Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/25/18

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
815 PM CST Mon Dec 24 2018 .UPDATE... /EXPAND FOG TONITE, LIGHT RAIN TUESDAY/ Mesoscale and rapid refresh models show an increased potential for fog to expand NW overnight as some dewpoints are already warming to a few degrees above forecast min temps. With this influx of moisture relfects more an advection fog property, have also expanded the potential for light rain or drizzle to form farther west as well for Tuesday morning. Some periods of dense fog could develop so will monitor trends for the potential need of a dense fog advisory. && .PREV DISCUSSION... /ISSUED 618 PM CST Mon Dec 24 2018/ AVIATION... VFR conditions this evening will quickly deteriorate to MVFR/IFR overnight as a 30 knot low level jet spreads stratus across the South Central Texas terminals. RAP forecast vertical wind profiles show the jet strongest near SAT/AUS between 04-10Z and would expect to see ceiling development begin during that time. Lighter near surface winds will allow for stratus to build down by sunrise, producing fog and LIFR to IFR visibilities. With IFR ceilings lingering into mid to late morning, delayed heating may allow for fog to linger at the terminals as late as 15-18Z. Ceilings are expected to lift to low-end MVFR during the afternoon with IFR possibly resuming after 00Z Wednesday. PREV DISCUSSION... /ISSUED 246 PM CST Mon Dec 24 2018/ SHORT TERM (Tonight through Tuesday Night)... Mid level shortwave moving across the Central Plains has allowed a southerly lower level flow and low clouds to return to South Central Texas today. An upper level trough approaching northern California moves southeast across California tonight to the Arizona/New Mexico region Tuesday night. Patchy fog is expected overnight into Tuesday morning across eastern areas. Deepening moisture and increasing upward forcing Tuesday into Tuesday night lead to the development, and then increasing coverage of showers. Well above normal temperatures are expected tonight through Tuesday night. LONG TERM (Wednesday through Monday)... The upper level trough will move across the Southern into Central Plains Wednesday through Thursday with the axis and associated Pacific cold front moving across South Central Texas Wednesday night. Upward forcing continues to increase ahead of the axis/front. Weak instability develops on Wednesday allowing for isolated sub- severe thunderstorms in the afternoon. Parameters become favorable for a squall line with isolated storms out ahead of it Wednesday night. CAPEs around 2K J/KG, steep 850 to 500 MB lapse rates of >7 C/km, and 0-6 km shear of 60 m/s indicate a potential of strong to severe thunderstorms with all types possible. The timing is expected from the evening into the overnight hours of Wednesday. In the wake of the trough/front passage, lower level ridging makes for a dry Thursday and Friday. Over the weekend, an upper level trough deepens over northern Baja California and Sonora state of Mexico while cold surface high pressure builds south across our area. Impulses moving in the southwesterly flow aloft over our area generate upward forcing for low chances of showers for Saturday into Sunday. There are significant disagreements with the timing of trough over our area on Monday as showers will end with its passage. The ECMWF/GEM bring it across early Monday with the GFS Monday evening which would lead to possible impacts to New Year`s Eve activities. There is a potential for thunderstorms across eastern areas, as well as, winter type precipitation across far northern reaches of the Edwards Plateau and Hill Country. Will leave out mention, for now, as chances are currently slight, at best. Above normal temperatures for Wednesday through Friday turn below well normal for Saturday through Monday. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 54 69 60 68 53 / 10 20 50 90 100 Austin Bergstrom Intl Airport 53 71 60 70 53 / 10 30 40 90 100 New Braunfels Muni Airport 53 71 61 71 54 / 10 20 50 80 90 Burnet Muni Airport 50 66 58 67 49 / 10 20 50 90 100 Del Rio Intl Airport 48 65 57 72 47 / 10 10 40 50 60 Georgetown Muni Airport 52 67 60 68 51 / 10 20 50 90 100 Hondo Muni Airport 50 72 60 73 49 / 10 20 50 70 90 San Marcos Muni Airport 54 71 61 71 53 / 10 30 50 80 100 La Grange - Fayette Regional 56 71 61 70 58 / 10 20 30 70 90 San Antonio Intl Airport 54 70 61 71 53 / 10 20 50 70 90 Stinson Muni Airport 54 72 63 73 55 / 10 20 50 70 90 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Aviation...Huffman Short-Term/Long-Term...Oaks
Area Forecast Discussion
National Weather Service Hastings NE
