Area Forecast Discussion
Issued by NWS Great Falls, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KTFX 281209
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
609 AM MDT THU MAY 28 2015

...UPDATE TO AVIATION...

.DISCUSSION...

TODAY THROUGH SATURDAY...UPPER LEVEL TROUGH OVER MONTANA WILL
CONTINUE TO MOVE TO THE SOUTHEAST TODAY. NORTHERLY FLOW BEHIND THE
TROUGH WILL USHER IN A CANADIAN COOL FRONT FOR INCREASING
NORTHERLY WINDS BY THIS AFTERNOON. UPSLOPE FLOW AT LOW LEVELS WILL
COMBINE WITH INSTABILITY AND UPPER LEVEL DYNAMICS TO FUEL
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS THROUGH THIS
EVENING. ANY COOLDOWN FROM THE FRONT WILL BE SHORT-LIVED AS AN
UPPER LEVEL SHORTWAVE RIDGE DEVELOPS ON FRIDAY WITH 1000-500 MB
THICKNESS VALUES HELPING TO WARM TEMPERATURES BACK ABOVE SEASONAL
AVERAGES. SLIGHT INSTABILITY CONTINUES ACROSS THE FORECAST AREA
BUT INCREASED STABILITY FROM THE UPPER LEVEL RIDGE WILL KEEP
CONVECTION AT THE ISOLATED TO SCATTERED LEVEL AND MAINLY OVER THE
WESTERN AND CENTRAL MOUNTAINS. CONTINUED WARMING ON SATURDAY WILL
FUEL ADDITIONAL INSTABILITY THAT COINCIDES WITH A DISTURBANCE IN
WESTERLY FLOW ALOFT FOR ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS
DURING THE AFTERNOON. MPJ

SATURDAY NIGHT THROUGH WEDNESDAY...A WESTERLY FLOW ALOFT OVER
MONTANA THIS WEEKEND RESULTS AS A GRADIENT BETWEEN A WESTERN
CANADIAN TROUGH AND AN GREAT BASIN RIDGE. MINOR IMPULSES IN THIS
FLOW...COMBINED WITH SURFACE DEWPOINTS IN THE UPPER 40S AND A NEARLY
LINEAR SHEAR PROFILE WILL MAINTAIN SCATTERED SHOWERS AND
THUNDERSTORMS SATURDAY NIGHT. WEAK RIDGING ALOFT ON SUNDAY WILL
SUPPRESS ALL BUT ISOLATED AFTERNOON SHOWERS AS THE UPPER LEVEL FLOW
TURNS MORE SOUTHWESTERLY. WIDESPREAD THUNDERSTORMS ARE INDICATED
MONDAY AFTERNOON WITH A CLOSED UPPER TROUGH APPROACHING FROM THE
PACIFIC. AN ACCOMPANYING SURFACE LOW FORMING IN SOUTHEAST MONTANA
WILL SUPPORT A HUMID EASTERLY FLOW OVER THE NORTH CENTRAL PLAINS.
DIVERGENT SOUTHWEST FLOW ALOFT WILL YIELD AN INCREASINGLY UNSTABLE
ENVIRONMENT. CONVECTIVE PARAMETERS DO NOT SUPPORT SEVERE STORMS...
BUT THE SETUP DOES WARRANT ATTENTION FOR A FEW STRONGER STORMS
INCLUDING SMALL HAIL AND GUSTY WINDS. TIMING WILL BECOME AN
IMPORTANT FACTOR TO CONSIDER. THE WAVE OPENS ON TUESDAY AND
WEDNESDAY AS DIFFERENCES BEGIN TO APPEAR AMONG MODEL SOLUTIONS.
HOWEVER THE OVERALL PATTERN REMAINS UNSETTLED THROUGH THE PERIOD
WITH CONTINUING SHOWERS AND ISOLATED THUNDERSTORMS. TEMPERATURES
TREND BELOW NORMAL THROUGH MIDWEEK. SNOW LEVELS COULD LOWER TO
AROUND 7500 FT MSL WEDNESDAY MORNING ALONG THE CONTINENTAL
DIVIDE...BUT AS YET VERY LITTLE CONFIDENCE IN THE POTENTIAL FOR ANY
ACCUMULATION. NUTTER

&&

.AVIATION...
UPDATED 1209Z.

UPPER-LEVEL TROUGH OVER MONTANA CONTINUES TO MOVE SLOWLY EASTWARD
BUT WIDESPREAD MOISTURE WILL LINGER OVER THE REGION THROUGH FRIDAY
MORNING. SURFACE COOL FRONT MOVES SOUTH OF THE CANADIAN BORDER AND
ADVANCES AS FAR AS A KHLN-KLWT LINE BY EARLY AFTERNOON. NUMEROUS
SHOWERS AND THUNDERSTORMS EXPECTED TO DEVELOP ALONG THE FRONTAL
BOUNDARY WITH MVFR/VFR CONDITIONS EXPECTED TO PREVAIL THROUGH THE
FORECAST PERIOD. IFR CONDITIONS ARE POSSIBLE IN HEAVIER
PRECIPITATION AND MOUNTAINS WILL LIKELY BE OBSCURED. MPJ

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  65  46  70  50 /  70  70  30  10
CTB  60  40  67  45 /  70  40  20  20
HLN  66  48  74  52 /  60  60  30  20
BZN  62  44  69  47 /  60  60  20  20
WEY  55  35  63  38 /  70  50  30  20
DLN  62  44  70  48 /  50  40  20  20
HVR  71  40  70  45 /  60  40  10  10
LWT  65  46  65  48 /  70  60  30  10

&&

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

$$

WEATHER.GOV/GREATFALLS


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.