Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 072352
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
550 PM MDT TUE JUL 7 2015

...UPDATE TO AVIATION...

.DISCUSSION...

TONIGHT THROUGH THURSDAY...A COLD FRONT SPREAD ACROSS NORTH
CENTRAL MONTANA TUESDAY AFTERNOON. A BAND OF LIGHT RAIN ORGANIZED
BEHIND THE FRONT. AFTERNOON TEMPERATURES WERE AROUND 5 TO 10
DEGREES BELOW FORECAST HIGHS WITH THE FRONTAL PASSAGE, SO LOWERED
EVENING TEMPERATURES ACROSS THE NORTH CENTRAL PLAINS. ISOLATED
THUNDERSTORMS WERE DEVELOPING OVER SOUTHWEST MONTANA WHERE THE
ENVIRONMENT REMAINED WARMER AND THEREFORE FAVORABLE FOR BRIEF
HEAVY RAIN AND GUSTY WINDS NEAR THESE THUNDERSTORMS. SEVERE STORMS
ARE NOT EXPECTED. WEDNESDAY WILL REMAIN DRY FOR OUR CWA WITH
STABLE SURFACE HIGH PRESSURE IN PLACE. THUNDERSTORM ACTIVITY
RETURNS TO SOUTHWEST MONTANA ON THURSDAY AS A VORTICITY MAXIMA
LEADS A STREAM OF SUBTROPICAL MOISTURE ASSOCIATED WITH AN UPPER
LEVEL CUT OFF LOW MOVING INLAND OVER CALIFORNIA. AT PRESENT THE
NAM MODEL DEPICTS SUBSIDENCE AND DRY MID LEVEL AIR OVER THE NORTH
CENTRAL PLAINS WHERE RELATIVE HUMIDITY SHOULD DROP BELOW 20
PERCENT ON THURSDAY AFTERNOON. LIGHT WINDS AS FORECAST WOULD
MITIGATE FIRE WEATHER CONCERNS BUT MAY NEED TO BE MONITORED FOR
CHANGES. NUTTER

THURSDAY NIGHT THROUGH TUESDAY...MONSOONAL MOISTURE AHEAD OF AN
UPPER LOW OVER CALIFORNIA WILL HAVE WORKED ITS WAY INTO SOUTHWEST
MONTANA BY THURSDAY EVENING AND SCATTERED SHOWERS AND
THUNDERSTORMS FROM THURSDAY AFTERNOON WILL LINGER INTO THURSDAY
NIGHT. FRIDAY THE UPPER LOW WILL WEAKEN AS IT MOVES INTO SOUTHERN
IDAHO AND WYOMING DURING THE AFTERNOON AND INTO MONTANA FRIDAY
NIGHT. MODEL RUNS DIFFER ON THE DETAILS OF THE REMNANTS OF THE
UPPER LOW AND THEIR ASSOCIATED PRECIPITATION PATTERNS. DUE TO
THESE DIFFERENCES HAVE DECIDED TO CONTINUE WITH THE INHERITED
FORECAST OF SCATTERED SHOWERS AND THUNDERSTORMS OVER SOUTHWEST
MONTANA AS WELL THE ROCKY MOUNTAIN FRONT WITH SHOWER AND
THUNDERSTORM ACTIVITY EXPECTED TO BE ISOLATED OVER THE NORTHERN
PLAINS. SATURDAY THE ECMWF MODEL RUN DEVELOPS AN UPPER RIDGE OVER
WESTERN MONTANA WHILE THE GFS MODEL RUN HAS THE AREA STILL BEING
AFFECTED BY THE REMNANTS OF THE UPPER LOW. EVEN WITH THESE
DIFFERENCES BOTH MODEL RUNS HAVE PRECIPITATION FORECASTS IN LINE
WITH THE INHERITED FORECAST OF SCATTERED SHOWERS AND THUNDERSTORMS
MAINLY OVER THE ROCKY MOUNTAIN FRONT AND SOUTHWEST MONTANA. SUNDAY
THROUGH TUESDAY THE GFS AND ECMWF MODEL RUNS HAVE SOUTHWEST FLOW
ALOFT WITH SOME EMBEDDED MOISTURE. THE INHERITED FORECAST WAS
PRETTY DRY DURING THIS PERIOD SO HAVE INCREASED THE CHANCES OF
PRECIPITATION TO AT LEAST HAVE A MENTION OF PRECIPITATION. BLANK

&&

.AVIATION...
UPDATED 2350Z.

SCATTERED SHOWERS AND THUNDERSTORMS WILL DIMINISH DURING THE MID TO
LATE EVENING HOURS LEAVING SCATTERED TO BROKEN MID-LEVEL CLOUDS
ACROSS THE FORECAST AREA OVERNIGHT. NORTHERLY FLOW ALOFT WILL
CONTINUE THROUGH THE DAY ON THURSDAY WITH MOSTLY CLEAR TO PARTLY
CLOUDY CONDITIONS PREVAILING NORTH OF A KGTF-KLWT LINE. SOUTHWEST
MONTANA WILL CONTINUE TO SEE SCATTERED TO BROKEN CLOUDS THROUGH THE
DAY WITH ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE
OVER THE MOUNTAINS. MPJ


&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  50  81  52  88 /  30  10   0   0
CTB  47  81  47  87 /  20   0   0   0
HLN  57  83  57  89 /  30  10   0  10
BZN  51  79  50  83 /  30  10   0  40
WEY  42  69  42  70 /  20  50  30  50
DLN  52  77  53  78 /  20  20  10  50
HVR  49  84  51  91 /  10   0   0   0
LWT  51  78  52  86 /  20  20   0   0

&&

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

$$

WEATHER.GOV/GREATFALLS


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