Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/27/22

National Weather Service Eureka CA
351 PM PST Mon Dec 26 2022 .SYNOPSIS...A potent storm will bring heavy rain and strong south winds to Northwest California tonight. Showers, isolated thunderstorms and high surf will follow on Tuesday. Additional periods of rain and high mountain snow will continue through Saturday. && .DISCUSSION...A powerful and wet storm has been bearing down on Northwest California this afternoon. A strong frontal boundary will move across the area tonight, generating strong winds and heavy rainfall rates. A 60-80 kt 925mb southerly pre-frontal coastal barrier jet will develop this evening in response to a developing surface cyclone, and when combined with a tight surface pressure gradient, will favor south winds gusting from 50-60 mph over the coastal plain and gusts from 60 to 75 mph across the ridges of Del Norte and Humboldt Counties. Winds will shift to the southwest early Tuesday morning after the front progresses southward and some gusts to 50 mph will remain possible. IVT`s or moisture flux will peak in excess of 1000 kg/m/s for a short duration tonight. The extreme moisture flux will support torrential rainfall rates of 0.50 to 1.00in/hr along/ahead of the cold front this evening into early Tuesday morning. Low flows on the rivers, low reservoir levels and the short duration (6 to 8 hours) of IVT`s over 750kg/m/s will limit the threat for major flooding. We maintained the flood watch for urban/small streams for much of the forecast area tonight into early Tuesday due to the anomalously high IVT`s. The frequency of occurrence of IVT`s over 1000kg/m/s for this time of year is about 1 day in every 10 years with respect to the CFSR-climatology. Latest NAEFS IVT`s return intervals are outside the CFSR-climatology. IVT`s this high have never occurred before for this time of year and are extremely rare. For that reason, the flood watch is warranted due to the potential for rapid rises on small rivers, streams and creaks and flooding of low-lying areas with poor drainage. Also, a flash flood watch for debris flows on burn scars, particularly the River Complex for the Coffee Creek basin has been issued. The Coffee Creek area is most vulnerable to debris flow. For the more recent burn scars of 2022, particularly the Six Rivers Lightning Complex, rain rates will need to be monitored closely for possible debris flow. The HRRR and blended/calibrated guidance continues to indicate rates below thresholds of 1.4in/hr. Snow levels will remain quite high through the duration of the heavy rain. Latest HREF guidance indicates increasing potential for convection and lightning late tonight. The potential for brief-locally heavy downpours will continue into the day on Tuesday due to the 500mb cooling and steepening mid level lapse rates. Snow levels will fall to 3500-4500 feet and some small hail will possible by Tuesday night, but will probably melt before hitting the ground. Some light snow is expected for the higher elevations of Trinity county Tue night into Wed, with low travel impacts expected for Scott Mountain Summit on HWY 3. Ensemble based 500 mb cluster analysis shows Northwest California remaining exposed to a long fetch of westerlies spanning across much of the North Pacific during the next 10 days. That pattern signals a prolonged period of mostly wet weather and potentially an increased threat for flooding into the first week of the new year. This our wettest time of year and we need the rain and mountain snow to mitigate our prolonged drought. && .AVIATION...Another winter weather system and associated front will continue to bring impactful weather hazards to the region today. Therefore conditions will further deteriorate as the front nears the coast. Southerly winds continued to accelerate through the day, with substantial LLWS probable at the coastal terminals today...and continuing at ACV through the TAF period. The strongest winds, along with heavy rain, are expected ahead of the frontal passage late tonight, then winds shift SW and weaken early Tuesday morning after the front passes overhead. Areas of inland valley fog should lift (particularly at UKI) by late afternoon. Rain will spread across the all airports/airfields in the afternoon. Prefrontal deteriorating conditions includes: light to moderate rain, MVFR to LIFR CIG/VIS, LLWS and notably strong southerly winds. Post frontal conditions at Coastal sites will include a threat of thunderstorms. /TA && .MARINE...Hazardous marine conditions will developed across the waters this evening into Tuesday as a storm system moves through, bringing widespread gale winds. Storm force gust up to 60 kts will be likely North of Cape Mendocino. The strongest winds are expected around midnight ahead of the front, then a brief period of high-end gale force southwesterly gusts is