Sunrise 6:27 AM   Sunset 8:42 PM Moonrise 3:20 AM   Moonset 2:27 PM

  Print   HELP   Reset   Save   Recall

FXUS65 KPIH 021934 AFDPIH

Area Forecast Discussion National Weather Service Pocatello ID 134 PM MDT Thu May 2 2024

SHORT TERM
Tonight through Friday night.
Another upper level trof will move through southern Idaho tonight with another batch of rain and snow showers late this afternoon through tonight. Snow levels will range between 4500 and 5500 feet through Friday morning. Generally 1 to 3 inches in the central mountains and eastern highlands with localized amounts up to 6 inches above 8 thousand feet. Very little snow forecast in the Snake River Plain although there is a low chance of an inch or two as a Snake Plain Convergence zone may develop late tonight and Friday morning, but at this point extremely low confidence in that possibility so for now very minimal low level snow accumulations are expected. A variety of freeze warnings and frost advisories are in effect once again. Will not be as cold as this morning with significant cloud cover expected to elevate overnight lows in the Magic Valley and Snake Plain although Idaho Falls and north are still likely to go below freezing. Lows tonight in the 20s and 30s with highs Friday in the 40s and 50s and it will be dry late Friday morning through Friday night everywhere. With clearing skies Friday will likely need more freeze warnings and frost advisories Friday night into Saturday morning with lows again in the 20s to lower 30s.
GK

LONG TERM
Saturday through next Thursday.
Confidence continues to increase on a return to widespread, moderate precipitation starting Saturday night and continuing into Sunday and Monday as a well organized H5 low moves onshore from the NE Pacific.
Saturday is still shaping up to be the warmest day in over a week with highs in the 60s/70s courtesy of a warm front and strong southerly flow ahead of the arrival of this next system. Winds aloft at 700 mb will steadily increase throughout the day Saturday into Sunday as a 40-50 kt jet streak is established over ERN Idaho. This will support strong winds out of the south for Saturday before shifting to being out of the west for Sunday as this low tracks directly over SRN Idaho and the NRN Great Basin. Winds will continue to remain elevated out of the west/southwest through Monday and Tuesday before lighter winds return for Wednesday aided by a ridge of high pressure in the ERN Pacific attempting to move inland.

The position and track of this weekend low remains supportive for widespread moderate precipitation with some locations forecast to see more precipitation in a 2-day period (Sunday/Monday) than during the entire month of April. This wet solution is reflected well amongst ensemble and deterministic solutions with the NBM showing a 40-80% chance of 0.50" of rain or more and a 10-20% chance of 1.00" of rain or more across the entire region. The latest forecast calls for 0.50-1.25" of rain with locally higher totals in the mountains around that 1.25-2.00" range. Snow levels will initially start off above 8000-9000' on Saturday before steadily decreasing into early next week as colder air settles in behind a cold front on Sunday.
This will support a mix of rain and snow in the valleys with predominant snow favored in the mountains. WINTER WEATHER ADVISORIES may also be needed along the Idaho/Wyoming border region where places such as Pine Creek and Teton Passes are currently seeing the potential for up to around 12-18" of snow. Expect these numbers to change over the coming days as there is increased uncertainty of snow amounts but with a moist, cool airmass in place, be mindful of the potential for a return to winter travel conditions.

As this low ultimately departs east onto the Great Plains for Tuesday, what will be left in its wake will be a broad troughing pattern over the PacNW and NRN Rockies. This will lead to continued below normal temperatures and precipitation chances through the work week but not to the extent of what we saw on Sunday/Monday given the lesser organized nature of several weaker troughs. Highs starting Sunday will be in the 40s/50s or about 10-25 degrees colder than Saturday and will continue to be there through the work week. Models remain in reasonable agreement heading into later in the week as an aforementioned ridge of high pressure remains on track to build in later in the week with over 75% of ensemble cluster solutions favoring this solution. The other 25% show a continued trough over the NRN Rockies which would delay any warmup however this remains the less likely solution at this time. MacKay

AVIATION
For the 18Z TAFS through 18Z Friday.
Predominant VFR conditions continue as early afternoon radar imagery shows scattered showers across WRN and CNTRL Idaho of which will continue to track east through this evening. Given dew point depressions around 20-30 degrees however, much of this precipitation is not reaching the ground and we are seeing more virga as a result.
Have continued with VCSH on the leading edge of this moisture before ultimately transitioning to a mix of rain/snow showers later today through the overnight hours as surface dew points increase. In addition to showers this afternoon, the HRRR model probability of thunder shows a 10-30% chance at KPIH, KBYI, and KSUN with best chances at KBYI where VCTS has been included. As precipitation shifts east overnight tonight into Friday morning, we are tracking the potential for an organized band of snow to work north to south across ERN Idaho with an emphasis on the Snake Plain corridor. This will support possible MVFR/IFR CIGS/VIS at KPIH, KIDA, and KDIJ with best chances at KPIH. MacKay

HYDROLOGY
Moderate flooding remains ongoing at the Portneuf River at Pocatello with the level remaining above moderate stage and forecast to do so through today and drop below Friday and continue before rising again late next week. Minor flooding continues for the Portneuf River at Topaz where the gauge remains above flood stage and will remain so for several days. Flood warnings also remain in effect for the Blackfoot River near Shelley at Wolverine Canyon where the river has gone above flood stage and also near Blackfoot where the river has also now gone above flood stage in the last 24 hours.
GK

PIH WATCHES/WARNINGS/ADVISORIES
Frost Advisory from 2 AM to 9 AM MDT Friday for IDZ051-054-055.

Freeze Warning from 2 AM to 9 AM MDT Friday for IDZ052-053.

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Pocatello/Idaho Falls, ID,