Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/20/20
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
640 PM CDT Wed Aug 19 2020
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...VFR conditions are expected through the next 24 hours.
Leftover convective cirrus this evening will fade to cumulus
tonight and through tomorrow. Light winds overnight will become
moderate during the daytime.
&&
.PREV DISCUSSION... /issued 301 PM CDT Wed Aug 19 2020/
SHORT TERM (Tonight through Thursday Night): Currently, KBRO
radar is indicating some isold conv firing over Zapata and Jim
Hogg Counties with little or no movement. Daytime heating may help
maintain this isold conv for a few more hours with the pcpn
diminishing later this evening with the loss of the diurnal
heating. The latest HRRR run maintains this spotty activity over
the next few hours. Vsbl satl imagery doesn`t show much in the way
of CU development at this time, so believe that the current conv
should remain confined primarily to the western counties
throughout the early evening hours.
The short term NAM/GFS and ECMWF guidance shows relatively drier
and more stable air pushing into the region throughout Thurs and
Thurs Night. This should shutdown the conv chcs tomorrow afternoon
and evening. So will go close to single digit pops throughout
tomorrow and tomorrow night.
With a relatively dry atms prevailing throughout the short term,
expect high temps tomorrow to edge up a couple of degrees. The
most recent short term temp guidance from the NAM/GFS/ECMWF are
all in reasonably good agreement for maxes/mins through tomorrow
night and will stick pretty close to this blend.
LONG TERM (Friday through Wednesday):The mid-level pattern to
start the long term period is in good agreement with the model
guidance indicating ridging focused across the Desert Southwest
while a large trough stretches from the Ohio Valley across the
western Gulf of Mexico. With limited low-level moisture through
Saturday, fair conditions are expected with temperatures at or
slightly above average and generally rain free. The pressure
gradient at the surface gradually strengthens, resulting in the
return of a light to moderate onshore flow.
The most active portion of the long term forecast concentrates
during the early to middle of next week. The mid-level trough
located over the western Gulf of Mexico is expected to gradually
weaken and eventually lift out. With varying model solutions on
how quick this process occurs, results in higher uncertainty on
the evolution of the tropical wave across the Carribean (invest
97L). This disturbance continues to be closely monitored by NHC
and continues to feature a high chance (80%) of developing into a
tropical cyclone within the next 5 days. Additional uncertainty
exists with the disturbance, in regards to how quickly the
tropical wave may try to organize and consolidate into a low-level
circulation, and how much impact could land interaction have on
the disturbance. Overall, despite the models diverging with the
location and intensity of the tropical wave (possible tropical
cyclone) for early next week, will increase rain chances across
Deep South Texas with the prospect for an incoming influx of gulf
moisture. Some heavy rainfall could be possible but it remains
too early for any discussion on rainfall amounts. Into the middle
of next week, I have elected to continue to keep lingering rain
chances in the forecast. We will also keep an eye on the progress
of the tropical wave to the east of the lesser Antilles (invest
98L) as that tropical wave could advance into the eastern Gulf of
Mexico, as a potential tropical cyclone as well. The increased
moisture and cloud cover should help to lower tempeatures
slightly for the early to middle portions of next week.
MARINE (Tonight through Thursday Night)...Swell data from
Buoy020 shows seas offshore at <1 foot with other surface obs
near the coastline showing relatively light onshore winds. So
marine conditions do not geet much better than this. However, the
S-SE low level winds will likely return tomorrow as the PGF
strengthens a bit due to a little stronger surface ridging across
the Gulf of Mex. No SCEC/SCA conditions expected through Thurs
Night.
(Friday through Monday night): Light to moderate onshore winds
along with low seas are expected Friday through the majority of
the weekend with a modest but gradually strengthening pressure
gradient. Seas will then gradually build late Sunday through
the end of the forecast period as a tropical wave/low pressure
system advances from around the Yucatan Peninsula into the Gulf
of Mexico.
&&
.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL 75 95 77 94 / 10 0 0 0
BROWNSVILLE 76 98 78 97 / 10 0 0 0
HARLINGEN 74 99 77 98 / 20 0 0 0
MCALLEN 76 100 77 100 / 20 0 0 0
RIO GRANDE CITY 76 103 76 103 / 20 0 0 0
SOUTH PADRE ISLAND 80 88 81 89 / 10 0 0 0
&&
.BRO WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
This product is also available on the web at:
HTTP://WEATHER.GOV/RGV
Area Forecast Discussion
National Weather Service Peachtree City GA
737 PM EDT Wed Aug 19 2020
.PREV DISCUSSION... /issued 348 PM EDT Wed Aug 19 2020/
SHORT TERM /Tonight through Thursday Night/...
Primary concern in the short term period is heavy rainfall/
isolated flash flooding and diurnal convection. PW on KFFC morning
RAOB was only 1.3in and 19Z RAP analysis 1.4in over all but far SE
counties, yet deep convection in north GA so far today have been
very efficient and moving just fast enough for some training/
redevelopment with favorable orientation and boundary interaction.
PW progged to increase significantly to 1.75-1.85in this time
tomorrow. Only hope for not seeing enhanced heavy rainfall and
flooding threat is if clouds will diminish sfc heating and
instability, which is a strong possibility. Vertical wind shear
will be limited as well, so storms should be less intense
Thursday. Guidance also indicating that convection Thurs night
will persist past midnight, which is also very possible if deep
moisture materializes to the extent forecast. Tried to modify
max/min temps to decrease diurnal range but NBM max temps already
quite cool tomorrow.
SNELSON
LONG TERM /Friday through Wednesday/...
Wet weekend ahead as the long term picks up on Friday with stalled,
sheared PV anomaly and associated 500 mb trough axis still to the
west of the CWA. Broad ascent is forecast to continue to
overspread the region focused in part by any vorticity maxima
rotating around the trough as well as general WAA the the low
levels which will also be bringing in plenty of gulf moisture.
Models are supportive of likely or higher PoPs across the region
both Friday and Saturday, though final coverage details may be
influenced by mesoscale details, such as remnant outflow
boundaries and leftover cloudiness from previous day`s/overnight
convection, that courser global models won`t properly resolve.
700-500 mb lapse rates will remain rather lack luster on Friday,
though ample day time heating and marginal shear will support some
strong thunderstorm potential. Lapse rates improve a bit on
Saturday as colder core of trough is expected to rotate through
the CWA on its way to being absorbed within polar jet, making for
somewhat better CAPE profiles and decent shear profiles, so some
potential will once again exist for stronger thunderstorms across
the area, though plenty of uncertainty remains with regards to
timing as well as placement of aforementioned mesoscale features
that could disrupt the larger scale set up.
Trough begins to dissipate on Sunday as PV anomaly gets sheared
out between large, persistent western ridge and another ridge
sliding in from the Atlantic. Still, plenty of moisture will be
wrapping into the CWA thanks to being on the western flank of that
Atlantic ridge, so while PoPs may not be as prolific, still
expect typical summer like coverage across the north, and possibly
even better coverage to the south thanks to outflows and
seabreeze type fronts. Similar situation on Monday, though more
uncertainty begins to creep into the forecast. 12Z GFS shows
tropical wave moving into the gulf during this time period.
Location of this tropical wave will be highly dependent on how
organized current system over the MDR of the tropical Atlantic
becomes as well as details of the ridge sliding to the west over
the Atlantic. Will carry this uncertainty in the PoPs, though
still expect some coverage given tropical airmass will still be in
place across the CWA.
Lusk
&&
.AVIATION...
00Z UPDATE...
Line of TSRA sliding past ATL are terminals at this hour but still
affecting AHN which will require a continued TEMPO group. Feel
activity will remain north of CSG and MCN through this evening and
will not include any mention of TS there. A brief period of IFR
possible toward daybreak Thu and will continue the mention in the
TAF. Have converted the predominant TSRA to SHRA for Thu afternoon
and then a Prob30 for TSRA. Winds look to remain on the east side
and generally light.
//ATL CONFIDENCE...00Z UPDATE...
Medium on IFR potential.
High on remaining elements.
