000
FXUS65 KTFX 172031
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
231 PM MDT SAT MAY 17 2008
.DISCUSSION...
TONIGHT THROUGH MONDAY...UPPER LEVEL RIDGE CONTINUES TO BE THE
DOMINANT WEATHER FEATURE IN THE SHORT TERM. THE DRY AND WARM
CONDITIONS UNDER THE RIDGE WILL MAINTAIN HYDROLOGIC AND FIRE WEATHER
CONCERNS THROUGH SUNDAY (SEE HYDRO AND FIRE WX PORTIONS OF AFD FOR
DETAILS). AFTER VERY MILD TEMPERATURES TONIGHT WILL SEE ANOTHER WARM
DAY SUNDAY WITH NEAR RECORD HIGHS IN A NUMBER OF LOCATIONS. SUNDAY
WILL ALSO BE QUITE BREEZY ACROSS THE REGION DUE TO A TIGHTENING
SURFACE GRADIENT. BY SUNDAY NIGHT THE RIDGE WILL BEGIN TO FLATTEN AS
A SERIES OF WEAK DISTURBANCES MOVE OVER THE TOP OF IT. PUT IN A
SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS ALONG THE HI-LINE LATE
SUNDAY NIGHT WITH ONE OF THOSE DISTURBANCES. WITH THE RIDGE
FLATTENING EXPECT COOLER TEMPERATURES ON MONDAY...BUT STILL ABOUT 10
DEGREES ABOVE SEASONAL NORMALS. THOMSON
MONDAY NIGHT THROUGH THURSDAY NIGHT...EXPECT A MAJOR CHANGE IN THE
WEATHER PATTERN DURING THIS PERIOD...AS A RETURN TO WETTER AND
COOLER CONDITIONS DEVELOP. A PACIFIC COLD FRONT WILL MOVE THROUGH
THE REGION ON TUESDAY...BRINGING IN COOLER AIR AND A CHANCE FOR
SHOWERS/THUNDERSTORMS ACROSS THE REGION AS THE COLD FRONT MOVES
THROUGH. EXPECT WINDY CONDITIONS AND MILD TEMPERATURES AHEAD OF THE
FRONT...BUT GRADUALLY COOLING TEMPERATURES ARE EXPECTED BEHIND THE
FRONT. THE CHANCES FOR SHOWERS CONTINUE ON WEDNESDAY...ESPECIALLY
OVER SOUTHWEST MONTANA. A STRONGER AND SLOW MOVING AREA OF LOW
PRESSURE WILL MOVE THROUGH THE REGION FROM WEDNESDAY NIGHT THROUGH
THURSDAY NIGHT. EXPECT INCREASING CHANCES FOR PRECIP...WITH PRECIP
CHANCES BECOMING LIKELY IN THE MOUNTAINS. TEMPERATURES WILL COOL TO
BELOW SEASONAL NORMALS...WITH AFTERNOON HIGHS GENERALLY 10 TO 15
DEGREES BELOW NORMAL FOR WEDNESDAY AND THURSDAY. ADDITIONALLY...SNOW
LEVELS WILL CONTINUE TO FALL...LOWERING TO NEAR 6000 FEET AT TIMES
DURING THE OVERNIGHT HOURS. BRUSDA
FRIDAY AND SATURDAY...LATEST LONG RANGE FORECAST MODELS ARE IN
REASONABLY GOOD AGREEMENT THROUGH THE EXTENDED PERIODS. A DEEP LOW
PRESSURE IS EXPECTED TO REMAIN OVER THE REGION CAUSING SCATTERED
SHOWERS AND COOLER BELOW SEASONAL TEMPERATURES FOR MUCH OF THE
STATE. SAUCIER
&&
.AVIATION...
UPDATED 1730Z.
EXPECT VFR CONDITIONS. THERE WILL BE VARIABLE CLOUDINESS ABOVE 20000
MSL THROUGH 18Z SUNDAY. THE MAIN FORECASTING CHALLENGE WILL BE THE
WINDS. FOR THIS AFTERNOON AM NOT REAL CONFIDENT OF WIND DIRECTIONS
UNTIL LATE AFTERNOON WHEN THEY SHOULD BE WEST TO NORTHWEST. SPEEDS
SHOULD GENERALLY BE LESS THAN 15 KTS. FOR TONIGHT WINDS SHOULD DO
THEIR TYPICAL DROP OFF BUT AGAIN AM NOT REAL CONFIDENT OF WIND
DIRECTIONS. AN EXCEPTION TO THE DROP OFF IN WIND SPEEDS IS AT KCTB
AND KGTF WHERE WINDS MIGHT NOT DROP OFF HARDLY AT ALL TONIGHT.
GUIDANCE SUGGESTS WINDS WILL REALLY PICK UP SUNDAY MORNING OVER THE
PLAINS. EXPECT GUSTY WEST TO NORTHWEST WINDS OF 20 TO POSSIBLY 30
KTS BY 18Z. BLANK
&&
.FIRE WEATHER...
A TIGHTENING SURFACE PRESSURE GRADIENT WILL CAUSE BREEZY AND GUSTY
WESTERLY WINDS ON SUNDAY. IN ADDITION...AFTERNOON RELATIVE
HUMIDITIES WILL DROP BELOW 20 PERCENT OVER MUCH OF THE PLAINS OF
NORTH CENTRAL AND CENTRAL MONTANA. WHILE FUELS ARE STILL GREENING UP
LATEST FIRE DANGER IS APPROACHING THE HIGH LEVEL AND FEEL THERE IS A
FIRE WEATHER THREAT. WILL ISSUE A FIRE WEATHER WATCH FROM 9 AM TO 9
PM SUNDAY FOR FIRE ZONES 112...113...114...115 AND 117. THE
MOUNTAINS OF ZONES 114 AND 117 SHOULD REMAIN ABOVE 20 PERCENT RH.
THOMSON
&&
.HYDROLOGY...
WITH NEAR RECORD HIGH TEMPERATURES...AND VERY MILD OVERNIGHT
TEMPERATURES...RAPID MOUNTAIN SNOW MELT WILL CONTINUE THROUGH
SUNDAY. THE TWO MEDICINE RIVER AND BADGER CREEK IN SOUTH CENTRAL
GLACIER COUNTY ARE ALREADY APPROACHING FLOOD STAGES BUT ARE RISING
A LITTLE SLOWER THAN EARLIER EXPECTED...WILL EXTEND THE SMALL
STREAM FLOOD ADVISORY THERE THROUGH 4 AM MONDAY. A FLOOD WATCH
REMAINS IN EFFECT FOR THE ROCKY MOUNTAIN FRONT...SOUTHERN PORTIONS
OF CENTRAL MONTANA...AND ALL OF SOUTHWEST MONTANA THROUGH SUNDAY
AFTERNOON. THE MAJOR RIVERS WILL ALSO RISE BUT DO NOT ANTICIPATE
ANY OF THEM TO FLOOD AT THIS TIME. THOMSON
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 58 85 53 76 / 0 0 0 0
CTB 56 81 48 74 / 0 0 10 10
HLN 59 87 56 81 / 0 0 0 0
BZN 48 88 49 79 / 0 0 0 0
WEY 40 74 40 70 / 0 0 0 0
DLN 49 85 46 81 / 0 0 0 0
HVR 52 84 48 77 / 0 0 20 10
LWT 47 82 48 75 / 0 0 0 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH THROUGH SUNDAY AFTERNOON FOR MTZ008-009-012-014-015-
048-050-052>055.
FIRE WEATHER WATCH FROM SUNDAY MORNING THROUGH SUNDAY EVENING
FOR MTZ112>115-117.
&&
$$
SHORT TERM...THOMSON
LONG TERM...BRUSDA/SAUCIER
AVIATION...BLANK
WEATHER.GOV/GREATFALLS
