Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/16/21
Area Forecast Discussion
National Weather Service Bismarck ND
Issued by National Weather Service Grand Forks ND
651 PM CDT Wed Sep 15 2021
.UPDATE...
Issued at 640 PM CDT Wed Sep 15 2021
RH values still in the 20-30 percent range, but are starting to
show their rise as temps start to dip for the evening. Winds still
gust up 20-30 mph, especially in northwest ND, but starting to
notice a decrease trend as well. Still thinking RFW expiration
time at 8 PM CDT is appropriate with critical fire weather
conditions still present, but likely to see improvement shortly as
we near sunset.
There is a trend within latest HRRR runs of a little more robust
elevated thunderstorm development on the nose of a thermal ridge
working its way eastward into the James River Valley and Devils
Lake basin after 00 UTC. There has been some weakly agitated Cu
within this ridge noted on satellite along a wind shift in central
ND this afternoon, which would be the area of clouds to monitor
for development. This coincides with a developing LLJ for the
evening feeding on weak MUCAPE within this thermal ridge. While
most CAMs have depicted thunderstorm development this evening into
eastern ND, the HRRR has been a little earlier in development
starting convection within far eastern FA. Given the weak
instability and potentially sufficient shear in place, there may
be the potential for this evening`s elevated convection to
produce some hail. Continuing to monitor trends in cloud
development before making any adjustments to PoPs and messaging.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 343 PM CDT Wed Sep 15 2021
Main focus for hazardous weather within the short term period
remains on fire weather concerns, both for this evening as well as
near critical fire weather conditions during the day Thursday in
western ND.
Warm and dry air mass currently over the western half of ND is
noted by temps in the low to mid 80s and widespread RH values
at or below 25 percent. This air mass coupled with wind gust up to
25-35 mph out of the west will continue critical fire weather
conditions through the remainder of the afternoon into early
evening. The Red Flag Warning for these conditions will remain in
effect until 8 PM CDT / 9 PM MDT. After sunset, temps/RH will
lower/rise with weakening winds, lessening fire weather concerns
for today.
A cold front moves through from the northwest tonight into early
tomorrow. Meager moisture streaming in from the Pac NW is
expected to overspread the front bringing some light rain showers
portions of the FA, although very little precip will accumulate if
at all. More notably is the very dry air mass edging into the
northern High Plains behind the front. This very dry air air mass
composed of PWAT values around 0.2 inches (below the 10th
percentile for this time of year per KBIS RAOB PWAT climatology)
should help push RH values down in the 25-30 percent range,
possibly lower. These RH values are in spite of temps staying
mild in the 60s. Driest conditions are expected for portions of
western ND. This dryness along with continued breezy northwest
winds during the afternoon will allow for near critical fire
weather conditions to develop again during the day Thursday for
western ND.
.LONG TERM...(Thursday night through Wednesday)
Issued at 343 PM CDT Wed Sep 15 2021
The very dry and seasonably cool post frontal air mass over the
northern High Plains will allow for temps to dip below 40 degrees
Friday morning for some. Those favored to see these temps mostly
reside in western portions of the FA, with the help of calm winds
induced by terrain. Otherwise, a steady light westerly wind will
prevent temps from bottoming out. Still, those that see temps in
the mid 30s have a chance for some frost. Hard to pinpoint these
locations at this time, but locations west of the Missouri
River/Lake Sak are currently favored for this potential.
The Thu/Fri cool spell will be shortlived as upper ridging sets
up over the central CONUS into the weekend. There is a strong
signal for above average temps, as indicated by EC EFI values
within MaxT over the Dakotas Sat, Sun, and Mon. Consensus between
ensembles is high enough to introduce low 90s back into the
forecast on Saturday.
Getting into early next week, ensembles depict a migration of the
ridge axis to the east allowing upper troughing to move towards
the central CONUS. While this should increase rain potential,
there remains large uncertainty in how much moisture moves towards
the western Dakotas. This moisture content, and details revolving
around shortwave trough passages within the long wave troughing
remains unclear. Therefore, while there is a chance for increased
precip early next week, confidence remains low at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 640 PM CDT Wed Sep 15 2021
VFR TAFs are expected throughout the period. Breezy northwest
winds will relax under 15 kt between 02-14 UTC before picking back
up Thursday afternoon after a cold frontal passage tonight. There
is a slight chance for light rain showers with the front tonight
into Thursday, however confidence in rain impacting any TAF site
was low enough to omit from TAFs for now. Will amend for potential
showers as needed.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM CDT /7 PM MDT/ this evening for
NDZ001-009-017-018-031>033-040-041-043-044.
