Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/07/17
Area Forecast Discussion
National Weather Service Taunton MA
1006 PM EDT Sat May 6 2017
.SYNOPSIS...
Below normal temperatures and occasional unsettled weather are
expected into this coming week as low pressure at the surface
and aloft remains stalled in the vicinity of New England. Some
moderation in temperature and less risk of showers Wednesday
through Friday but still considerable lingering cloudiness and
temperatures probably at least a little below normal.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Shortwave moving north across the region generating another
batch of showers. Radar trends and 00Z HRRR suggest scattered
showers through at least midnight, possibly an hour or so
longer. Second area of showers popped over the Hudson Valley
this evening, thanks to cold air aloft and resulting instability
as well as surface trough bringing low level convergence. This
area will affect the Berkshires and parts of the CT River Valley
through midnight.
Expect diminishing clouds overnight as drier air works in.
Dewpoints fall through the 40s and temperatures fall to the
upper 40s and low 50s.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Sunday into Sunday night...
Turning cooler with continued shower chances. Going to have to watch
continued vort-lobe action round the broader occluding low especially
as they cyclonically dive S latching into deeper moisture off the NW
Atlantic and rotate back N. Forecast models suggesting such activity
skirts E/SE areas of S New England with the development of a meso-
low along offshore regions of baroclinicity. However there is still
a fair amount of low to mid level moisture across the interior and
closer to the center of the low in regions of favorable ascent, more
so along the W slopes of high terrain. We may see additional shower
activity just by way of boundary destabilization beneath the cold
pool as was observed W earlier today (Saturday) across Upstate NY
and PA. Will forego a mention of thunder for now, if any thinking
isolated. Highs upper 50s to low 60s.
A bit challenging to forecast the spatial extent and timing of outcomes
with greater specificity, so will go with chance PoPs over the entire
S New England forecast area. Confident will see scattered to broken
cloud decks rotating around the region parent with the low given
the abundance of low to mid level moisture along with cooler air
wrapping into the region, this as winds become more westerly. Lapse
rates steepening with cold air advection within the low levels
should see some gusty winds, especially during diurnal heating.
One last note, as we go into the overnight period, given continued
low level moisture along with cold air advection, more than likely
we`ll still see some shower activity along the W slopes of high
terrain. H925 temperatures down around -2C, some shower activity may
fall in the form of wet snowflakes. Very atypical pattern for early
May when normal highs range around the mid 60s. Will also have to
monitor for the potential of frost advisories over CT and S of the I-
90 corridor. Lows in the 30s. Coolest over higher elevations.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
*/ Highlights...
- Cooler than normal temperatures and a risk of showers from
time to time look to be the weather theme for early in the
coming week
- May see a little moderation in temperatures and less risk of
showers Wednesday through Friday
*/ Overview...
The circulation over the USA will be dominated at the start of
forecast period by closed upper lows in the Northeast and Southwest.
Our weather will largely be modulated by large scale blocking upper
flow features. The Northeast upper low will be slow to move given
the blocking pattern. As noted in the prior discussion, computer
models have a tendency to move closed systems out too fast. Hence,
the sensible weather is likely to be slow to change over our area
this coming week. Although inherent uncertainty being late in the
forecast period, a consensus of models depict the upper low over New
England and southeast Canada splitting. The northwest upper low may
rotate back through the Great Lakes and possibly phase with energy
from the Southwest USA cutoff low that lifts slowly northeast late
in the week. This may spawn a surface low off the mid Atlantic
states. If it tracks close enough to the coast, we experience a a
cool steady rain this coming weekend, but this remains uncertain so
far out. We suspect that the models will likely depict in their
operational and ensemble runs a modification of the upper flow as we
get closer to the end of the week.
The combination of considerable cloudiness, a few showers from time
to time, and 850 mb temperatures within a few degrees of 0C will
likely keep temperatures below normal for most of the week,
although some modification is expected from early to late week.
*/ Details...
Monday...Will likely be challenging for temperatures to rise out of
the 50s given 850 mb temperatures -3C to -4C across most of southern
New England and considerable cloudiness underneath the broad upper
low. Any sunshine would likely induce some convection and then more
cloud formation in the moist air mass. Although the air mass remains
relatively moist, there is not organized forcing and so plan to keep
POPs relatively low.
Monday night...Will be cool but should be enough clouds to inhibit
radiational cooling.
Tuesday...With cyclonic flow and upper low in the vicinity
anticipate similar conditions as Monday with considerable
cloudiness. Evidence of a short wave trough passing along the base
of the closed upper low center may induce scattered showers. Air
mass temperatures moderate a little but still expect to remain below
normal.
Wednesday through Friday...Upper heights build a little Wednesday
and Friday and looks as though may see some subsidence and less
chance of showers. Temperatures at 850 mb slow moderate to a few
degrees above 0C, but will likely have trapped moisture and a fair
amount of cloudiness. Thus, may see temperatures a little warmer but
still probably at least a little below normal for the time of year.
Saturday...Energy lifting out of the Southwest USA may reach the mid
Atlantic coast and possibly spawn surface low pressure off the coast
south of New England. There may be phasing with a northern stream
lobe of low pressure that swings towards our region but too soon to
be sure. Saturday has the potential to be or become cool and wet
with a raw northeast wind. Will go for chance POPs at this time
given inherent uncertainty on how all of this will play out on day 7.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Sunday Night/...
Scattered showers early, but with drier air moving into the area
we expect mostly VFR conditions. Even so, a few showers will be
sufficiently moistening to bring a period of MVFR cigs.
Expect an overall drying trend overnight with decreasing sky
cover by morning. South winds turn from the southwest after
midnight.
Sunday into Sunday night...
Leaning towards BKN-OVC low-end VFR cigs mixed in with MVFR especially
over the high terrain. SCT SHRA activity though highest confidence
over E/SE MA. SW winds which will be breezy at times, gusts up around
20 kts. More than likely terminals will waver on prevailing conditions
as multiple CIG decks at various levels through MVFR to low-end VFR
exist. Can not rule out some IFR.
KBOS TAF...Partial clearing ongoing. Some stronger S gusts potentially
emerging up around 25 kts. Short-lived. Expected low-end VFR / MVFR
CIGs to fill back in around 21-22z, lowering to IFR overnight. Chance
SHRA. Could scour by morning.
KBDL TAF...Gusts up around 30 kts continue with SCT-BKN low-end VFR
cigs, through 21-22z. Thereafter BKN-OVC low-end VFR / MVFR CIGs and
SHRA move in from the S. IFR CIG conditions possibly developing over-
night. Could scour by morning.
Outlook /Monday through Thursday/...
