Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/22/21
Area Forecast Discussion
National Weather Service Amarillo TX
612 PM CDT Sat Aug 21 2021
.UPDATE...
Updated precip and temp trends based on how the storms are
unfolding this evening. HRRR seems to be doing well with storm
evolution tonight.
Beat
&&
.AVIATION...
00Z Issuance...All sites are currently VFR and look to remain
so through the period. KAMA and KGUY may still see some
thunderstorms in the vicinity over the next couple hours before
they start dissipating for the evening. Winds will be
southeasterly overnight and turning to southwesterly during the
day tomorrow with some gusts around 20-25kts possible.
Beat
&&
.PREV DISCUSSION... /Issued 110 PM CDT Sat Aug 21 2021/
SHORT TERM...
A surface low near Canyon TX had a stationary front extended
northeast to the east central Texas Panhandle. This stationary
front is expected to be the focus for initial thunderstorm
development. Southwest flow aloft should carry the storms to the
northeast. Some of the storms may become severe with large hail and
damaging winds. Heavy rain may cause localized flooding.
Thunderstorms will likely move out of our area or dissipate toward
midnight.
A thunderstorm will be possible across the northwest CWA on Sunday
afternoon or evening. But will decide at the last minute on whether
to insert this into the forecast. Not all models agree that there
will be a thunderstorm in the northwest, so confidence is not very
high at this time.
Highs on Sunday will be close to a little above normal with readings
in the upper 80`s to the mid 90`s.
LONG TERM...Monday through Friday
Upper high builds over the southern Plains states Monday through
Thursday and should keep a dry pattern across the Panhandles. A
shortwave trough over the southern Rockies late next week as the
upper high breaks down will allow for the possibility of
convection by late Friday and Friday night. The GFS hinting at the
possibility for convection as early as Thursday afternoon and
Thursday night mainly across the western or northwestern portions
of the forecast area with the shortwave trough.
Surface low over eastern Colorado and western Kansas Monday
through Wednesday will deepen and allow for tightening of the
surface pressure gradient resulting in gusty southerly to
southwesterly winds. Surface low late next week across the central
Plains states and central Rockies with surface trough extending
south into New Mexico Thursday into Friday. Warmer and drier
conditions expected next week with a few breezy to windy days.
Schneider
&&
.AMA Watches/Warnings/Advisories...
TX...None.
OK...None.
&&
$$
16/24
Area Forecast Discussion
National Weather Service Binghamton NY
946 PM EDT Sat Aug 21 2021
.SYNOPSIS...
A chance for showers and some thunder lingers into the evening,
then Hurricane Henri will bring additional periods of rain to
parts of the region later Sunday into early next week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Late this evening mesoscale models even the brand new HRRR do
not or poorly show the batch of showers across northern NJ into
the NYC area. This batch of showers continues to move northwest
into Sullivan and Pike counties. However, suspect this area of
showers will become more diffuse as it tries to push further
northwest as it gets farther away from the better forcing and
dynamics. This batch of showers has resulted in some 1-2 inch
rainfall totals further southeast toward NYC. For now, increased
shower coverage and QPF a bit to account for recent trends.
Later in the overnight, additional showers will be possible
mainly across the Catskills. Otherwise, look for cloudy skies
with some patchy fog likely given low level moisture and light
winds. Temperatures will stay mild, only falling as far as the
mid 60s to lower 70s.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/...
350 PM Update...
While some of the model solutions, particularly the NAM/GFS,
have trended slightly to the right with Henri`s landfall point,
these same models continue to pull the system further to the
west post-landfall, bringing significant rainfall further to the
west as well. CAMS are generally further west both with landfall
and with the axis of heavier precipitation, as has been the
overall trend.
A band of precip currently off the NJ coast associated with
low/mid-level moisture convergence may bring some scattered
heavier showers/thunderstorms into the Poconos by early Sunday
morning. Otherwise, this band looks to redevelop later in the
day across parts of Central NY, with the bulk of the Henri-
related moisture holding off until late afternoon or early
evening. Would not be surprised to see a significant precip-free
area develop somewhere in the far eastern CWA late in the day,
but it`s difficult to work this into the grids at this point
given the range of possibilities.
The heaviest rainfall with Henri looks to be Sunday evening into
Monday, with north to northwest flow causing some enhancement
along the north and west facing slopes of the higher terrain
areas.
Uncertainties crop back in again later on Monday. While Henri
looks to do a sort of stall and loop before ejecting off to the
northeast, a few CAMS execute this maneuver over the lower
Hudson or even the Poconos, extending the heavy rainfall even
further. Went a little long on the watch timeline in order to
account for this possibility.
Main impacts still are focused on flash flooding potential, but
some flooding on the upper reaches of the mainstem rivers may
also occur, lingering later into Monday or Tuesday. It would not
take too much of an increase in QPF to throw a few more forecast
points/gauges into flood stage.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Much of Wednesday remain dry amid upper level ridging, but
additional showers and storms will begin to push in for the
afternoon and evening with an influx of heat and moisture as our
next system moves in.
The cold front associated with this system will drag across NY
and PA on Thursday, setting off more thunderstorms. Lingering
instability will keep scattered showers in the forecast through
the end of the work week.
Otherwise, expect temperatures to stay quite warm through the
midweek, peaking in the mid and upper 80s before temperatures
turn more seasonal into Friday.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR conditions expected at all terminals through 5z this
evening. The showers this afternoon are coming to an end with
the skies clearing over CNY but mid and high clouds are
streaming into NE PA ahead of Hurricane Henri. ELM likely
develops fog tonight with uncertainty in how early it will start
to develop so a tempo group was put in between 5z and 7z.
Greater certainty exist for IFR or worse between 7z and 12z.
Other CNY terminals could get some patchy fog to develop around
the terminals that could cause brief MVFR restrictions late
tonight.
Tomorrow, VFR conditions return in the morning once the fog
lifts but MVFR conditions return in the late morning and early
afternoon as some rain bands move into the region associated
with the remnants of Henri. There is still uncertainty in how
far NW the rain will make it so ITH and SYR did not have showers
or restrictions put into this set of TAFs.
Outlook...
Sunday night through Monday...occasional showers/thunderstorms
bringing restrictions. Some late night vsby restrictions due to
valley fog, especially ELM.
Tuesday/Wednesday...Mainly VFR conditions expected. May see
early morning fog at ELM.
Thursday...Restrictions possible in afternoon showers and
thunderstorms.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...Flash Flood Watch from 6 AM EDT Sunday through Monday
afternoon for PAZ040-044-047-048-072.
NY...Flash Flood Watch from 6 AM EDT Sunday through Monday
afternoon for NYZ046-057-062.
&&
$$
SYNOPSIS...HLC
NEAR TERM...HLC/MWG
SHORT TERM...DJP/MPH
LONG TERM...DJP/HLC
AVIATION...AJG
Area Forecast Discussion
National Weather Service Caribou ME
910 PM EDT Sat Aug 21 2021
.SYNOPSIS...
High pressure builds across the Maritimes into Sunday. Henri
will approach southern New England tonight and move onshore in
southern New England late Sunday. Henri will dissipate while it
tracks across our region Monday into Tuesday. High pressure
will build over the area Wednesday. Low pressure approaches the
area on Thursday.
&&
.NEAR TERM /THROUGH SUNDAY/...
9:10 PM Update: Two main updates at this time. A dense fog
advisory was issued along the coast until 9 am Sunday morning.
