Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/21/20
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
541 PM MDT Thu Aug 20 2020
.AVIATION...
00Z TAF CYCLE
Upper high circulation will persist over northeast/east central
Arizona. Isold to sct showers and tstms along the central mt chain
and Contdvd will continue to drift to the south. Gusty erratic
outflow winds will be associated with many of the cells with brief
MVFR cigs/vsbys and mt obscurations in the stronger cells. Convection
may push swd over the northeast and east central plains aft 03Z while
diminishing over wrn NM. HZ due to wildfire smoke circulating around
the upper high will continue over western and central NM but in
general VFR conditions will prevail.
&&
.PREV DISCUSSION...301 PM MDT Thu Aug 20 2020...
.SYNOPSIS...
Hot and mainly dry condtions will continue Friday through the weekend
with strong high pressure remaining anchored over Arizona. Best
chances for a brief afternoon or evening shower or thunderstorm will
be in the mountains. High temperatures will continue to be well above
averages for late August but start to trend down a degree or two
each day starting next week.
&&
.DISCUSSION...
.SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)...
We have seen convection initiate over the Tunas Mountains as well as
the Sangre de Cristos Mountains but this activity has yet to move
south or southeast off the mountains. We are also seeing convection
form on the AZ/NM border west of Gallup and towards Grants.
Otherwise convection is pretty quiet and having issues getting
going. Part of this is due to the upper level ridge situated over
Arizona with 593-593dm 500mb heights. Precipitable water is also
below normal with 0.7" on the ABQ sounding. The GOES PWAT imager
shows similar values over much of central/western NM. Moisture is a
little higher to the east and this is where we find a marginal risk
for severe storms. The potential for an isolate severe storm is
there but there is some doubt as to how much instability will be
available given lower moisture. Drier air in the boundary layer will
support downburst winds but that is if there is enough overall
moisture and instability for a storm to develop. If a cluster of
storms can form off the mountains then we might see a more organized
threat with strong outflows driving more convection. Latest HRRR
model trends suggest the possibility so we will continue to monitor
but also leery of limited instability.
Going into Friday, it looks like overall moisture will be more of a
concern. Based off model consensus, 700-500mb flow from the NNW/N
will allow for drier air to move into New Mexico and drop PWAT down
below 0.7 inches and closer to 0.5 inches. Moisture is not much
better in the higher terrain so even having convection in the Sangre
de Cristo Mtns will be tough. Same can be said farther SW towards
Gila National Forest. As such, we have decreased chances of storms
for most areas tomorrow. That`s not to say there won`t be storms,
but that any storms will be very isolated in nature.
LONG TERM...(SATURDAY THROUGH WEDNESDAY)...
Crazy stagnate upper-level pattern continues through the weekend and
into early next week. Big bubble has nowhere to go through early next
week thanks to a low- latitude trough stuck over the deep south. Hot
and relatively dry continues Friday through the weekend with the best
shot at showers and thunderstorms over and due south of most mountain
ranges in the state. Eventually the southern upper-level trough
lifts out to the northeast and the Four Corners` high starts to shift
northeastward over CO early next week. This shift results in a more
favorable surface pattern to get low-level Gulf moisture in from the
southeast. GFS and ECMWF agree on this change with most activity
focused on western NM Monday and Tuesday. Despite the low-level
moisture in eastern and central areas of the state, dry air aloft
from the Southern Plains moves into eastern and central portions of
the state early next week, shutting down shower and thunderstorm
chances. By mid-week, models agree that a weak easterly wave gets
into the mix, generating deformation over northern NM and helping to
get storms going over the northern mountains during the afternoon.
These storms then slide westward over the northwest third during the
evening.
39/33
&&
.FIRE WEATHER...
The main change from today to Friday is that drier air works in from
the northwest. This means isolated afternoon showers and storms will
be confined to areas from the east slopes of the central mountain
chain east to the central and northeast highlands. Over the weekend
and into next week, it does not look like much improvement with
precip chances so dry conditions will continue. Granted it`s still
possible to get the typical shower/thunderstorm activity in higher
terrain but since the upper level ridge does not move much from the
Four Corners region, there will be little steering flow so most
storms will be pulse storms.
Smoke is becoming or has become more of a problem for New Mexico as
fires in Colorado continue to burn. The Medio fire north of Santa Fe
continues to burn but not producing the amount of smoke the fires in
Colorado are. Smoke will be a problem going into the weekend since
the upper level flow does not change but a lot of the smoke has
remained in upper parts of the atmosphere, not settling into
valleys. Still possible for that to happen especially each night but
for now most smoke projections keep the smoke lofted. This will be a
day to day situation to monitor.
39
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
149 PM AKDT Thu Aug 20 2020
.SYNOPSIS...
Above normal temperatures continue across Northern Alaska beneath
a ridge of high pressure. A few showers and isolated thunderstorms
are possible from Fairbanks east and in the Eastern Brooks Range
today, and from Tanana east tomorrow. Stratus remains on the North
Slope and on the West Coast with onshore flow. This beautiful
stretch of weather will come to an end this weekend as a weather
front will bring rain to the West Coast by Saturday morning,
eventually spreading east to Fairbanks and the Eastern Interior by
early Sunday morning.