Confidence...Moderate.
Mainly VFR conditions with scattered areas of MVFR ceilings possible
from time to time, especially over higher terrain. Visibility may
briefly lower to MVFR in widely scattered showers Monday and Tuesday.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Sunday Night/...Moderate confidence.
Low pressure wobbling across Upstate NY into S Canada. Round which
we`ll see continued low clouds and showers at times along with breezy
S winds becoming more W. This results in the continuance of rough
seas over the waters given a S/E swell. Some visibility issues with
any shower activity. SMALL CRAFT ADVISORIES continue with wave heights
of 8 to 10 feet on the outer waters and gusts up around 25 kts at
times, more importantly along the near-shores for Sunday.
Outlook /Monday through Thursday/...
Monday...Confidence is moderate. Left over swell above 5 feet may
linger into Monday morning across the outer coastal waters.
Tuesday through Thursday...Confidence is high. Winds and seas are
expected to remain below Small Craft Advisory levels.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ231>235-237-
250-251-254>256.
Small Craft Advisory from 2 AM to 6 PM EDT Sunday for ANZ230.
Small Craft Advisory until 6 PM EDT Sunday for ANZ236.
&&
$$
SYNOPSIS...WTB/Sipprell/Thompson
NEAR TERM...WTB/Sipprell/Thompson
SHORT TERM...Sipprell
LONG TERM...Thompson
AVIATION...Sipprell/Thompson
MARINE...Sipprell/Thompson
Area Forecast Discussion
National Weather Service Charleston SC
1022 PM EDT Sat May 6 2017
.SYNOPSIS...
A cold front will move off the coast Sunday morning. High pressure
will then build in through early next week. A backdoor cold front
will stall to the north during mid week, before a stronger cold
front impacts the area late in the week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 1015 PM: Recent images from KCLX radar indicated a fine
line, likely the cold front, sliding south across the Midlands
toward the Lowcountry. To the north, the stronger showers were
tracking east, with weak showers extending west across northern
GA. Based on the radar and IR satellite trends, I will increase
the coverage of sprinkles across the inland SC counties for late
this evening and early Sunday morning. In addition, I will
update the sky to increase mid evening cloud cover, sliding the
line between clear to mostly cloudy around a county south.
As of 735 PM: A band of showers was spreading across the
Midlands of SC. Sfc observations below the showers indicate that
rainfall rates generally ranged from 0.01-0.05/hr. The greater
reflectivity values were tracking east, poised to move north of
the forecast area. However, weaker showers to the west still
appear in line to brush the northern portion of the forecast
area late this evening. Based on the satellite and radar trends,
I will adjust sky and will continue to mention sprinkles to the
north. Temperatures and winds appear in good shape.
As of 630 PM: A well defined mid level vort max was rippling
over the southern Appalachians. At the sfc, low pressure was
pushing across the Midland, with a tailing cold front extending
west across northern GA. A band of showers and thunderstorms
have developed along and ahead of the low and associated cold
front. Recent radar images indicate that the leading edge of the
convection was weakening as it moved east. However, most recent
runs of the HRRR indicate that a few showers or sprinkles will
reach the inland SC counties before dissipating. The current
forecast looks good, I will update temp, sky, and winds to align
with latest obs.
Previous discussion:
An upper disturbance will rotate around the base of large east
coast upper low, passing through far northern GA and SC. A cold
front will approach from the north around midnight. Models
indicate some light showers with this front, but they will be
weakening/dissipating as they make their way to our far
northwest counties, especially in the vicinity of the Santee
Cooper Lakes. We maintained silent POPs for these locations and
hinted at some sprinkles for our NW tier for a few hours.
Measurable rainfall will be hard to accomplish. The remaining
parts of our area will stay dry. The more noticeable things with
this front will be a brief increase in clouds, mainly inland
and over the SC zones. Winds could increase a bit overnight with
the front, but nothing too significant. Lows will again be in
the lower to mid 50s most areas, warmer at the immediate coast.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Sunday through Tuesday: The mid/upper level pattern will essentially
remain the same through the period as the forecast area finds itself
within the larger scale circulation around the deep upper low over
the Northeast. This will result in persistent west to northwest flow
aloft. At the surface, a cold front will move away on Sunday and
high pressure will build into the region through Tuesday. Plentiful
dry air will dominate the period, and the forecast is rain free.
Instead the main points will be warming temperatures and breezy
conditions Sunday and Tuesday. Temperatures will warm Sunday and
Monday, but remain below normal with highs in the upper 70s for most
areas. Then by Tuesday there will be enough downslope and
compressional warming to produce a big jump to highs in the mid to
upper 80s.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Ridging over the Gulf of Mexico and MS valley during mid week will
slide east, but flattens overhead Thursday, before giving way to a
decent short wave that ejects from the SW states and reaches our
area late in the week. Simultaneously at the surface a stationary
front will remain off to the north, as high pressure prevails to the
south, before a cold front associated with the short wave arrives
late in the week. With no influx of either Gulf or Atlantic
moisture, there remains no chance of rainfall until the approach of
the cold front late in the forecast period. 850 mb temps are as much
as 2 or maybe 3 standard deviations above normal, so we`re back well
above normal in regards to both max and min temps through the
period.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR through 0Z Monday. A cold front is forecast to reach KCHS
around 6z, likely bringing a return of gusty west winds. NAM
forecast soundings indicate that gusts may continue through the
pre-dawn hours. KSAV and KCHS should veer winds from the WNW
during the early daylight hours on Sunday. Wind gusts should
range from 16-20 kts through the afternoon hours.
Extended Aviation Outlook: VFR.
&&
.MARINE...
Tonight: Small Craft Advisories are in effect for all of the
coastal waters tonight and for the CHS harbor into this evening.
Winds may ease a bit before sunset, only to increase again this
evening and overnight as a cold front quickly moves through the
area from north to south. Seas will respond by peaking after
midnight. The highest waves are expected across the outermost
portion of the Charleston waters and for the 20-60 nm GA
waters.
Sunday through Thursday: A cold front will pull away on Sunday and
high pressure will gradually build in thereafter. Winds will start
off elevated Sunday morning, but any remaining Small Craft Advisory
conditions will end. Northwest to west winds in the 15-20 knot range
will prevail through the day. Conditions will become increasingly
tranquil through Monday as the surface high passes just to the west.
Then by Tuesday the gradient will tighten as a backdoor front
approaches from the north. Winds will increase and could be 15-20
knots at times, with some potential for Small Craft Advisory
conditions into Thursday.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 7 AM EDT Sunday for AMZ350-352-354.
Small Craft Advisory until 10 AM EDT Sunday for AMZ374.
