Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/04/21
Area Forecast Discussion
National Weather Service Charleston SC
1020 PM EDT Sun Oct 3 2021
.SYNOPSIS...
High pressure will remain the primary feature through Monday. A
complex storm system will then bring periods of unsettled
weather through the end of the week.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Late evening observations indicated dewpoint depressions between
0 to 2 degrees across most of the SC Lowcountry. The latest
round of observations line up well with recent runs of the HRRR
and LAMP. The HRRR and LAMP indicates that at least patchy fog
will develop across the SC Lowcountry late tonight. The updated
forecast will feature the addition of patchy fog across the SC
zones. Later updates may need to expand the mention of fog,
possibly with dense fog. Temperatures are forecast to cool into
the 60s during the pre- dawn hours.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
The upper pattern will become more amplified early to mid week
as a mid level trough digs into the Lower Mississippi River
Valley and eventually closes off into a low. The low will
meander in this region through Wednesday. A deep moisture feed
will keep anomalously high precipitable water values over the
area. This pattern favors higher than normal rain chances,
especially Tuesday and Wednesday. Scattered to numerous showers
with isolated thunderstorms are expected. While coverage will be
maximized during the day, activity could linger/persist
overnight as well. High temperatures will be in the lower to mid
80s with lows in the mid to upper 60s/near 70 closer to the
coast.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
The persistent mid level low over the Mississippi River Valley
will lift northward and open up to a wave Wednesday night into
Thursday, before the trough axis shifts east and becomes aligned
over or near the East Coast. At the surface, high pressure will
likely be centered north of the area while an inverted trough
or weak low meanders off the Southeast coast. Given elevated
shear, this low has a low chance of becoming tropical. Ample
moisture and occasional upper level energy passing through will
support at least scattered showers in the forecast each day.
Perhaps less coverage over the weekend with models hinting that
some drier air could arrive as ridging edges eastward and pushes
the best moisture off the coast. Temperatures are expected to
be within a few degrees of normal.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Prior to the 0Z TAFs, KCLX detected a sea breeze passing just
inland of KSAV, pushing to the west. Terminals are forecast to
remain VFR through the TAF period. Winds are forecast to remain
steady from the SSW.
Extended Aviation Outlook: The chance for periodic flight
restrictions, mainly in showers, will increase Tuesday through
late week.
&&
.MARINE...
Tonight: Southerly flow will prevail across the local waters,
with speeds no higher than 10-15 knots. Seas are expected to
average 2-3 feet.
Monday through Friday: Southeast winds will persist early this
week with speeds 15 knots or less. Seas will average 1-3 feet.
There is still some uncertainty in the late week period but
winds and seas will likely increase. The forecast will largely
hinge on the position and strength of an inverted trough/weak
low. At this time, conditions remain below Small Craft Advisory
criteria.
Rip currents: Residual swell energy from Hurricane Sam, plus an
onshore flow will result in a Moderate Risk for rip currents at
all beaches through Monday.
&&
.TIDES/COASTAL FLOODING...
Due to the upcoming new moon (10/6) and perigee (10/8)
astronomical tide levels will steadily increase this week.
Onshore winds could drive tidal departures up enough to produce
minor coastal flooding as early as Monday evening. The time
period of primary concern will come late in the week when the
astronomical tide peak coincides with northeasterly winds. This
could produce moderate coastal flooding in the late week time
period, primarily in and around the Charleston area.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...NED
SHORT TERM...ETM
LONG TERM...ETM
AVIATION...NED
MARINE...BSH/ETM
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1022 PM CDT Sun Oct 3 2021
.SHORT TERM...(This Evening through Monday)
Issued at 327 PM CDT Sun Oct 3 2021
A well-mixed afternoon has pushed temps into the 70s and allowed
dewpoints to fall into the 40s. Winds which have been a bit breezy
in areas across southwest MN and northwest IA will come down quickly
this evening under the ridge axis, leading fairly strong radiative
conditions until generally clear skies overnight.
Small potential that some minor surface-based smoke seen across far
northeast SD and southeast ND could leak in toward northern portions
of southwest MN during the evening, but 12z-15z HRRR smoke guidance
suggests this will be washing out within mixing conditions this
afternoon before it can make any serious inroads, but some of the
later guidance suggest will need to keep a watch on this area.
Otherwise, will have to watch tonight for some patchy fog
developing, but this should be mainly the lowest and most wind
protected areas near water that run the risk of mainly very shallow
fog development for a couple hours very late tonight/early Monday.
After any fog dissipates early in the day, strong ridging aloft
builds across the region on Monday, leading to a very pleasant fall
day with the proximity of the ridge axis keeping winds fairly light.
Before any real advection begins for moisture near the surface,
should be able to kick temps into the mid 70s to around 80 during
the afternoon.
.LONG TERM...(Monday Night through Sunday)
Issued at 327 PM CDT Sun Oct 3 2021
Monday night, continued westward advection to near-surface
moisture beneath the stabilized pattern aloft will yield a better
chance for fog and lower clouds developing in the low-level east-
southeast flow at least into NW IA. Should yield at least a few
more daytime stratocumulus near/east of I-29, with the stable
profile and slight cooling likely taking a few degrees of highs
from the prior day. Tuesday night likely to provide an environment
for more lower clouds and some fog near the edge/along easterly
upslope areas. Clouds likely to be even a bit more prevalent into
daytime hours Wednesday as deeper easterly flow develops north of
a closed low wandering south of the zonal ridge folded over
through the Great Lakes. Easily may be even a shade cooler
Wednesday, depending on clouds.
