Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/14/20
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
553 PM MDT Thu Aug 13 2020
.AVIATION...
00Z TAF CYCLE
Isold evening convection is forecast to wind down an hour or two
after sunset. Gusty downburst winds will be the main aviation hazard.
Isolated relatively anemic convective activity will favor mountain
ranges south of I-40 as well as the eastern plains Friday afternoon.
Again, gusty downburst winds will be the main hazard.
33
&&
.PREV DISCUSSION...310 PM MDT Thu Aug 13 2020...
.SYNOPSIS...
Unseasonably strong high pressure over the desert southwest will
continue to deliver record heat to many areas through this weekend.
The greater chances for showers and thunderstorms will remain over
eastern New Mexico each afternoon. Isolated showers and storms are
still possible over central and western New Mexico however most
activity will be light with strong gusty winds the main threat.
Better moisture is expected to filter into all of New Mexico by
early next week as high pressure drifts west into the Great Basin.
The coverage of showers and storms may increase over the area in
this pattern through next week.
&&
.DISCUSSION...
SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)...
The dome of high pressure aloft has settled over southern NM today.
A weak low is offshore of CA, and some batches of cirrus are
squeezing northeastward between it and the high to its east. Shower
and thunderstorm activity may be slightly more widespread than this
time yesterday, but it is still a fairly paltry crop with minuscule
rainfall amounts. Look for the current high terrain cells to
collapse over the next couple of hours with outflows firing just a
few additional storms into the evening. The RAP model indicates a
few cells may even survive (mostly in eastern zones) beyond
midnight, so this has been built into the forecast.
For Friday, the high will side-step to the west into AZ. PWATs will
continue to remain fairly low (0.5 to 0.75) in many northern zones
Friday with slightly higher values (0.75 to 1.0) found in the south
central to southeastern zones. This, coupled with the hot surface
temperatures will again yield high-based dry thunderstorms,
especially for areas outside of the south central to southeastern
zones. Into Friday night, attention will focus on the mesoscale
surface high that will likely develop from afternoon/evening
convection, and a synoptically-driven backdoor cold front will also
be taking shape in eastern CO/KS/OK/TX.
LONG TERM...(SATURDAY THROUGH WEDNESDAY)...
The unseasonably strong 596dm H5 high centered over AZ on Saturday
will strengthen further to 600dm thru early next week while drifting
northwest into the Great Basin. 12Z NAEFS climate percentiles show
this ridge at max values observed for mid August. This upper level
pattern will generate north to northwest flow along the Front Range
thru next week with surface high pressure building south into the
Great Plains. Moist, low level return flow will deepen westward into
NM, partly aided by convective outflows each afternoon along and
east of the central mt chain. Meanwhile, a lobe of H7 high pressure
is shown developing over TX Sunday thru Tuesday. This will reinforce
mid level south-southwest flow into NM which helps transport better
moisture north from Mexico. This complicated pattern may bring a
noticeable increase in storm coverage with locally heavy rainfall as
PW values increase to near 1". Storm motions generally from north to
south will favor greater potential for precip within the RGV next
week.
By late in the week, the potent upper level high center is progged
to advance eastward into the Four Corners with decreasing coverage
of storms and hotter temps again by next weekend.
52/Guyer
&&
.FIRE WEATHER...
The hotter than average temperatures will persist, although readings
could decline a couple to a few degrees into early next week as high
pressure establishes west of the Four Corners. The dry thunderstorm
potential will continue into the weekend, but into early next week
storms are expected to gradually become slightly more efficient at
rainfall production as dewpoints and humidity climb in eastern zones
and eventually seep westward. That being said, much of northwestern
NM will likely miss the opportunity for wetting rainfall or relief
to drying fuels. Thunderstorm outflows will present the typical
short-lived and localized wind concerns each day, and there is
potential for some stronger gusts as back door fronts enter the
state, the first arriving Friday night into Saturday morning.
52
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM MDT this evening for the following zones...
NMZ236-238.
&&
$$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
912 PM MDT Thu Aug 13 2020
.UPDATE...
Issued at 902 PM MDT Thu Aug 13 2020
Another fire has started in the mountains and the smoke plume now
reaches to the eastern border of Colorado. We have increased sky
coverage in the forecast grids to account for this new plume.
