693 FXUS65 KPIH 101008 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 308 AM MST Wed Feb 10 2021 .SHORT TERM...Tonight through Friday. Expect to see breezy conditions today across much of the region as we await the next system. Winds look to remain below advisory levels. An outside chance for snow continues for the eastern highlands, but amounts look negligible. Stronger system arrives from the west-northwest Thursday afternoon. Models still disagree on some of the finer points. For example, the GFS remains colder with downvalley winds across the Snake Plain while the European and NAM are warmer with upvalley winds. However, the models are in agreement with who gets precipitation. And the answer to that is the western facing slopes of the central mountains and the eastern highlands. Precipitation will appear as a nearly-steady stream across the region with the Snake Plain and Magic Valley mainly shadowed. Best chances for snow in the Snake Plain and Magic Valley will be late Thursday night into Friday morning and Friday night after the cold front passes through. The upper Snake Plain may see a storm total of 1-3 inches while the lower Snake Plain and Magic Valley is looking at an inch or less as warm temperatures cut into totals as well. Many central mountain locations will be heavily sheltered as well. Galena summit and Stanley could see 4 to 8 inches. Much higher amounts are likely along the Smokeys and Banner Summit where up towards a foot is possible. Valley locations in the eastern highlands are looking at 3-6 inches. Driggs could overachieve with up towards 8 inches possible. The high country in the eastern highlands could see up towards a foot. Blowing and drifting snow will likely be a problem as well in the eastern highlands. For now, the watch remains in effect. Advisories may be possible for adjacent areas. Will issue an advisory for portions of the central mountains around Galena Summit and Stanley to match up with adjacent advisory areas in neighboring forecast offices. 13 .LONG TERM...Saturday through next Wednesday night. An active weather pattern remains in store for central and eastern Idaho through the long term portion of the forecast. While there is some glimmer of hope in terms of model agreement, some meaningful differences remain, particularly during the weekend. Starting with the good news, the GFS camp no longer sends a strong shortwave and attendant Arctic front through the area Friday night, instead opting to weaken that system, which is more in line with the European and Canadian deterministic and ensemble members. The latest runs are in fairly good agreement in their depiction of an eastward-expanding area of precipitation on Saturday, developing first across the central Idaho mountains early in the morning, then the eastern Magic Valley by late morning, before finally spreading across the remainder of the southern Snake plain, south hills and southern half of the eastern Magic Valley by late morning or early afternoon. This precipitation could be moderate at times and should linger through much of Saturday night before exiting to the south and east Sunday morning. Thermal profiles support all snow outside of the eastern Magic Valley. That said, there remain some detail differences, namely with the degree and southward extent of a shallow surface cold pool, and this could have some precipitation type implications across the above-mentioned eastern Magic Valley. The cold pool has been in place for several days now, with a stark temperature, wind and boundary layer contrasts between the northern and southern Snake Plain. This cold pool will likely remain in place through Saturday across the northern Snake Plain. Where things get interesting is models develop a downvalley (north to northeast flow) at the surface late Friday night through Saturday. Some models bring this flow and attendant cold air into the eastern Magic Valley while others keep it locked across the northern Snake Plain. How far south and west this cold air is able to ooze will have not only temperature forecast implications, but also precipitation type implications. There remains significant spread in the temperature forecast for the weekend as well as significant differences in the precipitation amount. WPC clusters indicate just over 50% of the solution space favors the warmer, wetter solution while the rest favor a colder, drier solution. The northern edge of the precipitation shield is in question as well, as the current model blend indicates a dry northern Snake Plain and a wetter southern Snake Plain with a sharp cutoff separating these areas. The forecast could still go either way with both the colder, dryer or warmer wetter ideas still very much in play. For now, will follow the NBM which splits the differences fairly well and maintains the sharp east-west precip cutoff. Should colder surface temperatures reach the eastern Magic Valley, some freezing rain will be possible there on Saturday, and this will bear watching. These are some remaining important forecast differences to sort out, and while some agreement has been reached, there are still many questions to answer, especially for Saturday. Sunday favors lingering snow showers across the south hills with mainly dry conditions elsewhere. The temperature spread remains nearly as wide as it is on Saturday, with possibilities ranging from Arctic cold to near seasonable temperatures. The NBM 50th percentile is much closer to the warmer envelope, and was followed. A brief break in the action is expected Sunday night before another wave of snow overspreads the area from west to east early Monday morning. The entirety of the forecast area is in line to see some accumulating snow in association with this system. By late in the day, the flow is forecast to shift northwesterly aloft, which should favor less snow for the Snake Plain and a continuation of snow in higher terrain areas. These higher terrain snow showers may linger not only through Tuesday, but perhaps into Wednesday as well. Winds will be on the increase Monday, and are forecast to peak in strength Tuesday. Winds may be strong enough to cause some blowing and drifting snow. Temperatures should be near seasonable values through this period. In the Monday-Wednesday period, deterministic and ensemble guidance is in surprisingly good agreement, lending to moderate confidence in the forecast during this timeframe, which is an improvement from the remaining low confidence weekend forecast. AD && .AVIATION...Generally expect VFR conditions through the daylight hours on Wednesday. There is a slight chance for fog or stratus development over or near KIDA this morning, but the potential is low enough to preclude its inclusion in the TAF at this time, but will continue to monitor. Breezy conditions will once again develop this afternoon, and winds will be strongest at KPIH once again, with W/SW winds increasing into the 15-25kt range with gusts around 30kt after 18Z. Winds will be a few knots less at KBYI, and shave off a couple more knots at KDIJ. Uncertainty remains in terms of wind direction for KIDA. All model guidance indicated winds would turn to the SW Tuesday afternoon (similar to what occurred Monday) but in fact the inversion remained in place there, causing light north winds to remain locked in place. The ultimate position of the surface boundary that separates the light north winds from the stronger southwest winds will lie between KIDA and Blackfoot. With a very similar pattern in place, it's quite possible the inversion remains locked in place for KIDA, but it will be close. Current forecast suggests SW winds will develop around 17Z. For consistencie's sake, will keep this idea going, but delay the potential wind shift until later in the afternoon -- opting for 21Z. Clouds will thicken and lower during the evening in advance of an approaching area of low pressure. Precipitation will be knocking on the doorstep at the end of the forecast period (12Z Thu), with precipitation and associated low ceilings likely moving into the terminals just after the end of the forecast period between 12-18Z Thu. At this time, favor Snow at KSUN, KIDA and KDIJ with rain or a rain/snow mix at KBYI and KPIH. AD && .PIH WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from Thursday morning through late Friday night for IDZ060-063>066. Winter Weather Advisory from 11 AM Thursday to 5 PM MST Friday for IDZ072. && $$