Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/03/20
Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
631 PM CDT Sun Aug 2 2020
.AVIATION...
For the 00Z TAFs, expect some showers and thunderstorms over
eastern New Mexico and southeast Colorado to track south southeast
into parts of the forecast area, with KDHT the most likely terminal
site to be impacted, followed by KAMA, with KGUY having the
overall lowest threat. Have only included VCTS at the terminal
sites for a few hours later this evening and tonight due to
uncertainty in whether or not any terminal site will be directly
impacted. Radar trends will be monitored closely this evening with
amendments possible if warranted.
02
&&
.PREV DISCUSSION... /Issued 354 PM CDT Sun Aug 2 2020/
SHORT TERM...Tonight.
Currently there is high pressure at H5 over AZ, NV, UT, southern
CA and far west NM. A positively tilted trough axis expands from
eastern TX all the way up to the Hudson Bay. This leaves the FA
under NNW flow. Later this afternoon this NNW flow will bring in
an upper level disturbance that will help fire off some
thunderstorms. Winds at the surface have been out of the northeast
to east helping to bring surface moisture up into the higher
terrain.
Have mostly kept with the PoPs from previous overnight forecast. A
few isolated showers and thunderstorms may occur this afternoon
before 5 PM. However, the most showers and thunderstorms will
likely be after 5 PM and into the overnight hours. Have some 50
PoPs in the far western FA with gradual decline into the east to
start out. Another disturbance will likely bring some 30 to 40
Pops in the eastern to northeastern FA after midnight. There is
some concern for severe storms mainly through 8 PM.
Depending on which model you believe there could be some severe
hail up to an inch possible in a storm or two, but severe wind
will be the main threat. Some models like the HRRR have surface
based CAPE capped off, and when the upper level disturbance moves
across the storm will most likely be elevated leaving the
effective CAPE around 1000 J/KG or less. The RAP on the other
hand has uncapped SBCAPE around 1800 J/Kg between 3 PM and 5 PM
in the NE, 1400 J/Kg in the NW and around 800 J/Kg around
Amarillo. After 6 PM the RAP starts to cap off surface based
convection and are left with 1200 J/Kg of effective CAPE. With
freezing/melting levels around 10,000 feet, one inch hail making
it to the ground will most likely be an isolated event if a storm
manages to produce severe hail. The one thing storms will have to
help with severe potential is DCAPE over 1000 J/Kg. On the other
hand, it is looking like Bulk Shear of 30 plus knots could keep
storms from collapsing on themselves and creating microbursts.
Bottom line is severe storms will be possible especially closer to
the 5 PM to 7 PM time frame. However, wide spread severe is not
anticipated at this time.
Hoffeditz
LONG TERM...Monday through Sunday.
Not much has changed in the long term from what was seen 24 hours
ago. The upper level ridge of high pressure is forecast to remain
centered around southern NM and far west Texas through Wednesday,
then slide eastward to west central Texas and expand northward by
Thursday and persist into next weekend. As this occurs, north
northwest flow aloft will gradually transition to more westerly by
the latter part of this week into the weekend. As a result, there
will be a continued threat for mainly late afternoon and nighttime
showers and thunderstorms across much of the area, with the
greatest likelihood expected in the western zones. NBM pops seem
plausible and were generally incorporated into the grids. In
addition, max temperatures over 100 degrees are forecast to return
to at least parts of the OK and TX Panhandles Thursday through
the weekend as the upper level ridge of high pressure expands
northward with a corresponding rise in the height fields.
02
&&
.AMA Watches/Warnings/Advisories...
TX...None.
OK...None.
&&
$$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
950 PM MDT Sun Aug 2 2020
.UPDATE...
Issued at 946 PM MDT Sun Aug 2 2020
Well, spoke to soon from early this evening as isolated strong to
severe storms developed across Elbert and Lincoln counties this
evening. Have had reports of damaging winds and large hail across
central Lincoln county late this evening but expect last storm to
be out of our county warning area around 1030 pm. Storms seemed
to fire on some outflow boundaries and we did have support of 45kt
jet streak over the area. Elsewhere, just a few light rain
showers over the higher mountains. Should be a quiet for the rest
of the night after the Lincoln county storm moves out.
UPDATE Issued at 642 PM MDT Sun Aug 2 2020
Have cancelled the severe thunderstorm watch for much of our
county warning area, except Lincoln county where an isolated
severe storm will hang around until 730 pm. Just a bit too stable
on the plains as earlier cloud cover over the Front Range kept us
too cool. 00Z DNR sounding not very impressive with still weak low
level stability. Mountain convection has also diminished with only
isolated light rain showers remaining. Have updated forecast for
lower pops this evening and removed the watch. Expect the Lincoln
county watch to go away by 8 pm.
&&
.SHORT TERM...(This evening through Monday)
Issued at 235 PM MDT Sun Aug 2 2020
Forecast still on track with strong storms developing over the
foothills. Low level moisture hanging on with dew points in the
lower to mid 50s north of Denver. This air mass is still weakly
capped, but the northerly component to the flow aloft is keeping
most of the clouds over the mountains. We`re still on track to
have enough CAPE for large hail. The one complication is not a
surprise. The HRRR is now trending toward more foothills
convection pushing an outflow boundary eastward in the mid to late
afternoon hours, before a storm drops southward out of Wyoming.
This is probably right. Depending on how fast it comes eastward,
it may be a little earlier than optimal for severe storms against
the foothills. This might push the greatest risk a little further
east--along or a little east of I-25. Another thing pointing to
this is that the easterly flow isn`t that strong in the I-25
corridor, it gets better further east. But the current storm over
the foothills is already pretty strong, so there is some severe
risk across the watch area. Main threat still looks to be hail
with moderate CAPE and shear. We`re seeing some heavy rain, but
the storms should move fast enough to limit the flood threat to
minor street flooding.
This afternoon`s convection should progress southeastward this
evening and be out of the area by about midnight. Monday looks
much like today, though a little warmer and drier so the storm
intensity might be more marginal again with a bit less of a hail
threat and a little more wind threat. Forecast highs are 3-5
degrees warmer and a little above guidance, which looks good.
.LONG TERM...(Monday night through Sunday)
Issued at 235 PM MDT Sun Aug 2 2020
On Tuesday, a persistent pattern will continue with an upper
level over the Desert Southwest with a northwesterly flow aloft
over eastern CO. ML CAPES still high with values 2100-2500 j/kg,
and precipitable water values at or above 1 inch. SPC keeps
eastern CO under a marginal risk of severe thunderstorms for
Tuesday. Large hail and damaging wind gusts the main threat. A
weak short wave is progged to pass to the north and east of CO
around 00z Wednesday with a weak front pushing into the northeast
plains. Temperatures on Wednesday will be a couple of degrees
cooler. The synoptic pattern remains similar as well. The airmass
over the northeast plains may be more stable with a slightly
cooler airmass in place. Focus at that time may shift more to the
Palmer Divide area. Thursday into Friday, a long wave trough move
onto the west coast, with the ridge axis getting pushed eastward
over the Southern Great Plains. The flow aloft over CO will
transition to southwesterly, with weak embedded short wave,
possibly moving southwest to northeast across the state late
Thursday into Thursday night. Friday through Sunday, the ridge
will be centered over Texas. Moisture around the ridge at that
point may shift more to eastern and southern CO, with a drier
airmass over the mountains. This will result in warmer
temperatures and less thunderstorm coverage in the afternoon
and evening.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 946 PM MDT Sun Aug 2 2020
VFR with mainly clear skies over night. surface winds shifting
drainage from the south and southwest at terminals. Another round
of storms possible for later Monday afternoon.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Entrekin
SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...Entrekin
Area Forecast Discussion
National Weather Service Boston/Norton MA
1043 PM EDT Sun Aug 2 2020
.SYNOPSIS...
A warm sultry air mass will be in place tonight through Tuesday.
Isolated severe thunderstorms are possible this evening in
western MA and northern CT. Mainly dry weather Monday. Showers
and a few thunderstorms, will develop Monday night, mainly in
western MA, ahead of Isaias, which is expected to impact
southern New England Tuesday night with heavy rain in western
areas and gusty winds in eastern areas. Heading into late week,
temperatures remain warm, but more comfortable with lowering
dewpoints.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
1030 PM Update...
No major changes in the latest update other than tweaking
precipitation chances based on the latest HRRR and other short
term high res guidance and expiring the Tornado Watch at 10 PM. Rest
of the forecast remains on track.
8 PM Update...
What an active afternoon of severe weather in the CT River
valley! WPC surface analysis shows a warm front just west of
I-91 corridor over Western MA/CT. A combination of 250 m2/s2
0-1km storm relative helicity, backed surface flow from the SSE,
40 kt effective bulk shear and 2000 J/kg of MLCAPE created a
favorable environment for severe thunderstorms that produced a
couple of tornadoes in Southern Berkshire county and Western
Hampden county in Massachusetts. The current Tornado Watch
coverage and forecast are still on track. Scattered
thunderstorms with heavy downpours are possible through midnight
then we are left with dry and very muggy conditions for the rest
of the night with overnight lows in the low to mid 70s and dew
point in the upper 60s to low 70s.
PREVIOUS DISCUSSION...
445 PM update...
Tonight...
A Tornado Watch is in effect for Hartford, Tolland, Hampden,
Hampshire, and Franklin Counties in northern CT and western MA
until 10 PM. Storms will be isolated due to mid level dry air
over eastern NY and lack of forcing. However, low level
helicity is very strong and any storms that do develop will
likely exhibit rotation this evening. Surface winds are still
backed somewhat in the CT River Valley, from the SSE, with SW
flow at 30-40 kt at 850 mb.
Elsewhere, scattered thunderstorms with heavy downpours will be
moving through eastern MA this evening, but not expected to be
severe.
Later tonight, low level southerly flow will keep temperatures
up, in the mid 70s with areas of fog in eastern areas.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Monday...
Monday should be mainly dry with westerly winds drying things
out briefly with dewpoints dropping to the mid 60s except still
lower 70s along the coast. Highs in the 80s.
Monday night...
Moisture flows rapidly into the region out ahead of Isaias.
There should be a round of showers and perhaps thunderstorms in
northern CT and western MA. Additional activity is expected to
move along the same area. Scattered showers could impact eastern
areas as well.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Highlights...
* Tropical Storm Isaias moves into southern New England Tuesday into
Wednesday
* Threats: Heavy rainfall, gusty winds, and minor coastal flooding
possible
* Quiet weather post Isaias and comfortable temperatures.
The focus of the long term focus continues with Tropical Storm
Isaias and the possible impacts it could bring to southern New
England. As of Sunday afternoon T.S. Isaias was located about 975
nautical miles (1,123 miles) southwest of Martha`s Vineyard. The
official track from the National Hurricane Center (NHC) does bring
Isaias into our neck of the woods sometime late Tuesday night
through early Wednesday morning. Steering Isaias into the northeast,
a Bermuda high (1020mb) and a frontal system extending along the
east coast. Now, there is still a bit of uncertainty with the track.
A western track would bring Isaias into northeast Florida/southeast
Georgia, then move inland thought the Carolinas. This time overland
would help to considerably weaken Isaias. An eastern track would
keep Isaias over the warmer waters before making landfall along the
outer banks of North Carolina, likely maintaining the strength of the
storm.
As previously discussed, the chances of Isaias remaining a tropical
storm as it reaches MA/CT/RI are continue to diminish. NHC has the
probability of tropical storm force winds between 20 and 30 percent;
with the most likely arrival time Tuesday evening. We did cap our
sustained wind speeds at 35 kts and wind gust to 45kts. It wouldn`t
be out of the question for an isolated gust or two to 50 kts. At 925
mb winds are 60kts to 70kts. Strongest winds will be located to the
east of the track. West of the track the the bigger threat will be
rainfall. Good news, as previously stated Isaias will be moving
through fairly quickly; the central low pressure is in and out in 6
hours. Additionally, heavy rainfall many end up occurring in
narrower/localized bands that amount between 2" and 4" - with
locally 6".
The second half of the week is fairly quiet with high pressure
returning and leading to drier weather. Warm with temperatures in
the low and middle 80s and muggy on Wednesday with dewpoints near 70
degrees. Mid 80s Thursday and Friday with dewpoints near 60 degrees;
talk about refreshing!
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
2345Z update...
Tonight...Moderate confidence
MVFR CIGS expected throughout, with areas of fog in eastern MA
and RI late. Isolated thunderstorms, some strong to locally
severe, with local IFR before midnight. Some improvement with
dry conditions throughout the region after midnight.
Monday...High confidence. VFR.
Monday night...Moderate confidence. VFR to start with scattered
showers and isolated t-storms mainly in western MA & northern
CT late. Areas of fog possible late near the south coast.
KBOS Terminal...Moderate confidence in TAF. Scattered tstms this
evening.
KBDL Terminal...Moderate confidence in TAF. Low risk for tstms,
possibly strong through 03Z.
Outlook /Tuesday through Friday/...
Tuesday: Mainly VFR, with local IFR possible. Breezy. Chance
SHRA, chance TSRA, patchy FG.
Tuesday Night: MVFR/IFR conditions possible. Strong winds with
gusts up to 50 kt. Chance SHRA, patchy BR.
Wednesday: VFR. Breezy. Chance SHRA.
Wednesday Night: VFR. Breezy. Slight chance SHRA.
Thursday through Thursday Night: VFR.
Friday: VFR. Slight chance SHRA.
&&
.MARINE...
750 PM update...
Small Craft Advisories continue into Monday for gusty winds this
evening and then a period of 5 ft seas Monday, mainly over the
southeastern waters.
Seas could subside briefly to below SCA criteria Monday night,
before winds and seas increase in association with Isaias
Tuesday into Wednesday.
Outlook /Tuesday through Friday/...
Tuesday: Winds less than 25 kt. Local rough seas. Chance of
rain showers, patchy fog.
Tuesday Night: Low risk for gale force winds with gusts up to
45 kt. Rough seas up to 11 ft. Chance of rain showers, patchy
fog.
Wednesday: Winds less than 25 kt. Areas of rough seas. Slight
chance of rain showers, patchy fog.
Wednesday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers.
Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers.
Thursday Night through Friday: Winds less than 25 kt. Slight
chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT Monday for ANZ231>234-250.
Small Craft Advisory until 5 PM EDT Monday for ANZ235-237-
254>256.
&&
$$
SYNOPSIS...Gaucher/GAF
NEAR TERM...BL/Chai/GAF
SHORT TERM...GAF
LONG TERM...Gaucher
AVIATION...Gaucher/GAF
MARINE...Gaucher/GAF
Area Forecast Discussion
National Weather Service Columbia SC
723 PM EDT Sun Aug 2 2020
.SYNOPSIS...
A moist airmass will remain over the region today with isolated
showers and thunderstorms mainly over the western Midlands.
Rainfall may be enhanced late tonight into early Tuesday with
Tropical Storm Isaias moving northward off the GS/SC coast.
Chances of showers and thunderstorms will continue next week as
a cold front and upper level trough approach the area.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Air mass across the area moderately unstable. Frontal boundary
across the Carolina Mountains into north Ga. Trough across
central SC/CSRA Ga with resulting weak convergence and a few
thunderstorms have developed. These showers should be short
lived with limited forcing and latest HRRR suggests limited
coverage by 00z.
Tonight the upper level trough will continue digging into the
central Gulf states with the axis through the MS River Valley.
Along with this will be a weak surface trough over the southern
and central Appalachians keeping the forecast area under weak
subsidence early tonight. The chance of showers and possibly a
thunderstorm may increase toward morning as onshore moisture
flux/isentropic lift develops in response to Isaias moving north
along the northeast coast of Florida. Most areas should stay dry
most of the night. Overnight lows in the mid 70s.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
Monday and Monday night...Isaias will continue tracking north-
northwestward Monday morning then turn north-northeastward for
the afternoon. On the current forecast track it will be south of
Charleston during the evening then move onshore around midnight
and be east of Raleigh by daybreak Tuesday. A tropical storm
watch remain in effect for Clarendon and Orangeburg counties
from Monday afternoon into Monday night. The strongest winds
will be in far eastern Orangeburg and Clarendon
counties...mainly along and east of I-95...where sustained winds
of 30 to 40 mph with gusts to 50 mph will be possible with
winds rapidly diminishing west of that area. Heavy rainfall is
also expected and a flash flood watch remains in effect for
Chesterfield, Lee, Sumter, Clarendon, and Orangeburg counties
where rainfall amounts will be 1 to 3 inches with some locally
higher amounts possible. WPC has maintained the slight risk of
excessive rainfall for the eastern Midlands and Pee Dee with
concern as there will be a tight gradient just east of the
forecast area and any westward movement in the track could
result in higher amounts. With the clouds and rain high
temperatures will be held in the low 80s for the northern and
central Midlands with mid to upper 80s elsewhere and overnight
lows in the low 70s.
Tuesday and Tuesday night...Isaias will track away from the area
Tuesday with some subsidence during the morning and early
afternoon. The upper level trough will be sliding eastward with
weak surface troughing over the area through the day. Highest
chances of convection will be over the northern Midlands and Pee
Dee where the best moisture and instability will linger from
Isaias. High temperatures will return to near normal ranging
from the upper 80s north to the low 90s south and overnight lows
in the low 70s.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
A broad upper trough over the Mississippi Valley will slowly track
eastward into the area from Wednesday through the end of the week.
Southerly or SW low level flow will develop as a weak surface trough
lingers over the Southeast. GFS and ECMWF Ensemble mean PWAT values
are around 1.5" mid week with a gradual increase through the end of
the long term. These conditions favor at least a chance of showers
and thunderstorms each day. The highest rainfall chances should be
Thursday and Friday when the upper level trough axis will be
crossing the region. Convection may also occur outside of the
typical Summertime afternoon and evening timeframe. Several
shortwave troughs are expected to move through the base of the broad
trough and enhance convective activity. Near normal temperatures are
forecast with highs in the upper 80s to mid 90s and lows in the
upper 60s to mid 70s.
&&
.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
Complicated TAF period on hand as Tropical Storm Isaias
approaches SC. Expecting VFR conditions to prevail overnight
through about 10 or 11z. Moisture begins increasing across the
region rapidly thereafter, and some of the guidance develops a
stratus deck, especially at CAE/CUB. Holding off on anything
too significant right now, as guidance is too inconsistent.
Still, begin bringing CIG down (into MVFR) around that time at
all sites as clouds approach from the incoming system. Showers
are expected to begin in the morning at CAE/CUB/OGB, with a
later start time at the Augusta sites. Any shower is expected to
reduce vis & may bring CIG down for a period of time. Winds
will be out of the east to start the day, and increase & move
with the system, ending the period nearly out of the north at
CAE/CUB/OGB. Greatest impacts expected in the 20-00z timeframe,
as the system will make its closest pass to the area. Gusts are
expected, and may approach 25-30kts at OGB. Rain should quickly
taper and lessen in intensity as the system moves to our
northeast on Tuesday night.
EXTENDED AVIATION OUTLOOK... The center of Isaias should be
making landfall just beyond our TAF period. The system`s
impacts are skewed largely to the east side of the system, so
after landfall, we`re expecting conditions to improve gradually
at all TAF sites.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Tropical Storm Warning for SCZ036-038.
Flash Flood Watch from Monday morning through Tuesday
afternoon for SCZ016-029-031-036-038.
&&
$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99
Area Forecast Discussion
National Weather Service Cheyenne WY
540 PM MDT Sun Aug 2 2020
.SHORT TERM...(This evening through Monday)
Issued at 121 PM MDT Sun Aug 2 2020
Forecast concerns with this forecast package deal with severe
thunderstorms today...followed by critical fire weather conditions
Tuesday across Carbon County. See Fire Weather Discussion below
for fire weather concerns.
Currently...Stalled out frontal boundary lays along a line from
Pueblo to Laramie to Greybull this afternoon. East of the
front...afternoon dewpoints have climbed into the mid and upper
50s across areas east of the Laramie Range. To the west of the
front...dewpoints in the low 30s being reported. Current surface
based CAPE off SPC Mesoanalysis page showing 2000 J/KG along the
eastern slopes with no CIN in low level southeast upslope flow.
Current sfc-6km shear around 40-45kts in this area. Beginning to
see convection developing over northern Carbon County. In the
northwest flow...storms have been moving at a pretty good clip to
the south southeast.
HRRR and NAMNEST simulated radar has been very consistent on
storms developing over northern Albany County this
afternoon...then dropping SSE to the I-80 Summit towards 2-3PM.
Expecting this cell to go severe here over the next couple hours.
