Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/03/18
Area Forecast Discussion
National Weather Service State College PA
1041 PM EDT Thu Aug 2 2018
.SYNOPSIS...
A weak cold front will linger off to the west of the state
through the rest of the week, gradually washing out. An
extensive plume of deep tropical moisture will stream north into
the Commonwealth ahead of it, and trigger numerous bouts of
showers and thunderstorms that will occur through the day
Friday. A ridge of high pressure will build into the region over
the upcoming weekend, bringing generally dry but still quite
humid conditions.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Locally heavy downpours lifting north of the Mason Dixon line
late this evening within area of weak sfc moisture convergence
and along deep layer moisture boundary separating 2" PW from
slightly drier air mass over southwest PA. The Laurel Highlands
are receiving a soaking currently where Flood Advisories have
been issued for the next few hours, and HRRR lifts overall
broken area of showers northward overnight to cover most of the
western and northern counties of central PA by the pre dawn
hours. Flash Flood Watch remains in effect for most of the
area overnight...with FF guidance remaining very low given
recent copious rains. However, most areas should escape higher
intensity rainfall overnight with lighter intensity showers
expected away from the Alleghenies.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Flood threat ramps up with reprisal of convection on Friday, but
much of the night could be quiet with only some light rain
moving overhead - sort of like Thurs AM.
Threat for FF is still there for Fri since the FFG is so very
low. Winds likely not a threat tmrw. Excessive rain outlook
still has us in the SLGT risk area. Support for this is easily
found in the 12Z NAM QPF - esp over the central mtns and even
Allegheny Plateau/Laurels.
Showers/storms should wane and slide to the east Fri night as
the trough to the west opens up a bit and we get more westerly
flow aloft.
Temps and dewpoints should continue at normal, summery levels.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
A weak cool front finally pushes east across the state late
Friday into Saturday followed by PWATs returning to near normal
values of 25-30mm for the weekend within a weak ridge of sfc
high pressure and generally fair/dry conditions. This should
reduce the coverage of heavier showers and thunderstorms.
Warmer temps, higher humidity and an increasing chance for
mainly afternoon/evening showers and thunderstorms returns for
early next week.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Widespread VFR conditions across central Pa early this evening.
However, do expect developing stratus/fog overnight, as the
lower levels cool and moisten. Model soundings and latest SREF
probability charts indicate IFR cigs will become likely across
the northern mountains, where a moist southerly flow is forced
to ascend the higher terrain. Elsewhere, MVFR cigs appear more
likely.
An area of low pressure will lift up the Appalachians tonight
and Friday, causing scattered showers to become more numerous
late tonight and Friday. An increased surge of moisture ahead
of this feature could potentially produce a fairly widespread
period of IFR cigs between 09Z-14Z. This low level moisture
should mix out by midday. However, numerous showers and possible
thunderstorms will likely result in occasional MVFR conditions
the rest of the day, with a brief dip to IFR possible in any
heavier shower or thunderstorm.
.Outlook...
Sat...AM low cigs/fog likely west. AM showers/cig reductions
possible east.
Sun...Patchy AM fog possible.
Mon...Isolated PM tsra impacts possible western Pa.
Tue...Scattered PM tsra impacts possible.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Friday evening for PAZ012-017>019-
024>028-033>037-041-042-045-046-049>053-056>059-063>066.
&&
$$
SYNOPSIS...Dangelo
NEAR TERM...Dangelo/DeVoir
SHORT TERM...Dangelo
LONG TERM...Lambert/Gartner
AVIATION...Fitzgerald
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1152 PM EDT Thu Aug 2 2018
.AVIATION...
Widely scattered convection should remain out of terminals for the
most part with an outside shot at a stray shower overnight and then
again with daytime heating Friday afternoon. Washed out weak frontal
boundary will allow for more pooled low level moisture and a better
cumulus field on Friday so expect a period of bkn lower vfr cigs. A
period of lower stratus/br will also be possible along boundary KFNT
north, but especially KMBS where rain has moistened boundary layer
considerably already.
For DTW...Diurnal cumulus on Friday may become broken near 5000
feet. Otherwise, forecast will be pretty quiet as any convection in
the vicinity should remain very isolated.
.DTW THRESHOLD PROBABILITIES...
* Medium in ceilings at or below 5000 ft at times Friday afternoon.
&&
.PREV DISCUSSION...
Issued at 337 PM EDT Thu Aug 2 2018
DISCUSSION...
