Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/10/19
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
948 PM CDT Thu May 9 2019
.UPDATE...
Rain chances and amounts are dropped significantly north of Hwy 90
and West of I-35. Strong north winds from a cold front will scour out
large amounts of low level moisture which will force the overrunning
lifting processes to be elevated. Southeast of I-35 locally heavy
rainfall and severe weather will remain possible through midnight,
but pockets of heavy rain could still occur over the far southeast
counties after midnight. CAMS models show minimal activity across the
area between 06Z and 10z with redevelopment from the next wave of
instability advancing north over the frontal inversion closer to
daybreak. This downward trend change for the overnight period is
only a minor and temporary deviation off the continued messaging of
daily 1-3 inch pockets of heavy rain and isolated pockets of 5 inch
totals through Friday night.
&&
.PREV DISCUSSION... /ISSUED 708 PM CDT Thu May 9 2019/
UPDATE...
We have updated to include the remainder of the eastern/southeastern
CWA in the Severe Thunderstorm Watch through 11 PM. HRRR shows
expanding line of storms through this region through the evening.
Mesoscale analysis reveals pockets of 4000-5000 J/kg SBCAPE through
this region coinciding with 40-50kts of deep layer shear. A threat
for very large hail exists over the next hour or two across southern
and eastern areas of the CWA transitioning to damaging straight-line
wind threat. An isolated tornado can`t be ruled out.
Southern and eastern areas of the CWA will also be under the threat
for locally heavy rainfall through the evening hours. 1-3 inches of
rainfall is possible with isolated pockets up to 5 inches (see WPC
latest Mesoscale Precip Discussion)
AVIATION...
SHRAs and TSTMS ongoing this evening across South Central Texas.
Threat for strong to severe storms will primarily will be east and
south of the TAF terminals. Threat of SHRAs and TSTMs should exit
east of the region around 04Z-07Z. Gusty N to NE winds will develop
at AUS/SAT/SSF through the evening and overnight hours, as pressure
rises increase behind the cold front. Gusts over 25 kts possible. In
addition, MVFR ceilings will develop 03Z-09Z areawide, possibly IFR
at SAT/SSF/AUS overnight.
PREV DISCUSSION... /ISSUED 332 PM CDT Thu May 9 2019/
SHORT TERM (Tonight through Saturday)...
Scattered showers and thunderstorms have developed across the
western parts of the CWA over the past couple of hours. A pre-frontal
boundary just before the cold front has provided the initial lift
for the convection. At the same time, a weak upper level disturbance
is expected to push into South-Central Texas from the west. Latest
high-res guidance continues to show these two features working
together with the bulk of the stronger thunderstorms remaining near
the boundary. The front is expected to continue to push south through
the region this afternoon and evening. By 7 PM, the front is
expected to be near our southern border with WFO CRP. The atmosphere
is quite unstable, with SBCAPEs near 5000 J/kg. This in combination
with 0-6km shear values near 40-50 knots will provide the ingredients
necessary for some of the storms to be quite robust with very large
hail being the main threat. A dry layer at 700 mb could inhibit
storms a bit, but with the instability amounts these should be able
to be overcome. A Severe Thunderstorm Watch has been issued for
locations generally south and east of a Fredericksburg to San Marcos
to Gonzales line to cover the initial threat through 04z. Another
watch may need to be issued at a later time for downstream depending
on how things evolve tonight.
As the front makes it near the southern boundary of the CWA late this
afternoon and evening, storms could increase in coverage with the
arrival of the best forcing. There are some indications in the latest
high-res models that this activity will eventually congeal into an
MCS tracking east into the Houston area overnight. If this does
occur, mesoscale subsidence on the backside of the complex should
limit rain chances after 06-09z tonight and into tomorrow morning.
The cold front is expected to push well into South Texas by tomorrow
morning. Additional activity is expected to move in from the
southwest by tomorrow afternoon as some weak lift above the frontal
layer moves into the area. This precip is shown best by some of the
CAMs, while the GFS is much drier. One last wave of rainfall is
expected Friday night into Saturday ending from west to east by
Saturday afternoon. The activity Friday through Saturday is not
expected to be severe, but the threat of locally heavy rainfall will
continue. The Flash Flood Watch will continue for areas east of a
Fredericksburg to Hondo to Pleasanton line through 00z Sunday. While
the bulk of the heavy rainfall will fall across the Coastal Plains, a
conditional threat of flash flooding remains for the Hill Country and
Austin metro areas within the Flash Flood Watch. As what was seen
yesterday, a quick inch of rainfall will cause additional flooding
concerns.
