Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/05/20
Area Forecast Discussion
National Weather Service Denver/Boulder CO
927 PM MDT Tue Aug 4 2020
.UPDATE...
Issued at 900 PM MDT Tue Aug 4 2020
Enough instability exists across the I-25 corridor along with a
weak shortwave trough for showers and storms to continue this
evening. They will be sub-severe as the instability and shear are
not sufficient to generate strong enough updrafts. PoPs were kept
until midnight as the storms are expected to dissipate around that
time. Considering how well the storms in Larimer and Weld
Counties have held together along with the storm complex in
southeast Wyoming, it is not out of the question that a few
showers and storms persist past midnight near the Colorado/Wyoming
border. Otherwise, the forecast remains on track.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 229 PM MDT Tue Aug 4 2020
Still expecting a fairly active afternoon. Best chance of severe
thunderstorms will be along and east of the I25 corridor this
afternoon and evening. ML CAPE 1500-2000 j/kg with Bulk Shear
35-45 kts this afternoon. Airmass is still capped over the plains,
but that should be done shortly. Storms fairly well from northwest
to southeast across the forecast area. Latest HRRR still develops
the strongest thunderstorms out of WY after 3 pm, and into the
Denver, Castle Rock and Limon areas 5-7 pm. Can`t rule out some
outflow boundaries triggering off more thunderstorms further west.
Large hail and damaging winds the main threat, but sufficient
shear for a short lived tornado or two. Most of the thunderstorm
activity should be done by 10 pm with some lingering showers
through midnight. The upper ridge will be centered along the AZ/NM
border this afternoon will shift more into the eastern NM by
Wednesday afternoon. This will allow for the northwesterly flow
aloft to have more of a westerly component to it on Wednesday, The
ML CAPE and Bulk Shear values are fairly similar for the northeast
CO on Wednesday. SPC has northeast CO in another Marginal/Slight
Risk category Wednesday. Only difference, is that the focus may
shift more to the northeast plains.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 115 PM MDT Tue Aug 4 2020
Scattered to numerous showers and thunderstorms are expected
across the eastern plains early Wednesday evening. With MLCAPE of
up to 2000 J/kg and Bulk shear near 40 knots some of the storms
are expected to be strong to severe. Isolated showers and storms
will remain possible into the early evening along the Front Range.
Except for a few showers over the eastern plains, all the
convective activity is expect to dissipate or be east of the area
by midnight.
The upper level ridge axis will drift east over the Central
Rockies on Thursday. A drier west/southwest flow aloft will
prevail under this pattern. Precipitable water values fall below a
half inch across the higher terrain and Front Range. A surface
trough sets up over eastern Colorado Thursday afternoon. To the
east of this, southeast winds will transport low level moisture
into the area with dew points staying the 50s. This will lead to
MLCAPE of 2000 J/kg. Bulk shear will be a little less, around 35
knots. Still could see some strong to severe storms here through
the early evening. With the drier air in place, high temperatures
are expected to climb into the lower 90s along the Urban Corridor.
On Friday, the upper level ridge continues to slowly drift
eastward and will be centered over the Central Plains. This will
put Colorado under a southwesterly flow aloft. The surface trough
is expected to be near the eastern Colorado border with Nebraska
and Kansas. Dry westerly flow across the area is expected to
result in dry conditions and warm temperatures. Highs should reach
the lower to mid 90s for most of northeast Colorado. A few high
based showers and storms can`t be ruled out over the higher
terrain. If this convection forms, it will produce more wind than
rain.
For the weekend, the upper level ridge over the Central Plains
Saturday will retrograde west over the Center Rockies Sunday due
to a trough tracking across southern Canada. For our weather, dry
west to southwest flow aloft and at the surface will prevail. This
is expected to keep very warm and dry conditions in place.
Dry conditions will persist into early next week as the upper
level ridge remains parked over the region. Highs will continue to
be very warm with 90s over northeast Colorado. Chances for
precipitation continues to be very low. It anything forms, it will
be high based and produce little if any rainfall.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 900 PM MDT Tue Aug 4 2020
VFR is expected through Wednesday evening. There remains some
instability this evening which is leading to a few showers and
storms developing across northern Colorado. These showers and
storms are not expected to impact any of the terminals but it
can`t be completely ruled out. Otherwise, southeasterly winds will
veer toward drainage tonight.
