403  
FXUS65 KTFX 260235  
AFDTFX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREAT FALLS MT  
835 PM MDT MON MAR 25 2019  
   
UPDATE
 
 
ONLY WEATHER UPDATE THIS EVENING WAS TO GENERALLY INCREASE  
OVERNIGHT RELATIVE HUMIDITY. THIS CHANGE WAS TO HELP CREATE MORE  
OF A CHANCE FOR FOG OVER THE NORTHEAST TFX PLAINS (INCLUDING THE  
HAVRE AREA) AND IN SOME SOUTHWEST VALLEYS. THE REMAINDER OF THE  
FORECAST IS ON TRACK.  
 
DID MAKE SOME CHANGES TO HYDROLOGIC STATEMENTS, BUT DETAILS ARE IN  
THE HYDROLOGY SECTION.  
 

 
   
SYNOPSIS
 
 
HIGH PRESSURE MOVING ACROSS THE REGION WILL BRING DRY CONDITIONS  
THROUGH EARLY TUESDAY AFTERNOON WITH TEMPERATURES ALSO WARMING TO  
SLIGHTLY ABOVE SEASONAL AVERAGES TUESDAY AFTERNOON. MORE RAIN AND  
SNOW SHOWERS WILL START TO AFFECT THE REGION BY TUESDAY EVENING,  
ESPECIALLY IN WESTERN AND SOUTHWESTERN MT. MUCH OF THE STATE WILL  
LIKELY SEE RAIN AND/OR SNOW BETWEEN WEDNESDAY NIGHT AND THURSDAY  
ALONG WITH A RETURN TO COOLER THAN AVERAGE TEMPERATURES.  
 

 
   
AVIATION
 
 
UPDATED 530 PM MDT MON MAR 25 2019  
 
VFR CONDITIONS ARE EXPECTED THROUGH THE NEXT 24 HOURS ACROSS THE  
FORECAST AREA. MOISTURE IN THE SOUTHWEST FLOW ALOFT WILL CAUSE MID  
AND HIGH LEVEL CLOUDINESS TO INCREASE OVER THE AREA. A DISTURBANCE  
MAY BRING SOME MAINLY MOUNTAIN PRECIPITATION TO THE NORTHWEST  
PORTION OF THE FORECAST AREA (INCLUDING KCTB) BETWEEN 09Z AND 18Z.  
PATCHY FOG MAY ALSO DEVELOP IN SOME SOUTHWEST VALLEYS (INCLUDING  
KHLN/KBZN) AND ALONG THE MILK RIVER (INCLUDING KHVR). HOWEVER, THE  
INCREASING HIGH CLOUDS MAY HINDER ITS DEVELOPMENT, SO HAVE STAYED  
WITH A VCFG FOG MENTION TO EXPRESS LOW CONFIDENCE IN FOG DIRECTLY  
IMPACTING THESE TERMINALS. OVERALL, SOUTHWEST DOWNSLOPE WINDS WILL  
INCREASE WITH THE PASSAGE OF THIS DISTURBANCE OVER THE PLAINS,  
LEAVING THE MAIN CHANCE FOR PRECIPITATION OVER THE MOUNTAINS AFTER  
18Z. COULSTON  
 

 
   
HYDROLOGY
 
 
THE FLOOD ADVISORIES REMAIN IN EFFECT FOR CASCADE, CHOUTEAU, JUDITH  
BASIN, FERGUS, PONDERA, AND TETON COUNTIES BASICALLY UNTIL FURTHER  
NOTICE. LATEST REPORTS INDICATE THAT SOME WATER HAS RECEDED, BUT  
THERE ARE STILL REPORTS OF MINOR FLOODING OVER MULTIPLE ROADWAYS IN  
THE AREA ALONG WITH STANDING WATER IN FIELDS. MILD TEMPERATURES  
THROUGH TUESDAY SHOULD INCREASE THE RATE OF MELTING AND RUNOFF, AND  
MAY EXTEND ISSUES INTO SOUTHWESTERN MONTANA. THE THREAT FOR  
PRECIPITATION FOR WEDNESDAY THROUGH THURSDAY COULD ALSO EXACERBATE  
ONGOING FLOODING.  
 
HAVE ALSO RECEIVED REPORTS OF SNOWMELT CAUSING WATER TO BACK UP IN  
CULVERTS AND FLOW OVER SOME ROADS ACROSS PORTIONS OF SOUTHWEST  
MONTANA (PRIMARILY BROADWATER, MADISON, AND GALLATIN COUNTIES AT  
THIS TIME). WITH CONTINUED WARMING EXPECTED THERE, AS WELL AS AN  
INCREASED THREAT FOR PRECIPITATION LATER THIS WEEK, THE POTENTIAL  
FOR FURTHER MINOR FLOODING WILL INCREASE. WILL THEREFORE ISSUE A  
FLOOD ADVISORY FOR ALL OF SOUTHWEST MONTANA, EXTENDING NORTH INTO  
LEWIS AND CLARK COUNTY.  
 
THE MISSOURI RIVER AT LANDUSKY (NEAR THE FRED ROBINSON BRIDGE)  
IS CURRENTLY STAYING JUST BELOW MODERATE FLOOD STAGE (29.0 FEET)  
AS OF MONDAY EVENING, SO AM CONTINUING THE FLOOD WARNING UNTIL  
FURTHER NOTICE, WITH THE LATEST FORECAST HAVING THE RIVER FALL  
BELOW FLOOD STAGE EARLY TUESDAY AFTERNOON. THE MAIN INFLOW LOOKS  
TO BE FROM THE JUDITH RIVER, WITH RUNOFF FROM JUDITH BASIN AND  
FERGUS COUNTIES, LIKELY EXACERBATED BY ICE BLOCKAGE ON THE  
MISSOURI.  
 
-HOENISCH/KREDENSOR/COULSTON  
 

 
   
PREV DISCUSSION
 
 
/ISSUED 530 PM MDT MON MAR 25 2019/  
 
TONIGHT THROUGH TUESDAY NIGHT...  
 
AN UPPER LEVEL RIDGE SHIFTS EAST ACROSS THE NORTHERN ROCKIES AND  
MONTANA TONIGHT FOR DRY CONDITIONS AND SEASONABLY COOL TEMPERATURES.  
ON TUESDAY, A WEAK SHORTWAVE EJECTING OUT OF A LARGE UPPER LOW  
EDGING TOWARD THE WEST COAST MOVES UP THROUGH SW FLOW ALOFT AND  
ACROSS ID AND WESTERN MT LATE TUESDAY AND TUESDAY NIGHT. THIS  
FEATURE WILL PUSH A WEAK COLD FRONT EAST ACROSS THE REGION TUESDAY  
AFTERNOON AND EVENING WITH SHOWERS DEVELOPING ALONG THE FRONT AND  
INCREASES AS THE FRONT MOVES SOUTHWARD IN THE EVENING. ENOUGH WEAK  
INSTABILITY MAY BE PRESENT TUESDAY AFTERNOON AND EVENING FOR AN  
ISOLATED THUNDERSTORM, PRIMARILY SOUTH OF A LINE FROM HELENA EAST TO  
LEWISTOWN. HOENISCH  
 
WEDNESDAY THROUGH NEXT MONDAY...  
 
SOME PRECIP MAY HANG ON OVER SW MONTANA THROUGH THE DAY WEDNESDAY AS  
THAT SHORTWAVE DEPARTS AND THE NEXT MAJOR SYSTEM MOVES ONSHORE THE  
WEST COAST. THIS SYSTEM WILL REALLY GET INTO GEAR OVER THE SOUTHERN  
PART OF THE CWA LATER WED AFTERNOON OR EVENING, THEN CONTINUE  
IMPACTING THE AREA THROUGH THURSDAY NIGHT. THERE REMAINS SOME MODEL  
DISAGREEMENT ON THE NORTHWARD EXTEND OF PRECIP, THOUGH IT APPEARS  
LIKELY THAT MUCH OF THE HI-LINE EAST OF GLACIER COUNTY COULD BE  
LOCKED OUT OF ANY SIGNIFICANT RAIN OR SNOW. SNOW TOTALS WERE  
INCREASED A BIT OVERALL, WITH 1 TO 5 INCHES EXPECTED FOR THE PLAINS  
SOUTH OF A LINE FROM CONRAD THROUGH CENTRAL FERGUS COUNTY, AS WELL  
AS FOR MANY OF THE SOUTHWEST VALLEYS FROM HELENA SOUTHWARD. MOST OF  
THE MOUNTAINS ARE FORECAST TO GET 5-10 INCHES OF SNOW, BUT SOME OF  
THE SOUTHERN MOUNTAINS, PARTICULARLY THE RANGES IN MADISON AND  
GALLATIN COUNTIES, COULD SEE OVER A FOOT.  
 
THIS SYSTEM WILL START TO WIND DOWN DURING THE DAY FRI, BUT SOME  
PRECIP COULD LINGER OVER SW MT DURING THAT TIME, UNTIL UPPER RIDGING  
PUSHES INTO THE AREA FRI NIGHT. SATURDAY CURRENTLY LOOKS CLEAR AND  
DRY, BUT MODELS DISAGREE ON WHETHER THE NEXT SYSTEM WILL PUSH INTO  
THE AREA ON SUN, OR HOLD OFF UNTIL THE MON/TUE TIME FRAME. -KREDENSOR  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
GTF 33 53 30 44 / 0 10 10 20  
CTB 29 53 26 44 / 10 10 0 10  
HLN 20 48 20 41 / 0 20 20 30  
BZN 18 48 21 43 / 0 10 20 40  
WEY 14 50 20 49 / 0 10 20 40  
DLN 24 44 25 41 / 0 10 20 30  
HVR 28 56 28 45 / 0 0 0 0  
LWT 30 58 30 45 / 0 10 30 20  
 

 
   
TFX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
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