Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/15/21
Area Forecast Discussion
National Weather Service La Crosse WI
636 PM CDT Wed Jul 14 2021
.SHORT TERM...(Tonight through Thursday Night)
Issued at 200 PM CDT Wed Jul 14 2021
...Severe threat continues into This Evening...
Later this afternoon will need close monitoring. The latest GOES
visible imagery is showing partial clearing over much of Iowa east
of the Omaha Neb centered low pressure center. Lower 70s dewpoints
are north of I-80 in IA. The key to the afternoon will be the
location of the warm frontal boundary later today which is about I-
80 at 17Z. A large stratiform region of rain across southern MN will
impact recovery there and shifts the severe storm threat further
south for late afternoon. By that time, the warm front seems to be
around highway 20 in IA (roughly!) per the latest RAP and
observational analysis.
The warm sector MLCAPE across much of IA should be in the 2500-3000
J/Kg range and with low-level moisture transport increasing, severe
storms will likely initiate on the boundary and in the vicinity of
the surface low/cold front as the low tracks toward La Crosse, WI.
Hodographs near the front, in near or north of highway 20, seem to
indicate a fairly looping profile with supercell shear. This shear
drops off south of highway 20.
Provided the instability from the warm sector makes it into
northeast IA and swrn WI, some supercells are likely with bowing
segment evolution. Tornadoes are possible but not probable based on
threshold 0-1km shear and SR helicity. Probably most likely on the
warm frontal boundary - and this will need to be monitored closely.
Large hail would also be possible.
Overall confidence in the location of the front isnt high, but
confidence is higher that where the high CAPE pool builds north
and/or impinges on the warm front will offer the best severe storm
probabilities. This appears to be mainly nern IA and swrn WI later
today. This area could see numerous rounds of storms within a few
hours near/north of the E-W boundary. While a flash flood watch was
considered, the dry soils may be ok with 4-5 inches of rain which is
possible.
Bulk of showers and storms should be pushed southeast of the area by
daybreak as the cold front pushes through. That frontal boundary
hangs up just to our south Thursday with possible
shower/thunderstorm redevelopment. Believe the bulk of this will
stay south but will maintain a slight chance across a small sliver
of northeast IA into southwest WI. Otherwise, the rest of the area
will see skies becoming mostly sunny (although may see some hazy
skies due to ongoing wildfires in southern Canada/northern MN) with
highs topping off in the upper 70s/lower 80s with slight drier dew
points in the upper 50s to mid 60s...highest south of I-90.
.LONG TERM...(Friday through Wednesday)
Issued at 200 PM CDT Wed Jul 14 2021
The long term will see building upper level ridge over the region.
This will provide drier weather pattern with warming through the
weekend into next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 636 PM CDT Wed Jul 14 2021
Main taf concern is potential for thunder for a couple of hours
this evening at LSE taf site. Then...MVFR/IFR conditions tonight
at both RST/LSE taf sites. Low pressure will track over Great
Lakes Region tonight. Latest KARX radar shows showers and storms
across much of the area and storms are mainly along south of
Interstate 90. Storms may impact the LSE taf site early in the taf
period. Metars across the area show MVFR/IFR conditions and these
conditions will continue into Thursday morning. High pressure
will build into northern half of Minnesota and low stratus deck of
clouds is expected to erode. VFR conditions are expected to
prevail by 14z Thursday.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Baumgardt/DAS
LONG TERM...DAS
AVIATION...DTJ
Area Forecast Discussion
National Weather Service Boise ID
903 PM MDT Wed Jul 14 2021
.DISCUSSION...The upper level flow will turn from westerly tonight
to southwesterly on Thursday. This will allow for some limited
moisture arriving from Nevada that will be available for a slight
chance of afternoon thunderstorms in eastern Valley County.
Otherwise, dry smokey conditions will prevail. High temps on
Thursday will be slightly cooler in eastern Oregon with little
change in southwest Idaho. No updates.
&&
.AVIATION...Generally low VFR with areas of MVFR due to smoke.
Significant visibility reductions aloft due to smoke layers from
wildfires. Surface winds: Variable 10 kt or less. Winds aloft at
10k feet MSL: generally SW 5-15 kt. Density altitudes will remain
high due to hot temperatures.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Friday night...Slightly cooler through
Friday as a weak Pacific trough comes inland and suppresses the
hot upper ridge southward. The trough will act on mid-level moisture
to the east of our CWA for a slight chance of thunderstorms Thursday
afternoon in eastern Valley County, ID. Smoke will continue to stream
northeastward from the Bootleg Fire in southern Oregon and from
other fires near Lewiston, ID. HRRR smoke model shows improvement
in eastern Oregon Thursday afternoon, but a resurgence of smoke
from the Bootleg fire Thursday night will again cover that area.
No real improvement on the Idaho side for now.
LONG TERM...Saturday through Wednesday...Hot, dry, and smoky
conditions to continue through the long term. Temperatures will be
around 10 degrees above normal through the period. Smoky conditions
should keep temperatures from reaching record highs. Monsoon
moisture will move northward over the region on Monday through
Wednesday, which will increase the chance of thunderstorms,
especially during the afternoons.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning until 11 PM MDT Thursday IDZ402-403-421.
OR...None.
&&
$$
www.weather.gov/Boise
www.facebook.com/NWSBoise
www.twitter.com/NWSBoise
DISCUSSION...BW
AVIATION.....ST
PREV SHORT TERM...LC
PREV LONG TERM....KA
Area Forecast Discussion
National Weather Service Caribou ME
1147 PM EDT Wed Jul 14 2021
.SYNOPSIS...
A warm front will slowly lift north across the area tonight,
bringing warmer and more humid air for Thursday and Friday. A
cold front is expected to approach late Friday and move across
the area Friday night into Saturday. Another low pressure system
will approach from the southwest on Monday.
&&
.NEAR TERM /THROUGH THURSDAY/...
1135 PM Update: The only chg this update was to increase cldnss
ovr Wrn areas near the QB border for most of the remainder of
the ngt based on latest avbl sfc obs which still indicated msly
cldy skies ovr Ern QB. Still xpct at least partial clrg earliest
ovr this ptn of the FA shortly after sunrise.
Prev Disc: As far as convection goes, seeing some embedded
tstms along the coast into Central Washington County as
instability has set up above the stable layer at the surface.
Tstms will contain heavy rainfall and perhaps a brief gust to 35
mph as they move through ovrngt. Further n and w, Just some
scattered and isolated showers attm, which should end overnight.
Adjusted the wx elements to remove tstms form northern and
western areas, while eastern areas will see a threat for a tstm
through midnight and then end. The latest HRRR and RAP guidance
point to this taking place and soundings showing airmass
stabilizing overnight.
Previous Discussion...
For most areas the main impact tonight will be low clouds, fog,
and drizzle. Fog will be locally dense, particularly along the
coast. However, the approach of the shortwave may cause dense
fog with visibilities of less than a quarter mile to be more
transient in nature, so confidence is not sufficient for a dense
fog advisory at this time. Forecast soundings across Downeast
Maine show over 500 j/kg of elevated instability protected by
about 50 to 100 j/kg of CIN from a parcel starting at 850mb and
above the stable low levels. Elevated thunderstorms are possible
as the shortwave acts as a forcing mechanism to overcome CIN.
Convection allowing models (CAMs) may not handle this situation
well, so wording for scattered thunderstorms was kept for
portions of Downeast Maine and the coastal waters overnight
despite not many CAMs showing significant convective activity.
By Thursday the shortwave will move off to the east with a
significant amount of dry air aloft moving in. The combination
of the July sun and briefly weaker southerly flow will allow
most areas to see more sunshine and drier conditions. Capping
will be strong across southern and central regions, but not as
strong across northern Aroostook County where isolated to
scattered showers will develop by the afternoon. High
temperatures will be well above normal in the 80s away from the
coast.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
The short term will feature a cold front moving thru the region on
Friday with drier weather moving in behind. Sfc lopres looks to be
located along the sw Quebec and Ontario border on Thu evening and
heading northeast overnight. This wl lead to another round of low
stratus and fog in marine layer by Fri morning possibly moving as
far north as Aroostook County with drizzle and/or isold showers over
Downeast after midnight. Temps wl be hard-pressed to drop much with
extensive cld cvr and humid airmass with mins falling into the mid-
60s.
Cold front wl be nearing the international border by 12z but with
very few breaks expected thunder looks to hold off until after 15z
as it slides closer to the CAR-PQI area and even at that coverage
looks to be limited to isolated thunder. As front pushes south and
east chances for thunder looks to increase drg the afternoon with
best chances existing over central areas. As cold front heads south
storms expected to become elevated with marine layer likely still
holding on with onshore flow.
Expect cold front wl move offshore Fri evening with lingering
showers expected over Downeast areas. Uncertainty continues to
surround how far offshore front wl be able to make it and any
additional waves that may ride up along it and hv continued idea of
diurnal showers on Saturday afternoon.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As mentioned int he short term section, how far south the frontal
boundary is able to make it still remains in question. 12z GFS and
GEM have front well offshore while EC keeps it confined closer to
the coast. This wl ultimately determine rain chances across the
south through the weekend.
Upper level trough wl persist across the northeast through the
middle of next week with continued chcs for showers and possible
thunderstorms in the afternoon. Continued warm and muggy thru
the end of the period with possible relief in sight twd the very
end of the long term.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
NEAR TERM: IFR ceilings and visibility are expected through
Thursday morning, with a period of LIFR also expected in low
clouds and fog. A thunderstorm is possible near KFVE this
evening and at Downeast Maine terminals later tonight. Ceilings
and visibility improve to MVFR and VFR by late Thursday morning
and early afternoon across the entire area. A PM shower is
possible at KFVE and KCAR. South winds 5 to 15 kts continue
through the period.
SHORT TERM:
Thu night...IFR in low cigs and vsbys, especially over Downeast
terminals though may be as far north as CAR and PQI. S 5-10kts
Fri...IFR early in then MVFR/VFR in showers and tstms along
front in the afternoon. SW 5-10kts.
Fri night-Sun...Mainly VFR across the north with MVFR/IFR
Downeast in fog/cigs. Light WNW.
Sun night...Mainly VFR over the north, MVFR/IFR over Downeast.
Light SW.
Mon...Mainly VFR, possible MVFR in showers and tstms. N 5kts.
&&
.MARINE...
NEAR TERM: Widespread fog is expected across the waters through
Thursday as warm, moist air moves over the cool Gulf of Maine
waters. Fog may be locally dense at times. A thunderstorm is
also possible tonight, mainly over the eastern waters of ANZ050
off the coast of Washington County. Otherwise, winds and seas
will remain below SCA thresholds through the period.
SHORT TERM: Seas and winds below SCA levels through the weekend
into early next week. Visibilities will be reduced in fog,
locally dense at time.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Dense Fog Advisory until 9 AM EDT Thursday for MEZ010-011-
015>017-029>032.
MARINE...None.
&&
$$
Near Term...VJN
Short Term...MStrauser
Long Term...MStrauser
Aviation...VJN/MStrauser
Marine...VJN/MStrauser
Area Forecast Discussion
National Weather Service Cheyenne WY
539 PM MDT Wed Jul 14 2021
.SHORT TERM...(This evening through Thursday night)
Issued at 215 PM MDT Wed Jul 14 2021
Easterly upslope flow east of the Laramie Range behind yesterday`s
cold frontal passage along with southwest flow farther west has
setup a dryline boundary along the South Laramie Range. CU fields
developing over the high terrain the past few hours has initiated
a couple storms early this afternoon and will continue to do so
along the CO/WY border into the early evening. Farther north,
lower level stratus has remained in place for longer duration and
minimal CU development has been noted on latest satellite imagery.
Latest RAP analyzes a narrow bullseye of over 1200 J/kg of MLCAPE
over the South Laramie Range which has been building as 1745z
research sounding from Fort Collins analyzed around 850 J/kg. Low
level inversion suggests storms might struggle once removed from
the higher terrain until later this afternoon, otherwise a fairly
moist profile was noted. Hi-Res guidance has storm activity mostly
ending around 9 PM this evening. Hail, heavy downpours, and
frequent lightning will be the main hazards. Temperatures will be
5-10 degrees warmer Thursday afternoon with the chance for storm
development along the Laramie Range once again, however coverage
should be more isolated than today.
.LONG TERM...(Friday through Wednesday)
Issued at 215 PM MDT Wed Jul 14 2021
Scattered showers and storms will be possible again on Friday over
the Laramie Range as well as near a boundary looking to set up
close to the Pine Ridge in the northern NE Panhandle. Shortwave
energy will provide additional lift for these storms before 500mb
height rises build a 5940+ meter upper level ridge across the
area this weekend and early next week. these anomalously high
500mb heights look to persist through much of next week which will
rise temperatures into the 90s for much of southeast Wyoming and
the Nebraska Panhandle for numerous consecutive days. Adjusted the
forecast towards the NBM 75th percentile MaxTs for Monday through
Wednesday. Models begin to attempt to breakdown this pattern late
next week into next weekend with multiple passing Pacific waves.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 527 PM MDT Wed Jul 14 2021
Showers and thunderstorms are moving across far southeastern
Wyoming and potentially KSNY as well. They are currently forecast
to end by 6Z. As they move through, they will temporarily lower
ceilings and visibilities. Some LIFR to IFR ceilings are possible
at KBFF, KSNY, and KAIA in the early morning hours, clearing by
16Z.
&&
.FIRE WEATHER...
Issued at 215 PM MDT Wed Jul 14 2021
Minimal fire weather concerns the rest of today and Thursday with
cooler temperatures ahead of the warm up headed into the weekend
and early next week. Slightly above normal temperatures this
starting Friday will continue through Sunday before the hot and
dry conditions arrive early next week. Afternoon RHs look to drop
into the teens west of the Laramie Range as well as over east-
central Wyoming, however winds look to remain below critical
levels as high pressure builds into the area.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...MB
LONG TERM...MB
AVIATION...LK
FIRE WEATHER...MB
Area Forecast Discussion
National Weather Service Dodge City KS
645 PM CDT Wed Jul 14 2021
...updated aviation section...
.SHORT TERM...(This evening through Thursday)
Issued at 111 PM CDT Wed Jul 14 2021
A frontal boundary is currently pushing into northwest Kansas. This
front will be the impetus for storms to develop this afternoon and
evening. Forecast CAPE is expected to peak at 1000 J/kg. Bulk shear
is expected to remain weak... 20 or so knots. Low level thermo profile
should be fairly well mixed with the current downslope southwesterly
wind. As a result, do expect the formation of DCAPE ahead of the front.
Storms will develop along the front and near the Colorado border and
slowly push east as the evening wears on. The main threats are winds
of 60-70 mph, heavy rainfall, and up to 1" hail. The most likely area
for strong to severe storms will extend along the Colorado border northeast
up across Scott and Lane counties. One thing that remains on the unclear
side is how far convective activity will reach. Some models are less
aggressive than others. Rainfall amounts of a quarter of a inch to
an inch will be possible in the heaviest storm cells.
Anyway, beside the sensible weather impacts, overnight lows tonight
will continue to remain on the warm side with a mix of 60s and 70s.
For tomorrow, the front will continue to move southeast and weaken/wash
out with time. Storms will be once again possible along this boundary.
The best chances will be located across the southeast zones. Strong
to marginally severe storms will be possible in this area. The main
threats will be convective outflows, some hail, and heavy rainfall.
Some good news for tomorrow is that we will get a break from the heat.
Highs should peak in the 80s. We will take that short break for mid
July in southwest Kansas.
.LONG TERM...(Thursday night through Wednesday)
Issued at 111 PM CDT Wed Jul 14 2021
The heat will quickly return on Friday. Highs should easily rebound
back into the 90s. Any storm activity should remain on the isolated
side.
The weekend is shaping up to be pretty normal for July. Seasonally hot
temperatures, breezy winds, and only isolated storms with much of the
FA remaining dry.
For the next business week, the mid level ridge is expected to eventually
shift from the Rockies over the Northern Plains. This will keep mainly
dry conditions across southwest Kansas with only isolated storm chances.
Temperatures will continue to remain seasonally hot. If the ridge does
eventually sink southward from the Northern Plains more closer to our
area, then of course we could see hotter temperatures than what are
currently forecast. Some to watch and see how the ridge evolves with
time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 640 PM CDT Wed Jul 14 2021
Clusters of multicell thunderstorms are rapidly developing in a
rather weak cape and little shear zone influenced convergence zone,
and advecting eastward from near the CO/KS line. The convection
is embedded in steep lapse rates in both the low and mid levels
and high LCLs should ensure rather high base ceilings with the
storms as they move toward the GCK LBL and DDC terminals by mid
evening. The weak CAPE will play a part in the demise of the storm
clusters probably by late evening, while storms linger over the
far northern counties (HAYS terminals possibly) thereafter. Large
uncertainty enters the picture overnight and early Thursday as
the 4km NAM/HiRes ARW and to a lesser extent the HRRR want to
linger an MCV like area of convection across west-central Kansas
while the FV3SAR would have largely cleared the area of
precipitation.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 69 84 64 93 / 40 40 20 10
GCK 65 85 62 91 / 60 20 10 10
EHA 65 87 63 93 / 60 30 10 10
LBL 67 87 64 93 / 40 40 10 10
HYS 67 83 62 88 / 60 30 10 10
P28 75 83 68 93 / 50 60 50 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Sugden
LONG TERM...Sugden
AVIATION...Russell
Area Forecast Discussion
National Weather Service Des Moines IA
621 PM CDT Wed Jul 14 2021
.DISCUSSION.../Tonight through Wednesday/
Issued at 236 PM CDT Wed Jul 14 2021
Previous from 113 PM CDT:
The initial morning convection has exited the forecast area and will
continue to move across northeastern Iowa and into southwestern
Wisconsin. The big uncertainty the past couple of days with this
event was with regards to how well the atmosphere would be able to
recover in the afternoon. Now that the convection has passed, the
atmosphere is showing that it is getting what it needs to recover.
Yes, there is still some stratiform rain over northwest Iowa early
this afternoon but is not overly concerning. The edge of the warm
front is located near the Hwy. 18 corridor, and there is a remnant
outflow boundary northwest of the Fort Dodge area and is oriented
from southwest to northeast. The surface cyclone over the NE-KS
state line continues to deepen this afternoon, which is
strengthening the south-southwesterly low-level flow across central
and eastern Iowa. Throughout the day, this has increased the
intensity of theta-e advection, and is noticeable in the surface
dewpoint observations in southwest Iowa that have already passed the
70 degree mark. This has even made it close to the Des Moines metro
by the early afternoon. This will continue this afternoon through
peak diurnal heating. Additionally, GOES-16 imagery is showing some
clearing (but not complete clearing) in the cloud cover that has
been present all morning, lining up with where the strongest theta-e
advection has been occurring. This is all happening on the warm side
of the remnant outflow boundary. Further, the cool side of this
outflow boundary is in the area where the stratiform rain has been
located. Thus, this has allowed for a few hours of considerable
differential heating to reinforce this boundary. So even with the
early morning convection, the instability and forcing needed for
initiation in this same part of northern Iowa should be conducive to
redevelopment this afternoon. As for southern and southeastern Iowa,
the warm sector remains potent with dewpoints steadily increasing,
and SBCAPE likely to approach between 3000-4000 J/kg. The only thing
areas further south and southeast is missing is stronger
convergence, as a second outflow boundary quickly moved across the
area and did not stall. However, redevelopment in northern Iowa will
eventually be able to move into this area. In addition to CAPE
parameters, this heating should allow favorable low-level lapse
rates to become nearly 8.0 C/km in the 0-1 km layer, and around 7.2
C/km in the mid-levels. If these lapse rates are not fully realized,
this may limit the extent of initial surface based development. But
the outflow boundary appears to be shaping up to provide enough
forcing.
In addition to the thermodynamic profiles becoming favorable, the
kinematic environment is also showing promise to support stronger
storms. As the flow continues to increase with the approaching
surface cyclone, deep layer shear has been on the rise this
afternoon, and should surpass 40 kts in the 0-6 km layer and
effective inflow layer after the 20z timeframe. The 0-3 km
hodographs (and even 0-6km) show moderate curvature as the jet
streak with the parent short-wave trough moves through. Initially,
this deep layer shear should have a strong enough component
perpendicular to the boundary that will allow for a discrete
supercell or two to develop. Initial cells moving with the 0-6 km
mean wind should have around 100 m^2/s^2 SRH to work with and
rotate. In close vicinity to the outflow boundary, supercells that
acquire right motion may be able realize 0-1 km SRH of at least 150
m^2/s^2. Storm relative flow should be quite strong, and the
environment will support ingestion of mainly streamwise vorticity
with initial convection. This is particularly concentrated between
the Hwy. 30 and Hwy. 20 corridors, and are based on RAP and HRRR
soundings sampled near Fort Dodge. Recent HRRR runs also are showing
stronger UH tracks across this area, which makes sense with the low-
level hodograph structure seen in soundings. Soundings and
hodographs sampled closer to the Des Moines metro after 20z also
have decent turning, but SRH values for both mean wind moving storms
and right moving storms are not nearly as high. But, should a
supercell develop, it will continue to move into a supportive
environment. Supercells if they develop will be capable of all
hazards. The discrete supercell threat will not be long lived
through. As 00z approaches, there continues to be a strong signal
for a robust LLJ development ahead of the initiating boundary over
the buoyant warm sector. Any discrete development will congeal as
this kicks in. The severe threat will continue though, as the
kinematic fields will still be able to foster the development of a
RIJ and could provide a bowing convective mode to the complex. Low-
level lapse rates may still be steep, especially as a complex moves
into eastern and southeastern Iowa where the air has destabilized
and remained mostly unpolluted from morning convection. This will
continue the threat for damaging wind swathes. With low-level lapse
rates remaining steep, the surface may not quickly become cut-off
from the complex. Further, 0-3 km bulk shear may reach as high as 50
kts as the LLJ strengthens. In this setup, it will not be hard
achieve 30 kt line-normal shear to the complex, which could lead to
the development of mesovortices along the leading edge, and the
dreaded nighttime QLCS tornado threat. Depending on the how the cold
pool dynamics would play out, balance with the ambient environment
may be achieved through eastern portions of the forecast area. The
one factor that may end a QLCS tornado threat though is if a
convective cluster releases a strong outflow and it rapidly
propagates ahead of the system, cutting off surface based inflow.
But, will still be looking at a damaging wind threat through the
evening.
Analysis throughout this event will heavily focus on what is
happening with vertical shear wind this evening, and how it orients
to the initiating boundary and eventual line of storms if it takes on
a linear mode. Subtle changes to the low-level winds will make all
the difference in the severity of this event.
Rest of the Forecast:
Still seeing a signal for amplified ridging over the wester CONUS
through the weekend and much of next week. There is still
potential for a few short-wave perturbations to move in from
Canada that may bring some shower chances. But overall flow will
be weak, and thus the weather not overly active. Expect mostly
seasonable temperatures while the ridge remains over the west,
and will not see an increase until the ridge axis begins to
propagate toward the central Plains. The biggest forecast concerns
will be for today, Wednesday July 14th, 2021.
&&
.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 621 PM CDT Wed Jul 14 2021
Main concern ongoing severe threats. Storms moving into eastern
Iowa continue to produce strong winds. Another round of storms may
impact central to southern Iowa from 05 through 12z. Aft 03z KFOD
and KMCW should be done with additional storms still possible
remainder of sites. /rev
&&
.HYDROLOGY...
Issued at 236 PM CDT Wed Jul 14 2021
Heavy rainfall is still possible for northern Iowa with today`s
event. Some CAMs are still producing 2-4 inches of rainfall in
some areas. These values are not expected to be widespread, but
may locally occur. The areas with heaviest rainfall forecast will
be able to handle a decent amount of rainfall. Urban and
developed areas may see some flooding issues. But given how
localized the impacts will be, have decided not to issue a Flash
Flood Watch at this time. Rises on local creeks and streams are
possible with rainfall this evening.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Krull
AVIATION...REV
HYDROLOGY...Krull
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
305 PM PDT Wed Jul 14 2021
.SYNOPSIS...A break in the persistent heat of the past couple of
weeks is in store for at least Thursday and Friday for inland
northwest California. Coastal areas will remain seasonably cool
and mostly cloudy, with only limited afternoon sunny breaks.
&&
.DISCUSSION...Upper-level low pressure will gradually settle
southward from the Gulf of Alaska toward the coast of southern
British Columbia through Friday. This will help to dig out a
somewhat deeper trough near the West Coast, as several shortwaves
rotate around it and past our area. Any clouds, let alone showers
associated with those features will stay well north and northwest
of our region, with the main impact here being progressively
`cooler` temperatures aloft and a deepening marine layer. The
cooling will manifest at the surface with interior valley high
temperatures dropping back to the 80s and low 90s Thursday and
Friday, which will be the first decent break in the persistent
heat we`ve seen since June 24th. Meanwhile, coastal areas will
likely remain seasonably cool with persistent marine layer
cloudiness. With a deeper marine layer and cooling aloft, along
with some uptick in onshore winds, we may see some drier and less
stable air mix with the marine layer and allow for a bit more
afternoon sunshine at the coast over the next few days...but don`t
hold your breath.
Heading through the weekend into early next week, ensemble and
deterministic modeling all generally support a strengthening ridge
over the `Four Corners Region` retrograding back toward the West
Coast, but also keeping a certain amount of troughing offshore.
While it looks like that will probably bring inland high
temperatures back into the mid or even upper 90s at times later in
the weekend or next week, the pattern does not support a return of
high heat risk, with only localized moderate values in the hottest
portions of northwest California. Dry weather is expected to
persist through next week as well, which is not unusual for mid
July. That said, there will be a surge of monsoonal moisture
around the Four Corners high, northward across California toward
Monday. We will likely be too far northwest for that to translate
to any thunderstorm activity, with the `reasonable worst case`
perhaps amounting to isolated storms near the Yolla Bolly
Mountains or Trinity Alps late Monday. Have not mentioned anything
in the forecast yet, but that at least bears watching. /AAD
&&
.AVIATION...Skies across the interior are clear this afternoon,
while coastal stratus lingers, particularly from KACV to Cape
Mendocino and up the Eel River Valley to between Pepperwood and
Bridgeville. Several elongated eddies are noted in the near shore
coastal waters. Drier air from SW OR continues to infiltrate the
stratus field along the North Coast. As a result, some brief periods
of scattered clouds remain possible at both KCEC and KACV.
Clouds are expected to fill back in and spread inland overnight.
Present marine layer depth is running around 2000 ft at both the
McKinleyville and Bodega Bay profiler locations. This supports
another night of MVFR to occasionally IFR visibility reductions in
low clouds and a bit of drizzle with ceiling heights of 200-500
feet. The latest HRRR guidance suggests that stratus may approach
KUKI from both the W and the S. The marine layer depth doesn`t
appear to support clouds making it to KUKI from the W, but feel a
scattered low deck may be warranted on the next package to account
for possible clouds from the S. Winds will be generally light, with
some late afternoon and early evening gustiness at KCEC. /SEC
&&
.MARINE...Northerly winds will gradually decrease tonight.
Northerlies will increase again on Thursday, mainly across the outer
waters S of Cape Mendocino. For this update, have hoisted a Small
Craft Advisory for the N outer waters to replace the expiring Gale
Warning. Have also moved the expiration time for the N inner waters
a bit earlier (3 PM Thursday). The Hazardous Seas Warning for the S
outer waters will continue until midnight tonight. Northerlies will
continue with near advisory-level conditions through the weekend.
A generally small NW mid-period swell and a periodic S long period
swell will continue. /SEC
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until
9 PM PDT Thursday for PZZ450.
Gale Warning until 3 PM PDT this afternoon for PZZ470.
Small Craft Advisory until 9 PM PDT Friday for PZZ455.
Hazardous Seas Warning until midnight PDT tonight for PZZ475.
&&
$$
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AREA FORECAST DISCUSSION
National Weather Service Hastings NE
631 PM CDT Wed Jul 14 2021
.DISCUSSION...(This evening through Wednesday)
Issued at 340 PM CDT Wed Jul 14 2021
Overview:
Strong to marginally severe tstms possible late this aftn into
overnight. Tstms chcs may linger across SE portions of CWA tmrw, but
most will be dry and cooler. Temps warm up Fri into Sat as upper
flows becomes highly amplified. PoPs return for the weekend w/
pattern becoming favorable for nightly MCSs. High pressure builds
over the Upper MS Valley early next week and recycles seasonably
cool/dry air into the area from the Great Lakes region.
Details:
Much of what was discussed in the 18Z update remains relatively on
track. Still looks like the primary instability axis for late
aftn/eve convection will be along and S of the persistent band of
shwrs/weak storms we`ve had throughout the day today. This is
where temps have warmed well into the upper 80s, if not low 90s,
and Tds are still in the upper 60s to near 70F. However, the
overlap of heat AND moisture is relatively narrow as TDs have
mixed out into the upper 50s to low 60s across our S tier of KS
zones, and S wind will help to advect this northward. Also a
limiting factor is is fairly poor wind shear. Latest SPC analysis
places eff shear around 20-25kt. This will tick upward thru the
eve, but not dramatically, as H5 flow is weak, also around
20-25kt. This will keep storm organization and hail threat pretty
limited. With the steepening lapse rates across the S and T-TD
depressions approaching 30-35 def, the greatest risk with any sfc
based storms this aftn/early eve would probably be gusty winds.
Last few runs of HRRR continue to hint at potential for uptick in
tstm coverage/intensity mainly S/E of Tri Cities in the 4-8PM time
frame, but it appears the severe threat remains on the "Marginal"
or low-end "Slight" range. The actual cold front currently lies
across the heart of the CWA from SW to NE and is forecast to
slowly sink S tonight. Models show an uptick in convection after
sunset along the elevated frontal slope around roughly the I-80
corridor in response to incr H85-H7 flow ahead of vort max/MCV
moving E across CO into KS. There could be just enough lingering
MUCAPE (1000-2000 J/kg) to combine with incr eff deep layer shear
to keep a marginal hail threat around through about midnight.
Overall, the next 6-12 hrs is characterized by a complex setup for
what looks to be a low end severe threat. Can`t rule out some
patchy fog across the far N near dawn as clds/winds decr.
PoPs linger across SE half/third of CWA on Thu, particularly thru
the AM, but overall trend has been for quicker departure for most
of the CWA. Expect dry conditions for Thu PM thru at least the
daytime hrs Fri as an axis of sfc high pressure shifts W to E
across the central Plains. The high pressure axis will provide
optimal radiational cooling conditions, so have introduced some
"patchy" and "areas" wording to account for ground fog potential.
SREF probs for vis <1mi is already around 40-50% and looks to be a
decent setup to meet crossover temps. Once the fog burns off, should
see a decent jump in temps to mid 80s/low 90s for Fri given
plentiful sunshine and incr Srly flow.
The return flow could set the stage for incr PoPs Fri night,
either in the form of elevated convection developing in response
to strengthening low level WAA/jet (like 00Z EC), or from arrival
of MCS off the High Plains (like 12Z NAM). Shwr/tstm chcs will
continue through the weekend, and likely even incr, as the upper
flow becomes highly amplified in response to strengthening ridge
over central/northern Rockies and developing trough over the
Midwest. This will result in active, meridional flow, with a
series of disturbances likely interacting with primary instability
axis forecast to stretch from Dakotas southward into central
NE/KS. From a synoptic and pattern recognition standpoint, this is
usually a good setup for repeated rounds of MCS activity each
eve/night. This looks to be the signal on some of latest GFS/EC
runs. In theory, the greatest potential would be Sat night as Sat
looks to be warmest day. Lingering cloud cover and incr E
component to wind may shave at least a couple deg off for Sun.
Early next week it appears the sfc high will strengthen over
Upper MS Valley, which should help deepen the Erly flow from the
cooler/drier Great Lakes region. Latest GEFS and EPS are in fairly
good agreement showing mainly dry conditions and near to below
normal temps for first half of next week, with more pronounced
warming trend for the second half.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 623 PM CDT Wed Jul 14 2021
Chances for isolated/scattered showers and storms will continue
across the area through the overnight hours, but confidence in
anything impacting the terminals is low enough that couldn`t go
more than a VCTS mention. Models continue to bring in lowering
ceilings with time overnight, and do have a period of IFR ceilings
near sunrise, with VFR conditions returning mid-late morning.
Winds through the period look to remain northeasterly, with speeds
topping out around 10-15 MPH.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
DISCUSSION...Thies
AVIATION...ADP
Area Forecast Discussion
National Weather Service Goodland KS
521 PM MDT Wed Jul 14 2021
.SHORT TERM...(This evening through Saturday)
Issued at 230 PM MDT Wed Jul 14 2021
Per latest satellite and radar imagery, cold front has settled
along a Sharon Springs to Colby to Norton line, about the
location forecast by the models. Insolation has been limited north
of the front due to cloud cover, but to the south there has been
some clearing. Convective initiation expected to occur on the
southern end of the front around 21-22z, between Sharon Springs
and Tribune, then additional storms developing northeastward along
the front into Logan and perhaps Gove counties between 22-00z.
The environment in that area is forecast to be moderately to very
unstable, with SBCAPE up to 3500 j/kg, with bulk shear of 30-40kts
according to latest RAP forecasts. Given those parameters in
addition to a well defined frontal boundary, may see a supercell
develop capable of large hail, damaging winds and perhaps a
tornado. These storms will move east to southeast and out of the
area by early this evening. Further west in Colorado, additional
development is expected along the Front Range in the post frontal
upslope regime. These storms will move east tonight and through
most of the forecast area through the evening and into the
overnight hours. Early evening storms may be capable of producing
damaging winds and large hail as they reach the better instability
axis, up to 2000 j/kg, towards the Kansas border area and along
the I-70 corridor in northwest Kansas, potentially interacting
with an outflow boundary from storms to the south. Any severe risk
will diminish after midnight as storms continue east and begin to
dissipate. Patchy fog may develop late in the wake of the storms
and persist into Thursday morning. Low temperatures will be in the
upper 50s to lower 60s.
For Thursday, will be under northwest flow aloft downstream of the
western ridge axis. A weak impulse will move out of the Rockies in
the afternoon, aiding convective development in the low level post
frontal upslope environment. Afternoon instability is forecast to
be weak to moderate, with an axis of up to 1500 j/kg in eastern
Colorado, and deep layer shear around 40kts. Initiation forecast
to occur along the Front Range by mid afternoon, then move south
to southeast with the mean flow, which would somewhat hinder
eastward extension of the thunderstorm threat. As a result,
relative best chance for thunderstorms will be far western Kit
Carson and Cheyenne counties in northeast Colorado, with only
slight chances further east towards the Kansas border area. Due to
limited instability, area is not currently outlooked by SPC for
severe storms, although coverage will be rather sparse. High
temperatures will be in the middle 80s and lows Thursday night in
the upper 50s to lower 60s.
For Friday, upper ridge axis will move just a bit eastward,
centered just about along the Rockies. Another impulse is forecast
to top the ridge and then drop southeastward in the afternoon and
evening, this time more directly over the forecast area due to the
location of the ridge. As a result, will see better chances for
showers and thunderstorms, mainly Friday evening. Instability axis
is forecast to develop along the Colorado and Kansas border area
with SBCAPE up to 3000 j/kg and deep layer shear of 30-40kts.
Areas is not outlooked by SPC at this time, but if those
parameters are correct would expect at least a marginal risk for
severe storms Friday afternoon/evening across much of the area.
High temperatures will reach the lower 90s and lows Friday night
in the 60s.
For Saturday, upper ridge axis continues to gradually shift
eastward, and now located along/just east of the Rockies. Another
impulse tops the ridge and moves across eastern portions of the
forecast area during the afternoon and evening. Moderate to very
unstable conditions are forecast, especially across southern parts
of the area, where rich moisture is being advected into the area
on southeasterly winds. Deep layer shear decreases a bit closer to
the ridge axis, but still forecast to be around 30kts, which
should be sufficient for a low-end severe threat with any stronger
storm that develops through the afternoon and evening hours.
Southern areas may be favored due to the stronger instability
forecast. High temperatures will be in the lower 90s and lows
Saturday night in the 60s.
.LONG TERM...(Sunday through Wednesday)
Issued at 141 PM MDT Wed Jul 14 2021
The extended period begins with a ridge over the western CONUS with
large area of high pressure associated with it, while a long wave
trough is situated over the eastern CONUS. Sunday morning, scattered
showers with possibly a rumble of thunder are possible mainly across
eastern portions of the CWA. Additional precipitation chances are
possible during the afternoon and evening with a weak disturbance
sliding down the eastward side of the western CONUS ridge.
Currently it doesn`t appear to be widespread showers/storms but
with uncertainty between guidance its difficult to nail down an
exact area at this time. It is worth noting that the ECMWF is more
aggressive with convection occurring earlier than the GFS. High
temperatures in the upper 80s to low 90s are anticipated with
overnight lows in the 60s.
Monday through the end of the extended period, the ridge moves
slowly to the east as the area of high pressure expands over the
CWA. As the high pressure moves over this will suppress any
meaningful precipitation chances through this period. Monday and
Tuesday guidance does hint at some convective feedback, roughly east
of Highway 25. Since the high pressure is expected to be over the
area, currently consider this to be a diurnally driven, short lived
shower/storm if it occurs; due to the expected nature pops were not
introduced. High temperatures during this time frame are expected to
be fairly consistent in the 80s, maybe a locale or two hitting 90
with overnight lows in the upper 50s to mid 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 521 PM MDT Wed Jul 14 2021
VFR conditions are expected at both KGLD and KMCK terminals to
start off this TAF period. Scattered thunderstorms are
anticipated to progress into the region from the west once again
this evening. Have insert a mention of VCTS at KGLD beginning at
03z, where storms impacting the terminal is a bit more likely. No
VCTS was mentioned at this time for KMCK however due to low
confidence in storms making it that far northeast. If a storm
would track across a terminal, lowered visibilities and gusty
winds will be likely. As storms exit/dissipate late tonight,
stratus and fog should develop causing sub-VFR conditions at both
sites. VFR conditions look to return midday Thursday. Otherwise,
north to northeast winds at 10 to 15 mph will be observed
overnight before shifting to the east Thursday afternoon.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...024
LONG TERM...TT
AVIATION...JBH
Area Forecast Discussion
National Weather Service Gray ME
1103 PM EDT Wed Jul 14 2021
.SYNOPSIS...
A cold front will approach the region later today which will
aid in the development of showers and thunderstorms to our west
that could affect New Hampshire and far western Maine with gusty
winds and heavy downpours through this evening. Low pressure
passes well to our north on Thursday and Friday with a warming
trend. Showers and thunderstorms will be possible each day
Friday through Sunday as a frontal boundary slowly crosses the
region through the weekend. A broad trough will linger across
New England early next week
&&
.NEAR TERM /TONIGHT/...
1100 PM Update... Blended in a bit of the HRRR for temperatures
and dew points which keeps most areas in a muggy, mild airmass
tonight with lows in the mid-60s. Reworked the fog a bit
according to these edits, but overall little change in thinking
for the coming overnight period.
845 PM Update... Issued a Dense Fog Advisory along the coast
extending into interior southern Maine. Visibilities are falling
fast along the coast with stratus expected to lower to dense
fog across the coastal plain, banking up against the Maine
mountains. For convection, the show is about over across the
south with showers and storms along the international border
behaving and showing a downward trend.
600 PM Update... Reworked PoPs according to latest radar trends
and hires data. At this time, strongest storms are sticking
just south of the Mass border... however surface obs show
temperatures in the low-80s near the 93 corridor in southern New
Hampshire show promise in stronger storms there through the
evening. Further east, onshore flow is lifting ceilings just a
hair and dissipating fog for the time being, however the trend
will be back down especially along the Midcoast tonight. Will
continue to monitor for dense fog and the possibility of another
dense fog advisory late tonight.
Previously...
A tale of two seasons across the forecast area this afternoon.
Coastal locations as well as a good portion of central Maine
continue to be locked into the marine layer with clouds and
temperatures around 70s. Around the periphery of the marine
layer, temperatures have risen to around 80 degrees with
dewpoint temperatures around 70F in spots. This has resulted in
about 1500 J/KG SBCAPE in the areas where the sun has come out.
Deep layer shear is a bit on the light side, but sufficient for
a few organized thunderstorms this afternoon and evening,
especially across NH. Thunderstorms are currently developing
across Vermont at this time. These should continue to push
eastward with a few possibly becoming severe across NH,
especially between 4 and 8 PM. Damaging winds would be the main
threat. Farther east in the marine layer, chances of storms will
diminish, but a few rumbles will be possible to the Maine
coastal plain this evening.
Fog is expected to redevelop tonight, especially across coastal
and central ME. It could become dense over a wide enough area
to allow for the issuance of a dense fog advisory, but a little
uncertain of the exact area right now so will hold off on that
for the time being.
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
Fog and a good portion of low cloudiness will burn off as the
morning progresses, allowing for a very warm day in most of the
forecast area on Thursday. There is an outside chance of an
isolated storm or two, but given lack of forcing for ascent will
keep the forecast dry. Low clouds and some fog are expected to
redevelop on the coastal plain Thursday night.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
By Friday, a frontal boundary will be pressing into northern
zones from Canada, and appears it will be slow to make much
progress through the weekend. This will equate to near average
temperatures after a warm Friday, but continued humid and
showery conditions persisting for much of the weekend. Friday
looks to be the warmest day in the long term period, with highs
near 90 across most southern locations, and high dew points
sending heat indices into the mid 90s Friday afternoon.
There is a growing consensus among the models that the best
chance for the heaviest rainfall amounts would be across
northern zones, many of which remain quite dry and have largely
missed out on most of the rainfall that central and southern
areas have seen over the last couple of weeks.
While the weekend won`t be a washout, numerous rounds of showers and
storms appear likely. The best chances for the most widespread
activity will be during the afternoon hours with the diurnal heating
maximum, and when any weak areas of low pressure pass through along
the boundary.
Trying to time out the best chances for rain... Friday afternoon
will be the first shot of widespread showers and storms away from
the coastline as the front pushes into northern zones. Then late
Friday night and Saturday morning a weak wave of low pressure will
likely bring a period of soaking rain, with the best chance being
across northern zones near the Canadian border. Saturday afternoon
will then likely feature widespread showers and storms across most
of the region, even to the coastline. Then, Saturday night the front
will be placed slightly farther south as the next wave of low
pressure rides along, likely bringing another round of widespread
heavier showers and storms to northern and central areas, and would
depart the area by mid morning Sunday. By Sunday afternoon the front
will most likely be placed near the coastline, concentrating the
threat of showers and storms near the coastal onshore flow will
continue into today with low clouds, areas of fog, and patchy
drizzle. A cold front will approach the region later today which
will aid in the development of showers and thunderstorms to our
west that could affect New Hampshire and far western Maine with
gusty winds and heavy downpours. Low pressure passes well to
our north on Thursday and Friday with a warming trend. Showers
and thunderstorms will be possible each day Friday through
Sunday.tline and southern New Hampshire.
By Monday it appears the front would likely have pushed into
southern New England, but will have done little to clear out the
humid airmass. Other than perhaps lowering the dew points by a few
degrees, early next will likely continue to feature similar
conditions with seasonable temperatures and only slightly less humid
conditions. Pop up afternoon showers will likely still develop
across the higher terrain, but won`t be as widespread due to a
lack of forcing.
By midweek next week there is decent agreement among the models
that a trough will be deepening across the Great Lakes, and
potentially the Northeast. It`s a little early to try to predict
how this feature will evolve, but if it`s a bit sharper and
farther west then we`ll likely see continued mild and humid
conditions. However, the trough being farther east across the
area would likely bring another extended period of cool and
shower conditions.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Short Term...IFR conditions on the coast and across central
Maine will deteriorate to LIFR this evening and tonight as low
clouds and areas of dense fog redevelop. Further inland,
conditions will be MVFR or better, but valley fog could develop.
On Thursday, it looks like the low clouds and fog will burn off
with all terminals except for perhaps RKD going to VFR by noon.
IFR or lower conditions then likely return to the coastal plain
Tuesday night.
Long Term...
Periods of showers and thunderstorms associated with a slow
moving frontal boundary will bring restrictions at times late
Friday and through the weekend. The greatest chances for rain
will be across northern terminals Friday afternoon and again
early Saturday morning, all terminals Saturday afternoon, and
then again across central and northern terminals Saturday night
and Sunday morning. Southern terminals have another chance of
showers and storms Sunday afternoon. VFR conditions will most
likely return early next week.
&&
.MARINE...
Short Term...Winds/seas stay below SCA levels through Thu.
However, fog will be persistent through tonight and Thursday
night, and may shift further offshore on Fri.
Long Term...
A slow moving frontal boundary will gradually push
across the waters late Friday and through the weekend. South-
southwesterly winds may occasionally gust to near SCA criteria
offshore ahead of the front on Friday-Sunday evening. The front
will likely clear the waters Sunday night. A broad trough will
remain across the waters behind the front for early next week.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Dense Fog Advisory until 10 AM EDT Thursday for MEZ012>014-
018>028-033.
NH...Dense Fog Advisory until 10 AM EDT Thursday for NHZ014.
MARINE...None.
&&
$$
NEAR TERM...Casey/Ekster
SHORT TERM...Ekster
LONG TERM...Clair
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
859 PM EDT Wed Jul 14 2021
.SYNOPSIS...
An upper level disturbance will move across the area this
evening. Weak high pressure will settle across the region
Thursday before shifting to our south on Friday. A cold front
will slowly approach the area this weekend, potentially stalling
nearby early next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
After a busy evening, thunderstorm activity has mostly wound
down. Still an isolated cell in northern MD and western VA, but
these are gradually weakening now that the sun has set. Any
remnant shower activity should cease by late evening as
overnight lows bottom out in the low 70s for areas mainly east
of I-95 and mid 60s elsewhere. Patchy fog is a concern,
especially in areas where it rained earlier.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Upper level trough will continue to swing through the area
Thursday morning. Thereafter, H5 ridging associated with the
Bermuda high banked off the Carolinas will restrengthen over the
remainder of the day into Friday. As a result, heat and
humidity will continue during this time. Conditions should
remain fairly dry Thursday as heights rise. Better conditions
for scattered showers and thunderstorms on Friday given the
unstable atmosphere, coupled with weak shortwave energy
traversing across the ridge axis.
One noticeable change compared to the last few days is that the
latest HRRR runs are showing a significant plume of western
wildfire smoke moving toward us aloft. This was picked up well
on the Geocolor satellite earlier today. The smoke will likely
result in milky skies on Thursday and Friday, versus the clearer
blues (when not obscured by clouds) we`ve enjoyed the last
couple of days.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
A slow moving front is forecast to drop down into our region
Saturday into Sunday. Ahead of the front, a warm and moist
environment will lead to formation of showers and thunderstorms.
Another warm and humid day is expected on Saturday with
afternoon temps rising once again up into the low to mid 90s.
The slow nature of the frontal passage along with a weak flow
will lead to an increased threat for flooding on Saturday.
Decent CAPE values will likely lead to a pulse thunderstorm
threat on Saturday that will be capable of producing heavy
rainfall and strong winds. The big flood threat will likely
occur on Sunday when the front is forecast to drop through our
region. The weak nature of the upper trough will mean the front
will be slow to exit our region. The stalling nature of front
boundary combined with the high PW`s will lead to another threat
for flooding on Sunday. The threat for flooding looks higher at
this time on Sunday as the front will become the focus for
continue shower and thunderstorm development. We will need to
monitor model trends to determine where the front will end up
stalling which will determine the highest threat area for
flooding.
The front is forecast to remain stalled near our region through
Monday. Flooding will continue to be a concern into early next
week but the front may sink far enough south on Monday to limit
the threat area. Cooler and drier conditions should build into
our region on Monday as our region becomes positioned on the
cooler side of the trough. A weak upper trough should finally
push the front southward away from our region on Tuesday.
Showers will continue to be possible on Tuesday as the upper
trough access moves overhead but the lack of deep moisture due
to a NW flow may limit shower coverage.
&&
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
Mainly VFR conditions are expected to continue through overnight.
However, expect patchy fog to develop overnight which may
reduce VSBYs through early Thursday morning, with the best
potential being over CHO and MRB. Weak high pressure and
southerly winds return for the remainder of the week as
conditions remain mostly VFR.
VFR conditions to start Saturday but increasing showers and
thunderstorms will likely lead to subVFR conditions Saturday
afternoon through Sunday. Winds will remain light out of the
south on Saturday but will slowly become northwesterly by
Monday. SubVFR conditions may continue into Monday.
&&
.MARINE...
Gusty showers and thunderstorms winding down, and additional
SMW`s now look unlikely. For the remainder of the week, mainly
sub- SCA conditions expected for most of the waters. However,
could see the potential for additional SCAs for the lower bay as
southerly channeling strengthens. SubSCA conditions mainly
expected this weekend except for within strong showers and
thunderstorms.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...MSS
NEAR TERM...MSS/RCM
SHORT TERM...MSS/RCM
LONG TERM...JMG
AVIATION...MSS/JMG/RCM
MARINE...MSS/JMG/RCM
Area Forecast Discussion
National Weather Service Melbourne FL
1000 PM EDT Wed Jul 14 2021
.UPDATE...
Currently, radar imagery shows the majority of east-central
Florida dry with only a few isolated showers located over the
southern waters. Analysis charts show a weak disturbance over
southern Florida indicated by cyclonic turning in the wind barbs -
which has triggered showers and isolated storms over areas mainly
south of central Florida. High pressure remains located over the
western Atlantic with the center situated just east of the
Carolina coasts. 00Z observed skew-t soundings showed drier air in
the low levels with some moisture present in the mid-to-upper
levels, in addition to very weak shear and moderate instability.
This suggests dry conditions should continue for the most part
through the overnight hours. However, a slight chance for showers
with embedded thunderstorms exists over the southern offshore
waters, as well as along and near the Treasure Coast through the
early morning hours. Most of the action should stay to the south
and west of the Space Coast - closer to where the minor upper-level
shortwave is located. The forecast remains on track for this
evening`s update with mostly dry conditions, partly cloudy skies,
and lows in the low-to-mid 70s.
&&
.AVIATION...
VFR conditions prevailing outside of convection through the TAF
period with dry air suppressing convection at all terminals. E-SE
winds backing off this evening and becoming light overnight, then
picking back up to 10-12 KTS tomorrow afternoon. Best chances for
showers and storms tomorrow afternoon are at the southern most
terminals where more moisture is available, and the western inland
terminals, depending on the position of the east coast sea breeze
around 18Z. That said, HRRR guidance has been backing off inland
showers and thunderstorms in a big way the last few runs, and VCTS
or even VCSH at inland terminals may be too generous. Will make
adjustments in the next couple TAF packages if this trend continues.
&&
.PREV DISCUSSION... /issued 232 PM EDT Wed Jul 14 2021/
Current-Tonight... Scattered to numerous showers and lightning
storms across the interior, mainly along and west of I-4, with
additional showers and storms pushing onto the coast from Cape
Canaveral northward. The strongest of these storms will be capable
of producing wind gusts of up to 40 mph, frequent lightning strikes,
and heavy downpours producing rainfall amounts of 2-3" in a 60 to 90
minute period. The 15Z XMR sounding shows a PW value of 1.98" with a
500 mb temperature of -8.9 degrees. The Shower and storm chances
will then diminish quickly into the evening hours, as drier air
moves in from the east, with no mentionable PoPs in the overnight
hours. Overnight lows will be in the low to mid 70s across the
interior, and mid to upper 70s along the coast under partly cloudy
skies.
Thu-Fri... (Modified Previous Discussion) Deep layer
high pressure at the sfc and aloft will remain across the Gulf of
Mexico and the FL peninsula/SW Atlc. The low level ridge axis will
stay north of the area which will maintain the E/SE flow. Drier air
is forecast to move in from the East on Thu resulting in noticeably
lower rain chances of 20-30 percent, with the highest chances
occurring along the far interior. A little higher mean moisture
advects back in for Fri so have drawn 30-40 PoP but holding near 20
PoP for Volusia county. Max temps look close to seasonable with
lower 90s inland and upper 80s coast. Could see a few mid 90s though
Thu aftn across the north interior given the drier airmass.
Sat-Tue...(Previous Discussion) Deep layer E/SE flow expected to
continue this weekend. A positive tilt northern stream trough is
forecast to develop across the eastern CONUS which should push the
low level ridge axis south across central FL Mon-Tue. As a result,
low level flow will become more southerly and favor a slight
increase in rain chances. NBM looks overdone (wet) with PoPs here
and have scaled back 10-20 percent from its numbers to generate 40-
50 PoPs which is very close to climatology. Temps will also remain
seasonably warm in the upper 80s coast, warming to near 90 Mon-Tue;
lower 90s through the period interior.
&&
.MARINE...
Current-Tonight... Scattered to numerous showers and isolated
lightning storms ongoing across the Atlantic. Cell movement is
towards the coast around 15 KT. Current buoy 41009 observations
show seas are 4 ft with a south-southeast wind around 10 KT.
Additional showers and lightning storms will continue to be
possible across the Atlantic through this afternoon, with rain
chances diminishing into this evening as drier air moves in from
the east. Winds will be onshore (east to southeast) around 10-15
KT through the overnight hours. Seas will be 2-3 ft in the near
shore waters and 3-4 ft in the offshore waters.
Thu-Sun...(Modified Previous Discussion) Atlantic ridge axis will
remain north of the local waters through the end of the week, then
begin to shift south across the local Atlantic waters Sun and into
early next week as a frontal boundary pushes into the deep South.
Drier air will produce lower coverage of showers/storms, esp Thu.
Winds will be E to SE around 10 to 15 KT through the period. Seas
will be 3-4 ft on Thu, 3 ft Fri, and 2-3 ft this weekend.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 87 75 88 74 / 40 10 20 10
MCO 88 74 90 73 / 60 10 20 10
MLB 87 77 88 77 / 40 10 20 10
VRB 87 75 88 76 / 40 20 20 10
LEE 89 74 91 74 / 60 10 20 0
SFB 88 74 91 74 / 60 10 20 10
ORL 88 75 91 76 / 60 10 20 10
FPR 87 75 88 76 / 40 20 20 10
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Fehling/Sedlock/Haley
Area Forecast Discussion
National Weather Service Marquette MI
845 PM EDT Wed Jul 14 2021
.SHORT TERM...(This evening through Thursday)
Issued at 421 PM EDT WED JUL 14 2021
WV imagery and RAP analysis indicated an upstream shrtwv and MCS
with thunderstorms draped from eastern MN through north central and
eastern WI. Additional strong/severe thunderstorms have developed
over portions of central and eastern upper Michigan along lake
breeze convergence areas where MLCAPE values were in the
1000-1500 J/Kg range.
CAMs and radar/satellite trends suggest that the MCS will continue
to lift northeast into Upper Michigan with rainfall amounts into the
0.5 to 1.5 inch rnage over much of the southeast half and the
heaviest rain through the south. Additional local rainfall amounts
to over 2 inches may be possible. Expect enough instability with
MUCAPE values remaining in the 1000-2000 J/Kg and modest effective
shear to 30 knots to support a few more strong storms.
Lingering shra/tsra are expected to lift out of central Upper
Michigan by mid morning with clearing from west to east into the
afternoon. Sunshine will help push temps back into the mid and upper
70s inland with readings closer to 70 near Lake Superior where
onshore northerly flow prevails.
.LONG TERM...(Thursday night through Wednesday)
Issued at 148 PM EDT WED JUL 14 2021
The longterm pattern will begin to trend warmer and drier, with
little to no pcpn chances expected outside of a diurnally forced pop-
up shower. Behind Thursday`s exiting remnant potential MCS, heights
begin to rise as anomalous ridging builds over the Rockies. While
this will tend to drive downstream troffing and NW flow over Upper
Michigan, deterministic models and their ens means show an elongated
trof stretching from New England southwestward through the
Appalachians, which will induce some uncertainty in the models
towards this weekend. GEFS 500mb spaghetti plot shows decent
predictability through the weekend, before solns begin to diverge
towards the start of next week. This is visible in the EPS model
spread as well. Deterministic models continue to kick off waves
through the Central Plains into the Ohio River Valley this weekend
into the start of next week that slowly meander through the Ohio
River Valley, limiting the eastern extent of the ridge. As this wave
pulls away early next week, more persistent NW flow will be seen
over Upper Michigan with troffing east of the UP and ridging to the
west. Highs will trend through the 80s this weekend, approaching 90
Sunday into Monday for the warmest locations, before trending back
towards normal to slightly above normal by the middle of next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 834 PM EDT WED JUL 14 2021
VFR conditions should prevail for the most part at KCMX and KIWD
through the forecast period. However, some light showers in the
vicinity of KIWD have caused some lower MVFR cigs to develop there
this evening and these lower cigs could linger into the early
overnight.
At KSAW, a larger rain shield from a system tracking across
northern Lake Mi tonight has caused IFR/LIFR conditions to
develop early this evening. Expect enough low level moisture with
the showers to keep conditions IFR to LIFR through much of
tonight. Conditions should improve to MVFR after sunrise
Thursday and then to VFR by afternoon as high pressure and drier
air moves in from the west.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 421 PM EDT WED JUL 14 2021
A low pressure moving through northern Lake Michigan tonight should
bring some northeasterly to northerly gusts up to 20 knots across
far southeastern Lake Superior early Thursday. Otherwise, expect
winds to be less than 20 knots for the forecast period.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...JAW
AVIATION...Voss
MARINE...JLB
Area Forecast Discussion
National Weather Service Pocatello ID
203 PM MDT Wed Jul 14 2021
.SHORT TERM...Tonight through Friday night. Weak shortwave passing
through Idaho this afternoon may be enough to spark isolated
thunderstorms across portions of the central mountains/Arco
Desert, and the Clark county portion of the Divide. We are seeing
a few early afternoon build ups already on satellite imagery in
the central mountains. Further south, there is more aggressive
thunderstorm development occurring across northeast
Nevada/northwest Utah, but so far that activity is struggling to
reach much further north than I-80. There are more developed build
ups along the Utah border, so this will be an area to watch for
potential additional development later today. A stronger shortwave
feature lifts through the region Thursday, so isolated
thunderstorm coverage is spreading over more areas in East Idaho.
If thunderstorm coverage increases much more, it would have
impacts on fire concerns for the day. One more weak feature
crosses through the panhandle into Montana on Friday, but
thunderstorm activity looks to be confined to regions north of the
Divide. Otherwise, smoke and haze continue to be a challenge in
the forecast. Once again opted to be more heavy- handed with the
expected coverage. Caveat will be impacts of the next couple
shortwave features, which may be enough to mix up some of the
smoke Thursday into Friday. If the HRRR holds true, there should
be some mitigation in smoke impacts beginning late Thursday into
Friday, but kept patchy mention all areas for now. DMH
.LONG TERM...Saturday through Wednesday. Upper ridge begins to
strengthen in the western states over the weekend. Center of the
high builds over northern Utah/southern Idaho/southwest Wyoming
per both GFS and ECMWF Sunday into Monday. Coincidentally, these
should be the hottest days of the extended period, though warm
temps may continue into Tuesday as well. Numerical guidance and
ensembles continue to trend upwards with forecast daytime highs
with good agreement in handling of the upper high in the ensemble
clusters. If these trends hold true, another round of heat-related
headlines will be needed. Moving toward midweek, there is strong
indication of seeing monsoonal moisture work through the Great
Basin. Have added isolated thunderstorms for each afternoon Monday
through Wednesday. Of course, any thunderstorms that do develop
may help squash some of the strongest temperature potential for
those days as well. DMH
&&
.AVIATION...
Main impact in short term will be extensive smoke which may
occasionally reduce visibilities at all sites but did not go under 6
statue miles and should be above that most of the time. Winds
should stay 10 knots or less through Thursday morning. Will have
more thunderstorm coverage Thursday afternoon and evening mainly in
the east and expect DIJ and IDA most likely to see one near the
station. May need VCTS Thursday afternoon.
GK
&&
.FIRE WEATHER...
Main impact will be isolated thunderstorms on Thursday mainly in
zones 475, 476, 411 and 413, but for now have no Watches or Warnings
as expect coverage to be isolated. May see more very isolated
storms on Friday as well in zone 411. Winds not expected to be
overly strong the next two days other than near thunderstorms on
Thursday. Hot and dry conditions expected Saturday and Sunday with
perhaps more monsoonal flow pushing northeast next week with a
chance of wetter conditions but confidence low right now.
GK
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Reno NV
238 PM PDT Wed Jul 14 2021
.SYNOPSIS...
Temperatures will begin a cooling trend through the rest of the
week, to near average temperatures by Friday. Thunderstorm chances
return to the region on Sunday, continuing through the middle of
next week as monsoonal moisture returns.
&&
.SHORT TERM...
A trough moves into the Pacific Northwest tonight and for the next
few days, bringing some changes to the weather. There is a very
slight chance of a thunderstorm developing over the White
Mountains in southern Mono County this evening, but other than
that, the forecast will remain pretty dry through at least Saturday.
Temperatures remain hot today, but will start a slight cooling
trend tomorrow into the weekend with temperatures back down to
near average. Highs Thursday and Friday will be back down into the
mid 90s for western Nevada and low 80s in the Sierra valleys.
We will get caught in the dry southwest flow over the Sierra and
western Nevada for the next few days as the Pacific troughs hangs
up along the coast. This will bring in very dry air aloft from
subsidence of the Pacific Ridge tonight and into Saturday, which
will decrease humidity across the area and bring poor moisture
recovery to the midslopes and ridges. This, combined with breezy
afternoon and evening winds, will create near-critical fire
weather conditions each day through the weekend. Please see our
fire weather discussion below for more details. The breezy winds
are also expected to create bumpy conditions for aviation and
rough lake waters the next few days. Winds are expected to remain
below lake wind advisory criteria. -Hoon
.LONG TERM...Sunday through next week...
Ridge of high pressure builds back over the Great Basin starting
this weekend and going into next week. This will increase
southeast flow over the Sierra and western Nevada, bringing
monsoonal moisture into the region and increasing our chances for
thunderstorms. Thunderstorms could begin as early as Saturday
evening, but more likely Sunday looks to be the first day of
lightning in the Eastern Sierra of Mono and Mineral counties.
Thunderstorms will start out initially on the dry or hybrid
wet/dry at first, with concerns for new lightning fires from the
recent heatwave and dry fuels. By Monday, the precipitable water
values over the region will continue to increase to near 0.8",
right in the sweet spot for heavy rainfall and flash flood
potential. Even though the rainfall will be a welcome relief,
areas downstream of newly burned areas such as the Beckwourth
Complex north of Reno could be susceptible to flooding.
Temperatures will remain slightly above average through next week
with 90s in northeast CA and western Nevada with 80s in the
Sierra. The increase of moisture and cloud cover at night will
likely keep low temperatures above average with will increase the
heat risk moderate. -Hoon
&&
.AVIATION...
Typical W/SW winds are expected each afternoon and early evening
the rest of this week - gusts on the order of 20-25 kts with the
occasional 30 kt. Tonight into early Thursday morning, some low-
end wind shear is possible over the Sierra as ECMWF shows a plume
of relatively stronger winds with 700mb flow peaking around
30-35kts.
Smoke and haze from fires in the region could produce some areas of
MVFR visibility in the E Sierra between MMH/BIH and TVL along with
areas north of RNO near the larger Beckwourth Complex. However based
on the latest wind forecasts and HRRR Smoke model, impactful smoke
is unlikely to affect the TAF sites in our region.
A few buildups possible today over the E Sierra near MMH. 5% chance
of a renegade t-storm, but based on latest HREF any storms would
more likely be over the White Mountains and eastward. -Chris/Hoon
&&
.FIRE WEATHER...
Marginally Enhanced Breezes:
* The area of high pressure over our region the past week continues
to weaken and move east this afternoon into Thursday as a trough
pushes near the Pacific Northwest coast. This pattern will
marginally enhance southwest-west afternoon breezes with gusts in
the 25-30 mph range, with a few wind-prone areas seeing near-
critical 30+ mph wind gusts for 1-3 hours, mainly east of US 395.
Dry Conditions:
* The return of southwesterly flow will also bring dry conditions to
the region through at least early Sunday. Daytime humidities will
drop into the single digits for valleys, while nighttime
recoveries will only be 20-30%. These poor recoveries can lengthen
the duration of fires, especially along the mid-slopes, well into
the evening and overnight hours.
Thunderstorms Early Next Week:
* Afternoon build-ups are expected the remainder of the afternoon
over the Sierra and the northern White Mountains, with a 5% chance
of an isolated storm. Storms look to return to the Eastern Sierra
Sunday, with coverage becoming more widespread early next week.
Low levels will be dry initially, so new fire starts and stronger
outflow winds are a concern. As the week goes on, storms will
transition to wetter storms.
-Johnston
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
...Update to aviation forecast discussion...
.DISCUSSION...
Issued at 303 PM CDT Wed Jul 14 2021
Plenty of high cloud overhead today downstream of an upper wave
over the northern Plains and monsoonal moisture in Arizona. A cold
front associated with the northern wave was located from
northwest Kansas into north-central Iowa at 18z with elevated
showers and storms just northwest of the local area in an area of
mid-level WAA.
Short-range models showing some variability in how far southeast the
current precip will reach over the next several hours, with some
indications of surface-based development. Recent RAP forecasts keep
some MLCIN in place across the area however. Latest dewpoint
observations show the boundary layer not quite as well mixed as
expected at this point but values into mid to upper 50s are not far
upstream in central Kansas. Instability also not impressive and
DCAPE values are also progged to fall below 1000 J/kg this
afternoon, but can`t completely disregard the potential for a
downburst near severe levels forming in the northwest counties into
this evening. More precip coverage is expected later this evening
into the overnight hours as convective remnants move northeast out of
western Kansas. A moderate low-level jet redevelops but MUCAPE
remains modest and severe potential is low. Continued cloud/blowoff
and moderate south winds should keep temps warm ahead of any precip.
