Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 190953

Area Forecast Discussion
National Weather Service Billings MT
353 AM MDT Thu Oct 19 2017

.SHORT TERM...valid for Tdy and Fri...

Another very mild day in store as flow backs and downslope
gradients increase. High temperatures will rise once again to the
mid to upper 70s with a few 80 degree readings not out of the
question. This warmth will allow for some mixing winds to develop
in the afternoon. 850mb winds do not look terribly strong, but are
progged at 20-25kts by afternoon and that should lead to some
gusts of 20-30 mph. Humidities will fall into the teens in the
afternoon. Winds do not look strong enough for a long enough
period of time for a Red Flag Warning. Will issue a Fire Danger
Statement to account for the deteriorating fire conditions in the
afternoon. This will line up well with other offices` fire
products where stronger winds are expected.

Winds at Livingston and Nye have been flirting with 50 mph all
night, and this in response to surface pressure falls swinging
across southern Canada inducing a lee trough. Gradient is expected
to relax through the morning, so do not expect Advisory level
winds to develop. That being said, gusts to 50 mph will continue
to be a threat this morning. Surface pressure gradient realigns
tonight, but should not be quite as strong, so will not issue any
wind highlights at this time. Friday should be an active day as a
cold front races through.

The above mentioned cold front has been slowed down by the models
just a touch. Front will enter the west early afternoon, central
zones in the mid afternoon, and the east early evening. Pre
frontal heating should allow for another mild day over the east.
The west will be coolest behind the front with highs held to
around 60 degrees. The east should reach the upper 70s once again.
Strong surface pressure rises behind the front (1-2mb/hr), will
combine with 35-40 kts winds at 850mb to create wind gusts of
40-50 mph as the front races through. The front will have ascent,
and thus, all these winds may not materialize as showers and a few
thundestorms form along and behind the boundary. More cloud cover
will be involved and allow humidities to climb quickly with the
front, into the 30s. The front will get into the east later, with
an evening frontal timing. Will strongly word the fire weather
forecast for now, as the above mention factors could limit a Red
Flag day. Will pass word on to the day crew to monitor further.

Pushed PoPs a little farther east Friday afternoon with the front
and bumped winds up. Expect a line of broken showers with pockets
of heavier rain and virga, as drier low levels try to moisten up
quickly. Showers will shift east and winds decrease, Friday
evening. TWH

.LONG TERM...valid for Sat...Sun...Mon...Tue...Wed...

At least the first part of the extended period will be windy, with
good model agreement Saturday through Monday. The ECMWF ensembles,
however, did show uncertainty with the pattern Sunday and Monday.
The period starts out with a strong Pacific jet pushing an
amplified trough out of the area. It will be a cooler day behind
Friday`s cold front with lingering low precipitation chances in
the western mountains and over the eastern zones. The NAEFS showed
a windy day in the E on Saturday, and GFS Bufkit soundings had
mixing above 700 mb with winds reaching the 30s in the column
across the area. Thus went windy across much of the area,
especially in the afternoon. It does not look windy enough for a
highlight on Saturday. A strong coupled jet will move across the
region in zonal flow on Sunday with some channeled vorticity in
the flow. Kept PoPs over the western mountains. Sunday looked like
a well-mixed day with winds in the column mainly in the 30s and
40s, with some areas in the 50s. Gap flow early in the morning
could push KLVM/Nye into high-end Advisory or Warning criteria for
winds. Otherwise, will need to watch Sunday for other possible
wind highlights. One challenging factor will be that areas of
ascent will be over the region which could limit the strength of
the winds. Humidities were forecast to be around 30 percent on
Sunday which will help lessen the threat of dangerous fire weather
conditions. Upper ridging building in from the W on Monday, turns
the jet energy more N to S over the area with continuing windy
conditions. Vorticity moving through the area will provide ascent,
making for another challenging wind forecast. Had areas of low
PoPs across the region with possible thunderstorms in the E. The
ascent should help keep the wind strength from reaching its full

Upper ridging will bring dry and less windy conditions to the area
Tuesday and Wednesday, although periods of gap flow are possible.
The model agreement was not very good for late in the period.
Blends gave highs around normal and a dry forecast for Thursday.



Surface wind gusts to around 40 kt are expected at KLVM and along
the western foothills today through tonight. Otherwise, VFR will
prevail through the period. Arthur



    Tdy Fri     Sat     Sun     Mon     Tue     Wed
BIL 076 047/066 039/057 041/067 047/062 038/060 041/067
    0/N 03/T    21/N    11/N    31/N    00/U    00/U
LVM 079 047/059 035/051 041/064 048/059 036/059 039/063
    0/N 06/T    41/N    22/W    32/W    00/U    00/N
HDN 080 043/072 037/059 036/069 045/064 035/062 036/068
    0/U 03/T    31/N    11/N    31/N    10/U    00/U
MLS 080 042/075 039/057 035/069 046/062 034/058 036/065
    0/U 01/N    42/W    01/N    21/N    10/U    00/U
4BQ 079 042/077 039/056 035/069 045/060 034/057 035/065
    0/U 01/U    21/N    01/N    22/T    10/U    00/N
BHK 080 042/079 040/054 034/067 044/058 034/055 034/063
    0/U 00/U    22/W    01/N    32/T    10/U    00/U
SHR 080 041/076 033/056 031/069 043/060 033/058 033/068
    0/U 02/T    20/B    11/B    32/W    10/U    00/U


MT...Red Flag Warning in effect from 11 AM this morning to 7 PM
      MDT this evening FOR ZONE 117.


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