Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 300545
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1140 PM MDT MON JUN 29 2015

AVIATION SECTION UPDATED

.UPDATED...

HAVE RECEIVED REPORTS OF DENSE SMOKE OVER PORTIONS OF BLAINE COUNTY
WITH VISIBILITY OF 1/2 TO 1 MILE. SMOKE IS DRIFTING IN FROM THE EAST
AND SHOULD CONTINUE TO ADVANCE INTO HILL COUNTY INCLUDING HAVRE
TONIGHT. A COLD FRONT WILL CROSS THE REGION OVERNIGHT CLEARING SMOKE
BY EARLY MORNING. HAVE ISSUED A LATE UPDATE TO ADD AREAS OF SMOKE TO
THE WEATHER GRIDS. PN

.PREVIOUS UPDATE... SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A
WEATHER DISTURBANCE ALOFT THAT WAS OVER CENTRAL MT EARLIER THIS
EVENING HAVE MOVED OUT OF THE EASTERN PLAINS WITH THE EXCEPTION OF
EASTERN FERGUS COUNTY AS OF 9 PM. ANOTHER WEATHER DISTURBANCE ALOFT
WILL BE MOVING THROUGH THE CENTRAL AND NORTHERN ZONES LATER TONIGHT.
AN AREA OF SHOWERS AND THUNDERSTORMS AHEAD OF THE LATTER DISTURBANCE
WAS AFFECTING NORTHERN PORTIONS OF SOUTHWEST MONTANA NORTH TO
EASTERN TETON COUNTY. THIS PRECIPITATION WILL BE MOVING NORTHEAST
THE REMAINDER OF TONIGHT AND DO NOT EXPECT A LOT OF DISSIPATION AS
SOME GUIDANCE SUGGESTS. THEREFORE HAVE INCREASED THE CHANCES OF
PRECIPITATION SIGNIFICANTLY FROM THE PREVIOUS FORECAST FOR CENTRAL
MONTANA FOR THE AFTER MIDNIGHT PERIOD. THERE SHOULD ALSO BE ENOUGH
INSTABILITY ALOFT FOR A FEW THUNDERSTORMS AFTER MIDNIGHT AS WELL.
BLANK

&&

.AVIATION...
UPDATED 0540Z. WEAK COOL FRONT CONTINUES TO MAKE ITS WAY THROUGH
CENTRAL MT TONIGHT WITH SEVERAL BANDS OF SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS.  CONVECTIVE ACTIVITY IS SHOWING SOME INITIAL SIGNS OF
DISSIPATING BUT WILL LINGER AROUND KHVR/KLWT/KGTF/KBZN UNTIL 07-09Z.
ALSO, CURRENT EASTERLY WINDS AT KHVR ARE CAUSING WILDLAND FIRE SMOKE
FROM CANADA TO DROP VISIBILITIES INTO IFR CATEGORY, BUT SHOULD SEE
IMPROVEMENT AFTER 07-08Z AS WINDS SHIFT TO WEST-SOUTHWEST BEHIND THE
FRONT.  WILL SEE GRADUAL DECREASE IN CLOUD COVER BY SUNRISE TUES AS
DRY AIRMASS MOVES IN FROM THE WEST.  WESTERLY SURFACE WINDS WILL BE
BREEZY TUES AFTN ALONG A KHLN-TO-KLWT LINE AND NORTH TO US/CAN
BORDER WITH GUSTS 25-30 KTS.
WARANAUSKAS

&&

.FIRE WEATHER...
LATE TONIGHT INTO TUESDAY MORNING, A COLD FRONT WILL MOVE EAST
THROUGH THE DISTRICTS, WHICH WILL BRING BREEZY WEST WINDS TO MUCH
OF THE AREA. GUSTS COULD REACH 40 MPH AT TIMES, BUT THE RELATIVELY
COOLER AIR BEHIND THE FRONT WILL HELP KEEP RELATIVE HUMIDITY ABOVE
20 PERCENT FOR MOST OF THE AREA. WILL THEREFORE HOLD OFF ON ANY
FIRE WEATHER HIGHLIGHTS FOR TUESDAY. COULSTON

&&

.PREV DISCUSSION...
/ISSUED 612 PM MDT MON JUN 29 2015/

TONIGHT THROUGH WEDNESDAY...TEMPERATURES TODAY ARE NOT GETTING
QUITE AS HOT AS YESTERDAY ACROSS MOST OF THE FORECAST AREA DUE TO
INCREASING MID AND HIGH LEVEL CLOUDINESS...BUT IT IS STILL QUITE
HOT AND A FEW RECORDS COULD STILL FALL. SCATTERED SHOWERS AND
THUNDERSTORMS HAVE ALSO DEVELOPED ALREADY THIS AFTERNOON WEST OF
INTERSTATE 15. ALTHOUGH SHOWERS DO NOT APPEAR TO BE REACHING THE
GROUND YET NORTH OF HELENA, THEY ARE REACHING THE GROUND SOUTH OF
HELENA TO THE IDAHO BORDER, BUT WITH LOTS OF LIGHTNING. AM STILL
THINKING THAT WITH PRECIPITABLE WATER VALUES IN EXCESS OF 1.25
INCHES ACROSS MUCH OF THE AREA, THERE SHOULD BE AT LEAST A MIX OF
WET AND DRY THUNDERSTORMS ACROSS THE ENTIRE FORECAST AREA THROUGH
THE EVENING, ALONG WITH GUSTY ERRATIC WINDS DUE TO THE DRY LOWER
LEVELS. ANY HAIL THAT COMES OUT OF THESE STORMS WILL LIKELY BE
SMALL DUE TO MELTING AS STONES FALL THROUGH THE WARM DRY AIR. THE
SHORTWAVE TROUGH RESPONSIBLE FOR THESE STORMS WILL MOVE EAST
THROUGH THE AREA LATE TONIGHT INTO TUESDAY, WHICH WILL GENERALLY
USHER IN DRIER AND SLIGHTLY COOLER AIR (HIGHS IN THE MID 80S TO
LOWER 90S), ALONG WITH INCREASING WESTERLY WINDS ALOFT. THIS
SHOULD TRANSLATE TO GUSTY WESTERLY WINDS FOR MOST OF THE AREA ON
TUESDAY, ESPECIALLY OVER THE PLAINS OF NORTH CENTRAL MONTANA,
WHERE 15 TO 20 MPH WINDS WITH GUSTS OF 30 TO 40 MPH WILL BE
COMMON. SOME GUSTS MAY EXCEED 50 MPH AT TIMES ALONG THE ROCKY
MOUNTAIN FRONT. THERE SHOULD ALSO BE ENOUGH INSTABILITY WITH THE
PASSAGE OF THE SHORTWAVE TO BRING A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS TO THE HI-LINE AND TO SOUTHWEST MONTANA. A SHORTWAVE
RIDGE OF HIGH PRESSURE WILL MOVE INTO THE AREA TUESDAY NIGHT,
WHICH WILL CAUSE THE WINDS AND SHOWERS/STORMS TO DECREASE. ANOTHER
WEAK DISTURBANCE WILL MOVE ALONG THE HI-LINE ON WEDNESDAY,
BRINGING A SLIGHT CHANCE OF SHOWERS/STORMS THERE ONCE AGAIN.
TEMPERATURES WILL ONLY COOL SLIGHTLY FROM TUESDAY TO WEDNESDAY,
WITH WEDNESDAY`S HIGHS GETTING INTO THE 80S. OVERNIGHT LOWS WILL
REMAIN MILD.

WEDNESDAY NIGHT THROUGH MONDAY...SCATTERED THUNDERSTORMS WILL
LINGER OVER EASTERN PARTS OF THE HILINE WED NIGHT AS WEAK
SHORTWAVE TROF MOVES ALONG THE US/CAN BORDER, WHILE REST OF OUR
REGION REMAINS RAIN-FREE. BROAD HIGH PRESSURE RIDGE THAT WAS
WEAKENED BY PASSAGE OF SHORTWAVES EARLIER IN THE WEEK STARTS TO
REDEVELOP OVER THE NORTHERN ROCKIES ON THURS. THIS WILL BRING DRY
CONDITIONS AND A RETURN OF HIGH TEMPS IN THE MID 80S TO LOW 90S ON
THURS AND MID-UPPER 90S ON FRI. BOTH GFS AND ECMWF MODELS NOW
INDICATE ARRIVAL OF THE NEXT CANADIAN TROF AND SURFACE COLD FRONT
ON SAT. NEITHER MODEL IS DEPICTING ANY PRECIPITATION ACCOMPANYING
INITIAL FRONTAL PASSAGE THROUGH THE HILINE AND CENTRAL COUNTIES,
BUT THE ECMWF DOES EVENTUALLY GENERATE ISOLATED THUNDERSTORMS FOR
LIBERTY/HILL/BLAINE COUNTY AREAS SAT NIGHT. A DRY WEST-TO-
NORTHWEST FLOW PATTERN ALOFT FOLLOWS ON SUN AS THE HIGH PRESSURE
RIDGE IS FLATTENED AGAIN AND NOTABLY, DRIFTS INTO THE FOUR CORNERS
AREA. THIS RE-POSITIONING WILL IMPACT OUR REGION ON MON AS A BROAD
PLUME OF MONSOONAL MOISTURE WORKS ITS WAY UP THE WEST SIDE OF THE
RIDGE, BRINGING SCATTERED THUNDERSTORMS MON AFTN/EVE.
WARANAUSKAS

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  66  92  58  89 /  60  10  10  10
CTB  59  87  55  84 /  20  10  10  20
HLN  66  96  61  94 /  70  10  10   0
BZN  55  92  50  90 /  50  20  10   0
WEY  48  83  42  82 /  30  30  10  10
DLN  58  90  54  89 /  50  10  10   0
HVR  64  92  57  88 /  30  10  10  30
LWT  63  90  58  86 /  50  10  10  10

&&

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

$$

WEATHER.GOV/GREATFALLS



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