Area Forecast Discussion
Issued by NWS Medford, OR
Issued by NWS Medford, OR
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212 FXUS66 KMFR 050525 AFDMFR Area Forecast Discussion National Weather Service Medford OR 1025 PM PDT Sat May 4 2024 ...New Aviation Section... .AVIATION (06Z TAFs)... Precipitation has diminished across the region, but expecting isolated showers to pick back up around sunrise and continue through the day. The hard part is timing if the terminals will be impacted or not, but due to isolated nature will go with vicinity mention for now unless it becomes clearer for impacts at the terminals. Otherwise, terminals should be mostly VFR with stints of MVFR. Confidence was not high enough to introduce IFR at this time, but low level saturation could lead to brief periods of IFR and may need to be reevaluated tonight if confidence increases in timing. -Guerrero && .PREV DISCUSSION... /Issued 839 PM PDT Sat May 4 2024/ DISCUSSION...An upper low is moving onshore into the region this evening as our recent wet front finally exits. Precipitation has become scattered and showery this evening. Showers will start to decrease in coverage tonight but see a re-surgence tomorrow (Sunday) morning as the low spins another round of moisture into the region. Cold temperatures from the low will lead to snow levels continuing to fall slightly to 2,500-3,000 feet early Sunday morning before rising again Sunday afternoon. This will also lead to chilly morning temperatures, and a Freeze Warning for the Shasta and Scott valleys in northern CA is in place from 2 AM to 8 AM Sunday. For more details, please see the previous discussion below. -CSP AVIATION...05/00Z TAFs...A strong frontal system has mostly passed through the region this afternoon, but low pressure following the main frontal band will lead to intermittent, showery precipitation continuing for most of the weekend. Widespread MVFR conditions and terrain obscurations are expected to continue, though some improvement to VFR tonight is expected in areas, including the Rogue Valley. This improvement may not be linear, with conditions bouncing between MVFR and VFR. Snow levels will continue to lower this evening and tonight, and rain showers will transition to snow east of the Cascades. Winds will continue to be gusty along the coast and east of the Cascades with the low pressure. Precipitation will begin tapering off later Sunday afternoon and conditions are expected to improve area wide. -CSP MARINE...Updated 830 PM Saturday, May 4, 2024...Showers will dissipate through this evening, with a very low chance for a thunderstorm before sunset. Isolated showers are expected to redevelop tomorrow around sunrise and go throughout the day. Moderate west winds and steep fresh short period west swell will continue through tonight, then southwest winds increase Sunday ahead of another front that will move through late Sunday night into Monday. Seas are likely to remain elevated Monday night into Tuesday with building west-northwest swell. After that, we expect high pressure to build in mid-late next week with a thermal trough strengthening along the coast. This will bring a return of stronger north winds and steep seas, highest south of Cape Blanco. PREV DISCUSSION... /Issued 234 PM PDT Sat May 4 2024/ SHORT TERM...Through Tuesday morning...A low pressure system continues to bring activity across northern California and southern Oregon. Reports have indicated 2 to 3 inches of rain along the Oregon coast in the past 24 hours, as well as 4 inches of snow in areas around Mount Shasta. The main band of rainfall is moving across Klamath and Lake counties while scattered showers continue west of the Cascades. Existing daytime hazards have all expired, as elevated winds over east side areas have slowed and the heaviest snowfall over western Siskiyou County and the Cascades has passed. Other hazards will continue through the night. Instability from the low pressure system brings the possibility of thunderstorms through the night tonight. Current chances are at 20-25% across areas west of the Cascades, with lower 10-20% chances to the east. These chances will remain into the last hours of Saturday before decreasing through Sunday morning. Additionally, a Freeze Watch has been elevated into a Freeze Warning for the Shasta and Scott Valleys in Siskiyou County. Temperatures in these valleys are forecast to be in the high 20s to low 30s tonight into early Sunday morning. The Freeze Warning will be in place from 2 AM until 8 AM on Sunday morning. Other areas, including the Illinois Valley and the southern Rogue Valley, may see temperatures at or near freezing. But the possibility of substantial periods of freezing temperatures are low (10-20%), so warnings were not issued for these areas. Near-freezing temperatures in the mid-30s are forecast, so extra care for sensitive plants and animals may still be beneficial. The low pressure system will follow the Oregon-California border through Sunday, keeping cooler temperatures and precipitation in the Forecast for Sunday. Snow levels are expected to rise to about 4000 feet, limiting snowfall to the Cascades and the highest terrain to the east. Thunderstorm chances are not in the forecast. A warm front will follow behind the low pressure system on Monday, bringing another round of precipitation across the area. This front looks to be non-impactful, with some limited thunderstorm chances over Klamath and Lake counties on Monday evening. Precipitation will be highest over the Cascades, with 3 to 6 inches of snow forecast over the Cascades and unremarkable rainfall amounts over lower elevations. -TAD Long Term...Tuesday (05/07) through Saturday (05/11)...The extended period starts as "third winter" comes to an end, and a familiar pattern of high pressure builds in. During this period of high pressure strong, gusty north winds will be present along the coast and east winds will develop inland. The warm bubble around Brookings due to the Chetco effect is expected to be on display at the end of the work week. This diurnal pattern of wind flow will bring in drier air to the region, but the magnitude of the warmth will be limited. The current forecast calls for the heat to peak either Friday or Saturday in the low to mid 80s and overnight lows barely scraping into the upper 40s or low 50s. The reason for this low peak in high temperatures appears to be a retrograding low pressure center, which is expected to undercut the ridge as it moves in from around Utah. -Miles AVIATION...05/00Z TAFs...A strong frontal system has mostly passed through the region this afternoon, but low pressure following the main frontal band will lead to intermittent, showery precipitation continuing for most of the weekend. Widespread MVFR conditions and terrain obscurations are expected to continue, though some improvement to VFR tonight is expected in areas, including the Rogue Valley. This improvement may not be linear, with conditions bouncing between MVFR and VFR. Snow levels will continue to lower this evening and tonight, and rain showers will transition to snow east of the Cascades. Winds will continue to be gusty along the coast and east of the Cascades with the low pressure. Precipitation will begin tapering off later Sunday afternoon and conditions are expected to improve area wide. -CSP MARINE...Updated 200 PM Saturday, May 4, 2024...Showers will dissipate through this evening, with a very low chance for a thunderstorm before sunset. Moderate west winds and steep fresh short period west swell will continue through tonight, then southwest winds increase Sunday ahead of another front that will move through late Sunday night into Monday. Seas are likely to remain elevated Monday night into Tuesday with building west- northwest swell. After that, we expect high pressure to build in mid- late next week with a thermal trough strengthening along the coast. This will bring a return of stronger north winds and steep seas, highest south of Cape Blanco. -BPN && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...Freeze Warning from 2 AM to 8 AM PDT Sunday for CAZ080-081. PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT Monday for PZZ350-356-370-376. && $$