Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/07/17
Area Forecast Discussion
National Weather Service Charleston SC
1124 PM EDT Wed Sep 6 2017
.SYNOPSIS...
A cold front will move through the area this evening and off
the coast overnight. High pressure will then prevail through
late week. Powerful Hurricane Irma will be near Florida and the
Bahamas this weekend. Refer to the latest advisory on Irma
issued by the National Hurricane Center.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 1120 pm: The cold front has pushed off the GA/SC coast,
resulting in north winds across the forecast area. Temperatures
are on pace to cool into the low to mid 60s inland over night.
Otherwise, the update will feature winds based on NHC guidance
through 0Z Tuesday.
As of 945 PM: Convection has largely dissipated across the
forecast area. I will issue a quick update to reduce PoPs and
mention of thunderstorms.
As of 735 PM: Inland showers and thunderstorms have pushed over
the inland counties of the SC Lowcountry early this evening.
The outflow associated with these storms is slowly outpacing the
convection, resulting in the cells to gradually weaken.
However, HRRR indicates that convection may develop as the
outflow nears the coast later this evening. I will update the
forecast to adjust PoPs, sky, and winds.
Previous Discussion: A cold front just upstream from the area
will arrive from the NW this evening, reaching the coastal
corridor around midnight, and then offshore and away from the
area thereafter. The cold front is being driven by a highly
amplified mid and upper trough over the eastern portions of the
country, as strong short wave energy passes through the OH
valley and eastern Great Lakes.
There is modest instability and shear, with 0-6 km Bulk Shear as
high as 30-40 kt. This will support at least a few strong storms
where multicellular clusters develop. Fortunately DCAPE is no
more than about 600-800 J/kg, so the severe risk is close to
zero.
PWat of 120-130% of normal and back-building and/or training of
a few cells will produce localized flooding and could
necessitate a couple of Flood Advisories. Many parts of
Charleston County were soaked by earlier activity, as much as
2-4 inches of rain in some communities, so it won`t take much
for additional flooding concerns to occur. Keep in mind that
high tide is around 9-10 pm, should heavy rains be ongoing near
or during that time to aggravate any flooding concern.
Upper difluence caused by a coupled jet structure over the area
this evening will aid in large scale forcing for ascent, and
with sufficient instability and elevated moisture this will
cause scattered to numerous showers and t-storms prior to
midnight, with coverage quickly dropping off with the frontal
passage overnight.
Behind the front there is a few hours of lingering boundary
layer moisture and light winds, which could allow for areas of
low stratus to form, before much drier air arrives before
morning to clear skies out further. There is likely too much
mixing to allow for fog to form, as geostrophic winds are 15-20
kt.
It`ll be quite a change in air mass when you awake Thursday
morning, with lows down into the lower 60s NW tier, mid and
upper 60s elsewhere.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Thursday and Friday: Any moisture lingering over the area will
quickly shift offshore with a departing cold front early Thursday.
The front is expected to stall well south of the region, aligning
west-east over Florida and offshore. Sfc high pressure will build
over the region behind the front while a large mid/upper lvl trough
of low pressure quickly loses amplitude and shifts over the
Northeast United States Thursday into Friday. Given the pattern,
fair weather conditions are expected into late week with dry and
cooler air filtering over the area within a northerly flow Thursday,
followed by a gradual modification in temps within a northeast flow
on Friday. High temps should peak in the lower 80s Thursday, then
low/mid 80s on Friday, warmest in Southeast Georgia. Overnight lows
will range in the upper 50s inland to mid/upper 60s closer to the
coast.
Saturday: Forecast confidence becomes slightly lower in regards to
the speed/strength of the mid/upper lvl trough of low pressure over
the Northeast. However, the main trough axis is anticipated to shift
off the Northeast seaboard during the day, resulting in a mid/upper
lvl ridge of high pressure to erode and/or retreat further over the
western Atlantic late weekend. The exact timing of the trough
shifting offshore and the weakening of the Atlantic ridge will play
an important role in regards to when Hurricane Irma makes a northern
shift near southern Florida, which appears to begin sometime
Saturday night as indicated by the latest NHC tropical forecast.
