Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/13/18
Area Forecast Discussion
National Weather Service Bismarck ND
914 PM CDT Sun Aug 12 2018
.UPDATE...
Issued at 910 PM CDT Sun Aug 12 2018
The main change for the late evening update was to increase smoke
cover a bit for Monday into Monday night. Visibilities behind a
progressing cold front have been reduced with smoke being pulled
in behind the front. This is expected to continue Monday into
Monday night as noted on the past few runs of RAP guidance.
Otherwise, going forecast remains on track.
UPDATE Issued at 709 PM CDT Sun Aug 12 2018
Many record high temperatures were broken today almost all of
western and most of central North Dakota pushed above the 100
degree mark. Temperatures remain toasty this evening, but will
gradually cool, so have allowed the heat advisory to expire. Winds
will continue to gradually shift to the west/northwest this
evening as a frontal boundary makes its way into the area.
&&
.SHORT TERM...(This evening through Monday)
Issued at 226 PM CDT Sun Aug 12 2018
Main highlights include the ongoing Red Flag Warning for western
and far south central North Dakota (see fire weather discussion
below), and the ongoing Heat Advisory for western and most of
central North Dakota. Record high temperatures also on target for
most of western and central North Dakota.
Both the Red Flag Warning and Heat Advisory remain on track.
Relative humidities are lowering into the 10 and 15 percent range
with sustained winds to 20 mph. The HRRR 2 meter relative humidity
with values around 8 percent look on track for this afternoon and
will maintain this in the grids.
The Heat Advisory looks good with heat indices in the mid to upper
90s west and central, thus expectations heat indices to at least
100F are also on target as we continue to approach our high
temperatures late this afternoon,
A surface cold front was currently just south of the Montana
border, and will slowly shift southeast overnight through Monday
morning. Slight chances for precipitation begin showing up in the
CAM`s between 06z-12z west, and this is also in agreement with the
GFS and NAM. With the front passing through the west early this
evening, boundary layer/northwest winds are forecast to quickly
increase to between 25kt-30kt between 03z- 06z, before decoupling
after midnight. Thus would expect a period of gusty northwest
winds of between 25-35 mph west early tonight.
The cold front will shift through central North Dakota into the
James River Valley between 12z-18z Monday, but not totally clear
the southern James River Valley until late Monday afternoon. Thus,
will mention slight chances for showers and thunderstorms along
and behind the cold front Monday. No severe weather is anticipated.
It will be noticeably cooler Monday with highs in the mid 70s
north to lower 80s south, with the exception of the far southern
James River Valley where highs will reach the upper 80s in close
proximity to where the cold front will be.
.LONG TERM...(Monday night through Sunday)
Issued at 226 PM CDT Sun Aug 12 2018
Dry and cooler Tuesday with highs in the 70s, then warming back
into the 80s Wednesday through Sunday. In terms of precipitation
chances, the ECMWF and Canadian are trying to take an open
shortwave and morph it into a closed low Tuesday night through
Wednesday night, producing precipitation for southwestern and
south central ND, while the rest of the model suites keep the
shortwave progressive, just grazing the southwest with
precipitation. The Forecast Builder appears to have a blend of
both solutions, with a slight chance of showers/thunderstorms
southwest and south central. Dry weather thereafter until the
upcoming weekend, when another round of showers and thunderstorms
are possible.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 709 PM CDT Sun Aug 12 2018
A cold front will move through the area overnight into Monday.
Additional smoke is expected to pull in behind the front, bringing
widespread MVFR visibility.
&&
.FIRE WEATHER...
Issued at 910 PM CDT Sun Aug 12 2018
Relative humidity values will continue to gradually increase
tonight as temperatures cool. Therefore, the Red Flag Warning for
western and portions of central North Dakota was allowed to
expire. A cold front will move through the area tonight, with
southerly winds shifting towards the northwest.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JJS
SHORT TERM...KS
LONG TERM...KS
AVIATION...JJS
FIRE WEATHER...JJS
Area Forecast Discussion
National Weather Service Birmingham AL
1059 PM CDT Sun Aug 12 2018
.UPDATE...
For 06Z Aviation.
&&
.SHORT TERM...
Through Tonight.
Scattered to almost numerous showers and thunderstorms have
developed across Central Alabama this afternoon in response to the
trough that continues to dig southward just to our north. In
addition, the old moisture gradient/surface boundary continues to
hang out just north of the I-20/I-22 corridors. That boundary is
helping to trigger additional convection as well. The coverage of
storms is certainly more numerous than anticipated this afternoon,
as high-res guidance this morning was certainly not very bullish
on anything higher than isolated coverage. Therefore, the trough
digging southward is certainly a little more potent than
previously indicated, and we`re more unstable as well. RAP
analysis is indicating between 4500 and 5000 J/kg of SBCAPE this
afternoon. In addition, the dry air aloft on the KBMX 12z sounding
is producing a threat of some downbursts, and storms this
afternoon will be capable of producing wind gusts of 40-50mph
at times. An isolated severe storm certainly can`t be ruled out.
Steeper lapse rates and cooler air aloft also have led to some of
these storms producing small hail. North of the boundary closer
to the trough, dry air continues to influence the weather across
north Alabama. We shouldn`t see much convective development north
of a line from Vernon to Jasper to Jacksonville with subsidence
aloft really taking over.
In terms of the forecast this evening and tonight, the increased
instability that is present will likely help convection persist
well into the evening hours tonight due to outflow boundary
interactions. Therefore chance PoPs will remain in the forecast
for the southern half of Central Alabama through late this
evening. Patchy fog formation will be likely once again overnight
tonight, especially in areas that received heavy downpours due to
the storms today.
56/GDG
.LONG TERM...
Monday through Saturday.
The eastern edge of skinny ridge axis will begin to move into West
Alabama on Monday, while a trough remains in place over the Plains
and another trough affects the Mid-Atlantic states. An axis of
deformation is expected to extend from Arkansas southeastward
across the western and southern parts of our forecast area. Lift
generated along this feature should correspond with higher PWAT
values and scattered convection. Our forecast indicates a sharp
drop in POPs toward the northeastern counties due to much drier
air being drawn into Northeast Alabama.
Tuesday may be somewhat of a repeat of Monday as the relatively
narrow axis of higher moisture content becomes more North-South
oriented and moves slowly eastward. The highest rain chances are
currently favored across our southern counties, where the greatest
moisture content is indicated by model guidance.
Wednesday appears to be a transition day as the ridge axis shifts
eastward across the region, bringing drier air aloft and lower
rain chances to Central Alabama. Rain chances may increase
significantly for Thursday through Saturday as two separate upper
troughs move through the region, resulting in a regime of rather
moist southwesterly flow.
87/Grantham
&&
.AVIATION...
06Z TAF Discussion.
Mid and high clouds stream across much of the area tonight, with a
few isolated showers continuing along outflow boundaries near TCL
and EET. Terminals are not in an immediate risk of impacts from rain
but cannot rule out another shower at TCL or EET for the next couple
hours. Activity should propagate to the south southeast and not
impact ant other terminals.
Areas of surface moisture should result in patchy fog, especially
with the late evening rain near TCL and EET. Have included some
reduced visibility at TCL-EET-MGM-TOI. Calm to very light breezes
are expected.
For Monday, a southwest-to-northeast moisture gradient will
exist, with the "wetter" side of the envelope encompassing TCL-
MGM-TOI where PROB30 is included for afternoon storms. Winds will
increase to between 5-10 knots with some sway either side of
northwesterly.
14/89
&&
.FIRE WEATHER...