&&
.DISCUSSION...
An upper level closed low that was located south of Yakutat
yesterday has moved to SW of Ketchikan. An upper level low
associated with this feature is centered south of Northway, with
the associated surface low near Glennallen. This feature continues
to advect moisture into the Interior from Fairbanks east,
providing clouds and scattered showers. From Fairbanks west,
ridging is dominant with mostly clear skies for all areas inland
of the coast. Onshore flow from the dome of high pressure over the
Bering Sea is allowing stratus and clouds to linger along the
coast.
Between the ridges extending from the Bering Sea NE and from
Ketchikan NW lies a weak thermal trough over the Eastern Brooks
Range. This area may see isolated thunderstorms this afternoon as
a shortwave trough passes to the north along the Arctic Coast.
The next notable weather system will arrive to the West Coast on
Saturday, bringing rain. Thunderstorms can be expected on the
leading edge of this front as it moves into the Western Interior
on Saturday afternoon, and again in the Eastern Interior on Sunday
afternoon as it progresses eastward. Behind this front, Northern
Alaska enters a troughing pattern with cooler temperatures and
more showers expected into next week across the forecast area.
Models...
The GFS and the NAM currently show better timing regarding the
weather front and associated shortwave moving west to east across
the North Slope, with the ECMWF and HRRR solutions being too
slow. Looking ahead into Sunday, the NAM is much sharper with the
shortwave at the leading edge of the longwave trough moving into
the West Coast and then into the Interior. As a result, forecast
rainfall totals are much higher than in the GFS and ECMWF model
runs that reached that time frame yesterday. The GFS has also
increased its rainfall totals for Saturday night and Sunday in the
Western Interior, with both models putting the highest amounts on
the west slopes of the Alaska Range. Thunderstorms can be
expected on the leading edge of the front where it passes during
the afternoon hours. At this time it appears that this will be in
the Western Interior on Saturday and east of Fairbanks on Sunday,
with stratiform rain beginning in Fairbanks early Sunday morning.
The timing of the forecast reflects the timing of the GFS and
ECMWF, while the NAM solution is a bit slower.
North Slope and Brooks Range...
Isolated thunderstorms are expected in the eastern Brooks Range
this afternoon as a shortwave trough passes just to the north of
the weak thermal trough in place. Otherwise expect mostly clear
skies and warm temperatures to continue through Saturday in the
Central and Eastern Brooks Range, with stratus lingering along the
coast. At this time, expect that the bulk of the precipitation
from the weather front moving in from the west will fall south of
the Brooks Range.
West Coast and Western Interior...
Fog and stratus remains over much of the West Coast, Lower Yukon,
and Yukon Delta from Kotzebue south. The Western Interior remains
clear. Expect these conditions to persist until Saturday when the
weather front arrives, spreading precipitation from west to east.
Isolated thunderstorms will occur ahead of the front in the
Western Interior on Saturday afternoon before the bulk of the
rainfall arrives. Expect showers and cooler temperatures behind
the front.
Central and Eastern Interior...
A few isolated showers and thunderstorms are expected from
Fairbanks east today, but otherwise expect mostly sunny skies and
warm temperatures to continue through Saturday. A weather front
will arrive on Saturday night and spread rain from west to east
with cooler temperatures and more showers behind it.
Coastal Hazard Potential Days 3 and 4...
Exposed south facing capes and shores in the Bering Sea including
Nome may see water levels 1-2 feet above the normal high tide
line on Saturday and Sunday with S and SE winds along and behind a
weather front. Flooding is not expected at this time.
&&
.FIRE WEATHER...
Above normal temperatures will continue into Saturday for most of
Northern Alaska. Minimum RHs will dip into the 30 and 40 percent
range over much of the Interior during the day, but overnight
recovery will be excellent. Isolated thunderstorms are expected
east of Fairbanks and in the Eastern Brooks Range this evening,
east of Fairbanks tomorrow, and in the Western Interior on
Saturday.
&&
.HYDROLOGY...
The Chisana River at Northway has been reported to be high after
~0.5" of rain fell in its basin overnight. The river is expected
to crest this afternoon and slowly fall afterwards. Flooding is
not expected. For the latest river forecasts and conditons, visit
www.weather.gov/aprfc
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
CHRIEST AUG 20
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
253 PM AKDT Thu Aug 20 2020
.SHORT TERM.../Thursday evening through Saturday night/ The short
term features a complex set us as a stacked area of low pressure
meanders around the southeast gulf with multiple waves rotating
into the Panhandle from British Columbia. As with many easterly
wave scenarios, guidance has a poor handle regarding the timing of
each wave impacting the area. Tried to incorporate hi-res models
into the precipitation forecast as they may be able to resolve the
smaller features better than the courser lower resolutions
models. No matter which model chosen to make the forecast, the
overall message stays relatively the same over the weekend with
waves of showers moving into the Panhandle from the south and east
and peaks of sun likely in between waves.
