Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
964 FXUS65 KBYZ 181924 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 124 PM MDT Thu Jul 18 2024 .DISCUSSION... Through Friday Night... Satellite imagery shows a weak upper low moving slowly along the MT/AB border, at crest of strong ridge overhead. Flow aloft is fairly weak but there is a 60kt H3 jet analyzed near Great Falls, and over time we will fall under its RRQ (i.e. weak synoptic scale ascent). Mesoanalysis shows cape slowly increasing but as of 19z there remains abundant CIN. As temps get into the 90s over the next couple of hours, we should achieve 500-1000 j/kg of SBCAPE while inhibition diminishes. Regional radar shows convection beginning to develop in south central MT, including near Gardiner, so everything seems to be on track. Main thunderstorm risk today is wind. Pwats currently ~0.80" expected to rise to 0.90-1.00" this afternoon, mid-high level moisture that along with steep low level lapse rates should support wet microbursts. Today`s HREF shows highest wind probs in the NW quadrant of our forecast area, as far east as Rosebud County. Outside of this area there is still a risk of t-storms and sub-severe gusts. Locally heavy rain and small hail are also possible with any of today`s storms. PV max will track thru north central and eastern MT over the next 18 hours, and this should yield more showers w/embedded non-severe t-storms over our east (east of Billings) overnight into Friday morning. The potential for multiple rounds of showers will obviously be good for our increasing fire concerns, but the chances of wetting rain (0.10"+) at any given location is still relatively low at 10-40% (highest eastern zones). Subsidence will spread over the region as NW flow develops behind the wave late tonight and Friday. Nonetheless, pwats will remain somewhat elevated tomorrow (near an inch in our east) and this should be enough to allow modest diurnal cape to be achieved even with warming at mid levels. Thus, look for isolated showers and weak t-storms tomorrow afternoon and early evening in our east and southern upslope areas. Billings will probably stay dry but should see cumulus and perhaps a few sprinkles. Any activity will diminish by sunset and the remainder of Friday night will be dry. Temps will cool somewhat behind tonight`s wave but remain warmer than normal. Look for highs tomorrow mostly upper 80s to mid 90s. One final thing: our region will remain impacted by lofted smoke from numerous wildfires to our west. That said, when the flow turns to northerly, we will need to watch for Canadian smoke as there are also many active fires in northern AB. JKL Saturday through Thursday... Clusters showed a slight cyclonic flow aloft on the eastern side of the upper ridge on Saturday. In addition, a weak backdoor front will slide SW into the area. Thus continued the idea of expanding low PoPs from Rosebud County E in the afternoon and had slight chance PoPs over most of the area Sat. evening. Monsoonal moisture supported 30-50% PoPs over the southern mountains. Highs will be in the upper 80s to mid 90s. Nudged wind gusts toward the NBM 90th percentile on Saturday based on signals from the ECMWF ensemble. Ridging will bring mostly dry conditions for Sunday, except for low mountain PoPs. It will be slightly cooler than Saturday. Upper ridging continues Monday with less monsoonal moisture, and thus a dry forecast. Temperatures will be similar to Sunday`s readings. For Tuesday through Thursday, the ridge remains over the region, but SW flow starts to edge E into the area ahead of the next trough late in the period. PoPs increase to 30-40% over the SW mountains and low chances for thunderstorms spread over the western zones Wednesday and Thursday afternoons. Airmass will be warming Tue. through Thursday with a 30-60% chance of reaching 100 degrees in the river valleys and over most of the climate sites on Wednesday. On Thursday, chances of reaching 100 degrees become more widespread across the forecast area with 30-60% probabilities. Several sites could reach or exceed record temps, including KBIL where the record on Thursday is 98 degrees. May need heat highlights in the mid to late part of the week. Regarding fire weather concerns...at this point, the Fosberg indices were low and the Hot Dry Windy Index was also not showing much. Arthur && .AVIATION... Expect scattered thunderstorms with movement from west to east this afternoon and evening. Storms have the potential to produce strong surface wind gusts (to 50+ knots) as well as local MVFR- IFR in heavy rain, and small hail. All TAF sites are at risk of seeing a TS (see table below). A weak disturbance passing thru eastern MT will keep the risk of showers and weak t-storms going thru the night and into Friday morning in southeast MT (east of KBIL). Otherwise, VFR conditions will prevail over the next 24 hours, while slant range visibility is reduced at times due to wildfire smoke. TS POTENTIAL TIMING TODAY: KBIL 22-06Z KLVM 20-04Z KMLS 02-12Z KSHR 21-06Z JKL && .PRELIMINARY POINT TEMP/POPS... Fri Sat Sun Mon Tue Wed Thu ----------------------------------------------------------- BIL 065/093 065/095 064/092 063/092 063/096 065/100 066/100 40/U 01/U 20/U 00/U 00/U 01/U 11/B LVM 055/093 054/092 055/091 053/091 054/096 058/098 059/097 41/U 01/U 11/U 00/U 01/U 12/T 12/T HDN 062/093 060/095 061/092 059/094 060/097 060/101 062/102 51/U 01/U 20/U 00/U 00/U 00/G 11/G MLS 066/091 064/092 065/090 064/091 064/094 065/098 066/099 52/T 12/T 20/U 00/U 00/U 00/U 00/U 4BQ 067/092 062/091 063/089 061/090 062/094 063/098 065/100 42/T 12/T 20/U 00/U 00/U 00/U 00/U BHK 065/090 060/090 059/088 059/088 059/091 061/095 062/096 54/T 12/T 20/U 01/U 00/U 00/U 10/U SHR 060/092 055/090 056/088 055/089 056/093 057/097 059/098 42/T 12/T 21/U 01/U 00/U 00/U 01/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings