371 FXUS65 KSLC 190452 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 952 PM MST Mon Nov 18 2019 .UPDATE... Overall forecast message remains unchanged, with only some continued minor refinement to the forecast with the latest forecast information coming in this evening. One of the key features to the upcoming southern Utah precipitation event is the evolution of a deformation band that is expected to develop over southwest Utah late Tuesday night through Wednesday morning. Global models this afternoon, including the EPS/GEFS, supported a slight westward nudge in the placement of this axis of heavier precipitation from being centered over Kanab to being centered closer to St George. 12Z/18 high resolution model members of the HREF largely continued to keep the deformation band a bit farther east over Kanab. However, watching the 00Z/19 models cycles come in this evening, the high resolution suite of guidance is catching up to this westward trend of the global models, focusing the axis of heavier precipitation through Washington County. Overall forecast precipitation totals generally remain unchanged outside of where this axis of heavier precipitation sets up. Previous forecast messaging has been for lower elevation rainfall totals of 0.5 to 1.5 inches, with localized areas around 2 inches possible (mainly where the axis of heavier rain sets up). These values continue to be supported now that more high resolution data is coming available in the 00Z/19 HREF cycle. Otherwise, minor edits to the forecast include a slight decrease in QPF amounts across northern Utah. While showers will likely encompass much of the state, forcing will be very minimal across northern Utah. This weaker forcing combined with poor low-level moisture advection into northern Utah will struggle to overcome the dry low levels. This will result a lot of virga or only very light precipitation, especially for areas from the Salt Lake Valley north and westward. Also slightly lowered snow levels across southern Utah with the anticipation of dynamical cooling from precipitation intensity. This brings roughly a couple to a few more inches of accumulation to locations in the 6500 to 7500 foot elevation range. && .SYNOPSIS... High pressure aloft will remain the dominant feature across the region through Tuesday. A deepening low pressure system will settle into California Tuesday night, then turn east and work slowly across southern and central Utah midweek. Widespread rain and snow will impact mainly southern and central Utah late Tuesday night through Thursday. && .SHORT TERM (THROUGH 00Z FRIDAY)... Southerly flow develops Tuesday in response to falling heights across the region as the cold piece of the anticipated storm drops down the West Coast. Air Quality should greatly improve due to the increasing southerly winds. Confidence continues to increase in regard to a significant storm beginning late Tuesday across southern Utah with rates peaking Tuesday night and Wednesday morning. GEFs/EPS have both remained consistent with the higher with precipitation totals seen yesterday, and the most recent guidance continues to support the northward shift in the areal extent of precipitation to include northern Utah (with much lower QPF). The ingredients remain the same, a strong shortwave with origins in much colder eastern Asia will round the Eastern Pacific ridge, deepen over the Southwest CONUS and stall. Significant moisture (300%+ of normal Precipitable Water) is drawn northward from a decaying Tropical Depression Raymond. The corresponding instability axis noses north toward southern Utah Tuesday night into Wednesday. This timing is coincident with significant dynamical forcing as portrayed by strongly falling heights, PVA as well as diffluence aloft. This combination looks to bring a threat of embedded thunder, and even without thunder, would support significant precipitation rates across southwest Utah Tuesday night into Wednesday morning. Southern mountains favored in southerly orographics will see significant snowfall linger beyond Wednesday. Mid and high elevation travel between Brian Head and Boulder Summit will be affected by Winter Driving conditions. Moisture trajectory noses toward the northeast through the event, with the central and northern mountains seeing modestly significant snowfall. Snow totals will trend lower the further northwest. The filling closed low passes over southern Utah Thursday, supporting generally lighter showery conditions. Pre-frontal winds are expected to be noticeable but under Wind Advisory criteria Tuesday. Winds are expected to increase from the north across northwest Utah later Tuesday night through Wednesday night, though at this time cold advection seems gradual enough to keep wind magnitude below Wind Advisory criteria as well. Another area to watch is the Wasatch Front as colder airmass filters in from Wyoming late Wednesday into Thursday. Will have to monitor trends of the 700mb cold advection and pressure gradient heading into this time period, as any strengthening beyond current guidance may warrant a headline. .LONG TERM (AFTER 00Z FRIDAY)... As Thursday's low shifts eastward overnight, remnant low level moisture along with a tighter surface gradient will support lingering upslope snow showers in the mountains of southern Utah into the early morning hours on Friday. Afterward, a drying trend establishes throughout the afternoon hours on Friday and into the weekend as northerly flow develops aloft. Slightly above average 500hPa geopotential height anomalies build into the region over the weekend and keep temperatures near normal, or slightly below normal through Sunday. A quiet weekend will give way to another system as ensembles are depicting the development of a trough over the Intermountain West. Thus far, deterministic models are suggesting that this next system will begin to make impacts across the northern portions of the CWA during the morning hours on Monday, however, the areal extent, precipitation amounts, and exact timing is yet to be determined. && .AVIATION... No significant impacts to aviation expected at KSLC through the TAF period with VFR conditions prevailing. Southerly winds will persist overnight and through Tuesday morning. Winds will again struggle to shift to the northwest Tuesday afternoon, with likely a delayed shift in the 21-23Z range. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Flash Flood Watch from Tuesday evening through Wednesday evening for UTZ016-019-020. Winter Weather Advisory from 5 PM Tuesday to 4 PM MST Thursday for UTZ009-010-517. Winter Storm Warning from 5 PM Tuesday to 4 PM MST Thursday for UTZ518. WY...None. && $$ UPDATE...Church SHORT TERM...10 LONG TERM...Webber AVIATION...Church For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity For frequently asked questions about the Area Forecast Discussion visit... http://weather.gov/saltlakecity/general/afd_faqs.php