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Office: MFR

FXUS66 KMFR 170409
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
909 PM PDT Tue Aug 16 2022

.DISCUSSION...Water vapor and IR satellite imagery is showing
moisture returning from the south on the western periphery of
high pressure aloft, which is centered over the Great Basin. Most
of this moisture is elevated and therefore, not causing much
notable here at the surface. However, there were a few pop-up
showers on radar earlier this evening across SE sections of CWA,
one of which managed to produce in-cloud lightning near Macdoel.
This wasn't shown by traditional ground-based lightning networks,
but rather the satellite based geostationary lightning mapper or
GLM. We're not expecting much activity tonight since instability
is fairly weak, though there could be some sprinkles/virga out
over the East Side.

The warmest air aloft will move in over the area tomorrow. So,
Wednesday will likely be the hottest day of the week. Heat
advisories are in effect, so please read and heed. Try to avoid
being outside during the hottest part of the day, but if you must
be outside, wear loose-fitting light colored clothing, stay
hydrated and seek out ways to cool off -- escape to an air-
conditioned building, jump in a cool pool/lake, or perhaps just
relax in front of fan for a few minutes (hours?). One thing that
could be a wild card with the heat is the moisture advancing
northward from the Sierra. Some guidance is showing quite a bit of
cloud cover with this, which could put a cap on the heat if the
clouds arrive soon enough and are widespread enough. Areas on the
periphery of this cloud cover, where it is sunniest the longest,
will become the most unstable on Wednesday. While just about
everywhere, except the coast will have a chance at showers and
thunderstorms, models are indicating best instability from western
Siskiyou County up into Jackson/Josephine and eastern Douglas
County. We've maintained the POPs/Wx forecast as is and will let
the night shift digest the 00z model runs to see if any
adjustments are necessary with the thunderstorm areas. -Spilde

&&

.AVIATION...17/00Z TAFs...Along the coast, areas of LIFR to IFR are
expected to return from Cape Blanco northward and near Brookings
this evening and persist into Wednesday morning. Inland, VFR
will persist into Wednesday afternoon. Additionally, gusty and
erratic winds and possible in the afternoon as isolated to
scattered thunderstorms develop across inland areas. -CC/Sven

&&

.MARINE...Updated 800 PM PDT Monday, 15 August, 2022...
A thermal trough near shore will weaken with north winds gradually
decreasing Wednesday into Wednesday night. However, seas are
expected to remain steep through Wednesday evening. The lower winds
will be short-lived, late Wednesday into Thursday evening, and
stronger north winds are likely to return Friday into Saturday
evening, especially south of Cape Blanco. -CC/Sven


&&

.PREV DISCUSSION... /Issued 244 PM PDT Tue Aug 16 2022/

DISCUSSION...A mostly clear and warm day across the region...with
temperatures generally a few degrees warmer compared to this time
yesterday. Clouds are beginning to build across Modoc...eastern
Siskiyou...and southern Lake counties...the locations which are
most likely to see a stray shower or thunderstorm this afternoon.
The short term models continue to indicate that if we do see any
precipitation...it will generally be in Modoc county. If showers
and thunderstorms do develop...expect dissipation this evening.

Upper level high pressure continues to nudge west over Oregon this
afternoon and is expected to continue its westward track...with
the ridge axis centered generally over Lake and Klamath counties
by tomorrow afternoon. Tomorrow is expected to be the warmest day
of the week...especially for the west side...with high
temperatures generally 10 to 15 degrees above normal for mid
August. For Medford...the NBM is indicating a 56% chance of
temperatures at or above 105...which is the current forecast.
Temperatures are expected to cool by a few degrees on Thursday.
Either way...it is going to be hot...don't forget to drink plenty
of water...avoid exercise or outdoor activities during the hottest
part of the day...and wear light colored...loose fitting
clothing.

In addition to our hot weather tomorrow...thunderstorm chances
increase early tomorrow...with showers and thunderstorms entering
our southern counties sometime generally between 12z and 16z.
Thunderstorms will spread northeast impacting much of the
area late morning into the afternoon hours...mainly along and
east of Josephine and the eastern half of Douglas counties. There
isn't much moisture associated with these showers...so we will
likely see quite a bit of virga and the possibility of dry
lightning. For more information on our fire concerns...please see
the fire weather section of the discussion below.