possible as the front sweeps overhead early Tuesday morning. Winds are expected to weaken significantly and veer to SW behind the front, dropping to the mid 20 kts range for all zones by dawn on Tuesday. This front will be followed by another solid W swell, with heights likely reaching 20 to 25 ft at 15 seconds across all zones. Conditions then look to settle down a bit later this week, although advisory-level seas and southerlies likely continue for the foreseeable future, with the next pulse expected Wednesday night and Thursday. && .HYDROLOGY...A strong to extreme atmospheric river (moisture flux or IVT`s over 1000kg/m/s) will result in heavy rain across all of Northwest California this evening through early Tuesday morning. Rainfall rates from 0.50in/hr to 1.00in/hr are forecast tonight resulting in an increase threat for debris flow on burn scars, particularly the River Complex burn scar in Northern Trinity county. The Coffee Creek drainage basin will be particularly vulnerable and flash flood watch has been issued for tonight. Hourly rates approach 1.00in/hr for the August complex burn scar from 2020 and the Six Rivers Lightning Complex burn scar from Summer of 2022, but are under thresholds of 1.20in/hr and 1.40in/hr, respectively. Otherwise, minor flooding of small creeks, streams, and urban areas will be possible due to heavy rainfall. Main stem rivers will rise rapidly by early Tuesday morning, however flood stages are improbable (less than a 10% chance) at this time due to the pre-existing low flows and the short duration of the heaviest rain rates, 6 to 8 hrs. All in all, 24 hour rainfall totals are forecast to range from 2 to 4 inches across valleys and the coastal plain, while 3 to 6 inches are expected for the mountains, particularly west and southwest facing terrain. Additional rainfall is forecast for the remainder of the week with the highest threat for hydrological concerns arriving late in the week and into Saturday. Ensemble mean peak IVT`s are under 500kg/m/s. Duration of IVT`s over 250kg/m/s range from 30-40 hours. Some ensemble members indicate higher IVT`s with similar durations which could yield a moderate to strong AR and higher rain rates. Right now it is looking like a weak AR. && .BEACH HAZARDS...A high surf advisory is in effect from Tuesday morning through late Tuesday night. A large westerly mid period swell near 25 feet will aid in breaking waves ranging from 22 to 26 feet along area beaches. The large breaking waves along the coast will lead to increased wave run-up on beaches with waves topping and washing over large rocks and jetties. These large waves can be erratic and unpredictable, and will be capable of sweeping people into the frigid and turbulent ocean water. In addition, mariners traversing the bar are urged to exercise extreme caution or stay in port until the threat subsides. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... High Wind Warning from 7 PM this evening to 4 AM PST Tuesday for CAZ101-102-104>106. High Surf Advisory from 6 AM to 11 PM PST Tuesday for CAZ101-103-104-109. Wind Advisory from 7 PM this evening to 6 AM PST Tuesday for CAZ103. Wind Advisory from 10 PM this evening to 4 AM PST Tuesday for CAZ107>115. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 4 PM PST this afternoon for PZZ450-455-475. Gale Warning from 4 PM this afternoon to 3 AM PST Tuesday for PZZ450-455-475. Storm Warning until 3 AM PST Tuesday for PZZ470. && $$ Visit us at Follow us on Facebook and Twitter at: For forecast zone information see the forecast zone map online:
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1044 PM EST Mon Dec 26 2022 .SYNOPSIS... A weak low pressure system could bring brief snow showers to the western and southern parts of the forecast area this evening into tonight. Then, surface high pressure will build in and keep dry conditions and a warming trend through much of the week. A low pressure system approaches from the west on Friday, increasing the rain chances through New Year`s weekend. && .NEAR TERM /THROUGH TUESDAY/... As of 1031 PM EST Monday: Extensive mid-level cloudiness has spread across the region ahead of an approaching clipper-type short wave approaching from the west. The radar mosaic has been gradually filling in with very light streams of echoes indicative of light precip aloft, but the lowest cut from the KGSP radar suggests that little is reaching the ground at this time because of sublimation in the very dry boundary layer. Better reflectivity was noted over N central GA and on the east side of metro Atlanta. Recent HRRR runs still fail to drop much light snow east of the mtns, but if anywhere stands a chance it would be the Lakelands/Lower Piedmont late tonight. Meanwhile, some light returns were gradually shrinking over northeast TN, but light snow was doubtless falling along the TN border still. Expect a few reports