Tomorrow, the plume is expected to travel more east-southeast with
shifting synoptic winds. We expect ongoing hot and dry conditions
to mean continued elevated fire danger, but winds have dropped
enough not to continue the Red Flag Warning in the northern
mountains.
&&
.SHORT TERM...(This evening through Friday)
Issued at 140 PM MDT Thu Aug 13 2020
Another hot afternoon across the plains with temperatures already
in the lower 90s across most locales. Just some cumulus clouds so
far this afternoon as airmass has already well mixed over the
Front Range. Across the far northeast plains, dewpoints in the
40s/50s but expect falling dewpoints there as well during the next
few hours with further mixing. Still an ever so slight chance for
a storm where the moisture is still holding, generally across
Logan, Phillips and Sedgwick counties. Elsewhere dry conditons
through tonight.
Main concern is the amount of haze and smoke expected over the
region through Friday from the Pine Gulch and Grizzle Creek Fires.
The westerly mid level flow will continue to influence the airmass
as the smoke from the fires comes right across the Interstate 70
corridor and into the Front Range and northeast plains. Latest HRRR
smoke forecast increases the smoke again towards 00z over Denver and
spreads over the plains through midnight and continues through
Friday morning. Will be adding more haze and smoke to the forecast
to account for this.
Later tonight and Friday morning an upper trof will traverse the
northern high plains which will increase the mid level flow (35kt)
and bring down an associated cold front across the plains during the
morning hours. Unfortunately there is not really any cold air with
it and no moisture to speak of along with a slightly subsident airmass.
Temperatures will again be well into the 90s while precipitable water
values remain around a third of an inch over the Front Range. The
only good news is that the flow aloft will begin to shift northwest
later in the day, so less smoke likely especially over northern
sections of Colorado by afternoon.
.LONG TERM...(Friday night through Thursday)
Issued at 140 PM MDT Thu Aug 13 2020
The upper level ridge axis builds across the western U.S. Friday
night and Saturday. The ridge amplifies and shifts eastward Saturday
and remains in place through midweek. Models show a disturbance
moving over the top of the ridge and flattening it a bit toward the
end of the extended period.
At the surface, low level upslope flow continues through the first
part of the weekend. The dry and warm airmass limits chances for
precipitation. Only widely scattered thunderstorms are possible
Saturday afternoon on the far eastern plains. On Sunday, another
frontal boundary moves south through the eastern plains. Could see a
few more thunderstorms develop farther west with deeper upslope flow
and slightly better moisture. Still kept pops to be in the 20-30
range.
Once the ridge axis shifts farther east, expect north to northwest
flow aloft across the area. Expect some thunderstorms to develop
each day with moisture trapped underneath the high and weak
disturbances moving through the flow.
Highs on the plains will be in the mid 80s to mid 90s Saturday and
Sunday. Highs drop back a few degrees for Monday through Thursday
with a bit more cloud cover. Stark
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 902 PM MDT Thu Aug 13 2020
Winds are taking longer to shift to drainage than anticipated so
those groups have been moved back in the terminal forecasts. Hazy
skies will persist overnight and in the morning due to ongoing
fires in the mountains. The smoke is not expected to reduce
visibility enough to impact airport operations tonight or
tomorrow.
&&
.FIRE WEATHER...
Issued at 140 PM MDT Thu Aug 13 2020
Slight recovery for humidity levels tonight while winds relaxing
this evening. Mountain top flow does increase later tonight and
Friday morning and could see gusts up to 30kt Friday morning. Flow
decreases Friday afternoon so won`t coincide with lowest humidity
levels in the afternoon. There will still be elevated fire danger
with the low humidities but expect winds under 20 mph with the
lowest humidities during the driest parts of the afternoon. Hence
no red flag warnings will be issued at this time. Fire danger will
remain elevated through Saturday, but winds will generally be
light. On Sunday, moisture increases on the eastern plains with
generally light winds. It will continue to be very warm and mostly
dry through the middle of next week with a slight chance of
thunderstorms Monday through Thursday.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Direnzo
SHORT TERM...Entrekin
LONG TERM...Stark
AVIATION...Direnzo
FIRE WEATHER...Entrekin
Area Forecast Discussion
National Weather Service Charleston SC
1039 PM EDT Thu Aug 13 2020
.SYNOPSIS...
