Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/04/22


Area Forecast Discussion
National Weather Service Lincoln IL
901 PM CST Mon Jan 3 2022 .SYNOPSIS... Issued at 248 PM CST Mon Jan 3 2022 After a brief and modest warm-up on Tuesday, a cold frontal passage early Wednesday morning will bring strong westerly winds and nearly steady temperatures during the day before a sharp cool-down occurs on Wednesday night. The next chance of snow comes to central Illinois on Thursday. && .UPDATE... Issued at 900 PM CST Mon Jan 3 2022 A pressure gradient will slowly increase across central IL overnight as a surface high pressure ridge moves farther to the east and low pressure moves into and deepens in the northern Plains. The resulting southerly wind should be modest, generally 5 to 10 mph, but increasing gradually toward morning. Temperature falls should be limited as a result, and expect lows ranging from 17 in Galesburg to 24 in Lawrenceville. Cloud cover will be just high and thin. Afternoon forecast package is on track with these features, and no significant updates are needed this evening. && .SHORT TERM...(This evening through Tuesday) ISSUED AT 248 PM CST Mon Jan 3 2022 Current day cloud phase satellite imagery depicts snow cover well, with at least some snow cover detected at most locations northwest of I-55. In addition, cloud cover is still hanging on in southeastern portions of the forecast area with broken stratocumulus observed mainly south of I-70. Blended sky cover forecasts are not handling this well, so relied heavily on the latest HRRR to incorporate current sky cover trends. Light west/southwest winds have developed at most locations in central Illinois as the surface ridge has moved off to the east of the area. Expect fairly light south winds to continue through the overnight hours, with a speed increase as well as some gustiness developing after sunrise. The surface pressure gradient will be increasing in response to the development of and movement of a surface low across the northern Plains. South winds will be elevated on Tuesday, and in addition daytime temperatures should be the warmest of the week with highs in the mid 30s to mid 40s. .LONG TERM...(Tuesday night through Monday) ISSUED AT 248 PM CST Mon Jan 3 2022 The shortwave trough digging from the northern Rockies into the Plains/Midwest from Tuesday into Wednesday, and the associated surface low, will bring the next cold front with it. Current timing has south winds continuing into Tuesday night with the front crossing central Illinois during the early morning hours on Wednesday. Given the pressure rises behind the front and potential for elevated wind speeds NBM wind speeds were boosted during the Tuesday night - Wednesday night period. ECMWF EFI values north of I-72 during this period are in the 0.7-0.8 range, indicating deviation of the ensemble membership from climatology for the wind speed forecast. Temperatures will struggle to warm at all during the day on Wednesday, with a sharp drop anticipated on Wednesday evening. On Thursday, the next short wave trough is expected to affect central Illinois. Unfortunately, there still isn`t great agreement amongst guidance as far as the strength/track of this wave and associated QPF amounts. WPC cluster analysis still shows about 55% of members with a weaker wave and very light QPF, about 25% of members with a stronger wave and greater than 0.25" south of I-72, and the other 20% somewhere in the middle. Translated, odds currently lean toward a light snow event for most of the forecast area on Thursday but with potential for several inches especially south of I-72. Snow ratios of 13-16:1 mean that it won`t take much of a QPF change to change snow amounts substantially. Notably, the ECMWF EFI for snow on Thursday depicts an area with values of 0.5-0.6 south of I-72 on Thursday, indicating deviation from ensemble climatology toward an unusual event. These values are a bit higher than yesterday, which is at least something. Following Thursday`s short wave trough, winds potentially continuing at 10-15 mph into the overnight hours along with temperatures in the single digits to a bit below zero will combine for some bitter cold wind chills. Wind chill temperatures by Friday morning may fall into the -15 to -20 deg F range or even colder. Following another day with highs in the teens on Friday, expect some warming on Saturday ahead of the next short wave trough, with high temperatures expected to be back above freezing. A chance of precipitation will exist southeast of the surface trough. Both the GFS and ECMWF deterministic models bring the cold front through early on Sunday morning with a return to colder temperatures, but WPC cluster analysis shows this agreement may be coincidental with about 35% of members delaying the front and keeping temperatures relatively warm on Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 522 PM CST Mon Jan 3 2022 VFR conditions with increasing high clouds over the upcoming 24 hours. Winds S 5-10 kts overnight, increasing to 10-14 kts with gusts around 20 kts after 12Z, and finally reaching 15-20 kts with gusts 25-30 kts by 17Z-18Z. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...37 SYNOPSIS...AAT SHORT TERM...AAT LONG TERM...AAT AVIATION...37
Area Forecast Discussion
National Weather Service North Platte NE
842 PM CST Mon Jan 3 2022 .UPDATE... Issued at 842 PM CST Mon Jan 3 2022 Just upgraded the high wind watch to a high wind warning for portions of the eastern Nebraska Panhandle, western Sandhills and far southwestern Nebraska. Looking at the latest HRRR and NAM12 soln tonight and their H85 wind forecasts, feel confident enough to upgrade the high wind watch to a warning for all counties except Sheridan county. After coordinating with CYS, will leave Sheridan county in a watch as there is some doubt as to how far north the axis of high winds will reach. Went ahead and added Perkins and Chase counties as HRRR and NAM12 Bufkit soundings indicate mixing potential around 60 MPH centered around 1 PM MST. For the high wind warning, it will run from 9 AM to 5 PM MST. && .SHORT TERM...(This evening through Tuesday night) Issued at 350 PM CST Mon Jan 3 2022 The forecast concern in the short term will be high wind potential on Tuesday with the arrival of an arctic cold front Tuesday night. Surface low pressure will extend from southwest SD and western NE 12Z Tuesday as a prefrontal trough moves east during the morning. A cold front will then drop southeast during the afternoon. This will bring the potential for high winds to the western Sandhills and southwest NE. The 18Z HRRR wind gusts support gusts to around 60 mph across the eastern panhandle into Grant, Arthur, and Keith County which remains within the current High Wind Watch area. The GFS and NAM bufkit soundings do not support expanding the High Wind Watch area. Used the NBM 90th percentile for winds, and windy conditions will also occur elsewhere with gusts from 35 to 50 mph expected. .LONG TERM...(Wednesday through Monday) Issued at 350 PM CST Mon Jan 3 2022 The forecast concern in the long term will be significant snowfall potential Wednesday into Wednesday night and bitter cold temperatures through Thursday night. Much colder temperatures will drop into western NE Tuesday night with lows from 0 to 5 below north central and wind chills approaching 20 below. Highs Wednesday only 5 to 10 above north to the upper teens and low 20s southwest. Computer models have come into better agreement on significant snowfall across wrn Nebraska Wednesday into Wednesday night. There are still track differences regarding the location of a 100 mile wide band of snow ranging from swrn Nebraska to the northern Sandhills. The SREF mean is farthest north, while the ECMWF and NAM are nearest the current forecast. The GFS, on the other hand is farthest south, although some members of the GFS also have varying solutions further north. The current forecast continues to focus the heavier snowfall in a 40 mile wide band centered along highway 26 in the Panhandle and then southeast to along I-80 through North Platte and Brady. This system will track southeast from WY into wrn and swrn NE. Fairly strong isentropic upglide will be present on Wednesday, with downglide increasing from west to east during the evening. Similar to the recent snow event on Dec. 31 into Jan 1st, snow ratios will be high, due to the presence of arctic air in place. Currently using a 17-18:1 ratio Wed. into Wed. night. Within the axis of highest QPFs, from 0.30 to 0.35 inches, resulting snowfall totals of 5 to 6 inches are forecast. Higher ratios of 25:1 are certainly possible, and have issued a Winter Storm Watch from 15Z Wednesday until 12Z Thursday for the southeast panhandle into much of west central NE. A very favorable snow growth environment should develop in the arctic air. Frontogenesis and lift is strong in the dendritic growth zone which, for this system, is quite deep, from 550-850mb. This further increases the concern that a light fluffy snow will occur with snowfall amounts greater than 6 inches in the heavier snow bands. In addition to the snow, northeast winds will become north by evening with frequent gusts from 15 to 25 mph. Blowing snow is forecast. The wind chill values are likely to fall to 20 to 29 below overnight Wednesday and possibly even colder, as temperatures fall to 5 below to near 20 below. The latest forecast suggest Wind Chill Advisories and Warnings may be needed across all of wrn and ncntl Nebraska Wednesday night and Thursday morning. Very cold Thursday, with highs only 5 to 15 above. Weak warm air advection aloft begins on Thursday, to bring a slight chance for light snow into Thursday evening, mainly across the western Sandhills and north central NE. A warming trend Friday into Saturday. The next upper trough moves into the region Saturday, which is forecast to bring a cold front into the area later Saturday into Sunday. Highs next Sunday will be colder on the 30s, but should warm back up by next Monday as upper ridging begins to build back in. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 606 PM CST Mon Jan 3 2022 Strong winds will be the main aviation concern over the next day. Gusty westerly winds are expected across the region by late tomorrow morning and continuing through the afternoon. Gusts up to 40 knots could be possible especially in the afternoon. Winds diminish slightly after sunset with the next chance of snow arriving after 00Z Wednesday. && .LBF WATCHES/WARNINGS/ADVISORIES... High Wind Warning from 9 AM to 5 PM MST Tuesday for NEZ022-023- 035-056>058-069. Winter Storm Watch from Wednesday morning through late Wednesday night for NEZ022-023-035-036-056-057-059. High Wind Watch from Tuesday morning through Tuesday afternoon for NEZ004. && $$ UPDATE...Buttler SHORT TERM...Roberg LONG TERM...Roberg AVIATION...Kulik
Area Forecast Discussion
National Weather Service Marquette MI
656 PM EST Mon Jan 3 2022 .SHORT TERM...(This evening through Tuesday) Issued at 258 PM EST MON JAN 3 2022 GOES imagery and RAP analysis show a low-amplitude wave passing to the north of Lake Superior today as increasing SW flow has brought increasing temperatures back closer to normal this afternoon. Some mid-level clouds are increasing upstream across northern WI in response to WAA. Benign conditions are expected through the rest of the day with only an isolated snow shower possible across the Keweenaw. Moisture is shallow, but as a sfc trof crosses the lake it could be just enough to spit out a few showers. Tonight, winds veer around to E to SE as the weak sfc low pulls away and a sfc trof approaches btwn two ridges. While this won`t amount to much, there could be some add`l light snow showers across the Keweenaw late tonight as easterly flow upslopes across the Peninsula. More likely will be some lower clouds by tomorrow morning. While winds relax tonight, clouds are expected to hang around through the night...then then increase towards tomorrow morning, which should help temps from crashing too much. Depending on the cloud cover, temps will be around zero to the low teens above zero where clouds persist the longest. Should any location go some time without clouds, single digits below zero will be possible...more likely across the interior and along the WI state line. Tomorrow, as the advertised mid-week low approaches from the Dakotas, southerly WAA flow will increase cloud cover across the UP with temperatures climbing up to around 30 across the east half. Moisture remains limited throughout the day, so not expecting much in the way of pcpn; however, there could be some isolated -shsn/fzdz across the east with some assistance from Lake Michigan. Some isolated shsn will continue across the Keweenaw, but moisture remains limited so accums through the day aren`t expected. The aftn will become breezy...especially across the east half. WAA downsloping into along the Superior shore could bring gusts to around 30mph for the aftn as well as along the Lake Michigan shoreline. .LONG TERM...(Tuesday night through Monday) Issued at 347 PM EST MON JAN 3 2022 The start of the long-term period will be marked by the incoming, well-advertised low that has decent definition in the lower levels, but only briefly tightens up in the upper levels as it crosses the Upper Great Lakes late Tuesday into Wednesday. The system will be accompanied by PWATs approaching the 90% moving average for early January (so just shy of a half inch). On Tuesday night into Wednesday, models depict low-level frontogenetical forcing initially offshore moving inland toward the SE across much of the U.P. On Wednesday, a LLJ develops over the Great Lake of Superior and noses into the U.P. At the surface, winds with a more Erly component overnight Tuesday becomes more NErly to Nrly on Wednesday. Putting all of this together, the picture comes together to form a forecast of continuing to support watch (to perhaps warning) level criteria for heavy snow within the areas that already have a headline going. The ingredients come together for the heaviest snow to fall in the late overnight to early morning period for the Keweenaw and west, and in the first half of Wednesday for Marquette and Baraga counties. Also note that blowing snow becomes increasingly likely near and along Lake Superior on Wednesday, adding to the less-than-ideal driving conditions expected. But, this system snow becoming lake enhanced event will turn into LES later Wednesday from west to east as the responsible low continues its ENE trek. Supportive wind and thermal profiles indicate the LES chances will persist for portions of primarily the northern U.P. through much of the remainder of this first full week of 2022, looking to taper off by week`s end. However, the rest of this long-term period looks to remain active as another system grazes past over the weekend. The aforementioned (see discussion above) WAA late Tuesday will be on the decline overnight, with CAA taking over Upper Michigan by late Wednesday. Near normal temps overnight Tuesday into Wednesday will be replaced by below normal temps for the second half of the week, but then rebounding back toward normal over the weekend. The coldest night looks to occur Thursday night into Friday morning, with widespread single digits on either side of the zero degree mark. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 656 PM EST MON JAN 3 2022 In the wake of a cold front that has passed CMX, lake aided postfrontal low-level moisture and upslope flow should maintain IFR cigs thru the evening. As the flow veers to a weaker upslope northerly direction overnight, cigs should lift to low MVFR. Winds will continue veering, settling to an easterly direction by morning. This should result in cigs slipping back to IFR. There may be slight improvement back to low MVFR in the aftn. At IWD, front will be weakening as it approaches, so postfrontal low- level moisture may not reach the terminal. Overall, VFR conditions should prevail tonight, but there will be a period late evening into the overnight where low MVFR cigs may occasionally appear. Expect VFR on Tue. Approaching low pres system may bring -sn/MVFR cigs near the end of the fcst period. At SAW, VFR should prevail thru the evening. Low-level moisture associated with the weakening cold front may lead to IFR cigs developing late tonight. A developing light upslope se wind developing Tue morning would then work to hold IFR cigs in place. Some improvement to low MVFR possible by aftn. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 258 PM EST MON JAN 3 2022 Westerly winds to around 30 knots will remain possible through this evening behind a passing low to the north of the lake. Winds will relax tonight as they veer around to the E to SE for Tuesday, increasing through the afternoon and evening as a low pressure system approaches from the west. This low will pass through the Mackinac Straits Wednesday afternoon. As this low moves through Tuesday night, NE gales to 45 knots are expected across the west and central, with a chance for a few hours of storm force gusts to 50kts. NE gales of 40 to 45 knots are expected across the east. As the low pulls away on Wednesday, winds will become northerly with gales to 40 knots possible through Wednesday evening. Freezing spray may be heavy at times as the low builds waves upwards of 16+ft. High pressure will return for Thursday and Friday, with seasonally light winds to around 20 knots expected; however, a cold air mass will remain over the lake with temps around 10 to the mid teens Thursday and Friday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Winter Storm Watch from Tuesday evening through Wednesday evening for MIZ001-003. Winter Storm Watch from Tuesday evening through Wednesday evening for MIZ002-009. Winter Storm Watch from late Tuesday night through Wednesday evening for MIZ004-005-084. Lake Superior... Gale Watch from Wednesday morning through Wednesday evening for LSZ267. Gale Watch from Tuesday evening through Wednesday evening for LSZ266. Gale Warning from 7 PM EST /6 PM CST/ Tuesday to 5 PM EST /4 PM CST/ Wednesday for LSZ162. Gale Warning from 7 PM Tuesday to 7 PM EST Wednesday for LSZ263- 264. Gale Watch from late Tuesday night through Wednesday evening for LSZ241>245-265. Gale Watch from late Tuesday night through Wednesday afternoon for LSZ240. Lake Michigan... None. && $$ SHORT TERM...JAW LONG TERM...lg AVIATION...Rolfson MARINE...JAW
Area Forecast Discussion
National Weather Service Phoenix AZ
400 PM MST Mon Jan 3 2022 .SYNOPSIS... High pressure with dry and mostly clear conditions will be persistent through the week. Localized freezing temperatures will again be possible Wednesday morning, but mainly away from population centers. Temperatures are forecast to warm to slightly above normal readings starting Thursday, likely lasting through the upcoming weekend. && .DISCUSSION... Upper level ridging has returned to the Desert Southwest with dry southwest flow aloft. RAP analysis soundings show a very dry atmosphere with PWAT near 0.15 inches this afternoon. Closer to the surface, lingering cold air remains entrenched in the wake of the previous storm system. This led to low temperatures in the 30s across many lower desert locations once again this morning, albeit a few degrees warmer than yesterday. A weak northerly gradient increased wind speeds a bit along the foothills north and east of Phoenix and contributed to the somewhat warmer lows seen there. Upper level heights will continue to rise the next few days as a strong area of high pressure builds in along the west coast and Desert Southwest regions. This will allow for temperatures to warm a few degrees each day. Temperatures will climb to above normal readings by mid week and remain there through the coming weekend. Wind speeds will remain very light for most of the week as well. An upper level trough will pass well to the north on Tuesday, slightly increasing the upper level relative humidity. Accordingly, periods of high clouds are possible Tuesday and Wednesday, but clouds should be thin enough that they will not impact daytime heating much. The warmest daytime highs this week are likely to fall on Thursday and Friday with readings topping out at around 70 degrees. The NBM shows about a 50% of reaching 70F or greater in Phoenix by Friday. In Imperial and Yuma, the odds are 65-70%. The amplified flow aloft later this week could eventually result in a weather system diving southeastward toward our region over the weekend, but the majority of ensemble guidance shows this system merely lowering geopotential heights and bringing a slight dip in temperatures on Saturday. WPC cluster analysis reveals that a minority of ensemble guidance do allow for this trough to dig deep enough to bring a slight chance of showers to the region. However, this appears to be very GEFS-centric, with the EPS and GEPS remaining completely dry and the latest NBM showing a less than 5% chance of precipitation. The most likely outcome is for dry conditions to continue with an increase in clouds, breezy conditions, and a drop in temperatures for a few days. && .AVIATION...Updated 2300Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and Southeast California/Southwest Arizona including KIPL and KBLH: No weather impacts are anticipated through Tuesday evening with only a few high cirrus decks. Trends in winds will be nearly identical to the past 24 hours with prolonged periods of light and variable character. && .FIRE WEATHER... Wednesday through Sunday: Weak high pressure will dominate across the region through the majority of the period with dry conditions prevailing through at least Saturday. Temperatures will return to seasonal normals by the middle of the week and likely slightly above normal by late week. Aside from some occasional light afternoon breezes, winds will generally be light through the entire period. Minimum RHs through the period will mostly be in a 25-35% range, while overnight max RHs mostly climb above 60%. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Hodges/Kuhlman AVIATION...18 FIRE WEATHER...Kuhlman
Area Forecast Discussion
National Weather Service Blacksburg VA
647 PM EST Mon Jan 3 2022 .SYNOPSIS... High pressure will build across the region tonight, resulting in significantly colder temperatures. The high will drift overhead Tuesday, maintaining a mostly clear sky with light and variable winds. A dry front is forecast to pass across the region Wednesday, then stall to our south Wednesday night. Thursday, an upper level trough dropping southeast from the upper midwest is expected to result in a wave of low pressure to develop along the stalled front to our south...which will be the next opportunity for wintry precipitation. && .NEAR TERM /THROUGH TUESDAY/... As of 630 PM EST Monday... Significantly colder tonight with potential for black ice. Have slowed down the clearing on the western slopes of the central Appalachians. Otherwise no changes in the forecast. High pressure will build across the forecast area tonight, passing overhead Tuesday. For areas with fresh snow cover, this will set the stage for a very cold night tonight, temperatures dipping into the teens. Some of the mountain valleys may see readings dip into the single digits. Any snowmelt which occurred today will refreeze with potential for patches of black ice on roads and sidewalks. Tuesday will feature a sunny but cold day. With temperatures starting off well below freezing, it will take much of the day to recover into the 30s. Southside may reach 40, but given the fact the airmass is so dry (dewpoints in the teens) the wetbulb zero will remain under 32 degrees through the day. As such, expecting little or no snow melt Tuesday. If anything, the snow may sublimate more than melt and/or compact due to the fact the ground is not froze underneath. At any rate, still have an opportunity to do some sledding. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 245 PM EST Monday... High pressure gives way to another potential quick-hitting system Thursday night... Longwave trough centered over the Great Lakes with several shortwaves embedded within the flow will continue to send quick moving systems across the CONUS. Tuesday night into Wednesday, surface low over the Great Lakes shunts high pressure east into the Atlantic. Weak southwest/west flow will allow for mild temperatures Wed/Thu ahead of a dry cold front that pushes through Thursday afternoon. The next system to keep our eyes on drops out of the northern Plains on Thursday. The big question here is how far south this piece of energy digs, along with how far west or east it is once it begins to take on a negative tilt. Should things line up perfectly with a negatively tilted trough over western North Carolina late Thursday, another light snow event will be entirely possible for the mountains of North Carolina, Virginia, and West Virginia as surface low pressure tracks along the cold front, exiting rapidly to the northeast. With the trend in the operational and ensemble guidance trending a little snowier today, added in some light accumulations mainly for the higher elevations Thursday night, but some still may spill into the Piedmont. Details on this will be ironed out in the next few days. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 245 PM EST Monday... Cold air returns Friday as high pressure settles in with another front approaching Sunday night/Monday morning... Quick shot of cold air and potentially gusty winds will be possible Friday morning behind a departing low pressure. Temperatures Friday morning will features widespread teens for the mountains and 20s in the east. For the mountains winds could be quite gusty at times and wind chill values will be in the single digits to below zero at times. We remain dry into Saturday as high pressure moves in overhead and winds relax. Temperatures could potentially be even colder Saturday morning with some single digits possible in the higher elevations, especially if there is any snow cover. Warmer on Sunday as flow turns back to the southwest in advance of another cold front which will bring another round of rainfall Sunday night into early Monday. High pressure returns once again for mid- week. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 630 PM EST Monday... High pressure will cross the Tennessee Valley this evening and will be centered over Virginia Tuesday morning. As a result, wind speeds will diminish overnight. By Tuesday afternoon, the high will be offshore and surface winds will turn to the south to southeast. Have slowed down the clearing of the upslope clouds over the west side of the Appalachians, similar to the HRRR and 3kmNAM. Most locations will become VFR before midnight, but expect the clouds to linger for most of the night at KBLF. Conditions will be VFR for Tuesday. Above average confidence for ceiling, wind and visibility. .Extended Aviation Discussion... Conditions will be VFR Tuesday night and Wednesday. Another storm system will impact the region Thursday night and Friday with potential for sub- VFR. Saturday will be another dry day in between low pressure systems. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PM NEAR TERM...AMS/PM SHORT TERM...BMG LONG TERM...BMG AVIATION...AMS/PM
Area Forecast Discussion
National Weather Service San Diego CA
113 PM PST Mon Jan 3 2022 .SYNOPSIS... Returning onshore flow will bring cooler days, breezy conditions over the mountains and deserts, and patchy low clouds to temper overnight lows west of the mountains through Tuesday. A weak ridge aloft and offshore flow will return fair, dry, and warmer conditions midweek, with temperatures climbing back above average. Onshore flow increases again to wrap up the week with more clouds, and a return to cooler weather. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Satellite imagery at midday showed some high clouds drifting SE across the State, and just beginning to affect SoCal. There were some lower, marine clouds, but they were still well offshore and showing no sign of advancing east across the Bight. The sfc pressure gradient across SoCal was very weak, but there is an onshore trend, and just after noon, we were just beginning to see some SW-W gusts exceed 30 MPH at higher elevations. Winds should continue to ramp up over the mountains and veer a bit more W-NW through tonight. We could see a few of those lower clouds develop along the coast later tonight, but trends suggest there won`t be much. It will be cool again tonight, but not as cold as last night, with patchy frost still likely well inland, in low, wind-sheltered areas and in the lower deserts. Tuesday will still be fair and cool. There may be a few morning clouds/patchy fog west of the mountains to start out the day though. By Wednesday, a weak ridge will be drifting east, approaching the West Coast. This will weaken the onshore flow and trend us back offshore, along with rising heights/ thickness. This will result in the warmest day in some time as afternoon temperatures climb to about average. The warmest day should be Thursday, before the ridge weakens and another shortwave pushes onshore for the weekend. We should see a surge in the marine layer on Saturday, but other than that, it looks to stay dry and cooler Friday and Saturday. For Sunday, a new ridge pops up along the West Coast and our surface winds turn back offshore. This means some warming should follow, and at least from the ensemble perspective, that is the temperature trend favored. There is a small chance that we could see some precipitation over the weekend, but it is only a handful of the GFS/ECMWF ensemble members that are highlighting this, so not something to count on at this point, and it is not in the forecast. && .AVIATION... 032100Z...A mostly clear sky will continue with just few-sct passing high cirrus cloudiness. Low clouds haven`t made any headway towards the coast today. HRRR shows the marine layer stratus remaining well offshore. Given these trends, have amended to keep VFR prevailing under a mostly clear sky through Tuesday at all terminals. && .MARINE... No hazardous marine conditions are expected through Friday. Occasional gusts exceeding 20 knots are expected around San Clemente Island Tuesday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE PZ...NONE. && $$ PUBLIC...10 AVIATION/MARINE/BEACHES...Gregoria
