Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 260917
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
317 AM MDT TUE MAY 26 2015

.SHORT TERM...VALID FOR TDY AND WED...

THE UNSETTLED WEATHER PATTERN WILL CONTINUE FOR A FEW MORE DAYS.
THE SYSTEM RESPONSIBLE FOR THE FLOODING IN SHERIDAN COUNTY AND
RECENT COOL AND WET WEATHER FOR OTHER LOCATIONS...HAS DRIFTED OUT
OF THE AREA. THIS SYSTEM HAS BEEN BRIEFLY REPLACED BY A SMALL
SCALE RIDGE. THE NIGHT HAS BEEN MOSTLY PRECIPITATION FREE WITH THE
EXCEPTION OF A FEW LIGHT SHOWERS OVER THE FAR WEST. THESE SHOWERS
WERE THE EARLY STAGES OF THE NEXT SYSTEM APPROACHING.

AN UPPER LOW HAS SLID INTO EASTERN WASHINGTON THIS MORNING.
WEAKLY DIFFLUENT FLOW WAS EVIDENT ON WATER VAPOR AND INFRARED
SATELLITE IMAGERY WITH COOLING CLOUD TOPS OVER WESTERN MONTANA.
SCATTERED SHOWERS HAVE SLID TO THE WESTERN EDGE OF OUR FORECAST
AREA. THIS ACTIVITY WILL MOVE SLOWLY EAST THROUGH THE DAY. WILL
KEEP HIGH POPS OVER WESTERN AND CENTRAL ZONES...WITH THE HIGHEST
POPS THIS AFTERNOON. GFS AND BUFKIT WAS INDICATING SOME DEEP BUT
NARROW CAPE THIS AFTERNOON AND EVENING. LIGHTNING WAS CERTAINLY
PRESENT ON MONDAY IN IDAHO AND WESTERN MONTANA...SO WILL JUST GO
WITH A SHOWER AND THUNDERSTORM WORDING TODAY. STEERING WINDS WERE
WEAK AND THEREFORE AM NOT EXPECTING STORMS TO BE TREMENDOUSLY
STRONG BUT WILL BE CAPABLE OF LOCALLY HEAVY RAIN WITH PWATS AROUND
THREE QUARTERS OF AN INCH WITH SLOW MOVING CELLS.

THE SHOWERS AND THUNDERSTORMS WILL SPREAD EAST THROUGH THE
EVENING WITH THUNDERSTORM ACTIVITY DECREASING AND PRECIPITATION
BECOMING MOSTLY SHOWERS. GFS HELD ONTO RAIN AMOUNTS THIS
EVENING...SO BUMPED POPS UP. THE UPPER LOW DOES NOT MOVE MUCH FOR
WEDNESDAY AS IT INCHES INTO CENTRAL IDAHO. THIS PLACEMENT WOULD
ACTUALLY BE IN A BETTER POSITION FOR DIFFLUENT FLOW...SO WEDNESDAY
COULD BE THE BETTER CHANCE OF PRECIPITATION FOR WESTERN AND
CENTRAL ZONES COMPARED TO TODAY. PARAMETERS WERE VERY SIMILAR IN
REGARDS TO CAPE AND SHEAR...SO SLOW MOVING CELLS WITH LOCALLY
HEAVY RAIN AGAIN A POSSIBILITY.

HYDRO...BIG GOOSE CREEK HAS FALLEN BELOW FLOOD STAGE...BUT LITTLE
GOOSE CREEK AND GOOSE CREEK REMAIN OUT OF THEIR BANKS IN AND NEAR
SHERIDAN. THE DECLINE ON THESE WATERWAYS HAS BEEN SLOW AND WOULD
EXPECT FLOODING TO CONTINUE AT LEAST INTO THE EARLY PART OF THE
MORNING. THE TONGUE AT MONARCH HAS SHOWN A RECENT DECLINE WITH THE
MAIN WAVE IN DECKER NOW WITH STEADY RISES. STRONG RISES WERE BEING
EXPERIENCED ON CLEAR CREEK AND POWDER RIVER IN EASTERN SHERIDAN
COUNTY. MODELS DO PLACE QPF OVER THE BIGHORNS BOTH TODAY AND
WEDNESDAY...SO THIS COULD CAUSE ADDITIONAL FLOODING...OR AT
LEAST...SLOW DOWN THE RIVER DECLINES. TWH

.LONG TERM...VALID FOR THU...FRI...SAT...SUN...MON...