Web cameras around MDI were showing dense fog around the time of
sunset, and it is likely to only become more widespread and
dense with time. Also, a SCA was hoisted for the coastal waters
starting on Sunday morning and running into Monday morning,
mainly for swell from Henri. Otherwise, there were no
significant changes planned at this time. The 8 pm advisory on
Hurricane Henri indicated very little in the way of changes from
the 5 pm advisory.
Previous discussion:
High pres will remain in place through Sunday. Henri will apch from
the wrn Atlc overnight heading toward NYC/LI region on Sunday. his
will play more of role for our region in regards to larger waves,
swells and minor overwash at high tide along the coast later Sunday
evening into Monday. More on that in the marine/coastal flood
section.
For tonight, convection threat is diminishing and will continue
to have that trend into the evening. Showers will dissipate
through the evening w/the loss of diurnal effects. The challenge
then becomes low clouds and fog as llvl moisture gets affected
northward from the Gulf of Maine. Kept the mention of fog in the
forecast w/the best coverage across the central highlands down
to the coast. Some of the high resolution guidance such as the
HRRR, NAMNEST and RAP guidance show some light QPF pushing
inland from the Gulf of Maine. The operational runs of the NAM
and GFS much later in showing some light QPF most likely in the
form of drizzle or light rain showers moving wnw from the Gulf
of Maine. The ridge axis holds in across the northern 1/2 of the
CWA to keep things dry. Mdl soundings do show deep llvl
moisture trapped in below 850 mbs w/that light SSE flow and
drier air above that layer, leading to more of a drizzle
scenario. Therefore, added the mention of drizzle into forecast
later tonight into Sunday morning.
For Sunday, ridge axis shifts to the n w/the onshore flow setting
up in earnest as 925 mb winds are expected to increase to 25
kts as Henri pushes to the NYC/LI area. Strong convergence
setting up across the downeast region into the central highlands
and w/the increasing winds at 925-850 mbs, showers/light rain
threat to increase. Decided to follow GYX`S lead w/expanding the
coverage & precip wnw into the Maine Central Highlands. Further
n, ridge continues to hold keeping things dry. Low clouds
hanging on a bit longer into late morning and w/the ESE wind
could keep daytime temps down from what they have been over the
last few days. Leaned in that direction w/temps at least 5
degrees cooler than they have been.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
By 00z Sunday, Hurricane Henri will be over southern New
England, slowing down in forward speed as it pushes further
inland. A plume of moisture out ahead of the system will lead to
humid conditions across our forecast area Sunday night into
Monday, with dewpoints in the 60s and PWATs surging above 2
inches. All of this moisture will support showers ahead of
Henri, which will move into the Downeast region Sunday evening.
Patchy fog will be possible across the forecast area Sunday
night into early Monday morning due to the abundant moisture.
After stalling over southern New England, Henri will begin to
push eastward as the subtropical ridge strengthens on Monday. As
the weakened system begins to approach our region, showers will
increase in number from south to north across the forecast area.
Winds will remain relatively light through the day on Monday,
especially as a persistent marine layer reaching up to Dover-
Foxcroft and Lincoln will provide enough stability to keep
higher winds from mixing towards the surface.
What remains of Henri will pass to the south on Tuesday,
clearing off into the Canadian Maritimes. Showers will remain
across the forecast area as the low passes, with the highest
rainfall accumulations concentrated along the coast with up to
an additional inch possible.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Skies will finally clear Tuesday night into Wednesday, but the
lack of rain will not equate to a lack in moisture. A warm,
humid airmass will remain through mid-week. Lingering moisture
and diurnal heating will result in the chance for convective
showers, especially Thursday afternoon. It will take a cold
front Thursday night to clear the humidity and bring drier
conditions across the entire forecast area. This cold front will
be our next chance for widespread rain. Drier weather is
expected heading into next weekend.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
NEAR TERM:
VFR across the northern terminals to gradually drop back to MVFR
later tonight and then could go down to IFR by early morning on
Sunday. MVFR for KBGR/KBHB this evening dropping to IFR/LIFR
overnight with dense fog possible at times at KBHB through mid
morning Sunday. ESE wind < 10 kt.
For Sunday, IFR/MVFR for all terminals in the morning
w/improvement across the northern terminals
to VFR by mid morning. KBGR and KBHB will see a gradual
improvement to MVFR by late morning. ESE winds 10 kts.
SHORT TERM:
Sun night - Tues...MVFR/IFR likely across southern terminals
with the approach of Hurricane Henri. Northern terminals will
fall to MVFR overnight Sunday night as showers move northwards.
Light SE winds will shift S to SW on Tuesday.
Tues night - Wed night...VFR across all terminals. Light W
winds.
&&
.MARINE...
NEAR TERM:
Seas are expected to gradually build for this term reaching 5-7
ft by Sunday afternoon w/12-14 second periods leading to large
swells. ESE winds increasing to 10-15 kt w/gusts 20-25 kt later
in the day over the outer zones. In collaboration with WFO Gray
have issued a SCA starting Sunday morning for the coastal marine
zones.
SHORT TERM: Seas will range from 6 to 8 feet late Sunday into
Mon morning before dropping below SCA levels Mon night. Remnants
of Hurricane Henri will cross the waters late Monday night into
Tuesday. Brief wind gusts approaching 25kts during the period.
Visibilities will be reduced in fog as humid air remains over
the water through the end of the week.
&&
.TIDES/COASTAL FLOODING...
High astronomical tides and TS Henri may bring minor coastal
flooding issues around the time of high tide Sunday night and
Monday night around midnight. Attm, given the latest setup,
some minor splash over is possible, but w/the long period
swells, and high surf, the risk of rip currents and big breakers
hitting the coast could be an issue.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Dense Fog Advisory until 9 AM EDT Sunday for MEZ029-030.
MARINE...Small Craft Advisory from 8 AM Sunday to 8 AM EDT Monday for
ANZ050-051.
&&
$$
Near Term...CB/Hewitt
Short Term...AStrauser
Long Term...AStrauser
Aviation...CB/Hewitt/AStrauser
Marine...CB/Hewitt/AStrauser
Tides/Coastal Flooding...Farrar/Hewitt/CB
Area Forecast Discussion
National Weather Service Grand Junction CO
546 PM MDT Sat Aug 21 2021
.SHORT TERM...(Tonight through Sunday night)
Issued at 248 PM MDT Sat Aug 21 2021
Isolated to scattered storms developed this morning further south
than most if not all of the hi res CAM models indicated across
southeast Utah and southwest Colorado. These storms tracked
northeast over the central valleys by mid to late morning, with a
few rumbles of thunder and light to moderate rain, much to the
surprise of many. However, these storms were very quick moving and
shallow with a dry sub cloud layer as indicated by the 12Z GJT
morning sounding and forecast model soundings. As a result,
precipitation amounts were very light (a few hundredths to a tenth
of an inch at best measured at gauges and estimated by radar). So
flooding concerns are minimal at this time and not much a
concern. After doing a deep dive in the mesoanalysis to see what
is sustaining this convection, looks like steep low level lapse
rates and an axis of effective bulk shear ahead of the shortwave
trough that is currently moving through the Pacific NW and
northern Great Basin. Makes sense. An 80 kt jet streak associated
with this shortwave trough will track across northeast Utah and
northwest Colorado tonight, helping sustain convection across the
north overnight into Sunday morning before dissipating by sunrise.
Temperatures have also been trending much cooler than guidance
due to the increase in cloud cover and shower activity that models
weren`t picking up on as well, so backed off the high
temperatures today as well as the next few days as the warming
trend seemed a bit too quick given recent trends.