Deese
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 68 84 68 81 / 50 80 80 70
Atlanta 69 83 70 80 / 60 80 80 70
Blairsville 63 78 64 74 / 50 80 80 80
Cartersville 68 85 69 80 / 60 80 80 70
Columbus 70 88 71 83 / 50 80 80 70
Gainesville 67 82 68 79 / 50 80 80 70
Macon 70 87 71 82 / 50 80 80 60
Rome 67 85 69 81 / 60 80 70 70
Peachtree City 67 84 69 79 / 60 80 80 70
Vidalia 71 89 72 85 / 40 70 70 60
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...SNELSON
LONG TERM....Lusk
AVIATION...Deese
Area Forecast Discussion
National Weather Service Grand Rapids MI
731 PM EDT Wed Aug 19 2020
LATEST UPDATE...
Aviation/Marine
.SYNOPSIS...
Issued at 242 PM EDT Wed Aug 19 2020
- Less risk for rain into the weekend
- Turning warmer
&&
.DISCUSSION...(This evening through next Wednesday)
Issued at 242 PM EDT Wed Aug 19 2020
- Less risk for rain into the weekend
Trends in the models keep the surface high pressure system over
Southern Lower MI into the weekend. This will act to keep the
frontal zone north of the CWA. Later Sunday and into Monday a
weakening cold front tries to drop on down through the CWA...but
the models show warm air advection returning on Tuesday. Thus any
lift looks weak with this feature and POPs will be kept low for
now.
- Turning warmer
Warm air advection strengthens over the next couple of days with
the low level thermal ridge pulling in for Friday and Saturday.
Temps at 850 mb reach the upper teens and that will support above
normal temperatures. We could make a run at 90 those
days...especially over interior parts of the state.
Rather big differences show up next week with the High Res Euro
drawing a significant low level thermal ridge in for the middle
part of the week. Temps at 850 mb are shown to top 20 deg C Tue
into Thu making 90s a possibility. The GFS is more
conservative...about 5 degrees lower with the 850 mb temps. For
now we will continue to feature above normal temperatures as the
low level thermal fields continue to suggest ridging in the CWA.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 730 PM EDT Wed Aug 19 2020
Surface high pressure will continue to provide mostly clear skies
tonight and light winds. It would not be out of the question for a
little patchy fog as there was last night but given how sunny and
warm it was today seems any fog would be rather limited. I did not
put fog in any of the TAF but JXN would be the most likely to have
fog if there were fog.
On Thursday a warm front passes by well to our north, this may
lead to some mid clouds in our northern TAF sites but otherwise
expect southwest winds to develop around 10 knots. Winds will be
stronger over the northern TAF sites than the southern TAF sites
due the proximity of the warm front. Any associated convection
will be well north of the GRR CWA.
&&
.MARINE...
Issued at 730 PM EDT Wed Aug 19 2020
I will issue both a Small Craft Advisory and Beach Hazard
Statement for our northern 2 lake zones and adjacent county zones
due to 3 to 5 foot waves and 15 to 25 knot winds late tonight
into Thursday evening.
Given the high high pressure ridge south of Michigan and the
frontal zone over upper Michigan, the pressure gradient between
those to features will allow for stronger winds over central and
northern Lake Michigan. Looking at the NAMNEST, HRRR and ECMWF
all showed winds in the range of 15 to 25 knots with gusts near 30
knots from around 06z tonight till after 00z Friday. This should
build 3 to 5 foot waves and result hazardous beach conditions.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 2 AM EDT Thursday through Thursday
evening for MIZ037-043.
LM...Small Craft Advisory from 2 AM to 11 PM EDT Thursday for LMZ848-
849.
&&
$$
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...WDM
MARINE...WDM
Area Forecast Discussion
National Weather Service Medford OR
848 PM PDT Wed Aug 19 2020
.DISCUSSION...Satellite imagery is showing a few clouds here and
there across southern Oregon and northern California with
predominantly clear skies. Some of the fire weather imagery shows
the Crane Fire near Lakeview being somewhat active. Overall
humidities have started to rise and winds have started to
decrease, so have allowed the Red Flag Warning to expire at 8pm.
Overnight, mostly clear conditions are expected with maybe some
advancing cloud cover associated with a weak frontal boundary.
Overall, the forecast is in good shape; so no changes are needed
at this time. -Schaaf
&&
.AVIATION...For the 20/06Z TAFs...Along the coast and over the
coastal waters...Areas of IFR cigs in marine stratus over the
coastal waters will return to the coast this evening, getting into
the coastal valleys tonight. The stratus will then burn back to the
coast by Thursday afternoon, moving back onshore Thursday evening.
Inland...VFR conditions will prevail across the area through
Thursday, except for southwest Siskiyou County, which will see some
reduced visibilities due to smoke from the Red Salmon Fire. Winds
will be gusty east of the Cascades and in the inland valleys west of
the Cascades for the remainder of this evening, and again Thursday
afternoon and evening.
&&
.MARINE...Updated 830 PM PDT Wednesday 19 August 2020...Relatively
light winds and low seas will persist through Friday night. There
will be periods of poor visibility in low clouds and fog. A weak
front will move onshore Friday, then a thermal trough will develop
near the coast. This will bring increasing north winds to the
area beginning Saturday, with steep to very steep seas Saturday
through Monday.
&&
.PREV DISCUSSION... /Issued 317 PM PDT Wed Aug 19 2020/
SHORT TERM...Today through Sat. morning...Beginning in the west,
current satellite shows marine stratus on the southern sides of
Cape Arago and Coquille Point. South of Cape Blanco, marine
stratus has thinned and lifted slightly, but buoy cameras from
buoy 015 (off Cape Blanco) and 027 (just north Point St. George)
show sunlight struggling to break though. With the lack of strong
northerlies the stratus will remain in place and thicken overnight
to a fog.
To the east, satellite reveals a mixture of smoke and mid-level
cloud over Sikiyou and Modoc counties in N. Cal. and in the SE
portions of Klamath and Lake Counties. The latest HRRR smoke
suggests that smoke related impacts will be light for most areas,
except around Alturas in Modoc County. Around Alturas the HRRR
smoke shows moderate amounts of surface smoke, but air quality
issues should remain low. The fires to our north and south have
enjoyed an active burning day, so we will continue to monitor
smoke and air quality issues closely. The thickest smoke, from the
S.F. Bay area, is being directed more NE towards Reno at the
moment and is helping to limit smoke impacts in our area.
Friday morning, a low off British Columbia will drag a front
through our area. The recent dry conditions will not favor
chances for much measurable rain as the front will struggle to
penetrate the current airmass. However, GEFS and Ecmwf members
have been holding on to rain further down the coast and is a sign
that this is not a totally weak front. Yet, the only places
expected to receive measurable rainfall are from Bandon north
along the coast. Inland, it is not anticipated much rainfall will
occur and have cut off measurable amounts along a line from Elkton
to Myrtle Point. This still seems unlikely, but have added
drizzle to the forecast along ridges in the coast range and as far
east as Diamond Lake, where upslope flow may aid to wring out
some moisture. May cut back on these areas if models dry out, but
there are enough ensemble members with decent mid-level moisture
to keep this element for the time being.
Friday evening, the momentum from the front will carry the winds
east of the Cascades, creating breezy surface conditions in
valleys and along ridges. We will also experience cooler night
time lows than have been recently occuring and is actually
approaching the climatological norms in northern half of our
forecast area, roughly from Medford north, excluding the Cascades
east. -Miles
LONG TERM...WITH THE FRONT DEPARTING, AREAS OF FOG COULD DEVELOP IN THE COASTAL
VALLEYS AND INTO POINTS OF THE UMPQUA BASIN ON SATURDAY MORNING.
THINGS START TO QUIET DOWN AFTER THE COLD FRONT MOVES EASTWARD AND
DRIER AIR FILTERS INTO THE AREA DURING THE DAY ON SATURDAY. ZONAL
FLOW ALOFT BEGINS TO TAKE SHAPE IN THE MID-TO-UPPER LEVELS OF THE
ATMOSPHERE. THIS WILL KEEP TEMPERATURES RIGHT AROUND NORMAL FOR THIS
TIME OF YEAR ACROSS THE AREA. TEMPERATURES WARMUP SLIGHTLY ON SUNDAY
AND CONTINUE TO DO SO INTO NEXT WEEK AS A THERMAL TROUGH BEGINS TO
SET UP SHOP ONCE AGAIN ACROSS THE SOUTHERN OREGON COAST.
OUR FOCUS TURNS TO THE BEGINNING AND MIDDLE OF NEXT WEEK AS A
TROPICAL SYSTEM WILL MOVE NORTH OUT OF THE TROPICS AND MAKE ITS WAY
TOWARDS THE CHANNEL ISLANDS OFF THE CALIFORNIA COAST. SOME OF THE
GUIDANCE HAS THE SYSTEM LOSING MOMENTUM AND SLOWING DOWN BECAUSE OF
HIGH PRESSURE MOVING IN FROM THE WEST INHIBITING ANY FURTHER
MOVEMENT. THERE IS STILL A LOT OF UNCERTAINTY IN MODEL GUIDANCE ON
HOW MUCH THIS SYSTEM WILL IMPACT THE AREA. THAT BEING SAID, IF ANY
EXTRA MOISTURE AND ENERGY MAKES IT TO THE REGION, SHOWER AND
THUNDERSTORM CHANCES WILL INCREASE. WE WILL CONTINUE TO MONITOR
THIS SYSTEM OVER THE NEXT SEVERAL DAY AS IT BEGINS TO MAKE ITS
NORTHERLY TRACK.
-ROGERS
MARINE...Updated 200 PM PDT Wednesday 19 August
2020...Relatively light winds and low seas will persist through
Friday night. There will be periods of poor visibility in low
clouds and fog. A weak front will move onshore Friday, then a
thermal trough will develop near the coast. This will bring
increasing north winds to the area beginning Saturday, with steep
to very steep seas developing over the waters Saturday through
Monday.
FIRE WEATHER...Updated 200 PM PDT Wednesday 19 August 2020...
The main concern into this evening will be gusty winds and low
relative humidity and a Red Flag Warning remains in effect for this
until 8 pm pdt.
An upper trough will move into the area later tonight and bring
cooling for most interior locations Thursday and slightly higher
relative humidities. Gusty winds are still expected both Thursday
and Friday afternoon and evening east of the Cascades. Were not
expecting Red Flag conditions to be met during this time, but it`s
something we`ll likely highlight in the fire weather forecast.
The threat for thunderstorms is zero through the weekend.
Friday, a weak front will brush by north of our area, but could not
rule out intermittent light rain in fire zones 615 and northwest
616, but amounts will probably be in the order of 0.01 to 0.03 of an
inch of rain, if anything. The main effect will be cooler
temperatures over most of the area and higher relative humidities in
the afternoon.
A west to southwest flow remains over the area Saturday into Sunday.
However the four corners ridge will slowly inch it`s way into our
area bringing a return to hotter temperatures and lower relative
humidity. Winds during this time are not expected to be a concern
(in terms of critical fire concerns).
Monday will warrant close watching. We`ll be keeping a close eye on
the track of Hurricane Genevieve. Because of the strong four corners
ridge, the general consensus is for this to move northwest, then
north up along the California coast by the start of next week. This
could bring another round of moisture and increasing instability
into the southeastern part of the area as early as Monday afternoon,
thus increasing the threat for thunderstorms. Right now, we do not
have anything in the forecast, but that does not mean the chance is
zero. It`s a small chance. Part of the reason we have nothing in is
because it`s still a long ways out and details are likely to change
over time. -Petrucelli
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.
CA...None.
