Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/11/16
Area Forecast Discussion
National Weather Service Albany NY
1107 PM EDT SAT SEP 10 2016
.SYNOPSIS...
Scattered showers and thunderstorms are expected tonight as a
strong cold front crosses the region. Cooler, drier and breezy
conditions are expected for Sunday. Then a period of very tranquil
weather is in the forecast for early next week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Convection associated with pre-frontal trough ahead of cold front
was much better organized as it moved through western NY earlier
this evening. The trough is currently crossing a region where
there is a pocket of drier air with dew points in the low 60s. So
perhaps not surprising that the activity as waned. Question for
overnight will be how much will the convection reinvigorate as it
comes into somewhat better instability (SPC mesonanalysis showing
about 1000 j/kg across much of the region now) and bulk shear
running around 40 knots. SPC continues slight risk for far
northwest CWA and marginal risk for remainder of CWA. The HRRR
model shows a few lines of convection coming across the CWA
overnight. Simulated radar reflectivity images suggest a couple of
the storms could be near severe limits. Have maintained gusty wind
wording for small area of slight risk overnight.
Radar is blossoming with SHRA across much of the CWA in an area
of high theta-e air and increasing 850mb winds.
So as far as the forecast goes for tonight have "coverage" wording
for entire CWA with SHRA/TSRA mentioned.
Overnight lows tonight are expected to remain very mild with
readings in the upper 50s to mid 70s with dewpoints remaining in
the 60s to lower 70s for much of tonight.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
on Sunday...After any showers end early in the morning expect
clearing with breezy and much less humid conditions. Highs on
Sunday will be in the mid 60s to lower 80s with dewpoints dropping
into the upper 40s to mid 50s by days end. Winds will be west at
10 to 20 mph with gusts to 30 mph.
Sunday night through Monday night...A large ridge of high pressure
will crest over the region early Monday morning and slide off the
eastern seaboard early Tuesday morning. Expect much more
seasonable conditions. Lows Sunday night are expected to be in the
40s to around 50 with highs on Monday in the upper 60s to upper
70s and lows Monday night in the upper 40s to mid 50s.
Tuesday...Expect milder conditions once again as a return flow
sets up wit high pressure off the coast. It will still be dry, but
highs will rebound to the mid 70s to lower 80s.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
The period starts out Tuesday night with a cold front and its
associated upper level trough approaching from the Great Lakes
region. There are some timing differences in the model guidance,
with the 12Z/10 GFS showing faster timing compared to the 12Z/10
ECMWF, which is a reversal from 00Z/10 guidance. Allowing for a
margin of error in timing, will mention slight to low chance pops
ahead of the front for areas north and west of the Capital District
starting late Tuesday night. A better chance for showers will be
during the day Wednesday as the front and upper trough axis push
through. Will only mention slight chance of thunder due to forecast
limited surface based instability, but slightly negative Showalter
values.
The ECMWF suggests that showers may linger well into Wednesday
night, so will keep chance pops at least into the evening hours,
especially for northern areas.
It will then turn much cooler and drier from Wednesday night through
the end of the work week, as a sprawling area of surface high
pressure builds in across the region. Temperatures will feel more
fall-like with cool crisp nights and seasonably warm sunny days
Thursday and Friday.
By Saturday, the high will begin shifting off the eastern seaboard,
with a moistening southerly developing. In addition, another frontal
system will be approaching from the Great Lakes. Some showers may
reach the region by late Saturday or Saturday night, especially for
areas north and west of Albany, where slight chance pops are
indicated.
As for temperatures, Tuesday night should be mild ahead of the
front, with lows ranging from the 50s across higher terrain, to the
lower/mid 60s in valleys. Wednesday high temperatures are forecast
to range from the 60s across northwest areas, to the upper 70s/lower
80s southeast valleys. If the front moves through slower, even
warmer high temperatures are possible, especially southeast areas.
The cooldown begins Wednesday night, with lows in the 40s for most
areas, except for some lower 50s in valley areas. Thursday highs
should be quite cool, with mainly 60s expected for most areas,
except for 50s across higher elevations of the Adirondacks and
southern VT, and lower 70s across southeast valley areas. Thursday
night/Friday morning will be chilly, with patchy frost possible
across portions of the western Adirondacks, southern VT, and higher
peaks in the Catskills, with upper 30s to lower 40s expected in
these areas, and lower 40s to around 50 elsewhere.
Slight warming for Friday and Saturday, with temperatures reaching
70s in valley areas, and 60s for higher elevations. Overnight
lows will be in the mid 40s to mid 50s.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Main issue for the TAF period will be timing of convection through
the terminals. Strong/severe thunderstorm activity no ongoing
across western NY. This will move east overnight. Computer models
show some weakening of the line as it moves east. However, severe
parameters remain favorable overnight with CAPE values up to 1000
j/kg, and bulk shear up to 50 knots. Taking a cue from the HRRR
have attempted to time the line through terminals overnight. Thus
have included "4SM SHRA" with VCTS at all terminals, except POU for
a period overnight. At POU, timing/intensity is a little murkier,
so keeping with just VCTS.
GFL should remain mostly clear through at least 03Z. With dew
points in low 70s there, have allowed for MVFR BR in the 00Z-03Z
window. Mid level clouds moving in should preclude any IFR
conditions.
Winds will become south to southeast this afternoon and increase
to 5-10 KT, with some gusts possibly up to 20 KT, especially at
KALB. Winds will be south to southwest tonight at 5-15 KT, with
some gusts of 20-25 KT possible, especially at KALB. Winds will
then shift into the southwest, then west as the front passes and
increase to 10-15 KT with gusts up to 25 KT possible by late
Sunday morning.
Low level wind shear may become problematic later this evening
through early Sunday morning, as winds around 2000 FT AGL increase
from the south/southwest at 35-40 KT. This issue will be mainly in
areas where surface winds decrease to less than 10 KT, which at
this time, appears most likely at KGFL, where it has been included
in TAFs.
Outlook...
Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: No Operational Impact. NO SIG WX.
Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: Moderate Operational Impact. Chance of SHRA...TSRA.
&&
.FIRE WEATHER...
Scattered showers and thunderstorms are expected tonight as a
strong cold front crosses the region. Cooler, drier and breezy
conditions are expected for Sunday. Then a period of very tranquil
weather is in the forecast for early next week.
Relative humidity values will recover to 85 to 100 percent
tonight, drop to 40 to 65 percent on Sunday, recover to 80 to 100
percent Sunday night, and drop to 35 to 45 percent on Monday.
Winds will be south to southwest at 10 to 20 mph with gusts to 30
mph tonight, west at 10 to 20 mph with gusts to 30 mph on Sunday,
northwest at 5 to 15 mph Sunday night, and west around 5 mph on
Monday.
&&
.HYDROLOGY...
Showers and thunderstorms are expected tonight. Some heavy
downpours are possible which may produce flooding of poorly
drained low lying areas. However, no flooding is expected on the
main stem rivers. QPF amounts through tonight generally look to be
between a quarter of an inch and an inch in most locations. Dry
weather is then expected to return later Sunday morning and last
at least through Tuesday.
For details on specific area rivers and lakes, including observed
and forecast river stages and lake elevations, please visit the
Advanced Hydrologic Prediction Service /AHPS/ graphs on our
website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...11/NAS
NEAR TERM...OKeefe/11
SHORT TERM...11
LONG TERM...KL/JPV
AVIATION...KL/OKeefe/JPV
FIRE WEATHER...11
HYDROLOGY...11/NAS
Area Forecast Discussion
National Weather Service Burlington VT
1004 PM EDT Sat Sep 10 2016
.SYNOPSIS...
A cold front will sweep across New York tonight reaching Vermont
around dawn accompanied by a band of showers and a few
thunderstorms, especially in northern New York, some with locally
heavy rain and gusty winds. The cold front will clear the area on
Sunday with gusty winds and drier and cooler weather. High
pressure will bring mostly sunny and seasonably mild weather
through Tuesday. A cold front on Wednesday will result in a taste
of fall for late week.
&&
.NEAR TERM /UNTIL 6 PM SUNDAY EVENING/...
As of 1004 PM EDT Saturday...Minor additional update to blend
latest HRRR output into extant pop/weather grids through 2 am or
so, after which going forecast remains largely unchanged. This
predicates keeping minimal pop values east of the St. Lawrence
Valley until after midnight, after which the surface front and
better forcing for showers/isolated storms moves bodily east into
our forecast area. Still watching quasi-stationary convective line
with embedded shorter segments moving from 220 deg true north-
northeast along the St. Lawrence River and to the immediate west.
Earlier more robust cell produced minor wind damage across the
southwestern portions of St. Lawrence County with KOGS AWOS
gusting to 40 kts. Will continue to monitor convective trends over
the next few hours given robust low level wind fields but overall
threat of additional severe weather across the St. Lawrence Valley
continues to gradually lessen with increasing CIN.
Prior discussion from 713 PM EDT Saturday...
Modest updates to sky cover, pops and sensible weather over the
next 6 hours to account for current observational trends. Warm
front has lifted bodily northward and is clearing north into
southern Canada as of 700 pm with deepening moist southerly flow
now surging into the forecast area. Meanwhile, a surface cold
front is trudging steadily east across the lower Great Lakes and
is oriented along or just west of a line of strong convection from
Lake Ontario south and west through the Buffalo metro area into
northeast Ohio. Based off latest CAM output, we`ve lowered pops
considerably east of the St Lawrence Valley until later this
evening, after which the eastward progress of the surface front
will push the then weakening band of showers/storms across the
forecast area. With a deeply moist airmass (PWATS to 2.0 inches)
advecting atop the area, locally heavy downpours will remain
possible. However, it increasingly appears the best threat of
strong to locally severe storms will be confined to the western
slopes of the Adirondacks into the St. Lawrence Valley where
juxtaposition of lingering instability and robust boundary layer
wind fields will occur this evening in a typical high shear/low
CAPE environment. Indeed, latest KTYX VWP profiles support recent
hi-res model output suggesting 40-50 kt southwesterly flow will
occur in the 1-2 kft band immediately preceding the line of
showers/storms this evening in this area. Thus any small low-
topped line segments and/or short bowing segments, if they
develop, will be watched closely - generally in the 8 pm to
midnight time frame.
By later tonight, the weakening band of showers/isolated storms
will push steadily through the forecast area, pushing into our
eastern VT by sunrise or shortly thereafter. Current forecast low
temperatures and cloud cover/dewpoint fields largely remain on
track so little other changes needed at this point.
Sunday: By sunrise...cold front is quickly approaching the
Champlain Valley with showers largely across VT quickly exiting as
cold front passes. Behind the front...developing strong cold air
advection under building high pressure will promote deep mixing
tapping into an exiting low/mid level jet around 30-40kt at
925-850mb. This should account for skies trending to partly sunny
by the afternoon and winds gusting through the day in the 25-35mph
range. After about a week of above normal temperatures, it will
seem cool BUT we`ll finally see a return to near normal highs
ranging from the mid 60s to mid 70s.
&&
.SHORT TERM /6 PM SUNDAY EVENING THROUGH TUESDAY/...
As of 221 PM EDT Saturday...Sunday night through Tuesday will be
largely dominated by high pressure building from the Ohio River
Valley into the Northeast before moving offshore with a warmer
return flow on Tuesday ahead of next cold front.
Mainly clear skies Sunday night with light winds and recent rainfall
will set the stage for dense radiational fog to develop in the climo
favored river valleys and mountain hollows. Also...new colder
airmass will help lower temps into the 40s with possibly some upper
30s in NEK and Adirondacks but 50s along the lake shore.
Highs Monday will be a few degrees milder than Sunday with plentiful
sunshine and lack of cold air advection...back to seasonable 70s.
Another mainly clear night on Monday night but one day removed from
precipitation and some slight gradient developing. Areas of fog
still likely but not as widespread as Sunday night/Monday morning
and not as cool.
On Tuesday...return flow and decent amount of sun until afternoon
will moderate temperature back to above seasonable levels in the mid
70s to lower 80s.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 221 PM EDT Saturday...Not much change from what we`ve been
talking about the past few days. A strong cold front Tuesday
night/Wednesday brings fall to the north country with High
pressure dominating the rest of the work week.
Tuesday night through Wednesday we continue to highlight the
chance for some showers as strong cold front looks to swing
through. Overall the system is pretty progressive so rainfall not
looking to be a big deal, but behind the front strong cold air
advection with high pressure building southeastward from
south/central Canada will usher in a seasonally cold airmass which
will dominate our weather right through the end of the work week.
Clearing skies Wednesday night then mainly clear through early
Friday with some clouds thereafter as return flow begins as high
pressure begins to slides south and east. A cold night both Wed
and Thu Nights and a cool day on Thursday despite plenty of
sunshine. On Friday...temperatures moderate back to seasonable
levels.
The combination of departing ridge and approaching northern stream
trough means southwest flow with more clouds...milder temperatures
on Saturday and leaning toward dry conditions although conflicting
guidance lends to lower confidence by Saturday afternoon.
&&
.AVIATION /02Z Sunday THROUGH Thursday/...
Through 00Z Monday...Complex forecast with immediate concern
being a combination of showers and thunderstorms around the Saint
Lawrence Valley and LLWS from low level jet moving in from the
west. VFR conditions expect throughout most of the period,
exception of MVFR vis/cigs with showers and t-storms with cold
frontal passage 03Z-12Z.
Wind shear expected out of the SW at 35-45kts around 2kft at KMSS
and KSLK this evening before gusts develop after 06Z. LLWS also
possible at KMPV and KRUT mainly between 05Z-10Z, while channeling
up the Champlain Valley will keep surface winds higher, especially
with gusts developing at KBTV 06Z through the rest of the period.
Front and associated showers will exit east mid to late Sunday
morning. Clouds will diminish but wind gusts will remain with
sustained NW 10-15kts gusts 20-30kts throughout the day.
Outlook 00Z Monday through Thursday...
00z Mon-06z Wed: Mainly VFR under high pressure except LIFR
nocturnal fog possible SLK/MPV Sunday night and again Monday
night, mainly 06-13Z.
06z Wed-06z Thu: VFR with MVFR possible in showers associated
with a cold front.
06z Thu onward: VFR under high pressure.
&&
.MARINE...
Southerly winds have been increasing to 15 to 20 kts with gusts as
high as 29 knots at Diamond Island in the last hour ahead of a
strong cold front. Waves increasing to 1 to 3 feet on average but
again could be higher on the open waters tonight. That strong cold
front will reach Lake Champlain between 5 and 7 a.m. and may be
accompanied by a band of heavy showers lasting an hour or so along
with a chance of a thunderstorm and potentially locally stronger
winds. Behind the cold front on Sunday, winds will shift to SW
then gradually W then NW during the afternoon again around 15 to
25 knots.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...SLW
NEAR TERM...JMG/KGM/SLW
SHORT TERM...SLW
LONG TERM...SLW
AVIATION...KGM
MARINE...Verasamy
Area Forecast Discussion
National Weather Service State College PA
1001 PM EDT SAT SEP 10 2016
.SYNOPSIS...
Showers will accompany a cold front as it pushes through western
and central Pennsylvania tonight. High pressure and much cooler
and drier weather will move in for Sunday and last through early
next week. A new cold front will push southward across the region
Wednesday, followed by another high pressure system with cooler
temperatures again for late in the week.
&&
.NEAR TERM /UNTIL 8 AM SUNDAY MORNING/...
Storms are all but done - especially the threat for severe.
Showers will, however, linger into the middle of the night over
the west. The cold front is over central OH now, behind the
showers, but may catch up as the cool air bump in pressure behind
the gust front levels out and reveals the actual front. Sct
showers in the east are moving steadily NE but are capable of
making ltg. No organization to them and CAMs and new NAM12 reveal
limited instability. They are worth 30-40 POPs for the next 4-6
hrs, but in between them and the dying showers over the west, it
will remain dry. Looks like many places in Central PA will have a
cfropa and 15F drop in dewpoint by noon Sunday without a drop of
rain for their tomatoes, or lawns, or...
Prev...
Latest update tweaked timing of precip. Just one or two
cells look big enough to continue to do damage - the ones on the
Warren Co threshold right now are not threatening. Bigger cells to
the south of Meadville are of more concern. Time will tell if they
are gasping as they near the CWA as well. There is a visible thin
line pushing ahead of the main line anywhere south of the Franklin
cell. That would most likely be the cool outflow/gust front.
Therefore, further weakening along that southern portion of the
line is expected. Watch 474 is well-placed and timed. will just
have to stare at the radar for another two hours as the watch
expires at 02z.
Prev...
A very warm and humid day is in progress. SPC meso anal shows
mixed layer Capes in the 1000-1500J so there is some instability
developing in the airmass out ahead of the cold front that is just
entering western Ohio. However local forcing and lapse rates
remain weak so little more than scattered pulse type activity is
expected for the bulk of the region during the daylight hours.
The HRRR shows the leading edge of a squall line entering Warren
County by 8PM, and it progresses east into the western portion of
the CWA before the model shows the convection diminishing in
coverage and intensity, which makes sense wince we will tend to
see stability increase after we lose the diurnal heating. Highest
pops will be over the Laurels up into the northern mountains with
chances dropping off over central and eastern areas.
Ahead of the cold front it will be a warm and muggy night over
most areas with lows averaging 10-15 deg above normal.
&&
.SHORT TERM /8 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
Sunday looks like a beautiful and increasingly less humid day as
high pressure is slated to build east out of the midwest. 12Z
deterministic models show a small area of very light QPF over the
northwest Sunday morning in the wake of the cold front, but the
SREF/GEFS show low to no pops. So while I won`t rule out a
lingering light shower or sprinkle, I chose an optimistic dry
forecast.
Sunday`s highs will be some 10-15 deg cooler than today. Closer to
seasonal normals.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Not a lot of change for this section of the package.
Monday looks like a cooler and sunny day, as heights rise
and the high builds east of the area.
Still looks mainly dry on Tuesday, but hints at low level
moisture works northward. There could be a very brief
sprinkle late.
A very warm airmass works eastward ahead of the next cold
front on Wednesday.
Thursday and Friday look dry.
Some hints of showers for Saturday, thus have some chc
in fcst.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
A cold front will trigger an advancing line of showers and
thunderstorms that will move into the NWRN mountains by 00Z with
storms reaching BFD between 01Z to 02Z and slowly moving bringing
locally reduced conditions. The showers and thunderstorms will
tend to fall apart as they move into the central mountains so
MVFR/IFR will also tend to become more scattered as the convection
diminishes.
More widespread restrictions, mainly lower ceilings, are expected
behind the front tonight, mainly over central and western
terminals. Conditions will improve rapidly after sunrise Sunday as
agusty and drier NW breeze develops.
Outlook...
Mon-Tue...No sig wx.
Wed...Chc shra/tsra.
Thu...no sig wx.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...La Corte/Martin
NEAR TERM...Dangelo/La Corte
SHORT TERM...La Corte
LONG TERM...Martin
AVIATION...La Corte/Ceru
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
649 PM CDT SAT SEP 10 2016
.UPDATE...
Have done a quick evening update to reflect the ongoingconvection
over Fayette and Lavaca counties. These storms are forming along
the front still draped across the area. The latest HRRR and 12Z
Texas Tech WRF suggests that a few more storms could pop up along
the Coastal Plains through the evening into the early overnight
hours. The front is currently located roughly from Pleasanton
northeast to La Grange and is not moving much.
Did see another boundary, a secondary surge of slightly cooler
air with winds gusting to 20 to 25mph move through the Austin area
over the last few hours. Have adjusted the hourly grids to reflect
this boundary continuing to push south increasing winds slightly
across the I-35 Corridor. Also made changes to the hourly
temperature and cloud cover grids. Rest of the forecast is on
track.
&&
.PREV DISCUSSION... /ISSUED 626 PM CDT SAT SEP 10 2016/
AVIATION.../00z Update/
VFR conditions are expected through the period. Low level moisture
will remain across the Rio Grande and all guidance is indicating
some MVFR cigs after 12z. Have included a tempo group to cover
this. A weak boundary is moving south across the area this evening
and will cause winds to become easterly ahead of the boundary then
shifting back to northerly and increasing to 10-20 knots with
higher gusts. Expect the stronger winds to decrease in the 02z-04z
period and overnight expecting northerly winds 5-8 knots
continuing into Sunday. KDRT will see southeasterly winds return
after 17z at speeds 8-10 knots. Boundary moving south could cause
a few sprinkles through 02z with convection expected to remain
well east of I-35. s
PREV DISCUSSION... /ISSUED 239 PM CDT SAT SEP 10 2016/
SHORT TERM (Tonight through Sunday Night)...
Upper air analysis this morning showed a weak low over east Texas
with a deep trough over the Great Plains. At the surface, a cold
front was stretched from La Grange to San Antonio to Pandale.
There were isolated showers and thunderstorms along the front. The
upper low will drift slowly toward the east beneath a broad ridge
during this period. The front will stall and dissipate along our
southern border tonight and Sunday. With the front hanging around
there will be continuing chances for showers and thunderstorms
tonight with decreasing chances Sunday. By Sunday night rain
chances should end.
LONG TERM (Monday through Saturday)...
Monday the upper low will continue to move away from the region
and there may be a few showers and thunderstorms over the coastal
plains. Tuesday another upper level trough will settle over the
western states and turn the flow over Texas to the southwest. The
low level flow will be from the east to southeast keeping low
level moisture high. This pattern will generally remain in place
through the end of the period and send short wave energy over
Texas which will generate showers and thunderstorms. In addition,
another frontal boundary will move through Central Texas
Wednesday. This will all lead to varying chances for rain through
the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 93 71 89 72 92 / 30 10 10 0 10
Austin Bergstrom Intl Airport 91 70 89 70 91 / 30 10 10 0 10
New Braunfels Muni Airport 92 71 90 70 92 / 30 20 10 0 10
Burnet Muni Airport 86 67 87 69 90 / 20 20 10 0 -
Del Rio Intl Airport 88 73 91 73 94 / 30 30 20 0 10
Georgetown Muni Airport 90 68 88 70 91 / 20 10 10 0 10
Hondo Muni Airport 92 71 91 71 93 / 30 20 10 0 -
San Marcos Muni Airport 91 70 89 70 90 / 30 20 10 - 10
La Grange - Fayette Regional 91 72 90 72 91 / 30 20 30 - 20
San Antonio Intl Airport 91 73 90 72 92 / 30 20 10 0 -
Stinson Muni Airport 93 74 91 73 93 / 30 20 10 - -
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...10
Synoptic/Grids...Treadway
Public Service/Data Collection...Treadway
Area Forecast Discussion
National Weather Service Green Bay WI
1040 PM CDT SAT SEP 10 2016
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Sunday
Issued at 231 PM CDT Sat Sep 10 2016
The latest RAP analysis and satellite/radar imagery show broad low
pressure and an associated cold front moving east over Michigan
early this afternoon. The band of showers behind the front has
exited to the east, but additional shower activity and isolated
thunderstorms have developed beneath a cold upper trough that is
moving across the region. These showers should impact the region
through the end of the afternoon before ending/exiting. Looking
upstream, surface high pressure is bringing clearing skies over the
northern Mississippi Valley. Additional mid and high clouds are
sliding southeast over the western Dakotas, but no sign of precip
associated with them. Precip and cloud trends are the main forecast
concern in the short term.
Tonight...A few showers may linger along the lakeshore areas early
this evening before moving over the Lake. Otherwise, should see
clearing skies take place as high pressure drifts into the region.
Though mid and high clouds will be arriving late, recent rainfall
and low temp/dewpoint spreads could lead to patchy fog developing
late over north-central WI and the WI River Valley. Lows ranging
from the mid 40s north to low 50s south.
Sunday...High pressure will quickly advance across the region during
the morning hours. Will see some scattered to broken mid and high
clouds through the morning and into the afteroon, so sky conditions
will likely fall into the partly cloudy range for most areas, but
with increasing sunshine in the afternoon. High temps ranging from
the low to mid 70s.
.LONG TERM...Sunday Night Through Saturday
Issued at 231 PM CDT Sat Sep 10 2016
Northern stream flow will dominate the regions weather for much of
new work week. A short wave trough with frontal system will slide
over the Great Lakes region later Monday into Tuesday. 850 warm
prod does produce steep mid level lapse rates Monday afternoon
but saturation appears to be a problem initially. As the air mass
begins to saturate later Monday evening the best instability and
850 warm air advection is pushed to the south. With the RRQ region
of the upper jet for large scale ascent just to the west and the
850 front and baroclinic zone dropping south over the state later
monday night into tuesday morning, anticipate a better chance for
showers. Could have more of band of steady rain event if the if
the upper jet support is a bit more eastward.
Upper heights build for the mid week ahead of western states
trough. A high pressure system drifts over the area for another
dry period with temperatures returning to near normal.
Medium range progs indicate a short wave from the western states
trough gets into the northern stream late in the week for the next
chance for precipitation. Timing of this system could be delayed
into the start of next weekend.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1039 PM CDT Sat Sep 10 2016
Excellent flight conditions are expected overnight and tomorrow,
with the possible exception of some patchy ground fog late
tonight. Surface winds could also be a little gusty tomorrow
afternoon.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Grand Rapids MI
1012 PM EDT SAT SEP 10 2016
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 324 PM EDT Sat Sep 10 2016
Dry conditions and lower humidities are expected through Monday
night. The next chance for showers and thunderstorms comes Tuesday
and Tuesday night. This will be followed by generally dry conditions
the rest of the work week. Temperatures through the period will be
much more seasonable with highs in the 70s.
&&
.UPDATE...
Issued at 1012 PM EDT Sat Sep 10 2016
Lake induced convection will be on the decline overnight with
passage of the mid level trough. Will keep a mention of isolated
showers for a few more hours, otherwise dry and turning partly
cloudy overnight.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 324 PM EDT Sat Sep 10 2016
This evening...main challenge is timing exit of precipitation. Most
of the high resolution convection allowing models such as the HRRR
are in decent agreement about timing and also with indicating a
window of lake effect rainshowers until around midnight before winds
become lighter and more anticyclonic.
Sunday through Monday night...high confidence of dry conditions with
rain chances approaching from the northwest overnight Monday.
.LONG TERM...(Tuesday through Saturday)
Issued at 324 PM EDT Sat Sep 10 2016
There are two major issues with this forecast... first and
foremost... it will be noticeably cooler through this coming week and
well beyond that. The other issue is the cold front that comes
through Tuesday into Wednesday. That will have a band of showers and
maybe a thunderstorm or two with it but I do not expect much rain
from this system... mostly it will just bring in even cooler
temperatures.
From this point forward it will feel more fall like in Southwest
Michigan. At GRR highs have frequently been in the 80s since the
23rd of May. Yesterday it got to 83...well guess what... the string
of days with highs mostly in the 80s is done for the year. With this
cold front (Saturday) from this point forward highs will mostly be
in the 70s and occasionally in the 60s. Not to say we could not have
the odd day with highs in the 80s yet. The frequency of highs in
the 80s at GRR by day is around 50% (1892 to 2016) by the 14th
that drops to 27% and by the 25th it is less than 10% of the days.
To me this is the most significant change in our daily weather
this coming week...highs will only 70s. The really warm weather is
done for the year.
What is curious about that though is the subtropical ridge is
expected to build westward into the central and even northern
plains by the end of this coming week. That will force the next
Pacific system to track farther north and not allow us to get as
deeply into the cooler air. Even so it will still get cooler
behind this cold front that the one coming thought today. The
polar jet...which is over Michigan today into tomorrow shifts
north into central Canada by the end of this coming week. That
will lead to a warm up toward next weekend but with a southern
stream system coming at us by then...it may well be a wet one too.
With the polar jet farther north with the cold frontal system coming
through Tuesday night into Wednesday the dynamics will also be
farther north and there will not be nearly as much moisture for this
system as has been available to that last few systems. So rainfall
will be more scattered and significantly lighter.
So the bottom line is cooler weather and much lower outside
humidities. The best chance for showers will be Tuesday night into
Wednesday morning then again Saturday (could be a very wet day).
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 800 PM EDT Sat Sep 10 2016
Primarily VFR conditions are expected this evening although
scattered showers/isolated tstms could lead to brief periods of
MVFR. This would be more likely at the terminals west of LAN/JXN,
closer to Lake Michigan.
Skies should clear later this evening and no fog issues are
anticipated overnight since much lower dew points have arrived
and the winds will stay up. VFR will continue on Sunday with some
scattered cumulus clouds around 4k ft and a higher deck above that
with bases above 10k ft.
&&
.MARINE...
Issued at 700 PM EDT Sat Sep 10 2016
Have updated the Nearshore Marine Forecast to include a mention
of thunder and a chance of waterspouts this evening. Mid level
trough and cold pool are coming through this evening and a few
cells over the lake have already had some lightning. Waterspout
nomogram, using a lake to 850 temp diff of 15C and a Cloud depth
of 15-20K ft, supports a few spouts. Also there have been some
reports of funnels on the Wisconsin side recently.
Previous marine discussion... We saw an impressive burst of winds
at many of the buoys and coastal sites with the cold frontal rain
band that passed through. We expect a brief lull in winds this
afternoon, but expect them to increase again this evening. Latest
WaveWatch3 guidance does a decent job depicting this and it
appears that a 8AM Sunday expiration for the SCA and Beach Hazards
still looks reasonable.
&&
.HYDROLOGY...
Issued at 211 PM EDT Sat Sep 10 2016
Rivers are running at or above normal for the time of year. Showers
and storms will continue through the afternoon. Less than a half
inch of precipitation is expected across the area through the week.
Small river rises are possible, but flooding is not expected.
&&
.GRR Watches/Warnings/Advisories...
MI...Beach Hazards Statement until 8 AM EDT Sunday for MIZ037-043-050-
056-064-071.
LM...Small Craft Advisory until 8 AM EDT Sunday for LMZ844>849.
&&
$$
UPDATE...Meade
SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...WDM
AVIATION...Meade
HYDROLOGY...63
MARINE...Meade
Area Forecast Discussion
National Weather Service Jackson MS
921 PM CDT SAT SEP 10 2016
.UPDATE...As of 2z, a mid/upper-level shortwave trough was located
across the Great Lakes/Ohio Valley region with an attendant cold
front draped across the country from the Appalachians, through
central MS, and down to the TX coast. A broken line of showers and
storms pushed into the NW CWA this afternoon ahead of the advancing
front. Compared to the last few days, tonight`s 00z KJAN sounding had slightly
better thermo parameters characteristic of 3000 J/kg of SBCAPE, 6 C
mid-level lapse rates and vertical totals of 26. This helped a few
storms become strong this afternoon, but the best shear and forcing
were to our north and kept the severe threat minimal at best. The
initial broken line of convection quickly became outflow dominant
after entering the CWA and dissipated as the outflow boundary
advanced well ahead of the storms. This boundary is currently located
just NW of the Jackson metro with an area of scattered storms to the
SE and isolated showers/storms to the NW closer to the front. For the
rest of tonight, convection should gradually diminish through the
evening, however a few lingering isolated showers and storms can`t
be ruled out as the front continues to push SE across the area.
Otherwise, adjusted temps to match the latest guidance/obs with
cooler overnight lows in the NW behind the front. Also added a few
small areas of patchy fog in the SE and parts of the Delta. /TW/
&&
.AVIATION...VFR conditions will prevail through 11/06Z with MVFR conditions
developing thereafter. These conditions will linger through late
morning Sunday. After noon, scattered SHRA/TSRA will develop as a
cold front slowly pushes through the area./26/
&&
.PREV DISCUSSION... /issued 358 PM CDT SAT SEP 10 2016/
SHORT TERM...Today through Monday...An upper-level shortwave trough
is sliding eastward across the country this afternoon, while a
cold front at the surface trails from a surface low over the Great
Lakes southwestward to East Texas. A moist airmass remains in place
to the east of this front, and a fair amount of instability has
developed along it with afternoon heating. RAP analysis currently
indicates around 2000 to 2500 J/kg of MLCAPE in the far northwest of
our CWA. A line of showers and thunderstorms will advance with the
front through the evening hours, with POPs declining overnight.
Though not a particularly strong cold front, temperatures should be a
few degrees cooler and dew points should be a few degrees lower
tomorrow for locations north of the Interstate 20 corridor. Locations
to the south of Interstate 20 will generally stay on the warmer and
humid side similar to recent days./NF/
LONG TERM...Tuesday through Saturday...A mid to upper level ridge of
high pressure is expected to build back over the southeastern CONUS
by early next week and last though most of the week. The ArkLaMiss
should remain generally on the humid southern edge of this ridge with
forecast PWAT values around 2 inches continuing across the region.
Have kept temperatures a few degrees above normal and POPs favoring
the southern and western portions of the area through the extended
periods given the expected pattern. Models indicate that another northern
CONUS trough/closed low will be moving across the country near the
end of next week, which should allow for another decent shot at more
widespread precipitation across the region./NF/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 72 88 70 91 / 30 37 7 22
Meridian 72 91 70 92 / 30 40 13 25
Vicksburg 72 89 67 92 / 30 24 4 19
Hattiesburg 73 91 72 91 / 30 56 16 37
Natchez 71 87 70 89 / 30 43 12 29
Greenville 68 86 63 90 / 25 10 2 11
Greenwood 69 87 65 91 / 27 10 2 11
&&
.JAN Watches/Warnings/Advisories...
MS...None.
LA...None.
AR...None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
729 PM EDT SAT SEP 10 2016
.SHORT TERM...(This evening through Sunday)
Issued at 406 PM EDT SAT SEP 10 2016
12Z raobs/latest wv imagery and RAP analysis shows fairly strong
shrtwv lifting e through the Upper Great Lakes. Combination of deep
layer q-vector convergence ahead of this shortwave and NNW flow off
Lake Superior bringing h85 temps of 6-7C across the lake sustaining
sct to numerous showers/lake enhanced showers over the ern two
thirds of Upper Mi this afternoon. Suspect this showers will persist
into the early evening hours before best dynamics exit e with
departing shortwave.