Sunday will provide much drier conditions behind this shortwave
trough with westerly flow up north helping pull more smoke in
from the California wildfires. A bit of good news in regards to
the smoke though is the latest HRRR smoke model seems to push most
of the smoke out of the central and southern areas and keeps it
concentrated across the north, thanks to more of a southwest
component to the upper level winds across that portion of the CWA.
While that is good news for areas along and south of I-70, not so
good news for those locales further north towards the Wyoming
border. Temperatures will be a bit warmer on Sunday compared to
today, but still around 5 degrees below normal.
.LONG TERM...(Monday through Saturday)
Issued at 248 PM MDT Sat Aug 21 2021
Eastern Utah and Western Colorado predominately fall under
southwesterly flow through the long term period. The region will
remain sandwiched between a broad rotation of high pressure over
the Southern Plains and lower heights anchored to the PacNW for
several days. A series of shortwave troughs rippling through the
PacNW low may generate a nudge of lift and instability aloft,
favoring isolated showers over higher terrain each afternoon.
However, the remaining forecast area will indulge in a warming and
drying period, with only increased surface winds from said
disturbances. High temperatures will climb from the low 90`s
across valley floors on Monday to nearly triple digits by mid-week
in some remote desert areas of southeast Utah. Meanwhile, PWATs
drop to around 0.25" to 0.5" across the Western Slope by
Wednesday. Forecast soundings reveal an inverted V signature
deepening each day, which will limit the showers that do try to
wring out precipitation from reaching the ground and thus, further
enhancing surface winds. In addition, this atmospheric profile is
favorable for deep, boundary layer mixing, which can transport
some of the stronger momentum aloft down to the surface.
Therefore, near critical RH levels and increased winds will
increase the concern for localized fire weather conditions each
afternoon; though, fuels may very well be a limiting factor
(considering all of the rain we`ve received earlier in the week).
Model consensus tries to push the stagnant low inland by the middle
to end of the week, which will suppress the mid level high to the
southwest. This synoptic set up could be more favorable for the CWA
to tap into Sub Tropical moisture, though, confidence in the
strength of the plume and its trajectory remain low, attm. Looking
ahead to next weekend, ridging slides back into the Western CONUS,
which would return a dry and warming trend back across the Western
Slope.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 546 PM MDT Sat Aug 21 2021
Isolated to low end scattered showers and thunderstorms will
continue this evening, mainly over the higher elevations in the
north. However, a disturbance passing north of the region
overnight may sustain some activity across the northern border
zones late. There is little chance this activity will impact TAF
sites however, so left VFR conditions at all TAF sites. LLWS is
expected as winds diminish this evening and will impact KHDN,
KEGE, KASE, KGUC and KTEX through sunrise. Breezy southwest winds
develop for most sites again Sunday afternoon.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...MDA
LONG TERM...ERW
AVIATION...NL
Area Forecast Discussion
National Weather Service Gray ME
1154 PM EDT Sat Aug 21 2021
.SYNOPSIS...
Warm and humid conditions will continue through Monday as
Henri moves up the coast and weakens over southern New England
tomorrow and tomorrow night. The effects on our region will be
occasional showers, possibly heavy, gusty winds at times
especially in showers, along with building surf. Thereafter,
summery weather continues through the week with mainly dry
weather, although a few rounds of scattered showers and
thunderstorms cannot be ruled out.
&&
.NEAR TERM /TONIGHT/...
1155 PM Update... Incorporated a fair amount of the 00Z HRRR
into a refresh of temperature and dew point trends through
tonight and tomorrow. With onshore flow and widespread clouds I
don`t expect temperatures to warm much tomorrow, except for over
the upper Connecticut River Valley with more breaks in the
clouds... and some downsloping.
855 PM Update... Issued a Dense Fog Advisory along the coast
through tonight with a strong onshore flow bringing the fog bank
in, shown well by satellite imagery... as well as crashing
ceilings at this hour. Brief period of dense fog have already
been observed, so anticipate more widespread dense fog to
develop tonight along the coast. Will be monitoring inland
trends for a possible expansion.
650 PM Update... Only a few minor tweaks to temperature and sky
trends for now, mainly to go harder with the marine layer for
the remainder of the evening and tonight. Satellite and
observations are showing crashing ceilings into tonight with
stratus over taking most of the region south and east of the
mountains. Will be monitoring for dense fog development in the
coming hours... in case a dense fog advisory needs to be issued
along the coast.
Previously...
Scattered convective showers will continue in the interior into
the early evening as very moist easterly low level flow gently
upslopes. This activity should wane this evening. Thereafter,
low stratus will become ubiquitous along with areas of fog. It
is not out of the question that we will need a dense fog
advisory for portions of the coastal plain as well as central
ME. Otherwise, some drizzle will be possible as well but
overnight temperatures will remain very warm.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
Henri makes landfall on Long Island NY or the New England south
coast during the day on Sunday. While it approaches, a
northeasterly low level jet will increase across southern zones,
to about 50 kt around 900 mb. While mixing heights will be
relatively low on Sunday, some gusts of 30-40 MPH will be
possible across southern zones starting in the morning on
Sunday. The most susceptible area will be the Monadnocks of NH,
with winds downsloping into the lower elevations such as Keene.
Several CAMs are in good agreement that a northward moving
feeder band will quickly move from south to north across the
forecast area during the day with a risk of very heavy
downpours for a short period of time. As far as timing goes on
that, there is general agreement that it will move into
southernmost NH between 8 and 10 am, then advancing quickly
northward to near a KLEB-KPWM line between noon-2 pm, then
likely weakening after that. A quick half inch to inch of rain
will be possible with this feature along with some gusty winds
that could be mixed down.
Other than that, fog and some drizzle remains on the coast
during the day with occasional showers. The day should not be a
complete washout, however. Went with isold thunder in the south
on Sunday, but have left thunder out of the forecast at this
time elsewhere due to very poor lapse rates and very high
freezing levels. Non-zero chance of a tornado across
southernmost zones in accordance with SPC marginal risk, but at
this time this far north, it appears that low level
thermodynamic profiles will not be conducive.
Fog, drizzle, and occasional heavy passing showers expected
Sunday night with attendant risk for localized flash flooding,
especially across southern NH but winds do not look to be an
issue at this time.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Focus on long term is the continued influence of TC Henri and then a
return to the heat. Expect the stable boundary layer over much of
the area starting the day off Monday with some fog/drizzle in the
midcoast areas with the tropical airmass in place. Clouds could help
hold temperatures down in the 70s for much of the region, with the
exception of s NH where highs could creep into the 80s away from the
stable air near the coast. Basing the forecast of the NHC 2PM
forecast for TC Henri, it is projected to slowly lift across
southern NH into southern ME on Monday Night into early Tuesday
morning. Have raised pops accordingly and mention flood concerns in
the hydro section below. As the low pushes east on Tuesday NW flow
will develop and we will see drier air filter into the region. Some
clouds will likely linger in the north, but for much of the area
some sun should allow temperatures to shoot quickly back into the
80s. Despite drying in the mid/upper levels the surface will remain
somewhat muggy. For Wednesday temperatures will be even warmer with
much of the area in the mid to upper 80s, with ongoing dewpoints in
the 70s. Expect diurnally driven convection, but without much shear
for support don`t see potential for any organized storms. Finally
the shift in the upper level pattern comes late in the period with
the cold front on Thursday. There will be some scattered showers and
thunderstorms with a notable drop in temperatures and humidity for
the end of the week into the weekend.
&&
.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
Short Term...IFR or lower tonight in fog and low clouds,
especially on the coastal plain and central ME terminals. Areas
of fog may be dense. The first rain bands from Henri will begin
to affect the area on Sunday with periods of squally rains.
While conditions may lift to MVFR for a time away from the coast
during the day Sunday, IFR will prevail. LIFR conditions
expected Sunday night.
Long Term...The tropical airmass over the area will support a
combination of low clouds, fog, drizzle Monday morning followed by
moderate and occasionally heavy rainfall by Monday night as the
remnants of TC Henri pass over the terminals. Moisture will erode
quickly on the backside of the system as it moves east of the area
on Tuesday, which should help improve ceiling to VFR in NW flow.
&&
.MARINE...
Short Term...Onshore easterly flow develops and strengthens
through Sunday as Henri approaches from the south. A small craft
advisory has been issued for the coastal waters for Sunday into
Monday.
Long Term...S swells will continue in the long term as the core of
TC Henri remains inland. Seas will be 4 to 6 ft mainly from a 11sec
swell from Henri. The S direction of the swell may be reduced along
NH and east facing zones in southern Maine due to some by blockage
from the Cape. The winds should remain below SCA as cool stable
marine air remains in place. Based on NHC latest track, the low will
move over the Gulf of Maine Tuesday morning as it moves east. The
expectation is that the intensity will have significantly diminished
while inland and will not pose a marine wind hazard as it moves by
the local waters. Winds will become NW behind the system which will
help dampen the lingering s swells to below 4 ft by later on
Tuesday.
&&
.HYDROLOGY...
High pressure from the north push into the area slightly reducing
the PWATs down to 1.75". As TC Henri lifts north the moisture surge
will spread into the region with PWATs rising to 2.25" along
southern ME/NH by this time tomorrow. As TC Henri lingers to the
southwest on Sunday and Monday, scattered showers and thunderstorms
are expected to develop over the area with pockets of torrential
rainfall. Given how weak the forcing is showers and thunderstorms
will be closely tied to the diurnal cycle, with peak coverage
this afternoon/evening. At this time concern is not high for
widespread heavy rainfall, but these locally high amounts could
add up if repeated areas are impacted. The increased support in
the upslope regions of the Monadnocks and White Mountains are of
particular concern for repeat development. The final track of
TC Henri could also bring a swath of moderate to heavy rainfall,
with the latest forecast bringing it over S NH and ME. RFC/WPC
QPF forecasts attempt to highlight the rainfall enhanced by
upslope, and do well for an overall rainfall assessment. However
we recognize there could easily be pockets of locally higher
amounts that could lead to flash flooding. Soil
moisture percentiles remain high in S NH due in part to Fred`s
passage a few days back. For now river flooding appears to be a
low threat as most rivers remain at or below normal
streamflows. Some lakes/reservoirs in S NH where heavy rains
have fallen over the last 6 weeks remain high, but there should
be enough storage to handle this storm. All of these factors
combine to support the Excessive Rainfall highlighting a slight
risk mainly over NH up to the White Mountains region.
&&
.TIDES/COASTAL FLOODING...
Prolonged onshore flow is expected to increase tonight through
tomorrow out of the NE before switching to the SE by late
Monday. Looking at the ESTOFS/ETSS/PETSS guidance all models
keep storm surge values around .8 to 1.2 feet through this
period. Potential exists for the models underdoing the surge on
Monday due to the prolonged nature of the onshore flow and
multiple tide cycles. The good news is the peak HAT cycle will
occur tomorrow night with slightly lower tide cycles heading
into Monday. This should keep TWL just below minor flood levels.
Its possible that Hampton Area could touch 11ft tomorrow night.
In addition, near shore seas will be building to near 5 feet by
high tide tomorrow night, so splash-over could be an issue on
vulnerable coastal areas. Waves will still elevated on Monday
along with water levels, so minor splash-over and beach erosion
can`t be ruled out on the Monday night high tide, but the
likelihood looks much lower.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Dense Fog Advisory until 9 AM EDT Sunday for MEZ023>028.
NH...Dense Fog Advisory until 9 AM EDT Sunday for NHZ014.
MARINE...Small Craft Advisory from 8 AM Sunday to noon EDT Monday for
ANZ150-152-154.
&&
$$
UPDATE...Casey
NEAR TERM...Ekster
SHORT TERM...Ekster
LONG TERM...Jamison
Area Forecast Discussion
National Weather Service Wichita KS
1028 PM CDT Sat Aug 21 2021
.SHORT TERM...(This evening through Tuesday night)
Issued at 225 PM CDT Sat Aug 21 2021
Bottom line up front: A slim chance of late afternoon storms along
the KS/OK border this afternoon. A chance of widely scattered
elevated convection after midnight. Then a return of very warm
temperatures to start the week.
Convective outflow from last nights complex of storms over southern
KS pushed south into central OK, but has all but washed out by this
afternoon. Main synoptic cold front is making slow progress thru
the Flint Hills into northern OK and SE KS at this time, with lower
70s surface dewpoints still pooling just southeast of the boundary
along the KS/OK line in SE KS. Latest SPC meso page shows SBCAPE
values of 3000-3500 J/kg pooling just south of the border across
northern OK.
For late this afternoon into early this evening, think convergence
and afternoon heating along the stalling cold front will be enough
for scattered storms to develop across northern OK, as inhibition is
lost and this area becomes uncapped. There appears to be a slight
chance that a few storms may develop close to the KS/OK border as
well, so will leave some slight pops in for this chance for the late
afternoon into the early evening. Bulk shear of 25-30kts and SBCAPE
values of 3500 J/Kg may lead to a few strong to severe storms, with
damaging winds being the main concern.
Most of the high rez model solutions keep the bulk of the afternoon
convective chances further south in nrn OK.
Low level moisture transport and warm advection really gets ramped
up across northern OK and southern KS late this evening and
overnight, which will lead to the frontal boundary lifting back
north as a warm front late tonight. This will probably lead to
scattered elevated convection developing across portions of southern
KS after midnight as mid level lift increase, with the convection
lifting NE across most of the forecast area through early Sun
morning.
High rez cam solutions only show isolated elevated convection
developing late tonight, with the RAP showing the best moisture
transport focused in areas west of the forecast area. Still plan on
going with a slight chance pops for this chance. Elevated
instability of 1750-2000 J/KG, lifting north back across the
forecast area may lead a few strong storms.
SW flow and a lee side trough reestablishing itself along the front
range, will lead to very warm and breezy conditions for Sunday,
Monday and possibly into Tue, as convective chances shift back north
into Neb. 1000-850h partial thickness values suggest max temps will
climb back into the mid to upper 90s for Sun and the upper 90s to
near 100 for Mon/Tue. The breezy conditions will help surface
dewpoints mix out for the afternoon hours, keeping Wet Bulb Globe
Temps (WBGT) and heat index values below heat advisory values.
Most of the convective chances will stay well north of the forecast
area through Wed. Could see some convection try to get going across
NW KS on Tue evening, but as this convection moves east, it will run
into warmer mid level temperatures, which will squash the convection
as it moves into central KS.
Ketcham
.LONG TERM...(Wednesday through Saturday)
Issued at 225 PM CDT Sat Aug 21 2021
Will keep some low pops across central KS for the Wed evening and
Thu, as a frontal boundary tries to sag south into nrn KS, but
confidence is low. Confidence in warmer than normal temperatures
remaining across the region is increasing.
Ketcham
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1027 PM CDT Sat Aug 21 2021
Scattered showers and storms will affect portions of southeast
Kansas overnight. Otherwise VFR conditions will prevail for the
next 24hrs across the region with easterly winds veering out to
the south and increasing on Sunday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 71 95 74 99 / 10 10 0 0
Hutchinson 69 95 74 99 / 10 10 0 0
Newton 69 92 73 97 / 10 10 0 0
ElDorado 70 92 74 96 / 10 10 0 0
Winfield-KWLD 72 95 73 99 / 30 10 0 0
Russell 67 97 74 100 / 10 10 10 10
Great Bend 67 94 73 96 / 10 10 0 0
Salina 67 95 75 99 / 10 10 10 0
McPherson 67 92 73 96 / 10 10 0 0
Coffeyville 73 94 74 98 / 30 10 0 0
Chanute 72 92 75 96 / 30 10 0 0
Iola 70 91 74 96 / 20 10 0 0
Parsons-KPPF 72 92 74 97 / 30 10 0 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Ketcham
LONG TERM...Ketcham
AVIATION...CDJ
Area Forecast Discussion
National Weather Service North Platte NE
709 PM CDT Sat Aug 21 2021
.SHORT TERM...(This evening through Sunday night)
Issued at 341 PM CDT Sat Aug 21 2021
Isolated POPs are in place tonight and Sunday. The focus tonight
will be increasing warm air advection from a low level jet and a
weak subtropical disturbance moving northeast out of Colorado. This
could produce isolated showers or thunderstorms across swrn and
ncntl Nebraska tonight.
Another chance for storms develops Sunday afternoon and Sunday
evening affecting ncntl Nebraska and perhaps parts of swrn Nebraska.
This storm chance is associated with an upper level disturbance
moving through Oregon this afternoon. The disturbance will move
through the Dakotas Sunday. The disturbance should send a dryline
and weak cold front through wrn Nebraska during the afternoon. The
models appear to triggering storm activity along the dryline - east
of highway 83 in the afternoon.
Winds aloft are very strong...50-75 kts at the h500-300mb level and
moisture robust across ncntl Nebraska where PWAT will approach 1.5
inches. The uncertainty in the POP forecast revolves around upper
level support, low level focus and the very strong shear. For this
forecast, the weak forcing aloft, modest focus and very strong shear
should limit storm coverage to isolated. SPC suggested a severe
storm risk for Sunday and this is certainly warranted given the
instability and shear expected to develop. Wind and hail would
appear to be the primary hazard. WPC suggested marginal excessive
rainfall and this is appropriate for 1.5 inches of precipitable
water predicted by the NAM and RAP models.
The temperature forecast uses the model blend plus bias correction
for lows in the 50s and 60s tonight and Sunday night. Highs in the
80s to lower 90s are in place Sunday. The temperature forecast
Sunday might be too warm given the recent rains but it is in the
middle of 12 models.
.LONG TERM...(Monday through Saturday)
Issued at 341 PM CDT Sat Aug 21 2021
The models are in very good agreement building an upper level
ridge across Texas north toward Nebraska early this week. Winds
aloft at h500-300mb will remain fairly strong at 20-25kts at h500
and 40-50 kts at h300. This belt of fairly strong westerlies and at
times southwesterlies, could potentially produce strong to severe
storms. The ridge will retreat south Wednesday with the approach of
and upper level trof moving through Pacific Northwest. The best
chance for thunderstorms arrives Wednesday into Thursday.
Warm air will build into the region Sunday and remain in place
through next Saturday. H700mb temperatures rise to 12C-15C during
this time supporting highs in the upper 80s to lower 90s Monday and
Tuesday. A back door cold front cools highs back into the 80s
Wednesday and beyond.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 658 PM CDT Sat Aug 21 2021
A few showers and TSTMS are expected to develop late tonight as a
southerly low-level jet develops. This will also lead to LLWS
across the area through the mid-morning hours Sunday. Winds will
be gusty at times from the south-southeast.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Taylor
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
900 PM EDT Sat Aug 21 2021
.SYNOPSIS...
An upper-level low will remain overhead through the weekend,
while Henri tracks northward toward Long Island/New England.
High pressure will build in for the first half of the week
before a cold front approaches from the north during the second
half of the week.
&&
.NEAR TERM /THROUGH SUNDAY/...
9:00 PM UPDATE: Current satellite observations depict an upper
low directly over the forecast area, particularly over our
western zones. This has re-invigorated convection over the
higher terrain, even now in the absence of daytime heating. A
few storms have gotten fairly tall, but have failed to become
severe thus far. The bigger concern is going to be for some
isolated instances of flooding/flash flooding, as storms
struggle to move much in the absence of significant steering
flow. Do expect this to gradually taper off over the next few
hours however, as stabilization continues. So, will maintain an
isolated severe/flash flood threat until radar activity tapers
off.
PREVIOUS DISCUSSION: As we move into the overnight hours,
attention will turn to our north, where an inverted surface
trough is expected to develop over PA/NJ to the northwest of
Henri/ahead of the upper low overhead. Model guidance indicates
that a very heavy band of precipitation may form within this
inverted trough, but thankfully CAM guidance has also been
consistent run to run in keeping this heavier precipitation just
to the north and east of our forecast area. However, this
feature does bear watching as we move through the rest of the
day into tonight, since it could potentially impact northeast MD
if its location were to trend further southwest over time.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
9:00 PM UPDATE: With the latest runs of the HRRR, now including
the 18z extended run, not much has changed in regards to our
forecast for tomorrow. Still far too much uncertainty at this
point to know for sure how much rain northeast Maryland sees
tomorrow. The 18z run throws a spiral band down through
northeast MD early tomorrow morning, then brings in wrap-around
precip late tomorrow night. Should this occur, we would likely
have some flooding issues, albeit isolated outside of the
Baltimore metro. Will have to monitor closely as the overnight
runs come in to see if some consensus is formed on the evolution
of things tomorrow regarding Henri. Think as the 00z guidance
trickles in, perhaps a decision can be made on any flooding
headlines.
PREVIOUS DISCUSSION: The aforementioned upper low will continue
to reside overhead during the day tomorrow. Meanwhile, Henri
will continue to track toward the north, likely making landfall
on Long Island some time tomorrow afternoon. Exactly how Henri
interacts with the upper low will have a strong influence on our
forecast for tomorrow, and an atypical amount of spread exists
in the forecast for tomorrow afternoon into tomorrow night,
especially across northeastern MD. Some members of the 12z HREF
(most notably the HRRR and WRF-ARW members) draw Henri much
further south than other model guidance, backing heavy rain into
northeastern MD by tomorrow evening. If this type of scenario
were to play out, some localized instances of flooding can`t be
ruled out. Thankfully, flash flood guidance is relatively high
over northeastern MD outside of Baltimore, so we may avoid hydro
issues as long as the heaviest rain stays out of Baltimore.
These HRRR and WRF-ARW solutions are outliers at the moment, so
it is very possible that the entire forecast area avoids heavier
rain, with just some lighter rain across northern MD tomorrow
afternoon into tomorrow night. Elsewhere, a stray shower or
thunderstorm can`t be ruled out tomorrow afternoon or evening,
but areal coverage of storms isn`t expected to be high and the
storms aren`t expected to be intense.
Any precipitation associated with Henri should exit off to our
north and east by daybreak Monday. The upper low will also
depart off to our north and east during the day Monday, but a
warm and humid airmass will still remain in place in its wake.
As a result, a stray afternoon or evening thunderstorm can`t be
ruled out in response to daytime heating. With limited
instability and weak flow, any storms that do form aren`t
expected to lead to any hazardous weather. Highs on Monday will
return to near normal, with highs in the upper 80s for most.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
High pressure returns to the region for the bulk of the week, with
hot and humid conditions and spotty afternoon thunderstorms. Hottest
and driest day looks likely to be Tuesday in the wake of Henri with
best compressional heating as the system moves away and high
pressure builds in. This wanes Wednesday and Thursday as high
pressure, initially just to our west, shifts east and we start to
get a stronger flow of moist tropical air back northward across the
region. By Friday into Saturday, we`ll be watching a front
approaching from the north, which may start to focus the storm
development Friday, then may stall in the area Saturday. Still lots
of uncertainty with this, but overall looks like a stormier and
cooling trend as we head into next weekend.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
Prevailing VFR conditions are expected through Monday.
Thunderstorms will be possible each afternoon, but areal
coverage of storms isn`t expected to be high. A steadier period
of rain associated with the outer fringe of Henri may
potentially work into MTN or BWI tomorrow evening, but
confidence in this occurring remains low. Winds will be light
out of the east or north today through tonight, before becoming
light out of the west to northwest tomorrow through Monday.
Generally VFR Tuesday through Thursday under high pressure. Main
concern is for patchy early morning fog and isolated to scattered
afternoon/early evening thunderstorms. Best risk of both will be at
MRB and CHO. The risk likely is lowest on Tuesday with a gradual
increase in chances through Thursday.
&&
.MARINE...
Sub-SCA level winds are expected through Monday. Winds will be
light out of either the east or north today, before becoming
light out of the west to northwest tomorrow and Monday. An MWS
may be needed this afternoon if a storm were to move over the
waters.
Light winds likely prevail over Tuesday thru Thursday under high
pressure. Only concern would be for an isolated thunderstorm
reaching the waters. The risk likely is lowest on Tuesday with a
gradual increase in chances through Thursday.
&&
.TIDES/COASTAL FLOODING...
Latest guidance has continued to keep tidal anomalies lower. Most
sites with the exception of DC Waterfront and Annapolis will remain
below action stage over the next few days. Otherwise, not
anticipating any minor tidal flooding issues over the next few
days.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...KJP
NEAR TERM...CJL/KJP
SHORT TERM...CJL/KJP
LONG TERM...RCM
AVIATION...RCM/KJP
MARINE...RCM/KJP
TIDES/COASTAL FLOODING...BRO
Area Forecast Discussion
National Weather Service Medford OR
856 PM PDT Sat Aug 21 2021
.UPDATE...
An update has been sent this evening to refine some forecast
elements based on newer data. Edits were made to sky cover
through Sunday evening, to smoke in the present weather grids
through Monday afternoon, and temperatures through Monday
afternoon.
&&
.DISCUSSION...
The thick smoke that has periodically plagued the Rogue Valley
from Medford to Ashland and surrounding areas in recent days has
shifted it`s focus northeastward this evening. Diamond Lake
Resort`s PurpleAir sensor was indicating an instantaneous AQI of
543 at last check. Poor air quality extends from that area
southeastward into the Klamath and Tule Lake Basins.
Overnight into the morning the HRRR Smoke Model suggests that the
smoke from the fires in the Umpqua Basin will split to areas on both
sides of the Cascades again, likely resulting in some spill over
into the Rogue Valley by morning. On Sunday afternoon this is
likely to flush eastward again, but an elevated smoke deck from
the California fires is expected to linger overhead through the
day over SE Jackson County. This is likely to keep temperatures
below guidance in many areas affected by the smoke, once again.
Otherwise, the forecast remains on track for little change in the
day to day weather through about the middle of next week, though
there is an upper level shortwave trough that will ride through
Tuesday into Wednesday that bears some watching for stirring
things up a bit more then. ~BTL
&&
.AVIATION...22/00Z TAFs...Along the coast and just offshore, VFR
conditions will continue into early this evening, then marine
stratus will once again form between 3-5z north of Cape Blanco with
MVFR ceilings to start, then lowering to IFR tonight into Sunday
morning. The marine stratus will gradually burn off with ceilings
improving to MVFR between 16-18z, then VFR around midday at North
Bend.
Inland west of the Cascades, VFR ceilings will continue into this
evening with marine stratus forming and/or pushing into the Coquille
Basin later this evening, then into the Umpqua Basin and Illinois
Valley later tonight with MVFR ceilings at Roseburg towards daybreak
Sunday. Medford is expected to remain VFR through the TAF period.
There is a slight chance visibility could lower to MVFR late tonight
into Sunday morning, but confidence is not high enough to include it
in the Medford TAF.
East of the Cascades, smoke from the fires in Douglas County will
result in MVFR visibility at Klamath Falls through Sunday morning,
then winds are expected to shift southwest resulting in improve
visibility Sunday afternoon. -Petrucelli
&&
.MARINE...Updated 120 PM PDT Saturday, 21 August 2021...A thermal
trough along the southern Oregon Coast will persist into early next
week with moderate to strong winds (strongest during the afternoon
and evening hours) and steep wind driven seas, especially south of
Cape Blanco. The remnants of a front will likely briefly weaken this
pattern Tuesday into Wednesday. Then then thermal trough will likely
restrengthen late Wednesday into Thursday and persist into the
weekend. /BR-y
&&
.FIRE WEATHER...Updated 130 PM PDT Saturday 21 August 2021...An
upper trough is moving through our area today. This trough produced
a strong marine push last night and the effects of this push are
still being felt across the area in the form of elevated humidities
and relatively cool temperatures. We will also see some gusty west-
northwest winds later this afternoon and evening as stronger winds
mix down from aloft. Stratus will surge onshore again tonight but to
a slightly lesser degree than last night. This will result in good
humidity recoveries again tonight. However, the air mass is
beginning to dry out aloft, so the higher elevations of western
Siskiyou County will see only moderate recoveries tonight.
Weak upper troughiness remains over the PacNW tomorrow through at
least Thursday, and this will promote near normal temperatures and
humidities, typical diurnal winds, and no threat for precipitation.
Guidance generally suggests a warming and drying trend late next
week into next weekend as a ridge builds over the area. However,
guidance is split as to the strength of this ridge and the resulting
warming. However, we do expect to warm to at least a little above
normal by next weekend with the potential for increasing offshore
(northeast) winds and poorer humidity recoveries. -Wright
&&
.PREV DISCUSSION... /Issued 449 PM PDT Sat Aug 21 2021/
Updated Aviation Discussion.
DISCUSSION...Satellite imagery shows mainly clear skies across
southern Oregon and northern California with a few cumulus here
and there. Additionally, smoke remains intermittent across
portions of Jackson County, the East Side, and northern California.
Breezy winds from the west may help Jackson County clear out
briefly this evening, but the other areas will remain smoky.
This set of circumstances is consistent with a trough that is
digging southeastward across the Pacific Northwest today and will
exit the area tonight into tomorrow. This gave us our strong
marine push early this morning, and expect another marine push
tonight with marine stratus returning to the Coast and Umpqua
Basin. There is a reasonable chance that the marine stratus could
spill over into Jackson County once again tonight.
Once this system leaves, the Pacific Northwest will remain in a
zonal flow pattern with very weak troughs continually moving
through through mid-week. This will create the potential for
additional marine pushes across the west side, breezy winds and
cooler temperatures for most of southern Oregon and northern
California. Precipitation, however, is not expected within the
forecast period except for light drizzle with the aforementioned
marine pushes, largely closer to the coast--but it likely would
not measure.