Scattered showers and storms will continue for the next several
days mainly across the South and West. Morning fog and low clouds
will be possible in locations that receive afternoon and evening
rainfall. There are no fire weather concerns at this time.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 68 91 67 91 69 / 10 10 10 10 10
Anniston 69 92 68 92 70 / 10 10 10 10 10
Birmingham 71 92 71 93 72 / 20 20 10 20 10
Tuscaloosa 73 93 72 93 72 / 30 30 20 20 10
Calera 71 90 70 91 71 / 30 20 20 20 10
Auburn 71 90 71 90 72 / 30 20 20 20 10
Montgomery 73 92 73 92 73 / 30 40 20 40 10
Troy 73 92 72 91 72 / 30 40 30 40 10
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service State College PA
848 PM EDT Sun Aug 12 2018
.SYNOPSIS...
A cut off upper low over Lake Erie will slowly lift east across
Pennsylvania Monday and Tuesday. A ridge of high pressure will
build into the region on Wednesday, followed by the arrival of
a weak cold front late in the week.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Heavy rain showers are slowly decresing in intensity this
evening. As conditions begin to improve, have allowed FLS and
FFW products to expire upon coordination with emergency
officials. While the area of heavy caused issues this evening,
about 95% of the forecast area enjoyed pleasant and dry
conditions.
Lift in the favored left exit region of potent upper jet streak
will keep slgt chc showers going overnight over the eastern
half of the state. Short term, high res HRRR shows another bout
of heavy rain over Schuylkill county overnight.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
Upper low becomes centered over central PA on Monday. With cool
air aloft, combined with diurnal heating and sufficient low
level and deep layer moisture, we should see a marked increase
in diurnally- driven convection Monday afternoon. Keeping POPs
in the likely to categorical ranges for Monday afternoon and
evening as a result. Some discussion of locally heavy rainfall
threat and while eastern areas appear more prone based on
synoptic setup and recent heavy rainfall, want to hold off on
any headline issuance to better place a Watch box in the 24 to
30 hour timeframe. The plume of anomalous pwats remain well
east of Pa, so the flash flood risk is on the lower side for
central and western PA.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Not much signal for any large pattern change. Looking at a
tendency to semi-phase 3 bundles of energy with time. New 12Z
GFS trending toward recent runs of the EC. Same trends all
season.
Anyway, not a lot of change.
For next Sunday, went with mainly the superblend, but lower
POPS.
Otherwise mainly small changes.
Still looking at showers and storms Monday night into Tuesday
evening. I did up POPS some across the south central areas
Monday night, given POPs, location of the upper lvl low, trends
this wet summer season, and to fit in better with others.
Wednesday into Thursday still look mainly dry, as weak ridging
occurs over western PA. There could be a shower across the far
northwest late Wednesday into Thursday morning. Showers and
storms more likely late Thursday evening into Friday, as warm
advection sets up.
Weak cold front moves across the region late Friday, so I still
think Saturday will be mainly dry.
For Sunday, highest chc of showers and storms looks to be
across the south, based on the 00Z EC and comparison of recent
runs of several models.
&&
.AVIATION /01Z MONDAY THROUGH FRIDAY/...
VFR conditions generally prevail across central PA this evening.
While there are some pretty heavy showers and thunderstorms
around likely reducing visibilities likely into the IFR range,
these have avoided TAF locations.
Light winds and low level moisture expected to produce
widespread fog and low stratus overnight at most airfields.
Problem for Monday is how quickly and efficiently these lower
clouds and fog will dissipate, with very light wind flow.
Short term guidance suggests that MVFR fog could prevail in the
east much of the day. Based on guidance and grids (official
forecast) have bumped up all TAFs to include VCSH during the
afternoon, with categorical SHRA in KMDT and KLNS in the
afternoon.
For Monday, convection expected to be more widespread that
Sunday.
.Outlook...
Mon-Tue...AM cig/vsby restrictions likely with slow improvement.
Additionally, SHRA/TSRA with associated restrictions especially
in the afternoon.
Wed...AM fog. Otherwise no six wx.
Thu-Fri...AM fog. Otherwise, scattered showers/tstms will bring
local restrictions.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...DeVoir/Martin
NEAR TERM...DeVoir/Tyburski
SHORT TERM...DeVoir
LONG TERM...Martin
AVIATION...Jung
Area Forecast Discussion
National Weather Service Dodge City KS
500 PM CDT Sun Aug 12 2018
...Updated Aviation...
.SHORT TERM...(This evening through Monday)
Issued at 347 PM CDT Sun Aug 12 2018
The afternoon water vapor loop and RAP analysis revealed two
distinct subtropical shortwave troughs -- a northern one moving west
across southwest KS into southeast CO and a southern one moving
slowly south across New Mexico. To the east of these features across
TX into OK and southern KS was an abundance of deep tropospheric
moisture, manifest as a large area of mid and high cloud along with
scattered to numerous thunderstorm activity. As of early this
afternoon, a few very weak/fleeting showers moved across portions of
Kiowa, Comanche, and Pratt Counties, but they have since dissolved
as of 2015z. Scattered convection was holding its own farther
southeast across northern Oklahoma. The official forecast will call
for 20 POPs across south central KS counties through the afternoon
and evening with POPs ramping up to 30-40 percent across south
central KS by daybreak Monday.
Early Monday, the two aforementioned distinct shortwave troughs will
merge into one formidable disturbance at 500mb, somewhere across the
Texas Panhandle. This will continue to move north through the day
Monday with deeper moisture pushing northwest across more of
southwest and central Kansas. Not much has changed in the overall
POP forecast with 60-70 percent across mainly central and south
central KS, tapering off to 20 percent across far southwest and west
central KS later in the afternoon. The very poor shear environment
along with deep moist profile will preclude any organized severe
weather activity through Monday Night. There is still some question
regarding how far west some of the heaviest rainfall will extend to,
with the latest ECMWF model now bringing 1"+ back as far west as
Dodge City-Cimarron-Jetmore again. Obviously, given the convective
nature to the activity, global models like the ECMWF and GFS can
only give a slight insight into the layout of potential rainfall
amounts with this event through Monday Night, but there is certainly
opportunity for some locations to see well over an inch of rain.
.LONG TERM...(Monday night through Sunday)
Issued at 347 PM CDT Sun Aug 12 2018
This first precipitation event will continue into Tuesday as the mid
level cyclone takes its sweet time pushing east out of
western/central Kansas. It will finally do so by Tuesday Night with
shortwave ridging moving in behind the system Wednesday. There
should be at least one full day of drying out on Wednesday before
precipitation chances increase again by late Thursday as western
Kansas starts to become under the influence of weak northwesterly
flow aloft. Abundant low level moisture will remain across the
region, especially the eastern half of the forecast area (along/east
of U283). As we head toward the next weekend, there is increasing
signal of a fairly sizable trough moving into the Rockies. This
will foster increased leeside troughing at the surface and
subsequent southeasterly winds. The latest deterministic GFS and
ECMWF models today show a healthy QPF signal over the weekend, so
this aspect of the forecast will certainly garner more attention in
the coming days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 500 PM CDT Sun Aug 12 2018
VFR will continue through this TAF cycle, but cloud ceilings will
be thickening and lowering on Monday as moisture increases. Only
scattered clouds most of the overnight, with light SE winds.
Clouds will increase quickly around 12z Mon, as a weak closed low
moves to near EHA. During the 15-18z timeframe, expect scattered
rain showers and embedded thunder to develop mainly east of a GCK-
LBL line. Placed the lowest cigs (4-5k ft AGL) at DDC/HYS Monday
afternoon, nearest the greatest moisture and strongest lift. Much
less activity expected near, and especially west of, GCK/LBL.