&&
$$
NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1036 PM EDT Sat May 6 2017
.UPDATE...
Issued at 1036 PM EDT SAT MAY 6 2017
Based on the latest NAM12 and HRRR model runs, and the latest
radar imagery, decided to remove precipitation from the forecast
for the rest of the night. It appears that any lingering rain
showers will remain east of the forecast area. Skies will continue
to gradually clear overnight, with mostly clear to partly cloud
conditions expected across the area by 12Z Sunday. The hazardous
weather outlook was also updated to remove mention of
thunderstorms for tonight as well.
UPDATE Issued at 736 PM EDT SAT MAY 6 2017
Made a few updates to the forecast. First, updated the zone
forecast text product to remove any afternoon periods or wording,
and replaced all that with current timing and wording. Also
decided to let mention of thunder to go ahead and drop out of the
text forecast product, as radar and lightning data indicate that
eastern Kentucky should remain thunder free for the rest of the
evening. Still expecting the rain to slowly taper off and be out
of the area between 5 and 6Z tonight. Lastly, ingested the latest
hourly data into the forecast grids freshen up the forecast
elements with new obs and to establish new trends.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 328 PM EDT SAT MAY 6 2017
Main batch of rain continues to push off to the southeast and
will be exiting our southeast counties over the next hour.
Scattered showers, and maybe a thunderstorm or two, will continue
to develop as breaks occur in the clouds and low level lapse rates
steepen. The showers will be driven by the sun and will die by or
shortly after sunset leaving decreasing clouds from west to east
overnight.
There is a little bit of uncertainty regarding fog/frost
potential tonight. With clearing skies, temperatures will fall
into the 30s for most locations, and potentially cold enough for
some frost in our western counties, which will clear first. The
problem is that a light breeze will stir through much of the night
and if winds do go calm, fog will want to form with wet ground
after the recent rains. With this in mind, think frost will stay
patchy at worst tonight and a frost advisory will not be issued.
High pressure and a drier airmass will build into the region
Sunday and Sunday night. Despite plenty of sun tomorrow, highs
will only reach around 60. Temperatures Sunday night should then
drop off quickly and head toward dewpoints which will be in the
30s, and even some upper 20s over northeast Kentucky. However,
models indicate that some mid level clouds will likely move
overhead at times and winds may also stir much of the night. So,
this complicates our low temperature and frost potential forecast
but at least patchy frost is again likely, especially over
northeast Kentucky.
.LONG TERM...(Monday through Saturday)
Issued at 328 PM EDT SAT MAY 6 2017
The period begins with a very blocky upper air pattern in place
across North America with deep closed lows centered in southwest
Quebec and near or just south of California. Upper level ridging
will extend from the western Gulf of Mexico into central Canada.
This pattern will only slowly change with the upper low in the
northeast possibly splitting with a low retrograding into Ontario,
and the upper low in the southwest U.S. gradually opening up and
moving east.
At the surface there will be a northwest-southeast oriented front
separating the cooler air to our northeast and warmer air to our
southwest. Initially this front will be to our southwest, but it will
move northeast as a warm front. However with the blocky pattern in
place the front will likely stall near our vicinity on Tuesday, and
remain somewhere in our vicinity into the latter part of the week.
The exact placement of the front will have a big influence on our
sensible weather, and it is uncertain at this point where the front
will be each day. With the nearness of the front and the uncertainty
of its exact position for most of the week, will need to carry
shower chances for the entire week, with thunderstorms possible from
Tuesday on.
By end of the week, the upper low in the southwest will have opened
up and moved east, possibly getting absorbed into the eastern North
America trough by next weekend. As the southwest upper low moves
east it will induce surface low development. With this stronger
system expected to affect the area late in the week, rain chances
will be on the increase for the latter part of the week.
As far as temperatures go, temperatures will warm through the first
part of the week as the warm front moves into the area and then
stalls. With the passage of the late week system, cooler air will
return for the end of the forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 736 PM EDT SAT MAY 6 2017
Isolated rain showers should continue to move across the area this
evening, and steadily taper off as the night wears on. Eastern
Kentucky should be free of rain by 6Z tonight. The TAF sights
should experience VFR conditions with scattered to broken middle
level cloud cover move from northwest to southeast across the area
for the next few hours. The clouds should scatter out nicely this
evening, giving way to mostly clear to partly cloudy skies by 8Z
tonight. Winds will generally be out of the west to northwest at 5
to 10 mph through around 4Z before slackening. Sunday should
feature mostly clear skies, northwest winds at around 10 mph with
some gusts of up to 20 mph possible, and dry conditions for all
the TAF sites, as high pressure settles over the region.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...AR
SHORT TERM...ABE
LONG TERM...SBH
AVIATION...AR
Area Forecast Discussion
National Weather Service Memphis TN
800 PM CDT Sat May 6 2017
.UPDATE...
Updated to remove evening rain chances.
&&
.DISCUSSION...
Weak lift and the lack of low level moisture ahead of a passing
cold front will produce only patchy cloud cover this evening
across portions of the Midsouth. So removed evening rain chances
accordingly. The other forecast parameters are currently on track.
JAB
&&
.PREV DISCUSSION... /issued 251 PM CDT Sat May 6 2017/
DISCUSSION...Surface analysis this afternoon places a ridge of
high pressure over Texas with a weak cold front beginning to enter
portions of Northwest Tennessee. As of 2 PM CDT, temperatures
across the Mid-South are in the 70s at most locations.
A weak cold front will drop through the Mid-South through this
evening. Short term models indicate there may be a potential for
some limited instability to produce isolated rain showers across
portions of West Tennessee and North Mississippi, especially near
the Tennessee River. Otherwise, most areas should remain dry
tonight.
A ridge of high pressure is expected to build in behind the front
bringing rain free weather to the Lower Mississippi Valley for the
remainder of the weekend through next Wednesday.
Long term models indicate the next chance for showers and
thunderstorms will come Wednesday night through Friday as a mid-
level trough moves through the region.
&&
.AVIATION...
18Z TAFs
VFR to prevail through the next 24 hours. A weak cold frontal
passage will bring midlevel clouds and perhaps isolated SHRA near
sunset east of MEM. Light winds prevail thereafter, as a surface
high settles in. HRRR and LAV guidance showing nil chances of
radiational fog, some overnight MVFR visibility may be added to
MKL and TUP TAFs in a later update.
PWB
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service San Francisco Bay Area
857 PM PDT Sat May 6 2017
.SYNOPSIS...Cool and breezy conditions will persist though the
remainder of Saturday evening. There is also a slight chance of
showers across the southeastern portion of our region overnight,
with showers chances also lingering across the far south into
Sunday. Otherwise, expect warmer weather on Sunday along with
lighter winds. Dry weather with seasonable temperatures are
forecast for Monday and Tuesday. Cooler conditions return by the
middle of next week.
&&
.DISCUSSION...As of 8:55 PM PDT Saturday...Saturday was a cool
and blustery day across much of our region, with high temperatures
mostly in the upper 50s and 60s...as much as 10 degrees cooler
than average for the date. Coastal and higher elevation locations
were buffeted by northwest winds that gusted as high as 40 mph.
Winds have been gradually subsiding this evening and will continue
to decrease overnight.
The upper low responsible for our cool and blustery weather is
currently centered to our south near Point Conception, and is
moving slowly to the southeast. Widespread showers and isolated
thunderstorms developed over southern and eastern California this
afternoon. Current radar shows all precipitation remains to our
south and east, although an area of showers that had developed
over the Sierra this afternoon is currently moving to the west and
directly towards the East Bay. That 00Z NAM shows this shower
activity taking a turn to the southwest and tracking across
southeastern Santa Clara County by late this evening and
eventually into Monterey and San Benito Counties later tonight.
The HRRR forecasts all precipitation overnight to remain south of
Santa Clara County. In any case, if shower activity does make it
into our area overnight, rainfall amounts are expected to be very
light. Finally, the airmass is not sufficiently unstable for
thunderstorms anywhere in our area this evening, and a forecast
update was completed earlier to remove thunderstorm chances.
As the upper low continues to move slowly to the southeast
overnight and into Sunday, shower chances in our area will
continue to diminish. Only far southern San Benito County and
southeast Monterey County will continue with a chance of showers
on Sunday and mainly during the morning hours. Otherwise, Sunday
is expected to be a dry day under partly cloudy skies with
temperatures about 5 to 7 degrees warmer than today. Also, winds
on Sunday will be much lighter compared to the past two days.
An upper ridge is forecast to build across northern California on
Monday and Tuesday. Temperatures on those two days are expected
to be near normal at the coast and slightly warmer than normal
inland. As the boundary layer become more stable early in the work
week, look for a marine layer to redevelop, resulting in
increasing areas of night and morning low clouds and fog.
Warmer temperatures early in the week will be short-lived as the
models agree that an upper trough will settle in along the West
Coast during the second half of the week and into next weekend.
Temperatures will cool beginning Wednesday and then likely remain
cool for several days thereafter. Precipitation with this next
trough is forecast to remain to the north of our area, so we can
generally expect dry, cool and locally breezy conditions during
the extended portion of the forecast.
&&
.AVIATION...As of 5:53 PM PDT Saturday...VFR. A closed mid level
low currently located 50 miles southwest of Santa Maria will
continue to move southward tonight into Sunday. Easterly mid-upper
level winds north of this low center will pull residual cloud
cover westward off the Sierra Nevada over the Central Valley and
toward the coast tonight.
Vicinity of KSFO...VFR. Gusty westerly winds this evening becoming
light southeast Sunday morning. Westerly winds redevelop Sunday
afternoon.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR. Gusty winds will gradually decrease
this evening. Onshore winds redevelop late Sunday morning and
afternoon.
&&
.MARINE...as of 01:45 PM PDT Saturday...Strong northwesterly gale
force winds will continue tonight and into tomorrow. Gale force
gusts will occur with isolated low end storm force gusts possible,
especially along and near the Big Sur and Sonoma coasts. This
will be a prolonged wind event with a long fetch for combined seas
to build in excess of 15 feet. Mariners should take action now to
prevent life and property damage for this strong gale.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...High Surf Advisory...Entire Coast.
SCA...Pigeon Pt to Pt Pinos 0-10 nm from 10 PM
GLW...Pigeon Pt to Pt Pinos 0-10 nm until 10 PM
GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm until 10 PM
GLW...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 10 PM
GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm
GLW...Pt Arena to Pt Reyes 0-10 nm
GLW...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Rough Bar Advisory for SF Bar until 4 AM
SCA...Mry Bay
SCA...SF Bay until 10 PM
&&
$$
PUBLIC FORECAST: Dykema
AVIATION: Canepa
MARINE: DRP
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Area Forecast Discussion
National Weather Service Raleigh NC
950 PM EDT Sat May 6 2017
.SYNOPSIS...
An upper level low pressure trough will cross the region tonight
through Sunday morning. Cool high pressure will build in from the
northwest through Monday. A warm front will move into the area from
the southwest on Tuesday and then stall over the Carolinas through
mid week.
&&
.NEAR TERM /through tonight/...
As of 950 PM Saturday...
Patchy light showers persist across the area, driven in part by low
level warm air advection ahead of a sharpening 850 mb trough slated
to cross the CWA tonight, and an upper divergence maximum in the
left exit region of a 100+ kt jet diving down from Ontario through
the Midwest into SE TN. The HRRR has done a fairly good job so far,
focusing the most widespread/heaviest precip just to our south
across W/N SC, within a band of low level mass convergence featuring
a WSW low level jet and where mid level DPVA is strongest. This band
of vorticity will continue to streak across the NC/SC border and
into eastern NC overnight, so will stick with chance pops persisting
overnight, translating east and increasing a bit late as we head
into Sun morning. Thunder chances appear slim, but a few sporadic
strikes are certainly possible given the presence of some saturation
and lift in the -10C to -20C layer on RAP soundings for a brief
period overnight. Expect skies to gradually clear out late tonight
as the mid level trough axis shifts to our east, with low level
downslope flow and rapidly rising mid level heights. Lows from the
low-mid 40s west (clearing and CAA) ranging to around 50 in the
east, where clouds will hold on through daybreak Sunday. -GIH
Earlier discussion from 100 pm: Convection is expected to re-develop
over and/or propagate downstream into west/southwest portions of the
state by mid/late afternoon as another potent shortwave (digging SE
through eastern KY/TN at 17Z) rounds the base of the trough over the
Carolinas. This second round of activity will better coincide with
peak heating and will likely be more intense than convection this
morning, and an isolated thunderstorm cannot be ruled out in the SW
Piedmont late this aft/eve. Diurnal destabilization will be limited
in nature this afternoon as the mixed-layer deepens and the low-
levels dry out, as will potential instability (theta-e neutral
w/height). As a result, severe weather is highly unlikely in central
NC. At most, convective wind gusts up to ~40 mph will be possible in
the SW Piedmont, Sandhills and Triangle area late this afternoon as
low/mid-level flow strengthens in advance of the shortwave in the
presence of a relatively deep /well-mixed/ boundary layer invof peak
heating. The latest convection allowing models indicate shower
activity will pivot from a W-E orientation to a SW-NE orientation
after 00Z. As a result, precip chances will initially be highest
along/south of Hwy 64 late this afternoon in the W/SW Piedmont, with
activity lifting NE toward the Triangle and expanding along/east of
the I-95 corridor AOA 00Z as the shortwave begins to eject NE toward
the coastal VA/NC border. Shower activity should end from west-east
in the coastal plain shortly after midnight.