&&
$$
UPDATE...CJ
SHORT TERM...CJ
LONG TERM...CJ
AVIATION...CJ
Area Forecast Discussion
National Weather Service Dodge City KS
620 PM CDT Wed Sep 15 2021
...Updated Aviation Discussion...
.SHORT TERM...(This evening through Thursday)
Issued at 347 PM CDT Wed Sep 15 2021
The afternoon water vapor loop and RAP analysis revealed a zonal
west-northwest flow pattern aloft across the northwestern half of
the CONUS. This has led to the redevelopment of the leeside trough
and thus a return of the breezy south winds. South winds will
continue all through the Short Term period, and the increasing lower
tropospheric thicknesses will support a continued warm up in surface
temperature as well. The MSLP gradient between the leeside trough
out west and a surface high across the mid Mississippi Valley will
be greatest across the western half of Kansas, thus surface winds are
expected to be in the 20-25 mph range sustained with gusts above 30
mph. As 850mb temperatures continue to warm, we will see resulting
surface temperatures warmer tomorrow vs. today with forecast highs
in the mid 90s along the Colorado border to around 90 across
portions of central and south central Kansas.
.LONG TERM...(Thursday night through Wednesday)
Issued at 347 PM CDT Wed Sep 15 2021
A shortwave trough will zip east quickly across the Northern Plains
with the larger scale zonal flow regime. This system will bring the
next cold front south across northern and western Kansas during the
day Friday. There will likely be enough convergence along this front
to promote some widely scattered thunderstorms. We will carry some
Slight Chance 20 POPs from Dodge City to Hays, and these may even
need to be increase and expanded in coverage as the latest global
models suggest this front will be a little stronger, with a more
aggressive push into southwest Kansas by early evening. All three of
the latest global spectral models (ECMWF, GFS, GDPS) have a QPF
signal in vicinity of this front Friday afternoon and/or evening.
Friday`s thunderstorm activity, should it materialize, will be in a
rather low deep layer shear environment, so organized severe weather
is fairly low probability.
The late Friday front will quickly dissolve as a mid-tropospheric
ridge builds from New Mexico northeast across Kansas over the
upcoming weekend. While this is occurring, the next storm system out
west will begin to take shape, which latest models show being a much
larger/deeper trough. This late weekend/early next week trough will
lead to two things: 1) hot to very hot days Sunday and Monday as
southwesterly downslope increases, and 2) a stronger cold front push
thereafter on Monday Night or early Tuesday. This is expected to be
a legitimate Fall storm system which is expected to organize into a
formidable mid-latitude cyclone to our north. We could be dealing
with very strong northwest winds behind the cold front tied to this
system, along with potentially much cooler temperatures. Since the
early next week storm will most likely form and mature to our north,
widespread precipitation chances look pretty bleak at this point for
much of western Kansas.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 615 PM CDT Wed Sep 15 2021
Gusty southeast winds at 23z Wednesday will fall back into the 10
to 15 knot range by 02z Thursday. The southeasterly flow will
become south southwest between 10z and 13z Thursday and then begin
to increase. Gusty southwest winds of around 20 knots are
expected to develop between 15z and 18z and then continue through
the remainder of the day. BUFR soundings indicating VFR conditions
overnight and Thursday. Scattered clouds in the 4000 to 8000ft
AGL level will be possible after 18z.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 64 93 65 91 / 0 0 0 20
GCK 63 93 63 89 / 0 0 0 10
EHA 62 94 61 89 / 0 0 0 0
LBL 62 92 63 93 / 0 0 0 10
HYS 64 92 66 86 / 0 0 10 20
P28 64 93 65 92 / 0 0 0 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Umscheid
LONG TERM...Umscheid
AVIATION...Burgert
Area Forecast Discussion
National Weather Service Grand Forks ND
703 PM CDT Wed Sep 15 2021
.UPDATE...
Issued at 653 PM CDT Wed Sep 15 2021
Warm front continues pushing east through the area with light
rain showers and weak thunderstorms near Bemidji continue east,
and should exit the FA in a few hours.
There is a trend within latest HRRR runs of a little more robust
elevated thunderstorm development on the nose of a thermal ridge
working its way eastward into the James River Valley and Devils
Lake basin after 00 UTC. There has been some weakly agitated Cu
within this ridge noted on satellite along a wind shift in central
ND this afternoon, which would be the area of clouds to monitor
for development. This coincides with a developing LLJ for the
evening feeding on weak MUCAPE within this thermal ridge. While
most CAMs have depicted thunderstorm development this evening into
eastern ND, the HRRR has been a little earlier in development
starting convection before 03 UTC. This potentially earlier onset
of thunderstorms may put northeastern ND and the northern two
thirds of the Red River Valley at play with this evening`s
convective potential.
Given the weak instability and potentially sufficient shear in
place, there may be the potential for this evening`s elevated
convection to produce some hail, some of which may briefly reach
severe criteria. Continuing to monitor trends in cloud development
before making any adjustments to PoPs and messaging.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 323 PM CDT Wed Sep 15 2021
Precip timing and strength continue to be the challenges for the
short term.
Scattered showers and a few thunderstorms have become more
widespread from the central and northern Red River Valley into
northwestern MN as warm air advection continues on the front side
of the incoming surface trough. MU CAPE continues to be lagging
behind the main lift from the warm air advection, so think
isolated lightning strikes will be the main impact. These showers
will move off into central MN by this evening. However, CAMs and a
few of the global models redevelop some showers and thunderstorms
along the northern Red River Valley late evening/around midnight
as the surface trough axis pushes into the area. This activity
will push into western MN during the early overnight hours. A few
of the CAMs develop some fairly robust convection during the
05-10Z time frame over our MN counties, and MU CAPES will be
increasing. Uncertainty with the timing of the trough overnight
prevents getting too gung ho for elevated severe potential, but
did increase POPs across our east for the early AM hours. Cloud
cover and winds will keep the temps a bit more mild tonight than
last night, mainly in the 50s to low 60s.
The main upper trough digs into Manitoba and the Dakotas tomorrow,
with a cold front pushing into our CWA. Much will depend on the
exact timing of the cold front and if we get some decent
instability in our southeastern counties before the boundary comes
through. There is some indication of some clearing and temps near
80 south of the I-94 corridor, with only low 60s in northeastern
ND where the front comes through early. Several of the
deterministic runs have some surface based CAPE values over 1500
J/kg in west central MN, with deep layer bulk shear around 40-50
kts. Some strong to severe convection with a few supercells
developing will be possible for a short window before the front
pushes through Thursday afternoon. Will continue to message severe
threat in the far eastern counties. Thunderstorm will move off
quickly to the east Thursday and high pressure building in should
drop temps back into the 40s.
.LONG TERM...(Friday through Wednesday)
Issued at 323 PM CDT Wed Sep 15 2021
Impactful weather chances will arise after the upcoming weekend, and
could last for a couple of days.
A breezy/windy and warm start to the extended period with zonal to
southwest flow aloft will be featured on Sat providing for above
average temps Sat and well above by Sun as ensembles depict a MAXing
out of 850 mb temps at 20C or better! 30 kts of 850 mb SW wind could
mix down efficiently to provide near surface speeds of 15 to 25 mph
with higher gusts. Afterwards, moisture will be increasing by later Sun
into Mon as sharp trough over intermountain west sharpens the S-SW flow
over the forecast area.
All is pointing toward a wetter time from later Mon/Mon night as the
upstream trough turns into closed/cutoff low proximal to our region by
Tue and even into Wed. GEFS plumes peg a dose of an inch or more of
rainfall, with the ops GFS climbing to somewhere near 3 inches during
this period of time. And given the slow transit of this feature from
west to east, it is entirely possible these amounts could be something
other than convective feedback within the model.
A cooling trend should kick in from the middle of next week and
beyond.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 653 PM CDT Wed Sep 15 2021
VFR TAFs are expected throughout the period. Light rain showers
near KBJI should end by 03 UTC. Breezy southerly winds start to
relax under 15 kt around 02-04 UTC as a warm front moves into the
area. There is a chance for widely scattered thunderstorms within
northeastern North Dakota into northwestern Minnesota after 03
UTC, some of which may produce hail. However confidence in
potential thunderstorms impacting any TAF site was low enough to
omit from TAFs for now. Will amend for potential storms needed.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...CJ
SHORT TERM...JR
LONG TERM...WJB
AVIATION...CJ
Area Forecast Discussion
National Weather Service Goodland KS
526 PM MDT Wed Sep 15 2021
.SHORT TERM...(This evening through Friday night)
Issued at 135 PM MDT Wed Sep 15 2021
Satellite and 500 mb RAP analysis showed a ridge building over the
Desert Southwest today, placing weak northwest flow over the region.
At the surface, a lee trough formed along the Front Range. Dense fog
and stratus gave way to sunny skies in the morning as southerly
winds increased with gusts at 20 to 30 mph by the afternoon. At 1 PM
MT, temperatures ranged in the upper 70s to mid 80s.
Flow aloft turns nearly zonal tonight as the aforementioned ridge
gradually moves east into the southern/central Plains, leading to
continued dry weather. Meanwhile, a trough traverses the western
Canadian border and northern Rockies. Expect lows in the mid 50s to
mid 60s.
Another warm day is forecast on Thursday with highs in the low 90s.
The lee trough prevails, aiding the development of some gusty south
winds, particularly in northwest Kansas and southwest Nebraska. That
being said, attention turns towards fire weather. Elevated to near
critical fire weather conditions are anticipated roughly along and
west of Highway 83. Relative humidities are forecast as low as 16 to
20 percent along and west of the Colorado border during the
afternoon, with 20 plus to the east. Fortunately, the gustier winds
are not collocated with the lowest humidities.
The Canadian border trough pushes east Thursday night and a cold
front is expected to push into the High Plains, including our area.
A line of thunderstorms will initiate along the boundary by the
evening hours. Most of this activity should remain north of the
region; however, a few storms skimming our area along the Nebraska
border cannot be ruled out. Have insert a slight chance of storms
during the evening and overnight hours as a result for Yuma county
and counties along the KS/NE border. Precipitation looks to largely
exit the area by Friday morning as temperatures fall into the low
50s to mid 60s. Severe weather is not currently anticipated.
A cooler day is forecast on Friday with the front stalling along our
southern zones. High temperatures range from the 70s in eastern
Colorado to the mid 80s in Gove and Graham counties. Conditions
should be dry, with a potential for some north winds gusting to 35
mph or so behind the boundary during the morning and afternoon.
Upper ridging strengthens through the nighttime hours, with lows
mainly in the 50s.
.LONG TERM...(Saturday through Wednesday)
Issued at 152 PM MDT Wed Sep 15 2021
A significant change in the pattern is expected early next week
as strong trough begins to move over the Rockies and into the
plains. Medium range models have decent agreement that this
pattern shift will occur, although the specifics remain uncertain.
Current data supports a significant cool down in the Tuesday-
Wednesday time period with temperatures dropping down into the 70s
behind the system and perhaps seeing low temperatures approach
the 30s by Wednesday morning. Timing of the system and associated
front will have a major impact on the exact temperature values,
confidence is high a major cool down will occur next week.
Despite the strong system, confidence in meaningful precipitation
not high at this point as hot and dry airmass will precede the
system with trajectories not really pointing to a good source for
advecting moisture into the area so precipitation chances appear
minimal. Will have to watch the Monday-Tuesday period closely as
potential for an afternoon strong frontal passage, a deepening
upper low could be a good set up for a period of strong winds and
blowing dust given the preceding hot and dry conditions.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 525 PM MDT Wed Sep 15 2021
VFR conditions /clear skies/ will rule through the TAF period.
Breezy S-SSW winds will decrease to 10-15 knots AOA sunset this
evening.. persist at that magnitude through the remainder of the
night.. then increase to 15-25 knots within a few hours after
sunrise Thu.. as the depth of the mixed layer increases.
A southerly LLJ will likely develop within a few hours after
sunset this evening, resulting in a potential for southerly LLWS
at both terminals. Guidance suggests that the MCK terminal is
more likely to be affected, however.. in typical southerly LLJ
regimes (e.g. western KS is situated on the immediate eastern
periphery of a lee trough/cyclone in CO).. guidance notoriously
under-represents the magnitude of southerly low-level jets (LLJs)
in far western KS.. especially near the KS/CO border -- where a
relatively tight H85 height gradient (and west-east gradient in
flow magnitude) is often present. With this in mind.. LLWS is
quite possible at the GLD terminal, as well. LLWS will abate AOA
sunrise Thu.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JBH
LONG TERM...JRM
AVIATION...VINCENT
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1007 PM EDT Wed Sep 15 2021
.SYNOPSIS...
Daily chances for afternoon showers and thunderstorms are in the
forecast through the upcoming weekend as moisture remains across the
area. Precip chances diminish next week with drier high pressure
building in. Temperatures will remain above normal through much of
the period.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 1000 PM EDT Wednesday: Forecast late this evening is tracking
decently well as weak upglide has sustained stratiform shower
activity across much of the area. If anything PoPs are a little
underdone, but expect the weather will catch up with the forecast
with waning coverage overnight. Lightning has been non-existent so
we are good to let the thunder mention go tonight with the latest
guidance continuing to support little if any lighting into Thursday
(although the latest RAP has trended towards modest instability
southeast of I-85). Low clouds have been slow to develop so far
tonight, but still think the remnant cool pool from earlier
convection and light rain will help gin up a low cloud deck,
especially across the Upstate of SC. The cloud cover will support
above normal overnight lows tonight.