For Thursday evening, a wave of energy moving into the Panhandle
from the SE will increase the chance of showers and thunderstorms
this evening. Hi-res model soundings indicate a marginally
unstable atmosphere across the far southern Panhandle with CAPE
values above 500 j/kg, LI around -1, and dew points in the upper
50s to near 60. The HRRR has convection moving into Misty Fjords
this evening and heading northward towards Petersburg/Wrangell.
With a 50 kt mid level jet streak over the south and effective
bulk shear 25 to 30 kt, the possibility is there for convection to
hold together through the evening and make its way north and west
towards the Central Panhandle. Thunderstorms will transition to
plain showers overnight and head up into the northern Panhandle.
The main threats with any shower or thunderstorm will be brief
periods of heavy rain, gusty winds, and lightning.
Waves continue to rotate into the Panhandle Friday and Saturday.
Current thinking is that the Northern Panhandle, along the Coast
Mountains, and the far SE Panhandle have the best chance of
receiving rainfall from these waves. Lower PoPs potentially along
the outer coast further away from the main energy. Kept a slight
chance for thunder in the forecast for Petersburg, Wrangell, and
Misty Fjords for Friday afternoon as the atmosphere may have a
chance to destabilize. In between waves, breaks in the clouds are
certainly possible allowing temperatures to spike in the
afternoon. Expect warmest temperatures to be Thursday
afternoon/evening with highs a few degrees cooler each day as 850
mb temps begin to cool and easterly downsloping flow weakens.
With such a convective/showery pattern, it`s very difficult to pin
point each individual shower that forms so temperatures may vary
greatly over short distances. Areas that receive more breaks in
the clouds could make a run for 70F while showers will keep other
areas cooler.
Impactful winds ongoing at the beginning of the short term are
expected to subside Thursday evening. A strong low offshore of
POW Island combined with a 50 kt jet streak at 850 mb and an
unstable atmosphere is producing Gales in the coastal waters from
Cape Edgecumbe down towards the Dixon Entrance. Gusty winds to 30
kt are being observed around POW and the Ketchikan area while
gusts to 35 kt are in Clarence Strait. Winds are expected to
diminish this evening as the low pulls away to the SW. Lighter
winds expected Friday into Saturday across the Panhandle.
Confidence in the forecast is below average for this time of year
as guidance does not have a good handle on the timing of each wave
passing through. Used Hi-res models to try to add detail to the
precipitation forecast. No major changes made to winds today.
.LONG TERM.../Saturday through Thursday/ The forecast for the
weekend has come into somewhat better consensus, featuring more
rain for the panhandle. While parts of the northern and central
panhandle may experience a brief period of lower chances of rain
early on Saturday, another easterly wave will likely take aim at
the panhandle during the afternoon hours, lasting through much of
Sunday. Just how much of the area the wave will cover is not yet
entirely certain, but currently have it progged to focus on the
central and southern panhandle. This second wave will bring with
it some degree of moisture, and so expect there to be some QPF
accumulation from it, helping to nudge the already impressive
summer totals which parts of SE Alaska have seen even higher. The
rain will continue until a ridge succeeds in displacing the by
this point weakening low. Still some model disagreement on how
long it will take the low to dissipate, but think that it will
meander into the Haida Gwaii area, and have largely faded away by
daybreak on Monday.
As this low leaves, still some indications that Monday may offer a
few breaks in the clouds, particularly for the southern and
central panhandle, as the ridge moves into SE Alaska. Given that
this ridge is centered largely over the Gulf and the panhandle as
opposed to the Yukon, am not expecting much in the way of a
substantial boost in temperatures from it, though temperatures may
climb into the low to mid 60s in fortunate parts of the area.
This break may prove to be fleeting in nature as guidance has been
hinting at the emergence of another system which could impact the
panhandle late Monday and through the middle of the week, though
model disagreement by this point is substantial, making it hard to
give specifics this far out.
&&
.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind until 7 PM AKDT this evening for AKZ027.
Strong Wind until 6 PM AKDT this evening for AKZ028.
MARINE...Gale Warning for PKZ041-042.
Small Craft Advisory for PKZ022-036-043-051.
&&
$$
CM/GFS
Visit us at http://www.weather.gov/Juneau
Area Forecast Discussion
National Weather Service Charleston SC
1047 PM EDT Thu Aug 20 2020
.SYNOPSIS...
A stationary front over the area will gradually weaken late
this week. High pressure is then expected to prevail early next
week as Tropical Depression 13 moves northwest, possibly into
the eastern Gulf of Mexico as a tropical storm or hurricane.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 1045 PM: The Coastal Flood Advisory has been cancelled.
The forecast products will be updated to remove product
headline. Otherwise, the forecast appears on track.
As of 930 PM: KCLX indicates an isolated thunderstorm over
Tattnall County, with isolated showers across portions of SE GA.