A trough of low pressure will persist inland, while high
pressure remains over the Atlantic through Friday. A weak cold
front will approach the area this weekend and pass through on
Monday. A trough will then redevelop over the area during the
middle of next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Earlier convection has transitioned into a large area of mostly
light to moderate stratiform rain with embedded heavier convective
elements. The atmosphere has been largely overturned this
evening except for areas along/south of I-16 where some late
afternoon clearing allowed for some instability to redevelop.
RAP soundings suggest the nocturnal inversion is already
starting to set up in that area, but with some shortwave energy
poised to pass through aloft later tonight, some redevelopment
is possible later tonight. Still expect most of the convection
to transition back into the coastal waters early Friday. Pops
have been readjusted to take current radar trends into account,
ranging from 80-100% across the Charleston Tri-County area into
Colleton and Beaufort Counties to 50-70% across interior
Southeast Georgia with 20-40% south of I-16. Temperatures have
been heavily augmented by convection and some areas have likely
already reached their overnight lows. Lows will range from the
lower 70s inland to the upper 70s/near 80 at the coast.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A fairly active pattern will continue Friday through Sunday. The
upper trough axis will steadily shift east through the period,
gradually pushing a weak cold front toward the area. A weak
surface trough will precede the front. Atmospheric moisture will
remain unseasonably high Friday and Saturday with PW around
2.2". Some drying is possible late Sunday which could result in
slightly less convective coverage during the afternoon. Daytime
highs will be in the lower 90s each day.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Models are in fair agreement in the long term period. A weak cold
front will stall over the region during the early to middle part of
next week. The upper pattern will become more amplified with
time as a strong shortwave drops into the Ohio River Valley.
While rain chances will be in the forecast each day, the most
active convective days of the set appear to be Tuesday and
Wednesday as vort energy and deeper moisture moves into the
area. Temperatures will be fairly close to normal.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
The core of the strongest tstms should be south of KCHS by 00z,
but may need to hang onto a mention of TSRA through 01z pending
last minute radar imagery. The outflow that is helping to
concentrate the convection should remain north of KSAV, but this
will be monitored. Scattered showers/tstms are likely again
tomorrow afternoon, but the details on the convective evolution
is still a bit uncertain. No mention of TSRA will be included at
this time at either KSAV or KCHS.
Extended Aviation Outlook: Flight restrictions possible in
showers and thunderstorms each day, mainly in the afternoon and
evening.
&&
.MARINE...
Tonight: Winds have turned northwest along parts of the South
Carolina waters with the passage of an outflow boundary. Winds
should turn more uniformly southwest late with speeds 10-15 kt
and seas 1-3 ft.
Friday through Tuesday: Outside of any showers and
thunderstorms, no marine concerns are anticipated through mid
next week. South to southwest winds will prevail with speeds at
or below 15 knots, generally highest late week into the weekend
with a slightly tighter pressure gradient. Seas will average 2
to 3 feet.
&&
.EQUIPMENT...
There was no 14/00z sounding from KCHS due to unfavorable weather
conditions during the launch window.
The Green Pond/Beaufort NOAA Weather Radio transmitter remains
off the air. Electronic technicians are working with the local
phone company to resolve the problem.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
Area Forecast Discussion
National Weather Service Grand Forks ND
843 PM CDT Thu Aug 13 2020
.UPDATE...
Issued at 843 PM CDT Thu Aug 13 2020
Severe thunderstorms continue northeast of the F-M area, up toward
the northwest side of the Upper and Lower Red Lakes. These storms
have not been moving too much, so heavy rain may still be an issue
in some areas. Radar estimated storm total precipitation shows
some heavier amounts in eastern Pennington and eastern Norman
counties. Otherwise, the latest SPC discussion mentions the
potential for continued development over the next few hours as the
low level flow picks up.
UPDATE Issued at 632 PM CDT Thu Aug 13 2020
Thunderstorms have been firing from just east of the Fargo-
Moorhead area, northeast toward the Upper and Lower Red Lakes.
This seems to be along the western fringe of the low level jet and
in the warm sector with ample instability and moisture. The SPC
has issued a severe thunderstorm watch that includes most of our
counties along and east of the Red River Valley. With the high
amount of moisture in the area, will have to keep an eye on heavy
rain, or training of storms over the same area.
