Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/13/16
Area Forecast Discussion
National Weather Service La Crosse WI
814 PM CDT MON SEP 12 2016
...Evening Forecast Update....
.UPDATE...Late this evening into the overnight.
Issued at 814 PM CDT Mon Sep 12 2016
Forecast updated to delay the onset of numerous showers and
isolated thunderstorms. Currently watching a cold front meander
southeast across the region this evening. Meanwhile...a shortwave
was working across eastern Nebraska/Kansans lifting northeast
toward the Upper Mississippi River Valley. There remains a fair
amount of MUCAPE to work with across the forecast area for
showers and thunderstorms but the RAP holds the cap through
around 6Z...then as the shortwave moves in, convection goes with
parcel being lifted from 775 mb. A look at the 109Z composite
radar across Iowa, starting to see the convection go in these
areas. Will continue to monitor trends closely this evening.
Cannot rule out a strong storm or two given the CAPE profiles.
Thinking isolated large hail would be the main hazard along with
frequent lightning.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 303 PM CDT Mon Sep 12 2016
Water vapor satellite this afternoon showed a short wave trough
over eastern Colorado that was moving to the northeast. At the
surface, a cold front extended from northern Minnesota into
western Kansas. As these two features move east through Tuesday,
they will combine to provide the next chance of rain to the
region.
The short wave trough will continue to move northeast and is
expected to pass over the area late tonight through Tuesday
morning. The 12.12Z GFS looks to be a little bit stronger with the
wave and produces some moderate pv advection in the 500-300 mb
layer tonight ahead of the wave. As the front slides through, both
the GFS and 12.12Z NAM show a band of weak, to at times moderate,
frontogenesis in the 1000-700 mb layer. The warm air advection
ahead of the wave looks to be strong enough to produce 1 to 2
ubar/s of up glide on the 305K isentropic surface. The low level
moisture transport does not look all that strong and primarily
through the area until late tonight when a split in this flow
develops with part of the flow briefly becoming focused on the
southern sections of the forecast area. Expecting to see a broken
line of mainly showers work across the area with the passage of
the front and will continue to show a band of 60-80 percent rain
chances along the front. The instability with this system looks to
be rather limited with maybe up to 1500 J/Kg of MU CAPE to work
with this evening and then dropping back to 500 J/Kg or less after
midnight. Plan to carry showers with scattered storms this evening
and then drop back to isolated storms after midnight. Once the
front clears the area Tuesday morning it looks to remain just
close to the area to keep some lingering rain chances across the
far eastern and southern sections.
High pressure with cooler and drier air then settles in over the
Upper Midwest for Tuesday night into Wednesday night. Lows both
nights will dip into the 40s to lower 50s. Some potential for it
to be even cooler Wednesday night over portions of central
Wisconsin with clear skies and light winds. For now, will go with
some lower 40s but upper 30s not out of the question.
.LONG TERM...(Thursday through Monday)
Issued at 303 PM CDT Mon Sep 12 2016
The high pressure will move off into the Ohio River ahead of the
next incoming system. The upper level low currently over the
central Rockies will be lifting northeast into the High Plains and
then tracking east across the Upper Midwest from Thursday night
into Saturday. An area of low pressure is expected to pass by
north of the area with this system as it pushes a cold front
across the region. Will carry some 60 to 70 percent rain chances
late Thursday night into Friday and then have some linger 20 to 40
percent chances into Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 636 PM CDT Mon Sep 12 2016
Showers and isolated thunderstorms will move across the TAF sites
late this evening into Tuesday morning with MVFR to IFR conditions
possible. Ceilings look to lower mainly into the MVFR range at
1500 to 2500 ft but will lower further late tonight as steadier
rains set in. Plan on the lowest ceilings falling to around 800
ft. Conditions will improve to MVFR by mid to late morning Tuesday
as the front exits to the east.
&&
.ARX Watches/Warnings/Advisories...
WI...None.
MN...None.
IA...None.
&&
$$
UPDATE...WETENKAMP
SHORT TERM...04
LONG TERM...04
AVIATION...WETENKAMP
Area Forecast Discussion
National Weather Service Bismarck ND
946 PM CDT Mon Sep 12 2016
.UPDATE...
Issued at 943 PM CDT Mon Sep 12 2016
Expecting a cool night despite the widespread strato-cumulus cloud
deck that persists through much of western North Dakota and
southern Canada. Current satellite loops suggest some clearing
after midnight northwest and this should allow temperatures to
fall. Current forecast ok.
UPDATE Issued at 645 PM CDT Mon Sep 12 2016
Current forecast has low temperatures at or below 32 far
northwest with mid 30s immediately surrounding this area. Current
cloud forecast seems a bit optimistic in clearing clouds since
there is a large area of strato-cumulus across northwest North
Dakota and upstream into southern Canada. Meanwhile mid/high level
clouds continue to stream across southern portions of North
Dakota this evening.
Believe the clouds north will eventually dissipate although the
GFS and NAM continue to show low level cold advection which may
tend to hold clouds in a bit longer tonight..possibly past
midnight. However current temperatures are already in the
lower/mid 40s across southern Saskatchewan so not too much of a
stretch to get 10 degree diurnal fall by morning. Will leave the
advisories in place and not expand them. Otherwise remainder of
the forecast looks ok.
&&
.SHORT TERM...(Today through Wednesday)
Issued at 323 PM CDT Mon Sep 12 2016
Forecast highlights in the short term period will be frost and
freeze headlines for tonight west, possibly needed again for
Wednesday morning north central.
Currently, west-southwest/cyclonic flow aloft as a long wave
trough moves slowly east across the region. At the surface, strong
high pressure centered over far southeast Alberta/southwest
Saskatchewan moving slowly east-southeast into the Northern High
Plains. Embedded energy and cold temperatures aloft contributing
to extensive cloud cover across the Northern Plains, with a few
breaks here and there.
Will maintain frost/freeze headlines as is with this forecast
issuance for northwest and west central ND late tonight into
Tuesday morning. High res models remain in agreement with upper
20s to low 30s far northwest (Williams/Divide) where the center of
the sfc high will be located at 12Z. This should allow
temperatures there to drop fairly rapidly as winds taper off and
the sky clears. Sfc Tds 28-32F shown over all of western ND and
into the north central by both the RAP and HRRR, with frost a
concern for all but the southwest then east into central areas of
the state where cloud cover and/or wind should keep temps above
35F.
High pressure moves over the entire state for Tuesday. Beautiful
fall-like day with a sunny sky, light winds, and temperatures
extremely comfortable in the mid to upper 50s.
For Tuesday night, guidance indicates mid 30s over far north
central ND into the Turtle Mountains. Possible we may need
frost/freeze headlines there but will have to see how Tds pan out
in addition to winds which may be a bit stronger Wed morning with
southerly return flow increasing across the Dakotas. Wednesday
remains dry with temperatures moderating into the mid 60s and
lower 70s.
.LONG TERM...(Wednesday night through Monday)
Issued at 323 PM CDT Mon Sep 12 2016
An ejecting upper level low from the Intermountain West will
shift northeast toward ND beginning Wednesday night, lifting
through the region Thursday night. This feature will bring
increasing chances for showers and thunderstorms into Friday.
Narrow band of instability with MUCAPE forecast in the 1500-2500
J/kg range Thursday into Thursday evening with 0-6km shear
25-35KTs along with plenty of forcing mechanisms with the
approach of the upper low and an associated surface trough over
the central Dakotas. Appears to be a fairly decent setup for
strong thunderstorms Thursday aft/eve and will be interesting to
see what outlook SPC puts the region in with their Day 3 update
later tonight.
Upper level ridging for the weekend with warming and drying
conditions. Highs this weekend will fall in the 70s to near 80.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 645 PM CDT Mon Sep 12 2016
For the 00Z TAF cool air with widespread low VFR ceilings around
4 thousand AGL will gradually diminish and become scattered KISN-
KMOT-KDIK-KBIS after 03z. Then VFR through the TAF period with
scattered to broken clouds at or above 7 thousand AGL.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 9 AM CDT /8 AM MDT/ Tuesday for NDZ002-010-
017-018-031>033.
Freeze Warning until 9 AM CDT Tuesday for NDZ001-009.
&&
$$
UPDATE...WAA
SHORT TERM...NH
LONG TERM...NH
AVIATION...WAA
Area Forecast Discussion
National Weather Service Charleston SC
1003 PM EDT Mon Sep 12 2016
.SYNOPSIS...
A weakening cold front across the area will dissipate tonight. An
area of low pressure will move into northern Florida on Tuesday
and linger through mid to late week. A cold front could approach
from the north late Thursday into Friday, before stalling over or
just north of the area this weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
The last of the diurnally induced convection west of Claxton will
fade prior to midnight, while the attention then shifts to the
Atlantic and coastal sections. Of note is an enhanced region of
convection in association with a tropical wave that is lifting NW
from near the northern Bahamas to the east-central parts of FL.
There will be an increase in low level convergence from off the
ocean now that the adjacent land areas have been cooled due to
widespread earlier convection and nocturnal influences. There is
plenty of deeper moisture to work with, as PWat is shown be near
120-135% of normal. That along with the coastal trough north of
the tropical wave sharpening even further, as nearshore winds
have backed around to the N-NE, and increasing isentropic ascent
will suggest that convective rain chances will start to climb
again from the E overnight. We have a solid 30-40% chance E of
US-17, but even though convergence slackens further inland, we
still have 20% elsewhere given the continuation of isentropic
upglide. It`s very possible that a few locations south of Beaufort
to Sapelo could experience a better risk for showers/t-storms, but
given that the HRRR is not showing too much activity we are
hesitant to go as such.
Average QPF will be less than 1/4 inch through the night, but
where persistent bands settle in there certainly could be rainfall
rates as much as 1-1.5 inches per hour. High tide doesn`t occur
until 5-6 am, and it is by far the lower of the 2 high tides
Tuesday. But this still could be a problem if heavy rains are
ongoing at and/or near that time. Stay posted.
Given rain-cooling from the convection Monday afternoon and
evening, we`re already down at or near our lows in many areas
tonight. Expect 70-73 far inland, mid or upper 70s on the beaches.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
An area of low pressure over the northern Bahamas will slowly
drift west northwest into northern Florida on Tuesday, then lift
north and linger over southern Georgia into Wednesday. Deep
southeast flow between the surface high to the north and the low
pressure approaching from the south will result in a steady stream
of Atlantic moisture advecting into the area. Precipitable Water
values will hover near 2" on Tuesday, gradually rising to as much
as 2.3" by Wednesday afternoon. Scattered showers and
thunderstorms are expected on Tuesday, especially in the afternoon
as the sea breeze provides additional forcing. Later Tuesday night
into Wednesday we expect numerous showers and thunderstorms as the
low moves closer, upper level divergence increases, and PWs reach
their maxima. Though heavy rainfall will be possible with any
convection, there is perhaps a better chance for localized
flooding from the activity late Tuesday night into Wednesday due
to better forcing and expected greater coverage.
Extensive cloud cover and cooler onshore flow will limit high
temps Tuesday to the mid 80s inland with mainly lower 80s on
Wednesday.
Thursday, the weak low pressure is expected to dissipate and/or
move east away from the area while the upper ridge rebuilds.
However, a weak residual surface boundary may linger across the
area, which combined with continued deep moisture will support
scattered daytime showers/storms.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Latest guidance indicates an even weaker signal in regards to a
wedge type pattern developing east of the Appalachian Mountains
during late week. However, a cold front should approach the
Carolinas from the north Thursday into Friday with a slightly cooler
airmass within a northeast flow regime. However, the latest trend
indicates the front will have a tough time making it into the
forecast area late week, likely stalling just north of the area
through Saturday. Given this scenario, deep moisture characterized
by PWATS above 2.0 inches should remain over much of the
Southeast, supporting chances of showers and thunderstorms during
peak heating Thursday and potentially into Friday. A large
mid/upper lvl ridge of high pressure is then expected to develop
over much of the Southeast and Deep South this weekend, somewhat
suppressing greater coverage of precip and allowing temps to warm
a few degrees. In general, afternoon highs are expected to reach
the mid 80s on Friday, then warm into the mid/upper 80s over the
weekend. A could front could approach from the northwest early
next week, promoting additional showers and thunderstorms, mainly
over inland areas.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
It looks to remain VFR at KCHS through tonight and mostly VFR at
KSAV. But conditions will deteriorate late tonight and Tuesday as
considerable moisture arrives from off the Atlantic in response to
a tropical wave moving over northern FL and high pressure to the
north. This will result in an increasing chance of SHRA and
possible TSRA throughout the day. Until radar trends are better
defined we have no more than low-end VFR conditions at both
airfields. However, any direct impact from convection will result
in flight restrictions along with gusty E-NE winds.
Extended Aviation Outlook: Flight restrictions will be possible,
mainly resulting from scattered to numerous showers/storms. The
greatest coverage is expected Tuesday night into Wednesday.
&&
.MARINE...
Tonight: A tropical wave/weak area of low pressure is expected to
move northwest from the Bahamas into east-central FL with a trough
extending northward near the GA/SC coasts. NE and E winds will
increase a bit, but mostly stay around 15 kt or less. Seas will
build slightly up to 3 ft, mainly over the GA waters. Mariners
should be prepared for an increase in both the coverage and
strength to storms overnight, some of which will produce gusty
winds, heavy rains reducing visibility and frequent lightning
strikes.
Tuesday through Saturday: A tighter gradient is expected Tuesday
into Tuesday night as low pressure over northern Florida interacts
with high pressure to the north. Sustained winds of 15-20 kt
possible Tuesday with some gusts approaching 25 kt over the GA
waters. Seas may briefly top 5 ft mainly due to short-period wind
waves. Southeast winds become more southerly late in the week with
speeds remaining well below advisory levels.
Rip Currents: An elevated risk is possible Wednesday into Friday
due to some longer period southeast swell making its way to the
coast. We also expect modest onshore winds and an increased tidal
range due to the approaching full moon.
&&
.TIDES/COASTAL FLOODING...
Shallow coastal flooding is possible late this week into the
weekend along the SC coast due to the full moon. A lot will depend
on wind directions as we will need a few tenths of a foot of surge
above the astronomical factor to reach 7.0 ft MLLW.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...JRL
LONG TERM...DPB
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Quad Cities IA IL
952 PM CDT MON SEP 12 2016
.UPDATE...
Issued at 941 PM CDT Mon Sep 12 2016
Good post-frontal rises support latest trends of hi-res models
showing cold front arriving northwest cwa around daybreak.
This may have implications on Tuesday highs with portions of
northeast Iowa potentially a few degrees cooler depending on
extent and duration of lower clouds. Upper wave ejecting
northeast from Nebraska along with pooling of moisture at 850
suggest bulk of rain to our west and northwest overnight, with
chances arriving early morning west of Dubuque to Washington axis.
Have slowed arrival of clouds a bit, although with continued
southerly winds this shouldn`t have too much impact on lows and
still expecting fairly widespread lower 60s with some upper 50s
possible eastern cwa.
&&
.SYNOPSIS...
Issued at 255 PM CDT Mon Sep 12 2016
High pressure remains entrenched across the area this afternoon
as deep diurnal mixing lead to highs in the low to mid 80s and
winds gusting to around 25 knots in some places. This will
continue for the next couple of hours before the flow turns
southwest and additional moisture pools into the area ahead of a
cold front that will serve as the main weather producer in the
short term.
&&
.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 255 PM CDT Mon Sep 12 2016
Main forecast concern are the chances for showers and
thunderstorms with the cold frontal passage tomorrow across the
area. Guidance has continued slowing the progression of the front
as previous shifts have noted.
H5 leading wave is expected to pass mainly north of the CWA
tonight. The best chances for rain and even isolated thunderstorms
will be with this wave across the north. Far NW zones will see
likely showers with possibly embedded thunder. The HRRR is the
most aggressive in terms of convection breaking out in close
vicinity of the H5 wave. Do not think that this will affect the
area and will likely stay north. Some of the hires guidance
suggests that the precip will weaken near sunrise and actually
miss most the area. H85 jet weakens during this time as well, so
it is likely that the chances for rain will diminish across the
area.
Later development of showers looks possible across the area on
Tuesday with the fropa. ARW and NMM core CAMs have some light
showers across the area near 21z tomorrow. At this time have
maintained current chc pops for Tuesday. Overall threat for
thunderstorms will be low, so isolated T will be maintained.
.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 255 PM CDT Mon Sep 12 2016
The rain with embedded thunderstorms will slowly end from northwest
to southeast Tuesday night as the front pushes south of the area.
The better rain chances appear to be across the southern half of the
area where the better forcing exists.
On Wednesday, lingering showers will end during the morning across
the south third of the area. Temperatures are expected to average
below normal due to the clouds.
Quiet and dry conditions will be seen across the area Wednesday
night as high pressure moves through the Midwest.
Clouds will be on the increase Thursday as the high moves into the
eastern Great Lakes and moisture moves back north. Most of the area
will remain dry Thursday with the exception of the far west and
southwest areas during the afternoon.
Thursday night on...
Thursday night moisture moves back into the area. The first of
several upper level disturbances will move into the area allowing
rain with embedded thunderstorms to develop from west to east. Based
on moisture flow and forcing, the better rain chances look to be
across the western half of the area.
Friday/Friday night another upper level disturbance moves through
the area. Rain with embedded thunderstorms should be fairly
widespread on Friday with rain slowly ending from west to east
Friday night.
Starting Saturday disagreements among the models develop. Some
models indicate a third upper level disturbance will move through
the area on the heels of the second disturbance helping to prolong
the rain. Other solutions start pushing a new high pressure into the
area with dry conditions. As a result, the model consensus has
slight chance to chance pops Saturday with the higher pops over the
northeast half of the area.
Saturday night there may or may not be lingering showers over the
northeast third of the area. Everything depends upon how quickly the
upper level disturbance exits the area.
On Sunday there is a weak upper level disturbance moving through in
the flow aloft. Moisture availability is questionable but some
isolated showers/sprinkles may develop during the afternoon east of
the Mississippi and north of I-80.
Sunday night/Monday the model consensus has dry conditions for the
area as another high pressure builds into the Midwest.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
ISSUED AT 640 PM CDT Mon Sep 12 2016
A cold front will sag through the terminals on Tuesday and accompanied by
scattered showers, which have been handled with VCSH wording for now.
A few thunderstorms are also possible. Flight conditions with the frontal
passage are likely to become MVFR for mainly cigs and possibly visibility at
times in any precipitation, with potential for IFR conditions especially at
the northern TAF sites.
&&
.DVN Watches/Warnings/Advisories...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
UPDATE...McClure
SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...08
AVIATION...McClure
Area Forecast Discussion
National Weather Service Grand Forks ND
950 PM CDT MON SEP 12 2016
.UPDATE...
Issued at 950 PM CDT Mon Sep 12 2016
Upper level trough extended from northern MAN to northern CA. Upper
level trough over Canada expected to shear off to the east and begin
a split flow pattern over North America tonight and Tue. Canadian
upper trough will move across the area Tue. Precipitable water
around an inch in the southeast zones this evening. Lower
precipitable water will move in from the northwest overnight.
Tweaked pops for overnight to match current radar trends with
sprinkles/very light showers south and southeast. No change to low
temp.
UPDATE Issued at 659 PM CDT Mon Sep 12 2016
Water vapor loop indicated an upper level short wave was located
over southern UT. Another upper level trough was over the southern
MAN/SASK border.
Model soundings indicate cold air has moved in below the 800-850 hpa
layer in a backed flow and with an inversion at the top of the
layer. Tweaked winds down a bit for tonight. Radar indicated light
showers from southeast ND to Beltrami county MN. Precip was not
reaching the ground.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 318 PM CDT Mon Sep 12 2016
Cloud cover and temperatures will be the main forecast challenges
for the period.
A few streaks of clearing have developed from southwest to
northeast across the CWA, but plenty of cloud cover over the
region and upstream. The upper level flow becomes more split
tonight with the northern branch shortwave moving into the
Dakotas. RAP has high RH in the 925-850mb layer throughout the
night. A few of the models even have some light rain in the
northeastern counties late tonight as a reinforcing cool front
comes down out of Canada. Not overly excited about showers but
included an isolated mention near BDE during the early morning
hours. Winds will be diminishing after sunset but with the surface
high centered out over western ND we will at least have some
northerly flow continuing overnight. This, along with lingering
clouds and dewpoints in the 40s, should keep us from getting too
cold tonight. Will continue to keep lows mainly in the low to mid
40s although the usual cool spots of the far northwest near
Langdon and near Fosston could see lows dipping into the upper
30s.
Surface high pressure will be centered over the Red River Valley
during the day on Tuesday. There should be some clearing late in
the day but with clouds early and 850mb temps getting close to the
zero C mark, temps will not rise too much during the day.
Have highs mainly in the 50s although the southern Red River
Valley could see some 60s.
.LONG TERM...(Tuesday night through Monday)
Issued at 318 PM CDT Mon Sep 12 2016
First challenge in the long term will be just how cold to go Tuesday
night and the associated frost potential. Surface high pressure will
be centered right over the Red River Valley to start the period and
slowly propagate towards central Minnesota. Skies will quickly clear
from west to east allowing temperatures to drop to the lowest
readings thus far this season. The latest model runs are in very
good agreement with 850 mb temperatures dropping into the lower
single digits. The good news is that the main push of cold advection
begins to die down closer to Wednesday morning. This should
hopefully keep temperatures in the upper 30s but a few sites dipping
a bit lower with the potential for frost is not out of the question.
High pressure will keep conditions dry through Wednesday night with
high temperatures remaining below normal (mid to upper 60s). With
modest southerly winds and clouds moving in, Wednesday night will be
much milder than the previous night with readings around the 50
degree mark.
Next forecast challenge will be the return of precipitation chances
for the second half of the week. As the high finally moves off
towards the lower Great Lakes, an upper low will move through the
northern Rockies and towards the Dakotas. Several impulses will
swing through the forecast area with this feature allowing
precipitation chances to linger to end the work week. Weak upper
level ridging will then return which should provide for a decent
fall weekend with highs back into the 70s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 659 PM CDT Mon Sep 12 2016
VFR conditions were across the area with cigs aoa 33 hundred ft. The
lower vfr cigs were mainly over the northern Red River Valley.
Expect clouds deck to shift south overnight especially on the MN
side. Some MVFR to IFR conditions may be possible around the BJI
area by morning.
&&
.FGF Watches/Warnings/Advisories...
ND...None.
MN...None.
&&
$$
UPDATE...Hoppes
SHORT TERM...JR
LONG TERM...Lee
AVIATION...Hoppes
Area Forecast Discussion
National Weather Service Green Bay WI
1030 PM CDT MON SEP 12 2016
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Tuesday
Issued at 226 PM CDT Mon Sep 12 2016
The latest RAP analysis and satellite/radar imagery show the central
and eastern parts of Wisconsin located between high pressure
centered over the east coast and a cold front moving across
Minnesota. Mostly clear conditions are prevailing ahead of the
front thanks to very dry mid-level air as depicted on 12z area
soundings. The front is also largely inactive, except for some
shower activity over northern Minnesota, and some scattered storms
moving across southeast South Dakota. Some storms may fire along
the front later this afternoon, but there is considerable inhibition
and any storms should remain upstream of the region prior to 7 pm
anyhow. As the the front moves across the forecast area,
precipitation timing and coverage are the main forecast concerns.
Tonight...The cold front will slowly move east across western WI
during the evening and far northeast/central WI overnight. The 12z
models have again slowed down the front slightly. With upper level
support arriving from the southwest via a weak shortwave and
increasing pwats to around 1.5 inches, should see precipitation
gradually become more widespread through the night. Though chances
of thunderstorms will be present along the front, appears the best
chances will occur late in the evening and early overnight over
central and north-central WI. ML capes of 500-700 j/kg, MU capes
over 1000 j/kg, and steep mid-level lapse rates suggest that
isolated strong storms will be possible, but the threat of severe
storms is low. As instability diminishes overnight, should only see
an isolated thunderstorm even with better forcing arriving. Temps
should remain mild in the evening due to the southerly winds, and
then fall into the mid 50s to low 60s as the rain arrives late.
Tuesday...The front will continue to pass across central and
northeast WI during the morning before exiting. With shortwave
energy still passing overhead and ample mid-level fgen just behind
the front, should see widespread rain showers continue for much of
the morning before they exit east during the afternoon. Some
clearing may try to work into central WI by late in the afternoon,
but expecting a mostly cloudy or cloudy day to prevail. Temps
cooling down into the low 60s north to near 70 southeast.
.LONG TERM...Tuesday Night Through Monday
Issued at 226 PM CDT Mon Sep 12 2016
Primary weather systems during this period will be a departing
upper trough Tuesday night, and then remnants of the western
states upper trough with frontal system lifting over the area
late in the week and into this weekend.
Trends with the departure timing of the upper trough Tuesday
night continues to be slower along with the RRQ region of the
upper jet passing through. The surface front is progged to be well
southeast of the area by Tuesday night, but the mentioned
dynamics may continue to support light shower activity well into
tuesday night while the 850 baroclinic zone drops south.
Eventually drier boundary level will end any lingering shower
activity.
Surface high pressure and an upper level ridge drifts over the
area Wednesday into Thursday for a dry forecast with cooler than
normal temperatures for Wednesday. Mesoscale Lake Michigan clouds
may become an issue while the high pressure system is drifting
over. Onshore flow combined with some marginal lake induced cape
due to cool boundary layer temperatures over the lake may produce
more clouds. An isolated shower is also possible. Will increase
cloud coverage a little toward the lakeshore as forecast soundings
showing a saturated layer around 1500 feet.
Cool temperatures may produce some overnight lows in the 30s,
especially over the climatological cool spots over the north.
Next chance of precipitation arrives Friday with the next short
wave trough and frontal system. Progs have been fairly consistent
with the timing from Friday into Saturday. Warm air return may
attempt to spread showers and storms back into the western half of
the state late Thursday night.
After a cool start Wednesday, temperatures overall near normal.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1029 PM CDT Mon Sep 12 2016
Incoming cloud deck has broken apart a bit, but should fill back
in during the night as the front nears the area. Ceilings will
eventually lower once showers become more prelavent across the
area. Still suspect guidance visibilities and ceilings are a
little too low, so will continue with slightly higher values in
the TAFs.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement until 1 AM CDT Tuesday FOR WIZ022-040-
050.
&&
$$
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1011 PM CDT Mon Sep 12 2016
.UPDATE...
Quick forecast update to increase PoPs (20 to 30 percent) across
the coastal waters for the remainder of the night and pull the
mention of isolated showers and thunderstorms farther north
towards the Highway 59 corridor. Outflow from thunderstorms
earlier this evening over south central Louisiana continues to
push eastward, with scattered showers and thunderstorms developing
along this feature per KHGX/KLCH radar imagery. Expect this
boundary to move into the Upper Texas Coastal waters before
midnight, with additional development expected across the coastal
waters and along the coast overnight as deeper moisture associated
with a weak tropical wave over the central Gulf arrives. Also
updated temperatures and dewpoints based on latest observations,
with overnight lows expected to fall into the 70s under partly to
mostly cloudy skies.
Huffman
&&
.PREV DISCUSSION... /ISSUED /
AVIATION...
Shra/tsra will dissipate with the loss of daytime heating and
skies are expected to clear. Clouds may begin to redevelop after
09z as fcst soundings show saturation increasing between 2000-3000
feet. The RAP continues to advertise showers developing after 09z
near coastal TAF sites and will maintain a VCSH for KHOU/KSGR and
southward to the coast. Confidence in this scenario is low.
Daytime heating on Tuesday should allow for additional shra/tsra
during the aftn with VFR cigs near 5000 feet. Winds should remain
light and generally E-SE. 43
PREV DISCUSSION... /ISSUED /
DISCUSSION...
Activity beginning to percolate across SE TX this afternoon generally
along and south of I-10. These storms should dissipate at to just
after sunset with the loss of daytime heating. Otherwise, not a
lot of changes with the forecast going forward with the return of
a seemingly familiar wet pattern for the rest of the week.
Models continuing to build the upper ridge over the SE U.S. these
next few days as an upper low develops and deepens out west and
moves across the central Rockies. This resulting pattern is
expected to deepen/strengthen the onshore flow over SE TX during
this period. This in turn will help to draw much deeper moisture
into the area from the Gulf (likely associated with the weak
system in/near the FL straits). Progged PWs of 2-2.3" along with
daytime heating and the seabreeze should produce decent coverage
for our CWA from Wed into the weekend. Will have to keep an eye on
storms for Thur/Fri as PWs peak and locally heavy rains could be
possible. Long-range guidance with these runs are not very
consistent for next week... one has a ridge atop the region while
the other is trying to draw a trof/shear axis in from the west. 41
MARINE...
Unsettled weather should continue over the Gulf waters for most of
this week, with showers and thunderstorms possible each day.
Persistent east to southeast winds are expected throughout the week,
and the pressure gradient could be tight enough to allow the winds
to reach near caution thresholds at times in the next couple of days
before relaxing for the rest of the week into the weekend. Some 3-4
foot seas may be expected in the middle of the week, with smaller
waves forecast otherwise.
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 72 91 74 92 74 / 10 30 20 30 20
Houston (IAH) 74 89 74 90 76 / 20 30 20 40 30
Galveston (GLS) 80 85 81 85 80 / 20 30 30 50 30
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
Discussion...14
Area Forecast Discussion
National Weather Service Miami FL
805 PM EDT MON SEP 12 2016
.AVIATION...
Scattered showers are expected to continue overnight across the
east coast, with an increase in coverage Tuesday. For now, will
handle with VCSH becoming VCSH by Tuesday afternoon, but will
likely need TEMPO groups as confidence in timing increases.
Generally, VFR conditions prevail but periods of VSBY/CIG
restrictions quite possible as tropical disturbance approaches the
northeastern portions of the area.
Winds will be light and east tonight then increase out of the
southeast to 10 knots or so Tuesday.
&&
.UPDATE...
Scattered showers and an isolated thunderstorm or two continue
this evening over South Florida. Tropical disturbance appears to
be centered just west of northwestern-most Bahamas, and will move
west and northwest overnight and approach the Palm Beach or Martin
county coastline early Tuesday. Guidance depicts most of the
convection associated with it will remain on the east side, thus
remaining mainly offshore. Have adjusted POPs accordingly.
&&
.PREV DISCUSSION... /issued 527 PM EDT MON SEP 12 2016/
DISCUSSION...
A broad surface trough across the northwest Bahamas continues to have active
convection and still lacks a surface circulation this afternoon.
Recent observations indicate widespread cloudiness and isolated to scattered
thunderstorms across most of the Bahamas chain.
Forecast for tonight...
The global models, the HRRR model and the short range ensemble
model all indicate a broad surface trough across the Palm Beach
county Atlantic waters generally after midnight. An ASCAT pass
earlier today indicated winds across the northeastern periphery
around 20 to 25 knots. The latest short range ensemble model
indicates that there is a chance of winds greater than 25 knots on
the northeastern side but does not indicate any potential for
winds greater than 34 knots. Chances of tropical development
remain low but consult and closely monitor the products from the
National Hurricane Center for any potential for tropical
development. As the trough tracks northwest the strongest winds
should stay to the northeast of the Atlantic waters of South
Florida. So the wind forecast indicates winds in the 15 to 20 knot
range mainly across the off shore Atlantic waters early this
evening and over night. However chances of showers and
thunderstorms are forecast to increase steadily through the early
evening hours and over night as the trough approaches Palm Beach
and Martin counties over night. During this period the most
widespread showers and scattered thunderstorms are expected across
the Atlantic waters east of Palm Beach county, but showers and
thunderstorms will radiate outward from the trough and could
impact the Atlantic coast metro areas over night. While deep
tropical moisture will increase tonight and the potential for
heavy rain will increase, the guidance trends indicate that the
trough will move steadily northwest with showers also moving
steadily in bands, For that reason a flood watch is not being
considered at this time. However, with additional guidance and
radar trends later this evening and over night a watch may be
considered later if need be.
Forecast for Tuesday and Wednesday...
The surface trough is forecast to track northwest over the next
couple of days with a continuous influx of deep moisture and cloudiness
region wide with a chance of showers and thunderstorms. On Tuesday
the trough is forecast to be in central Florida, with surface and
low level southerly flow bringing additional tropical moisture
with widespread showers and scattered thunderstorms possible on
Tuesday. The trough is forecast to be in north Florida Wednesday
but southerly flow and residual moisture will likely linger with a
chance of showers and thunderstorms.
Forecast for late this week...
The global models indicate some relatively drier air moving into
the region across the Bahamas Thursday into Friday but
southeasterly flow and residual moisture should allow for
diurnally driven showers and thunderstorms late in the week.
MARINE...
As the broad surface trough tracks northwest the strongest winds
should stay to the northeast of the Atlantic waters of South
Florida. However, uncertainties will continue for the marine
forecast over the next couple of days, but more likely for the
Atlantic waters, especially east of Palm Beach county tonight into
Tuesday. As mentioned in the discussion above, the wind forecast
indicates winds in the 15 to 20 knot range mainly across the off
shore Atlantic waters early this evening and over night. However,
a short fused Small Craft advisory may be necessary later this
evening or over night for these waters if the winds are under
forecast.
By mid-week east to southeast winds around 10 knots are forecast
into the upcoming weekend with seas 2 feet or less through this
period.
BEACH FORECAST...
A slight risk of rip currents is expected across the Gulf coast
beaches through mid-week. Will maintain a moderate risk of rip
currents for tonight through Tuesday for the Atlantic beaches.
However, given the uncertainties with the passage of the trough
tonight through Tuesday, there could be periods for a high risk of
rip currents mainly across Palm Beach county beaches. By mid-week
the Atlantic coast beaches are forecast to have a slight risk.
&&
.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach 77 89 77 89 / 40 70 50 40
Fort Lauderdale 77 89 78 89 / 40 60 40 40
Miami 76 89 78 89 / 40 70 40 40
Naples 77 90 76 90 / 40 70 40 60
&&
.MFL Watches/Warnings/Advisories...
FL...None.
AM...None.
GM...None.
&&
$$
DISCUSSION...60/BD
MARINE...60/BD
AVIATION...23/SK
UPDATE...23/SK
BEACH FORECAST...60/BD
Area Forecast Discussion
National Weather Service Melbourne FL
948 PM EDT MON SEP 12 2016
.UPDATE...
...Locally heavy rainfall into mid week as a tropical wave or weak
tropical low lifts north across the area...
Tonight...The models continue to show a weak low pressure center
forming near the west end of Grand Bahama Island, along an advancing
tropical wave, and move it to the northwest. A few bands of showers
with isolated lightning storms have been pushing into the coast this
evening. A more concentrated area of convection was occurring near
the developing low, over/south of Grand Bahama Island, with recent
satellite imagery showing cooling cloud tops. As the models lift the
low northwest, little strengthening is shown as it reaches the
Brevard coast towards sunrise.
Expect numerous showers and isolated storms ahead of the low to
spread onshore from Cape Canaveral southward and start to affect
areas farther north later in the night. The steady northward
movement of the system should somewhat limit rainfall totals, though
the HRRR model has been suggesting local amounts 3-4 inches.
Overall soil moisture conditions and retention pond levels have been
a bit lower than normal, especially in Volusia county, where the
models have been painting the highest precip amounts. Therefore,
have chosen not to issue a Flood Watch, though if the low
slows/strengthens, one may become necessary for a part of the area
into mid week.
(Previous Discussion)
Tuesday...GFS/NAM move weak low pressure NW which will allow all of
east central FL to be enveloped by an area deep tropical moisture
with PWATs progd to 2.2 to 2.5 inches over most of the area. GFS/NAM
both pinpoint max QPF area from Volusia county into the interior
where widespread 1-2 inches rain amounts are likely with isolated
max amounts to 3-4 inches where any persistent banding sets up with
moist SE inflow to the east of any weak low pressure center. A Flood
Watch may be considered pending future model runs and evolution of
the tropical wave as it moves closer to the east coast. The main
concern continues to be locally heavy rain. Coordinated with WPC to
include portions of east central FL on upcoming Day2 Excessive
Rainfall Outlook. POPs will be categorical around 80 percent with
cloudy/mostly cloudy skies and highs in the mid to upper 80s.
Wed-Thu...Very moist airmass will linger across CWA in the wake of
the tropical disturbance. Surface high pressure ridge well to the
north will promote long fetch of light easterly gradient. As Mid-
level anticyclone builds northeast of the NW Bahamas with ridge axis
extending across CWA, southerly steering flow will generally be
favored...trending a bit more SE across southern CWA and SW across
northern CWA. Period of enhanced cloud cover will persist, along
with above normal rain chances, becoming more diurnally driven with
time. Trended POPs toward highest north/lowest south given most
likely moisture profiles. Temps fairly close to normal for mid Sept.
Fri-Sun...Return to more typical late summer convective pattern as
moisture pools lessens. Surface ridge axis to the north slowly drops
south...toward northern CWA by late weekend. Daytime POPs respond by
lowering to 30/40 percent by the weekend, with greatest coverage
over coastal counties during the morning/mid day and afternoon
inland...lingering into early evening over far interior.
Near climo temps.
&&
.AVIATION...
Showers will increase over the Atlantic waters overnight and spread
into the coast. This will cause a few periods of IFR-MVFR at
coastal sites, through a little past sunrise KSUA-KMLB and from
about 06z until at least late morning north of there. Rainfall is
not expected to be as heavy for the interior terminals, but MVFR
should become prevailing by sunrise and persist into midday with
local IFR also possible.
&&
.MARINE...
Tonight-Tue...Model guidance continues to show weak low pressure
forming near Settlement Point and lifting northwest. An increasing
pressure gradient was already indicated over the southern waters, so
small craft advisory conditions will be developing and spreading
northward, mainly over the offshore waters. These hazardous boating
conditions will linger into Tuesday, especially over the northern
waters. Winds/seas will also produce poor conditions for small
craft operation near shore.
A high coverage of showers with isolated storms will also produce
adverse weather conditions. Some wind gusts to around 35 knots
are expected in these showers/storms.
Wed-Fri...Flow weakens to 10 kt or less. Long fetch of onshore
flow...albeit light...will keep seas a bit elevated...2-4 ft.
Coverage of showers/storms will less...but generally remaining
scattered.
&&
.MLB Watches/Warnings/Advisories...
FL...None.
AM...Small Craft Advisory from 8 PM this evening to 5 AM EDT Tuesday
for Sebastian Inlet to Jupiter Inlet 20-60 nm.
Small Craft Advisory from 11 PM this evening to 11 AM EDT
Tuesday for Volusia-Brevard County Line to Sebastian Inlet
20-60 nm.
Small Craft Advisory from 5 AM to 5 PM EDT Tuesday for Flagler
Beach to Volusia-Brevard County Line 20-60 nm.
&&
$$
FORECASTS...Lascody
IMPACT WEATHER/RADAR...Ulrich
Area Forecast Discussion
National Weather Service Marquette MI
735 PM EDT MON SEP 12 2016
.SHORT TERM...(This evening through Tuesday)
Issued at 400 PM EDT MON SEP 12 2016
Water vapor imagery and RAP analysis show a trof with a strong
positive tilt extending from Hudson Bay to the W Coast. Associated
sfc cold front runs from James Bay to sw MN. Front is almost to
western Lake Superior. Ahead of the front, dry/capped environment
per 12z soundings at KMPX/KGRB has prevented any pcpn development
ahead of the front so far. In fact, with the dry prefrontal
environment, there has been abundant sunshine today across the fcst
area, and temps have risen well into the 70s with some locations
reaching 80F. Regional radar imagery has shown very little pcpn in
the vcnty of the cold front so far, but in the last hr, shra/tsra
are beginning to develop along the front in ne MN.
With the approaching mid/upper level trof having a strong positive
tilt, the associated sfc cold front will be slow to move e and se
tonight. Front should reach far western Upper MI around mid evening
and not clear the se fcst area until around mid morning on Tue.
Given the dry/capped prefrontal environment, shra/tsra should be
confined mostly right along and behind the sfc cold front. As
moisture continues to increase in the vcnty of the cold front, sct
shra/tsra should expand slowly along/behind front tonight. Then, it
appears subtle shortwave aiding shra/tsra across portions of
KS/NE/SD will arrive late tonight/Tue morning. With the cold front
moving thru the s central/se fcst area at the time that this subtle
wave arrives very late tonight/Tue morning, an area of more
organized/heavier shra/tsra should spread across that area at that
time. Bulk of model guidance generally supports this scenario. So,
fcst will show a general trend for pops to increase gradually in the
vcnty of the front as it moves across the area, reaching categorical
s central and se. Mucape values are upwards of 1000j/kg or so ahead
of the front, and with deep layer shear 30-40kt, there could be some
strong to perhaps svr storms if any storms do manage to develop
ahead of the front.
The main area of shra should be out of the se fcst area by Tue aftn.
Although cold front continues to move se into Lower MI during the
day, models indicate a nw-se oriented sfc trof setting up, roughly
from just sw of Isle Royale into nw Upper MI in response to another
shortwave that will be moving over northern MN in the aftn. With
850mb temps falling to around 6C, combination of weak deep layer
forcing and low-level trof/convergence should support lake enhanced
shra development in the aftn. If a sharp sfc trof develops, setup
could support waterspout development with some of the shra. Max
temps Tue will be as much as 15-20F lower than today across the w
and n central where highs should be in the low/mid 60s. Temps may
rise close to 70F far s central/se.
.LONG TERM...(Tuesday night through Monday)
Issued at 438 PM EDT MON SEP 12 2016
Models suggest that a progressive pattern will continue to prevail
with the nrn Great Lakes mid/upper level trough sliding to nrn New
England Wednesday as another moves into the nrn Rockies. The trough
will then move to the Upper MS valley by Friday night and to Quebec
by Sunday as a ridge builds over the western Great Lakes.
Tuesday night, expect additional lake enhanced rain as a sfc trough
drops to the south through Upper Michigan. 850 mb temps to around 4C
combined with deep moisture and favorable low level conv along the
trough will support at least sct -shra through the nw half of the
cwa. There may be enough CAPE below 700 mb combined with low level
convergence near the trough for the potential of a few waterspouts
on Lake Superior.
Wednesday, there may be some leftover -shra over the west and north
central which, locations favored by ne low level flow. Otherwise,
lake moisture/clouds will slow any clearing as highs struggle to the
lower 60s north and mid 60s south.
Wednesday night and Thursday, high pressure building over the area
with good radiational cooling will allow temps to drop to the lower
end of guidance with mins in the lower 40s inland and around 50 near
the Great Lakes.
Friday into Saturday, the models, especially the ECMWF have trended
toward a faster and weaker trough moving through the region. With
lingering uncertainty with this feature, only chance pops for
showers were mentioned. There may be enough elevated instability for
isold tsra Friday night.
Sun-Mon, expect dry weather as mid level ridging moves in Sunday.
Although there are larger model differences by Monday, no pcpn is
expected as temps remain near or slightly above normal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 729 PM EDT MON SEP 12 2016
A cold front just west of IWD will slowly move across Upper MI
tonight. After it passes, cigs will fall to MVFR along with an
increasing potential of shra. While thunder is possible, potential is
too low right now more than a VCTS mention. At KIWD/KSAW, post
frontal winds will have a more pronounced upslope component along
with more substantial low-level moistening, and this should result in
cigs falling to IFR and perhaps even LIFR at IWD. During Tue morning
into early afternoon, conditions will remain MVFR at KCMX. At
KIWD/KSAW, conditions will gradually improve to higher end MVFR
perhaps briefly reaching VFR at IWD. &&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 400 PM EDT MON SEP 12 2016
Lingering s to sw winds of 20-30kt over eastern Lake Superior will
diminish this evening under weakening pres gradient just ahead of a
cold front that will move across Lake Superior tonight. With passage
of the front, winds will shift northerly, but probably not much
higher than around 20kt thru Tue. Arrival of high pres on Wed will
result in winds diminishing to under 15kt. Winds will become
southerly for Thu/Fri as the high shifts e. While winds should
remain blo 20kt, there may be a period of stronger winds depending
on how tight pres gradient becomes btwn the departing high and the
next approaching low pres. That low will move over the western Great
Lakes region on Sat.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...JLB
AVIATION...Voss
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Nashville TN
856 PM CDT MON SEP 12 2016
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Ill defined but it looks like a small trough or circulation on
RAP around 500 mbars to our south down through Alabama and
Georgia. Radar loop showing convection from northern Alabama
across north Georgia. Could see some convection work northward up
into the southeast half of the Mid State on Tuesday. Lows tonight
in the low to mid 60`s. Not expecting much in the way fog tonight
but there could be some around area lakes.
&&
.AVIATION...
00Z TAF DISCUSSION.
Other than a little mvfr fog in the late night good flying weather
for the next 24 hours as surface high and upper ridge dominate.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......01/Boyd
AVIATION........01/Boyd
Area Forecast Discussion
National Weather Service Phoenix AZ
900 PM MST MON SEP 12 2016
.SYNOPSIS...
An early fall cold front will move into the western states north of
Arizona tonight and Tuesday. This will result in breezy south to
southwest winds Tuesday, region wide, with a renewed threat of
afternoon and evening thunderstorms over central and eastern
Arizona. A much drier airmass will return to the region Wednesday,
and result in widespread dry weather through the weekend, with
temperatures staying near to slightly cooler than normal.
&&
.DISCUSSION...
A typical September pattern is upon us. In Sept the monsoon wans
then waxes, or the wax and wan idiom in which we get a break in the
monsoon with the descending early fall storms over the west,
followed by a stronger fall storm near AZ and resurgent south wind
and moisture from Mexico.
As the storm track from the north shifted closer to AZ last night, a
moderate Mexican moisture surge and increased vertical wind shear
resulted in a few organized thunderstorms Tuesday between Phoenix
and Tucson. The strongest meso-cyclones were noted in open desert
between Casa Grande and Tucson, and may have been weakly super-
cellular. At 8 pm most storms between Phoenix and Tucson had
weakened with the onset of nightfall.
Tuesday could also be an equally interesting day. Evening weather
balloon soundings showed moderately high monsoon moisture strewn
across southern AZ south of Phoenix and westward to Yuma. There were
two Yuma Proving Ground balloon launches provided by the Army
measuring between 1.00-1.20 inches of precip water, mainly below 500
mb. Much higher moisture amounts were noted south of the border.
Now, as clearly seen in evening water vapor imagery, a second and
stronger shortwave trof is forecast to deepen from northern CA this
evening, to just north Las Vegas by Tuesday evening. Strong 300/250
mb height falls are forecast Tuesday in the 100-120 meter range
across southern Nevada and southwest Utah. These are the strongest
late summer height falls close to AZ so far. As a result,
fundamentally there should be an ageo-strophic atmospheric response
in which moderately strong south to southwest winds develop over AZ,
ahead of these height falls, with increasing Mexican moisture.
Therefore, with the combination of moisture, afternoon heating, and
and increasing jetstream winds, a threat of afternoon and evening
thunderstorms are possible, especially mountains.
Our current Tuesday forecast has no mention of thunderstorms in our
Phoenix and Pinal County zones, with just minimal chances in the
mountains of southern Gila County zone 24. Evening Updates will be
to put a slight chance of storms back into the Phoenix and Pinal
County forecasts for Tuesday, with an increase in probabilities over
the southern Gila mountains zone 24. Also, updates were made to
increase the magnitude of developing south winds for Tuesday and
Tuesday evening.
Our dry Wednesday forecast looks good.
.PREVIOUS TO PREVIOUS DISCUSSION...157 PM MST...
Isolated strong storms developed earlier this afternoon across
portions of eastern Pinal and Gila counties. The strongest storms exhibited
modest organization with radar signatures even suggesting a BWER and
large hail. Storms have diminished in intensity since then, however
the environment remains conducive for isolated strong storms
containing brief heavy rain, strong wind gusts and small hail
through this evening.
Pocket of deeper moisture still resides across southern Arizona
extending into southern Gila County with low-level mixing ratios in a
10 to 12 g/kg range. Latest AMDAR sounding measured temperatures as
cold as -11C at 500 mb associated with the broad trough across the
Pacific Northwest, which is approaching a record low for the date.
This is contributing to steep mid-level lapse rates and MLCAPE
approaching 1000 J/kg in spots.
Prime areas for redevelopment this afternoon again include Pinal and
southern Gila counties in the vicinity of the deeper moisture,
though latest satellite imagery suggests that isolated storms will be
possible as far west as La Paz/Yuma County, including the Phoenix
area. Latest runs of the HRRR also point to the potential for an
outflow boundary propagating northwestward out of Pinal County and
towards the Phoenix area, which would initiate additional
development. PoPs have been increased in these areas, but still
generally remain less than 10 percent. Consensus amongst the CAMs is
that shower and thunderstorm activity will then subside later this
evening.
&&
.PREVIOUS DISCUSSION...
The formerly mentioned Pacific Northwest trough will swing into
cntrl Nevada Tuesday, becoming more neutrally tilted, and temporarily
stall/fill (before lifting out later in the week). Height falls will
continue to spread into SE California and Arizona through Wednesday
allowing temperatures to cool a few more degrees from today. In fact,
best performing guidance indicates Tuesday and/or Wednesday will
result in highs across the entire forecast area remaining below the
100F threshold (first time this has happened in many months) - truly
a harbinger of upcoming autumn weather. Otherwise despite jet energy
through the region and moisture not completely scoured east, a vast
majority of model output fails to develop storms during the afternoon
hours (even at the preferred higher elevation locations). Kept some
lower end slight chance POPs valid for southern Gila County with dry
air still holding solid over the western half of the CWA.
Very little forecast uncertainty for the latter half of the week as
one trough lifts northeast into the plains, yet weaknesses in the
height fields off the California coast allows for renewed energy to
fill in its place. This will reinforce stronger deep westerly flow
through the SW Conus pushing appreciable moisture east of the
Continental Divide and well into central Mexico. H5 heights will dip
into a 582dm range keeping temperatures in a slightly below average
range. In fact, with cooler daytime temperatures, a very dry
airmass, and clear skies, overnight lows will plummet into the 60s
for many lower elevation locations (and even some 50s in the coolest
communities). Another sign that desert southwest autumn weather is
not that far away.
&&
.AVIATION...
South-Central Arizona Including KPHX, KIWA, and KSDL:
Through 15z Tue...slowly increasing clouds aoa 15 thsd agl.
Southeast wind 6 to 10 knots. From 15z Tue to 23z Tue...sct clouds
aoa 10 thsd agl, increasing south wind 15 to 25 knots, a slight
chance of a thunderstorm mainly toward KIWA after 20z Tue.
Southeast California/Southwest Arizona including KIPL and KBLH:
Through 18z Tue...slowly increasing clouds aoa 15 thsd agl.
West to southwest wind 10 to 15 knots. From 18z Tue to 23z
Tue...sct clouds aoa 14 thsd agl, increasing southwest wind 15 to 20
knots.
&&
.FIRE WEATHER...
Thursday through Monday...
Temperatures will be near normal but the region should expect drier
air. That means minimum humidities near 10% for the lower deserts
and 20% in the higher elevations through Saturday. There will be
some improvement in humidities by Sunday. No real chance for any
storms, but some afternoon breezes are possible.
&&
.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...Vasquez/Hirsch/MO
AVIATION...Vasquez
FIRE WEATHER...Deemer
Area Forecast Discussion...UPDATED
National Weather Service Reno NV
839 PM PDT MON SEP 12 2016
.UPDATE...
The cold front continues to push south through Nevada with the
airmass slowly working westward toward the eastern Sierra this
evening. Isolated to scattered showers developed along the east
side of this cold frontal boundary from Susanville to near Reno
and Hawthorne on the south end. Most of the showers have been
light with only trace amounts to a few hundredths. The exception
was southwest of Susanville where as much as 0.25" may have fallen
(Pierce RAWS site measured 0.14"). So some rain fell on the
Willard Fire and humidity levels will remain elevated there
overnight into Tuesday.
00Z NAM takes upper low to just southwest of Lake Tahoe by
daybreak Tuesday and then eastward into the Great Basin Tuesday.
Cooling aloft should erode warm layer just above 500MB and allow
for more widespread and deeper convection by Tuesday morning. We
removed thunder for most areas this evening but maintained
previous thinking of increasing potential for showers and a few
storms late tonight and especially Tuesday. The 00Z NAM places
a band of showers across the Basin and Range although much of the
Sierra and western NV will see some showers and extensive clouds.
Where more steady showers develop Tuesday, temperatures may stay
a few degrees below current forecast levels. In fact the NAM MOS
guidance gives Reno a high of only 64 degrees Tuesday. Hohmann
&&
.PREVIOUS DISCUSSION... /Issued 234 PM PDT MON SEP 12 2016/
SYNOPSIS...
Much cooler temperatures along with showers and isolated
thunderstorms can be expected into Tuesday. There is potential
for spotty frost in colder western Nevada valleys Wednesday
morning. Otherwise, a gradual warming trend along with dry
conditions are expected the remainder of the week into next
weekend.
SHORT TERM...
The cold front today is slowly moving south and is located around
the Highway 50 corridor as of 2 pm. Locally critical fire weather
conditions are being observed for areas south of Highway 50 due to
20 to 30 mph wind gusts and low humidity. North of the front,
humidity values have begun to increase but gusty winds are still
a concern. Winds will become light overnight, except over ridges,
where breezes will continue into Tuesday morning. Gusty winds are
also bringing choppy conditions to Lake Tahoe and a Lake Wind
Advisory remains in effect through this evening.
Light showers are being observed on radar along and just behind
the cold front through the central Nevada Basin and Range into
eastern Nevada. As the upper low begins to drop south into
northern California and Nevada this evening, a vort max rotating
around the base will help to trigger showers and thunderstorms
through the Lassen/Plumas county areas. HRRR simulations have been
consistently showing this in addition to the GFS and NAM for late
this afternoon into the evening. Wetting rains are possible, but
it will be very hit or miss. These storms also have the potential
to impact the Willard Fire with brief heavy rain, small hail, and
gusty outflow winds.
Additional showers and thunderstorms are possible under the cold
core of the low on Tuesday, but precipitation amounts will
generally be light. One exception is under a deformation axis where
0.25" is likely. Deformation band placement is notoriously hard to
pinpoint and small differences of just 50 miles will have a
significant impact on the amount of precipitation locations
receive. Most forecast simulations are showing the band extending
through central Nevada, but a few take it farther west. For now,
am leaning toward the eastern solution and have trended the
forecast in this direction. The other concern is the potential for
light snow accumulation down to about 9000 feet. Anyone with
outdoor plans in the high Sierra should plan accordingly.
Much cooler temperatures are expected on Tuesday, with highs
running 10 to 15 degrees below normal. As the system exits Tuesday
night, skies will begin to clear and patchy frost is possible
through colder valleys early Wednesday morning. A good rule of
thumb is if your forecast low temperature is 40 degrees or lower,
you may want to cover sensitive vegetation. -Dawn
LONG TERM...Thursday through Monday...
General troughiness remains over the Southwest for the end of the
week heading into the weekend with ridging building into the
Pacific Northwest. This will bring a gradual warming trend along
with dry conditions and light winds.
There is still some uncertainty regarding the end of the weekend
into the early part of next week with the potential for a weak
trough to either brush by to the north of the region, or drop
farther south. Most guidance and ensembles are pointing toward a
northern track, which would bring some light afternoon breezes
Sunday and Monday, but not as strong as a southern track would
produce. The forecast looks to remain dry through the period.
-Dawn
AVIATION...
The cold front has already passed through all terminals north of
Highway 50 with gusty southwest to west winds up to 25 kts
continuing through this evening. The low level wind shear threat
has likely ended north of the front, but for areas south of
Highway 50 a short period of wind shear is likely along the cold
front as wind turn from the west to the north northeast.
Surface winds will become east north east north of Interstate 80
with north to northwest south of there heading into Tuesday, but
will be light. Wind aloft will generally be from the north.
Isolated showers and thunderstorms are possible this afternoon and
evening north of KSVE-KNFL line and east of Highway 95. Chances
will expand across much of the Sierra and northwest Nevada
overnight into Tuesday with a cold area of low pressure overhead.
Storms may produce brief heavy rainfall, small hail, and erratic
wind gusts in addition to obscuring terrain.
Drier conditions are expected Wednesday and through the remainder
of the week along with light winds. -Dawn
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Charleston WV
1033 PM EDT MON SEP 12 2016
.SYNOPSIS...
Broad area of high pressure through Wednesday. A weak cold front
crosses Wednesday night. High pressure passes to the north
Thursday. Next cold front arrives late in the weekend.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 1030 PM Monday...
Broad area of high pressure bringing mostly clear skies for warm
afternoons and cool nights. Likely will see some morning valley
fog with light flow under subsidence, longer nights, and clear
skies. Expect any fog that develops to burn off rather quickly
after sunrise.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 130 PM Monday...
Frontolytic cold front pushes into the Ohio Valley late Wednesday
into Wednesday night with decreasing coverage of convection as it
does so. Timing is such that the best chance for precip comes at
the onset into the CWA up in Perry/Morgan counties in southeast
Ohio...with slight chance POPs dissolving after 00Z. Front should
push through the mountains...but a lingering band of cloud cover
should remain over the central CWA into Thursday.
Meanwhile...upper level features should drift up from the south
into the central Appalachians Thursday. This moisture push will
warrant low end chances for convection during peak heating for
the mountains.
Despite the front passing through...no real change of airmass is
in the forecast...so expecting temperatures to be above normal mid
week with the ridge centered over Florida.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 930 AM Monday...
High pressure Thursday into Friday will move east allowing a warm
front to push north Friday night into early Saturday. A cold front
will then push southeast late Sunday into Sunday night with an
area of high pressure building in by Monday.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
As of 1030 PM Monday...
VFR for now. Expect IFR/LIFR conditions to develop under dense
valley fog as a result of light surface flow, long nights,
subsidence, and warm rivers. Fog should dissipate by 13-14Z.
Then, VFR conditions are anticipated for the rest of Tuesday.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z WEDNESDAY...
FORECAST CONFIDENCE: Medium.
ALTERNATE SCENARIOS: Timing of valley fog formation may vary
overnight tonight. Not super confident in fog at KBKW as a result
of some stronger 925 mb flow indicated by the HRRR which may keep
it mixy enough to inhibit fog.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE TUE 09/13/16
UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11
EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07
CRW CONSISTENCY H H H H H H H M M M L L
HTS CONSISTENCY H H H H H H H H H M L L
BKW CONSISTENCY H H H H H H H H H H H M
EKN CONSISTENCY H H H H L L L L L L L L
PKB CONSISTENCY H H H H H H H H H L L L
CKB CONSISTENCY H H H H H H H H H H L L
AFTER 00Z WEDNESDAY...
IFR possible in valley fog Wednesday morning.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.
&&
$$
SYNOPSIS...JW/26
NEAR TERM...JW
SHORT TERM...26
LONG TERM...JSH
AVIATION...JW
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
314 AM EDT TUE SEP 13 2016
.DISCUSSION...
Models have changed little over the last 24 hours regarding an upper
level trough pushing a cold front through lower MI tonight into
Wednesday morning. The trough is already laid out from northern
Quebec southwest through the Mid Mississippi Valley but will
progress very slowly southeastward as there is weak flow on the
backside of the trough. This is a result of the strongest upper
level jet support racing east while trailing cutoff upper low back
over the west coast keeps a steeply positive tilt to the trough. The
front itself does not support much more than scattered showers.
Though models continue to support nearly 40 knots of shear today,
there remains little instability due to a cap around 850-750mb
preventing convection as the lead theta e gradient works into the
Saginaw Valley and through the Thumb. The only real chance is that
peak heating this evening can spark a shower or two over that
region, which could tap into the shear and strengthen. Confidence is
not high with this scenario but with dry air in the boundary layer
lingering from the high pressure system, could see a few stronger
wind gusts as DCAPE nears 500j/kg for several hours. Again, most
likely the area will stay dry through this evening. Both the HRRR
and ARW now advertise a shortwave to ride along the front through
the straits which would keep the convective activity further north.
Better chances of showers will come tonight as the narrow ribbon of
theta slides over southern lower MI. Kept pops in the chance
category as we continue to lack any real forcing to spark these
showers and thunderstorms. Yet another wave may ripple along the
front after 06Z which may coincide with some right entrance region
dynamics sliding into the area. This may require a boost in pops,
but timing these short waves with a front that may be slowing down a
touch will not be easy. Will allow things to play out a bit and
adjust as necessary. The slow moving front will not reach the
Detroit Metro til early Wednesday. This could allow a little
destabilization with the onset of daytime heating so will keep the
pops running through the late morning hours. PWATS around 1.5 inches
may result in heavy rainfall with any cells that develop.
Strong surface high will build into the area Wednesday evening and
overnight. High pressure, clearing skies, and weak winds will allow
good radiative cooling Wednesday night. Temperatures should fall
into the upper 40s to near 50 for most locations. Upper level ridge
will then slide in on Thursday keeping the weather quiet into
Friday. Southerly flow will return on Friday ahead of the next
system, which is the aforementioned cutoff low that has tracked
across the country through the week. Models are struggling with the
strength and positioning of this system, but do tend to agree that a
cold front should pass through the area on Saturday spreading
showers and maybe some thunderstorms across lower MI. It then looks
like low level cold advection behind the system could increase lapse
rates in the afternoon sparking some scattered afternoon showers. So
could see a few rounds of precipitation over the weekend.
&&
.MARINE...
Moderate south to southwest winds will persist into tonight, ahead
of an approaching cold front. This frontal boundary will trigger
scattered showers and thunderstorms tonight into Wednesday morning.
Southwest winds will peak around 20 knots across central Lake Huron
in advance of the front with northwest winds then gusting to 20
knots or slightly more in its wake tonight. Expect building waves on
Wednesday as winds veer to the north and remain elevated. Small
craft advisories may be needed for the nearshore waters of Lake
Huron as wave activity propagates south across the lake.
&&
.PREV DISCUSSION...
Issued at 1155 PM EDT Mon SEP 12 2016
AVIATION...
Lingering high pressure will sustain this stretch of clear sky and
light winds through the morning period. Environment may support a
brief period of shallow fog /MVFR/ right around sunrise, but
confidence still too low to include. Modest increase in southwest
winds in advance of a cold front on Tuesday. Highs clouds will
thicken and gradually lower with time through the daylight period.
Cold front begins to enter from the northwest Tuesday night.
Associated lower of ceiling heights and an increasing potential for
showers thereafter late Tuesday night into Wednesday morning.
//DTW Threshold Probabilities...
* None.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
DISCUSSION...DRK
MARINE.......DG
AVIATION.....MR
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Fort Worth TX
324 AM CDT TUE SEP 13 2016
.DISCUSSION...
The upper level ridge over the region will start to weaken as a
an upper level low digs into northern California. This low will
move east across the Great Basin later today and then lift off
the northeast Wednesday and Thursday but a large trough will
remain across the western United States. A shortwave will dig down
the western part of the trough and deepen across southern
California/western Arizona by Saturday. The GFS indicates that
this shortwave will cutoff over southern California/Arizona
whereas the ECMWF just shows a deep trough. Either way, Texas will
be in an unsettled weather pattern with southwesterly flow aloft
allowing a series of upper level disturbances to move across the
state through at least early next week. The differences in model
solutions won`t matter too much for most of this forecast period,
but when the rain chances will start to decrease next week will
depend on whether the more progressive ECMWF or the slower GFS
solution is correct.
The 00z KFWD RAOB showed that we had Precipitable Water values
of slightly over 1 inch versus the 0.64 inches that we had 24
hours ago. Southerly flow will result in PWs climbing to around
1.5 inches today. With diurnal heating today, we should see some
isolated to scattered showers and thunderstorms develop by this
afternoon mainly across Central Texas but there will be low
chances across all but the northeastern counties. A cold front is
expected to move south across Oklahoma before stalling tonight.
This will result in the best chances of showers/thunderstorms (30
percent PoPs) across the northwestern counties tonight. Although
this front won`t make it into North Texas, surface winds across
the region will become easterly by Wednesday morning. We will have
a 20 to 30 percent chance of showers and thunderstorms area wide
Wednesday. Winds will veer back around to the southeast and south
by Thursday morning as surface cyclogenesis occurs as a short wave
moves out of the Rockies towards the northern and central Plains.
Expect continued scattered showers and thunderstorms across the
region through Friday. More widespread rain is possible across the
north Friday night as a cold front moves into the region. With
generally southwesterly flow aloft expected to continue for the
weekend through at least the early part of next week, we will
continue to have decent chances of showers and thunderstorms
daily.
Highs will be in the upper 80s to lower 90s through Friday. With
the front expected to move through the region late Friday night
and Saturday and increased cloud cover, expect slightly cooler
temperatures for the weekend into early next week with highs in
80s. Lows will be mostly in the 70s through Thursday night and
then upper 60s to lower 70s Friday night through early next week.
58
&&
.AVIATION...
/ISSUED 1129 PM CDT MON SEP 12 2016/
The primary concern for this forecast will be the potential for
stratus in the morning. The latest HRRR indicates a swath of high
RH at 925 MB surging north from Central TX overnight, which is
consistent to earlier model data. We will indicate MVFR cigs
beginning 11Z at KACT and 13Z in the Metroplex, with cigs
scattering out late Tuesday morning.
Isolated convection is a slim possibility Tuesday afternoon but
coverage would be far too low to mention in any of the forecasts.
We will also keep an eye out to the north and west Tuesday Night
for any ongoing convection that attempts to approach the DFW
TRACON area, but this also is too low of a probability to include
in the TAFS.
30
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 92 75 92 75 92 / 20 20 30 20 30
Waco 92 73 93 73 92 / 30 20 30 20 20
Paris 91 72 91 72 90 / 10 20 30 20 40
Denton 90 71 91 71 90 / 20 20 30 20 40
McKinney 90 72 91 72 91 / 20 20 30 20 40
Dallas 93 75 92 75 92 / 20 20 30 20 30
Terrell 91 73 92 73 91 / 20 20 30 20 30
Corsicana 91 74 92 74 92 / 20 10 30 20 20
Temple 90 72 91 72 91 / 30 20 20 20 20
Mineral Wells 89 71 90 70 90 / 20 20 30 20 40
&&
.FWD Watches/Warnings/Advisories...
None.
&&
$$
90/58
As noted in last nights forecast discussion, the weekend
is shaping up to be a nice one weather-wise. Temperatures should
range from the mid 70s to the upper 70s for near seasonable
temperatures this time of year. Mostly clear skies and light winds
are also forecast. Its going to be a nice fall weekend to end the
week after some unsettling weather leading up to the weekend. On a
side note--and yes it is pretty far out--but Saturday morning has
the right ingredients for a foggy start to the day. After all the
moisture and cloudy skies leading up to Saturday morning, we
could see some fog as radiational cooling kicks in with clear
skies and light winds. Like I said, its pretty far out, and I am
not going to hang my hat on it, but there could be some fog
Saturday morning across the local area.
&&
.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Tuesday night)
Issued at 1114 PM CDT Mon Sep 12 2016
Both of the terminals will be between VFR and MVFR for the
majority of this TAF period as ceilings go in and out of these
categories, mainly 2K to 4K foot ceilings. There is a little
uncertainty for thunderstorms later today with timing and
coverage now that the atmosphere has worked itself over with these
storms currently across the region. Will amend the TAF if needed
after further investigation for any potential impacts to the
terminals. Otherwise, expect low ceilings throughout the TAF
period around 2K to 4K feet.
&&
.GID Watches/Warnings/Advisories...
NE...None.
KS...None.
&&
$$
SHORT TERM...Guerrero
LONG TERM...Guerrero
AVIATION...Guerrero
Area Forecast Discussion
National Weather Service Phoenix AZ
245 AM MST TUE SEP 13 2016
.SYNOPSIS...
A weather disturbance will move north of the area today resulting in
breezy conditions and scattered afternoon and evening thunderstorms
over higher elevations of central and eastern Arizona. A much drier
airmass will envelop the region through the remainder of the week
yielding widespread dry weather and temperatures remaining near to
slightly cooler than normal.
&&
.DISCUSSION...
A rather distinct PV anomaly was descending towards KOAK early this
morning with objective analysis indicating a 60kt H5 jet streak
beginning to round the trough base through cntrl California. The
most notable height falls were already translating eastward and will
spread into central Nevada and Utah throughout today as the
shortwave/cold core starts lifting into the Great Basin. Further to
the south, subtle height rises and warming aloft were noted in
regional Arizona 00Z sounding data and hourly objective analysis
such that midlevel lapse rates and elevated instability were far
more muted than 24 hours ago. Adding to the atmospheric complexity,
fairly robust shallow moisture was sampled in the far SW portion of
AZ, however the vast majority of the area could only muster 7-9 g/kg
sfc-H7 moisture levels early this morning.
This leads to a tricky forecast through the afternoon and early
evening hours as this shallow moisture in SW Arizona will be pulled
northeast towards the best pressure falls in nrn AZ/Utah, yet into a
H7-H5 layer that continues to warm and dry limiting overall
instability and heightening Cinh. Comparison of NAM and GFS Bufr
soundings shows a small window late this afternoon where lower
elevation MLCape approaches 400 J/kg with minimal Cinh, albeit only
briefly before drier air around the H7 layer begins to dominate. As
of this writing, really only the HRRR suggests lower elevation
convection with even the typically overzealous UA-WRFs and EMC WRF-
NMM core highlighting storms only at higher elevations of far
eastern Maricopa/eastern Pinal/southern Gila counties in the 21Z-03Z
time frame. There is also the distinct possibility of more extensive
mid/high clouds blanketing much of cntrl AZ later today further
limiting overall instability.
Thus, conceptually feel the best opportunity for deep convection
will lie with terrain forced ascent of shallow moisture profiles
within the stronger deep SW flow over the foothills and mountains
just east of the Phoenix metro. This activity would quickly
propagate downstream into eastern Pinal and southern Gila county
given the mean steering wind profiles. Similar to yesterday, sfc-6km
bulk shear values will approach 30kt yielding some chance for better
organized storm structure; however, the aforementioned muted
instability and lapse rates may be the primary limiting factor for
wind and hail producing storms. Otherwise, the other notable feature
this afternoon will be an enhanced breeziness as the pressure
gradient tightens ahead of height falls to the north. While somewhat
unusual for mid September, wind speeds do not look overly strong but
potentially enough to lift a suspended dust layer - particularly in
areas that have seen little to no rainfall this summer (i.e. SE CA
and far western AZ).
Medium range models continue to project very little forecast
uncertainty for the latter half of the week with the primary
shortwave trough lifting into the plains, yet weak negative height
anomalies and persistent dry westerly flow lingering through the SW
Conus. This flow pattern will push any appreciable moisture east of
the Continental Divide and well into central Mexico starting
Wednesday afternoon dictating no chance of rainfall throughout the
entire region for at least several days. A deepening low over
Arizona may try to pull moisture back into parts of the forecast
area later in the weekend, however the quicker forward motion to
this wave may only allow some wrap around midlevel moisture into the
far eastern parts of the state. H5 heights will languish in a 582-
584dm range keeping temperatures in an average to slightly below
average range. In fact, with cooler daytime temperatures, an
extremely dry airmass, and clear skies, overnight lows will easily
plummet into the 60s for many lower elevation locations (and even
some 50s in the coolest communities). A definite sign that desert
southwest autumn weather is not that far away.
&&
.AVIATION...
South-Central Arizona Including KPHX, KIWA, and KSDL:
Through 15z Tue, slowly increasing clouds aoa 15 thsd agl. Southeast
wind 6 to 10 knots. From 15z Tue to 23z Tue, sct clouds aoa 10 thsd
agl, increasing south wind 15 to 25 knots, a slight chance of a
thunderstorm mainly toward KIWA after 20z Tue.
Southeast California/Southwest Arizona including KIPL and KBLH:
Through 18z Tue, slowly increasing clouds aoa 15 thsd agl. West to
southwest wind 10 to 15 knots. From 18z Tue to 23z Tue, sct clouds
aoa 14 thsd agl, increasing southwest wind 15 to 20 knots.
&&
.FIRE WEATHER...
Thursday through Monday...
Temperatures will be near normal but the region should expect drier
air. That means minimum humidities near 10% for the lower deserts
and 20% in the higher elevations through Saturday. There will be
some improvement in humidities by Sunday. No real chance for any
storms, but some afternoon breezes are possible.
&&
.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...MO
AVIATION...Vasquez
FIRE WEATHER...Deemer
Area Forecast Discussion
National Weather Service Tallahassee FL
409 AM EDT TUE SEP 13 2016
.NEAR TERM [Through Today]...
A tropical airmass with plenty of deep moisture will remain in place
today. In fact, deep moisture will be increasing today with PWATs
above 2 inches expected by the end of the day. As of 08z this
morning, area radars and surface observations show a fairly small
but well defined area of low pressure moving northwestward from near
Vero Beach. The overnight HRRR runs move this low to near Ocala by
this evening. Scattered to numerous showers and thunderstorms are
expected to develop across the area this afternoon given the
tropical airmass and weak forcing, especially across the eastern
half. Given the expected cloud cover and convective coverage today,
high temperatures are expected to hold in the upper 80s to near 90,
although with dewpoints in the low to mid 70s, heat indices will be
in the mid to upper 90s this afternoon.
.SHORT TERM [Tonight Through Thursday]...
Interesting forecast this cycle with a tropical wave moving across
the Florida Peninsula and into the region by late tonight into
Wednesday. Model guidance is actually fairly split with two
main solutions. The GFS prefers to keep much of the activity with
the tropical wave across SE GA. The NAM is decidedly the more
western (and stronger) outlier with a weak low pressure area
moving toward Panama City on Wednesday afternoon. The 13/00z Euro
represents a bit of a compromise solution between these two
drastically different solutions. The ECAM package was useful in
constructing the short term forecast given all the differences in
the model guidance.
Where all the models agree is that precipitable water values will
be increasing considerably tonight and remaining high through
Thursday. While widespread heavy rainfall is not anticipated at
this time, given then generally weak forcing with the tropical
wave, the especially moist environment will support locally heavy
rainfall, especially across the eastern portion of the region.
For this cycle, will keep rain chances in the 70-80 percent range
across the Central and Eastern portion of the region late tonight
through Wednesday, with slightly lower rain chances off to the
west. By Thursday as the wave is likely to dissipate, leaving
just a very moist tropical airmass in place, expect fairly good
coverage of showers and thunderstorms, so have increased PoPs into
the 60-70 percent range across the entire forecast area.
With extensive cloud cover and convection, afternoon high
temperatures should generally stay in the mid 80s both Wednesday
and Thursday.
.LONG TERM [Thursday Night Through Tuesday]...
With the tropical wave dissipated by the start of the long term
period, all that will remain across the region is a very moist
tropical airmass that will support scattered to numerous showers
and thunderstorms across the area. It`s not really until Sunday
that the airmass begins to dry out a little - and really Tuesday
before significantly drier air arrives from the NE. As a result,
rain chances remain well above normal through Sunday and then
decrease toward the end of the long term period. High temperatures
will initially be in the upper 80s at the start of the period and
then as convection/cloud cover decreases late in the period, high
temperatures should return to the lower 90s.
&&
.AVIATION [Through 06Z Wednesday]...
A tropical airmass will remain in place today. Some areas of MVFR
ceilings are expected this morning, followed by scattered
convection this afternoon. The terminals that have the highest
chance of seeing thunderstorms this afternoon include VLD, TLH,
and ABY, although storms are also possible at ECP and DHN.
&&
.MARINE...
A tropical wave will move across the Florida Peninsula tonight and
increase winds to near cautionary levels across the coastal
waters. As this wave dissipates on Thursday, winds and seas will
return to typically low levels into the weekend.
&&
.FIRE WEATHER...
Red flag conditions are not expected for the next several days with
RH remaining above critical levels.
&&
.HYDROLOGY...
With tropical moisture increasing considerably late tonight and
the airmass staying very moist through at least Friday, the
potential for locally heavy rainfall will exist across the region.
While widespread average totals in the 2-2.5 inch range are
expected across the central and eastern portions of the region,
locally heavier totals to near 5 inches will be possible through
Thursday. This suggests that the flood threat during the short
term period will be limited to urbanized flooding from heavy
downpours.
While most area rivers can accommodate this sort of rainfall
event, the Steinhatchee River remains just above action stage and
will need to be closely monitored if the heavier rains are focused
across the Southeast Florida Big Bend.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 89 74 85 74 87 / 60 50 70 40 60
Panama City 87 74 85 75 85 / 60 40 50 40 60
Dothan 89 71 85 72 85 / 50 30 50 40 70
Albany 90 73 85 72 86 / 60 50 80 50 70
Valdosta 87 73 85 72 87 / 70 70 80 50 70
Cross City 86 73 86 73 87 / 70 70 80 40 60
Apalachicola 87 75 85 77 85 / 60 40 50 40 50
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&
$$
NEAR TERM...DVD
SHORT TERM...Godsey
LONG TERM...Godsey
AVIATION...DVD
MARINE...Godsey
FIRE WEATHER...DVD
HYDROLOGY...Godsey
Area Forecast Discussion
National Weather Service Denver/Boulder CO
1003 AM MDT TUE SEP 13 2016
.UPDATE...
Issued at 1003 AM MDT Tue Sep 13 2016
An east to southeast low level upslope flow is expected to keep
low clouds along the Front Range through early to mid afternoon.
This flow favors keeping low clouds over the northern Front Range
longer. Adjusted temperatures and sky slightly to reflect longer
overcast skies for the northern Front Range. Other than morning
drizzle, looks like the main chance for precipitation will be
scattered showers and storms over the higher terrain where it is
partly cloudy and will become unstable this afternoon. As the
showers and storms move off the higher terrain, expected them to
decrease as they encounter a stable airmass. The HRRR is showing
some of the activity surviving onto the near by plains this
evening due to a wave a lot, so will make sure to have 20-30 pops
during the evening hours out onto the plains.
&&
.SHORT TERM...(Today and tonight)
Issued at 457 AM MDT Tue Sep 13 2016
Low clouds have spread across northeastern Colorado this morning
as the low level easterly flow continues. Surface pressure pattern
will be steady today feeding this cool air in from the east.
However there will be some drying aloft which should bring some
midday clearing to the mountains and help to eat away the edges of
the low clouds along the foothills. The plains will remain cool
enough to prevent surface based convection, so after the current
batch of showers leaves it will likely just be cloudy and cool.
Some weak instability over the mountains should lead to some
showers and weak storms developing this afternoon, but some lift
will move in from the southwest this evening to increase the
shower activity. There is a chance some of this could spread onto
the plains overnight, but the best lift will still be further
west. Some low clouds will redevelop over the plains, but Denver
may be sheltered by the more southerly low level flow off the
Palmer Divide.
Cool forecast temperatures look alright, with highs mainly in the
60s on the plains.
.LONG TERM...(Wednesday through Monday)
Issued at 457 AM MDT Tue Sep 13 2016
On Wednesday morning...the upper level low pressure system will be
centered over the Great Basin with an upper level trough extending
south across Arizona and southern California. An upper level ridge
of high pressure will be over the Central Plains States. Colorado
will lie along the leading edge of the trough under the influence of
a moderate southwest flow aloft. In addition...the GFS...NAM and
ECMWF all show a 50-60kt jet moving over the mountains during the
morning hours and spreading over the plains by evening.
The morning may start out with some low clouds or fog on the
plains east of Denver...with a few showers over the high country.
As the day wears on...the combination of daytime heating...some
subtropical moisture and QG forcing from the jet should produce
scattered afternoon and evening showers and thunderstorms across
north central and northeastern Colorado. The Nam and GFS are
indicating a band of cape greater than 1000 j/kg across
Washington...Logan...northeastern Weld and eastern Morgan Counties
by late afternoon...along with decent shear. IF this verifies...we
could see strong storms with hail...gusty winds and locally heavy
rain in these areas during the late afternoon and evening hours.
However...the models do differ quit a bit in QPF. The GFS has the
most QPF during the evening hours with the NAM having the least.
The ECMWF shows a good batch of precipitation across the far
northeastern Colorado but not until after midnight. Due to QPF
fields and weather parameters...have decided to raise pops across
for these areas.
On Thursday...the upper trough is forecasted to move across
Colorado...with the winds at the surface becoming westerly. In
addition...models show downward QG forcing associated with the left
entrance region of the upper jet moving over the area. This pattern
should bring drier air into the region...resulting in lower
precipitation chances. Once again...could see some morning low
clouds or fog across the far northeastern plains which should break
up by late morning.
On Friday...the upper trough moves into the upper Great Plains States
...with a secondary upper trough developing over the western United
States. Some subtropical moisture ahead of this trough combined with
an upper level disturbance moving into the region from the southwest
may produce isolated to scattered showers and storms across the
mountains and adjacent plains. the best chance for precipitation
looks to be in the mountains and foothills along and south of
interstate 70 during the afternoon hours. The models then show the
precipitation spreading into the southern Denver Metro area and
Palmer Divide during the late afternoon and evening hours.
By the weekend...the models begin to diverge somewhat. The GFS shows
an upper level low pressure system deepening over Arizona on
Saturday. This low slowly tracks across the Desert Southwest and
into New Mexico by early next week. The ECMWF has an open trough
moving across the central and southern Rockies over the
weekend...with upper level high pressure building over Colorado by
early next week. Despite the differences...both solutions keep most
of the moisture and energy south of our area...with only isolated
afternoon and evening showers and storms possible mainly across
southern portions of the CWA.
Below normal temperatures are expected through Saturday...with
near normal temperatures returning by Sunday.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1003 AM MDT Tue Sep 13 2016
Southeast to east low level flow will keep a moist airmass over
the area today. Ceilings will slowly rise through 20z. The lower
ceilings will be found from KBJC to KFNL. Expect ceilings to lift
sooner KDEN and KAPA with ceilings reaching 3000 feet by 17-18z.
Low level flow is expected to turn southwest after 00z. This
should bring enough dry air to prevent low clouds from forming
over the Denver area and to the south. However, a Denver cyclone
may form and could pull moisture in from the north and bring low
ceilings towards 12z Wednesday for KBJC and KDEN.
&&
.BOU Watches/Warnings/Advisories...
None.
&&
$$
UPDATE...Meier
SHORT TERM...Gimmestad
LONG TERM...Kalina
AVIATION...Meier
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
945 AM EDT TUE SEP 13 2016
.UPDATE...
A remnant MCV has been lifting northward across nrn Lake Mi this
morning. This is quite a bit faster than earlier model solutions
suggested. This wave is already forcing the mid level frontal zone
southward across central Michigan. While mid level subsidence will
overspread far nrn Lower Mi in the wake of this feature this
afternoon, the elevated frontal zone and associated mid level
theta e plume will settle into the Saginaw Valley and thumb. This
will support a chance of convection in these areas through the
afternoon. Convective potential will be limited by rather low
0-1KM ML CAPE (under 500 J/KG per RAP). While the strong mid level
capping (as shown on the 12Z DTX sounding) will be suppressed
across srn Lower Mi this afternoon, RAP soundings still suggest
some weak capping holding across the Saginaw Valley and thumb.
These factors support just low type pops across the north today.
Despite the strong deep layer shear, severe convective potential
will likely be limited by the overall weak instability today.
With locations farther south remaining under stronger capping, a
dry forecast through the afternoon remains valid.
&&
.PREV DISCUSSION...
Issued at 646 AM EDT Tue SEP 13 2016
AVIATION...
Modest southwest flow, peaking 12-15 knots, can be expected today
within tightening pressure gradient between high pressure to the
east and an approaching cold front. With this forecast, will
adjust timing of fropa forward several hours as mesoscale
influences of MCS entering northern lower MI should bring quicker
wind shift to NW. Given extensive area of MVFR stratus positioned
north of the cold front, will adjust CIGS lower by late tonight
with PROB30 for shras.
For DTW, timing of fropa late tonight looks to be in the 08z-09z
time frame with trailing shortwave most likely bringing an area of
shras into terminal at about that time. CIGS should at least be on
the MVFR/VFR borderline along/behind front.
//DTW Threshold Probabilities...
* Medium in CIGS aob 5kft after 09z tonight.
PREV DISCUSSION...
Issued at 314 AM EDT Tue SEP 13 2016
DISCUSSION...
Models have changed little over the last 24 hours regarding an upper
level trough pushing a cold front through lower MI tonight into
Wednesday morning. The trough is already laid out from northern
Quebec southwest through the Mid Mississippi Valley but will
progress very slowly southeastward as there is weak flow on the
backside of the trough. This is a result of the strongest upper
level jet support racing east while trailing cutoff upper low back
over the west coast keeps a steeply positive tilt to the trough. The
front itself does not support much more than scattered showers.
Though models continue to support nearly 40 knots of shear today,
there remains little instability due to a cap around 850-750mb
preventing convection as the lead theta e gradient works into the
Saginaw Valley and through the Thumb. The only real chance is that
peak heating this evening can spark a shower or two over that
region, which could tap into the shear and strengthen. Confidence is
not high with this scenario but with dry air in the boundary layer
lingering from the high pressure system, could see a few stronger
wind gusts as DCAPE nears 500j/kg for several hours. Again, most
likely the area will stay dry through this evening. Both the HRRR
and ARW now advertise a shortwave to ride along the front through
the straits which would keep the convective activity further north.
Better chances of showers will come tonight as the narrow ribbon of
theta slides over southern lower MI. Kept pops in the chance
category as we continue to lack any real forcing to spark these
showers and thunderstorms. Yet another wave may ripple along the
front after 06Z which may coincide with some right entrance region
dynamics sliding into the area. This may require a boost in pops,
but timing these short waves with a front that may be slowing down a
touch will not be easy. Will allow things to play out a bit and
adjust as necessary. The slow moving front will not reach the
Detroit Metro til early Wednesday. This could allow a little
destabilization with the onset of daytime heating so will keep the
pops running through the late morning hours. PWATS around 1.5 inches
may result in heavy rainfall with any cells that develop.
Strong surface high will build into the area Wednesday evening and
overnight. High pressure, clearing skies, and weak winds will allow
good radiative cooling Wednesday night. Temperatures should fall
into the upper 40s to near 50 for most locations. Upper level ridge
will then slide in on Thursday keeping the weather quiet into
Friday. Southerly flow will return on Friday ahead of the next
system, which is the aforementioned cutoff low that has tracked
across the country through the week. Models are struggling with the
strength and positioning of this system, but do tend to agree that a
cold front should pass through the area on Saturday spreading
showers and maybe some thunderstorms across lower MI. It then looks
like low level cold advection behind the system could increase lapse
rates in the afternoon sparking some scattered afternoon showers. So
could see a few rounds of precipitation over the weekend.
MARINE...
Moderate south to southwest winds will persist into tonight, ahead
of an approaching cold front. This frontal boundary will trigger
scattered showers and thunderstorms tonight into Wednesday morning.
Southwest winds will peak around 20 knots across central Lake Huron
in advance of the front with northwest winds then gusting to 20
knots or slightly more in its wake tonight. Expect building waves on
Wednesday as winds veer to the north and remain elevated. Small
craft advisories may be needed for the nearshore waters of Lake
Huron as wave activity propagates south across the lake.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
UPDATE.......SC
AVIATION.....DG
DISCUSSION...DRK
MARINE.......DG
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Rapids MI
1125 AM EDT TUE SEP 13 2016
LATEST UPDATE...
Update/Marine
.SYNOPSIS...
Issued at 315 AM EDT Tue Sep 13 2016
A cold front will track slowly southeast through the Great Lakes
region today and tonight. Showers and even a few thunderstorms
could accompany the passage of this system. A large area of high
pressure will then build in over the region for Wednesday into
Thursday. This fair weather system will provide the region with
mainly dry weather and near seasonable temperatures.
&&
.UPDATE...
Issued at 1125 AM EDT Tue Sep 13 2016
In the 0-3 forecast hour time range, convection allowing models
including the HRRR had been underestimating the extent of
convection. Water vapor imagery indicates a compact upper
potential vorticity maximum moving east across southern WI at this
time, and we estimate it will pass the forecast area by mid-
afternoon, allowing for strong subsidence greatly limit
precipitation chances from late afternoon into early tonight.
Prior to that there is a relatively low threat for thunderstorms
with limited severe potential. Have updated the forecasts to
reflect this.
UPDATE Issued at 637 AM EDT Tue Sep 13 2016
The convection has created a tighter pressure gradient over Lake
MI. As a result the impactful waves and winds will occur over a
larger area. I expanded the MWW and SCA.
UPDATE Issued at 553 AM EDT Tue Sep 13 2016
The area of convection pushing off of Green Bay has not been
decreasing in intensity. Thus the forecast was updated to reflect
a risk for showers and thunderstorms this morning for a much
larger area and also much higher pops than previously forecasted.
It looks like 15z to 17z this feature will move away from the
area.
&&
.SHORT TERM...(Today through Thursday)
Issued at 315 AM EDT Tue Sep 13 2016
The area of convection tracking into southwest Wisconsin is
expected to weaken as it tracks towards my northwest counties.
They should move in by mid morning. So will maintain the elevated
POPs for Ludington and Hart to start the day.
Forecast soundings show a cap for most of today for surface based
storms. Thus despite building instability...how much if any
thunderstorm activity should be limited. It appears tonight a
better potential for showers and a few storms exists. This is when
the frontal zone will be pushing through and pwat values peak.
Some lift from a shortwave tracking through may also enhance the
precipitation from 00z to 06z. An isolated strong to severe storm
could occur with SPC featuring part of the region in a marginal
risk. Deep layer shear is over 30 knots. Localized wind gusts are
the main risk.
Dry conditions return for Wednesday and Thursday as high pressure
moves back in.
.LONG TERM...(Thursday night through Monday)
Issued at 315 AM EDT Tue Sep 13 2016
High pressure will continue in control of the wx pattern Thursday
night and result in mostly clear skies with seasonable temperatures.
Clouds will be on the increase on Friday out ahead of the next low
pressure system approaching from the west and there is a small
chance for a shower as early as Friday morning or afternoon.
Continued southerly flow in advance of this next system will
result in increasing low level moisture and a better chance for
showers and perhaps a few thunderstorms Friday night through
Saturday. The convective threat is fairly low due to weak
instability.
A few showers may linger into Sunday before a cooler and drier
airmass advects in behind that system late in the weekend into early
next week. Temperatures by Sunday and Monday will return to near
normal for that time of year after averaging around 5-10 degrees
above normal Friday through Saturday.
&&
.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 734 AM EDT Tue Sep 13 2016
The showers and thunderstorms tracking through parts of Southwest
Lower MI will continue to diminish. Their impacts on the TAF sites
are forecasted to be limited...with KMKG perhaps seeing a VCTS.
Will need to monitor the second area of storms upstream near
KDBQ...as they could move into MI in a few hrs if they survive.
Tonight a greater risk for impacts exists...with even possible
IFR. A slow moving cold front will push in as the low level
moisture increases. Thus cloud bases will lower...and MVFR looks
likely. Some instability will be present...so a thunderstorm could
also form. Winds will shift to the northwest then northeast behind
the front late tonight into Wed AM.
waves
&&
.MARINE...
Issued at 1125 AM EDT Tue Sep 13 2016
Extended the small craft advisory and beach hazards headlines until
4 pm this afternoon based largely on buoy observations and strong
winds associated with the low level jet. Given the orientation of
the jet, we could see briefly elevated winds and waves around the
Holland area for the next couple hours. Otherwise..the jet will
continue its diurnal weakening and the overall pressure gradient
will become baggier as the cold front drops south into the area.
&&
.HYDROLOGY...
Issued at 120 PM EDT Mon Sep 12 2016
Rivers are running near to above normal for the time of year.
Fortunately, only a tenth to quarter inch of basin-average precip
is expected Tuesday into early Wednesday. Somewhat heavier totals
are possible Friday into Saturday. Flooding is not expected.
&&
.GRR Watches/Warnings/Advisories...
MI...Beach Hazards Statement until 4 PM EDT this afternoon for MIZ037-
043-050-056.
LM...Small Craft Advisory until 4 PM EDT this afternoon for
LMZ846>849.
&&
$$
UPDATE...TJT
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...Laurens
AVIATION...MJS
HYDROLOGY...CAS
MARINE...TJT
Area Forecast Discussion
National Weather Service Lake Charles LA
1044 AM CDT TUE SEP 13 2016
.UPDATE...
Sctd showers and tstms continue over the coastal waters this
morning. Hi-Res, NAM and RAP all indicate convection should stay
mainly acrs the srn half of the area today, and widely sctd in
coverage. Outside of those locations lucky enough to get some
cooling fm showers, expect mainly warm and muggy conditions today
with aftn highs around 90 degrees. Made minor adjustments to PoPs
to reflect recent trends but overall fcst is on track. 24
&&
.PREV DISCUSSION... /issued 622 AM CDT TUE SEP 13 2016/
AVIATION...Mostly VFR conditions are expected during the period,
however scattered showers and storms will develop around mid
morning and linger through the afternoon. Lower vis and ceilings
will be possible around storms. Winds will be generally east and
around 10KTS or less.
AT
PREV DISCUSSION... /issued 228 AM CDT TUE SEP 13 2016/
DISCUSSION...
Wx map shows surface low pressure trough over the central and
eastern Gulf of Mexico across Florida, generating scattered to
numerous thunderstorms. For our region, seeing nocturnal showers
and thunderstorms across the coastal waters, generally moving west
in the easterly flow.
Abundant moisture (area PW near 2" again) combined with a weak
upper level low off the Louisiana coast will continue scattered
showers and thunderstorms. The best chances of showers and
thunderstorms will be across the coastal waters from Midnight
through late morning, and further inland for the afternoon. This
cycle will likely continue through the weekend, diminishing
slightly by early next week. Temperatures will be running about 5
degrees above normal for lows, and near to a couple of degrees
above normal for highs (depending on any given area receiving
rainfall and cloud cover before high temperature potential
reached) through the period.
MARINE...
Easterly winds will prevail this week as a surface low pressure
trough over the central and eastern Gulf of Mexico moves west.
Elevated tides of 1 to 1.5 feet above astronomical tides will
continue the next couple of days. The pressure gradient is
expected to relax by Friday into the weekend. Otherwise, abundant
moisture combined with a weak upper level low off the Louisiana
coast will continue scattered showers and thunderstorms.
DML
&&
.PRELIMINARY POINT TEMPS/POPS...
AEX 92 73 92 74 / 30 30 40 20
LCH 89 75 90 76 / 40 30 50 20
LFT 89 74 90 74 / 40 30 50 20
BPT 90 76 90 76 / 40 30 50 20
&&
.LCH Watches/Warnings/Advisories...
LA...None.
TX...None.
GM...None.
&&
$$
Area Forecast Discussion
National Weather Service Phoenix AZ
840 AM MST TUE SEP 13 2016
&&
.SYNOPSIS...
A weather disturbance will move north of the area today resulting in
breezy conditions and scattered afternoon and evening thunderstorms
over higher elevations of central and eastern Arizona. A much drier
airmass will envelop the region through the remainder of the week
yielding widespread dry weather and temperatures remaining near to
slightly cooler than normal.
&&
.DISCUSSION...
A quiet morning across our cwa today, with the KYUX and KIWA radars
not showing any precip at this hour, and with most locations only
reporting SCT-BKN mid-high level cloud decks. Dewpoints remain
elevated across most of south-central and SW AZ (in the 50s and low
60s), with dewpoints down in the upper 20-mid 40 range across SE CA.
The latest WV satellite loop continues to show a 60KT jet steak
rounding the base of the main upper trof, now extending eastward
across northern baja into extreme SW AZ. This jet is expected to
provide the lift to generate some shower/TS activity across south-
central AZ this afternoon. Current HRRR high-res model runs continue
to show the convection developing over the higher terrain east of
Phoenix, with little, if any storm development in the lower deserts,
which is in-line with current forecasts. Given the consistency of
the HRRR, along with the latest (12Z) NAM 4km model run, and the 1st
few frames of the 12z GFS, our current forecasts still are looking
best, and (outside of some minor adjustments to the hourly grids),
no updates are planned at this time.
&&
.PREVIOUS DISCUSSION...
A rather distinct PV anomaly was descending towards KOAK early this
morning with objective analysis indicating a 60kt H5 jet streak
beginning to round the trough base through cntrl California. The
most notable height falls were already translating eastward and will
spread into central Nevada and Utah throughout today as the
shortwave/cold core starts lifting into the Great Basin. Further to
the south, subtle height rises and warming aloft were noted in
regional Arizona 00Z sounding data and hourly objective analysis
such that midlevel lapse rates and elevated instability were far
more muted than 24 hours ago. Adding to the atmospheric complexity,
fairly robust shallow moisture was sampled in the far SW portion of
AZ, however the vast majority of the area could only muster 7-9 g/kg
sfc-H7 moisture levels early this morning.
This leads to a tricky forecast through the afternoon and early
evening hours as this shallow moisture in SW Arizona will be pulled
northeast towards the best pressure falls in nrn AZ/Utah, yet into a
H7-H5 layer that continues to warm and dry limiting overall
instability and heightening Cinh. Comparison of NAM and GFS Bufr
soundings shows a small window late this afternoon where lower
elevation MLCape approaches 400 J/kg with minimal Cinh, albeit only
briefly before drier air around the H7 layer begins to dominate. As
of this writing, really only the HRRR suggests lower elevation
convection with even the typically overzealous UA-WRFs and EMC WRF-
NMM core highlighting storms only at higher elevations of far
eastern Maricopa/eastern Pinal/southern Gila counties in the 21Z-03Z
time frame. There is also the distinct possibility of more extensive
mid/high clouds blanketing much of cntrl AZ later today further
limiting overall instability.
Thus, conceptually feel the best opportunity for deep convection
will lie with terrain forced ascent of shallow moisture profiles
within the stronger deep SW flow over the foothills and mountains
just east of the Phoenix metro. This activity would quickly
propagate downstream into eastern Pinal and southern Gila county
given the mean steering wind profiles. Similar to yesterday, sfc-6km
bulk shear values will approach 30kt yielding some chance for better
organized storm structure; however, the aforementioned muted
instability and lapse rates may be the primary limiting factor for
wind and hail producing storms. Otherwise, the other notable feature
this afternoon will be an enhanced breeziness as the pressure
gradient tightens ahead of height falls to the north. While somewhat
unusual for mid September, wind speeds do not look overly strong but
potentially enough to lift a suspended dust layer - particularly in
areas that have seen little to no rainfall this summer (i.e. SE CA
and far western AZ).
Medium range models continue to project very little forecast
uncertainty for the latter half of the week with the primary
shortwave trough lifting into the plains, yet weak negative height
anomalies and persistent dry westerly flow lingering through the SW
Conus. This flow pattern will push any appreciable moisture east of
the Continental Divide and well into central Mexico starting
Wednesday afternoon dictating no chance of rainfall throughout the
entire region for at least several days. A deepening low over
Arizona may try to pull moisture back into parts of the forecast
area later in the weekend, however the quicker forward motion to
this wave may only allow some wrap around midlevel moisture into the
far eastern parts of the state. H5 heights will languish in a 582-
584dm range keeping temperatures in an average to slightly below
average range. In fact, with cooler daytime temperatures, an
extremely dry airmass, and clear skies, overnight lows will easily
plummet into the 60s for many lower elevation locations (and even
some 50s in the coolest communities). A definite sign that desert
southwest autumn weather is not that far away.
&&
.AVIATION...
South-Central Arizona Including KPHX, KIWA, and KSDL:
Upper low centered over northern California as of 10Z will lead to
increasing mid clouds this morning (AOA FL100-120). Not expecting a
repeat of morning thunderstorms but a stray weak shower couldn`t be
ruled out. As the morning progresses, surface winds will strengthen
with gusts of 25 kts becoming common by 18Z. Initially, directions
will favor southeasterly, then southerly before slowly trending
southwesterly. Expect thunderstorm development to begin over Gila and
Pinal Counties after 20Z. Isolated thunderstorms are quite possible
over metro Phoenix after 21Z. Thus VCTS in the TAFs (more likely
affecting eastern half of Valley). Moderate to strong southwesterly
steering flow will make for more coherent storm motion than we often
have during the Monsoon. Clouds and storms (if any) will diminish
after sunset and winds will start to weaken.
Southeast California/Southwest Arizona including KIPL and KBLH:
Lingering dust over portions of southeast California has caused
locally reduced visibilities...down to 4SM...including KIPL.
Anticipate some improvement later this morning. Breezy to locally
windy conditions redevelop this afternoon with gusts of 25 kts
common. Some locally reduced visibilities in blowing dust will be
possible again. No clouds except perhaps some minor cirrus. Winds
will weaken during the evening...lingering longer near higher terrain
as well as Imperial Valley.
&&
.FIRE WEATHER...
Thursday through Monday...
Temperatures will slowly increase Friday through Monday after
starting off a few degrees below normal on Thursday. Dry air will be
in place with minimum humidities in the single digits on the lower
deserts Thursday and Friday (15-20% higher terrain) with fair to good
overnight recovery. Anticipate some modest improvement early next
week. No thunderstorms are expected across the forecast area through
Monday.
&&
.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...Percha/MO
AVIATION...AJ
FIRE WEATHER...AJ
Area Forecast Discussion
National Weather Service Tallahassee FL
1025 AM EDT TUE SEP 13 2016
.UPDATE...
No major changes to the going forecast needed at this time. Mostly
cloudy skies across our CWA with showers across the coastal
waters. Watching towards the east for convection developing and
moving into our eastern sections in the next few hours. The center
of the tropical wave which moved inland earlier is west of
Titusville and moving slowly northwestward. Influx of tropical
moisture will feed the east coast seabreeze, along with rainbands
moving onshore the Florida east coast, will spread into our CWA
through the day. 50-70 PoPs today look reasonable. Will keep an
eye on temperatures in case we need to lower based on widespread
cloud cover so far this morning.
&&
.PREV DISCUSSION [628 AM EDT]...
.NEAR TERM [Through Today]...
A tropical airmass with plenty of deep moisture will remain in place
today. In fact, deep moisture will be increasing today with PWATs
above 2 inches expected by the end of the day. As of 08z this
morning, area radars and surface observations show a fairly small
but well defined area of low pressure moving northwestward from near
Vero Beach. The overnight HRRR runs move this low to near Ocala by
this evening. Scattered to numerous showers and thunderstorms are
expected to develop across the area this afternoon given the
tropical airmass and weak forcing, especially across the eastern
half. Given the expected cloud cover and convective coverage today,
high temperatures are expected to hold in the upper 80s to near 90,
although with dewpoints in the low to mid 70s, heat indices will be
in the mid to upper 90s this afternoon.
.SHORT TERM [Tonight Through Thursday]...
Interesting forecast this cycle with a tropical wave moving across
the Florida Peninsula and into the region by late tonight into
Wednesday. Model guidance is actually fairly split with two
main solutions. The GFS prefers to keep much of the activity with
the tropical wave across SE GA. The NAM is decidedly the more
western (and stronger) outlier with a weak low pressure area
moving toward Panama City on Wednesday afternoon. The 13/00z Euro
represents a bit of a compromise solution between these two
drastically different solutions. The ECAM package was useful in
constructing the short term forecast given all the differences in
the model guidance.
Where all the models agree is that precipitable water values will
be increasing considerably tonight and remaining high through
Thursday. While widespread heavy rainfall is not anticipated at
this time, given then generally weak forcing with the tropical
wave, the especially moist environment will support locally heavy
rainfall, especially across the eastern portion of the region.
For this cycle, will keep rain chances in the 70-80 percent range
across the Central and Eastern portion of the region late tonight
through Wednesday, with slightly lower rain chances off to the
west. By Thursday as the wave is likely to dissipate, leaving
just a very moist tropical airmass in place, expect fairly good
coverage of showers and thunderstorms, so have increased PoPs into
the 60-70 percent range across the entire forecast area.
With extensive cloud cover and convection, afternoon high
temperatures should generally stay in the mid 80s both Wednesday
and Thursday.
.LONG TERM [Thursday Night Through Tuesday]...
With the tropical wave dissipated by the start of the long term
period, all that will remain across the region is a very moist
tropical airmass that will support scattered to numerous showers
and thunderstorms across the area. It`s not really until Sunday
that the airmass begins to dry out a little - and really Tuesday
before significantly drier air arrives from the NE. As a result,
rain chances remain well above normal through Sunday and then
decrease toward the end of the long term period. High temperatures
will initially be in the upper 80s at the start of the period and
then as convection/cloud cover decreases late in the period, high
temperatures should return to the lower 90s.
.AVIATION...
[Through 12z Wednesday] A tropical airmass will remain in place
today. A brief period of LIFR ceilings is possible at VLD through
14z this morning before lifting. For this afternoon, scattered
to numerous showers and thunderstorms are expected. The terminals
that have the highest chance of seeing thunderstorms this
afternoon include VLD, TLH, and ABY, although storms are also
possible at ECP and DHN.
.MARINE...
A tropical wave will move across the Florida Peninsula tonight and
increase winds to near cautionary levels across the coastal
waters. As this wave dissipates on Thursday, winds and seas will
return to typically low levels into the weekend.
.FIRE WEATHER...
Red flag conditions are not expected for the next several days with
RH remaining above critical levels.
.HYDROLOGY...
With tropical moisture increasing considerably late tonight and
the airmass staying very moist through at least Friday, the
potential for locally heavy rainfall will exist across the region.
While widespread average totals in the 2-2.5 inch range are
expected across the central and eastern portions of the region,
locally heavier totals to near 5 inches will be possible through
Thursday. This suggests that the flood threat during the short
term period will be limited to urbanized flooding from heavy
downpours.
While most area rivers can accommodate this sort of rainfall
event, the Steinhatchee River remains just above action stage and
will need to be closely monitored if the heavier rains are focused
across the Southeast Florida Big Bend.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 89 74 85 74 87 / 60 50 70 40 60
Panama City 87 74 85 75 85 / 60 40 50 40 60
Dothan 89 71 85 72 85 / 50 30 50 40 70
Albany 90 73 85 72 86 / 60 50 80 50 70
Valdosta 87 73 85 72 87 / 70 70 80 50 70
Cross City 86 73 86 73 87 / 70 70 80 40 60
Apalachicola 87 75 85 77 85 / 60 40 50 40 50
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk until 8 PM EDT this evening for Coastal
Franklin.
GA...None.
AL...None.
GM...None.
&&
$$
UPDATE...Scholl
NEAR TERM...DVD
SHORT TERM...Godsey
LONG TERM...Godsey
AVIATION...DVD
MARINE...Godsey
FIRE WEATHER...DVD
HYDROLOGY...Godsey
Area Forecast Discussion
National Weather Service Denver/Boulder CO
204 PM MDT TUE SEP 13 2016
.SHORT TERM...(This evening through Wednesday)
Issued at 204 PM MDT Tue Sep 13 2016
Southeast low level flow around a surface high over the Central
Plains is producing downslope north of the Palmer Divide providing
some clearing. This southeast flow is also keeping the stratus
over northern parts of the Urban Corridor and also the eastern
plains. Expect the stratus to continue to erode from the edges
through the afternoon. Low level flow eventually turns south-
southwest which will bring slight drying and help erode the
stratus this evening. Surface winds will remain south to southeast
over the eastern plains and into the Greeley-Fort Collins area. So
expect low clouds for tonight and Wednesday morning in these
areas.
As far as precipitation goes, airmass is somewhat unstable over
the higher terrain where scattered showers and isolated
thunderstorms are expected form. Most of the convection should
dissipate as it moves off the higher terrain and into more stable
air. However, a weak wave over Utah may provide enough lift to
help showers persist through the evening as they move onto the
plains. Some models, such as the HRRR show showers through about
06z. Will keep scattered pops in the forecast for this.
On Wednesday, partial clearing will allow temperatures to climb
into the 70s for most of northeast Colorado. CAPE will climb up to
1000 J/kg. This instability combined with a weak wave aloft is
expected to produce scattered afternoon thunderstorms. Area of max
instability will be small, so the threat for severe weather should
be low, though a couple of severe storms will be possible. Because
of the cool airmass, small hail will be possible with most of the
thunderstorms.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 204 PM MDT Tue Sep 13 2016
The closed low/upper trof now over Northern California will slowly
move Northeast into the Northern Rocky mountain region Wednesday
night and Thursday. This trof will send an associated jet streak
across Colorado with a batch of showers and storms moving over the
plains through Wedneseday evening. Some of these storms could get
quite strong with ample shear and surface based capes of
1000-1500j/kg. As the upper trof sweeps across the Northern
Rockies and high plains Thursday night, an associated cold front
will push southward over Eastern Colorado with a reinforcing shot
of cooler air. Thursday will be drier yet remaining on the cool
side under a more subsident airmass behind the trof. However there
will still be enough moisture for isolated storms mainly over
higher terrain.
For Friday and Saturday, Colorado still under some weak influence
of sheared out trof with some lingering moisture and shallow
upslope flow. This will result in continued chance for
showers/isolated thunderstorms especially over mountains and east
slopes. Drier again for Sunday and Monday under a bit drier West
to Southwest flow.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 204 PM MDT Tue Sep 13 2016
Low clouds are expected over the eastern plains and over northern
parts of the Front Range, KFNL and KGXY, with ceilings of 500 to
2000 feet. Southerly flow may limit low clouds in the Denver area.
However a Denver Cyclone may bring northerly winds around 12z and
usher in the low clouds and possibly fog. Will have reduced
visibility at KBJC with low clouds. For KDEN, it will be a close
call for low clouds and fog. Added VCFG for the threat of fog and
added a low scattered cloud layer. Later shifts will need to keep
an eye of the chance for low clouds and fog at DIA. If low clouds
move in, they will clear much sooner Wednesday. With some sun
expected Wednesday, the airmass will become unstable and scattered
thunderstorms are expected after 20z.
&&
.BOU Watches/Warnings/Advisories...
None.
&&
$$
SHORT TERM...Meier
LONG TERM...Entrekin
AVIATION...Meier
Forecast discussion for routine afternoon forecast issuance
.SHORT TERM...Tonight and Wednesday
Issued at 231 PM CDT Tue Sep 13 2016
The latest RAP analysis and satellite/radar imagery show a cold
front exiting eastern WI early this afternoon. However, scattered
light showers and drizzle are lingering behind the front and mainly
over northeast WI. Expect a chance of light precip will depart
northeast WI later this afternoon. Behind the front, colder and
drier air is filtering southeast across the state. Combined with
unstable conditions over western Lake Superior, steepening low level
lapse rates are producing a cu field behind the stratiform cloud
mass right over north-central WI. Not out of the question that a
few showers could also pop here late this afternoon as well. Besides
small precip chances, cloud trends are the main forecast concern.
Tonight...Cold advection will continue behind the front tonight, as
Canadian high pressure settles across the region. Think most light
precip will have exited eastern WI behind the front by the start of
the evening. However, the tail of a shortwave passing over Lake
Superior in addition to increasing unstable conditions could lead to
a few showers over far northern WI during the evening, before
becoming confined to the lake effect belts in Vilas Co. overnight.
Cloud cover is more difficult to project. Low stratus will likely
exit to the east this evening, but plenty of broken strato-cu lies
upstream over the northwest part of the state. In addition, a large
mid and upper cloud shield will spread across much of central and
northeast WI by this evening. The end result should yield mostly
cloudy conditions through the evening, then partial clearing
arriving from the west overnight. Cooler with lows in the mid 40s
north to mid 50s south.
Wednesday...Canadian high pressure will be building into the region
through the day. Some clouds may linger over far northern WI during
the morning before the flow backs around midday. Though flat
diurnal cu is possible elsewhere, should see a partly cloudy to
mostly sunny day. High temps mainly in the mid to upper 60s.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 231 PM CDT Tue Sep 13 2016
Primary focus during this period is the frontal system and short
wave trough late this week into early this weekend.
An upper ridge and surface high pressure system will drift over
the region Wednesday night into Thursday evening. 850 mb temps
from 4 to 6 above zero with light winds and a dry air mass may
produce patchy to areas of frost across parts of north central
wisconsin Wednesday night. Longer nights may promote fog
development as well. cooler air over the lakeshore regions may
produce more lake clouds Wednesday night into Thursday if the
onshore wind can remain persistent.
Return flow begins Thursday as the high pressure system drifts
eastward and a low pressure system approaches from the west. This
low pressure system is associated with an upper trough which
originated over the western states.
Medium range progs track the upper trough over the Northern
Plains starting Thursday night before departing the northern
Great Lakes region later Saturday. Best dynamics and instability with
the warm air advection and height falls over the northern plains
and northwest Wisconsin late Thursday night into Friday morning,
then with the fropa later Friday or Friday evening over eastern
Wisconsin. A dry slot working over the area later friday night
may end precipitation a bit quicker. Upper low and cyclonic flow
with wrap around showers may work back into mainly northern
Wisconsin on Saturday.
Another high pressure ridge with surface high pressure will build
into the region Sunday into the new work week for another quiet
period of weather and gradually warming temperatures to slightly
above normal.
Getting beyond this forecast period and confidence is low, but
do note the GFS continues to produce a very deep trough over the
northern plains by mid week next week with pwats climbing to near
2.00 inches. The ECMWF on the hand trended from a zonal pattern
to a broad upper ridge over the mid section of the country for
much of the week. The ECMWF is there warmer and holds of any
precipitation until late next week.
&&
.AVIATION...for 18Z TAF Issuance
Issued at 1203 PM CDT Tue Sep 13 2016
A cold front will be exiting eastern WI this afternoon.
But scattered light showers and drizzle will linger right behind the
boundary through mid afternoon over the Fox Valley and towards the
end of the afternoon along the lake shore. Widespread mvfr cigs
will be lingering in these areas into early this evening. Cigs are
improving into the vfr range over north-central WI and this trend
should spread southeast into central and far northeast WI later this
afternoon. Though some uncertainty remains, will probably see
improving cigs into the vfr range over eastern WI this evening. Once
vfr conditions arrive, they will likely persist through the end of
the taf period.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......TDH
AVIATION.......MPC
Area Forecast Discussion
National Weather Service Huntsville AL
205 PM CDT TUE SEP 13 2016
.DISCUSSION...
Looks like a low/mid level convergence zone mainly from nrn AL thru
mid TN and into wrn VA, was responsible for sct shra/tsra over much
of the cwa. However the best coverage of shra/tsra attm is over nw
AL. Main threats from these slow moving tsra will be hvy rain and
gusty winds. The HRRR shows shra/tsra dissipating not too long after
sunset. Otherwise the TN valley is between a weak tropical system off
the sern coastline and a cdfnt over the midwest.
By Wednesday the above mentioned cdfnt will drift towards the TN
valley along with a weak building upper high. The chc of pcpn will be
on the low side, however with daytime heating and enough instability
during the aftn hours, will go with a slight chc of pops across the
cwa. Again the chc of shra/tsra will taper off by the evening.
On Thursday and Friday, there may be enough subsidence (thanks to an
upper ridge) across the area to keep pcpn at a minimum. However will
keep a low pop in mainly for the aftn hours to match with surrounding
offices. Also for now the models are showing that the previous
mentioned weak tropical system should not have much affect across
the TN valley, as it is progged to keep well east of the area.
By the weekend another cdfnt will be affecting the TN valley with a
better chc of pcpn. Attm the ECMWF looks to be more bullish with
pcpn than the GFS for the upcoming weekend. Also by the beginning of
next week, the ECMWF has an upper trof across the region on Monday
while the GFS shows an upper ridge. Since this period is so far out
in the fcst period, confidence is very low attm. Thus will maintain low
pops in fcst for this timeframe.
007
&&
.AVIATION...
(Issued 100 PM CDT TUE SEP 13 2016)
For 18Z TAFs: Convection will continue to develop across the area
through the afternoon, with more widespread coverage expected over NW
AL. As such, VCTS was included in the TAF at KMSL through sunset
this evening, with conds temporarily falling into the MVFR category
with the direct impact of a thunderstorm. At KHSV, convection should
be a bit more spotty, but went ahead and included VCSH through sunset
as well given upstream trends. Otherwise, skies will clear out a bit
overnight and patchy fog will be possible after midnight, but should
remain in the MVFR category through sunrise. VFR conds are expected
after 14/14Z, with only an isolated shower/storm possible at the
terminals.
12
&&
.PRELIMINARY POINT TEMPS/POPS...
Huntsville 69 91 68 91 / 20 20 10 20
Shoals 70 93 70 92 / 20 20 10 20
Vinemont 68 91 67 90 / 20 20 10 20
Fayetteville 67 90 67 88 / 20 20 10 20
Albertville 67 90 68 90 / 20 20 10 20
Fort Payne 67 90 68 89 / 20 20 10 20
&&
.HUN Watches/Warnings/Advisories...
AL...NONE.
TN...NONE.
&&
$$
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
259 PM CDT TUE SEP 13 2016
.SHORT TERM...
245 PM CDT
Through Wednesday...
A cold front lies across southern WI through eastern IA and is
slowly pushing southeast. Convective allowing models are over doing
precip development over the next few hours. However, the latest RAP
analysis shows around 1000 J/kg with little to no CIN to speak of. A
few light echoes are appearing on radar, but doubting that any
precip is reaching the ground. Expecting isolated to scattered
storms to form ahead of the front late this afternoon into this
evening. Best coverage will be along & south of I-88 this evening
and overnight. Shear is not fantastic so not expecting severe
storms. However, PWAT values are 1.25-1.5 inches and the front is
moving very slowly. Therefore some storms may produce heavy
downpours that may result in localized ponding. Winds become
northwest to north behind the front.
Winds turn northeast off of the lake Wednesday. Expecting a few lake
effect rain showers to form and push onshore in the morning thanks
to the elongated fetch and high lake induced CAPE values.
Conditions become more stable in the late morning, and showers come
to an end. Clouds are slow to clear, but cooler air moves in behind
the cold front. High temps tomorrow will be in the mid to upper 70s
away from the lake. Highs will be around 70 along the lake shore.
JEE
&&
.LONG TERM...
245 PM CDT
Wednesday night through Monday...
High pressure will settle east of Lake Michigan Wednesday night
into Thursday, which will maintain southeast flow across the region.
The cutoff low currently over California will be meandering
eastward across the Northern Great Plains on Thursday. This will
induce downstream ridging, which coupled with a drier low level
flow should keep precipitation to the west.
Eventually warm advection and height falls ahead of the approaching
low will eventually lead to an expansion of shower coverage, but
these forcing mechanisms appear to remain fairly weak even
Thursday night. We do still maintain southeast surface flow as the
upper low and surface convergence remain favored off to our
northwest which should limit the impacts. Still some disagreement
as to how much of the overnight activity survives into Friday
morning, therefore have maintained some chance pops, but the best
combination of moisture return and forcing would be later
Friday/Friday night when moisture transport/convergence is
maximized along the front. Diurnal timing would suggest just
showers.
Eventually the surface frontal trough will come through Friday
night into Saturday as the main upper low finally pushes east
across Lake Superior. High pressure returns Sunday for a sunny and
seasonal day with highs in the lower 70s. The high shifts east
Monday for warmer but still dry.
KMD
&&
.AVIATION...
For the 18Z TAFs...
A cold front lies just northwest of IL across southwest WI and
northeast IA. The cold front will slowly shift southeast and
isolated to scattered showers and storms should form ahead of and
along the front. Have limited confidence in thunderstorm coverage
and location so kept VCTS in the TAFs. Winds shift to the
northwest behind the front. Rain showers should accompany the
front and persist through most of the night. Guidance is no longer
hitting MVFR cigs as hard, but MVFR cigs are currently being
observed along and behind the front. Decided to trend up to
slightly higher MVFR cigs through early Wed morning. Winds become
northeast early Wed morning and still expecting isolated to
scattered lake effect rain showers. Not expecting much of an
impact from them. Showers dissipate and cigs raise to VFR by noon.
JEE
&&
.MARINE...
245 PM CDT
A weak cold front will sweep across the Great Lakes region
tonight. Modest high pressure will develop across the plains
tonight. Northeast winds ahead of the high will lead to some
higher waves across southern Lake Michigan Wednesday, and lead to
hazardous conditions to small craft. The high will shift over the
lake Wednesday night and then to the Atlantic coast by Friday. Low
pressure across the northern Rockies/Plains will slowly drift to
southern Ontario by the weekend. This will result in lighter
southerly/southeasterly flow across the lake through Friday,
increasing some as the wind shifts southwest ahead of the low
Saturday before a weak cold frontal passage Saturday night.
KMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement...ILZ006-ILZ014...4 AM Wednesday TO 10
PM Wednesday.
IN...Beach Hazards Statement...INZ001-INZ002...4 AM Wednesday TO 10
PM Wednesday.
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...4 AM Wednesday TO 10 PM Wednesday.
&&
$$
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Area Forecast Discussion
National Weather Service Phoenix AZ
123 PM MST TUE SEP 13 2016
.UPDATE...Updated Aviation and Fire Weather Discussion.
&&
.SYNOPSIS...
A weather disturbance passing through the region this evening will
continue to trigger scattered showers and thunderstorms through this
evening, mainly over the higher terrain of central and eastern
Arizona. A much drier airmass will then envelop the region through
the remainder of the week, and into the upcoming weekend, yielding
widespread dry weather, with temperatures remaining near to slightly
cooler than normal.
&&
.DISCUSSION...
Tonight...
latest radar imagery is now showing convective activity beginning to
develop at this hour over the Rim County southward into Gila county,
with some light showers also showing up over northern Pima/extreme
southern Pinal County. These activity is being kicked off by a
shortwave/70kt upper jet max that is now rotating northeastward into
SW and south-central AZ. Although this jet max is generating
considerable mid and high cloudiness over SW and south-central AZ
(which will likely inhibit convective development over the lower
elevations), the latest SPC Mesoscale analysis is showing decent
MLCAPE (500-1000 J/KG) over the higher terrain east of Phoenix.
Thus, have raised pops a bit over Southern Gila County through the
early evening hours, which the HRRR also shows where most convective
activity should occur. Like last night, convective activity should
rapidly diminish after sunset as the atmosphere rapidly stabilizes
due to loss of solar heating and mid-level drying. The main impacts
from any storms that do form will be brief heavy rain and gusty
winds, as well as a chance for some small hail. Storm movement
should be quick enough to limit residence time over any one
location, limiting the the flood threat potential.
Wednesday through Monday...
Medium range models continue to project very little forecast
uncertainty for the latter half of the week with the primary
shortwave trough lifting into the plains, yet weak negative height
anomalies and persistent dry westerly flow lingering through the SW
Conus. This flow pattern will push any appreciable moisture east of
the Continental Divide and well into central Mexico starting
Wednesday afternoon dictating no chance of rainfall throughout the
entire region for at least several days. A deepening low over
Arizona may try to pull moisture back into parts of the forecast
area later in the weekend, however the quicker forward motion to
this wave may only allow some wrap around midlevel moisture into the
far eastern parts of the state. H5 heights will languish in a 582-
584dm range keeping temperatures in an average to slightly below
average range. In fact, with cooler daytime temperatures, an
extremely dry airmass, and clear skies, overnight lows will easily
plummet into the 60s for many lower elevation locations (and even
some 50s in the coolest communities). A definite sign that desert
southwest autumn weather is not that far away.
&&
.AVIATION...
South-Central Arizona Including KPHX, KIWA, and KSDL:
Gusty winds will be the main story today at Phoenix terminals.
Sustained westerly winds near 10 to 15 kts with gusts up to 30 kts
will persist for the remainder of the afternoon before lightening
early this evening. Scattered to broken mid-high clouds will
continue to cover the Phoenix terminals before becoming few to
scattered early tomorrow morning. Slight chances for thunderstorms
still exist today, primarily from the McDowell Mountains eastward,
however a low chance exists that a storm will pop overhead at any of
the Phoenix terminals. An outflow with an easterly component is not
out of the question this afternoon and early evening, however, it`ll
be tough for it to push its way westward with these strong westerly
winds.
Southeast California/Southwest Arizona including KIPL and KBLH:
Gusty south to southwesterly winds will persist at both TAF sites
for much of the TAF period before gradual weakening occurs after
midnight. Skies will remain mostly clear with a few scattered high
clouds passing overhead. Due to the strong winds at KIPL, blowing
dust with periods of visibilities down to 1SM have been included in
the TAF.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Friday through Tuesday... Temperatures will slowly increase Friday
through Monday. Dry air will be in place with minimum humidities in
the 5 to 20 percent through Saturday and then slightly increasing
Sunday through Tuesday(with the highest humidities over the higher
terrain east of Phoenix). Overnight, fair to good overnight
recoveries are expected. Winds will follow typical diurnal trends
with light winds. No thunderstorms are expected across the forecast
area through Tuesday.
&&
.SPOTTER INFORMATION STATEMENT...
Amateur radio Skywarn net activation is not expected at this time.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
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DISCUSSION...Percha/MO
AVIATION...Hernandez
FIRE WEATHER...Hernandez