Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/19/23
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
837 PM CDT Fri Aug 18 2023
.UPDATE...
Issued at 836 PM CDT Fri Aug 18 2023
No major changes expected for tonight, forecast is doing fine.
&&
.DISCUSSION...
Issued at 244 PM CDT Fri Aug 18 2023
Breezy southerly winds ahead of an approaching low and trailing cold
front will gradually diminish this evening from west to east.
Ridging aloft will be the dominant feature through the middle of
next week. This ridge will translate to well above normal
temperatures most days through Wednesday with highs climbing into
the 90s across much of the area. The one respite from the heat will
be a cold front that moves through on Saturday and the caa that
follows with the Canadian high that builds south. Transient
shortwave energy that moves through the flow concurrently with the
edge of the caa could set off a few showers and thunderstorms mainly
west of the James Valley, but no severe weather is expected. Highs
on Sunday will top out in the 70s to low 80s.
A mitigating factor for Saturday`s high temps could be some near
surface smoke as per the HRRR. The HRRR brings in a plume of thicker
smoke from north to south in the mid afternoon through the evening.
That could hinder daytime heating, especially north of Hwy 212.
The ridge begins to collapse on Thursday of next week with more
seasonable temperatures possible going into Friday. The majority of
the forecast period looks dry.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 611 PM CDT Fri Aug 18 2023
Terminals KABR,KATY,KPIR,KMBG
VFR skies/vsbys are expected through tonight.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...TDK
DISCUSSION...Wise
AVIATION...TDK
Area Forecast Discussion
National Weather Service Gaylord MI
1145 PM EDT Fri Aug 18 2023
.UPDATE...
Issued at 945 PM EDT Fri Aug 18 2023
Large area of strong high pressure is centered across much of the
Great Lakes region southward into the Ohio Valley late this
evening. Skies are mostly clear across this entire area thanks to
strong subsidence and dry air thru the column. Winds have become light/calm
as the high center builds overhead. Little will change as we head
into the overnight hours. Under clear skies...light/calm winds and
with a relatively cool airmass in place...overnight lows will cool
into the mid 40s to around 50 degrees.
&&
.NEAR TERM...(Through Tonight)
Issued at 335 PM EDT Fri Aug 18 2023
High Impact Weather Potential...none.
999mb surface low is departing across central Quebec, while a
ridge of high pressure extends north across Lake MI and central
upper MI. The pressure gradient between these features, though
relaxing, remains tight enough (aided by diurnal heating/mixing)
to generate gusty winds. Winds are gustiest in northern and
eastern areas. Those winds will quickly diminish this evening,
especially toward dusk, as vertical mixing ends and the pressure
gradient relaxes some.
Surface ridging gradually transits the region from w to e tonight,
and will be over Lk Huron Sat morning. 500mb shortwave ridging
will remain just upstream. Leftover diurnal cu will diminish this
evening, and be gone by sunset. A bit of cirrus will work in
western and central areas tonight. In addition, some smoke/haze
aloft will also increase. Not at all certain that surface vsby
restrictions will result; HRRR guidance brings a little haze into
parts of nw and n central lower MI overnight, and will let that
ride. Will also have a touch of fog in well-sheltered locales.
A chilly night by recent standards, with lows mostly in the 40s,
with some 50s along the Lake MI coast.
&&
.SHORT TERM...(Saturday through Monday)
Issued at 335 PM EDT Fri Aug 18 2023
High Impact Weather Potential: Low for now. Slight chance for
thunderstorms Sunday afternoon across parts of northern lower
Michigan.
Pattern Synopsis:
Impressive ridging encompassing most of the central CONUS will
amplify through the period as current Major Hurricane Hilary works
northward along the Pacific Coast and gets absorbed into the
pattern. Meanwhile, a closed upper-level low will pivot across New
England/Quebec through the first half of this weekend as shortwave
ridging slides overhead. This will keep relatively high pressure in
place across the region into Sunday before a cold front looks to
swing from northwest to southeast across northern Michigan. Surface
high pressure is expected to build back into the Great Lakes behind
this frontal passage on Monday.
Forecast Details:
Quiet weather is expected across northern Michigan through Saturday
night. Chilly temperatures in the 40s and low 50s look to quickly
warm on Saturday with southwesterly low-level flow advecting warmer
airmass northward across the area -- aiding high temperatures to
reach into the low 80s and even mid 80s across some areas south of
the bridge. Mild overnight temperatures in the 60s are in store for
Saturday night as enhanced southwesterly flow continues into Sunday.
Even warmer temperatures are expected Sunday afternoon, but how high
areas get will depend on the timing of the aforementioned cold
frontal passage. Should the cold front hold off swinging across
northern Michigan until the afternoon, areas ahead of the front look
to warm into the upper 80s and even low 90s -- particularly
northeast lower with downsloping winds. Slight chances for showers
and storms will also partially depend on frontal timing. While
confidence is certainly low at this time, a later frontal passage
would open the door for warmer temperatures as discussed above and
potentially better chances of breaking the cap in place ahead of the
front. Mid to upper-60s dewpoints would be in place with buoyancy on
the order of 1,500+ J/kg MLCAPE and deep-layer shear around 25-30
kts -- which would be sufficient to support strong thunderstorms. It
is reiterated that this chance is highly conditional and depends
heavily on frontal timing and storm initiation, which appears
unlikely at this time. However, slight chance PoPs are included in
the forecast across parts of northern lower to account for this
risk. Otherwise, high temperatures look to cool back into the 70s on
Monday behind the cold front with partly sunny skies.
.LONG TERM...(Monday night through Friday)
Issued at 335 PM EDT Fri Aug 18 2023
High Impact Weather Potential: Low for now
Dominant ridging will continue to grip much of the CONUS east of the
Rockies through the first half of next week as northwest flow drapes
across the Great Lakes and New England. Relatively high uncertainty
exists in rain chances through the period due to the impacts that
current Major Hurricane Hilary will have on the pattern once it gets
absorbed upstream. With that being said, current confidence is that
mainly dry weather will be in place across northern Michigan through
the first half of next week as surface high pressure continues to
build into the region behind the frontal passage discussed in the
short term. Better chances for showers and storms may return during
the second half of next week with southerly flow on the backside of
aforementioned high pressure advecting a more favorable airmass into
northern Michigan to support activity. Otherwise, high temperatures
look to be in the upper 70s and low 80s through most of the period.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1145 PM EDT Fri Aug 18 2023
High pressure centered south of Michigan will slowly slide
eastward thru the Ohio Valley over the next 24 hours. Strong
subsidence and dry air thru the column will maintain clear skies
and solid VFR conditions thru Saturday night. light/variable winds
overnight will become SW at 10 to 20 kts on Saturday.
&&
.MARINE...
