Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 201803
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1203 PM MDT WED MAY 20 2015

...UPDATE TO AVIATION...

.UPDATE...SATELLITE IMAGERY AND LATEST MODEL RUNS ARE SHOWING
PARTLY CLOUDY SKIES IN SOUTHWEST MONTANA. HAVE UPDATED TO LOWER
SKY CONDITION IN THIS AREA FOR TODAY AND THIS EVENING. HAVE ALSO
MADE SOME MINOR TWEAKS TO SURFACE WINDS WHICH WILL REMAIN EASTERLY
AND GUSTY THROUGH THE DAY. REMAINDER OF THE FORECAST IS IN GOOD
SHAPE WITH ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
EXPECTED OVER SOUTHWEST MONTANA WHILE THE REST OF THE FORECAST
AREA REMAINS DRY. MPJ

&&

.AVIATION...
UPDATED 1803Z.

MOSTLY CLEAR SKIES AND WIDESPREAD VFR CONDITIONS ARE EXPECTED ACROSS
CENTRAL AND NORTH CENTRAL MONTANA THROUGH LATE THURSDAY MORNING.
PARTLY TO MOSTLY CLOUDY SKIES WITH VFR CONDITIONS WILL PREVAIL
ACROSS SOUTHWEST MONTANA. SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE EXPECTED IN FAR SOUTHWEST MONTANA DURING THE
AFTERNOON AND EVENING HOURS. GUSTY SURFACE WINDS OF 10 TO 20 MPH
FROM THE EAST/SOUTHEAST WILL DIMINISH BY ABOUT 02Z THURSDAY. MPJ

&&

.PREV DISCUSSION...
/ISSUED 525 AM MDT WED MAY 20 2015/
WEDNESDAY THROUGH FRIDAY...A QUIET MIDDLE OF THE WEEK WILL SLOWLY
TRANSITION TO A MORE SHOWERY PATTERN TO BEGIN THE WEEKEND.
TEMPERATURES WILL TREND SLIGHTLY WARMER EACH SUCCESSIVE DAY WITH
ADDITIONAL MOISTURE AND INSTABILITY MOVING INTO THE AREA FROM THE
SOUTH. MOST OF THE SHOWER ACTIVITY WILL AGAIN BE LIMITED TO THE
SOUTHERN BORDER WITH IDAHO, WITH A MORE NORTHWARD EXTENT INTO
SOUTHWEST MONTANA ON THURSDAY FOLLOWED BY SHOWERS AND
THUNDERSTORMS EXTENDING INTO CENTRAL MONTANA BY FRIDAY
AFTERNOON. SUK

FRIDAY NIGHT THROUGH TUESDAY...DO NOT SEE ANY WEATHER SYSTEMS THAT
WOULD HAVE A WIDESPREAD NEGATIVE IMPACT ON TRAVEL OR OUTDOOR
ACTIVITIES OVER THE LONG HOLIDAY WEEKEND. THERE WILL BE SEVERAL
UPPER LOWS TO CONTEND WITH DURING THE PERIOD BUT ALMOST ALL OF THEM
WILL NOT BE OVER THE FORECAST AREA. MODELS ARE IN BETTER AGREEMENT
TONIGHT WITH THEIR HANDLING THESE UPPER LOWS. ON SATURDAY ONE UPPER
LOW WILL BE OVER FAR SOUTHEAST MONTANA WITH ANOTHER OVER THE GREAT
BASIN AND A THIRD IN THE VICINITY OF THE PACIFIC NORTHWEST. NONE
WILL HAVE MUCH BEARING ON OUR FORECAST AREA. SCATTERED SHOWERS AND
POSSIBLY A FEW THUNDERSTORMS WILL BE DUE PRIMARILY TO UPSLOPE FLOW.
ON SUNDAY AN UPPER LOW WILL BE OVER THE WESTERN DAKOTAS WITH ANOTHER
IN THE AREA FROM NORTHERN CALIFORNIA TO TO OREGON. THERE MIGHT BE A
LITTLE LESS SHOWER ACTIVITY THEN ON SATURDAY. ON MEMORIAL DAY AN
UPPER LOW IS FORECAST TO BE OVER THE GREAT BASIN WHICH COULD LEAD TO
SCATTERED SHOWERS OR THUNDERSTORMS OVER SOUTHWEST MONTANA. FARTHER
NORTH MODELS DIFFER WITH THE GFS HAVING AN UPPER TROUGH OVER CENTRAL
MONTANA AND SCATTERED SHOWERS IN THAT SAME AREA. THE ECMWF ON THE
OTHER HAND DOES NOT SHOW THIS FEATURE AND IS DRY. TUESDAY
DIFFERENCES CONTINUE WITH THE UPPER AIR PATTERN AS THE ECMWF HAS AN
UPPER LOW OVER SOUTHERN IDAHO WITH SHOWERS OR THUNDERSTORMS FOR
SOUTHWEST MONTANA. THE GFS ON THE OTHER HAND HAS AN UPPER RIDGE OVER
IDAHO AND WESTERN MONTANA BUT DUE TO PRIMARILY TERRAIN EFFECTS HAS
SCATTERED SHOWERS OR THUNDERSTORMS MAINLY OVER THE WESTERN
MOUNTAINS. SEASONABLE HIGH TEMPERATURES M0STLY IN THE 60S CAN BE
EXPECTED OVER THE HOLIDAY WEEKEND. BLANK

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  63  38  69  42 /   0   0  10  10
CTB  61  34  67  38 /   0   0   0  10
HLN  65  42  70  46 /  10  10  30  20
BZN  60  39  66  41 /  10  20  30  30
WEY  57  32  60  32 /  40  40  40  50
DLN  61  41  65  42 /  20  30  40  50
HVR  66  35  72  38 /   0   0   0   0
LWT  60  38  66  41 /   0   0  10  10

&&

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

$$

WEATHER.GOV/GREATFALLS


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