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FXUS65 KBYZ 230833 AFDBYZ

Area Forecast Discussion National Weather Service Billings MT 233 AM MDT Tue Apr 23 2024

DISCUSSION

Today through Wednesday night...

Heights build through the day today. Weak shortwave energy slides through southern Montana late morning through the afternoon, bringing some mid level moisture. Warming aloft will keep the vertical extent of the clouds down, so expect mainly flat mid level clouds with the wave that will preclude precipitation chances. GFS was painting some light QPF over the Bighorns this afternoon, so can not rule out a light sprinkle or flurry there but will leave PoPs out today.

Heights continue to build tonight and Wednesday as the flow backs slowly. The developing southwest flow at mid levels will pull some weak energy and mid level moisture into the southwest mountains Wednesday evening and overnight. Will keep the chance of showers low (20-40%), with a slight chance (20%) of these showers leaking out onto the foothills Wednesday evening.

Winds will be much lighter today and Wednesday with a lack of a surface pressure gradient. Temperatures will be similar today to Monday (if not just a touch warmer). A brief two day warmup will start on Wednesday with highs in the lower to mid 70s. TWH

Thursday through Tuesday...

The extended forecast remains active with chances for precipitation each day as large scale troughing with waves of moisture and energy sets up over the western US. At this time, precipitation chances range from 15-50% over eastern areas and 50-90% over central and western areas Thursday through Saturday.
While chances decrease Sunday through Tuesday as uncertainty grows in the upper level pattern, near zonal flow looks to allow additional waves of energy and moisture to continue low to moderate chances for precipitation across portions of the region.

A lot of uncertainty remains on how much precipitation may accumulate through this period, but ensembles (GFS and ECMWF) are holding on to very beneficial amounts over western and central areas. The NBM has a 60 to greater than 95% chances for at least 0.25 inches of liquid precipitation around and south/west of a line from Harlowton to Billings to Sheridan. East of Billings, there is a 30 to 70% chance, highest in far southeastern Carter County. However, the latest deterministic runs are much drier outside of the immediate foothills and mountains as they develop a dry slot around Billings to Miles City. The convective nature of the showers Thursday, more on that below, will likely amount to varied amounts across the region as well. As far as precipitation type goes, we are looking at all rain for the lower elevations, with snow generally above 7,000-8,000 feet during the most impactful time of precipitation (Friday into Saturday).

While most of this precipitation will just be showers, there may be a few thunderstorms Thursday with modest instability and increased precipitable water values over the western mountains and far eastern Montana. The best chance is in eastern Montana where brief heavy rain with lightning looks to be the main threat.

High temperatures are forecast to range from the 60s to mid 70s Thursday and 50s to 60s Friday through Sunday. A slight warm up Monday into Tuesday looks to nudge temperatures back into the 60s to lower 70s. Arends

AVIATION

No significant hazards to aviation are expected with VFR conditions prevailing through the forecast period. Mid to high level clouds will move through this afternoon and evening. Arends

PRELIMINARY POINT TEMP/POPS

Tdy Wed Thu Fri Sat Sun Mon ------------------------------------------------------- BIL 062 038/075 047/069 048/059 043/058 041/064 043/067 0/U 00/U 13/R 56/R 57/R 44/R 24/R LVM 060 036/071 044/065 042/050 038/049 036/058 037/061 0/B 00/U 26/T 79/R 78/R 45/R 35/R HDN 063 035/076 044/072 047/065 043/061 041/066 041/070 0/U 00/U 01/B 45/R 46/R 44/R 23/R MLS 061 038/074 046/074 047/067 043/060 041/064 042/070 0/U 00/U 01/B 12/R 23/R 32/R 12/R 4BQ 060 038/075 047/075 047/065 042/057 040/061 041/069 0/U 00/U 02/R 34/R 35/R 33/R 12/R BHK 059 035/072 042/074 044/064 038/056 035/057 037/067 0/U 00/U 04/T 34/R 33/R 33/R 12/R SHR 061 034/072 042/069 045/059 038/055 037/060 037/068 0/B 00/U 14/T 66/R 67/R 55/R 23/R

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

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