Challenging temperature forecast given ongoing shower activity /evap
cooling/ and cloud cover, with additional convection and cloud cover
expected by late afternoon. Will reduce highs this afternoon by
several degrees, to the lower/mid 60s. Expect lows tonight in the
mid/upper 40s, coolest NW where skies will clear earlier. -Vincent
&&
.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 100 PM EDT Saturday...
Although a short period of sprinkles cannot be completely ruled out
in the far NE Coastal Plain early Sun afternoon in assoc/w
additional shortwave energy on the western periphery of the upper
level trough as it begins to offshore, dry conditions will otherwise
prevail with a dry W/NW flow throughout the column. Expect mostly
sunny skies with highs in the upper 60s/lower 70s. With a drier
airmass in place, clear skies, and calm winds, optimal radiational
cooling should allow for relatively chilly low temperatures Monday
morning, in the lower to mid 40s. -Vincent
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 140 PM EDT Saturday...
Continuation of strongly negative H5 height anomalies associated
with the deep lower over the Northeast/New England will result in
another cool and dry day on Monday.
The persistent omega block will begin to shift eastward Tue-Wed,
with models showing the low splitting over the NE US/Southern Canada
by Wednesday, with central NC under the increasing influence of the
shortwave ridge building in from the west. Expect gradual warming as
heights aloft increase. Rain chances also look to be on the
increase, with models showing the potential for episodic-ridge
riding disturbances in NW flow aloft to support scattered showers
along a quasi-stationary frontal boundary forecast to extend from
the Upper MS valley SE invof the Carolinas. The exact location of
this front is the next forecast challenge and will ultimately be the
key wx feature that will go a long way in determining temperatures
and rain chances Wed-Thu. For now will show a rather sharp north to
south temperature gradient, coolest across the north where low
clouds and rain could support wedge-like air mass, while maintaining
slight to low chance pops everywhere due to uncertainty/low-
predictability with the NW flow disturbances and the location of the
front. Meanwhile, the former closed low over the SW US will eject
eastward across the central US as an open wave. This wave will
approach the area from the west on Friday, where it will interact
with the aforementioned stalled frontal zone, bringing the potential
for storms Friday afternoon and into Saturday.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 750 PM EDT Saturday...
24 Hour TAF period: A few scattered showers around this evening but
the main shortwave causing a more intense shield of precipitation is
diving south of the area. Expect most of the remaining shower
activity this evening to be concentrated in the eastern half of the
area although an isolated shower anywhere cannot be ruled out.
Ceilings at this time have all returned to VFR and for the most
part, wind gusts have begun to subside. Expect winds out of the west
or northwest overnight at 5-10 kts. For Sunday, VFR conditions
should prevail with skies clearing and winds out of the west at 10
kts.
Long Term: Weather should remain quiet until Tuesday when a
shortwave in the upper flow approaches from the northwest and could
bring some precipitation to the area. This will begin a train of
weak disturbances that may keep weather unsettled through the end of
next week.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Hartfield
NEAR TERM...Hartfield/Vincent
SHORT TERM...Vincent
LONG TERM...CBL
AVIATION...Ellis
Area Forecast Discussion...UPDATED
National Weather Service Reno NV
647 PM PDT Sat May 6 2017
.UPDATE...
Based on continued accumulations of snow around Tahoe will expand
winter weather advisory northward to include that region. Snow
levels have been more problematic than normal today, ranging from
6000 to 8000 feet. Example - South Lake Tahoe picking up snow
accumulations while Donner Pass has been mainly just wet. Travel
impacts could increase after sundown when temperatures cool, even
if precipitation rates/coverage decrease per radar and HRRR
trends. Only a few inches expected but it`s late season so
travelers are less prepared.
Rest of forecast and WWA`s unchanged for the time being. So far
river and stream responses have not been overly impressive, but
will wait to see how precipitation evolves next 1-2 hours before a
go/no-go decision on continuing flood watch.
-Chris
&&
.PREVIOUS DISCUSSION... /Issued 242 PM PDT Sat May 6 2017/
SYNOPSIS...
Moderate to heavy rain and high elevation snow will continue
tonight through Sunday. There is potential for minor flooding of
creeks and streams with the rainfall this afternoon and evening.
Rises on mainstem rivers are also expected.
SHORT TERM...
Low pressure moving through CA/NV tonight will bring moderate to
heavy rainfall to the region, with high elevation snow mainly
above 7500 feet. Precipitation continues to develop this afternoon
across the Sierra and western Nevada, as we get good diffluence
aloft, broadscale lift and low level convergence in association
with the deformation zone as the upper low passes to our south.
Models have been in good agreement since yesterday showing this
deformation precip since yesterday, so forecaster confidence is
high for the banded moderate to heavy precip.
Precip will continue through the evening and into early Sunday
morning, with rainfall totals around 0.50-1.0". A few localized
areas could see precip amounts of greater than one inch. CAPE
values are rather weak today, but a few embedded thunderstorms may
be possible in the main precip that could intensify precipitation
amounts as well.
There are flooding concerns for the region, mainly for smaller
creeks and streams, but there are a few concerns for mainstem
rivers as well. Please see our hydrology section below for more
details on flood potential.
Snow levels are currently over 8000 feet and expected to come down
to near 7000 feet after midnight. This will bring several inches
of heavy wet snow (3 to 8 inches) for the high Sierra tonight
through Sunday morning, with snow impacts likely for the higher
Sierra Passes including Mount Rose Summit, Carson, Echo, Deadman,
Devils Gate and Sherwin Summits. There could be some areas that
receive up to a foot of snow or more, but those elevations will be
mainly over 8500 feet. Several inches of snow are likely for the
Mammoth Lakes area tonight and Sunday morning as well. Winter
Weather Advisory has been issued for Mono-Eastern Alpine Counties
for snow above 7500 feet.
The cutoff low will move east across southern CA and NV Sunday
night with another band of deformation zone precip Sunday night
into Monday. There could be some continuing precipitation in Mono-
Mineral Counties through this time, but the heaviest precipitation
looks to remain south and east of our area. Hoon
LONG TERM...Monday and beyond...
While the main upper low is expected to continue moving away from
the Sierra, a lingering band of wrap around moisture could still
bring showers and a few thunderstorms to areas south of US-50
Monday. Coverage and projected precip amounts will be much
lower compared to this weekend`s event.
