Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/05/18
Area Forecast Discussion
National Weather Service Bismarck ND
1030 PM CDT Sat Aug 4 2018
.UPDATE...
Issued at 1028 PM CDT Sat Aug 4 2018
Thunderstorms are in the process of weakening and diminishing in
coverage over the James River valley. The forecast looks to be on
track. Just tweaked the precipitation chances and blended the
latest observations with the going forecast.
UPDATE Issued at 643 PM CDT Sat Aug 4 2018
Isolated to scattered showers and thunderstorms have developed
over parts of central North Dakota and points east this evening as
expected. With plenty of CAPE and modest shear available, these
storms have been very pulse-like in nature - they build quickly
and diminish almost just as fast. The past few iterations of the
HRRR suggest storm coverage and intensity will increase over the
next couple of hours as they approach the southern James River
valley. SPC mesoanalysis shows much better shear values in this
area, and the RAP suggests an increase in shear across the south
as the sun sets. Thus, if storms can sustain themselves as they
approach the southern James River valley, the HRRR and RAP would
suggest there may be a brief window for some of these storms to
become stronger and perhaps severe. However, this threat is
conditional and we are in wait and see mode at this time. For this
update, I tweaked the precipitation chances using a blend of the
latest time lagged HRRR, radar/satellite observations, and the
previous forecast.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 157 PM CDT Sat Aug 4 2018
Main forecast challenge is convective potential for this afternoon
and evening. At 17Z, surface trough/wind shift was running
approximately from Minot through Dickinson, progressing eastward
across the state. Clear skies prevail with temps in the 80s.
GOES-17 water vapor imagery showed upper level cyclonic
circulation just north of the International Border with broad
cyclonic flow in place, though currently more zonal across ND. An
area of mid-upper level clouds was located upstream over Canada
and just beginning to nudge into northwestern ND. Models have
hinted at potential for showers and possibly a thunderstorm with
weak instability in place. Added some low pops to northwest ND to
account for this.
Farther east, some uncertainty with convective potential as the
surface trough progresses eastward. Global models all indicate
weak instability, mainly less than 1000 J/Kg. NAM is a little
more aggressive, but appears to be overdone when compared to
latest SPC mesoscale analysis. Deep layer shear is also marginal
around 30kts and strongest across the southern part of state.
Synoptic scale support is also somewhat limited with generally
weak height falls expected in nearly zonal flow. Some weak waves
do appear in water vapor imagery closer to SD border, which could
help support some convective development. Latest CAM solutions
initiate convection across south central ND late afternoon, which
seems reasonable. For now, have included mainly slight chance pops
for thunderstorms later today and this evening.
On Sunday, the region remains under the influence of upper level
cyclonic flow, supporting a continued chance of showers and
thunderstorms, mainly north. Forecast soundings show weak
instability during the afternoon with little/no inhibition. Deep
layer shear also on the low side, generally below 20 kts.
.LONG TERM...(Sunday night through Saturday)
Issued at 157 PM CDT Sat Aug 4 2018
Upper level trough pushes across the state and eventually brings
an end to chance of showers and thunderstorms by Monday evening.
Upper level ridge across western CONUS amplifies during the rest
of the week, resulting in dry weather for the Northern Plains
along with a warming trend. High temps initially around 80 on
Monday will quickly reach the 90s by Tue/Wed.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 643 PM CDT Sat Aug 4 2018
VFR conditions are expected through the period. This evening,
thunderstorms have developed along a line from just southwest of
Devil`s Lake to south and east of Elgin. Some lightning strikes
will be possible in the vicinity of KBIS over the next couple of
hours and thunderstorms will approach KJMS. Due to the
isolated/scattered nature of these storms, it is uncertain if KJMS
will have a thunderstorm move over or not, but VCTS is certainly
expected. More showers and thunderstorms will be possible Sunday
afternoon and evening, but placement is uncertain at this time.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...ZH
SHORT TERM...JNS
LONG TERM...JNS
AVIATION...ZH
Area Forecast Discussion
National Weather Service Des Moines IA
936 PM CDT Sat Aug 4 2018
.UPDATE...
Issued at 922 PM CDT Sat Aug 4 2018
Rest of tonight...clouds continue to dissipate from west to east
this evening with any remaining showers confined to far eastern
Iowa. Temperatures are relatively comfortable with readings
generally in the 70s as of 9pm. Overall - a rather pleasant
evening.
Keeping an eye on a couple areas of thunderstorm activity...the
first is over SD with a second area over west-central Nebraska.
These scattered storms continue to drift slowly e/sewd. The latest
RAP/HRRR/ESRL HRRR guidance is not to excited about this activity
making it into Iowa...per weak upper forcing and a relatively
poor orientation and strength of the nocturnal LLJ. Will keep
token PoPs over the north and west in case activity shows a rapid
uptick but not too concerned.
Still looking like a hot and breezy day on Sunday with readings
well into the 90s across central and southern Iowa. Storm
potential still there in the afternoon and evening but will defer
to midshift for a thorough examination of all the overnight
guidance.
Fowle
&&
.SHORT TERM.../Tonight through Sunday/
Issued at 348 PM CDT Sat Aug 4 2018
A band of light to moderate showers and thick clouds has been
slow to progress from west to east across the forecast area today.
While measurable rain has been confined to northern Iowa for the
most part, instability has been limited to the extent that no
additional convection is anticipated in wake of this activity.
Other than the showers currently departing our northeastern
counties in the next few hours, the area should remain dry
through midnight. Meanwhile, thunderstorms will develop across
central Minnesota later this evening and rocket eastward into
Wisconsin. Some high-resolution short-range models depict an
outflow boundary surging southward from these storms toward the
Iowa border, with associated storms possibly reaching our far
northern counties after midnight. Such storms could carry a
marginal severe weather threat, but this is highly conditional on
the development of the parent boundary and the degree to which
destabilization occurs by that time. The result is only a low-end
severe weather outlook right up by the border, as outlined by SPC
products. Other than these far northern counties, we should stay
quiet overnight.
On Sunday Iowa will reside beneath quick zonal flow aloft, through
which a subtle shortwave impulse will approach in the afternoon.
Between temperature/cloud differences from rain today, the
possible remnant outflow boundary from Minnesota convection
discussed above, and modest frontogenetical forcing ahead of the
approaching impulse, we should see the development of a weak
effective warm front somewhere across northern Iowa during the day
on Sunday. This will serve as a focus for fairly robust
thunderstorm development in the afternoon/evening as broad forcing
ahead of the impulse overcomes any capping and initiates
convection. There is some uncertainty regarding the location of
the resulting thunderstorms, but somewhere across the northern
half of the state is likely. Parameter space indicates a risk of
severe wind/hail, and SPC has upgraded our far northern counties
to a slight risk accordingly. Meanwhile, south of the front and
storm area, much warmer air will advect into southern and central
Iowa aided by mostly clear skies and decent mixing. This will
bring temperatures up into the mid-90s from around I-80 southward.
However, dewpoints will likely fall into the low to mid-60s,
resulting in heat index values only a few degrees above
temperatures. Therefore, no heat headlines have been considered.
.LONG TERM.../Sunday night through Saturday/
Issued at 348 PM CDT Sat Aug 4 2018
On Sunday night, a broader 500 mb trough will approach from the
west and bring stronger, larger-scale forcing for ascent across
much of the region. The lingering quasi-synoptic boundary
discussed in the short term section above, reinforced by
afternoon/evening convection, will likely serve as a focus
mechanism for additional thunderstorms overnight, especially after
midnight as the nocturnal low-level jet impinges upon the
convective zone. This will result in some severe weather threat in
the form of wind/hail, but will also bring a heavy rain threat
across our northern counties given the high atmospheric moisture
content and potential for robust updraft development/training
along the boundary. WPC has issued a slight risk of excessive
precipitation which appears warranted. However, with that said,
recent dry weather has resulted in a large amount of capacity,
especially with the flatter topography of northern Iowa, and it
would take a lot to produce significant flooding. The only
exception would be in urban areas, where rapid rainfall rates
could theoretically cause some issues late Sunday night.
On Monday the 500 mb flow will begin to turn more northwesterly,
pushing a large high pressure area down over the Upper Midwest and
slowly shoving the lingering synoptic boundary south of our area.
While this occurs, remnant thunderstorms from overnight convection
will continue to affect parts of the forecast area in the morning
hours, and if the boundary has not exited our area by late
afternoon additional diurnal convection could clip our
south/southeast late in the day. Any such storms would carry a low
threat of severe weather, however, this is highly conditional as
the location of the boundary and amount of debris clouds and
destabilization will be heavily dependent on multiple rounds of
convection earlier in the forecast period.
Once the boundary finally pushes south of Iowa late Monday or
Monday night, a quieter and drier weather regime will return to
the area for the remainder of the 7-day forecast. Light
northwesterly flow aloft will moderate and slow any warming trend,
and while instability may be sufficient for a few pop-up
showers/storms from time to time, no organized storms or severe
weather are expected. Despite the influence of a northwesterly
flow aloft, airmass modification will allow for slow warming, with
temperatures ticking up a degree or two each day from around
mid-week onward. By Friday and Saturday this should bring highs
into the mid-80s north to lower 90s south, give or take.
&&
.AVIATION.../For the 00Z TAFS through 00Z Sunday evening/
Issued at 631 PM CDT Sat Aug 4 2018
VFR conditions will persist through the overnight and into much
of Sunday. A few light showers will push east of ALO by sunset,
with just residual high cirrus clouds in place tonight. Still
watching the potential for storms developing across southern
Minnesota to approach far northern Iowa after midnight but
confidence in reaching MCW/FOD is too low to include in the TAFs
at this time. Breezy southerly winds from 15 to 25 kts will
decrease after sunset. VFR conditions with breezy southerly wind
expected again on Sunday. The best potential for storms will be
across northern IA Sunday afternoon, and introduced VCTS for now
due to uncertainty in timing and spatial coverage.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Fowle
SHORT TERM...Lee
LONG TERM...Lee
AVIATION...Fowle
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1201 AM EDT Sun Aug 5 2018
.AVIATION...
VFR conditions will persist throughout the forecast period with
varying degrees of cirrus and just few-sct diurnal cumulus again
Sunday afternoon. Better gradient flow will promote southwest winds
of 10-13kts with gusts to 18-20kts during best afternoon mixing.
For DTW...No aviation concerns anticipated through the period with
southwest flow operations.
.DTW THRESHOLD PROBABILITIES...
* None.
&&
.PREV DISCUSSION...
Issued at 337 PM EDT Sat Aug 4 2018
DISCUSSION...
Large scale pattern throughout the weekend period will remain
characterized by expansive upper level ridging largely oriented west
to east throughout much of the central and southern conus. Southeast
Michigan now residing along the northern expanse of this elevated
upper level height field, with a renewed increase in heights
underway within the 700-500 mb layer. A standard mixing profile
under full insolation netting a modest warming trend within this
moderating mid level enviroment today. High temperatures closing in
on 90 degrees in some locations. A weakly unstable low level
environment remains effectively capped by warm mid level
temperatures and lack of forced ascent through the column. An axis
of slightly higher moisture /dewpoints near 70 degrees/ is
augmenting some cu growth from northeast IN into south-central lower
MI, but lack of cu locally indicative of the limited low level
moisture quality relative to points upstream. Should a cell or two
ultimately emerge within the higher moisture gradient /as suggested
by the HRRR and ARW/, little support exists for this activity to
drift into far western zones this evening /west of Hwy 23/. Shallow
patchy fog possible overnight, but enough gradient flow and overall
drying near surface conditions should preclude a greater response.
Lows tonight near 70.
Little change in the underlying environment on Sunday, as southeast
Michigan holds position within the periphery of the upper ridge. A
virtual carbon copy in terms of the thermal and moisture profiles,
but with the mixing potential a touch greater. Highs in the vicinity
of 90 degrees areawide, with the effective heat index reaching into
the lower and middle 90s. A capped mid level environment and lack of
greater boundary layer moisture or forcing will maintain dry
conditions to finish the weekend.
SE Michigan positioned Monday at the interface of the exiting upper
ridging and the eastward expansion of stronger height falls spilling
into the plains. A more energetic southwest flow preceding the
height falls will likely provide a focus for convective development
late Sunday into Sunday night upstream. The downstream propagation
of this initial activity more likely to remain focused to the north
overnight into early Monday, given the orientation of the mean
thickness fields and placement of higher mid level theta-e air
across this corridor. Treatment of this convective response does
muddle the picture locally on Monday if using the NAM guidance,
which is likely displaying a usual bias toward overdeveloping lead
mid level energy or convectively enhanced waves within a moistening
lower amplitude pre-frontal southwest flow. Ultimately, some degree
of mid level moisture advection and subsequent destabilization tied
to early day activity could become a catalyst for late day
development locally, particularly with northward extent. Otherwise,
looking at simply hot and humid pre-frontal conditions during the
daylight hours. Forced ascent will increase Monday night into early
Tuesday, as stronger height falls ease a cold front across the lower
peninsula. Greater potential for showers and thunderstorms during
this time.
Model differences in timing/placement of the shortwave passage and
associated cold front pushing through SE Michigan will dictate the
forecast for Tuesday. The GFS and CMC solutions continue to
advertise a quicker frontal passage early Tuesday with precip
chances ending by Tuesday afternoon. Meanwhile the ECMWF favors a
slower shortwave passage with showers and thunderstorms continuing
throughout the day. For now will maintain chance for thunderstorms
across the southern CWA with slight chance to the north for Tuesday.
Both solutions agree that temperatures will fall closer to average
on Tuesday with highs in the lower 80s.
