Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/31/20
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1159 PM EDT Sat May 30 2020
High pressure will bring generally clear skies (aside from a few
diurnal cu/strato-cu Sunday afternoon) and light winds under 10
knots. Winds will back from northwest to west to southwest with time
tonight into Sunday evening.
DTW THRESHOLD PROBABILITIES...
Issued at 324 PM EDT Sat May 30 2020
The initial surface ridging that developed over Southeast Michigan
in post cold frontal environment late Friday has now since faded and
generally expanded to the Mid Atlantic. Much stronger surface high
pressure exists over the Upper Mississippi River Valley and is being
forced by strong synoptic scale support of jet dynamics with
confluence aloft and differential anticyclonic vorticity advection.
Southeast Michigan remains sandwiched between these features at the
moment, influenced by the deep polar trough that is in place from
James Bay southward through Lake Huron.
Strong shortwave within broader H5 trough axis swung through the
Straits to N. Lake Huron as of 18Z. Numerous showers invof of Grand
Traverse Bay throughout the morning persisted due to combo of steep
900-800mb lapse rate plume, 1000-850 mb shoreline convergence, and
lead edge of 1000-500mb geopotential height fall region. For the
remainder of the afternoon, tail end to absolute vorticity max will
settle into the remainder of Southeast Michigan with axis of lower
tropospheric frontogenesis becoming organized north to south along
Thumb/Lake Huron shoreline due to the difference in diabatic surface
heating across land/water interface. Providing relatively greater
support for shower coverage in the Thumb between 19-23Z is pool of
higher 825-675mb ThetaE content that gets shoved southward in
advance of +65kt midlevel jetlet. HRRR soundings corroborate with
some better support for high based-low topped shower activity north
of I 69/east of I 75. Increased PoPs into entry level chance late
Coherent midlevel anticyclone center will settle to Lake Superior
tonight. Loss of depth to planetary boundary layer due to nocturnal
cooling will then allow for overwhelming increase in near surface
anticyclonic flow trajectories and systematic cold air advection
overnight complete with requisite increase in 900-800mb static
stability. A drying out of this layer will lead to extremely quiet
and sunny conditions Sunday. No environmental wind in the lowest
6kft agl will yield light northwesterly winds.
Significant low to midlevel thetaE plume will advance towards
Southeast Michigan from the west on Monday as southerly flow tries
to bust into the state. Some uncertainty with how fast the
warmer/moist midlevels will arrive. Current timing suggests Monday
will remain under a more influence of the anticyclonic trajectories.
However, there is some signal that enough warmth/moisture will bleed
in on southerly flow to allow for some overachievement potential on
Textbook warm advection wing is forecasted to track across Lower
Michigan Monday evening and Monday night. The warm advection will
likely support a mature MCS type structure tracking through northern
Wisconsin/U.P. during the day on Monday then for the forecast area
that evening. Convective updraft strength appears limited due to
lapse rates remaining at moist adiabatic with high static stability
in the lowest 3.0 kft agl. Quality and depth of moisture could be
impressive with PWATS spiking up toward a 1.5 inch. Most interesting
aspect is the potential for a longer duration convective rain Monday
night as the eastward push to the elevated warm front could be on
the slower side. Will need to monitor QPF trends for Monday night.
Current model signal suggests shortwave anticyclonic gyre rolling
across Southeast Michigan for a good part of Tuesday. Much warmer
and more humid conditions set for Tuesday with heat indices
approaching 90 degrees possible. A zonal cold front is then progged
to settle due southward late Tuesday/Wednesday morning. A severe
weather threat will exist conditional on timing of this cold front
boundary. Also, there appears to be some potential for a boundary
parallel flow that could bring a training of thunderstorm activity
during this timeframe.
Moderate northwest flow continues through the evening before
weakening late tonight. Small craft advisories are up for the
Saginaw Bay due to gusts around 25kts and along the Thumb due to
higher waves clipping the nearshore waters. Strong high pressure
builds over the region early Sunday and remains overhead through the
day Monday bringing quiet marine conditions for the period. Shower
and thunderstorm chances increase again late Monday into Tuesday as
the next low pressure system begins to move into the central Great
MI...Lakeshore Flood Advisory until 10 AM EDT Sunday for MIZ049-055-063.
