Area Forecast Discussion
Issued by NWS Pocatello, ID
Issued by NWS Pocatello, ID
484 FXUS65 KPIH 210911 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 311 AM MDT Tue May 21 2024 .SHORT TERM...Today through Wednesday night. Expect a dry day for the most part with the exception of some showers mainly in the extreme east along the Wyoming border. It will remain very cool but a couple of degrees warmer than Monday as a weak short wave ridge moving east ahead of the next system which will spread showers and thunderstorms back into southeast Idaho Wednesday morning into the central mountains and into the remainder of southeast Idaho Wednesday afternoon. Highs today will be in the 50s and 60s with milder lows tonight ahead of the next system with lows in the 30s mountains and 40s valleys tonight. This next system system will drive through another cold front with widespread precipitation across the region above 0.10 in the Snake River Plain and higher amounts of 0.20 to 0.50 in the eastern highlands and central mountains. Snow levels will drop from 7 to 8 thousand feet to 5 to 6 thousand feet overnight. Snow amounts of 1 to 3 inches may fall in the Island Park area and Stanley. highs amounts of 3 to 6 inches are possible above 8 thousand feet. Winds will increase Wednesday as well especially in the Snake River Plain but will be mainly below advisory level with the highest in the Arco Desert where will see 30 to 40 mph gusts with 20 to 30 mph gusts in the interstate corridor expected. Gusts potentially higher near thunderstorms Wednesday afternoon. Low temperatures Wednesday night will be much cooler in the 20s mountains and 30s valleys and expect will likely see more frost advisories in the Magic Valley and Snake River Plain. GK .LONG TERM...Thursday through next Tuesday. Behind a cold front on Thursday, temperatures will be well below normal with highs only reaching the 40s/50s as a mix of rain/snow showers and isolated thunderstorms continue associated with a H5 low situated directly overhead. This system will continue to track east into Wyoming and Montana throughout the day Thursday into early Friday which will bring a return to dry conditions as we begin to see a warming trend return through the weekend. Before we get carried away with this warming trend however, another system will begin to move into SRN Idaho for Saturday into early Sunday as a cold front helps to bring another round of rain/snow showers and isolated thunderstorms to kick off Memorial Day Weekend. High confidence amongst ECMWF/GFS ensembles and deterministic models will make this weekend system a quick moving one in nature as a H5 ridge of high pressure builds into our area throughout the day Sunday into Monday. For those heading outdoors this Memorial Day Weekend, outside of some isolated showers/storms on Saturday and Sunday, it will be a great weekend out there with highs in the 50s/60s for Saturday and Sunday before warming up to the 60s/70s on Memorial Day as dry conditions return regionwide to kick off next week. That warming trend will continue into Tuesday and Wednesday as a H5 ridge axis shifts overhead, supporting highs rebounding back into the 70s/80s as soon as Tuesday which would mark the warmest air mass moving into our region so far this year. Taking a look at climatology in Pocatello, our first average 80 degree day falls on May 10th making this year in the top 10 latest years since 1939 of reaching that 80 degree mark. Similarly elsewhere, all of our climate sites have not reached 80 degrees yet this year but with high confidence on all sites except Stanley reaching 80 degrees on either Tuesday or Wednesday next week, warmer weather is on the way! The EPS/GEFS ensemble models show little in ways of preventing this ridge feature from being overhead through much of next week with the only caveat to that being a deep H5 trough in the NE Pacific up into the Gulf of Alaska. Long range models keep that trough at bay through the work week with the potential for a weakened form of this system moving onshore later in the week as our blocking H5 ridge begins to shift east onto the Great Plains. Stay tuned. MacKay && .AVIATION...For the 12Z TAFS through 12Z Wednesday. Predominant VFR and dry conditions will continue for Tuesday under partly to mostly clear skies. Outside of very isolated showers early this morning, another round of rain/high elevation snow showers and isolated thunderstorms will develop this afternoon and evening (mostly across ERN Idaho) with the HREF model showing a 10-20% chance of thunder at KDIJ and less than a 10% chance at all other terminals. Dry conditions will return regionwide for sunset tonight with our next system arriving tonight and throughout the day on Wednesday NW to SE with a mix of rain/snow showers, thunderstorms, and elevated W/SW winds of which will continue into Thursday. MacKay && .FIRE WEATHER... Unsettled and seasonably cool weather will continue through Thursday as isolated showers/thunderstorms today transition to more scattered to numerous for Wednesday/Thursday as a H5 low works directly overhead SRN/CNTRL Idaho. The most widespread precipitation will accompany a cold front as it passes through on Wednesday with those chances building in NW to SE throughout the day. A mix of rain/snow showers and thunderstorms will accompany this front with well below normal temperatures settling in for Thursday with highs only in the 40s/50s. QPF/rainfall and snow amounts for this midweek system remain similar to previous forecasts showing around 0.10-0.40" with locally higher totals in FWZ 411 and especially in Lemhi County where around 0.50-1" is expected. Even higher totals in excess of 1" will be possible across northern portions of FWZ 475 and 476. Best chances for any accumulating snow will remain above 5500-6000` with light snow possible across our northern and eastern mountain valleys as more moderate to heavy snow accumulations are expected in the high country of FWZ 411, 422, 475, and 476. We may also see light snow accumulations down to around 4500-5000` dependent on where bands of precipitation set up with this system. As this H5 trough departs east into Wyoming and Montana Thursday night into Friday, drier conditions will return regionwide ahead of a secondary H5 low building in for Saturday into early Sunday. This 2nd system will support another round of rain/snow showers and thunderstorms but with lesser QPF than the midweek system. Conditions will ultimately dry out for Sunday and Monday associated with a H5 ridge of high pressure building in from the Pacific. This will bring a return to seasonably warm temperatures with highs in the valleys back in the 70s/80s as soon as Tuesday, marking the warmest airmass so far this year moving into our area. MacKay && .HYDROLOGY... Elevated river levels continue on the Portneuf River at Pocatello and Topaz. River levels are expected to gradually recede over the upcoming week but will likely remain high enough to warrant continued flood products for much of the week. McKaughan && .PIH WATCHES/WARNINGS/ADVISORIES... Frost Advisory until 9 AM MDT this morning for IDZ051>055. && $$