Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 041534
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
934 AM MDT SAT JUL 4 2015

.UPDATE...
HOT DAY ON TRACK. WATCHING WIND SHIFTS OVER NORTHERN MONTANA AND
MONITORING AIRMASS BUT LOOKS LIKE THIS FIRST PUSH WILL STALL
BEFORE IT GETS INTO SOUTHERN MONTANA. NO UPDATES. BORSUM

&&

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

MADE A FEW ADJUSTMENTS TO THE POPS FOR THIS PACKAGE...OTHERWISE
THE GOING FORECAST WAS ON TRACK. FORECAST AREA WILL BE UNDER WEAK
ZONAL FLOW TODAY...IN BETWEEN CANADIAN LOW PRESSURE OVER
ALBERTA/SASKATCHEWAN AND A MONSOONAL RIDGE TO THE S. ONLY WEAK
SHORTWAVES WILL BE MOVING ACROSS THE AREA WHICH WILL NOT BE ENOUGH
TO TRIGGER CONVECTION. WRF SOUNDINGS SHOWED AN INVERTED-V PROFILE
OVER THE AREA...SIGNALING HOT AND DRY CONDITIONS. MODELS DID
AGREE ON POSSIBLE CONVECTION OVER THE NE BIGHORNS SO WILL HAVE A
POP THERE THIS AFTERNOON. OTHERWISE...HIGH TEMPERATURES WILL REACH
WELL INTO THE 90S GIVEN MIXING ABOVE 700 MB WHERE TEMPERATURES
WERE +12 TO +16 DEGREES C. RELATIVE HUMIDITIES WILL BE IN THE
TEENS AND 20S AND WINDS WILL BE LIGHT.

WEAK JET DIVERGENCE WILL MOVE INTO THE REGION TONIGHT AS THE
RIGHT-REAR QUADRANT OF A JET ROUNDING THE BASE OF THE CANADIAN LOW
MOVES OVER THE AREA. A SHORTWAVE MOVING AROUND THE LOW WILL PUSH A
COLD FRONT S INTO THE AREA BY 06Z. CONDITIONS AHEAD OF THE FRONT
WILL CONTINUE TO BE MAINLY DRY BASED ON DRY SOUNDINGS AND A LARGE
AMOUNT OF CIN OVER THE AREA...SO HAVE LOWERED EVENING POPS. KBHK
SOUNDING DID NOT HAVE AS MUCH CIN AS OTHER AREAS AND AN INVERTED
TROUGH MAY HELP KICK OFF SOME CONVECTION IN THAT AREA SO WILL KEEP
A LOW POP THERE. MODEL CONSENSUS PUSHES THE FRONT THROUGH THE
AREA BY 12Z SUN. ECMWF WAS HOLDING UP THE FRONT AND WAS THE
OUTLIER SO WENT WITH MODEL CONSENSUS. CHANCES FOR PRECIPITATION
WILL INCREASE WITH THE FRONTAL PASSAGE...BUT MODELS WERE NOT IN
GOOD AGREEMENT WITH QPF DISTRIBUTION...SO USED A COMPROMISE AND
KEPT POPS LOW. WOULD NOT EXPECT SEVERE WEATHER AS CAPES WILL BE
DECREASING OVERNIGHT. REGARDING WINDS...PRESSURE RISES WILL BE ON
THE ORDER OF 2 TO 4 MB/3HR WITH THE FRONTAL PASSAGE. SOUNDINGS
SHOWED WINDS ABOVE THE SURFACE IN THE 20 TO 30 KT RANGE. THESE
FACTORS COMBINED WITH COLD ADVECTION WILL LEAD TO A PERIOD OF
GUSTY WINDS BEHIND THE FRONT ON THE ORDER OF 20 TO 30 MPH. THESE
GUSTY WINDS ARE EXPECTED LATE AT NIGHT WHEN MOST FIREWORK
CELEBRATIONS WILL BE OVER. WILL CONTINUE TO HEADLINE THE FIRE
WEATHER FORECAST WITH THE EXPECTED CONDITIONS THROUGH TONIGHT.

THE JET DIVERGENCE WILL CONTINUE OVER THE AREA THROUGH SUN
EVENING...AND SHORTWAVES WITH INCREASED Q-VECTOR CONVERGENCE WILL
ROTATE THROUGH THE AREA. MODELS STILL HAD QPF DISCREPANCIES ON
SUN...BUT PRECIPITABLE WATERS WILL BE OVER AN INCH AND THE ABOVE-
MENTIONED LIFT WILL SUPPORT PRECIPITATION. SO WILL HAVE SCATTERED
POPS ACROSS THE AREA WITH LIKELY POPS IN THE MOUNTAINS. SOUNDINGS
WERE NOT UNSTABLE...SO WILL GO WITH SHOWERS WITH NO THUNDER.
MIXING WILL BARELY GET TO 700 MB AND WILL COMBINE WITH THE ABOVE
FACTORS TO MAKE FOR A MUCH COOLER DAY WITH HIGHS IN THE 60S AND
70S. THE GFS AND WRF PUSH PRECIPITATION S OF THE AREA DURING SUN
NIGHT WHILE THE ECMWF AND CANADIAN MODELS KEEP QPF OVER THE AREA.
GIVEN STRONG HIGH PRESSURE MOVING IN...HAVE FOLLOWED THE GFS/WRF
SOLUTIONS AND DECREASED POPS THROUGH THE NIGHT. ARTHUR

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

A WARMING TREND IS EXPECTED NEXT WEEK ALONG WITH SEVERAL...MAINLY
LOW-END OPPORTUNITIES FOR SHOWERS AND THUNDERSTORMS. ON THE LARGE
SCALE...A PREVAILING NORTHWEST FLOW REGIME WILL BREAK DOWN BY LATE
WEEK AS A PACIFIC TROUGH NUDGES INLAND. THE NET RESULT IS EXPECTED
TO BE BUILDING 500-MB HEIGHTS AND A TRANSITION BACK TO A WESTERLY
OR EVEN SOUTHWEST FLOW ALOFT...WHICH SHOULD PUSH HIGHS BACK ABOVE
90 F BY THURSDAY AND FRIDAY AFTER EARLY-WEEK HIGHS ONLY IN THE 70S
AND 80S. THE 00 UTC GFS AND ECMWF BOTH SHIFTED AWAY FROM THE IDEA
OF A STRONGER NORTHWEST-FLOW SHORTWAVE TROUGH PASSAGE TUESDAY AND
WEDNESDAY...AND THEY OFFERED UP SOME DIFFERENCES WITH REGARD TO
LATE-WEEK CONVECTIVE POTENTIAL. THEREFORE...WE HELD FORECAST POPS
MAINLY IN THE 20 TO 30 PERCENT RANGE...AND BASED OTHER FORECAST
ELEMENTS ALMOST ENTIRELY ON A 00 UTC MULTI-MODEL BLEND. SCHULTZ

&&

.AVIATION...

VFR CONDITIONS WILL PREVAIL TODAY AND TONIGHT. A COLD FRONT WILL
MOVE SOUTH ACROSS THE AREA TONIGHT...AND WINDS BEHIND THE FRONT
WILL SHIFT TO THE NORTH AND INCREASE WITH GUSTS UP TO 30 KT. A FEW
SHOWERS AND THUNDERSTORMS WITH LOCAL SUB-VFR CONDITIONS MAY FOLLOW
THE FRONT AS WELL...MAINLY AFTER 06 UTC. SCHULTZ

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY SUN     MON     TUE     WED     THU     FRI
-------------------------------------------------------
BIL 096 060/070 052/077 056/084 058/083 060/090 063/091
    1/U 23/W    21/B    12/T    23/T    32/T    22/T
LVM 095 054/071 046/078 050/084 051/082 053/088 056/088
    1/U 23/W    32/T    23/T    33/T    33/T    32/T
HDN 099 059/073 052/079 055/087 057/085 059/092 062/094
    1/U 23/W    21/B    12/T    23/T    32/T    22/T
MLS 098 060/073 051/076 054/085 058/084 060/091 064/092
    0/U 23/W    11/B    02/T    22/T    22/T    22/T
4BQ 095 060/077 053/076 054/084 058/083 060/089 063/092
    1/U 24/W    21/B    12/T    22/T    22/T    22/T
BHK 092 058/073 050/072 050/078 054/079 056/086 060/087
    0/U 24/W    21/B    02/T    32/T    21/B    22/T
SHR 092 056/071 049/073 052/081 054/079 054/086 057/087
    0/U 24/W    31/B    22/T    33/T    32/T    22/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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