Lakeshore Flood Advisory until 4 AM EDT Sunday for MIZ054.
Lake Huron...Small Craft Advisory until 10 AM EDT Sunday for LHZ441>443.
Small Craft Advisory until 5 AM EDT Sunday for LHZ421-422.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
You can obtain your latest National Weather Service forecasts online
Area Forecast Discussion
National Weather Service Hanford CA
132 PM PDT Sat May 30 2020
Low pressure will move northward along the coast today bringing
a threat of showers and a thunderstorms to the northern half of
the district. Another area of low pressure will develop off the CA
coast next week for continued seasonal temperatures and a chance
of showers in the Sierra.
Short term focus this afternoon will be the chance of showers and
thunderstorms in the Sierra and SJV, primarily north of Fresno
County. Current GOES17 mid-level water vapor imagery and 500 mb
RAP analysis is indicating a vorticity max moving into the
northern half of the district. In combination with decent
instability, SBCAPES of ~500 J/kg, will help initiate showers and
thunderstorms this afternoon. Storms will be capable of producing
heavy rain as well as small hail. Snow can not be ruled out in
the higher elevations above 10,000 feet toward the Yosemite area.
With the continued synoptic cooling aloft, high temperatures this
afternoon across the central California interior are very
pleasant, with mostly upper 70s to low 80s.
From Sunday into Monday, the NAEFS and deterministic models are
showing a trough setting up just offshore, keeping a cool onshore
flow in place and a chance of showers in the Sierra on Monday.
500 mb heights do slightly increase during this period, and
temperatures will trend back up to seasonal conditions by Monday.
From Tuesday through Thursday, deterministic models and ensembles
show an area of low pressure setting up off shore. This will
increase our chances of precipitation across the Sierra.
Temperatures will stay near seasonal averages.
Mountain obscuration in showers and storms over the Sierra Nevada
are possible through 03Z. Showers and thunderstorms are possible
in Merced and Mariposa counties after 19Z Saturday through 03Z.
Otherwise, VFR conditions will prevail across the interior of
Central California through the next 24 hours.
.AIR QUALITY ISSUES...
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.
Area Forecast Discussion
National Weather Service Marquette MI
746 PM EDT Sat May 30 2020
.SHORT TERM...(This evening through Sunday)
Issued at 342 PM EDT SAT MAY 30 2020
Still a bit chilly for the end of May across Upper Michigan this
afternoon as colder air aloft and morning CAA has allowed plenty of
low-level clouds across the region. RAP analysis and soundings
earlier this morning actually showed a very small amt of CAPE with
the low-level CAA and steep lapse rates. This aided the early
morning -SHRA given the relatively shallow saturation. As rising
heights, increasing 850mb temps, and sfc high pressure continue
across Upper Michigan, skies will continue to clear into this
afternoon. Expecting temperatures to increase this afternoon
slightly under increasing sunshine, but should remain generally in
the 50s with low 60s across the south.
With sfc high pressure tonight and generally lighter winds expected
tonight, opted to issue a frost advisory across much of the CWA.
Model guidance was a little separated with deterministic and BC
guidance suggesting a little warmer lows than MOS and adjusted MOS
guidance. Looking upstream and running backwards HYSPLITs suggest
our airmass tonight will be similar to that over Dryden, Ontario
(CYHD) last night. The winds last night there remained near 5kts or
so with a little more clouds than were expecting here tonight. Their
lows fell to around 34F last night which brings the best chances for
frost tonight across much of the interior, away from the Great Lakes.
By tomorrow, high pressure will be over Upper Michigan with mostly
sunny skies expected. There may be some clouds across the far east
in the morning on the edge of an exiting shortwave and mid-level
ridge shifting east. Model soundings backed off slightly on deeper
mixing tomorrow, with mixing up to 5k-6kft. With this, raised the
Tds only slightly from the going forecast, but still on track to
bring minimum RH values into the mid 20s tomorrow across the
interior. High temperatures will be generally in the 60s with low
70s across the west and south.
.LONG TERM...(Sunday night through Saturday)
Issued at 339 PM EDT SAT MAY 30 2020
Models suggest that the high amplitude pattern with a ridge from the
Southern Plains to northwest Canada and a trough through Quebec and
the mid Atlantic will become more zonal through much of next week as
the ridge expands through the southern CONUS. Models then indicate
the pattern will become amplified again next weekend as a deep
trough digs into the West Coast, inducing a broad amplified
downstream ridge across much of the central CONUS. Temps will climb
above average next week and likely remain that way into next
Beginning Sun night, high pressure over the western Great Lakes will
continue the dry conditions over the area. The approach of a
shortwave rounding the Plains ridge and the WAA/isentropic ascent
response ahead of it should result in increasing mid-high clouds
from the west after midnight. The increasing clouds combined with
increased low-level mixing should keep min temps from dropping off
too much. Expect readings generally in the 40s.
Mon-Tue, models generally in good agreement showing thickening
clouds and increasing rain chances in association with the northern
Plains shortwave moving through the area, especially Mon afternoon
into the Mon evening, supported by strengthening WAA and moisture
transport. Elevated instability should generally remain farther to
the south and west, but could be enough elevated CAPE (near 400
j/kg) to support isolated thunderstorms near the Wi border. Most
places should see overall rainfall amounts in the 0.10-0.25 inch
range, although amounts up to 0.50 could be possible south with any
t-storms that occur. Increasing clouds will help keep max temps in
the upper 60s and lower 70s Mon. Much warmer air will move in Tue
with drier conditions as 850 mb temps climb to 14C-17C supporting
inland temps into the mid and upper 80s west and the mid 70s east.
Wed-Sat, confidence is lower given model differences and variability
in handling any additional shortwaves moving through the area. Right
now it looks like a shortwave moving through the area could bring
shower and possibly t-storm chances on Wed with another shortwave
bringing in another round of showers late Thu into Fri time frame.
At some point next weekend, most likely late Sat into Sun, the
deterministic GFS and ECMWF advertise a more vigorous shortwave
rounding the Plains ridge into the Upper Great Lakes resulting in a
strengthening WAA southerly flow and increasing moisture return and
instability to support showers/t-storms into the area.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 744 PM EDT SAT MAY 30 2020
SKC will roll into Upper Michigan over the next few hours as high
pressure and dryer low levels continue to work their way into the
region. Gusty winds blo 20 knots have ended for today, although they
will return again tomorrow. VFR conditions will last at all TAF
sites through the TAF period.
.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 148 PM EDT SAT MAY 30 2020
Northwest winds will back more to the west by this evening as high
pressure moves over Upper Michigan. This high pressure will then
linger over the lake for Sunday bringing west to southwest winds
over the lake. A warm front on Monday evening may bring gusts up to
25 knots from the south across the east half of Lake Superior,
otherwise winds are expected to remain blo 25 knots through the rest
of the forecast period.
Frost Advisory from midnight EDT /11 PM CDT/ tonight to 9 AM EDT
/8 AM CDT/ Sunday for MIZ002-004>007-009>014-084-085.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
449 PM PDT Sat May 30 2020
.SYNOPSIS...Scattered showers and isolated thunderstorms will
continue through late afternoon as an area of low pressure passes
across the Bay Area. Precipitation is expected to end by this
evening as the low shifts north of the area. Seasonable to
slightly below normal temperatures are forecast for Sunday into
Monday, along with dry conditions. Midweek warming is then likely,
especially inland, although the magnitude of the warming is
uncertain at this time.
.DISCUSSION...As of 1:35 PM PDT Saturday...The center of an upper
low is currently passing directly over the SF Bay Area as it
continues to move to the northeast. KMUX radar indicates shower
activity has been increasing since late morning, especially across
interior portions of the East Bay where heaviest showers are
currently located. In addition, an isolated thunderstorm recently
developed over Henry Coe State Park in eastern Santa Clara County
and a cloud flash was recently detected near Clayton in Contra
Costa County. Isolated thunderstorms will likely continue for the
remainder of the afternoon.