A PACIFIC WAVE WILL CROSS THE AREA DURING THURSDAY. THE GFS IS
STILL A LITTLE SLOWER MOVING THE TROUGH THROUGH THAN IS THE
ECMWF. BUT WITH BOTH MODELS SHOWING EASTERLY FLOW DURING THE DAY
PRODUCING UPSLOPE FLOW...RAIN CHANCES WILL BE ENHANCED ACROSS THE
AREA. MODELS CONTINUE TO SHOW INSTABILITY AROUND AREA...SO THE
POTENTIAL IS THERE FOR THUNDERSTORMS. WITH THE EASTERLY FLOW
PRECIPITABLE WATER VALUES WILL REMAIN THREE QUARTERS OF AN INCH TO
AN INCH. THE POTENTIAL IS THERE FOR SOME OF THESE SHOWERS AND
THUNDERSTORMS TO HAVE SOME GOOD RAIN TOTALS. THIS INCLUDES AROUND
THE BIGHORN MOUNTAINS IN SHERIDAN COUNTY.

FRIDAY WILL BE COOLER FOLLOWING THE PASSAGE OF THE MAIN TROUGH
AXIS AS THE WESTER EDGE OF SOME COOLER AIR WORKING DOWN INTO THE
NORTHERN PLAINS. THESE COOLER TEMPERATURES WILL NOT LAST LONG AS
A FLAT RIDGE BUILDS IN TO THE AREA THIS WEEKEND. THIS RIDGE WILL
GENERALLY LIMIT RAIN CHANCES...ESPECIALLY EAST OF THE MOUNTAINS
WHERE WESTERLY WINDS WILL BE MORE DOWN SLOPING. WITH WESTERLY FLOW
SOME RAIN CHANCES WILL REMAIN MOSTLY IN THE MOUNTAINS. AS THE NEXT
PACIFIC LOW BEGINS TO DISLODGE THE RIDGE...SOME PREFRONTAL WARMING
WILL HELP TO PUSH TEMPERATURES TO NEAR 80 DEGREES MONDAY. RAIN
CHANCES WILL BEGIN TO INCREASE NEXT WEEK AS FLOW BECOMES MORE
SOUTHWESTERLY AND SOME OF THE ENERGY FROM THE APPROACHING SYSTEM
WORKS INTO THE AREA. REIMER

&&

.AVIATION...

EXPECT MAINLY VFR CONDITIONS OVER THE NEXT 24 HOURS. SOME FOG IS
POSSIBLE THIS MORNING MAINLY EAST OF MILES CITY TO BROADUS. THIS
SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE. CONDITIONS MAY
BRIEFLY DROP IN THESE SHOWERS. REIMER

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY WED     THU     FRI     SAT     SUN     MON
-------------------------------------------------------
BIL 072 050/073 050/071 048/065 047/075 051/078 053/080
    4/T 56/T    56/T    54/T    32/T    22/T    23/T
LVM 067 044/068 044/066 044/064 043/073 047/076 048/076
    7/T 66/T    56/T    64/T    43/T    33/T    33/T
HDN 075 049/076 049/074 048/067 046/077 050/080 052/082
    3/T 46/T    35/T    54/T    42/T    22/T    23/T
MLS 076 052/075 052/076 048/067 045/073 049/077 053/079
    2/T 46/T    43/T    33/T    32/T    21/B    22/T
4BQ 073 050/074 050/073 049/065 043/070 049/075 052/078
    2/T 46/T    44/T    45/T    42/W    12/T    22/T
BHK 073 047/073 048/073 044/062 038/066 043/072 049/075
    1/B 36/T    53/T    33/T    21/B    11/B    22/T
SHR 069 046/070 046/068 046/060 043/070 046/074 049/076
    4/T 55/T    36/T    65/T    52/T    22/T    23/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS


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