016 FXUS65 KSLC 040617 CCA AFDSLC Area Forecast Discussion...Corrected Synopsis National Weather Service Salt Lake City UT 1217 AM MDT Thu Jul 4 2019 .SYNOPSIS... A dry cold front will press south Thursday as an upper level trough lifts northeast through the Northern Rockies. The trough will move into the High Plains early Friday, allowing a dry westerly flow to prevail across the region. High pressure aloft will return for the weekend. && .DISCUSSION... Strong shortwave embedded within the trough to our northwest is currently crossing into southwest Idaho from north central Nevada. This feature, along with the right entrance of the upper level jet and associated height falls are supporting convective activity across far northwest Utah. Shear profile is quite strong, however this evening it appears to have overcome modest destabilization built during the heating of the afternoon hours. Carried low PoPs across far northwest Utah and the Idaho border region overnight, as most all Simulated Reflectivity from available Convective Allowing Models support this general idea. Convective Allowing Models also show increasingly gusty northerly flow from outflow of the aforementioned convective activity. This eventually strengthens the surface boundary (roughly west of Delta to near Evanston currently), then encourages the boundary to build southward especially across the West Desert overnight. This scenario is well supported by Doppler Radar detection of two outflows propagating SE and S across northern Utah, with 30-45 mph wind gusts reported associated with these features. Tomorrow looks like another active convective day across northern Utah and southwest Wyoming. Portions of the region are under a Marginal Risk for severe thunderstorms per the SPC. Anyone with outdoor plans should maintain strong awareness of the potential for threatening weather. && .PREVIOUS DISCUSSION... A shortwave over central Nevada as seen on satellite is forecast to move northeast across the northwest corner of Utah this evening producing isolated thunderstorms. High resolution models are mostly all on board that strong outflow winds are expected to spread southeast from these storms and possibly impact the northern and central Wasatch Front this evening. Gusty southwest winds will weaken early this evening over the western and southern valleys as the winds aloft decouple. The trough over the PACNW this evening will move across Idaho Thursday and will push a cold front into northern Utah as far south as about Dugway to Provo line by late afternoon. Although moisture is somewhat limited this frontal boundary may act as a focusing mechanism for thunderstorms early Thursday evening. Farther north, the cooling impact of the higher levels will combine with the entrance region to the jet to destabilize the air mass and isolated to scattered thunderstorm are expected across the central and northern portion of the Wasatch Front and Mountains into the Cache Valley. South of this cold front, dry and warm conditions are expected. Ridging will move in Friday into Saturday for warm and dry conditions statewide. Temperatures will average slightly below normal in the north through Friday but will rebound to above by Saturday. Farther south, slightly above normal temperatures are expected through the short term. The long term forecast period starts out with a closed low over the Pacific Northwest and mean trough over the West Coast with a ridge in place over the southern Plains. This pattern keeps Utah under an warm and relatively dry southwesterly flow aloft. The closed low is progged to eject northeastward during the day Sunday while the ridge over the southern Plains amplifies a bit. This amplification is progged to draw a bit of midlevel moisture into the eastern half of Utah which could lead to some isolated high- based convection Sunday afternoon/evening initiating off the higher terrain. The main difference between the GFS and EC is still how much of the trough is left behind after the ejection of the closed low. The GFS is still trending towards more zonal pattern for Monday as the trough weakens and slides by to the north while the EC and CMC both keep a more amplified mean trough over the West Coast. This difference just serves to increase model spread heading into the midweek period. Nevertheless, it seems that the airmass will dry slightly during first half of the work week. && .AVIATION... A frontal boundary pushing across northern Utah will keep winds northerly through much of the night, with some higher gusts between 03-06z. Winds are expected to return to light southerly near or just after sunrise, although there is 20 percent chance that south winds do not become firmly established before north winds increase again late tomorrow morning. Otherwise, VFR conditions are expected, with mid and high CIGS through much of the night. && .FIRE WEATHER... A weak upper level disturbance will bring a threat of showers and strong thunderstorms to northern fire wx zone 478 this evening. An upper level trough will move across Idaho Thursday which will push another cold front south to a Dugway-Provo-Western Uintas line by late Thursday afternoon. Cooler temps with a slight chance of thunderstorm will occur north of this line while dry and warm conditions will prevail south of this line. Dry and warmer conditions are expected through the weekend as a ridge builds into the region. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...None. WY...None. && $$ PUBLIC...10/Struthwolf/Cheng AVIATION...Cheng FIRE WEATHER...Struthwolf 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