A broad region of high pressure then builds into the region for the
midweek period bringing dry, pleasant weather with highs in the
lower 80s and lows in the upper 50s to mid 60s. Shortwaves pivoting
through the broader longwave trough centered over the Northeast US
will then bring additional chances for showers and thunderstorms
late next week as temperatures remain near to slightly above average.
MARINE...
Generally favorable boating conditions will prevail with light south
wind today will become moderate south to southwesterly for the
latter half of the weekend with weak high pressure overhead. A cold
front will approach the region late Monday into Monday night
bringing scattered to numerous showers and thunderstorms. Drier
weather and light northwesterly flow will prevail in the wake of the
frontal passage for the middle of next week.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....DG
DISCUSSION...MR/JD
MARINE.......IRL
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Sioux Falls SD
1053 PM CDT Sat Aug 4 2018
.SHORT TERM...(This evening through Sunday)
Issued at 334 PM CDT Sat Aug 4 2018
Per water vapor satellite drier air has begun to enter the CWA from
west. At the surface, a weak trough will continue to slide through
the area, bringing the potential for thunderstorms this evening into
the overnight hours. However, with dry air/subsidence already
sweeping through the region, any thunderstorm development looks to
be isolated. In fact, Hi-Res guidance, including HRRR show
minimal activity towards daybreak. That said, kept an isolated
mention this afternoon and evening, and up to a 30 percent chance
in the nighttime, mainly for southwest Minnesota. If storms do
develop, one or two storms could become marginally severe with
gusty winds as the main threat. Lows are expected from the mid to
upper 60s.
Various perturbations will continue to affect the area over the
next few days in a quasi-zonal upper level flow. An upper-level
shortwave trough will move over the central Dakotas on Sunday,
while at the surface a cold front extending from the Upper
Mississippi Valley to the Northern Plains will continue to slide
southward into the CWA. Decent forcing will be in place thanks to
the upper level jet and abundant surface moisture, with dewpoints
in the upper 60s and low 70s ahead of the front. That said,
scattered showers and thunderstorms return in the afternoon hours.
With increasing low to mid level lapse rates and 0-6 km bulk
shear (30-45 knots), strong to severe storms will be possible.
.LONG TERM...(Sunday night through Saturday)
Issued at 334 PM CDT Sat Aug 4 2018
Sunday night will have a better setup for thunderstorms and heavy
rainfall. Scattered showers and thunderstorms will be on the
increase through the overnight hours. Model soundings suggest a deep
saturated layer over northwest Iowa and adjacent areas with PWATs
near to slightly above 2 inches; therefore confidence in periods of
heavy rainfall is increasing. Agreed with WPC in keeping the area
under a slight risk of excessive rainfall.
Several impulses of energy embedded in the flow aloft will continue
to bring chances for showers and storms Monday and Tuesday. It does
not look like a complete washout, but with diurnal heating
isolated storms cannot be ruled out.
Upper-level flow pattern changes by the middle of the week with the
upper ridge building over region from the Pacific Northwest.
Precipitation chances look minimal, though temperatures will trend
slightly upward (near average for August normal) by the end of the
week.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1041 PM CDT Sat Aug 4 2018
Isolated thunderstorms will be possible across the area
overnight, and could briefly affect TAF sites. There will be
increasing chances across the area on Sunday afternoon and
evening, with the greatest chances at KFSD and KSUX.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
SHORT TERM...05
LONG TERM...05
AVIATION...JM
Area Forecast Discussion
National Weather Service Glasgow MT
732 PM MDT Sat Aug 4 2018
.DISCUSSION...
Evening Update...
Overall, the forecast was in good shape. Updated winds and pops
with the latest reasonable looking near term models. The HRRR has
been very good at catching wind gusts from both convection and
outflow boundaries the last couple of days, so blended heavily
toward that solution for tonight. Pops were a little more
problematic, so blended to get as close as possible to reality,
then hand edited the rest of the way.
Showers and thunderstorms have been slowly moving across northeast
Montana this afternoon and evening, with the main forecast
challenge centering around the timing of the outflow boundaries
and whether any storms would form along them, especially in light
of the concert at the Glasgow fairgrounds this evening. As of 7:15
PM this evening, both storms and their associated outflows have
significantly diminished, and the expectation holds that they will
be completely fizzled out by around 9 PM.
Sunday, another disturbance wrapping around the upper low in
Canada will make its way across Montana, bringing more showers and
storms, mainly in the afternoon and evening. Expect very little
precipitation with these however, as there still will not be much
surface moisture to work with. Hickford
Previous Discussion...
Numerous tiny individual storm cells have developed over southern
Saskatchewan and have moved toward the ESE into portions of
northern and northeastern Montana. A few of the stronger cells are
generating isolated lightning in some places.
Expect these showers and thunderstorms to continue this afternoon
and evening. Best organization will be a rough line of these cells
merging together from Opheim to Medicine Lake. Most of the rest of
our area will see spotty coverage. Anywhere from sprinkles/trace
up to a few hundredths of an inch of accumulations are generally expected.
Some calming and clearing is expected late tonight, but convective
activity with showers and thunderstorms will quickly return
Sunday afternoon and evening as the low pressure influence slowly
erodes away toward the east.
On Monday, most of our area will be clear of any chance of rain,
but away southeast, beyond the corner of our CWA, there might be
a little bit of rain.
Monday night through the rest of the week, a strong ridge of high
pressure will return to the entire large-scale region. High
temperatures will easily reach to 100 and low humidities will drop
into the teens. At this time, winds are expected to be widespread
near calm, but as we get closer to that time, the wind forecast
may increase and could raise fire weather concerns as fuels are
beginning to dry out more this time of year.
BMickelson
&&
.AVIATION...
FLIGHT CAT: Mainly VFR.
DISCUSSION: Hit and miss showers and thunderstorms will prevail
during the afternoon and evening hours both today and tomorrow.
Amendments may be needed.
WINDS: From the west or northwest at 13 to 17 kts, then calming
to less than 10 kts overnight.
BMickelson
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
weather.gov/glasgow
Area Forecast Discussion
National Weather Service Grand Junction CO
543 PM MDT Sat Aug 4 2018
.SHORT TERM...(Tonight through Sunday night)
Issued at 236 PM MDT Sat Aug 4 2018
Storms initiated late this morning over the higher terrain with
the best coverage this afternoon north of I-70. Storms appeared
strong at first but satellite shows the anvils or tops of the
storms shearing quickly downstream. So as of right now the
updrafts are having a tough time sustaining themselves resulting
in pop and drop type storms. The NAMNest has been nearly spot on
with convection timing and placement while the HRRR did not
indicate any precipitation until after 3 pm. So, leaning strongly
on the NAMNest for this near term forecast. Precipitable water
(PW) on the 12Z GJT sounding indicated 0.82 inches with downdraft
CAPE of 1333 J/kg. So plenty of moisture and instability to
generate storms, more capable of strong gusty outflow winds. We
have already had some reports of small hail and radar estimates up
to 0.5 inch of rain in the stronger storms earlier today. We
haven`t received many heavy rain reports though but storms are
definitely capable of brief heavy downpours.
Forecasted CAPE is anywhere from 800 to 1200 J/kg focused more
across the north and central areas this afternoon and evening.
There is decent shear with the best helicity and shear coming in
after 3 pm through about 7 pm. This is a similar type environment
to what happened yesterday where storms were unimpressive at first
and became stronger late afternoon into the early evening. The
NAMNest is picking up on this trend and given the above
conditions, thinking some storms late this afternoon and early
evening could be strong, with some rotation possible with better
updraft strength given the amount of shear and helicity. Brief
heavy rain, strong gusty outflow winds and small hail seem
possible with the stronger storms, especially along and north of
I-70.
Activity appears to wind down after sunset but looks to pick back
up again after midnight as a shortwave moves through across the
north. Models appear consistent in showing this trend with the
NAMNest honing on an increase in convection, shear and updraft
helicity between 1 am and 6 am. The shear and helicity signatures
would appear to indicate some nocturnal convection with
thunderstorms rumbling through the night and having a good chance
of sustaining themselves, focused basically along and north of
I-70, so across northeast and east-central Utah and northwest and
west-central Colorado. Storm activity winds down by sunrise Sunday
morning with drier air advecting in from the west. There is less
shear on Sunday with the best instability focused along the
western Colorado mountains and divide. Enough moisture remains to
get storms firing over the mountains Sunday afternoon with heavy
rain possible. However, coverage appears more scattered in nature.
Elsewhere, conditions will be drier with marginal fire weather
conditions over eastern Utah and northwest Colorado with breezier
conditions. Do anticipate the relative humidity to be borderline
and not as dry so will not issue any fire weather highlites with
this package. The west-southwest flow should help keep smoke out
of the region with just some patchy smoke lingering in some areas
resulting in hazy skies.
.LONG TERM...(Monday through Saturday)
Issued at 236 PM MDT Sat Aug 4 2018
Conditions dry out even further on Monday as the ridge of high
pressure begins to slide back to the west. Some lingering moisture
and low to marginal instability will allow thunderstorms to fire
Monday afternoon but remain more isolated in nature and focused
over the southern and central Colorado mountains near the divide.
PW values drop to below 0.5 inches across much of the area Monday
and especially Tuesday through the end of the week. This will
result in a return to very dry and hot conditions with very little
in the way of thunderstorm activity. Cannot rule out an isolated
storm or two over the high terrain mainly over the divide, but the
better moisture and storms will remain over the Front Range.
Nudged daytime temperatures a bit above guidance as we have seen
this trend in the drier northerly flow regime. The models are
hinting at moisture seeping into the Four Corners late this week
into the weekend but not biting off on this solution yet as we
have seen this before and anticipating the model solutions to jump
around a bit before settling on a solution. Overall, this coming
week will be dominated by high pressure ridge building to the west
over the Great Basin, keeping our area in a northerly flow pattern
resulting in very dry and hot conditions.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 543 PM MDT Sat Aug 4 2018
Scattered showers and thunderstorms will occur across much of
eastern Utah and western Colorado through late tonight as a weak
upper level disturbance passes through. Gusty outflow winds to 40
knots and brief heavy rainfall will be the primary threats with
storms. Local MVFR CIGS will occur in the vicinity of the
stronger storms. Isolated nocturnal showers will continue
overnight across the northern tier of the region with coverage
once again increasing by 18Z Sunday.
&&
.FIRE WEATHER...
Issued at 236 PM MDT Sat Aug 4 2018
Drying across eastern Utah and northwest Colorado by Sunday may
lead to a few hours of marginal critical fire weather conditions.
However, fire weather highlights are not expected at this time.
In addition, the upcoming week will see a strong ridge of high
pressure building to the west across the Great Basin. Very dry
and hot conditions are expected with the potential for poor
overnight humidity recoveries between Tuesday and Friday of next
week.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...MDA
LONG TERM...MDA
AVIATION...TGJT
FIRE WEATHER...TGJT
Area Forecast Discussion
National Weather Service Wilmington NC
905 PM EDT Sat Aug 4 2018
.SYNOPSIS...
Scattered showers and thunderstorms will prevail much of the
upcoming period. This will maintain a chance of localized flooding
across the region since grounds are already very wet. An upper
trough to west and northwest of the region, interacting with the
Bermuda High, will maintain plentiful moisture across the area most
of the upcoming week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 905 PM Saturday...The far inland convection from earlier this
evening has dissipated with debris cloudiness lingering across the
Pee Dee and Lumberton areas. As the subtropical ridge builds
westward expect skies to become mostly clear/partly cloudy
overnight. Not much in the way of support for additional convection
overnight, and have lowered POPs accordingly with the latest update.
While the HRRR shows Sunday`s initial convection developing near the
Cape Fear coast during the morning the steering flow will change and
prevent the storms from moving onshore. However, with heating the
next round of storms will develop inland during the afternoon.
Localized flooding is possible with any storm that does develop
given precipitable water values of 2 to 2.1 inches.
Previous discussion...The strength and extent of convection so far
today has been limited by weaker instability than previous days,
although there has been some organization at times along surface
outflow boundaries. Storm motion based on radar trends is 240 around
15 knots, and this will allow the ongoing showers and thunderstorms
to approach the coast through mid to late afternoon. Further west,
visible imagery shows the cumulus field across the interior CWA
slowly evolving, but with limited vertical extent. Some of these
will probably develop into showers with a few possible lightning
strikes, and linger for a few hours past sunset.
Expecting mainly isolated activity overnight as ridge builds in
from the Atlantic. We`ve tried to remain optimistic that the
upper ridging will minimize convection on Sunday, however it
appears that a few extra degrees of surface heating will combine
with substantial moisture below 700 mb to overcome the added
convective inhibition. Consensus of MOS guidance still projects
PoPs in the 40-50 percent range, and this doesn`t seem
unreasonable. There is concern that development may focus along
a resultant sea breeze boundary, and with precipitable water
values refusing to fall below 2", localized flooding issues
could quickly materialize because of the antecedent conditions.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 330 PM Saturday...High pressure ridge elongated across
the area will retrograde to re-center west of the area during
Monday as surface high expands across the Southeast. This will
continue warm and humid air into the Carolinas, with temps on
Monday likely climbing into the low 90s away from the coast.
This heat and humidity will create a very unstable atmosphere on
Monday, with forecast soundings suggesting 1500 J/kg of MLCape
during the aftn. As the mid-level high re-centers to the west,
much of the flow within the column shifts to the W/NW. This will
slowly cause some drying of the column, especially NE zones,
but it will take much of the day for this to occur. Guidance
indicates a weak impulse will try to push overhead during Monday
aftn, which should enhance convective potential already likely
to develop along the sea breeze and Piedmont trough. That being
said, PWATs initially around 2-2.1 inches will fall through the
evening, somewhat offsetting the convective potential otherwise
favored during the aftn. Will carry CHC POP during the aftn for
the entire area, but best chance for tstms may be the SC portion
of the sea breeze. Expect most convection will wane with loss
of heating Monday night but temps will remain in the mid 70s for
lows near the coast, low 70s well inland, very similar to mins
on Sunday night.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 330 PM Saturday...`Unsettled, potential flooding` may be
one description of the extended period, as PWAT analysis
suggests local flooding is apt to rear its head this period.