Pacific Coastal Waters...None.
$$
Area Forecast Discussion
National Weather Service Pueblo CO
246 PM MDT Wed Aug 19 2020
.SHORT TERM...(This evening through Thursday)
Issued at 242 PM MDT Wed Aug 19 2020
The upper level high will be centered over northern AZ tonight and
central AZ on Thu. This evening, a disturbance will move thru the
flow aloft over eastern CO and could enhance the thunderstorm
chances. The HRRR shows the potential for a line of storms coming
off the eastern mtns early this evening and across El Paso and
Pueblo Counties, with the possibility of some stronger cells in
these areas. The line is then forecast to work its way east across
the plains through the rest of the evening and maybe into the late
night hours, although the HRRR generally shows weaker storms over
the far southeast plains. The 18Z run of the NAM Nest shows a
similar trend, but after 04Z shows some stronger isolated cells over
the far southeast plains through about 06-07Z. Over western areas
the models just show some weaker isolated to scattered
showers/storms. SPC continue to show a marginal risk of severe
storms over the I-25 corridor and southeast plains, with the main
risk being strong wind gusts. However, cannot rule out a storm or
two producing hail one inch in diameter.
Thursday looks similar to today, with another disturbance moving
over eastern areas and enhancing the chances for storms. The
forecast models show limited shower/storm activity, but still some
isolated to scattered storms should develop. Over eastern areas, it
looks like storms will form over the mtns in the early to mid
afternoon, with the potential for a line of storms moving across the
I-25 corridor in the late afternoon and/or early evening and then
progressing across the eastern plains through the evening. The
eastern mtns and plains are again under a marginal risk for severe
storms for Thu, with severe wind gusts being the main risk. However
a couple stronger cells could produce hail around one inch in
diameter.
If stronger storms move over the Decker, Hayden Pass, Junkins, or
Spring burn scars, there could be a flash flood risk this evening
and again Thu afternoon/evening.
.LONG TERM...(Thursday night through Wednesday)
Issued at 242 PM MDT Wed Aug 19 2020
Thursday night the remains of existing showers and thunderstorms
should drift southeast and quickly move out of our area. Although
insolation and instability should be somewhat weakened by that point
in the evening, storms encountering more favorable conditions could
still potentially produce wind gusts over 50 mph and some hail.
More isolated thunderstorms are expected in the afternoon Friday
through Monday, with moisture and northwest flow aloft mainly driven
by the upper-level high to the west. Light easterly upslope flow
will continue to supply the low-mid levels with moisture through the
Friday night , although most of the convective activity will remain
over the higher terrain. Given the weaker steering flow at higher
levels, a few storms could potentially move over I-25 by the time
evening comes around, but the storms should quickly move south and
out of our area. A few strong to severe storms are still possible,
and more organized storms could produce winds near 60 mph and hail
up to an inch in diameter. Monitoring for flash flooding over burn
scars will be the primary concern.
The weekend should be slightly drier as flow turns more westerly
aloft, but some chances of convection still exist over the mountains
in the afternoon-evening hours. While storm motions should be
relatively slow, a main concern will be monitoring for new fires
started by lightning strikes in areas with no precipitation,
especially with less moisture at lower levels.
Monday through Wednesday will see a transition in the synoptic
pattern as an upper level trough sets in from the northwest by
midweek, displacing that persistent high pressure and bringing some
southwesterly flow into the region. A cold front will likely drop
south across the plains by the end of the day on Wednesday, bringing
some more moisture and increased chances for convective activity
across our area during late afternoon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 242 PM MDT Wed Aug 19 2020
Thunderstorms will be possible at KCOS, KPUB and KALS this evening.
The main storm risks will be strong outflow wind gusts and possibly
brief heavy rain which could temporarily lower ceilings and
visibility. It looks like chances for storms at the terminal
forecast sites will decrease or end by about 02Z. Storms will again
be possible at the three sites Thu afternoon and evening. Otherwise
VFR conditions are expected.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...28
LONG TERM...GARBEROGLIO
AVIATION...28
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
945 PM EDT Wed Aug 19 2020
.SYNOPSIS...
A pair of fronts will weaken over the Southeast and Carolinas
through Thursday, while high pressure otherwise builds across the
middle Atlantic.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 945 PM Wednesday...
00Z surface analysis and radar trends indicated a the primary
trough/front has been aided south into the southern Piedmont and
coastal plain by fairly vigorous but non-severe convection this
evening. scattered showers also continue to develop along outflow
over the NE Piedmont. Aloft, the positive trough continues to sink
into the lower MISS Valley, with a few disturbances in the SWrly
flow over the SE states evident in water vapor. The most notable
disturbance is off the N FL coast, and the RAP suggests this will
lift along the Carolina coast late tonight and early Thursday. The
00Z GSO and MHX raobs were still fairly uncapped. Given the
presence of the frontal zone/outflows and some ripples in the SW
flow aloft, will maintain some slight chance to chance POPs for most
of the night, with radar trends suggest the ongoing NE Piedmont
convection likely to shift west toward the NW Piedmont. patchy fog
and stratus are possible by sunrise, most likely from the Triangle
to the NE behind the early outflows. Lows 67-71
&&
.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 345 PM Wednesday...
Downstream of the record-breaking sub-tropical ridge over the
Southwest, a mid-upr level low will develop and become generally
stationary over the lwr MS Valley through Thu night. Light swly flow
will result downstream across cntl NC, between that trough/low and
another subtropical ridge expanding from the sw Atlantic to the
Carolinas. Weakly rising heights and light swly flow will result
through the mid levels over cntl NC.
At the surface, a trough/front is forecast to extend from the cntl
and srn NC coast wswwd to a weak low over cntl NC, while high
pressure ridges across the middle Atlantic. Prevailing ely flow and
associated cooler than average temperatures in the lwr-mid 80s will
result over cntl NC, with a related good chance of overnight
stratus. Lows again 65 to 72.
Although the column overall will moisten in the aforementioned swly
flow aloft, to around 1.7-2.0", the wwd expansion of the subtropical
ridge will likely limit convective coverage to generally scattered,
to locally numerous. The increasing deep layer moisture and only
weak flow aloft will limit downdraft intensity and risk of severe
wind gusts. Instead, localized, mainly urban and poor drainage
flooding will be possible from slow-moving convection.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
As of 355 PM Wednesday...
Very little change to the overall weather pattern through the
extended forecast period. Central NC will remain on the NW periphery
of the Bermuda High, with a trough sitting over the MS/TN Valley.
The high over the Desert Southwest will remain in place through
Wednesday. The trough to the west will weaken with time this weekend
before shifting eastward through the mid-Atlantic early next week.
The southerly return flow around the high/ahead of the trough will
continue to advect warm air in to the region. Temperatures will
moderate back to normal by the weekend, with highs in the upper 80s
to low 90s and lows in the upper 60s to mid 70s. The RH percentages
should decrease into the 60s over the weekend, dropping into 50s
across by early next week. Best chances for diurnal convection will
be across the south and west Friday and Saturday, with decreasing
chances and coverage expected thereafter.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 745 PM Wednesday...
Scattered SHRA/TSRA will continue through this evening over portions
of the Sandhills, NE Piedmont and northern Coastal Plain. Reduced
vIS to 1 SM or less, gusty and erratic winds to 30 mph, lightning
and strong up/down drafts are expected near storms. Stratus and fog
will develop late tonight through early Thu creating areas of
IFR/MVFR ceilings and VIS, with the relative highest probability of
occurrence at RDU, FAY, and RWI. Scattered SHRA/TSRA will develop
again Thu afternoon-evening.
Outlook: Late night early morning stratus and fog is possible
through early next week, and the coverage of storms will gradually
decrease by this weekend.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...MWS
NEAR TERM...bls
SHORT TERM...MWS
LONG TERM...KC
AVIATION...JJT
Area Forecast Discussion
National Weather Service Reno NV
223 PM PDT Wed Aug 19 2020
.SYNOPSIS...
Smoke and wind are the main impacts the next couple days with a
few thunderstorms across Mono and Mineral Counites this evening.
Some cooling overnight will provide relief from the heat for the
end of the week. After a couple dry days, thunderstorms may return
to the eastern Sierra and western Nevada by Sunday.
&&
.SHORT TERM...
Temperatures will cool the next couple days as low pressure off
the Pacific northwest coast pushes the ridge east for a couple
days. Unfortunately the low is going to maintain a west to
southwest flow the next couple days, driving smoke from the
northern CA wildfires into the Sierra and western NV. While
wildfire smoke dispersion is a challenge to predict, as long as
there are large active wildfires across northern CA, we are going
to be vulnerable to smoke and unhealthy air quality for the
foreseeable future.
