807
FXUS65 KPIH 231958
AFDPIH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
158 PM MDT WED SEP 23 2020
SHORT TERM...TONIGHT THROUGH FRIDAY
SOUTHEAST FLOW IS FORECAST
THIS PERIOD WITH HIGH PRESSURE SITUATED TO OUR SOUTH. CHANCES FOR
PRECIPITATION IN CENTRAL IDAHO BEGIN THURSDAY WITH WEAK
SHORTWAVES PULSING EASTWARD ASSOCIATED WITH A LOW PRESSURE TROUGH
AND SUBSEQUENT COLD FRONT THURSDAY INTO FRIDAY. INCREASING WIND
SPEEDS ARE EXPECTED THURSDAY AFTERNOON AND EVENING WITH GUSTS
AROUND 40 MPH IN PORTIONS OF THE SNAKE PLAIN 30 TO 40 MPH AT
RIDGETOPS. BECAUSE OF THESE ANTICIPATED STRONG WINDS, WE WILL
ISSUE A WIND ADVISORY ACROSS THE UPPER SNAKE RIVER PLAIN AND ARCO
DESERT ZONE AS WELL AS A LAKE WIND ADVISORY FOR AMERICAN FALLS
RESERVOIR. THE FRONT ITSELF IS RATHER DRY AND SHOULD NOT ALLOW
FOR WIDESPREAD CHANCES FOR SHOWERS AND THUNDERSTORMS.
ND
LONG TERM...SATURDAY THROUGH WEDNESDAY
A VERY MILD WEEKEND IS
FORECAST UNDER ZONAL FLOW. THERE ARE SLIGHT CHANCES FOR SHOWERS IN
THE ISLAND PARK/EAST IDAHO AREAS SATURDAY AS WEAK IMPULSES
TRAVERSE THROUGH THE AREA. TEMPERATURES WILL BE MILD AND PLEASANT
IN THE 70S; A TREND THAT WILL PERSIST THROUGH EARLY NEXT WEEK. A
HIGH PRESSURE RIDGE WILL ONLY STRENGTH AS WE HEAD INTO THE MIDDLE
PORTION OF NEXT WEEK, CONTINUING THE TREND OF FALL LIKE
TEMPERATURES AND PRECIP-FREE DAYS.
ND
AVIATION
CONTINUED VFR CONDITIONS ARE AGAIN EXPECTED TODAY WITH
BREEZY CONDITIONS LIKELY FOR PIH, IDA AND DIJ THIS AFTERNOON. THERE
MAY BE BRIEF MVFR CONDITIONS THIS AFTERNOON FOR SMOKE, ESPECIALLY
KSUN. BRIEF MVFR CONDITIONS MAY BE POSSIBLE AS WELL FOR SMOKE FOR
THE SNAKE RIVER PLAIN INCLUDING KIDA, KPIH AND KBYI THIS EVENING
INTO EARLY MORNING.
TW
FIRE WEATHER
EXPECT BREEZY WINDS AGAIN TODAY AHEAD OF A SYSTEM
THAT WILL MOVE THROUGH THURSDAY INTO SATURDAY MORNING. BY
THURSDAY AFTERNOON, WINDS WILL PICK UP GUSTING TO 25 TO 35 MPH
WITH LOCALIZED AREAS OF 40 MPH MAINLY FOR THE ARCO DESERT AND SOME
RIDGE TOPS AS THIS NEXT SYSTEM/WEAK COLD FRONT MOVES THROUGH. ON
THURSDAY AFTERNOON RELATIVE HUMIDITY LOOKS TO BE AROUND 20 TO 30
PERCENT FOR VALLEYS WITH THE LOWER AMOUNTS NEAR 20 PERCENT IN THE
ARCO DESERT AND ALONG THE UTAH BORDER. HAINES INDEX WILL DROP TO 2
AND 3 BY THURSDAY AFTERNOON AS WELL. DUE TO RELATIVE HUMIDITY
ABOVE CRITICAL VALUES OF 15 PERCENT AND A LOW HAINES INDEX, HAVE
NOT PUT OUT A RED FLAG. THIS IS COORDINATED WITH OUR FIRE WEATHER
PARTNERS. THERE IS A SLIGHT CHANCE OF PRECIPITATION THURSDAY FOR
MAINLY ZONES 475, 476 AND 411, THOUGH OVERALL AMOUNTS LOOK LIGHT.
CHANCE OF WETTING RAIN LOOKS UNLIKELY AND CERTAINLY WOULD NOT BE
WIDESPREAD IF OCCURS. FRIDAY CONTINUES TO BE WINDY, MEETING RED
FLAG CRITERIA FOR A LOT OF AREAS WITH 20 TO 30 MPH GUSTS. THERE IS
ANOTHER SLIGHT CHANCE OF PRECIPITATION FOR OUR NORTHERN AREAS.
RELATIVE HUMIDITY DOES RISE EVEN MORE. AS A RESULT FRIDAY RELATIVE
HUMIDITY WILL BE IN THE 25 TO 35 PERCENT RANGE AND TOO HIGH TO
CONSIDER ANY RED FLAG WARNINGS. FRIDAY AND SATURDAY TEMPERATURES
WILL DROP TO NEAR TO SLIGHTLY BELOW NORMAL. LATE SATURDAY INTO
SUNDAY LOOK FOR HIGH PRESSURE TO BUILD BACK IN BRINGING WARMER AND
DRIER CONDITIONS SUNDAY THROUGH THE BEGINNING OF NEXT WEEK.
TW
AIR STAGNATION
DEGRADED AIR QUALITY FROM WILDFIRE SMOKE IS LIKELY
THIS AFTERNOON AND EVENING AS SOUTHWESTERLY FLOW IS FORECAST OVER
OUR AREA. AT TIMES, SPEEDS WILL BE RATHER STRONG THIS AFTERNOON AND
AGAIN THURSDAY AFTERNOON; ALLOWING THE SMOKE TO QUICKLY MOVE THROUGH
THE AREA. THERE MAY BE LOCAL SMOKE INFLUENCE FROM BADGER/WOODHEAD
FIRES UNDER THIS REGIME. CHANCES FOR PRECIPITATION IN CENTRAL IDAHO
BEGINNING THURSDAY WOULD HELP ALLEVIATE THE DEGRADED AIR QUALITY. A
PASSING COLD FRONT THURSDAY INTO FRIDAY SHOULD CLEAR OUT CONCERNS
FOR SMOKE ACROSS OUR AREA.
ND
PIH WATCHES/WARNINGS/ADVISORIES
LAKE WIND ADVISORY FROM NOON TO 8 PM MDT THURSDAY FOR IDZ054.
WIND ADVISORY FROM NOON TO 8 PM MDT THURSDAY FOR IDZ052-053.
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