525 PM CST Mon Dec 24 2018 .SHORT TERM...(This evening through Tuesday) Issued at 252 PM CST Mon Dec 24 2018 After a quiet day this Christmas Eve, the weather pattern will turn more active for the middle/latter part of the week. The pattern aloft was fairly zonal today and the system which will impact our area Wed/Thur was just off the coast of Oregon and northern California. Ahead of this system, a subtle disturbance will translate across KS/southern Neb late this afternoon and evening. The majority of models suggest any precip associated with this system will develop just east of our cwa, however HRRR runs occasionally suggest precip may develop in Thayer County near Hebron and will need to monitor. Fog potential tonight...Low level moisture increases across eastern Kansas/Nebraska tonight which advects into our area late tonight/Christmas Day morning. Models suggest the development of low clouds/fog and latest SREF/high resolution models suggest that the fog may become dense, with the lowest visibilities expected mainly along/east of Highway 281. Overnight low temps will be below freezing and if dense fog does develop, will need to monitor for light icing. If fog does develop tonight, it is expected to erode mid/late morning Tuesday, then a fair amount of cloud cover is forecast Christmas Day. The NAM is the most robust with persistent low cloud cover and therefore reflects colder temps than the GFS which suggests more mid/high level clouds and warmer temp guidance. Given the spread in guidance for temps Christmas Day have went with a blend which reflects slightly cooler readings than previous forecast. .LONG TERM...(Tuesday night through Monday) Issued at 252 PM CST Mon Dec 24 2018 A storm system is still on track to produce widespread precip(rain/snow) Wednesday and Thursday. Models...Have disregarded GFS solution with its southern track solution in favor of other model solutions...which emerge the system from the south central Rockies Wednesday night, with the upper low tracking through NW KS, central/northeast Neb, into southern MN Thursday. Tuesday night...clouds thicken/lower and light precip develops in isentropic lift ahead of the approaching upper low/storm system reaching the four corners region. Precip type favors a messy mix at the onset with the potential drizzle/freezing drizzle or rain/sleet/snow before transitioning to rain as temperatures rise Wednesday. Light icing may occur. Wednesday...Wet weather expected with periods of widespread rainfall ahead of the upper system over the Rockies. Precipitable water values range from around a half inch in our western zones to near an inch in our southeast...high for this time of year. Model instability parameters indicate several hundred j/kg of MUCAPE across north central KS into southern Neb from late morning Wednesday through Wednesday evening and have included thunder in the forecast for non-severe storms. Rainfall amounts and impacts...Precipitation amounts (rain and melted snow) are expected to range from an inch to an inch and a half, with the majority of the precipitation falling as rain. These amounts are significant and to put in perspective, normal precipitation for the entire month of December ranges from a half inch to just over three quarters of an inch across our cwa. The ground is frozen, with a frost depth of two inches measured at NWS Hastings this morning. Rainfall on the frozen ground is expected to lead to runoff, ponding, and rises in streams and rivers...similar to the December 1st event when several areas received an inch of rain or more. Snow...Cold air is slow to arrive, reaching our western zones between 03Z and 06Z Thursday with rain changing over to snow. All but our far southeast zones are expected to change to snow by Thursday morning, with the southeast areas expected to transition to snow Thursday before the precip ends. Snow amounts are tricky given the wet ground from the initial rainfall and it may take some time to accumulate. The current track of the system orients the heaviest snowfall across our western zones roughly from Ord to Lexington and west where amounts of 2 to 5 inches (and locally higher amounts) are possible. Snow amounts are expected to drop off sharply to the southeast where more rain vs snow is forecast. Snow amounts south of the tri-cities and into north central Kansas are expected to average an inch or less. Snow tapers off during the day Thursday as the system lifts northeast and dry slot moves in. Wind...Northwest winds ramp up with the arrival of the cold air late Wednesday night and the wind remains strong Thursday/Thursday night into Friday. Wind speeds are expected to average 25-30 mph with gusts of 40 mph. Locations which receive accumulating snowfall may see areas of blowing snow/reduced visibility especially as the initial wet snow becomes drier as the cold air deepens. Headlines...A winter storm watch will be in effect for our northwest counties late Wednesday night through Thursday evening where the greater snow accumulations are expected, and the combination of snow/wind may cause travel impacts. If snow amounts continue to trend lower, the watch may need to be converted to an advisory, but if amounts trend higher, a warning may be warranted. Friday/Saturday...Cold weather settles in with wind chills in the single digits above/below zero Thursday night/Friday morning and Friday night/Saturday morning. The airmass moderates some Sunday/Monday (New Year`s Eve)...then models suggest another surge of cold air around New Year`s Day next week. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday) Issued at 523 PM CST Mon Dec 24 2018 Mid and high clouds will move out of the area tonight and the radiational cooling will allow for some fog to form. KGRI is expected to have lower visibility than KEAR. The fog will lift in the morning, but clouds will increase during the afternoon. && .GID WATCHES/WARNINGS/ADVISORIES... NE...Winter Storm Watch from late Wednesday night through Thursday evening for NEZ039-040-046-060. KS...None. && $$ SHORT TERM...Fay LONG TERM...Fay AVIATION...JCB
Area Forecast Discussion
National Weather Service Lincoln IL
843 PM CST Mon Dec 24 2018 .UPDATE... Issued at 843 PM CST Mon Dec 24 2018 Radar returns across Missouri look rather impressive this evening, though surface obs and mPING reports are indicating the precipitation has just started to reach the surface. Evening sounding from our office shows a rather dry layer below 700 mb. GFS forecast soundings show the lowest 5,000 feet of atmosphere with a dearth of moisture, while the NAM only has a few hour window where the low layers moisten. If the precipitation ends up very light, the evaporative cooling may not take place, which would favor more of a rain scenario. Latest RAP model actually keeps us dry the entire night, while the HRRR has only a few small areas of light rain or snow. Fresh runs of the NAM, ARW and NMM are also featuring lesser amounts of precipitation, mainly between midnight and sunrise. Have recently sent out some updated grids/zones to pull back a bit on the PoP`s and snow amounts, not that they were that great to begin with. && .SHORT TERM...(This evening through Tuesday) ISSUED AT 240 PM CST Mon Dec 24 2018 Our next weather system tracking east out of southeast Colorado is forecast to move across our area late tonight and into Christmas morning bringing a period of light snow and rain to the area. QPF amounts not real impressive with mostly less than a tenth of an inch with any snow accumulations generally less than one half inch. Most of the forecast soundings indicate our boundary layer starts out on the warm side as the precipitation approaches later this evening but with a dry layer indicated from the surface up to around 8000 feet, there will be enough evaporative cooling once the rain begins to become a mix of rain and snow. A few locations north of I-74 may see a brief turn over to all snow, but again, with the speed of the system and a lack of deep moisture with this upper wave, it appears precipitation amounts will be on the light side. Low temperatures should be around the freezing mark most areas tonight. The upper wave should push off to our east by afternoon with upper level ridging building over the central U.S. in response to the deep upper low pushing across the southwest U.S. This should bring another round of unseasonably mild temperatures tomorrow afternoon accompanied by a mix of clouds and sun with highs in the mid to upper 40s. .LONG TERM...(Tuesday night through Monday) ISSUED AT 240 PM CST Mon Dec 24 2018 The southwest storm system is forecast to slowly push east and northeast into the southern Plains by Wednesday but its associated precipitation shield is forecast to remain mainly to our west through most of the day. Rain chances start to increase from west to east Wednesday night as a strengthening southerly flow draws moisture north out of the Gulf of Mexico into the Midwest. The NAM model indicating a 65-70 kt low level (~850mb) jet drawing PWAT values of over an inch across the northern half of Missouri by Thursday morning. The deepening surface low will be between Omaha and Des Moines by Noon Thursday with the axis of deep moisture (PWAT values approaching 1.25 inches which is well above normal for late December) aligned from south to north right across our forecast area Thursday morning. Not much in the way of instability noted on the latest NAM but 0-6km shear values of 60-65 kts is a concern for Thursday late morning through the mid afternoon hours using the timing of the current NAM model, which does depict a narrow squall line racing northeast across southern Illinois at this time. Models continue to indicate widespread deep convection across the lower Mississippi Valley in addition to the rain and extensive cloud cover further to the north in our area. Will see what affect, if any, this has on our chances for more organized strong convection Thursday afternoon, especially over our south and southeast counties. The warmest temperatures this week will be Thursday just ahead of the storm and associated cold front with highs well into the 50s with 60s not out of the question over the southern half of the forecast area. The mid level dry slot will race across our area late Thursday afternoon or early evening taking any threat of rain off to our east and northeast. Gusty southerly winds, of 20 to 30 mph will shift more into a southwest to west direction overnight Thursday ushering in cooler weather overnight, but lows are only forecast to drop off into the mid 30s to mid 40s from north to south. Those are our average high temperatures for this time of year. Much quieter weather forecast to move in for the end of the week but additional shortwave energy ejecting out of the mean longwave trof over the southwest U.S. is forecast to drift northeast into the region later Saturday into Sunday with low chance POPs introduced with the threat for some light snow Saturday night and a slight chance for a rain snow mix on Sunday with temperatures closer to where they should be for the end of December, mostly in the 30s for daytime highs with early morning lows dropping into the 20s. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 516 PM CST Mon Dec 24 2018 Main focus will be the period from about 06-15Z, as a storm system brings light rain and snow to the area. Lower levels below 8,000 feet are dry and will cut down some on the precipitation, at least at the start. Will continue with the VCSH mention and keep conditions VFR for now, though a switch to snow could at result in some MVFR conditions at times. Precipitation will lift northeast of the area after 15Z, with VFR conditions expected to prevail after. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Geelhart SHORT TERM...Smith LONG TERM...Smith AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Lake Charles LA
1002 PM CST Mon Dec 24 2018 .DISCUSSION... Dense fog is developing and will become more widespread across Southwest Louisiana and Southeast Texas, as well as the inland lakes tonight. Latest HRRR and NAM12 guidance shows the dense fog affecting SE TX and portions of SW LA for the remainder of tonight. With dense fog forming further east across most of Cameron and Calcasieu parishes, included dense fog across Jeff Davis, spreading inland across Beauregard, ALlen, and Vernon parishes, as well as the remainder of SE TX, overnight. Thus, issued a Dense Fog Advisory for these areas through 9 am Christmas morning. && .PREV DISCUSSION... /issued 508 PM CST Mon Dec 24 2018/ AVIATION...Lower ceilings and vis are expected across the region this evening through mid Tuesday morning. The MVFR and IFR conditions will spread from SW to NE. Winds will be light and generally southeast. PREV DISCUSSION... /issued 316 PM CST Mon Dec 24 2018/ DISCUSSION... Return flow already ongoing this afternoon and this will continue into through the short term resulting in increasing clouds overnight and warmer temperatures. Areas of fog are also expected to develop during the overnight and some could be dense. The evening and overnight shifts will need to monitor for dense fog advisory potential. Fog should gradually burn off Tuesday morning with some light showers possible through the day with warm temperatures expected. The main concern for this forecast continues to in the Wednesday through Thursday time frame as the system entering the west coast today moves towards the east. There has been a slight slowing noted in the guidance today and thus Wednesday rain chances have been lowered a bit from the previous forecast, however showers should overspread the area Wednesday afternoon with breezy conditions developing as well. The main forcing will move through Wednesday night into Thursday. There will be a potential for strong to severe storms along with a heavy rainfall threat in addition to strong southerly winds. Front pulls up stationary Thursday night and while there may be a brief lull in the rain Friday off and on showers and possibly Thunderstorms is possible much of the weekend into early next week. Guidance continues to waffle on the details, so still lots of room for tweaks beyond Friday. && .PRELIMINARY POINT TEMPS/POPS... AEX 48 66 54 67 / 10 20 10 30 LCH 54 70 57 69 / 10 20 10 50 LFT 53 69 56 68 / 10 20 10 40 BPT 56 70 58 69 / 10 20 10 60 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...Dense Fog Advisory until 9 AM CST Tuesday for LAZ041-073-074. Dense Fog Advisory until 9 AM CST Tuesday for LAZ027-030-031-042. TX...Dense Fog Advisory until 9 AM CST Tuesday for TXZ215-216. Dense Fog Advisory until 9 AM CST Tuesday for TXZ180-201-259>262. GM...Dense Fog Advisory until 9 AM CST Tuesday for GMZ430-432. && $$ PUBLIC...08