Issued at 335 PM EDT Fri Aug 18 2023
Gusty nw winds on Lakes Huron and Superior will diminish this
evening, as high pressure transits the region from w to e tonight.
Winds will back and become southerly on Saturday behind the high.
Additional small craft advisories could be needed, especially
toward the northern tip of Lake MI.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&
$$
UPDATE...MLR
NEAR TERM...JZ
SHORT TERM...DJC
LONG TERM...DJC
AVIATION...MLR
MARINE...JZ
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
942 PM CDT Fri Aug 18 2023
.UPDATE...
Issued at 935 PM CDT Fri Aug 18 2023
While northern North Dakota reflectivities failed to produce much
for precipitation, showers and thunderstorms in eastern Montana
have been approaching the western North Dakota border this
evening. This activity is tied to a lower level front and
associated shortwave aloft, which may cause convection to persist
longer into western North Dakota than current convection allowing
models are advertising. Instability however is weak, especially in
western North Dakota. Convection in Montana has been producing
isolated strong wind gusts in an environment characterized by
steep low level lapse rates and high DCAPE. Low level lapse rates
are currently forecast to drop off near the North Dakota border,
which should subsequently cut off impactful thunderstorm
potential. Given the forcing associated with this activity
however, precipitation chances were extended a bit further into
western North Dakota than current guidance indicated, but with low
probabilities. Winds may become gusty with this convection, but
again the probability for this should fall off with the increased
capping in western North Dakota. Further updates may be needed if
convection overcomes the lackluster environment.
UPDATE Issued at 750 PM CDT Fri Aug 18 2023
Quick update to expire Heat Advisory as planned.
UPDATE Issued at 638 PM CDT Fri Aug 18 2023
Radar reflectivities are moving across northwest North Dakota this
evening, though without much sign of precipitation reaching the
surface. XWA radar and a few automated stations indicate ceilings
are mostly >10k ft, which given the very dry sub-cloud layer
measurable precipitation is very unlikely so far. As convection
develops in Montana and moves into western North Dakota, a very
isolated shower or thunderstorm is a bit more probable, but these
chances will remain low as instability also fades with sunset.
The Heat Advisory continues until 01Z. A few sites have heat index
values still around 100 F, but these conditions should gradually
improve this evening.
&&
.SHORT TERM...(This Evening through Saturday)
Issued at 343 PM CDT Fri Aug 18 2023
The main concerns for the short term period include hot and humid
conditions this afternoon, followed by windy and smoky conditions on
Saturday.
A longwave upper level ridge is located over the central CONUS early
this afternoon. At the surface, a warm front extending south from an
area of low pressure over southern Saskatchewan is moving east
across western North Dakota. Strong moisture advection is ongoing
ahead of the warm front, with dewpoints rising into the 60s across
central North Dakota. Behind the warm front, temperatures have risen
into the lower and mid 90s, but increased cloud may inhibit further
warming for most of the rest of the afternoon. The Heat Advisory
will remain in effect, though it now appears that the hottest
conditions will be focused over south central North Dakota where
dewpoints are around 65 to 70.
Most CAMs produce some widely scattered showers and thunderstorms
over the eastern half of Montana during the late afternoon and early
evening in response to mid level shortwave energy. Buoyancy over
western North Dakota is forecast to be virtually nonexistent, so any
upstream activity that crosses the border should be in the form of
very light showers or sprinkles given cloud bases around 10-15 kft.
The only concern with these showers would be the potential for
gusty winds.
The cold front attendant to the surface low moving east across
southern Canada will enter northwest North Dakota early Saturday
morning and track southeast across the state through the morning.
Some stronger cold air advection and pressure rises are indicated in
deterministic guidance, so could see some higher gusts to around 35
mph with the frontal passage. It will remain windy for most of the
day behind the cold front, with highs forecast to range from the mid
70s northwest to near 90 southeast. HRRR smoke modeling brings
thicker smoke aloft over the state later tonight into Saturday
morning and then mixes the smoke down to the surface across southern
North Dakota Saturday afternoon, which may result in visibility
restrictions and poor air quality.
.LONG TERM...(Saturday Night through Friday)
Issued at 343 PM CDT Fri Aug 18 2023
The main highlight for the long term period is high chances of rain
across western North Dakota Saturday night into Sunday, and across
northern North Dakota Sunday night into Monday.
Ensemble systems are consistent in keeping a large upper level high
over the Lower Missouri River Valley through the middle of next
week, resulting in southwest to quasi-zonal flow over the Northern
Plains. Two main pieces of energy are forecast to round the top of
the ridge and bring widespread chances for rain to parts of the
region through Monday. The first of these will arrive Saturday night
into Sunday. Both the highest rain probabilities and QPF are focused
over western North Dakota, but all of the state could see some
measurable rainfall. Thunderstorms are not likely, and
any lightning that does occur should be limited to south of
Interstate 94 as there is forecast to be no CAPE to the north. The
cooler air mass from the previous day`s front will remain in
place, and combined with the rain and cloud cover will likely
limit high temperatures to the mid and upper 60s on Sunday. The
second wave is more likely to bring rain to the northern half of
the state Sunday night into Monday. While the rain will likely end
across the north by Monday afternoon, high temperatures could
still be limited to the 60s there, with 70s and lower 80s likely
elsewhere.
Warmer temperatures are likely to return for Tuesday and Wednesday
as the upper ridge becomes more amplified. This would also favor a
period of dry weather before ensembles hint at a flattening of the
ridge by the end of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 638 PM CDT Fri Aug 18 2023
A very isolated shower or thunderstorms possible in western North
Dakota this evening, but probability at any one point is very low.
A front will move through the state Saturday morning, bringing
gusty northwest winds, with gusts to 20 to 25 kts in the
afternoon. Some wildfire smoke should also filter in on Saturday,
which may reduce visibilities at time.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...AE
SHORT TERM...Hollan
LONG TERM...Hollan
AVIATION...AE
Area Forecast Discussion
National Weather Service Billings MT
848 PM MDT Fri Aug 18 2023
.UPDATE...
With temps on their way down have cancelled the heat advisory for
our central and eastern zones.
As expected, unorganized convection capable of producing strong
and erratic winds impacted our region since mid afternoon. Line of
showers and embedded lightning has moved east of Miles City and
will exit southeast MT before midnight. A somewhat potent Canadian
cold front has moved into north central MT and will reach our
forecast area late tonight and early Saturday (approx timing at
Billings is 12z). Tomorrow will be a good 20F cooler than today
with developing N-NE winds. With so much Canadian smoke upstream,
will need to monitor surface conditions tonight behind the front.
Cannot rule out reduced surface visibility as upslope winds
develop tomorrow. The HRRR is suggestive of increasing surface
smoke thru the day.
JKL
&&
.DISCUSSION...
