000
FXUS65 KBYZ 182129
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
329 PM MDT SAT MAY 18 2013

.SHORT TERM...VALID FOR SUN AND MON...

DEEP UPPER TROUGH OF LOW PRESSURE HAS BROUGHT SOME MUCH NEEDED
PRECIPITATION TO THE ENTIRE FORECAST AREA. THE TROUGH WILL MOVE
SLOWLY ACROSS THE AREA AND THE COOL AND WET TREND WILL CONTINUE
TONIGHT THROUGH MONDAY.

TONIGHT...SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER MOST OF
THE AREA TONIGHT AS A JET SPEED MAX AND STRONG VORTICITY MOVES
ACROSS THE AREA. RAINFALL HAS BEEN HEAVY AT TIMES TODAY AND THIS
TREND WILL CONTINUE OVERNIGHT. A FEW STRONG THUNDERSTORMS MAY BE
POSSIBLE OVER EXTREME SOUTHEAST MONTANA THIS EVENING AS SURFACE
BASED CAPES PROGGED AROUND 1200 J/KG AND LI`S NEAR -4C. SURFACE
TROUGH OVER THIS AREA WILL PROVIDE GOOD SURFACE CONVERGENCE ALONG
WITH INCREASING SHEAR ALOFT. THESE FACTORS WILL AID IN THE
DEVELOPMENT OF A FEW STRONG THUNDERSTORMS OVER SOUTHERN CARTER
COUNTY THIS EVENING. THE MAIN THREAT FROM STORMS THIS EVENING WILL
BE HEAVY RAINS AS PW`S ARE AROUND 1 INCH. UPPER FORCING WILL
DIMINISH BY LATE EVENING BUT HAVE STILL CONTINUED LIKELY POPS
ACROSS THE ENTIRE AREA. FOG WILL ALSO BE POSSIBLE AFTER 06Z
TONIGHT AS LOW LEVELS WILL BE SATURATED ALONG WITH LIGHT WINDS.

SUNDAY THROUGH MONDAY...SOME DISCREPANCIES STILL EXIST WITH THE
MODELS PLACEMENT OF A DEVELOPING CLOSED UPPER LOW SUNDAY. THE
POSITIONING OF THIS LOW WILL DETERMINE HOW MUCH ADDITIONAL QPF WE
WILL RECEIVE. THE UPPER LOW WILL WRAP ENERGY BACK INTO OUR AREA
DURING THIS TIME PERIOD SO WILL CONTINUE HIGH POPS FOR NOW WITH
SOME UNCERTAINTY OF WHERE THE HEAVIEST RAINFALL WILL SETUP. THE
BEST CHANCE FOR SIGNIFICANT PRECIPITATION LOOKS TO BE OVER OUR
EASTERN ZONES WITH STRONG UPSLOPE FLOW BRINGING DECENT RAINFALL TO
OUR UPSLOPE AREAS ALONG THE FOOTHILLS AS WELL AS THE NORTHEAST BIG
HORN MOUNTAINS. WE COULD SEE AN ADDITIONA 1 TO 2 INCHES OF
PRECIPITATION ACROSS THE ENTIRE FORECAST AREA BEFORE THIS STORM
SYSTEM MOVES OUT OF THE AREA MONDAY NIGHT. LOOK FOR TEMPERATURES
TO RUN 10 TO 20 DEGREES BELOW SEASONAL NORMALS SUNDAY AND MONDAY.
RICHMOND


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

MINIMAL CHANGES FOR THE EXTENDED PERIOD AT THIS TIME...AS SOME
DISCREPANCY IN MODELS REMAIN THROUGH PERIOD AS TO DETAILS.
HOWEVER THE OVERALL PATTERN REMAIN PRETTY COMPARABLE. TEMPERATURES
THROUGH THE PERIOD WILL BE ON THE RISE...WITH AROUND NORMAL
TEMPERATURES EXPECTED FOR TUESDAY AND WEDNESDAY...AND A FEW
DEGREES ABOVE NORMAL THEREAFTER.

SOME DEGREE OF RIDGING IS PROGGED TO DEVELOP ACROSS THE
REGION...BETWEEN SYSTEMS...BEGINNING TUESDAY. THE CURRENT
WEATHER SYSTEM ACTS AS A BLOCKING FEATURE IN THE EAST HOLDING UP
THE PROGRESSION OF THE NEXT SYSTEM. SOUTHWEST FLOW AHEAD OF THE
THE LOW CENTERED OVER NORTHWESTERN WASHINGTON BY WEDNESDAY
NIGHT...AND SENDS A SIGNIFICANT SHORTWAVE ACROSS THE REGION
OVERNIGHT. GFS IS MUCH DRIER THAN THE EC WITH THIS SYSTEM...BUT
CAN SEE SOME POTENTIAL WITH HEATING...SHORTWAVE...AND POSSIBLE TAP
INTO GULF MOISTURE SETTING UP. SOUTHWEST FLOW REMAINS IN
PLACE...BUT APPEARS TO TAP IN TO DRY AIR ALOFT FOLLOWING THIS
WAVE...HOWEVER THERE CONTINUES TO BE SOME INDICATION OF A GULF
MOISTURE TAP AT THE SURFACE THROUGH THE REMAINDER OF THE EXTENDED
PERIOD. SFC MOISTURE FROM RECENT RAINS AND POSSIBLE GULF MOISTURE
INFLUX...COMBINED WITH DAYTIME HEATING AND LIKELY WEAK SHORTWAVES
RADIATING THROUGH THE FLOW SHOULD ALLOW FOR AT LEAST ISOLATED
THUNDER POTENTIAL IN THE AFTERNOON...AND POSSIBLE REMNANT SHOWERS
INTO THE OVERNIGHT HOURS. KEPT INHERITED POPS IN PLACE...BUT
SPREAD SLIGHT POPS ACROSS THE PLAINS THROUGH THE LATTER HALF OF
THE EXTENDED PERIOD. AAG
&&

.AVIATION...

SHOWERS AND THUNDERSTORMS CONTINUE TO BECOME INCREASINGLY
WIDESPREAD...IMPACTING MUCH OF THE REGION WEST OF KMLS. SHOWERS
AND THUNDERSTORMS ARE EXPECTED TO SHIFT FURTHER EAST AND
NORTHEAST THROUGHOUT EVENING...AND PERSIST OVERNIGHT AND THROUGH
SUNDAY. SOME OF THE STORMS WILL CONTAIN MODERATE TO BRIEFLY HEAVY
RAINFALL AND COULD LOWER CONDITIONS TO MVFR/IFR. MOUNTAINS WILL BE
OBSCURED IN SHOWERS AND CLOUDS THROUGHOUT THE DAY. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    SUN     MON     TUE     WED     THU     FRI     SAT
-----------------------------------------------------------
BIL 048/058 048/062 044/071 047/072 049/073 049/076 050/076
    88/T    86/W    31/B    12/T    42/T    22/T    22/T
LVM 041/057 040/059 037/067 041/072 040/069 041/071 042/071
    87/T    85/W    31/B    14/T    43/T    33/T    33/T
HDN 048/062 047/062 045/071 045/074 049/076 048/078 049/078
    98/T    86/W    31/E    12/T    32/T    22/T    22/T
MLS 051/063 049/062 046/068 046/072 050/073 048/075 051/076
    +8/T    86/W    53/W    22/T    22/T    22/T    22/T
4BQ 048/059 047/060 044/065 044/072 048/073 047/075 050/076
    +8/T    87/W    53/W    11/B    22/T    22/T    22/T
BHK 048/060 047/060 043/062 043/068 048/069 048/073 050/076
    +8/T    87/W    63/W    21/B    22/T    22/T    22/T
SHR 047/056 043/057 041/065 040/074 046/074 045/076 047/076
    77/T    87/W    42/W    12/T    32/T    22/T    22/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS