Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 052047
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
247 PM MDT SUN JUL 5 2015

.DISCUSSION...
TONIGHT THROUGH TUESDAY...AN UPPER LEVEL DISTURBANCE WILL CONTINUE
TO MOVE SLOWLY SOUTHEASTWARD THRU THE REGION TONIGHT. EXPECT
LIGHT RAIN TO CONTINUE INTO THE EVENING HOURS OVER NORTH CENTRAL
MT. AN ISOLATED RUMBLE OF THUNDER IS ALSO POSSIBLE...ESPECIALLY
NEAR THE DIVIDE. THE CLOUDS CONTINUE TO RESIDE OVER THE NORTH ON
MONDAY MORNING...BEFORE DECREASING DURING THE AFTERNOON HOURS.
OVER THE SOUTHWEST...A FEW THUNDERSTORMS WILL ROTATE AROUND AN
UPPER LEVEL LOW. A FEW OF THESE STORMS WILL AFFECT AREAS MAINLY
NEAR THE MT/ID BORDER ON MONDAY. FOR TUESDAY...THE FLOW ALOFT WILL
BE NORTHERLY AS AN UPPER LEVEL DISTURBANCE WORKS ITS WAY SOUTHWARD
INTO THE REGION. THE CHANCES FOR SCATTERED SHOWERS/THUNDERSTORMS
WILL BE ON THE INCREASE AS WELL DURING THE AFTERNOON HOURS.
TEMPERATURES WILL REBOUND A BIT ON MONDAY AS SKIES CLEAR OUT A BIT
BY THE AFTERNOON HOURS. ON TUESDAY...THE WARMING TREND
CONTINUES...WITH AFTERNOON HIGHS NEAR NORMAL IN MANY AREAS. BRUSDA

TUESDAY NIGHT THROUGH SUNDAY...A PASSING SHORTWAVE TROUGH IN A MOIST
NORTHWESTERLY FLOW ALOFT WILL COMBINE WITH NORTHERLY UPSLOPE SURFACE
WINDS TO BRING A CHANCE OF SHOWERS AND THUNDERSTORMS TO THE AREA
TUESDAY NIGHT, ESPECIALLY ALONG THE NORTH AND EAST FACING SLOPES.
THE FLOW ALOFT WILL THEN TRANSITION TO WESTERLY ON WEDNESDAY THEN
SOUTHWESTERLY ON THURSDAY AS AN UPPER LEVEL LOW MOVES ONSHORE INTO
CALIFORNIA. THIS WILL KEEP A CHANCE OF MAINLY AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS OVER THE MOUNTAIN AREAS. THIS UPPER LOW
THEN OPENS UP INTO A SHORTWAVE TROUGH, BUT THE FORECAST MODELS
DIFFER ON THE SPEED OF THIS SHORTWAVE MOVING INTO MONTANA. THE GFS
IS THE FASTER OF THE TWO MODELS (AND IS FASTER THAN LAST NIGHT`S
MODEL RUN), BRINGING THE SHORTWAVE INTO THE STATE FRIDAY
AFTERNOON/EVENING. THE ECMWF MOVES IT IN ON SATURDAY AND IS A BIT
MORE SHALLOW WITH THE SHORTWAVE THAN THE GFS. THERE IS ALSO A
DIFFERENCE IN THE PLACEMENT OF THE SHORTWAVE. THE GFS MOVES IT ALONG
THE SOUTHERN MONTANA BORDER, WHILE THE ECMWF KEEPS IT ALONG THE
NORTHERN BORDER. BECAUSE OF BOTH THE TIMING AND PLACEMENT
DISCREPANCY, HAVE DECIDED TO GO WITH CHANCES OF SHOWERS AND
THUNDERSTORMS FRIDAY THROUGH SATURDAY SIMILAR TO CLIMATOLOGICAL
NORMALS. THE MODELS AGREE ON BUILDING AN UPPER LEVEL RIDGE OF HIGH
PRESSURE INTO THE STATE ON SUNDAY, SO HAVE GONE WITH A DECREASING
CHANCE OF SHOWERS AND THUNDERSTORMS TO END THE PERIOD. TEMPERATURES
WILL GRADUALLY WARM FROM ABOUT 5 DEGREES ABOVE NORMAL ON WEDNESDAY
TO AROUND 10 TO 15 DEGREES ABOVE NORMAL ON FRIDAY, THEN THE PASSAGE
OF THE SHORTWAVE WILL COOL TEMPERATURES BACK DOWN TO AROUND 5
DEGREES ABOVE NORMAL FOR SATURDAY THROUGH SUNDAY. COULSTON

&&

.AVIATION... UPDATED 1755Z. MIX OF VFR TO IFR CONDITIONS ACROSS
CENTRAL AND SOUTHWEST MT THIS AFTN AS AN UPPER-LEVEL TROF CONTINUES
TO MOVE SLOWLY EASTWARD ACROSS THE STATE.  LOWEST CEILING CONDITIONS
ARE MOSTLY ASSOCIATED WITH BANDS OF DRIZZLE/LIGHT RAIN FROM KGTF
NORTH TO US/CAN BORDER.  AS TROF AXIS MOVES INTO SOUTHWEST MT LATER
THIS AFTN THERE WILL BE A CHANCE FOR ISOLATED -TSRA VCNTY KBZN.
SHOULD SEE GRADUAL IMPROVEMENT BACK TO VFR ACROSS THE REGION THIS
EVE AS THE TROF SWINGS INTO EASTERN MT.  WINDS REMAINING AT/BELOW 15
KTS TODAY.
WARANAUSKAS

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  42  77  50  79 /   0   0  10  40
CTB  41  74  48  75 /   0   0  10  30
HLN  51  82  56  84 /  10   0  10  30
BZN  48  79  49  81 /  20  10  10  30
WEY  41  73  41  72 /  40  10  20  30
DLN  50  78  52  80 /  20  10  10  20
HVR  44  76  48  81 /   0   0   0  20
LWT  45  74  50  78 /  20  10   0  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

WEATHER.GOV/GREATFALLS



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