For Tuesday, the main low will move slowly east across Arizona with
the outermost moisture band possibly producing a few very light
showers in southern Mono-Mineral counties. Otherwise, drier and
warmer conditions will prevail with ridge axis building into
northern CA.
By Wednesday, ridge axis builds into the Sierra and western NV. With
a few more degrees of warming and weak flow aloft over the Sierra,
afternoon cumulus are probable. Farther north, additional cumulus
could develop in the Lassen convergence zone, but limited forcing
and warmer mid level temperatures arc likely to cap convective
development in both of these areas.
Later next week, medium range guidance is in reasonable agreement
with a strong low pressure approaching the Pacific Northwest coast
Thursday, then moving inland across Washington by early next
weekend. The main effects will be a notable increase in winds
Thursday with breezy conditions continuing Friday and Saturday.
Temperatures are also likely to cook back to a few degrees below
average by Saturday.
As for precipitation chances, the main moisture feed and dynamics of
the low are projected to remain north of the Oregon border so
significant rain or snow is unlikely. Shortwave energy rotating
around the base of the trough could trigger a few light showers at
times from Thursday through Saturday in portions of northeast CA and
northwest NV mainly north of I-80.
Looking ahead to mid-May, it appears that the main trough axis will
remain near the west coast with reinforcing shortwaves potentially
bringing additional precipitation chances, along with continued
below average temperatures. MJD
AVIATION...
The main weather concern through early Sunday will be periods of
rain and higher elevation snow over the Sierra and much of western
NV. The peak rainfall intensity is expected between 22z-06z for
areas near and north of US-50 (including KTVL-KTRK-KRNO-KCXP). MVFR
conditions with widespread mountain obscurations are likely, with
brief IFR visibility possible in heavier rain areas. Farther south
for Mineral and Mono Counties (including KMMH), another area of
widespread rain and mountain snow is expected to develop later this
evening and continue into early Sunday, with peak intensity between
06-12Z. While we are not anticipating snow accumulations at KMMH,
periods of brief rain-snow mix are possible during heavier precip
bursts. Wind gusts up to 30 KT are also possible at times around the
region through this evening.
There remains a low potential for isolated thunderstorms until 00z
for the Tahoe and Reno-Carson terminals until 00Z, but the better
potential shifts to west central NV near and east of US-95, where a
few cells could linger until 03Z.
For Sunday, the better shower potential will shift to areas south of
US-50 and east of US-95. Overall intensity and coverage are expected
to be less compared to today, with brief MVFR conditions possible.
MJD
HYDROLOGY...
Rivers, creeks, and streams are already running pretty high from
the recent warm temperatures and snowmelt, so this additional
precipitation tonight will only add to the problems of minor
flooding around the region. A areal flood watch remains in effect
for the Eastern Sierra and western Nevada, including around the
Tahoe Basin. The areas of highest concern will be the creeks and
streams around the Tahoe Basin and Carson Range west of Reno-
Carson City where flows are already running high and fast.
We have issued a Flood Advisory for the East and West Forks of
the Carson River as well, as minor flooding is already occurring
from snowmelt and irrigation, and additional rainfall will only
exacerbate the situation. Rises on the Truckee and Walker Rivers
are expected as well, although no major flooding is expected.
Truckee River at Truckee will be at minor flood stage through
Sunday, with minimal impacts according to the emergency management
there. The Truckee River at Vista is expected to rise sharply
overnight due to runoff from rainfall. We do not expect to reach
flood stage, but it will be very close.
Lastly, terminal lakes such as Swan, Silver, Washoe, and White
Lakes will likely see an increase of inflow over the next 24
hours from rainfall and snowmelt. Hoon
&&
.REV Watches/Warnings/Advisories...
NV...Flood Watch until 5 AM PDT Sunday NVZ002-003.
Lake Wind Advisory until 9 PM PDT this evening for Pyramid Lake
in NVZ004.
CA...Flood Watch until 5 AM PDT Sunday CAZ071>073.
Winter Weather Advisory until 11 AM PDT Sunday above 7500 feet
in CAZ073.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Blacksburg VA
944 PM EDT Sat May 6 2017
.SYNOPSIS...
A large upper level area of low pressure will drift slowly
northeast along the Appalachians through tonight. This system
should finally exit on Sunday followed by weak high pressure
that will gradually build in from the west by Sunday night. This
area of high pressure will then cover most of the Mid Atlantic
region Monday and Tuesday keeping dry and cool weather in place.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 945 PM EDT Saturday...
Showers and even a few thunderstorms have continued in southeast
WV and small part of Virginia ahead of upper level disturbances
rotating around an upper low across northern WV and southwest
PA. The 00Z RNK soundings indicated freezing levels around 3200
ft MSL which is contributing to the thunder despite shallow
cloud tops.
The 00Z HRRR has performed well on the location of precipitation
this evening, and continue to expect an decreasing trend in
coverage tonight with skies clearing east of the mountains after
midnight. Otherwise, dropped temps a couple of degrees based on
current observations, but with 5-10kt winds expected, do not
expect a significant drop from current levels.
Threat of upslope showers diminishes around midday Sunday as
vort axis shifts northeast to the Shenandoah Valley to eastern
NC. Anticipate plenty of sunshine across the region by Sunday
afternoon, after clouds in the morning over southeast WV to the
Blue Ridge of VA erode/lift northeast. Still looking at a
gradient in the pressure fields between 994 mb low over Quebec
and weak high over the mid-MS Valley.
Temps tomorrow at or just above today`s highs in the east, and
warmer in the west with sunshine returning and 8h temps warming.
Look for readings from the mid to upper 50s west, to lower to
mid 60s east.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 225 PM EDT Saturday...
Our weather pattern will still be under the influence of the trough
axis of a slow moving, cold upper low that will be making
progression eastward through New England. Closer to the surface,
high pressure will nose its way way into the area Sunday night into
Monday. The result will be dry weather with limited cloud cover.
Winds will still be a bit gusty given the pressure gradient between
the departing low and the approaching high.
While the upper low makes its slow progression eastward, an upper
ridge of high pressure will build into the Central Plains states.
The result will be the development of a NW-SE oriented baroclinic
zone that develops from the Upper Mississippi River valley into the
central Appalachians by Monday night into Tuesday. A elongated nose
of vorticity is expected to extend the length of this feature with
showers becoming more common across the area, spreading from
southwest to northeast. Prior to the arrival of the associated
precipitation and increased cloud cover, some frost is possible late
Monday night into early Tuesday morning across parts of far eastern
Greenbrier County WV and Bath County VA. During the afternoon
Tuesday, there may be enough instability from the development of
isolated thunderstorms across the far southwestern sections of the
region.
Temperatures during this portion of the forecast will average ten
degrees below normal.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 250 PM EDT Saturday...
Wednesday through the start of next weekend will be an active
weather period for showers and some storms. The New England closed
low is progged to either retrograde to near Hudson Bay, or split
into to distinct lows with one remaining near New England and its
counterpart retrograding to the Hudson Bay region. Either solution
is accompanied by a breakdown of the central U.S. upper ridge to
more of a zonal flow with a developing low in the lee of the Central
Rockies ejecting into the mid-Mississippi Valley by the end of the
week.
This scenario is progged to result in the baroclinic zone across the
area making gradual progression north through the region. Also,
shower coverage is expected to become greater with better chances of
moderate or heavier rainfall as pieces of energy eject eastward from
the closed low along this feature heading into next weekend.
Temperatures during this portion of the forecast will average five
degree above normal.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
As of 750 PM EDT Saturday...
The cold pool of air aloft associated with a large closed low
over the northeast US is keeping steep lapse rates over the
region. This combined with diurnal heating and short wave energy
rotating around the upper low has generated some scattered
showers and a few isolated thunderstorms across the region,
though the radar is trending down as we are past peak heating.
Expect the trend for decreasing precipitation will continue and
expect TAf sites to be free of any lingering precipitation by
03Z to 06Z. Cigs are expected to remain VFR east of the Ridge,
while conditions to the west will trend down to MVFR as
orographic forcing combines with low level moisture to generate
lower clouds.
Any sub VFR conditions will dissipate shortly after daybreak and
expect VFR conditions all sites for the latter portion of the
valid period as the upper trof slowly starts to move eastward.
Expect a bloom of Cu mainly north and east as diurnal heating is
once again able to bubble up some clouds, but do not see enough
support to generate any precipitation of sub VFR conditions.
Winds will be a bit gusty early tonight before stratifying
overnight. However, increasing low level flow coupled with
diurnal mixing will bring gusty conditions back to TAF sites by
late Sunday morning with gusts up to 25kts possible.
Extended Aviation Discussion...
VFR conditions will persist into Monday. Moisture increases
ahead of the next front Tue-Thu so looking at rain chances
increasing along with sub-VFR conditions, especially west of the
Blue Ridge.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...AMS/WP
NEAR TERM...PH/WP
SHORT TERM...DS
LONG TERM...DS
AVIATION...MBS/WP
Area Forecast Discussion
National Weather Service Sacramento CA
321 PM PDT Sat May 6 2017
.SYNOPSIS...
Cooler with a chance of mountain showers and thunderstorms this
weekend. Gusty north winds Sunday. Turning warm again early next
week.
&&
DISCUSSION (Today through Tuesday)...
Upper low will be dropping SEwd along the central CA coast today and
into SOCAL tonight and Sun. Given the steering flow will be turning
from meridional to cyclonic over Norcal tonight and Sun, the precip
chances will trend Wly, from the Sierra today, and into the Sierra
Foothills and possibly portions of the Ern Central Valley tonight.
The last several runs of the HRRR Model REF prog shows the precip
trending Wwd over Norcal (from the "backdoor") and towards the I-5
corridor between 8-10 pm Sat. This higher resolution model seems to
be capturing the short waves/impulses that are forecast to rotate
Wwd this evening to the N of the closed low. The forecast REFs
weaken as they move into the Valley and given the forecast soundings
indicate a mid level cap, would expect showers but no thunder in the
Valley, and have confined mention of thunder to the Foothills.
Radar shows echoes generally expanding in areal coverage from early
this morning as moisture wraps around the low center. Although we
can`t rule out thunder entirely due to the forecast short waves/
impulses that are forecast to move over the area this evening, deep
or significant instability looks to be lacking for widespread storms.
Dual Pol radar data indicates the snow level is generally at/above
7000 ft with WBZs forecast to lower to around 6500 ft along the I-80
corridor and 5000-5500 ft in Wrn Plumas Co later tonight and Sun
morning. Sierra peaks along and south of I-80 are forecast to
receive up to about 4 inches or so of snow through tonight. Little
impacts expected for the 80/50 corridor.
Building surface high pressure system off the coast will increase
the pressure gradient across the valley and the northern mountains
starting this afternoon into Sunday. This will bring breezy winds
for the northern Sacramento Valley today with gusty winds for most
of the valley Sunday. Forecast pressure gradients increase from 10
mbs to 13-14 mbs this evening and overnite which should push winds
to near/above WAD criteria mainly on the W side of the Valley and
lee-side of the coastal range. Gradients and 925 mbs wind support
decreases rapidly Sun afternoon. Would expect winds to decouple
enough in the Valley tonight but increase to WAD levels late this
evening for the lee-side of the coastal range as the Nly barrier
jet develops on the W side of the Valley and surrounding foothills.
Thus, the two distinct beginning times for the WAD.
As the upper level ridge builds from the west on Sunday, dry
conditions will return for the forecast area with high temperatures
will warm to slightly above normal for Sunday and between 5 and 10
degrees above normal for Monday/Tuesday. Increasing anticyclonic flow
will account for adiabatic warming and should shunt precip chances
mainly well to the S of our CWA, save for the are just N of Yosemite
NP. JHM
.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)
High confidence in cooler and breezier conditions returning for
interior NorCal after mid-week as upper ridge breaks down and
shifts east as another trough sets up near the West Coast.
Shower chances expected to be confined to mainly the mountains
late next week. JClapp
&&
.AVIATION...
VFR conditions expected next 24 hours except local MVFR/IFR
vicinity scattered showers and isolated thunderstorms over the
northern Sierra Nevada 20Z-06Z this weekend. Northerly surface
wind gusts 15-25 kts continuing northern Sac Valley overnight,
especially between 1-2K MSL. Northerly winds developing for
remainder of Sac Valley overnight, especially westward of Hwy 99.
JClapp
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 11 PM to 4 PM PDT Sunday for Clear Lake/
Southern Lake County-Mountains Southwestern Shasta County to
Northern Lake County.
Wind Advisory from 8 AM to 4 PM PDT Sunday for Central
Sacramento Valley-Northern Sacramento Valley.
&&
$$
Area Forecast Discussion
National Weather Service Las Vegas NV
750 PM PDT Sat May 6 2017
.SYNOPSIS...A low pressure system will be impacting the region
through the weekend bringing cooler temperatures and breezy to
gusty winds along with showers, thunderstorm chances, and mountain
snow.