&&
.SHORT TERM...(This afternoon through Friday night)
Issued at 352 PM CDT Thu Aug 13 2020
Warm front continues to work north, but so far we appear to remain
capped with only elevated showers/weak storms transitioning north
early this afternoon. As the surface trough continues to slide east
and the CAP weakens we should see combination of low level
convergence and at least some synoptic support associated with trough
passage through southern Canada. This should allow thunderstorm
initiation in highly unstable air mass this evening (ML CAPE already
over 4000 J/KG according to SPC RAP mesoanalysis). Effective shear
is shown by SPC Mesoanalysis in the 30-45 kt across northeast ND into
northwest MN, and if concurrent with thunderstorm activity could
help with discrete supercell potential before mergers take place and
activity transitions east. Best signal is still mainly in northwest
MN based on CAMs, but I wouldn`t want to rule out severe potential
anywhere this evening along convergence zone (may be more isolated
further into eastern ND).
Stronger synoptic/mesoscale ascent arrives after 03Z as shortwave
moves along the ND/SD border, with very high shear associated with
LLJ and strong mid level speed max. WIth lingering high
moisture/instability there will be a potential for elevated discrete
cells and eventually upscale growth potential into another MCS that
would then transition into eastern ND and northwest MN 4-9AM period.
This period may actually have the best overall potential for severe
convection in eastern ND.
Regarding impacts this evening/overnight tonight: Where supercells
develop environment could support potential for hail to 2 inch,
downburst potential to 75 mph and tornadoes. While activity may
mainly be elevated late tonight considering the high shear/CAPE
environment there is at least a conditional risk for tornadogenesis
and large hail with discrete cells. If more of an upscale trend
occurs then a transition to a widespread wind event may become
favored.
How this potential MCS late tonight/Friday morning holds together
and tracks eastward ahead of the main cold front will likely
determine impacts and timing of any redevelopment during the day
Friday and Friday afternoon. If this moves through quick enough, we
may see a window for destabilization and another round of
supercells/discrete storms ahead of the cold front in our east. If
this complex lingers through the day then the tendency may be
embedded pulse type convection with widespread heavy rain through the
afternoon. Cold front should push east of our CWA based on current
model timing by late Friday afternoon/early Friday evening with
drier/more stable conditions then ending thunderstorm and severe
threat.
.LONG TERM...(Saturday through Thursday)
Issued at 352 PM CDT Thu Aug 13 2020
Saturday... The upper level trough will begin to exit the CWA
overnight Friday and into Saturday. A weak shortwave is expected to
move across the northern part of the CWA during the afternoon on
Saturday and some spotty rain showers in this area cannot be
completely ruled out. Otherwise, temperatures look to stay in the
upper 70s/low 80s with dewpoints in the mid to upper 50s.
Sunday through Thursday... Northwesterly flow will begin to dominate
the upper levels and will usher in a calmer weather pattern to close
the weekend and move into the beginning of the work week. Along with
the upper level ridging, high pressure at the surface will persist
for much of the forecast period. Calmer, cooler, and drier
conditions will accompany this transition with high temperatures in
the mid 70s/low 80s and dewpoints in the 50s for much of the
forecast area. Towards the end of the forecast period the chance for
a slightly more active weather pattern appears to emerge and could
bring with it the chance for rain once again.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 632 PM CDT Thu Aug 13 2020
With limited time due to the recent issuance of a severe
thunderstorm watch, have basically gone with continuity from the
previous set of TAFs. Added some definition for the first few
hours, and will take a closer look beyond the first 6 hours with
the next TAF issuance. As it stands right now, KTVF and KBJI look
to have the best chance for storms this evening.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...Godon
SHORT TERM...DJR
LONG TERM...NCR/DJR
AVIATION...Godon
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
638 PM CDT Thu Aug 13 2020
.SHORT TERM...(This evening through Friday)
Issued at 333 PM CDT Thu Aug 13 2020
Scattered cumulus remains over portions of central and eastern
Nebraska, largely a result of the residual moisture from this
morning`s stratus. This should continue to diminish as we head into
the late afternoon and evening.