of flurries elsewhere thru the early morning hours. We will continue to let the fcst ride for better or for worse. Either way, no significant snow accum is expected. Otherwise, expect most of the forecast period to be dry outside of the little bit of excitement for later this evening. Overnight lows will be 5-10 degrees below normal for most locations. Any precipitation will shut down by daybreak Tuesday as the axis of the shortwave slips east of the CFWA and DNVA filters in. Surface high will extend across the East Coast during the day Tuesday following the exiting shortwave. Expect decreasing clouds during the morning and mostly sunny skies by the afternoon. Temperatures will start a "warming" trend that will continue through the rest of the week, but most locations will still remain 5-10 degrees below normal for highs on Tuesday. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... As of 200 PM EST Monday: The short term looks pretty quiet, with a nice warming trend continuing thru the middle of the week. Temps starting out a few deg below normal Tuesday night, then warming to a few deg above normal for Thursday`s highs. This will be thanks to an upper ridge building across the Southeast within an amplifying upper pattern across the CONUS, setting up along the Eastern Seaboard by Thursday. At the sfc, high pressure will become anchoring along the East Coast, with a persistent SLY/SWLY low-level flow atop the forecast area advecting in warmer temps. Dry conditions are expected thru the period. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... As of 215 PM EST Monday: A deep trough axis will eject east of the Rockies on Friday, with strong southerly flow developing well ahead of this feature across the central and eastern U.S. The warm-up will continue in earnest as the surface high over the southeast moves off the Atlantic seaboard. Temperatures Friday will rise to 5 to 10 degrees above normal in most areas, with upper 50s to near 60 maxes feeling downright balmy after the recent weather. The 12z model runs are in decent agreement on the upper trough slowly tracking east across the Great Plains Saturday, bringing an embedded shortwave trough thru the Southeast that takes on a negative tilt and lifts northeast of the area Sunday. A low pressure system is expected to develop in response, and activate a warm front across the Deep South. Increasing moisture over the front will allow PoPs to ramp up late Friday thru early Saturday. Temps will remain about 15 deg above normal Friday night due to the cloud cover and strong WAA, and several deg above normal Saturday. So no wintry p-types are expected with showers that break out ahead of the front. The low pressure occludes over the Ohio Valley and brings a cold front thru the area on Saturday. The front should bring a fairly solid band of rain showers across the area. Will cap PoPs at likely for now, given slight timing differences in the guidance. There will be some in-situ CAD that may keep sfc-based CAPE to our south. But some elevated CAPE may result in at least isolated rumbles of thunder Saturday aftn-eve. The GFS and ECMWF bring a dry slot into the area Sunday, while the Canadian keeps things unsettled. The Canadian seems to be an outlier. Either way, Sunday looks like a warm day, with mid 60s possible across the Piedmont behind the "cold front." The upper ridge rebounds quickly across the eastern U.S., and another deep trough digs into the Rockies by Monday. This could bring another front toward the area and returning rain chances late Monday. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/... At KCLT and elsewhere: VFR through the period at all terminals. Cloudiness associated with a passing clipper-type wave is expected to remain mostly above 050 thru late tonight. A mid-level ceiling may persist thru the early morning, but should scatter out by late morning Tuesday. If there is a forecast problem it will be the coverage and chances of light snow thru the early morning hours. Recent guidance has backed off with the precip coverage, so until we see a better indication of snow reaching the ground, most terminals get a VCSH for passing light snow. The exception is KCLT where the TEMPO was kept from the previous forecast for continuity purposes for the time being, because the worst-case scenario depicted remains reasonable. The wave should pass well before daybreak Tuesday. From mid-morning onward, expect only a few patches of cirrus and a light/variable wind. Outlook: Drier VFR weather is expected to last into early Friday before rain chances return for all terminals late Friday into the weekend as a low pressure system approaches out of the west. Temperatures will be on a gradual warming trend throughout the week. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...ARK NEAR TERM...CAC/PM SHORT TERM...ARK LONG TERM...ARK AVIATION...PM
Area Forecast Discussion
National Weather Service Northern Indiana
617 PM EST Mon Dec 26 2022 .SYNOPSIS... Issued at 337 PM EST Mon Dec 26 2022 Cloudy skies will persist through tonight with pockets of light snow and freezing drizzle winding down this evening. Fog may develop later tonight into Tuesday morning across portions of the area. A trend towards much warmer temperatures will continue through the upcoming week. && .SHORT TERM...(This Evening through Tuesday) Issued at 337 PM EST Mon Dec 26 2022 Clipper system, nicely depicted on water vapor with the center over far west central IL, will continue to drift SE out of the area this evening. Although this feature will pass well SW of the area, large scale, weak low level lift was expanding across the area with some pockets of light snow (mainly very light) and even some patchy freezing drizzle as the DGZ continues to flirt with the better lift residing just below it. Not expecting much in the way of impacts at this point but will monitor into the early evening hours when the low level lift hopefully diminishes. Next, and potentially much more problematic issue will be risk for freezing fog, possible dense later tonight into Tuesday morning. Hi res models to some extent or another all show a very shallow but strengthening near sfc inversion with plenty of lingering moisture from the departing clipper and slightly ripening snowpack. The challenge will be how far south the drying works in behind the clipper and if, despite no break in the stratus, can freezing fog develop and potentially become dense. After coordination with surrounding offices, have added a mention of patchy freezing fog to mainly SE sections to start things off. LAV and HRRR all sock in these areas with 1/4 mile or less vsby which would cause some travel issues and warrant headlines. Will defer any further expansion of the fog and headlines to the evening shift. Last, but not least, a vort lobe extends from the clipper north and then east across southern Lk MI with radar returns over the past hour or 2 trying to enhance some. Models continue to show some weak omega lingering in the vicinity of the trough through much of the night, but a fair amount of drying will be underway in the low level as a NW low level flow sets up. The greatest lift will exist into this evening before slowly weakening. Delta Ts will be sufficient in the mid to upper teens with inversion heights in the 4-5Kft range. However DGZ will be above the main omega, which should limit flake size and overall threat. Will maintain slgt chc or may low end chc that was inherited, but not expecting much (1/2 inch to maybe inch) through 12Z Tue. Drier air should finally begin to move in during the day Tuesday, but the low sun angle and strength of the inversion may delay the clearing in the SE areas much of the day. Continued with clearing taking place, but may need to slow even further. Tuesday will be the last day for most, if not all areas, to be below freezing. && .LONG TERM...(Tuesday Night through Monday) Issued at 337 PM EST Mon Dec 26 2022 Pattern shift will continue going from one extreme to the other as closed upper low moving into the NW US opens with the energy dropping southeast, carving out yet another longwave trough across the western US. Increasing SW flow will setup up with highs climbing above freezing Wednesday. Snow pack across most of the area of generally 1 to 3 inches, with locations closer to Lk MI seeing upwards of a foot more more in spots. The lesser snowpack should quickly release and melt off Wednesday for most areas (maybe even start Tuesday afternoon where sunshine is realized), but deeper pack will take a bit more time. The Gulf of Mexico will be wide open for business as the trough begins to move towards the Great lakes for the second half of the forecast, bringing in abundant low level moisture which will not only help get rid of even the deeper snow pack, but also bring increasing chances for rain Thursday night into Saturday as well as some fog and the main push commences. The fog will likely start as early as Thursday and could become dense in some areas, but for the time being has been left out of the forecast. In terms of precip, likely to categorical pops have been maintained. With dewpoints expected to climb well into the 40s (maybe even some 50s in far SE areas) should see the potential for a decent amount of rainfall. Hopefully by the time it arrives the ground is sufficiently thawed (was frozen around 2.5" thick here this morning) to allow the ground to start absorbing it. Rivers should be able to handle it in most areas. The area to be monitored will be where the greater snowpack exists with roughly one half to 1 inch of water trapped and set to release. At this point the heaviest rain may remain southeast of this area but a lot of factors to monitor in later forecasts. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening) Issued at 603 PM EST Mon Dec 26 2022 FZDZ and -SN continue to exit eastern Indiana. Dry conditions are expected for the remainder of the TAF period. Lake effect clouds are likely to roll over KSBN within the next couple hours according the satellite data and derived GOES flight rules. This stratus is rather broken, however, so flight categories may bounce around. Drier air moves into the low-levels and LL wind becomes westerly such that confidence is high that VFR conditions will prevail prior to 12z. The KFWA TAF is low confidence with regard to the previously (18z discussion) mentioned FZFG chance. My pattern recognition leans toward this not being a slam-dunk FZFG case, especially in the absence of a surface stationary front. Forecast soundings are split with regard to low- level saturation. Upstream dew points are in the single-digits with no hints of FG quite yet. Additionally, while stratus is slowly exiting, high clouds are rushing in from WI which may negate the FZFG chance as well. Overall, I cannot completely discount the FZFG chance, but I do have doubts. Therefore, this portion of the TAF is unchanged. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SYNOPSIS...Fisher SHORT TERM...Fisher LONG TERM...Fisher AVIATION...Brown Visit us at Follow us on Facebook...Twitter...and YouTube at:
Area Forecast Discussion
National Weather Service Marquette MI
735 PM EST Mon Dec 26 2022 .SHORT TERM...(This evening through Tuesday Night) Issued at 306 PM EST MON DEC 26 2022 Water vapor imagery and RAP analyses show mid-level ridging along the western US and troughing over the east half of CONUS. In the resulting nw flow across the central U.S., a well-defined shortwave is tracking well to our southwest, into western IL this afternoon. Closer to home, under low-level NW flow and 850mb temps of -15 to -18C, lake effect snow continues to stream off of Lake Superior. Inversion heights remain modest at around 4 to 6kft, but with the DGZ generally occurring at around 2 to 4kft. So, this is helping to keep in some fairly high snow ratios and lighter, fluffy snowflakes. We continue to see a brief burst of heavier snowfall rates at times with some higher-reflectivity echoes on radar. This type of setup is also favorable for flurries and snow showers to extend well inland from the lake, possibly crossing hwy 28 into the central UP at times. The rest of the afternoon, winds start to back more to the west. This will cause lingering lake effect to become more isolated to the Keweenaw and eastern Superior shorelines. With some deepening of the moisture profile from the NW UP into eastern Upper MI, LES may get a little boost in intensity tonight. While lower inversions will be a negative, the DGZ dominating the convective layer will support 1-2 inches, possibly isolated 3 inches, of fluffy snow accumulation into the eastern forecast area where longer fetch will support deeper convection than over the west. The Keweenaw may end up with an inch to locally 2in by the time lake effect snow shifts north of the area early Tuesday. The weather turns somewhat active for Tuesday with a clipper moving through and bringing in a quick burst of precipitation into the afternoon. Persistent southwesterly flow will lead to robust warm air advection aloft through Tuesday, with a fairly prominent warm nose developing in soundings by the afternoon as 850mb winds increase to 40 to 50kts and the shortwave drops southeast through the area. While much of the current deterministic and ensemble guidance allows for some QPF across most of the UP, there is a general consensus now for a swath of higher QPF across the Keweenaw and the eastern half of UP and fairly light amounts elsewhere. A local maximum across the southeastern UP may be owing to some localized enhancement from Lake Michigan amid southwest flow. With that warm nose extending well into the area according to latest model soundings, precipitation should pretty quickly change over to a wintry mix with snow and sleet - though some icing is not totally out of the question in the southern UP, where the re-freezing layer may become rather shallow. It should be noted that surface temperatures are only expected to peak in the teens to lower 20s area-wide. Snow and sleet totals will be highest across the Keweenaw and eastern UP, with a potential for some spots to flirt with the 2 to 4in range by the time precipitation starts to move out late Tuesday night. However, there is still a bit of uncertainty with totals, as a more northerly track could result in much of the area missing out on any precipitation at all. In addition to a potential quick round of wet snow or snow/sleet, winds will also be turning gusty on Tuesday with quick pressure falls and the low level jet nosing in. Gusts to 20 to 25mph are possible across much of the area by Tuesday afternoon, through the first half of Tuesday night. Higher gusts around and even in excess of 30mph are possible closer to the water, especially the Lake Michigan shoreline. This marriage of wet, heavy snowfall and gusty winds will be something to keep an eye on, as fallen tree limbs and power outages may become a concern. .LONG TERM...(Wednesday through Monday) Issued at 148 PM EST MON DEC 26 2022 Starting off 12z Wednesday, upper level pattern begins to amplify across CONUS as broad troughing exits out of the Rockies and pushes ridging over the eastern half eastward. As this progression occurs into the weekend, Upper Michigan will find itself on the western flank of the ridge in southwesterly flow as the trough approaches. Within this pattern, a system is expected to lift northeastward into the northern Plains/Upper Great Lakes Thursday night. Overall, with the airmass aloft supporting above normal temperatures during this period, the forecast period includes a mix of ptype possibilities. Mid-upper level ridge axis shifts through the forecast area Wednesday as a warm front is draped across the forecast area. Guidance suggests a mixed bag of options for where the boundary is expected to be, but confidence is high that eventually Upper Michigan will find itself south of the boundary in the warm sector and under the influence of increasing increasing moisture. Model soundings suggest that periods of light mixed precip, drizzle, and fog will be possible until at least Friday, when a low`s cold front swings through the region. Model spread in the track of the low still exists, but there is increasing confidence that the low will track to our west, resulting in highs and dewpoints climbing above freezing. As the cold front swings through, deeper moisture and frontal forcings may support a mix of ptypes. Beyond this, the pattern continues to be muddy, but its now looking possible that the New Year`s Eve Holiday may be dry. The next system of note on the horizon looks to lift northeastward through central CONUS early next week. Similarly to the late week low, the airmass with this system continues to suggest mixed precip type could be on the table. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 734 PM EST MON DEC 26 2022 VFR conditions have returned to all TAF sites this evening with a shift in wind to the WSW. However, the good conditions will be short-lived as another system enters the area tomorrow. Conditions will quickly deteriorate back to MVFR and even some IFR by the afternoon. In addition, southwest winds will become strong with sustained speeds in the 12 to 15 kt range, gusting to 27 kts. LLWS will be a threat at KIWD from mid morning tomorrow through tomorrow afternoon. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 148 PM EST MON DEC 26 2022 Northwest flow today has resulted in winds across Lake Superior of around 25-35 kts, with a decreasing trend observed in observations through the morning. For the remainder of the afternoon and overnight tonight, expecting similar conditions, expect winds shift to westerly in the east and southwesterly in the west ahead of another system moving through the region. Winds look to remain around 25kts through the day Tuesday midday. By Tuesday afternoon and into the evening, pressure falls and a LLJ moving overhead will support winds increasing to around 30kts in the east. Some gales of ~35kts could mix in during this period, but confidence is low. After this system exits east, a couple weak systems could move through the region, but guidance suggests winds of 20kts or less could persist over the lake through the end of the week. Patches of moderate freezing spray are possible across the lake tonight with more widespread moderate freezing spray diminishing on Tuesday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...LC LONG TERM...JTP AVIATION...TDUD MARINE...JTP
Area Forecast Discussion
National Weather Service Pocatello ID
739 PM MST Mon Dec 26 2022 .UPDATE...Dense fog has developed on ITD observation sites and at the KRXE and KIDA ASOS sites. Since it appears widespread, and with only warm advection expected tonight, do not see any mixing of faster air to the surface and so only expect the fog to worsen. A Dense Fog Advisory has been issued to highlight the hazard. Messick && .PREV DISCUSSION... /issued 211 PM MST Mon Dec 26 2022/ SHORT TERM...Tonight through Tuesday night. Atmospheric river event set for southeast Idaho tonight through Tuesday night with heavy precipitation and warm temperatures expected. Right now it appears heaviest snow will be above 6,500 feet with rain at lower elevations. Wind gusts of 40 to 50 mph also expected at the highest elevations where 8 to 20 inches of snow are expected at pass level. Winter storm warnings have been issued in the central mountains and Sawtooth region overnight tonight through Tuesday and for the eastern