Area Forecast Discussion
National Weather Service Paducah KY
922 PM CST Mon Dec 24 2018 .UPDATE... Issued at 920 PM CST Mon Dec 24 2018 A look at VAD Wind profiles from KSGF, KLZK, and KPAH suggest that very light precipitation is slowly working toward the ground. Lowest wind estimates detected is near 2kft msl at KSGF and KLZK and near 10kft AGL. Differential reflectivity and Correlation Coefficient from north of the KSGF radar suggest some ice crystal development aloft, but given the level of warm advection, anticipate further rain further west initially. The 13 km RAP sounding over western sections of southeast Missouri are suggestive of decent ice nucleation in the favorable dendritic growth zone (-13 to -18 C) as of 9 pm CST this evening. The challenge is the degree of evaporative cooling through midnight in the face of lower level warm advection. Most locations may not see any precipitation reaching the ground through midnight. However, where weak or non-existent southerly surface flow is in place, a few locations may see trace precipitation reach the surface as snow flurries or sprinkles of rain, especially in the northern and eastern sections of the WFO PAH forecast area. The most intense period of lift and precipitation potential will likely be between 06z (midnight) and 10z (4 am). As cloud ceilings drop down near 5-7kft between 5 am and 7 am CST, may see more sprinkles of rain than snow flurries. At the same time, the depth of moisture across the area will be shrinking, so even trace precipitation amounts should be waning by mid-morning Tuesday. Do not anticipate any trace precipitation (sprinkles or flurries) to cause any travel impact for the holiday at this time. UPDATE Issued at 608 PM CST Mon Dec 24 2018 && .SHORT TERM...(Tonight through Wednesday night) Issued at 308 PM CST Mon Dec 24 2018 A fast moving, upper level disturbance will race westward to eastward across the area late tonight-early Christmas day. It should have little to no impact, with gridded time/height cross sections and sounding data showing a very dry layer below about 10K FT AGL. The 12Z Nam and Gfs both produced zero for most of the FA, with some .01" qpf pixels in the Ozarks. The thermodynamic profile suggests sprinkles/flurries or, collaboratively, slight chance mention in the 10-14z time frame of vort passage. Preceding the system will be increasing/lowering clouds, and these should decrease generally later Christmas day and night, in the wake of its departure. Clouds will increase again fairly rapidly Wednesday, from the southwest toward the northeast. This will occur as the column starts to pre-saturate ahead of our next incoming weather system, which impacts the area later in the week. Lows in the 30s tonight and tmrw night rise into the 40s with the saturation column Wed night, as Pcpn sets in late. Christmas day highs largely in the 40s, will bump into the 50s the day after. .LONG TERM...(Thursday through Monday) Issued at 308 PM CST Mon Dec 24 2018 A strong storm system will move northeast across the Plains Thursday and Thurs night. This system may have some impacts on our area, primarily in the form of wind and/or strong convection. The potential for either hazard still appears rather low. Regarding wind potential, a southerly low level jet will increase to over 70 knots at 850 mb Thursday morning. The 12z nam showed its typical high bias, with a few winds to 90 knots at 850 mb Thursday. As usual, the question is how much wind will actually reach the surface. The models indicate widespread rain during the period of strongest winds aloft, which should minimize mixing. However, any convective elements would potentially contain very strong winds. There could also be strong surface winds if the models are too quick to bring in the widespread rain. A conservative estimate of peak wind gusts Thursday is 30 to 40 mph. Much will depend on the low level lapse rates, and those will depend on the timing of the stratiform rainfall. As far as convective potential, there has been little change in the model parameters. A narrow axis of marginally unstable air will nose into our region Thursday. A few recent runs of the gfs