizona and southeast
California...Isolated areas of showers and a slight chance of
thunderstorms will occur overnight along with the potential of
seeing gusty outflow winds. Shower and thunderstorm chances will
again be possible Tuesday afternoon with the main threat being gusty
outflow winds between 25-35 kts. Clouds should remain around 14k or
higher except near showers where CIGS could drop to as low as 10k
feet.
&&
.SHORT TERM...Tonight through Tuesday.
This morning`s convection produced frequent lightning across Clark
County resulting in at least one fire in the Spring Mountains.
Additional development is beginning to occur this afternoon across
southern Nevada and northwest Arizona. While isolated in nature,
this will continue to be a concern from a fire potential standpoint
since low level atmosphere is still quite dry, with this morning`s
sounding showing dry adiabatic environment just below 500 mb. CAMs
have been handling this convection better than some of the coarser
models and have edged confidence towards the HRRR for the short
term. As of the 19Z run, elevated thunderstorm potential continues
to be maximized along the Sierra as well as Spring/Sheep Range,
northern Mohave, Lincoln, and Nye counties. On satellite, we are
continuing to note what appears to be a weak MCV just east of the
test site. It is worth noting that HRRR/HRRRX does not seem to be
capturing this mesoscale feature and thus it`s a bit unclear how
much effect this will have on convection the rest of the afternoon.
Should convection overachieve this afternoon from CAMs, the biggest
concern beyond fire starts will be gusty outflow winds of 40+ mph.
Furthermore, noted PV advection looks to wrap back into southern
Nevada tomorrow morning as well which could result in another round
of showers and storms tomorrow afternoon and possibly as early as
tomorrow morning. This PV anomaly does appear in the RAP to exist a
bit farther north and east, which should keep the Las Vegas Valley
dry but continuing light precip chances for northern Mohave and
Lincoln counties. Neighbors have also upgraded their watches
(LKN/SLC) for Tuesday, so we have issued a RFW for southern Nevada
and northwest Arizona fire zones through Tuesday evening.
.LONG TERM...Wednesday through the Weekend.
Ensemble output continues to indicated a stronger shortwave trough
moving through central California Wednesday night, then across
southern Nevada Thursday and Thursday night. Strengthen southerly
flow preceding the shortwave will advect `richer` moisture northward
up the Colorado River Valley and western Arizona. Some of this will
likely leak westward into eastern San Bernardino, Clark and eastern
Lincoln Counties. This will form a `sharp` moisture gradient;
similar to the southern plains dryline. Forcing will come from a jet
streak moving overhead while the `richer` moisture will lead to
higher CAPE values. Again, don`t be surprised to see some nocturnal
storms Wednesday night. During this period, some thunderstorms could
produce brief heavy rain, gusty winds and hail.
On Friday and through the weekend some form of a trough will remain
intact over the Nevada and California. This should keep most of the
area dry and thunderstorm free as moisture is shifted back east into
Arizona for the most part. The only exception could be eastern
Mohave County where moisture is always difficult to get scoured out
so a slight chance of thunderstorms exists each day.
Temperatures will be running at or slightly below normal during the
period.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
UPDATE...Pierce
DISCUSSION...Adair/TB3
AVIATION...Gorelow
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