Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 061605
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1005 AM MDT WED MAY 6 2015

.DISCUSSION...UPPER LOW IS DROPPING SOUTH ALONG THE CASCADES THIS
MORNING. WATER VAPOR SATELLITE SHOWING MOISTURE FEEDING NORTH
THROUGH CENTRAL AND EASTERN IDAHO WITH HIGH BASED SHOWERS FORMING
OVER S-CENTRAL ID THIS MORNING. SHOWER AND THUNDERSTORM
DEVELOPMENT WILL EXPAND TO COVER THE EASTERN BOISE AND WEST-
CENTRAL MTNS THIS AFTERNOON. IN SE OREGON...THE DYNAMICS FROM
UPPER LOW WILL FEED SHOWER AND THUNDERSTORM DEVELOPMENT OVER
HIGHER TERRAIN. THE LOWER VALLEYS TO INCLUDE THE SNAKE PLAIN AND
WEISER VALLEY WILL REMAIN DRY TODAY. GUSTY WINDS NORTHWEST WINDS
AGAIN TODAY THROUGH THE SNAKE RIVER VALLEY WITH GUSTS TO 30 MPH IN
THE UPPER TREASURE VALLEY TO INCLUDE MOUNTAIN HOME. CURRENT
FORECAST IS ON TRACK SO NO UPDATES AT THIS TIME.

&&

.AVIATION...VFR. SCATTERED TO BROKEN MID LEVEL CLOUDS. ISOLATED
SHOWERS AND THUNDERSTORMS WILL REDEVELOP THIS AFTERNOON...MAINLY
OVER HIGHER TERRAIN. SURFACE WINDS WEST-NORTHWEST 5-15 KNOTS WITH
GUSTS TO NEAR 20 KNOTS...EXCEPT IN THE SNAKE RIVER VALLEY AND THE
BAKER CITY VALLEY WHERE 15-25 KNOTS WITH GUST TO NEAR 30 KNOTS IS
EXPECTED. WINDS ALOFT WEST-NORTHWEST AROUND 20 KNOTS UP THROUGH 10K
FEET MSL...BECOMING SOUTHWESTERLY 35-40 KNOTS ABOVE 10K FEET MSL.

&&

.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH THURSDAY...UPPER LOW WILL DROP FROM
WASHINGTON SOUTH INTO NRN CA BY 12Z THU...THEN INTO CENTRAL CA BY
00Z FRI. AS A RESULT...THE UPPER FLOW OVER OUR AREA WILL BACK FROM
SW TODAY TO S TONIGHT TO SE THROUGH E ON THU. MOISTURE WILL SURGE
NORTHWARD OVER THE AREA THROUGH THIS PERIOD. THE BEST CHANCE FOR
PRECIP IS THU AFTERNOON...AS A DEEPER LAYER OF MOISTURE MOVES
NORTH MAINLY ACROSS OUR SW IDAHO ZONES. POPS HAVE BEEN RAISED A
LITTLE MORE FOR THIS TIME PERIOD. FOR TODAY...THERE IS JUST
BARELY ENOUGH INSTABILITY TO RETAIN THE MENTION OF THUNDERSTORMS
IN THE FORECAST FOR THIS AFTERNOON AND EVENING. TOMORROW...
INSTABILITY IS BEST OVER THE SOUTHEASTERN 2/3RDS OF THE CWA...AND
THE MENTION OF THUNDER REMAINS THERE. TEMPS WILL BE COOL TODAY AND
TOMORROW... WITH HIGHS GENERALLY IN THE 60S. THERE IS A LARGE
DISCREPANCY IN THE MOS GUIDANCE FOR BOISE TOMORROW...WITH THE WARM
MET AT 70 AND THE COOLER MAV AT 58. WE STAYED IN BETWEEN BUT
CLOSER TO THE MAV AS WE EXPECT SHOWERS IN THE AFTERNOON WILL
GREATLY IMPACT THE AREA/S ABILITY TO WARM UP. WINDS WILL BE BRISK
OUT OF THE NW TO NORTH THROUGHOUT MOST OF THE PERIOD.

LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...MODEL TREND CONTINUING
WITH GOOD AGREEMENT EARLY IN THE EXTENDED BUT THEN BEGINNING TO
DIVERGE BY EARLY NEXT WEEK. CUTOFF LOW WILL BE OVER CENTRAL
CALIFORNIA THURSDAY NIGHT THEN SHIFT SOUTHEAST TO SOUTHERN NEVADA
FRIDAY. THE FLOW PATTERN AROUND THIS LOW WILL BRING CHANCE POPS TO
SOUTHWEST IDAHO BUT MOSTLY DRY CONDITIONS TO SOUTHEAST OREGON.
CUTOFF LOW WILL SLOWLY MOVE EAST AND WEAKEN AND WILL BE NEAR THE
FOUR CORNERS AREA BY SATURDAY. BEST CHANCE FOR PRECIPITATION
REMAINS OVER SOUTHWEST IDAHO BUT AS THE LOW MOVES EAST EXPECTING
POPS DECREASING TO SLIGHT CHANCE WITH SOUTHEAST OREGON REMAINING
DRY. SATURDAY NIGHT THE LOW WILL SHIFT EAST WITH MODELS DEVELOPING
A RIDGE OVER THE PACIFIC NORTHWEST. THIS WILL BRING MOSTLY DRY
CONDITIONS TO THE WHOLE FORECAST AREA...BUT THERE COULD BE SLIGHT
CHANCE POPS OVER EXTREME EASTERN ZONES AS THE LOW PUSHES EAST.
SUNDAY LOOKS TO REMAIN MOSTLY DRY BUT LATEST MODEL RUNS NOW HAVE A
FASTER TIMING OF THE NEXT UPPER LEVEL TROUGH THAT WILL BE MOVING
INTO THE PACIFIC NORTHWEST. PREVIOUS MODEL RUNS HAD THE AREA DRY
BUT WITH THE FASTER TIMING OF THE UPPER LEVEL TROUGH THERE COULD
BE A SLIGHT CHANCE OF PRECIPITATION SUNDAY AFTERNOON OVER
SOUTHEAST OREGON AND THE HIGHER TERRAIN OF SOUTHWEST IDAHO. LATEST
FORECAST ALREADY HAS SOME MENTION OF PRECIPITATION SO WILL NOT
MAKE ANY CHANGES AT THIS TIME. SUNDAY NIGHT AND MONDAY MODELS
DEVELOP A CUTOFF LOW JUST OFF THE PACIFIC NORTHWEST COAST AND
SLOWLY MOVE IT SOUTH THROUGH TUESDAY. MONDAY THE GFS IS A BIT
FURTHER SOUTH THAN THE ECMWF WITH THE CUTOFF LOW BUT BY TUESDAY
MODELS CURRENTLY HAVE THE SAME LOCATION OF THE CUTOFF LOW OVER
WESTERN OREGON. SOME DIFFERENCES IN THE MODELS AS TO LOCATION OF
PRECIPITATION FROM SUNDAY NIGHT THROUGH TUESDAY BUT WILL KEEP THE
TREND OF CHANCE POPS OVER HIGHER TERRAIN AND SLIGHT CHANCE OVER
THE REST OF THE FORECAST AREA. TEMPERATURES THROUGH THE EXTENDED
WILL BE AT OR A FEW DEGREES ABOVE NORMAL.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...DG
AVIATION.....JS
PREV SHORT TERM...SP
PREV LONG TERM....JA


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