Through Saturday night...
Another hot day was observed with temperatures climbing into the
90s to lower 100s. A Heat Advisory remains in effect through this
evening. Moisture streaming in from the southwest brought periods
of clouds and light showers this morning. Isolated to widely
scattered showers and thunderstorms will lift north and east
through the area this afternoon and evening. Main threats will be
localized wind gusts to 60 mph along with brief heavy rain given
PWATs up to 1.25 inches. A cold front is on track to drop through
the area tonight bringing cooler conditions for Saturday, along
with some smoke from wildfires to the northwest, that could cause
some visibility reductions at times.
Highs on Saturday will range from the lower 70s to lower 80s,
coolest over the west. Another round of showers and thunderstorms
will move in from the south during the afternoon, persisting into
the overnight hours as southwest flow aloft sets up. PWATs will
again be high, 1.25 inches or higher, thanks to moisture streaming
in from the Gulf as well as from the southwest. Thunderstorms
will have the potential to produce heavy rainfall. That being
said, precipitation will be scattered in nature, and not everyone
will get rainfall. Current NBM probabilities of 0.25 inches for
Saturday through Saturday night range from 30-50%. STP
Sunday through Friday...
The extended period continues to feature a cool day Sunday with a
steep increase in atmospheric moisture through at least Tuesday.
This anomalous moisture will bring a risk for scattered, and
potentially heavy, showers/thunderstorms to the region through
Tuesday.
Precipitable water values will increase to near record levels
Sunday afternoon as Monsoonal moisture pushes in from the
southwest flow aloft and easterly winds advect plains/Gulf of
Mexico moisture in over the lower levels. This near record
atmospheric moisture anomaly will persist through at least
Tuesday. With this moisture, energy from and ahead of the remnants
of Hurricane Hilary will push north across the Western U.S.
Sunday through Monday rounding the upper level ridge to our east.
On Sunday, the initial push of energy will bring the best chance
(30-70%) for scattered showers and isolated thunderstorms across
our region. On Monday, the ridge is forecast to keep most of the
energy west of our area, limiting precipitation chances to our
western zones (15-40%). By Tuesday, the upper heights begin to
back off across our area allowing diurnal showers and
thunderstorms to return back across our area. However, general
energy to promote storm growth will be lacking. Any showers and
thunderstorms that do develop during this period will be capable
of tapping into the anomalous moisture to produce heavy rainfall.
One thing to note during this period, some uncertainty still
remains in the exact path and extent of energy from the remnants
of Hurricane Hilary. Should upper level energy become more
organized or shift, precipitation chances and coverage could
change. While the moisture decreases Wednesday through Friday,
limiting the heavy rain threat, we will continue to see chances
(20-40%) for afternoon/evening showers and thunderstorms these
days.
High temperatures Sunday are expected to hold in the mid 70s to
lower 80s with cloud cover and easterly winds in place. By Monday,
temperatures will increase into the 80s to lower 90s as the
remnants of Hurricane Hilary push winds to the south/southwest.
Tuesday will be warm with highs in the mid to upper 90s before
80s to lower 90s return for the rest of the week. Arends
&&
.AVIATION...
Isolated thunderstorms capable of producing 35-45 knot wind gusts
have moved east of KMLS as of 0245z, and will exit southeast MT
by 04z. VFR will prevail through the remainder of the night. A
Canadian cold front will arrive early Saturday bringing a shift to
N-NE winds. Slant-range visibility will be reduced tomorrow due
to wildfire smoke, and pockets of post-frontal reduced surface
visibility are possible (though confidence of this impacting a TAF
site is low at this time). By Saturday afternoon the chance of
showers and a few thunderstorms will increase from the south. JKL
&&
.PRELIMINARY POINT TEMP/POPS...
Sat Sun Mon Tue Wed Thu Fri
-----------------------------------------------------------
BIL 064/078 058/076 060/089 064/095 064/090 061/085 060/085
12/T 53/W 51/B 21/U 21/B 32/W 33/W
LVM 055/079 052/070 055/086 060/088 057/086 053/083 052/081
14/T 67/T 83/T 32/T 23/T 34/T 34/T
HDN 060/080 055/081 059/091 060/097 059/091 058/085 056/086
21/H 61/E 40/B 11/U 21/B 32/W 32/W
MLS 066/078 056/076 062/088 065/097 066/091 063/083 060/084
40/H 83/W 50/B 10/U 21/U 32/W 33/W
4BQ 066/081 060/081 062/093 067/098 065/092 063/085 060/083
20/H 71/E 30/B 10/U 20/U 42/W 43/W
BHK 064/078 053/071 056/085 062/095 064/090 059/083 056/081
30/H 73/T 40/B 10/U 11/U 32/W 33/W
SHR 061/082 056/083 059/092 062/096 060/088 057/082 055/082
02/T 61/E 20/B 11/U 21/U 33/T 54/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Red Flag Warning in effect until 9 PM MDT this evening FOR
ZONE 117.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Jackson MS
854 PM CDT Fri Aug 18 2023
...New MESOSCALE UPDATE...
.MESOSCALE UPDATE...
Issued at 854 PM CDT Fri Aug 18 2023
Rest of tonight...
Evening RAP & synoptic/00Z upper air analysis indicates mean
ridge, up to 596DM, centered over the Plains to ArkLaTex. As the
Great Lakes/CONUS longwave trough/frontal system swings east, the
ridge is progged to build east. With northerly mean low-level
flow & only around 1.2-1.6 PWs in evening regional soundings/GOES
East total PWs, moisture return aloft or into the low-levels
will remain at a minimum. This will keep more seasonable lows
around in the upper 60s northeast to low 70s. Some patchy ground
fog can`t be ruled out in cool spots in northeast MS but will be
very shallow at most. Updates are out. /DC/
&&
.DISCUSSION...
Issued at 222 PM CDT Fri Aug 18 2023
Tonight into Tomorrow:
Mostly clear skies and warming temperatures continue today into
tomorrow as the upper-level ridge builds east over the Mississippi
River Valley. Lowered dew points slightly through this afternoon,
with some of the driest air coinciding with hottest temps. Low RH
values and the above normal temperatures will exacerbate the drying
trend and fire danger concerns in southern/central MS and
central/northern LA, while also mitigating the worst heat stress
potential today. We have struggled to reach 105 heat index values,
but given the hot temps and no clouds for relief, will leave the
current Advisory in effect through this afternoon. Tomorrow, a
shortwave ridge axis pivoting around the core of the ridge will
boost mid-level heights and increase subsidence over our region. The
axis of greater 850mb temps will overspread northeast LA to southwest
MS, and have better confidence we should hit those 105 heat indices
tomorrow. A Heat Advisory will be in effect for tomorrow,
accordingly. /NF/
Sunday through Friday:
Hot and dry weather will be the primary concern throughout the
forecast period. Strong mid/upper level ridging over the southern
Plains with an accompanying surface high will continue will continue
strengthening across the ArkLaMiss region. As a result, impactful
heat and additional dry air will continue this weekend and well into
next week. Upper 90s to the low 100s F high temperatures can be
expected with heat indices ranging from 105-110F will be possible
throughout the area through early next week.
