534
FXUS65 KPIH 082301
AFDPIH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
501 PM MDT THU OCT 8 2026
KEY MESSAGES
- FINAL DAY OF QUIET WARMTH TODAY; BREEZY FRIDAY: TODAY BRINGS
ONE LAST AFTERNOON OF TRANQUIL AUTUMN WEATHER. FRIDAY REMAINS
WARM BUT INTRODUCES GUSTY SOUTHWEST WINDS OF 25 TO 35 MPH
ACROSS CENTRAL AND EASTERN IDAHO, WITH MOUNTAIN GUSTS REACHING
40 MPH.
- TROPICAL MOISTURE & WIDESPREAD HEAVY RAIN (SATURDAY–EARLY
NEXT WEEK): SPLIT FLOW OVER THE WEST WILL DRAW REMNANTS OF
TROPICAL CYCLONE RACHEL NORTHWARD, DELIVERING A MAJOR RAIN
EVENT. EXPECT 1.0"–2.0" ACROSS THE SOUTHERN/EASTERN HIGHLANDS
(2.25"–2.5" ON HIGH RIDGES), 1.0"–1.5" ACROSS THE SNAKE PLAIN
FROM POCATELLO TO REXBURG, AND 0.10"–0.30" IN CENTRAL MOUNTAIN
VALLEYS.
- POTENTIAL FLOOD HEADLINES: HIGH-END QPF TOTALS OVER THE
EASTERN AND SOUTHEASTERN HIGHLANDS MAY REQUIRE FLOOD OR FLASH
FLOOD WATCHES IN UPCOMING FORECAST UPDATES AS THE WEST-EAST
MOISTURE PLACEMENT LOCKS IN.
- HIGH-ELEVATION SNOW & FROST/FREEZE RISKS: COLD ADVECTION WILL
LOWER SNOW LEVELS TO 7,000 FEET, BRINGING SEVERAL INCHES TO
HIGH PEAKS AND MAYBE INTO ISLAND PARK. COOLER TEMPS EARLY NEXT
WEEK WILL BRING WIDESPREAD FROST AND FREEZE RISKS.
DISCUSSION
ISSUED AT 217 PM MDT THU OCT 8 2026
TODAY MARKS THE FINAL AFTERNOON OF TRANQUIL, PRISTINE WEATHER
ACROSS EASTERN IDAHO BEFORE A MAJOR AUTUMN STORM SYSTEM ALTERS
THE REGIONAL PATTERN. UNSEASONABLY MILD TEMPERATURES AND DRY AIR
WILL HOLD THROUGH FRIDAY, WITH A FEW LOCALIZED SPOTS ACTUALLY
TOPPING TODAY'S HIGHS BY A DEGREE OR TWO. THE MAIN CHANGE ON
FRIDAY WILL BE A TIGHTENING SURFACE PRESSURE GRADIENT, WHICH
WILL DRIVE BREEZY SOUTHWEST WINDS ACROSS THE FORECAST AREA. WIND
GUSTS OF 25 TO 35 MPH ARE EXPECTED ACROSS MOST LOWER
ELEVATIONS, WITH GUSTS TOPPING 40 MPH ALONG CENTRAL MOUNTAIN
RIDGELINES. WHILE GUSTY, THESE SPEEDS ARE ANTICIPATED TO REMAIN
BELOW ADVISORY CRITERIA OUTSIDE OF LOCALIZED FIRE WEATHER
IMPACTS. SEE FIRE WEATHER DISCUSSION BELOW.
A DRASTIC SYNOPTIC TRANSITION UNFOLDS SATURDAY AS SPLIT FLOW
ESTABLISHES ITSELF ACROSS THE WESTERN UNITED STATES. GLOBAL
GUIDANCE (GFS AND ECMWF) AGREES ON DROPPING A CLOSED UPPER-LEVEL
LOW SOUTH ALONG AND OFF THE CALIFORNIA COAST BEFORE IT TRACKS
EASTWARD. OUT AHEAD OF THIS SYSTEM, TROPICAL MOISTURE ASSOCIATED
WITH THE REMNANTS OF TROPICAL CYCLONE RACHEL WILL BE ENTRAINED
NORTHWARD DIRECTLY INTO CENTRAL AND EASTERN IDAHO.
SHOWER AND THUNDERSTORM COVERAGE WILL SURGE SATURDAY AND REMAIN
ACTIVE INTO EARLY NEXT WEEK. THIS RICH MOISTURE PLUME WILL
SUPPORT HEAVY RAINFALL TOTALS AS PWAT VALUES ARE NEARING
CLIMATOLOGICAL MAXIMUMS. CURRENT FORECAST CALLS FOR 1.0 TO 2.0
INCHES FORECAST ACROSS THE SOUTH HILLS, ALBION MOUNTAINS, AND
THE SOUTHEASTERN/EASTERN HIGHLANDS. HIGHEST RIDGELINES EAST OF
I-15 COULD PUSH 2.25 TO 2.50 INCHES. DOWNSTREAM QPF SPILLOVER
WILL BRING 1.0 TO 1.5 INCHES TO THE SNAKE PLAIN FROM POCATELLO
NORTHWARD THROUGH REXBURG. FARTHER WEST, CENTRAL MOUNTAIN
VALLEYS WILL SEE LIGHTER AMOUNTS RANGING FROM 0.25 TO 0.75
INCHES. WHILE THESE EASTERN HIGHLAND TOTALS REPRESENT THE UPPER
TIER OF MODEL ENSEMBLE BLENDS, THEY REMAIN WELL WITHIN THE REALM
OF POSSIBILITY GIVEN THE TROPICAL ORIGIN OF THE AIR MASS.
BECAUSE MINOR SHIFTS IN THE TRACK OF RACHEL'S MOISTURE AXIS
COULD ALTER LOCALIZED TOTALS, FLOOD OR FLASH FLOOD WATCH
ISSUANCES HAVE BEEN DEFERRED TO FRIDAY'S FORECAST CYCLE BUT STAY
TUNED.
COLDER AIR WRAPPING INTO THE SYSTEM SUNDAY AND MONDAY WILL DRIVE
SNOW LEVELS DOWN TO AROUND 7,000 FEET ACROSS THE CENTRAL
MOUNTAINS AND ALONG THE CONTINENTAL DIVIDE. WHILE LOWER
ELEVATIONS WILL SEE MOSTLY RAIN, SEVERAL INCHES OF WET SNOW ARE
POSSIBLE FOR HIGH PEAKS AND PASS LEVELS TOWARD ISLAND PARK. A
SECONDARY UPPER-LEVEL TROUGH IS FORECAST TO DROP INTO THE
INTERMOUNTAIN WEST DURING THE MIDDLE OF NEXT WEEK, REINFORCING
COLD AIR ADVECTION AND KEEPING TEMPERATURES WELL BELOW SEASONAL
AVERAGES. FROST/FREEZE HEADLINES WILL LIKELY BE NEEDED FOR A FEW
DAYS EARLY NEXT WEEK BEFORE THE "GROWING SEASON" IS OFFICIALLY
DECLARED OVER FOR THE YEAR.
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 500 PM MDT THU OCT 8 2026
VFR CONDITIONS CONTINUE THROUGH TONIGHT AND MOST OF FRIDAY. THERE
WILL BE FEW UPPER LEVEL CLOUDS AROUND IDA AND DIJ OVERNIGHT, BUT
CLOUD COVER SHOULD BE ON THE INCREASE FRIDAY AFTERNOON AND EVENING.
OUR SHORT-RANGE MODELS ARE SHOWING SOME SPOTTY RAIN SHOWER CHANCES
FRIDAY EVENING, BUT CONFIDENCE IS LOW, SO WILL HOLD OFF ON ANY VCSH
IN THE TAFS FOR NOW, BUT THAT COULD BE A POTENTIAL CHANGE WITH
FOLLOWING TAF UPDATES. WHILE WINDS REMAIN GENERALLY LIGHT OVERNIGHT,
LOOK FOR INCREASING GUSTS ON FRIDAY AFTERNOON, TO AROUND 20-25KTS.
FIRE WEATHER
ISSUED AT 217 PM MDT THU OCT 8 2026
DRY CONDITIONS CONTINUE INTO FRIDAY, BUT CONDITIONS ARE
BEGINNING TO CHANGE AS A VIGOROUS LOW PRESSURE SYSTEM WORKS INTO
THE REGION. WINDS WILL BEGIN GUSTING ACROSS THE REGION DURING
THE AFTERNOON FRIDAY. ALONG WITH THE DRY HUMIDITIES, AT LEAST
LOCALIZED CRITICAL CONDITIONS ARE POSSIBLE, BECOMING MORE
WIDESPREAD ACROSS THE SOUTHERN SAWTOOTH ZONE 427. THUS A RED
FLAG WARNING WILL BE IN PLACE FOR ZONE 427 FOR FRIDAY AFTERNOON
AND EARLY EVENING. BREEZY WINDS CONTINUE INTO SATURDAY, BUT
TEMPERATURES BEGIN TO SLIDE AS MOISTURE SHIFTS INTO THE REGION,
HERALDING A VERY QUICK TRANSITION TO A WET FALL SYSTEM.
PRECIPITATION STARTS TO EXPAND ACROSS EAST IDAHO SATURDAY AND
CONTINUES INTO EARLY TO MID WEEK NEXT WEEK. 48 HOUR
PRECIPITATION PROBABILITIES THROUGH SUNDAY NIGHT FOR TOTALS OVER
1.0" EXCEED 60% FOR ALL BUT THE CENTRAL MOUNTAINS AND EASTERN
MAGIC VALLEY REGIONS, AND ARE 80+% FOR ALMOST THE ENTIRETY OF
THE EASTERN AND SOUTHERN HIGHLANDS. IF THE DEEPER MOISTURE FROM
REMNANTS OF TROPICAL SYSTEM RACHEL WORK THIS FAR NORTH, THOSE 48
HR TOTALS COULD RANGE 1.5-2.5" FOR THE EASTERN AND SOUTHERN
HIGHLANDS, POSSIBLY EXTENDING INTO THE SNAKE RIVER PLAIN. EXACT
TOTALS WILL BE DEPENDENT ON THE TRACK OF THE SYSTEM AS IT DROPS
INTO THE REGION, BUT THE TREND IS CLEAR. AFTER A PROLONGED DRY
AND UNSEASONABLY WARM PERIOD, WE WILL TRANSITION TO MUCH COOLER
AND WETTER. TEMPERATURES WILL BE COLD ENOUGH BY LATE IN THE
WEEKEND TO SEE ACCUMULATING SNOW AT HIGHER ELEVATIONS, BRIEFLY
DIPPING CLOSER TO MID SLOPE ESPECIALLY DURING THE OVERNIGHT
PERIODS. AS OF RIGHT NOW, THERE IS POTENTIAL FOR A RELATIVE
BREAK IN THE PRECIPITATION TUESDAY, BUT ANOTHER ROUND IS
EXPECTED WEDNESDAY INTO THURSDAY. THE TREND IS TOWARD THE
SYSTEMS SHIFTING EAST OF IDAHO LATE NEXT WEEK INTO THE WEEKEND,
LEADING TOWARD DRIER CONDITIONS AND TEMPERATURES WARMING BACK TO
NEAR NORMAL.
PIH WATCHES/WARNINGS/ADVISORIES
RED FLAG WARNING FROM 2 PM TO 8 PM MDT FRIDAY FOR IDZ427.
DISCUSSION...MCKAUGHAN
AVIATION...AMM
FIRE WEATHER...DMH
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