Given the setup, dry conditions could persist into at least
afternoon hours. However, higher moisture levels should begin to
return late as the sfc flow gradually veers and becomes slightly
more onshore. For this reason, a slight chance of showers and
thunderstorms will remain in the forecast, mainly for coastal
locations. Further south, coverage could be slightly higher along
the Georgia coast. High temps should range in the lower 80s over
most locations.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
The trough to our north will continue moving eastward and offshore
Saturday night as surface high pressure over the Great Lakes Region
prevails. Focus undoubtedly will be on powerful Hurricane Irma,
which will likely be just southeast of Southern FL. The question of
how quickly and where Irma makes it`s turn to the north is still
murky. Both the 12Z GFS and ECMWF have the track to the east of
Florida and then tracking almost due north. Everyone is reminded
that by no means is this scenario a certainty. This is only a single
run. Weather models can change and are known to change several days
out. But what is becoming more certain is that our area will
experience significant impacts from Irma.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
Inland showers and thunderstorms have pushed over the inland
counties of the SC Lowcountry early this evening. The outflow
associated with these storms is slowly outpacing the convection,
resulting in the cells to gradually weaken. However, HRRR
indicates that convection may develop as the outflow nears the
coast and terminals through 4z, I will highlight with an TEMPO.
Late tonight, guidance indicates that a small area of
restrictive clouds or ceilings will develop during the pre dawn
hours, especially over the SC counties. I will continue to
indicate SCT MVFR level clouds at this time. In the wake of the
cold front, winds are forecast to veer to the NNE by Thursday
afternoon.
Extended Aviation Outlook: VFR conditions are expected at both CHS
and SAV terminals Thursday through Saturday. Flight restrictions are
then likely Sunday as conditions rapidly deteriorate while Hurricane
Irma approaches the region.
&&
.MARINE...
Tonight: An unusually early autumn season or late summer season
cold front will move through the waters during the late evening
and early post-midnight hours, and then pass to the SE of the
area thereafter. Warm advection in advance of the cold front
will limit mixing, but a tight pressure gradient and sea breeze
circulations will allow for winds as high as 15-20 kt and gusty
early on. The gradient slackens from about 03-06Z as the cold
front moves through, allowing winds to drop about 10 or 15 kt,
and winds veer around to the NW and N overnight. CAA and small
isallobaric pressure rises will allow for a little increase
again by morning. Seas on average will hold between 3 and 5
feet, a mix of wind waves around every 5 or 6 seconds, and long
period swells that originated from Hurricane Irma on the order
of every 14 to 16 seconds.
Mariners should be aware that scattered to numerous showers and
t-storms prior to the frontal passage can produce frequent
lightning, strong wind gusts in excess of 30 kt and very heavy
rains reducing visibility to near zero.
Thursday through Monday: Dry high pressure will build over the
waters from the north/northwest and persist into late week.
There will likely be stronger winds late in the week due to an
enhanced pressure difference between continental high pressure
to the northwest and Hurricane Irma far to the south-southeast.
Small Craft Advisories for seas will likely be needed Thursday
afternoon beginning in offshore Georgia waters, then continuing
into Friday for remaining coastal waters as winds increase. By
Saturday, rapidly deteriorating and very hazardous conditions
are looking much more likely as powerful Hurricane Irma
approaches from the south.
Rip Currents: We still have a Moderate Risk of rip currents the
rest of the day due to long period swells, sea breeze effects
and sea breeze influences at all beaches.
Distant swell associated with Hurricane Irma should
slowly increase this week as Irma tracks west-northwest. Although
swell height over the coastal waters will initially be small, on the
order of 2-3 ft, waves will be quite powerful with most of it likely
reaching the surf zone. This will be enough to support a moderate
risk for rip currents at area beaches this evening through Thursday.
High risks are expected late week.
Long period swells will continue to impact the surf zone into the
upcoming weekend and possibly into early next week depending on the
track Irma takes. This will result in an enhanced risk for powerful
and dangerous rip currents.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...
Area Forecast Discussion
National Weather Service Cheyenne WY
623 PM MDT Wed Sep 6 2017
.SHORT TERM...(This evening through Friday night)
Issued at 258 PM MDT Wed Sep 6 2017
The negatively tilted upper ridge currently situated over the
intermountain west will slowly shift east the next couple of days.
By tomorrow, it should line up along the spine of the Rockies
with a shortwave embedded in northwest flow expected to move NW-SE
across the forecast area. Moisture progs with this wave continue
to be low, although there could be just enough moisture to squeeze
out a shower/storm or two over the mountains. As the ridge
builds, may also see a return of wildfire smoke from west to east
although latest HRRR model guidance projects the smoke to be of
relatively low concentration near the surface. For Friday, an even
stronger shortwave will drop down from the northwest while a
better fetch of subtropical moisture advects into the region
within midlevel WSW flow. Maintained slight chance to chance PoPs
across the area especially Friday afternoon and evening as this
pattern will be more favorable for convective development. After a
cool day today, temperatures will climb back to more normal
values for this time of year through Friday.
.LONG TERM...(Saturday through Wednesday)
Issued at 258 PM MDT Wed Sep 6 2017
Warm conditions will hold across the CWA through the period with
max temperatures above seasonal averages. Some moisture seeping
up from the south on the back side of an upper ridge over the
southern Rockys will allow for at least isolated afternoon/evening
convection Saturday and Sunday. An upper trough should then move
across the northern Rockys into the northern plains Monday and
push a minor front across the CWA bringing drier air so Monday
through Wednesday looking mainly dry.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 623 PM MDT Wed Sep 6 2017
VFR with scattered to broken high clouds and light winds.
&&
.FIRE WEATHER...
Issued at 258 PM MDT Wed Sep 6 2017
The very dry airmass will persist through the next several days
with afternoon humidities dropping into the low to mid teens
especially across southeast Wyoming. Higher readings in the mid
20s are likely in the Nebraska Panhandle tomorrow and Friday.
Winds on the whole will remain relatively light, however gusts of
20 to 25 mph cannot be ruled out across the Plains on Friday. A
series of disturbances moving overhead in northwest flow will
increase chances for showers and thunderstorms across the region
on Friday and Saturday. Expect light rainfall amounts to accompany
this activity.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...RJM
LONG TERM...RE
AVIATION...MAJ
FIRE WEATHER...RJM
Area Forecast Discussion
National Weather Service Duluth MN
657 PM CDT Wed Sep 6 2017
.UPDATE...
Issued at 634 PM CDT Wed Sep 6 2017
Updated aviation section below for 00Z TAF TAF issuance.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 245 PM CDT Wed Sep 6 2017
Scattered showers that have developed over portions of northwest
Wisconsin this afternoon due to northerly on-shore flow from Lake
Superior will eventually dissipate as we lose diurnal heating, along
with the flow becoming more off-shore this evening.
An upper-level trough will continue to very slowly shift off to the
east tonight through the day Thursday. A strong northerly 130+ kt
upper-level jet and a few pulses of mid-level positive vorticity
advection (PVA) will support chances of showers overnight and
through much of the day Thursday, especially over the eastern
portions of the forecast area where the better isentropic lift will
be located. Also, the coolest 925 to 850 mb layer temperatures will
linger over the eastern areas as well. RAP and NAM model soundings
both indicate that mid to high level clouds will linger over the
region overnight. While a sfc high pressure ridge will be in place
over the region, leading to light flow near the sfc, the clouds
should preclude any significant mention of fog, although some light
patchy fog may develop over northwest Wisconsin tonight. There will
be a brief respite from precipitation chances, mainly this evening,
as the sfc high pressure builds in. Due to the lingering cloud
cover, temperatures should be moderated a bit, which should inhibit
any frost development. Lows tonight will range from the lower to
middle 40s across the area.
Another mid-level PVA impulse will bring our next chances of showers
overnight. The convective-allowing models (CAMs) are in pretty good
agreement regarding scattered chances of showers as this impulse
makes its way out of southwestern Ontario Canada. I bumped up POPs
some Thursday morning, especially from INL to the Twin Ports and
southeast over Hayward due to the good agreement from the CAMs. By
Thursday afternoon, the mid-level trough should make its way off to
the east, so chances of showers will diminish accordingly,
eventually coming to an end by Thursday evening. Highs Thursday will
range from the upper 50s over the east into the middle to upper 60s
over the west, with some lower 70s possible over the extreme western
areas.
.LONG TERM...(Thursday night through Wednesday)
Issued at 245 PM CDT Wed Sep 6 2017
A broad area of high pressure will build across the Great Lakes
region this weekend leading to mainly sunny skies and warming
temperatures Friday into Saturday. As this area of high pressure
builds eastward, an upper level disturbance will approach from the
southwest leading to a chance for increasing clouds in the southwest
flow, though chances for precipitation across the Northland are very
low. Early next week a cold front moves from west to east across the
Upper Midwest leading to a chance for precipitation, mainly in
northern Minnesota. Next week an active zonal flow pattern develops
which will lead to another chance or two for showers throughout the
week.
Thursday night will be the coldest of the next seven days with
lows approaching the low 30s in parts of the MN Arrowhead and inland
areas of northwest Wisconsin (mainly southern Ashland/Iron and all
of Price county). Then a warming trend into next week with highs in
the 60s Fri, near 70 Sat, then low/mid 70s Sunday through at least
mid-week. Confidence in temperatures next week are below normal and
could range from as cool as the low 60s to as warm as the mid 80s.
For fellow gardeners, beyond Thursday night there appears to be
little to no risk for a frost/freeze throughout the Northland
through the middle of next week (and probably through next weekend).
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 634 PM CDT Wed Sep 6 2017
VFR conditions across the Northland as of issuance time. A
shortwave diving out of northern Manitoba tonight will bring a
period of rain showers and MVFR ceilings with VFR visibilities
beginning around 08z tonight, continuing south-southeast across
most of the terminals. It should move out of the area from the
north beginning around 15z, and all of the terminals should return
to VFR no later than 20z.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 47 59 41 63 / 40 60 0 0
INL 44 62 38 67 / 40 40 0 0
BRD 45 68 45 66 / 10 0 0 0
HYR 44 60 39 65 / 30 60 0 0
ASX 47 60 39 65 / 40 40 0 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
UPDATE...LE
SHORT TERM...JTS
LONG TERM...JJM
AVIATION...LE
Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
500 PM MDT Wed Sep 6 2017
.SHORT TERM...(Tonight through Thursday night)
Issued at 247 PM MDT Wed Sep 6 2017
High pressure centered over the eastern Great Basin has begun its
slow retreat this Wednesday afternoon. 500mb heights will slowly
lower each day into Saturday as a weak trough sags south along
the Pacific coast, nudging our high pressure to the south and east.
Today, mid- level cloud cover has helped curtail convective
development across much of west- central Colorado. In the south,
topographically aided convection has developed as expected and
will continue to drift generally southeastward through the
evening. Smoke from wildfires across the Pacific Northwest also
continues to drift across northern Colorado and Utah. Short-term
guidance is in excellent agreement showing a decrease in activity
overnight. HRRR smoke guidance now includes point sources from
wildfires in the northern Park range of Colorado, and shows a slow
westward drift of these plumes overnight. Have added areas of
smoke specifically to NW Colorado to address these higher
concentrations, and expanded the coverage of haze area-wide to
account for the wider distribution of smoke aloft from PACNW
wildfires.
The smoke and haze forecast for Thursday morning has also been
updated in this package following similar logic as stated above.
Guidance indicates that light northwesterly flow will carry smoke
back to the south and east of Steamboat by later Thursday
afternoon. Regarding convection, a slight uptick in moisture south
of I-70 will result in a bit more areal coverage of showers and
thunderstorms in the afternoon hours. Temperatures will creep
downward as well with the additional cloud cover, running about
2-4 degrees cooler than Wednesday.
.LONG TERM...(Friday through Wednesday)
Issued at 247 PM MDT Wed Sep 6 2017
A weak trough along the Pacific Coast is expected to cut off and
drift just west of the California coast from Friday through the
middle of next week, before absorbing back into the mean flow by
next Thursday. This system will remain close enough to the Four
Corners to aid in the return of moisture along its eastern
fringes from Friday through the weekend. PWAT values appear to max
out on Saturday and PoP values are highest that afternoon area-
wide. 12z ensemble guidance has remained on track showing a
westward drift of the upper-level low by Sunday and Monday. The
forecast reflects this and shows a gradual decrease in afternoon
PoP chances through early next week. Overall confidence is high
for all periods in today`s forecast. Confidence drops toward the
end of next week (beyond day 7) as guidance struggles to
consistently depict exactly how the cutoff low is absorbed into
the next Pacific trough.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 458 PM MDT Wed Sep 6 2017
Little change in conditions are expected through the next 24
hours, except models suggest a decrease in smoke along and south
of the I-70 Corridor. Meanwhile, showers and thunderstorms are
expected develop over southwest CO and southeast UT after 18z
Friday. This activity may generate strong outflow winds with best
chances for impact at KTEX, KDRO, KGUC and possibly KMTJ as well.
There is a slight chance of showers or thunderstorms moving over
KTEX and KDRO from 19Z through 02Z, though it`s unlikely this
will cause CIGS or VSBY to lower below VFR levels and CIGS will
remain above ILS breakpoints. Otherwise, VFR conditions are
expected to persist through the next 24 hours.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...MAC
LONG TERM...MAC
AVIATION...CC
Area Forecast Discussion
National Weather Service Omaha/Valley NE
653 PM CDT Wed Sep 6 2017
.SHORT TERM...(Tonight through Saturday)
Issued at 245 PM CDT Wed Sep 6 2017
The primary forecast concerns in this period are the chance for
showers and thunderstorms Friday night into Saturday. Will stay
fairly close to a blend of GFS and NAM MOS for temperatures.
Water vapor imagery in combination with most recent RUC model
initializations showed a mid tropospheric trough from the Hudson
Bay area down to the Gulf coast. A closed low was offshore from
central CA and a ridge stretched from the Four Corners region up
into British Columbia.
Model consensus indicates that this pattern will deamplify as the
ridge to our west weakens and the trough to our east lifts
northeast and fills into Friday. It appears that a weak mid level
disturbance will move toward our area on Saturday. At the surface,
a ridge of high pressure extended from the Dakotas and MN down
into TX. That should move east, allowing southerly flow to develop
which will bring warmer air into the region. Moisture return is
forecast to be weak, as the surface ridge should extend from the
Great Lakes into TX by Saturday evening. The meager moisture would
mean only light precipitation amounts if any through Saturday. We
have some low POPs for parts of the area on Saturday. Will
monitor this as some model solutions indicate a low potential for
precipitation as early as Friday night with increasing atmospheric
moisture and a modest low level jet.
For tonight, did mention some patchy fog, especially late. Winds
will be light and expect temperature/dewpoint spreads to be low
around sunrise. Temperatures should bottom out mainly in the 40s.
High temperatures are expected to moderate from mainly upper 70s
and lower 80s Thursday to mainly lower and mid 80s for Friday and
Saturday.
.LONG TERM...(Saturday night through Wednesday)
Issued at 245 PM CDT Wed Sep 6 2017
Most eyes will be watching Hurricane Irma and potential impacts
on FL Saturday night, but will continue the small chance of
showers and thunderstorms for our area for Saturday night into
Sunday. 500 mb flow is expected to be moderately strong from the
northeast Pacific into southwest Canada Saturday night, then that
will translate east through Sunday. Model spread of the 500 mb
pattern starts to increase by Tuesday. The ECMWF would give us a
cooler pattern for the mid part of next week, compared to the
Canadian, 12Z GFS and GFS ensemble forecasts. At this time, the
ECMWF looks like an outlier and was not given much weight.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 641 PM CDT Wed Sep 6 2017
VFR conditions through the period. Surface high pressure will
remain over the area tonight and slip to the south Wednesday.
Light northwest winds under 8kts will become light southwest
Wednesday.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Pocatello ID
234 PM MDT Wed Sep 6 2017
.DISCUSSION...
An elongated ridge of high pressure will continue to provide warm,
dry weather through tonight. Very light northerly winds will keep
our stagnant airmass in place, and significant amounts of smoke will
continue to blanket the region. Lowered afternoon highs by just a
couple degrees this afternoon based on current surface obs and smoke
trends. The ridge begins to break down/shift east Thurs, signaling a
return to a S/SW flow each afternoon right into next week. This MAY
allow for some gradual improvement in our smoke woes, but any
improvement will likely be slow as no strong/dynamic systems are on
the horizon. Thus, we continue to carry areas of smoke in the
forecast for the entire region right through the next 7 days. The
southerly flow will allow moisture to creep into the region Thurs
which may initiate a few isolated showers/t-storms over the Central
Mntns and SW Highlands.
Precip chances increase Friday. Convection should again be terrain-
driven, but with the potential for t-storm outflow to provide some
lift in the lower elevations, have expanded low-end 15% PoPs Fri
afternoon to include the Snake Plain. High temps may hold a few
degrees cooler Fri, still reaching the mid to upper 80s at lower
elevations.
A trough may brush our area Sat, but this feature appears very weak
and should largely pass north of us. A slight chance of showers/t-
storms will again exist in/near mountain areas. Weak high pressure
looks to build in Sun-Tues with moderate forecast confidence in dry
weather and a slight warming trend.
Computer model guidance diverges Wed, with some models suggesting
that moisture and perhaps low pressure may start approaching the
state. Have introduced a slight, low-confidence chance of showers/t-
storms across our higher terrain areas for now, with changes likely
as we get closer. - KSmith/Valle
&&
.AVIATION...
Smoke continues to be problematic, though some improvement is
expected throughout the day. HRRR smoke model suggests we may see
conditions deteriorate yet again tonight. Projecting MVFR
visibility again tonight, though some brief dips to IFR cannot be
ruled out. Hinsberger
&&
.FIRE WEATHER...
High Haines indices across the South Central Highlands today, as
well as some spots in the Central Mountains. Tomorrow, upper
ridging will begin shifting to the east, bringing a more southerly
flow in the mid and upper levels. This will begin drawing in some
moisture from the Southwest Monsoon, and may trigger some isolated
thunderstorms. The concern is that the fuels have been sitting in
very hot and dry weather for the past several days, and could
easily be ignited--even with isolated coverage. Cloud cover may
curtail widespread convection on Friday. Surface humidity should
see some improvement as well, but lightning will still be a
threat. Hinsberger
&&
.AIR STAGNATION...
Smoke from wildfires continues to lead to hazy skies across the
region. This evening, expect the worst of the smoke to be
concentrated over the Central Mountains and Eastern Magic Valley.
For tomorrow and Friday, a stagnant weather pattern continues and
upper-level winds really do not significantly increase. Winds do
start to increase a bit out of the south by late Thursday into
early Friday for the western portions of our forecast area,
perhaps helping to mix out some of the smoke. Moisture will
brought into these same areas as well which may help the
situation. By the end of the day Friday, these southerly winds
will have spread to the rest of SE Idaho. NP/TW
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Tucson AZ
850 PM MST Wed Sep 6 2017
.SYNOPSIS...Isolated thunderstorms Thursday afternoon and evening
followed by greater coverage of showers and thunderstorms Friday
into Saturday. Expect less coverage of showers and thunderstorms
early next week, with isolated thunderstorms mainly confined to the
eastern mountains. High temperatures lowering closer to average by
Saturday with warmer temperatures returning early next week.
&&
.DISCUSSION...Clear skies to mostly clear skies across southeast
Arizona at this time. A few thunderstorms were ongoing just east of
the White Mountains or in southwest New Mexico. IR satellite imagery
depicted cooling cloud tops associated with a cluster of
thunderstorms over central Sonora Mexico. The HRRR has been
generally discounted for this update due to several erratic
solutions late this afternoon and evening.
Quick glance at the 07/00Z Univ of AZ WRF-NAM suggests precip-free
conditions will occur the rest of tonight. Have noted that the WRF-
NAM then depicts a few showers/tstms may potentially advect into far
western Pima County perhaps from the developing tstm complex
presently over central Sonora around daybreak Friday. Believe this
scenario may be overdone, however. At any rate, based on satellite/
radar trends primarily, have lowered PoPs late tonight to single-
digits area-wide. Thus, precip-free conditions are expected late
tonight into Thursday morning.
07/00Z WRF-NAM then depicts showers/tstms to initiate just south of
Tucson early Thursday afternoon followed by fairly widespread
coverage of showers/tstms mainly west of Tucson late Thursday
afternoon and early Thursday evening. Subsequent shifts may need to
adjust PoPs upward if additional model solutions concur.
Please refer to the additional sections for further detail.
&&
.AVIATION...Valid thru 08/06Z.
Isolated to scattered -TSRA/-SHRA Thursday afternoon and evening
mainly west of KTUS, and isolated -TSRA/-SHRA near mountains east of
KTUS to New Mexico border. Otherwise, clear skies or mostly clear
skies into Friday morning, then scattered to broken clouds around 8k-
15k ft AGL Friday afternoon and evening. Surface wind ely to sly 5-
15 kts with occasional gusts near 20 kts. Aviation discussion not
updated for TAF amendments.
&&
.FIRE WEATHER...Isolated thunderstorms Thursday afternoon and
evening followed by scattered thunderstorms Friday into Saturday. A
drying trend will prevail early next week with afternoon and evening
thunderstorms mostly near the eastern mountains. 20-foot winds will
generally be less than 15 mph into next week.
&&
.PREV DISCUSSION /203 PM MST/...As the mid/upper level high
continues to locate itself across New Mexico into Texas Thursday
into Friday, this will allow deeper south to southeasterly flow and
moisture to move into much of the forecast area. Areas to the east
include Cochise County may tend to hang onto the drier air longer
but the overarching theme is greater shower and thunderstorm chances
starting Thursday especially from Tucson westward. Main concern will
be storms capable of producing strong outflow winds and areas of
blowing dust.
Friday looks to be the most convectively active afternoon/evening
with more widespread coverage across the entire area and the focus
of the strongest storms being from Tucson westward. Still plenty of
moisture remaining on Saturday but many questions remain in terms of
cloud cover and atmospheric recovery from a potentially active
Friday. By Sunday into early to mid next week, the mid/upper level
high will shift to the west back towards Arizona. This will result
in a drying pattern with much reduced storm coverage, though enough
moisture remains on Sunday for a slight chance of showers and
thunderstorms for much of the area.
Above normal temperatures will continue through Thursday.
Thereafter, a return to seasonal temperatures Friday and Saturday
with temperatures then warming back up above normal early next week.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Francis
PREVIOUS DISCUSSION...GL
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