Latest HRRR indicates very little coverage through the rest of
the evening into the late night hours. The update will generally
feature changes to hourly temps to align with observations.
As of 745 PM: Deep convection and associated outflow boundaries
have advanced well inland this evening. Lingering instability
may support isolated convection through the rest of this
evening. Near-term guidance indicates that a mid-level short
wave will lift from south to north on the east side of a closed
H5 low. This feature should produce another round of showers and
thunderstorms around dawn. I will update the forecast to adjust
PoPs and rain-cooled temperatures.
Previous Discussion:
This evening and tonight: A few of the thunderstorms are now
starting to show a little more vertical development with higher
reflectivity reaching closer to the -20 C level. Overall, still
not much change to the forecast thinking and the severe weather
potential. Effective wind shear of 20-25 knots is available,
with MLCAPE values peaking around 2,000 J/kg. DCAPE values are
quite modest, in the 600-700 J/kg range. Still, we could see a
couple of clusters become organized and produce strong wind
gusts. Diurnal convection should dissipate as usual later this
evening. Then through the overnight, models depict shortwave
energy streaming through in the southwest flow which should help
to drive nocturnal convection. The bulk of the activity should
be over the coastal waters, but could again impact land areas
with isolated to scattered showers and thunderstorms. Patchy,
mainly shallow, ground fog will be possible but isn`t expected
to be widespread enough to explicitly mention in the forecast.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Moderate confidence this period. The area will remain between
troughing to the west and ridging to the east which will keep
abundant moisture and periodic upper-level forcing in place.
Combine these factors with mesoscale boundaries from the sea
breeze and convective outflows and the result will be higher
than normal rain chances, with most of the rain likely each
afternoon/evening. In general areas near the coast will see the
highest rain chances early in the day with inland areas seeing
the best chances later in the day as the sea breeze pushes
inland. Deep layer shear looks to be a bit stronger the next few
days which would support a greater risk for severe storms but
instability appears like it will remain limited so not expecting
widespread severe weather at this time. Temperatures should
remain near to slightly above normal.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The upper-level trough stretching from the OH Valley to the
Lower Mississippi Valley will begin to weaken and lift Sunday
night. Meanwhile, high pressure in the Atlantic will gradually
shift towards the Southeast U.S. and approach the coast early
next week. Additionally, high pressure is expected to develop
over the Mid- Appalachians early next week. Sea breeze
convection will be possible each afternoon and evening. Though,
coverage should be near or just below normal. The convection is
forecasted to dissipate each night. Temperatures will be near
normal.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Deep convection and associated outflow boundaries have advanced
well inland this evening. Lingering instability may support
isolated convection through the rest of this evening. Near-term
guidance indicates that a mid-level short wave will lift from
south to north on the east side of a closed H5 low. This feature
should produce another round of showers and thunderstorms around
dawn, highlighted at KCHS with VCSH from 9-15Z. In the wake of
the shortwave, convection placement and timing is more
uncertain.
Extended Aviation Outlook: Main concern is for periodic flight
restrictions from showers and thunderstorms, especially each
afternoon and evening.
&&
.MARINE...
Tonight: Enhanced flow along the land/sea interface will
dissipate late this evening. Winds will then generally top out
around 10 knots through the rest of the night. Seas will average
2-3 feet, peaking around 4 feet in the outer Georgia waters. We
will likely again see shower and thunderstorm activity increase
across the waters late.
Friday through Tuesday: Moderate to high confidence through
Sunday night with no significant concerns. However, confidence
is low thereafter as the forecast becomes a bit more uncertain
starting Monday as much will depend on the evolution of TD #13.
Mariners should be alert for the potential for waterspouts along
the land breeze each morning through at least the weekend.
Rip Currents: Moderate Risk of rip currents for all beaches
Friday. Increasing swells could lead to an enhanced risk along
the entire coast starting Monday.
&&
.TIDES/COASTAL FLOODING...
Astronomical contributions from the new moon and perigee will
result in elevated tides (the Perigean Spring Tides) through
Friday. Another Coastal Flood Advisory could be needed with the
Friday night high tide for the southeast South Carolina coast.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...NED
SHORT TERM...RJB
LONG TERM...MS
AVIATION...NED/RJB
MARINE...BSH/RJB
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Des Moines IA
714 PM CDT Thu Aug 20 2020
...Updated for 00Z Aviation...
.DISCUSSION.../Tonight through Thursday/
Issued at 226 PM CDT Thu Aug 20 2020
Summary...
Overall, not much to write home about weather wise. Temperatures
will continue to slowly march back into the low to mid 90s for
highs, but oppressive dew points should remain at bay. Generally low-
end precipitation chances will periodically move thorugh the state
over the next few days, then remain dry for much of the new work
week.
Today through Tomorrow Morning...
