Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 290532
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1120 PM MDT SUN JUN 28 2015

.DISCUSSION...
ISOLATED SHOWERS HAVE DIMINISHED ACROSS THE AREA THIS EVENING. THE
CURRENT FORECAST LOOKS ON TARGET, SO NO CHANGES ARE PLANNED. DB

&&

.AVIATION...
UPDATED 0520Z.
VFR CONDITIONS WILL CONTINUE ACROSS THE AREA THROUGH 30/00Z WITH
ONLY PATCHY HIGH CLOUDS. THE HEAT WAVE CONTINUES INTO MONDAY
AFTERNOON...PRODUCING UNUSUALLY HIGH DENSITY ALTITUDES. CLOUD COVER
INCREASES MONDAY AFTERNOON AS SCATTERED THUNDERSTORMS DEVELOP ALONG
THE CONTINENTAL DIVIDE. STORMS MOVE EAST OF THE CONTINENTAL DIVIDE
AROUND 30/00Z AND MAY PRODUCE ERRATIC GUSTY WINDS AT AREA TERMINALS.
PN

&&

.PREV DISCUSSION...
/ISSUED 531 PM MDT SUN JUN 28 2015/
TONIGHT THROUGH TUESDAY...AN UPPER LEVEL RIDGE OF HIGH PRESSURE
WILL CONTINUE TO RESIDE OVER THE REGION THROUGH MONDAY AFTERNOON.
AS A RESULT...VERY WARM/HOT TEMPERATURES WILL CONTINUE DURING THE
DAY...WITH A MILD/WARM NIGHT EXPECTED TONIGHT. ISOLATED
THUNDERSTORMS ARE POSSIBLE THRU THIS EVENING...BUT MOSTLY OVER AND
NEAR THE MOUNTAINS. ON MONDAY...AN UPPER LEVEL DISTURBANCE WILL
MOVE NORTHEAST THRU THE REGION DURING THE AFTERNOON/EVENING HOURS.
EXPECT A BETTER CHANCE FOR STORMS OVER THE REGION...WITH SOME
STORMS BEING STRONG. THE STRONGEST STORMS ARE EXPECTED TO AFFECT
AREAS MAINLY NORTHWEST OF GREAT FALLS. THE MAIN THREAT FROM THE
STRONGER STORMS WILL BE GUSTY WINDS. FOR TUESDAY...THE UPPER LEVEL
RIDGE FLATTENS OUT A BIT OVER CENTRAL MT...RESULTING IN A BIT
LOWER AFTERNOON TEMPERATURES BUT BREEZY CONDITIONS. AFTERNOON
TEMPERATURES WILL STILL BE WELL ABOVE NORMAL ON
TUESDAY...ESPECIALLY OVER THE SOUTHWEST. BRUSDA

TUESDAY NIGHT THROUGH SUNDAY. PERIOD BEGINS WITH COOLER NORTHWEST
FLOW ALOFT AS WEAKENED HIGH PRESSURE RIDGE REMAINS CENTERED ALONG
PACNW COAST.  THAT PATTERN WILL HELP KEEP HIGH TEMPS IN THE MID 80S
WHILE ALSO STEERING A QUICK-MOVING SHORTWAVE TROF AND ACCOMPANYING
SCATTERED SHOWERS AND THUNDERSTORMS FROM SOUTHWEST ALBERTA INTO THE
HILINE AND EASTERN MT AREAS ON WED AFTN/EVE. AS THE TROF EXITS INTO
THE DAKOTAS, THE WESTERN RIDGE WILL BEGIN TO GRADUALLY BUILD BACK
INTO THE NORTHERN ROCKIES. BOTH GFS AND ECMWF MODELS ARE PICKING UP
ON A WEAK SECONDARY TROF SLIDING ALONG THE RIDGE`S EASTERN BOUNDARY
THURS NIGHT THAT COULD BRING ISOLATED THUNDERSTORMS TO THE ROCKY MTN
FRONT AND CENTRAL MOUNTAIN RANGES.  GIVEN THIS DISTURBANCE`S WEAK
STRUCTURE AND SPOTTY MOISTURE, WOULDN`T BE SURPRISED IF SUCCEEDING
MODEL RUNS REMOVE IT IN FAVOR OF DRIER CONDITIONS FROM THE
STRENGTHENING RIDGE.

AFTER A COUPLE OF DAYS WITH MARKED DIFFERENCES IN EXPECTED
CONDITIONS FOR THE UPCOMING HOLIDAY WEEKEND, MODELS ARE CURRENTLY IN
BETTER AGREEMENT FOR THIS PERIOD. DRY AND WARM CONDITIONS NOW
LOOKING MORE LIKELY ACROSS THE REGION ON FRIDAY AS THE RIDGE AXIS
PUSHES THROUGH THE STATE AND INTO SOUTHWEST CANADA.

MIDNIGHT SHIFT FORECASTER NOTED BETTER AGREEMENT IN MODELS REGARDING
HOLIDAY WEEKEND WITH UPPER LEVEL RIDGING AND DRY/WARM CONDITIONS.
HOWEVER, THE 28/12Z GFS MODEL RUN IS NOW TRYING TO BREAK DOWN THE
RIDGE ON SUNDAY (SIMILAR TO BOTH THE 28/00Z AND 28/12Z RUNS OF THE
ECMWF), BRINGING IN MUCH COOLER TEMPERATURES THAN PREVIOUSLY
FORECAST. WITH THIS VOLATILITY IN THE FORECAST, HAVE DECIDED TO
TREND TEMPERATURES DOWN A BIT FOR NOW ON SUNDAY, USING A BLEND OF
THE PREVIOUS FORECAST AND THE NEW NEW MODEL CONSENSUS. WILL NEED TO
MONITOR THIS FOR FUTURE ADJUSTMENTS.
WARANAUSKAS/COULSTON

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  63 102  68  93 /   0  10  30  10
CTB  58 101  59  87 /  10  10  30  10
HLN  69 103  67  96 /   0  20  40  10
BZN  57  98  54  91 /  10  20  30  10
WEY  46  89  49  82 /  10  20  30  20
DLN  60  97  58  89 /  10  30  30  10
HVR  61 104  65  92 /   0  10  20  10
LWT  62  97  64  91 /  10  10  20  10

&&

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

$$

WEATHER.GOV/GREATFALLS


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