Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 230941
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
341 AM MDT SAT MAY 23 2015

.SHORT TERM...VALID FOR TDY AND SUN...

BROAD TROUGHING WILL BE OVER THE FORECAST AREA THROUGH THE
WEEKEND. THIS PATTERN WILL LEND TO UNSETTLED WEATHER IN THE FORM
OF SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS.

AN UPPER LOW WITHIN THE BROAD TROUGH WAS SITTING OVER SOUTHEAST
UTAH THIS MORNING. THIS LOW WILL SLOWLY SLIDE TOWARD SOUTHEAST
COLORADO BY TONIGHT. WEAKER ENERGY WILL ADVECT INTO THE FORECAST
AREA FROM WYOMING AS IT GETS EJECTED OFF OF THE MAIN LOW. THIS
COMBINED WITH WEAK DIFFLUENT FLOW AND PERSISTENT LOW LEVEL UPSLOPE
WITH BE ENOUGH TO GENERATE SCATTERED SHOWERS. INSTABILITY WAS NOT
GREAT BUT ENOUGH FOR A FEW LIGHTNING STRIKES...SIMILAR TO FRIDAY.
RELATIVELY LOW FREEZING LEVELS WILL LEAD TO THE POSSIBILITY OF
SMALL HAIL. WEAK STEERING WINDS WOULD ALSO LEAD TO SLOW MOVING
CELLS AND THUS LOCALLY HEAVY RAIN. STORMS WILL BE PULSY IN NATURE
AND THUS SHOULD NOT BE TERRIBLY STRONG.

THE UPPER LOW TO THE SOUTH WILL CREEP INTO WESTERN SOUTH DAKOTA
SUNDAY AFTERNOON. MODELS ALL HAVE BEEN ADVERTISING AN INCREASE IN
PRECIPITABLE WATER AMOUNTS AS PWATS RISE TO AROUND AN INCH OVER
SOUTHEAST MONTANA. THE GFS WAS DEEPER WITH THE NORTHERN EXTENT OF
THE MAIN UPPER LOW...AND FARTHER WEST IN PLACEMENT. THUS...THE GFS
WAS HEAVIER IN QPF TOTALS COMPARED TO THE ECMWF. HIGH PWATS OVER
THE EAST WOULD LEAD TO THE POSSIBILITY OF HEAVY RAIN. THE AXIS OF
HEAVY RAIN LOOKS TO BE EAST OF A FORSYTH TO SHERIDAN LINE.

HIGH TEMPERATURES TODAY WILL BE COOLER COMPARED TO FRIDAY WITH
ADDED CLOUD COVER. A SURFACE LOW FORMING OVER WESTERN NEBRASKA
WILL PULL IN EVEN COOLER AIR FOR SUNDAY. TWH

.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...

MODELS CONTINUE TO PAINT A GENERALLY UNSETTLED PATTERN FOR THE
EXTENDED. MONDAY WILL SEE SOME WEAK RIDGING WORKING INTO THE
AREA...SLOWLY DISPLACING THE WEEKEND LOW PRESSURE SYSTEM. SOME
INSTABILITY WILL WRAP AROUND THE BACKSIDE OF THE LOW...WHICH
WILL GIVE THE EASTERN HALF OF THE AREA A CHANCE OF RAIN...WITH
BETTER CHANCES CLOSER TO SOUTH DAKOTA. THE AREA WILL CONTINUE TO
BE IN A WEAKLY RIDGY PATTERN TUESDAY...BUT AS THE THE PATTERN
BEGINS SHIFTING INTO AN UNSETTLED SOUTHWESTERLY PATTERN THE
SOUTHWEST MOUNTAINS WILL AGAIN SEE A CHANCE AT PRECIP DURING THE
AFTERNOON TUESDAY.

THE REMAINDER OF THE EXTENDED IS DOMINATED BY A TROUGH SETTING
OVER THE PACIFIC NORTHWEST AND THE AREA REMAINING IN UNSETTLED
SOUTHWEST FLOW ALOFT. THIS WILL GIVE DAILY CHANCES FOR RAIN AS
WEAK SHORTWAVES STREAM ACROSS THE AREA. BOTH THE GFS AND ECMWF
HAVE TRENDED TOWARDS A SLOWER SOLUTION...ALONG THE LINES OF THE
00Z GFS FROM YESTERDAY...FOR THE PROGRESSION OF THE TROUGH. LOW
LEVEL FLOW WILL BE EASTERLY THROUGH MUCH OF THE EXTENDED...WHICH
WILL GIVE THE AREA DECENT MOISTURE ADVECTION...AND BY MIDWEEK
PRECIPITABLE WATER VALUES WILL BE THREE QUARTERS OF AN INCH TO AN
INCH ACROSS MUCH OF THE AREA. THERE IS SOME CAPE THAT DEVELOPS
DURING THE AFTERNOONS SO ISOLATED THUNDERSTORMS ARE POSSIBLE.

TEMPERATURES WILL REMAIN RELATIVE SEASONABLE THROUGH THE
EXTENDED. HIGHS WILL GENERALLY BE IN THE UPPER 60S TO LOWER 70S.
REIMER

&&

.AVIATION...

SOME ISOLATED MVFR TO IFR CONDITIONS WILL BE POSSIBLE THROUGH
SUNRISE. OTHERWISE VFR CONDITIONS ARE EXPECT THROUGH THE DAY.
SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE AGAIN THIS
AFTERNOON. BRIEF MVFR CONDITIONS ARE POSSIBLE WITH THE
THUNDERSTORMS. REIMER

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY SUN     MON     TUE     WED     THU     FRI
-------------------------------------------------------
BIL 065 045/062 045/069 047/071 048/070 048/069 047/064
    3/T 24/T    32/T    23/T    33/T    33/T    33/T
LVM 060 041/061 039/068 044/068 043/065 043/068 042/064
    6/T 43/T    33/T    34/T    44/T    43/T    33/T
HDN 067 046/063 045/069 046/074 048/072 048/072 047/066
    3/T 35/T    43/T    23/T    33/T    33/T    33/T
MLS 067 045/062 047/067 046/073 049/072 049/070 048/065
    3/T 46/T    45/T    22/T    33/T    32/T    23/T
4BQ 063 046/059 046/066 044/072 048/071 049/069 047/064
    3/T 67/T    55/T    22/T    34/T    43/T    33/T
BHK 061 045/060 045/064 044/070 047/069 047/067 045/062
    3/T 67/T    66/T    32/T    34/T    43/T    33/T
SHR 061 043/056 042/064 042/069 045/068 045/068 044/064
    4/T 46/T    44/T    24/T    43/T    33/T    33/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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