Area Forecast Discussion

KEY MESSAGES

- Hot and mostly dry conditions continue this week.

- Smoke continues across the region this week, reductions to visibility and air quality are possible.

- Isolated strong thunderstorms in Southeast Montana this afternoon and evening capable of producing wind gusts of 65 mph over far southeast MT.

- Daily chance (10-30%) for afternoon and evening showers and thunderstorms through the week.

UPDATE

Isolated showers and weak thunderstorms persist over parts of southern Montana this evening. A few of the latest HiRes model runs depict additional convection developing from west to east later this evening and overnight. Any storms will be capable of producing brief heavy rainfall, erratic wind gusts, and lightning. Otherwise, smoke continues to impact the region with several locations seeing reductions to visibility and air quality. Will have to monitor the overnight temperature trends as the smoke may keep things a bit warmer. Matos

DISCUSSION

Rest of Today through Sunday...

There are already a lot of mid level clouds building in across the CWA associated with lingering convection. This combined with the wildfire smoke will play a role in limiting our temperatures today. The extent to which the temperatures will be suppressed is still a question due to the fact that the smoke and clouds are not uniform and breaks in either or both could result in quick heating.

A shortwave trough is forecast to push through the area similar to what happened yesterday. Showers and thunderstorms are forecast to form over the mountains and move off the terrain this afternoon. Stronger storms are possible in extreme southeast MT where the temperatures may be hotter with a slight increase in mid-level moisture. Inverted-V forecast soundings suggest a primarily wind threat and with saturated mid levels, wet microbursts are possible in the SPC marginal risk area this afternoon. The surface temperature question posed above will play a role in convection later today for the marginal area. If we are unable to heat up enoug then there will probably be much less coverage in storms that will require the main CVA ahead of the trough to initiate. Bulk wind sheer is slightly better today with much of the CWA forecast to be between 20-30 kts which, in theory, should support storm maintenance more than we saw yesterday. Long straight hodographs with good cloud level moisture will support the upscale growth of storm clusters as they progress eastwards.

There continues to be no progressive flow aloft through the entire work week and thus the ridge shows little to no signs of changing for several days. Highs in the 90s to 100s appear likely to stick around into for the remainder of July. This could pull some monsoonal moisture up into the region with the chance for some showers and storms each day, particularly near the mountains, however coverage will be scattered any given day therefore resulting in a low chance for wetting rain. That being said, climatologically high PWATS will allow for downpours under the stronger storms resulting in an very quick wetting rain for those localized areas. Additionally, wildfire smoke from the several complexes in Eastern OR will also continue to be around the area due to the predominately westerly flow. This smoke, or lack of smoke, will play a large role in our temperatures over the next several days.

Models are now showing an increase in moisture over the eastern 1/4 of the CWA into the middle of the week which could turn into a heavy rain and marginal severe weather risk every day through Friday. This will need to be monitored as wildfire smoke, the strength of the monsoonal flow, the position and strength of the vort maxes, and just how much surface moisture is advected out of the plains are all variables that we still have questions around.

There continues to be a signal that a ridge crasher event may impact our area next weekend which would usher in cooler temps behind it. This type of event would also bring the potential for gusty winds and maybe some storms as well which would be a potential concern for fire weather after a prolonged stretch of hot and quasi-dry conditions. WMR

.AVIATION...

Isolated to scattered showers and thunderstorms will gradually move east through southern Montana and northern Wyoming this evening into Tuesday morning. An additional round of scattered showers and thunderstorms are then forecast Tuesday afternoon and evening over central/southern Montana and northern Wyoming. With this activity, gusty and erratic winds are the main threat, especially Tuesday afternoon and evening when wind gusts around 50 knots could occur (low chance).

Wildfire smoke from distant wildfires will continue to reduce slant range visibility over much of the area into Tuesday. Surface visibility will be reduced below 10SM at times as well, with occasional reductions below 6SM. LA

PRELIMINARY POINT TEMP/POPS

Tue Wed Thu Fri Sat Sun Mon ----------------------------------------------------------- BIL 066/098 066/097 065/098 066/097 066/102 069/102 066/088 33/T 33/T 41/U 20/U 00/G 00/G 00/U LVM 057/095 057/093 056/096 057/096 058/101 060/100 056/086 33/T 22/T 30/U 10/U 00/G 00/U 10/U HDN 064/100 064/099 064/098 063/099 063/104 067/102 064/089 23/T 33/T 41/U 10/U 00/G 00/G 10/U MLS 067/101 068/101 068/097 066/099 067/102 072/105 068/089 02/T 32/T 42/W 11/U 10/G 00/G 10/U 4BQ 068/098 068/099 067/095 064/098 066/100 071/102 068/089 22/T 35/T 72/T 11/U 10/U 00/G 10/U BHK 064/098 065/101 064/094 061/097 062/098 066/104 065/091 22/T 33/T 73/T 11/U 10/U 00/G 11/U SHR 062/095 061/096 061/095 060/096 061/100 064/101 062/089 22/T 24/T 31/U 01/U 00/U 00/G 00/U

BYZ WATCHES / WARNINGS / ADVISORIES

MT...Heat Advisory in effect until midnight MDT Tuesday night FOR ZONES 30-31-169. Extreme Heat Warning in effect until midnight MDT tonight FOR ZONES 32-33-37. Heat Advisory in effect from midnight tonight to midnight MDT Tuesday night FOR ZONE 32. Heat Advisory in effect until midnight MDT tonight FOR ZONES 36-58. WY...None.