indicate this instability will be surface-based, while the ecmwf has shown slightly elevated instability. In either case, the values of cape are below 500 j/kg. Given the extremely strong winds aloft, these small values are still a concern. Another complicating factor is a pronounced mid-level dry slot that will surge northeast across the Ohio Valley. The models indicate this would occur in the afternoon, ending the widespread rainfall. This looks somewhat similar to the December 1 storm system, when a dry slot inhibited convection over our forecast area despite sufficient instability. However, the fine details such as the depth of the dry air can make a big difference. The dry air will win out by Friday morning, when all precipitation will come to an end. West winds will become northwest during Friday, bringing cooler air. Highs will still reach the 50s due to the mild start to the day. The cooling trend will continue through Saturday, when highs will be mainly in the 40s. The models are still hinting that southwest flow aloft will bring precipitation sometime Saturday night into early next week. The 12z gfs is especially bullish with precipitation Saturday night. The forecast will contain chance pops for Sat night. This precip will most likely not be all liquid as lows fall to around 30. There is good model agreement (including the ensemble means) that the western US trough will deepen early next week. Some deterministic runs are ejecting a 500 mb shortwave northeast out of this trough, bringing precip to our area. The track and strength of any such system will determine precip type and intensity. Based on the faster gfs timing, the forecast will contain chance pops for Monday. && .AVIATION... Issued at 608 PM CST Mon Dec 24 2018 Cigs may flirt with MVFR levels west of the MS River late Tue morning; otherwise VFR conditions can be expected throughout the 24 hour TAF period. An eastward-moving disturbance aloft will probably generate some showers of light rain or snow, mainly west, early on Christmas Day. However, with plenty of dry air near the surface, significant vsby restrictions are not likely, as much of the pcpn is not expected to reach the ground. Winds will be quite variable in direction, but mostly out of the southeast, and light. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ UPDATE...Smith AVIATION...DB
Area Forecast Discussion...UPDATED
National Weather Service Reno NV
500 PM PST Mon Dec 24 2018 .UPDATE... The latest HRRR and 3KM NAM show front/NCFR band pushing quickly east across the area early this evening. It is behind these features that wet bulb temperatures will finally cool and allow snow levels to begin falling. Much of the precipitation from about 6500 feet and lower is in the form of rain as of 5 pm but dewpoints are slowly inching down in the Tahoe Basin. So the rain should turn over to snow by 7 pm at lake level but intensity may decrease considerably once the NCFR passes to the east - thus limiting snowfall amounts at lake level. Areas above 6500 feet, especially west of Highway 89, are going to see some appreciable snowfall before the snow begins to taper off later tonight. We only made a minor update to adjust rain/snow at lake level through 7 pm. We kept the snow amounts as is, although at lake level, latest trends are favoring less accumulations due to the late drop in snow levels. Hohmann && .PREVIOUS DISCUSSION... /Issued 229 PM PST Mon Dec 24 2018/ SYNOPSIS... The second half of a moderate winter storm will move through the region tonight bringing continued travel impacts into Christmas morning due to rain and snow. Temperatures will fall tonight and drop snow levels to near the lowest valley floors. This will be followed by much colder temperatures and periods of snow showers later this week through next weekend. SHORT TERM... The first wave associated with a broader upper level area of low pressure has pushed through much of the forecast area early this afternoon. This first wave brought rain and snow...briefly moderate to heavy in the Sierra...with snow levels dipping below 6000 feet in the heaviest precipitation. As the precipitation intensity decreased...snow levels rose. The main upper low remains just off the coast. Satellite imagery shows convection forming east of the low as it pushes toward the coast of California. As this low moves onshore and into our region this evening and overnight...we expect another round of moderate to heavy precipitation in northeast California and the Sierra. This should drive snow levels down again overnight. Snow levels are quite tricky with this system...not just in northeast California and the Sierra...but in western Nevada as well. Much of our internal guidance