Area Forecast Discussion
Issued by NWS Billings, MT

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647
FXUS65 KBYZ 200228
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
828 PM MDT Fri May 19 2017

.UPDATE...

Quiet evening with clear to partly cloudy skies across the
forecast area. An upper low over the southern plains continues to
rotate some clouds and isolated light showers northward into
western South Dakota, eastern Wyoming and southeast Montana, as
well as along the Montana/Wyoming border. Any shower activity
across our southern and southeast areas is expected to dissipate
within the next couple hours. Outside this area, the remainder of
the forecast area is expected to be dry with just some mountain
snow showers. Another cool night is expected but not as cool as
many areas experienced this morning.

As for hydro concerns, river gages have been showing a steady
decline in levels after the recent rain and snow. We have also not
had any reports of flooding today. Temperatures will be a bit
warmer tomorrow with 60s common and near 70 for Sunday. At this
time, we believe this gradual warmup will not be enough to warrant
a continuation of the current flood advisories that are out for
portions of the area. As a result, we will cancel the small stream
flood advisories with this update. Hooley

&&

.SHORT TERM...valid for Sat and Sun...

Upper low over northern Colorado spinning shortwave energy around
it up into northeast Wyoming and northwest South Dakota. Weak
instability and lingering mid level moisture, should be enough to
generate a few showers over southeast Montana and along the
foothills in weak upslope flow. Showers should dissipated rather
quickly with the loss of day time heating.

The upper low lifts northeast into the central plains tonight and
Saturday. A sneaky little shortwave working into British Columbia
will produce the next chance of showers on Saturday. Have raised
PoPs to likely over western zones Saturday afternoon and evening
as the shortwave cuts a path through Idaho. This will allow
upslope to kick back in. Precipitable water values were progged
mostly below a half inch, so not expecting a lot of moisture with
the showers, but isolated locations could pick up a quarter inch
of rainfall if a shower hangs up, (mainly along the foothills).
Instability is not deep, so will limit thunder mention.

Cyclonic flow continues for Sunday. Will keep low PoP mention
with a weak wave scooting across the forecast area in northwest
flow. A stronger wave slides south across eastern Montana Sunday
night. Timing is a little quicker with this system and have raised
PoPs for late Sunday night with it in mind.

Temperatures will be slow to moderate in cyclonic, northwest
flow. Expect moderation to around 70 Sunday, with another cool
down with the wave passage Sunday night and Monday. This slow warm
up will help to keep mid level snow melt down.

Hydrology, a look at early afternoon water levels continued to
indicate the downward trend from this morning. This in response to
precipitation ending, combined with a cool day yesterday and
chilly night last night. Do expect some rises this afternoon and
evening as mid level snow melt increases, but these rises will be
tempered by cloud cover and high temperatures only reaching to
around 60 degrees today. Will watch water levels through the
evening and have the evening crew evaluate flood highlights then.
Otherwise, main stem rivers still have room for more water as
tributaries dump into them. TWH

.LONG TERM...valid for Mon...Tue...Wed...Thu...Fri...

The long term forecast continues to look fairly consistent with a
general continuation of progressive and unsettled pattern.

A backdoor cold front will cross the region by midday Monday,
resulting in increased shower and thunderstorm potential for the
afternoon/evening.

Models point to upper level ridging sliding into the region for
Tuesday and Wednesday, for a period of drier and warmer
conditions. High temperatures climb to around 80 Wednesday, with
some assistance from downsloping flow.

Model solutions diverge a bit for Thursday into Friday. The GFS
mostly maintains the upper ridge through Thursday, finally giving
way to zonal or slightly southwesterly flow, with Canadian upper
low flattening the flow. This should give at least a slight chance
for shower and thunder across the region for Friday. The ECMWF
shows upper low diving into the Dakotas and dragging a cold front
across the region Thursday, and a second reinforcing shortwave
Friday evening. The CWA will remain under unstable cyclonic fow
throughout this period, resulting in greater potential for showers
and thunder for both Thursday afternoon/evening and Friday.

High temperatures will generally be in the 60s early in the week,
climb to around 80 Wednesday and Thursday, then fall a few
degrees to the 70s for Friday. AAG

&&

.AVIATION...


VFR conditions will prevail across most of the region throughout
the TAF period. Showers will produce obscurations over the
northeast Bighorns. Rain and snow showers are expected to develop
in the Beartooth/Absaroka and Crazy Mountains early Saturday
morning, with increasing obscurations through the day. AAG/STP

&&

.PRELIMINARY POINT TEMP/POPS...

    Sat     Sun     Mon     Tue     Wed     Thu     Fri
-----------------------------------------------------------
BIL 040/066 044/070 047/066 044/070 048/079 052/081 050/076
    02/T    22/T    35/T    21/B    11/B    12/T    22/T
LVM 036/062 038/067 040/066 037/071 041/077 044/078 043/074
    16/T    63/T    34/T    21/B    11/U    12/T    22/T
HDN 037/068 042/071 045/067 041/071 045/080 049/081 048/078
    11/U    12/T    35/T    31/B    11/B    12/T    22/T
MLS 039/066 043/071 047/065 043/070 047/079 051/080 050/078
    11/B    02/T    43/T    21/B    11/B    12/T    22/W
4BQ 037/063 039/068 044/062 039/067 043/076 049/078 048/076
    21/B    02/T    45/T    31/B    11/B    12/T    22/T
BHK 034/061 036/068 042/061 037/065 041/073 046/075 046/073
    11/B    02/T    45/T    21/U    11/B    12/T    22/W
SHR 033/061 038/063 041/060 038/064 040/074 045/076 044/074
    22/T    22/T    45/T    41/B    11/B    12/T    22/T

&&

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

&&

$$
weather.gov/billings



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