227  
FXUS65 KTFX 231956  
AFDTFX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREAT FALLS MT  
156 PM MDT SAT JUN 23 2018  
   
SYNOPSIS
 
 
A LOW PRESSURE SYSTEM WILL BRING ANOTHER ROUND OF SCATTERED  
SHOWERS AND THUNDERSTORMS TO THE REGION THROUGH SUNDAY. SOME  
STORMS COULD PRODUCE BRIEF HEAVIER RAIN. THE PASSAGE OF THIS  
SYSTEM WILL KEEP TEMPERATURES BELOW NORMAL THROUGH TONIGHT. THE  
SHOWERS AND THUNDERSTORMS WILL DECREASE FROM THE WEST ON SUNDAY  
WITH A SLIGHT REBOUND IN TEMPERATURES, AS THE SYSTEM EXITS TO THE  
EAST. HIGH PRESSURE WILL BRING WARMING AND DRYING CONDITIONS  
SUNDAY NIGHT INTO MONDAY, AS TEMPERATURES WARM TO AT LEAST 10  
DEGREES ABOVE NORMAL.  
 

 
   
DISCUSSION
 
 
TONIGHT THROUGH SUNDAY...MID TO UPPER LEVEL CIRCULATION CENTER  
EMBEDDED WITHIN A BROADER UPPER LEVEL TROUGH CONTINUES TO SHIFT  
VERY SLOWLY SE ACROSS THE FORECAST AREA THIS EVENING AND  
EVENTUALLY ON INTO WY SUNDAY FOLLOWED BY A AN UPPER LEVEL RIDGE  
BUILDING INTO THE NORTHERN ROCKIES AND MT BY LATE SUNDAY.  
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL AFFECT THE  
AREA THROUGH THIS EVENING BEFORE SLOWLY DIMINISHING OVERNIGHT  
THROUGH SUNDAY MORNING. STORMS ACROSS NORTHERN PORTIONS OF THE  
FORECAST AREA WILL BE IN AN ENVIRONMENT WITH DEEPER MOISTURE AND  
SLOW STORM MOTION, SUPPORTING A THREAT FOR LOCALLY BRIEF BUT  
INTENSE RAINFALL, WHILE STORMS OVER SW MT SHOULD MOVE QUICKER WITH  
SOMEWHAT DRIER CONDITIONS AT THE SURFACE SUPPORTING THE THREAT  
FOR GUSTY WINDS. WIND SHEAR IS MARGINAL AT BEST ACROSS THE ENTIRE  
AREA LIMITING THE POTENTIAL FOR SEVERE THUNDERSTORMS. SOME SHOWERS  
AND ISOLATED THUNDERSTORMS COULD LINGER INTO EARLY SUNDAY  
AFTERNOON IN NORTHERLY FLOW BEHIND THE EXITING LOW WITH CLEARING  
SPREADING EAST ACROSS THE REGION SUNDAY AFTERNOON AND EVENING AS  
THE UPPER RIDGE BUILDS IN FROM THE WEST. HOENISCH  
 
SUNDAY NIGHT THROUGH SATURDAY...THE LATEST FORECAST MODEL HAVE  
BEEN FAIRLY CONSISTENT WITH THE SOLUTION DURING THIS PERIOD. HIGH  
PRESSURE ALOFT IN THE WAKE OF THE WEEKEND SYSTEM WILL BRING  
WARMING AND DRYING CONDITIONS SUNDAY NIGHT INTO MONDAY, AS  
TEMPERATURES WARM TO AT LEAST 10 DEGREES ABOVE NORMAL. A LOW  
PRESSURE TROUGH WILL ALSO MOVE INTO WESTERN NORTH AMERICA ON  
MONDAY, AND A PACIFIC COLD FRONT AHEAD OF THIS SYSTEM WILL MOVE  
INTO MONTANA MONDAY AFTERNOON. THE COMBINATION OF INCREASING WINDS  
ALOFT AND SHIFTING WINDS WITH THE FRONT COULD CAUSE INCREASING  
WIND SHEAR, AND THE WARM TEMPERATURES AHEAD OF THE FRONT WILL MAKE  
FOR AN UNSTABLE AIRMASS. AS A RESULT, SCATTERED STRONG STORMS MAY  
DEVELOP MONDAY EVENING WITH SOME SHOWERS LINGERING OVERNIGHT. A  
MORE WESTERLY FLOW ALOFT WILL KEEP THE AREA DRY TUESDAY THROUGH  
WEDNESDAY, AS TEMPERATURES REBOUND FROM THE COLD FRONTAL PASSAGE.  
HOWEVER, A DEEPENING LOW PRESSURE TROUGH WILL BRING COOLING  
TEMPERATURES AND AN INCREASING CHANCE FOR SHOWERS AND  
THUNDERSTORMS TO THE FORECAST AREA BEGINNING THURSDAY AFTERNOON  
AND CONTINUING INTO THE WEEKEND, WITH THE BEST CHANCE FOR MORE  
WIDESPREAD SHOWER ACTIVITY ON SATURDAY. WE WILL CONTINUE TO  
MONITOR THIS SITUATION TO DETERMINE JUST HOW WIDESPREAD AND HEAVY  
THE PRECIPITATION COULD BE, AS THERE IS STILL SOME UNCERTAINTY IN  
THE FORECAST MODEL DEPICTIONS.  
COULSTON  
 

 
   
AVIATION
 
 
UPDATED 1800Z.  
 
SCATTERED SHOWERS AND THUNDERSTORMS WILL BECOME MORE NUMEROUS THIS  
AFTERNOON AND ARE EXPECTED TO CONTINUE THROUGH THIS EVENING BEFORE  
DIMINISHING AS AN UPPER LEVEL TROUGH SHIFTS EAST ACROSS THE REGION.  
BRIEF BUT INTENSE RAINFALL AND LOCALLY GUSTY WINDS ARE THE MAIN  
THREATS THIS AFTERNOON AND EVENING.VFR CONDITIONS WILL GENERALLY  
PREVAIL WITH MVFR AND IFR CONDITIONS POSSIBLE IN THE VICINITY OF  
SHOWERS/THUNDERSTORMS. SHIFT TO N/NW FLOW BEHIND THE THE LOW COULD  
BRING LOWERING CLOUD BASES AND A PERIOD OF MVFR SAILINGS TO KCTB  
AREA LATER TONIGHT. HOENISCH  
 

 
   
HYDROLOGY
 
 
AS OF SATURDAY MORNING, RIVERS GENERALLY CONTINUE TO FALL, BUT  
WATER IMPACTING NEARBY AREAS WILL TAKE A BIT MORE TIME TO TOTALLY  
RECEDE OR SOAK INTO THE GROUND. THEREFORE, THE WARNINGS WILL  
CONTINUE FOR NOW.  
 
ALSO, SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND  
EVENING COULD BRING BRIEF HEAVY RAIN, WHICH CONTINUES THE THREAT  
FOR BRIEF MINOR ADDITIONAL FLOODING.  
 
SPECIFIC COUNTY/RIVER SITUATIONS...  
 
TETON COUNTY INTO WESTERN CHOUTEAU COUNTY...FLOOD WARNING WILL  
CONTINUE. THE TETON RIVER NEAR DUTTON HAS FALLEN BELOW FLOOD  
STAGE AS OF SATURDAY MORNING, BUT FARTHER DOWNSTREAM NEAR LOMA IT  
HAS YET TO FALL.  
 
JEFFERSON RIVER...BETWEEN WHITEHALL AND TRIDENT...FLOOD WARNING  
CONTINUES. THE RIVER IS STILL ABOVE FLOOD STAGE, BUT IT IS  
EXPECTED TO FALL BELOW FLOOD STAGE THROUGH THE WEEKEND.  
 
FERGUS COUNTY...A FLOOD WARNING IS IN EFFECT FOR THE MISSOURI  
RIVER, ESPECIALLY AT THE JAMES KIPP CAMPGROUND. THE RIVER LEVEL  
APPEARS TO BE CRESTING ABOUT HALFWAY BETWEEN MINOR AND MODERATE  
FLOOD STAGE, AND IT IS FORECAST TO GRADUALLY FALL INTO EARLY NEXT  
WEEK.  
 
COULSTON  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
GTF 55 76 56 88 / 40 20 10 0  
CTB 54 77 53 84 / 30 20 10 10  
HLN 53 76 53 86 / 40 30 10 10  
BZN 47 71 49 85 / 30 20 10 0  
WEY 38 65 39 74 / 40 20 10 0  
DLN 45 69 47 82 / 50 10 10 0  
HVR 57 78 56 88 / 60 30 10 0  
LWT 52 69 51 82 / 40 50 20 0  
 

 
   
TFX WATCHES/WARNINGS/ADVISORIES
 
 
FLOOD WARNINGS ARE IN EFFECT UNTIL FURTHER NOTICE  
FOR PORTIONS OF THE TETON AND MISSOURI RIVERS IN CENTRAL MONTANA,  
AND FOR A PORTION OF THE JEFFERSON RIVER IN SOUTHWEST MONTANA.  
 

 
 

 
 
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