Throw diurnal, differential heating into the mix, and slight
upper support at times, and a result of robust convection
should be the result. The mix of high precipitable, August
heating, and saturated ground may result in more water woes.
Daytime temperatures running near normal, with night-time
temperature curves holding a bit above normal this period.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 23Z...The area of convection across the Pee Dee will gradually
weaken as it passes north of KFLO and west of KLBT through 01-02Z.
Other than convective debris cloudiness VFR conditions are expected
to prevail this evening. Latest HRRR supports this thinking with any
new convection holding off until after sunrise near the coast. In
the meantime tempo MVFR VSBYs are possible during the early morning
hours. Expect any convection to shift inland during the afternoon.
Extended Outlook...MVFR/IFR from scattered SHRA/TSRA each afternoon
and evening across all sites through the extended period.
&&
.MARINE...
NEAR TERM /THROUGH SUNDAY/...
As of 905 PM Saturday...A weak pressure gradient currently prevails
across the adjacent coastal waters with speeds around 10 knots and
seas in the 2-3 ft range. Widely scattered showers and thunderstorms
are possible during the morning. No major changes made with the
latest update.
Previous discussion...The orientation of the high pressure ridge
will result in the center remaining just south of the waters through
Sunday, resulting in southwesterly flow across the waters. The
gradient will weaken with the approach of the high, and winds are
expected to fall off to 10 knots or less overnight and early Sunday.
By late morning, speeds will likely increase to 10-15 knots as a
resultant sea breeze develops. Shower and thunderstorms over the
waters should remain spotty.
SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 330 PM Saturday...High pressure offshore will ridge
westward into early next week. This will continue SW return flow
across the waters, with the relatively weak gradient keeping
wind speeds around 10 kts. A SE swell of around 2 ft at 8-9 sec
will be the primary wave group thanks to these light winds, so
significant seas will hover around 2 ft through the period.
LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 330 PM Saturday...A typical summer pattern this period,
in that we can expect S-SW winds of 10-15 kt, with a few higher
gusts inshore in the afternoon. What may be atypical is TSTM
coverage on the higher end, numerous to scattered in the early
mornings inshore, and again potentially in mid/late afternoon.
Seas spectrum a mix of S-SW waves 1-2 ft every 3-4 seconds, and
SE waves 1-2 ft every 8 seconds.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
NEAR TERM...SRP
SHORT TERM...JDW
LONG TERM...MJC AVIATION...SRP
Area Forecast Discussion
National Weather Service Indianapolis IN
1121 PM EDT Sat Aug 4 2018
.UPDATE...
The AVIATION section has been updated below.
&&
.SYNOPSIS...
Issued at 350 PM EDT Sat Aug 4 2018
Isolated storms will be possible through early evening in a warm
and humid airmass supported by broad southwest flow over the
region. A frontal system will drop into the region for the start
of the work week and bring more substantial chances for storms to
the area. Conditions will be a bit quieter later in the week as
high pressure returns.
&&
.NEAR TERM /Rest of Tonight/...
Issued at 938 PM EDT Sat Aug 4 2018
Convection has ended across the area with only some remnant high
clouds around. Have thus ended PoPs. Overall the forecast is in
good shape, so only made some minor tweaks. Can`t rule out some
patchy fog, especially for the isolated areas that saw rain, but
do not believe it to be widespread enough to mention.
Previous discussion follows...
Satellite imagery shows a few areas of agitated cumulus mainly
southeast of a Terre Haute to Tipton line this afternoon. HRRR and
mesoanalysis supports the threat for an isolated storm or two to
pop up in the next few hours, and this threat may linger into the
early evening. Have included a 15 pop for this potential through
01Z. Remainder of the night will be mostly clear, but warm and
humid with lows around 70. Some patchy fog will be possible,
particularly in areas where rain may fall.
&&
.SHORT TERM /Sunday through Tuesday/...
Issued at 350 PM EDT Sat Aug 4 2018
Short term focus will be on Monday into Tuesday as a frontal
boundary drops into the region. This will likely trigger one or
more rounds of thunderstorms, with chances highest Tuesday with
the most substantial upper level support coinciding with the
presence of the boundary in the area.
Raised temps a bit Sunday with low level thicknesses consistent
with today`s, otherwise consensus numbers appear on point.
&&
.LONG TERM /Tuesday Night through Saturday/...
Issued at 318 PM EDT Sat Aug 4 2018
After a wet and unsettled start to the extended...drier weather is
poised to return for much of the latter part of the work week.
After a brief cool down...expect temperatures to recover back to
above normal levels next weekend.
Scattered convection will continue to impact mainly the southern
half of the forecast area Tuesday night into Wednesday as a cold
front slowly shifts to the south of the region. Weak high pressure
will build south as the front departs with mainly dry weather and
a knock back in temperatures and humidity levels. Expect highs
predominantly in the low to mid 80s Wednesday through Friday.
Some hints for subtle moisture return by next weekend as ridging
aloft reestablishes over the Ohio Valley. Introducing low chance
pops focused mainly in the afternoon both Friday and Saturday
with possibility for greater impacts later in the weekend as a
weak wave aloft drops south out of the Great Lakes.
&&
.AVIATION (Discussion for the 050600Z TAF Issuance)...
Issued at 1121 PM EDT Sat Aug 4 2018
VFR conditions expected through the period.
Expect just some passing high clouds overnight with scattered
cumulus developing mid-morning Sunday.
Uncertainty has increased for fog potential overnight, with KBMG
already having a 1 degree dewpoint depression. However, most model
data indicates VFR overnight and still some mixing expected. Thus
most items point to no or little fog, so will keep it out of the
forecast for now. However, would not be surprised to see brief
restrictions at times, especially near sunrise.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...Nield
NEAR TERM...Nield/50
SHORT TERM...Nield
LONG TERM...Ryan
AVIATION...50
Area Forecast Discussion
National Weather Service North Platte NE
652 PM CDT Sat Aug 4 2018
.SHORT TERM...(This evening through Sunday)
Issued at 319 PM CDT Sat Aug 4 2018
Upper level high pressure continues across the southwest. A weak
disturbance will continue to make its way across Nebraska,
providing some weak forcing that will aid in thunderstorm
development late this afternoon and evening.
Main concern this forecast period is in thunderstorm coverage. At
this time confidence is low in any widespread coverage of
thunderstorms. The HRRR and the HREF suggest isolated to scattered
thunderstorms will move into western Nebraska after 22z and move
across parts of north central Nebraska. Widespread severe weather
is unlikely however and isolated chance for severe weather does
exist and the SPC does have our western CWA in a marginal risk for
damaging winds and large hail.
.LONG TERM...(Sunday night through Saturday)
Issued at 319 PM CDT Sat Aug 4 2018
Upper level High pressure will continue to build across the
western CONUS towards the end of the week, with a trough
developing across the east by Thursday.
Another chance of thunderstorms possible on Sunday. Confidence is
increasing in seeing more scattered to widespread shower and
thunderstorm chances late Sunday afternoon and evening.
After Sunday only slight precipitation chances exist with chances
Monday evening and Tuesday evening.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 632 PM CDT Sat Aug 4 2018
Thunderstorms may affect the KLBF terminal until 02z to contain
breif heavy rain andf gusty winds possible. Additional developemnt
possible 03Z-06Z, which may also spread into north central
Nebraska. Any of this activity shuold remain east of the KVTN
terminal tonight. On Sunday, isolated thunderstorms to remain
possible. No mention in the current TAFS, as confidence in
location remain low.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Gomez
LONG TERM...Gomez
AVIATION...Roberg
Area Forecast Discussion
National Weather Service Lake Charles LA
1012 PM CDT Sat Aug 4 2018
.UPDATE...
Convection has dissipated acrs the region with the exception of
some isolated showers over the Atchafalaya Basin east of
Lafayette. The atmosphere remains considerably moist over the
region with KLCH 00Z sounding showing precip water of 1.6 inches
while recent GPS-MET and LAPS analysis show values closer to 1.9.
The combination of moisture and a weakness aloft will maintain an
elevated chc of showers overnight into Sunday.
After a lull in activity this evening, expect widely sctd showers
and tstms developing over the nearshore waters after midnight,
gradually spreading over coastal areas by early Sunday morning
then further inland as daytime heating interacts with the
seabreeze and any lingering mesoscale boundaries. Made some small
changes to PoPs for tonight and also tweaked temps/dewpoints/winds
to account for recent obs and trends.
24
&&
.PREV DISCUSSION... /issued 533 PM CDT Sat Aug 4 2018/
DISCUSSION...
00Z taf issuance.
AVIATION...
Radar showing most inland SHRA/TSRA dissipated over the region,
with a light to moderate rain shield offshore. HRRR and other
guidance not showing any significant redevelopment this evening
and overnight, thus have removed VCTS until 15z Sunday. With the
higher chances of 40-50% by afternoon for the I-10 corridor,
inserted PROB30 group from 18-24z for TSRA & MVFR visibility &
ceilings for BPT/LCH/LFT/ARA.
DML
PREV DISCUSSION... /issued 311 PM CDT Sat Aug 4 2018/
DISCUSSION...Sufficient tropical moisture remaining in place
along with a weakness aloft will result in a daily chance for
shower and thunderstorm development into mid-week across the
region. Temperatures will trend toward seasonal norms, while
established southerlies will maintain abundant low level
moisture/humidity. Thus along with continued rain chances,
will be looking for hot and humid days, as well as warm and
muggy nights.
Models continue to suggest an increase in rain chances moving into
the latter part of the week as several shortwaves advance
southeast through the plains advancing a cold front toward the
region.
MARINE...A light mainly onshore flow will continue as high
pressure ridges west across the Gulf of Mexico. Sufficient
tropical moisture over the region with a weakness aloft will
allow for a a daily chance for shower and thunderstorm
development.
&&
.PRELIMINARY POINT TEMPS/POPS...
AEX 71 93 73 94 / 20 30 10 20
LCH 74 91 75 90 / 20 40 20 40
LFT 74 92 75 92 / 30 50 20 40
BPT 77 91 77 90 / 20 40 20 30
&&
.LCH WATCHES/WARNINGS/ADVISORIES...
LA...None.
TX...None.
GM...None.
&&
$$
PUBLIC...24
Area Forecast Discussion
National Weather Service Medford OR
836 PM PDT Sat Aug 4 2018
.UPDATE...Smoke from area wildfires largely stifled convection
across the area. A healthy short wave did pass through the area
and looks to be situated over Lake/Modoc County. There were 32
strikes observed in the MFR CWA this afternoon/evening, all in
Klamath and Lake County. Portions of the east side could see an
isolated thunderstorm, over the next few hours, but generally
conditions are stabilizing.
Marine clouds are blanket the coast, and will probably stick
around through tomorrow morning. They could make a run into the
Umpqua Basin, but it`s looking more likely that clouds won`t be
deep enough to make in.
A ridge will start building in tomorrow, starting a quick warm-up
throughout the week. A vaguely familiar pattern. Besides some
updates to winds and temperatures tonight, the going forecast is
on track; see previous discussion for more details. -McAuley
&&
.AVIATION...For the 05/00Z TAFs...Heavy smoke has made its way into
the Rogue Valley, bringing vsby down to 1 SM. Smoke will continue to
impact vsby over much of the west side south of the Umpqua
Divide...and seems to have stifled convection. While some cells
continue to develop over Klamath and Lake Counties, it`s unlikely to
see any strikes west of the Cascades, and even a shower or two looks
unlikely. Along the coast, the marine layer will thicken and bring
cigs down to IFR later tonight. Expect some marine stratus to make
it into the Umpqua Basin, but only have moderate confidence that it
will be enough to bring cigs down a category.
&&
.MARINE...Weak high pressure over the waters will lead to
diminishing winds and seas into Sunday. Westerly swell will then
build to a light to moderate peak on Monday while a strengthening
thermal trough inland will bring increasing northerly winds on
Tuesday, but the general consensus suggest winds will remain below
small craft. Relatively calm conditions are expected Wednesday
through Friday next week.
&&
.FIRE WEATHER...Updated 200 PM PDT Saturday, 4 August 2018...For
this afternoon, most guidance suggests winds will be similar to
slightly higher than yesterday. The windiest and driest conditions
will be in Modoc County. The latest model data and satellite imagery
suggests a slightly better chance for thunderstorms mostly east of
the Cascades and in Eastern Siskiyou County and Modoc County. This
is enough to warrant a Red Flag Warning, given how dry fuels are,
how efficient any lightning strikes will be at starting fires, and
how breezy and dry it is today. There is a lesser, slight chance of
thunderstorms over Jackson and Josephine Counties. Most likely,
there will just be buildups there because of the dry air moving in.
On Sunday, winds will trend lower in all locations and afternoon
humidity will trend similar or lower over the forecast area. Flow
aloft will shift from westerly of the past several days to
southerly, and this will push smoke further north than past days.
Marginal instability will bring a slight chance for an isolated
thunderstorm or two to the Cascades north of Crater Lake, but
thunderstorms are not expected for most of the forecast area.
Monday through Thursday will feature a warming and drying trend, and
burning periods will get longer each day. Monday morning humidity
recoveries will become moderate in most high terrain areas, and will
worsen through the middle of the week.
The warm and dry pattern will begin to change towards the end of the
week as an offshore upper low pushes inland over British Columbia or
Washington. This will bring cooler conditions but will also likely
bring gusty winds. Most model guidance now shows Thursday and Friday
afternoon being particularly windy and dry for areas east of the
Cascades. We`ll be evaluating this and keeping an eye on trends as
this gets closer. Keene
.PREV DISCUSSION... /Issued 335 PM PDT Sat Aug 4 2018/
DISCUSSION...Earlier models were showing more stability over the
west side, but the 18Z runs of the NAM, GFS and HRRR showed
increased instability over the west side, pretty much from the
current west side fires to the southeast. This is also pretty much
exactly were cumulus is popping up at this time. have added slight
chance thunderstorms to this area and kept coverage based wording
over Siskiyou county and the Cascades eastward. Transport winds
are marginal, and with the uncertainty of any cells latching to
terrain, have filled in the valleys with slight chance pops as
well.
Tomorrow the area of instability is confined to the Cascades
north of Crater Lake and is marginal until 3Z when a cooler air
mass shifts over the region with the deepening upper level trough
offshore.
As we head into next week the upper level ridge over the great
basing builds with heights rising into Thursday. This will return
high temperatures into the triple digits. As we head into the
Friday time frame the GFS shifts the ridge east with the EC
holding on to it a little longer. The EC has been more consistent
with this and have gone with the higher EC guidance for Friday.
Sven
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Air Quality Advisory.
CA...None
Pacific Coastal Waters...None.
$$
MSM/NSK/SBN
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1047 PM EDT Sat Aug 4 2018
.SYNOPSIS...
Strong Bermuda high pressure will extend over Eastern NC through
Sunday, and weaken slightly early next week as a weak inland
trough develops. A front will slowly approach from the west by
late week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 1030 PM Saturday...Lowered PoPs further for the overnight
with KMHX radar showing showers have dissipated and HRRR and
NSSL WRF mainly dry overnight. They do show a few showers
possible along the coast late and keep slight chance PoP after
09z.
Latest sfc analysis shows high pressure anchored off the
Eastern US, extending into Eastern NC. The high will ridge in
from the south overnight, and developing westerly flow should
dry out the region slightly, albeit not all that much. Some
patchy fog will be possible inland late tonight and early Sunday
morning with light winds and minimal dewpoint depressions.
Overnight lows in the 70s.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
As of 3 PM Sat...High pressure will remain anchored off the
coast Sunday, though a weak boundary will move into the northern
forecast by afternoon. Expect winds to shift more E/SE across
the NE forecast area, and this could also serve as an
additional focus for convection. Another day of scattered
showers and storms with brief heavy downpours expected. Low
level thickness values support highs in the mid to upper 80s.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
As of 3 am Sat...Not much variation through the long term with
typical summertime conditions forecast. Mid-state trof will be
in place each day with a frontal boundary approaching by
midweek. Deep moisture will be in place over the region with
chance PoPs each day. Convection will be initiated mainly by
seabreeze combined with mid-level vort centers moving through
the flow. There may be an increase in activity by mid to late
week as the front sinks into the area, becomes stationary and
gradually dissipates. Highest PoPs appear to be for Wednesday
as the front approaches the area and a strong shortwave ahead
of it passes through. Have capped PoPs on Wed at 50% for now.
Temperatures will be in the mid 80s coast to upper 80s inland
through the period. Lows will range from the lower 70s inland
to mid 70s coast and Outer Banks.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Short Term /through Sunday/...
As of 8 PM Saturday...VFR conditions expected through much of
the overnight with only isolated showers/storms possible, but
could see patchy fog/stratus develop between 08-13z as winds
will be light/calm with minimal dew point depression. Scattered
showers and thunderstorms expected across the region again
Sunday afternoon will bring periods of sub-VFR conditions,
otherwise VFR will prevail.
Long Term /Sunday night through Thursday/...
As of 3 am Sat...Similar conditions each day through the long
term. Sub-VFR conditions possible each day at the 4 terminals
in scattered showers and thunderstorms. Patchy late night/early
morning low clouds/fog also possible at terminals that receive
convection. Surface winds will be from the south to southwest at
10 knots or less through the period.
&&
.MARINE...
Short Term /through Sunday/...
As of 830 PM Sat...Forecast on track with little changes needed
for the evening update. Latest obs show SW/W winds 5-15 kt with
seas 2-3 ft. Expect that to continue through most of tonight,
with winds becoming more westerly early Sunday morning. A weak
boundary will push into the northern waters by Sunday afternoon,
with winds becoming more E/SE 5-10 kt during the afternoon and
remaining SSW across the central and southern waters with seas
2-3 ft.
Long Term /Sunday night through Thursday/...
As of 3 am Sat...A very benign marine forecast is expected
through the extended period as high pressure continues offshore
and a mid- level trough remains well to our west. This will lead
to S/SW winds 5-15 knots through the period with seas 2-4 feet.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...CQD/SGK
NEAR TERM...SK/CQD
SHORT TERM...CQD
LONG TERM...HSA
AVIATION...SK/HSA/BM
MARINE...SK/CQD/HSA
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
1056 PM CDT Sat Aug 4 2018
.UPDATE...
Issued at 913 PM CDT Sat Aug 4 2018
ACCAS showers now entering southwest MN show no real signs of
strengthening into thunderstorms due to meager forcing despite a
rather unstable atmosphere. The boundary layer will be stabilizing
this evening and any storms that may develop overnight will
likely be elevated unless they develop an organized cold pool. The
most likely storms to affect the area are now in the central
Dakotas and models have slowed the arrival to very late tonight or
closer to sunrise. The 00Z HRRR actually slowed it down even
further to mid morning Sunday. Confidence is decreasing we`ll see
much tonight, but we will maintain mid range PoPs overnight for
now.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 300 PM CDT Sat Aug 4 2018
Short term concern remains convective threat overnight and again
into Sunday.
Latest water vapor imagery showing initial upper wave moving into
western MN at this time. Rain shield exiting to the east early
ahead of this wave. Latest SPC mesoanalysis showing 2000 J/kg
MLCAPE moving into western MN along/ahead of surface boundary.
This worked into western Mn this evening. However, surface winds
more southwest ahead of this boundary, and with the upper trough
exiting already to the east, not seeing significant forcing to
generate convection over the west at least at the moment. Looking
farther west, appears to be some mid level moisture trying to
move across South Dakota, which is where most deterministic
models were indicating a secondary wave. The 12z HREF/along with
the deterministic GFS and ECMWF brought this feature into the
southwest this evening and did generate at least some scattered
convection over the southwest through the evening. HIRES cams were
showing a more expansive development east overnight. Will have to
continue to monitor overall trends early evening to see if indeed
the HIRES models are correct (they were last night). Certainly
looks more conditional than last night. Pretty much matches
overall SPC outlook. We will continue to hold onto some chance
PoPs overnight and spread them east and south.
The next convective threat develops ahead of weak boundary over
mainly the southern half of the CWA into Sunday. SPC Day2 outlook
indicates a slight risk over the southern third, closer to better
instability and moisture. Also another short wave is progged to
move in to the area later Sunday afternoon and overnight which
will likely generate enough forcing to continue the high end PoPs
over far south central MN Sunday night.