&&
.UPDATE...So far this afternoon and early evening, showers and
thunderstorms have been rather isolated across mainly Inyo, San
Bernardino, and Nye Counties. As the upper low which is currently
just off the southern CA coast shifts east this evening we are still
expecting a band of showers and isolated thunderstorms to develop
out ahead of the low. Current radar is showing this band starting to
take shape across far eastern San Bernardino County. The HRRR and
other hires models do continue to indicate showers developing in
this area and rotating north and west between 9pm and midnight. How
far east this rain band makes it is still in question and right now
the best area for seeing rain will be over eastern San Bernardino,
western Clark, southern Nye, and Inyo Counties. It`s still possible
that Las Vegas may see some measurable rainfall, but its more likely
west of town. After midnight the models indicate a pretty good dry
slot moving into the area from the south which is expected the bring
an end to much of the shower activity. However, we should see
moisture fill back in on Sunday along with a little more instability
as the upper low moves over San Bernardino County. Will go ahead and
let the Wind Advisory and Red Flag Warning expire at 8pm this
evening, but will let the Winter Weather Advisory ride into Sunday.
&&
.AVIATION...For McCarran...Southwest winds should persist the rest
of tonight and could gust to 25 kts at time until around 06z. Clouds
will continue to fill in this evening and lower with showers and
cigs around 5 kft possible mainly between 06z and 09z. Showers
Sunday will mainly be over the mountains with clouds at LAS sct-bkn
about 10 kft. Winds Sunday will favor a southeasterly direction 8-15
kts.
For the rest of southern Nevada, northwest Arizona and southeast
California...Southerly flow will dominate through the weekend and
through the beginning of next week. Breezy southeast to southwest
winds of 15-30 with gusts up to 40 kts winds will persist through
this afternoon and diminish this evening. Scattered chance of rain
across our region will cause periods of lower ceilings, but should
remain within VFR conditions. Best chance of rain for most TAF sites
between 06-12Z this evening, slight chances of rain continuing
through tomorrow afternoon for BIH and DAG. Gusty winds will begin
to diminish around 02-03Z tonight across the region, lingering
longer at DAG. Less gusty winds tomorrow with sustained winds 8-15
kts with occasional gusts up to 22 kts in the afternoon.
For the rest of southern Nevada, northwest Arizona and southeast
California...Southerly flow will dominate through the weekend and
through the beginning of next week. Breezy southeast to southwest
winds of 15-30 with gusts up to 40 kts winds will persist through
this afternoon and diminish this evening. Scattered chance of rain
across our region will cause periods of lower ceilings, but should
remain within VFR conditions. Best chance of rain for most TAF sites
between 06-12Z this evening, slight chances of rain continuing
through tomorrow afternoon for BIH and DAG. Gusty winds will begin
to diminish around 02-03Z tonight across the region, lingering
longer at DAG. Less gusty winds tomorrow with sustained winds 8-15
kts with occasional gusts up to 22 kts in the afternoon.
&&
PREV DISCUSSION
212 PM PDT Sat May 6 2017
.SHORT TERM...Through Monday Morning.
Gusty winds have developed basically as expected this afternoon,
if not slightly stronger than forecast across the Las Vegas
Valley. The Wind Advisory and Red Flag Warning currently in place
look good and will continue through 8pm this evening.
As of 2 PM this afternoon, showers and thunderstorms were just
beginning to develop across the NNSS and the southern Sierra,
slightly behind the timeframe expected earlier this morning. In
any case, additional development is expected across southern
Nevada and Inyo County tonight, mainly to the north and west of
Las Vegas. Then after sunset, rapid development is expected across
eastern San Bernardino and southern Mohave County (including the
Colorado River Valley). This area will expand north overnight,
likely spreading across the Las Vegas Valley between 10pm and 4am.
This slug of activity is expected to wrap west across the Sierra
Sunday morning before diminishing Sunday afternoon. Models are
still holding on to the idea of a dry slot making its way across
the middle of the forecast area during the day Sunday, with
showers lingering around the periphery. The main threats with any
storms through this period will be gusty winds, lightning, hail,
and brief heavy rain/snow.
Speaking of snow, a Winter Weather Advisory was issued earlier
today for the Spring Mountains today into Sunday morning, and for
the Sierra and White Mountains for today through Monday afternoon.
This decision was made based on the recent warm spell and the
likelihood of outdoor enthusiasts enjoying the mountain wilderness
this weekend. They may be caught off-guard by sudden winter
weather conditions such as heavy snow in addition to lightning,
hail, and gusty winds. Snow levels will drop from around 10000
feet today to 7000-8000 feet overnight. Snow totals will be highly
variable, but in general a trace to 8 inches is likely, with
higher amounts possible near the Sierra crest.
.LONG TERM...Monday through Friday.
The cutoff low and its assortment of weather will be the main
focus for the first half of this period. Models are tightly
clustered, and also agree well with previous runs, so confidence
in the large scale pattern is above average, but confidence in
details such as precip placement and point temperatures is below
average. On Monday, the low has dived well south of the area, with
models indicating a significant dry slot over most of our CWA
between higher precip chances near the low center and also in a
SW-NE oriented band from the Sierra through the Great Basin.
Tuesday, as the low tracks northeast across Arizona, models
suggest the northern band will fall apart and precip chances will
consolidate in the western semicircle of the low. Raised PoPs for
our eastern zones, particularly Mohave County, for this period. As
the low pulls away to the east Wednesday, precip chances will
decrease from west to east, with dry weather expected areawide
from Wednesday night through Friday. Temperatures are expected to
increase overall from the abnormally chilly day on Sunday, but as
noted earlier, confidence in point temperatures is low because of
dependence on exact placement of cloud cover and precip/virga. As
the area dries out and skies clear up Thursday and Friday, temps
should return to near normal.
&&
.FIRE WEATHER...Gusty winds will continue into this evening across
much of the region. Low relative humidity along with the gusty
winds have led to critical fire weather for northwest Arizona and
the Colorado River Valley, where Red Flag Warnings are in effect.
Expect calmer, cooler, and more moist conditions as the low
pressure system lingers over the region into early next week.
&&
.SPOTTER INFORMATION STATEMENT...An area of low pressure will
impact the region through the weekend, bringing showers,
thunderstorms, and gusty winds. Spotters are encouraged to report
any impacts from the wind, such as damage or blowing
dust/visibility restrictions as well as rain amounts according to
standard operating procedures.
&&
$$
UPDATE...Gorelow
SHORT TERM...Wolcott
LONG TERM....Morgan
AVIATION.....Harrison/Kryston
For more forecast information...see us on our webpage:
http://weather.gov/lasvegas or follow us on Facebook and Twitter