This cell looks to throw off an outflow boundary that moves east
into Cheyenne towards 23Z this afternoon. Given the shear and
instability...we need to be watching for additional storm
development over southern Laramie County. Storms continue into
this evening...dying off towards 8-9PM.
Need to be watching for possibility of a few tornado touchdowns
with these outflow boundaries enhancing spin. GFS 21Z sounding
was showing sfc-3km helicity at 230 m2/s2. These outflow
boundaries could enhanced low level helicity even more.
Conditions similar Monday across southeast Wyoming as that front
stays in the general area. A Marginal Risk area is identified for
our area Monday afternoon.
.LONG TERM...(Tuesday through Saturday)
Issued at 233 AM MDT Sun Aug 2 2020
Upper ridge rebuilds from the Four Corners to the Northern Rockies
mid-week, then slowly translates east into the Great Plains by the
end of the week. Consequently, the flow aloft backs from northwest
to southwest. Surface front draped near the Laramie Range through
mid-week, plentiful subtropical moisture and passing disturbances
aloft will produce scattered to numerous afternoon and evening
showers and thunderstorms over and east of the mountains Tuesday
and Wednesday. MLCAPEs of 1000-1500 j/kg and 0-6 km bulk shear along
and east of the Laramie Range will support marginally severe
thunderstorms producing hail and strong winds. Locally heavy rainfall
will be possible with precipitable water values exceeding an inch.
Convective coverage will become more widely scattered late in the
week as drier air aloft spreads west to east (precipitable water
values decreasing by a third of an inch). Less convection will
allow temperatures to warm to above seasonal normals with highs in
the mid 80s to mid 90s Friday and Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 525 PM MDT Sun Aug 2 2020
All TAF sites remain in VFR conditions. Sites KCYS and KLAR could
see thunderstorms starting at 0Z and ending around 02Z. Wind gust
could reach 25kts at KLAR from those storms. Otherwise, KRWL and
the rest of the Nebraska Panhandle sites will stay dry with light
winds mostly from the south; cloud cover will remain low ranging
from SCT to BKN at five thousand feet. Winds will increase for the
Nebraska panhandle sites around 17Z. For Wyoming, the chance of
showers increase in the afternoon which may lead to VCSH in the
next TAF issuance.
&&
.FIRE WEATHER...
Issued at 200 PM MDT Sun Aug 2 2020
Critical humidity continues across Carbon County this afternoon
with 1 PM humidity below 15 percent for several areas.
Fortunately...winds remain light as high pressure remains over the
area. Areas along and east of the Laramie Range will continue to
see daily afternoon chances for showers and thunderstorms through
the upcoming week. Carbon County (FWZ 303 and 304) starting to see
an increase in westerly winds Tuesday that could combine with low
afternoon humidity. Isolated to widely scattered dry thunderstorms
possible across western Carbon County Tuesday afternoon as well. A
Fire Weather Watch has been issued for FWZ 303 and 304 for Tuesday
afternoon for these conditions.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Fire Weather Watch from Tuesday morning through Tuesday evening
for WYZ303-304.
NE...None.
&&
$$
SHORT TERM...GCC
LONG TERM...MAJ
AVIATION...AW
FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Peachtree City GA
725 PM EDT Sun Aug 2 2020
.UPDATE...
Hi-res models are progging a convergence zone to set up across far
NE GA very early tomorrow morning and last well into the day. There
are differences in timing when the zone sets up, but both the ARW
and the HRRR are progging roughly the same area. So have taken
somewhat of a compromise and increased the pops overnight into
tomorrow across NE portions of the CWA.
Have also tweaked the hourly temps/dews to reflect current trends.
Will likely have to adjust temps/dews again later tonight.
&&
.PREV DISCUSSION... /Issued 322 PM EDT Sun Aug 2 2020/
SHORT TERM /Tonight through Monday Night/...
A broad upper trough extending from the Great Lakes to the Gulf
will persist through the short term. This will keep our forecast
area in a moist southwest flow aloft. Minimal impacts are expected
as Tropical Storm Isaias skirts the GA coast on Monday...mainly in
the form of increased pops. Enhanced tropical moisture associated
with the storm will remain east of the area...but have continued
chance to likely pops for the eastern portion of the forecast area
for Monday. Isaias exits the area overnight Monday, with drier
air filtering in behind it.
Increased cloud cover and convection on Monday will keep
temperatures notably cooler over much of northern and eastern
Georgia...with highs only in the upper 80s to near 90. West
central Georgia...being the farthest from the storm`s influence
can expect to warm back into the low mid 90s.
41
LONG TERM /Tuesday through Sunday/...
LONG TERM /Tuesday through Sunday/...
Only tweaks to the long term based on the latest guidance.
BDL
PREVIOUS DISCUSSION...
As a broad upper level trough builds over the eastern CONUS,
Isaias will continue to curve along the Atlantic coastline and
rapidly move away from the area through Tuesday.
The upper trough will remain centered over the Mississippi Valley
through the remainder of the period. At the surface a cold front
will enter northwest Georgia on Tuesday and slowly push south and
east before becoming stationary near the southern border of our
forecast area by Thursday morning. A slightly cooler and drier
airmass is expected to filter into the area behind the cold front as
it pushes into south-central Georgia. North Georgia will thus
experience marginally cooler temperatures (back to near
climatological normals), primarily during the morning, and slightly
lower dewpoint values through the remainder of the week. Scattered
diurnally driven convection is expected to continue each afternoon
and evening through the remainder of the week, with the highest
chances focused across eastern Georgia, which will be underneath the
the eastern periphery of the trough and southwesterly flow aloft.
King
&&
.AVIATION...
00Z Update...
Have raised the pops early in the morning. Hi-res models are
progging a convergence zone setting up across NE GA and
backbuilding through the day tomorrow. Winds may flip flop on
either side of due north overnight and speeds will be pretty
light, so just went variable. As soon as mixing begins, winds
should settle on the east side during the mid/late morning. A bit
more covective coverage expected tomorrow afternoon.
//ATL Confidence...00Z Update...
Med condfidence all elements.
NListemaa
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 72 88 68 90 / 40 70 60 20
Atlanta 73 87 70 89 / 30 60 60 20
Blairsville 66 78 62 82 / 50 70 60 30
Cartersville 71 87 68 90 / 40 60 50 20
Columbus 74 93 72 94 / 30 40 40 10
Gainesville 71 83 68 88 / 40 70 60 20
Macon 73 92 71 92 / 30 50 40 20
Rome 70 88 68 90 / 40 60 40 20
Peachtree City 72 87 69 90 / 30 60 50 20
Vidalia 75 87 72 94 / 60 80 50 30
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM/update...NListemaa
LONG TERM....BDL
AVIATION...NListemaa
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
637 PM CDT Sun Aug 2 2020
.SYNOPSIS...
Issued at 312 PM CDT Sun Aug 2 2020
A high amplitude pattern was noted across the CONUS and
Canada this morning. High pressure was located over Arizona with a
high amplitude ridge, extending north of this feature into eastern
portions of the NW Territories of Canada. East of this feature, a
high amplitude trough of low pressure extended from far Northern
Quebec, south southwest into the Arklatex. East of this trough, high
pressure was anchored over Bermuda with TS Isaias located just off
the Atlantic coast of Florida. West of the western CONUS ridge, low
pressure was located in the Gulf of Alaska with a trough extending
south to approximately 500 miles west of the Oregon coast. At the
surface...high pressure was centered over southern North Dakota. A
stationary front extended from north central Wyoming south southeast
into northeastern New Mexico. Skies were partly cloudy this
afternoon with abundant fair weather CU noted. Temperatures as of 2
PM CT, were in the mid to upper 70s.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 312 PM CDT Sun Aug 2 2020
The main forecast
challenge is minimal precipitation chances overnight tonight and
overnight Monday night. For tonight, in light of steep lapse rates
through mid evening, drier air has pushed into the area this
afternoon with dew points in the lower to middle 50s. This drier air
should limit thunderstorm development through the evening hours
across the forecast area. This evening, winds will shift around to
the east, then southeast, with some limited moisture advection
noted. This advection will be most pronounced in the west and far
northeastern forecast area. In the west, the latest NAM12 and GFS
solns, indicate some mid level warm air advection spreading into SW
Nebraska and Wrn Kansas overnight tonight. Couldn`t rule out at
least some isolated showers/thunderstorms in the far SW CWA
overnight, however, the bulk of this activity should be off to the
south in western Kansas. The CONSMOS and HRRR have a little hint of
fog formation toward daybreak Monday morning. The NAM12, GFS, MAV,
MET and SREF are not indicative of fog. That being said, will leave
out a fog mention with this forecast and advise the evening shift to
monitor model trends this evening. On Monday, winds will be light
from the south and southeast. Based on forecast H85 temps, highs
will be similar to this afternoons readings with slightly warmer
temps possible in the eastern panhandle. By Monday evening,
thunderstorms will develop over the higher terrain of eastern
Wyoming and northeastern Colorado. Increased mid level warm air
advection will spread east into the eastern panhandle and SW
Nebraska late Monday night. Inherited forecast had a mention of
isolated thunderstorms late Monday night. With the decent mid level
warm air advection and mid level moisture noted in these areas
overnight, do not see any reason to eliminate pops and they will be
retained in this forecast package.
.LONG TERM...(Tuesday through Sunday)
Issued at 312 PM CDT Sun Aug 2 2020
On Tuesday, a decent shortwave
will traverse the Dakotas, forcing a warm front through the forecast
area Tuesday afternoon into Tuesday night. This will lead to
thunderstorm development. The FB initialized with 70-80 POPs with
this forecast. Given the latest NAM12 and Euro solution, will limit
these to 50-60 percent. Even this may be too optimistic ATTM.
Northwesterly flow will continue through Thursday with periodic
chances for thunderstorms during the afternoon and evening hours.
Ridging will then build east late in the week, aided by a deepening
trough of low pressure along the west coast of the CONUS.
