Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 062357
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
555 PM MDT MON JUL 6 2015

.DISCUSSION...
TONIGHT THROUGH WEDNESDAY...A WEAK WEATHER SYSTEM MOVING ACROSS
SOUTHERN IDAHO WILL BRUSH FAR SOUTHWEST MONTANA THIS AFTERNOON
AND EVENING TRIGGERING THE DEVELOPMENT OF A FEW SHOWERS AND SOME
ISOLATED THUNDERSTORMS. LATE TONIGHT AND TUESDAY...THE SOUTHERN
PORTION OF A LOW PRESSURE TROUGH TRACKING ACROSS CANADA WILL SWEEP
ACROSS THE FORECAST AREA STEERING SEVERAL EMBEDDED SMALL WEATHER
SYSTEMS ACROSS NORTH CENTRAL AND CENTRAL MONTANA. THE DYNAMICS OF
THESE SYSTEMS COUPLED WITH SOME RELATIVELY MOIST AIR AND ANOTHER
PUSH OF COOL AIR FROM CANADA WILL BRING A GOOD CHANCE OF SHOWERS
AND THUNDERSTORMS TO THE AREA TUESDAY AND TUESDAY NIGHT. WITH THE
NORTHERLY PUSH OF COOL AIR...WINDS WILL BECOME MORE NORTH TO
NORTHEAST GIVING NORTH AND EAST FACING SLOPES A BETTER CHANCE OF
RECEIVING SOME PRECIPITATION. ENERGY WITH THIS TROUGH WILL SLOWLY
WORK IT WAY EASTWARD...AND SOME SHOWERS AND THUNDERSTORMS ARE
STILL POSSIBLE WEDNESDAY. THE COOLER AIR FROM CANADA WILL KEEP
TEMPERATURES A FEW DEGREES BELOW NORMAL.

ADDITIONALLY...WESTERLY WINDS THIS AFTERNOON AND EVENING WILL
PULL SMOKE FROM FIRES IN THE PACIFIC NORTHWEST INTO CENTRAL
MONTANA. THIS IS EXPECTED TO PERSIST...AND POSSIBLY WORSEN...UNTIL
THE WIND SHIFTS TO THE NORTH-NORTHEAST ON TUESDAY. AT THAT
TIME THE INFLUX OF SMOKE FROM WESTERN FIRES WILL BE CUT
OFF...HOWEVER THERE MAY INSTEAD BE A PUSH OF MORE SMOKE INTO THE
AREA FROM FIRES IN CANADA.

WEDNESDAY NIGHT THROUGH MONDAY...MODELS ARE IN GOOD AGREEMENT ON
GENERAL TRENDS. EXPECT SCATTERED SHOWERS AND THUNDERSTORMS OVER
SOUTHWEST MONTANA WEDNESDAY EVENING IN PART DUE TO TERRAIN EFFECTS
AND AN UPPER TROUGH. MOISTURE AHEAD OF AN UPPER TROUGH OVER
CALIFORNIA WILL WORK ITS WAY INTO SOUTHWEST MONTANA THURSDAY FOR
MORE SCATTERED SHOWERS AND THUNDERSTORMS. LATER THURSDAY NIGHT THE
LATEST GFS MODEL RUN BRINGS SOME PRECIPITATION INTO CENTRAL
MONTANA BUT THE ECMWF MODEL RUN HAS MORE OF AN UPPER RIDGE OVER
SOUTHWEST MONTANA THAN THE GFS MODEL RUN AND ENDS UP BEING DRY.
FOR FRIDAY BOTH MODEL RUNS BRING A WEATHER DISTURBANCE ALOFT INTO
SOUTHWEST MONTANA DURING THE EVENING AND TO CENTRAL MONTANA LATE
THAT NIGHT. THE LATEST GFS MODEL RUN IS STRONGER WITH THE
DISTURBANCE AND HENCE WETTER THAN THE CORRESPONDING ECMWF RUN.
HAVE STUCK PRETTY CLOSE TO THE IDEA OF SCATTERED SHOWERS AND
THUNDERSTORMS OVER SOUTHWEST MONTANA WITH MORE ISOLATED ACTIVITY
OVER THE PLAINS. SHOULD THE ECMWF COME AROUND TO THE WETTER GFS
THE CHANCES OF PRECIPITATION FOR FRIDAY AND FRIDAY NIGHT WILL NEED
TO BE RAISED. ON SATURDAY THE DISTURBANCE MOVES INTO EASTERN
MONTANA BUT LINGERING INSTABILITY LEADS TO ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS. BOTH MODEL RUNS ARE ON THE SAME PAGE IN
HAVING AN UPPER RIDGE OVER MONTANA SUNDAY AND MONDAY WITH
GENERALLY LESS SHOWER AND THUNDERSTORM ACTIVITY. HIGH TEMPERATURES
WILL BE ABOVE NORMAL BUT DO NOT EXPECT ANY RECORD-BREAKING HEAT
SUCH AS OCCURRED LAST WEEK. BLANK
&&

.AVIATION... UPDATED 2355Z.

VFR CONDITIONS ACROSS AREA EARLY IN PERIOD. ISOLATED SHOWERS AND
THUNDERSTORMS EXTREME SOUTHWEST UNTIL 03Z. SURFACE WINDS GENERALLY
AT OR BELOW 10 KTS. EXPECT INCREASING CLOUDINESS AND LOWERING CIGS
TUESDAY AS SURFACE HIGH PRESSURE PUSHING SOUTH FROM CANADA SHIFTS
WIND TO NORTH-NORTHEAST. SCATTERED SHOWERS AND THUNDERSTORMS
POSSIBLE AFT 10Z NORTH...AFTER 18Z SOUTH. EXPECT MOUNTAIN
OBSCURATION IN LOW CLOUDS.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  51  76  51  79 /   0  40  50  10
CTB  50  72  46  78 /  10  50  30  10
HLN  56  82  57  82 /   0  30  40  20
BZN  50  81  51  79 /  10  30  40  20
WEY  42  73  40  69 /  20  40  40  50
DLN  51  80  52  77 /  10  20  30  30
HVR  50  78  49  82 /   0  30  20  10
LWT  51  78  50  76 /   0  30  40  20

&&

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

$$

WEATHER.GOV/GREATFALLS



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