Tomorrow, winds will veer toward to northeast and will increase in
the afternoon. Showers and storms may develop during the afternoon
and early evening which could bring strong winds and hail to the
terminals.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Danielson
SHORT TERM...Cooper
LONG TERM...Meier
AVIATION...Danielson
Area Forecast Discussion
National Weather Service Dodge City KS
615 PM CDT Tue Aug 4 2020
...Updated aviation discussion...
.SHORT TERM...(This afternoon through Wednesday night)
Issued at 1200 PM CDT Tue Aug 4 2020
Midlevel clouds across the eastern zones as of midday will
continue to dissipate into a cumulus field through this afternoon,
beneath continued NWly flow aloft. SE winds will continue to
increase through this afternoon, gusting 30-35 mph at times.
Temperatures will continue to trend well below normal, in many
zones just getting close to 80. SW zones will be well into the
80s. All zones will be dry through about 7 pm this evening.
Scattered convection is expected to develop along the Front Range
this afternoon, with NWly flow subsequently spreading the activity
toward SW KS tonight. Latest HRRR iterations and other CAMs
suggest storms will be along the CO/KS border by 8 pm. The highest
risk of large hail/damaging winds will be across these far western
zones (roughly west of US 83), and relatively early this evening
per SPC`s 1630z outlook. With time and with eastward extent, any
discrete storms will evolve into clusters, and also become
strongly elevated, with 12z NAM progging near zero surface based
CAPE in SW KS tonight. With modest elevated CAPE/NW flow aloft,
expect some activity to survive into at least the central zones by
midnight. With an unfavorable environment with eastward extent,
confidence is less say east of US 283. Pops are in the likely
category for much of the western/central zones tonight. Short term
models suggest stratus will fill in behind the storms Wednesday
morning, with sunrise temperatures once again in the upper 50s and
lower 60s.
Below normal temperatures will continue Wednesday afternoon,
ranging from the lower 80s east, to mid 80s SW zones. Daylight
Wednesday will be dry, with lighter SEly winds. A strong 594 dm
upper high is forecast to be centered near Midland, Texas
Wednesday evening. More weak shortwaves rounding the northern
periphery of this high will probably encourage more nocturnal
thunderstorms late Wednesday night/early Thursday morning. Pops
are mainly in the chance category after midnight, favoring the
E/NE zones per the NAM/ECMWF solutions.
.LONG TERM...(Thursday through Tuesday)
Issued at 143 PM CDT Tue Aug 4 2020
The balance of the long term will be quiet and dry as the
subtropical upper anticyclone expands its influence across the
plains. Temperatures will begin showing a warming trend Thursday,
with max readings in the upper 80s and lower 90s. Friday will be
noticeably hotter, with 12z ECMWF building a 594 dm ridge centered
over SW Oklahoma. NBM`s max temp grid of upper 90s was accepted
for Friday, with some triple digits along the Oklahoma border.
Saturday promises to be at least as hot, before models forecast
the upper high to ever so gradually weaken Sunday through Tuesday,
with a few degrees of cooling each day. NBM sprinkles some slight
chance pops here and there in the long term. Did not remove them,
but the prospects of organized rainfall/convection appear minimal
with little if any forcing.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 615 PM CDT Tue Aug 4 2020
There is some uncertainty as to the track and coverage of thunderstorms
moving out of eastern Colorado this evening. Most of these storms may
track across far southwest Kansas into the OK/TX Panhandles. Additional
thunderstorms could develop across portions of central and southwest
Kansas toward south central Kansas between 04z-06z before tracking into
Oklahoma later tonight. Given the uncertainties, will carry VCTS
at the terminals but will hold off on any prevailing coverage at
this time. There is also some small potential for MVFR cigs to
develop later tonight across southwest Kansas.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 59 84 63 88 / 70 10 50 0
GCK 59 83 62 88 / 70 10 40 0
EHA 61 87 63 92 / 60 10 30 10
LBL 61 88 64 94 / 70 10 30 10
HYS 59 81 63 86 / 30 10 30 10
P28 61 82 65 91 / 60 20 40 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Turner
LONG TERM...Turner
AVIATION...Gerard
Area Forecast Discussion
National Weather Service Goodland KS
1000 PM MDT Tue Aug 4 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 205 PM MDT Tue Aug 4 2020
A Severe Thunderstorm Watch is in effect through 9 PM MDT for
Yuma, Kit Carson, and Cheyenne Counties in Colorado as well as
Sherman, Wallace, and Greeley in Kansas.
