textproduct: Billings

KEY MESSAGES

- Storm system Tonight into Friday: Widespread rain transitioning to snow during the day Today. Snow accumulations confined to the foothills.

- Moderate to heavy snow for all mountains.

- Warmer and Dry this Weekend.

- Active weather continues next week.

UPDATE

A few changes to the forecast this morning. Cold front has pushed to a Miles City to Ashland line at 430 am. A defined band of precipitation has developed along the 700mb frontogenesis line over eastern Yellowstone county, shifting slowly to the east as colder air deepens up. Updated forecast highs to go about 5 degrees cooler than previous forecast. Temperatures are falling quickly behind the cold front and with cloud cover and precipitation all day expect highs to stick fairly close to early morning readings through the day. Also adjusted precipitation probabilities for the latest model trends, and tweaked the precipitation type toward more snow as change over is happening much faster than most models are advertising. Kept snow and precipitation amounts pretty close to previous forecast, accounting for what has already occurred overnight. No changes to the going winter weather highlites at this time. Chambers

AVIATION

12z TAF Discussion...Cold front is working through SE Montana early this morning with a pronounced band of precipitation trailing behind it. Snow is falling down to around 4500 feet MSL. Expect snow levels to drop to around 3000 feet MSL by late afternoon, sticking around that elevation through Friday. Expect gusty northwest winds of 20 to 30kts through early this evening.

TAFs are tricky this morning with models showing differing solutions due to a splitting trof putting precipitation in different areas along with differing wind fields that in some cases brings a lot less precipitation than others. 12z TAFs lean on the RAP solution that has done the best so far this morning with the frontal passage, winds, and precipitation but also tries to take into account the broader GFS/NBM thoughts.

Expect periods of MVFR to IFR conditions with precipitation. A shift to a more northerly wind direction (possibly more northeasterly) arriving between 16 and 22z has a good probability of increasing precipitation coverage and lowering ceilings to more widespread IFR/LIFR. Any breaks in the wind this afternoon will also increase the potential for fog development to further impact flight conditions. Foothills/mountain snowfall will continue into tonight. Expect continued mountain and pass obscuration through tonight. Flight conditions across the northern tier of the forecast area will improve by mid evening through the rest of tonight. Chambers

PRELIMINARY POINT TEMP/POPS

Tdy Fri Sat Sun Mon Tue Wed ------------------------------------------------------- BIL 041 026/049 028/060 034/072 043/078 045/080 048/072 9/O 54/J 20/U 00/U 00/B 01/U 24/W LVM 035 021/042 021/056 030/067 037/072 042/074 043/064 8/S 57/T 30/U 00/U 00/B 12/W 35/W HDN 043 023/050 026/061 031/073 038/079 042/082 047/075 8/O 54/J 20/U 00/U 00/B 11/U 24/W MLS 045 023/042 023/055 030/070 040/076 043/080 049/072 4/O 20/B 00/B 00/U 00/U 00/U 13/W 4BQ 051 025/043 024/054 030/069 040/077 044/080 048/073 7/R 71/B 00/B 00/U 00/U 00/U 23/W BHK 051 022/038 018/050 025/066 037/073 040/075 044/069 4/R 51/N 00/B 00/U 00/U 00/U 13/W SHR 045 021/042 021/054 028/067 035/075 041/077 043/071 9/T 96/J 31/U 00/U 00/B 11/U 24/W

BYZ WATCHES/WARNINGS/ADVISORIES

MT...Winter Weather Advisory in effect until 6 AM MDT Friday FOR ZONES 40-56-64>66. Winter Storm Warning in effect until 6 AM MDT Friday FOR ZONES 67-68. Winter Weather Advisory in effect from noon today to 6 AM MDT Friday FOR ZONE 138. Winter Weather Advisory in effect from 9 AM this morning to 6 AM MDT Friday FOR ZONE 171. WY...Winter Weather Advisory in effect from noon today to 6 AM MDT Friday FOR ZONE 199. Winter Weather Advisory in effect from 9 AM this morning to 6 AM MDT Friday FOR ZONE 198.