Upper low to the south retains at least a weak tie to the western
troughing, and a split dynamical filament shears across the area
Thursday. Could see a spotty bit of precip from mere presence of
this feature, but overall stability and somewhat lacking moisture
would suggest not much for coverage. Temps above normal, but fairly
similar to Wednesday with clouds in the mix and persistent
southeasterly surface flow.
Fairly strong consensus of another shortwave ridge present on
Friday, prior to more northern stream energy driving a cold front
across the area on Saturday. More dynamics north than south, and
will have to knock down the capping inversion somewhat to get
showers/thunder to develop. May need a but higher chance across the
Highway 14 corridor along the boundary, but for now a chance seems
sufficient. Both Friday and Saturday will be fairly warm, mainly
70s, but could be warmer Friday in southeast SD and Saturday across
northwest Iowa given 22-25C 925 hPa temps ahead of the boundary.
Have nudged temps up just slightly from initial blends to account
for this. By Sunday, some lower pops remain in the forecast mainly
due to timing uncertainty, but trends would surely suggest a mainly
dry period, somewhat cooler, with the next threat of precipitation
likely into the following week as the western trough/eastern ridge
pattern throws more energy our way.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1020 PM CDT Sun Oct 3 2021
With calm winds, can`t rule out some shallow fog later tonight,
mainly in low lying areas, but chances too remote to include
restrictions. Otherwise, light winds and VFR conditions expected
through the period.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...Chapman
LONG TERM...Chapman
AVIATION...Kalin
Area Forecast Discussion
National Weather Service Grand Rapids MI
1002 PM EDT Sun Oct 3 2021
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 330 PM EDT Sun Oct 3 2021
- Threat for swaths of locally heavy rain this evening/tonight
- Rain gradually tapers off Monday into Monday night
- Another round of rainfall expected Wednesday night into Friday
- Warmer than normal temperatures to continue
&&
.UPDATE...
Issued at 1002 PM EDT Sun Oct 3 2021
Coverage and intensity of showers has been rather limited so far
this evening and instability is now falling off. However slow
moving mid level circulation evident near the MI/IN border will
continue to generate areas of rain overnight. While the heavy
rain threat looks to have diminished, relatively high pops are
still warranted overnight.
&&
.DISCUSSION...(This evening through next Sunday)
Issued at 330 PM EDT Sun Oct 3 2021
- Threat for swaths of locally heavy rain this evening/tonight
An upper low can be seen in the vicinity of Southern Lake Michigan
this afternoon with a trough extending south to a vort max that is
now swinging northeast into Indiana. Showers and thunderstorms
have broken out in a fairly widespread fashion this afternoon in
the area ahead of the upper low and trough. Southwest Lower
Michigan is in line to see this activity move through this
afternoon and evening especially. Surface dew points are in the
mid 60s across the area with PWAT values around 1.50 inches. CAPE
values have reach the 1000-2000 J/Kg range and surface based LIs
are near -5 over Southwest Lower Michigan. We also are in the left
exit region of a jet streak moving through around 250mb. Bottom
line plenty of parameters coming together to produce showers and
storms and the threat of locally heavy rain. The probability
matched mean 24HR rainfall from the HREF would suggest many areas
through Monday morning will see 0.50 to 1.25 inches of rain with
some swaths of 2.00+ inches possible. No Flood Watch given
antecedent conditions that do not favor it. Feel we will handle
areas of heavy rain with short term areal Flood Advisories if we
need those. Overlapping swaths of rainfall will be where
advisories may be needed. A slow storm motion will aid in the
chance of locally heavy rainfall.
- Rain gradually tapers off Monday into Monday night
The upper low gradually moves south of the area on Monday and
fills into Monday night. So, the heavy rain threat will be
tapering off with time. Based on the 6HR probability matched mean
rainfall values from the HREF not expecting heavy rain tomorrow.
It should come to an end overnight tonight. Plenty of low clouds
hang on for Monday and Monday night, so the dreary weather will
likely continue.
- Another round of rainfall expected Wednesday night into Friday
We look to be dry for a bit from Tuesday into Wednesday as high
pressure nudges into the area from the north. A drying northeast
to east flow at the surface is expected.
Another round of rainfall is forecast though from Wednesday night
at least into Friday as an upper low moves our direction from
Arkansas and Missouri mid to late week. By Thursday the low/upper
trough will be moving in and by Friday it should be overhead.
Showers and a few thunderstorms can be expected during the latter
half of the work week. So, overall we will be in an active pattern
for awhile with a short respite on Tuesday/Wednesday. It appears
there could be more rain into the weekend with a cold front moving
our direction from the plains.
- Warmer than normal temperatures to continue
Normal highs this time of year should be dipping back into the
lower to middle 60s. 850mb temperatures do not change much the
next 7 day, roughly staying between +11C and +14C. We should see a
fair amount of days with highs in the 70s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 758 PM EDT Sun Oct 3 2021
MVFR cigs/vsbys becoming more widespread this evening then
conditions trending down further overnight to widespread IFR with
areas of LIFR. Cigs gradually lifting back to MVFR levels by
Monday afternoon. Scattered rain showers continuing tonight and
Monday but have left thunder out of the TAFs since the coverage
should remain very isolated.
&&
.MARINE...
Issued at 330 PM EDT Sun Oct 3 2021
We have issued a fairly short duration Small Craft Advisory for
Monday afternoon and evening north of Grand Haven. The worst of
the conditions, winds around 20 knots and 3-5 footers, will be
found up near Big and Little Sable Points. Winds in the higher
resolution models like the HRRR and the WRF-ARW have the best
handle on this event. North flow wind event will be driven by a
surface high in the Northern Great Lakes and a low in Northern
IN/OH.
Otherwise, there is the potential for areas of fog over the lake
as well with surface dew points (mid 60s) which are higher than
the lake surface water temps (lower 60s). Winds pick up a bit out
of the north tonight which may tend to temper the fog a bit, but
we will have to monitor lakeshore webcams tonight.
Winds after Monday evening look to be off shore much of the time
and below SCA criteria. So the marine concerns are essentially in
the first two periods tonight (fog) and Monday (waves/wind).
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory from 2 PM to 11 PM EDT Monday for
LMZ847>849.
&&
$$
UPDATE...Meade
SYNOPSIS...Duke
DISCUSSION...Duke
AVIATION...Meade
MARINE...Duke
Area Forecast Discussion
National Weather Service Gray ME
1056 PM EDT Sun Oct 3 2021
.SYNOPSIS...
Persistent clouds and scattered showers will continue tonight
as a frontal boundary remains stationary over the area. This
boundary will waver some on Monday and Tuesday for continued
mostly cloudy skies with chances for showers primarily over
southern areas. High pressure slowly builds in from the north
towards midweek for mostly dry and mild weather the second half
of the week.
&&
.NEAR TERM /OVERNIGHT/...
11PM UPDATE...
Made some adjustments to POP forecast based on latest radar
trends. Southern NH will get rain most of the night although the
northern edge will continue to get squeezed by the dry air
advancing from the north.
9PM UPDATE...
Just some small tweaks to the forecast based on current radar
and satellite trends. Drier air has pushed in from Waldo County
to Rangeley with some breaks in the cloud cover, but cloud deck
is making slow progress now, with not much clearing expected
further south. Rain will be on the increase over the next few
hours across southern NH, while the small area of showers across
Maine begins to pull off the coast with maybe some patchy
drizzle across SW Maine tonight, but should remain mostly dry
for the remainder of the forecast area.
5PM UPDATE...
Have updated the forecast early this evening to adjust pops
over northern New Hampshire and central portions of Maine where
periods of light rain will continue. Second area of rainfall
remains over southern New Hampshire. This region will receive
rain throughout the night and into Monday per latest mesoscale
models.
Otherwise, just minor tweaks to the ongoing near term portion
of the forecast.
ORIGINAL DISCUSSION...
The latest HRRR and HREF solutions depicts the stationary front
will begin to retreat southward to some extent overnight as
slightly drier air returns from the north. The focus for periods
of light rain will shift mainly to southern areas overnight
with rain likely over southernmost New Hampshire and scattered
showers elsewhere.
There will be patchy fog developing during the overnight hours,
most likely more than last night. Temperatures will bottom out
in the 40s north to the 50s south however there will be some
temperatures in the 30s over the far northern mountains with
scattered frost.
&&
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
An upper level trough and associated weak area of low pressure
at the surface will advance eastward on Monday and Monday night.
While light rain will be confined to southern New Hampshire
Monday morning, moisture will make another push towards the
north and east. This will allow for periods of rain and some fog
to advance into central New Hampshire and extreme southwest
Maine by late in the day.
The low cloud cover will prevent temperatures from climbing
higher than the upper 50s to lower 60s for afternoon high
temperatures in most areas. The coolest readings will be over
New Hampshire where the lowest cloud deck will be in place with
lower 60s over eastern areas where some sunshine will remain.
12Z guidance consensus suggests periods of light rain will be
limited mainly to southern New Hampshire Monday night as the
rain shield once again is on the move, this time drifting south
as a weak disturbance begins to exit the region.
QPF/Locally Heavy Rainfall: The rainfall may be heavy at times
tonight through Monday night over southernmost New Hampshire.
Currently, the ongoing forecast for one to two inches mean basin
average appears reasonable. With the precipitation falling over
a two day period, these amounts should not cause any issues.
However, minor flooding is possible and this portion of the
Granite State remains as a marginal risk in the excessive
rainfall outlook. Echoes should be fast moving, however training
is a possibility as the flow remains parallel to the front. Also
PW values will remain on the high side in this region as well.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
High pressure is set to move in quickly behind the exiting
system Tuesday morning. Along with it returns dry air. This
should shut off precip rather early Tuesday, with skies on a
thinning trend. NE areas will undergo this by mid-afternoon,
with the remainder of the CWA thinning by mid evening.
The clearing trend Tues night across central ME will lead to
temps falling into the lower 40s north of Augusta, with mid 30s
possible in the northern valleys with the chance of some frost.
To the south, have kept temps a bit warmer as long as clouds do
stick around, even then, it may just be a thin cirrus shield
remaining with mid clouds increasing into central New England.
Dry weather is then expected Wed through late week. The region
will be dominated by high pressure overhead. This keeps temps on
the mild side with highs warming towards 70 in the coastal plain
and overnight lows in the upper 40s to around 50. With
relatively calm winds and mostly clear skies under the high,
rad cooling could help drop temps a couple of degrees cooler
than current forecast/guidance. But even then, many areas will
keep frost free outside of the far northern valleys early this
week.
The next chance for area precip comes late this weekend. Sunday,
the slowly exiting high pressure will slide out of New England.
Whether it takes a more easterly slip or dips further south is
the debate between guidance. A more easterly drive would allow
return flow to combine with SW flow, introducing the slight
chance of showers amid good moisture transport. A southerly dip
would mean keeping this at bay. Plenty of time for this to
evolve given the complex blocking patterns, and have kept precip
chances low.
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Short Term...Cigs will lower overnight with most terminals
dropping to IFR/LIFR. Overcast skies and occasional -ra will
continue Monday with a mix of MVFR and VFR cigs. Lowest cigs in
the south. Conditions lowering once again to IFR/LIFR most areas
Monday night.
Long Term...Remaining MVFR Tues morning will trend VFR through
at least Sat night. The exception will be any nightly valley fog
that develops in the CT valley near KLEB and KHIE. Winds light
and variable.
&&
.MARINE...
Short Term...Long period swell from distant tropical activity
has entered the Gulf of Maine with seas topping out around 4 to
5 ft. A stationary front draped west to east across New England
will lead to to easterly winds tonight through Monday night
with gusts topping out around 20 kts Monday. Patchy fog will
restrict visibilities at times, mainly during the night.
Long Term...Waves briefly increase Tuesday night, before a
northerly wind shift takes them down, 2 to 3 ft. Winds and waves
are expected to remain below SCA through the period under high
pressure. The exception will be breezy winds in the afternoon up
to 15 kt.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM UPDATE...Kimble
SHORT TERM...Cannon
LONG TERM...Cornwell
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1159 PM EDT Sun Oct 3 2021
.UPDATE...
Issued at 1159 PM EDT SUN OCT 3 2021
Trimmed PoPs across the southwest as convection took a sudden
downturn in intensity and coverage. Otherwise, the forecast
remained generally on track. Only needed to tweak grids to
incorporate latest hourly obs. Updated zones and grids have been
issued.
UPDATE Issued at 1027 PM EDT SUN OCT 3 2021
Have been watching a broken line of showers and thunderstorms
pushing eastward across south central Kentucky and convection has
held together nicely. HRRR is currently showing this activity
holding together long enough to affect portions of our southwest,
though there continues to be a weakening trend in guidance
overall. However, HRRR has shown a tendency to weaken this
activity too rapidly through the evening, at least until the last
run or so. Beefed PoPs back up across the far southwest but did
trend PoPs lower as the activity moves through our southern zones
during the overnight. Increased QPF just a bit across the
southwest as well. Updated zones have been issued. Grids will be
sent shortly. No other changes at this time. Convection is
expected to continue to wane through the overnight as patchy fog
and lower clouds develop across the area.
UPDATE Issued at 805 PM EDT SUN OCT 3 2021
Seeing a general downward trend in shower and thunderstorm
activity across the area. However, still watching a band, or at
times, line of scattered showers and thunderstorms associated
with a surface cold front moving eastward into central Kentucky.
Model solutions and guidance suggest a general decrease in
activity as the line pushes eastward into eastern Kentucky, along
with a slowing of the front and eventual stalling out across
central portions of the Commonwealth. However, convection may
hold together just long enough to affect some of our most western
zones. Will watch and make necessary adjustments to the forecast
if the activity holds together longer than expected. Otherwise,
adjusted grids for latest hourly trends. Updated grids sent and
zones will be out shortly.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 512 PM EDT SUN OCT 3 2021
An upper level trough was over much of the eastern CONUS on
Sunday afternoon, with its axis over the upper Great Lakes, and a
shortwave trough rotating around it over the mid Mississippi and
lower Ohio Valleys. A surface low was over Lake Michigan, with a
cold front extending down the Mississippi Valley. Abundant
moisture was flowing north and northeast over our region, and
being acted upon by the shortwave and an associated upper level
jet max to bring rounds of showers and thunderstorms.
Models agree on the trough amplifying and closing off an upper
low over the lower Mississippi Valley during the period. The
frontal boundary will slowly advance southeast into KY, restricted
in movement by the stagnant upper air pattern. The shortwave
trough and jet affecting our area will move past on Monday.
Another round of showers/thunderstorms could affect the region as
it moves through, with the NAM being the most bullish on this late
tonight into Monday. After this, while precip can`t be ruled out,
support will be less and the POP will be considerably lower
Monday night, especially with loss of heating.
.LONG TERM...(Tuesday through Sunday)
Issued at 320 PM EDT SUN OCT 3 2021
The weather will remain unsettled Tuesday through the end of the
work week as an upper level low over the deep south slowly drifts
north during the week and eventually opens up into a broader trough
towards the end of the week into the weekend. This will keep the
chances of daily showers and thunderstorms in the forecast Tuesday
through Friday, with the highest chances for thunderstorms being
during the afternoon and evening each day. Rain chances finally
begin to diminish over the weekend as the trough axis moves east of
the area into New England and the Mid Atlantic.