mountains Tuesday morning through Tuesday night. Rain is expected for the Magic Valley and Snake River Plain and even the lowest mountain region valleys with the system. At elevations where snow does fall extensive blowing snow is expected with very hazardous driving conditions. Highs Tuesday are expected to be in the low to mid 40s along the interstate corridor in the Snake Plain with 30s in the mountains. It is expected to drop below freezing again Tuesday night behind the cold frontal passage. GK LONG TERM...Wednesday through Monday. Afternoon highs will drop for Wednesday behind the cold front with most of the Magic Valley and Snake Plain in the low to mid 30s and the Upper Snake Plain and Eastern Highlands a couple degrees cooler, in the upper 20s to low 30s. Highs drop a couple of degrees more by Thursday afternoon with more low 20s to low 30s before we gain those couple of degrees back by Friday and Saturday. Cooler air begins to work its way in on Sunday and Monday with highs mostly in the 20s with some low 30s as you head west through the Magic Valley. Wednesday will still be a bit breezy throughout the Snake Plain with gusts in the 20-30kts range. Now to precip chances in the extended forecast. As the trough shifts eastward on Wednesday, snow will still be falling in the Bear River Range and upper elevations of the Eastern Highlands before beginning to taper off in the second half of the day. Light snow is possible on Thursday as we remain in northwest flow. The next bigger push of moisture moves in on Friday as another shortwave passes through and returns us to more westerly flow. Models want Friday`s precip to be all snow, but with highs for some of us above freezing, we could see a mix at times. For now, the NBM 4.1 is showing a 20-50 percent chance of at least 2 inches of snow by Saturday morning for those of us at the lower elevations. Yet another trough moving through on Saturday brings the potential for some moisture along the Idaho/Utah state line, but the bulk of that looks to stay just a bit farther south. It will bear watching as it could bring some moisture to more of our CWA according to the GFS as the trough shifts northeastward. The ECMWF would rather dig it farther south and east, allowing brief ridging to build in over us on Monday. AMM Aviation...18Z Monday to 18Z Tuesday. Conditions throughout the better part of Monday look to stay generally VFR at all sites with borderline MVFR CIGs at times at DIJ. For now, we`re actually getting to see some sunshine and fog has lifted north of Idaho Falls, though looks like it settles back in around 03-04Z tonight, approaching minimums. Moisture will move in from west to east overnight though and winds will pick up on Tuesday. With the winds, LLWS looked marginal overnight into early Tuesday, so have kept it out of TAFs for now, but it will be worth watching. At SUN, precip looks to stay all snow, arriving around 10Z and drops VIS and CIGs to IFR. At BYI and PIH, mostly rain which arrives around the 12-13Z time frame Tuesday morning. Conditions drop to MVFR, but IFR looks more likely at PIH closer to 18Z. Outside of fog issues at IDA, more moisture arrives around 14Z, but with temps right at or just below freezing, the NAM and HRRR both agree we could see brief FZDZ or rain/snow mix before switching over to all rain. For DIJ, have kept it all SN once moisture arrives around 14Z with VIS and CIGs dropping quickly once it begins. The wind is already beginning to increase at BYI, but look for more widespread gusts generally 25-35kts at BYI, PIH, and DIJ after 13Z with IDA following suit shortly after. Wind doesn`t really pick up at SUN until closer to 20Z Tuesday. AMM HYDROLOGY...Temperatures will gradually warm up through mid- week, with lower elevations pushing into the low/mid 40s and generally no colder than low/mid 30s elsewhere. Overnight lows tonight will remain right at or below freezing, with the exception of portions of the eastern Magic Valley and lower Snake Plain which could remain in the mid 30s. Overnight lows Tuesday into Wednesday will be cooler, with mostly everywhere reaching at or below freezing. Rain and mixed precipitation will be likely as snow levels rise, increasing the potential for minor flooding and ponding concerns. AIR QUALITY...An Air Quality Advisory is in effect for Franklin County due to stagnant air and degraded air quality. Members of sensitive groups may experience health effects and are encouraged to limit their exposure. Air quality is expected to improve Tuesday, once the next system arrives and the atmosphere becomes mixed. && .PIH WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until noon MST Tuesday for IDZ052-053-065-068. Winter Storm Warning from 5 AM Tuesday to 5 AM MST Wednesday for IDZ058-060-062>064-066. Winter Storm Warning from 11 PM this evening to 11 PM MST Tuesday for IDZ071>075. && $$