Temperatures will trend higher into the 90s Friday through Sunday
with drier conditions developing.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 636 PM CDT Sun Aug 2 2020
Isolated showers or thunderstorms may drift through southwest
Nebraska late tonight or early Monday morning (06z-14z). There is
also a slight chance for patchy fog across ncntl Nebraska (08z-
14z Monday morning) but this chance would appear to be less than
20 percent. Otherwise, high pressure centered over Manitoba will
continue to provide stable weather conditions across wrn and ncntl
Nebraska tonight and Monday.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC
Area Forecast Discussion
National Weather Service Portland OR
124 PM PDT Sun Aug 2 2020
.SYNOPSIS...An upper level trough will move across the Pacific
Northwest late tonight and Monday. High pressure returns late Monday
and should hold through Wednesday. This results in seasonal
conditions. A stronger trough is expected to move across the area
Thursday. This system will bring the highest chance of precipitation
to the northern half of the area in quite awhile. High pressure
returns next weekend.
&&
.SHORT TERM...Tonight through Wednesday...Early afternoon GOES-17
water vapor satellite loop showed a strong 500 mb ridge extending
from the the four-corners region to the Northern Rockies. Meanwhile,
a long-wave upper trough could be seen over the NE Pac with the
parent 500 mb low in the Gulf of Alaska. A few embedded short-wave
features continued to rotate through the upper trough. Early
afternoon visible imagery showed a narrow band of mid-level clouds
streaming across the area.
The short term looks to be rather benign as onshore low-level flow
varies in strength. The 12Z model runs are in good agreement with an
upper level trough moving across southern British Columbia and much
of the Pacific NW late tonight through Mon. This trough passage will
result in a deeper marine layer Mon and stronger onshore low-level
flow, especially through the Columibia River Gorge. 12Z GFS and
higher-resolution HRRR model soundings for KAST valid early Mon
morning suggest a fairly deep marine layer, up to around 5000 ft AGL.
Models do not generate much QPF over southwest WA and far NW Oregon
late tonight through Mon morning. In fact, the NBM 1-D viewer
suggests 0.01 at KAST Mon morning. Have added areas of drizzle for
much of the south Washington and north Oregon coast late tonight
through Mon morning as well as the Willapa Hills and far north Oregon
Coast Range. GFS 850 mb temps valid 00Z Tue look to be a couple
degrees cooler across the north compared to today. Thus, afternoon
temps will likely end up a touch cooler, especially in the southwest
Washington coastal valleys.
Models indicate slightly higher 500 mb heights Mon night and Tue and
weaker onshore low-level flow. The HREF low-cloud guidance and Hi-Res
ARW boundary layer condensation pressure deficit output indicate less
low cloud coverage Tue morning, with the coast, central coastal river
valleys and southwest Washington coastal lowlands the favored areas.
The 12Z models show a weak 500 mb trough developing off the north
California coast Tue. This will result in south mid-level flow into
southwest and south-central Oregon Tue afternoon. GFS model sounding
for a point near McKenzie Pass valid 00Z Wed indicates minimal to no
convective support. Tue looks to be a little warmer than Mon as 850
mb temps warm about 2C and with a little less low-level marine
influence. Not much change from Tue to Wed. The weak northern Cal
upper trough drifts inland Wed afternoon. The GFS and ECMWF generate
some spotty light precip near Willamette Pass late Wed afternoon.
This may be another case when convection develops around Diamond Lake
and brushes the far southern Lane County Cascade crest. There appears
to be just enough of a west component to the 700mb flow to keep any
thunderstorms just east of the crest. Weishaar
.LONG TERM...Wednesday night through Sunday...The most interesting
period will be late Wed night through Thursday. The 12Z deterministic
model runs and respective ensembles are in good agreement with a
deeper 500 mb trough moving across the area Thu. The 500 mb cluster
analyses show reasonable continuity with a somewhat negatively-tilted
upper trough impacting the Pac NW Thu. The CMC-dominated cluster
indicates higher 500 mb heights over the forecast area Thu, with the
brunt of the trough energy over southern British Columbia. Will not
side with this solution. The total mean 500 mb cluster shows
below-normal 500 mb heights extending more south, into far northwest
Oregon. This trough looks to be the best chance for more widespread
precip since at least late June. The NBM 1-D viewer gives about a 30
percent chance of at least 0.05 inches at KPDX Thu. This probability
falls to around 20 percent at KSLE. However, the 12Z ECMWF ensembles
show a much different story. A high percentage of the ensemble
members show a tenth of an inch or more at KPDX, with the mean around
0.25 inches. Should the ECMWF verify, it would be a welcome relief to
the overall fire danger across the area.
The trough axis moves east of the Cascades Thursday night into
Friday, with west to northwest flow developing aloft. Fri will be a
few degrees warmer, with afternoon temps close to normal values.
Would anticipate plenty of morning clouds, however. Larger model
differences in the deterministic runs crop up over the weekend. The
deterministic GFS shows another upper trough moving across southern
British Columbia Sat morning. The operational ECMWF is much weaker
with this feature, as is the GFS ensemble mean. Thus, would expect
the typical morning cloud/afternoon sun pattern with near-normal
afternoon temperatures. Weishaar
&&
.AVIATION...VFR across the region as surface high pressure
continues. Light and variable northerly winds inland and
southerly winds along the coast. Patchy fog is likely south of
KTMK starting around 03Z tonight. A weakening front will move
inland along the northern coast late tonight. Light drizzle and
reduced visibility north of KTMK is expected around 09Z. Onshore
flow will continue to move moisture inland. Mix of VFR to MVFR
ceilings are expected to fill in after 12Z.
KPDX and APPROACHES...VFR conditions are expected by 18Z. Marine
stratus to rebuild back into the northern Willamette Valley
between 12Z and 18Z. This will most likely materialize as low
end VFR, to high end MVFR. -BPhillips
&&
.MARINE...Southerly winds will continue into this evening as a
weak system moves toward Vancouver Island. Winds associated with
this system will not meet Small Craft Advisory criteria. However,
the warm air advection coupled with cold upwelling waters will
promote another night of poor visibility south of Tillamook.
High pressure to rebuild over the waters Monday night and persist
through much of the week. Gusty, afternoon northerly winds should
be expected. A weakening front may bring gusty southerly winds
to the waters Friday, but confidence in timing, duration and
strength of southerly winds remains low at this point. Overall,
expect seas to generally hover in the 3 to 5 ft range for the
next several days before climbing into the 5 to 7 ft range late
Thursday and into next weekend. -BPhillips/Neuman
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&
$$
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Area Forecast Discussion
National Weather Service Reno NV
116 PM PDT Sun Aug 2 2020
.SYNOPSIS...
Warm and dry conditions continue with gusty afternoon winds today
and Monday. A gradual cool down to near normal will occur through
the week with chances for thunderstorms returning the middle into
the end of the week.
.DISCUSSION...
Incredibly dry today, even by our usual dry summer standards.
Several midslope, ridge, and desert sites around the region only saw
humidity "recoveries" last night in the 10-20% range. This means
another afternoon today of single digit humidity values. Today
looks to be the worst of it, with a gradual return to normal dry
the early part of the week. The dry air along with a slight uptick
in the usual zephyr breezes (gusts 25-35 mph) today and Monday
will contribute to enhanced fire danger and localized critical
conditions. These conditions are not widespread or long enough in
duration for a warning, but be especially careful not to cause a
spark.
Speaking of fires, smoke from both the Stump Fire and Red Salmon
Complex in northern CA appear to be causing a larger area of hazy
conditions than HRRR smoke guidance is indicating, so have
expanded the haze/smoke areas south along the Sierra/Sierra Front
for the next 24 hours. Density of the smoke and air quality impact
depend on the fire activity, but currently the worst impacts
appear to be reaching southwestern Lassen County.
The ridge currently over the region is replaced by a saggy baggy
trough, going into the middle of next week. Recent ensemble
clustering is indicating this trough will be a bit deeper than it
previously looked with a gradual downward trend in temperatures to
near normal. With the trough deepening, we`re seeing a slower
advance in moisture increases. EPS PWAT is solidly showing a rise in
values by midweek, but it`s looking like thunderstorm chances are
best beginning Thursday, which aligns well with the NBM tstorm
guidance. With the dry air in place ahead of this, and lack of
deep moisture (PWAT values around 0.5"), hybrid storms are likely
with a definite concern for dry lightning starts. Storm coverage,
however, looks to remain isolated.
Overall pattern into next weekend would favor near normal
temperatures, with westerly flow aloft likely limiting thunderstorm
due drier air working into the region. -Dawn
&&
.AVIATION...
The biggest flight weather concern for this period will be some
reductions to slant-wise visibility on terminal approach. Smoke
from fires in northern California will continue to produce hazy
conditions for the next 24 hours, possibly longer if fire activity
increases.
Otherwise, typical afternoon breezes can be expected with dry, VFR
conditions. The chances of thunderstorms will be Wednesday and
Thursday as a trough moves into the region. However, these storms
will be isolated and limited to locations north of a Susanville
to Gerlach line and along the Sierra/Sierra Front of Mono County.
Boyd
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Sacramento CA
217 PM PDT Sun Aug 2 2020
.SYNOPSIS...
Dry and seasonably hot conditions are expected to continue across
the region through Monday. Cooling returns this week.
&&
.DISCUSSION...
Quiet pattern continues across interior NorCal as the region
remains sandwiched between the southwest ridge and a trough along
the PacNW. Today`s highs will peak in the upper 90s to around 102
degrees in the Valley and 70s to 90s in the mountains and
foothills. Daytime temperatures on Monday will trend a degree or
two cooler from today`s highs. With a moderate Delta breeze in
place, marine/Delta influenced areas will cool into the upper 50s
to low 60s this evening.
The upper trough is still slated to move through NorCal heading
into mid-week, resulting in a cooling trend and increased onshore
flow. Temperatures will cool to near or slightly below normal
Tuesday and as much as 5 to 10 degrees below normal by Wednesday.
In addition, models suggest the potential for a few showers or
thunderstorms across extreme northwestern Shasta County as the
upper level feature moves overhead. Locally breezy winds are
possible at times, especially through the Delta and adjacent
Valley locations.
Wildfire smoke from the Stump Fire and the Red Salmon Complex
could impact portions of Tehama, Shasta, Plumas, and Lassen
counties per latest HRRR Smoke.
&&
.EXTENDED DISCUSSION (Thursday THROUGH Sunday)...
Ensembles indicate weakening trough along the West Coast later in
the week into next weekend with dry weather continuing.
Temperatures are forecast to be a little below average Thursday,
then warm to a little above average next weekend.
&&
.AVIATION...
VFR conditions next 24 hours. Local southwesterly surface wind
gusts 20-30 kts vicinity Carquinez Strait/West Delta, and local
gusts 10-20 kts elsewhere 21Z-03Z Monday.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$