High temps will be near seasonal norms Tuesday through Friday in the
low to middle 70s, before warming up to the mid and upper 70s for
the weekend. Overnight lows remain mild and above normal starting
off in the lower 60s Tuesday and Wednesday night and retreating a
bit to the upper 50s by the end of the week into the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 805 PM EDT SUN OCT 3 2021
Seeing a general downward trend in shower and thunderstorm
activity across the area. However, still watching a band, or at
times, line of scattered thunderstorms associated with a surface
cold front tracking eastward across central Kentucky. Model
solutions and guidance suggest a continued decrease in activity as
the line pushes eastward, along with a slowing of the front and
eventual stalling out. However, convection may hold together just
long enough to affect SME, less so LOZ but that is not out of the
realm of possibilities. Flight conditions worsen through the
overnight as mainly CIGS lower into MVFR, and for a short period
of time around dawn into IFR territory before lifting and
scattering out toward the end of the forecast window. Some light
mist leading to MVFR VSBYS will be possible as well. Winds will
generally be light and variable through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
UPDATE...RAY
SHORT TERM...HAL
LONG TERM...CMF
AVIATION...RAY
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
836 PM EDT Sun Oct 3 2021
.SYNOPSIS...
Broad upper level low over the Ohio valley will migrate
southward through midweek as high pressure develops across our
north. The combination of the two will yield a stationary front
across the area throughout most of the upcoming week. As a
result, daily chances for showers and thunderstorms will
persist as temperatures remain slightly above average.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Latest analysis shows a broad area of low pressure residing over
the Great Lakes region this evening as high pressure remains banked
off the Carolina coastline. As a result, an increase in
humidity continues thanks to a light southerly flow. Latest
satellite imagery depicts increasing high clouds across the
Alleghenies that continue to propagate eastward. Meanwhile,
latest radar loop shows a few showers continuing to move
northward out of north-central MD into southern PA while a
second batch of showers moves into southern Nelson county.
Latest runs of the HRRR have matched up well with current obs,
and indicate mostly dry conditions overnight for areas mainly
east of the Blue Ridge. Elsewhere, weak shortwave advection will
persist which will allow scattered showers to continue through
the overnight hours, albeit expecting shower activity to remain
light in nature. Patchy fog is expected to develop overnight
into the early morning hours Monday with overnight lows in the
mid to upper 60s for most, cooler across the higher terrain.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
With the aforementioned low pressure system tracking further
southeastward, stronger forcing will be available which will
help usher in better chances for showers and a few isolated
thunderstorms on Monday. Temperatures will be a few degrees
cooler with an extended period of increased clouds expected
before. Latest guidance continues to depict a line of
potentially convective storms by 18 to 21z on Monday, extending
from the Mason-Dixon line to our SW areas along and west of the
Blue Ridge Mountains and should persist further east over the
course of the afternoon into the early evening hours before the
loss of diurnal heating ceases the bulk of the convective
activity.
As we continue into Tuesday, forecast confidence diverges as
guidance solutions struggle to grasp the interaction of the low
residing across our southwest and high pressure to our north.
The Rex Blocking pattern appears to keep us more under the
influence of the high than the low, which would keep the CWA
drier than previously anticipated. However, given the
uncertaintyof the forecast, have kept the mention the showers
and thunderstorm chances status quo for the time being, until
greater confidence can be obtained. Temperatures will remain on
the mild side with highs in the upper 70s to low 80s both days
and overnight lows in the 60s.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A cold front is forecast to move through our area sometime on
Wednesday and become stalled to the south of our region through the
second half of our week. An upper low positioned over the southern
US on Wednesday is forecast to shift back north along the
Mississippi River area. High pressure positioned to the northeast of
the upper level low over the NE US will lead to a persistent on-
shore flow in our region. This onshore flow pattern will lead to
increase advection of moisture into our region. Skies will likely
remain mostly overcast through most of the long term period with the
possibility for periods of overnight advection fog especially along
the Chesapeake Bay.
The combination of the stalled boundary to the south along with the
upper low moving off to the west of our region will lead to
continued chances for rain each day in the long term. Based on the
positioning of the upper low as it moves off to the west and the
continued easterly flow, the heaviest precipitation will likely be
focused west of the Blue Ridge Mtns near the Allegheny front. There
remains some uncertainty on the strength of the onshore flow along
with the track the upper low will take as it shifts back northward.
If the upper low tracks further eastward, the heaviest rain would
shift over the metro areas where extended periods of rain could lead
to a flooding threat. As the flow will be mainly onshore and skies
will be overcast, think there is potential that statistical models
could overforecast on high temperatures this week and the raw models
will handle temperatures a little better. This would argue highs in
the 70s for the second half of the week with lows in the upper 50s
and into the 60s.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
A light southerly flow continues across the terminals this
evening with mostly VFR conditions. A few showers may arise
overnight over MRB and CHO. Otherwise, mostly dry conditions are
expected. Patchy fog is expected to develop overnight. However
confidence remains low if any of the terminals will be subject
to any low end CIG/VSBY restrictions overnight.
Mainly VFR conditions and a southerly wind continue throughout
the morning hours Monday. However, the development of showers
and thunderstorms are expected Monday afternoon into Monday
evening which may briefly result in CIG/VSBY restrictions.
There`s a better signal for more widespread fog overnight into
Tuesday with an increase in moisture and near calm winds.
Additional periods of sub-VFR conditions are possible on
Tuesday. However, confidence remains low at this time.
An onshore easterly flow will form on Wednesday as a front stalls to
the south of the region and high becomes positioned over the NE US.
Low stratus decks may lead to sub-VFR conditions Wednesday through
the end of the week. Rain will be possible each afternoon at all
terminals with CHO and MRB having the highest threat at this time to
receive the heaviest rain.
&&
.MARINE...
Increased winds overnight over the lower Chesapeake Bay and the
lower Potomac River as high pressure pushes further offshore to our
SE, yielding a SCA for these areas through Monday morning. A few
SMWs may be possible Monday afternoon if any isolated
thunderstorms make it to the waters. Otherwise, no other marine
hazards expected for the short term period.
High pressure over the NE US along with an upper level low to the
southwest of our region will lead to persistent onshore flow through
the second half of this week. The onshore flow will lead to the
threat for some marine fog Wednesday and Thursday. Sub-SCA
conditions expected at this time.
&&
.TIDES/COASTAL FLOODING...
Elevated water levels will persist through much of the week with
southerly flow initially and then easterly/onshore flow by the middle
portion of the work week.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 11 PM this evening to noon EDT
Monday for ANZ533-534-537-541>543.
&&
$$
SYNOPSIS...SOUZA
NEAR TERM...SOUZA
SHORT TERM...SOUZA/ADM
LONG TERM...JMG
AVIATION...SOUZA/JMG
MARINE...ADM/JMG
TIDES/COASTAL FLOODING...ADM
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
706 PM CDT Sun Oct 3 2021
.UPDATED for 00Z Aviation Discussion...
Issued at 654 PM CDT Sun Oct 3 2021
&&
.SHORT TERM...(This evening through Monday night)
Issued at 253 PM CDT Sun Oct 3 2021
Surface analysis this afternoon shows high pressure across the
Rockies starting to make its way eastward as a surface cold front
just east of the Mississippi River continues to move off to the east
in conjunction with a sharp upper level trough. A dome of high
pressure aloft over the Four Corners region is also nudging its way
northeast.
Over the next 24-36 hours, these deep ridging features will slide
east northeast, moving atop the Upper Midwest tonight through Monday
night. As the trough exits to the east, the lingering stratus deck
over extreme eastern MN into western WI will gradually erode to the
east and diminish, allowing clear skies to prevail late tonight
through tomorrow night. In addition, winds will diminish tonight
through late tomorrow morning, become light and variable during the
day tomorrow, then become nearly calm once again tomorrow night
through Tuesday. Combined with highs in the low-mid 70s today and
tomorrow and lows in the mid 40s to lower 50s, these conditions
would seemingly be ideal for the first week of October. Not to say
they aren`t but there is one blemish with this synoptic setup - the
appreciable potential for dense fog overnight through Monday morning
and fog again Monday night into Tuesday morning.
Plentiful rainfall over eastern MN into northwest WI yesterday,
generally in the range of 1/4 to 3/4 inch with localized spots over
1 inch of rain, along with the stoic low stratus not allowing for
daytime evaporation will maintain plenty of low level moisture
across the eastern half of the WFO MPX coverage area overnight. This
moisture will become trapped underneath the nightly inversion,
occurring during what will be nearly ideal radiational cooling
conditions tonight. These conditions will promote fog, and
potentially dense fog, development overnight through Tuesday morning
over and areas from roughly Little Falls to Mankato and points
eastward to the WI state line, including the non-urban portions of
the Twin Cities metro. HRRR progs also advertised the dense fog
potential. Therefore, have opted to issue a Dense Fog Advy for late
tonight for much of east-central into south-central MN, and a bit of
west-central WI. There is some potential again for dense fog Monday
night into Tuesday morning but will evaluate how conditions go
tonight plus see what models do with that potential before
heightening the messaging for dense fog tomorrow.
.LONG TERM...(Tuesday through Sunday)
Issued at 253 PM CDT Sun Oct 3 2021
As mentioned above, areas of fog are possible early Tuesday before
we see more sunshine and temperatures once again warming into the
low to mid 70s. Ridging will be in full swing with winds slowly
becoming southeasterly through the day as the surface high pulls
away to the east over Quebec. Much of the same is in store for
Wednesday before we see our next set of systems approach the area
Thursday. The first comes in the form of a 500mb cutoff low moving
up from the mid Mississippi Valley towards the Great Lakes. While
the majority of impacts from this feature will be felt well to our
southeast, our western Wisconsin counties and eastern Minnesota have
a slight chance of seeing some afternoon showers lingering into the
overnight hours.
On the heels of this system is a stronger, negatively tilted trough
that will swing through late Friday into Saturday. WAA looks to be
strong ahead of it, allowing for one last run at 80 degrees. The
limiting factor will likely be cloud cover with an abnormally moist
airmass in place. Model PW values are running well above 1" from
late Thursday through Saturday evening. There are still some timing
differences regarding the onset of precip and the overall strength
of the surface low, but feel comfortable with widespread slight to
chance PoP values from Friday evening into early Sunday morning. As
of now, highest rainfall totals look to be across central and
northern Minnesota due to the proximity of the best forcing.
By the end of the period, more fall-like weather will settle in
behind the front with highs in the mid 60s and a few lingering
showers through Sunday. The more active pattern will continue into
early next week, but there are still no temperatures below freezing
in sight. Our normal first freeze date typically falls sometime
during the first two weeks of October.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 654 PM CDT Sun Oct 3 2021
VFR conditions at KAXN and KRWF, but areas of dense fog is expected
to develop tonight at the rest of the TAF sites. As of now it appears
that LIFR conditions are most likely at KMKT, KSTC, and KRNH. The
winds will be light, and that will make it difficult to mix out the
fog if it does form, so have it lasting into the late morning. No
precipitation is expected.
KMSP...
The clear skies this evening should give way to fog development
overnight. Guidance continues to suggest as low as LIFR conditions,
so have trended the tafs down a bit but kept the visby at 3/4 mile.
It is certainly possible it could be lower early Monday morning. The
fog should break up by late morning.
/OUTLOOK FOR KMSP/
Tue...VFR. Wind SE 5-10 kts.
Wed...VFR. Wind SE 5-10 kts.
THU...VFR. Wind SE 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Dense Fog Advisory from 11 PM this evening to 9 AM CDT Monday for
Anoka-Benton-Carver-Chisago-Dakota-Hennepin-Isanti-Kanabec-Le
Sueur-McLeod-Meeker-Mille Lacs-Morrison-Nicollet-Ramsey-Rice-
Scott-Sherburne-Sibley-Stearns-Washington-Wright.
WI...Dense Fog Advisory from 11 PM this evening to 9 AM CDT Monday for
Barron-Polk-St. Croix.
&&
$$
SHORT TERM...JPC
LONG TERM...Dye
AVIATION...JRB
Area Forecast Discussion
National Weather Service Marquette MI
755 PM EDT Sun Oct 3 2021
.SHORT TERM...(This evening through Monday)
Issued at 340 PM EDT SUN OCT 3 2021
The pattern remained blocked with RAP analysis 500mb heights showing
a rex block over eastern Canada with our area remaining under the
influence of an upper level trough moving under the northern ridge.
A weakening MCV remained nearly stationary over the west today
bringing several hours of rain, sometimes heavy, particularly in
Houghton and Keweenaw counties. Showers were forming along a
boundary in the central U.P where skies had broken and allowed for
additional destabilization.
Though Monday the blocking over Eastern Canada breaks down and the
ridge shifts east. Additional ridging begins to build into the
central US, extending from the eastern Rockies / High Plains to MN
by Monday evening. Meanwhile, weak troughing over the Great Lakes
today begins to cut off under the building ridge and sink south.
For the rest of the afternoon and evening we will continue to see
areas of showers with a few thunderstorms in the southeast. The
forcing mechanisms look like they will continue to decrease in the
area of the MCV with models showing isentropic ascent and fgen
weakening and shifting east. It looks like there will still be
enough lift to promote additional areas of showers over the central
and east, all with rather slow movement under weak steering flow.
With PWATs remaining high showers or thunderstorms could produce
heavy rainfall. Fog will be a concern again tonight with onshore,
upslope flow along with rainfall promoting fog development. We
should see drier air and better mixing over the area tomorrow with
fog dissipating though the morning hours.
.LONG TERM...(Monday night through Sunday)
Issued at 433 PM EDT SUN OCT 3 2021
The extended forecast will consist of a occluded upper level low
meandering to the southeast from the Great Lakes, and a building
ridge pattern causing above average temperatures dry weather across
the area through most of the week. Toward the end of the week, the
weather regime looks to pick up and become more active once again,
bringing multiple opportunities for rainfall across Upper Michigan.
Monday night will see the broad, surface low pressure slowly meander
south-southeast. This is the same weather system that has plagued
the Great Lakes with multiple rounds of showers over the last couple
of days. As this broad, low pressure slowly moves to the south,
surface high pressure will overtake the Upper Great Lakes. We
anticipate that sky cover will quickly dissipate as dry air from the
midlevels is brought toward the surface Monday night into Tuesday
morning. This will be most apparent in the west half where the cloud
cover will dissipate the quickest. Overnight lows will bottom out in
the upper 30s to lower 40s over the interior west, with the
remainder of the area remaining in the 40s.
The upper level ridge pattern will build across the Central and
Northern CONUS on Tuesday through Thursday. This ridge pattern will
continually bring WAA to the area, despite surface high pressure
bringing onshore flow along the Lake Superior shoreline, and cooler
temperatures localized to these areas. Temperatures will be above
average across the interior, mainly in the middle 60s to middle 70s.
Due to surface high pressure being over the area from Tuesday
through Thursday, and WAA at 850mb creating nocturnal inversions,
patchy fog will be possible for several mornings.