Tonight and Sunday...The strong NNW winds gusting to 30-35 mph over
mainly the Ern cwa wl diminish later this evng as the sfc low exits
ne into Quebec and sfc hi pres builds toward the area under quickly
rising h5 hgts ahead of an approaching shortwave ridge. The incoming
airmass, with h85 temps down to 5C, wl probably be sufficiently cool
to maintain some lake clouds over the Keweenaw and the E into this
evening, but fcst soundings suggest the near sfc lyr wl be too dry
for any pcpn. Influx of cooler air wl drop min temps into the 40s
away fm moderation off Lk Sup. Min temps near 40F possible over the
western interior.
Sfc ridging and anticyclonic sw flow ahead of an incoming cold front
will result in a pleasant Sunday under mostly sunny skies. Expect
highs in the lower to mid 70s across much of the forecast area.
.LONG TERM...(Sunday night through Saturday)
Issued at 357 PM EDT SAT SEP 10 2016
Sunday night through Monday: A surface ridge and drier air will be
in place with anticyclonic flow across the Upper Great Lakes Sunday
night. This will keep mostly clear skies in place across the U.P.
with fairly light westerly winds. Aloft, nearly zonal flow will be
in place through this time period. Monday, the high center will
slide to the east, allowing warmer and more moist southerly flow to
push back into the Upper Great Lakes region. This will happen at the
same time that low pressure slides from central Canada eastward to
near James Bay. A cold front will extend southwest from the low into
the Arrowhead of MN by Monday afternoon. The main impacts from this
in the U.P., for Monday afternoon, will be increasing cloud cover
over the west with a few showers.
Monday night through Tuesday night: The aforementioned low pressure
center will slide from near James Bay Monday evening to northeast
Quebec Tuesday night. As this happens, the cold front will slide
southeastward into the western U.P. Monday evening, the eastern U.P.
by Tuesday morning and into the lower Great Lakes by Tuesday
evening. Along and ahead of the cold front rain showers are expected
to develop and slide across the area Monday night into Tuesday.
There could be some isolated thunderstorms Monday night as the front
slides through, but instability does not look overly impressive at
this point. As the cold front sags southeast of the U.P. Tuesday
night, high pressure and drier air will begin to filter into the
U.P. allowing for decreasing clouds and an end to the precipitation.
The clearing skies, calm winds and PWATs dropping to around 50
percent of normal overnight will make ideal conditions for maximum
radiational cooling. This should allow temperatures to fall into the
30s over the inland west portions of the U.P. The eastern U.P. will
be on the eastern fringes of the ridge so winds may be strong enough
and moisture will be high enough to keep that area a bit warmer.
Patchy frost may be possible over the inland west, late Tuesday
night. There is a possibility that some lake effect cloud
cover/light rain showers may linger a little longer into the
evening, which may keep temperatures from getting as low as some of
the coldest guidance. Either way, it still looks like its going to
be a chilly night.
Wednesday through Thursday: High pressure will be in place through
this time period keeping dry air in place along with fairly light
winds. Wednesday night will be another cool night, with the coolest
readings expected across the eastern U.P., closer to the high
pressure center. Thursday through Friday will see continued Fall-
like weather with a gradual warming trend as winds turn southerly on
the western side of the surface high pressure ridge.
Rest of the extended: Models are trending toward increased moisture
flowing into the area with increased cloud cover. A low pressure
system and associated cold front are expected to approach or slide
through the area Friday into Saturday; however, significant timing
and intensity differences are noted in the model comparisons. With
that in mind will stick with a consensus of the models at this point.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 727 PM EDT SAT SEP 10 2016
VFR conditions will prevail over the three TAF sites through the
forecast as high pressure builds into the region. Winds remain at or
below 10 knots through the forecast, with winds backing from NW to
SW overnight and Sunday.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 406 PM EDT SAT SEP 10 2016
As a low pres moves ne of Lake Superior this evening, expect NNW
winds on its backside to persist to 30 kts over much of the E half
of the lake. There could still be some gale force gusts over the
eastern portion of the lake into the evening before the low pres
moves farther away and an approaching hi pres ridge cause the winds
to diminish tonight into Sun. As the hi pres shifts to the E and a
tighter pres gradient develops again on Sun night into Mon ahead of
an approaching cold front, expect SSW winds to increase up to 30
kts. Winds will shift back to the NNE Mon night into Tue following
the cold frontal passage, but these winds are not expected to be
higher than 20 kts. Winds will diminish and back to the W as
trailing hi pres moves thru the Western Lakes on Wed.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Beach Hazards Statement until 10 PM EDT this evening for MIZ005-
006.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...KEC
AVIATION...RJT
MARINE...Voss
Area Forecast Discussion
National Weather Service Morristown TN
819 PM EDT SAT SEP 10 2016
.DISCUSSION...
Convection associated with frontal boundary over Middle Tennessee
this evening continues to move East as forecast. Scattered showers
and thunderstorms have developed out ahead of the main line over
portions of the Plateau in the last two hours. This is in fairly
good agreement with latest HRRR run which indicates this activity
and that with the main line of showers and thunderstorms should
weaken in the next few hours due to loss of daytime heating and
upper level support which is lifting out to the NE of our area.
Have updated early overnight POPs for current precipitation trend
and brought temperatures in line with current observations.
Otherwise forecast is on track.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 69 86 65 89 / 30 0 10 10
Knoxville McGhee Tyson Airport, TN 69 84 62 87 / 30 0 10 10
Oak Ridge, TN 67 85 61 87 / 40 0 10 10
Tri Cities Airport, TN 65 82 58 85 / 40 10 10 10
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&
$$
Area Forecast Discussion
National Weather Service Mount Holly NJ
921 PM EDT SAT SEP 10 2016
.SYNOPSIS...
A cold front will cross the Appalachians this evening and move
eastward through the mid- Atlantic region late tonight into Sunday
morning. High pressure build in behind the front Sunday afternoon
through early next week. The next cold front is forecast to
approach from the northwest Wednesday morning and move through the
region Wednesday afternoon or evening hours. High pressure returns
to the area late in the week before retreating off the coast by
next weekend.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Precip has ended acrs the area, though there are a few showers to
the w. Expect most, if not all locations to be dry through later
tonight when precip chcs increase again with the fropa. Best pops
are n and w and much less as you go s and e. Earlier guid was
completely dry over most of the area, but latest HRRR shows at
least some pops over central and srn areas.
Therefore, have made some additional adjustments to pops. Hot
and humid conditions will continue for this one last night before
a cold front brings a more seasonable air mass for Sunday. This
cold front will cross the region from west to east well after
midnight and it will be preceded by showers and sct thunderstorms.
Severe weather is not expected, but downpours and gusty winds
possible. Overnight lows will only drop into the 70s across the
area.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
The cold front will move offshore Sunday morning and drier and
somewhat cooler air will move across the area. Except for a few
scattered showers S/E during the morning, the day will be dry. High
temperatures will be about 10 degrees cooler than Saturday, with
highs in the low/mid 80s. It will feel much more comfortable
however with the dew points lowing through the 50s during the day.
Winds will become W or NW during the morning and gust up to 20 mph
through the afternoon.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Surface high pressure will build in from the Ohio Valley Sunday
evening. The center of the surface high and /H8 ridge is then
forecast to positioned over the mid-Atlantic region early next week.
The resultant pattern will yield sunny skies and a return to much
more seasonable temperatures for the middle of September for Sunday
night-Monday night.
The high will slowly lose its hold on our area during midweek as the
center of the high starts to progress offshore and a cold front
approaches from the northwest. A return flow around the high will
become established along the eastern seaboard, resulting in a
warming trend Tuesday into Wednesday. Temperatures on Wednesday will
be highly dependent on the timing of the cold front. If the is
slower to arrive from the west and the area is still situated in the
heart of the pre-frontal warm sector during the afternoon, there
looks to be a narrow opportunity to reach 90 degrees, especially in
the warmer cities along the I-95 corridor. Highs on Wednesday with
the latest forecast package were about 2-4F higher than previous
versions. Models continue to show limited forcing with the front and
modest instability ahead of it while the deeper lift associated with
an upper shortwave trough passes to our north. Accordingly, PoPs
were kept low (near 30 percent north of I-78 and 20 percent farther
south) with the fropa Wednesday afternoon and evening.
Behind the cold front, a broad area of high pressure over the Great
Lakes builds into the area Thursday and Friday. Expect sunny skies
and much cooler temperatures. With highs only in the 70s and low in
the 50s to perhaps 40s in the sheltered valleys of northeastern
PA/northwestern NJ/the NJ Pine Barrens, it will start to feel more
like early fall.
The center of the high starts to move offshore as we head into next
weekend. A warming trend is likely with return flow developing over
the region. Highs in the 80s are forecast for Saturday but it will
still remain dry.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Mostly good flying weather is expected into the early overnight
period. There could be a few pop-up showers or perhaps a
thunderstorm across the northern and western areas.
Tonight a cold front will approach from the west. More
clouds and better chc for showers/tstms will develop from NW to SE
across the area. We have tried to time the best chc for precip
with temps groups in the tafs. Lower conditions are possible in
tstms, but overall confid in a tstm occurring at a taf site is
low. Winds will shift to wrly behind the front around daybreak
Sunday.
Sunday will feature improving conditions from W to E as the front
and its associated showers move offshore. VFR conditions will
return to the area by mid-morning. Winds will turn NWrly at 10
to 15 knots with gusts up to 20-25 knots.
OUTLOOK...
Sunday night through Thursday...Mainly VFR. Low confidence in
showers and storms with a cold fropa Wednesday afternoon and evening.
&&
.MARINE...
We will continue with the SCA flag as it was earlier set
up. Winds still haven`t reached SCA conditions yet, but soon will
with the increasing winds ahead of the approaching cold front. Sct
tstms will occur this evening and overnight with locally higher
winds and seas. SCA winds will continue Sunday with cooler and drier
air arriving on a decent W/NW fetch. Winds and seas should decrease
through the afternoon. Fair weather expected Sunday after some
lingering showers during the morning.
OUTLOOK...
Sunday night...N-NEly winds will increase from N to S as high
pressure builds into the area. Forecast wind speeds look to be 15-20
kt when this pressure surge occurs. The overwhelming majority of
model forecast soundings show sub-25 kt in the boundary layer, it
does not appear to be favorable for widespread 25 kt gusts to mix
down. Held off on issuing a 3rd period SCA for now w/o much support
from the guidance.
Monday through Wednesday...No marine headlines are anticipated.
Wednesday night and Thursday...NW winds behind a cold front is
forecast to strengthen and become Nly. SCA conditions are possible
late Wednesday night into Thursday morning.
RIP CURRENTS...
The probable risk for the development of dangerous rip currents
on Sunday into early next week is low.
&&
.CLIMATE...
Today is the last day of the late season heatwave. Below list the
number of consecutive 90-degree days that have occurred with this
current heat wave count (includes today, Saturday):
ILG- 6 days
PHL/ABE/RDG- 4 days
GED/TTN- 3 days
Through 4 PM today, the high temperature so far today at ABE was
95F, which is only 1 degree shy of the daily record high
temperature of 96F set back in 1983. The rest of the climate sites
should fall comfortably short of their respective daily record
high temperatures.
So far Philadelphia International Airport has recorded 44
90-degree days this calendar year, which is sixth most on record.
Several other years that had more days 90-degrees days include
2010 with 55 days, 1991 with 53 days, 1995 and 1988 with 49 days,
and 2002 with 46 days.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 1 PM EDT Sunday for ANZ450>453.
Small Craft Advisory until 10 AM EDT Sunday for ANZ454-455.
&&
$$
Synopsis...Klein
Near Term...Nierenberg/O`Hara
Short Term...O`Hara
Long Term...Klein
Aviation...Klein/Nierenberg/O`Hara
Marine...Klein/O`Hara
Climate...
Area Forecast Discussion
National Weather Service Phoenix AZ
850 PM MST SAT SEP 10 2016
.SYNOPSIS...
Low pressure off the California coast is expected to pull monsoon
moisture back northward into central and eastern AZ through Monday.
This will allow the development of isolated- scattered showers and
thunderstorms across south-central AZ each day. A turn to more
westerly flow aloft will then push much drier air back into the
desert southwest from Tuesday onward into the end of next week, with
dry conditions and mostly clear skies returning back to the region.
&&
.DISCUSSION...
Weak upper low was situated off the southern California coast this
evening, giving a southwest flow aloft into far southeast California
and much of western/central Arizona. The deep south-southwest flow
aloft was easily seen in the evening raob data, and this flow was
keeping drier air in place over much of the lower deserts, mainly
areas to the west of Phoenix. PWAT at Phoenix this evening was
moderate at 1.05 inches and there was virtually no MLCAPE present in
the sounding. Due to rather dry and stable conditions today there
were no storms present over the lower deserts, and just isolated
weak to moderate storms developed from the central Mogollon Rim
southeastward into the eastern mountains. A few storms persisted
across southern Gila County during the afternoon and early evening
hours, with the strongest storms near Roosevelt. The storms prompted
the issuance of a few Significant Weather Advisories but no
warnings. Shortly after sunset, the storms dissipated and skies over
south central Arizona were mostly clear at 830 pm. For the rest of
tonight expect no more than a 10 percent chance of a shower or storm
across southern Gila county with clear or mostly clear skies
elsewhere. Current forecasts look to be in good shape and no updates
are needed.
.PREVIOUS DISCUSSION...
Latest satellite imagery shows CU developing along the Mogollon Rim
and the higher terrain of southeastern AZ. Meanwhile, water vapor
imagery shows drier air being transported north and eastward across
southeastern CA ahead of a closed low off the southern CA coast.
Cooler temperatures aloft associated with the low extend eastward
into northern AZ. Further west, surface dewpoints have dropped into
the upper 30s across the southwest deserts while temperatures are
approaching 110 degrees in the Imperial Valley.
Latest CAMs including the HRRR depict isolated convection across the
higher terrain of southern Gila County late this afternoon. However,
CAPE is generally lacking while CIN is predominant, associated with
the relatively dry boundary layer. PoPs for this afternoon and
evening remain near 10-15 percent across these areas.
Conditions will become more favorable for shower and thunderstorm
activity Sunday and Monday, particularly across eastern Arizona as
the aforementioned closed low opens up and migrates east through the
Mojave Desert. Latest operational and ensemble guidance (including
the SREF and GEFS) shows an increase in uncertainty with regard to
the magnitude of the overall moisture, however model consensus
indicates that scattered thunderstorms will develop across eastern
Pinal and southern Maricopa County Sunday afternoon. Deep-layer
shear also increases, suggesting some modest organization to the
cells.
Setup will be similar for Monday with scattered strong storms
again mostly likely across southeastern Arizona, extending back
through Pinal and southern Gila counties. Sharper theta-E gradient
and forcing for ascent ahead of the approaching trough also suggests
an earlier onset to the convection.
&&
.PREVIOUS DISCUSSION...
Tuesday through Friday...
A drying trend is expected during this period as another, stronger
upper low that will be dropping southward over northern CA helps to
kick out the afomentioned upper low/trof to our east, and turn the
flow aloft more westerly over the region. This should end the threat
for convective activity over the region as much drier air is pulled
in from the west, with PWATs falling aob 0.50 inch by Thursday.
High temperatures are expected to hold at near, or slightly below
normal levels through this period, with highs near or slightly below
100 across the lower deserts. Lows will likely end up below normal,
as the very dry airmass allows for very efficient radiational cooling
each night, with lows in the 60s possible at many of the normally
cooler locations.
.AVIATION...
South-Central Arizona Including KPHX, KIWA, and KSDL:
Storms that formed earlier over the higher terrain east of Phoenix
have dissipated; gusty outflow winds moving into the greater Phoenix
area do no appear likely and as such TAFs will reflect a more normal
and diurnal tendency with light east winds developing after
midnight. Isolated thunderstorms may develop again over the
mountains of central and eastern Arizona tomorrow afternoon but
chances for outflows moving into the deserts are low and no mentions
of thunder or gusty winds will be made in the upcoming 06z TAF
package.
Southeast California/Southwest Arizona including KIPL and KBLH:
Generally clear skies expected next 24 hours. Winds to be on the
light side, favoring the west at KIPL into the morning hours
tomorrow and favoring the south to southwest next 24 hours at KBLH.
No aviation concerns at the TAF sites for at least the next 24 hours.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Tuesday through Saturday...
A return of Monsoon moisture across Arizona will continue through
the early week period, allowing for scattered thunderstorm
development over the mountains with slight chances for storms to last
or develop over the lower AZ desert elevations. Expansion of moisture
across the area will be held mostly east of the Colorado River Valley
across AZ as dry air off the Pacific is brought into southeast CA.