Light SE winds near 10 kts outside of convection.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 65 83 65 84 / 20 40 50 60
GCK 62 83 63 84 / 0 30 40 40
EHA 62 88 63 86 / 10 20 20 10
LBL 64 86 64 86 / 10 30 40 30
HYS 66 80 65 80 / 10 70 50 60
P28 68 83 67 84 / 40 70 40 60
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Umscheid
LONG TERM...Umscheid
AVIATION...Turner
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
734 PM CDT Sun Aug 12 2018
.UPDATE...
Showers and thunderstorms were on a downward trend but new
development has been noted near San Antonio and points to the
South/Southwest on converging outflow boundaries. The latest run of
the HRRR has this axis of new precip fairly well and tracks it north
and out of the CWA over the next several hours. Have increased PoPs
in this corridor while decreasing PoPs a bit in the near term for the
western CWA. Overall this activity is moving at a fairly decent
speed, but any possible training could lead to locally heavy rainfall
and the threat for additional flooding. Only made some other
adjustments to the hourly grids based on current trends.
&&
.PREV DISCUSSION... /ISSUED 628 PM CDT Sun Aug 12 2018/
AVIATION.../00Z TAFS/
Upper level low to the NW of the region will keep a moist and
unstable atmosphere in place into Monday. With this pattern
convection will be possible throughout the period. Best chances
should remain to the west of I-35 tonight and into Monday morning.
I-35 sites will still have a chance to see more convection into
Monday, most likely during the morning into the afternoon. With so
much uncertainty at this time will either leave out or mention
vicinity until we have a better idea once convection develops.
MVFR/IFR cigs should develop after 07Z-08Z tonight and continue
through 15Z Winds will be light and variable overnight except in or
near convection. Expecting to see S/SE winds at 10-15 knots to
develop after 16Z and could gust to near 20 knots.
PREV DISCUSSION... /ISSUED 257 PM CDT Sun Aug 12 2018/
SHORT TERM (Tonight through Monday Night)...
Widespread showers and thunderstorms have overspread much of south
central Texas this afternoon. Very heavy rainfall occurred this
morning across portions of Uvalde and Kinney Counties, with localized
areas receiving up to 10 to 11 inches in northwestern Uvalde County.
This caused significant flash flooding along the Nueces River and
other surroundings creeks. The flash flood threat continues into this
afternoon and evening, as extremely moist conditions (with PWATs
ranging from 1.8 to 2.1 per SPC mesoanalysis), tall, skinny CAPE
profile, and a high melting layer will yield very efficient rain
makers. Weak steering winds and favorable Corfidi vectors will also
yield the threat for slow moving showers/storms and the possibility
for training storms. WPC has a mesoscale precipitation discussion in
effect that summarizes the threat quite well, with the primary risk
area being along and west of the Interstate 35 corridor. Storms
along the I-35 corridor presently are producing some gusty winds, but
severe threat is marginal at best.
Models differ a bit in regards to the focus for showers and
thunderstorms for the rest of today and through tonight. The SPC High
Resolution Ensemble Forecast (HREF) highlights the I-35 corridor for
San Antonio to Austin this afternoon before shifting the primary
rain focus to out west again by tonight and Monday morning. The 12z
GFS seems to agree with this solution for the most part. The 12z
ECMWF keeps things mostly west of I-35 for the duration. WPCs most
recent QPF forecast seems to align more closely with the GFS. For
PoPs, have gone with up to 80 percent out west with 40 to 60 percent
across the Interstate 35 corridor (and only slight chances across
the coastal plains) for the rest of the afternoon through Monday
morning.
The upper level low currently located across northwest Texas will
start to drift off to the northeast by Monday afternoon. This will
shift rain chances more toward the Hill Country by Monday afternoon
and evening. High temperatures on Monday will be cooler than normal
for the vast majority of the region, except for the far southern and
southwestern areas that have managed to avoid the recent rains.
LONG TERM (Tuesday through Sunday)...
As the upper level low that has helped bring us all this much needed
rain continues to exit to the northeast, high pressure begins to
build back in over the region. This will generally suppress
convection and lead to a warming trend through the week, with high
temperatures back to near seasonal normals by Wednesday and
continuing through Sunday. There will be a slight chance for isolated
sea breeze initiated showers and storms for the afternoons of
Wednesday through Sunday across the far southeastern counties of
Lavaca and Fayette.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 76 94 75 95 76 / 50 30 - - -
Austin Bergstrom Intl Airport 76 94 74 95 75 / 50 30 - - -
New Braunfels Muni Airport 75 94 75 95 74 / 50 20 - - -
Burnet Muni Airport 73 89 73 92 73 / 70 60 10 - -
Del Rio Intl Airport 74 90 76 94 76 / 80 60 20 10 -
Georgetown Muni Airport 74 92 75 95 75 / 60 40 - - -
Hondo Muni Airport 75 95 75 96 74 / 70 30 - - -
San Marcos Muni Airport 75 94 75 95 75 / 40 20 - - -
La Grange - Fayette Regional 77 95 75 96 76 / 20 10 - 10 -
San Antonio Intl Airport 76 94 76 95 76 / 60 20 - - -
Stinson Muni Airport 76 95 76 96 76 / 60 20 - - -
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...10
Synoptic/Grids...Hampshire
Area Forecast Discussion
National Weather Service Flagstaff AZ
240 PM MST Sun Aug 12 2018
.SYNOPSIS...Typical monsoon conditions will continue across Arizona
this week, bringing scattered afternoon and early evening
thunderstorms to much of the area. The highest chances will remain
along and south of the Mogollon Rim. Some storms will produce
heavy rainfall, hail, and strong winds.
&&
.DISCUSSION...Scattered convection has fired along the Mogollon Rim
and southwest of the Black Mesa and Chuska Mountains this
afternoon. The environment south and west of the Mogollon Rim is
conducive for severe thunderstorm development with SPC`s
mesoanalysis painting MUCAPEs around 2000 J/kg and effective bulk
shear around 20 knots. Thunderstorms and the severe threat (1"
hail, 60 mph winds) should continue through the late afternoon
into the early evening hours. The latest HRRR progs convection
ending across all of northern Arizona after 9pm MST. Mainly dry
conditions are then forecast overnight.
For Monday through Tuesday, high pressure will slowly meander
southeastward into Arizona and become centered over the White
Mountains Tuesday. This could result in a slight downward trend
in afternoon convective activity. However, scattered storms along
the higher terrain (Mogollon Rim, Black Mesa, and Chuskas) are
still forecast each afternoon. Storm motions will be primarily
instability driven with weak steering flow expected.
For Wednesday through Saturday, the aforementioned high pressure
then slides east into New Mexico and is progged to open up Gulf of
California moisture into Arizona. A little more active monsoonal
thunderstorm pattern is forecast during the latter half of the week.
The medium range models around now a day slower with high pressure
rolling into the Great Basin with Sunday now looking to show a
drying trend. Will hold off on making any significant changes in the
precip forecast given the model to model and run to run
inconsistencies. Stay tuned.