.LONG TERM...(Sunday night through Saturday)
Issued at 300 PM CDT Sat Aug 4 2018
The longer term has a chance of convection over the southern CWA
into Monday with the slow moving surface boundary exiting the
area. Following the front, the upper flow pattern becomes more
northwest aloft. This should drive in drier air with weak high
pressure through midweek. Timing of the next boundary is about
midweek with the next small chance for thunder indicated. Overall,
riding builds eat later in the week and into next weekend which
should provide above normal temperature and a mainly dry trend.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1056 PM CDT Sat Aug 4 2018
Removed the thunder threat from all the TAF sites overnight due to
too low of confidence. Recent model runs have backed off quite a
bit on coverage and current convection shows no signs of
strengthening. The next best chance will come Sunday afternoon and
evening across southern MN. VFR conditions are expected otherwise
through the period.
KMSP...No additional concerns.
/OUTLOOK FOR KMSP/
Mon...VFR. Wind NW 5-10 kt.
Tue...VFR. Wind NW 5 kt.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
UPDATE...BORGHOFF
SHORT TERM...DWE
LONG TERM...
AVIATION...BORGHOFF
Area Forecast Discussion
National Weather Service Pocatello ID
247 PM MDT Sat Aug 4 2018
.DISCUSSION...Today Through Next Saturday.
SE Idaho is in the midst of an absolutely gorgeous afternoon, with
temps cooler than anything we have seen over the past month. That`s
courtesy of a slightly fresher air mass that filtered into the
region behind a departing trough/surface front. Smoke/haze has even
diminished a bit across the region, although we won`t be rid of it
for the foreseeable future. See the AIR STAGNATION section below.
We ARE going to trend back into a very hot and dry weather pattern,
but we have one weak shortwave trough to deal with first for tonight
and Sunday. This trough is looking just a bit more pronounced in the
model guidance today compared to the past couple of days, and it may
provide enough lift and instability for a few showers and t-storms.
Model blends are fairly dry, but the 12Z suite of HREF CAMs along
with the latest NAM/GFS/RAP all carry some plan-view precip echoes,
although the HREF 40+ dBZ paintball plot is pretty quiet.
Considering the more pronounced nature of the trough and echoes
running around on a majority of models, am not completely
comfortable keeping the forecast dry. Thus, introduced some light
PoPs (15-25%) this eve and tonight across the Central Mntns, Upper
Snake Highlands, and Bear Lake region, continuing Sunday but
shifting east, enough to trigger mention of isolated showers and t-
storms in the forecast. NAM/RAP soundings and surface obs indicate a
lot of dry low-level air that would need to be overcome, but
soundings do show mid-level moistening. Envisioning most locations
will remain dry as just a few showers and t-storms drift through,
with some light precip making it to the ground. Bottom line,
nuisance activity that should not significantly impact anyone`s
plans. IF a stronger cell were to develop, some gusty winds would be
possible supported by pseudo-inverted-V signatures and some marginal
DCAPE, but this isn`t likely for most.
We continue to have high confidence in the forecast for Monday
through Friday, as all long-range models advertise a ridge of high
pressure developing over Arizona/New Mexico, strengthening
significantly and building north over the week, centered over Nevada
by Thursday. As the amplitude of the ridge axis builds north over
Idaho and west/southwest flow becomes established, progressive
warming is expected, under dry conditions and sunny skies. High
temps look to exceed 90 degrees once again by Monday or Tuesday in
lower elevations from the Snake Plain southward and the Challis
area, with mid to upper 90s likely by Wednesday and Thursday. Friday
currently looks the hottest, with values of 97-100+ possible in the
eastern Magic Valley, lower Snake Plain, Challis area, and valleys
across the southern Highlands. Record high temperatures may be in
jeopardy at various sites Thursday and Friday, and we will have to
monitor this period as well for the need for a Heat Advisory, which
will in part depend on how well our temps recover (cool) at night.
We noticed our model blends were coming in a bit cooler than actual
observed high temps during the heat of past two weeks, thus, added 1-
2 degrees to the forecast on top of the model blend for large
portions of the region each day next week. Generally light winds are
expected throughout the week. The GFS/ECMWF/Canadian all try to
bring a pronounced trough of low pressure across the northern
Rockies by next Saturday, but this is a week out, and the models
differ in the track/strength of this system and in placement of t-
storm chances. For now, will maintain a dry/sunny forecast Sat, with
a slight increase in winds/clouds. Stay tuned. - KSmith/KB
&&
.AVIATION...
A weak disturbance will move across the area tonight, bringing
increased mid-level clouds and possibly a few isolated showers or
thunderstorms. Will carry a VCSH mention later this evening into
Sunday morning at KSUN, but chances appear too low for any mention
at the other terminals. VFR conditions are expected to prevail
through Sunday. Will continue to see some smoke from various
wildfires across the region, but not expecting it to become thick
enough near the surface to drop visibilities below VFR. Slightly
breezy winds gusting to around 20 kts this afternoon will
dissipate after sunset. - KB
&&
.FIRE WEATHER...
A weak disturbance will advance across Sawtooth/Challis Forest
area tonight. As a result, isolated showers and perhaps an
isolated thunderstorm will be possible across portions of the
Sawtooths/Challis from roughly 9PM this evening through 9AM
Sunday morning, with perhaps another chance late Sunday afternoon,
although this second chance looks very limited with any
thunderstorms likely confined to those areas very near the Montana
border. Southwest wind gusts of 25-30 mph around Craters and on
the highest Sawtooth/Challis ridgetops will continue through just
before Sunset this evening (8PM or so). This is a fairly limited
area and marginal for critical weather concerns, thus decided to
not go with a Red Flag for the remainder of this afternoon. Wind
gusts in the mountains should stay below 25 mph. The remainder of
the forecast into next week looks dry with minimal winds while the
high pressure ridge rebuilds over the Great Basin by about
Thursday. Nighttime relative humidity recovery each night this
coming week looks rather poor, 20 and 30 percent range for middle
and upper slopes, especially in the Sawtooth and Caribou Forests.
Daytime minimums not much different, 5 to 15 percent range.
- AD/RS/KB
&&
.AIR STAGNATION...
Varying degrees of degraded air quality will continue across SE
Idaho for the foreseeable future due to smoke and haze from numerous
wildfires burning both in Idaho and across the rest of the Pacific
Northwest. With today`s fresh airmass/breezy conditions, we have
seen some improvement in smoke/haze levels, and air quality has
improved to "Good" or Green across the region according to the Idaho
Department of Environmental Quality (ID DEQ). The HRRR smoke model
does hint at some increase in smoke and haze tonight and tomorrow,
however. Have added areas of smoke and haze to the weather grids for
the entire CWA from this afternoon through Monday morning. We will
likely extend smoke/haze in the forecast into much of the upcoming
week, as a more stagnant weather pattern with light winds should
favor continued slow-moving plumes across the region. - KSmith/KB
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$