At the same time, visible satellite and radar show additional
convection developing along and west of a line from Goodland to
Thedford. CAMs continue to support strong to severe storms in this
vicinity, but they have also been very consistent in weakening and
dissipating storms as they approach the local area. We have
maintained some slight PoPs as far east as Buffalo, Kearney, and
Franklin counties, but this may end up being too generous.
For Friday, the advancing upper trough will push a cold front into
the region. The 18Z HRRR shows this front sliding into central
Nebraska in the early afternoon, therefore we should still see a
good warmup to around 90 degrees ahead of it.
Scattered thunderstorms are anticipated to develop along the front
by mid afternoon. Models disagree slightly on timing and location,
but the overall consensus is that the better chances will be roughly
southeast of a line from Phillipsburg to Hastings to Columbus.
MUCAPEs over 4000J/kg and 0-6 shear around 35kts are supportive of
some severe updrafts and perhaps a few isolated supercellular
structures. The main threats will be large hail and damaging wind.
Given poor low-level shear, the tornado threat remains pretty low.
With the progressive nature of the front, I do not expect a
significant risk for flooding, and dry conditions will prevail
across most of the area by around midnight Friday night. Models have
also trended cooler for Friday night, with lows now expected to be
in the 50s for most of central Nebraska.
.LONG TERM...(Friday night through Thursday)
Issued at 333 PM CDT Thu Aug 13 2020
As the post-frontal high pressure slides to the east on Saturday and
we see more easterly, upslope flow, southwestern portions of the
area could see an isolated storm or two. That said, most of the
area will likely stay dry.
Beyond that, chances for rain and thunderstorms remain rather low.
Periodic perturbations moving through the northwesterly flow will
keep at least a few small PoPs in the forecast, but overall the
pattern appears rather dry.
Seasonable temperatures will also continue through the weekend and
into next week due to continued northwesterly flow aloft. High
temperatures will generally be in the low to mid 80s each day, only
possibly reaching back into the upper 80s late next week.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 636 PM CDT Thu Aug 13 2020
Thunderstorms should remain to the west of the terminals tonight.
There will be some MVFR ceilings in the morning for a few hours. A
cold front will move into the area toward the end of the TAF
period.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT TERM...Mangels
LONG TERM...Mangels
AVIATION...JCB
Area Forecast Discussion
National Weather Service North Platte NE
654 PM CDT Thu Aug 13 2020
.SHORT TERM...(This evening through Friday night)
Issued at 301 PM CDT Thu Aug 13 2020
Near-term concerns revolve around the potential for isolated to
widely scattered strong storms later this afternoon and evening
across portions of southwest through central Nebraska. Current
satellite imagery shows a line of bubbling cumulus stretching from
just east of Mullen southwest into Arthur County with additional cu
located over far northeast Colorado into portions of Deuel County.
This is along a weak convergent boundary/pseudo dryline in place.
Morning sounding analysis from LBF depicts a warm layer of air
between the h85 and h7 levels maxing out around 22-24 degrees
celsius. RAP guidance suggests these temperatures will remain
similar if not increase through the daytime hours thus increasing
the capping. Instability is not lacking with steep mid-level lapse
rates overtop a warm and humid airmass. RAP guidance advertises
MLCAPE values in excess of 3000 j/kg. Limiting factor will be shear,
given lagging mid-level jet max not anticipated to arrive until this
evening. Because of this, 0-6km BWD will be less than 25 knots until
these stronger winds arrive. Given relatively weak shear, thinking
damaging wind gusts from multicell clusters will be the main threat
as DCAPE values will be in excess of 1600 j/kg and 0-3km max theta-e
differences approach 30-40k. Cannot rule out some hail as well given
the steep lapse rates and SBLI values approaching -8 to -10, but
believe this will be more isolated in nature. Shortly after sunset
as the boundary layer stabilizes, believe storms will weaken as
capping increases. Even with the development of a stout LLJ,
thinking this will not be enough to sustain convection well into the
evening and as such have PoPs ending by 14/03z. Did bump up
temperatures tonight with lows generally ranging from the low 60s in
the west to near 70 in the east.
