FXUS65 KTFX 221759
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1100 AM MST TUE DEC 22 2009
UPDATED AVIATION
.UPDATE...
INHERITED FORECAST WAS IN PRETTY GOOD SHAPE. FOG SITUATION HAS
IMPROVED OVER MOST OF THE AREA BUT VISIBILITIES CONTINUE NEAR OR
BELOW A QUARTER OF A MILE AT LEWISTOWN AND GREAT FALLS AND LOOKING
AT WEB CAMERAS IT LOOKS LIKE DENSE FOG IS ONGOING AT OTHER AREAS
IN CENTRAL MONTANA. SO WILL CANCEL THE DENSE FOG ADVISORY EXCEPT
OVER CASCADE/JUDITH BASIN/FERGUS COUNTIES AND FOR THOSE AREAS WILL
EXTEND THE ADVISORY INTO THE AFTERNOON. COOL AIR HAS SPREAD INTO
FERGUS COUNTY AND DO NOT SEE IT MOVING OUT OF THAT AREA SO WILL
LOWER HIGH TEMPERATURES FOR FERGUS COUNTY FOR TODAY. WINTER
WEATHER ADVISORY STILL LOOKS ON TRACK. BLANK
&&
.AVIATION...
UPDATED 1800Z.
LOW CLOUDS AND AREAS OF DENSE FREEZING FOG REMAIN ACROSS PORTIONS OF
CENTRAL MONTANA THIS MORNING BUT ARE BEGINNING TO SHOW SIGNS OF
IMPROVING. SPECIFICALLY KGTF AND KLWT TERMINALS ARE THE HARDEST HIT
WHERE IFR AND OCCASIONAL LIFR CONDITIONS CONTINUE. AS NORTHERLY
WINDS INCREASE SO SHOULD CIGS/VIS AT CURRENTLY LOW SITES. THE NEXT
WINTER STORM IS HEADED INTO MONTANA THIS AFTERNOON THOUGH...BRINGING
WIDESPREAD SNOW FROM NORTH TO SOUTH. LIGHT SNOW IS EXPECTED TO BEGIN
THIS AFTERNOON AT KCTB AND KHVR...AND LATER THIS EVENING FOR THE
REST. CONDITIONS WILL ONCE AGAIN DROP TO MVFR AND POSSIBLY IFR WITH
MOUNTAIN OBSCURATION PRETTY MUCH A GUARANTEE. SNOW ACCUMULATIONS OF
2 TO 5 INCHES ARE EXPECTED IN THE PLAINS AND VALLEYS...WITH HIGHER
AMOUNTS IN THE MOUNTAINS. DRIFTING SNOW IS LIKELY AS NORTHERLY WINDS
INCREASE BUT WINDS SHOULD NOT BE VERY STRONG SO VISIBILITIES SHOULD
MOSTLY BE AFFECTED BY SNOW AND LOW CLOUDS. EXPECT VIS LESS THAN A
MILE AT TIMES OVER THE REGION. SNOW WILL END THURSDAY AFTERNOON.
&&
.PREV DISCUSSION...
/ISSUED 515 AM MST TUE DEC 22 2009/
TODAY THROUGH THURSDAY...COMPLICATED WEATHER PATTERN WILL CONTINUE
TO CAUSE PROBLEMS ACROSS THE REGION THROUGH MID-WEEK. LOW CLOUDS
AND AREAS OF FOG REMAIN ENTRENCHED ACROSS MUCH OF NORTH CENTRAL
MONTANA THIS MORNING. ALTHOUGH WIDESPREAD DENSE FOG HAS GENERALLY
DISSIPATED IT APPEARS THAT AREAS OF DENSE FOG COULD STILL PLAGUE
THE REGION THROUGH THE MORNING HOURS. HAD EARLIER CONSIDERED
DROPPING THE DENSE FOG ADVISORY BUT DECIDED IT WOULD BE PRUDENT TO
ALLOW IT TO CONTINUE. MOISTURE WILL CONTINUE TO STREAM OVER THE
ARCTIC AIRMASS AND IS EXPECTED TO SQUEEZE OUT SCATTERED SNOW
SHOWERS THIS MORNING. AS THE NORTHERLY SURFACE WINDS INCREASE AND
UPSLOPE FLOW DEVELOPS ALONG THE NORTH SLOPES OF THE ISLAND RANGES
IT APPEARS THAT NUMEROUS SNOW SHOWERS COULD DEVELOP ACROSS CENTRAL
MONTANA THIS AFTERNOON. HOWEVER... SNOW ACCUMULATIONS ARE EXPECTED
TO BE GENERALLY LIGHT. A MORE WIDESPREAD AND HEAVIER SNOW EVENT
WILL TAKE SHAPE OVERNIGHT AS AN UPPER LEVEL TROUGH SWEEPS ACROSS
THE NORTHERN ROCKY MOUNTAINS AND DRAGS AN ARCTIC FRONT INTO NORTH
CENTRAL MONTANA. SNOW WILL DEVELOP IN MY FAR NORTHWEST ZONES THIS
EVENING AND SPREADS ACROSS ALL OF CENTRAL MONTANA BY
MORNING...BEFORE QUICKLY EXITING THE FORECAST AREA WEDNESDAY
AFTERNOON. WILL ISSUE A WINTER WEATHER ADVISORY FOR SNOW FOR ALL
OF NORTH CENTRAL AND CENTRAL MONTANA FOR TONIGHT AND WEDNESDAY.