&&
.AVIATION...For the 00Z package...VFR conditions will continue
across northern Arizona for the next 24 hrs with southwest and
west winds at 5-10 kts and possible gusts of 10-20 kts. Showers
and thunderstorms near KGCN, KFLG, KSEZ are beginning to move to
the southwest near KPRC. Near thunderstorms, expect gusty and
erratic winds along with possible localized local MVFR/IFR
conditions. Storms will weaken after sunset. Thunderstorms near
KFLG, KSOW and other high terrain areas Monday after 19Z. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Scattered thunderstorms will develop both Monday and
Tuesday afternoons along and south of the Mogollon Rim, Black Mesa,
and Chuska Mountains. Storm motions will be erratic due to weak
winds aloft.
Wednesday through Friday...Afternoon monsoonal thunderstorm chances
will continue each day primarily along and south of the Mogollon
Rim, with a gradual uptick in activity forecast each day through
Friday.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
PUBLIC...TM
AVIATION...NL
FIRE WEATHER...TM
For Northern Arizona weather information visit
weather.gov/flagstaff
Area Forecast Discussion
National Weather Service Glasgow MT
724 PM MDT Sun Aug 12 2018
.DISCUSSION...
Evening update: Models don`t have a good handle on the smoke
across the region, with all locations reporting smoke in their obs
and visibilities lowered at most locations. Lowered visibilities
and added "areas of smoke" to the grids (vs. "patchy smoke" for
this evening), using HRRR smoke for guidance. However, that model
suggests even lower visibilities in our western CWA (Phillips and
Petroleum Counties, possibly the western halves of Valley and
Garfield Counties as well) overnight tonight. HRRR smoke doesn`t
really begin to clear the air so to speak until tomorrow evening,
hence why "areas of smoke" for sensible weather during the day on
Monday.
Temperature changes were cosmetic for tonight and tomorrow.
Avery
Previous discussion follows...
Afternoon Update: Much of the update work was completed this
morning, as the midday and early afternoon model runs were
consistent with the morning, much of the update was merely
cosmetic cleanup with shared borders.
Bigelbach
PREVIOUS DISCUSSION: One more day of excessive heat near the
border with North Dakota as a cold front moves through the region
today. Impactful advisory and warning products include. Near
record high temperatures for most locations near and east of
Highway 13, a Lake Wind Advisory, A Red Flag Warning, and an
Excessive Heat Warning. By sunset tonight, all these impacts are
expected to ease and much more comfortable conditions will settle
across all of northeast Montana.
After the initial wind shift this morning, more widespread
northwest winds will spread through the area later today, gusting
up to 25 mph at times. Cloud cover and a few isolated rain
showers accompany the movement of the front. Throughout the day,
expect to see off-and-on periods of isolated or scattered rain
showers with a few lightning strikes here or there. The dry
conditions may only allow for a few sprinkles for most locations.
Tonight, temperatures will drop into the 50s and 60s as humidities
finally make the decent recoveries we all have been waiting for.
Monday and Tuesday, the re-enforcing cooler air mass from the
Canadian Rockies will provide much more comfortable weather
conditions. Unfortunately, no rainfall is expected, but at least
the temperatures will be bearable.
Through the middle of the week, the strength of the western states
high pressure ridge will return and will spread high temperatures
in the 90s across the region. Thankfully, triple digit heat seems
to be in the rear-view mirror for the foreseeable future.
Most of the chances for rain showers and thunderstorms seem to be
confined to western and southern Montana through this coming week.
BMickelson
&&
.AVIATION...
FLIGHT CAT: VFR to MVFR (some haze and smoke).
DISCUSSION: Expecting smoke/haze to continue to lower visibilities
to MVFR conditions at times through Monday.
Avery
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening for
MTZ120-122-134>137.
Lake Wind Advisory until 9 PM MDT this evening For Fort Peck
Lake for Central and Southeast Phillips...Central and Southern
Valley...Garfield...McCone...Petroleum.
Excessive Heat Warning until 9 PM MDT this evening for Dawson...
Eastern Roosevelt...McCone...Prairie...Richland...Sheridan...
Western Roosevelt...Wibaux.
&&
$$
weather.gov/glasgow
Area Forecast Discussion
National Weather Service Gray ME
1018 PM EDT Sun Aug 12 2018
.SYNOPSIS...
An onshore flow will persist over New England to the east of a
stationary low pressure system over the Great Lakes. This will
keep clouds and occasional showers in the forecast through
Tuesday. A cold front will arrive on Wednesday.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
1015 PM...Radar is clear of precip attm, and have lowered pops
to compensate for this. The HRRR continues to push a few light
showers from east west across the srn zones late tonight, and
have left slt chc pops in after midnight for this areas, but
otherwise should be dry overnight, with some patchy fog. Mins
mostly in the 60-65 range, but milder in srn NH and in the upper
50s in some spots in the mtns.
620 PM...Decided to trim pops back to slt ch across most of the
CWA for this evening. Did keep the chc pops over srn NH, which
is closer to sfc boundary over srn New England, and remnants of
convection further south could make it. Otherwise, let the chc
pops creep NE along the coast after midnight, as we start to see
better cyclonic flow aloft as the closed low at 500 MB noses in
from the SW. Still any showers should be mainly light and sct.
Mins will drop off in the low to mid 60s in most places, around
60 and in the upper 50s in the mtns.
Previously...Pesky cut off low to our west will keep an onshore
low level southeast flow going through tonight. Should see the
clouds hang on tonight and maybe even lower to the ground as
fog. Some occasionally showers are also possible with the
onshore flow, but there is not a significant forcing mechanism
for widespread lift, so these should be scattered or drizzly in
nature. Temperatures only drop into the 60s tonight considering
the cloud cover and low level moisture.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
As the upper low rotates to our west, it looks like a shortwave
trough will rotate around it from south to north through the Mid
Atlantic and upstate New York on Monday. This will bring a more
concentrated area of showers and thunderstorms, but it should
stay mainly to our west. Models are indicating some increased
moisture moving in off the Atlantic as well, so we may see more
onshore flow showers and drizzle or fog there. Otherwise it
should be fairly similar to today. Cool and damp except for the
other side of the mountains where there will be a bit more sun.
Low pressure moving north from southern New England may bring
more widespread rain Monday night, especially over New
hampshire.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Models in good agreement lifting the upper low from the Ohio
valley northeast toward New England Tue and across the area Wed.
Widespread showers and scattered tstorms expected in advance of
the system Tue into Tue night. Much of the convection will be
elevated due to the saturated low level maritime air mass being
produced by the persistent light onshore flow with the weak
surface wave to our south.
Going with high POPs for Tue into Tue night due to significant
UVV and high level diffluence in advance of the approaching
upper low. Models differ some in how to handle lingering showers
for Wed but will hedge on how much improvement expected.
QPF amounts Tue into Tue night should average .25-.75 inches
but as always in these situations some locally heavier amounts
possible.
Models agree on a short lived upper ridge to build over the
area Thu. Models generally agree on the next digging trof
approaching for Fri that will bring more showers and
thunderstorms that will last into the weekend.
Temps will be in the 70s Tue but will warm into the 80s for
Wed/Thu before cooler returns for the end of the week due to the
next approaching trof.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Short Term...Cloud cover remains locked in over southwest Maine
and eastern New Hampshire as an onshore southeast flow banks up
against the mountains. This is leading to prolonged MVFR to IFR
conditions here. Should see this cloud layer lower tonight to
IFR or LIFR. Could even see some fog. It will raise up a bit again
tomorrow during the day, but may not fully go away.
Long Term...MVFR to IFR conditions Tue and Tue night in
scattered showers and tstorms with areas of fog along the
coastal plain. Conditions improve Wed but still can lower to
MVFR in lingering widely scattered showers. VFR conditions
expected Thu under high pressure.
&&
.MARINE...