Attention for this afternoon and evening will revolve around a mid-
level trough axis coupled with a low-level frontal boundary that
will produce rain and thunderstorm chances mainly across the Tri-
Cities into Thumb. Latest hi-res CAM suite develops a line of
thunderstorms along the frontal boundary across central lower
Michigan between 20 - 22Z, and pushes the thunderstorms across the
northern CWA during this timeframe into the evening hours. The bulk
of thunderstorm development is expected to stay sub-severe as mid-
level lapse rates and deep layer shear remain modest at around 6.0
C/km and 20 knots respectively, with frequent lightning and heavy
downpours being the main threats. Additionally, morning and early
afternoon convection (which was not simulated well within the 12Z
CAMS), have likely increase stability across the Tri-Cities into the
Thumb, increasing confidence that storms will mostly be sub-severe.
However, instability will have the chance to rebound due to August
heating before expected CI associated with the front, thus will not
completely ignoring the chance for an isolated severe storm producing
brief gusts up to 60 mph.
Lingering showers and thunderstorms will be possible across the
northern Metro region late this evening into the early morning as
mean layer flow continues to transport moisture into SE MI (PW
values between 1.2 - 1.4 inches at 09Z across Metro region) as mid-
level troughing resides aloft, however, forcing will significantly
diminish across the northern CWA late tonight. In fact, latest 18Z
HRRR run keeps all of the precipitation north of I69 corridor and has
weakened forcing well before reaching the northern Metro area, thus
have opted to leave the Metro region with only a slight chance for
precipitation tonight and overnight.
Otherwise, mean flow will turn to the northwest throughout Friday
and will start to advect a drier air mass across the CWA. Isolated
to scattered showers and thunderstorms will remain possible mainly
across the eastern half of the CWA on Friday, as eastern Michigan
holds onto residual moisture through the afternoon. Precipitation
chances will then end late Friday evening as an upper-level ridge
begins to build back into the Great Lakes. Increased subsidence from
the ridge of high pressure in conjunction with southwest flow will
make for a warm a warm start of the weekend, as highs peak in the mid
to upper-80s.
Another day of upper-level ridging will prevail over the region
Sunday as northern stream troughing amplifies upstream over the
northern Plains. Slightly cooler temperatures moving in may allow
for isolated thunderstorms Sunday afternoon across the Tri-Cities
and northern Thumb, with dry conditions otherwise. Forecast
confidence begins to decrease significantly heading into early next
week with the approach of the northern stream trough and associated
slow-moving cold front. Long term guidance is in disagreement with
the timing of the energy, with the GFS more progressive (Monday-
Tuesday) than the ECMWF (Tuesday-Wednesday). Regardless of the
eventual timing, scattered to locally numerous showers and
thunderstorms will be possible for the early to middle of next week.
Hot and humid conditions will persist through Monday with
temperatures on Sunday nearing 90 for most areas, and mid/upper 80s
Monday with dewpoints well into the 60s. Temperatures will trend
towards the lower 80s Tuesday and Wednesday, but with continued
humid conditions with dewpoints remaining in the 60s.
MARINE...
Light winds out of the south across southern Lake Huron, Lake St.
Clair, and western Lake Erie ahead of a slow moving cold front
through Michigan. Front will push southward through the evening and
reach southeast Michigan before stalling out. Chances for showers
and thunderstorms will be possible ahead of the front for Saginaw
Bay and portions of the nearshore along the northern Thumb this
afternoon and evening. A weak low pressure will develop across
Michigan and bring north to northeast winds across Lake Huron for
tomorrow. Chances for showers and thunderstorms remain for tomorrow
as well before high pressure moves in bringing light and variable
winds into the weekend.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....DG
DISCUSSION...AM/IRL
MARINE.......AA
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Junction CO
459 PM MDT Thu Aug 2 2018
.SHORT TERM...(Tonight through Friday night)
Issued at 324 PM MDT Thu Aug 2 2018
Showers and storms have formed this afternoon over higher terrain
as expected. A weak wave can also be seen further west in central
Utah but models really downplaying any convection from the wave as
it moves into our area. In fact, previous model runs were showing
some fairly widespread convection from this wave for much of the
night time hours but now, all that`s changed. The HRRR shows a
wave moving through but not until daybreak when some isolated
showers and storms are possible. The HRRR is also favoring the
Bookcliffs and areas north. The NAMNEST brings convection to the
area between 6 and 7AM but favors the Uncompahgre Plateau and
Grand Mesa and areas east. The RAP13 not much help either as it
shows some `splotchy` convection across the area but nothing too
impressive. Will be interesting to see how tomorrow morning pans
out. For now, kept chance to slight chance pops for most of the
higher terrain due to uncertainty in the models. The good news
from all this: smoke. These waves `should` force the smoke we`ve
seen lately eastward. We`ll still see some smoke but not like
we`ve seen over the last few days.
On Friday, models are picking up on another short wave to move
through though again, convection looks fairly isolated. Some
concerns will be the amount of cloud cover over the area from the
earlier showers and storms. If the clouds stick around, convection
may be delayed as significant heating will keep convective
initiation in check. Either way, higher terrain will be favored
for showers and storms. Gusty outflow winds will be the main
concern with some brief, heavier rain also possible.
.LONG TERM...(Saturday through Thursday)
Issued at 324 PM MDT Thu Aug 2 2018
A trough will approach the Pacific Northwest at the start of the
long term period and as it moves across the northern tier states,
it`ll flatten our area of high pressure. Plenty of moisture will
remain in eastern Utah and western Colorado to allow some
convection Saturday as a weak shortwave moves through. By Sunday,
high pressure starts building back in but it will have shifted to
New Mexico. This location will cause upper level flow to become
more northwesterly, thereabouts, causing a decrease in PWATs.
This, in turn, will cause a downtick in precipitation across the
region. The Front Range and New Mexico look to see plenty of
convection but looks like we`ll be returning to more dry
conditions.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 455 PM MDT Thu Aug 2 2018
Smoky and hazy skies will continue across the region with
visibility locally reduced at some TAF sites to no lower than 6
miles. Isolated to scattered thunderstorms will continue over the
higher terrain through much of the night with some gusty outflow
winds potentially impacting a few sites, with KASE, KEGE, KRIL,
KTEX and KDRO having about a 20 percent chance being impacted. The
better chance of rain and thunderstorms will occur this evening
after 03Z through 15Z Friday morning as a disturbance moves through
the area. Thunderstorms will redevelop after 18z Friday.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...TGR
LONG TERM...TGR
AVIATION...CC
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1047 PM EDT Thu Aug 2 2018
.SYNOPSIS...
A hot and humid air mass will remain in place over the
region through the weekend and into next week as a Bermuda high
remains parked off the east coast. A trough lifting through
western New England will trigger some showers and thunderstorms
Friday and Saturday. Expect a break in the showers Sunday and
Monday, but it will remain warm and humid. The threat of showers
and storms returns for the mid to later part of next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Update...Showers are all drying up or exiting the forecast area
currently...so I have walked back PoP a little bit for the next
several hours. Then we will watch how the showers/storms down by
NYC develop thru the overnight. Latest HRRR runs dissipate that
convection as well as it approaches the NH border well after
midnight. The next best chance for rain looks to be after
sunrise towards mid morning.
Previous discussion...Weakening shortwave approaching from the
west will bring an increasing threat of showers to the region
overnight...mainly in western zones after midnight. This
activity already showing up in the lower Hudson Valley and may
see some of these showers edging into southwest New Hampshire
later this evening. Remainder of the forecast area will see a
muggy and warm night with increasing clouds. Low temps will
range from the mid 60s north to the mid 70s south.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Steady rain will set up over the mountains on Friday as the
shortwave continues to slowly push in from the west. May see
some isolated thunder in the afternoon. Farther south expect
showers and thunderstorms. SPC showing a marginal risk for
severe in southwest New Hampshire where the best CAPE will set
up...but with PWAT`s in the 2 inch range...heavy rainfall and
localized urban flooding may also be an issue. Highs on Friday
will be somewhat cooler than today with highs ranging from the
upper 70s to mid 80s.
Rain will continue Friday night and once again highest amounts
will be in the mountains where storm totals will reach 1 to 2
inches. Farther south scattered showers will persist into
daybreak on Saturday. Lows overnight will bottom out in the mid
60s to mid 70s.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Upper trough lifts out of the Ohio Valley and through New
England on Saturday, bringing an added source of lift for
showers and storms which may be ongoing at daybreak Saturday.
With a humid air mass available to be lifted, flash flooding
will be a threat in any area of training storms. As the trough
pushes across the area Saturday into Saturday night, expect the
shower and thunderstorm threat to move east as well, leaving us
in the clear on Sunday. Although we do have a trough/front move
through, the air mass behind it does not change all that much as
the Bermuda High slides westward underneath the departing low,
keeping the warm/humid air flowing north and east into our
region. But in the subsidence behind the departing trough, we
should see little in the way of rain chances Sunday and Monday
with temperatures warm, in the mid 80s to low 90s with moderate
to high humidity leading to heat index values closing in on 95
degrees in the afternoon in the warmer spots.
A pattern change is in store for the middle to later part of the
week as the western US ridge becomes dominant, opening the
eastern US up to troughing. As the trough gets closer to our
area, expect better upper level support for lift producing
showers and thunderstorms in the humid air mass. A cold front
being driven by this trough will cross the area around
Wednesday, again forcing some showers and storms. But behind
this front will exist a cooler and much less humid air mass.
Looking even further ahead to next weekend and we may have a
cool/dry air mass drop down straight from the Arctic, so our
pattern of warm/humid conditions may finally be coming to an end
for now.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Short Term...
VFR tonight with areas of IFR /LIFR ceilings/vsby in Valley fog.
VFR Friday and Friday night with areas of MVFR/IFR ceilings.