In addition to the rainfall tomorrow, temperatures will be well below
normal behind the front. Highs tomorrow will be in the low 60s to
near 70 degrees. Austin Bergstrom should break a daily record low
maximum temperature. The current record is 75 degrees, and the
current forecast high is 66. The other 3 climate sites should not
break any records.
LONG TERM (Saturday Night through Thursday)...
Will show no PoPs Saturday night as activity should be east of the
area. Mother`s Day should be mostly dry as well. The GFS is showing
some precip with an approaching trough through Monday, but the Euro
remains dry. Will show slight chance PoPs for the beginning of the
long-term forecast to cover this threat. Slightly higher PoPs are in
the forecast through the mid-week period as models have slightly
better consistency on the placement of the trough axis. Temperatures
in the extended will moderate but will be cooler than normal.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 56 66 60 74 60 / 60 60 80 70 10
Austin Bergstrom Intl Airport 57 66 60 75 60 / 70 60 80 70 10
New Braunfels Muni Airport 58 67 59 76 60 / 70 70 80 70 10
Burnet Muni Airport 53 63 57 72 58 / 40 60 80 60 10
Del Rio Intl Airport 59 67 59 79 61 / 40 60 70 20 10
Georgetown Muni Airport 54 63 59 73 59 / 40 50 80 70 10
Hondo Muni Airport 59 68 59 77 60 / 50 70 70 50 10
San Marcos Muni Airport 56 65 59 74 60 / 70 70 80 70 10
La Grange - Fayette Regional 60 70 64 78 63 / 80 70 80 90 10
San Antonio Intl Airport 58 68 61 78 61 / 70 70 80 70 10
Stinson Muni Airport 60 70 62 78 63 / 70 70 80 70 10
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Saturday evening for Atascosa-Bandera-
Bastrop-Bexar-Blanco-Burnet-Caldwell-Comal-De Witt-Fayette-
Gillespie-Gonzales-Guadalupe-Hays-Karnes-Kendall-Kerr-Lavaca-Lee-
Llano-Medina-Travis-Williamson-Wilson.
&&
$$
Aviation...Oaks
Short-Term/Long-Term...Oaks
Public Service/Data Collection...EWilliams
Social media/Coordination...Runyen
Radar...CP/BW
Area Forecast Discussion
National Weather Service Hastings NE
657 PM CDT Thu May 9 2019
.SHORT TERM...(This evening through Friday)
Issued at 322 PM CDT Thu May 9 2019
Showers appear to be under-producing today so far today, with
radar returns struggling to make it into southern parts of our
forecast area. Short term models have backed off on this as well,
therefore I believe that most of the area will just see spotty
sprinkles through the rest of the afternoon.
Tonight, attention shifts to the potential for freezing
temperatures. High pressure moving in will make winds light and
variable and should also clear out skies this evening. The
complicating factor will be high clouds moving back in with an
approaching upper level jet streak. It may end up being a
situation where temperatures plummet quickly after sunset, then
level off as high clouds move in. As a result, I am a little
concerned that some locations may remain warmer than
forecasted...especially when looking at temperature forecasts from
the HRRR and RAP that are notably warmer. Nevertheless, I
continue to think that the current warning/advisory cover the
threat well.
Winds will remain light on Friday as the surface high slowly
shifts off to the east, but we will likely see continued high
cloud cover into the afternoon which will limit our temperatures
getting any higher than the low 60s.
Friday night will be warmer than tonight, but its still possible
that we see some patchy frost in northwestern portions of the
forecast area.
.LONG TERM...(Friday night through Thursday)
Issued at 322 PM CDT Thu May 9 2019
A cold front moves through the area on Saturday. This will likely
bring some scattered showers to the area during the afternoon and
evening, and models even show some very modest instability. As
such, I added a slight chance for thunderstorms, but it shouldn`t
be anything more than an isolated rumble or two.
Once again Saturday night we will have to watch for some patchy
frost in northwestern areas, but most of the area will only drop
into the low 40s.
A warming trend begins on Sunday as highs are forecasted to reach
the mid 60s to near 70 degrees. This trend will continue Monday
and Tuesday as the upper level ridge moves in from the west. Highs
are actually forecast to reach the 80 degree mark on Tuesday.
The area should remain dry Sunday and Monday, but there should be
at least some chance for rain and thunderstorms Tuesday into
Wednesday. The timing and positioning of the cutoff low exiting
the southwest are significantly different between the GFS and
Euro, and as a result our blends probably don`t reflect the
overall precipitation chances very well.
Beyond that, the pattern appears to become a little more active
as we move into the latter half of next week.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 649 PM CDT Thu May 9 2019
The wind will quickly die off this evening and become calm to
light and variable after midnight. Clouds will also thin out
tonight and VFR conditions are expected to continue throughout
the forecast period. We could see a heat of the day scattered deck
of clouds on Friday but should be above 4000 ft agl.
&&
.CLIMATE...
Issued at 337 PM CDT Thu May 9 2019
...First time in 6 years that 4-CONSECUTIVE MAY DAYS have failed to
reach 60 degrees in the Tri-Cities...
- Today (Thursday) marks the 4th-consecutive day with high
temperatures falling short of 60 degrees at all 3 official Tri
Cities airport stations (Grand Island/Hastings/Kearney). While this
sort of thing happens occasionally in May, it is not very common.
- The last time all three Tri Cities stations went 4 CONSECUTIVE
MAY days without reaching 60 degrees was six years ago from May
1-4, 2013.
- Based on our latest forecast, this streak is expected to end
Friday (albeit barely), as highs are forecasted to reach the low 60s.
- The record streaks for consecutive May days without reaching 60 in
the Tri Cities all occurred back in 1935, and are as follows:
Grand Island: 8 days...May 13-20, 1935
Hastings: 8 days...May 13-20, 1935
Kearney: 9 days...May 12-20, 1935
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Frost Advisory from 1 AM to 10 AM CDT Friday for NEZ041-048-049-
062>064-074>077-084>087.
Freeze Warning from 1 AM to 10 AM CDT Friday for NEZ039-040-046-
047-060-061-072-073-082-083.
KS...Frost Advisory from 1 AM to 10 AM CDT Friday for KSZ005>007-
017>019.
&&
$$
SHORT TERM...Mangels
LONG TERM...Mangels
AVIATION...Wesely
CLIMATE...Pfannkuch
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
903 PM CDT Thu May 9 2019
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
The region remains in a relative lull in activity this evening,
with remaining light showers along the I-59 corridor on a
continued decreasing trend. The storms from earlier today have
temporarily stabilized the atmosphere across the area, and there
has been a decrease in deep layer moisture over much of the area.
However, overnight a disturbance currently instigating convection
along the TX coast will track northeastward. The low level jet
will increase, helping to spread deeper moisture right back into
our area by tomorrow morning. The next round of rain and storms,
associated with the aforementioned disturbance, looks to arrive
early Friday morning, spreading across the area through the day.
The latest HRRR runs suggest this system may be weakening as it
arrives but a remnant MCV could help kick off new development
during the afternoon hours. The forecast has been updated to
refine POPs/wx timing, showing lower rain chances this evening
areawide, with increasing rain chances across the southwest
overnight into early tomorrow morning. /DL/
Prior discussion below:
Tonight through Saturday...
It has been a rather busy day as a line of storms moved through
the region and is now located across the Gulf Coast. This line
brought some wind damage to the region but it also brought heavy
rain and plenty of flooding. This is just the first round of
storms to move through the region, with plenty more to come over
the next several days. The actual cold front is still to the
northwest and will progress into the region this evening and
tonight and stall across the area. There should be a lull in the
rain activity overnight. However, model guidance is in decent
agreement that a disturbance will move northeast into the region
tomorrow. This will bring another round of showers and storms to
the region through the day tomorrow. Some of these storms could be
knocking on our doorstep in the southwest as early as daybreak or
a little thereafter and continue through the afternoon into the
evening. SPC has highlighted the southeast part of the forecast
area in a marginal risk for severe storms tomorrow. Given somewhat
steep lapse rates and vertical totals around 26-27C, and
sufficient deep layer shear across the region, I cannot rule out a
few severe storms during the morning into the afternoon. I do not
anticipate it being a setup like today was across the area. Will
mention this in the HWO and graphics for tomorrow. Given another
wave moving through on Saturday, there likely will need to be
another outlook for severe storms(at this point marginal risk) for
the area, but will leave out of the HWO/graphics for now and
focus one day at a time, given uncertainty in how convection
evolves each day and what residual boundaries may develop and
linger.
Of greater concern will be the continued risk for heavy rain and
flash flooding across the region. With copious amounts of rain
that fell today, the entire area is primed for more flooding with
just about any rain that falls over the next few days. With
continued southwest flow aloft and ample moisture in place, heavy
rain and more flooding will likely occur. That being said, we have
gone ahead and expanded the Flash Flood Watch to include the
entire forecast area through Saturday night. It may need to be
expanded in time later, but will let future shifts make that
assessment. We have also included the entire area in an elevated
flood risk in the HWO/graphics. An additional two to five inches
of rain will be possible, with locally higher amounts as well.
/28/
Saturday night into next week...
A pattern change will finally begin to bring some relief to our
region beginning Saturday night as a deep closed low approaches the
Great Lakes and helps to finally push a front through our region on
Sunday.
The front will begin to slowly push into the region on early SUnday
morning, a little later than previously expected. Showers and storms
will continue along and ahead of the front resulting in at least a
threat of flash flooding remaining into Sunday.
There are still uncertainties at this point in severe weather
becoming a threat through the day. Rain and storms will begin to
taper off from west to east by Sunday afternoon as drier air begins
to filter into the region.
NW flow aloft and high pressure near the surface will help to keep
the region clear and temperatures below normal through the early
week period. Rain chances will return to the region by mid week as a
few upper level disturbances embedded within the persistent upper NW
flow pattern could result in showers in the northern portions of the
region while a few weak disturbances embedded within the southern
stream could result in showers/storms in the southern portions of
the region.
&&
.AVIATION...
00Z TAF discussion:
The latest round of SHRA/TSRA continues to exit the area, with
only lingering -RA across parts of south MS. Considerable low
stratus exists across the area, with conditions ranging from MVFR
to LIFR. Ceilings are expected to deteriorate overnight with some
reductions in visibility possible as well. Conditions will be slow
to improve through the morning and afternoon hours. Another round
of SHRA/TSRA will move into the area Friday morning, continuing
eastward through the day. With that, temporary ceiling/visibility
reductions are possible in TSRA/+RA. /DL/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 65 77 66 78 / 46 93 67 94
Meridian 64 78 67 80 / 20 92 60 94
Vicksburg 67 75 66 76 / 62 93 70 93
Hattiesburg 66 80 69 81 / 38 93 49 93
Natchez 66 77 67 78 / 80 93 67 94
Greenville 65 72 64 73 / 32 76 68 94
Greenwood 66 73 64 75 / 25 80 71 94
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Flash Flood Watch through Saturday evening for MSZ018-019-
025>066-072>074.
LA...Flash Flood Watch through Saturday evening for LAZ007>009-015-
016-023>026.
AR...Flash Flood Watch through Saturday evening for ARZ074-075.
&&
$$
DL/28/JPM3
Area Forecast Discussion
National Weather Service Key West FL
1014 PM EDT Thu May 9 2019
.DISCUSSION...
Area radars show a cluster of showers and thunderstorms moving
south from the Gulf waters off Mainland Monroe toward the Lower
and Middle Keys, with scattered showers and isolated thunderstorms
also present over the Atlantic waters east of Miami-Dade County
and the far Upper Keys. A few showers moved over parts of North
Key Largo earlier, otherwise dry conditions have prevailed over
the Keys island chain so far this evening. Skies have become
partly to mostly cloudy, as high cloudiness emanating from the
convection to our north spreads southward. Temperatures are
dropping into the lower 80s, and winds on land are from the east
at 10 to 15 mph.
Surface analysis depicts a large high pressure area centered east
of New England and sprawling southward along the eastern seaboard
and over the western Atlantic. The Keys lie along the southwestern
edge of this high, driving gentle easterly breezes over our area.