Otherwise, given better moisture content across the board, the
development of fog/low stratus is possible in mountain valleys. With
enhanced WAA and moisture flux compared to Wednesday morning,
Thursday morning may see a more robust stratus deck break out across
the southeast Piedmont and Upstate; where today the deck did not
reach the Charlotte-Mecklenburg area, current thinking is that it
may extend farther north Thursday morning and introduce some
visibility restrictions. Thursday afternoon, CAMs once again
predict scattered showers and with perhaps some thunder in the
strongest cells, owing to increasingly moist tropical air building
into the area. Extensive cloud cover will cap daytime highs near or
just below normal.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 210 PM EDT Wednesday: Short waves will ripple across the area
Friday and Saturday in the general southwesterly flow aloft. At the
surface, weak high pressure noses in from the north as the remnants
of Nicholas dissipate along the Gulf coast and a potential tropical
cyclone moves from near the NC coast to the northeast. Southeasterly
low level flow will keep moisture over the area through the period.
However, the flow is rather weak. PW values aren`t especially high
through the period, but will be higher on Friday than Saturday with
higher values over the western CWFA both days. Instability will be
on the weak side as well with values below 1000 J/kg each day. There
will be some weak upper divergence to go along with the weak short
waves. Therefore, expect enough forcing, moisture, and instability
for convection each day, favoring the mountains both days. There
will be a diurnal trend in coverage, but showers my linger through
the night, especially across the mountains.
Can`t rule out an isolated strong thunderstorm, or some brief heavy
rainfall, but overall chance of severe storms or flash flooding is
low. Lows will be above normal through the period. Highs on Thursday
will be near normal for the CLT metro and a little below normal
elsewhere. Highs will be above normal all areas Saturday.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 230 PM EDT Wednesday: An upper ridge builds over the East
Coast Sunday and Monday then slides east on Tuesday and Wednesday as
an upper low moves into the Mid-west. At the surface, high pressure
over the northeast US remains ridged into our area despite sliding
off shore on Tuesday. The ridge does weaken Wednesday as a cold
front approaches from the west. Drier air moves in from the
northeast on Sunday and remains in place through the period. The
guidance is showing better agreement on overall lower precip chances
with the drier air and ridges in place. Although there is an
increase in PoP on Wednesday as the front approaches, better chances
remain to our west closer to the front. Have isolated east to
scattered west mainly diurnal chance of convection through the
period. Lows and highs start out above normal then drop to near
normal by the end of the period.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Below normal confidence in 00Z TAFs. Waning
SHRA with isolated -TSRA has roughly a 40 percent chance of hanging
together into the I-85 corridor including KCLT and KGSP through 06Z.
Associated cool pool from earlier convection will likely support
MVFR or lower cigs developing by 12Z with slower than normal
improvement after 12Z due to extensive mid to high clouds.
Outlook: A relative lull in activity is possible by Friday,
especially east of I-26 as drier air works into the area. More
widespread active weather may return this weekend as a front
approaches from the west. Night to morning low cigs/vsbys possible,
especially across mountain valleys.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...RWH
NEAR TERM...MPR/Munroe
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...Munroe
Area Forecast Discussion
National Weather Service Gray ME
926 PM EDT Wed Sep 15 2021
.SYNOPSIS...
Cold front continues to cross the area this evening bringing
strong to severe storms to the area. Storms will weaken towards
sunset with lingering showers and some patchy fog expected
overnight. High pressure crosses the area Thursday for mostly
fair weather. Low pressure passes well offshore through the
weekend while a cold front approaches from the northwest late
Saturday. High pressure builds in Sunday bringing fair weather
through the first half of next week.
&&
.NEAR TERM /TONIGHT/...
920 PM Update...Thunderstorm threat has greatly diminished this
evening with the surface front sagging south out of the area
and forcing exiting to the north and east. Therefore have taken
thunder out of the forecast... however I did bump up PoP through
the overnight period with a swath of stratiform rain over
central/northern New Hampshire extending into western Maine.
Elsewhere showers are more common. Observing mainly light rain
but pockets of moderate rain are making it in as well.
550 PM Update... Have updated the near term PoP and weather
forecast based on latest observed trends with line segments of
severe convection clearing southeast of the foothills.
Stratiform rain continues behind these lines of convection and
as the severe threat has passed across the north and interior
have cancelled the severe thunderstorm watch for these areas.
Storms continue to maintain themselves into the coastal counties
as well as southeastern NH and the severe thunderstorms watch
continues here until 8 pm. If current trends prevail the severe
threat may drop off sooner than 8 pm. Latest RAP analysis does
show favorable CAPE and shear along the coastal plain so people
are encouraged to maintain aware of ongoing severe warnings
along the coast into southern New Hampshire.
ORIGINAL DISCUSSION...
Severe Thunder Storm Watch remains in effect for the entire
forecast area through 8 PM EDT. Latest radar shows storms
oriented in linear segments from SW to NE from Albany, NY
through northern NH and the western mountains of Maine. These
storms will slide southeast through this evening with damaging
winds and large hail the primary threats along with locally
heavy rainfall. Latest RAP analysis shows the environment
downstream of ongoing convection with 1000 to upwards of 2000
J/kg of MLCAPE juxtaposed with 45 to 50 kts of effective bulk
shear. This overlap is maximized over central NH through
interior SW Maine where there is also some low level helicity.
It is this area where we have been highlighted as the greatest
risk of rotating severe storms that will capable of producing a
tornado.
Storms are expected to move into coastal areas and southern New
Hampshire between 6 and 8 PM while upper level support from jet
streak moves north of the area. CAMs continue to suggest that as
storms approach the coast and southern New Hampshire they will be
less intense than over the interior. The overall severe threat is
expected to drop off after 8 PM.
Tonight the cold front will be pushing offshore while mesoscale
guidance show anafrontal showers continuing over areas south of the
mountains. Plenty of low level moisture will be around for areas of
patchy fog to develop tonight. Drier air will work into northern
areas as high pressure builds in from the NW towards morning. Low
tonight will range from the low 50s north to mid 60s south.
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
Thursday will be much cooler with high pressure crossing the
area. The cold front that crosses tonight will get hung up over
southern New England leading to more clouds across far southern
areas along with slight chances for showers. On the whole it
will be a fair weather day across much of the area with highs in
the 70s.
High pressure continues off into the Atlantic Thursday night while a
subtropical low spins off the Mid-Atlantic coastline.
Persistent onshore flow will lead to increasing low clouds south
of the mountains with slight chances for showers across
southern areas. Lows Thursday night will range from the upper
40s north to low 60s south.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
High Impact Weather Potential: Minimal.
--Pattern and Implications--
The long term forecast period opens with the primary teleconnection
signals being a +EPO / -PNA with no significant downstream blocking
which overall indicates an ample opportunity for Pacific flow across
the lower 48 which is a warm signal. Through the weekend, heights
will fall along the Pacific Coast as a longwave trough settles into
the region. This, in turn, will force the downstream pattern to
amplify...with ridging across central North America and a trough
across the northeast. With a lack of downstream
blocking...however...the increasingly amplified pattern will remain
mobile...with the first half of next week suggesting a trough-ridge
setup across the United States...with rather impressive heights over
the eastern United States given middle/latter September.
Overall...the only sensible weather impacts are with the initial
trough that builds into the region Saturday night-Sunday.
Beyond this...an extended period of anomalously warm and dry
conditions looks likely as a sprawling area of high pressure
sits over or just east of the region.
--Daily Details--
Friday: Ridge of high pressure overhead with low pressure well south
of New England south of stalled frontal boundary. As mentioned by
the overnight shift...the position of the high allows for a push of
maritime moisture through the day with model soundings suggesting
the potential for drizzle or a few light showers. Do at least
expect plenty of clouds which will likely keep temperatures a bit
below fully mixed values...with upper 60s/lower 70s likely
here...with some mid 70s possible along the CT Valley and across the
north where more sun will likely be realized.
Saturday - Sunday: Slow moving cold front will be near the St.
Lawrence Seaway to start the day Saturday...crossing the region late
in the day or Saturday night with drier air moving into the region
for Sunday. Despite some continuation to the fog/stratus overnight
Friday night...expect improving conditions ahead of the front during
the day Saturday. Consensus timing on the front itself would bring
it into the mountains Saturday evening...crossing from north to
south across the region Saturday night. With mid/upper level
forcing quickly departing the region overnight..expect at least some
shower activity to reach the mountains by Saturday evening...but
likely drying up south of the mountains overnight. Instability
profiles are not that supportive for thunder...and neither is the
timing...so will continue to leave any thunder mention out of the
forecast. As for temperatures T9s warm to the upper teens ahead of
the front...and step back to around +15C behind it on Sunday.
Therefore...highs will likely reach the upper 70s with a few spots
touching 80 Saturday...with lower to mid 70s more the rule on
Sunday.
Monday through Wednesday: Warm and dry will be the story for next
week with amplified mid level ridge overhead with ample sun and T9s
in the mid/upper teens suggesting high temperatures in the upper 70s
to around 80 with the dry airmass allowing lows back into the 50s to
around 60 each night. These airmasses can have the tendency to over
perform in terms of temperatures...so it is possible that these
values may need some upward adjustments in the coming days.
&&
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
Short Term...
SHRA and TS will cross the area from NW to SE bringing periods
of MVFR and IFR in heavier cells through 00Z. TS transition to
more scattered SHRA overnight with areas of fog and low cigs
bringing IFR/LIFR to most terminals. Conditions improve to VFR
Thursday as high pressure crosses the area. Clouds with thicken
and lower Thursday night with persistent onshore flow and
MVFR/IFR conditions south of the mountains.
Long Term /Friday through Monday/...
Could see restrictions in low clouds and potential drizzle
Friday/Friday night especially coastal terminals with conditions
likely improving on Saturday. Beyond this...VFR conditions will
dominate the remainder of the long term period with some potential
for showers Saturday night into Sunday LEB/HIE/AUG with isolated
restrictions. Winds will generally be light through the period.
&&
.MARINE...
Short Term...
Cold front approaches from the NW with southerly winds gusting
to 25 kts through the first part of tonight. Showers and
thunderstorms will approach the waters towards 8 pm, but are
expected to become less intense as the enter the waters. Seas
will run 5-6 feet through the first part of tonight with winds
and seas dropping below SCA conditions around midnight. High
pressure crosses to the north of the waters Thursday for quiet
conditions on the waters.
Long Term...
Watching waves in the Saturday night-Sunday period in response to
the potential development of a tropical system /see National
Hurricane Center for more details/ that looks to remain well south
and east of the Gulf of Maine waters...but with waves potentially
reaching SCA levels as the system makes it/s closest approach.
Otherwise...no hazards are expected.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
UPDATE...Casey
NEAR/SHORT TERM...Schroeter
LONG TERM...Arnott
Area Forecast Discussion
National Weather Service Marquette MI
738 PM EDT Wed Sep 15 2021
.SHORT TERM...(This evening through Thursday)
Issued at 411 PM EDT WED SEP 15 2021
Seasonable day across Upper Michigan with highs near 70 and diurnal
cu across much of the area. GOES wv imagery and RAP analysis show a
ridge of high pressure shifting overhead of the UP with plenty of
dry air as a deeper sfc trof is approaching from the west from the
Canadian Prairies into the Dakotas. Radar and sfc obs suggest a lake
breeze moving in through Marquette County with 69 for a high here at
the office at 2 and now back down to 65. As we head further into
this evening, expect some higher clouds to move into the area as
winds back more to the W and then to the SW with WAA beginning.
Tonight, ridge axis shifts east as the trof approaches, bringing the
chance for some light showers across the western lake, but dry air
ahead of this trof should hinder the pcpn chances previous fcsts had
across the land. An anomalously strong LLJ of 50+kts looks to
approach the UP late tonight into tomorrow morning, bringing some
gusty conditions around sunrise tomorrow across the west. In typical
WAA stability fashion, gusts will probably not be consistent to
begin, but more intermittent until the day gets going and PBL
decouples.
While we could see a few showers/storms persist into the wern UP or
Keweenaw on Thursday morning, model soundings suggest dry air should
limit this chances quite well. Strong theta-e adv admist a 40-50kt
LLJ could be enough to overcome a small cap and bring some elevated
instability...but low-level dry air will still be abundant, limiting
accums and potential. I held off on PoPs for now, but future updates
may need to include these again. The main story on Thursday will be
the gusty southerly winds. Upstream obs in the Dakotas and Manitoba
suggest a bit of what`s to come with gusts in the upper 20 to low
30kt range and Upper Michigan should see similar conditions through
the day tomorrow. These stronger southerly winds will also downslope
into Marquette and Munising, bringing the higher temps in the UP to
those locations...around 80 or a little below, with 70s everywhere
else...low 70s d/s of Lk Michigan.