Long Term...Could see ocean fog and low clouds developing and
affecting coastal terminals through Saturday, though the impact
will be greatest to the east of Portland. Showers and storms are
expected Friday and Saturday with a front pushing eastward
across the area. VFR conditions expected Sunday into Tuesday,
though nighttime fog is possible in the interior valleys.
&&
.MARINE...
Short Term...No flags.
Long Term...Southwest flow increases Friday into Saturday ahead
of a front, but should remain near or just below advisory
levels. We get a brief westerly flow behind the front before
shifting back to southwest again.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM...Legro
Area Forecast Discussion
National Weather Service Pocatello ID
244 PM MDT Thu Aug 2 2018
.DISCUSSION...Today Through Next Thursday.
The two main weather concerns this afternoon and evening will be
critical fire weather conditions and potential for strong t-storms.
CRITICAL FIRE WEATHER: Red Flag Warnings remain in effect until
midnight tonight across the Central Mntns, for a combination of dry
surface fuels, dry low-level air with RH values of 10-15%, and
strong winds gusting 25-30 MPH with higher gusts near peaks and
ridges. Isolated t-storms will also be possible in eastern
portions of the Central Mntns, with threats for lightning and
strong/erratic wind gusts in excess of 50 MPH. See the FIRE
WEATHER section below for more details.
STRONG THUNDERSTORMS: Yet another day of isolated to scattered t-
storms is anticipated, with the overall threat focused on the
eastern Central Mntns and Island Park region, along and east of
I-15, and along and south of I-86. HREF ensemble CAMs light up
the MT border region and the Southern Highlands into the Bear Lake
region for the most widespread activity, with coverage perhaps
just slightly less than yesterday. Atmospheric parameters are very
similar to yesterday, with NAM forecast soundings again
displaying inverted-V signatures with plenty of sub-cloud dry air
and fairly impressive DCAPE values of 1,100 to 1,600 J/kg, again
suggesting that t-storms will be capable of producing strong
downdraft/outflow winds in excess of 50 MPH. Latest SPC
mesoanalysis confirms these DCAPE values and also shows MUCAPE of
500-1,000 J/kg and slightly negative LIs. Deep-layer shear values
in excess of 30 knots (effective bulk) are largely confined to the
north, which may assist with storm organization/longevity in the
Island Park region. As we saw yesterday, isolated severe t-storms
producing damaging winds in excess of 60 MPH cannot be ruled out
anywhere. PWATS have backed off just slightly since yesterday,
running around 0.75, and temp-dew point depressions are fairly
significant in the low-levels, so generally heavy downpours should
be confined to the strongest cells and should be short-lived as
some of the precip evaporates on the way down. Overall instability
and shear values, particularly a lack of MUCAPE and modest CAPE
profiles in the hail growth zone, do not strongly favor large
hail, but cannot rule out small hail with the strongest updrafts.
The combination of frequent lightning and gusty winds will be of
concern to fire weather partners across the region, although
t-storm coverage was not quite high enough to justify a Red Flag
Warning south and east of the Central Mntns.
The trough brushing by the region to the north may be slow to leave,
and we carry low PoPs for some additional showers/t-storms Fri
afternoon along the MT and WY borders, and across the Bear Lake
region. Otherwise, fairly low RH values and gusty winds Fri-Sun
may again push portions of the region close or into critical fire
weather thresholds. Additional Red Flag Warnings are possible. In
general we should be dry from Sat right into next week as a strong ridge
of high pressure builds across the western US, centered over NV
and UT. A weak disturbance moving overhead Sun could produce a
shower or t-storm, but so far the models are spitting out very
little precip and confidence is low. High temps will cool by 5-10
degrees over the weekend in the wake of the trough, but will
progressively warm once again next week back into the 90s by Mon
or Tues, and potentially mid to upper 90s by Wed or Thurs in lower
elevations from the Snake Plain south. - KSmith/TW
&&
.AVIATION...
Upper level high pressure ridging continues to moves east as a
mostly dry cold front/trough moves through the area. Expect breezy
winds this afternoon and vicinity thunderstorms particularly at
KDIJ and to a lesser degree KIDA and KPIH. Expect mostly VFR
conditions though there will continue to be some smoke/haze
particularly for KSUN and KIDA. Winds will increase slightly more
tomorrow afternoon after the mostly dry cold front/trough moves
through. - TW
&&
.FIRE WEATHER...
The upper level high pressure ridge has continued to move east
today with a surface front/trough located around the Arco Desert
area. Drier air will continue to move in from the northwest
through the day. A Red Flag Warning remains in effect for the
Salmon- Challis and Sawtooth Forests. The surface front/trough
will move through southeastern Idaho on Friday pushing surface
winds stronger and lowering the relative humidity even more. Zone
427 south of Burley may be spared some of the stronger winds and
there is some uncertainty in Zone 413, otherwise winds and low
humidity will combine to create a critical day for the rest of the
area (outside of Zone 411 due to non-critical fuels) warranting a
red flag warning. Winds will decrease on Saturday in most areas,
but the Arco Desert may still be strong enough to consider the
area as critical. There will be a weak trough move through early
Sunday bringing very light precipitation/thunderstorm chances,
though models keep bringing this system through a little later
each model run. Models are starting to agree on high pressure
rebuilding in late Monday and remain through most of next week.
Expect well above normal temps to return by mid next week. - TW
&&
.CLIMATE...
Multiple heat-related records were set/broken during the month of
July 2018 among our SE Idaho climate sites. Pocatello Airport (KPIH)
spent a 28 day run from July 4th through July 31st at or above 90
degrees, shattering their previous all-time record for longest
streak of consecutive days with high temps at or above 90 degrees
which was 22 days ending August 10th, 2000. That streak continues
through today, now at 30 consecutive days. Pocatello also ended
the month of July in 10th Place for highest mean average
temperature, at 73.5 degrees. Records at KPIH date back to
January of 1939.
Burley Airport (KBYI) spent 20 days at or above 90 from July 12th
through July 31st, a streak that continues at 21 consecutive days
through yesterday (08/01). This ties KBYI in 3rd Place for
longest streak of consecutive days at or above 90. Burley also
ended July in 7th Place for highest mean average temperature, at
74.0 degrees. Records at KBYI go back to August of 1948.
Challis Airport (KLLJ) also impressively broke its all-time record
for longest streak at or above 90 since records began there all the
way back in January of 1895, reaching 28 consecutive days as of
yesterday (started July 5th). July 2018 was the hottest July on
record ever at Challis for mean average temperature, at 73.8
degrees. Challis also tied or broke 2 daily record high
temperatures during the month (July 9th and July 24th). Stanley
Ranger Station (KSNT) also tied 2 daily record high temperatures
during the month of July (the 9th and 25th).
There is good news on the horizon for those tired of the heat. High
temps Fri may be just cool enough to threaten these ongoing heat
streaks, but it will be close. By Sat, our confidence increases
significantly that our streaks at or above 90 will come to an end
at all climate sites, with high temps projected to hold in the
mid 80s. - KSmith/TW
&&
.AIR STAGNATION...
Varying degrees of degraded air quality will continue across SE
Idaho for the next couple days, as numerous wildfires burning across
Idaho and the Pacific Northwest produce smoke and haze. The Idaho
Department of Environmental Quality (ID DEQ) continues to rate air
quality "Moderate" or Yellow across the entire region, meaning 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. We have maintained areas of
smoke in the weather grids for the entire CWA through Sat morning.
Winds are expected to increase this afternoon, and again Fri
afternoon as a trough brushes by the state. This may help to
scour out some of the smoke and haze entrenched across the region
and trend us toward improved air quality. However, confidence is
low, as these winds could just as easily continue to advect in
smoke from large fires burning in northern CA and southern OR. A
review of the latest HRRR smoke model guidance does hint at some
possible improvement tomorrow, but also shows a fresh plume moving
NE toward the region out of NV. It is possible that significant
improvement may not come until additional progress can be made on
the source fires. -KSmith/TW
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until midnight MDT tonight for IDZ422-475-476.
&&
$$
Area Forecast Discussion
National Weather Service Pueblo CO
242 PM MDT Thu Aug 2 2018
.SHORT TERM...(This evening through Friday)
Issued at 237 PM MDT Thu Aug 2 2018
Models show the potential for isolated to scattered showers and
tstms over the mtns thru the evening hours, with the possibility of
a few moving off over the adjacent lower elevations, including the
high valleys and the I-25 corridor. The HRRR ends precip acrs the
forecast area by about midnight, while the GFS and NAM show the
possibility of some lingering light precip thru the night over the
mtn areas. The HRRR then brings some light precip to some of the
mtns along the Continental Dvd by about 12Z, ahead of a disturbance.
Friday, precipitable water values increase a little over southern CO,
and a weather disturbance will be moving eastward across the state.
This will lead to a higher chance for showers and thunderstorms acrs
the area. Storms should begin over the mtns in the late morning
hours, then spreading over the high valleys and portions of the I-25
corridor in the early afternoon, then moving acrs the southeast CO
plains in the mid to late afternoon. Although storms will be
moving, there will be the risk of recent burn scar flooding if
stronger storms track over those locations. There may also be one
or two severe storms over the southeast plains, with the far
southeast plains probably being the most favored area.
.LONG TERM...(Friday night through Thursday)
Issued at 237 PM MDT Thu Aug 2 2018
Synoptic Overview... The southwest US ridge weakens by the end of
the work week, and west to west/southwest mid/upper level flow
prevails over Colorado for the weekend. By later Monday, the ridge
begins to build over the Great Basin, increasing northwest to
northerly flow over Colorado Tuesday through Thursday. Moisture in
the atmosphere decreases slightly this weekend behind a Friday
shortwave, but increases again to over 1" of TPW (normal is around
0.75") by later Sunday and into the start of the work week. Guidance
indicates moisture decreases again by midweek as drying northerly
flow increases. Given elevated moisture content through at least the
start of next week and daily isolated or better thunderstorm chances
over the high terrain, flash flooding over burn scars remains a
concern. Models are in generally good agreement on the large scale
pattern through the long-term period, with differences lying in the
exact location of convection.
Friday night...Thunderstorms continue across the far eastern
Colorado plains as the mid-level shortwave exits Colorado. With
CAPE around 1000 j/kg and deep layer shear as high as 30 knots,
strong to low end severe storms are possible. Heavy rain is also
possible given TPW close to 1.5". The forecast area west of the far
eastern tier of Colorado counties should dry out pretty quick under
subsidence behind the shortwave.
Saturday through Sunday...Continued large-scale subsidence behind
the Friday shortwave and TPW decreasing to less than 1" should keep
convection more limited on Saturday. Will still see isolated to
scattered diurnal thunderstorms develop during the afternoon over
the high terrain, but don`t expect much to make it east onto the
plains. The exception may be the far eastern parts of the forecast
area (mainly Kiowa and Prowers Counties) late, where NAM model runs
continually hint at a MCS advancing southeast out of northeast
Colorado. Thunderstorm coverage appears similar during the afternoon
on Sunday. However, a fairly potent shortwave trough is forecast to
advance through the northern Rockies. Associated convection will
help send a boundary down the eastern Colorado plains, along which a
few showers and thunderstorms may develop late Sunday evening with
help from convergence along a lee trough. Given uncertainty with
timing of boundary and degree of forcing, along with model
differences in degree of thunderstorm coverage, kept coverage
isolated over the plains Sunday afternoon/evening. Temperatures
across the forecast area this weekend will be quite warm, with highs
in the mid to upper 90s across the plains, and mid to upper 80s in
Colorado Springs and the high valleys.
Monday...Low-level flow is forecast to become upslope easterly by
Monday afternoon/early evening across the plains behind the Sunday
evening boundary. This helps increase moisture again across a lot of
the forecast area, including surface dew points into the upper 50s
to low 60s across the plains. Thunderstorms shouldn`t have much
trouble developing over the eastern mountains Monday
afternoon/evening, and advancing west onto the plains through the
evening, supported by upslope low-level flow and weak energy in the
westerly flow aloft. Surface easterlies under west to northwest flow
aloft will yield deep layer shear supportive of strong to severe
thunderstorms. Given high surface dew points, instability will also
support strong to severe storms, particularly across the far eastern
plains. Temperatures will be just a few days cooler on Monday vs
over the weekend.
Tuesday through Thursday...Tuesday is looking slightly wetter across
the forecast area than previous forecasts have shown. Moisture
remains in place as northwest flow increases with embedded shortwave
energy and surface easterlies. Strong to severe storms will again be
possible but across most of the plains and eastern mountains. As
flow shifts from northwest to northerly into Wednesday and Thursday,
moisture in the atmosphere should begin to decrease, as will
thunderstorm chances. Temperatures should return to near climatology
during this period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 237 PM MDT Thu Aug 2 2018
VFR conditions are expected at KCOS, KPUB and KALS the next 24 hrs.
Some showers/tstms over the mtns this evening could drift off the
mtns and into the KCOS area. Friday, there will be an increased
chance for showers and thunderstorms at the three terminal forecast
sites, as a weather disturbance moves acrs the area. Storms will be
possible Friday afternoon and evening.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...28
LONG TERM...LINE
AVIATION...28
Area Forecast Discussion...UPDATED
National Weather Service Reno NV
847 PM PDT Thu Aug 2 2018
.UPDATE...
No significant changes this evening. Winds were dropping off with
only a few spots still seeing gusts 25-30 mph. So we will be
allowing the red flag and lake wind headlines for this evening to
expire at 9 pm. Humidity levels remain very low with single digits
and lower teens and little improvement is anticipated for mid and
upper slopes as a very dry airmass was in place. The 00Z KREV
sounding showed a deep dry layer through the entirety of the
column. This drier air will be working south into Mono-Mineral
County tonight and early Friday.
As far as the smoke, meso-scale models indicate smoke will
continue to pour into northeast CA and northwest NV into early
Friday morning. Smoke was more variable in Mono County with some
areas seeing a slight improvement while others showed worsening
conditions. We will keep the dense smoke advisory going although
the HRRR showed the smoke plume gradually turning to the north
overnight. The night shift will re-evaluate and make necessary
adjustments for Friday morning as the advisory goes until 11 am.
Hohmann
&&
.SYNOPSIS...
Breezy afternoon and evening winds will lead to critical fire
weather conditions and hazardous boating conditions through
Saturday. Conditions will be very dry for the next week or so. A
welcome cool down this weekend won`t last as hot temperatures
return by Tuesday.
&&
.PREVIOUS DISCUSSION... /Issued 215 PM PDT Thu Aug 2 2018/
SYNOPSIS...
Breezy afternoon and evening winds will lead to critical fire
weather conditions and hazardous boating conditions through
Saturday. Aside from a few thunderstorms over Mono and Mineral
Counties the rest of today, conditions will be very dry for the
next week or so. A welcome cool down this weekend won`t last as
hot temperatures return by Tuesday.
DISCUSSION...
Big story the next few days will be the breezy afternoon and
evening winds. Typical zephyr winds (gusts 25-30 mph) for today
with a slight uptick in speeds tomorrow as the trough over the
northeast Pacific approaches the west coast. The trough moves well
inland with good jet support for Saturday which will lead to the
strongest gusts (35-45 mph) over the next couple days. Winds will
impact fire weather and boating, stay safe and wildfire aware.
Smoke, haze and poor air quality will also be a problem for at
least the next day or so, especially for Mono County where the
Ferguson and Lions fire are pushing out quite a bit of smoke
today. Smoke plume for the Carr and Shasta-Trinity fires will
also push into Lassen and Plumas Counties, so there could be
periods of unhealthy air quality there as well.
The trough will bring a noticeable cool down, but highs will only
drop off into the low to mid 90s for the NV valleys with upper 70s
and 80s in the Sierra. Overnight lows should dip into the 30s in
the Sierra valleys, perhaps down to freezing if strong radiational
cooling sets up with very dry air in place this weekend. NV
valley lows should at least fall off into the 50s.
Unfortunately, the cooler conditions won`t last long as the
strong ridge of high pressure returns to Nevada on Tuesday. Heat
will rebuild with highs at 95-105 for most of next week in the
lower valleys with mid 80s to low 90s for the Sierra. The Reno
airport only needs two more 100 degree days to set the most 100
degree days in a year. Seems almost certain at this point. Brong
AVIATION...
A few thunderstorms over southern Mineral and Mono Counties should
dissipate by this evening. Otherwise dry conditions and almost
cloud free conditions will prevail for the next week or so.
Smoke will bring the greatest visibility reductions to Lassen,
Plumas and Mono Counties through Saturday. Periods of visibility
near and below 2 miles is possible for the Mono County terminals.
Breezy afternoon and evening winds will continue into Friday
before stronger winds with a trough of low pressure arrives for
Saturday. Surface gusts should remain below 30 kts, then rise to
30-40 kts for Saturday. With the trough and jet overhead Saturday
some mountain waves and turbulence is possible. Brong
FIRE WEATHER...
Some changes were made concerning fire weather through Saturday.
The largest, and most serious, is that weather conditions Saturday
will be hazardous in terms of the potential for extreme fire
behavior and growth - this is a Particularly Dangerous Situation.
All Fire Weather Watches have been upgraded to Red Flag Warnings
for Friday and Saturday.
We`re on track for today`s Red Flag conditions with RH dipping
into the single digits for many locations in western Nevada while
RH is 15-20% in the Sierra. Recoveries tonight will be moderate
for Sierra locations while remaining poor in western Nevada.
Mono/Mineral Counties will see the largest RH change as
thunderstorm coverage has been much more isolated as compared to
the last few days.
The Tahoe Basin was added to Friday`s Red Flag warned areas which
also includes the Sierra Front of Nevada and extreme northeastern
California as well as the Basin and Range. The warned areas were
extended into the overnight hours as winds rise. There is ample
evidence suggesting that winds above around 6000 feet will not
drop off Friday night warranted the inclusion of the overnight
period.
A dry slot moves in Friday and Friday night ahead of a strong
upper level wave moving into the region. This will result in
anomalously low RH and strong gusty winds Saturday, especially for
downslope areas and along upper slopes and ridges. Wind gusts will
be generally up to 45 mph for valley locations with higher gusts
expected for wind prone locations and ridge tops. Any ongoing
fires may experience a large increase in fire activity that could
break containment lines while new fire starts are likely to grow
and spread extremely rapidly. Air support operations would likely
be heavily impacted by winds as well. Any personnel working on or
near existing or new fires would be in danger. Western Lassen
County, Mono County, and Mineral County have been added to
Saturday`s list of Red Flag warned areas - our entire forecast
area.
Conditions improve Sunday with lighter breezes that will be around
typical afternoon speeds. While RH doesn`t rise sharply, the
decrease in winds is welcomed. Winds decrease further through
early next week. Temperatures do cool which should allow for
improved recoveries overnight for Sierra valleys at least.
Temperatures turn hot again by Tuesday and Wednesday with triple
digit heat in the forecast. Boyd
&&
.REV Watches/Warnings/Advisories...
NV...Red Flag Warning from 1 PM Friday to 10 PM PDT Saturday
NVZ450-453-458.
Red Flag Warning from noon to 10 PM PDT Saturday NVZ459.
Lake Wind Advisory from noon to 10 PM PDT Saturday NVZ002.
Lake Wind Advisory from noon to 10 PM PDT Saturday NVZ001.
Lake Wind Advisory from 2 PM to 9 PM PDT Friday for Washoe Lake
in NVZ003.
Lake Wind Advisory from noon to 10 PM PDT Saturday for Washoe
Lake in NVZ003.
Lake Wind Advisory from noon to 10 PM PDT Saturday NVZ004.
CA...Lake Wind Advisory from noon to 10 PM PDT Saturday CAZ071.
Red Flag Warning from 1 PM Friday to 10 PM PDT Saturday
CAZ270-272-278.
Red Flag Warning from noon to 10 PM PDT Saturday CAZ273.
Lake Wind Advisory from noon to 10 PM PDT Saturday CAZ073.
Dense Smoke Advisory until 11 AM PDT Friday CAZ073.
Lake Wind Advisory from noon to 10 PM PDT Saturday CAZ072.
Red Flag Warning from noon to 10 PM PDT Saturday CAZ271.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Las Vegas NV
239 PM PDT Thu Aug 2 2018
.SYNOPSIS...
Active convective pattern persists through the next 12 to 18
hours then diminishing moving into the weekend. High pressure will
return early next week and persist through much of the week
resulting in heat concerns through at least Thursday and possibly
into next weekend.
&&
.SHORT TERM...Today through Sunday night.
Isolated to scattered showers and thunderstorms continue across
many parts of the CWA this afternoon. Impressive 850mb moisture
flux into the region combined with modest upper level support and
an unstable environment is fueling convection this afternoon that
will persist through the evening, if not into the overnight hours.
GOES-16 water vapor imagery shows a developing upper level jet
feature which will help provide lifting to the already moist and
unstable environment over the CWA. Throughout the rest of the
afternoon, scattered convection is expected, with PWAT values
ranging from 1-1.3 inches in the northern half of the area and
increasing up to ~1.7 in the southernmost areas. Strong 2-6 km
lapse rates and mixed layer instability will be a concern for
frequent cloud to ground lightning and gusty outflow winds over
50 mph could be possible as well as DCAPE values over 1500 j/kg
have been noted in RAP mesoanalysis in areas along and south of
I-15. These areas should begin to decrease in coverage as we lose
heating into the evening, but farther north, activity driven by
the jet should continue into the overnight period. The main
question will be how quickly this activity will exit east. HREF
and other hi-res models clear almost all PoPs out of the area by
12Z Friday, but some synoptic models, namely the Canadian and GFS,
linger enough moisture Friday to keep low PoPs in for Mohave and
eastern Lincoln and Clark Counties. Decided to keep these low
PoPs in the forecast through 00Z Saturday due to this uncertainty.
Afterwards, the upper level shortwave clears out the area and PoPs
drop to nil. The weekend looks much drier with zonal flow aloft
for a brief time before temperatures look to rise into early next
week.
&&
.LONG TERM...Monday through Wednesday.
The main concern for the upcoming week will be the potential for
heat impacts as 12Z guidance is in much better agreement compared
to yesterday. Both MEX and ECE guidance suggests temperatures
nearing 110+ for the Las Vegas Valley as high pressure returns and
drier air dominated the region. The persistent ridging evident in
both the ECMWF and GFS means these temperatures would likely
persist through the mid-week, and potentially through the next
weekend. As a result, the need for special heat products may be on
the table should these temperatures continue to be advertised with
later model progression.
&&
.AVIATION...For McCarran...Scattered showers and storms have
overspread the Las Vegas Valley this afternoon. Gusts with this
activity have been primarily between 20 to 30 knots from the south
to southwest and a general storm motion towards the northeast is
expected to persist. A stronger storm close to the terminal could
produce gusts in excess of 35 knots. Activity may persist through
06z with a brief lull between 01z-04z but is not expected to be as
intense late tonight as seen this afternoon. Late tonight southwest
winds around 10 knots will take over which will become light and
variable early Friday morning. Lower coverage of storms is expected
on Friday.
For the rest of southern Nevada, northwest Arizona and southeast
California...Widespread showers and storms have developed this
afternoon across most areas. Strong and erratic wind gusts,
dangerous lightning, and locally heavy downpours are possible with
storm activity. After 00z, storms look to be focused across the
southern Great Basin, Clark County, and Mohave County; lingering
longest across Mohave County potentially into early Friday morning.
Lower coverage of storms is expected on Friday.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT/LONG TERM...Boucher
AVIATION...Guillet
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