Current smoke plume over the Sierra and western NV should shift
east, bringing some relief this evening but additional smoke will
move into the Sierra and western NV around 10 pm. If you are
trying to cool your home tonight, remember to close the windows
before heading off to bed. HRRR Smoke is predicting dense smoke
and poor air quality by early Thursday AM.
Showers and thunderstorms have built over Mono and Mineral
Counties early this afternoon. Expect some gusty outflow winds
over 50 mph, brief heavy rain and hail through 9 PM. Brong
.LONG TERM......Saturday through Wednesday...
Some changes were made to increase t-storm chances for Sunday PM
through Monday, including possible showers for Sunday night.
Overall, above average temperatures are likely to continue, but
not quite as hot as our recent heat advisory event.
For this weekend, Saturday still looks dry with typical afternoon
zephyr breezes, as high pressure remains centered over the
southwest US. This ridge isn`t quite as intense as this week
(500 mb heights around 594 DM after peaking over 600 DM) so while
we continue to stay on the warm side (highs mid-upper 90s for
lower elevations, mid- upper 80s near the Sierra), record highs
and heat-related headlines are unlikely.
Sunday through Monday look more like a return to thunderstorm
activity, as another trough approaches the Pacific Northwest.
Meanwhile, a push of moisture from the southwest US could combine
with remnant tropical moisture from Hurricane Genevieve. The time
frame may fluctuate depending on the track of the hurricane, but
overall the best chances for thunder appear to remain south of
US-50 Sunday afternoon. The moist air mass with warmer overnight
temperatures may be capable of keeping some shower activity going
through Sunday night/Monday morning. Then for Monday afternoon as
instability increases, the chances of thunder look more favorable,
with storms possibly advancing farther north.
Tuesday is a little more of a wild card for thunder chances, as
some model guidance showed one final shortwave passage which
could kick up a few afternoon storms, while others dry things out.
For now, we will keep a low end possibility of thunder south of
US-50, but may need to add some thunder chances for northeast CA,
northwest or west central NV if more of the ensemble data trends
toward the higher instability scenario. There is somewhat better
agreement for Wednesday being dry so we will not include any
thunder chances. For both days, temperatures look to ease down a
bit to the lower-mid 90s in lower elevations/80s near the Sierra
with modest afternoon zephyr breezes. MJD
&&
.AVIATION...
Reduced visibility due to wildfire smoke will impact much of the
Sierra and western NV through at least Thursday. Visibility may
drop below 1 mile at times.
Winds will remain gusty this evening with mountain wave turbulence
east of the Sierra Crest. Winds may be a bit slow to diminish
tonight and should turn gusty once again in valleys by late
Thursday morning. Brong
&&
.FIRE WEATHER...
Gusty west to southwest winds on track for critical fire weather
conditions through at least 9 PM this evening. Jet stream will
pass over the Sierra tonight, which may allow winds to stay gusty
on mid and upper slopes past 9 PM.
Newest addition to the forecast is another period of red flag
conditions with gusty afternoon and evening winds along the Sierra
Front Thursday afternoon and evening. Winds will also be gusty
across eastern Lassen and northern Washoe, but appears wind speeds
will remain just below red flag conditions. Humidity is looking
rather low the next couple days with very minimal overnight
recovery, which is typical for mid-August. Brong
&&
.REV Watches/Warnings/Advisories...
NV...Red Flag Warning until 9 PM PDT this evening NVZ420-423-458.
Red Flag Warning from 2 PM to 9 PM PDT Thursday NVZ420-421.
Lake Wind Advisory until 9 PM PDT this evening for Washoe Lake
in NVZ003.
Heat Advisory until 11 PM PDT this evening NVZ001-003>005.
Dense Smoke Advisory until 11 AM PDT Thursday NVZ002-003.
Lake Wind Advisory until 9 PM PDT this evening NVZ004.
CA...Red Flag Warning until 9 PM PDT this evening CAZ270-271-278.
Dense Smoke Advisory until 11 AM PDT Thursday CAZ071-072.
Lake Wind Advisory until 9 PM PDT this evening CAZ071.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno