627 FXUS63 KGLD 240805 AFDGLD Area Forecast Discussion National Weather Service Goodland KS 105 AM MST Fri Nov 24 2023 .UPDATE... Issued at 620 PM MST Thu Nov 23 2023 For the latest ESTF update, some minor temperatures changes across the area based on latest obs, otherwise forecast remains on track. The latest CAM runs of the HRRR, RAP and NAMNest all show some light snowfall beginning to enter the CWA around 06z-09z Friday, then picking up in intensity for much of the CWA by 10z-12z Friday. The latest RAP40 500mb analysis and mid level water vapor imagery are showing the main low currently diving south-southeast towards western Utah. There remains an amplified ridge nosing NW over the western Plains. The upper flow between the two systems is creating a N-NW flow aloft. At the surface, much of the area is seeing northeast flow, but guidance is showing a shift to more of an upslope easterly flow towards 06z Friday. This will allow more low level moisture to feed into the region. The current regional radar is showing most if not all QPF is moving on a south to north track at this time not impacting the CWA. The slow progression eastward does increase overnight as the upper ridge breaks down and the aforementioned upper low moves further into the central Rockies. As a result based on current data, still looking for two phases of snowfall, the one Friday with a break followed by the moisture associated with the upper low as it swings through the CWA Saturday- Saturday night. No change at this time to forecasted snow amounts. Will continue to monitor guidance/system trends for any further slowing of the system. && .SHORT TERM...(This evening through Saturday) Issued at 112 PM MST Thu Nov 23 2023 The latest upper air analysis shows a deepening trough over the Great Basin. Water vapor imagery showed a large mass of higher water vapor over the western CONUS with the trough. At the surface the cold front which moved through last night was crossing into Oklahoma. For the rest of today the northeast winds will become light around sunset as mixing ends. Cloud cover will continue to thicken ahead of the approaching storm system. Tonight winds will be light from the east to northeast. Overnight the environment will begin to saturate down toward the surface as the storm system nears. Latest model data has slowed the start time of the snow moving in. Current forecast has the snow starting to enter the forecast area after midnight. However new data is indicating that may be too early by a couple of hours. Based on this, am thinking snow should be over the western half to third of the forecast area by sunrise Friday. Friday snow will continue to spread east across the forecast area. During the morning the first round of snow will move through the forecast area. This round will be focused over the northern half of the forecast area. Up to three inches of snow is currently forecast for the day, with the higher amounts in Nebraska. What has changed with this round is the lift associated with it is much weaker than what was seen yesterday. This could be due to the minor short wave trough associated with it being shallower than what was forecast yesterday. In addition the environment is much more stable than what was seen yesterday. Both of these changes could be due to the trough not deepening as much as what was forecast yesterday before moving over the forecast area. Friday night there may be some light snow over the forecast area due to weak lift persisting through the night. Am not anticipating much accumulation or impacts from this very light snow. Toward sunrise the next round of snow may begin to move into the southeast part of the forecast area from the southwest. Lapse rates in the dendritic zone become or near dry adiabatic, very unstable. In addition saturated geostrophic equivalent potential vorticity develops, which will allow the snow formation process to be even more efficient with the increasing lift and instability. Saturday the second round of snow continues across the southeast part of the forecast area. Am forecasting up to five inches of snow for the day, with most of the snow over the southeast part of the forecast area. Southwest Kansas looks to have the bulk of this round. Despite the latest snow forecast shifting more over the southeast part of the forecast area, continue to wonder how much snow we will actually see with this round. Looking at CIPS Analogs, the best match using the GFS from yesterday's run is a very close match pattern-wise to what this system is forecast to look like. That system produced over a foot of snow in Southwest Kansas. Am thinking a similar setup is likely with this current storm system. With this in mind, the snow amounts for the southeast part of the forecast area could be too high (if the system continues to shift the snow southeast), or too low if the forecast lift and instability are realized over the southeast part of the forecast area. During the afternoon the snow ends from west to east. Highs for the day will warm some from the night. Saturday night the sky will clear out, making a perfect setup for radiational cooling. Lows will be dependent on how low the dew points fall in the cold air. Confidence in snow amounts: Confidence is between moderate and high. The southeast shift is very reasonable given the trajectory the storm system is going as it moves into the forecast area. Based on past events, and given this pattern is resembling split flow, am thinking the snow amounts will continue to shift southeast. A band of snow could certainly setup over the southeast part of the forecast area producing a narrow corridor of higher snowfall amounts. Or the current forecast could be correct with around six inches of snow occurring over the southeast. However am thinking the more likely scenario is higher snow amounts will continue to shift southeast. Timing: Wouldn't be surprised if the snow ends up starting a couple hours later than what is forecast. There is snow starting before the advisory begins. However if the snow does start prior to the advisory, there will be little to no snow accumulated at that time. Impacts: Due to there being very little wind with this snow, am not anticipating much for impacts besides the typical snowpacked, icy roadways. Snow rates during each round of snowfall will likely reduce visibility some. The second round of snow on Saturday will likely cause more of an impact in regard to snow on the roads and visibility than the one on Friday. .LONG TERM...(Monday through Thursday) Issued at 105 AM MST Fri Nov 24 2023 Monday...similar to 24 hours ago, the 500mb pattern shows a large trough covering the eastern half of the country with an upper level ridge to our west. The temperature forecast may be challenging given the possibility of lingering snow cover, especially east of the CO/KS border. Presently, under a sunny sky, high temperatures are forecast to be in the middle 30s to lower 40s, warmest along and west of the CO/KS border. Under a clear sky, low temperatures are forecast to fall into the lower to upper teens. Tuesday...we remain under dry northwest flow aloft, in between a large/broad upper trough across the eastern half of the country and ridging that has moved east toward the Continental Divide. High temperatures warm into the middle 40s to lower 50s with low temperatures in the lower to upper teens. Wednesday...dry weather continues. This mornings GFS/ECMWF/GEM/GEFS models now show an upper level trough organizing over the Nevada/Utah areas with southwest flow aloft over our area. It appears we'll see some increase in high clouds after midnight ahead of this system. Very little change in 850mb temperatures compared to Tuesday and will continue with high temperatures in the middle 40s to lower 50s. Low temperatures again generally in the middle to upper teens. Thursday...the upper trough west of us Wednesday doesnt move much Thursday. There could be a piece or pieces of the trough that eject across the area under southwest flow aloft, bringing periodic increases in cloudiness. The ECMWF model does bring some qpf into the area during the night while the NBM/GFS/GEM models keep us dry. For now, no need to go against the NBM which is dry for the moment. High temperatures are forecast to be in the lower to middle 40s with low temperatures in the lower to upper teens. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 942 PM MST Thu Nov 23 2023 For KGLD, VFR conditions through about 10z Friday, then lowering as light to moderate snow develops. Looking for visibility around 1-3sm and ceilings ranging widely from MVFR to IFR by 01z Saturday then MVFR again as snow ends by 04z Saturday. Winds, east-northeast around 10-15kts through 04z Saturday, then southeast around 10kts. For KMCK, VFR conditions through about 12z Friday, then lowering as light to moderate snow develops. Ceilings will start off as MVFR by 15z Friday then mainly LIFR/IFR thereafter. Visibility 1-3sm through 17z, then less than 1sm. By 00z Saturday, snow ending. Winds, northeast around 10kts, becoming east by 17z-21z Friday. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...Winter Weather Advisory from 5 AM MST /6 AM CST/ early this morning to 5 PM MST /6 PM CST/ Saturday for KSZ001>004- 013>016-027>029-041-042. CO...Winter Weather Advisory from 5 AM early this morning to 5 PM MST Saturday for COZ090>092. NE...Winter Weather Advisory from 5 AM MST /6 AM CST/ early this morning to 5 PM MST /6 PM CST/ Saturday for NEZ079>081. && $$ UPDATE...JN SHORT TERM...JTL LONG TERM...99 AVIATION...JN