Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/08/17
Area Forecast Discussion
National Weather Service La Crosse WI
600 PM CDT Thu Sep 7 2017
.SHORT TERM...(This evening through Friday)
Issued at 308 PM CDT Thu Sep 7 2017
At 3 PM, a short wave trough was moving southeast through
Wisconsin. Strong 900 to 700 mb frontogenesis associated this
system has resulted in showers across Wisconsin. The RAP shows
that this frontogenetic band will shift south tonight. So unlike
earlier this week where the showers dissipated with loss of
diurnal heating, these showers will continue through the night.
This is in good agreement with the meso models. The RAP actually
shows that this forcing continue into Friday morning across
northeast Iowa and southwest Wisconsin. However, BUFKIT soundings
at this time are showing that the depth of moisture will on the
decrease, so did not carry them into this time period. This is in
good agreement with the meso models which are dry at this time.
The combination of mostly cloudy skies and a well mixed boundary
layer will likely keep valley fog from developing tonight.
.LONG TERM...(Friday night through Thursday)
Issued at 308 PM CDT Thu Sep 7 2017
On Friday night and Saturday night, the combination of light
surface winds, dry dew points, and mostly clear skies will allow
temperatures in central and north-central Wisconsin to fall into
the 30s. Due to this, kept the mention of patchy frost in the
forecast.
On Monday night and Tuesday morning, a cold front will move
through the area. Bufkit soundings are very dry, so not
anticipating any rain from this system.
A much stronger cold front will move through the region on
Wednesday night. Like its predecessor, the air mass looks very
dry, so once again not expecting any rain from this system. One
thing this system is that it will pick up the remnants from Irma
over the Tennessee and Ohio valleys and take it out to sea.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 559 PM CDT Thu Sep 7 2017
Water vapor satellite this evening shows a short wave trough over
eastern Wisconsin that will move away from the region overnight.
At the surface, a weak area of low pressure was over north central
Minnesota with a weak front extending east into northern
Wisconsin. As the short wave trough moves away from the region,
the surface low is expected to fill in and dissipate while the
weak front gets pushed south through the area as high pressure
builds in from Canada. The showers over central Wisconsin tied to
the short wave trough will diminish in coverage but could linger
until the front moves through due to some frontogenesis along the
front. Not expecting these to move westward so will maintain the
dry forecast for both airports. A broken VFR ceiling will continue
into the evening until drier air starts to filter in behind the
front. This should keep any fog from forming overnight as skies
become mostly clear. Look for the mostly clear skies to continue
through Friday.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...04
Area Forecast Discussion
National Weather Service Caribou ME
1013 PM EDT Thu Sep 7 2017
.SYNOPSIS...
A cold front will exit the area this afternoon. A weak ridge of
high pressure will cross the area tonight. An upper level low
will cross the region Friday through Saturday.
&&
.NEAR TERM /THROUGH FRIDAY/...
1010pm Update...
Update to add isolated storms for much of Interior Downeast.
Just enough instability in the showers that a few strikes have
been reported just W/NW of Bangor.
645pm Update...
Update to introduce isolated to scattered showers this evening
to just after midnight. Although drier air is indeed moving in,
there is a well defined shortwave back in VT/NH that is
spawning some showers out ahead of it. HRRR and RAP have this
handled well and adjusted forecast accordingly.
Previous Discussion...
The cold front is rapidly moving across the state with
decreasing cloudiness and lower dewpoints behind the front. The
transient ridge will provide clearing tonight with the exception
of northern Aroostook County. Cold air advection behind the
front will drop tonight`s lows into the lower 50s. Dewpoints
will also drop towards the lower 50s. For Friday, an upper level
trough and accompanying surface trough will propagate towards
the western border by afternoon. These features will generate
scattered showers by afternoon with the highest likelihood
towards the Moosehead Lake region and the lowest chance along
the Down East coast. Humidity will remain low, but highs will
climb into the low to mid 60s in the Crown of Maine while highs
near 70F are expected for Bangor and most locations south of
Millinocket and Houlton. Clouds will tend to increase in the
form of diurnally-driven cu/stratocu by afternoon. Instability
parameters look rather modest and do not prompt mention of any
convection.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
Upper level low pressure will remain across the region Friday night
through Saturday night. The upper low will begin to exit across
the maritimes Sunday while surface high pressure begins to
build east toward the region. Skies will be mostly cloudy north
Friday night with a slight chance of showers, with
partly/mostly cloudy skies Downeast with also a slight chance of
showers. The upper low and cold pool aloft will be located
across the region Saturday. Mostly cloudy skies and showers are
expected Saturday. With steep mid level lapse rates, could also
have the chance of an afternoon thunderstorm. Could still have
a chance of mostly evening showers. Otherwise, skies will remain
mostly cloudy across northern areas Saturday night, with
mostly/partly cloudy skies Downeast. Generally expect partly
cloudy skies Sunday, though with the exiting cold pool aloft
could still have the slight chance of an afternoon shower.
Temperatures will be at slightly below normal levels
Saturday/Sunday.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
High pressure will cross the region Sunday night through
Tuesday with generally mostly clear skies. High pressure then
begins to exit across the maritimes Wednesday with a cold front
approaching northwest areas late though the exact timing is
still uncertain. Moisture will begin to increase with the
return flow in advance of the approaching cold front later
Wednesday, with a chance of showers Wednesday night. The cold
front should then begin to cross the region Thursday with a
chance of showers. Temperatures will be at near normal, to
slightly above normal, levels Monday through Thursday.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: Tonight and Friday will be VFR with the exception of
FVE and perhaps some other Northern Maine sites. There will be
cigs developing Friday between 3-5K ft with some low-topped
showers.
SHORT TERM: Occasional MVFR conditions are possible across
northern areas Friday night, with VFR conditions Downeast.
Occasional MVFR conditions are possible across the entire region
Saturday through Saturday night. Showers are possible Friday
night into Saturday night. The most numerous showers are
expected Saturday afternoon, along with the chance of a
thunderstorm. Generally expect VFR conditions across the region
Sunday through Tuesday.
&&
.MARINE...
NEAR TERM: Converted regular small craft advisory to a small
craft with hazardous seas since seas will remain up into Friday
night, but winds have died down to below small craft levels.
SHORT TERM: Small craft advisory level seas are possible Friday
night. Conditions are expected to be below small craft advisory
levels Saturday through Sunday. Could have a chance of showers
Saturday afternoon.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory for hazardous seas until 6 AM EDT
Saturday for ANZ050-051.
&&
$$
Near Term...Foisy/MCW
Short Term...Norcross
Long Term...Norcross
Aviation...Foisy/MCW/Norcross
Marine...Foisy/MCW/Norcross
Area Forecast Discussion
National Weather Service State College PA
1106 PM EDT Thu Sep 7 2017
.SYNOPSIS...
The deep mid-level trough will weaken and lift to our east and
be replaced by a strong mid-level ridge. At the surface a
massive anticyclone moves into our region and will dominate our
weather through Monday night. Then the flow from Irma and the
waning high may bring us some rain by mid-week. High confidence
in forecast Sat-Monday. Low confidence forecast by Tuesday due
to Irma extratropical transition.
&&
.NEAR TERM /UNTIL 9 AM FRIDAY MORNING/...
Radar shows the rain over western NY coming off Lake Erie. The
HRRR seems to show this as does most guidance and thus the
blends. This puts chance POPS in our NW and likely in our
extreme northwest overnight. Most of the significant rainfall
should stay north.
There are other more progressive showers over western PA.
Leading edge entering Cambria County. Most guidance weakens this
so slight chance in West/Southwest.
GOES-16 microphysics implies partly cloudy central PA, cloudy in
NW and mostly clear in southwest.
Will be a chilly early September overnight.
&&
.SHORT TERM /9 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Most guidance implies chance to likely POPS from northwest PA
along NY border to chance/slight chance central areas on Friday.
most of southern tier is forecast to be rainfree.
Any rain will be very light and the 0.01 values in the models
and ensemble members likely made the probabilities (PDF of the
member not true POP) show the slight chance in central PA. The
PW values are very low and thus any QPF would be very light.
CAMS will likely show the potential rain near NY border better
when the forecast range extends into that timeframe.
Except along NY border it should turn out to be pretty good day
and improving later in the day as the high to our northwest
builds in. GEFS and CME EFS show the high building in during the
afternoon. Weather should improve later in afternoon and
evening.
A cooler than normal day temperatures could struggle to reach 60
in colder spots of NW PA and just topping 70 in the southern
areas.
Betting on no rain and will cycle 35 miles tomorrow morning.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Updated Sat-Sunday. Cool dry weekend. Key feature Saturday for
us in monster high over eastern Great Lakes. It expands over
into our region overnight Saturday into Sunday. Should be chilly
morning Sunday but nice dry day. Weekend looks great if not
cool.
Previous:
The highly amplified, longwave trough that has influenced the
weather across the Northeast U.S. with below normal temps (and
will play a role in the ultimate course of powerful Cat 5
Hurricane Irma) and her impact on Florida and the SE U.S..
The trough will lift off to the northeast across the northern
Atlantic over the weekend and be replaced, by a large, slow-
moving and highly amplified sfc and upper high across the Glakes
and NE U.S. that will form a temporary rex-block pattern over
the Eastern U.S. with the sfc/upper high to the north, and Irma
to the south early next week.
The big question for the medium range still surrounds exactly
how this high and the eventual remnants of the currently
category five Hurricane Irma will interact. Any effect from the
remnant low and moisture plume from Irma wont occur here in
central PA until later Tuesday night or Wednesday at the
earliest. Any model solution tracking the remnant low northward
across the Central Appalachians will be faced with drawing in
the dry/CP airmass dissolving the circulation and drying up the
moisture.
The timing of the northern edge of the precip shield is fairly
consistent, and the central pressure will be filling to a rather
tame 995-1000mb as well as the circulation moves up to anywhere
near our latitude.
Prior to any visit from a much weakened Irma next week, this
weekend will feature nil pops and splendid late Summer weather
with abundant daytime sunshine and low humidity, and afternoon
high temps in the 60s...to lower 70s in the SE (or 8-10F below
normal).
The highest probability of rain falling in central PA will be
in the Tues PM through Wed PM time frame...with the greatest
chance coming Tues night with POPs at 60s, and raise to 50 POPs
on Wed.
A northern-stream upper level trough will be crossing the
Canadian plains right about (a-boot) the time Irma gets this far
north, and could catch ol` Irma and kick her out to the east,
or as the EC does, wrap her in and make a fairly deep storm over
the Upper Great Lakes and Lower Ontario. Will make no changes
to the forecast for the last few days of the cycle.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
For the 03Z TAFS, added in more VCSH.
Area of showers to the west moving eastward into our area
now, some thunder across southwestern NY, given very cold
air aloft. Steep lapse rates at BUF at 00Z up to 300 mb.
Still mainly VFR conditions overnight and on Friday.
Aside from the showers tonight, perhaps a few more showers
across the north early Friday.
.Outlook...
Sat...Early AM fog/low cigs possible KBFD/KJST.
Sun...Early AM fog possible KBFD.
Mon...Patchy AM fog possible.
Tue...Chance of rain.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Grumm
NEAR TERM...Grumm
SHORT TERM...Grumm
LONG TERM...Grumm/Lambert
AVIATION...Martin
Area Forecast Discussion
National Weather Service Cheyenne WY
830 PM MDT Thu Sep 7 2017
.UPDATE...
Issued at 827 PM MDT Thu Sep 7 2017
Mostly clear skies and light winds will prevail tonight. Latest HRRR
smoke progs indicate patchy coverage west of Interstate 25 tonight.
Updated weather grids to reflect these trends.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 305 PM MDT Thu Sep 7 2017
A few clouds have persisted overhead today, otherwise warm and dry
conditions have been the rule. Do not anticipate many changes for
the rest of today, with the one exception being wildfire smoke.
Smoke is evident on visible imagery especially west of the Laramie
Range although CYS ASOS has shown variable visibilities of 6-9mi
through the day as well. The movement of the upper ridge eastward
and resultant change in mid/upper level flow to the WSW will
likely advect in additional smoke from the west tonight through
early Friday. HRRR smoke progs show portions of Carbon County in
higher concentrations of smoke especially tonight under the
inversion, so take precautions if you`re sensitive to smoke by
closing windows and staying inside over the next 24hrs or so.
Friday is still looking more active as a shortwave trough drops down
from the northwest while moisture increases from the west and
southwest. Increasing jet energy and midlevel dynamics by peak
heating combined with upslope flow and convergence along the Laramie
Range should support development of convection over the mountains
and especially the Laramie Range by early afternoon. Sfc dew
points east across the plains are progged to be in the mid to
upper 40s, with resultant SBCAPES of 500-1000 J/kg. Thus, could
certainly see convection become more vigorous east off the
mountains through the afternoon and evening. Models do show a bit
of a cap across this area so not anticipating severe storms, but
bulk shear values are expected to be on the order of 40kts.
Therefore, will continue to advertise the possibility of small
hail and strong thunderstorm outflow winds. Rainfall and gusty
winds could help clear out some of the smoke, although not
confident as to exactly how much smoke will clear, and also
whether smoke will inhibit thunderstorm development.
The ridge will build overhead on Saturday as the shortwave trough
shifts to the east. Looks as though we`ll be in between systems and
within the subsident ridge so the chance for showers and storms will
be less. However, cannot rule out mountain convection as we will
remain in the fetch of midlevel moisture. Temperatures by Saturday
will be warm back into the 80s to low 90s.
