285
FXUS65 KBOI 180336
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
836 PM MST SUN FEB 17 2019
DISCUSSION
NO UPDATES. THE DEEP UPPER LEVEL TROUGH CENTERED
OVER THE GREAT BASIN WILL CONTINUE TO CIRCULATE MOIST AND
UNSTABLE AIR NORTH AND WEST ALONG THE IDAHO-NEVADA BORDER, WITH
MOST SNOW FALLING ON SOUTHERN TWIN FALLS AND EASTERN OWYHEE
COUNTIES TONIGHT AND MONDAY MORNING. AS THE TROUGH EDGES EAST OVER
THE ROCKIES, OUR AREA WILL SEE A DRYING AND COOLING TREND THROUGH
TUESDAY UNDER NORTHERLY FLOW ALOFT ON THE WESTERN MARGIN OF THE
TROUGH. THE NEXT PRECIPITATION EPISODE WILL BEGIN TUESDAY NIGHT
AND CONTINUE THROUGH WEDNESDAY NIGHT AS ANOTHER UPPER LEVEL TROUGH
DROPS SOUTH FROM CANADA. SNOWFALL AMOUNTS IN THE LOWER VALLEYS
ARE EXPECTED TO RANGE FROM LESS THAN AN INCH TO AROUND 2 INCHES,
WITH HEAVIER AMOUNTS IN THE MOUNTAINS. FOLLOWING A BRIEF BREAK
THURSDAY AND FRIDAY, THE NEXT TROUGH WILL BRING MORE SNOW FOR THE
WEEKEND, BUT TIMING IS STILL UNCERTAIN.
AVIATION
MAINLY VFR CONDITIONS AS SHOWERS DIMINISH. EXCEPTION FOR MAGIC
VALLEY AND ID/NV BORDER WHERE IFR/LIFR POSSIBLE DUE TO LINGERING
SNOW SHOWERS AND MOUNTAIN OBSCURATIONS THROUGH MONDAY MORNING.
PATCHY STRATUS AND FOG POSSIBLE OVERNIGHT. SURFACE WINDS: WEST TO
NORTHWEST 5-15 KTS. WINDS ALOFT AT 10K FEET MSL: NORTHWEST 15-25 KTS.
PREV DISCUSSION
SHORT TERM...TONIGHT AND MONDAY...SATELLITE IMAGERY AND MODELS
SHOW A LARGE AND COMPLEX UPPER LOW OVER THE WESTERN US WITH
SEVERAL EMBEDDED DISTURBANCES. THIS PATTERN GET INTERESTING FOR
TONIGHT SHOWING AN UPPER DIFFLUENCE AREA LOCATED OVER SOUTHERN
IDAHO. NAMNEST/ARW SHOWS THIS DEFORMATION ZONES SLOWLY PUSHING
TOWARDS THE NV/ID/UT BORDER REGION AND WILL BE THE MAIN FOCUS OF
SNOW AT LEAST THROUGH SUNRISE. AT THIS TIME, GENERALLY 1-2 INCHES
OF SNOW ARE POSSIBLE ACROSS SOUTHERN TWIN FALLS COUNTY INCLUDING
HIGHWAY 93...LESSER AMOUNTS ALONG STATE ROUTE 51. HIGHER
ACCUMULATIONS POSSIBLE OVER THE HIGHER MOUNTAINS. OTHERWISE, THE
BROAD UPPER LOW SAGS SOUTH AND EAST WITH TROUGHINESS LINGERING
OVER THE SPINE OF THE ROCKY MOUNTAINS AS AN UPPER RIDGE EDGES INTO
THE PACNW. LINGERING SNOW SHOWERS ARE POSSIBLE MONDAY OVER IDAHOS
MOUNTAINS.
LONG TERM...MONDAY NIGHT THROUGH SUNDAY...RELATIVELY DRY
NORTHERLY FLOW ALOFT WILL LAST INTO EARLY TUESDAY AFTERNOON. A
SIGNIFICANT SYSTEM WILL MOVE IN FROM THE NORTHWEST AT THAT TIME,
BRINGING SNOW TO ALL ELEVATIONS. SNOW WILL MOVE INTO EASTERN
OREGON TUE AFTERNOON, THEN OVERSPREAD THE REMAINDER OF THE AREA
TUESDAY NIGHT. THE BEST CHANCE FOR SNOW WILL BE WEDNESDAY, AS AN
UPPER LEVEL SHORTWAVE TROUGH MOVES THROUGH THE AREA. ADVISORIES
AND/OR WARNINGS MAY BE NEEDED FOR THIS SYSTEM. IT IS LIKELY THAT
ROADS WILL BE SNOW-COVERED THAT MORNING OVER MOST OF THE AREA. A
REINFORCING COLD AIR MASS WILL FOLLOW THURSDAY, ALONG WITH
SCATTERED SNOW SHOWERS. SHOWERS WILL DIMINISH THURSDAY NIGHT AS
THE TROUGH MOVES AWAY, BUT ANOTHER WILL ARRIVE FRIDAY NIGHT AND
BRING SNOW TO THE REGION THROUGH NEXT WEEKEND. TEMPS WILL REMAIN
BELOW NORMAL THROUGH THE PERIOD.
BOI WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY UNTIL 11 AM MST MONDAY IDZ015-030.
OR...NONE.
WWW.WEATHER.GOV/BOISE
WWW.FACEBOOK.COM/NWSBOISE
WWW.TWITTER.COM/NWSBOISE
DISCUSSION...JT
AVIATION.....SH
PREV SHORT TERM...CR
PREV LONG TERM....SP
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