Weak convection in SE South Dakota should generally continue to
wane/struggle, leaving majority of the area dry as we move into the
evening hours. A few more scattered showers and storms continue to
appear possible overnight as an arm of the 850mb LLJ works into W/NW
Iowa. Earlier runs of the HRRR were a bit more robust with
showers/storms tonight, though sub-severe, while more recent runs
have backed off but still depict a few showers. Overall, of little
to no consequence. Have introduced low end POPs over much of NW Iowa
and portions of W and C Iowa overnight.
Tomorrow Afternoon through Sunday...
As shortwaves continue to crest the western CONUS ridge and work
into the Plains, they will predominantly split around the state.
With weak flow overhead, the shortwaves will slide southward
along/west of the Missouri River and/or southeastward across the
Dakotas and Minnesota. As a result, northern Iowa will see the best
chances for any showers/storms as a potent shortwave works into and
through central and southern Minnesota Friday night into Saturday.
Much more than occasional lightning will be hard to come by with
relatively weak CAPE and support for any organization. As broad
surface high pressure works in behind the shortwave, a weak boundary
will work into and across the state late Saturday through Sunday.
NBM has been slow to pick up on scattered showers/storms along the
boundary as it moves through, so have introduced POPs 06-12z Sunday,
and may need to be extended into the 12z-18z time frame. Once again,
nothing more than nuisance storms with support for organization
lacking.
Monday through Thursday...
An overall flattening of the upper level pattern to weak riding will
prevail during the week, pushing any chances for showers/storms away
through at least the middle of the week. Additionally, temperatures
will continue to warm, peaking into the low to mid 90s. With
oppressive dew points remaining at bay, heat index values will
generally be at or within a degree or two of the air temperature.
Toward the end of the week, flagship ECMWF/GFS models depict a
stronger upper wave and surface low moving across Canada, eventually
dragging a cold front and shower/storm chances into the region.
&&
.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 706 PM CDT Thu Aug 20 2020
VFR conditions with light south/southwesterly winds will continue through
the TAF period. Slight chances remain for KFOD (and a lesser
extent KMCW) to see a scattered shower or two during the
overnight hours as the LLJ picks up, but have left mention of rain
out of the TAF due to low confidence and any precipitation that
does occur would likely be isolated.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Curtis
AVIATION...KCM
Area Forecast Discussion
National Weather Service Grand Junction CO
917 PM MDT Thu Aug 20 2020
.UPDATE...
Issued at 906 PM MDT Thu Aug 20 2020
Still some outflow boundaries causing some gusty winds across the
area but these should die down over the next hour or two.
Convection has ended, and with it, the chance for any new storms
so the Red Flag Warnings for dry lightning has been allowed to
expire. Smoke will continue to plague areas south of both the Pine
Gulch and Grizzly Creek fires overnight. Not much relief in sight
as far as the smoke is concerned as the latest HRRR smoke
guidance is suggesting smoke from the California fires will be
pulled into our region tomorrow evening reaching the northern
valleys just after sunset. We shall see.
&&
.SHORT TERM...(Tonight through Friday night)
Issued at 330 PM MDT Thu Aug 20 2020
Morning accas across the north along with a shortwave passing
through has acted on mid level moisture and instability to produce
isolated to scattered thunderstorms as expected. Most of this
convection has been over the high terrain with a few cells already
tracking over the Pine Gulch and Grizzly Creek Fire areas. The
morning sounding indicated the sub-cloud layer is very dry below
450 mb, so not expecting much in the way of significant wetting
rain with these cells. Reports have indicated that some small hail
has fallen in a few of these cells with brief light rain reaching
the ground. Rain is enough to wet the pavement in some of the
higher country but very brief in duration. The fire areas will
continue to be closely monitored but with so much dry air
entrainment in the low levels, don`t anticipate much is reaching
the ground. The NAM Nest is continuing to indicate some more
robust outflow winds arriving early this evening as these storms
collapse and the flow shifts from west to northwest and then north
overnight. Outflow winds could gust upwards of 45 mph, so this
will need to be watched as it can lead to extreme and erratic fire
behavior over existing fires. This wind shift may also end up
bringing smoke back into areas to the south of these fires and
along I-70 as the drainage winds kick in and transport the smoke
down valley. So, we could be waking up to another round of ash
fall and smoke if the outflow winds and wind shift comes to
fruition. Dry thunderstorm threat should end late this evening
around or after sunset for most areas. A couple areas to watch for
are the Pine Gulch and Grizzly Creek Fires though as any outflow
boundaries interacting with the heat of the fire could result in
nocturnal convection as seen a few nights ago. Red Flag Warning
continues until 9 pm this evening, but evening shift will have to
monitor conditions if it looks like the threat will continue into
the evening.
High pressure shifts southwest of the area and builds allowing for
drier northerly flow to take hold on Friday. The chance for
thunderstorms appears much less than today, so only anticipate
very isolated storms over the high terrain. For the majority of
areas, it will be another hot and dry day with perhaps a bit more
hazy to smoky conditions due to the northerly wind shift.
.LONG TERM...(Saturday through Thursday)
Issued at 330 PM MDT Thu Aug 20 2020
Hot and mostly dry period looks to remain in place this weekend as
the ridge of high pressure builds back to the southwest Saturday and
shifts overhead by Sunday. Some recycled moisture may result in
isolated storms over the higher terrain but otherwise, expecting
mostly dry and hot conditions to prevail as no discernible
forcing is moving through the CWA during this period and ensemble
guidance is indicating a fairly strong ridge dominating overhead.
Triple digit heat and near record high temperatures appear to be
the norm for many lower valleys of eastern Utah and west-central
Colorado this weekend into early next week.
Some hope for moisture appears to be on the horizon heading into
next week. Remnants from currently named Tropical Storm Genevieve
off the southern tip of the Baja in the eastern Pacific looks to
track northward along the western California coast late Sunday and
gets absorbed a bit in the flow as a Pacific Northwest low pulls it
northeast into the Intermountain West by Monday. Another shortwave
trough will approach the west coast as this happens, allowing the
high pressure ridge to shift eastward enough to allow sub-tropical
moisture to increase from the southwest early next week. The initial
onset of moisture looks weak late Sunday into Monday with the ECMWF
quite a bit drier. However, ensemble model guidance is showing signs
of the ridge breaking down by Tuesday and Wednesday, which presents
our best chance of seeing decent moisture in the form of wetting
rains. Precipitable water values by Tuesday look to reach the 0.75
to 1.0 plus range for much of the area. While this moisture is much
needed due to the persistent heat, drought and ongoing wildfires and
smoke impacts, this also poses an elevated concern for potential
flash flooding on any burn scars, especially for areas recently
burned and still burning like the Pine Gulch and Grizzly Creek
fires. It would only take a couple tenths of an inch of rain in a
short period of time to cause impacts on these hydrophobic soils, so
not much. Time will tell though as models looking this far out have
had a tendency to be more aggressive with the moisture. Models also
don`t appear to be resolving the significantly drier low levels due
to the persistent heat and severe drought, so while the mid levels
may be sufficiently saturated, this has more often than not resulted
in more gusty outflow wind potential and lightning than wetting
rain. It usually takes a few days for the lower atmosphere to
completely saturate after the initial onset of moisture, in order to
produce significant wetting rains. This potential is something to be
aware of though as we head into the early to mid week timeframe.
However, a more conservative approach is the best forecast at this
time until details come into greater focus and if models remain
consistent as we head closer to this timeframe. If this pans out,
increased clouds and showers will provide some relief from the
triple digit heat with highs in the 80s for the higher valleys and
90s for many lower valleys.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 539 PM MDT Thu Aug 20 2020
Plenty of outflow boundaries are bringing variable and gusty winds
to many TAF sites this evening. Wind speeds vary from 20 to 30kts
with a few spots reaching near 40kts. As the sun sets, convection
will also weaken which will cause the winds to subside. A few
showers and storms have formed and may affect KEGE, KASE, and KHDN
but by 03Z, most convection will end. Skies will lift and clear
out overnight though smoke may reduce visibility for KEGE, KRIL,
and KGJT.
&&
.FIRE WEATHER...
Issued at 330 PM MDT Thu Aug 20 2020
The Red Flag Warning remains in effect for dry thunderstorms
across much of the forecast area. Mid-level moisture is generating
isolated to scattered thunderstorms over higher terrain this
afternoon and they are expected to continue into the evening.
Given the lack of moisture in the near surface layer, many of
these storms will produce little to no rain. Fuels are extremely
dry so there is a high likelihood of new fire starts with today`s
storm activity. In addition, strong outflow winds to 45 mph will
spread fires already burning in unpredictable directions
potentially resulting in extreme fire behavior. Thunderstorm
chances are much lower Friday into the weekend, but hot and dry
conditions will remain.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
UPDATE...TGR
SHORT TERM...MDA
LONG TERM...MDA
AVIATION...TGR
FIRE WEATHER...TGJT
Area Forecast Discussion
National Weather Service Goodland KS
947 PM MDT Thu Aug 20 2020
.UPDATE...
Issued at 941 PM MDT Thu Aug 20 2020
A broken line of storms have begun to form ahead of the outflow
approaching from the west. This line is roughly along Highway 27.
Once the outflow moves underneath the storms, am doubtful they
will last much longer. At this time am not sure if there continue
to be a line of storms ahead of this outflow boundary or not as it
moves east across the forecast area. The best upper level support
for storms will be along the Highway 27 corridor.
Severe wind gusts are still a threat. However, storms have formed
in much better effective shear, so this may make them more
suitable to produce larger hail. Mid level lapse rates are still
around 7.5, which is not ideal. In addition, storms won`t have
much time to strengthen before the outflow moving east cuts them
off. Therefore confidence of large hail occurring is still on the
low side.
UPDATE Issued at 829 PM MDT Thu Aug 20 2020
Updated forecast to reflect latest trends in radar and near term
data. Storms that have been moving south in Nebraska have been
fading over the last hour or so. RAP sounding for McCook has begun
to show the potential for an elevated thunderstorm around
midnight. However other near term data has not been supporting
that, so confidence is low this will occur.
Meanwhile am thinking the storm activity over East Central CO will
continue to move south of the forecast area. There is an outflow
boundary moving east from the storm, so will be curious if it
triggers any storm development when it runs into the LLJ near the
stateline.
There may be isolated storms which move in from the northwest late
tonight. However the current storms to the northwest seem to be
fading. Just incase these do manage to survive, have left a
mention of isolated chances in for East Central CO.
Continue to think the main threat with the strongest storms will
be wind gusts of 60 MPH.
&&
.SHORT TERM...(This evening through Friday)
Issued at 145 PM MDT Thu Aug 20 2020
Next shortwave trough rounding the western ridge will arrive this
evening accompanied by widely scattered showers and thunderstorms.
Environment will be similar to yesterday, with a slight uptick in
MLCAPE, while DCAPE and effective shear are more or less the same.
Expecting wind to be the primary hazard with gusts up to 65 mph
possible with stronger storms. Despite a gradual decline in
coverage through the evening, isolated showers/storms may persist
through the overnight before ending by 12z Saturday. Low
temperatures will be in the 60s.
Upper ridge nudges into the area on Friday with rising heights. A
few of the CAMs suggest isolated thunderstorms developing at peak
heating along a surface trough from northeast Colorado into
central Nebraska, moving east and weakening Friday evening. Weak
instability remains a limiting factor, but cannot rule out an
isolated severe wind gust with any storm that develops.
Temperatures will warm into the middle to upper 90s and lows
Friday night in the 60s again.
.LONG TERM...(Saturday through Wednesday)
Issued at 131 PM MDT Thu Aug 20 2020
The long term period will see the continuation of the warm and dry
pattern we have seen this past week. On Saturday the upper level
high will be centered over Arizona with the ridge over majority of
the western CONUS. The cut-off low is expected to slowly move east
towards the Tennessee Valley setting up northerly flow across the
Central Great Plains. The ridge will continue to move east into next
week centering over the High Plains region by Tuesday. As the high
moves into the Four Corners region early next week, the ridge will
extend into central Canada. Wednesday, a shortwave trough will move
east along the northern extent of the ridge in Canada sending a cold
front south. Looking at current guidance, it doesn`t seem like the
cold front will make it`s way into the Tri-State area.
High temperatures will be in the 90s each day. Low temperatures are
expected to be in the 60s. Dry conditions are expected through the
period. There is some concern for fire weather during the long term
period. Relative humidity values are expected to drop down into
middle to lower 20s each day in eastern Colorado. Sunday through
Tuesday the concern is little higher as the low humidity levels will
be co-located with southerly wind gusts approaching 25 mph.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 514 PM MDT Thu Aug 20 2020
VFR conditions forecast for the 0z TAFs. Confidence of storms
moving near a TAF site for the evening is low enough to not put in
the TAFs. If one of the sites were to have storms move nearby, am
thinking it would be KMCK during 3-4z. Otherwise winds will be on
the light side through the period.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JTL
SHORT TERM...024
LONG TERM...KMK
AVIATION...JTL
Area Forecast Discussion
National Weather Service Midland/Odessa TX
620 PM CDT Thu Aug 20 2020
.DISCUSSION...
See 00z aviation discussion below.
&&
.AVIATION...
VFR conditions are expected for the next 24 hours. Winds will
mostly be out of the southeast for HOB, INK, MAF, and FST. Winds
will be somewhat variable for CNM and PEQ.
&&
.PREV DISCUSSION... /issued 245 PM CDT Thu Aug 20 2020/
DISCUSSION...
Not much change to the current forecast. WV imagery shows the ridge
centered over ern AZ this afternoon, maintaining meridional flow
over West Texas and Southeast New Mexico. The latest HRRR repeats
last night`s scenario in a shortwave developing convection in NE NM
late this afternoon, and drifting down into SE NM overnight. Friday,
convection looks confined to the higher terrain during the day.
Friday night, models are in pretty good agreement in bringing a
shortwave through the ern CWA, especially the SREF, which may
combine w/convection out west in the mtns to provide the best chance
of convection this forecast. That said, chances won`t be anything
to write home about.
Over the weekend, the ridge will meander NE, settling over the Four
Corners by 00Z Mon, and leaving West Texas and Southeast New Mexico
high and dry into the extended.
Regarding temperatures, Fri still looks to be the hottest day,
w/probably a few Heat Advisories needed for the higher elevations.
Thicknesses drop off over the weekend as the ridge moves to the Four
Corners, w/most locations seeing highs below the century mark by Mon
afternoon. Temps should remain above-normal, but cooler than they
have been lately, into the extended.
&&
.PRELIMINARY POINT TEMPS/POPS...
Big Spring 73 101 73 99 / 0 10 20 10
Carlsbad 72 101 73 101 / 10 10 20 0
Dryden 75 104 75 100 / 0 0 20 20
Fort Stockton 75 102 73 100 / 0 10 10 10
Guadalupe Pass 72 95 70 93 / 10 20 30 0
Hobbs 70 98 69 98 / 0 10 10 0
Marfa 64 98 65 94 / 0 20 30 10
Midland Intl Airport 74 100 74 99 / 0 10 10 10
Odessa 75 101 74 100 / 0 10 10 10
Wink 74 104 74 102 / 0 10 10 0
&&
.MAF WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...None.
&&
$$
99/99/99
For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php
Area Forecast Discussion
National Weather Service Tucson AZ
800 PM MST Thu Aug 20 2020
.SYNOPSIS...
Expect storm coverage and chances to increase into the weekend.
High temperatures will moderate through the weekend, but will
still be 2-5 degrees above normal. Next week storm chances
decrease and temperatures climb back up to near record levels.
&&
.DISCUSSION...
An active monsoon pattern brought several thunderstorms across the
forecast area this afternoon and evening. A few of these
thunderstorms were severe, with a few reports of wind damage in
Drexel Heights and Rio Rico. There were also multiple reports of
visibility reductions related to dust in Tucson...before the
complex transitioned to more of a hydrologic concern. As of this
writing, flood advisories and warnings have been posted across
much of Tucson with slow-moving thunderstorms moving across the
city. Showers and thunderstorms could continue into early morning
before dissipating.
&&
.AVIATION...
FEW-SCT clouds 10k-15k ft MSL increasing in coverage through this
afternoon as SCT TSRA/SHRA develops. This activity continues into
the evening hours, dissipating overnight. Surface wind gusts to 40
kts with strongest TSRA along with MVFR CIGS/VSBYS and mountain
obscurations. Otherwise, winds WLY-NWLY this afternoon 10-15 kts
with gusts to 25 kts, becoming light and variable later in the
evening. Similar wind regime returns tomorrow afternoon with another
round of SCT TSRA/SHRA. Aviation discussion not updated for TAF
amendments.
&&
.FIRE WEATHER...
&&
.PREV DISCUSSION... /issued 245 PM MST Thu Aug 20 2020/
.SYNOPSIS...Expect storm coverage and chances to increase today
into the weekend. High temperatures will moderate through the
weekend, but will still be 2-5 degrees above normal. Next week
storm chances decrease and temperatures climb back up to near
record levels.
&&
.DISCUSSION...Gulf surge continues this afternoon, thanks to
Tropical storm Genevieve, with Yuma Vad wind profile showing
southerly winds up to 5k deep with dewpoints in the 60s to lower
70s across Yuma county. Closer to home dewpoints were in the 40s
to lower 60s. PW values ranges from 0.90" near the AZ/NM border
to 1.5" over far western Pima county.
Interesting CAM solutions with the 20/12z UofA WRFNAM the most
active with line of thunderstorms, some severe, producing areas
of blowing dust, moving propagating W-SW across the area this
evening and continuing into the overnight hours out west while the
WRFGFS was the least active. The most recent runs of the HRRR was
in between, still active but not like the WRFNAM. SPC has most of
the area under marginal risk of severe storms for strong gusty
winds. Localized heavy rain also a threat.
Friday: Tropical Storm Genevieve will be weakening as it moving
west of the Baja Spur. For southern Arizona, enough moisture will
be around for isolated to scattered showers and thunderstorms
under easterly flow aloft with upper high near the 4 corners.
Weekend: Isolated to scattered showers and thunderstorms in the
afternoon and evening. What will be noticeable will be the cooler
daytime temperatures, especially Saturday, versus what has been
occurring this month. Enjoy it for it won`t last long. There is
chance, around 33%, that the Tucson airport could record the first
sub-triple digit high of the month. Fingers crossed.
Next week: We heat up again with record or near record highs with
heat risk issues raising its ugly head once again. Likely will
need another round of Excessive Heat Warnings for most of the
week. Thunderstorm activity each day will be isolated at best.
&&
.AVIATION...Valid through 22/00Z.
FEW-SCT clouds 10k-15k ft MSL increasing in coverage through this
afternoon as SCT TSRA/SHRA develops. This activity continues into
the evening hours, dissipating overnight. Surface wind gusts to 40
kts with strongest TSRA along with MVFR CIGS/VSBYS and mountain
obscurations. Otherwise, winds WLY-NWLY this afternoon 10-15 kts
with gusts to 25 kts, becoming light and variable later in the
evening. Similar wind regime returns tomorrow afternoon with another
round of SCT TSRA/SHRA. Aviation discussion not updated for TAF
amendments.
&&
.FIRE WEATHER...Due to a surge of moisture, expect broader
coverage of afternoon/evening showers and thunderstorms starting
today into early next week. The best chance for widespread
precipitation occurs this weekend. 20-foot winds generally remain
less than 15 mph outside of any thunderstorm gusts which could reach
upwards of 40 mph. Minimum relative humidities increase to 25-30
percent across the valleys Friday through Sunday along with good
overnight recoveries.
&&
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Public...Dang
Aviation...Dang
Fire Weather....Zell
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