####018006063#### FXUS63 KDMX 040508 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1208 AM CDT Sat May 4 2024 ...Updated for the 06z Aviation Discussion... .KEY MESSAGES... - Storms and showers arriving after midnight tonight near and east of Highway 71 - severe risk is small hail, gusty winds possible - Stormy weather returns later Monday into Monday night with severe weather possible, perhaps redeveloping later Tuesday - More clouds than sunshine, fleeting showers, and trending towards seasonal levels mid to late next week && .DISCUSSION... Issued at 232 PM CDT Fri May 3 2024 Morning fog was rather impressive from visible satellite this morning highlighting the numerous river valleys across portions of Iowa. This fog was able to fully dissipate between 9 and 10am. Now, upper level water vapor imagery shows a parent upper low that is spinning into the Manitoba province. Dropping through the Intermountain West into the northern/central Rockies around this parent upper low is the shortwave trough that will bring thunderstorms into Iowa late this evening and our forecast area after midnight. An area of instability up to around 500 J/kg of MUCAPE is expected ahead of a cold front along with steep mid-level lapse rates and sufficient shear for storm organization. Forecast soundings show storms will be elevated in nature and thus pose a risk of primarily small to around 1" hail with isolated gusty winds possible. Convective allowing models show a few healthy updraft helicity tracks entering western Iowa, but their strength quickly wanes as they move toward central Iowa. Further, even the more aggressive WRF-ARW and FV3 are showing wind gust potential topping out between 30 to 40 knots. Overall, the marginal risks by the Storm Prediction Center on day 1 into day 2 seems to handle this risk well. Rainfall amounts look to be highest over western into portions of central Iowa, mainly east of I-35 with 12z HREF localized probability matched mean values of half an inch with small areas of 1.25 to 2 inches possible. The water issues over our southeastern forecast area - namely Monroe and parts of Appanoose and Wayne counties including the Cedar Creek basin - may then be spared from a return of water problems. These storms will be over eastern Iowa around midday leaving behind breezy winds from the north-northwest, decreasing clouds, and highs in the 60s in most central Iowa cities. With a clear sky over much of central Iowa, decreasing winds, and the rainfall from Saturday morning, we are looking to be set up for another round of dense fog. However, drier air will be pulled into Iowa and brings into question whether this will negate the other favorable factors. After any fog dissipates Sunday morning, weak ridging will pass overhead and a southern stream wave continues to trend south of the state with the latest NBM PoPs staying south of Iowa. At the same time, a potent shortwave trough over the western CONUS will move eastward toward the region and take on a negative tilt as it lifts northeastward into our region Monday into Monday night. Low level kinematics will be favorable at 40 to 50 knot Monday night in the region with resulting deep layer shear looking healthy for organized convection. This wind field will draw moister air into the region with low 60 surface dewpoints making their way to near if not into at least southern Iowa later Monday. MUCAPE values will be over 1000 J/kg and mid-level lapse rates rates will be steep around sunset Monday, but both are forecast to diminish into the evening to some degree. Forecast sounding continue to show an elevated warm layer that may keep storms elevated; however, given the strong kinematic fields in the 0-3km layer, cannot rule out a tornado risk with any line of storms if the orientation can become favorable to the low level shear vector. So, at a minimum, at least strong storms look favored, especially over the western half of the state Monday night, with severe weather possible. Like yesterday, SPC maintains probabilities largely southwest of our area on Monday and southeast of our area on Tuesday. Latest Colorado State's machine learning random forest outlook and CIPS Experimental Analog- Based Severe Probability Guidance continues to paint 5 to 15% probabilities of severe over more of central Iowa each day lending credence to the idea of some strong to if not severe storms in portions of our forecast area. The strong to severe storm risk may persist Tuesday afternoon given the SPC, CIPS, and CSU mentioned above, but if things speed up then this may all be pushed off to the east on Tuesday. Wednesday through Friday has broad brushed PoPs in our current forecast as the shortwave trough that will bring our storms chances the first two days of next week will lift up and meander over the Montana and western Dakotas area. This will keep weak shortwaves passing over the state and thus keep varying degrees of clouds, fleeting showers, and temperatures trending closer to normal in the 60s by late next week. Severe weather Wednesday through Friday looks unlikely as the instability will be away from the state. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1205 AM CDT Sat May 4 2024 MVFR to IFR cigs to move in with rain and thunderstorms. Have added thunder mentions to to all terminals as confidence is increasing in thunderstorms for even KMCW and KALO. Highest confidence at KFOD, KDSM and KOTM with vsby reductions and gusty winds also possible for KFOD and KDSM in the next 6 hours. Will continue to evaluate trends. Gusty northwest winds to follow departing rain, easing at sunset. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Ansorge AVIATION...Jimenez ####018005563#### FXUS65 KFGZ 040508 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 1008 PM MST Fri May 3 2024 .SYNOPSIS...Warm and mostly dry conditions will continue through tomorrow. Winds will start to increase ahead of an incoming low pressure system on Saturday, peaking on Sunday. Slight chance for isolated showers along the Kaibab Plateau on Sunday, elsewhere will remain mostly dry. Elevated winds will continue through much of next week, and warm/dry conditions will persist. && .UPDATE...Winds are decreasing this evening, with the remnants of some high-based cumulus persisting in northeast Arizona. Look for overnight lows similar to last night's values. The deep low pressure system set to really increase our winds this weekend is starting to move onshore the Pac NW and northern California this evening. A High Wind Watch is in effect for most of northern AZ on Sunday, be prepared for strong and possibly damaging winds. Current forecasts are in good shape this evening with no updates needed. && .PREV DISCUSSION /453 PM MST/...Above normal temperatures, breezy afternoon winds and mostly dry conditions have been our main song and dance for the last several days. Our tune will shift over the weekend, as a strong low-pressure system slides down the Great Basin region. The first indication of this invading pressure system will be increasing winds on Saturday. Look for southwest winds 15-25 mph, gusting 25-35 mph, throughout the afternoon. Stronger winds may be present along our Mohave County border, and elevated winds look to continue overnight for many areas along higher terrain. Sunday is when the main impacts of this storm system will unveil. Gusty southwest winds will start around 7AM MST/8AM MDT and continue through at least 9PM MST/10PM MDT. Gusty in this case is referring to sustained winds 30 to 40 mph, with gusts between 45-65 mph. Keep in mind, winds might not jump to these high of speeds first thing in the morning, but will continue to increase throughout the morning/afternoon. As a result of these strong winds, a High Wind Watch has been issued for much of northern Arizona for Sunday. Hazards may include, but are not limited to, difficult travel for high profile vehicles, power outages, and areas of blowing dust. Strong/damaging winds are not the only point of focus for Sunday though. There is also a near-critical to critical fire weather concern for portions of eastern Arizona. Relative humidity values do increase slightly on Sunday, but even so, there are still some areas that will be very susceptible to rapid fire starts/spreads. Thus, a Fire Weather Watch has been issued for Sunday for areas near Eagar, Springerville and St. Johns. This watch is valid between 11AM MST/12PM MDT to 7PM MST/8PM MDT. Check back for any updates to the High Wind Watch and/or the Fire Weather Watch. Early next week, this storm system will push northeast and allow a zonal flow to return over northern Arizona. Temperatures will slowly warm from Sunday, but still remain a couple degree below normal through the middle of next week. Winds will also remain gusty near our eastern border with the exit of the storm system, but typical spring-like breezes should return for much of next week. && .AVIATION...Saturday 04/06Z through Sunday 05/06Z...Expect VFR conditions with scattered mid-level clouds. Light and variable wind overnight through most of Saturday morning. South-southwest winds gradually increasing after 17Z, reaching sustained speeds 15-20 kts gusting 25-30 kts during the afternoon and evening. OUTLOOK...Sunday 05/06Z through Tuesday 07/06Z...Mainly VFR conditions will persist but with increasing clouds late Saturday night into Sunday, along with a 10-30% chance of light rain or snow showers along/north of a KGCN-KRQE line Sunday afternoon and evening. Southwest winds 15-25 kts Saturday night, strengthening to 25-35 kts gusting to 40-55 kts on Sunday. Periods of MVFR visibility in blowing dust are likely from KINW-KSJN-KRQE northward for Sunday afternoon. Winds gradually decreasing Sunday night, with west winds 15-20 kts gusting 20-30 kts on Monday. && .FIRE WEATHER...Saturday and Sunday...Mild temperatures and dry