Surface boundary associated with northern high plains system will
enter the local area on Friday bringing an abrupt wind shift from
the southwest to northwest. This will also bring contrasting
temperatures across the area with slightly cooler daytime highs
expected across the region. The frontal boundary will clear the area
by the afternoon but as fgens encounters the more humid airmass to
the southeast, rain and thunderstorms will become possible during
the afternoon. General thoughts are that the majority of this
activity will remain east to southeast of the area. Because of this,
have limited PoPs to the eastern tier of counties and only Slight
Chance at that. SPC covers much of central Nebraska in a Day 2
Marginal risk of severe weather. Thinking this is adequate with any
favored changes being to trim it further east and out of the area
but will defer to later forecasts to address this. High temperatures
tomorrow will range from the low 80s across the north to low 90s in
the far south. Any precipitation chances will exit the area by late
evening leaving the area dry for the overnight hours into Saturday.
Lows will fall into 50s thanks in part to the drier air.
.LONG TERM...(Saturday through Thursday)
Issued at 301 PM CDT Thu Aug 13 2020
Beginning 12z Saturday. Period begins with modest northwest flow
aloft as upper ridge across the desert southwest strengthens through
the weekend. Mid-level flow amplifies as aforementioned ridge shifts
slightly north into early Sunday. While strength of the developing
ridge varies between the global models, placement is in fairly good
agreement. For Saturday evening, on the backside of departing weak
surface high pressure, southerly low-level flow should return across
portions of central and southwest Nebraska helping advect some
better moisture into far southwest Nebraska. This may set the stage
for some thunderstorm chances, limited to areas south of I-80 and
west of Highway 83. The ECMWF is slightly more bullish on this
potential, likely due to cooler mid-level temperatures and thus
weaker capping. Meanwhile, the GFS advertises most if not all
precipitation chances remain south of the local area. With the NAM
playing the middle ground, will keep PoPs in place for now. Given
enhanced flow at h5, will have to monitor for potential for a few
strong storms, however, given limited moisture this remains a low-
confidence threat. Temperatures will generally be near normal values
for mid-August with highs in the low 80s northeast to upper 80s
south and west. Strengthening low-level jet will allow for rain and
thunderstorms to persist into the early morning hours on Sunday with
gradual decrease by mid-day Sunday.
Weak high pressure works through the area on Sunday with
precipitation chances possible in the afternoon, though consensus
between models vary a bit. Will keep additional low-end PoPs for
this time frame, mainly driven by diurnal heating so peaking during
the afternoon hours and waning in the evening. Additional ridge
riding shortwaves are likely to move across the high plains in the
Tuesday through Friday period. During this time, the upstream ridge
is expected to strengthen to near 600 dam with highly amplified flow
across the central plains. As the ridge begins to weaken and shift
slowly south and east, the ridge axis and with it the thermal ridge
will approach towards the weekend suggesting an upwards trend in
daytime temperatures for the latter half of the week. Periodic
thunderstorm chances will exist owing to the lack of any substantial
surface boundary that will scour out any local moisture. Timing of
this activity is difficult at range but situations like this tend to
follow diurnal swings so will keep day-to-day PoPs highest during
the afternoon and early evening hours. Temperatures look to return
to above normal values by the end of the forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 652 PM CDT Thu Aug 13 2020
VFR conditions expected to prevail at both terminals for the TAF
period. Have included VCTS at LBF with a few anvil strikes in the
area though convection will largely stay off to the west and
northwest of the terminal. Otherwise, expect backing winds at both
LBF and VTN into Friday with the approach of a cool front. Winds
look to be gusty from the north tomorrow afternoon behind the
front. Have included LLWS at VTN into tomorrow morning but left it
out of LBF for now. Future LLWS inclusion appears possible at LBF
if confidence can grow.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Jurgensen
LONG TERM...Jurgensen
AVIATION...Brown
Area Forecast Discussion
National Weather Service Phoenix AZ
440 PM MST Thu Aug 13 2020
.UPDATE...Updated aviation discussion.
&&
.SYNOPSIS...
Strong high pressure will remain situated across the Southwestern
U.S. into next week bringing continued hot conditions. High
temperatures across the lower deserts will approach or exceed 115
degrees starting today and lasting through at least early next
week. Isolated showers and thunderstorms are possible today before
chances decrease tomorrow. Potential for a slightly better
monsoon set-up will develop this weekend or early next week.
&&
.DISCUSSION...