Thunderstorm chances continue...but shift east...late Wednesday
into Thursday afternoon and evening...as a series of upper level
disturbances move northeast out of the region.

Otherwise...late this work week into the weekend...temperatures
will generally cool to near to slightly above normal levels with
precipitation chances ending.

According to the Climate Prediction Centers 8 to 14 day
outlook...we are looking at a high probability of above normal
temperatures and the possibility of below normal precipitation.

FIRE WEATHER...Updated 200 PM PDT Tuesday 16 August 2022...
With an upper ridge to the east and a trough offshore, monsoonal
moisture has started to feed into the area today with increasing
temperatures and instability. As a result, hot, dry, and unstable
conditions will be the rule through hat least Friday. As monsoonal
moisture increases, an isolated thunderstorm or two is possible this
afternoon and evening in the Modoc area. Activity will be more
widespread Wednesday. Isolated thunderstorms are possible early
Wedensday morning, becoming scattered by the afternoon and evening
as activity spreads to much of the region. Frequent lightning, dry
thunderstorms, and gusty, erratic outflow winds are the primary
threats. The Fire Weather Watch has been upgraded to a Red Flag
Warning for abundant lightning on dry fuels. See PDXRFWMFR for
details.

Isolated thunderstorm activity is expected through Wednesday night
and into Thursday, but activity will be concentrated from the
Cascades east. Friday and Saturday look to be dry. Another closed
upper low may approach the coast this weekend, lowering temperatures
a bit and perhaps producing some gusty southwest winds by the end of
the weekend. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from Wednesday afternoon through Wednesday
     evening for ORZ617-621>625.
     Heat Advisory until 11 PM PDT Wednesday for ORZ029-030.
     Heat Advisory from 11 AM Wednesday to 11 PM PDT Thursday for
     ORZ024-026.
     Heat Advisory from 11 AM to 11 PM PDT Wednesday for ORZ027-028.

CA...Red Flag Warning from Wednesday afternoon through Wednesday
     evening for CAZ280-281-284-285.
     Heat Advisory until 11 PM PDT Wednesday for CAZ084-085.
     Heat Advisory from 11 AM Wednesday to 11 PM PDT Thursday for
     CAZ080>082.

Pacific Coastal Waters...
     Small Craft Advisory until 11 PM PDT Wednesday for PZZ356-376.
     Gale Warning from 2 PM this afternoon to 2 AM PDT Wednesday for
     PZZ356-376.
     Small Craft Advisory from 2 PM this afternoon to 2 AM PDT
     Thursday for PZZ350-370.

