####018005645#### FXUS66 KMFR 231157 AFDMFR Area Forecast Discussion National Weather Service Medford OR 457 AM PDT Tue Apr 23 2024 ...Updated AVIATION discussion... .DISCUSSION...The upper level pattern will transition with low pressure developing off the California coast and low pressure pushing toward the British Columbia Coast. This will put our region in southwest flow and some mid level moisture will move into the area. This combined with some model indicated instability (-2 to -4 LIs, 300-500 J/kg CAPE) is boosting confidence in thunderstorm potential for today and Wednesday. Right now, today looks to be the bigger day in terms of thunderstorm coverage. The best chances (40%-70%) look to be over western Siskiyou County and Modoc County with some potential (20%-40%) extending into the southern portions of Jackson/Klamath/Lake Counties. Storm motion will be from the southwest, but current thinking is that any storms that develop over the Siskiyous would likely stay stuck on the terrain and not really drift into the Rogue Valley...though it's not out of the question (10% chance) a storm skates by Ashland Tuesday afternoon. The focus for storms on Wednesday shifts farther east on Wednesday over eastern Siskiyou, Modoc and southern Lake Counties and the trigger looks weaker for Wednesday, so thunderstorm coverage looks less overall. For the remainder of the area, conditions will remain dry, though expect an uptick in afternoon winds and cloud cover with temperatures trending cooler. The pattern turns cooler and wetter as we head into the extended period. Previous Extended Discussion (Thursday through Monday)...Generally it will be cool and unsettled during the forecast period. A stronger front will approach the coast Thursday morning, then moving inland during the day. The bulk of the precipitation will be along the coast, coastal mountains, Cascades and north of the Umpqua Divide. The front will move east of the Cascades Thursday afternoon with precipitation becoming scattered. Snow levels will also lower to around 5500 feet along the Cascades late Thursday afternoon and hover around that elevation Thursday night. This in combination with a higher mid-late April sun angle, will put a cap on snow concerns due to warm road surface temperatures, and should be mainly confined to Crater Lake and Diamond Lake areas Thursday night. Upper troughing remain over the area Friday, although the upper trough axis will shift east late Friday afternoon and we could see showers gradually diminish in coverage. The operational ECMWF and GFs show different solutions Saturday with the GFS showing more ridging and a relative break in the action. The ECMWF brings another upper trough and front into the area Saturday morning. No surprise the majority of the respective ensemble members also show varying solutions. Even taking the operational GFS at face value the ridding is weak and with a weak upper trough just offshore, but still hints at a progressive pattern. Therefore we'll keep showers and cool afternoon temperatures in the forecast. Upper troughiness remains over our area Sunday through Monday, and possibly through the middle of next week which will result in cooler temperatures and high chance for showers over a good portion of the forecast area. -Petrucelli && .AVIATION...23/12Z TAFs...VFR levels continue across much of northern California and southern Oregon this morning. Marine stratus is moving north along the Oregon coast, bringing IFR levels to Gold Beach. Additionally, stratus may develop near North Bend, but will only linger briefly this morning if it does. Marine stratus could return on Wednesday morning. Chances for showers (30-60%) and thunderstorms (20-40%) remain in the forecast for Siskiyou and Modoc counties as well as southern Klamath and Lake counties for this afternoon. The highest chances for activity are over the California counties, and these chances decrease quickly near the end of the TAF period. Isolated thunderstorms may bring lightning and strong winds as well as locally lower ceilings and visibilities. -TAD && .MARINE...Updated 200 AM Tuesday, April 23, 2024...Elevated northerly winds continue under a thermal trough. Early this morning, the strongest winds remain south of Cape Blanco and beyond 10 nm from shore. Very steep and hazardous seas will continue in this area early this morning, with steep seas in all other waters. The thermal trough will weaken through the day, but steep seas will remain. A Small Craft Advisory will be in place for all waters from 5 AM through 5 PM today, then will continue for waters south of Cape Blanco until 8 PM. Seas will remain calm through Wednesday and into Thursday morning before active weather returns to the area. Westerly fresh swell and gusty southerly winds could rebuild steep seas by late Thursday