indicates snow levels should start higher than we currently show in our forecast...but may be accounting for better mixing than we have seen in some areas. While winds have increased in the Mono County area and parts of the basin and range in western Nevada...the winds overall have not been quite as strong as advertised. This may have more to do with the increased moisture and light precipitation over the northern half of the forecast area than it does with a decreased gradient. So...for some areas...high temperatures are a little lower than forecast due to decreased mixing. This would argue for lower initial snow levels. But the increased moisture in the boundary layer will inhibit the ability for snow levels to fall this evening due to a higher wet bulb temperature. We will show snow levels falling in the evening as the heaviest precipitation moves into the forecast area...but try to balance out the factors mentioned above. Varying snow levels could result in widely varying snow amounts between 5500 and 6500 feet this evening and overnight. Most areas below 5500 feet will struggle to see any snow before the main cold front passes Tuesday morning. So the lowest valley floors are not likely to see much more than 0.5 to 1 inch of snow. Areas above 7000 feet in the Sierra may see between 8 and 16 inches. That area between 5500 and 7000 feet could vary from a few inches to as much as 8 inches...depending on the snowfall intensity and duration. This is a fast moving storm so most of the precipitation will end Tuesday morning. There will be lingering showers through the day and northwest winds are likely to become gusty over parts of Mineral County where stronger northwest winds are favored. Lake enhancement of snow showers is possible off Pyramid Lake from Nixon to Fernley and Lake Tahoe around Stateline across Dagget Pass. Temperatures Tuesday and Wednesday should be a little below normal. By Tuesday night a ridge begins to build with partial clearing. This is likely to allow for colder low temperatures by Wednesday morning with teens and 20s common. LONG TERM...Wednesday night through the New Year... A secondary cold front is forecast move into the region along the backside of large scale trough in the intermountain west Wednesday night into Thursday. This will bring colder temperatures, breezy north winds, and chances for snow showers back to the region. Current simulations have the front moving through from the northwest to the southeast as it moves through the region creating only a few snow showers in far western Nevada. However, this is the pattern where we can get a slider cold front through western Nevada that can bring snow accumulation to the lower valleys, especially if the frontal passage takes a more southerly track, something we`ll have to keep an eye on. On Thursday there is a pretty good chance of some upslope showers in Alpine and Mono counties and a chance for some lake enhanced showers south of Pyramid Lake. The end of the week will be relatively cold behind the front with highs likely in the mid 30s on Friday for the valleys. Low temperatures could be in the teens for much of the region Saturday morning with single digits in colder valleys. Temperatures will slowly warm up going into the weekend. -Zach AVIATION... The main part of the current storm system will move through the forecast area through early Tuesday. Periods of IFR in rain and snow develops for northeast California...northwest Nevada...and the Sierra this evening. Cigs/vsbys should be no worse than MVFR for areas east of the Sierra this evening...but could briefly drop to IFR with the main cold front around the midnight time frame. Wind shear is also likely...especially near frontal passage tonight. Mountain obscurations and turbulence are likely as well. Little in the way of snow accumulation is expected for the western Nevada terminals; KCXP and KRNO could get between 0.5 and 1 inch of snow in a brief burst. For the Sierra terminals...KTRK and KTVL have the best chance at accumulating snow with between 3 and 7 inches possible...higher at KTVL than KTRK. KMMH could get up to 4 inches...but the snow will be lesser in intensity there. Behind the front Tuesday...snow showers will linger through the day and decrease in the evening. So there could be isolated areas of reduced cigs/vsby. && .REV Watches/Warnings/Advisories... NV...Winter Weather Advisory until 7 AM PST Tuesday NVZ005. Winter Weather Advisory until 7 AM PST Tuesday NVZ002. CA...Winter Weather Advisory until 7 AM PST Tuesday CAZ071. Winter Weather Advisory until 7 AM PST Tuesday CAZ070. Winter Weather Advisory until 7 AM PST Tuesday CAZ072. && $$ For more information from the National Weather Service visit...