$$

MAS/SBN/CCR/CC/BPN



Office: PQR FXUS66 KPQR 170455 AFDPQR Area Forecast Discussion National Weather Service Portland OR 954 PM PDT Tue Aug 16 2022 .SYNOPSIS...High pressure across the Great Basin will expand northwest over the forecast area tonight through Wednesday. The upper ridge slowly shifts east Wednesday night and Thursday. Southerly flow Wednesday through Thursday will all mid-level moisture to spread into the area for a slim threat of thunderstorms over the Cascades. A strong marine surge Thursday night will bring much cooler conditions Friday. Seasonable temperatures then continue through the weekend. && .UPDATE...Main update to this evening was to add the south Willamette Valley zone to the Heat Advisory. Latest NBM incrementally rose high and low temperatures, putting most of the zone into advisory category. Deterministic model trends also show this incremental increase in temperatures. Overall does not look like record setting high temperatures Wed, but a few records could be broken on Thu. But the warm nights will increase heat stress for those without air conditioning. .DISCUSSION... Key Messages: * Above normal temperatures will occur inland through Thursday. Wednesday and Thursday continue to appear the hottest days. * High Heat Risk is forecast for much of the population across the North and Central Willamette Valley, Clark County, and the Columbia Gorge/Upper Hood River Valley on Wednesday. Moderate Heat Risk is forecast for sensitive groups Thursday. * A thunderstorm threat will exist for the higher Oregon Cascades Wednesday evening and then expand to the south Washington Cascades late Thursday. Detailed Discussion (Tonight through next Tuesday)...Early afternoon water vapor imagery revealed expansive high pressure over much of the Western U.S.. Meanwhile, an upper level trough was spinning over the Gulf of Alaska. A weak short-wave disturbance could be seen pushing east across southern British Columbia. This feature was responsible for the additional morning low clouds. At 20Z visible satellite showed clear skies over the area, including the coastal waters. The main weather story for the short term will be the mini heat wave Wednesday through Thursday. The 12Z NAM shows a weak surface thermal trough forming over the Willamette Valley tonight late tonight. This will bring light offshore flow to the Cascades and foothills for reduced humidity recovery. The KTTD-KDLS gradient switches to negative, or offshore, shortly after midnight and then strengthens to around -2.5 mb Wednesday morning. By Wednesday afternoon models show the thermal trough extending from the south Washington Cascade foothills through the Gorge to the north Oregon Cascades. Model 850 mb temps rise from 18-20C today to 22-25C by 00Z Thursday. This will result in widespread mid to upper 90s inland, with local 100-degree readings possible. There is about a 60 percent chance of 100 degrees Wednesday at KPDX, 55 percent chance for KSLE, but only 22 percent for Hood River. Although our Heat Risk program shows Warning criteria for much of the Willamette Valley, the Gorge and Upper Hood River Valley Wednesday, will continue with the current advisory due to the short-duration of this event. There will be below-average temperature relief Wednesday night with some locations only dropping to around 70 degrees. Thursday looks to be just as warm as Wednesday, although there continues to be more model variance regarding max temperatures. Based on our latest temperature forecast, the Heat Risk output valid Thursday shows more high risk, or category 3, area compared to 24 hours ago. Again, will stick with the current advisory. If max temperatures Friday were to be similar, mid to upper 90s, this would necessitate the possible upgrade to a Heat Warning. South mid and upper level flow continues over the area Wednesday through Thursday. This will allow mid and high-level moisture over the Great Basin and Desert Southwest to migrate north. Model soundings for a point near Willamette Pass valid Wednesday afternoon show marginal elevated instability. The GFSBufr sounding is much less favorable for possible convection compared to the NAMBufr output. The SREF 12-hr calibrated thunderstorm probability product paints a 10-20 percent contour in the southeast corner of the Lane County Cascades late Wednesday afternoon. Thursday's convective threat is a little more difficult to assess. The NAM, GFS and, to a certain extent the ECMWF, want to show a 500 mb trough over central Oregon 00Z Friday. This allows southeast to south mid-level flow to spread north into the south Washington Cascades. Various model soundings for a point near Mt. Adams valid late Thursday afternoon show some degree of elevated CAPE/instability. The GFS indicates nearly as much convective inhibition (CIN) as CAPE. The 3km NAM sounding shows a much higher degree of elevated instability. The SREF calibrated thunder guidance valid 03Z Friday shows a 10 percent contour over the south Washington Cascades. Have opted to expand the thunder threat late Thursday to cover much of the north Oregon Cascades and also include the part of the south Washington Cascades. Expect a significant marine surge Thursday night/Friday morning as a short-wave trough moves into southwest British Columbia, clipping the forecast area. The EPS ensembles for KAST continue to suggest some light QPF will be possible late Thursday night through Friday morning, with the EPS mean QPF around 0.05 inches. Even the deterministic GFS and ECMWF paint some QPF along the coast and into the coastal valleys 12Z Friday. NBM guidance shows close to 15 degrees cooling from Thursday to Friday over the interior. In fact, the 10th percentile Friday max temp at KPDX is 76. Temperatures look to remain near to slightly above normal Saturday as the area remains under southwest flow between the Great Basin high and a large trough over the eastern Pacific. The deterministic models then swing the upper level trough toward Vancouver Island Sunday. The WPC 500 mb clusters valid 00Z Monday show some agreement that weak troughing will be situated somewhere over the eastern Pacific. Despite the deterministic GFS showing the upper trough axis just off the coast 00Z Monday, nearly half of the GEFS members maintain some degree of ridging over the area. There is the potential for at least another marine surge Saturday night/Sunday morning, but forecast confidence is below average for this scenario. WPC clusters maintain a general ridging pattern early next week for slightly above-normal daytime temperatures. The much longer range, days 8-10, suggest yet another possible hot spell for the area. Weishaar && .AVIATION...06Z TAFs: Building high pressure will continue to support VFR conditions under mostly clear skies through the TAF period. Areas of smoke will continue between Oakridge and Waldo Lake due to the Cedar Creek wildfire burning just to the west of Waldo Lake. Also expect VFR to prevail at the coastal terminals overnight as the surface pressure gradient turns weakly offshore and keeps marine stratus confined to the immediate coastline. KONP has the best chance for some intermittent MVFR cigs after 12z, with HREF probs around 40-50 percent through daybreak Wed. Coastal stratus should push farther offshore again by 18z Wed and yield mostly clear skies along the coast into Wed evening. For detailed Pac NW aviation weather information, go online to: https://weather.gov/zse KPDX AND APPROACHES...Expect clear sky VFR flight conditions and light winds through the period. CB/TK && .MARINE...High pressure will remain anchored offshore over the next several days, with thermal low pressure along the south Oregon coast into northwest California. This will maintain moderate northerly pressure gradients over the south Oregon coastal waters, resulting in a prolonged period of northerly winds over the coastal waters. Northerly winds will be strongest during the mid to late afternoon and evening hours each day, especially to the south of Cascade Head. A Small Craft Advisory is currently in effect for the coastal waters through Wednesday evening. Gusts 20 to 25 kt are expected during this time, with the strongest and most frequent gusts to south of Cascade Head. Seas should generally range between 4 and 6 ft, with the choppiest seas likely to occur to the south of Newport. Not much change on Thursday aside from decreasing northerly winds, which should fall to around 10 to 15 kt. North winds should increase again late Friday afternoon and evening as the pressure gradient restrengthens over the waters, which may bring the return of marginal small craft wind gusts to 25 kt for the central waters. -TK For information about upcoming marine zone changes, go online to: https://www.weather.gov/pqr/marinezone && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Heat Advisory from noon Wednesday to 10 PM PDT Thursday for Cascade Foothills in Lane County-Cascades in Lane County- Central Columbia River Gorge-Central Willamette Valley- Greater Portland Metro Area-Lower Columbia-Northern Oregon Cascade Foothills-Northern Oregon Cascades-South Willamette Valley-Upper Hood River Valley-Western Columbia River Gorge. WA...Heat Advisory from noon Wednesday to 10 PM PDT Thursday for Central Columbia River Gorge-Greater Vancouver Area-I-5 Corridor in Cowlitz County-South Washington Cascade Foothills-South Washington Cascades-Western Columbia River Gorge. PZ...Small Craft Advisory until midnight PDT Wednesday night for coastal waters from Cape Shoalwater WA to Florence OR out 60 nm. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland
Office: PDT FXUS66 KPDT 170340 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 840 PM PDT Tue Aug 16 2022 .UPDATE...High pressure is forecast to dominate the areas weather with dry conditions and hot temperatures for the remainder of the week. Afternoon high temperatures across the Columbia Basin are expected to climb toward 100 degrees and higher and a heat advisory remains in effect for a large part of the region into Friday. Meanwhile high pressure just to our east will remain nearly stationary and some moisture may rap around and into portions of central Oregon tomorrow afternoon that could produce an isolated thunderstorm. Otherwise minor changes were done to sky and overnight temperatures tonight and the present short term forecast appears on track. && .PREV DISCUSSION... /issued 445 PM PDT Tue Aug 16 2022/ SHORT TERM...The main challenges with the short-term forecast revolve around