Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 210913
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
313 AM MDT TUE JUL 21 2015

.DISCUSSION...DEEP POOL OF MOISTURE OVER NORTHERN GREAT BASIN
CONTINUING TO MOVE SLOWLY TOWARD EAST IDAHO THIS MORNING. BROAD
TROUGH OFF BC CANADA COAST SWINGING SHORTWAVE ENERGY TOWARD PACNW
IS EXPECTED TO SHIFT INTO THE COAST LATE TODAY. LAYER PRECIPITABLE
WATER VALUES STEADILY INCREASE THROUGH THE DAY TODAY WITH MOST OF
THE REGION .75 TO AROUND ONE INCH. BEST CHANCES FOR THUNDERSTORMS
TODAY MAINLY HIGHER ELEVATIONS WITH UPPER TROUGH STILL ALONG
COAST. CHANCES INCREASE WEDNESDAY WITH SHORTWAVE EMBEDDED IN
TROUGH SWINGING NORTHEAST ACROSS IDAHO. WITH PRECIPITABLE WATER
VALUES AROUND AN INCH...LOCALLY VERY HEAVY RAIN LIKELY. STORM
MOVEMENT SHOULD BE SUFFICIENT ENOUGH TO PRECLUDE WIDESPREAD THREAT
FOR FLASH FLOODING. PRECIP CONTINUES OVERNIGHT AND INCREASES AGAIN
INTO THURSDAY AS UPPER TROUGH AXIS SHIFTS TOWARDS IDAHO.
PRECIPITABLE WATER VALUES REMAIN HIGH FOR CONTINUED HEAVY RAIN
THREAT. TROUGH AXIS DOES SHIFT ACROSS THE REGION THURSDAY NIGHT
INTO FRIDAY WITH DRIER AIR MASS. LINGERING MOISTURE ESPECIALLY IN
THE EASTERN HIGHLANDS REGIONS COULD KEEP THREAT FOR THUNDERSTORMS
GOING DURING THE DAY.

BOTH GFS AND ECMWF DROP ANOTHER UPPER LOW ALONG BC CANADA COAST
SATURDAY...TAKING IT ON A SIMILAR TRACK THROUGH TUESDAY. DRY
CONDITIONS SATURDAY SHIFT TO RETURN THREAT OF DIURNAL THUNDERSTORM
ACTIVITY. MISSING INGREDIENT IS THE DEEP TROPICAL MOISTURE SO
HAVE KEPT PRECIP CHANCES CLOSER TO CLIMO FOR SUNDAY AND BEYOND.
DMH


&&

.AVIATION...AN INCREASINGLY MOIST AND UNSTABLE SW FLOW IS EXPECTED
ACROSS THE REGION TODAY INTO WEDNESDAY AS THE REMNANTS OF DOLORES
SHEAR NE THROUGH THE GREAT BASIN AND A PAC TROUGH ADVANCES INTO THE
NW STATES. MAY SEE VCTY THUNDERSTORM ACTIVITY AT TERMINALS TODAY
WITH KSUN SEEING BIGGEST THREAT WITH AN INCREASING THREAT AT ALL
TERMINALS WEDNESDAY. VFR CONDITIONS ANTICIPATED THROUGHOUT WITH
INCREASING SW WINDS WEDNESDAY AFTERNOON. HUSTON


&&

.FIRE WEATHER...A BROAD UPPER TROUGH WAS POSITIONED OVER NRN BRITISH
COLUMBIA EARLY THIS MORNING AND IS EXPECTED TO MIGRATE EAST THROUGH
CANADA OVER THE NEXT SEVERAL DAYS WHILE THE ASSOCIATED TROUGH AXIS
ADVANCES THROUGH SRN IDAHO THURSDAY AFTERNOON/EVE. THE REMNANT OF
DOLORES WAS ALSO VISIBLE SHEARING NE THROUGH CNTRL UTAH WHILE SOME
OF THE ASSOCIATED MOISTURE EXTENDED FROM CNTRL CALIFORNIA THROUGH SE
IDAHO. INCREASING THUNDERSTORM ACTIVITY IS EXPECTED TODAY THROUGH
THURSDAY AS THE AFOREMENTIONED TROUGH AXIS ADVANCES EAST INTO THE
REGION ENCOUNTERING THE LINGERING SUB-TROPICAL MOISTURE. LOCALLY
HEAVY RAIN IS EXPECTED WITH THE DEVELOPING CELLS WEDNESDAY AND
THURSDAY WHILE MINIMUM HUMIDITY LEVELS RUN MOSTLY IN THE 30S TO
LOWER 40S...MUCH TOO HIGH TO SUPPORT ANY RED FLAG CONSIDERATIONS
FROM ME. BREEZY SOUTHWEST WINDS ARE ALSO ANTICIPATED WEDNESDAY AND
THURSDAY AS THE TROUGH APPROACHES. ALTHOUGH THE MODELS HAD
PREVIOUSLY PROMISED A DRIER WEST FLOW BREAKING ACROSS IDAHO FOR
FRIDAY...TODAY THEY SHOW SOME LINGERING MOISTURE AND INSTABILITY
PRIMARILY ALONG THE WYOMING BORDER REGION WHICH MAY YET SUPPORT
ISOLATED AFTERNOON CONVECTION. A SECOND PAC LOW SETTLES INTO BRITISH
COLUMBIA SATURDAY...MUCH DEEPER AND STRONGER THAN YESTERDAYS PROGS
AND VERY MUCH RESEMBLING THE CURRENT WAVE ADVANCING THROUGH
CANADA...MINUS THE SUB-TROPICAL STEROID INJECTION FROM DOLORES. THUS
THIS SYSTEM WILL BRING BREEZY AFTERNOON WINDS SUNDAY/MONDAY AND
SCATTERED THUNDERSTORM ACTIVITY. HUSTON


&&

.PIH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$


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