838
FXUS65 KBOI 160228
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
828 PM MDT THU MAY 15 2008
DISCUSSION
HOT WX ON ITS WAY AS INTENSE HIGH PRESSURE ALOFT ALONG
THE COAST SHIFTS SLOWLY INLAND. NO ARGUMENT WITH CURRENT FORECAST
EXPECTING RECORD HIGH TEMPS SATURDAY AND SUNDAY. LATEST GFS SHOWS
850-700 MB THICKNESS AT 1664M AT BOI SATURDAY AFTERNOON WHICH EQUATES
TO THE 94F HIGH TEMP WE HAVE OUT...BUT SUNDAY MAY BE EVEN HOTTER AS
THICKNESS INCREASES TO 1672M FOR 96F OR 97F. WHILE IT IS TRUE THAT
THE UPPER HIGH IS PROGGED TO WEAKEN AS IT MOVES INLAND...IT IS ALSO
TRUE THAT THE SURFACE THERMAL TROUGH UNDER IT WILL INTENSIFY AND
MAINTAIN THE HIGH THICKNESS AND HOT TEMPS. EVEN MONDAY LOOKS AS HOT
AS SATURDAY. CLEAR SKIES THROUGHOUT. A SIGNIFICANT PACIFIC COLD
FRONT WILL COOL DOWN ALL ZONES TUESDAY. HYDRO SEGMENT HAS BEEN
REPEATED...SEE BELOW.
AVIATION
VFR CONDITIONS TONIGHT UNDER CLEAR SKIES. SURFACE WINDS
WILL BE LIGHT AND VARIABLE TONIGHT WITH MODERATE NORTH WINDS ALOFT.
PREV DISCUSSION
SHORT TERM...NO CHANGES TO PRIOR THINKING. INTENSE UPPER RIDGE TO
BUILD OVER THE FORECAST AREA AND REMAIN STATIONARY THROUGH THE
WEEKEND AND POSSIBLY EVEN LONGER. RAN ANALOG TEMPERATURE PROGRAMS
THROUGH THE PERIOD AND IT IS PRODUCING RECORD OR NEAR RECORD HIGHS
SATURDAY...SUNDAY AND MONDAY. WINDS BE LIGHT THROUGH THE PERIOD AND
EVEN LOW TEMPERATURES SATURDAY AND SUNDAY WILL FLIRT WITH RECORD
WARM MAXIMUMS...BUT THIS WILL NOT BE MENTIONED IN THE PNS STATEMENT
WHICH WILL BE ISSUED WITH THE AFTERNOON PACKAGE. ALONG WITH THE HOT
WEATHER COMES INCREASING HYDRO CONCERNS. SEE SPECIAL HYDROLOGY
SECTION OF DISCUSSION FOR DETAILS.
LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...MODELS HAVE COME INTO
LINE WITH GOOD AGREEMENT THROUGH TUESDAY EXCEPT FOR MINOR TIMING
DIFFERENCES. THE DGEX IS THE SLOWEST STILL KEEPING THE RIDGE AXIS
OVER THE NORTHERN ROCKIES TUESDAY AFTERNOON. PRIOR TO THEN
CONFIDENCE IS GOOD THAT VERY WARM AND DRY CONDITIONS WILL PREVAIL.
WE ADJUSTED MAX TEMPERATURES A COUPLE OF DEGREES HIGHER SUNDAY AND
MONDAY BASED ON ANALOG BLENDS. OTHERWISE ALL MODELS BRING A FAIRLY
DEEP SHORTWAVE TROUGH OVER THE PACIFIC NORTHWEST ON TUESDAY. THE
AIRMASS WILL STILL BE QUITE WARM ACROSS OUR CWA AHEAD OF THE COLD
FRONT. UNCERTAINTIES INCLUDE THE TIMING OF THE FRONT AND HOW MUCH OF
THE SUBTROPICAL MOISTURE PRESENT TODAY WILL REMAIN ON TUESDAY. THE
GFS DOES SHOW ADEQUATE THETA-E FOR CONVECTION ESPECIALLY OVER OUR
CENTRAL MOUNTAINS. SO WE ARE INCLUDING A SLIGHT CHANCE OF
THUNDERSTORMS.
HYDROLOGY
AREA RIVERS WILL SEE SIGNIFICANT RISES THROUGH THE
SATURDAY AND SUNDAY IN RESPONSE TO RECORD HIGH TEMPERATURES WHICH
WILL CAUSE HIGH ELEVATION SNOW MELT. AT THIS TIME RIVER LEVELS ARE
NOT ANTICIPATED TO REACH FLOOD STAGE. HOWEVER RIVER FLOW WILL
INCREASE DRAMATICALLY AND PEOPLE SHOULD EXERCISE CAUTION NEAR RIVERS
AS THE CURRENT WILL BE SWIFT AND DANGEROUS. RIVERS WITH NOTABLE
RISES EXPECTED THIS WEEKEND INCLUDE INCLUDE THE BOISE... PAYETTE...
AND WEISER WHICH WILL BE NEAR BANKFULL. THE BOISE RIVER IS EXPECTED
TO REACH A FLOW OF 5300 CFS AT GLENWOOD BRIDGE BY FRIDAY AFTERNOON
WHICH WILL BRING WATER CLOSE TO THE LEVEL OF THE GREEN BELT PATH IN
LOWER SECTIONS ADJACENT TO THE RIVER. THESE LEVELS ARE STILL WELL
BELOW FLOOD STAGE WHICH IS EQUAL TO 7000 CFS WHEN MEASURED AT THE
GLENWOOD BRIDGE STREAM GAGE.
BOI WATCHES/WARNINGS/ADVISORIES
ID...NONE.
OR...NONE.
WEATHER.GOV/BOISE
DISCUSSION...LC
AVIATION.....JA
PREV SHORT TERM...GS
PREV LONG TERM....JT/MT
HYDROLOGY....JB
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