a couple shortwaves anticipated to ride around the upper-level ridge on Wednesday and Thursday. The first of these waves is currently visible off the northern California coast on water vapor imagery. Monsoonal moisture transport up the back side of the ridge will reach central Oregon and the Cascade crest Wednesday morning and afternoon. This moisture, combined with some weak synoptic lift from the shortwaves may facilitate elevated showers and isolated thunderstorms for the central Oregon Cascades, central Oregon, and Ochocos Wednesday afternoon. Overnight into Thursday, guidance advertises another vorticity maximum moving onshore and forming a weak mid-level low. The current track is forecast to move southwest to northeast across eastern Oregon or northern Nevada, though guidance is still struggling with this feature. Thus, while additional lift will be provided by the low, confidence in exact placement of showers and isolated thunderstorms is low for Thursday afternoon into Thursday night. The majority of the moisture is anticipated to push along the Cascade crest Thursday, with perhaps some spilling into the rest of eastern Oregon Thursday evening and night. Have a slight chance of thunderstorms forecast for the Cascade crest on Thursday, as this is where the best instability and moisture is expected. The other concern for Wednesday and Thursday will be very hot temperatures for much of our CWA. Widespread highs in the 95-105 range are forecast Wednesday, and multiple Heat Advisories will be in effect Wednesday morning through Friday evening. Thursday, more uncertainty surrounds afternoon temperatures with potential mid- level cloud cover due to the monsoonal moisture and potential convective debris from any activity on Wednesday. Highs in the 95-105 range are still forecast, but these may come down a few degrees should cloud cover inhibit daytime heating. Regardless, advisory level heat will likely continue through the short term. Plunkett/86 LONG TERM...Friday through Tuesday...Upper ridge will continue to weaken as an upper trough off the coast tries to move into the region. The forecast area will be in the saddle between the upper ridge to the east and the upper trough off the coast to the northwest, and another upper ridge to the southwest along the CA coast. There will be some weak instability, but very little moisture, so Friday looks to be dry. However, cannot rule out an isolated weak thunderstorm over Wallowa County, but the chances are very small, with low confidence. Temperatures still look to be in the upper 90s to lower 100s in the lower elevations and mostly 80s to lower 90s mountains on Friday. Friday night and Saturday, the upper trough off the coast and the upper ridge over Montana will cause a southwest to west flow over the forecast area. There will also be a subtle upper low over the great basin, but that will have no effect on the weather in the CWA. Therefore, at this time, it looks to remain dry through Saturday night into early Sunday. However, the upper trough off the coast is now forecast by both the ECMWF and GFS to move into the region and forecast area by Sunday afternoon. This will result in a slight chance of thunderstorms over mainly the Elkhorn and Wallowa Mountains. However, elsewhere it will stay dry. A slight chance of thunderstorms will persist Sunday evening, and then dissipate overnight. There may still be a few showers, mainly over Wallowa County and the northern Blue Mountains Sunday night and Monday morning. Then with afternoon heating on Monday, combined with the upper trough that will still be moving across the region, there will be another slight chance of thunderstorms over Wallowa County. Then on Tuesday, a drier northwest flow will develop behind the trough as it departs the region. Tuesday looks to be dry. Temperatures on Monday and Tuesday will be cooler, with highs in the 90s in the lower elevations, and mid 70s to mid 80s mountains. While these temperatures are still above normal, it will feel cooler compared to the triple digit heat in the short term and in the early long term forecast period. It will be breezy to windy in the eastern Columbia River Gorge/north central OR area, as well as possibly the Kittitas Valley Friday afternoon and evening. After that winds look to be mostly light, except for the usual locations where winds tend to increase during the afternoons and evenings, such as the eastern Columbia Gorge and Kittitas Valleys. AVIATION...vfr conditions are expected to continue for the next 24 hours. Winds are forecast to remain between 5 to 20 mph. Meanwhile taf sites krdm and kbdn may experience few-sct100 after 20z. && .PRELIMINARY POINT TEMPS/POPS... PDT 61 101 65 99 / 0 0 0 0 ALW 63 104 67 102 / 0 0 0 0 PSC 64 104 68 103 / 0 0 0 0 YKM 60 101 67 103 / 0 0 0 0 HRI 62 105 67 103 / 0 0 0 0 ELN 60 102 66 103 / 0 0 0 0 RDM 56 99 64 95 / 0 20 20 10 LGD 59 100 62 96 / 0 0 0 0 GCD 59 104 64 97 / 0 0 0 0 DLS 67 105 75 103 / 0 0 0 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Heat Advisory from 11 AM Wednesday to 11 PM PDT Friday for ORZ041-044-049-050-502-503-505>508-510-511. WA...Heat Advisory from 11 AM Wednesday to 11 PM PDT Friday for WAZ024-026>030-520-521. && $$ SHORT TERM...97 LONG TERM....99 AVIATION...97