The cold front makes steady southeast progress from north-central
into southeast Kansas Thursday into Thursday night. The trend for a
stronger mid-level wave developing from the west continues though
the 12Z larger-scale runs (particularly the NAM and to a lesser
degree the GFS) suffer from convective feedback with a potent MCV
moving ENE out of southwest Kansas through the day. Some HREF runs
also have MCV production but are overall less robust with the mass
field responses. The setup still supports heavy rains with warm mid-
levels, fairly unidirectional wind fields and weak to moderate
skinny CAPE in PW values of 1.5 to 2 inches. The more favored HREF
suite still produces some bands of a few inches of rain and seem
reasonable. Ground conditions have well-recovered from the
precipitation four days ago and keep the flash flood that somewhat
localized. The area of concern seems to have shifted a bit more
north to south with some agreement in a weak surface low moving
northeast along the front through the day with moisture convergence
shifting north with time. Enough instability may remain in the warm
sector for some downburst wind potential from midday to early
evening as well. The mean upper wave swings through during the night
into early Friday for drying and much quieter conditions. Have kept
some small precip chances in southeastern areas though the a drier
trend continues to show itself.
The upper flow pattern becomes rather stagnant from the weekend into
early next week. The front may linger just west of the area early in
the period with some potential for additional weak upper waves to
move through for small precip chances in mainly western areas
through much of the weekend. The upper ridge axis looks to push
enough east by late Monday allowing surface high pressure to sink
enough south west for a dry Tuesday and Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 632 PM CDT Wed Jul 14 2021
Maintaining a VFR forecast for now but some bases may be as low as
2kft. Still monitoring for LLWS impacts as the LLJ intensifies
this evening. Overall impacts look marginal right now but if LLWS
impacts occur the likely area would be over the KTOP/KFOE
terminals into the 09-12Z time frame.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...65
AVIATION...Drake
Area Forecast Discussion
National Weather Service Tucson AZ
751 PM MST Wed Jul 14 2021
.SYNOPSIS...An active period of daily scattered showers and
thunderstorms during the next 7 days. High temperatures will be
below normal through the remainder of the week into next week.
&&
.DISCUSSION...A few storms developed around the edges of the earlier
cloud shield as those area had the most sunshine. Even these are
dying off at this time with a few light showers popping up every now
and then. Will need to keep an eye on the far western part of Pima
county for the next several hours though (Ajo west).
For much of the night would expect it to be fairly quiet but given
how moist we are it won`t take much of a bump to kick off
convection. A few CAM solutions have suggested another flare up
across parts of Pima and into Santa Cruz county very late tonight
into tomorrow morning, associated with the feature currently driving
the convection over west-central and NW AZ at this time. It seems
like a decent possibility. The 18Z WRFNAM has done a good job with
the afternoon early evening convection and suggests that possibility
as well as several HRRR runs. The 12Z WRFGFS was pretty much out to
lunch for today and has been ignored. So, I tweaked pops upward late
tonight into early Thursday from Tucson west and south to account
for that potential.
Tomorrow, CAMs are kind of all over the place at the moment with the
HRRR somewhat concerning late in the day Thursday into the evening
hours. Basically we have plenty of moisture and enough instability
around that we only need subtle sources of lift including sunshine,
then areas of developing storms influence development or suppression
of convection. Difficult for models to capture. Hopefully the 00Z/06Z
runs with the latest data for initialization will converge on a
solution to help pinpoint the more likely areas for trouble bubbles.
&&
.AVIATION...Valid through 16/00Z.
BKN-OVC layered clouds AOA 8k-12k ft MSL will continue into this
evening, except becoming SCT-BKN tonight through early Thursday.
Isolated showers and maybe a thunderstorm is possible overnight with
good potential for renewed development of SHRA/TSRA after 15/08Z.
Wind gusts to 45 kts possible near any TSRA along with mountain
obscurations. Otherwise, SFC wind generally less than 12 kts.
Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...
There will be a good chance of showers and thunderstorms across
southeast Arizona each day into next week. Gusty outflow winds and
heavy rainfall will be the primary concern with the daily storms. Min
RH values will be in the 25-35 percent range at the lower
elevations, with higher values in the mountains. 20- foot winds will
generally be less than 15 mph and follow normal diurnal trends when
not influenced by thunderstorms.
&&
.PREV DISCUSSION... /issued 247 PM MST Wed Jul 14 2021/
After an active morning with widespread heavy rainfall and flash
flooding, things have quieted down a bit early this afternoon.
However, we did see a few storms pop up most recently across eastern
and southern areas where a bit more surface heating was able to take
place. Most other locations are still socked in under a broken to
overcast cloud deck from the decaying activity earlier today. These
clouds were keeping temperatures down for many locales, with
temperatures valid 14/21z running 10-15 degrees cooler than 24 hours
ago. Surface dewpoints were holding steady in the upper 50s to upper
60s under satellite PWAT estimates between 1 and 2 inches in a fairly
uniform east-to-west gradient across the CWA.
With that in mind, we cannot completely rule out convection late
this afternoon or this evening, though it will take breaks in the
cloud cover and quick surface heating to tap into the 1000-2000 J/kg
of MLCAPE sitting atop a cap of 50-150 J/kg. If a few cells break
through, they will struggle to move and will have that deep moisture
to work with so flash flooding will continue to be a concern.
The Flash Flood Watch for our western zones will expire at 15/06Z as
originally planned, but in coordination with our neighbors, the
remaining zones of SEAZ will have the watch in effect through
16/06Z. This now includes all of Cochise County along with all of
the Sky Island zones including the White Mountains.
The impetus for this extension is to highlight an elevated flash
flooding threat through Thursday night as convection continues to
take advantage of a saturated atmosphere. We`ll also watch to see if
any MCVs develop from this decaying complex moving into Sonora, and
if they aid convective development especially tonight and Thursday
morning. Otherwise, we should clear out better on Thursday afternoon
and surface heating will get things going once again. The focus will
likely be from Tucson eastward under north to northwest flow that
gradually becomes more northeast to east Friday into this weekend.
With high pressure building north again over the weekend into early
next week, we`ll be back in a northeasterly flow regime watching
storms roll off the Mogollon Rim into the valleys. Moisture isn`t
going anywhere, so daily shower and thunderstorm chances continue
through the forecast period in this setup. Additionally, on the
temperature front highs look to remain below normal over the next 7
days.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Thursday evening for AZZ503>515.
Flash Flood Watch until 11 PM MST this evening for AZZ501-502.
&&
$$
Public...Cerniglia
Aviation...Lader
Fire Weather....Carpenter
Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Area Forecast Discussion
National Weather Service Las Vegas NV
101 PM PDT Wed Jul 14 2021
.SYNOPSIS...Showers and thunderstorms are expected for
only the extreme northeastern and eastern portion of the area this
evening. Then a brief period of drier conditions prevail Friday into
Saturday before storm chances increase Sunday through the middle of
next week.
&&
.DISCUSSION...through next Wednesday.
Starting to sound like a broken record, but overall synoptic pattern
has not changed much so we are expecting our third active evening in
a row, if only slightly further eastward.
Storms that develop across Lincoln County and southwest Utah this
afternoon will once again propagate south-southeastward through
northeast Clark County and northwest Arizona this evening before
dissipating in the early hours of Thursday morning. Any of the
stronger storms will be capable of producing wind gusts of 50+ mph
in Lincoln, eastern Clark and Mohave Counties. Some of the near term
guidance, specifically the HRRR has been indicating the potential
for heavy rainfall increasing across northern Mohave County this
evening. This prompted the issuance of the Flash Flood Watch until
midnight MST.
Potential still exists on Thursday evening for storms to move out of
Utah and clip northern Mohave County. However, intensity of storms
does not look to be as significant as the previous days.
Still looking at Friday as the quietest day but can rule out an
isolated shower or thunderstorm over parts of northern Lincoln
County and northwest Arizona. NBM PoPs now showing isolated storms
possible as early as Saturday over the higher terrain of southern
Nevada and eastern San Bernardino County as monsoon moisture starts
to surge back northward. Upward swing in storms will then continue
to spread north and west Sunday through the middle of next week as
PW values surge northward into the Great Basin.
Temperatures will be running at or slightly above normal during the
period.
&&
.AVIATION...For McCarran...Winds at the terminal will favor a
northeast to east direction through the afternoon, with occasional
gusts over 10 knots possible. Isolated thunderstorms may develop
over the local mountains, but are not expected to affect the
terminal. The bigger concern comes late this evening around 06Z,
when thunderstorms passing by to the east could send gusty northeast
winds to the terminal for a few hours. Quieter weather is likely
Thursday.
For the rest of southern Nevada, northwest Arizona and southeast
California...Isolated thunderstorms are expected to develop over the
higher terrain of Esmeralda, north central Nye, and far northeast
San Bernardino counties this afternoon. The greater concern is a
complex of thunderstorms forecast to develop over Lincoln county
late this afternoon and track south into extreme northeast Clark and
northern Mohave counties this evening and tonight. As in previous
evenings, the main threats will be strong and erratic winds, locally
heavy rain, and low ceilings with terrain obscuration. Less
thunderstorm coverage is expected Thursday.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSION...Pierce
AVIATION...Morgan
For more forecast information...see us on our webpage:
https://weather.gov/lasvegas or follow us on Facebook and Twitter