textproduct: Medford

Updated AVIATION Discussion

AVIATION...18/12Z TAFs

VFR conditions prevail across the region with mid and high level clouds lingering over the area. LIFR conditions are spreading north over the marine waters and along the coast, currently around Crescent City. This will impact Brookings/Gold Beach by around 15z, eventually making it north of Cape Blanco this afternoon and reaching North Bend around 03z/19. Additionally, showers/thunderstorms will be possible this afternoon south of the OR/CA border.

PREV DISCUSSION

/Issued 335 AM PDT Thu Jun 18 2026/

DISCUSSION...High pressure responsible for the recent heat has moved east of the region, and in it's place, an open/weak trough has developed offshore over the eastern Pacific and will be the main weather influencer through Saturday. The two main impacts from this trough will be high temperatures lowering closer to seasonal normals (though still above normal) and a thunderstorm pattern today through Saturday (more below). 500 mb heights will lower today, which typically indicates somewhat cooler temperatures. At the surface, however, the thermal trough will push inland this morning, resulting in a slight uptick in temperatures (mid-upper 90s West/upper 80s-low 90s East) compared to yesterday's readings. Temperatures trend cooler for Friday and Saturday the weak trough passes through the region. Afternoon highs will still be above normal, but instead of being 15-25 degrees above normal like earlier this week, it'll "cool" to only 5-10 degrees above normal. Saturday will be the "coolest" day of the forecast period as high temperatures start trending upward on Sunday, and even more so early next week.

The upper level trough offshore will bring a few days of thunderstorms to the region, starting today and peaking in terms of activity on Friday. Upper level moisture and instability is evident on satellite imagery this morning with an area of cloud cover lingering over southern OR/northern CA. Satellite derived lightning detection shows some in cloud lightning activity out beyond 130 W. Guidance indicates moisture and instability will be in the region today, focused mainly along the Sierras and into Siskiyou/Modoc counties, and this is where we expected shower/thunderstorm activity today. There could be some cumulus buildups north of the OR/CA border today, but model guidance maintains the best chances (20-30%) for thunderstorms is across southern areas.

The upper trough moves closer to the coast Thursday night into Friday (a somewhat faster timing trend in the model guidance), bringing increasing moisture and instability to the region for Friday. Current guidance maintains the best chances (40-60%) in the typical areas, across northern California and east of the Cascades, but there is the potential for as far west as Jackson County (10- 30%, highest for SE areas). With the faster arrival, shower/thunderstorm activity could get going by early afternoon across northern California, with storms moving into south-central OR as the afternoon progresses. Storm motion is more southwesterly, shifting to westerly as the afternoon progresses and mid-level moisture sharply drops off farther west and north. While, this should limit storm activity west of the Cascades and north of the Siskiyous, guidance is showing the potential for shower/thunderstorm activity to move into portions of Jackson/Josephine Counties, highest chances for SE half of Jackson County (10-30% chance). Adjustments may be needed to the forecast if model trends continue this. Overall, storms are likely to be a mix of wet/dry with strong outflows (30-40 mph), lightning and small hail being the main threats.

The trough axis moves through the region Friday night, taking the moisture and instability father east for Saturday. It's possible that shower and isolated thunderstorm activity continues across Lake/Modoc Counties Friday night, which could hinder instability for Saturday. Current guidance, however, maintains enough instability to overcome this and shows some lingering thunderstorm chances across Siskiyou County northeastward into northern Modoc/southern Lake Counties. The coolest temperatures of the forecast period are expected Saturday as this trough passes through.

For Sunday through the first half of next week, lingering weak troughing on Sunday transitions to shortwave ridging on Monday, then to southwesterly flow on Tuesday as a weak trough swings through to the north. Temperatures tick upward on Sunday by a few degrees with a more notable warm up on Monday under building heights. Temperatures could flirt with the triple digit mark (25% chance) again on Monday and Tuesday for the Rogue Valley. We'll need to monitor model guidance for that trough passing through to the north in the Tuesday/Wednesday timeframe. Some guidance is hinting at the potential for thunderstorms across far eastern areas Tuesday afternoon, but we'll also need to monitor for any potential gust winds/low RH resulting in fire weather concerns that typically accompany a dry frontal/upper level trough passage. Stay tuned for updates.

MARINE...Updated 100 AM PDT Thursday, June 18, 2026...The thermal trough will push inland later this morning, bringing gradually improving conditions today into Friday. Gales will persist south of Cape Blanco and generally beyond 10 nm from shore, with very steep and hazardous seas expected beyond 5 nm from shore through this morning. Winds ease below gales later this morning and steep seas will gradually retreat westward to the outer waters by this evening, with steep seas expected for all other areas. Conditions improve moreso on Friday as winds ease below advisory criteria and steep seas retreat to the outer waters. This improvement looks shortlived, however, as gusty north winds and steep seas return south of Cape Blanco by Saturday and persist into early next week.

FIRE WEATHER...Updated 300 AM PDT Thursday, June 18, 2026...The thermal trough will push inland today, bringing another uptick in temperatures across the region. Additionally, this pattern will bring dry and unstable conditions across northern California and east of the Cascades today.

Meanwhile, an open trough develops offshore over the eastern Pacific on today, moving inland late Friday and east of the region on Saturday. This pattern sets up the potential for thunderstorms during this time frame, focused across northern California and east of the Cascades. Chances for thunderstorms are highest on Friday, but could begin as early as Thursday for southern Siskiyou and Modoc counties. Thunderstorm activity today looks focused south of the OR/CA border, across Siskiyou/Modoc Counties and the Sierras.

As the upper level low moves closer to the coast on Friday, the chance of showers and thunderstorms increases. Current guidance maintains the best chances (40-60%) in the typical areas, across northern California and east of the Cascades, but there is the potential for as far west as Jackson County (10-30%, highest for SE areas). Storm motion is more southwesterly, shifting to westerly as the afternoon progresses and mid-level moisture sharply drops off farther west and north. While, this should limit storm activity west of the Cascades and north of the Siskiyous, guidance is showing the potential for shower/thunderstorm activity to move into portions of Jackson/Josephine Counties, highest chances for SE half of Jackson County (10-30% chance). Overall, storms are likely to be a mix of wet/dry with strong outflows (30-40 mph), lightning and small hail being the main threats. A Fire Weather Watch is in effect for abundant lightning on dry fuels for Friday afternoon/evening, including fire weather zones (FWZs) 280/281/284/285/624/625.

By Saturday, the best moisture/instability shifts east, leaving some lingering chances along/east of the Warners/Winter Ridge, as well as portions of Siskiyou County from the Trinity Alps to the Medicine Lake area.

MFR WATCHES/WARNINGS/ADVISORIES

OR...Fire Weather Watch from Friday afternoon through late Friday night for ORZ624-625.

CA...Fire Weather Watch from late tonight through Friday evening for CAZ280-281-284-285.

PACIFIC COASTAL WATERS...Hazardous Seas Warning until 8 PM PDT this evening for PZZ356.

Small Craft Advisory from 8 PM this evening to 5 AM PDT Friday for PZZ350-356-370-376.

Hazardous Seas Warning until 8 PM PDT this evening for PZZ350.

Hazardous Seas Warning until 5 AM PDT Friday for PZZ370.

Gale Warning until 8 AM PDT this morning for PZZ376.

Hazardous Seas Warning from 8 AM this morning to 5 AM PDT Friday for PZZ376.