500mb RAP analysis and water vapor imagery showed a ridge prevailing
over the western half of the country with a trough dominating the
eastern CONUS. This pattern placed the region under northwest flow,
with a shortwave approaching from Wyoming. Earlier convection
cleared the area by mid morning, leaving cloud cover across the
eastern part of the region. At 2:00 PM MT, temperatures ranged in
the 70s to low 80s, with breezy south winds gusting around 30 mph
along the Colorado border. A line of weak storms had also developed
over the northeastern CWA.
As the aforementioned shortwave moves towards the region, southerly
flow at the surface filters moisture into the High Plains. Diurnal
heating will aid thunderstorm development along the Front Range
during the afternoon hours. With 40 to 50 knots of shear, MLCAPE
around 2,000 J/kg near and west of the Colorado border, and
steepening lapse rates, scattered severe thunderstorms are expected,
with the best chance along and west of the Colorado border. Severe
storms are also possible east of this line; however, coverage would
be more isolated.
Storms developing along the Rockies should gradually work their way
east/southeast through the evening hours. Supercells will be
possible initially, with a clustering storm mode favored in the
evening. Large hail, damaging winds, and locally heavy rainfall
resulting in flash flooding are all hazards. All of that being said,
today`s cloud cover has had an impact on daytime heating thus far
(especially in the east) which may have an effect on storm chances
through the evening. Currently, it looks as though storms will exit
the region to the southeast around midnight. Temperatures fall into
the mid 50s to low 60s with partly to mostly cloudy skies tonight.
Temperatures climb into the mid to upper 80s on Wednesday as the
upper ridge builds east into the Plains. Another round of
thunderstorms is forecast from the late afternoon into the evening
as a shortwave works through the northwest flow around the
northeastern periphery of the ridge. Storms should develop along the
Rockies once again and move east across the area through the
evening. Scattered severe storms will be possible along and west of
a line from Flagler, Colorado to Haigler, Nebraska. Isolated severe
storms could spread east from this line into adjacent northwest
Kansas and southwest Nebraska. Large hail and damaging winds will be
the main threats. Locally heavy rainfall may also occur.
Expect low temperatures in the upper 50s to low 60s.
.LONG TERM...(Thursday through Tuesday)
Issued at 229 PM MDT Tue Aug 4 2020
At the beginning of the forecast period on Thursday, forecast
guidance shows the Tri-State region under an upper air ridge which
is between an upper air low in the Pacific Northwest and another low
over eastern Ontario. This ridge is amplified by an upper air high
over southwestern TX and Mexico. This ridge persists over the area
into Friday, but models show that the Pacific Northwest low begins
to move east across Canada suppressing the amplitude of the ridge.
There is some model discrepancy as the ECWMF has this Canadian low a
little more east than where the GFS has this low placed. This
pattern continues until Saturday when an upper air trough associated
with the Canadian low moves into the Northern Plains and pushes the
ridge east of the Tri-State area leaving a generally westerly flow
aloft starting Sunday. This upper air pattern continues for the
remainder of the forecast period.
At the surface, model guidance shows warmer temperatures returning
to the Tri-State area due to the ridge aloft and winds coming from
the south through the weekend. Thursday evening shows a slight
chance of isolated showers and thunderstorms associated with an
upper level shortwave moving through the ridge for the areas west of
the CO/KS border. Areas along and east of the CO/KS border expect to
see a slight chance of showers and thunderstorms associated with a
upper level shortwave troughs on Saturday and Tuesday. There is also
a slight chance of showers and thunderstorms possible for areas east
of Hwy 27 on Sunday and Monday as well due to upper level shortwave
troughs passing through the area.
As the warmer temperatures return during the forecast period, there
is a chance for possible fire weather conditions on Friday for the
western portions of Yuma, Kit Carson, and Cheyenne counties of CO as
RH values are expected to be below 20%. However, current model
guidance shows that expected wind gust values for Friday do not
support elevated fire weather conditions.
High temperatures for the Tri-State area are expected to warm into
the upper 80s by Thursday followed by highs in middle 90s through
the weekend and highs in the lower 90s on Monday and Tuesday to
finish the forecast period. Low temperatures will remain in the
lower to middle 60s across the Tri-State area during the forecast
period with the exception of Monday and Tuesday when the CO counties
of the Tri-State area are expected to see lows in the upper 50s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1000 PM MDT Tue Aug 4 2020
KGLD, vfr conditions expected from taf issuance through about 09z
with winds from the south under 10kts. From 10z-14z there is
medium confidence of stratus clouds and sub vfr cigs developing
over the terminal some some light reductions in visibility. A
brief period of south winds around 12kts with some higher gusts
expected from 22z-00z. After 00z there is medium confidence in an
organized cluster of strong to potentially severe thunderstorms
moving through or near the terminal somewhere in the 03z-06z
timeframe. Erratic wind gusts and potentially very heavy rainfall
are possible which could produce sub vfr conditions.