Rain totals from last night and today have generally been less
than a tenth of an inch. The exception is in the Santa Lucia
Mountains near the Big Sur Coast. Upslope precipitation
enhancement near the Big Sur Coast has resulted in rain totals of
between a quarter and a half inch. One location in far southwest
Monterey County (Three Peaks) has picked up nearly an inch of
The upper low is forecast to accelerate to the northeast by late
this afternoon and most models indicate shower activity will
quickly come to an end by early evening. However, the latest HRRR
keeps isolated pockets of light rain near the coast well into the
evening hours. Considerable low level moisture left over from
this system will likely result in widespread low cloud cover
The upper low will have moved well to our northeast by Sunday,
and dry weather is expected to return to all areas. However,
temperatures will remain slightly cooler than normal through
Monday as the next trough deepens offshore along 130W. Also,
residual low level moisture and onshore flow may mean persistent
low cloud cover in coastal areas into the afternoon hours.
The trough will continue to deepen offshore and form a cutoff low
off the southern California coast by Tuesday. It is at this point
when the models diverge significantly on temperatures. The ECMWF,
which develops the cutoff low farther offshore compared to the
GFS, and therefore develops higher highs and a warmer airmass over
California, forecasts significantly warmer temperatures than the
GFS from Tuesday through Thursday. The model temperatures
differences peak on Wednesday when the ECMWF MOS forecast high
temperatures are anywhere from 10 to 15 degrees warmer than the
GFS MOS guidance. The model blend (NBM) temperatures are in
between, as would be expected, but slightly favor the warmer
ECMWF. The NBM temperatures are probably the best option for now.
In the longer range, models agree that another trough will
approach from the west late in the week, ejecting the cutoff low
to the east. The latest GFS develops precip across the far
southern portion of our area late on Thursday as the upper low
moves inland across southern California. Rain chances then develop
across the northern portion of our area next weekend as that next
trough moves in.
.AVIATION...as of 4:48 PM PDT Saturday...for 00z TAFs. Scattered
showery activity is ongoing around the Bay Area, but the heaviest
of rainfall is done. Lingering showers will continue for the North
Bay as the system moves northeastward out of our region. Winds
have already begun to switch to the northwest behind the center of
low pressure and will continue to do so through the evening. Cloud
cover will remain overnight. Most terminals will be MVFR, with
isolated areas becoming IFR. VFR returns Sunday afternoon, with
clouds remaining in the area above 3000 ft AGL. Winds will be more
predominantly onshore and breezy in the afternoon.
Vicinity of KSFO...With the exception of a few low clouds,
conditions are VFR with strong southerly winds. Scatter showers
remain east of the terminal, and are decreasing. Lingering shower
activity is expect tonight in the North Bay as the system moves
northeast. Winds will slowly shift to the west through the
evening, before easing overnight. Expect lowering cigs after 9z
for MVFR conditions overnight. Cigs will lift above 3000 feet
after 18z Sunday, but expect cloud cover to linger. Winds will be
out of the northwest and breezy in the afternoon.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR with clouds bases above 3500 feet. A
few weak showers are over the ocean, but not expected to impact
terminals overnight. Cigs will lower to MVFR after 4z, with IFR
cigs possible early Sunday morning. A return to VFR Sunday
afternoon as onshore winds return with a few stronger gusts in
the Salinas Valley tomorrow.
.MARINE...as of 01:56 PM PDT Saturday...Low pressure west of San
Francisco will bring scattered showers and possible thunderstorms
through the afternoon hours. Moderate southerly winds along the
inner waters will turn southwest tonight and decrease. Northwest
winds will increase Sunday and Sunday night. A mixed northwest
swell and a building southwest swell will impact the waters
through the weekend.
SCA...Pigeon Pt to Pt Pinos 0-10 nm
PUBLIC FORECAST: Dykema
MARINE: W Pi
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Area Forecast Discussion
National Weather Service Riverton WY
545 PM MDT Sat May 30 2020
.SHORT TERM...Tonight through Sunday Night
This afternoon and evening look to be fairly active with widespread
convection. SPC has much of our CWA in a marginal risk, with the
exception of our southwest zones. A well developed circulation just
off the San Francisco Coast will move northeast through tonight and
morph into an open wave/vigorous shortwave. This shortwave will
track northeast across western Wyoming by 15Z Sunday. In addition, a
"ridge rider" or vort max will crest the exiting ridge across our
northern zones around 00Z this evening ahead of the main approaching
shortwave. This means two distinct periods of convection and two
distinct areas of enhanced convection. The HRRR depicts the first
thunderstorms to lead off this afternoons performance across
Sweetwater County by as early as 18Z this afternoon. This activity
will eventually migrate into juicier air over our northern and
eastern zones by 00Z this evening, coincident with the
aforementioned lead vort max. The highest capes are progged to be
over northeast Natrona and Johnson Counties between 21Z and 03Z this
evening. The GFS has been insistent on placing a bulls eye of higher
precip over southern Johnson County between 01Z and 03Z this evening
for the last couple of days. PW values are 160 percent of normal. It
could be that right around 00Z, when the "ridge rider" vort lobe
rides right over the ridge axis, which will likely be overhead by
00Z this evening, could slow down these anticipated heavy rainers
enough to where we actually do see some copious amounts of rainfall
in the area of the progged bulls eye over Johnson County as depicted
by the GFS. Something to watch for anyway. In addition, lifted
indices are progged to be -7 in northern Johnson County by 00Z this
evening (-9 in nearby Sheridan County).
Lifted indices of -4 are expected in far western Wyoming as early as
18Z this afternoon (minus 6 in nearby eastern Idaho). However,
moisture and lift will not arrive in that particular area unto 00Z
this evening when the far west gets grazed by some thunderstorm
activity by the aforementioned lead vort lobe. Scattered less
intense thunderstorms are expected across the rest of the CWA this
afternoon and evening, more so east of the Divide, with the greatest
threats locally heavy rainfall, small hail, and gusty winds.
Then later tonight, the actual main shortwave trough tracks across
the CWA from the southwest. The increasing southwest flow will
become more difluent ahead of this approaching shortwave. The last
of the significant thunderstorm activity should be exiting our
northeast zones to the northeast by around 06Z tonight. By 04Z, the
second wave of thunderstorm activity associated more directly with
the main shortwave will move northeast over the southwest quarter of
the southwest zones. The HRRR depicts enhanced activity as late as
08Z tonight, with one enhanced area of thunderstorm activity over
South pass and the other over the Jackson area. Then this convective
activity will continue to march northeast across the northeast half
of the CWA in the form of decreasing shower activity before exiting
to the northeast in the wee hours of the morning.
The shortwave, as mentioned earlier, should come through around 15Z
Sunday morning tracking southwest to northeast. Then drier air will
filter in from the southwest behind it more anticyclonically,
leading to an influx of dry stable air for an enhanced critical fire
weather day. With southwest winds of 25 to 35 mph, minimum relative
humidity 13 to 15 percent east of the Divide and in Sweetwater
County, and some temperatures east of the Divide will ranging from
90 to 96 degrees (hottest temperatures so far this season), an RFD
may be needed for some of our zones for Sunday afternoon, especially
in areas that may not see much rainfall form todays thunderstorms.
Even though 700mb temps will climb to around 15C on both sides of
the shortwave, there will be more solar insulation Sunday. One side
note, northeast Johnson County could see a rogue strong thunderstorm
due to lingering dynamics and instability, with SPC placing this
area in a marginal risk. Sunday night will be clear and cool.
Another side note, we will continue to monitor area streams and
creeks as river stages continue to rise due to very warm ambient air
temperatures and anticipated rainfall on snow pack. Right now,
significant main stream river flooding is not anticipated, but river
stages due to spring run off conditions will continue to rise.
.LONG TERM...Monday through Saturday
Medium-range forecast models in very good agreement with overall
pattern evolution on the synoptic scale. Monday will find southwest
flow across the forecast area as an upper-level ridge axis stretches
north through the Northern Plains. Surface wind speeds Monday
afternoon should be similar to those seen Sunday with widespread
southwest 15 to 30 mph. Temperatures will be 15 to 20 degrees above
normal with the southwest and areas east of the Continental Divide
in the 80s to lower 90s. Temperatures will be cooler across the far
west where 700mb temperatures are 3-5C cooler. Monday and Monday
night will be dry although a stray shower cannot be ruled out across
the far northwest Monday night. Any stray shower would likely be
associated with the tail end of a shortwave set to swing through
Alberta. This tail end will drape west-to-east across the far north
Tuesday afternoon thereby improving shower and thunderstorm chances
across the far north. A weak frontal boundary will also begin a
southward trek Tuesday afternoon with a better push coming Tuesday
evening. Temperatures will be cooler Tuesday as this shortwave
dampens the upper ridge and the flow becomes more zonal.
This zonal pattern will prevail Wednesday and Thursday with
diurnally-driven convection anticipated. Temperatures will still be
10 to 15 degrees above normal. The next chance for more widespread
convection is likely to be Friday in response to an upper low off
the California Coast moving onshore and through the Great Basin
Friday. Moisture and instability will increase Friday and linger
Friday night as this feature approaches and cross the forecast area.
The track and timing of this system could impact the potential for
stronger convection, especially across southwest Wyoming, Friday
afternoon. Drier conditions along with a slight cool-down can be
expected Saturday in the wake of this upper low. The next upstream
system approaches the Pacific Northwest Saturday, which will again
place Wyoming in southwest flow aloft. Expect an increase in
southwest Wind in the Wind Corridor.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 544 PM MDT Sat May 30 2020
Convection already erupting across southwest Wyoming and then higher
terrain of central and northern Wyoming this afternoon. The
convection will begin to merge and intensify east of the Continental
Divide later Saturday afternoon with the potential for strong
thunderstorms. These storms are likely to produce small hail and
gusty outflow wind by early Saturday evening. Moisture profiles for
late May are plenty wet, so heavy rain will produce brief periods of
IFR/MVFR conditions between 00Z-04Z/Sunday. The best chance for
heavy rain will be at KCPR, and to a lesser extent KRIW and KLND.
All terminals to be VFR after 06Z/Sunday. A secondary weather
disturbance will approach from the southwest late Saturday evening.
After a dry afternoon, this secondary wave may provide an
opportunity for showers and a lone thunderstorm at KJAC toward
06Z/Sunday. Expect at least isolated light showers through the
overnight hours in association with this wave. Conditions dry out
around sunrise Sunday with much drier weather Sunday afternoon as
the moisture is shunted to our east.
Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.
A series of weather disturbances will cross Wyoming from southwest
to northeast between Saturday afternoon and early Sunday morning.
The showers and thunderstorms will produce brief bursts of heavy
rain, particularly over Johnson and Natrona counties, most likely
Saturday evening. Some thunderstorms could become strong east of the
Continental Divide. Coverage is expected to be much less across the
Teton and Yellowstone dispatch areas. Conditions turn drier Sunday
and Monday regionwide. Cooler air will slide into far west Wyoming,
while a return to southwest flow aloft will boost temperatures east
of the Divide. This southwest flow will also favor gusty southwest
wind across the High Desert District northeast into Natrona County
both days. The wind will further aid warming temperatures and lower
relative humidities. This combination could lead to elevated fire
weather conditions both afternoons. Smoke dispersal will be
excellent each afternoon for almost all areas, buy most definitely
across the windy areas of southwest and central Wyoming. The trend
Tuesday will be toward slightly cooler temperatures and at least
widely scattered afternoon showers and thunderstorms across the
Teton, Yellowstone, and northern Cody dispatch areas.