FXUS65 KTFX 221648
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
948 AM MST TUE DEC 22 2009
.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 1200Z.
LOW CLOUDS AND AREAS OF DENSE FREEZING FOG REMAIN ENTRENCHED ACROSS
MUCH OF NORTH CENTRAL MONTANA THIS MORNING...SPECIFICALLY AFFECTING
KGTF..KLWT AND KCTB TERMINALS WHERE LIFR AND OCCL IFR CONDITIONS
CONTINUE. IFR CONDITIONS WILL PERSIST AT KHVR WITH OCCL LIFR IF
CIGS/VIS CONTINUE TO LOWER. ALSO ADDED VCFG TO KHLN WHERE WINDS ARE
LIGHT AND DEW POINT SPREADS ARE SMALL BUT AM NOT ANTICIPATING DENSE
FOG TO DEVELOP. AS NORTHERLY WINDS INCREASE...CIGS/VIS SHOULD
IMPROVE SLIGHTLY...HOWEVER PREDOMINANT IFR WITH OCCL MVFR CONDITIONS
ARE EXPECTED. JUST AS CONDITIONS IMPROVE...ANOTHER STORM SYSTEM WILL
MOVE INTO MONTANA BEGINNING THIS AFTERNOON BRINGING WIDESPREAD LIGHT
SNOW FROM NORTH TO SOUTH. LIGHT SNOW IS EXPECTED TO BEGIN EARLY THIS
AFTERNOON AT KCTB AND KHVR...LATE THIS EVENING FOR KGTF..KLWT AND
KHLN AND OVERNIGHT AT KBZN. MOUNTAIN OBSCURATION IS ALSO
ANTICIPATED. SNOW ACCUMULATIONS OF 2 TO 5 INCHES ARE EXPECTED IN THE
PLAINS AND VALLEYS...WITH HIGHER AMOUNTS IN THE MOUNTAINS. BLOWING
AND DRIFTING SNOW IS ALSO POSSIBLE AS NORTHERLY WINDS
INCREASE...THUS KEEPING REDUCED VISIBILITIES TO LESS THAN ONE
QUARTER OF A MILE AT TIMES OVER THE REGION. SNOW WILL TAPER BY
THURSDAY AFTERNOON WITH IMPROVING CONDITIONS ACROSS CENTRAL AND
NORTH-CENTRAL MONTANA. MLS
&&
.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