KMCK, vfr conditions expected through the period. Winds through
the period from the south to southeast at speeds 10kts or less.
Similar to KGLD there is medium confidence in an organized cluster
of strong to potentially severe thunderstorms impacting the
terminal sometime in the 03z-06z timeframe. There is a bit higher
confidence in thunderstorms actually impacting the terminal so
have added some sub vfr visibility reductions in moderate rain.
Erratic wind gusts likely as it moves through.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JBH
LONG TERM...076
AVIATION...99
Area Forecast Discussion
National Weather Service North Platte NE
656 PM CDT Tue Aug 4 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 240 PM CDT Tue Aug 4 2020
A weak shortwave is evident late this morning across northern WY per
WV imagery. This will slowly track southeast through the afternoon.
Mid-level lift and weak WAA continues to aid in some scattered
elevated showers and isolated thunder. A leeward surface trough will
be located across eastern WY southward to near the Denver metro by
late this afternoon. Persistent upslope flow and lift associated
with the shortwave will lead to the development of scattered
thunderstorms near the surface trough. These will attempt to push
eastward into the Nebraska Panhandle early this evening. Sufficient
instability should be present in this area along with 35-40 kts of 0-
6km bulk shear. This should allow for storm organization with a few
supercells producing large hail possible initially. The last several
runs of the HRRR have brought the activity about as far east as
Highway 2 (near Ogallala) by mid evening. After mid-evening
convection quickly diminishes as convection tries to push farther
east. This could be due to earlier cloud cover and less instability
with eastward extent. There is at least some chance that convection
could become elevated and continue moving east/southeast through the
night, but models have been struggling with this scenario. In fact,
most of the HREF members have activity done by late evening in our
area. The low-level jet really isn`t very strong tonight and there
is a lack large scale lift. For these reasons will lower pops some
tonight and focus chances mainly this evening across portions of
west central and southwest Nebraska.
Another round of convection is expected to develop along the leeward
surface trough across eastern WY into northern CO Wednesday
afternoon. Most models actually have more robust development
tomorrow (compared to today). Better instability also exists farther
east with activity moving farther east Wednesday evening. Activity
Wednesday evening could be supported by a better shortwave which is
indicated in the NAM. 0-6km shear is once again sufficiently strong
(30-40 kts) for storm organization.
Otherwise warmer temperatures (mid to upper 80s) expected Wednesday
as heights slowly rise with the upper ridge building northward. The
axis of the ridge will be oriented south to north across the
Rockies. Low-level moisture will also be slowly increasing with dew
points rising into the lower 60s.
.LONG TERM...(Thursday through Tuesday)
Issued at 240 PM CDT Tue Aug 4 2020
Upper level ridge axis gradually shifts eastward and will be
centered along the western High Plains by Saturday morning. As
heights continue to rise and the flow aloft decreases, so will the
scattered thunderstorm chances. Temperatures will continue to warm
with highs in the 90s most areas by this weekend. Rather humid
conditions expected as well with upper 60s to lower 70s surface dew
points working there way to the west into western Nebraska by Friday
into Saturday. The ridge may flatten a little by early next week as
a stronger shortwave with flow aloft increasing from the west a bit.
A weak cold front could also move southward into the area by Monday
which could provide focus for scattered storms once again. Highs
cool slightly by early next week into the mid 80s to around 90F.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 635 PM CDT Tue Aug 4 2020
VFR conditions expected to prevail at both TAF sites through the
period. Backing winds are expected at VTN into tomorrow afternoon
with the approach and passage of a cool front. Watching convective
debris north of LBF, but left out mention for now with lower
confidence in its progression southward. Even if this convective
debris does make it into LBF, CIGs are still expected to remain
VFR. Don`t anticipate the need to include even VCTS at LBF with
the thunderstorm activity to the northwest expected to diminish
over the next couple hours.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Taylor
LONG TERM...Taylor
AVIATION...Brown
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
957 PM EDT Tue Aug 4 2020
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
A weak boundary is located across the central valley this evening
with a few convective rain showers. These showers are forecast to
dissipate with the loss of daytime heating and a stabilizing
boundary layer which is what CAMs such as the HRRR indicate. With
satellite imagery already showing a clearing sky for most areas,
fog is expected to develop across river valleys and areas that
received rain this afternoon. Forecast continues to progress as
expected and only made minor adjustments to hourly forecast
elements.
JB
&&
.AVIATION...
00Z TAF DISCUSSION.
Showers and thunderstorms expected to dissipate after sunset with
clearing conditions. Fog is forecast to develop along river
valleys, and this will impact TRI. Guidance is in agreement with
IFR/LIFR fog late tonight and early Wednesday morning near TRI, so
included in the TAF for TRI. Fog development is less likely at TYS
and CHA, but is possible with recent rainfall this afternoon.
Included MVFR fog potential for CHA and TYS, but lower vis will be
possible. Additional showers and thunderstorms will be possible at
all TAF sites Wednesday afternoon, but the probability is low
enough to include in a Prob30 group for tsra.
JB
&&
.PREV DISCUSSION...
/ISSUED 329 PM EDT Tue Aug 4 2020/
SHORT TERM...(Tonight through Wednesday)...
Scattered showers continue across the TN valley this afternoon in
part due to a strengthening jet entrance region over the southern
Appalachians in response to Isaias phasing with a large scale
trough anchored over the Great Lakes region. Forecast soundings
from across the CWA showed a notable warm layer in place around
15,000 ft or so earlier today, and this was forecast to
essentially remain in place through the afternoon and evening
hours. With meager instability in place updraft maintenance has
struggled, with few showers on the whole extending much beyond the
15-16k ft AGL mark. Showers that did manage to break through that
warm layer have gone on to produce some brief gusty winds,
supported by DCAPE values in the 800 J/kg range. However lack of
robust updrafts means that there hasn`t been much to work with in
regards to large precipitation cores and resulting damaging winds.
If there were an area to be leery of through the evening it would
be the TN valley between the Knoxville and Chattanooga metro areas
and along the I-75 corridor where sun has been most prevalent.
This area has the best overlap of instability and DCAPE values.
Tonight, showers will largely follow a diurnal pattern, dying off
quickly after sunset this evening. A cold front is draped
NE-SW across the TN valley this afternoon and will shift east
of the Appalachians late tonight. However, there isn`t a strong
push of dry air behind this. Thus with the lack of strong dry air
advection and the scattered rain from today, think that fog and
low clouds will be somewhat prevalent again late tonight into the
pre-dawn hours tomorrow. The forecast accounts for this. Tomorrow,
expect another round of showers, though mostly over the
mountains, as the region remains beneath cyclonic upper flow as
well as upslope flow across the mountainous area. High res
guidance does show rain chances extending into the valley later in
the day, but lesser chances are warranted there.
CD
LONG TERM...(Wednesday Night through Tuesday)...
The region will remain underneath persistent longwave cyclonic flow
through the late week and into the weekend. Several perturbations
will likely rotate through this flow but forecasting timing is of
low confidence. A moist and unstable airmass will be in place each
day this week which results in afternoon showers and thunderstorms
Thursday, Friday, and Saturday afternoon. Temperatures will remain
near normal Thursday through Saturday. Start to see a pattern change
during the late weekend period as a ridge of high pressure aloft
begins to nudge north and east out of the plains. Upper level
heights will increase in response to this. Afternoon showers and
thunderstorms will be possible. Temperatures should warm in response
to increased heights aloft.
Early next week, the ridge will begin to break down in response to a
trough moves out of the Pac NW. Low level winds will veer toward the
southwest advecting low level moisture northward. Lowered heights
and moisture should contribute to afternoon showers and
thunderstorms Sunday through Tuesday. The lack of any upper level
support or low level boundaries should mean that strong to severe
potential will remain very low. Temperatures will continue to be
above normal for early next week. Highs in the lower 90s are
forecast. This combined with higher dewpoints may allow heat index
values to approach 100 degrees.
Diegan
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 69 89 69 91 70 / 10 30 10 30 10
Knoxville McGhee Tyson Airport, TN 67 88 68 89 68 / 20 40 20 50 20
Oak Ridge, TN 67 87 66 88 68 / 20 30 10 40 10
Tri Cities Airport, TN 62 85 63 86 65 / 10 50 30 60 20
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$