conditions will persist through Saturday. Saturday will see afternoon southwest winds at 10 to 20 mph gusting to 30 mph. On Sunday much stronger winds develop becoming southwest at 20 to 30 mph gusting of 40 to 55 mph before noon. Areas prone to downsloping winds, including along and directly east of the Mogollon Rim, White Mountains, and across portions of the Navajo Nation, will experience even stronger winds of 60+ mph for much of the day. Near critical to critical fire weather conditions are likely on Sunday over far east Arizona. A Fire Weather Watch has been issued for portions of east central Arizona. Monday through Wednesday...Dry and a bit warmer. Westerly winds at 10 to 20 mph gusting to 35 mph each afternoon. && .FGZ WATCHES/WARNINGS/ADVISORIES... High Wind Watch from Sunday morning through Sunday evening for AZZ004>017-039-040. Fire Weather Watch from Sunday morning through Sunday evening for AZZ114. && $$ PUBLIC...JJ/Konieczny AVIATION...JJ FIRE WEATHER...McCollum For Northern Arizona weather information visit weather.gov/flagstaff ####018009719#### FXUS66 KMFR 040509 AFDMFR Area Forecast Discussion National Weather Service Medford OR 1009 PM PDT Fri May 3 2024 .UPDATE...Included marine discussion. && .DISCUSSION...Radar imagery this evening is showing a widespread band of precipitation moving east through the region, with the leading edge of the band at just about the border between Jackson/Douglas counties and Klamath. So far we've seen about 0.40-0.80" reported by stations in Coos, Curry, and northwest Douglas counties; 0.10-0.20" in Josephine and the remainder of Douglas; and a whole 0.01" in Medford and along the Cascades, where rain is juts getting going. Precipitation will continue in the aforementioned areas as well as continue to spread east through the region overnight into early Saturday. Most of the precipitation out there is hitting the ground as rain right now, with snow levels above 7,000 feet. This will swiftly change overnight into Saturday morning as very cold air (for this time of year) filters into the region and snow levels crash. For more details on this system and those upcoming, please see the previous discussion below. No major changes to the forecast were needed this evening besides slight adjustments to how fast precipitation was moving eastwards. -CSP && .AVIATION (00Z TAFs)... A robust system is making its way on shore which will lead to widespread MVFR and IFR conditions across the region. Rain intensity and low level moisture will lead to both visibility restrictions and low ceilings through this cycle. It wont be until tomorrow afternoon that we start to see some relief from these diminished conditions. Until then, expect clouds to increase and rainfall to spread over the region tonight and overnight. We may see a mix of rain and snow on the eastside which would impact the terminal at Klamath falls tomorrow. At times, precipitation rates could limit visibility to 2 miles or less, with IFR to perhaps LIFR at times. Overall, unfavorable flying conditions are expected to start soon for at least the next 18 hours. -Guerrero && .MARINE...Updated 800 PM Friday, May 3, 2024...A cold front moving through the region will continue to bring moderate to heavy rain, gusty south winds and steep seas as it passes onshore this evening. Following the front, seas will remain steep, dominated by fresh short period west swell through tonight. Showers continue with a slight chance of thunderstorms (20%) on Saturday. West seas trend less steep Saturday afternoon through Sunday. Another front arrives Sunday night into Monday with the potential for gusty south to southwest winds followed by building west- northwest seas into Tuesday. 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. -Spilde/BPN && .PREV DISCUSSION... /Issued 304 PM PDT Fri May 3 2024/ SHORT TERM...Through Monday morning...An approaching low pressure system is already bringing rainfall to the Oregon coast. Rainfall will continue through the night over Coos, Curry, and western Douglas counties. Precipitation will steadily move eastward across the area through Saturday. Coastal areas will see about 2 to 3 inches of rainfall while west side valleys will get between half an inch and an inch of rain. Klamath and Modoc counties will get similar amounts of rainfall while Lake County will generally get half an inch of rain or less. The heaviest amounts will be late tonight through early Saturday morning. This system is bringing unseasonably cold air aloft, which will bring snow levels down from their current 8000 feet to 3000 feet by Saturday morning. While most snowfall will remain over higher terrain, the amount of moisture and the fast drop in snow levels will bring periods of heavy snow to the Cascades and to western Siskiyou County. Currently, 4 to 6 inches of snow are expected at elevations above 4000 feet for the Cascades and Siskiyou ranges, with a 20-30% chance of