Minimum humidities will range from driest in the western district
10-15 percent improving towards the east with 20-35 percent into the
Gila County mountains. Overnight recoveries will range from good to
excellent. A turn to more westerly flow during the Tuesday- Friday
period will begin to push the moisture/storms back to the east into
extreme eastern AZ/NM. Minimum humidities will drop to the 10 to 15
percent range from by Friday, with good to excellent overnight
recoveries. Outside of any thunderstorms, winds will remain mainly on
the light side with some afternoon gustiness up to 15 to 20 mph area-
wide on Monday and Tuesday with the strongest gusts along and west of
the Colorado River.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters activation is not expected this weekend.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
Visit us on Facebook...Twitter...and at weather.gov/phoenix
DISCUSSION...CB
PREVIOUS DISCUSSION...Hirsch/Percha
AVIATION...CB
FIRE WEATHER...Waters
Area Forecast Discussion
National Weather Service Shreveport LA
828 PM CDT SAT SEP 10 2016
.UPDATE...
The cold front and associated isolated to scattered showers and
thunderstorms were pushing southeast towards central and north
central Louisiana tonight, though a few showers managed to
backbuild across portions of north Louisiana. Have therefore
updated pops /and sky/ to reflect latest radar trends, and
increased pops a bit where coverage is best across central and
north central Louisiana. Furthermore, this cold front has ushered
in a cooler and drier airmass, and the current forecast did not
quite reflect this trend. Thus, have updated the dewpoint and
minimum temperature for tonight.
Once the precipitation shifts southeast of the region, may see the
development of a stratus deck and/or fog overnight.
&&
.PREV DISCUSSION... /issued 645 PM CDT SAT SEP 10 2016/
AVIATION...
Bkn line of convection has developed, moving out of keld, kshv,
and klfk, and movg into kmlu attm. Further north and west, skies
becmg vfr skc across ktxk, ktyr, and kggg terminals. Vfr skc
except for possibly mostly scattered decks, expected areawide by
11/06z, and to continue thru 12/00z fcst cycle. North winds 10 to
15 kts possible for brief period following fropa, becmg lgt and
then increasing to ne 5 to 10 kts durg the day Sunday. With much
cooler dewpoints falling into the 50s, no fog expected./VII/.
PREV DISCUSSION... /issued 405 PM CDT SAT SEP 10 2016/
DISCUSSION...
Sct convection is just now beginning to fire over Union County AR
SW into portions of extreme NW LA and adjacent E TX...along the
weak cold front and line of agitated cu over these areas. The air
mass ahead of the front has become moderately unstable...indicative
of MLCapes of 2000-2500 j/kg. The latest run of the HRRR continues
to suggest this convection continuing to expand through early
evening across the warm sector as the front slowly slips SE into
Ncntrl LA/lower Toledo Bend Country...before diminishing with the
loss of heating/instability. Have raised pops to low chance this
evening for the aforementioned areas...reducing pops to slight
chance after 06Z for the Srn/Ern zones as the front sags S. The
short term progs are now depicting even cooler temps than earlier
runs tonight through Sunday night...with temps falling into the
upper 50s late over McCurtain County OK and adjacent sections of
Wrn AR. Can/t argue with this given that current dewpoints have
fallen off into the upper 40s to near 50 across Ern OK...with the
clearing line just NW of these areas attm. The progs are also
suggesting the front pushing farther S than earlier
indicated...into Srn LA to the SE TX coast Sunday...although the
drier air will lag the front a ways to the N over Cntrl LA/lower
Toledo Bend Country. In addition...upper ridging will begin to
build E across the Srn Plains Sunday before expanding across the
Ark-La-Tex Sunday night and Monday. Thus...any isolated convection
Sunday should be concentrated farther S mainly across the Srn
counties and parishes...and have trimmed pops down to slight
chance for these areas...with any isolated convection diminishing
by sunset.
Sfc ridging will persist over the region Sunday night resulting
in cooler temps filtering over more of the region. This will be
short-lived though as the air mass will begin to gradually modify
Monday as the sfc bndry to our S will begin to wash out...and
bndry lyr moisture begins to return NNW. Upper ridging will
persist over the region Tuesday and Wednesday...with any isolated
convection confined mainly across the Srn zones where the ridge
will be weakest. The ridge should begin to drift E of the MS
Valley by Thursday...with shortwave troughing developing across
the Srn Plains ahead of the next Cntrl Plains trough/attendant SW
flow developing. Thus...convection should become more sct over E
TX/SE OK Thursday before expanding areawide by week/s end. Have
adjusted pops to mid-chance to match for now...with needed rain
and slightly cooler temps possible as much of the region is going
on in excess of 2 weeks with little to no rain and abnormally warm
temps.
Prelims to follow below...
15
PREV DISCUSSION... /issued 123 PM CDT SAT SEP 10 2016/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 66 88 66 92 / 20 0 0 0
MLU 67 86 65 91 / 30 10 0 10
DEQ 55 85 57 88 / 0 0 0 0
TXK 61 86 60 89 / 10 0 0 0
ELD 62 84 59 89 / 20 0 0 0
TYR 64 88 66 91 / 10 0 0 0
GGG 64 88 66 91 / 10 0 0 0
LFK 69 90 70 92 / 30 10 10 10
&&
.SHV Watches/Warnings/Advisories...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
29/07/15
Area Forecast Discussion
National Weather Service Columbia SC
336 AM EDT SUN SEP 11 2016
.SYNOPSIS...
A weak cold front will move into the forecast area today and
stall. The diffuse front will remain in the area through Tuesday.
Moisture will be directed into the forecast area in the easterly
flow between high pressure over and off the Mid-Atlantic coast
and low pressure in the Florida area early this week. Another
cold front will push into the region Thursday.
&&
.NEAR TERM /THROUGH TONIGHT/...
Convergence associated with the cold front moving into the area
supports showers and thunderstorms today and tonight but expect
limited coverage because of shallow moisture and little upper
support. The HRRR and ARW indicate just scattered coverage. Strong
heating ahead of the front may lead to moderate instability. The
NAM has surface-based LI values near -7. The GFS indicated less
instability and a diminished chance of severe thunderstorms. The
weaker instability may be correct because of little upper lift.
The temperature guidance was consistent.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY/...
The models indicate a diffuse front lingering in the area but
moisture a bit deeper because of the low-level easterly flow
between high pressure to the north and low pressure in the Florida
area. Followed the guidance consensus for the pop forecast. The
guidance was consistest with high temperatures lower than what we
have experienced lately and this appeared reasonable because of
increased cloudiness.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
The GFS and ECMWF show considerable moisture lingering in the
forecast area into Wednesday with an onshore flow between surface
high pressure moving off the Mid-Atlantic coast and low pressure
in the Florida area. The models display a weak backdoor cold front
moving into the area Thursday. This front may also stall in the
region. The models show general upper ridging continuing through
the medium-range period which should limit shower coverage. The
GFS, ECMWF, and EKD MOS have pops 20 to 30 percent during the
period.
&&
.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
The upper level ridge will continue to weaken early this morning as
an upper trough and associated cold front approach the area. Mid-
Level moisture advection and a few shortwaves moving over the
weakened ridge should promote cloud development. VFR CIGS are
expected but could approach MVFR during the early morning hours.
Model guidance continues to indicate VFR CIGS through early this
morning. With a 25 to 30 kt LLJ and increasing cloud cover fog is
not expected.
The upper trough lifts northward today, stalling the front across
the forecast area. Generally expect S/SW winds but could become
variable at times with the front over the area. Chance of showers
and thunderstorms in the afternoon may bring restrictions to TAF
sites.
EXTENDED AVIATION OUTLOOK...An unstable air mass could produce
convection related restrictions through Thursday as a frontal
boundary remains in the area.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
352 AM EDT SUN SEP 11 2016
.SHORT TERM...(Today and tonight)
Issued at 351 AM EDT SUN SEP 11 2016
00Z raobs/latest wv imagery and RAP analysis show a shrtwv rdg bldg
toward the Upr Great Lks in the wake of the departing shrtwv
responsible for ydays rain that is now moving into Quebec.
Combination of large scale subsidence/incoming dry airmass with 00Z
pwat only a bit above 0.50 inch at INL ahead of the shrtwv rdg and
acyc llvl flow associated with sfc hi pres over the western Great
Lakes are bringing quiet wx to the cwa early this mrng. There is a
zonal flow behind the shrtwv rdg near the Cndn border, and extensive
hi/some mid clds associated with waa on the wrn flank of the hi pres
rdg are spreading ewd into NW Ontario/MN within this strong w flow.
But the llvls are too dry per the 00Z Bismarck raob, so there is no
pcpn.
Main fcst concerns in the short term wl be on temps. Although some
of the upstream hier clds wl spill into the area today, a dry llvl
sw flow wl keep the area pcpn free.
Tday...As the aprchg shrtwv rdg axis spreads over the Upr Lks, the
sfc hi pres rdg axis is fcst to shift to the e as well, shifting
llvl winds to the sw. Although the hi clds to the w wl move into the
Upr Lks, rising hgts may tend to suppress the coverage with time,
especially over the scentral. The incrsg sw wind under tightening
pres gradient behind the departing sfc hi is fcst to lift h85 temps
to btwn about 10C over the e and 13C over the w, which wl support
max temps up to about 75 in the downslope wrmg sites over the nw cwa.
Tngt...Combination of some hi clds/steady sw winds wl limit the
diurnal temp drop despite lingering llvl dry air. Min temps in the
downslope areas near Lk Sup wl remain aoa 60. Even at the interior
cool spots, temps wl have a hard time falling blo 50-55.
.LONG TERM...(Monday through Saturday)
Issued at 335 AM EDT SUN SEP 11 2016
A SFC trough/cold front will move into the area from the NW Mon
afternoon, slowing some over the south-central to eastern CWA as a
shortwave rides up the front Late Mon night into Tue Morning. This
will produce showers and thunderstorms along the front from Late Mon
through Tue, with areas NW Upper MI not expected to see synoptic
rain on Tue as the front will be over the SE.
A strong shortwave will then drop through the area Tue evening into
early Tue night, but will be in a moisture fight with a large SFC
high moving in from the W, so widespread precip is not expected.
However, 850mb temps will drop to AOB 2C Tue night, so the N winds
between the intruding SFC high and lower lakes troughing will lead
to lake effect/upslope showers/drizzle and clouds. Think the cloud
cover from the shortwave and lake effect/upslope will keep Tue night
warmer, so brought the temps up and took frost out of the forecast.
May see precip continue into Wed morning near Lake Superior, but the
high moves in and airmass temps increase quickly so think any precip
will be done by late morning or afternoon.
After seeing highs in the 60s Tue and Wed, the airmass looks to be
warmer through the rest of the long term. Unfortunately, not a lot
of confidence past Thu, especially with precip chances. Certainly
seeing precip potential Fri into Sun, but just ran with a broad
model blend for that time period given the uncertainty.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 123 AM EDT SUN SEP 11 2016
VFR conditions will prevail over the region as a high pressure ridge
moves through the Upper Great Lakes. Winds will remain at or below
10 knots through much of the day Sunday but will pick up a bit
Sunday evening with the approach of a low pressure trough Sunday
night.
&&
.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 351 AM EDT SUN SEP 11 2016
A passing hi pres ridge will bring light winds under 20 kts today.
But as this ridge shifts to the e and a tighter pres gradient
develops tonight into Mon ahead of an approaching cold front, expect
SSW winds to increase up to 30 kts. Not out of the question there
could be some gale force gusts to 35 kts tonight over the ncentral
portion of the lake, especially between Isle Royale and the Keweenaw
Peninsula. Winds will shift back to the nne Mon night into Tue
following the cold frontal passage, but these winds are not expected
to be higher than 20-25 kts. Winds will diminish and back to the w
and then the ssw as trailing hi pres moves thru the Western Lakes on
Wed and toward New England on Thu.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...KC
LONG TERM...Titus
AVIATION...RJT
MARINE...KC
Area Forecast Discussion
National Weather Service Omaha/Valley NE
320 AM CDT SUN SEP 11 2016
.SHORT TERM...(Today through Tuesday)
Issued at 320 AM CDT SUN SEP 11 2016
The main forecast concerns are still in regards to the chance for
showers and thunderstorms from Monday through Tuesday.
Primary features noted in the upper air charts from last evening
included the following. At 850 mb...moisture was displaced well to
the south...with a ridge from TX into MN. Warmer air was already
moving in from the west. At 500 mb...12 hour height falls of up to
80 meters were noted in southwest BC. That was somewhat supported
by a 120 knot jetstreak over southern BC...just a little north of
the strongest height falls.
Water vapor satellite imagery and recent RAP model initializations
showed a trough (associated with previously mentioned height falls)
starting to dig into southwest Canada and the Pacific Northwest.
Zonal flow at 500 mb will continue to turn to the southwest through
tonight.
As pressures fall over the high plains today...pressure gradient
in our area with strengthen...allowing breezy/windy conditions to
develop. Rain chances today and tonight look low...since it will
take a while for lower and mid level moisture to return. Highs
today should reach the upper 70s and lower 80s...with lows tonight
in the mid 50s to around 60.
On Monday...a cold front will be moving into the area from the
northwest. Deeper moisture will start to return...especially in
the afternoon...but overall the trend has slowed. The best chance
for showers and thunderstorms Monday will be behind the front. The
previously mentioned cold front should drift slowly southeast
Monday night into Tuesday as high pressure builds into the
Dakotas. The highest rain chances will shift more into southeast
NE and southwest IA Tuesday.
.LONG TERM...(Tuesday night through Saturday)
Issued at 320 AM CDT SUN SEP 11 2016
Rain chances for the daytime Wednesday look relatively low...but
will be increasing Wednesday night as high pressure at the surface
moves off to the east and southerly flow strengthens. A closed low
at 500 mb...over northern NV at 12Z Wednesday...should track
northeast into the Dakotas on Friday.
Kept a mention of showers and thunderstorms for much of the area
for the period from Wednesday night through Saturday...with the
highest chances Thursday night. High temperatures should be mostly
in the 70s...with lows in the 50s to lower 60s.
&&
.AVIATION...(06Z TAFS for KOFK...KLNK and KOMA.)
Issued at 1144 PM CDT SAT SEP 10 2016
VFR conditions through the period. Light southerly winds less than
6 knots initially, increasing to 14 to 26 knots by 14-17z. KOFK
will also experience non convective LLWS from 09-14z with winds
around 2000 feet 35-45 knots. Wind gusts diminish at TAF sites by
12/00-01z. LLWS should also redevelop by 12/04-06z toward the end
of the TAF period, but too far out to include at this time.
&&
.OAX Watches/Warnings/Advisories...
NE...None.
IA...None.
&&
$$
SHORT TERM...Miller
LONG TERM...Miller
AVIATION...DeWald
Area Forecast Discussion
National Weather Service Blacksburg VA
305 AM EDT Sun Sep 11 2016
.SYNOPSIS...
A cold front will pass east across the region this morning before
stalling over the Carolinas Monday into Tuesday. High pressure
behind the front will build north of the area later Sunday into
Sunday night, reaching the mid-Atlantic coast Monday. Another weak
cold front passes through the region by Wednesday with reinforcing
high pressure building to the north of the area through late in
the week.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 230 AM EDT Sunday...
Passing upper trough well to the north will finally swing its associated
cold front through the region this morning. Much drier air aloft to
the west per water vapor loop should quickly advect in through the
afternoon. In addition low level northwest flow in advance of high
pressure across the Tennessee valley should help lower dewpoints
over the mountains by midday, and out east later on. Although the
actual 850 mb boundary may get stuck crossing the Blue Ridge,
models suggest even enough drying across the Piedmont to preclude
much convective potential as forecast PWATS and instability get
shunted to the south/east. This drier scenario also supported by
most solutions with downsloping also helping to limit added convection
in the east. Thus have trimmed back pops to isolated coverage
mainly southeast of a South Boston to Mount Airy to Wilkesboro
line, and kept elsewhere dry this afternoon under increasing
sunshine. Still cant rule out some added showers south/west along
the front before sunrise per latest HRRR so left in some early
mention before dry advection increases.
Should finally be a bit closer to normal on highs west this afternoon
with most in the 70s under decent cooling aloft which will be offset
by heating of dry air. Cooler air will be slower to reach the east
as suggested by 850 mb progs showing advection weakening during
max heating. This while downsloping likely boosts spots into the
mid/upper 80s from Roanoke east although less humid under lowering
dewpoints.
Surface high builds to the north overnight and wedges in along the
eastern slopes of the mountains late. This should allow for a better
surge of cooler/drier air to finally swing into areas east of the Blue
Ridge overnight. Also appears enough low level dry air to keep things
mainly clear elsewhere although may see low clouds redevelop toward the
southern Blue Ridge late as the low level trajectory turns more
southeast. However latest Nam not too aggressive in returning low level
moisture north until around daybreak so opted to leave out until late
for southern sections but something to watch. Otherwise mostly clear
and quite comfortable with lows low/mid 50s north and west, with
lingering low/mid 60s southeast.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 230 AM EDT Sunday...
Surface high pressure will move off the Mid Atlantic coast on Monday
and remain there through Tuesday night. The wedge boundary along and
east of the Blue Ridge will continue to sit across the Carolinas
through the period, but will erode some across the mountains each
day. While this wedge is in place, low level flow will become
southeasterly. This marine influenced southeasterly flow will
gradually increase moisture into the region. Cloud cover will
increase each day with a chance for afternoon showers along the
North Carolina Blue Ridge.
The wedge and southeasterly flow will keep temperatures uniform each
day. Monday`s afternoon temperatures will range from the upper 70s
to lower 80s, mountain ridges in the lower 70s. Temperatures will
moderate some Tuesday ranging in the low to mid 80s.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 355 PM EDT Saturday...
By Wednesday, a new cold front arrives from the north as a short
wave tracks along the Canadian border. This will finally give the
early week cold front just to our south a shove to move further
south into the southeast states. By contrast, this will leave only
limited moisture with which the second/new front has to work as
it arrives in the area Wed afternoon/evening. With the better
dynamics also far removed to the north, again only look for
scattered showers and thunderstorms with the front. Instability
should be sufficient given time of arrival during peak heating for
a few thunderstorms.
High pressure will once again slide across the OH valley toward
the northern Mid-Atlantic Thursday into Friday as the second front
drifts into NC/SC and also stalls and or weakens. Once again it
will not track too far south before encountering broad upper scale
ridging. Thursday should be dry, but return moisture by Friday
could support isolated showers across far southwest VA or
northwest NC. In addition, there is some potential for a tropical
wave to develop/move into south GA or along the SC coast. Any
effects of that system will be beyond this forecast package.
Cooling will again be modest at best with 850mb temps even behind
the second front still lingering in the +15C or better range. This
will still leave surface temperatures 5-7 degrees above normal
with lows in the 50s mountains and 60s elsewhere, with highs in
the 70s west to lower and even mid 80s east.
&&
.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
As of 1250 AM EDT Sunday...
Cold front currently passing through the western mountains should
slide east across the Blue Ridge late tonight and to the east of
the region Sunday morning. Broken band of showers along the front
continue to fade and expect only widely scattered coverage at best
as the front moves across the remainder of the night. Thus may
include a VCSH mention at KBLF/KLWB, otherwise leaving out
mention with VFR conditions to start.
Once the front passes the west, an IFR/MVFR cigs are expected to
develop as the low level flow turns to a more northwest upslope
trajectory. Residual low level moisture will help produce lower
cigs across southeast West Virginia and possibly at least one tier
of neighboring southwest Virginia counties.
Drier air will push in behind the front Sunday afternoon with any
lingering sub-VFR cigs likely fading by midday over the west with
heating. This should also help scour any residual cloudiness out
farther east before heating redevelops a cumulus field east of the
mountains Sunday afternoon. This could also allow isolated
convection to develop over the far southern/eastern sections if
the front slows more. However for now appears most shra/tsra will
be mainly southeast of the taf sites so leaving out mention.
Otherwise looking at mainly VFR Sunday afternoon with this trend
continuing for most of Sunday night as high pressure builds in
from the north.
Extended aviation discussion...
As of 145 PM EDT Saturday...
Late Sunday night into Monday, the frontal boundary to our south
stalls while high pressure works its way into the area. As low
level winds become southeast, the potential for additional
overnight sub-VFR cloud cover returns to the area, especially
across the mountains.
Tuesday into Wednesday, isolated to widely scattered showers and
storms return to the forecast as the boundary lifts back north
into the region. Anticipate pockets of sub-VFR conditions espcly
Wednesday with deeper moisture return in advance of the next cold
front.
Wednesday night into Thursday a cold front is expected to sweep
through the region. Appears the best coverage of showers and
storms will be across the western sections of the region with
possible periods of sub-VFR.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...DS/JH
NEAR TERM...JH
SHORT TERM...RCS
LONG TERM...AMS/RAB
AVIATION...DS/JH
Area Forecast Discussion
National Weather Service Shreveport LA
1143 PM CDT SAT SEP 10 2016
.AVIATION...
Frontal boundary nearly stalled out, with convection nearly
diminished along and south of boundary across area, although a few
tstsm persist over south LA as well as se AR further east along
boundary. Mostly vfr skc to prevail at ktxk, ktyr, and kggg, with
some mid lvl decks to persist further south and east tonight. Lgt
north winds overnight becmg ne 5 to 10 kts durg day Sunday, before
areawide vfr skc and lgt winds after 12/00z./VII/.
&&
.PREV DISCUSSION... /issued 828 PM CDT SAT SEP 10 2016/
UPDATE...
The cold front and associated isolated to scattered showers and
thunderstorms were pushing southeast towards central and north
central Louisiana tonight, though a few showers managed to
backbuild across portions of north Louisiana. Have therefore
updated pops /and sky/ to reflect latest radar trends, and
increased pops a bit where coverage is best across central and
north central Louisiana. Furthermore, this cold front has ushered
in a cooler and drier airmass, and the current forecast did not
quite reflect this trend. Thus, have updated the dewpoint and
minimum temperature for tonight.
Once the precipitation shifts southeast of the region, may see the
development of a stratus deck and/or fog overnight.
PREV DISCUSSION... /issued 405 PM CDT SAT SEP 10 2016/
DISCUSSION...
Sct convection is just now beginning to fire over Union County AR
SW into portions of extreme NW LA and adjacent E TX...along the
weak cold front and line of agitated cu over these areas. The air
mass ahead of the front has become moderately unstable...indicative
of MLCapes of 2000-2500 j/kg. The latest run of the HRRR continues
to suggest this convection continuing to expand through early
evening across the warm sector as the front slowly slips SE into
Ncntrl LA/lower Toledo Bend Country...before diminishing with the
loss of heating/instability. Have raised pops to low chance this
evening for the aforementioned areas...reducing pops to slight
chance after 06Z for the Srn/Ern zones as the front sags S. The
short term progs are now depicting even cooler temps than earlier
runs tonight through Sunday night...with temps falling into the
upper 50s late over McCurtain County OK and adjacent sections of
Wrn AR. Can/t argue with this given that current dewpoints have
fallen off into the upper 40s to near 50 across Ern OK...with the
clearing line just NW of these areas attm. The progs are also
suggesting the front pushing farther S than earlier
indicated...into Srn LA to the SE TX coast Sunday...although the
drier air will lag the front a ways to the N over Cntrl LA/lower
Toledo Bend Country. In addition...upper ridging will begin to
build E across the Srn Plains Sunday before expanding across the
Ark-La-Tex Sunday night and Monday. Thus...any isolated convection
Sunday should be concentrated farther S mainly across the Srn
counties and parishes...and have trimmed pops down to slight
chance for these areas...with any isolated convection diminishing
by sunset.
Sfc ridging will persist over the region Sunday night resulting
in cooler temps filtering over more of the region. This will be
short-lived though as the air mass will begin to gradually modify
Monday as the sfc bndry to our S will begin to wash out...and
bndry lyr moisture begins to return NNW. Upper ridging will
persist over the region Tuesday and Wednesday...with any isolated
convection confined mainly across the Srn zones where the ridge
will be weakest. The ridge should begin to drift E of the MS
Valley by Thursday...with shortwave troughing developing across
the Srn Plains ahead of the next Cntrl Plains trough/attendant SW
flow developing. Thus...convection should become more sct over E
TX/SE OK Thursday before expanding areawide by week/s end. Have
adjusted pops to mid-chance to match for now...with needed rain
and slightly cooler temps possible as much of the region is going
on in excess of 2 weeks with little to no rain and abnormally warm
temps.
Prelims to follow below...
15
PREV DISCUSSION... /issued 123 PM CDT SAT SEP 10 2016/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 66 88 66 92 / 20 0 0 0
MLU 67 86 65 91 / 30 10 0 10
DEQ 55 85 57 88 / 0 0 0 0
TXK 61 86 60 89 / 10 0 0 0
ELD 62 84 59 89 / 20 0 0 0
TYR 64 88 66 91 / 10 0 0 0
GGG 64 88 66 91 / 10 0 0 0
LFK 69 90 70 92 / 30 10 10 10
&&
.SHV Watches/Warnings/Advisories...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
301 AM EDT SUN SEP 11 2016
.SYNOPSIS...
07Z water vapor and H4 RAP analysis shows a sharp progressive
shortwave trough migrating through the eastern Great Lakes/Ohio
Valley toward the northeastern states. This northern stream
feature will be staying to the north of our region as the southern
extent of its influence only reaches south to AL/GA/Carolinas.
Closer to home we find the Florida peninsula in between an upper
ridge over the central/eastern Gulf and an elongated upper low off
the southeast CONUS coast. The upper ridge has taken a more
dominant influence over our heads during the past 12-24 hours...as
the 00Z KTBW RAOB shows the mid/upper level winds have backed more
to the northeast since Friday evening. With the slightly increased
deep layer subsidence aloft...the mid levels have also dried out a
bit...and this will likely result in even less coverage of
storms...and shallower depth convection for the final day of the
weekend.
At the surface...the forecast area resides between high pressure
centered to our north and northeast...and a weak trough of low
pressure over the south-central Gulf. The pressure gradient between
these two features is providing a synoptic east to southeast flow
across the FL peninsula. Early morning regional radars are
quiet...and these near zero rain chances will persist through the
morning hours. Temperatures are in the mid/upper 70s region-wide
in these pre-dawn hours...and should only fall perhaps another
couple of degrees from the current readings before sunrise.
&&
.SHORT TERM (Today through Monday)...
A familiar synoptic pattern and resulting forecast for the second
half of the weekend compared to the previous couple of days. Rain
free conditions continue through midday with a light easterly flow
and temperatures rising through the 80s. Will begin to see widely
scattered showers and isolated storms begin to develop by the mid
afternoon hours. This convection will move quickly east to west
across the peninsula within the low level flow. Rain chances and
coverage should generally range from 15-30% north of the I-4
corridor and 30-50% for the southern half of the region. Even
those locations that do see a passing shower or storm...the
movement of the storms should keep the duration of rain rather
limited. In addition...slightly more atmospheric suppression and
dry air aloft should work against storm depth and keep the
convection rather shallow. The shallow nature of the convection
should also keep the overall amount of lightning low...as charge
significant updrafts within a favorable zone for charge separation
should be few and far between. Similar to Saturday...afternoon
high temperatures look to end up a few degrees above normal.
Widespread lower 90s are forecast with warmer locations reaching
the middle 90s. While will not be explicitly forecasting any
record high temperatures...would not be surprised to see a station
or two set or tie a record. We shall see...
Lingering widely scattered evening showers should migrate offshore
and dissipate by 02-03Z...setting up a mostly dry and warm overnight
period over the landmass. A slow advection of mid-level moisture
from the south and southeast overnight may allow for a few more
nocturnal showers over the marine zones after midnight...and will
likely keep at least a slight chance PoP over the coastal waters.
Monday... The first day of the work week will see a slight increase
in the rain chances from Sunday as the upper ridge slowly breaks
down and allows an influx of moisture aloft. This influx of moisture
will result in a more favorable environment to support
afternoon/evening diurnal convection. The low level flow will still
be from the east...just the amount of shower activity migrating
westward is likely to be greater than what was seen the previous day
(Sunday). Good agreement in the NWP ensemble guidance that an mid
level disturbance and associated surface trough will be approaching
the peninsula from the Bahamas during the day. The current set of
guidance suggests that moisture will increase over our region head
of this feature...but that any associated synoptic support for lift
will stay too far to our southeast for much impact on our forecast
through Monday evening. Overnight monday...the surface trough looks
to cross the peninsula. The NAM/Canadian are both trying to close
off a low...with a more concentrated area of lift/rain arriving over
the peninsula from the east...while the GFS/ECMWF are holding with a
prediction of an open inverted trough arriving over the
central/southern peninsula. This latter open trough solution is
highly preferred to the much more aggressive NAM/Canadian given
the overall mid/upper level environment...with unfavorable > 20
knots of vertical shear over the system as it approaches Monday
eve/Monday night.
&&
.MID/LONG TERM (Tuesday through next Saturday)...
Surface high pressure will be positioned north of the peninsula
through the period keeping us in a easterly wind flow pattern. Deep
tropical moisture associated with a weak tropical wave will move
towards the area late Monday into Tuesday. This deep moisture will
remain in place for much of the extended period keeping rain chances
fairly high over the area along with cloud cover. Daily high-end
scattered to numerous showers and thunderstorms can be expected
especially during the afternoon and evening hours. Storm motion
should be east to west given the low-level flow in place.
Temperatures will remain seasonable, with highs in the upper 80s to
near 90 although some areas may only reach the mid 80s if precip
begins a bit earlier in the day.
&&
.AVIATION (06Z TAFs)...
General VFR conditions can be anticipated through the morning hours
across west-central and southwest Florida. Easterly flow will
dominate the forecast through this evening with widely scattered
showers and perhaps a few isolated storms migrating west to east
toward the I-75 corridor after 19Z. Storm coverage should be limited
and can be handled with a VCTS mention for this TAF forecast
package.
&&
.MARINE...
East to southeast flow will dominate the eastern Gulf of Mexico
through Monday between a ridge of high pressure to our north and
northeast...and a weak trough of low pressure in the south-central
Gulf. Winds and seas are forecast to generally remain below
cautionary levels...with the only boater concerns coming from widely
scattered mainly late afternoon/evening storms migrating offshore.
&&
.FIRE WEATHER...
Easterly flow will continue across the Florida peninsula through
Monday as high pressure remains centered to the north and northeast
of the region. Sunday looks to be the driest of the upcoming days
into the early and middle portion of the week...however relative
humidity is still anticipated to remain well above critical levels.
Increasing low level moisture and slightly better rain chances will
begin to arrive through the early portion of the week. No
significant fire weather concerns are anticipated through the week.
Fog Potential...Patchy late night fog is anticipated in normally fog
prone areas away from the immediate coast...however not significant
areas of dense or widespread fog are anticipated over the next
several night.
&&
HYDROLOGY...
A few area rivers continue to run at minor flood stage in
response to runoff from past heavy rainfall associated with
hurricane Hermine. The rivers still in minor flood include Cypress
Creek at Worthington Gardens. This river is expected to slowly
fall through the week...but remain at minor flood until at least
Thursday. The Myakka River at Myakka River State Park will
continue to subside this week and is forecast to fall below minor
flood stage late Monday or early Tuesday. Finally, the Peace River
at Arcadia will continue to subside this week...and is forecast to
fall below minor flood stage on Tuesday. River observations and
forecasts across west-central and southwest Florida can always be
monitored at water.weather.gov/ahps2/index.php?wfo=tbw.
&&
.Preliminary Point Temps/PoPs...
TPA 93 76 90 76 / 30 20 60 30
FMY 91 75 89 75 / 50 30 70 20
GIF 93 75 90 75 / 30 20 60 20
SRQ 91 76 89 75 / 30 20 60 40
BKV 93 73 91 73 / 20 20 60 20
SPG 92 77 89 77 / 30 20 60 40
&&
.TBW Watches/Warnings/Advisories...
FL...None.
Gulf waters...None.
&&
$$
SYNOPSIS/SHORT TERM/AVIATION/MARINE/FIRE WX/HYDROLOGY...Mroczka
MID TERM/LONG TERM/DECISION SUPPORT...McKaughan
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
835 AM CDT SUN SEP 11 2016
.DISCUSSION...
Radar is showing boundary going through extreme southern portions
of South Texas, with models showing some mid level drying moving
in a bit faster than anticipated. Appears that it will be harder
to get convection going than first anticipated. As a result, have
lowered POPs most areas, with no rain mentioned over the NW by
this afternoon. Do not think rain chances over the Northern
Coastal Bend/Victoria area are that good either, but did keep a
mention of showers there for the afternoon (10 POPs), as HRRR is
showing some weak development proximate to area later today (think
it may be over-doing it like it likes to do). Kept daytime highs
today about the same, as they are a tad cooler which should be
the case given the tad cooler boundary which is moving through.
Adjusted temperatures and dew points as-needed. Overall remainder
of forecast is good to go for now. Updates have been issued.
&&
.PREVIOUS DISCUSSION... /Issued 604 AM CDT SUN SEP 11 2016/
DISCUSSION...
See aviation discussion below for the 12Z TAFs.
AVIATION...
A weak cold front that has moved across S TX this morning has
resulted in sct shra`s and isol tsra`s across mainly the southern
portions of the CWA. Outflow bdries from the convection is
resulting in vrb wind direction, but should predominantly be north
through the morning hours then become more easterly this
afternoon. VFR conditions are expected to prevail through much of
the TAF period except for in and near convection. Late tonight
into early Mon morning, brief MVFR vsbys will be possible due to
patchy fog.
PREVIOUS DISCUSSION... /Issued 401 AM CDT SUN SEP 11 2016/
SHORT TERM (Today through Monday)...
A weak frontal boundary moving south across the CWA this morning is
resulting in sct shra`s and isol tsra`s. Models are in pretty good
agreement with increasing areal coverage through the morning hours.
Am expecting convection to be isol to sct this morning across the
southern portions of the CWA, then across the eastern CWA through
this afternoon due to low level moisture convergence and a
moderately unstable environment. The frontal bdry is progged to
become increasingly ill-defined as it washes out through the day,
but the convergence area is fcst to remain across the east, being
enhanced by the afternoon sea breeze. Only isol convection is
expected over the waters tonight as drying takes place in the mid
levels. The isol precip then shifts inland with the sea breeze on
Monday. Temps are expected to be a couple of degrees cooler today
and tonight, then warmer once again Mon. Winds will generally be
light through the period and varying from N this morning to E by
this afternoon.
LONG TERM (Monday Night through Saturday)...A brief window of
slightly drier conditions is expected early in the fcst pd as a
mid/upr low across the northwest Gulf of Mexico advects drier
conditions into the CWA. However, this drying trend will not last
long. A weak tropical wave in the southeast Gulf of Mexico is
expected to continue moving westward and impact the CWA by Wednesday
morning. A plume of deep moisture (PWATS between 2 and 2.5 inches)
on the northern and eastern side of this tropical wave will advect
into the eastern CWA between Wednesday and Friday. Will therefore
maintain chc pops for most of the area with good chc pops for the
eastern portions through this particular timeframe. Although the
tropical wave will have pushed inland and weakened by Saturday,
residual high PWATs along with the seabreeze and differential
heating will be sufficient for isolated scattered convection.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 94 75 95 76 93 / 20 10 20 10 20
Victoria 91 72 92 73 91 / 10 10 20 10 30
Laredo 95 75 98 75 97 / 20 10 10 0 10
Alice 94 72 96 74 94 / 20 10 20 10 20
Rockport 89 77 91 78 91 / 20 10 20 10 30
Cotulla 94 73 98 76 96 / 10 10 10 0 10
Kingsville 94 73 95 74 94 / 30 10 20 10 20
Navy Corpus 91 78 89 79 92 / 20 10 20 10 20
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
GW/86...SHORT TERM
Area Forecast Discussion
National Weather Service Melbourne FL
1010 AM EDT SUN SEP 11 2016
.DISCUSSION...
Update...12z central FL morning soundings indicate PWAT values
slightly above climo levels at 1.75 inches at KTBW and 1.82 inches
at Cape Canaveral. Mid levels temps have cooled over the past 24
hours to -8 to -9 degs C at 500 mbs. Low level southeast flow
continues across the srn half of east central FL with deepest
moisture progd to continue from KMCO southward. Subtle low lvl
trough continues across the far nrn areas where drier air is
forecast to linger in the h8-h7 layer from nrn Lake to Volusia
county. Only minor adjustments planned for morning update. Will
nudge POPs up slightly from Orlando westward into srn Lake county
where some of the high resolution model guidance including the HRRR
forecasts slightly more coverage than currently forecast. Highs will
be in the upper 80s coast to the lower 90s interior. An east swell
will contribute to a moderate risk for rip currents at east central
FL beaches again today.
Previous Discussion...
Current...Cape wind profilers show increasing light southeasterly
low-level winds below 6.0 Kft early this morning around 10 kts.
Water vapor imagery shows a pocket of drier mid/upper level air
sneaking into east central FL. Shower activity over the coastal
waters has been very minimal overnight with only an occasional
light shower showing up on KMLB`s WSR-88D radar. A general weak
pressure gradient exists across the area with weak high pressure
ridging over the north-central FL peninsula. Temperatures remain
mild and in the 70s. Winds have been light/variable.
Today-Tonight...The pressure gradient will remain fairly weak with
surface high pressure ridging remaining just north of the central
peninsula. The low to mid level wind pattern will remain light
onshore during the period. The east coast sea breeze will be able to
develop by late morning and move inland during the afternoon.
Precipitable water values will range from 1.50-1.70 inches along the
I-4 corridor with slightly deeper moisture southward in the 1.70-
1.90 inch range. 500 mb temperatures will remain slightly cooler in
the -7C/-8C range.
One would expect to see an uptick in coastal shower activity by
sunrise with a few of these showers moving onto the east coast,
mainly southward from the Cape. Activity will spread inland during
the late morning/afternoon ending up in WCFL by early evening. Local
models are not terribly optimistic for convection in general, but
suspect greatest chances will lie south of Orlando where moisture is
deepest. Will go with 20 percent POPs for mainly afternoon along the
I-4 corridor and 30 to 40 percent southward toward Okeechobee. By
late afternoon believe convective activity will remain west of the
east coast counties. Will keep interior counties dry past 00Z this
evening with a small threat overnight for coastal counties from
north Brevard southward. Highest threat will remain near the
Treasure Coast and across the local coastal waters.
High temperatures will manage the U80s to near 90 degrees across the
coastal counties and generally L90s over the interior. Heat indices
will approach the U90s/L100s areawide. Overnight lows will continue
mild and in the 70s with humid conditions.
Monday-Wednesday...low-mid level high pressure ridge will shift
well north of central Florida while axis of inverted trough
approaches NW Bahamas early Monday. Band of increased Precipitable
Water (PW) advances to CWA ahead of trough axis, within deepening
easterly flow resulting in the onset of an extended period of
cloud cover and an upward swing of POPs areawide. GFS/ECMWF
similar with trough axis reaching FL east coast late Monday/early
Tuesday with increasingly deep SE flow further raising PW values
toward 2.25+ inches. Increased moisture convergence within
tropical airmass will greatly enhance marine showers/storms with
high coverage (likely POPs) spreading onshore and inland through
mid week. Perturbed pattern likewise favors scattered overnight
showers and isolated storms, with highest chances across coastal
counties. Max temps near climo, with mins 3-5 degrees above
normal.
Thursday-Saturday...with influence of inverted trough no longer a
factor, persistent long fetch of easterly flow will dominate to the
south of building surface high near mid-Atlantic coast. Ridge axis
may begin to shift southward toward northern peninsula toward the
weekend, but no significant change of deep, light easterly flow
through the forecast period. Will trend POPs downward more toward
climatological normals. Highest coverage over coastal areas late
at night through mid day and over interior during the afternoon
through early evening periods. Temps remain near normal for highs,
with lows several degrees above climo.
&&
.AVIATION...
Scattered SHRA/TSRA forecast to develop along east coast sea breeze
as it moves inland mainly along and south of KTIX-KMCO line. Lower
rain chances (slight) expected for KSFB/KDAB terminals where some
low level drier air lingers. Isolated onshore moving showers again
expected later Tonight from KMLB south along the east coast.
&&
.MARINE...
Update...Forecast on track. Modified previous discussion follows...
Today-tonight...Weak high pressure ridging over the area. Light/variable
early morning winds becoming E/ESE up to around 10 kts late
morning/afternoon with ESE winds 7-12 kts continuing this evening.
Winds may increase this evening/overnight up towards 15 kts
offshore of St. Lucie/Martin counties. Seas 2-3 ft in a
persistent ENE swell. Isolated to scattered showers and a few
lightning storms across the waters into the afternoon. Should see an
uptick in shower/tstm coverage after midnight, some of which will
approach the Treasure coast late.
Monday-Thursday...Light to occasionally moderate easterly flow
will increase to around 15 knots and veer to the southeast Tuesday
as axis of tropical wave moves from the NW Bahamas to the
south/central FL peninsula. The onshore flow will back to more of
an easterly component by Thursday while slackening to 5-10 kt.
Seas will build to near 3 feet nearshore and up to 5 feet offshore
Tue/Wed. Coverage of showers and isolated storms will increase and
become numerous Monday night into Wednesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 89 75 88 76 / 20 10 50 40
MCO 92 75 90 75 / 30 10 60 30
MLB 88 78 89 77 / 30 20 50 50
VRB 88 76 87 76 / 30 30 60 50
LEE 93 75 92 75 / 20 10 60 30
SFB 92 76 91 75 / 20 10 50 30
ORL 92 76 90 75 / 20 10 50 30
FPR 88 76 88 76 / 30 30 60 50
&&
.MLB Watches/Warnings/Advisories...
FL...None.
AM...None.
&&
$$
Volkmer/Weitlich
Area Forecast Discussion
National Weather Service Marquette MI
724 AM EDT SUN SEP 11 2016
.SHORT TERM...(Today and tonight)
Issued at 351 AM EDT SUN SEP 11 2016
00Z raobs/latest wv imagery and RAP analysis show a shrtwv rdg bldg
toward the Upr Great Lks in the wake of the departing shrtwv
responsible for ydays rain that is now moving into Quebec.
Combination of large scale subsidence/incoming dry airmass with 00Z
pwat only a bit above 0.50 inch at INL ahead of the shrtwv rdg and
acyc llvl flow associated with sfc hi pres over the western Great
Lakes are bringing quiet wx to the cwa early this mrng. There is a
zonal flow behind the shrtwv rdg near the Cndn border, and extensive
hi/some mid clds associated with waa on the wrn flank of the hi pres
rdg are spreading ewd into NW Ontario/MN within this strong w flow.
But the llvls are too dry per the 00Z Bismarck raob, so there is no
pcpn.
Main fcst concerns in the short term wl be on temps. Although some
of the upstream hier clds wl spill into the area today, a dry llvl
sw flow wl keep the area pcpn free.
Tday...As the aprchg shrtwv rdg axis spreads over the Upr Lks, the
sfc hi pres rdg axis is fcst to shift to the e as well, shifting
llvl winds to the sw. Although the hi clds to the w wl move into the
Upr Lks, rising hgts may tend to suppress the coverage with time,
especially over the scentral. The incrsg sw wind under tightening
pres gradient behind the departing sfc hi is fcst to lift h85 temps
to btwn about 10C over the e and 13C over the w, which wl support
max temps up to about 75 in the downslope wrmg sites over the nw cwa.
Tngt...Combination of some hi clds/steady sw winds wl limit the
diurnal temp drop despite lingering llvl dry air. Min temps in the
downslope areas near Lk Sup wl remain aoa 60. Even at the interior
cool spots, temps wl have a hard time falling blo 50-55.
.LONG TERM...(Monday through Saturday)
Issued at 335 AM EDT SUN SEP 11 2016
A SFC trough/cold front will move into the area from the NW Mon
afternoon, slowing some over the south-central to eastern CWA as a
shortwave rides up the front Late Mon night into Tue Morning. This
will produce showers and thunderstorms along the front from Late Mon
through Tue, with areas NW Upper MI not expected to see synoptic
rain on Tue as the front will be over the SE.
A strong shortwave will then drop through the area Tue evening into
early Tue night, but will be in a moisture fight with a large SFC
high moving in from the W, so widespread precip is not expected.
However, 850mb temps will drop to AOB 2C Tue night, so the N winds
between the intruding SFC high and lower lakes troughing will lead
to lake effect/upslope showers/drizzle and clouds. Think the cloud
cover from the shortwave and lake effect/upslope will keep Tue night
warmer, so brought the temps up and took frost out of the forecast.
May see precip continue into Wed morning near Lake Superior, but the
high moves in and airmass temps increase quickly so think any precip
will be done by late morning or afternoon.
After seeing highs in the 60s Tue and Wed, the airmass looks to be
warmer through the rest of the long term. Unfortunately, not a lot
of confidence past Thu, especially with precip chances. Certainly
seeing precip potential Fri into Sun, but just ran with a broad
model blend for that time period given the uncertainty.
&&
.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 724 AM EDT SUN SEP 11 2016
Although a good deal of hi cld wl invade the Upr Lks today, a SW
flow arnd hi pres departing to the e wl tap dry air and result in
VFR conditions at all the TAF sites this fcst period. As the pres
gradient tightens this aftn btwn the exiting hi pres and a slowly
aprchg cold fnt, expect gusty SW winds at IWD. These stronger winds
spreading to the e above a nocturnal radiation invrn wl result in
LLWS at CMX and SAW tngt.
&&
.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 351 AM EDT SUN SEP 11 2016
A passing hi pres ridge will bring light winds under 20 kts today.
But as this ridge shifts to the e and a tighter pres gradient
develops tonight into Mon ahead of an approaching cold front, expect
SSW winds to increase up to 30 kts. Not out of the question there
could be some gale force gusts to 35 kts tonight over the ncentral
portion of the lake, especially between Isle Royale and the Keweenaw
Peninsula. Winds will shift back to the nne Mon night into Tue
following the cold frontal passage, but these winds are not expected
to be higher than 20-25 kts. Winds will diminish and back to the w
and then the ssw as trailing hi pres moves thru the Western Lakes on
Wed and toward New England on Thu.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...KC
LONG TERM...Titus
AVIATION...KC
MARINE...KC
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1059 AM EDT SUN SEP 11 2016
.DISCUSSION...
THE COLD FRONT HAS PUSHED WELL SOUTH AND EAST OF OUR AREA, AND A
DRIER AND SLIGHTLY COOLER AIR MASS WILL BE BUILDING INTO THE AREA
THROUGH THE DAY. THE NAM CONTINUES TO SHOW SOME CONVECTION
DEVELOPING IN THE NC MOUNTAINS NEAR OUR SW NC COUNTIES, BUT THIS
APPEARS OVERDONE DOES NOT HAVE SUPPORT FROM THE LATEST HRRR OR
RAP. WILL CONTINUE THE CURRENT FORECAST WITH NO CHANGES.
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&
$$
DGS
Area Forecast Discussion
National Weather Service Omaha/Valley NE
613 AM CDT SUN SEP 11 2016
.SHORT TERM...(Today through Tuesday)
Issued at 320 AM CDT SUN SEP 11 2016
The main forecast concerns are still in regards to the chance for
showers and thunderstorms from Monday through Tuesday.
Primary features noted in the upper air charts from last evening
included the following. At 850 mb...moisture was displaced well to
the south...with a ridge from TX into MN. Warmer air was already
moving in from the west. At 500 mb...12 hour height falls of up to
80 meters were noted in southwest BC. That was somewhat supported
by a 120 knot jetstreak over southern BC...just a little north of
the strongest height falls.
Water vapor satellite imagery and recent RAP model initializations
showed a trough (associated with previously mentioned height falls)
starting to dig into southwest Canada and the Pacific Northwest.
Zonal flow at 500 mb will continue to turn to the southwest through
tonight.
As pressures fall over the high plains today...pressure gradient
in our area with strengthen...allowing breezy/windy conditions to
develop. Rain chances today and tonight look low...since it will
take a while for lower and mid level moisture to return. Highs
today should reach the upper 70s and lower 80s...with lows tonight
in the mid 50s to around 60.
On Monday...a cold front will be moving into the area from the
northwest. Deeper moisture will start to return...especially in
the afternoon...but overall the trend has slowed. The best chance
for showers and thunderstorms Monday will be behind the front. The
previously mentioned cold front should drift slowly southeast
Monday night into Tuesday as high pressure builds into the
Dakotas. The highest rain chances will shift more into southeast
NE and southwest IA Tuesday.
.LONG TERM...(Tuesday night through Saturday)
Issued at 320 AM CDT SUN SEP 11 2016
Rain chances for the daytime Wednesday look relatively low...but
will be increasing Wednesday night as high pressure at the surface
moves off to the east and southerly flow strengthens. A closed low
at 500 mb...over northern NV at 12Z Wednesday...should track
northeast into the Dakotas on Friday.
Kept a mention of showers and thunderstorms for much of the area
for the period from Wednesday night through Saturday...with the
highest chances Thursday night. High temperatures should be mostly
in the 70s...with lows in the 50s to lower 60s.
&&
.AVIATION...(12Z TAFS for KOFK...KLNK and KOMA.)
Issued at 612 AM CDT SUN SEP 11 2016
VFR conditions are expected through the TAF cycle. Southwesterly
surface winds will increase and gust to near 20-25kts this
afternoon but should diminish with sunset.
&&
.OAX Watches/Warnings/Advisories...
NE...None.
IA...None.
&&
$$
SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Kern
Area Forecast Discussion
National Weather Service Pueblo CO
405 AM MDT SUN SEP 11 2016
.SHORT TERM...(Today and tonight)
Issued at 405 AM MDT Sun Sep 11 2016
Westerly flow aloft will be found over the forecast area
today, becoming more southwesterly tonight as an upr trof drops
southward thru the Pacific Northwest. A weak disturbance will move
across the area today, and an increase in moisture over the area
should lead to isolated to scattered showers/tstms over the
mountains and high valleys. The NAM and GFS show the potential for
some pcpn moving into the Continental Divide by noon and then
spreading eastward across the mountain areas through the afternoon,
and then along the I-25 corridor by evening. The NAM and GFS then
shows some isolated activity ovr the sern plains in the evening
hours. The HRRR has much less activity than the NAM, and holds off
on pcpn until around 20-21Z ovr the mountains. With relatively dry
low levels this afternoon and evening over the southeast plains, any
shower/tstms that develop or move over the plains should produce
mainly a lightning and gusty wind threat. High temps today should be
about 10 degrees warmer than yesterday over the southeast plains,
which is about 10 degrees above average. In the high valleys, temps
should be around 5 degrees above average.
The NAM shows dry weather across the forecast area by about
midnight, and overnight lows are expected to fall into the 50s
across the southeast plains, and into the 40s over the high valleys.
.LONG TERM...(Monday through Saturday)
Issued at 405 AM MDT Sun Sep 11 2016
...Cooler and more unsettled weather expected into the middle of
next week...
Moderate southwest flow aloft progged across the region through the
middle of next week, as a broad upper trough translates across the
northern Tier of States on Monday, with secondary energy digging
across the Pac Northwest. This secondary energy is progged to carve
out a broad upper low across Great Basin on Tuesday, which slowly
weakens as it lifts out across the Northern Rockies on Thursday.
Latest models are a tad slower with front sliding across the eastern
Plains and keep the coldest air north of the area through Monday
afternoon. With that said, have bumped up highs a tad across the
area on Monday. Kept isolated to scattered pops for areas over and
near the higher terrain on Monday, with pops spreading across the
eastern plains Monday night, as moisture increases behind passing
front. Cool low level upslope flow across the plains, combined with
minor disturbances within the southwest flow aloft will keep
isolated to scattered pops and temperatures below seasonal seasonal
averages in the forecast, with Tuesday likely the coolest day of the
week. With the cool air aloft. will likely see some light snow
accumulations across the higher mountain peaks both Tuesday and
Wednesday.
Flow aloft becomes more westerly on Thursday as open wave lifts out
across the Northern Rockies. Westerly flow helps boost temps across
the plains Thursday with pops decreasing from west to east Thursday
night. Passing wave sends another weak front down across the plains
with temps cooling once again for Friday. Some differences into next
weekend, as latest models are keeping a baggy trough in place across
the Rockies, which would keep better chances of showers and cooler
temps in place through the weekend, especially over the higher
terrain.
&&
.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 405 AM MDT Sun Sep 11 2016
VFR conditions are expected at the terminal forecast sites today and
tonight. Showers/tstms will be possible over and near the mountains
this afternoon and evening, and could move into the vcnty of the
forecast sites.
&&
.PUB Watches/Warnings/Advisories...
NONE.
&&
$$
SHORT TERM...28
LONG TERM...MW
AVIATION...28
Area Forecast Discussion
National Weather Service Blacksburg VA
958 AM EDT Sun Sep 11 2016
.SYNOPSIS...
A cold front will pass east across the region this morning before
stalling over the Carolinas Monday into Tuesday. High pressure
behind the front will build north of the area later today into
tonight, reaching the mid-Atlantic coast Monday. Another weak
cold front passes through the region by Wednesday with reinforcing
high pressure building to the north of the area through late in
the week.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 940 AM EDT Sunday...
The morning update will reflect limited changes to the ongoing
forecast. A band of light rain showers was heading southeast
through the New River Valley. This feature should dissipate as it
nears the crest of the Blue Ridge. Drier air will continue to
progress into the region and erode the cloud cover in the west. In
the east, northwest flow will limit any shower or storm
development, but nearest the outgoing front a slight chance will
remain this afternoon. Have tweaked hourly temperatures, dew
points, wind and sky cover based upon the latest observations and
expected trends into the early afternoon.
As of 230 AM EDT Sunday...
Passing upper trough well to the north will finally swing its associated
cold front through the region this morning. Much drier air aloft to
the west per water vapor loop should quickly advect in through the
afternoon. In addition low level northwest flow in advance of high
pressure across the Tennessee valley should help lower dewpoints
over the mountains by midday, and out east later on. Although the
actual 850 mb boundary may get stuck crossing the Blue Ridge,
models suggest even enough drying across the Piedmont to preclude
much convective potential as forecast PWATS and instability get
shunted to the south/east. This drier scenario also supported by
most solutions with downsloping also helping to limit added convection
in the east. Thus have trimmed back pops to isolated coverage
mainly southeast of a South Boston to Mount Airy to Wilkesboro
line, and kept elsewhere dry this afternoon under increasing
sunshine. Still cant rule out some added showers south/west along
the front before sunrise per latest HRRR so left in some early
mention before dry advection increases.
Should finally be a bit closer to normal on highs west this afternoon
with most in the 70s under decent cooling aloft which will be offset
by heating of dry air. Cooler air will be slower to reach the east
as suggested by 850 mb progs showing advection weakening during
max heating. This while downsloping likely boosts spots into the
mid/upper 80s from Roanoke east although less humid under lowering
dewpoints.
Surface high builds to the north overnight and wedges in along the
eastern slopes of the mountains late. This should allow for a better
surge of cooler/drier air to finally swing into areas east of the Blue
Ridge overnight. Also appears enough low level dry air to keep things
mainly clear elsewhere although may see low clouds redevelop toward the
southern Blue Ridge late as the low level trajectory turns more
southeast. However latest Nam not too aggressive in returning low level
moisture north until around daybreak so opted to leave out until late
for southern sections but something to watch. Otherwise mostly clear
and quite comfortable with lows low/mid 50s north and west, with
lingering low/mid 60s southeast.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 230 AM EDT Sunday...
Surface high pressure will move off the Mid Atlantic coast on Monday
and remain there through Tuesday night. The wedge boundary along and
east of the Blue Ridge will continue to sit across the Carolinas
through the period, but will erode some across the mountains each
day. While this wedge is in place, low level flow will become
southeasterly. This marine influenced southeasterly flow will
gradually increase moisture into the region. Cloud cover will
increase each day with a chance for afternoon showers along the
North Carolina Blue Ridge.
The wedge and southeasterly flow will keep temperatures uniform each
day. Monday`s afternoon temperatures will range from the upper 70s
to lower 80s, mountain ridges in the lower 70s. Temperatures will
moderate some Tuesday ranging in the low to mid 80s.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 355 PM EDT Saturday...
By Wednesday, a new cold front arrives from the north as a short
wave tracks along the Canadian border. This will finally give the
early week cold front just to our south a shove to move further
south into the southeast states. By contrast, this will leave only
limited moisture with which the second/new front has to work as
it arrives in the area Wed afternoon/evening. With the better
dynamics also far removed to the north, again only look for
scattered showers and thunderstorms with the front. Instability
should be sufficient given time of arrival during peak heating for
a few thunderstorms.
High pressure will once again slide across the OH valley toward
the northern Mid-Atlantic Thursday into Friday as the second front
drifts into NC/SC and also stalls and or weakens. Once again it
will not track too far south before encountering broad upper scale
ridging. Thursday should be dry, but return moisture by Friday
could support isolated showers across far southwest VA or
northwest NC. In addition, there is some potential for a tropical
wave to develop/move into south GA or along the SC coast. Any
effects of that system will be beyond this forecast package.
Cooling will again be modest at best with 850mb temps even behind
the second front still lingering in the +15C or better range. This
will still leave surface temperatures 5-7 degrees above normal
with lows in the 50s mountains and 60s elsewhere, with highs in
the 70s west to lower and even mid 80s east.
&&
.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
As of 640 AM EDT Sunday...
Surface cold front has pushed out to along the Blue Ridge with the
trailing dewpoint boundary now entering the far western mountains
preceded by a narrow band of light showers per radar loops. Thus
may need to include a brief VCSH or prevailing -shra mention at
KBLF and perhaps KBCB pending release coverage. Otherwise IFR/MVFR
upslope driven cigs have filled in across parts of the west with
this expected to continue across the southeast West Va counties
through at least mid morning. Some of these MVFR cigs may also
spill east to KBCB and perhaps briefly at KROA early this morning
as well with mostly high/mid cloud canopy to the east.
Drier air will push in behind the secondary front this afternoon
with any lingering sub-VFR cigs likely fading by midday over the
west with heating/mixing. This should also help scour any
residual cloudiness out farther east before heating redevelops a
cumulus field east of the mountains this afternoon. This could
also allow isolated convection to develop over the far
southern/eastern sections if the front slows more. However for now
appears most shra/tsra will be mainly southeast of the TAF sites
so leaving out mention. Otherwise looking at mainly VFR this afternoon
with this trend continuing for most of tonight as high pressure
builds in from the north. Expect some dense fog to develop around
KLWB later tonight given light winds and cooler air along the
river so including localized IFR/LIFR in fog/stratus late. Elsewhere
scattered to perhaps broken low clouds may push back north espcly
along the Blue Ridge late tonight which should limit fog for the
most part.
Extended aviation discussion...
By Monday, the frontal boundary to our south stalls while high
pressure works its way into the area. As low level winds become
southeast, the potential for early morning sub- VFR cloud cover
returns to the area, especially across the mountains, but mainly
south of the TAF locations.
Tuesday into Wednesday, isolated to widely scattered showers and
storms return to the forecast as the boundary lifts back north
into the region. Anticipate pockets of sub-VFR conditions espcly
Wednesday with deeper moisture return in advance of the next cold
front.
Wednesday night into Thursday a cold front is expected to sweep
through the region. Appears the best coverage of showers and
storms will be across the western sections of the region with
possible periods of sub-VFR.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...DS/JH
NEAR TERM...DS/JH
SHORT TERM...RCS
LONG TERM...AMS/RAB
AVIATION...DS/JH
Area Forecast Discussion
National Weather Service Tucson AZ
852 AM MST SUN SEP 11 2016
.SYNOPSIS...Moisture will increase across much of the area for the
next couple of days. This will result in scattered showers and
thunderstorms, especially today and Monday for areas from Tucson
eastward. Temperatures will fall to slightly below average values for
mid September this upcoming week.
&&
.DISCUSSION...Clear skies this morning west of Tucson with mostly
clear to partly cloudy skies from Tucson eastward. Atmospheric
moisture has been on the increase with the 12Z TWC sounding showing
PWAT values up to 1.22 inches. This is in response to a low to mid
level southerly flow which has brought in some moisture from Sonora.
Meanwhile, the mid and upper level ridge axis lies just to the
southeast of this forecast area. We`ve gone ahead and made some
tweaks to the forecast today to lower PoPs primarily in the Tucson
metro as the latest HRRR and 12Z UofA WRF-NAM and 6Z WRF-GFS depict
convection developing in the higher terrain from
the Catalina/Rincons/Santa Ritas then shifting eastward. This also
lies in the best area of lower level convergence as well. We`ve also
removed patchy dust from the forecast for areas north and west of
Tucson later today.
A fairly similar scenario is setting up for Monday. As an
upper level low now across Central California open up and pushes to
the east across a great basin, increased southwesterly flow will
help to draw up additional moisture from the Gulf of California and
Sonora. This will result in continued thunderstorm chances, with the
back edge of the fairly widespread coverage farther west compared
to today.
Drier air will really start to make inroads across a much greater
portion of the forecast area starting on Tuesday with continued
southwesterly flow starting to advect in drier air due to continued
troughing across the western CONUS. We still can`t rule out a slight
chance of thunderstorms, especially for eastern areas though on
Wednesday and then right along the New Mexico border through the end
of the week.
Temperatures will be near normal today, then drop slightly becoming a
on average a couple of degrees below normal through the week.
&&
.AVIATION...Valid through 12/18Z.
Sct-bkn cloud bases 7-11k ft AGL. Sct SHRA/TSRA developing mainly
east of a KTUS-KOLS line aft 12/19z...some with gusty outflow winds
and mountain obscurations. SHRA/TSRA ending by 12/03z with skies
clearing. SFC winds generally under 12kts through the period.
Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Expect scattered afternoon and evening
showers and thunderstorms this afternoon and Monday from the Tucson
to Nogales area east to the New Mexico border, basically everywhere
except zone 150. Any storms that develop will generally move to the
east or northeast. Tuesday and Wednesday convection will be forced
further east and be limited to closer to the New Mexico border.
Thursday onward much drier air invades the area bringing an end to
the convection along with forcing dewpoints down significantly.
Winds through the period will generally be 15 mph or less except in
the vicinity of thunderstorms where strong outflows are possible.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
PUBLIC...Lader
AVIATION/FIRE WEATHER...Drozd/Cerniglia
Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Area Forecast Discussion
National Weather Service Birmingham AL
345 PM CDT SUN SEP 11 2016
.SHORT TERM...
Tonight through Monday Night.
A quasi-stationary front was located from near Demopolis, to near
Clanton, to near Wadley this afternoon. The front is expected to
move very little through the overnight hours. The latest RAP
analysis indicates an unstable atmosphere in the vicinity of the
front. The various Cape measurements depict 2000-3000 values, DCape
values in the 800 neighborhood, decent low level lapse rates,
limited mid level lapse rates, and virtually no shear or winds
aloft. This will make storm motion rather slow and mergers and
outflows important. Some locations may receive up to two inches of
rain and some gusty winds. Small hail is also possible in the
strongest storms. The northward progression of storms will be
governed by outflows from the southern convection. Currently, the
rain chances have a very high gradient north to south due to this
uncertainty and position of the front. The storms will continue into
into the evening hours and a generally decrease by midnight.
On Monday, there will be some upper level energy moving west to east
into the area and additionally some weak wave moves northward into
the southeast areas. Currently have 50-55 pops advertised with the
uncertainty based on the convection today and how the airmass
recovers. If it does recover sufficiently, pops will need to be
raised tomorrow for the southern half of of the area. Once again,
some gusty winds, hail and locally heavy rain will be possible.
75
.LONG TERM...
Tuesday through Saturday.
General upper level ridging will be in place across the region
thru the remainder of the week. Wind shear is expected to remain
non-existent under the ridge and there doesn`t appear to be any
significant forcing mechanisms. However, models continue to
indicate elevated moisture levels, generally PW values at or above
1.6 inches. This should be sufficient for some mainly diurnally
driven isolated to scattered convection each day thru the end of
the work. Did not make any major changes to rain chances. Temps
will be slightly above normal, highs in the upper 80s and low 90s
and lows in the upper 60s and low 70s.
Deeper southerly/southwesterly flow returns by the weekend as the
upper ridge shifts eastward and a trough deepens across the
central CONUS. In response, rain chances will be on the rise.
Models also try to push a front toward the Tennessee Valley in
the extended, but unfortunately, doesn`t look like it will have
enough support to push through. We`ll just have to keep waiting
for that first true taste of fall.
19
&&
.AVIATION...
18Z TAF Discussion.
Generally a VFR forecast this period with a few wrinkles. Showers
and thunderstorms were developing along and south of a nearly
stationary front this afternoon. It appears that MGM/TOI will be
impacted the most. Therefore, kept the mention of VCTS and Tempo
TS for both of these sites this afternoon. Brief heavy rain and
gusty winds are possible with the convection. Any ceilings should
remain VFR for the terminals into this evening. Did not mention
any lower ceilings overnight and into Monday but think there will
be some clouds/ceilings around 4k.
75
&&
.FIRE WEATHER...
Shower and storm development will continue along/south of a
frontal boundary this afternoon/evening, impacting the
southeastern half of Central Alabama. Isolated to scattered rain
chances, mainly diurnally driven, continue through the week as
moisture remains high. No fire weather concerns are anticipated at
this time.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 65 89 68 89 69 / 10 20 10 30 10
Anniston 68 89 69 88 70 / 20 40 20 30 20
Birmingham 69 91 71 90 72 / 10 20 20 30 10
Tuscaloosa 68 91 71 92 72 / 10 30 20 30 10
Calera 69 91 70 90 71 / 20 40 20 30 20
Auburn 72 88 70 88 71 / 30 50 20 30 20
Montgomery 73 93 71 92 73 / 30 50 20 30 20
Troy 70 91 70 89 70 / 40 50 20 30 20
&&
.BMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Green Bay WI
604 PM CDT SUN SEP 11 2016
Updated aviation portion for 00Z TAF issuance
.SHORT TERM...Tonight and Monday
Issued at 251 PM CDT Sun Sep 11 2016
The latest RAP analysis and satellite/radar imagery show a large
high pressure system centered over the mid-Mississippi Valley early
this afternoon. Mid and high clouds are passing across the Lake
Superior region, with a few returns showing up over
western Lake Superior earlier. No threat of precip farther south
based on the 12z GRB sounding. Mostly clear conditions prevail
upstream thanks to a dry airmass in place. Since the next front is a
long way off still (northern Montana), temps and marine weather are
the main forecast concerns.
Tonight...Mid and upper flow will become more southwesterly, causing
the jet stream to lift north of Lake Superior. As a result, cloud
cover will mainly reside north of the region, so should see a clear
or mostly clear night. Surface high pressure will be sliding to the
east and the pressure gradient will tighten slightly in response.
South to southwest winds will strengthen over the Lake and Bay,
which will generate building waves through night. Waves of 2 to 4
feet will be possible south of the Door, and 3 to 5 feet near
Washington Island.
Monday...The surface cold front will slide into the northern
Mississippi Valley by late in the afternoon. Showers and storms
will exist along and behind the front, and will mostly likely remain
northwest of the forecast area. Clouds will be on the increase,
however, over north-central WI. Temps should still rise into the
low 70s north to upper 70s in the hot spots. Southwest winds will
continue to be breezy ahead of the front, which will cause waves to
build to 4 to 7 feet on Lake Michigan. Will need a beach hazards
statement at some point, but with some uncertainty when waves rise
above 4 feet, will let later shifts issue the statement.
.LONG TERM...Monday Night Through Sunday
Issued at 251 PM CDT Sun Sep 11 2016
The next chance for precipitation will be Monday night into
Tuesday as a northern stream short wave with a frontal system
slides over the western Great Lakes region. Models in fairly good
agreement on timing of the system and anticipate pops could be
increased in later periods if a few more parameters come together.
Best instability arrives Monday night with the warm air advection
but saturating the air mass could be a challenge at first.
Anticipate the precipitation will be on the increase later Monday
night into Tuesday morning as the surface to 850 cold front drops
south over the area. Precipitation could be more post frontal if
saturation issues remain. Morning progs suggests the RRQ region of
the upper jet is now lagging further back with the upper trough
and trailing the fgen region. As a result progs are trending with
a later period of precipitation later Tuesday and even into East
Central Wisconsin Tuesday evening.
An upper ridge eventually builds into the area mid week. A cooler
drier regime will settle into the state as surface high pressure
drops into the Great Lakes region. Depending on the timing of the
ridge axis before the warm air advection pattern returns, chilly
temperatures near frost levels possible across the north.
A deeper upper trough is progged to arrive later next week or
into next weekend for another chance of precipitation.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 559 PM CDT Sun Sep 11 2016
The main aviation forecast concern is low-level wind shear
tonight. Will continue carrying LLWS in the 00Z TAFs. Excellent
flight conditions expected Monday once mixing deepens and the LLWS
dissipates.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Marquette MI
355 PM EDT SUN SEP 11 2016
.SHORT TERM...(This evening through Monday)
Issued at 353 PM EDT SUN SEP 11 2016
Water vapor imagery and RAP analysis show pattern transitioning to a
lower amplitude flow. Broad low amplitude ridge is pushing into the
Great Lakes region ahead of a positive tilt trof extending from
northern Manitoba to the Pacific NW. This trof will bring the next
opporunity of pcpn Mon night into Tue. Mid and high clouds that
spread into the area this morning have been thinning out and have
been replaced by sct to at times bkn cu. To the nw across ne MN into
northern Ontario where best waa/isentropic ascent is occurring,
mid/high clouds clouds persist. Temps across the fcst area have
risen into the lower 70s for the most part.
Despite continued waa/isentropic ascent tonight, relative dryness of
the air mass advecting into the area will ensure pcpn is of no
concern. In fact, fcst soundings suggest not much in the way of
cloud cover. Steady sw winds will limit the temp fall tonight with
many downslope locations near Lake Superior probably not falling blo
60F. At the interior cool spots, temps shouldn`t fall blo 50F.
On Mon, aforementioned positive tilt trof will shift e, extending
from Hudson Bay to the northern Rockies. Disorganized shortwave
energy in the trof will slowly push associated cold front across MN
and out over western Lake Superior in the late aftn/early evening.
Consensus of 12z model runs has been to slow down slightly the
progress of the cold front. Given the dry air mass ahead of the
front, shra and possible tsra will likely be confined to right along
or more likely just behind the sfc cold front. Have thus dropped
schc pops over the far w prior to 00z. With fcst soundings
suggesting abundant sunshine, raised max temps a bit with much of
the area likely to be in the 75-80F range. Fcst sounding suggest max
temps could be mostly around 80F away from Lake Michigan.
.LONG TERM...(Monday night through Sunday)
Issued at 315 PM EDT SUN SEP 11 2016
Forecasted upper air pattern shows a 500 mb trough in the western
U.S. and a shortwave in the northern plains and a broad 500 mb ridge
across the ern U.S. 00z Tue. This shortwave moves southeast and
affects the upper Great Lakes on Tue and Tue night. Nam shows some
850-500 mb q-vector convergence moving in for Mon night along with
some deeper moisture with the moisture remaining on Tue while the q-
vector convergence moves out. Does get cold enough aloft at 850 mb
off the nam, gfs and ecmwf tue night into Wed morning for lake
effect pcpn as 850 mb temperatures are from 4C to 6C while Lake
Superior temperatures are from 16C to 19C which is enough lake-850
mb delta-t for clouds and some lake effect rain showers. Kept in
chance pops for north lake effect pcpn belts for Tue night and Wed
morning. Did go likely pops for Mon night into Tue morning. Overall,
did not make too many changes to the going forecast for temperatures.
In the extended, GFS and ECMWF show a 500 mb ridge across the Ern
U.S. and a trough in the Rockies and western high plains 12z Thu.
This trough moves into the northern and central plains 12z Fri and
into the Upper Great Lakes 12z Sat. This trough remains over the
area into Sun, so the area will see this storm system from Fri into
Sun. Temperatures look to be near normal for this forecast period.
&&
.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 117 PM EDT SUN SEP 11 2016
Although high pres ridge is shifting e and a cold front is moving
across the Northern Plains, low-level air mass will remain dry
across the area during this fcst period, allowing VFR conditions to
continue at KIWD/KCMX/KSAW. As the pres gradient tightens btwn the
exiting high pres ridge and the approaching cold front, expect sw
winds to become gusty at KIWD. These stronger winds spreading to the
e above a nocturnal radiation inversion will result in LLWS at
KCMX/KSAW tonight.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 353 PM EDT SUN SEP 11 2016
Tightening pres gradient btwn departing high pres ridge and an
approaching cold front will result in increasing s to sw winds to 20-
30kt tonight into Mon. Some gale force gusts will probably occur at
the higher observation platforms over n central Lake Superior,
especially btwn Isle Royale and the Keweenaw Peninsula. Winds will
shift to the nne Mon night into Tue following the cold frontal
passage, but these winds are not expected to be higher than 20-25kt.
Arrival of high pres on Wed will result in winds diminishing to
under 15kt. Winds will then become southerly and should remain 20kt
or less Thu/Fri.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...07
AVIATION...Rolfson
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Phoenix AZ
201 PM MST SUN SEP 11 2016
.SYNOPSIS...
Low pressure off the California coast is expected to pull monsoon
moisture back northward into central and eastern Arizona through
Monday. This will allow the development of isolated to scattered
showers and thunderstorms, mainly across the higher terrain south and
east of Phoenix. A turn to more westerly flow aloft will then push
much drier air back into the Desert Southwest from Tuesday onward
into next weekend, with dry conditions and mostly clear skies
returning back to the region.
&&
.DISCUSSION...
As in past afternoons, latest satellite imagery shows scattered CU along
with the Mogollon Rim, with more robust convection initiating across
the White Mountains stretching back into southeastern Arizona. Some
CAPE is present in these areas, mainly associated with richer low-
level moisture, steep mid-level lapse rates and cooler temperatures
aloft extending from the upper low across central CA. Further west,
conditions are drier with dewpoints generally in 40s across the lower
deserts.
Latest suite of WRFs including the HRRR continue to indicate that
afternoon and early evening shower and thunderstorm activity will
remain confined to the higher terrain with the deep-layer
southwesterly flow. Activity will dissipate this evening. However,
latest NCAR ensemble suggests that some convection may redevelop
overnight across Central Arizona. No other spectral or convective-
allowing models are depicting this, though it can`t be ruled out
entirely with the increased vorticity-forced ascent moving through
ahead of the upper-low. PoPs are somewhat higher in the 06z- 12z,
but still generally remain 10 percent or less across much of the
area.
A stronger upper low will move into northern CA Monday with height
falls overspreading the Desert Southwest. This will translate into
several degrees of cooling across the region, with high temperatures
likely only reaching the upper 90s across the lower deserts. Similar
thermodynamic setup will mean that convection will again be favored
across the higher terrain east of Phoenix and towards eastern and
southeastern AZ. There is also somewhat more deep-layer shear
associated with the aforementioned CA trough, but it would be unfair
to classify any potential storms as anything other than ordinary.
Nevertheless, any storms that do develop have the potential to
produce strong wind gusts and brief heavy rain. It is also worth
mentioning that previous runs of the SREF had suggested that activity
would be possible as early as Monday morning, though the latest runs
have again trended towards the afternoon.
&&
.PREVIOUS DISCUSSION...
Tuesday through Saturday...
A drying trend is still expected during this period as another
stronger upper low, that will be dropping southward over northern
CA, helps to kick out the afomentioned upper low/trof to our east,
and turn the flow aloft more westerly over the region. This should
end the threat for convective activity over the region as much drier
air is pulled in from the west, with PWATs falling aob 0.50 inch by
Thursday. High temperatures are expected to hold at or slightly
below normal levels through this period, with highs near or slightly
below 100 across the lower deserts. Lows will likely end up below
normal, as the very dry airmass allows for very efficient radiational
cooling each night, with lows in the 60s possible at many of the
normally cooler locations.
&&
.AVIATION...
South-Central Arizona Including KPHX, KIWA, and KSDL:
Skies will remain mostly clear with some mid-high clouds (coverage
mainly in the FEW-SCT range) overspreading the region from late this
afternoon into Monday morning. Winds will follow typical diurnal
trends, with afternoon westerly winds persisting a little later than
usual at Phoenix terminals. Speeds will remain on the lighter side,
with a few gusts up to 15 kts possible this afternoon. There will be
a slight chance for thunderstorms over the higher terrain east of
Phoenix later today, but the chances for storms over the airports is
extremely unlikely. However, an outflow from the east is not out of
the question but chances are very low, and due to that there is no
mention in the TAF.
Southeast California/Southwest Arizona including KIPL and KBLH:
Skies will remain clear through the TAF period. Winds will remain
mainly out of a southwest at both KIPL and KBLH. Periods of
gustiness up to 25 kts is possible this afternoon at KBLH and early
this evening through tomorrow morning at KIPL.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Wednesday through Sunday...Minimum humidities will be in the 10 to
30 percent range on Wednesday and Thursday, dropping into the 10 to
20 percent range Friday, and then slightly increasing back into the
10 to 30 percent range on Saturday and Sunday (greatest moisture in
southern Gila county). However, overnight recoveries will be fair to
good. This drier air in the region will also keep precipitation
chances near zero with very very light chances (less than 10
percent) over the higher terrain east of Phoenix. Winds will remain
mainly on the light side with some afternoon gustiness up to 15 to
20 mph along and west of the Colorado River Wednesday through Friday.
&&
.SPOTTER INFORMATION STATEMENT...
Amateur radio Skywarn net activation is not expected at this time.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
Visit us on Facebook...Twitter...and at weather.gov/phoenix
DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Percha
AVIATION...Hernandez
FIRE WEATHER...Hernandez
Area Forecast Discussion
National Weather Service Raleigh NC
347 PM EDT SUN SEP 11 2016
.SYNOPSIS...
A slow moving cold front will move southeast across central NC
this afternoon and evening and then stall near the South Carolina
border early Monday before dissipating on Tuesday. Another cold
front will cross the area late Wednesday.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
As of 325 PM Sunday...
The latest surface analysis at 18Z shows a northeast-southwest
oriented cold front stretching from west of Roanoke Rapids
southwest to near Raleigh to near Rockingham. The front is noted
by a wind shift and a drop in surface dewpoints into the lower to
mid 60s with the dew point down to 59 at KINT at 19Z. Ahead of the
front, a southwest wind with dew points in the lower 70s are noted
across the Coastal Plain and Sandhills.
NWP guidance generally slides the front very slowly east into the
overnight with the front stalling a bit or becoming confused with
localized cooling from convection. The low and mid level flow
behind the front is largely westerly so the southward advancement
of the boundary will gradually slow with the main push moving the
front eastward across southeast VA and northern NC such that the
front increasingly becomes oriented west to east across southern
NC by tonight.
The air mass ahead of the front is generally weakly unstable with
MLCAPE values ranging from 500 to 1500 J/Kg. Instability is
inhibited a bit a some mid level warming centered near 600 hPa
which results in weak mid-level lapse rates of around 5.5 C/Km.
Agitated cumulus has developed mainly south and east of I-85 with
the taller towers located ahead of the front near and east of U.S.
Route 1. Isolated thunderstorms have developed near the front in
the Roanoke Rapids area and near Fayetteville. Expect convection
to fill in along the front during the next few hours impacting the
eastern parts of the Triangle area to Rocky Mount and Goldsboro.
Precipitation chances across the Triad are limited given the lack
of instability and forcing, so we`ve include a dry forecast for
that area. Look for individual convective cells to move east and
perhaps east- northeast at 20 mph with the overall area of showers
gradually shifting east this evening. Given the limited updraft
strength, weak low and mid level flow, limited bulk shear with
0-6km shear values of around 10 kts, severe weather is not
expected this afternoon and evening. The scattered convection will
continue into the evening hours as it shifts south but gradually
diminish into the late evening hours as the atmosphere stabilizes.
Higher resolution guidance including the HRRR and RAP signal a
secondary surge of northeasterly flow will move into central NC
from the Hampton Roads area this evening. In time, weak isentropic
lift over the surface northeast flow behind the front will result
in redeveloping clouds and perhaps some drizzle north of the
front across the Piedmont and toward the Yadkin Valley. Lows
tonight will range in the mid- upper 60s north and northwest well
behind the front to the lower 70s across the south southeast
closer to the front. -Blaes
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
As of 340 PM Sunday...
After 5 consecutive days of highs in the 90s at most locations in
central NC, Monday will feature noticeably cooler temperatures.
The cold front will likely stall near the South Carolina border on
Monday and Monday night providing a weak focus for mainly
afternoon and evening convection and supporting a good deal of
cloudiness across the area. Best precipitation chances will be
across the south near the front and closer to deeper moisture
while drier and more stable conditions near the VA border should
result in little to no shower activity. High temperatures will
range in the lower 80s northwest to mid 80s far southeast.
More of the same for Monday night with partly to mostly cloudy
skies and a small chance of showers across the south. Some pockets
of drizzle may develop develop overnight, mainly across the
western Piedmont and Yadkin Valley area after midnight. Low
temperatures will range in the mid to upper 60s. -Blaes
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
As of 200 PM Sunday...
Tuesday through Thursday: Tuesday the frontal zone washes out south
of the area but a fair amount of residual moisture will be left over
and and precipitation chances will extend northward through the
southern counties up to about highway 64. Instability is almost non-
existent in the latest forecast soundings and so showers will be the
most likely mode of precipitation. Some of that instability returns
on Wednesday and and so showers and thunderstorms will still be
possible, again with the main threat across the southern counties
and everyone else remaining mostly dry. On Wednesday night a cold
front is progged to move through the area as a dry front with
showers and thunderstorms in the afternoon on Thursday again across
the southern tier as diurnal timing becomes more favorable. Highs in
the upper 80s Tuesday and Wednesday will be cut back to the lower
80s on Thursday after the frontal passage.
Friday through Sunday: High pressure to the northeast takes over the
pattern for the weekend bringing moist easterly flow across the
area and possibly helping to increase cloud cover in the west as
moisture banks up against the mountains. Aside from that, mostly dry
conditions are expected during this time period with temperatures in
the low to middle 80s, warmest late in the weekend as a more
southerly component returns to the flow ahead of a more robust
frontal system that will approach the area early next week.
&&
.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
As of 240 PM Sunday...
Widespread VFR conditions across central NC early this afternoon
will give way to an increasing threat of adverse aviation
conditions with low ceilings late tonight and Monday morning and
local restrictions from scattered showers and thunderstorms,
mainly from Raleigh south and east.
A slow moving cold front will transverse central NC this
afternoon and evening and produce some scattered showers and
thunderstorms southeast of Interstate 85 and mainly from route
U.S. 1 eastward. The convection will bring brief visibility
restrictions and perhaps MVFR ceilings. Outside of convection,
VFR conditions are expected to dominate through around midnight.
After midnight, a northeast flow will promote the development of
a layer of BKN-OVC stratus between 04-08Z with bases between
1-2kft. The best chance of ceiling restrictions will be across the
southeast near the KFAY and KRWI terminals. The stratus will
likely persist into at least the mid morning hours and perhaps
midday across the south with VFR conditions returning on Monday
afternoon.
Winds will initially be driven by the location of the front which
stretched from near KIXA southwest to near KRDU to near KFAY at
18Z. Winds behind the front will be northwest to northerly at 6 to
9kts with a light southwest wind ahead of the front. The front
will move slowly east and southeast tonight allowing winds across
most/all of central NC to become light northerly with a trend
toward northeasterly overnight.
Looking further ahead... Generally VFR conditions are expected for
Monday and Tuesday with a small threat of some isolated to scattered
afternoon and evening convection across the south and southeast
including KFAY. Another cold front will cross the region
Wednesday night with just a small threat of showers. Fair weather
is expected behind the front for Thursday into Friday.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...BLAES
NEAR TERM...BLAES
SHORT TERM...BLAES
LONG TERM...RE
AVIATION...BLAES