Area Forecast Discussion
National Weather Service Sacramento CA
220 PM PST Mon Jan 3 2022 .SYNOPSIS... Mountain snow and Valley rain showers continue through Tuesday along with strong winds. Another chance for wet weather possible late in the week. && .DISCUSSION... Showers began over Shasta County and the Coastal Range early this morning and are slowly moving inland this afternoon. Snow levels began around 1500-2000 feet this morning for the northern mountains. Based on area webcams, spotter reports, and snow level radar observations, snow levels have risen to closer to 2500-3000 feet this afternoon as forecast. Snow levels will be higher over the western Plumas County mountains and northern Sierra when snow starts, around 4000-5000 feet. As the front moves through interior Northern California late this afternoon and evening, NAM 3k and HRRR depict precipitation rates will increase, especially snow amounts over the mountains north of Highway 50. This is also when showers will move south through the Valley south of Shasta County, though Valley showers will remain fairly light. Snow levels will continue to rise to around 5000-6000 feet by tomorrow morning across the region. The majority of snow and rain will taper off by early tomorrow, with lighter showers continuing into early Wednesday. A strong upper jet is set up over Northern California/Southern Oregon associated with the upper trough. Surface pressure gradients have tightened over Northern California, causing winds to ramp up over the area throughout the morning hours. Current MFR-RDD gradient is around -10 to -12 mb, RDD-SAC gradient is around -8 mb, and SAC-RNO gradient is around +9 mb. Northern Sacramento Valley and adjacent foothills will see winds 20-30 mph with gusts up to 35-50 mph. In the mountains, winds could be up to 30-40 mph with gusts up to 45-60 mph, locally higher over wind prone peaks, ridges, and canyons. Strongest winds will be generally north of Interstate 80 for all elevations, and especially in the Plumas County and Shasta County mountains. These winds could cause damage to trees and powerlines, especially combined with moderate to heavy snow in the mountains. Mountain travelers should plan on difficult travel conditions, reduced visibility, chain controls, travel delays, and potential road closures this afternoon through tonight, especially during the evening commute. Ensembles show shortwave ridging forming over the eastern Pacific and Northern California late Wednesday into Thursday. Dry weather is expected for most areas except for a chance of warm air advection showers over Shasta County. -HEC && .EXTENDED DISCUSSION (Friday THROUGH Monday)... Ensemble guidance is in agreement that another upper trough will move through interior Northern California Friday, bringing another chance of light to moderate rain to the lower elevations and snow in the mountains, mainly for the Sierra and Western Plumas County. Snow levels will be higher than with the current system at around 5000-6000 feet. Ensembles and cluster analysis indicate fairly high agreement that ridging will build for the weekend over California, bringing dry weather, near normal temperatures, and a chance of morning Valley fog. Uncertainty remain for early next week as some guidance suggests a weak trough could bring another chance of precipitation. However, clusters suggest a higher chance that high pressure will continue into early next week. -HEC && .AVIATION... MVFR/IFR/ LIFR conditions in lowering ceilings and visibility restrictions as a weather system moves through, mainly I-80 northward. In the Valley, LLWS with widespread southerly surface wind gusts up to 35-40 kts possible N of I-80 and gusts up to 20-25 kts possible S of I-80 until 12Z- 15Z Tuesday. Southwesterly surface wind gusts up to 60+ kts poss over higher mountain terrain through 12Z- 15Z Tuesday. && .STO WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until 7 AM PST Tuesday for Western Plumas County/Lassen Park. Winter Weather Advisory until 7 AM PST Tuesday for West Slope Northern Sierra Nevada. Wind Advisory until 4 AM PST Tuesday for Central Sacramento Valley-Northeast Foothills/Sacramento Valley-Northern Sacramento Valley. Winter Storm Warning until midnight PST tonight for Shasta Lake Area / Northern Shasta County. && $$