352  
FXUS65 KGGW 082143  
AFDGGW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GLASGOW MT  
243 PM MST THU DEC 8 2022  
   
DISCUSSION
 
 
AFTERNOON UPDATE:  
LAKE EFFECT FOG FROM FORT PECK LAKE HAS PERSISTED FOR MUCH LONGER  
THAN PREVIOUSLY EXPECTED. UPON LOOKING AT THE SETUP OF  
SOUTHEASTERLY WINDS THROUGH TOMORROW MORNING, THE DECISION WAS  
MADE TO ISSUE A DENSE FOG ADVISORY FOR CENTRAL AND SOUTHERN VALLEY  
COUNTY. AT THIS TIME, THE FOG BANK IS EXPECTED TO LIFT AS WINDS  
BECOME LIGHT AND VARIABLE TOMORROW AFTERNOON HOWEVER THIS  
SITUATION WILL NEED TO BE MONITORED IN CASE SOUTHEASTERLY WINDS  
CONTINUE.  
 
TEMPERATURES NORTH OF THE MISSOURI HAVE CONTINUED TO RUN COLDER  
THAN NBM PREDICTIONS AND ADJUSTMENTS WERE MADE TO BOTH THE LOW  
TONIGHT AND THE HIGH TOMORROW.  
 
LOOKING AHEAD TO THE WINTER SYSTEM NEXT WEEK, THE MODELS ARE  
STARTING TO POINT TOWARDS THE POTENTIAL FOR THE LOW RETROGRADING  
SLIGHTLY STARTING AROUND TUESDAY AFTERNOON. THIS HAS HAD THE  
EFFECT OF RAISING SNOW TOTALS FOR THE SOUTHEASTERN ZONES  
SIGNIFICANTLY OVER THE THREE DAY PERIOD STARTING MONDAY MORNING  
AND ENDING LATE THURSDAY MORNING. THERE IS STILL ENOUGH SPREAD IN  
MODEL DISAGREEMENT THAT SOME OF THE HIGHEST SNOW AMOUNTS ARE STILL  
SUSPECT BUT THE FACT THAT MULTIPLE MEMBERS OVER MULTIPLE RUNS  
KEEP SIGNALING THE POTENTIAL FOR A SIGNIFICANT SNOW EVENT DOES  
RAISE THE CONCERN A BIT. AS OF RIGHT NOW, IT'S TOO EARLY TO SAY  
HOW MUCH SNOW WILL FALL BUT THE PATTERN IS DEFINITELY SETTING UP  
TO PRODUCE AN EVENT THAT MAY HAVE SIGNIFICANT IMPACTS ACROSS  
SOUTHEASTERN MONTANA INTO NORTH DAKOTA.  
 
-THOR  
 
MORNING DISCUSSION:  
SYNOPTIC SETUP: ON THE LARGE SCALE THE FORECAST BEGINS WITH A  
RIDGE RUNNING DOWN THE FRONT RANGE FROM NORTHERN BRITISH COLUMBIA  
TO WYOMING WHICH IS TRAPPED IN A PROGRESSIVE PATTERN. JUST OFF  
THE COAST LIES THE TROUGH JOGGING SOUTH FROM OFF OF BC TO OFF OF  
NORTHERN CALIFORNIA. BEHIND THAT IS A RAPIDLY DEVELOPING  
SHORTWAVE THAT WILL QUICKLY AMPLIFY INTO A SYNOPTIC TROUGH JUST  
OFF THE COAST BY SATURDAY. MEANWHILE THE COLDEST AIR IS DRAINING  
OUT OF THE HUDSON INTO THE NORTHWEST TERRITORIES WHERE IT WILL  
HAVE ANOTHER CHANCE TO DROP SOUTH DOWN THE CANADIAN PLAINS.  
 
TODAY THROUGH TONIGHT: ARCTIC AIR AT THE SURFACE WILL CONTINUE TO  
SHALLOW INTO THE AFTERNOON WHILE THE RIDGE ALOFT MOVES ACROSS THE  
REGION GENERATING A STRONG INVERSION. TEMPERATURES WILL BE ABOVE  
FREEZING JUST A FEW HUNDRED FEET OFF THE DECK TODAY, BUT THIS  
SHALLOW COLD DENSE AIR WILL ALSO KEEP WINDS LOW FOR TODAY AS WELL.  
BY TONIGHT CONDITIONS SHOULD STRIATED OUT AGAIN SIMILAR TO THIS  
MORNING WITH MOST TEMPERATURES ACROSS THE AREA STANDING OUT BY  
ELEVATION MAP.  
 
FRIDAY TO SATURDAY NIGHT: A WEAK SURFACE TROUGH WILL MOVE ACROSS  
THE AREA FRIDAY BUT MAY HAVE AN UNUSUAL WARMING EFFECT AS ITS  
SCOURS OUT THE REMAINING ARCTIC AIR. BY SATURDAY ANOTHER WEAK  
RIDGE ALOFT COULD WARM THE AREA FURTHER. CONDITIONS SHOULD REMAIN  
DRY HERE. MEANWHILE, THE SECOND PACIFIC TROUGH STEPS ON SHORE AND  
MOVES ACROSS THE ROCKIES WHILE THE ARCTIC AIR UP NORTH POOLS UP  
FOR A PLUNGE INTO IT.  
 
SUNDAY THROUGH SUNDAY NIGHT: PACIFIC TROUGH IS EXPECTED TO DIG  
SOUTH INTO THE LOWER INTERMOUNTAIN WEST AND ALLOW THE ARCTIC AIR  
TO FILL INTO MONTANA IN THE FORM OF AN INITIALLY DRY COLD FRONT.  
 
MONDAY THROUGH WEDNESDAY NIGHT: AS THE INTERMOUNTAIN TROUGH DROPS  
OFF THE FRONT RANGE OF COLORADO IT WILL FOR A COLORADO LOW THAT  
IS EXPECTED TO JOG NORTH TO NORTHEAST OVER THE DAKOTAS AND BE  
FURTHER INTENSIFIED BY THE ARCTIC AIR DROPPING SOUTH BEHIND IT.  
THIS LOW IS EXPECTED TO DRAG GULF MOISTURE UP AHEAD AND AROUND  
THE TOP OFF IT WHICH MAY LEAD BACK INTO A STRONG SNOW STORM THAT  
SETS OVER THE SOUTHWESTERN HALF OF THE CWA FOR ROUGHLY 48 HOURS  
THROUGH THE EARLY WEEK. THE REAL QUESTION IS WHAT DIRECTION DOES  
THE COLORADO LOW TAKE WITH ITS EXIT, AND HOW STRONG WILL IT BE?  
THIS WILL CONTROL THE SNOW TOTALS IN MT BY A WILD MARGIN OF RANGE  
AND ENOUGH POSSIBLE BACKSIDE WIND TO GENERATE A SMALL CHANCE OF  
BLIZZARD CONDITIONS AS WELL. WILL HAVE TO KEEP AN EYE ON THIS  
SYSTEM WITH FURTHER UPDATES TO SEE HOW IT EVOLVES. GAH  
 

 
   
AVIATION
 
 
ISSUED: 2130Z  
 
FLIGHT CATEGORY: VFR FOR KOLF, KSDY, KGDV. IFR/LIFR AT KGGW.  
 
DISCUSSION: MOSTLY CLEAR SKIES ARE EXPECTED ACROSS MOST OF THE  
TERMINALS.  
 
THE EXCEPTION IS KGGW WHICH WILL BE IMPACTED BY LAKE EFFECT  
FREEZING FOG COMING FROM FORT PECK LAKE. FOR MOST OF TODAY, LIFR  
CONDITIONS HAVE PERSISTED AND THIS IS EXPECTED TO CONTINUE THROUGH  
18Z FRIDAY.  
 
WIND: LIGHT AND VARIABLE THROUGH THE CYCLE.  
 
-THOR  
 

 
   
GLASGOW WATCHES/WARNINGS/ADVISORIES
 
 
DENSE FOG ADVISORY UNTIL 11 AM MST FRIDAY FOR CENTRAL AND  
SOUTHERN VALLEY.  
 

 
 

 
 
WEATHER.GOV/GLASGOW  
 
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