.LONG TERM...(Sunday through Thursday)
Issued at 305 PM MDT Thu Sep 7 2017
The extended period will be dominated by above normal temps and
limited storm chances. Midlvl ridge center will be located near the
Colorado-New Mexico border on Sunday with the sfc trough across the
western Nebraska Panhandle. Isolated/scattered afternoon storms
look possible mainly over the higher terrain along the Colorado
Border with the main threat being gusty outflow winds. Heights
aloft do rise some by early next week. Without any real forcing
mechanism and only weak instability, will keep slight chance PoPs
mainly confined to the Sierra Madre and Snowy Ranges from Monday
through Wednesday. Despite the warm temps, fire weather concerns
will be minimal due to weak winds and min RH values remaining mostly
above 20 percent.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 555 PM MDT Thu Sep 7 2017
VFR. Some high clouds will primarily cover southeast WY tonight.
Winds will be light. Mid and high clouds increase across southeast
WY Friday. Widely scattered afternoon convection will develop,
mainly over the southeast WY mountains and plains. Included VCTS
at KCYS and KLAR after 18Z. Southerly winds will be become breezy
at times, especially over western NE. There may be brief visibility
reductions to 6SM in patchy smoke, especially along and west of the
Laramie Range.
&&
.FIRE WEATHER...
Issued at 305 PM MDT Thu Sep 7 2017
Humidity values between 10-20 percent have been observed along and
west of I-25 this afternoon, with higher humidities further east.
Winds overall have been light although occasional gusts of 15 to
20 mph have been observed. Expect improving humidities and
continued light winds after sunset. We`re still looking at
increased moisture and chances for showers/thunderstorms tomorrow
afternoon and evening as a weather disturbance approaches from
the northwest. Do think wetting rains are possible especially with
the potential for a few stronger storms, however lightning
strikes could still impact dry fuels. Gusty downdraft winds are
expected as well. This weekend we are looking another chance of
thunderstorms mainly in the mountains. Otherwise, mostly dry and
very warm conditions will continue to be the rule due to the
influence of the upper level ridge.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...MAJ
SHORT TERM...RJM
LONG TERM...ZF
AVIATION...MAJ
FIRE WEATHER...RJM
Area Forecast Discussion
National Weather Service Dodge City KS
616 PM CDT Thu Sep 7 2017
...UPDATE TO AVIATION...
.SHORT TERM...(This evening through Friday)
Issued at 318 PM CDT Thu Sep 7 2017
The large scale pattern showed a ridge centered across the
Intermountain West and upper level troughing across the Great Lakes
region. In the northwest flow pattern across the Western Plains,
there were a couple of notable shortwave troughs evident on water
vapor satellite and RAP analysis. The southern of these two features
continued to move toward western Kansas, and will push through late
tonight. This will prompt some weak frontogenesis around 700mb,
allowing some isolated to widely scattered showers and thunderstorms
to develop, mainly along/east of U283 corridor in the 06-12z time
frame overnight/early Friday morning. Otherwise, no changes required
in the grids. South winds will be 10 to 15 mph through the night,
keeping temperatures from dropping below the upper 50s for lows.
Highs Friday will be similar to today in the upper 80s to around 90.
.LONG TERM...(Friday night through Thursday)
Issued at 318 PM CDT Thu Sep 7 2017
The latest SuperBlend guidance looks pretty good, other than the
diurnal winds. We went with a modified CONSMOS forecast for diurnal
surface winds Saturday through Monday with the persistent leeside
trough in place. Persistence will be a good forecast method in the
quiet weather regime with rather weak flow aloft and similar 850mb
temperatures each day. After Monday, the forecast gets a bit
complicated as remnants of Hurricane Irma interact with an upper low
over the Tennessee Valley. This wouldn`t affect us directly, but
could alter the MSLP field enough to make for less breezy days as it
would help eliminate the leeside trough across eastern Colorado.
There are no formidable precipitation chances through the Long Term
period
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 613 PM CDT Thu Sep 7 2017
VFR conditions will prevail at all TAF sites through early Friday
afternoon. Southerly winds 5 to 15kt will persist across western
Kansas through early Friday morning as a lee side trough of low
pressure remains anchored across eastern Colorado. Southerly winds
will then increase 15 to 25kt through Friday afternoon as the lee
side trough strengthens.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 59 88 61 87 / 20 10 0 10
GCK 59 89 60 88 / 10 10 0 10
EHA 60 87 60 87 / 10 10 10 10
LBL 61 89 61 88 / 10 10 10 10
HYS 59 88 62 87 / 20 10 10 10
P28 62 87 61 86 / 20 20 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Umscheid
LONG TERM...Umscheid
AVIATION...JJohnson
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1151 PM EDT Thu Sep 7 2017
.AVIATION...
Cool and fairly moist low levels along with some weak convergence
off a sfc trough will support some degree of low cloud development
this morning. The expectation is that there will be large
variability in cloud heights during the morning before daytime
heating leads to the development of a VFR strato cu field. A cold
front will move across the area from Lake Huron this morning across
Se Mi late this afternoon. This front may lead to some lower cloud
development, with its passage being marked by a wind shift to the
north-northeast.
For DTW...A wide range of variable ceilings heights during the
morning will give way to a strato cu field (4-5k ft deck) by
afternoon. The frontal passage and resulting wind shift to the north
is expected around 21Z.
//DTW THRESHOLD PROBABILITIES...
* Moderate in ceilings below 5000 ft today.
&&
.PREV DISCUSSION...
Issued at 921 PM EDT Thu Sep 7 2017
UPDATE...
The coverage of showers will decrease during the course of the
overnight as the mid level short wave impulse slides east of the
state. A cold front now over far northern Lake Huron will however
push into the thumb region toward daybreak. The combination of low
level convergence and good over-lake instability will contribute to
some lake enhanced showers across the thumb region Fri morning. The
current forecast looks in good shape. A zone forecast update will be
issued later in the evening simply to remove evening wording.
PREV DISCUSSION...
Issued at 305 PM EDT Thu Sep 7 2017
DISCUSSION...
Much below normal temperatures to continue through the Weekend.
For the second day in a row we wait for late arriving showers, as
there is a modest moisture release from southwest lower Michigan as
seen in 850-700 MB Theta-E fields. Latest radar trends support
numerous to categorical pops. 18z DTX sounding came in with 500 MB
temp of -24 C, but low levels are fairly dry, as indicated by
surface dew points in the mid to upper 40s. Even so, the RAP
soundings still indicating sufficient cape, albeit skinny, to
support a couple of thunderstorms before loss of daytime heating.