Short Term...Light winds and seas expected with a light onshore
southeast flow.
Long Term...Winds and seas are expected to be below SCA criteria.
&&
.TIDES/COASTAL FLOODING...
Tide tonight in Portland is 11.7 FT. With a 0.3 FT residual
still out there, we should see the water level come close to
flood stage again tonight. Have issued a Coastal Flood Statement
on this, though we are not expecting significant impacts due to
the lack of wind or wave action.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM...Cempa/Kimble
SHORT TERM...Kimble
LONG TERM...Marine
Area Forecast Discussion
National Weather Service Houston/Galveston TX
759 PM CDT Sun Aug 12 2018
.UPDATE...
Just made a few slight adjustments to forecast taking rain
chances out of NW zones for the night and lowering hourly and
overnight temps in the north...where rain from this afternoon has
already knocked temps down to near forecasted mins. Some concern
for patchy fog in these northern zones...given afternoon rain, wet
soils and temps near the dew point. Ensemble guidance and HRRR
visibility guidance not showing this perhaps due to cloud cover
so not including any fog mention just yet but will evaluate for
any possible update later this evening. 18
&&
.PREV DISCUSSION... /ISSUED 616 PM CDT Sun Aug 12 2018/
AVIATION...
Drier air has moved into SE TX and precipitation has been shifted
to the north and west of area TAF sites. Some cirrus is expected
this evening but this will begin to thin between 02-05z with a
brief period of clear skies possible. MVFR ceilings are expected
to develop between 08-10z especially across northern TAF sites
which experienced some rain earlier today. A brief window of IFR
ceilings is possible toward KCLL around sunrise. Drier air aloft
will mix down on Monday afternoon with generally clear skies by
late afternoon at most TAF sites. 43
PREV DISCUSSION... /ISSUED 323 PM CDT Sun Aug 12 2018/
DISCUSSION...
The line of strong storms has finally progressed out of the area
to the northeast. As the cirrus plume behind the convection
scatters out to partly cloudy skies this afternoon, expect
sufficient heating for an additional chance of showers and
thunderstorms. Convection should not last beyond this evening due
to loss of heating. Drier air gradually progresses into the CWA
from the Gulf tonight and tomorrow. The dry airmass will keep
rain chances negligible for the majority of Southeast Texas, in
addition to an upper level ridge building over the Texas coast
tomorrow. High temperatures will reach back up to the mid 90s and
stay there for the majority of next week. No heat advisories
should be required.
A more moist airmass from over the Gulf will gradually make its
way over Southeast Texas beginning Tuesday. A slight chance for
afternoon showers and thunderstorms along the seabreeze returns to
the area through Thursday. Beginning on Friday, an inverted
trough will move in from the east as the upper level ridge shifts
westward and settles over the Pacific. With decreasing 500 mb
heights, several shortwave troughs progressing through the
Southern Plains will increase rain chances for the area late this
week through the weekend. There is low confidence at this time
that the troughs will dig far enough into Texas to bring high
chances of rain, so POPs were capped at 30 percent this weekend.
22
MARINE...
Winds over the coastal waters remaining just under SCEC criteria
this afternoon and this trend is expected to continue through tonight
and tomorrow. As the upper low finally exits to the NE, a weakening
gradient will allow for decreased winds/seas starting Tues, and
for much of this week. A building upper ridge will also be a major
factor in limiting shower/thunderstorm development for the next
few days across the coastal waters.
41
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 75 94 74 96 75 / 10 20 10 10 10
Houston (IAH) 77 94 77 94 77 / 10 10 10 10 10
Galveston (GLS) 82 89 82 89 82 / 10 10 10 20 20
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until 8 PM CDT this evening for the
following zones: Brazoria Islands...Galveston Island and
Bolivar Peninsula...Matagorda Islands.
GM...NONE.
&&
$$
Discussion...18
Area Forecast Discussion
National Weather Service Lincoln IL
902 PM CDT Sun Aug 12 2018
.UPDATE...
Issued at 900 PM CDT Sun Aug 12 2018
Spotty sprinkles that approached McLean county earlier this
evening have dissipated. Forecast soundings are pointing toward
clear skies the rest of the night. Late night cooling to near
saturation at the surface will allow for patchy areas of fog again
toward morning. In general, the fog will be very shallow. However,
a few locations west of PIA to SPI could see some dense fog, per
the latest RAP updates. Most areas the get fog tonight should just
experience light fog. Will leave patchy fog wording in the
forecast as is. Lows tonight look on track for the low to mid 60s,
with light and variable winds.
No changes were needed to the forecast database this evening.
&&
.SHORT TERM...(This evening through Monday)
ISSUED AT 210 PM CDT Sun Aug 12 2018
Large upper low was centered near Cleveland this afternoon, which
will keep the high pressure area across our area through Monday.
A lake breeze is pushing west-southwest toward the I-39 corridor,
though the cumulus clouds along it haven`t done much in the way of
any precip so far. Can`t rule out a stray shower across the
northern CWA with this boundary this afternoon. The clouds will
fade with sunset, with another clear night, aside from the smoke
aloft.
A repeat performance is expected Monday, with scattered diurnal
cumulus and temperatures rising into the mid-upper 80s, warmest
west of I-55.
.LONG TERM...(Monday night through Sunday)
ISSUED AT 210 PM CDT Sun Aug 12 2018
Upper low that will bring our next rain chances is getting
organized over the Oklahoma panhandle this afternoon, with a
prominent curl noted on water vapor imagery. Not much change with
the model trends on this feature, with the NAM/GFS more aggressive
with rain chances beginning Tuesday afternoon vs. the ECMWF/GEM.
Still not really looking for any severe weather chances through
mid week with this system. The upper wave will slowly push
through, with the cold front not really exiting until later
Thursday. Thus, periodic rain will occur across the area through
this time.
Still a bit of model spread with the sharp upper wave swinging
southeast into the Great Lakes region late week. The GFS is a bit
faster than the ECMWF/GFS with its passage, with the ECMWF in
particular being more aggressive with rain chances early in the
weekend due to its slower movement. Still a fair amount of
uncertainty, and will not go higher than chance PoP`s at this
time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 647 PM CDT Sun Aug 12 2018
The main concern to aviation for the 00z TAF period is fog
potential later tonight. High res guidance is mainly indicating
MVFR fog in the western half of our CWA. While there is potential
of pockets of IFR vis, but kept only MVFR in the tempo`s for PIA
and BMI. Forecast soundings indicate any fog would be very
shallow, and would likely lift/burn off within an hour or so after
sunrise.
The remainder of the 00z TAF period should remain VFR, with
scattered CU again tomorrow afternoon. A funnel cloud was
photographed this afternoon near Champaign, and a repeat
performance is possible tomorrow afternoon, with similar
instability params expected.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Shimon
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Shimon
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
954 PM EDT Sun Aug 12 2018
.SYNOPSIS...
High pressure will ridge in from well offshore through most of
the week. A weak trough will remain over the central part of the
state through the middle of the week, bringing a period of wet
weather to the area through Tuesday.
&&
.NEAR TERM /TONIGHT/...
As of 955 PM Sun...Latest analysis shows upper low over the OH
Valley area, with weak frontal boundary draped through SE VA and
Central NC. No significant changes needed to previous forecast.
Main change was to update pops based on latest radar trends.
Latest radar imagery shows decent coverage of showers and storms
extending from SE VA/NE NC down into Central NC late this
evening (along and ahead of the front), with a separate line
forming right along the southern coast. HRRR is trying to catch
up to ongoing convection, but still seems overdone while the
NSSL WRF was too quick to dissipate convection and is underdone.
The main threat for the overnight hours, is still the threat of
locally heavy rain. PWAT value around 2.1" on 00z MHX sounding
with shear values 20-30 kts. Training cells could cause some
minor flooding issues. Inland activity likely to transition
towards the coast late tonight. Low temps overnight are expected
to be near normal, reaching the low 70s inland, and the mid to
upper 70s near the coast.
&&
.SHORT TERM /MONDAY/...
As of 245 PM Sun...As the base of an upper trough slowly moves
down over NC on Monday, another day of scattered to numerous
showers and thunderstorms is expected. Similar to today, a round
of ongoing coastal convection is expected for the morning, and
then showers and storms should develop inland by early
afternoon. Precip may be a little less widespread than today,
but still warrants likely PoPs. Similar severe and heavy rain
parameters will exist on Monday, so possible minor flooding, and
some isolated strong to severe wind gusts are possible. High
temps will only reach the mid to upper 80s with decent cloud
cover expected.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
As of 240 PM Sunday...A period of wet weather continues through
early this week as a nearly stationary upper low develops over
the Ohio River Valley and front remains stalled to the west. The
low pressure system is expected to lift out with a cold front
pushing through the area by the middle of the week with rain
chances diminishing.
Monday night through Tuesday...An upper trough will remain
quasi- stationary to the NW this period with unsettled weather
continuing across the region. The upper low begins to lift out
Monday night and Tuesday with deeper moisture axis shifting
offshore but shower chances continue with the upper trough axis
remaining to the west and will keep 20-40% PoPs. More sunshine
Tuesday will lead to highs around 90 inland and mid/upper 80s
coast.
Tuesday night through Thursday...The upper low lifts out
Tuesday night with a cold front pushing across the area with
deeper moisture pushing offshore and shower chances gradually
diminishing trough the overnight. Limited convective activity is
expected Wednesday and Thursday with shortwave ridging aloft
bringing subsidence. Cannot rule out isolated showers developing
along the sea breeze each afternoon but guidance has trended
drier, especially Wednesday. The warming trend warming trend
continues with high expected in the lower 90s inland to
mid/upper 80s coast.
Thursday night through Saturday...Shower and thunderstorm
chances increase for the latter half of the week as the upper
ridge pushes east and a robust mid level shortwave approaches
from the west. Temps expected to be near normal with highs
around 90 inland and mid 80s coast.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Short Term /through Monday/...
As of 7 PM Sunday...Mixed bag of VFR and LIFR conditions
currently across the terminals, reduced in convection over ISO
and OAJ. Scattered to numerous showers and storms will continue
across the area this evening and tonight. Similar to previous
nights, there is a threat of some patchy fog/low stratus
overnight, especially in the inland TAF sites (KPGV/KISO). Any
fog/low stratus will diminish Monday morning...with VFR
conditions returning. Expect more showers and thunderstorms to
develop late Monday morning and afternoon.
Long Term /Monday Night through Thursday/...
As of 240 PM Sunday...An upper level system stalls to the
northwest with wet weather continuing across the area Monday
into Tuesday bringing the likelihood for periods of sub-VFR
conditions. The system lifts out late Tuesday with rain chances
diminishing and only isolated showers or storms expected
Wednesday through Thursday. Cannot rule out patchy late
night/early morning fog each morning bringing reduced
visibilities and possibly ceilings.
&&
.MARINE...
Short Term /Through Monday/...
As of 955 PM Sun...Latest obs show S/SW winds 10-20 kt with
seas 2-4 ft. S/SW winds 10-20 kt expected to continue into
Monday, with perhaps a few gusts to 25 knots over the outer
southern and central coastal waters overnight. Seas will build
to to 3-5 ft tonight, with some isolated 6 ft seas possible on
the outer waters. Will hold off on a SCA, thinking that if any
small craft conditions were to develop it will be very isolated
and over a short duration.
Long Term /Monday Night through Thursday/...
As of 240 PM Sunday...A front will remained stalled to the west
with high pressure offshore through early next week. S/SW winds
10-20 kt continue into Monday and Monday night with seas 3-5
ft. Gradients relax a bit as we move into the middle of the week
with SW winds around 10-15 kt Tuesday and Tuesday night and
5-15 kt Wednesday and Thursday. Seas expected to subside to 2-4
ft Tuesday through Thursday.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...SGK
NEAR TERM...CQD/SGK
SHORT TERM...SGK
LONG TERM...SK
AVIATION...SK/CQD/BM
MARINE...SK/CQD/SGK
Area Forecast Discussion
National Weather Service Pocatello ID
236 PM MDT Sun Aug 12 2018
.DISCUSSION...Today Through Next Sunday.
A fresher, slightly cooler air mass has arrived! This is courtesy
of a low pressure system/trough moving across southern Canada
that swung a cold front across SE Idaho. This system is still
producing some lift, and we are seeing some light radar echoes
this afternoon across the eastern Magic Valley, Cassia County, and
Island Park region. Low-level air may be dry enough that some of
this is falling as virga and not reaching the ground, and so far
no lightning strikes have been detected. We do carry a chance of
isolated showers/t-storms as this activity shifts east, but this
should be low-impact with most locations remaining dry. Breezy
conditions will continue through sunset, and hazy skies remain due
to wildfire smoke. See the AIR STAGNATION section below. A few
light showers may linger tonight in the Southern Highlands.
As the aforementioned low pressure system departs, we transition
into more of a zonal long-wave pattern across the Continental US
for the upcoming week, quite evident at 500mb and higher. There is
some indication that weak high pressure may try to develop over
AZ/NM by late week, but at this time it doesn`t appear to
significantly modify the flow. This overall pattern will result in
a relatively weak/chaotic surface flow across the Rockies, where
our day-to-day sensible weather will be governed by some
increasing monsoonal moisture working in from the south, and
short-wave low pressure troughs that become embedded in the zonal
flow. Unfortunately, the long-range suite of models
(GFS/ECMWF/Canadian) are not in great agreement in the
track/timing of these features, and have had some issues with run-
to-run consistency as well. Thus, forecast confidence in precip
chances Mon through Sun is low. Tues has trended a bit drier,
while Wed and Thurs afternoons appear to be the wettest as one of
the more organized shortwaves crosses the region, although the GFS
remains much wetter than the other models with this system. We
continue to cautiously adjust PoPs based on the latest model
guidance, but have opted to fairly liberally broad-brush the areas
that may be affected each day. Confidence in fairly light winds
and steady temps throughout the week is better under this pattern.
Highs look to reach the upper 80s to lower 90s each day at lower
elevations, running just slightly above normal for this time of
year, but cooler than what we have seen the past month.
The latest 6-10 day, 8-14 day, 3-4 week, 1 month, and 3 month
outlooks from the CPC all favor a decent chance of continued above
average temperatures through October. - KSmith/RS
&&
.AVIATION...
VFR conditions are in place across all of SE Idaho this afternoon,
and we expect VFR conditions to continue tonight, Mon, and Tues at
all TAF terminals with moderate to high confidence. The greatest
concern for aviation will be some decent W-SW winds through sunset
this eve, particularly at KPIH, KIDA, and KSUN (more S-SW here), but
not expecting any LLWS issues. Widespread smoke and haze continues
across the region from wildfires both in ID and upstream into
CA/OR. KIDA and KSUN have seen vsbys drop to 6-8 miles at times,
but we have pretty high confidence that 6SM will be the worst we
will see. Finally, seeing some light radar returns near KSUN and
KBYI this afternoon, pushing NE. Some of this is likely virga, and
in general this activity should be low-impact, but will continue
to monitor. Included a low-confidence VCSH overnight today at
KBYI, but IF we see showers, best chance is south of the terminal
into the Southern Highlands. - KSmith/RS
&&
.FIRE WEATHER...
Satellite water vapor imagery currently shows a dry band across
Oregon and northern Idaho. This has been progressing gradually
east. Expect this dry air and gusty winds will move into the
Salmon-Challis NF area this afternoon, perhaps 1500 hours to
midnight. Winds across that area should pick up as well, then drop
off with sunset this evening. Zones 475/476 and perhaps the
northern third or so of Zone 422 still has a better than even
chance of reaching Red Flag criteria for wind/RH. Difficult to
rule out the Craters of The Moon and Arco Desert area just yet,
the afternoon minimum humidity may be too high. Craters of The
Moon was gusting to 29 mph last hour. There is real marginal
instability for any thunderstorms this afternoon. This disturbance
moves east tonight and Monday, leaving a slight chance of
thunderstorms near Island Park Monday afternoon. Monsoon moisture
will try to slip into Idaho from the south. Both Monday and
Tuesday afternoon will have to size up potential for more than
isolated thunderstorms in Zone 427 and 413. The high pressure
ridge builds northward Wednesday. Afternoon humidity increases to
15 to 20 percent most everywhere and current focus for
thunderstorms Wednesday will be the Southern Sawtooth and Caribou
Forest areas. Some cells may produce 0.10 inch rain. Thursday may
be less active, plenty of moisture around but forcing and
instability could be less under the ridge. Friday looks more
interesting with a disturbance off the Pacific moving inland and
perhaps being able to take advantage of the monsoon moisture. The
central mountains may be targeted for some good shower activity
and possibly some wetting rains, and thunderstorms. - RS
&&
.AIR STAGNATION...
Widespread wildfire smoke and haze continues across almost all of SE
Idaho early this afternoon per webcam imagery, with the KIDA and
KSUN airport ASOS stations even reporting smoke at times. This has
resulted in continued degraded air quality. Real-time air monitoring
data from The Idaho Department of Environmental Quality (Idaho DEQ)
currently rates air quality as "Moderate" or Yellow across our CWA.
This means that air quality is acceptable, however, for some
pollutants there may be a moderate health concern for a very small
number of people who are unusually sensitive to air pollution.
Remember, all air quality monitoring is handled by Idaho DEQ. The
latest information can be found at airquality.deq.idaho.gov.
With the recent cold front and stronger westerly winds across the
region this afternoon, some improvement in smoke/haze and air
quality is possible, but confidence is very low. Current air
quality upstream into far western ID and OR is generally rated
Good/Green, but several model solutions including the NAAPS do not
show any strong signal toward improvement in the days ahead. We also
do not have the HRRR or RAP smoke model guidance available today
due to an outage. Thus, we continue to carry haze in the forecast
for the entire CWA through Tues, and this matches up well with the
neighboring forecast offices. - KSmith/RS
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 10 PM MDT this evening for IDZ410-422-425-
475-476.
&&
$$
Area Forecast Discussion
National Weather Service Phoenix AZ
509 PM MST Sun Aug 12 2018
.UPDATE...
Updated aviation discussion for Phoenix TAF sites.
&&
.SYNOPSIS...
Enhanced thunderstorm activity will continue this afternoon and
evening before somewhat drier air pulls into the region temporarily
decreasing activity Monday and Tuesday. Temperatures will also
increase back to near to slightly above normal levels through
Tuesday. A substantial increase in moisture during the middle of the
week should bring more showers and thunderstorms for both the higher
and lower elevations while lowering temperatures back below normal.
&&
.DISCUSSION...
Afternoon WV imagery clearly showed a distinct cyclonic circulation
over central New Mexico with at least one arm of vorticity sweeping
westward through Arizona, and potentially another vorticity center
poised over NE Arizona. Objective analysis depicts a very favorable
mid and upper tropospheric pattern of divergence with an enhanced 20-
30kt H5 easterly flow and northerly cyclonic H3 jet level winds.
Meanwhile, the 12Z KPSR sounding looked extremely favorable for
thunderstorms spreading into lower elevations as deep mixed 10 g/kg
moisture existed towards the top of the boundary layer with a
healthy 14 g/kg around 850mb. While some of the more robust H8
moisture will mix out through the afternoon and H7 layer may dry a
bit, mesoanalysis already shows MLCapes in excess of 1000 J/kg
materializing and inhibition weakening. Enhanced winds aloft should
pull convection south and westward into this favorable environment
while DCapes at or above 1500 J/kg will support strong
outflow/downburst winds.
12Z high resolution models have only reinforced the trend from 00Z
HREF members and multiple HRRR iterations bringing scattered
organized convective bands into north/northwest Maricopa county, as
well as northern Pinal County. There`s also indications that a small
wave along the international border could support scattered storms
into SW Arizona/SE California. Deeper outflows may maintain
convective structure into the evening, however most guidance
indicates activity waning after loss of heating and slow transition
towards a more subsident flow pattern aloft.
On Monday, the aforementioned New Mexico low pressure system will
translate into the central high plains allowing mid and upper level
ridging to descend back closer into the forecast area. This will
allow some further erosion of midlevel moisture while also creating
a substantial weakening of winds aloft. While this will not preclude
deep convective activity over higher terrain areas of northern and
eastern Arizona, propagation into lower valley communities will be
muted. All model output generally portrays this outcome with just
some distant traveling outflow boundaries (and possible a rogue
storm outside of Gila County). This general scenario should hold
through Tuesday evening as well providing a brief respite from the
recent convectively active period. Otherwise with H5 heights near
592dm becoming centered over the forecast area, temperatures near to
slightly above average look likely with some SE California
communities flirting with 110F.
The center of the high pressure ridge will continue to reposition
into central New Mexico on Wednesday forcing a deep southerly flow
pattern to take shape over the SW Conus. An initial shallow Gulf
surge looks probable Tuesday night followed by much stronger, deep
theta-e advection Wednesday. Both the operational GFS and ECMWF
continue to advertise a well defined inverted trough/vorticity
center surging north from Mexico late Wednesday ushering in an
impressive plume of moisture. While lapse rates and overall
instability will naturally suffer from such a transition, the shear
magnitude of theta-e advection and well mixed 12 g/kg mixing ratios
should result in at least scattered storms Wednesday evening into
the overnight.
Initially a threat of strong winds and blowing dust with the first
surge of moisture into the region, a steady stream of moisture
advecting north and total column Pwats potentially exceeding 2
inches may yield persistent storm formation into Thursday morning.
The 12Z ECMWF hints at this possibly of widespread early morning
convection, and historically similar output from this model has
resulted in flooding rainfalls. Confidence is low in such an
outcome, though the pattern and environmental profiles match heavy
rainfall events. After this initial surge and convective event, the
evolution of daily weather trends might become driven more in the
mesoscale as excessive cloud cover from antecedent widespread
convection could restrict further development on any given day.
Over the weekend, the high center is shown shifting well to our
northwest which could allow for a drying northerly flow. This may
bring a decreasing thunderstorm threat with storms mostly confined
to high terrain areas by next weekend. The drying conditions will
bring temperatures upward from the near to below normal readings
seen on Wednesday and Thursday.
&&
.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
A broken line of strong to severe thunderstorms has pushed into
eastern Maricopa County. These storms should affect KIWA and KSDL
within the next hour and KPHX around 01Z. Wind gusts up to 45
knots appear to be possible with these storms, with at least
isolated severe wind gusts to 50-55 knots. Although blowing dust
does not currently appear to be a major threat for the terminals,
this threat may increase if an outflow boundary is able to push
ahead of the storms. At the current moment, it appears that the
wind shift will be closely tied to the broken convective line of
storms, so visibility decreases will most likely be caused by
brief heavy rain. Thunderstorms and wind gusts above 20 knots
should end between 02-03Z with this relatively fast-moving line,
with all showers ending by 6Z. E-SE winds should return after 06Z
with a typical early afternoon shift to westerly tomorrow.
Southeast California/Southwest Arizona including KIPL and KBLH:
Models advertise a chance for thunderstorms at KIPL this
afternoon/evening creating gusty and erratic winds. However, as it
stands right now, there is only a 10-20% chance of this occurring
and have left it out of the TAF for now. Otherwise, expect
westerly sundowner winds at KIPL in the 00-03Z timeframe. There is
also a chance KBLH could see some thunderstorm activity, although
later around 02-06Z but again, confidence is too low to include
in the TAF at this point.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Wednesday through Sunday:
Elevated moisture levels will surge into all districts during the
middle of the week resulting in enhanced chances for thunderstorms
and wetting rains. Some locally heavy rain will be possible,
especially throughout central Arizona. Slightly drier air may slowly
pushing into the region by the weekend, but afternoon storms will
still be possible over higher terrain areas. With the increases
moisture, minimum afternoon humidity levels will only fall into a 25-
40$ range following good to excellent overnight recovery. Brief
periods of gusty south to southwest winds will be likely with the
initial surge of moisture, but otherwise wind speeds will be typical
for mid summer.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...MO/Kuhlman
AVIATION...Wilson
FIRE WEATHER...MO
Area Forecast Discussion
National Weather Service Blacksburg VA
1000 PM EDT Sun Aug 12 2018
.SYNOPSIS...
A weak cold front will shift southeast tonight beneath an upper
level area of low pressure that will travel east tonight into
Monday. Rounds of showers and stronger storms will accompany the
front into tonight with lingering scattered showers and a few
thunderstorms into Monday. Weak high pressure builds in with
somewhat drier weather for the middle of next week.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
As of 1000 PM EDT Sunday...
Showers still moving through the far eastern section of the
forecast area and will likely be slow to move off to the east,
however, have dialed back the PoPs significantly in the west as
current radar is verifying the trends in the HRRR`s past several
runs. Further, adjusted sky forecast to better represent
clearing that is occurring, mainly in the west, but beginning to
advect east. Fog forecast has remained largely unchanged but
will need to be monitored as it begins to develop overnight.
As of 316 PM EDT Sunday...
Closed upper low will drop southeast tonight into Monday. Several
shortwaves will rotate around the low this afternoon into Monday.
Low level moisture convergence will combine with heating and surface
boundaries to generate scattered to numerous showers and
thunderstorms which will move east across the region this afternoon
into tonight. Some of the thunderstorms will be strong to severe
with damaging winds, hail and heavy rains. Area coverage of flooding
will be too small to post a flash flood watch for this afternoon
into tonight.
HiResW-ARW-EAST and HRRR have the stronger thunderstorms exiting the
east by 03z this evening. However with the cold pool lingering, may
see additional showers especially central/northern sections through
midnight. Clearing in the wake of the convection per developing
light northerly flow aloft to allow more fog to form overnight into
Monday morning especially where it rains. Low temperatures tonight
will range from the upper 50s in the mountains to the mid 60s in the
piedmont. The upper low across our region will slowly lift northeast
Monday into Monday night. Scattered showers and thunderstorms will
develop Monday afternoon into Monday evening. The day two
convective outlook highlights a marginal threat for severe
thunderstorm in the far east. High temperatures Monday will vary
from around 70 degrees to the mid 80s in piedmont.
Forecast Confidence Level-Moderate.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY NIGHT/...
As of 100 PM EDT Sunday...
Upper trough slowly lifts out to the northeast during this period to
be replaced by relatively small wavelength yet strong ridge at
500mb, as well as continuing to filter in drier airmass. This will
result in a couple of primarily dry days but warmer as well.
Scattered showers and isolated thunderstorms may linger primarily in
the mountains into Monday evening still under some influence of
upper trough with steeper lapse rates but there should be a strong
diurnal signal so expect any lingering activity to rapidly diminish
by late evening.
Tuesday definitely a drier airmass but with some influence still of
slowly exiting upper trough over the NE U.S. there are a couple
models that still suggest something isolated popping up in the
afternoon. Many other models are totally dry though. Leaving some
slight chance PoPs for the mountains mainly and into the
foothills for the northern part of the forecast area.
For Wednesday feel more confident that ridge will dominate along
with dry air mass and subsidence inversion seen in forecast model
soundings to keep things dry for the day time hours at least. Models
than suggest weakening short wave could try and break this down and
some showers could move in during the evening but 12Z GFS slower
this wave and indicating nor precip late Wed or overnight. Will keep
only a very small area of slight chance for far SW part of forecast
area late Wed and Wed night, but really think it will remain dry
through this period. Also noticeably hotter Wed under influence of
the aforementioned ridge, with temps low to mid 80s west and upper
80s to lower 90s east, and may end up needing to bump those up a
couple more degrees as we get closer.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 100 PM EDT Sunday...
General trend through the late week and into the weekend is for weak
troughing to develop again to the west with gradual increase in
moisture again and thus chances for afternoon/evening scattered
storms, with best coverage likely in mountains. Some embedded short
waves moving through to flatten trough at times so somewhat of a
progressive pattern, but trying to time any of these waves this far
out, since influenced heavily by upstream convection, is nearly
impossible. Thus there could easily be a day in this stretch with
much more coverage, and other days with less, but for now will
indicate a general ramp up of shower and thunderstorm chances
through the period Thursday through Sunday.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
As of 720 PM EDT Sunday...
Showers and thunderstorms that were widespread during the
afternoon hours today will become more isolated as we enter
the TAF period as they begin to move east. While the main axis
of stronger storms will be mostly east of the region, isolated
convection will continue to be an issue in the mountains going
into the overnight hours beneath an upper level low. Conditions
will be VFR outside of any showers or thunderstorms.
Some clearing can be expected during the overnight hours which
will likely lead to widespread fog formation in areas that
received rain today. Will expect that worst conditions will
mainly be in the typical mountain valley locations, but still
will be seeing IFR at DAN and LYH. After sunrise, fog should
dissipate fairly quickly and should be completely gone by the
13-14Z time frame.
During the afternoon hours, will again be seeing typical
summertime conditions with showers and thunderstorms developing.
As of this writing, severe potential appears to be limited to
the east of the forecast area, but may still be able to impact
DAN and LYH.
Extended Discussion...
Model solutions are coming into better agreement with cutting
off an upper level low over Ohio into Monday night. This
situation should put the Mid Atlantic in an unsettled and wet
pattern throughout this time period. Localized MVFR ceilings and
visibilities will likely occur in scattered showers and
thunderstorms. The upper level low should progress eastward by
Tuesday and Wednesday to bring drier weather and a better chance
of VFR conditions into midweek.
&&
.EQUIPMENT...
As of 300 PM EDT Sunday...
KFCX WSR-88D may be down as late as Tuesday with parts on order.
If the repair parts arrive quicker, radar service will be
returned faster.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JR/KK
NEAR TERM...KK
SHORT TERM...SK
LONG TERM...SK
AVIATION...JR/KK
EQUIPMENT...RAB
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