Although this pattern continues for most of the week, models
diverge their trend with the GFS ensemble trying to show more of
a ridging pattern and the ECMWF ensemble showing more of a
progressive "troughy" pattern. Although have largely based the
forecast on the National Blend of Models, did not allow the full
trend back to the thermal trough ridge with triple digit
temperatures in west side valleys and mid 90s east of the
Cascades. This is largely due to the fact that the NBM is leaning
heavily on the GFS in this instance, and the GFS ensemble is not
100 percent on board with the strong ridge/thermal trough pattern.
As such, it will be prudent to monitor these trends as another 100
degree day in Medford would have us break our record of the number
of hundred degree days in a year. The current record is 23 days of
100 degrees or more, and it was set in 1990. For 2021 in Medford,
we are currently sitting at 23 days of 100 degree plus days this
year. -Schaaf
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...
CA...None.
Pacific Coastal Waters...
- Small Craft Advisory until 5 PM PDT Monday for PZZ356-376.
- Small Craft Advisory from 11 AM Sunday to 5 PM PDT Monday for
PZZ350-370.
$$
BTL/MAP/MNF
Area Forecast Discussion
National Weather Service Marquette MI
749 PM EDT Sat Aug 21 2021
.SHORT TERM...(This evening through Sunday)
Issued at 242 PM EDT SAT AUG 21 2021
Water vapor imagery and RAP analysis show a vigorous, well-defined
shortwave lifting ne into nw Ontario. Extending southward from the
associated 992 mb sfc low is a pre-frontal sfc trough into central
Upper Mi with the cold front lagging back into western Lake Superior
and nw WI. Ahead of the trough, an area of stratocu is noted over
central Upper Mi on visible satellite imagery. A broken/narrow line
of convection (shra with some embedded isold thunder) is noted on
radar from eastern Lake Superior into western Alger and eastern
Delta counties where dewpoints are around 70F and MLCAPEs are noted
in the 500-1000 j/kg range. As time goes on this afternoon, the
better instability (MLCAPEs up to 1000 j/kg) will continue to get
pushed into the eastern counties of the U.P. As a result, have
generally confined convective PoPs the rest of the afternoon into
the east half counties per latest 18Z HRRR run, which seems to have
the best handle on the ongoing convection. Afternoon temps thus far
under partly cloudy to cloudy skies have risen into the upper 70s to
lower 80s.
The vigorous shortwave over southern Manitoba will continue lifting
ne, reaching Hudson Bay tonight. With best forcing/height falls
shifting ne with it, forcing will be diminishing with the cold front
moving across the fcst thru this evening. Expect breezy s winds
gusting up to 25-30mph ahead of the cold front, strongest at Grand
Marais in downsloping southerly flow. Postfrontal westerly winds
will likely gust to around 40mph on the Keweenaw based on potential
momentum transfer from mixing off fcst soundings. With incoming pres
rises around 4mb/3hr providing an isallobaric wind component aligned
with the gradient wind, would not be surprised if some gusts to
around 45mph occur at times for a few hrs late afternoon/early
evening. The southerly winds up Lake MI in advance of the cold front
today will continue to build waves this afternoon so the high swim
risk along the Lake MI beaches of Schoolcraft County still looks
warranted into this evening.
Shower potential will continue over the eastern fcst area this
evening until the cold front exits. In the wake of the front, high
pres will build toward the Upper Lakes tonight, bringing cooler and
drier air into the area. Temps tonight should slip down into the
upper 40s over the interior w trending up to around 60F along Lake
Superior.
Sunday, expect dry, cooler and less humid conditions as sfc high
pressure builds in quickly from the west in the wake of the cold
front. Max temps will probably be slightly cooler than seasonal
normals with highs from the upper 60s/lower 70s north to the mid 70s
interior west and south central. The cooler air in combination with
dew points falling back into the upper 40s to mid 50s should make
for a comfortable day. Waves generated from fairly gusty nw-n winds
behind the front will likely warrant a high swim risk for Alger
County and probably a moderate swim risk for Marquette County.
.LONG TERM...(Sunday night through Saturday)
Issued at 436 PM EDT SAT AUG 21 2021
This extended period looks to be somewhat active, with most of the
chances for rain looking to happen near the later half of the period.
To start off, we have a lifting low over northern MN that could
bring some showers and thunderstorms over our far west. However, as
the better forcing for the convection lifts upward and the front
associated with it dies out over us, expect precip chances to be
limited to the west Monday night. No severe weather is expected
Sunday night as the instability should be too low.
As height rises and WAA moves over us Monday, expect warmer
temperatures, mainly in the west. A lot of the U.P. could see highs
getting into the mid 80s Monday as a high pressure block remains
over the southern US. Expect warmer temperatures again Tuesday as
that same block remains pretty stationary and allows warmer
temperatures from the Desert SW to advect over us. May see some
showers Tuesday in the west as a low over the Canadian Prairie brings
height falls over us. As this low traverses east through northern
Ontario Tuesday and early Wednesday, expect shower and thunderstorms
to move through Upper MI. Expect drier conditions Thursday as
ridging begins to shift over us.
Model guidance does hint at a pretty long-lived precip event early
next weekend as troughing digs across the Northern Plains.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 737 PM EDT SAT AUG 21 2021
VFR conditions are anticipated to prevail through the period as a
much drier airmass moves into Upper Michigan behind today`s fropa.
The most significant impact continues to be the gusty winds,
although KSAW has already begun dropping off, with indications
pointing to KIWD on the decline as well. However, KCMX remains
impressively gusty, still reporting 40 knots there. This shouldn`t
last much longer, and have also indicated the downward trend there
as the evening progresses. For Sunday, weather conditions are
anticipated to be fair for aviation interests as surface high
pressure regains control of the region through the remainder of
this TAF period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 242 PM EDT SAT AUG 21 2021
A cold front will sweep across this afternoon and evening. After
frontal passage, incoming pres rises from the w will give
postfrontal west winds a boost. Until the axis of the pres rises
passes, there will be the potential for some gale force gusts to
around 35kt for a few hrs late aftn/early evening, particularly at
higher obs platforms. The area from just w and n of the Keweenaw
Peninsula toward Granite Island/Stannard Rock should be favored for
the higher wind gusts. Winds will then diminish to under 20kt from w
to e overnight thru Sun morning as high pres arrives. At the moment,
it appears winds will remain generally under 20kt Mon thru Wed.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Beach Hazards Statement until 10 PM EDT this evening for MIZ014.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...TAP
AVIATION...lg
MARINE...Voss
Area Forecast Discussion
National Weather Service Pocatello ID
223 PM MDT Sat Aug 21 2021
.SHORT TERM...Tonight through Mon night. Showers and thunderstorms
until late tonight with a frontal passage during the late evening.
We are still in an area of a marginal threat for thunderstorms.
Strongest thunderstorms if you believe the HRRR are tonight around
2100-2200 MDT in the Snake River plain, so an uneasy and unsettled
night weather-wise. The front will continue its eastward trek Sun
and poses a thunderstorm threat only over the ID-WY border. By
Mon, skies will clear and the temperature will be up 5 to 10
degrees for afternoon highs after a seasonally cool overnight.
Warming trend continues into the extended. With the upper level
ridge returning, wind will calm down Sun but get breezy again Mon
afternoon. Messick
.LONG TERM...Tuesday through Saturday.
Through the entire extended period Idaho is under a trof. Occasion
short waves will move through the westerly flow, which will likely
becmome more northwesterly as the week progresses. Timing of these
short waves seems moot at this point, because they will be glancing
blows to the north resulting in little to no threat of precipitation
to Idaho through the period. Temperatures starting out relatively
cool will finally push to normal levels by about Thursday.