Large scale upper level trough east of the Mississippi, with one
more shot of cold air to be delivered to Lower Michigan as another
good upper wave descends from Lake Superior, with 850 mb temps
forecasted to bottom out between 2 to 4 C over the Central Great
Lakes late Tonight. Trough axis pulling east into the Eastern Great
Lakes by early Friday afternoon, with strong northerly confluent
flow allowing large high pressure (1030+ mb) to build in for the
weekend. Low level airmass probably cold enough to support a few
Lake enhanced showers over Thumb region during Friday, before the
pronounced anti-cyclone takes hold and inversions heights crash down,
although still would not totally rule out an isolated shower Friday
night across the northern thumb region. Otherwise, favorable
radiating conditions will lead to a cold night, with good radiators
potentially slipping into the upper 30s. For reference, both MBS/FNT
record lows are in the upper 30s for September 9th. Early September
insolation on Saturday will help boost temps back into the mid to
upper 60s, but expecting a pretty good diurnal CU up for the
afternoon hours with light northeast flow off Lake Huron continuing.
An amplified upper-level ridge and surface high pressure system will
continue to bring pleasant conditions to Michigan Sunday into the
early part of next week. Temperatures will remain below seasonal
normals as Sunday daytime highs in the mid to upper 60s slowly climb
back into the lower 70s by Monday and into the mid-week period.
Despite the cooler than normal temperatures, high pressure will
suppress cloud cover, bringing plenty of sunshine to the region
through Monday.
An increase in cloud cover and possible rain chances will be
introduced into the forecast late Tuesday into Wednesday as remnants
from Hurricane Irma travel northwest from the Southeastern U.S. The
ECMWF and GEM long range model runs keep precipitation just to the
southeast, thus PoP values will remain sub-30 through the mid- week
period. While the GFS does show precipitation chances during this
time frame, it also features a secondary upper-level ridge building
in behind the low pressure, which would quickly push remnants of the
hurricane off to the east Thursday into Friday.
MARINE...
Fresh northwest winds will continue into this evening as decent
mixing depths support wind gusts into the 20 to 25 knot range over
the open waters of Lake Huron. Convection will remain rather active
over Lake Huron as well given the unstable conditions in place with
the cool airmass crossing the relatively warm lake waters. This will
also support a continued chance of waterspouts into Friday.
A cold front will to push south across the region tonight into
Friday morning. Post frontal winds will veer to the north. This
front will bring another push of cold air, boost over lake mixing
depths and supporting gusts around 20 knots on southern Lake Huron
on into Friday. The onshore flow will allow waves to build to near
Small Craft Advisory criterion from the tip of the Thumb south to
Port Huron.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from 8 AM to 7 PM EDT Friday for LHZ421-441-
442.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....SC
UPDATE.......SC
DISCUSSION...SF/AM
MARINE.......DG
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
539 PM MDT Thu Sep 7 2017
.SHORT TERM...(Tonight through Friday night)
Issued at 330 PM MDT Thu Sep 7 2017
As mentioned in previous discussions, the pattern was in the
process of changing subtly over the past 24 to 36 hours. Low
pressure off the West Coast has caused high pressure to weaken
over the area with two separate circulations having formed. The
first was over centered over central Idaho and the second was to
the south over west-central New Mexico according to 12Z model
initializations. This shift in circulation caused flow to shift to
a mean westerly direction over the forecast area which has
resulted in a reduction in smoke over the southern half of the
CWFA. However, smoke remained entrenched across northeast Utah and
northwest Colorado. Meanwhile, moisture levels have increased
over the area according to GJT`s 12Z sounding which has risen from
0.50 of an inch to 0.67 of an inch in the last 24 hours. This
increase was primarily in response to increased and lingering
showers in the deformation zone between the two circulation
centers discussed previously.
The increased moisture will translate into expanded areal
coverage of showers and thunderstorms late this afternoon and
evening with the southern and central mountains favored. Expect
this activity will be largely high based, producing strong outflow
winds with light accumulations. During this period expect
isolated storms to drift from higher terrain over adjacent lower
elevations. Some shower activity may continue in the deformation
zone into the early morning hours.
Moisture levels will continue to climb on Friday as flow aloft
shifts more to the southwest tapping into modest moisture over
northeast Arizona and southern Utah. This will result in increased
clouds and showers/thunderstorms and cooler temps. As the sub-
cloud layer moistens, expect convective cells will become more
efficient rain producers. Meanwhile, southwest flow is expected to
reduce smoke density across northeast Utah and northwest Colorado
according to latest experimental HRRR forecast. However, Deep
Creek, and Big Red Fires are likely to keep it smoky in and around
Steamboat Springs and surrounding areas. Increased moisture
levels and difluent flow aloft may again yield nocturnal showers
late Friday night.
.LONG TERM...(Saturday through Thursday)
Issued at 330 PM MDT Thu Sep 7 2017
Flow will continue from the west to southwest this weekend with
showers and thunderstorms reaching their greatest coverage Sunday.
As moisture levels rise, storms will become increasingly capable
of producing heavy rain. In response to increased moist convective
activity, temperatures will trend cooler but still a little above
normal for most locations.
High pressure reasserts itself over the forecast area early next
week as the low pressure along the coast closes off and drifts
south and retrogrades slightly. This will cause coverage of showers
and thunderstorms to trend downward and conversely, temperatures
will trend back upward. By the middle of the coming week, ECMWF
and GFS are in poor agreement resulting in low forecast
confidence.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 535 PM MDT Thu Sep 7 2017
VFR will prevail at the TAF sites for the next 24 hours. Isolated
thunderstorms in the higher terrain in central and southern
Colorado until about 02z which may impact KEGE, KASE, and KTEX
however any storm should be brief wind gusts to 30kts. Remaining
dry elsewhere with a tranquil overnight expected. After 18z Friday
isolated to scattered showers and thunderstorms are expected over
the mountains, most numerous in the south.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...NL
LONG TERM...NL
AVIATION...CC
Area Forecast Discussion
National Weather Service Grand Rapids MI
805 PM EDT Thu Sep 7 2017
LATEST UPDATE...
Update/Aviation/Marine
.SYNOPSIS...
Issued at 316 PM EDT Thu Sep 7 2017
The showers will gradually come to an end overnight and we will see
clearing skies through Friday morning, with most areas becoming
mostly sunny by noon. Then fair weather will continue into the
weekend. The dry weather is expected to linger until Wednesday when
we may see scattered showers that may last into Thursday.
We will remain cool through the weekend with highs in the upper 60s
to lower 70s. Then a warming trend is expected into next week, with
mid and upper 70s expected Monday through Wednesday. A slight cool
down is expected again by Thursday.
&&
.UPDATE...
Issued at 806 PM EDT Thu Sep 7 2017
While it is true the primary area of showers associated with the
shortwave is now moving out of the area there is yet another area
of showers over WI and Northern LK MI that has yet to move through
the area. The HRRR and ESRL HRRR both seem to like the idea of
bringing these showers through before midnight so I adjusted our
short term forecast to have conditional pops into mid evening.
With the sun setting the risk of thunderstorms goes with it so I
have dropped the risk of thunderstorms after 8 pm or so.
After that is done we have the issue of fog later tonight and
early Friday morning. There is some indication we could see enough
breaks in the clouds toward morning that fog could form. I put
patchy fog in the grids for that.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 316 PM EDT Thu Sep 7 2017
The combination of a short wave passing through and chilly air over
Lake Michigan will continue to produce showers and perhaps a
thunderstorm into this evening. Then fair weather moves in by late
tonight and continues through Saturday night.
The pcpn will continue as a short wave passes over the area
overnight. The showers will be enhanced by the lake, with deep
moisture and H8 temps of around +4C, over the +20C waters. The mean
flow will remain WNW this evening, but then an abrupt swing to the
NNE will occur late tonight, essentially ending the risk of rain
prior to daybreak Friday.
Surface and upper ridging builds in into the weekend producing fair
weather. Skies should start out fairly cloudy Friday morning, but
these should erode toward the noon hour. Thereafter expect mostly
clear skies continuing through the rest of the short term.
There will be the risk of frost Friday night over Central Lower
where some areas dip into the 30s. We may need a frost advisory for
interior areas like Evart and Harrison. Otherwise the bulk of the
CWA should mainly see Friday night lows of 40 to 45. Meanwhile
daytime highs will begin to inch upward as the high pressure moves
in. 60s for Friday, warming to 65 to 70 for Saturday.
.LONG TERM...(Sunday through Thursday)
Issued at 316 PM EDT Thu Sep 7 2017
A pretty stellar weather pattern is developing that will bring
abundant sunshine, mild temperatures, and lower humidity to the
region during the long term.
A large area of high pressure will slowly drift east during the
period. As winds become southeasterly, temperatures will slowly warm
from highs around 70 Sunday to the mid 70s Monday. Lows will range
from 45 to 55 through the period. Dry weather is expected under the
ridge. However late in the period, Wednesday and Thursday, the
models are showing the remnants of Irma drifting north toward the
Ohio valley. We may see a few showers develop from this, but that`s
far from certain.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 806 PM EDT Thu Sep 7 2017
There are two primary issues to me. First is the risk for short
term intense rain showers (thunder not out of the question but to
low a risk to put in tafs) between now and 9 pm. Then there is the
issue of dense fog possibly forming toward sunrise.
The primary shortwave is still moving out of the area but there
are still some intense rain showers moving through central lower
Michigan so I have for our eastern TAf sites. Also there is
another shortwave coming into our area for early this evening. As
a result have put in tempo for IFR/MVFR visibility showers till
around 04z for most of our eastern TAF sites.
Winds will become light and variable overnight and if skies even
partly clear with all the moisture from the rain today still
around, I could see patchy dense fog developing. For this I put
IFR VSBY in the 10z to 13z time frame for all but MKG. After that
we could see some low clouds until midday, but by mid afternoon
enough dry air should come in and clear the skies.
&&
.MARINE...
Issued at 806 PM EDT Thu Sep 7 2017
The winds and waves have all subsided so I allowed the SCA to
expire as it was forecast to. I put water spouts back in the near
shore zones till around midnight since another area of convection
is forecast to move through the area and winds will be lighter
allowing a better chance of water spout spin-ups.
&&
.HYDROLOGY...
Issued at 316 PM EDT Thu Sep 7 2017
River levels range from below normal for this time of year in
southern Michigan to above normal in central Michigan, and none are
near bankfull. The U.S. Drought Monitor (from the National Drought
Mitigation Center, University of Nebraska-Lincoln) has drawn areas
south and east of Grand Rapids in the D0 (Abnormally Dry) category.
Recent lake-enhanced rain the past few days has provided portions of
the lakeshore and central interior with a half to one inch of
rainfall. Much of the south-central interior, where it has already
been abnormally dry, has received less than a quarter inch. Dry
weather will again dominate over the next week as high pressure
returns. At the moment, significant moisture from Irma does not
appear it will reach this far north, except for perhaps light rain
showers on Wednesday/Thursday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...WDM
SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...04
AVIATION...WDM
HYDROLOGY...CAS
MARINE...WDM
Area Forecast Discussion
National Weather Service Marquette MI
1144 PM EDT Thu Sep 7 2017
.SHORT TERM...(This evening through Friday)
Issued at 357 PM EDT THU SEP 7 2017
Water vapor imagery and RAP analysis show a highly amplified pattern
across N America with a strong ridge extending from the Rockies into
n central Canada and a deep trof from Hudson Bay thru the Great
Lakes into the eastern CONUS. 500mb height anomalies in the ridge
and trof are a little over 200m. Last shortwave dropping into the
trof and passing across the western Great Lakes today has aided shra
coverage. There were even a few lightning strikes noted across
western Lake Superior and far western Upper MI early in the day.
Main fcst concerns in the short term revolve around ending -shra
this evening, potential of lake effect -shra and potential of frost
and/or freeze. With departure of shortwave and setting sun, expect
lingering -shra to end from nw to se this evening. During the night,
850mb temps are fcst to fall slightly with the lowest readings over
the eastern part of the lake at 0 to 1C. With water temps close to
15C over s central Lake Superior and NNE winds across the lake, not
out of the question that a few lake effect -shra or sprinkles could
develop into n central Upper MI. If this occurs, it would likely
occur late tonight/Fri morning during the min of the diurnal cycle
when lake effect processes are maximized. These NNE winds across the
lake also bring into question sky condition for much of the fcst
area, and thus increased uncertainty on min temps and potential
frost/freeze. The abundance of low clouds currently ne of the lake
will further support an increase in lake effect cloudiness later in
the night at least over the central and eastern fcst area. The w is
most challenging as low-level winds will generally be more
anticyclonic/divergent. At this point, it seems that there will be
low enough cloud coverage to support temps down to around 30F into
the mid 30s over portions of Gogebic/Ontonagon/southern
Houghton/Baraga/Iron counties, warranting a frost advy. If it ends
up clear most of the night, a widespread freeze would occur in that
area. On the other hand, if clouds dominate the night, there would
be no frost. For now, will hoist advy for the aforementioned area.
Evening shift will need to monitor cloud trends that might require a
change in areal coverege of headline.
On Fri, even if there isn`t much in the way of cloud cover off the
lake before sunrise, thermal trof over the area combined with
moisture added by the lake will likely lead to a blossoming of
stratocu during the morning as daytime heating gets underway. These
clouds would then dissipate during the aftn. Increase in sunshine
will lead to somewhat warmer conditions than today. Expect high
temps in the upper 50s to possibly mid 60s.
.LONG TERM...(Friday night through Thursday)
Issued at 445 PM EDT THU SEP 7 2017
Models indicate that the high amplitude pattern with a mid/upper
level trough over eastern Canada and the NE U.S. will give way to
ridging building into the region this weekend into next week. In
response, below normal temps Fri will give way to moderating
conditions this weekend into early next week with temps at or above
seasonal averages by early next week.
