906  
FXUS65 KTFX 212259  
AFDTFX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREAT FALLS MT  
458 PM MDT FRI JUL 21 2017  
 
UPDATED AVIATION  
   
SYNOPSIS
 
 
DRY AND BREEZY CONDITIONS PREVAIL TODAY, ALONG WITH AREAS OF SMOKE  
AND HAZE. TEMPERATURES WILL BE CLOSE TO AVERAGE. MOSTLY CLEAR AND  
GRADUALLY WARMER WEATHER CONTINUES INTO THE WEEKEND. A BETTER  
CHANCE OF THUNDERSTORMS MAY RETURN NEXT WEEK.  
 

 
   
DISCUSSION
 
 
REST OF TODAY THROUGH SUNDAY...THE MAIN CONCERN IN THE SHORT TERM IS  
FIRE WEATHER AND RELATED IMPACTS FROM SMOKE. GUSTY WESTERLY WINDS  
CONTINUE THIS AFTERNOON, WITH 20-35 MPH GUSTS COMMON ACROSS MUCH OF  
CENTRAL MT. WINDS HAVE BEEN GUSTY AT TIMES ACROSS SW MT, BUT NOT AS  
STRONG AS FURTHER NORTH. WINDS SHOULD DROP OFF FAIRLY QUICKLY THIS  
EVENING AS WINDS ALOFT DECREASE AND AS THE NOCTURNAL TEMP INVERSION  
SETS IN. RH VALUES HAVE ONCE AGAIN DROPPED INTO THE 8-15 PERCENT  
RANGE AND COMBINED WITH THE GUSTY WINDS MAKES THE RED FLAG WARNING  
VALID, SO NO CHANGE THERE (SEE THE FIRE SECTION BELOW FOR ADDITIONAL  
FIRE WEATHER DETAILS). AS FOR SMOKE IMPACTS, IT VARIES ACROSS THE  
CWA, BUT HAS BEEN DENSE ENOUGH TO REDUCE THE VISIBILITY AT TIMES  
(NOTE THE RECENT OBSERVATION AT DILLON WHERE THE VISIBILITY WAS DOWN  
TO 4 MILES). SMOKE WILL CONTINUE TO PUSH INTO SW MT AND SOUTHERN  
SECTIONS OF CENTRAL MONTANA THROUGH THIS EVENING. TONIGHT, SMOKE MAY  
ALSO MOVE INTO THE AREA FROM FIRES IN CANADA. GIVEN ALL THIS, I KEPT  
A MENTION OF PATCHY SMOKE IN FOR THE ENTIRE AREA OVERNIGHT. THE  
INVERSION TONIGHT MAY ACTUALLY HELP TO LOCK IN THE SMOKE THAT  
ADVECTS IN THIS AFTERNOON.  
 
FOR THE REST OF THE WEEKEND, RIDGING BUILDS BACK IN WITH STEADILY  
WARMING TEMPERATURES. OTHER THAN CONTINUED SMOKE AND HEAT IMPACTS,  
SIGNIFICANT WEATHER IMPACTS ARE NOT EXPECTED. MARTIN  
 
SUNDAY NIGHT THROUGH FRIDAY...AS WE GET INTO THE BEGINNING OF NEXT  
WEEK, MODELS ARE IN GOOD AGREEMENT IN A BREAK IN THE LONG DURATION  
WEATHER PATTERN. BEGINNING WITH MONDAY AND TUESDAY, THE UPPER LEVEL  
PATTERN WILL FEATURE A QUICK MOVING SHORTWAVE TO OUR NORTH, COMBINED  
WITH WEAK CUT OFF CLOSED UPPER LOW SPINNING OF THE CALIFORNIA  
COASTLINE. AT THE SURFACE, A COLD FRONT WILL SWING THROUGH THE AREA  
DURING EARLY HOURS ON MONDAY, FOLLOWED BY GUSTY WINDS DURING THE DAY  
WITH ONLY AN ISOLATED CHANCE AT A SHOWER OR STORM. HOWEVER BY  
TUESDAY, THE AFOREMENTIONED CLOSED UPPER LEVEL LOW WILL BEGIN TO GET  
ABSORBED IN THE WESTERLIES THANKS TO AN APPROACHING TROUGH OFF THE  
COAST OF BRITISH COLUMBIA. AT THE SURFACE, IT IS LIKELY SEVERAL  
CLUSTERS OR WAVES OF SHOWERS AND THUNDERSTORMS WILL DEVELOP WELL TO  
OUR WEST, DELIVERING PERIODS OF SHOWERS AND STORMS TO THE FORECAST  
AREA GIVEN PERSISTENT SW TO NE FLOW ALOFT, AND INCREASING MOISTURE.  
DETAILS ON EXACT TIMING AND HOW MUCH RAIN THESE SHOWERS AND STORMS  
WILL PRODUCE IS STILL IN QUESTION. ADDITIONALLY, SOME OF THE STORMS  
MAY BE STRONG TO SEVERE AT TIMES TUESDAY AFTERNOON AND EVENING GIVEN  
MODEST SURFACE BASED INSTABILITY AND WEAK, BUT NOTABLE SHEAR ALOFT.  
 
THIS ACTIVE PATTERN WILL TRANSITION INTO WEDNESDAY AND THURSDAY AS  
WHAT'S LEFT OF THE SHORTWAVE MOVES IN DELIVERING MORE ROUNDS OF  
SHOWERS AND STORMS. I'VE KEPT POP CHANCES ON THE HIGHER END OF MOST  
MODEL GUIDANCE AS PRECIPITATION AT THIS TIME LOOKS TO BE WIDESPREAD,  
WITH BETTER CHANCES OVER CENTRAL AND SOUTHERN AREAS. THE EXCITING  
NEWS IS THIS WILL BE HELPFUL GIVEN THE DROUGHT SITUATION AREAWIDE.  
HOWEVER, FIRE WEATHER CONDITIONS WILL NEED TO BE MONITORED CLOSELY  
WITH INCREASED LIGHTNING ACTIVITY. BY FRIDAY, WE RETURN TO A ZONAL  
PATTERN ALOFT WITH SLIGHTLY DRIER CONDITIONS RETURNING. KLG  
 

 
   
AVIATION
 
 
UPDATED 2258Z.  
 
MAINLY VFR EXPECTED NEXT 24-HOURS AS HIGH PRESSURE RIDGING ALOFT  
PREVAILS. BREEZY WESTERLY TO NORTHWESTERLY SURFACE WINDS OVER NORTH-  
CENTRAL MT AND PORTIONS OF SOUTHWEST MT SHOULD EASE BETWEEN 01Z AND  
03Z/SAT. PATCHY SMOKE FROM WILDFIRES WILL PERSIST, BUT CONFIDENCE IN  
SMOKE REDUCING VSBY TO MVFR OR WORSE AT ANY TAF SITE IS LOW.  
JASZKA  
 

 
   
FIRE WEATHER
 
 
CRITICAL OR NEAR-CRITICAL FIRE WEATHER CONDITIONS CONTINUE TO BE  
EXPERIENCED ACROSS A LARGE PORTION OF OUR FIRE WEATHER ZONES AT THIS  
TIME. EVEN IN AREAS WHERE THE WIND IS MORE MARGINAL, THE RH HAS ONCE  
AGAIN FALLEN TO VERY LOW LEVELS, IN SOME CASES BELOW 10 PERCENT.  
CRITICAL FIRE WEATHER CONDITIONS SHOULD CONTINUE INTO EARLY THIS  
EVENING, BUT A TEMP INVERSION SHOULD ALLOW A QUICK DECREASE IN THE  
WINDS AFTER 2000 MDT. RH RECOVERY LOOKS TO BE A BIT BETTER OVER THE  
WEEKEND COMPARED TO LAST NIGHT, BUT STILL NOT GREAT. TEMPERATURES  
STEADILY WARM OVER THE WEEKEND, BUT THE WIND DOES NOT LOOK TO BE  
NEARLY AS GUSTY AS THE PAST COUPLE OF DAYS. ALTHOUGH, SUNDAY COULD  
BE AT LEAST AN ELEVATED DAY WITH A SLIGHT INCREASE IN SW WINDS  
COMBINED WITH LOWER ELEVATIONS WARMING INTO THE 90S. IT IS WORTH  
NOTING THAT CONFIDENCE CONTINUES TO INCREASE IN A PATTERN CHANGE  
NEXT WEEK WITH A GREATER POTENTIAL OF WET THUNDERSTORMS (ALTHOUGH,  
STILL SCATTERED IN COVERAGE). LIGHTNING ACTIVITY WILL INCREASE AS  
WELL, SO PERHAPS A MIXED BLESSING. MARTIN  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
GTF 53 88 57 96 / 0 0 0 0  
CTB 50 85 54 90 / 0 0 0 0  
HLN 54 90 59 96 / 0 0 0 0  
BZN 48 87 52 94 / 0 0 0 0  
WEY 43 80 40 84 / 0 0 0 10  
DLN 49 86 51 91 / 0 0 0 0  
HVR 54 90 58 97 / 0 0 0 0  
LWT 52 85 56 94 / 0 0 0 0  
 

 
   
TFX WATCHES/WARNINGS/ADVISORIES
 
 
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING CENTRAL AND EASTERN  
LEWIS AND CLARK NATIONAL FOREST AREAS...CHOUTEAU AND FERGUS  
COUNTIES...EASTERN GLACIER/TOOLE/CENTRAL/EASTERN  
PONDERA/LIBERTY...HELENA AND TOWNSEND RANGER DISTRICTS OF THE  
HELENA NATIONAL FOREST...HILL AND BLAINE COUNTIES...LEWIS AND  
CLARK NATIONAL FOREST ROCKY MOUNTAIN DISTRICT-ROCKY MOUNTAIN  
FRONT...LINCOLN RANGER DISTRICT OF THE HELENA NATIONAL FOREST.  
 

 
 

 
 
WEATHER.GOV/GREATFALLS  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab MT Page Main Text Page