Area Forecast Discussion
Issued by NWS Great Falls, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KTFX 292058
AFDTFX

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

.DISCUSSION...

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

&&

.AVIATION...

UPDATED 1747Z.

AN UPPER LEVEL HIGH PRESSURE RIDGE REMAINS OVER THE AREA BUT AN
UPPER LEVEL SHORTWAVE WILL MOVE INTO THIS RIDGE AND CAUSE
THUNDERSTORMS OVER THE ROCKIES LATE THIS AFTERNOON AND EVENING.
THESE STORMS WILL MOVE EAST WITH THE SHORTWAVE AND BRING A CHANCE OF
THUNDERSTORMS TO CENTRAL AND SOUTHWEST MONTANA DURING THE NIGHT. THE
MAIN THREAT WITH THESE STORMS WILL BE ERRATIC AND GUSTY WINDS.
BREEZY CONDITIONS WILL DEVELOP ACROSS THE REGION TUESDAY AS THE
SHORTWAVE MOVES EAST. WIDESPREAD WEST WINDS 15-20 KTS WITH HIGHER
AFTERNOON GUSTS ARE EXPECTED.

&&

.FIRE WEATHER...
SCATTERED THUNDERSTORMS WILL SPREAD OVER THE FIRE DISTRICTS THIS
EVENING. THE AIRMASS IS HOT AND DRY, WHICH WILL CAUSE GUSTY
ERRATIC WINDS, BUT HIGH PRECIPITABLE WATER VALUES COULD BRING
BRIEF HEAVY RAIN AT TIMES. THIS MIX OF WET AND DRY THUNDERSTORMS
WILL INCREASE THE RISK OF FIRE STARTS, BUT WILL HOLD OFF ON FIRE
WEATHER HIGHLIGHTS, AS THE RISK FOR RAPID SPREAD IS LOW DUE TO THE
POTENTIAL FOR WET STORMS.

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 AS WELL.
COULSTON

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  66  92  58  89 /  40  10  10  10
CTB  59  87  55  84 /  50  10  10  20
HLN  66  96  61  94 /  50  10  10   0
BZN  55  92  50  90 /  30  20  10   0
WEY  48  83  42  82 /  20  30  10  10
DLN  58  90  54  89 /  40  10  10   0
HVR  64  92  57  88 /  30  10  10  30
LWT  63  90  58  86 /  20  10  10  10

&&

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

$$

WEATHER.GOV/GREATFALLS


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.