FXUS65 KBOI 261649
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
948 AM MST SAT DEC 26 2009
.DISCUSSION...STRATUS CONTINUES TO ADVANCE WESTWARD THIS
MORNING...COVERING MOST OF THE VALLEYS OF SOUTHEAST OREGON BELOW
ABOUT 5000 FEET...ALONG WITH THE SNAKE RIVER PLAIN IN SOUTHWEST
IDAHO. THE EASTERLY SFC PRESSURE GRADIENT IS PROVING SOME
WIND...THUS REDUCING THE AMOUNT OF FOG THAT OTHERWISE MIGHT BE
PRESENT IF THE WINDS WERE LIGHT. THERE IS SOME FOG...HOWEVER...IN
TWIN FALLS AND MCCALL...OTHERWISE NO OTHER OBSERVATIONS HAVE BEEN
REPORTING VISIBILITIES LESS THAN 10 MILES. STILL EXPECT MOSTLY SUNNY
SKIES TODAY OUTSIDE THOSE AREAS IN THE STRATUS...WHICH SHOULD
PROVIDE SOME BREAKS IN THE CLOUDS THIS AFTERNOON...BUT OVERALL
EXPECT THE STRATUS TO PERSIST. WILL UPDATE FORECAST FOR MORE CLOUDS
IN SOUTHEAST OREGON...OTHERWISE FORECAST IS ON TRACK.
&&
.AVIATION...WIDESPREAD MVFR/IFR STRATUS COVERS THE SNAKE RIVER
VALLEY AND ADJACENT LOWER ELEVATIONS...INCLUDING THE NORTHERN HALF
OF MALHEUR...HARNEY...AND BAKER COUNTIES. SOME BREAKS CAN BE
EXPECTED IN PLACES DURING THE DAY TODAY BUT NO BIG CHANGES EXPECTED.
A WEAKENING PACIFIC WEATHER FRONT WILL SEND HIGH CLOUDS OVER THE
AREA FROM THE SOUTHWEST LATER TODAY AND TONIGHT. THIS WILL BE A SLOW
MOVING SYSTEM WITH HIGH CLOUDS AFFECTING ONLY THE AREA SOUTHWEST OF
BOISE BY SUNDAY MORNING. LITTLE CHANGE IN THE STRATUS SITUATION
THROUGH TONIGHT.
&&
.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH SUNDAY...STRATUS HAS CONTINUED TO WORK
WESTWARD INTO NORTH CENTRAL MALHEUR COUNTY/JORDAN VALLEY...WEISER
RIVER BASIN AND BAKER VALLEY AS WELL AS TO DREWSEY AND NEW PRINCETON
BASED ON SATELLITE SPLIT WINDOW /11-3.9MICRON/ IMAGERY. IT CONTINUED
ACROSS THE TREASURE AND MAGIC VALLEYS. LOCALLY SLICK CONDITIONS ARE
EXPECTED WITH DENSE FOG WITH SUB-FREEZING TEMPERATURES IN THE MAGIC
VALLEY THIS MORNING. UPPER LEVEL SHEAR AXIS SEEN ON WATER VAPOR TO
THE ORE-IDA BORDER LOOKS TO PUSH WEST THROUGH NE OREGON THIS MORNING
HELPING TO DRAG STRATUS TO BAKER/BURNS BEFORE THE SHEAR AXIS BECOMES
NEARLY STATIONARY NW-SE ACROSS OREGON TONIGHT AND SUNDAY. SO THE
STRATUS LOOKS TO REMAIN SOLIDLY ACROSS THE LOWER TREASURE VALLEY
THROUGH SUNDAY. CUT OFF UPPER HIGH OVER SW CANADA AND DEVELOPING
UPPER LOW OFF THE COAST RESULT IN DRY WEATHER UNTIL SUNDAY WHEN A
SLIGHT CHANCE OF SNOW NUDGES INTO HARNEY COUNTY DUE TO THE LOW
OFFSHORE. ANY QPF WILL BE VERY LIGHT AS SPLIT FLOW REMAINS OVER SE
OREGON AND SW IDAHO. HIGH PRESSURE CENTERED TO OUR EAST AND LOWER
PRESSURE OFFSHORE WILL BRING LIGHT NE TO SE WINDS ACROSS THE REGION
THE NEXT TWO DAYS EXCEPT CHANNELED AREAS SUCH AS JEROME WHERE 10-20
MPH NE WINDS ARE EXPECTED AT TIMES.
STAGNANT CONDITIONS IN OREGON MAY IMPROVE SOME THIS AFTERNOON AS
EAST WINDS AT THE SURFACE INCREASE SLIGHTLY THE NEXT TWO DAYS.
THIS INCREASE IN WIND IS IN RESPONSE TO THE OFFSHORE LOW MOVING
CLOSER WHILE HIGH PRESSURE SURFACE AND ALOFT CONTINUE FROM SW
CANADA THROUGH THE NORTHERN ROCKIES...INCREASING THE GRADIENT OVER
OREGON.
LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...WITH THE FLOW SPLIT OFF
THE COAST AND MOST OF THE ENERGY WELL SOUTH OF US WE ARE KEEPING
POPS LOW THROUGH MONDAY NIGHT. AS A RIDGE BEGINS TO BUILD OFFSHORE
...MOIST NORTHWEST FLOW ALOFT WORKS ITS WAY FAR ENOUGH NORTH TUESDAY
AND WEDNESDAY TO RAISE POPS TO A LITTLE ABOVE CLIMATOLOGY. THE GFS40
AND ITS ENSEMBLE MEAN...AND THE CANADIAN...MOVE THE RIDGE INLAND
THURSDAY AND FRIDAY. ENOUGH FLOW CONTINUES THROUGH THE RIDGE TO KEEP
POPS NEAR CLIMATOLOGY. THE ECMWF WANTS TO BRING A SHORTWAVE TROUGH
OVER THE PACIFIC NORTHWEST ON FRIDAY...AND THIS WOULD ALSO SUPPORT
POPS AT LEAST NEAR CLIMATOLOGY. MODEL SOUNDINGS SHOW A STABLE
BOUNDARY LAYER WITH A SURFACE BASED INVERSION THROUGH THE PERIOD. SO
WE ARE KEEPING TEMPERATURES A FEW DEGREES BELOW NORMAL THROUGH
THURSDAY...THEN NEAR NORMAL FRIDAY.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...AIR STAGNATION ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR
ORZ061-ORZ062.
&&
$$
WEATHER.GOV/BOISE
DISCUSSION...BW
AVIATION.....PF
PREV SHORT TERM...VM
PREV LONG TERM....JT