more than 6 inches over the Cascades by Sunday morning. Additionally, high resolution guidance shows a 40- 80% chance of snowfall rates of 1 inch per hour Saturday morning. Due to the dangerous travel conditions that these conditions are expected to make, a Winter Weather Advisory is in place for parts of western Siskiyou County from 2 AM to 11 AM on Saturday and for the Cascades from 2 AM to 11 PM on Saturday. This system will also bring elevated winds, especially across elevated terrain east of the Cascades. A Wind Advisory is in place for higher terrain in Lake County from Saturday at 5 AM through 5 PM. Gusty winds reaching over 40 mph are expected in this time, while wind gusts could still exceed 30 mph in other areas of Klamath, Lake, and Modoc counties. One final impact from this system will be a drop in nighttime temperatures from Saturday to Sunday. Temperatures will drop to the high teens to mid 20s for areas east of the Cascades. Below freezing temperatures are also possible west of the Cascades, although right now only the Shasta and Scott valleys look to be significantly below freezing. A Freeze Watch is in place for those valleys on Sunday morning, but below freezing temperatures are possible for the Rogue and Illinois valleys as well. Future guidance will help determine if additional products will be needed, bur right now that looks unlikely. The effects of the system continue through Sunday, but are most likely limited to post-frontal showers over the Oregon coast and the Cascades. Cool daytime temperatures will continue and nighttime temperatures look to warm from Saturday night's levels. -TAD LONG TERM DISCUSSION...Models continue to show a front moving across the area on Monday with high chances (60 to 100 percent) across most the area. Precipitation amounts with this front on Monday will be mainly light with some moderate amounts (0.25 inches or more) over the Cascades, coastal mountains and along the coast. Snow levels will range from 4000 to 5500 feet. Additionally, models and ensembles support a slight chance (20%) for thunderstorms Monday afternoon across portions of southwest Oregon, including Coos, Douglas, Klamath and Lake Counties. Brief downpours and gusty winds may occur with any thunderstorms that develop. Then, moist, onshore flow will allow for lingering showers on Tuesday, especially across southwest Oregon zones with lesser chances across Northern California. High pressure builds into the area Wednesday and remains in place through the end of the wee. This will bring drier and much warmer weather. By Friday, high temperatures will likely be in the 80s for valleys west of the Cascades and in the 70s for valleys east of the Cascades. AVIATION...03/18Z TAFs...Prevailing VFR this morning will drop back to MVFR with local IFR cigs/vsbys as a potent cold front moves in, with periods of moderate to occasionally heavy precipitation this afternoon. VFR will prevail elsewhere inland through late this afternoon/early this evening. The front will spread moderate precipitation across the rest of the west side tonight, reaching east of the Cascades Saturday morning. Expect widespread MVFR conditions and local IFR in rain with higher terrain obscured in rain/snow. A rapid drop in freezing levels will occur overnight (~09-15Z) from west to east and especially around 12Z Saturday morning near the Cascades. Rain will change to snow down to as low as 2500 feet with brief heavy snow in the mountains, reducing visibility to LIFR at times. Breezy south winds are expected with the front too, with peak gusts in the 40-50 mph range. Despite the increasing winds, low level wind shear is not a concern at this time. Conditions should improve a bit behind the front with precipitation becoming more showery, but still with a good amount of MVFR ceilings/visibility through tomorrow morning. -Spilde/BPN MARINE...Updated 200 PM Friday, May 3, 2024...A cold front will move through today into this evening with moderate to heavy rain, gusty south winds and steep seas. Following the front, seas will remain steep, dominated by fresh short period west swell through tonight. Showers continue with a slight chance of thunderstorms (20%) on Saturday. West seas trend less steep Saturday afternoon through Sunday. Another front arrives Sunday night into Monday with the potential for gusty south to southwest winds followed by building west-northwest seas into Tuesday. 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. -Spilde/BPN && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory from 2 AM to 11 PM PDT Saturday above 4000 feet for ORZ027-028. Wind Advisory from 5 AM to 5 PM PDT Saturday for ORZ030-031. CA...Winter Weather Advisory from 2 AM to 11 AM PDT Saturday above 4000 feet for CAZ080. Freeze Watch from late Saturday night through Sunday morning for CAZ080-081. PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT this evening for PZZ350-356-370-376. && $$