Aloft, a weak mid/upper level trough is dropping southeastward
across the Florida peninsula. The 00Z Key West sounding shows a
moderately moist and conditionally unstable airmass in place, with
PW of 1.65 inches and no significant inversions. GOES derived TPW
imagery shows similar estimated PW values surrounding the Keys.
The overnight forecast remains tricky. While little rainfall has
occurred over the Keys so far this evening, increasing northerly
flow aloft appears to now be pushing the convective cluster to
our north down toward the Lower and Middle Keys, where it could
interact with pre-existing boundaries, or other shower activity
riding in from the Straits on easterly low level flow. The airmass
in place certainly will support convection, and is only lacking a
trigger, which could be provided by boundary interaction as noted
above. In addition, the Upper Keys may also be impacted later
tonight by convection moving WSW from the Atlantic waters east of
Miami. The latest HRRR does show increasing rainfall coverage
around and over the Keys late tonight. Have maintained 50 percent
rain chances throughout the Keys for the overnight period.
Otherwise, mostly cloudy skies will prevail, with low temperatures
varying from the mid 70s to around 80, depending on if a
particular location receives rainfall or not.
&&
.MARINE...
Evening marine observations show winds backing to E or even ENE
with speeds mostly in the 10 to 15 knot range. Expect little
change overnight, although locally stronger and shifting winds
will be possible with any thunderstorms. No significant changes
are planned for the late evening forecast issuance.
&&
.AVIATION...
The cluster of showers and storms pushing south toward the Lower
and Middle Keys may bring MVFR or even brief IFR impacts along
with gusty and shifting winds to the EYW and MTH terminals from
03Z through 06Z, and have included VCSH and TEMPO groups in both
TAFs for that time period. Shower/storm chances should decrease
by Friday morning, and currently expect VFR conditions to prevail
during the day. Surface winds will remain generally from the east
around 10 knots, outside of any convective influences.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...Jacobson
Aviation/Nowcasts....Jacobson
Data Collection......DR
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Area Forecast Discussion
National Weather Service Medford OR
856 PM PDT Thu May 9 2019
.DISCUSSION...The forecast is relatively straight-forward in the
short term. A strong ridge centered offshore will build inland
into Saturday.
Wind speeds will not be as strong on Friday, and will
continue a weakening trend into Saturday. But, it will remain
unusually warm and dry. There was an update sent earlier this
evening to enhance the cloud cover this evening to overcast at the
coast south of Cape Blanco. Also, late this evening, the RAP and
NAM models support a forecast of low level northeast winds pushing
the stratus away from the shoreline with a gradual diminishing
through Friday. The thermal trough that was at the coast today
will push inland on Friday. This will result in a warming trend
inland and slightly warmer at Brooking on Friday while the
remainder of the coast will have weak winds and the beginning of a
cooling trend.
By Sunday, the ridge will be flattened/weakened by a trough moving
into Canada while another trough will be moving into the Gulf of
Alaska before deepening over the eastern Pacific. As such, Sunday
will be a transition day with a modest increase in cloud cover and
relative humidity, with slight cooling west of the Cascades.
Monday`s weather will resemble that of Sunday while the broad
trough approaches and brings afternoon winds from very slightly
weaker to very slightly stronger than normal.
Model differences are important beyond Monday, but there is
confidence in a transition to a seasonable, active, occasionally
wet pattern. The first point in question is whether the first wet
front approaching from the west will bring rain to any part of
our area before the end of Tuesday afternoon. The highest
probability is for rain to reach the coast early Tuesday evening.
The next question regards whether precipitation during next week
will be very light, light, or moderate in any given area during
any given period. As the time draws nearer, clarity in the
appropriate answers is likely. This return to more typical spring
weather is likely to persist in the day 8 to day 14 time frame.
&&
.AVIATION...For the 10/00Z TAFS...Along the coast south of Cape
Blanco and the adjacent coastal waters...Widespread IFR cigs/vsbys
in low clouds and fog with higher terrain obscured will move
offshore during the day Friday, then return Friday night. Over the
remainder of the area...VFR conditions will prevail through Friday
night.
&&
.MARINE...Updated 800 PM PDT Thursday 9 May 2019...The thermal
trough has weakened and winds and seas are now subsiding. Small
craft advisory conditions will persist into Friday morning due to
residual wind waves and fresh swell. A southerly wind surge is
bringing low clouds and fog to areas south of Cape Blanco that will
persist into Friday morning at the least. Relatively calm winds and
seas will persist Friday afternoon through Monday.
A weak front will arrive Tuesday night. Small craft advisory
conditions are not expected at this time.
&&
.PREV DISCUSSION... /Issued 211 PM PDT Thu May 9 2019/
DISCUSSION...Current observations are showing mainly clear skies
with some cumulus moving westward across portions of northern
California and east of the Cascades in southern Oregon. These
winds from the east are responsible for the very dry conditions as
well as warm temperatures ongoing, especially at places like
North Bend. In stark contrast, the marine layer continues to be
difficult to forecast as a small eddy (circulation) is off the
coast of Humboldt County. This has kept fog and low stratus across
the southern Oregon coast of Brookings to Gold Beach. Meanwhile,
the easterly winds at Red Mound (1753 feet) have been gusting to
25 mph and bringing temperatures into the 80s as of 11 AM. These
east winds have remained aloft and have not mixed into the
boundary layer. This is why Brookings has only reached the upper
50s and North Bend is already reaching the mid 80s.
The thermal trough will move inland overnight into tomorrow, and
the coast could reach warm temperatures yet again, and they should
peak in the morning. This is dependent on the east winds keeping
overnight temperatures from dipping back to normal. Then, winds
turn to be westerly, and the marine influences will cool things
out. Meanwhile, temperatures on Friday are expected to really
soar, especially in the valleys west of the Cascades.
Additionally, expect the coastally trapped wind reversal to surge
up the Oregon coast on Friday and begin to wash out on Saturday as
the marine layer returns Saturday afternoon.
Temperatures remain pretty warm on Saturday but will slowly begin
a cooling trend on Sunday. Models are conflicted with possible
precipitation on Sunday in the form of Thunderstorms in the area.
The ECMWF is showing completely dry conditions, while the GFS and
GEFS ensemble are showing some convective potential in southern
Siskiyou County. This could be convective feedback (or it could be
legitimate and I could be wrong), and would make sense that it
would make its way into the blend of models. Have used the blend
of models, but have toned down the probabilities of precipitation
on Sunday. Should any precipitation actually form, expect an
isolated thunderstorm to occur with it.
Monday returns to mainly dry conditions, and cooler. Then the
pattern begins to shift for midweek and a low pressure system with
cold front approaches the Pacific Northwest. Models are confident
in the cool down of high temperatures, and the standard
differences in precipitation are occurring (the GFS being more
progressive and stronger with more precipitation as opposed to the
ECMWF which is weaker and somewhat drier, but still with some
precipitation). Have gone with the blend of models ensemble at
this point as this system will need to be monitored in the coming
days. -Schaaf
FIRE WEATHER...Updated 200 PM PDT Thursday 9 May 2019...Gusty
east to northeast winds and very low humidities will produce
critical to near-critical fire weather conditions across the area
this afternoon and evening. A Red Flag Warning remains in effect
for the foothills of eastern Douglas County and for a significant
portion of northern and central Klamath County. Conditions will
improve slightly overnight, but east winds will continue and
overnight to early morning recoveries will trend moderate to poor,
especially over high terrain along and west of the Cascades.
The thermal trough will continue its slow slide inland Friday and
Saturday, producing the warmest temperatures of the week over all
but the very-near coastal areas. Humidities are expected to be very
similar to today, but winds will be significantly weaker. While this
should keep the region free of any Red Flag conditions, many areas
could still get very close with the typical afternoon breezes. Also
worth noting will be the increased instability Friday afternoon,
mainly west of the Cascades and down along the coast, where Haines
values of 5 to 6 are expected. These conditions could promote plume
dominated growth over any new or existing fires.
After another hot and dry day Saturday, conditions should begin to
improve Sunday into early next week, with cooling temperatures,
gradually rising humidities, and improving recoveries. There will be
a slight chance for showers and isolated thunderstorms over southern
Siskiyou and modoc counties Sunday afternoon, and across portions of
northern California and south central Oregon Monday afternoon. It is
looking increasingly likely that widespread rain may enter the area
by midweek, although the timing and amount of rain remains
uncertain. -BPN
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.
CA...None.
Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Friday
for PZZ350-356-370-376.
$$
DW/JRS
Area Forecast Discussion
National Weather Service Sacramento CA
326 PM PDT Thu May 9 2019
.SYNOPSIS...
Showers and thunderstorms are possible today over the northern
Sierra, potentially spreading into the northern San Joaquin Valley
this evening. Chances of showers and thunderstorms continue into
the weekend, mainly south of I-80. A pattern change is currently
projected for the middle of next week bringing cooler, potentially
wetter weather across Northern California.
&&
.DISCUSSION...
Delta flow earlier brought a thick band of low stratus clouds to
the Sacramento region northward toward Oroville and Chico.
Gradually increased mixing from the early May solar angle allowed
this band of clouds to burn off leading to mostly sunny skies
across the Valley.
Further east across the Sierra, diurnal heating in conjunction
with forcing from the retrograding upper low has sparked a few
thunderstorms over Tuolumne County. At this point they appear to
be locked to the terrain with heavy rainfall and lightning noted
in the MRMS data. Farther north, any capping issues have eroded
given the expansion of radar echoes stretching from Highway 50
southward along the western slopes of the Sierra. The latest RAP
objective analysis shows MUCAPE values in excess of 1000 J/kg over
the Sierra (mainly south of I-80) with more capping issues toward
the foothills and Valley floor. Thus, anticipate any storms moving
off the terrain to initially struggle to sustain their updraft
given downstream convective inhibition. However, will maintain the
threat for showers and thunderstorms across the northern San
Joaquin Valley through the evening hours as high-resolution
guidance has shown.
The other aspect of this "Inside Slider" is the modest wind field
on its western periphery. Maximum wind gusts thus far have been
around 30 mph observed at the Redding Municipal Airport (KRDD). A
Wind Advisory remains in effect for the northern Sacramento
Valley through 9 PM with north-northeasterly gusts possibly up to
35 mph in some locations. Closer to the Delta, Mesowest
observational data has shown sustained southwesterly winds around
20 to 25 mph with slightly higher gusts. Winds should maintain a
decent strength into the evening hours with occasional gusty
northerly flow continuing into early Friday afternoon.
Looking to Friday and into the weekend, much of the region will
dry out as the parent upper low continues its southward push into
the coastal waters of southern California by Friday afternoon.
With an upper ridge building to the north over the Pacific
Northwest, a rex block configuration sets up for the weekend. Net
mid/upper-level easterly flow will maintain daily shower and
thunderstorms chances for the Sierra. Coverage may be widely
scattered at times given the lack of meaningful perturbations in
the flow aloft. Regarding winds, it appears the Delta breeze kicks
up again over the weekend which would influence cloud cover
forecasts in its vicinity. Otherwise, the region can expect a warm
weekend with Valley highs in the low/mid 80s with perhaps near 90
degrees around Redding and Red Bluff. ~BRO
&&
.EXTENDED DISCUSSION (Monday THROUGH Thursday)
Ensemble solutions continue to support a shift in the synoptic
pattern along the West Coast. As the ridge/trough couplet will
have advanced into the Rockies by Monday, a broad longwave trough
centered between 150W-135W longitude should have an opportunity to
impact the state by mid-week onward. While the week begins dry
accompanied by slightly above average temperatures, conditions
will change during the middle to latter portion of next week. This
would favor increased cloud cover, decreasing temperatures, and
chances for showers and thunderstorms. Given deterministic
solutions continue to waver, ensembles will remain the best path
to follow. By next Thursday (May 16), the mean upper trough axis
is forecast to settle just offshore with the 12Z GEFS/ECMWF
ensemble means in near spatial agreement. Looking farther ahead,
the central/eastern Pacific flow becomes quasi-zonal which could
keep conditions wet somewhere along the West Coast into further
forecast periods. The Climate Prediction Center highlights above
average precipitation during the May 15-23 timeframe. ~BRO
&&
.AVIATION...
Mainly VFR conditions next 24 hours except local MVFR conditions
possible in showers or thunderstorms for areas south of I-80
through 03z Friday, and again over higher terrain south of I-80
after 21z Friday. Northerly wind gusts 20-30 kts northern
terminals through 03z Friday; increasing again after 14z
Friday.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 9 PM PDT this evening for Northern
Sacramento Valley.
&&
$$