Deterministic GFS/ECMWF both show significant wave moving through
next Saturday. While this still may be too far east to provide any
wx, it should help keep temperatures from getting too warm.
Crawford
&&
.AVIATION...
Scatteered light shower activity affecting various parts of the
basin at this time, but some thunderstorms have already fired up
over the favored southeastern Idaho area. Showers are featured as
predominant wx at all TAFs this evening with the exception of SUN
where they become less likely as system swings through from west to
east tonight. Moisture will be deepest over the eastern highlands
overnight, with some signifncant rains expected there. Thus have
kept previous TAF depiction of MVFR cigs at DIJ after 05Z. Most
areas will be clear and dry before 12Z with VFR outlook for Sunday.
Only DIJ may still have some low level clouds to clear out first
thing after sunrise before going SKC.
Crawford
&&
.FIRE WEATHER...Thunderstorms continue late tonight, some of them
strong to severe in outflow wind with areas of heavy rain
possible. Humid conditions will continue tonight and partially
into Sun, but really dry air starts entering the Salmon-Challis
NF and other Central Idaho Dispatch areas by then. This will
spread to the southeast by Mon, with a few low elevations
returning to below 15 percent. Mon is expected to see a return to
gusty wind, so depending on fuels, there may be some critical fire
weather conditions as early as that day. Lows continue to track
through southern Canada during the upcoming week, not enough to
bring any showers or thunderstorms except to perhaps the Targhee
NF and northern end of the Idaho Falls BLM. The main benefit is
that temperatures do not get really hot again until just beyond
the upcoming 7 day period. The drawback is that these lows will
bring breezy conditions while the landscape gets a chance to dry
out. Messick
.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 11 PM MDT this evening for IDZ422-425-427.
&&
$$
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Area Forecast Discussion
National Weather Service Sacramento CA
158 PM PDT Sat Aug 21 2021
.SYNOPSIS...
Smoke and haze from wildfires will continue to impact portions of
interior Northern California. Below normal high temperatures will
persist through early next week, warming to above normal Thursday
into Friday.
&&
.DISCUSSION...
Water vapor satellite imagery depicts a trough tracking through
the region this afternoon. This feature has resulted in increased
onshore flow and cooler temperatures across interior NorCal.
Forecast highs for this afternoon will range from the upper 70s to
upper 80s in the Valley. However, thick wildfire smoke may
inhibit warming at some locations. The HRRR smoke shows
improvement across the Sacramento Valley as winds will continue to
push smoke off to the east.
GOES-West fire temperature product is showing intense heat
signatures associated with the Caldor Fire this afternoon. Observed
wind gusts have ranged in the 20-30 mph range across the higher
elevations of the northern Sierra and southern Cascades. Local
gusts up to 40 mph are still possible. These increased southwest
winds will continue to bring elevated fire weather conditions to
portions of interior NorCal. A Red Flag Warning remains in effect
for portions of El Dorado County including the Caldor Fire until 8
PM PDT this evening given the potential for rapid spread of
the existing fire. Lighter winds are expected tonight and Sunday
as today`s trough ejects eastward.
Ensembles and clusters favor troughing remaining along the West
Coast early next week into mid-week. Temperatures will remain
below normal through early next week with seasonal temperatures
returning by mid-week. Locally gusty wind possible at times,
mainly in the Delta and over higher terrain in the afternoons into
evenings.
&&
.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...
Ensembles indicate that gradual warming and drying is likely to
continue during the second half of next week as the weak trough
gradually gives way to ridging from the eastern Pacific.
Temperature will be close to average at mid-week, then warm to
around 10 degrees above average by next weekend. Some increased
north wind possible Thursday and Friday, which may bring smoke
back to the valley.
&&
.AVIATION...
Smoke from area wildfires will continue to impact interior NorCal
today. Local south to west surface wind gusts 15-30 kts in the
Central Valley, strongest near the west Delta and mainly after
00Z. Widespread southwest surface wind gusts 15-30 kts Sierra
Nevada through 02Z Sunday.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM PDT this evening for Northern Sierra
Including the Tahoe and ElDorado NF/S West of the Sierra Crest.
&&
$$
...Update to aviation forecast discussion...
.DISCUSSION...
Issued at 307 PM CDT Sat Aug 21 2021
20Z water vapor shows one shortwave trough lifting north of MN
while another upper low propagates east over OR. Ridging was noted
along the gulf coast. This placed the forecast area in a weak
west southwesterly flow aloft with no obvious forcing upstream. At
the surface, a cold front had pushed into the TX panhandle and
the Ozarks. Drier air had moved through the northern parts of the
forecast area and the north breeze has been somewhat refreshing.
The pattern over the next several days keeps the upper ridge over
the southern plains while the mean westerlies impact the northern
tier of the country. So forcing for precip does not look
overwhelming from the model progs. However there may be some
isolated showers and thunderstorms over the coming 24 to 36 hours.
The first opportunity looks to be Sunday morning. There is
reasonable agreement from the operational solutions for a return
flow to develop late tonight and the RAP and NAM have some decent
theta-e advection along with good isentropic upglide. Forecast
soundings suggests there could be some elevated CAPE on the order of
1000 J/kg. While QPF progs are not overwhelming, there is some
signal for isolated showers and storms developing around daybreak
across central KS. So have inserted a slight chance POP through mid
morning to cover this potential. The second opportunity should be
Sunday evening. Models continue to show storms developing across
central NEB within an axis of low level moisture convergence. The
general flow may allow for some of these storms to skirt the state
line and move into some of the northern counties. The NAM and GFS
show plenty of instability developing as low level dewpoints in the
70s surge back north through the day and 0-6KM bulk shear may be a
little better for organized updrafts. So we`ll need to be on the
lookout for some severe weather affecting parts of northern KS
Sunday evening. With the dry air moving south tonight and skies
mainly clear, think lows will fall into the lower and middle 60s. A
southerly wind develops early Sunday with the warm air and moisture
returning north through the day Sunday. With this highs are expected
to be back into the upper 80s and lower 90s. We could even see some
heat indices around 100 across central KS is the dewpoint forecast
is correct.
The forecast for Monday through Wednesday is for hot and dry weather
to return. The overall pattern changes little with the center of the
upper ridge drifting north over OK. So prospects for decent forcing
look low and flow is likely to be pretty weak. because of this POPs
were kept at 10 percent or less. Will need to watch out for heat
indices in the afternoons as forecast highs are expected to climb
back into the middle 90s to around 100. Lows look to be mild with
middle 70s forecast.
Thursday through Saturday does not see a significant change to the
pattern. the National Blend of Models (NBM) has some 20 to 30 percent
POPs in the forecast with the potential for a weak boundary to slide
into northern KS. However the 12Z operational runs look to stall the
boundary out near the NEB state line. Confidence in POPs is marginal
and have not changed what the NBM has inserted since it basically is
close to climatology. With the 12Z models keeping the boundary north
of the area Thursday, trended temps warmer with highs remaining in
the middle to upper 90s for Thursday. Looking just beyond the
forecast, the ECMWF and GFS have a shortwave trough digging into the
central plains with a cold front moving in. Timing differences add
some uncertainty, but think the better potential for widespread rain
may be Saturday night or Sunday of next weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 542 PM CDT Sat Aug 21 2021
VFR conditions continue through the overnight with dry air in
place. Moisture return takes place into the morning tomorrow with
cumulus developing as mixing takes place with some stronger winds
mixing to the surface making for generally breezy conditions from
the south.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Wolters
AVIATION...Drake