Area Forecast Discussion
Issued by NWS Billings, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KBYZ 212109
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
309 PM MDT THU AUG 21 2014

.SHORT TERM...VALID FOR FRI AND SAT...

ACTIVE WEATHER PATTERN WITH A MAJOR STORM SYSTEM BRINGING
WIDESPREAD PRECIPITATION TO THE REGION. UNSEASONABLY COLD
TEMPERATURES...MOIST CONDITIONS AND WINDS WILL CERTAINLY IMPACT
OUTDOOR ACTIVITIES. THERE ARE ALSO PERIODS WHERE SOME STRONG
THUNDERSTORMS ARE POSSIBLE...MAINLY FOR SOUTHEAST MONTANA.

MOIST AIRMASS IN PLACE THIS EVENING WITH A STRONG SHORTWAVE
APPROACHING FROM SOUTHWEST MONTANA. PLENTIFUL SHOWER AND
THUNDERSTORM ACTIVITY ALREADY OVER THE WESTERN CENTRAL ZONES AND
EXPECT INTENSITY TO PICK DURING THE EARLY EVENING HOURS. MODELS
TRY TO TRIGGER A ROUND OF STRONGER THUNDERSTORM ACTIVITY FOR
SOUTHEAST MONTANA BUT BELIEVE ATMOSPHERE TOO UNCAPPED FOR DISCRETE
STRONG STORMS BUT WILL HAVE TO WATCH BECAUSE THAT AREA IS
EXPERIENCING BETTER HEATING. STORMS ARE SLOW MOVING SO ACROSS THE
REGION FOLKS MAY SEE .50 TO .75 RAINFALL IN A SHORT PERIOD OF
TIME.

FRIDAY STARTS OFF IN BETWEEN WAVES WITH SHOWERS AND THUNDERSTORMS
EXITING EASTERN MONTANA. BACKING FLOW ALOFT BECOMING DIFFLUENT
DURING THE DAY WILL SUPPORT DEVELOPMENT OF MORE SHOWERS AND
THUNDERSTORMS WITH STRENGTHENING LOW LEVEL EASTERLY FLOW. ONE
SHORTWAVE ROTATES OUT OF THE LOW FRIDAY EVENING WHICH REALLY
INCREASES THE SHOWER AND THUNDERSTORM ACTIVITY AND WIDESPREAD
HEAVY RAIN BECOMES LIKELY FRIDAY NIGHT THROUGH EARLY SATURDAY
EVENING. MAX TEMPERATURES WILL BE BELOW 70 FOR MOST AREAS THOUGH
SOUTHEAST MONTANA STILL HAS A WINDOW FOR WARMING.

AS SATURDAY PROGRESSES MAIN MECHANISM FOR PRECIP SWITCHES FROM
UPPER LEVEL DYNAMICS TO INCREASING UPSLOPE FLOW AS FRONTOGENESIS
OCCURS OVER CENTRAL MONTANA. BUFKIT SOUNDINGS SHOW SATURATED
AIRMASS TO 300MB WITH LONG SKINNY CAPE BUT GOOD WIND SHEAR SO SLOW
MOVING TALL GROWTH CELLS REDEVELOPING OVER THE SAME AREA LOOKS
GOOD. THIS SCENARIO ALLOWS SOME AREAS TO DEVELOP LOCALLY HEAVY
RAIN...WITH RAINFALL TOTALS THROUGH THE EVENT OF 2 TO 3 INCHES IN
LOCALIZED AREAS POSSIBLE. SMALL STREAMS AND BURN AREAS MAY SEE A
RESPONSE TO THIS SO WILL HAVE TO WATCH RAINFALL AMOUNTS THROUGH
THE WEEKEND. ALSO AS TEMPERATURES COOL SATURDAY NIGHT...SOME
SNOWFALL WOULD BE POSSIBLE OVER THE HIGH COUNTRY FOR ELEVATIONS OF
10000 FEET AND ABOVE.

STORM SYSTEM WILL BEGIN TO PULL OUT LATE SATURDAY NIGHT BUT LOW
LEVEL AIRMASS WILL BE COOL AND MOIST SO WHILE HEAVIEST RAIN MAY
END IT COULD BE REPLACED BY MORE OF A DRIZZLE AND LIGHT RAIN
SCENARIO. BORSUM




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

ALTHOUGH THE MODELS ARE GENERALLY IN AGREEMENT WITH REGARD TO THE
OVERALL PATTERN TO START THE EXTENDED...THEY CONTINUE TO HAVE SOME
SIGNIFICANT DISAGREEMENT. THE GFS IS MORE PROGRESSIVE WITH UPPER
TROUGH AND IS PROBABLY THE OUTLIER IN THE NEAR EXTENDED PERIODS
AS THE NAM AND ECMWF HOLD A QUASI CLOSED OFF UPPER LOW OVER OUR
FORECAST AREA SUNDAY AND PRODUCE CONSIDERABLE QPF IN A TROWAL LIKE
FASHION BEFORE IT FINALLY EXITS THE AREA SUNDAY NIGHT. I WILL
TREND OUR POPS AND TEMPS TOWARD THE WETTER SOLUTIONS A BIT...AS
CONFIDENCE IN ANY PARTICULAR SOLUTION IS RATHER LOW AT THIS TIME.
THE ECMWF HAS TRENDED MORE TOWARD THE GFS MONDAY AND TUESDAY
DRAGGING ANOTHER PIECE OF ENERGY UNDER THE TROUGH THROUGH THE
CENTRAL ROCKIES RATHER THAN DROPPING IT SOUTH AS IN ITS PREVIOUS
RUN. DUE TO THE INCREASED CONSISTENCY ACROSS MODELS...WITH A
ZONAL/WEST COAST RIDGE TYPE PATTERN OVER THE REGION BY
WEDNESDAY...WE WILL LEAN HARDER ON A DRIER AND MORE SEASONALLY
TEMPERATE FORECAST FOR THE LATTER PART OF THE EXTENDED. BT

&&

.AVIATION...

SCATTERED SHOWERS WILL INCREASE OVER THE FORECAST AREA THIS
AFTERNOON. THERE WILL BE EMBEDDED THUNDER AS WELL AS DISCRETE
THUNDERSTORMS...ESPECIALLY SE OF A KMLS/KBIL LINE THIS EVENING.
INTENSITY WILL VARY...BUT SOME STORMS WILL BE CAPABLE OF MVFR AND
BRIEF IFR IN HEAVY PRECIPITATION AND LOW CLOUD CEILINGS. THE
SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO THE EVENING WITH THE
POTENTIAL OF A BREAK AFTER 06Z. MOUNTAINS TOPS WILL BE FREQUENTLY
OBSCURED. BT

&&

.PRELIMINARY POINT TEMP/POPS...

    FRI     SAT     SUN     MON     TUE     WED     THU
-----------------------------------------------------------
BIL 053/068 053/064 048/067 049/072 050/076 053/082 057/087
    68/T    99/T    54/T    23/T    32/T    21/U    01/U
LVM 050/066 049/062 044/068 044/071 044/076 048/083 051/086
    79/T    97/T    63/T    25/T    52/T    21/U    12/T
HDN 054/074 055/066 051/069 047/075 050/078 051/083 055/088
    48/T    99/T    54/T    23/T    32/T    21/U    01/U
MLS 057/074 057/070 052/065 049/072 051/075 053/082 057/087
    64/T    98/T    55/T    21/B    32/T    21/U    01/U
4BQ 056/078 059/074 053/066 048/072 052/074 051/081 056/087
    64/T    98/T    63/T    22/T    43/T    31/U    01/U
BHK 057/072 055/070 052/065 046/070 047/072 048/078 053/083
    74/T    99/T    84/T    22/B    33/T    21/U    01/U
SHR 051/073 053/068 048/067 045/074 048/075 048/081 051/087
    46/T    87/T    53/T    23/T    33/T    21/U    01/U

&&

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

&&

$$
WEATHER.GOV/BILLINGS



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.