THE CHANCE FOR WIDESPREAD PRECIPITATION AND ADVISORY CRITERIA SNOW
AMOUNTS IN SOUTHWEST MONTANA DOES NOT APPEAR FAVORABLE FOR
HIGHLIGHTS AT THIS TIME. THE ARCTIC AIR WILL REMAIN OVER THE
FORECAST AREA WEDNESDAY NIGHT AS SKIES CLEAR AND TEMPERATURES DROP
BELOW ZERO ONCE AGAIN. HOWEVER...THIS OUTBREAK WILL NOT BE AS COLD
AS THOSE SEEN EARLIER THIS MONTH. ON THURSDAY THE ARCTIC AIRMASS
IS EXPECTED TO BEGIN MOVING EAST WITH WINDS SHIFTING TO THE WEST
AND SOUTHWEST ACROSS WESTERN PORTIONS OF MY FORECAST AREA AND
TEMPERATURES WARMING BACK INTO THE TEENS ABOVE ZERO. MPJ
CHRISTMAS EVE THROUGH TUESDAY...AN UPPER-LEVEL RIDGE OF HIGH
PRESSURE BEGINS TO BUILD OVER THE PACIFIC NORTHWEST ON CHRISTMAS DAY
WITH DRY NORTHERLY FLOW AND MODERATING TEMPERATURES. OVERALL...A
QUIETER PATTERN IS ANTICIPATED FOR THE FORECAST PERIOD WITH THE
STRONG UPPER RIDGE PERSISTING OVER THE WESTERN U.S. THROUGH THE
HOLIDAY WEEKEND. THOUGH TEMPERATURES WILL TREND TOWARDS AVERAGE...A
FRESH SNOWPACK MAY STILL KEEP READINGS AROUND TO SLIGHTLY BELOW
SEASONAL AVERAGES. RIDGE AXIS WILL MOVE EAST BY SUNDAY WITH WESTERLY
FLOW DEVELOPING. DRY CONDITIONS ARE EXPECTED TO CONTINUE THROUGH
MONDAY...WITH INCREASING PACIFIC MOISTURE BY MONDAY NIGHT INTO
TUESDAY AS OUR NEXT SHORTWAVE APPROACHES. MLS
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 27 5 9 -6 / 60 80 80 10
CTB 20 0 7 -11 / 50 90 40 10
HLN 30 13 15 -6 / 50 70 70 10
BZN 34 15 21 -7 / 40 60 70 20
WEY 31 9 22 -11 / 60 50 80 30
DLN 33 14 24 -6 / 70 50 60 10
HVR 20 4 9 -13 / 40 80 80 10
LWT 31 7 9 -10 / 40 80 80 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 11 AM MST
WEDNESDAY FOR EASTERN TETON...SOUTHERN ROCKY MOUNTAIN FRONT.
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 5 PM MST
WEDNESDAY FOR BLAINE...CASCADE...CHOUTEAU...FERGUS...HILL...
JUDITH BASIN...LIBERTY...MEAGHER.
DENSE FOG ADVISORY UNTIL 3 PM MST THIS AFTERNOON FOR CASCADE...
FERGUS...JUDITH BASIN.
WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 11 AM MST
WEDNESDAY FOR EASTERN GLACIER...EASTERN PONDERA...NORTHERN ROCKY
MOUNTAIN FRONT...TOOLE.
&&
$$
SHORT TERM...BLANK
LONG TERM...GUSTAFSON
AVIATION...GUSTAFSON
WEATHER.GOV/GREATFALLS