By Thursday night into the weekend, the upper level ridge will break
down. Multiple shortwave troughs will brings chances for rainfall to
the area. This will be welcomed relief to areas that are
experiencing drought conditions across Upper Michigan. A strong cold
front will be moving through the region by the end of next weekend,
and into the beginning of next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 743 PM EDT SUN OCT 3 2021
Very moist airmass remains in place across Upper Michigan,
ensuring LL stratus and fog persists at all three terminals.
Drier air will slowly make its way into the area from west to
east, but not until tomorrow. Even then, model soundings struggle
to depict any sort of drastic, immediate improvement, so some SCT
stratus could linger, particularly at KSAW where it appears to be
slower to clear out. Generally light N to NNE winds will prevail
through the TAF period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 340 PM EDT SUN OCT 3 2021
The wind stays at or below 20 knots through the forecast period.
Dense fog could remain an issue tonight though somewhat drier and
less stable air will filter into at least the western portion of the
lake which could mitigate the fog threat. Kept the dense fog
headlines but confidence has become lower.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Dense Fog Advisory until 8 AM EDT /7 AM CDT/ Monday for LSZ162-
240>251-263>267.
Lake Michigan...
Dense Fog Advisory until 9 AM EDT Monday for LMZ221-248-250.
&&
$$
SHORT TERM...NL
LONG TERM...BW
AVIATION...lg
MARINE...NL
Area Forecast Discussion
National Weather Service Reno NV
209 PM PDT Sun Oct 3 2021
.SYNOPSIS...
Warm and dry conditions continue into the start of the week with a
slight uptick in winds starting Monday. A weather pattern change
then appears likely midweek onward with some afternoon breezes,
increased clouds, and a cooling trend. Precipitation chances may
also return later in the week into next weekend.
&&
.SHORT TERM...
No appreciable changes to the ongoing forecast with a couple more
mild and very dry days on tap. There will be a slight uptick in
winds Monday and Tuesday afternoon across northeast CA and
northern Nevada with gusts of 20-30 mph possible. Single digit RH
values on Monday will increase by about 5% Tuesday, with further
increases into midweek. There are enhanced fire weather concerns
Mon/Tues, however widespread critical conditions are not expected.
The only other concern through Tuesday would be smoke and haze,
primarily from the KNP Complex near Sequoia National Park. We
already can see the haze aloft today, with thicker near-surface
smoke likely to drift northward into southern Mono County this
evening, based on HRRR smoke models. Southerly flow may continue
to bring an increase in haze along the western Nevada Sierra front
overnight into Monday as well. Increasing afternoon breezes
Monday should push smoke further into western Nevada, with similar
patterns for Tuesday. -Dawn
.LONG TERM...Wednesday through next weekend...
The evolution of the weather pattern change later in the week
continues to be in flux, with the latest guidance favoring
Thursday and Friday having the best overall precip chances, and
the coolest temperatures from Thursday-Saturday. More details on
the highlights:
* RAIN/SNOW: While not all ensemble members are on board, an
increasing percentage are showing an improved moisture tap on
Thursday, even with the main trough splitting near the northern
CA coast. While overall totals still look modest, there could
be some bands of moderate rainfall producing low end wetting
amounts (0.10"-0.25") even for lower elevation sites. Then from
late Thursday night through Friday, the better precip chances
appear to favor areas south of US-50. By this time, snow levels
could fall to near 7500 feet, with best potential for light
accumulations near the crest in Alpine and Mono counties.
* WINDS: Not a big wind producer with the peak gusts expected for
Wednesday (around 30 mph, maybe a few sites seeing gusts to 35
mph), followed by lighter winds from Thursday onward. Humidity
values will be on the rise Wednesday, which will limit fire
weather concerns.
* TEMPERATURES: A sharp cooling trend will begin Wednesday with
highs in the lower-mid 70s for western NV valleys and 60s for
eastern CA communities. Then from Thursday-Saturday, highs are
only projected to reach the lower-mid 60s for lower elevations
and 50s for Sierra valleys, then rebounding slightly on Sunday.
Potential for freezing temperatures in areas that have yet to
see a fall freeze will increase by next weekend.
* EVEN COLDER EARLY NEXT WEEK?: After a break in most precip
activity for Saturday night-Sunday, the medium range guidance
has a reasonable agreement this far out for a reinforcing cold
front dropping in from the north for the Monday-Tuesday (October
11-12) time frame, with some moisture and lift potentially
bringing a rain-snow mix even down to some lower valleys by next
Monday night. Although there is plenty of time and variance in
the ensemble guidance, this is an early "heads-up" for a
potential touch of winter weather early next week for parts of
eastern CA-western NV. MJD
&&
.AVIATION...
Pleasant flying conditions today into the start of the week,
though haze is present across the Sierra and western Nevada Sierra
front due to the KNP Complex wildfire. Southerly flow is likely to
bring thicker smoke to southern Mono County this evening with
potential terrain obstruction and surface visibility reductions
for KMMH. This flow pattern may transport thicker haze northward
into Monday as well, but afternoon winds will clear haze for most
areas north of US-50.
Light winds this afternoon will increase a bit for areas north of
I-80 Monday-Tuesday, then across the region Wednesday as a colder
system moves into the west. At this point, most gusts should
remain near or below 20-25 kts for terminal sites. This system
could bring rain and snow showers to the region by the end of the
week or possibly next weekend with falling snow levels and much
colder temperatures. -Dawn
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno