Sunrise 6:29 AM   Sunset 8:16 PM Moonrise 2:04 PM   Moonset 3:47 AM

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FXUS65 KBYZ 181954 AFDBYZ

Area Forecast Discussion National Weather Service Billings MT 154 PM MDT Thu Apr 18 2024

DISCUSSION

Through through Friday night...

Satellite imagery shows an upper low over southern Manitoba with chilly cyclonic flow extending westward through the northern Rockies. Surface high near 1040mb is centered up in northern AB currently, but we will continue to be under the influence of this fairly cold air mass through the short-term period as the surface high sags southward. In short, expect much below normal temps to continue with lows tonight and Friday night in the upper teens to mid 20s, and highs Friday mostly mid 30s to lower 40s. In fact, the daily record low of 19F at Miles City on the 20th will be challenged.

Brisk NW winds have somewhat overachieved today with gusts near 50 mph in an area from northern Rosebud thru Custer and Fallon Counties. These well-mixed winds will continue thru the afternoon then drop off quickly by sunset. Though winds tonight will become largely decoupled in our east, gradients will support breezy NW winds again tomorrow
beginning fairly early in the day
though not as strong as today at 25-35 mph.

We are starting to see light snow showers develop over our west, as expected, and there is some banding noted downwind of the Crazy, Little Belt and Snowy Mountains. Boundary layer is quite dry (dewpts in the single digits to lower teens) so there will likely be a lot of virga around, but will keep 10-20 pops going over the west half of our forecast area through the evening. In fact, some activity may linger over the western high terrain overnight per the mid level instability and cyclonic flow. By Friday morning, a wave dropping thru eastern MT with moistening shallow instability should be enough for areas of light snow for a period of time from northern Rosebud County eastward. Otherwise, look for a few diurnal snow showers once again over the mountains and near the foothills Friday afternoon and early evening. Surface high finally settles over eastern MT Friday night bringing clearing and light winds. As already alluded to, tomorrow night looks like the potentially coldest night of the current cool spell.

JKL

Saturday through Thursday...

Saturday will remain cool with temperatures generally in the 40s to low 50s. The upper troughing and high surface pressure will gradually move off to the east, being replaced by more zonal westerly flow. A low pressure system will form to our north in Alberta which will bring impacts on Sunday. Breezy southerly winds out in front of the low will build a thermal ridge, bringing temperatures into the 60s. These winds don't appear to be advecting in any moisture so we will have to wait for the wave to move in to bring the moisture needed for more widespread precipitation chances. At this time the best chance (70%) for precipitation will be late Sunday through Sunday night. Models are hinting at this system having a well defined dry slot leading to a reduction in precipitation chances before they pick back up again on Tuesday. Low level lapse rates will be strong in the 7-8C/km range leading to the possibility of some thunder. With low level moisture and RH values lacking, CAPE will be limited leading to elevated non- severe convection being most likely.
Overall precipitation with this system is expected to remain light with most of the area having a <20% chance of getting over 0.25 inches of rain.

The passage of the cold front will bring windy conditions and a cooldown for Monday and Tuesday morning with highs in the mid to high 50s and lows in the upper teens to mid 20s. Winds on Monday will be out of the northwest and gust into the 30s mph for most.
After the passage of the low and upper troughing we move into a more westerly downsloped flow leading to higher temperatures and lower RH values. By the time we get to Wednesday and Thursday, southeast Montana will have a 50-70% chance of seeing high temperatures greater than 70 degrees. Torgerson

AVIATION

Isolated light snow showers/flurries will impact the region late this afternoon and evening. VFR will prevail, but cannot rule out local MVFR especially close to the foothills, and the mountains will be obscured at times. NW winds will be brisk with gusts of 25-40 knots until sunset, greatest east of KBIL. On Friday, areas of light/snow flurries from KMLS to KBHK may produce MVFR, especially in the morning. Mountains will be obscured at times in light showers. Winds tomorrow will once again be breezy with gusts of 20-30 knots east of KBIL. JKL

PRELIMINARY POINT TEMP/POPS

Fri Sat Sun Mon Tue Wed Thu ----------------------------------------------------------- BIL 025/043 024/050 030/065 039/057 033/062 038/071 045/070 10/B 00/U 03/R 63/R 00/B 02/R 24/R LVM 020/041 019/050 030/063 032/054 031/060 036/068 042/067 11/B 00/U 04/R 42/R 00/B 02/R 24/R HDN 023/043 020/052 028/068 038/059 033/064 037/073 043/074 00/B 00/U 01/B 73/R 11/B 01/B 23/R MLS 023/040 020/048 027/066 040/055 033/059 037/070 044/072 02/J 00/U 00/B 54/R 10/B 01/B 12/R 4BQ 022/040 020/049 028/068 039/057 033/059 037/071 044/073 00/B 00/U 00/U 53/R 10/B 01/B 12/R BHK 020/038 018/046 024/063 036/054 031/055 034/066 039/069 02/J 00/U 00/U 55/R 11/B 01/B 12/R SHR 018/040 017/048 024/067 033/055 028/059 034/069 040/070 11/B 10/U 01/B 53/R 10/U 01/B 24/R

BYZ WATCHES/WARNINGS/ADVISORIES
MT...None.
WY...None.

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