Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 190234
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
834 PM MDT MON AUG 18 2014

.UPDATE...
FLAT RIDGE SUPPRESSING MOST OF THE MONSOONAL IMPULSES AND THUS
CONVECTION TO THE SOUTH OF OUR FORECAST AREA. RADAR ECHOES ARE
WEAK AND FEW BETWEEN AT THIS TIME. WILL LEAVE SOME LOW POPS IN THE
SW MOUNTAINS THROUGH THE EVENING. ADJUSTED SKY COVER A BIT.
RELATIVELY QUIET EVENING. NEWEST WRF INDICATES A MORE ACTIVE
EVENING TOMORROW AHEAD OF APPROACHING UPPER TROUGH. BT

&&

.SHORT TERM...VALID FOR TUE AND WED...

SHORT TERM FORECAST REMAINS ON TRACK...WITH MAINLY DRY CONDITIONS
TODAY...FOLLOWED BY INCREASING SHOWER AND THUNDERSTORM POTENTIAL
TOMORROW EVENING THROUGH WEDNESDAY. MODELS REMAIN IN GOOD
AGREEMENT AS WELL...SO ONLY MINOR TWEAKS TO THE INHERITED
FORECAST.

A SHALLOW UPPER RIDGE WILL DEVELOP OVER THE REGION TODAY...KEEPING
THE REGION MAINLY DRY. THE HIGHER TERRAIN WILL BE THE EXCEPTION
HOWEVER...AS SHORTWAVE SLIDES UP THE BACKSIDE OF THE RIDGE.
MOUNTAIN ACTIVITY IS NOT EXPECTED TO SURVIVE FAR FROM THE SUPPORT
OF OROGRAPHIC LIFT...AND SHOULD NOT LAST LONG AFTER SUNSET EITHER
AS DIURNAL HEATING WANES.

RIDGE REMAINS IN PLACE OVERNIGHT AND INTO TUESDAY...WITH SOUTHWEST
FLOW ALOFT KEEPING TEMPS UP...WITH HIGHS IN THE LOWER 90S IN MOST
AREAS. A STRONGER SHORTWAVE IS PROGGED INTO THE REGION TUESDAY
AFTERNOON / EVENING...WHICH WILL BRING SHOWER AND THUNDERSTORM
POTENTIAL ACROSS THE REGION. STORM DEVELOPMENT MAY BE HAMPERED BY
WARM 700MB TEMPS DURING MUCH OF THE AFTERNOON/EVENING
PERIOD...BUT A STRONGER SECOND WAVE IS EXPECTED LATER IN THE
EVENING AND THROUGHOUT THE NIGHT. FURTHERMORE...MONSOONAL FLOW
WILL THE BEGIN TO REACH THE REGION...WHICH WILL ERODE THE
CAP...AND GIVE US IMPROVED POTENTIAL OVERNIGHT TUESDAY NIGHT.

THE TROF OVER THE NORTHERN ROCKIES CONTINUES TO DEEPEN THROUGH
THE DAY WEDNESDAY...WITH MULTIPLE SHORTWAVES MOVING THROUGH THE
FLOW INTO THE REGION. THIS WILL FURTHER BOLSTER MONSOONAL FLOW
INTO THE REGION...WHICH CONTINUES TO BECOME MORE ESTABLISHED.
THEREFORE...SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED
CONTINUE ON WEDNESDAY...BECOMING MORE WIDESPREAD THROUGHOUT THE
DAY. ADDITIONALLY...TEMPERATURES WILL BEGIN DOWNWARD TREND...WITH
MORE SIGNIFICANT CLOUD COVER AND PRECIPITATION EXPECTED THROUGH
THE DAY. AAG


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

BIG PICTURE...PERSISTENT TROUGHING TO DOMINATE THE EXTENDED
PERIOD AND HISTORICAL COMPARISONS INDICATE TEMPERATURES IN THE
LOWER 70S...AT BEST..SHOULD BE EXPECTED THIS COMING WEEKEND.
PRECIPITATION CHANCES ARE STRONGEST THURSDAY NIGHT AND
FRIDAY...WITH THE REMAINDER OF THE WEEKEND LOOKING MORE UNSETTLED
WITHOUT QUITE AS STRONG OF FORCING.

THURSDAY NIGHT INTO FRIDAY LOOKS TO BE THE BEST PERIOD FOR
PRECIPITAN AS SURFACE LOW PRESSURE DEVELOPS OVER SOUTHEAST
MONTANA AND A STRONG SHORTWAVE MOVES THROUGH THE AREA EARLY FRIDAY
MORNING. MODELS HAVE CONSISTENTLY ADVERTISED PWS IN EXCESS OF AN
INCH FOR THIS TIMEFRAME.

THURSDAY NIGHT LOOKS CONVECTIVE AND NEEDS TO BE WATCHED
CLOSELY. 06Z GFS AND 12Z NAM BUFKIT SOUNDINGS SHOW TRANSITION FROM
INVERTED V THURSDAY AFTERNOON TO A DEEP INSTABILITY AND GOOD SHEAR
SOUNDING IN THE LATE EVENING HOURS. SEVERE WEATHER...FROM EITHER
THE WIND GUSTS IN INVERTED V PATTERNS OR IN THE LATER BETTER
ORGANIZED SHEAR SIGNATURE COULD BE POSSIBLE. WILL WATCH THIS TREND
CAREFULLY NEXT FEW DAYS...AS MODELS HAVE BEEN SHOWING BULLSEYE
PRECIPITATION SIGNATURES WHICH ARE A TRADEMARK OF BIG
THUNDERSTORMS IN THE MODEL OUTPUT.

GENERAL TREND AFTER FRIDAY IS TO HAVE THE ENERGY LIFT INTO CANADA
AND WEAK TROUGHING REMAINS IN ITS PLACE WITH LIGHT UPSLOPE FLOW.
DIURNAL SHOWER ACTIVITY A GOOD BET WITH THIS PATTERN BUT LESS
ORGANIZED OR PRODUCTIVE THAN THURSDAY NIGHT - FRIDAY. TEMPERATURES
WILL BE 10 TO 15 DEGREES BELOW NORMAL FOR THIS TIME OF YEAR AS
LACK OF STRONG WARMING ALLOWS OVERNIGHT MINIMUMS TO BECOME COOLER.
A DAYTIME HIGH LESS THAN 70 COULD BE POSSIBLE OVER THE WEEKEND.
BORSUM
&&

.AVIATION...

AN ISOLATED THUNDERSTORM WILL BE POSSIBLE NEAR THE
MONTANA/WYOMING BORDER THROUGH 04Z. OTHERWISE...SKIES WILL BE
MOSTLY CLEAR OVERNIGHT WITH VFR CONDITIONS PREVAILING. HOOLEY
&&

.PRELIMINARY POINT TEMP/POPS...

    TUE     WED     THU     FRI     SAT     SUN     MON
-----------------------------------------------------------
BIL 060/092 063/085 058/079 057/074 053/071 051/073 049/072
    02/T    33/T    34/T    45/T    54/T    33/T    22/T
LVM 051/091 053/082 051/076 049/072 047/070 048/072 045/072
    12/T    34/T    46/T    65/T    54/T    43/T    33/T
HDN 058/093 059/086 054/083 056/078 054/073 052/076 050/074
    01/U    32/T    34/T    45/T    54/T    33/T    22/T
MLS 061/092 064/085 058/083 059/078 055/074 053/074 050/073
    00/U    22/T    24/T    45/T    54/T    33/T    23/T
4BQ 060/091 061/085 058/085 059/079 057/074 054/075 051/072
    00/U    33/T    23/T    45/T    54/T    32/T    22/T
BHK 057/088 059/082 054/081 055/076 056/073 055/071 046/070
    00/U    34/T    34/T    45/T    53/T    33/T    23/T
SHR 054/091 055/083 052/082 053/077 051/072 049/074 049/072
    01/B    33/T    34/T    44/T    44/T    33/T    33/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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