Influence from the strong high pressure has also resulted in the
lack of rain chances, however a stalled frontal boundary just
south of our coverage area has kept moisture confined to the Gulf
coast. This has also aided in minimal rain chances for us. With
the lack of moisture, relative humidity values range from 30-45%
area wide continuing fire weather danger concerns. We`ll continue
the current `Limited` risk for fire danger advertised in the HWO
through Monday. Numerous burn bans are in effect across the CWA.
Extra caution is advised with open burning.
Models continue to show the mid/upper ridge intensifying to 600 dam,
potentially bringing near record to record breaking high
temperatures late next week. Although, dry air will help with
daytime mixing of low level moisture, dangerous heat stress will be
possible as high temperatures are expected to climb to the low 100s
with heat indices ranging between 105-115F. Heat warnings and/or
advisories will be necessary with later forecast packages.
A tropical wave just north of Hispaniola is projected to move into
the western/central Gulf of Mexico early next week. As this wave
moves westward, the previously mentioned front will lift
northward slightly, possibly bringing light rain chances Monday
along/south the HWY 84 corridor. We`ll continue to monitor NHC`s
forecast on this feature.
&&
.AVIATION...
(00Z TAFS)
Issued at 642 PM CDT Fri Aug 18 2023
VFR conditions will prevail at all sites the next 24 hours. Other
than patchy ground fog in the northeast areas, no flight restrictions
are expected. Winds will be light & variable, generally under
10mph, through Saturday aftn. /DC/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 73 102 75 103 / 0 0 0 0
Meridian 70 99 72 100 / 0 0 0 0
Vicksburg 73 102 75 102 / 0 0 0 0
Hattiesburg 73 103 76 102 / 0 0 0 10
Natchez 74 103 77 102 / 0 10 0 0
Greenville 70 96 72 99 / 0 0 0 0
Greenwood 71 97 72 100 / 0 0 0 0
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Heat Advisory from 10 AM to 8 PM CDT Saturday for MSZ034-040-041-
047-053-054-059>064-072.
LA...Heat Advisory from 10 AM to 8 PM CDT Saturday for LAZ007>009-015-
016-023>026.
AR...Heat Advisory from 10 AM to 8 PM CDT Saturday for ARZ074-075.
&&
$$
DC/SW/DC
Area Forecast Discussion
National Weather Service Louisville KY
950 PM EDT Fri Aug 18 2023
.Forecast Update...
Issued at 950 PM EDT Fri Aug 18 2023
High pressure slipping from Indiana to West Virginia will bring us a
quiet night with mostly clear skies, light winds, and temperatures
falling into the middle and upper 50s. It will be over a week before
we see temperatures this cool again.
&&
.Short Term...(This evening through Saturday)
Issued at 310 PM EDT Fri Aug 18 2023
This afternoon... Very pleasant weather for a mid August afternoon
as we continue to see unseasonably cooler temperatures for this time
of year. Current mesonet data is showing highs hovering just below
80 for most of the region. So far this afternoon, satellite
indicates a narrow cu field has been developing across most of
central Kentucky, with the densest pockets of clouds being observed
in the eastern part of the state. Surface high pressure just to our
north is keeping conditions relatively nice dry. We should continue
to see light winds from the north until later this evening when
winds begin to shift eastward as the center of high pressure makes
it way east along the rust belt.
Tonight... Expect mostly clear skies and calm winds throughout the
night as the nearby high pressure will keep things fairly quiet and
dry. Guidance indicates some upper level clouds will start to make
their way into the region from the north early tonight but it should
clear out by early morning as the clouds continue south through out
the night. HRRR smoke guidance indicates some higher values of
vertically integrated smoke following this flow of upper level
clouds but it should have little impact on visibility and air
quality.
Tomorrow... Model soundings show that the surface high pressure and
subsidence should keep the region fairly dry. Fog should be confined
to mostly, rivers, lakes and valleys to our south and east where
there seems to be some lingering moisture. The slight cloud cover
overnight should not affect radiational cooling too much as low
temperatures in the 60s are expected early inn the morning with some
valleys across eastern kentucky seeing cooler temps in the upper 50s.
Winds throughout the day should remain calm and mostly easterly.
Expect highs in the mid 80s for most of the region.
.Long Term...(Saturday night through Friday)
Issued at 255 PM EDT Fri Aug 18 2023
-------------------------------------------------------------
Key Messages:
- Hot and dry conditions through forecast
- Heat indices ranging from the upper 90s to exceeding 100 degrees
approaching heat related headline criteria.
-------------------------------------------------------------
The next several days will be dominated by a strong anomalous 600 dm
500mb ridge centered over the central CONUS. This will result in dry
and hot weather conditions across southern IN and central KY. While
confidence remains high we will have highs in the mid/upper 90s
through the extended forecast the main challenge remains dew points
and the impacts this will have on heat indices and any potential
headlines that could be needed next week related to heat.
Given the recent wet weather we`ve had over the last couple of weeks
and the green vegetation (evapotranspiration) have continued the
trend to keep highs below the very warm GFS (100 plus MaxT) and
closer to NBM/EURO (mid/upper 90). Along the same idea of
evapotranspiration keeping daily highs in the 90s, it could also be
used in seeing high dew point values through the forecast. NBM
seemed to be a good blend of the models keeping dew points in the
low 70s for much of next week. As was mentioned in previous
discussion, puts max heat indices close to 105F each day. As for
headlines, after some discussion with neighboring forecast offices,
have decided to hold off on any issuances at this time but leaning
towards some heat related headline be it a Heat Advisory or
excessive Heat Watch being issued over the next couple of days.
Current forecast values do not look to break any daily record high
temperatures during the next several days as most of those values
are near or even over 100 degrees. The days where daily record highs
are not in the triple digits on (upper 90s) Tues and Wed for
Lexington and Louisville highs could be close but may still come up
short.
Subsidence over the region will help supress convective chances
while the northern and eastern extent of the ridge will place any
MCS track well to our north and east through the forecast period.
Models hint a slight break down of the ridge Thu and Fri with a
potential shortwave passing to our north but models continue to keep
highs in the mid/upper 90s for the end of the week.
&&
.Aviation...(00Z TAF Issuance)
Issued at 647 PM EDT Fri Aug 18 2023
Dry high pressure will drift slowly through the Ohio Valley during
this TAF period providing the region with mostly clear skies and
light winds. Can`t entirely rule out some patchy shallow fog at the
non-SDF terminals, but chances for prevailing sub-VFR vsbys are low
enough (10-20%) to keep out of the TAFs for now.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...13
Short Term...NMP
Long Term...BTN
Aviation...13
Area Forecast Discussion
National Weather Service Medford OR
843 PM PDT Fri Aug 18 2023
.DISCUSSION...
Thunderstorm activity continues this evening with most of the
activity in northern California. One of the storms did show some
strength just west of the Shasta Valley this evening and was
pretty close to severe based on some of KMAX`s base data. In any
case, the potential for thunderstorms will continue into this
evening with the high resolution ensemble forecast system
diminishing activity after 6Z. Smoke from area fires continues to
fill the atmosphere. A few plumes were seen on radar this evening
with a layer of smoke stratified above the office this evening.
No big changes to the forecast this evening with the exception of
updating the smoke forecast.
-Smith
&&
.AVIATION...19/00Z TAFs...Wildfire smoke and thunderstorms remain
the main aviation impacts tonight. A few storms will approach
terminals east of the Cascades and some outflow winds are producing
gusty winds near Klamath Falls. Otherwise, smoke will reduce
visibilities near the active fires in northern California. The HRRR
smoke model drops visibilities down to 1/2 mile in spots closer to
the fires, although farther away from the fires visibilities should
be higher and within MVFR thresholds.
The threat of storms continues into Saturday afternoon. The
probability of one cloud to ground flash within 25 miles of any
point is roughly 15 percent with 30 percent more likely around
Klamath Falls Airport(KLMT). Smoke may be a major issue on Saturday
as burnout and fire fighting operations introduce fresh smoke
into the atmosphere. Upper level flow around 9000 feet still
remains out of the south, so the smoke has the potential to impact
KMFR.
&&
.MARINE...Updated 830 PM PDT Friday, August 18, 2023...A thermal
trough will maintain moderate to strong north winds across the area,
with gales expected south of Port Orford and between 5 and 40 nm
from shore. Very steep and hazardous wind driven seas are expected
area wide through Saturday evening, then winds ease Saturday night
into Sunday. Conditions will remain hazardous to small craft through
the weekend, however, and very steep and hazardous seas will
continue beyond 10 nm from shore.
The thermal trough pattern gets disrupted early next week as the
remnants of Hurricane Hilary move into the region. This will bring a
period of relatively improved conditions late Monday into early
Wednesday. Gusty north winds look to return for the latter half of
next week and conditions may become hazardous to small craft at that
time. /BR-y/Hermansen
&&
.FIRE WEATHER...Updated 200 PM PDT Friday, August 18,
2023...Above normal temperatures will continue the weekend. Isolated
thunderstorm activity is expected to track north today across
Western Siskiyou County and into Modoc County to Lake or SE Klamath
County. As these temperatures break at the start of next week
humidities will begin to improve as well. In the mean time, the one
concern with humidities is for Saturday night. Light east flow will
develop that will bring some relative drying. The lowest any
guidance is showing is 40%, but that`s a worst case scenario, which
is still 10% above criteria. This should also be contained to mostly
just the peaks, with mid and even some upper slope sections still
seeing fair recoveries around 50-60%. Worse drying conditions are
expected in the central and northern Cascades from roughly The
Sisters north.
Next is the lightning forecast. There is ample instability to
suggest that even an isolated cell could produce a large amount of
lightning. Further supporting this is the SREF showing low
probabilities for 100+ CG strikes. As with the lightning activity
yesterday, storms should be wet. Under the cores we observed 0.25
plus inches of rain (some exceeding 1 inch), and this will be
expected again today.
Scattered storms are expected on Saturday across NorCal (20-35%) and
a 20-30% chance for isolated to scattered coverage east of the
Cascades. Along the Cascades and into the foothills of the Siskiyous
& Cascades of Jackson County has a 15-25% chance for isolated
thunderstorms. There should also be some showers mixed in and the
chance for rain is between 20-45%, highest in Modoc County.
Low chances for isolated thunderstorm coverage continue Sunday into
the start of next week. By this time in the forecast tropical
moisture will be coming into the region. With the influence of
tropical moisture comes a lot of uncertainty, so stay tuned for
details Monday onward besides that things will moisten up.
&&
.PREV DISCUSSION... /Issued 233 PM PDT Fri Aug 18 2023/
DISCUSSION...Looking at the big picture, we are basically
sandwiched in between the cutoff upper low off the California coast
and an upper trough moving into southern B.C./northern Washington,
which is resulting in a area of convergence/deformation zone. The
net result is a band of scattered to broken cloud cover is
orientated southwest to northeast in portions of Josephine, Jackson,
Douglas, northern Klamath and Lake County.
At the same time, smoke is pretty extensive in similar locations
noted above from the fires in northwest California. Instability and
sufficient mid level moisture exist for at least a slight chance of
thunderstorms later this afternoon and early evening for portions of
northern Cal and east of the Cascades. However given the extent of
the smoke, there could be a limit on the amount of storms because
the extent of the smoke will act to put a cap on the amount of
instability.
Even so, isolated storms cannot be ruled out and will be kept in the
forecast to the above mentioned areas. Dry weather is likely tonight
with smoke continuing to impact portions of the area, especially in
western Siskiyou County. However, some of the smoke models suggest
we could see improving conditions for Jackson, and Josephine county
as the afternoon progresses into tonight.
Any improvement in the smoke will be brief with smoke likely to
return to these areas during the day Saturday, and possibly
worsening Saturday afternoon.
In terms of thunderstorms Saturday, the cutoff upper low is expected
to inch closer to our area which will allow more monsoonal moisture
to get drawn up from the south into portions of northern Cal and
east of the Cascades. However, there there is some evidence
supporting increasing mid level moisture into portions of Josephine
and Jackson County. Instability and trigger is also sufficient for
thunderstorm development and it could end up being more widespread
in terms of coverage area compared to this afternoon. Also, some
evidence is supporting isolated storms pushing into portions of
Jackson and Josephine County late Saturday afternoon and early
evening and we added a slight chance to those areas. One thing of
note, some of the high resolution models suggest there could be
gusty outflow winds, especially east of the Cascades.
Thunderstorms will end early Saturday evening with convective
showers lingering Saturday night in southeast Klamath, Lake,
Siskiyou, and most of Modoc Counties.
Sunday into Sunday evening, the best chance for thunderstorms are
expected to be confined to east of the Cascades and northern Cal.
However, there is a better chance for these storms to produce
rainfall, some of which could result in brief heavy downpours.
Monday, is the day where we`ll start to get affected by the remnants
of Hillary. Basically the remnants of Hillary will get drawn up north
as it encounters the cutoff upper low Sunday night, with tropical
moisture moving into our area Monday. The general consensus among
the several of individual models that show the track of Hillary take
it into central Nevada which compared to the last few runs is
trending east. However, there are a couple of outliers that show a
track farther west. At any rate, there will be plenty of cloud cover
and it appears we`ll be on the west side of the track which will do
two things. One, keep the coverage of thunderstorms over a smaller
area, (right now, southeast Lake and most of Modoc County, with
showers or even steady precipitation elsewhere inland away from the
coast Two bring beneficial rain to the above mentioned areas.
Tuesday, the cutoff upper low will finally get drawn north into our
area as an upstream upper trough approaches. Showers and isolated
thunderstorm chances remain Tuesday, then we should encounter dry
and calmer weather by the middle of next week. -Petrucelli
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.
PACIFIC COASTAL WATERS...Hazardous Seas Warning until 11 PM PDT
Saturday for PZZ350-356-370-376.
Small Craft Advisory from 11 PM Saturday to 5 AM PDT Monday for
PZZ350-356-370.
Gale Warning until 11 PM PDT Saturday for PZZ356-376.
&&
$$
Area Forecast Discussion
National Weather Service Pendleton OR
858 PM PDT Fri Aug 18 2023
.EVENING UPDATE...Mostly clear skies across the forecast area this
evening, except for remnants of convective activity that developed
across south central OR. At the surface however, and barely
present on the nighttime fog microphysics satellite imagery, are
bands of smoke aloft that have originated from the fires burning
east of Eugene, OR as well as smoke making it`s way south from
fires in northern WA and in Canada. Winds will continue to weaken
across the forecast area tonight, with light to locally breezy
winds prevailing through tomorrow. However, winds will be turning
mainly from the north, with easterly winds developing along the
Cascade east slopes through tomorrow morning. On these winds will
come a layer of smoke originating from northern WA and Canada,
with impacts to air quality and visibility expected as it moves
across the region. HRRR near-surface smoke indicates that this
smoke layer will arrive as soon as midnight in the northern
portions of the forecast area, and by the afternoon across the
southern reaches, with the smoke layer persisting through at least
Sunday. Besides smoke, a monsoonal wave moving across southeastern
OR tomorrow will clip portions of central OR and the northeast OR
mountains, resulting in slight chances of isolated thunderstorm
activity in the afternoon and evening. Afternoon temperatures will
be in the mid 80s to lower 90s across much of the forecast area,
with 70s to lower 80s in the mountain zones. Lawhorn/82
&&
.PREV DISCUSSION... /issued 507 PM PDT Fri Aug 18 2023/
.SHORT TERM...Tonight through Sunday night...An upper trough
persists, and an associated cold front has moved across the
forecast area today. The cold front has now moved east of the
forecast area. The air behind the front is very dry, and warm, but
not excessively hot. The band of showers that was over the CWA
this morning has now moved to the east of the CWA. Temperatures
have risen to the mid 80s to lower 90s in areas where clouds have
cleared and in the mid 70s to mid 80s where clouds have lingered.
The air is very dry with RHs in some areas in the single digits
percent. This combined with windy conditions are creating critical
fire weather conditions. Red Flag Warnings are in effect for much
of the forecast area. Please see the Fire Weather discussion for
details.
Windy conditions will persist this afternoon and early evening
before diminishing to light winds overnight. The winds in the
Kittitas Valley will be the strongest...25-35 mph with gusts to 50
mph. As such, a Wind Advisory is in effect for the Kittitas
Valley until 9 PM PDT this evening (high confidence 90-100%).
There will still be some instability this afternoon and evening
from central OR to the northeast mountains, mainly south and east
of the Blue Mountains. There will be a 10-20% chance of
thunderstorms in these areas this afternoon and evening. Then
later tonight conditions will become stable with diminishing winds
and cooler temperatures than recently seen. Lows tonight will be
in the 50s to around 60 lower elevations, and in the 40s to lower
50s mountains.
On Saturday, the deterministic models and ensembles are in very
good agreement that the upper trough will retrograde, with a
closed upper low slowly moving north along the CA coast. This
will keep cooler temperatures over the forecast area than recent,
with still some moisture and instability in central OR to the
northeast mountains, along the SE border in the afternoon and
evening. There will once again be a 10-20% chance of afternoon
and evening showers and thunderstorms again in these areas. Winds
will be much lighter, except for locally breezy conditions in the
more wind prone areas through the Cascade gaps and areas along the
east slopes. Due to the light winds, there will be an increase in
smoke from regional wildfires that will fill into the forecast
area. If the smoke becomes thick enough, it may cause temperatures
to be held down a couple to a few degrees. High temperatures are
expected (80-90% chance) to be in the mid 80s to around 90 in the
lower elevations, and in the 70s to lower 80s mountains. Low
temperatures will be very similar to tonight`s low temperatures
with readings in the 50s to around 60 lower elevations and 40s to
mid 50s mountains. Winds will be light, which will not allow any
mixing of the smoke that will be entrenched over the CWA.
On Sunday, things become more interesting, as moisture begins to
increase from the south, mainly in southern and eastern portions
of the forecast area. The source of this moisture will be mostly
from monsoonal moisture from the southwest at first, and then
eventually moisture from the remnants of Hurricane Hillary, which
is projected to move north into the northwest USA by Monday. This
will have a potential to bring an abundant amount of rainfall over
eastern portions of the CWA in the extended period. The areas
most threatened will be eastern Grant County, southern Union
County and most of Wallowa County. There is still too much
uncertainty (confidence only 15-25%) of this occurring.
Therefore, will hold off for now on issuing any hydrology
highlights or statements.
High temperatures on Sunday will again be very similar to
Saturday`s highs, with readings in the mid 80s to around 90 lower
elevations, and 70s to mid 80s in the mountains. Winds will
continue to be light on Sunday, except for locally breezy winds in
the more wind prone areas. 88
.LONG TERM...Monday through Friday...The main weather challenge
in the long term period will be the extremely rare arrival of
tropical moisture from the remnants of Hurricane Hilary on Monday
and Tuesday and determining just how much rainfall will fall over
the eastern half of the forecast area, particularly over the
eastern mountains and Union and Wallowa counties.
Models are in excellent agreement Monday and Tuesday in having a
large ridge of high pressure from the Rockies to the east coast
while off the west coast, there will be a trough with a strong
closed low near Vancouver island and a weaker low off the central
California coast. The lows will pull moisture from Hilary northward
through Nevada into eastern Oregon and Washington and Idaho. The
ridge will prevent the moisture from moving further east. On Tuesday
the upper low near Vancouver Island will move ashore and then into
the southern Canadian Rockies Tuesday night with the main portion of
the moisture plume moving into Montana and Alberta. On Wednesday and
Thursday, models have some differences about the departure of the
low in Canada, whether the ridge expends westward into our area and
how the trough offshore redevelops. By Friday, the ECMWF and
Canadian have a front moving ashore and through the area while the
GFS has a much weaker front further north mainly in British
Columbia.
The Extreme Forecast Index highlights QPF Monday and Tuesday with
values of 0.85 to 0.91 centered over the eastern mountains. It also
has an impressive shift of tails of 2 to 5 on Monday and only
slightly lower on Tuesday. Wednesday continues to show a shift of
tail above zero though with a EFI value of 0.60. Temperatures also
show EFI values of -0.70 to -0.80 over the eastern mountains as the
rain is expected to keep temperatures cool.
As the moisture arrives Monday, precipitable waters will be 250
percent of normal over the eastern mountains and heavy rain is
expected over the mountains. From the Ochoco-John Day Highlands
northeastward through the Blue Mountains will get around 0.75" of
rain with 1" to 1.5" in Wallowa County. The Blue Mountain Foothills
will get 0.20" to 0.45" while the rest of the area will have less
than a tenth of an inch. These amounts will be highly dependent on
the track of the moisture and the current forecast leans more
towards the wetter GFS and Canadian solutions while the ECMWF has
the plume a little further east and has lighter amounts mainly over
Wallowa County. With this much rain falling, the potential is there
for flash flooding and debris flows over burn scars and this will
have to be watched closely as the event unfolds. Along with the
chance of rain, there will be enough instability for a slight chance
of thunderstorms over central Oregon and the Ochco-John Day
Highlands. Temperatures Monday will be in the 80s in the lower
elevations with lower to mid 70s in the mountains. Temperatures will
be down a few degrees from Sunday. Dewpoint temperatures in the
lower to mid 60s in the eastern half of the area on Monday will give
the air an unusually humid feel. This will improve only slightly on
Tuesday,
Tuesday again shows the chance for heavy rain over the mountains as
a frontal system moves through the area and taps into the lingering
moisture from Hilary. This time, models are in better agreement with
the ECMWF having the central low of the trough closer and therefore
being wetter than the other two models. Rain amounts will be lighter
with Wallowa County getting 0.50"-0.75", the rest of the mountains
0.25"-0.50" and 0.10"-0.20" in the northern Blue Mountain Foothills
while the rest the area has less than 0.10". The low will
destabilize the atmosphere further and the astern mountains will
have a slight chance to chance of thunderstorms.
Wednesday and Thursday will continue to have a chance of showers
over the eastern mountains though with much lighter amounts of less
than 0.10". The rest of the area will be dry. Thunderstorms will be
limited to a slight chance in far eastern Wallowa County on
Wednesday afternoon. Temperatures will be up slightly Wednesday then
a couple more degrees Thursday to the 80s with mid 70s to lower 80s
in the mountains. Friday will have another slight chance of rain
showers, this time over the Washington Cascades and eastern
mountains with very light amounts. Temperatures Friday will be
similar to Thursday. Perry/83
.AVIATION...00Z TAFs...Mostly VFR conditions are expected through
the period, however sites RDM/BDN will see MVFR to VFR conditions
prevail. For sites RDM/BDN, smoke impacts will continue to produce
periodic MVFR vsby due to wildfires to the west of the sites.
While smoke impacts continue at those sites, smoke spilling south
from fires in Canada and northern WA will impact most northern
sites by early tomorrow. Current expectation is for sites to drop
down to 6SM, with vsby down to MVFR conditions possible at sites
PDT/YKM/ALW/PSC tomorrow afternoon. While CIGs will mostly be
clear to few AOA 12kft to 25kft AGL through the period, smoke may
produce sct-bkn CIGS down to 2kft to 3kft AGL. Breezy winds 10 to
15kts with gusts up to 20kts possible at sites RDM/BDN/YKM/ALW/PSC
through this evening, becoming light overnight and tomorrow.
Winds at sites DLS/PDT of 12 to 20 kts with gusts up to 30kts will
be possible through this evening, becoming light overnight and
tomorrow. Lawhorn/82
.FIRE WEATHER...Red Flag Warnings will continue to be in effect
this afternoon and evening for the Lower Columbia Basin, Blue
Mountain foothills, Central Oregon (except for fire zone OR611),
the eastern Columbia River Gorge, the east slopes of the Oregon
Cascades, and the Yakima/Kittitas Valleys until 9 PM this evening
for winds and low RH. Winds will be at least 15-25 mph with gusts
to 35 mph this afternoon (except 25-35 with gusts to 50 in the
Kittitas Valley). RHs will be in the teens, with some single
digits (high confidence...80-90%). This combination of winds and
low RH will result in Red Flag Conditions in the above listed
areas. The strongest winds will be this afternoon until 5 PM PDT.
After that the winds will begin to diminish and RH`s will slowly
increase to above critical fire levels by late evening. RH`s will
be very low again on Saturday (10-20%), however, the winds will
be much lighter, which will result in non-critical fire
conditions on Saturday. On Sunday, similar conditions will exist
in western and northern areas. In the eastern and southeast areas
of the district, RH`s will be increasing as the monsoonal moisture
and moisture from the remnants of Hurricane Hillary begin to move
into the district from the south. 88
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 52 86 56 86 / 0 0 10 10
ALW 56 89 58 90 / 0 0 10 10
PSC 59 90 61 93 / 0 0 0 10
YKM 56 87 55 91 / 0 0 0 0
HRI 56 90 58 92 / 0 0 0 10
ELN 52 85 54 92 / 0 0 0 0
RDM 49 85 52 86 / 0 0 10 10
LGD 53 88 58 86 / 0 10 20 30
GCD 53 91 57 86 / 10 20 20 30
DLS 56 92 61 94 / 0 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...
WA...
&&
$$
EVENING UPDATE...82
SHORT TERM...88
LONG TERM....83
AVIATION...82
FIRE WEATHER...88
Area Forecast Discussion
National Weather Service Portland OR
207 PM PDT Fri Aug 18 2023
.SYNOPSIS...Onshore flow will transition to offshore flow this
weekend, bringing warmer temperatures as well as areas of smoke and
haze from wildfires burning across the region. Trending back towards
seasonable temperatures early next week as onshore flow returns and
areas of smoke/haze begin clearing the area from west to east.
Remnants of Hurricane Hilary will likely bring beneficial rain to
central and/or eastern Oregon Sunday night into Monday, however it
appears western Oregon and Washington will remain dry.
&&
.SHORT TERM...Friday night through Sunday night...Satellite and
surface weather observations from Friday afternoon depicted clear
skies across nearly all of northwest OR and southwest WA as surface
high pressure strengthened a bit over the area. An onshore flow
regime was keeping areas of smoke and haze from the Bedrock and
Lookout fires confined to mainly eastern Lane County and far eastern
Linn County. The westerly flow has maintained good air quality in the
Eugene area, however Oakridge was still experiencing degraded air
quality due to smoke.