Fri night, expect a good chance for more widespread frost on Friday
night as the sfc high becomes centered over a larger portion of
Upper michigan with PWAT values to around 0.35 inches. Many inland
locations expected to be in the upper 20s to lower 30s.
Sat-Sun, High temps should rebound into the mid 60s Saturday, into
the upper 60s to lower 70s on Sunday and into the lower to mid 70s
on Monday as sfc high pressure continues to dominate and warm
advection gradually increases in a ssw flow.
Mon-Tue, Although the models continue to show decent height falls
across especially central Canada on Mon/Mon night with a mid-level
trough moving toward Hudson Bay, a weakening shortwave and
associated sfc trough is expected to move through the northern Great
Lakes. With the stronger forcing staying well north into Ontario,
the fcst will remain dry for the cwa.
Wed-Thu, larger model differences develop as the ECMWF/GEM maintain
the ridge over the cntrl CONUS into the wrn Great Lakes while the
GFS brings a front along with a a mid level trough into the Great
Lakes. Although confidence is lower, no pcpn is expected.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1143 PM EDT THU SEP 7 2017
Mainly VFR conditons are expected at each of the TAF sites through
the TAF period. The only exception will be KSAW where lake effect
clouds and low level moisture may bring some MVFR conditions through
early this morning. Additionally, some ground fog will linger near
the KIWD TAF site through the early morning hours; therefore, have
added a tempo group for that possiblity. With trough axis nearby,
daytime heating will likely provide some additional afternoon cloud
cover with a BKN ceiling possible around 3500ft. This should be
diurnal; however, and should dissipate during the evening.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 357 PM EDT THU SEP 7 2017
Lack of any significant weather systems in the vcnty of the Upper
Lakes will keep winds mostly blo 20kt thru the period.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Frost Advisory until 9 AM EDT /8 AM CDT/ Friday for MIZ002>005-
009>011-084.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...JLB
AVIATION...KEC
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Omaha/Valley NE
642 PM CDT Thu Sep 7 2017
.SHORT TERM...(Tonight through Sunday)
Issued at 250 PM CDT Thu Sep 7 2017
The primary forecast concerns are the chance for showers and a few
thunderstorms from Saturday into Sunday for parts of the area, and
temperatures on Friday.
Water vapor satellite imagery this afternoon in combination with
recent RUC model initializations showed a mid tropospheric ridge
from the Four Corners region up into Alberta. A trough was to the
east, from Hudson Bay down into the Ohio Valley. There were some
shortwaves troughs/vorticity maxima of interest. The first was
over far southwest NE. That feature should continue to drop
southeast but not have much impact on our area. The system along
the west coast near the CA/OR border. That will help weaken the
ridge to our west, and at the same time the trough to our east
will fill, resulting in deamplification of the pattern.
The KOAX 12Z sounding this morning only showed around 0.73
precipitable water. That should increase to around 1 inch Saturday
night and then remain between 1 and 1.50 inches through Sunday.
For the mid level pattern, by 12Z Saturday, a low should be over
the Dakotas. This may become a closed low briefly, then move into
MN by late Sunday as an open wave. At the surface, southerly winds
should remain mainly under 15 knots Friday. A warm front is
expected to lift northward, with far southeast NE making it into
the warm sector. Highs south of the warm front should reach the
mid and upper 80s. Low level moisture will be limited with a low
level ridge blocking moisture return from the Gulf of Mexico, but
there is expected to be enough (surface dewpoints 55-60 F) for
isolated to scattered showers and isolated thunderstorms. Highs
both Saturday and Sunday should reach the lower and mid 80s.
.LONG TERM...(Sunday night through Thursday)
Issued at 250 PM CDT Thu Sep 7 2017
There will be some chance of thunderstorms lingering into Sunday
night. For now, did not include any mention of precipitation for
Monday, although the 12Z GFS did suggest that was possible. The
rest of the week looks mainly dry, with highs averaging in the
lower and mid 80s.
Confidence drops to around or slightly below normal by Thursday,
in regards to details in our area, mainly due to a moderately
high spread of model solutions by that time. Some patchy clouds
with moisture increasing
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 636 PM CDT Thu Sep 7 2017
VFR conditions through the TAF period. There may be some patchy
fog in river valleys...however confidence too low to include in
tafs. Some scattered clouds in the a few layers from fl050 to
fl150 overnight and Friday.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Pocatello ID
245 PM MDT Thu Sep 7 2017
.DISCUSSION...
We are not forecasting any strong/dynamic weather systems to move in
and REALLY swap out our air mass, but there is good news for those
tired of the smoke! The high pressure ridge that has kept SE ID dry
is in the process of breaking down/shifting east. This will allow
winds to shift into the S/SW later this eve, with this flow
anticipated each afternoon and eve into next week. This may start to
slowly clear out some of our smoke, and sure enough, the latest run
of the HRRR smoke model shows this trend beginning tonight over SW
parts of the forecast area. The southerly winds will allow moisture
to start creeping in late this afternoon, which may trigger a few
isolated showers over the higher terrain of the Central Mntns and SW
Highlands. Fri will feature increasing moisture with a chance of
showers/t-storms expanding to the entire area. Greatest coverage and
forecast confidence exists over the Central Mntns, but isolated
storms cannot be ruled out anywhere, including the Snake Plain where
t-storm outflow boundaries may serve as a source of lift where
terrain is lacking. Sat looks nearly identical with greatest precip
over the Central Mntns and Southern/Caribou Highlands, as a weak
through swings through in the afternoon.
Confidence is increasing in weak high pressure building across the
region Sun-early Wed, providing another stretch of dry weather with
slowly warming high temps each day.
Model guidance continues to diverge Wed afternoon, resulting in a
very low-confidence forecast Wed-Thurs. Long range models all
feature a low pressure system moving onshore over central
California. The GFS maintains a closed low SW of us into Thurs,
while the EC/Canadian collapse the low into a trough that pushes
across the region Wed night/Thurs AM. In either case, precip is
possible. Have expanded low-end 15% PoPs across the entire forecast
area Wed, with 20-25% in the mntns. Will carry 20-40% chance of
precip Thurs, lowest in the Snake Plain and highest in all of our
mntns. Expect adjustments in the coming days as the models try to
get a better handle on this system. - KSmith/Valle
&&
.AVIATION...
HRRR smoke model seems in general agreement with eastward shift
of upper ridge. Smoke should begin to drift back northward as broad
southerly flow picks up this evening. Moisture will increase as a
result of the southerly flow and, by tomorrow afternoon, isolated
thunderstorms may be present over the Central Mountains. Thus,
including VCTS for KSUN. Other sites should remain dry, but
showing gradual increase in mid-level moisture. - Hinsberger
&&
.FIRE WEATHER...
HRRR smoke model seems in general agreement with eastward shift
of upper ridge. Smoke should begin to drift back northward as
broad southerly flow picks up this evening. Moisture will increase
as a result of the southerly flow and, by tomorrow afternoon,
isolated thunderstorms may be present over the Central Mountains.
Thus, including VCTS for KSUN. Other sites should remain dry, but
showing gradual increase in mid-level moisture. - Hinsberger
&&
.AIR STAGNATION...
Poor air quality due to wildfire smoke continues today across all
of southeast Idaho, with values ranging from Unhealthy to
Unhealthy for Sensitive Groups along with poor visibilities in
some areas. Light southerly winds are expected to develop this
evening, and exist each afternoon and evening for the next several
days. This, combined with a chance of a few showers and
thunderstorms Fri/Sat may help to start clearing some of the smoke
out of the region, with gradual improvement possible each day
starting tomorrow. - KSmith/NP/TW
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Pueblo CO
304 PM MDT Thu Sep 7 2017
.SHORT TERM...(This evening through Friday)
Issued at 251 PM MDT Thu Sep 7 2017
Thunderstorms have been more prevalent this afternoon thanks to the
presence of a shortwave moving through the upper ridge. Low level
moisture is still fairly limited, particularly across northern and
western portions of the area which has limited CAPE and storm
intensities quite a bit. Main threats will be lightning, gusty
erratic winds up to 45 mph and some brief moderate to heavy rain.
Better CAPE will remain across southern sections of the area,
particularly in and near the southern Sangres. CAPEs could approach
1000 J/kg which may allow storms to have some brief small hail.
Overall though severe thunderstorm threat looks nil. Will have to
monitor younger burn scars for heavy rainfall threat through this
evening, but even this threat looks fairly low for now.
Thunderstorms will diminish this evening though some lingering
convective debris cloudiness may help to hold temperatures up a
couple degrees across the mountains. Colder valley locations in the
mountains could see some upper 30/lower 40 degree readings by
morning, similar to last night. Friday looks similar to today.
Residual moisture and weak embedded disturbances will trigger
another round of thunderstorms across the mountains during the
afternoon. Primary threats will be gusty winds, lightning, and
brief moderate to heavy rainfall.
Will continue with haze in the forecast over the next 24 hours
though have seen some improvements across Chaffee and Lake counties
this afternoon in webcams. Experimental HRRR CONUS Smoke products
suggest smoke may increase through the evening across the eastern
half of the forecast area which will carry over into Friday morning.
Since restrictions to vis have been greater than 6 miles for most
areas yet still highly noticeable, will continue to carry Haze in
the grids for now. -KT
.LONG TERM...(Friday night through Thursday)
Issued at 251 PM MDT Thu Sep 7 2017
Not much change to the forecast thinking through the extended
period with continued higher ensemble spreads and less certainty
as the forecast goes out in time. The one thing that both the
operational solutions and ensembles agree on, is that it appears
the monsoonal ridge over the west will break down and be replaced
by troughing, likely ending the traditional monsoonal pattern.
Friday night through Monday...high pressure is forecast to
dominate the pattern into early next week, while several
disturbances move across Colorado. This will lead to daily
afternoon and evening showers and thunderstorms across the region.
Initial development is forecast over the mountains, spreading east
through the evening hours. The latest model solutions favor areas
along the Palmer Divide and Raton Mesa with less activity out over
the far eastern Plains. The best activity appears to be Friday
night and again on Saturday. By Sunday and Monday, the upper ridge
retreats westward a bit, helping to dry out the Plains, especially
east of I-25. Temperatures will remain warm with highs in the
upper 80s to mid 90s across the lower elevations.
Tuesday through Thursday...a cold front is forecast to arrive late
Monday night into Tuesday morning. Expect drier conditions across
the region with more isolated to scattered shower and thunderstorm
activity over the mountains on Tuesday. By Wednesday the upper
pattern begins to change. There are model differences in how
quickly this occurs, but an upper low that is forecast to sit off
the west coast will finally begin to push eastward into the
western US Thursday. This will transition flow aloft more
southwesterly. With moisture still across the Desert Southwest, we
will likely remain wet across the mountains, and possibly into
the Plains. But this will likely bring an end to the true
monsoonal pattern by the end of the week. How quickly this pattern
takes shape is where the models are different. Slightly cooler air
is expected later in the week with generally 80s across the
region. Mozley
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 251 PM MDT Thu Sep 7 2017
VFR conditions expected at the terminals with VCTS most likely at
both KCOS and KALS through this evening. Main threats with
thunderstorms will be erratic wind gusts up to 40 kts, along with
some brief moderate rainfall. This threat should diminish after 02-
03z. Haze from wildfire smoke originating across the Pacific
Northwest and northern U.S. Rockies will continue to cause hazy
conditions across southern CO over the next 24 hours. VIS is most
likely to stay in the VFR range though some high res models suggest
it could briefly thicken this evening into the overnight period. For
now TAFs do not carry any vis restrictions for this, but this will
need to be monitored. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...KT
LONG TERM...MOZLEY
AVIATION...KT
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Friday)
Issued at 251 PM CDT Thu Sep 7 2017
Sfc high pressure in control this afternoon over northeast Kansas
with light and variable winds through early evening. Upper air
pattern is characterized by steady northwesterly flow across the
central conus with the poignant low pressure centered in the Great
Lakes region. Lee troughing builds over the CO Rockies during the
early evening hours as a weak perturbation shifts southeast into
central Kansas between 00 and 12Z tonight. Mid level lapse rates are
more ideal in these areas, becoming weaker towards our CWA in north
central KS. Moisture profiles are also pretty limited with cloud
bases around 9 kft and ample dry air below. Short term models,
particularly the past few runs of the HRRR and RAP develop a few
showers and thunderstorms this evening towards central KS, driven
primarily by the upper forcing. As they move southeast, they should
weaken west of the CWA so have kept dry pops for the period.
Increasing high clouds and southerly winds bump overnight lows at
least 10 degrees compared to yesterday around 60 degrees.
Southwesterly winds increase on Friday afternoon with the sfc trough
to our west, advecting h85 temps to near 20C. Decent mixing below
850 mb under mostly sunny skies result in forecast highs in the
middle to upper 80s.
.LONG TERM...(Friday night through Thursday)
Issued at 251 PM CDT Thu Sep 7 2017
Little change to the medium and extended forecast this period with
seasonal temperatures and mainly dry conditions. Models show a
subtle wave moving across Nebraska and northern Kansas Friday night,
but expect only some high and mid clouds with its passage as
sounding continue to show little moisture below 700 mb. The next
chance for any precipitation arrives Saturday night after midnight
as an upper level wave moves across the northern and central Plains.
Forecast soundings suggest some elevated showers and perhaps a clap
or two of thunder is possible as models show some skinny CAPE.
Better moisture and forcing for ascent will be north of Kansas but
the far northwest corner will have the best chance of receiving any
rain while the rest of the area remains dry. From Sunday night into
the later part of next week and upper level high will park itself
over the Rockies with a upper cut off low in the west allowing for a
northwest flow aloft across eastern Kansas. The upper patter begins
to transition late next week as an upper trough moves on shore, with
the ridge moving over the Plains then upper flow transitioning to a
more active pattern late next weekend.
Persistence forecast for temperatures through the period. Did
increase winds slightly over model blend for the weekend with tighter
pressure gradient and mixing during the daylight hours.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 630 PM CDT Thu Sep 7 2017
VFR conditions anticipated. Some cloud down to near 15kft
possible mainly 06Z-18Z as a weak disturbance moves through. Low
level jet increases to the southwest around 30kts around 1kft AGL
in the 04Z-15Z window though not expected to reach LLWS levels as
surface winds veer to the south and the jet is from the
southwest.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Prieto
LONG TERM...53
AVIATION...65
Area Forecast Discussion
National Weather Service Tucson AZ
905 PM MST Thu Sep 7 2017
.SYNOPSIS...Increasing moisture will bring a good chance of storms
Friday into Saturday. Thunderstorm chances will decrease early in
the new week as high pressure builds overhead and we lose a little
moisture.
&&
.DISCUSSION...A cluster of thunderstorms west of Tucson managed to
produce a large dust storm that spread north into Phoenix and west
toward the Colorado River early this evening. Radar was just showing
a few lingering showers and thunderstorms across southeast Arizona
late this evening. Latest HRRR solution suggested that a few
thunderstorms will continue overnight, especially west of Tucson.
Thus, will keep the current POP forecast going for now. Otherwise,
the overall model consensus indicated an upswing in thunderstorm
activity for tomorrow. Please refer to the previous discussion for
more details.
&&
.AVIATION...Valid thru 09/06Z.
Isolated -TSRA/-SHRA. Coverage increasing Friday. Surface wind ely
to sly 5-15 kts with occasional gusts near 20 kts, stronger winds
near thunderstorm outflows. Aviation discussion not updated for TAF
amendments.
&&
.FIRE WEATHER...Increasing storms Friday into Saturday. A modest
drying trend will see a lesser chance of thunderstorms early in the
new week. 20-foot winds will generally be less than 15 mph into next
week.
&&
.PREV DISCUSSION...As the pattern phases a little further east, the
favorable area for enhanced thunderstorm development will shift east
with it, including more of our CWA Friday and Friday night into
Saturday. Our main concern with that scenario is debris and boundary
layer cooling from any activity we have tonight. Best guess is that
we will recover enough for storms, but they may not have quite the
punch they might have had. Enough moisture for locally heavy rain as
well.
By later Sunday and Monday, the ridge is expected to build back
westward again in response to the low lifting northward from off the
southern California coast, and extensive modification of the pattern
downstream from tropical influences. That will inhibit thunderstorm
development once again as we do the typical September thing of more
frequent interruptions to the waning monsoon flow.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Area Forecast Discussion
National Weather Service Las Vegas NV
852 PM PDT Thu Sep 7 2017
.SYNOPSIS...Moisture is expected to increase Friday through
Sunday leading to more widespread showers and thunderstorms over
portions of the southern Great Basin and Mojave Desert. Temperatures
will cool to below normal readings Friday and Saturday with the
additional cloud cover.
&&
.UPDATE...Still some weak convection going on in the eastern half of
the forecast area this evening and the latest HRRR still indicates
some potential for a few showers or thunderstorms overnight mainly
in Mohave County. Forecast looks to be in pretty good shape and no
updates planned this evening. -Harrison-
&&
.PREV DISCUSSION...
320 PM PDT Thu Sep 7 2017
.SHORT TERM...tonight through Sunday.
Moisture and instability over the eastern half of the forecast area
has led to scattered showers and thunderstorms over Mohave, Clark
and San Bernardino Counties this afternoon. The strongest storms are
occurring over portions of eastern San Beranrdino and Clark counties
where strong wind gusts have been an issue. DCAPES are generally
around 1700 J/KG and we have seen several microbursts in the area.
With ongoing outflow boundaries we may see storms continue through
the evening before dissipating late.
Upper low off the central California coast will move inland
overnight and the associated trough will help pull low level
monsoonal moisture northward early Friday. This moisture is expected
to increase through the afternoon and into Saturday. Dynamics
associated with low combined with increasing instability will lead
to more widespread thunderstorms over Mohave, Clark, Lincoln,
southern Nye, and eastern San Bernardino Counties Friday and
Saturday. A sharp moisture/instability boundary stretching from
roughly western Lincoln down through eastern San Bernardino County
should keep things dry to the west, but storms along this boundary
could become more organized. With the increased moisture and
potential for training storms, heavy rain and long duration rainfall
could be an issue. Have gone ahead and issued a flash flood watch
for those aforementioned areas starting mid Friday morning and
continuing into Monday morning.
Moisture will remain on Sunday, but the upper low that moved inland
over central California will retrograde and the moisture boundary is
expected to shift further west. This could bring more of the heavy
rain and thunderstorms to western San Bernardino and Inyo Counties
Sunday. At this time will not issue any statements for those areas,
but as we get close a Watch may be needed.
.LONG TERM...Monday through Thursday.
Lingering chances for thunderstorms, though lower than Saturday,
will remain over much of the forecast area Sunday as moisture wraps
around the closed low off the southern California Coast. Although
moisture decreases, there will be broad diffluence over much of the
forecast area and more surface heating to support thunderstorm
development. There is good agreement among the GFS and ECMWF that a
drier southwest flow will spread over the region Monday through
Wednesday as the closed low slowly lifts toward central California
then moves inland. The ECMWF depicts a deep broad trough diving out
of the Pacific Northwest that looks like will scour all moisture out
of the region by Thursday along with a noteworthy cooling trend. If
this plays out, it will be the end of monsoon season about on
schedule with the transition to a fall pattern as troughs drop down
from the northwest.
&&
.AVIATION...For McCarran...Afternoon thunderstorms will subside and
gusty south winds will subside and favor the usual southwest
overnight. By late tomorrow morning, southeast winds will kick in,
bringing a push of monsoon moisture and thunderstorms to the region.
Training thunderstorms will be possible much of the day into
overnight, capable of producing gusty winds and very heavy rain.
Ceilings may come down to below 10 kft under thunderstorms.
For the rest of southern Nevada, northwest Arizona and southeast
California...Increasing moisture will bring increasing thunderstorm
chances and lowering ceilings across much of the region, especially
along the Colorado River Valley. Storms are likely to be more
widespread by the evening, with gusty winds and heavy rain the main
threats. Ceilings look to fall to or under 10 kft under
thunderstorms.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT TERM...Gorelow
LONG TERM....Adair
AVIATION.....Steele
For more forecast information...see us on our webpage:
http://weather.gov/lasvegas or follow us on Facebook and Twitter