Latest water vapor imagery reveals an increase in mid and
upper-level moisture across the Desert Southwest associated with
remnants of post-TC Elida. Meanwhile, streamline analysis depicts a
southwesterly flow around a strong anticyclone centered across
southern New Mexico.
Although conditions are drier than average at the surface, overall
PWATs above 1.3 inches are sufficiently high to yield a
large area of MLCAPE exceeding 500+ J/kg across the lower deserts.
Isolated convection has already initiated across the higher terrain
east of Phoenix, and additional isolated activity is expected across
the lower deserts this afternoon and evening. Latest HREF suggests
any storms that develop have the potential to produce heavy rain
and strong/severe wind gusts. DCAPE values above 1500 J/kg, per the
latest mesoanalysis also point to the potential for blowing
dust. Most recent runs of the HRRR are still highlighting western
Maricopa County for the highest potential.
Latest ECMWF ensemble mean indicates the aforementioned anticyclone
will lift northward over the next several days with height anomalies
becoming more prominent across the Rockies. Excessive Heat will
remain the big story through the weekend. Latest NBM forecast for
Phoenix Friday is 116 deg, which would fall only one degree short of
the daily record.
Models remain consistent indicating the Monsoon High will drift into
southern Utah as soon as Sunday. This will give us our first taste
of northeasterly/easterly steering flow, which is generally more
favorable for lower desert convection. This pattern will persist
through much of next week, resulting in a continuation of the
well-above normal temperatures and increasing chances of
precipitation. The Excessive Heat Warning was extended through next
Wednesday, however there is a chance it may need to be canceled a
day or two early if widespread storms do materialize.
&&
.AVIATION...Updated at 2340Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
High confidence that winds will remain westerly through the evening
hours. TS activity well to the west is not expected at this point to
directly affect the terminals due to the existence of drier air over
the greater Phx area. A more likely impact from these storms will be
to just enhance the westerly winds that are already in place.
However, significant blowing dust is not expected at this point. TS
activity is expected to pretty much end around/just below 03Z.
Typical diurnal wind shift to easterly is expected around/shortly
after midnight. As far as the outlook for Friday is concerned, a
period of light southerly crosswinds is possible between 17Z and 20Z
before winds become westerly. TS activity on Friday afternoon is
expected to remain well to the east of the greater Phx area.
Southeast California/Southwest Arizona including KIPL and KBLH:
For KIPL, winds are expected to follow typical diurnal trends at
speeds mostly AOB 10 kts. At KBLH, light westerly winds through the
night to become southerly during the day on Friday. Otherwise, there
may also be extended periods of a light/variable wind at both sites.
&&
.FIRE WEATHER...
Sunday through Thursday:
High pressure will persist across the Desert Southwest next week,
resulting in a continuation of the above normal temperatures. The
pattern is expected to become more favorable for thunderstorm
activity, even across the lower deserts. Minimum humidities
through the period will drop into the teens each day with
overnight recoveries generally between 25 and 50%. Winds will
generally remain light aside from some typical afternoon breezes.
However, any storms that develop have the potential to produce
gusty, erratic winds.
&&
.CLIMATE...
Record high temperatures:
Date Phoenix Yuma El Centro
---- ------- ---- ---------
8/13 115 in 2012 117 in 2012 116 in 2012
8/14 117 in 2015 115 in 2019 116 in 2015
8/15 115 in 2015 117 in 2015 118 in 2019
8/16 113 in 2013 115 in 1992 117 in 2016
8/17 114 in 2013 114 in 1992 115 in 2015
8/18 112 in 2011 116 in 1960 115 in 2015
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Wednesday for AZZ530>556-
559>562.
Heat Advisory until 8 PM MST Wednesday for AZZ557-558-563.
CA...Excessive Heat Warning until 8 PM PDT Wednesday for CAZ565>567-
569-570.
Excessive Heat Warning from 10 AM Friday to 8 PM PDT Wednesday
for CAZ560>564-568.
&&
$$
DISCUSSION...Hirsch
AVIATION...Percha/Rogers
FIRE WEATHER...Hirsch
CLIMATE...MO
Area Forecast Discussion
National Weather Service Pueblo CO
325 PM MDT Thu Aug 13 2020
.SHORT TERM...(This evening through Friday)
Issued at 323 PM MDT Thu Aug 13 2020
Dry line has been gradually mixing eastward with dew points having
dropped into the 30s along the I-25 corridor with single digits to
20s across the mountains. Some 50 to near 60 dew points still
linger across the far eastern counties as of 21z. This has led to
CAPE values to near 1500 J/kg near the KS border and with with deep
layer shears running around 40-50 kts...can`t rule out an isolated
strong to near severe storm across eastern portions of Kiowa and
Prowers counties where a few CAMs runs have shown some convection
develop through the evening. Better odds will be just north and
east of the CWA. Elsewhere, convection will be high based and more
likely to produce gusty winds up to 40 mph and only some spotty
sprinkles. Activity will diminish with loss of heating this evening.
Once again, dry line will retreat back westward overnight across the
plains. Will have to monitor the potential for some stratus or
patchy fog near the eastern border, but high res models keep
northerly winds off the Palmer Divide into KCOS and KPUB which
should keep any stratus to our east. Have also introduced some
smoke from the Pine Gulch and Grizzly Creek fires into portions of
Chaffee, Lake and Teller counties based on output from the hrrr
smoke runs. This may spread eastward into portions El Paso county by
early Friday morning which then spreads southward across a large
portion of the southeast plains during the day on Friday as a front
moves through the plains. This will more likely produce some hazy
skies so have not introduced smoke into the Friday morning grids
just yet.
For tomorrow...upper high out west will put CO under west northwest
flow aloft with some increase in mid level moisture across southern
and western portions of the area. Winds across the plains will
shift out of the northeast then east behind the front, but moisture
actually mixes out along the I-25 corridor and adjacent plains in
the afternoon which keeps best CAPE values near the Kansas border.
GFS and NAM differ with sfc dew points along the eastern border with
CAPE values ranging from under 1000 J/kg in the GFS to over 1500-
2000 J/kg in the NAM12. NamNest runs suggest potential for one or
two severe storms near the Kansas border Friday afternoon and will
carry some isolated pops to account. With the increase in moisture
across the southern mountains within the upper high, there will be a
better chance for some high based showers and thunderstorms. Main
risks will be gusty winds up to 45 mph and lightning along with some
brief light rainfall. Temperatures tomorrow should be pretty similar
to today with not much cooling expected behind the front until a
stronger moves in Friday night. -KT
.LONG TERM...(Friday night through Thursday)
Issued at 323 PM MDT Thu Aug 13 2020
Friday night and Saturday...The upper-level ridge is expected to
continue sliding northwest to the Great Basin region, resulting in
northwest flow aloft over Colorado. Meanwhile, post-frontal easterly
flow is expected at the surface, advecting some low-level moisture
to the area, especially across the plains. The increase in moisture
is expected to bring isolated to scattered showers and thunderstorms
to much of the area for Saturday afternoon and evening. Afternoon
highs are also expected to drop compared to the past several days
across the plains where temperatures are expected to reach the upper
80s to low 90s. Highs in the high valleys are expected to remain
about the same in the 80s to around 90.
Sunday through Thursday...The ridge is expected to remain over the
western U.S. with the high centered over the Great Basin through
late next week, keeping northwest flow over Colorado. Periodic
shortwaves are anticipated to propagate around the upper-level high
during this time. The periodic shortwaves, along with moisture being
recirculated around the high pressure, are expected to bring isolated
to scattered PM showers and thunderstorms to much of the area each
day. A gradual increase in moisture as the week progresses is
plausible as the circulation around the high is able to tap into
additional Pacific moisture, which would increase the instability
and potential for some of the storms to be strong to severe at times
next week. Afternoon highs are expected to be in the mid 80s to
lower 90s across the plains, and lower to mid 80s in the high
valleys.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 323 PM MDT Thu Aug 13 2020
VFR conditions expected overnight though areas of smoke
may spread over the mountains into the Pikes Peak region towards
morning. Not expecting a significant reduction in vis, but some VFR
haze will be possible Friday morning for KCOS and possibly for KPUB
by mid day. Winds will generally remain light and diurnally driven
until the front moves through the plains Friday morning bringing a
wind shift from the north to northeast 10-20 mph by afternoon.
Overall, TAF sites are more likely to stay dry with isolated
afternoon thunderstorms confined to the southern mountains and far
eastern plains. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...KT
LONG TERM...CARLBERG
AVIATION...KT