That being said, changes are on the way Friday night into Saturday.
The deterministic NAM/GFS/EURO are all showing a "backdoor" cool
front moving southwestward from central/eastern Washington towards
Oregon while surface high pressure strengthens over the Columbia
Basin behind the front. At the same time, a thermally-induced surface
trough will remain along the northern California coast and
southern/central Oregon coast. This set-up will bring a transition to
offshore flow, which will result in relatively warmer temperatures
over the weekend along with increasing haze and smoke for northeast
to southwest. At this time, the HRRR Smoke model suggests all of
northwest OR and southwest WA will at the very least experience hazy
skies Saturday through Sunday due to upper level smoke coming mainly
from wildfires burning in Canada and Washington (except for localized
areas near the Bedrock and Lookout fires). However, it is unclear how
much of this smoke will mix down to the surface and potentially
degrade air quality. At this time, the HRRR Smoke model suggests at
least some smoke will mix down to the surface, but likely not dense
enough to result in drastically degraded air quality. However,
depending on how dense the upper level smoke layer becomes, high
temperatures may wind up at least a couple of degrees cooler than
expected. Therefore, decided to nudge the high temperature forecast
towards the NBM 25th percentile to bump down temperatures by a degree
or two. Nevertheless, it still looks to be quite warm on Saturday and
Sunday with widespread high temperatures in the upper 80s to lower
90s, except 70s at the coast. Aside from the heat, east winds around
5-15 mph are expected Saturday night through Sunday morning, except
up to 20-30 mph in the Columbia River Gorge. It appears the flow
regime will turn back onshore Sunday afternoon or evening, which will
set the stage for cooler temperatures Sunday night into Monday. -TK
.LONG TERM...Monday through Thursday night...All eyes will be on
now-category 4 Hurricane Hilary as we head into next week, as this
system will very likely impact southern California and Nevada with
heavy rain as it accelerates northward Monday and Tuesday. Latest
model guidance and the 2 AM PDT bulletin from the National Hurricane
Center maintain a track near western Baja California as the system
accelerates northward. The NHC is forecasting landfall of Hilary as a
Tropical Storm near San Diego Sunday night, with a rapid
deterioration of its circulation as it accelerates northward across
Nevada and into eastern Oregon. By the time Hilary gets as far north
as Oregon, it should be a largely disorganized mass of moisture-rich
air. While this may spell impressive rainfall for points to our south
and east, we will see little, if any rain, across SW Washington and
NW Oregon. As a result, NBM PoPs are only around 5-15%, highest over
the Cascades. This could certainly change if the track of Hilary`s
remnants end up further to the west, but as of right now only ~10% of
the latest ensemble guidance suggests a track that is far enough west
to bring beneficial rain to the Cascades.
Given the persistence of this pattern in guidance, it still appears
the most likely outcome would be to lock in seasonable temperatures
for southwest WA and northwest OR as associated waves of low pressure
pass east of the Cascades and lead to reinforcing surges of onshore
low-level flow. That said, much can change, especially considering
we`re dealing with a tropical cyclone that may have its sights on
southern California. -TK/Weagle
&&
.FIRE WEATHER...Main fire weather concerns are this weekend,
specifically from Saturday afternoon through at least Sunday morning.
On Saturday afternoon, model guidance is in good agreement that a
surface thermal trough will shift westward over the Cascades towards
the foothills and far eastern portions of the Willamette Valley. This
will result in increasing instability, and when coupled with the
expected critical relative humidities around 20-25%, may result in
plume-driven fire growth on existing fires. Concerns then linger
Saturday evening through Sunday morning as easterly winds develop
over the Cascades and increase to around 5-15 mph (thankfully not
overly strong, but just enough to warrant at least some concern),
strongest along the mid and upper slopes. In addition, poor overnight
humidity recoveries are likely over the Cascades Saturday night due
to a lowering subsidence inversion. Many locations in the Cascades
will likely see max RHs between 30-45%. It appears east winds will
weaken Sunday afternoon before winds transition back to westerly by
Sunday evening, which will bring some improvement. However, still
concerned for dry and unstable conditions on Sunday before onshore
flow returns late in the day.
Given all of these factors combined, have decided to maintain a Red
Flag Warning for the Cascades Saturday afternoon through Sunday
evening. Fire weather concerns are minimal early next week as stable
onshore flow returns to the area and relative humidities improve.
-TK
&&
.AVIATION...Predominantly VFR conditions are expected through the
forecast period. Along the coast, there`s a 40-50% probability of
MVFR ceilings returning after 08-10z Saturday, dissipating from
north to south 14-18z. North to northwest winds with gusts up to
20-30 kts forecast along the coast through 06z Saturday. Inland
areas will see winds increase to 10-15 kts with local gusts up to
20 kts 23z Friday to 06z Saturday.
Smoke/haze may be observed due to wildfires which could impact
slant-range visibilities.
KPDX AND APPROACHES...VFR conditions expected through the forecast
period. North to northwest winds increasing to 10-15 kts 23z
Friday to 06z Saturday. Otherwise, winds generally less than 10
kts. -HEC
&&
.MARINE...High pressure remains offshore with low pressure over
eastern Oregon and eastern Washington through the weekend,
causing tightening surface pressure gradients. Expect diurnally
driven northerly winds with periodically steep, wind- driven seas.
Gusts generally up to 20 to 25 kts possible through Saturday
morning, up to 30 kts in outer waters of PZZ273. Winds increase
Saturday with gusts up to 20 to 25 kts in the inner waters, 25 to
30 kts in the outer waters, lasting through Sunday. Seas 8 to 11
ft through the weekend.
Hurricane Hilary remains situated off of the coast of western
Mexico and is forecast to move north to impact Baja California.
Remnants of this system are forecast to move north along the
western US and into the Pacific Northwest early next week, which
could bring an enhancement of winds and seas to the waters off of
NW Oregon and SW Washington. -HEC
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 11 AM Saturday to 9 PM PDT Sunday for Mt.
Hood National Forest West of Cascade Crest-Willamette
National Forest.
WA...Red Flag Warning from 11 AM Saturday to 9 PM PDT Sunday for
Eastern Gifford Pinchot National Forest Mt Adams Ranger
District-Extreme South Washington Cascades and Foothills.
PZ...Small Craft Advisory until 5 PM PDT Saturday for Coastal waters
from Cape Shoalwater WA to Florence OR out 10 NM.
Small Craft Advisory until 5 AM PDT Sunday for Coastal waters
from Cape Shoalwater WA to Florence OR from 10 to 60 NM.
&&
$$
www.weather.gov/portland
Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland