Area Forecast Discussion
Issued by NWS Boise, ID

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KBOI 290330 CCA
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
830 PM MST SUN DEC 28 2014

.DISCUSSION...UPDATED FOR AREAS OF VALLEY FOG...LOCALLY DENSE...TONIGHT
BECOMING PATCHY MONDAY MORNING.  PATCHY DENSE FOG HAS ALREADY FORMED IN
THE TREASURE VALLEY FROM BOISE WEST.  SCATTERED SNOW SHOWERS ALSO
OCCURRING IN VARIOUS PARTS OF THE CWA...THESE WILL CONTINUE INTO MONDAY
AS AN UPPER TROUGH MOVES SOUTH THROUGH OUR CWA.  THE TROUGH WILL BECOME
A CLOSED LOW IN SRN NEVADA TUESDAY AND WILL CONTINUE TO MOVE SOUTH.
UPPER LEVEL WINDS IN OUR CWA WILL BECOME NELY AND BRING ARCTIC AIR INTO
OUR CWA...ESPECIALLY ON THE IDAHO SIDE...TUESDAY THROUGH THURSDAY...
ALREADY IN FORECASTS.

&&

.AVIATION...ADDED FOG TO MOST TAFS THROUGH THE NIGHT...BECOMING PATCHY
AFTER 12Z.  AT BOISE SURFACE WINDS WILL BECOME LIGHT SOUTHEAST AFTER
10Z AND SHOULD PUSH SOME OF THE FOG WESTWARD LEAVING BEHIND A LOW
STRATUS OVERCAST.  SCATTERED -SHSN IN ALL AREAS TONIGHT AND MONDAY WITH
LOCAL IFR CONDITIONS AND MOUNTAIN OBSCURATION.  SURFACE WINDS VARIABLE
10 KNOTS OR LESS.  WINDS ALOFT NORTHWESTERLY 10 TO 15 KNOTS AT 10K FEET
MSL.

&&

.PREV DISCUSSION...
SHORT TERM...TONIGHT THROUGH TUESDAY...UNSETTLED COOL CONDITIONS
THROUGH MONDAY EVENING WILL BECOME VERY COLD TUESDAY WITH A SNAKE
RIVER CONVERGENCE ZONE LIKELY OVER SW IDAHO LATE MONDAY EVENING
THROUGH TUESDAY. LIGHT WINDS ACROSS MUCH OF THE TREASURE VALLEY
TONIGHT SHOULD KEEP STRATUS LAYER BUT ANY BREAKS WILL ALLOW FOR
PATCHY DENSE FOG TO FORM OVER FRESH SNOW COVER AIDED BY MOISTURE
FROM THE AFTERNOON MELT /BOISE HAS NUDGED ABOVE FREEZING AS OF
240 PM./

AN ARCTIC FRONTAL BOUNDARY AT 2PM WAS ALONG THE WASHINGTON -
BRITISH COLUMBIA BORDER TO ALONG THE ID-MT BORDER. THIS FRONT WILL
SINK SOUTH INTO IDAHO AND CENTRAL OREGON TONIGHT...AS AN UPPER LOW
FOLLOWS BEHIND IT. LIGHT SNOW SHOWERS ARE EXPECTED WITH THE FRONT
AND THE UPPER LOW. ON MONDAY A VERTICALLY STACKED SURFACE AND
UPPER LOW OVER THE COLD FRONT IS EXPECTED OVER SW IDAHO. THIS
LOOKS TO BE THE SNOWIEST PERIOD /MONDAY AFTERNOON AND EVENING/ BUT
AMOUNTS WILL BE LIGHT. SCATTERED TO NUMEROUS LINGERING LIGHT SNOW
SHOWERS MONDAY EVENING WILL DIMINISH LATE MONDAY NIGHT. THEN A
CONVERGENCE ZONE IS EXPECTED TO SET UP OVER SOUTH PARTS OF
ADA/ELMORE OR CANYON COUNTIES WITH A SLIGHT CHANCE OF SNOW
CONTINUING THROUGH TUESDAY AFTERNOON GENERALLY FROM IDAHO CITY
THROUGH BOISE TO THE OWYHEES.

ANOMALOUS NE WINDS ALOFT DOMINATE BEHIND THE ARCTIC FRONT AND THE
NORTH SIDE OF THE UPPER LOW...WHICH WILL BRING IN VERY COLD /BUT
NOT RECORD TEMPS/ AND VERY DRY DEW POINTS TUESDAY.

LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...HIGH PRESSURE WILL BEGIN
TO BUILD OVER THE THE REGION TUESDAY NIGHT AS AN UPPER LEVEL TROUGH
SLOWLY DIGS SOUTH TO SOUTHERN CALIFORNIA AND FORMS A CUTOFF LOW.
AS THE REGION TRANSITIONS FROM THE TROUGH TO THE RIDGE...
NORTHEASTERLY FLOW ALOFT WILL BRING IN COLDER AIR. THE COLDEST AIR
WILL REMAIN EAST OF THE CONTINENTAL DIVIDE...BUT WE WILL SEE LOW
TEMPERATURES WEDNESDAY MORNING IN THE SINGLE DIGITS ABOVE ZERO IN
THE TREASURE VALLEY AND 5 BELOW TO 15 BELOW ZERO IN THE REST OF THE
FORECAST AREA.  SOME LOCATIONS IN THE WEST CENTRAL AND BOISE
MOUNTAINS WILL BE NEAR 20 BELOW ZERO. HIGH TEMPERATURES ON WEDNESDAY
WILL ONLY WARM INTO THE TEENS. FLOW ALOFT WILL SHIFT TO THE NORTH BY
WEDNESDAY AFTERNOON WITH SLOWLY WARMING TEMPERATURES. MOUNTAINS WILL
WARM FASTER THAN VALLEYS AS COLD AIR WILL BE TRAPPED UNDER VALLEY
INVERSIONS. WITH THIS WEATHER PATTERN WILL SEE DRY CONDITIONS OVER
THE REGION THROUGH THURSDAY NIGHT. MODELS DIFFER ON THE TIMING OF
THE NEXT SYSTEM THAT WILL MOVE OVER THE FORECAST AREA FOR THE
WEEKEND...BUT COULD SEE THE NEXT ROUND OF PRECIPITATION MOVING INTO
THE FORECAST AREA FRIDAY OR SATURDAY. WITH LOW CONFIDENCE IN THE
MODELS WILL HAVE SLIGHT CHANCE TO CHANCE POPS OVER NORTHERN ZONES
FRIDAY THROUGH SUNDAY...WITH DRY CONDITIONS ALONG THE NEVADA BORDER.

&&

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

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...LC
AVIATION.....LC
PREV SHORT TERM...VM
PREV LONG TERM....JA/WH/LC



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.