or early Friday, especially in outer waters. However, current guidance suggests that waves only have a 10-20% of exceeding 9 feet through the weekend. So while steep seas are possible, more hazardous conditions are not expected. -TAD && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT this evening for PZZ350-356-370-376. Hazardous Seas Warning until 5 AM PDT early this morning for PZZ376. && $$ SBN/SBN/SBN ####018004735#### FXUS63 KFGF 231158 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 658 AM CDT Tue Apr 23 2024 .KEY MESSAGES... - The probability for widespread hazardous weather through Monday is low (less than 10%). - Watching dew points and relative humidity values for potential near critical fire weather conditions Wednesday. - Increased rain chances Friday into Saturday with chance for isolated thunderstorms. && .UPDATE... Issued at 653 AM CDT Tue Apr 23 2024 500 smb low is near Park Rapids moving south-southeast. Spin in clouds noted and showers are to the west and north of the upper low from Lake of the Woods to east of Fargo. Last of the spotty showers are in far SE Manitoba and far northeast ND moving south. So idea of scattered showers in MN fcst area and the RRV is good with trends indicating them moving out of our forecast area 16-17z or so. Cloud cover with this is far less extensive than thought with plenty of clearing holes in cloud cover in E ND/RRV with thicker cloud cover confined to around the upper low center. Overall trends of the fcst are good. We are seeing the NNW winds increase as anticipated within the RRV and E ND with gusts to 25 kts as pressure rises move into the valley. && .DISCUSSION... Issued at 342 AM CDT Tue Apr 23 2024 at 08z 500 mb low is located near Grand Forks with spin on radar noted with showers over the Grand Forks area. This will continue to move east-southeast thru the early morning hours with lingering showers spreading more into Minnesota and then exiting the forecast area by 16z. The question arises is winds this morning. As upper level low moves away there is a period of NNW winds that could gust to 35 kts within the Red River valley with mixed layer up to around 925 mb early this morning rise to 870 mb by 17z. By then the winds aloft do diminish. Also in question is sky cover/types of clouds. Havent seen low clouds form yet but never discount what happens by 12z. So going with idea of mostly cloudy this morning most areas then clearing working southeast thru the aftn. Highs today with late day sun reaching the low-mid 50s. HRRR did well with sfc temps on Monday and looks good today. They also are very near NBM 4.1 temps used in the fcst. Winds diminish overnight as high pressure ridge moves, with center of high moving southeast thru far NW Ontario. Winds will be northeast tonight then turn south-southeast on Wednesday as high moves farther east. Surface gradient initially isnt that tight so not expecting a big jump in wind speeds Wednedsday. Dry airmass in place due to high pressure to our north/east, though driest of dew pts more favored over NE MN. Warming Wednesday with plenty of sun, with RH values dropping in to the mid 20s across the area. Winds to be near 10 kts. So borderline near critical fire weather day Wednesday based on RH values. A warm Thursday as south winds ramp up into the 20-30 mph range with higher gusts. Highs 60s to mid 70s. Thereafter an unsettled pattern starts as several 500 mb short waves and surface lows will move northeast from the central Rockies toward Minnesota. First wave brings chances for rain into the area Thursday overnight but the highest chances (60-80 percent from northwest to southeast across the area) are Friday afternoon thru Saturday morning. WPC rain amounts show 0.75 average Baudette to Grand Forks to Jamestown and areas southeast. NBM 4.1 indicates similar amounts with probs for more than 0.50 inch at 60-80 percent in the same area. Instability looks weak as surface low is more southeast MN and instability focused south of there Friday. But embedded t-storm is possible so will maintain some mention Friday. Next wave arrrives Sun aftn-Monday but trends are weaker and a bit farther southeast with this system. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 653 AM CDT Tue Apr 23 2024 The widespread MVFR cloud deck that the short term models had advertised is not happening. There is some MVFR ceilings since 10z that formed right near the upper low center including Bemidji, Detroit Lakes, Fosston, Park Rapids but otherwise into the RRV cloud ceilings are at or above 4000 ft agl. Gusty NNW winds 25-30 kts esp in the RRV this morning diminishing slowly this aftn but no noticeable decrease probably not til closer to 22/00z. Clear with light wind tonight. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Riddle DISCUSSION...Riddle AVIATION...Riddle