FXUS65 KBYZ 230416
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
916 PM MST TUE DEC 22 2009
.SHORT TERM...VALID FOR WED AND THU...
PUSHED OUT A QUICK UPDATE THIS EVENING TO ACCOUNT FOR MORE
WIDESPREAD FREEZING DRIZZLE ISSUES. THE DRIZZLE HAS NOW PERSISTED
LONG ENOUGH IN MANY AREAS THAT A THIN ENOUGH GLAZE WAS DEVELOPING
TO PRODUCE SLICK ROADWAYS OVER THE PAST HOUR IN MANY AREAS. HAVE GONE
AHEAD AND STARTED THE WINTER WEATHER ADVISORY AT CURRENT TIME TO
INCORPORATE THE FREEZING DRIZZLE ISSUES AND DETERIORATING TRAVEL
CONDITIONS A BIT SOONER. CLOUDS/FOG LAYER REMAINING WARM ENOUGH FOR
SUPERCOOLED WATER DROPLETS AS DEEPER MOISTURE AND SATURATION LAYER
HAS NOT TAPPED COLD ENOUGH AIR YET FOR SNOW CRYSTALS TO FORM. A DEEPER
SATURATION COLUMN SHOULD DEVELOP AFTER MIDNIGHT AND BEGIN CHANGING
THE FREEZING PRECIP OVER TO SNOW. REST OF THE FORECAST STILL
APPEARS ON TRACK. A PERIOD OF DECENT SNOWFALL SHOULD PROGRESS
ACROSS THE REGION FROM NORTHWEST TO SOUTHEAST WITH FORCING AHEAD
OF STRONG SHORT WAVE ENERGY DROPPING SOUTH ACROSS THE REGION. THE
EVENT SHOULD BE SHORT LIVED AS OVERALL DOWNSLOPE PATTERN PREVAILS
BEHIND THE SYSTEM. A QUICK 2-5 INCHES OF SNOW STILL LOOKS
REASONABLE. SOME BLOWING AND DRIFTING SNOW CONCERNS WILL PERSIST
INTO WEDNESDAY NIGHT FOR THE EASTERN HALF OF THE FORECAST AREA.
CONDITIONS IMPROVE QUICKLY FOR THURSDAY AS THE MAIN SHOW HAMMERS
THE PLAINS AND MIDWEST. FRIEDERS
.LONG TERM...VALID FOR FRI...SAT...SUN...MON...TUE...
THE EXTENDED STARTS CHRISTMAS WITH A DEEP LOW OVER THE MISSISSIPPI
RIVER VALLEY CONTINUING TO PULL COLD AIR FROM CANADA INTO MONTANA.
BOTH THE 12Z ECMWF AND 12Z GFS HAVE COME INTO GOOD AGREEMENT ON
THE FATE OF THIS SYSTEM FINALLY AND ARE PULLING IT OUT BY SUNDAY
MORNING. THIS WILL ALLOW LEE-SIDE TROUGHING AND SOUTHWESTERLY FLOW
TO WARM US UP OVER THE WEEKEND AND HAVE WARMED HIGH TEMPS INTO THE
LOW THIRTIES. IF THE 12Z MODEL RUNS FROM TODAY VERIFY IT COULD BE
MUCH WARMER...POSSIBLY THE LOW 40S.
EARLY NEXT WEEK COOLED TEMPERATURES DOWN A LITTLE AS GFS BRINGS US
ANOTHER SMALL SHOT OF COLD AIR AND GEFS IS STILL INDICATING THE
THREAT OF AN ARCTIC FRONT MOVING THROUGH THIS PERIOD. EXPECT GEFS
WILL TREND AWAY FROM THE ARCTIC FRONT SOLUTION SINCE BOTH ECMWF AND
GFS HAVE BEEN TRENDING AWAY FROM IT. ECMWF SETS UP STRONGER LEE-
SIDE TROUGHING AS IT DIGS A DEEPER LOW OFF THE PACIFIC NORTHWEST
COAST...SO IT IS MUCH WARMER DURING THIS PERIOD. GEFS ALSO SHOWS
CONSIDERABLE UNCERTAINTY WITH THE DIGGING TROUGH OFF THE PACIFIC
NORTHWEST COAST...BOTH THE 12Z GFS AND ECMWF SOLUTIONS ARE COVERED
BY THE GEFS. GEFS ALSO SHOWS A LOT OF UNCERTAINTY IN 850 MB
TEMPERATURES OVER MONTANA DURING THIS TIME. NEED TO KEEP AN EYE ON
THE PATTERN THIS PERIOD...IF LEE SIDE TROUGHING SETS UP WINDS IN
THE WESTERN ZONES COULD BE AN ISSUE.
FOR TUESDAY AND WEDNESDAY THE ENSEMBLE UNCERTAINTY DECREASES WITH
850 MB TEMPERATURES SUGGESTING HIGHS IN THE 20S. MODELS SUGGEST
POTENTIAL FOR A SHORTWAVE OR SOUTHWEST FLOW TO IMPACT THE
ABASAROKE MOUNTAINS SO HAVE CONTINUED ELEVATED POPS IN THE
MOUNTAINS FOR THIS TIME FRAME. LEACH/SOLUM.
&&
.AVIATION...
LOW CEILINGS AND FOG WILL CONTINUE TO CAUSE IFR TO VLIFR ACROSS
THE ENTIRE REGION FOR THE NEXT FEW HOURS. AREAS OF FREEZING
DRIZZLE...LIGHT FREEZING RAIN...AND LIGHT SNOW HAVE ALSO DEVELOPED
ACROSS CENTRAL AND EASTERN MONTANA AND WILL TO IMPACT THE KBIL...KMLS
AND KLVM AREAS FOR THE NEXT COUPLE OF HOURS. AS A COLD FRONT
PUSHES INTO THE AREA FROM THE NORTH...PRECIPITATION WILL CHANGE
TO ALL SNOW LATER TONIGHT. LIFR TO IFR CEILINGS AND VISIBILITY
WILL PERSIST ACROSS THE REGION INTO WEDNESDAY DUE TO THE AMPLE LOW
LEVEL MOISTURE AND FALLING SNOW. EXPECT MOUNTAIN OBSCURATIONS
THROUGH THE NIGHT. CAMPBELL/FRIEDERS.
&&
.PRELIMINARY POINT TEMP/POPS...
WED THU FRI SAT SUN MON TUE
-----------------------------------------------------------
BIL 016/018 002/013 002/020 008/025 009/031 013/018 010/023
6+/S 20/B 01/U 11/B 11/B 11/B 11/B
LVM 017/018 000/016 002/024 006/033 014/033 016/027 013/024
7+/S 20/N 01/B 11/B 11/B 11/B 21/B
HDN 016/019 001/013 904/019 902/029 005/031 001/023 004/023
6+/S 50/B 01/B 11/B 11/B 11/B 11/B
MLS 015/020 901/008 905/009 903/021 901/024 002/014 004/020
6+/S 70/E 22/S 11/B 11/B 11/B 11/B
4BQ 016/024 001/013 904/017 902/026 002/027 005/024 007/023
6+/S 83/S 22/S 11/B 11/B 11/B 21/B
BHK 011/018 902/009 906/011 903/021 000/023 000/016 004/017
6+/S 83/S 32/S 11/B 11/B 11/B 11/B
SHR 017/022 004/015 000/021 002/029 006/031 003/024 005/026
7+/S 72/S 02/S 11/B 12/S 12/S 21/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY IN EFFECT UNTIL 5 PM MST WEDNESDAY
FOR ZONES 28>30-34-35-39>42-56-63>66.
WINTER WEATHER ADVISORY IN EFFECT UNTIL 11 PM MST WEDNESDAY
FOR ZONES 31-32-38-57-58.
WINTER WEATHER ADVISORY IN EFFECT UNTIL 5 AM MST THURSDAY FOR
ZONES 33-36-37.
WY...WINTER WEATHER ADVISORY IN EFFECT UNTIL 11 PM MST WEDNESDAY
FOR ZONE 99.
&&
$$
WEATHER.GOV/BILLINGS