.LONG TERM...(Thursday night through Wednesday)
Issued at 431 PM EDT WED SEP 15 2021
The extended should start with a dying cold front moving into the
U.P. from the northwest Thursday night. Expect the rain showers and
thunderstorms to start moving over the western CWA around midnight
EDT. As the convection continues eastward throughout the night,
expect shower and thunderstorm activity to die down as the cold
front stalls out and dies. No heavy rainfall is expected from this
cold front, though having some more rainfall in the west would
definitely be nice to have out there considering the drought
conditions. There is a possibility for some strong thunderstorms,
but I`m not quite sold 100% yet, as models predict a large cap for
convection at the sfc to overcome, instability seems rather modest
(~500 to 1000 J/kg), and the storms should be coming over us during
the night (when there is no diurnal heating). On top of that, the
front is dying as it passes over us, which means there should be
less forcing as the night goes on. However, 0-6 km bulk shear values
are going to be around 35 to 50 knots during Thursday night; if
anything did happen, it would be wind and hail damage related. One
thing worth noting is that is should be fairly breezy across the
area Thursday night, as a strong pressure gradient is expected
behind and ahead of the cold front. As the front dies, expect the
wind gusts to weaken.
On Friday, as the front continues eastward, expect rainfall to get a
little extra `umph` with a weak shortwave passing through Upper MI.
This should bring some more light rainfall over us, especially in
the east where the cold front is expected to be during the morning
hours. Limited thunderstorm chances to slight Friday as MUCAPEs look
to be around 500 J/kg or less. Chances for strong storms/severe
weather look to be lower Friday than on Thursday night (though I
suppose there is a very, very small chance some severe weather still
given the bulk shear values still remaining 35 to 50 knots across
the area and the slight increase in forcing from the weak
shortwave). Expect rainfall to get out of our area by early Friday
evening.
Saturday should be a sunny and pleasant day, as ridging moves over
us due to high pressure from the Desert SW advecting northeast to
the Ohio River Valley. Cool Canadian air should keep temperatures
rather modest, with high temps only expected to get into the low
70s. As the high pressure slowly progs east, expect WAA to move back
over us Saturday night as a low pressure from Alberta approaches
from the west.
We could approach record high temps Sunday as the ENS and NAEFS show
temps around the 99th percentile. I wouldn`t be surprised if we saw
some diurnal showers and thunderstorms Sunday given abundant
instability, but not quite sold on them occurring quite yet as there
is a convective complex over the Southeast US; there is also some
capping in the 850mb level. Another very warm day looks to be in
store for us next Monday as southwest winds are expected to keep
feeding us air from the Desert SW.
Models diverge a bit for the later half of the extended period.
However, what they do agree on is that a low pressure should form
just east of the Colorado Rockies early next week. This low should
form a warm front just north of us in northern Ontario and a cold
front by the middle of next week. This low is expected to approach
the U.P. sometime during the middle of next week, bringing with it
rainfall across the area. Some model guidance has the comma head of
the low moving over us near the end of the extended period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 737 PM EDT WED SEP 15 2021
VFR conditions are expected at KIWD/KCMX/KSAW thru this fcst period.
There is a small potential that shra could affect KIWD/KCMX late Thu
morning/early aftn, but potential is too low to include mention with
this fcst issuance. A strong low-level jet will approach western
Upper MI late tonight/early Thu morning, resulting in LLWS at KIWD,
KCMX and possibly KSAW as well before boundary layer mixing begins
later morning. Gusty southerly winds to 25-30kt should be the rule
Thu aftn into Thu night.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 411 PM EDT WED SEP 15 2021
Sfc ridge of high pressure this aftn will shift east as a trof
approaches western Lk Superior tonight. Ahead of this trof, a strong
low-level jet of near 50 kts will shift over the western part of the
lake, which could bring gusts up to 30 knots by sunrise Thursday
across the west. Winds across the west will remain elevated in the
20 knots range through the day, but the strongest winds will then
shift across the east. Southerly gusts will approach gale criteria
by tomorrow afternoon, especially along the shoreline and at higher
observation platforms. Increasing stability with warmer air
advecting into the area brings some uncertainty, but there is a
chance the eastern lake could see gales approach 40 knots on
Thursday night, and opted to issue a watch at this time.
.
A weaker cold front will then pass over the lake on Friday, bringing
W winds around 20, to 25 across the west, knots or so through the
day. By Saturday, light NW winds are expected across the lake. For
Sunday and Monday, a strong push of warm air from the south is
expected. This will bring increased stability over the lake with
southerly gusts to around 20 knots both days.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Gale Watch from Thursday evening through late Thursday night for
LSZ267.
Gale Watch from Thursday evening through late Thursday night for
LSZ266.
Lake Michigan...
None.
&&
$$
SHORT TERM...JAW
LONG TERM...TAP
AVIATION...Rolfson
MARINE...JAW