Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/15/20
Area Forecast Discussion
National Weather Service Des Moines IA
300 PM CDT Fri Aug 14 2020
.DISCUSSION.../Tonight through Friday/
Issued at 256 PM CDT Fri Aug 14 2020
Primary forecast concerns will be over the next 6 to 12 hours with
the potential for strong to severe storms, including damaging winds
and hail as threats. More details in the sections below.
The remainder of the forecast will remain on the quieter, a bit
cooler, and much less humid side with northwest upper level flow
prevailing and only periodic chances for a shower/storm or two.
Today through Tonight...
Mid and upper level troughing continues to work its way across the
Dakotas and into Minnesota this afternoon, including a surface low
reflection sliding NE currently positioned in the ND/SD/MN tri-state
border region, yielding a surface cold front stretching back to the
S/SW. Ahead of the cold front, a remnant elevated outflow/gravity
wave continues to kick off scattered showers and the odd lightning
strike or two, but being away from the bulk of the forcing and
support will continue to predominantly struggle as it continues into
western Iowa. Back along the approaching front, deep convection has
begun to initiate in the Sioux City and will be the area to watch.
Across the state, established southerly flow kept the region on the
warm and humid side with temperatures in the mid 80s and dew points
regularly into the low 70s.
Ultimately, the question is whether or not we have enough support
for severe storms late this afternoon and evening. Let`s take a
With the warm and humid conditions established, and a degree of
moisture pooling ahead of the front, MUCAPE values in excess of 4000
J/kg and MLCAPE values in excess of 2500 J/kg respectively have been
established across W/NW IA by mid afternoon today. Generally,
forcing will not be in question either with a potent cold front,
attached to the parent surface low north of the region, that will
traverse the state through the evening. Shear profiles are at least
marginally supportive with effective shear depictions remaining in
the 30-35 kt range. The better veering profiles reside north of the
area, yielding environmental 0-3km SRH values around or less than
150 m2/s2, especially as you work south. Areas of steep lapse rates
in excess of 8 deg C/km continue to suggest at least some large hail
potential, especially should storms efficiently tap into available
shear. Strong winds may also be seen with drier low-mid levels and
DCAPE values in 1000 J/kg.
Working against severe potential are depictions of convection ahead
of the better/most supportive 0-3km and 0-6km shear profiles and
shear vectors losing orthogonal position through the event.
Additionally there are continued depictions of a stronger EML within
HRRR family than originally anticipated by overnight and early
morning synoptic and hi-res models, suggesting more of a broken
line of convection versus traditional QLCS.
Overall, anticipate broken line segments of convection to work
their way across the state through the late afternoon and evening
hours, with the best severe potential over the northwest third of
the area, lining up well with existing SPC Day One Outlook. A few
cells may be able to efficiently take advantage of the
anticipated effective shear profiles and yield periods of severe
hail and winds. Otherwise, expect majority of the activity to be
sub- severe. As the convection and front work into central Iowa,
waning instability will reduce the severe threat further,
especially on the hail side, but stronger winds could continue
into the evening.
While severe threat into central and eastern Iowa will reduce
through the evening, given the continuing recovery efforts from
the Monday derecho, recovery crews and the public will want to
keep an eye out on vulnerable trees, power poles, etc... as they
may be susceptible to additional damage from sub-severe winds, let
alone severe winds, given their already weakened nature.
Saturday through Friday...
Expected weather becomes much more comfortable, and predominantly
quiet through the rest of the forecast. Why? A large 500mb high will
develop over the SW US and result in amplified western CONUS ridging
that will yield prevailing NW flow over the region. Other than
periodic shortwaves yielding lower end shower/storm chances at
times, a dry forecast will prevail much of the time.
.AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/
Issued at 1238 PM CDT Fri Aug 14 2020
Main concerns predominantly over the next 12 hours with potential
for MVFR and brief IFR conditions due to TSRA opportunities at all
sites. KFOD/KMCW/KALO most likely to see impacts, with more
uncertainty at KDSM and KOTM with potential for storms to be more
scattered in nature at the latter locations. With frontal passage,
winds will quickly shift from S/SW to NW with gusts persisting to
around 15-20 kts behind the front before subsiding towards the
early morning hours. Once storms pass through concurrent with the
front, remainder of TAFs will be VFR.
Area Forecast Discussion
National Weather Service Green Bay WI
1028 PM CDT Fri Aug 14 2020
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Saturday
Issued at 257 PM CDT Fri Aug 14 2020
The latest RAP analysis and satellite/radar imagery show low
pressure over the eastern Dakotas and a cold front extending from
the low southwest across the central Plains. Strong to severe
convection continues ahead of the low over northern Minnesota,
though has been weakening over the past few hours. A much more
stable airmass prevails across the eastern half of Wisconsin, as
evident by little in the way of cu formation. As the front slides
across the region tonight, forecast concerns mainly revolve around
Tonight...The cold front will continue to march east and move into
central and north-central WI after midnight. Widespread
thunderstorms are expected to develop along the front this
afternoon before they push into western Wisconsin this evening.
With diminishing instability and upper level forcing lifting off
to the northeast, the short range models continue to show
convection diminishing as it approaches north-central to central
WI shortly after midnight. Still though, most unstable capes up to
1000 j/kg could lead to an isolated strong storm persisting into
north-central WI. Probably the most significant threat would be
heavy rainfall. Convection should continue to diminish along the
front into northeast WI by 12z. A widespread low overcast deck
will likely move into the area behind the front. Even though winds
will shift to the northwest, the clouds should keep temps mild.
Lows ranging from the upper 50s to middle 60s.
Saturday...The front will continue to move east over northeast
Wisconsin in the morning before exiting by midday or early
afternoon. Some guidance indicates that a few strong cells could
develop late in the morning along the lakeshore areas before the
front departs. Not sure if there will be enough time to
destabilize in the morning, especially since cloud cover should be
plentiful. Will show a slight uptick in precip chances, but the
unfavorable timing will keep any severe threat as very low. With
partial clearing in the afternoon, temps to warm into the middle
70s to near 80, which is about 5 degrees cooler than today.
.LONG TERM...Saturday Night Through Friday
Issued at 257 PM CDT Fri Aug 14 2020
Looks like a seasonable weather pattern setting up
for next week with a western ridge and eastern trough producing a
northwest upper flow across the Great Lakes. This should result in
pleasant summer weather with a few days slightly cooler than
normal and a couple days a little above normal by the end of next
There could be a shower or thunderstorm during the middle of the
week as a shortwave moves through the upper flow. The models
forecast the upper flow to flatten out towards the end of the
work week, with a chance of showers or thunderstorms ahead of
another cold front.
.AVIATION...for 06Z TAF Issuance
Issued at 1025 PM CDT Fri Aug 14 2020
A cold front continues to slowly approach from the west. The
front will bring an increase and lowering of the clouds as is
pushes into the area. Some convection will accompany the front
into the area overnight, but it will be weakening. The likelihood
of thunder occurring at the western TAF sites has increased, and
timing is now clearer, so will include a TEMPO group for the
thunder there. It looks less likely in the east, so will continue
with just SHRA in the eastern TAF sites with the 06Z issuance.
Area Forecast Discussion
National Weather Service Huntsville AL
942 PM CDT Fri Aug 14 2020
.NEAR TERM...(Rest of tonight)
Issued at 942 PM CDT Fri Aug 14 2020
Warm upper level ridging remained over the Desert SW, while upper
troughing was amplifying over eastern CONUS. A weak upper level low
within the troughing over the IN/OH border had trough extending
towards the Tennessee Valley. A vorticity maxima over western
Tennessee featured an area of showers and thunderstorms, moving to
the SE. This activity per the new NAM, along with hourly updates from
the RAP and HRRR had it gradually dissipating as it nears the
forecast area - with it generally gone after 2-3 AM.
Given uncertainty with this convection, left rain chances as is for
tonight. Will revisit this and raise rain chances for our NE areas
if the storms and other newer guidance keeps it going. The rest of
the forecast output looked okay for now.
.SHORT TERM...(Saturday through Sunday night)
Issued at 242 PM CDT Fri Aug 14 2020
Much of the central and western part of the forecast area may be
completely dry on Saturday in the wake of the trough passage. Our
eastern counties may experience a few more showers and thunderstorms,
mainly through early afternoon. However, coverage should not be
widespread. With afternoon mixing, dew points should lower below 70
degrees in many areas. The more noticeably airmass change will occur
after a cold front drops southeast on Sunday. So, one more muggy day
is expected just ahead of the front Sunday. Isolated thunderstorms
are possible, but with a more limited deep moisture profile and
generally weak QG forcing, will keep PoPs/coverage more limited.
Will not rule out a strong storm or two, but this doesn`t appear to
be a linear/widespread convective event. Noticeably drier air will
arrive by Monday morning when lows should dip into the 60s areawide
except near the larger lakes still retaining warmth. Went 1-2 degrees
above suggested blends for highs Saturday and Sunday.
.LONG TERM...(Monday through Thursday)
Issued at 242 PM CDT Fri Aug 14 2020
General pattern of ridging over the western CONUS will lead to
general troughiness over the eastern CONUS. This will lead to
northwesterly flow bringing drier air into the Tennessee Valley
through the first half of next week. This will limit the shower and
thunderstorm potential, with mostly dry weather Monday and Tuesday.
Both the GFS and ECMWF show a secondary wave developing, bringing a
low pressure system down out of Oklahoma into the Mississippi River
Delta region midweek. This will lift a warm front north and southerly
flow will bring back moisture to the Tennessee Valley maybe as early
as Wednesday, but more likely on Thursday. This will lead to
increasing shower and thunderstorm chances again later next week.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 637 PM CDT Fri Aug 14 2020
Broad weak surface low pressure over the region will slowly move
eastward into Sat. Despite its presence, cooler conditions and a more
stable environment should result in shower activity diminishing this
evening. Late night stratus and/or fog formation is possible across
the area in the predawn hours and on Sat. Stayed with low IFR CIGs at
KHSV, and LIFR CIGS and MVFR fog at KMSL. Conditions should improve
within a few hours of sunrise, with VFR condition expected
thereafter. Light winds this evening and in the overnight, should
become NW, increasing into the 5-10 kt range from the mid morning
into the afternoon.
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AREA FORECAST DISCUSSION
National Weather Service Charleston WV
1150 PM EDT Fri Aug 14 2020
Heavy rain heading into Saturday with a slow moving disturbance.
Another round of thunderstorms ahead of a cold front Sunday
night. Drier for early next week.
.NEAR TERM /THROUGH SATURDAY/...
As of 1145 PM Friday...
Adjusted PoPs down with less coverage per latest radar imagery.
Rainfall activity seems to diminish considerably, and seems like
the RAP model have a good handle of the current situation.
Coverage and intensity of showers and storms return by Saturday
morning. Rest of forecast remains on track.
As of 850 PM Friday...
Based on latest discussion from WPC, which focuses on the
possibility for increased activity overnight across parts of VA
into WV due to enhanced convergence along a boundary along
higher terrain counties and overrunning, elected to go ahead
and expand the FFA into much of WV counties. Was generous in
areal coverage due to the uncertainty in where heaviest rains
may occur, and the fact that soils are primed from recent
As of 630 PM Friday...
Tweaked pop grids to add more coverage cross southeast Ohio
zones and lowered hourly temperatures in rain cooled locations.
Otherwise, forecast still looks to be on track.
Many of the slow moving storms this evening have produced a good
2 inches or more of QPF in spots. Fortunately, most of this has
hit in our drier areas. The flash flood watch will remain in
effect across southern zones through at least late this evening,
with the other watch progged to take effect late tonight across
southeast Ohio and adjacent WV counties as low level forcing
takes hold in vcnty of a surface low. Models seem to be
struggling a bit with placement of heavier precipitation
tonight, but some of the CAM`s seem to still be hitting the Ohio
Valley region the hardest, so will leave the watch as is.
Additional rounds of showers and storms will develop once again
As of 145 PM Friday...
Clearing skies coupled with increasing influence from an approaching
upper level disturbance will spawn scattered showers and
thunderstorms again this afternoon and evening. The main threat with
any slow moving storms developing afternoon will be locally heavy
rain. Did elect to hoist a flash flood watch across our eastern
Kentucky, southwest West Virgina and Southwest Virginia counties in
collaboration with our neighbors for this early activity. While
widespread issues are not expected, rainfall over the last few days
has tempered flash flood guidance in these locations in a spotty
fashion with isolated high water impacts possible under
persistent cells producing 1 to 2 inch per hour rainfall rates.
The larger concern will be potentially very heavy and persistent
rainfall associated with a developing low level circulation forming
in response to a weakly phased shared energy area at H250. While
instability is not terribly impressive, synoptically forced, near
tropical columns coupled with very slow storm motion with
significant training potential may yield local rain accumulations in
excess of 3 inches across portions of the Middle Ohio Valley early
Saturday morning through early afternoon. While flash flood guidance
in this area is generally on the higher end, thunderstorms yesterday
along with potential additional showers and storms this afternoon
will somewhat temper these values. Have issued another flash flood
watch from late tonight through early Saturday afternoon for
locations with the highest confidence of slow moving storms along
the track of the low level circulation. This may eventually need to
be expanded further east or south, but confidence levels in
flooding impacts are lower with storm motions accelerating.
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 228 PM Friday...
While the majority of heavy precipitation should taper off
Saturday night into Sunday as an upper level trough departs to
the east of the area, some showers and perhaps a few embedded
storms may linger into Sunday afternoon, particularly in the
mountains. Otherwise, expecting highs on Sunday to be in the low
to mid 80s across the lowlands and 60s to mid 70s in the higher
By Sunday night, a line of showers and thunderstorms is expected to
approach western portions of the CWA as a low pressure system across
southern Ontario pushes a cold front across the Ohio Valley. While
this activity should be weakening by the time it reaches our area
due to decreasing instability late Sunday evening into the overnight
hours, a few stronger storms may be able to move into portions of
our southeast OH counties if enough instability can hang on by the
time the front arrives. Regardless, any threat for stronger
storms should be isolated at most Sunday night before
precipitation fizzles out during the overnight hours as the
better upper support will be north of the area. While Monday
should be mainly dry as surface high pressure across the Upper
Midwest builds into the area, upper troughing aloft may support
a few showers and isolated storms in the mountains Monday
afternoon and evening.
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 228 PM Friday...
Upper air pattern early next week features strong upper ridging
across the Intermountain West and broad troughing across much of
the Great Lakes and Ohio Valley. This pattern will support a WNW
flow aloft across the region in the early to middle portions of
the work week with embedded shortwaves triggering occasional
chances for showers and storms through mid week.
By the end of the week, there is some uncertainty in where an
upper level closed low may develop with models for now placing
this feature generally across the lower Mississippi Valley.
Ahead of this feature, southwesterly flow is expected to be on
the increase and may reach into our area depending on the
placement of the upper low, so for now have used a consensus
blend of PoPs in the forecast through the end of the period
until better model agreement occurs as precipitation chances
could increase by late week.
.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
As of 730 PM Friday...
Showers, along with isolated thunderstorms will continue through
at least 03Z when a decrease in activity will be noted. However,
post rain fog and stratus is expected, with widespread MVFR and
areas of IFR or worse conditions expected to develop,
particularly after 06-09Z.
Focus then shifts to the potential for a period of heavy
rainfall and embedded thunderstorms across much of southeast
Ohio and WV counties closer to the Ohio River, generally in the
06-15Z time period. Expect areas of LIFR or worse conditions in
Some improvement expected after 15Z across the area, however,
widespread MVFR, and possibly local IFR conditions will
continue to linger for much of the remainder of the TAF period.
Showers and thunderstorms will redevelop again, mainly after
18Z, and mainly south of the Ohio River.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z SUNDAY...
FORECAST CONFIDENCE: Medium.
ALTERNATE SCENARIOS: Timing, duration, and extent showers and
storms may vary from forecast. Extent of post rain fog and or
stratus overnight tonight may vary from forecast.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE SAT 08/15/20
UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14
EDT 1HRLY 23 00 01 02 03 04 05 06 07 08 09 10
CRW CONSISTENCY M H M L L L L L M H M H
HTS CONSISTENCY H H H H L H H H H M M H
BKW CONSISTENCY M M H H M M L L L M M M
EKN CONSISTENCY H H H H L M L L L M L H
PKB CONSISTENCY H H H H H H H M H H H M
CKB CONSISTENCY H H H H H H H H M M L H
AFTER 06Z SUNDAY...
Rounds of showers and thunderstorms possible Saturday evening
and night with additional brief IFR restrictions. Areas of IFR fog
possible Monday and Tuesday mornings.
WV...Flash Flood Watch through Saturday afternoon for WVZ006>011-
Flash Flood Watch until 2 AM EDT Saturday for WVZ005-013.
OH...Flash Flood Watch through Saturday afternoon for OHZ067-075-
KY...Flash Flood Watch through Saturday afternoon for KYZ101.
Flash Flood Watch until 2 AM EDT Saturday for KYZ102-103-105.
Area Forecast Discussion
National Weather Service Las Vegas NV
819 PM PDT Fri Aug 14 2020
.SYNOPSIS...Excessive heat lasting through the weekend, and through
the bulk of next week due to a pungent ridge of high pressure.
Isolated, dry afternoon thunderstorms possible over the southern
Sierra as well as the higher elevations of south-central Nevada and
northwest Arizona. Otherwise, clear skies with light afternoon
.UPDATE...The isolated thunderstorms that formed from the Morongo
Basin, northwest across the western Mojave Desert then north up the
southern Sierra already dissipated leaving behind an orphaned anvil
here and there. monitoring wildfires via satellite showed that the
Lake Fire is burning the hottest. Vertically integrated smoke product
from the HRRR indicates smoke/haze spreading out across across parts
of Inyo, southern Nye, Clark and San Bernardino Counties tonight.
Updated to adjust POPs/Weather grids the rest of tonight, otherwise
.DISCUSSION...Today through Thursday.
The heat is here. That said, there aren`t many changes to the
forecast to highlight.
We have an Excessive Heat Warning now in effect for much of the
region including southern Nevada, southeastern California and
northwestern Arizona through Wednesday night. In addition, we have a
Heat Advisory now in effect for the Spring Mountains and Sheep Range
of Clark County through Wednesday night. What is the difference? Why
are there two different heat-related headlines? We want to emphasize
something... It`s going to be hot - even by Desert Southwest
standards. We`re expecting record-breaking temperatures for mid-
August this week as we ramp up for an incredibly climatologically
abnormal heat event. Though we`re relatively accustomed to heatwaves
here and there, the distinction is that those typically range from 2
to 4 days in length. The heatwave for which we`re currently gearing
up is looking like a week-long affair. That said, the inclination is
going to be to head up to the mountains or other regions of higher
terrain. Though, sure, temperatures will be "cooler" than the
valleys, their temperatures are still forecast to be well-above
their seasonal normals, providing little relief. For this reason, we
hoisted a Heat Advisory for the Clark County mountains.
In addition to the higher terrain not cooling down, neither will the
overnight/morning low temperatures, which are also expected to be
record-breaking. The unfortunate result of having nearly a week of
excessively hot temperatures with little-to-no elevation nor diurnal
(nighttime)-derived cool downs will be a stark increase in heat-
related illnesses, or worse, if precautions are not taken. We
strongly urge you to limit time spent outdoors. If this can`t be
done, take frequent breaks in the shade or in the A/C, hydrate
frequently, and wear light-colored, loose-fitting clothing. Heat is
the #1 weather-related killer. Let`s, as a community, team together
to beat the heat. What does this look like? Check on family,
friends, and neighbors who fit into sensitive population categories
such as the elderly, sick, or children. Urge the homeless to seek
out or help point them to cooling shelters. Leave items essential to
your trip in the back seat such as a purse, wallet or cell phone to
remind yourself to never leave a child or pet in a vehicle
unattended. Without A/C, vehicles can reach fatal temperatures.
Remind or let those know who may be without internet or cable that
temperatures this week will be dangerous.
Other than the heat, today through the weekend may be accompanied by
smokey skies for some, most notably in San Bernardino and southern
Clark counties due to fires in southern California as well as the
Baja including the Lake Fire and Ranch2 Fire. Populated the forecast
using HRRR Smoke. Additionally, isolated convection is possible
today over the Sierra Mountains as well as the higher terrain of
south-central Nevada and northwestern Arizona. This convection will
likely take the form of dry thunderstorms, with primary impacts
being associated winds and potential fire starts. As mentioned in
the previous briefing, this persistent, strong ridge of high
pressure will greatly limit instability potential. However, the
ECMWF Ensemble and GEFS members continue to allude to upper-level
moisture getting trapped under this ridge. Coupled with modest
instability from daytime heating, this could be enough for daily,
isolated dry thunderstorms in the higher terrain through the week.
DAILY RECORD HIGH MAXIMUM TEMPERATURES
TDY 8/14 SAT 8/15 SUN 8/16 MON 8/17
Las Vegas, NV 111 (2016)* 111 (2002)* 113 (1939)* 111 (1939)*
Bishop, CA 106 (2002) 105 (2002)* 106 (1994)* 106 (2015)*
Barstow, CA 112 (2002)* 112 (2002)* 114 (1994)* 111 (2015)*
Needles, CA 117 (2012)* 118 (2019)* 118 (2015)* 117 (1892)*
Kingman, AZ 109 (1933) 106 (1933)* 110 (1933)* 106 (2001)*
Death Valley 124 (2002) 124 (2002)* 125 (1994)* 124 (2001)*
DAILY RECORD HIGH MINIMUM TEMPERATURES
SAT 8/15 SUN 8/16 MON 8/17 TUE 8/18
Las Vegas, NV 86 (2016)* 88 (2008)* 89 (2015)* 86 (2018)*
Bishop, CA 65 (1958) 67 (1992) 65 (1992)* 67 (1970)
Barstow, CA 83 (1996)* 81 (1994)* 82 (2012)* 80 (2001)*
Needles, CA 92 (1962)* 93 (1892)* 94 (1903) 91 (2018)*
Kingman, AZ 78 (1972)* 77 (1917)* 81 (1903)* 80 (2001)
Death Valley 97 (2008)* 98 (2008)* 99 (2013)* 98 (2013)*
*-Current forecast may be close to current record values.
.AVIATION...For McCarran...Light and variable winds continue this
afternoon. A brief period of gusts to 15-18 kts out of the southwest
is possible this afternoon but confidence is low at the terminal.
After sunset winds will be generally light and variable with a
general favoring from the southwest overnight. Light, diurnal trends
expected tomorrow with VFR cloud cover expected to clear out through
For the rest of southern Nevada, northwest Arizona and southeast
California...For the Las Vegas Valley sites, gusty west-
southwesterly winds will pick up this afternoon, with speeds 8-12
kts expected and gusts to 20 kts possible. KBIH could experience
southerly wind gusts to 20 kts as well this afternoon, with gusts
areawide dying down after sunset. Elsewhere, diurnal trends with
speeds generally below 10 kts expected through the forecast period.
Cloud cover will continue to clear out this afternoon, with no
operationally significant cloud cover expected through the TAF
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
For more forecast information...see us on our webpage:
https://weather.gov/lasvegas or follow us on Facebook and Twitter