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Area forecast discussion 
National Weather Service Great Falls Montana
1137 am MDT sun Apr 19 2015

..update to aviation...

Update...Montana will remain beneath north to northwesterly flow
aloft today through Monday evening as an upper ridge lingers
along the West Coast. This pattern will continue to advect middle and
upper level clouds through the forecast area at times. However,
cloud cover is not expected to be as widespread as earlier
forecast models were indicating. As such, I have trended sky cover
downward and have also made tweaks to lower probability of precipitation. Temperature and
wind forecast remains pretty much on track so have made no changes
to these parameters. Weather should remain generally uneventful
with a warming trend through middle-week as the upper trough
gradually moves over the northern rockies. Mpj


Aviation... updated 1737z. North to northwest flow aloft will
continue over Montana through Monday afternoon with widespread VFR
conditions expected through the period. Winds will remain generally
light to breezy. Mpj


Previous discussion...
/issued 525 am MDT sun Apr 19 2015/
today through Tuesday evening...short-term forecast period shaping
up to be relatively uneventful with mostly dry conditions and
gradually warming temperatures for the first half of the week. With
a deep low pressure trough over the Midwest states and high pressure
ridging along the West Coast, central and southwest Montana will
remain under northwest flow aloft through Monday with occasional
bands of moisture sliding through the flow. This will result in
periods of widespread middle- and high-level clouds covering areas
along and west of the Interstate 15 corridor, with less cloud
cover further east. Other than a slight chance for a stray shower
or two along the Rocky Mountain front and high peaks of the southwest
mtns, no precipitation is expected over the next 48 hours. The
Pacific Ridge will make very slow eastward progress through the
period, becoming centered along the Washington/or/ID border by midday
Tuesday. This will allow the winds aloft to gradually turn to the
west-southwest, which will bring some moisture from Idaho into the
southwest counties. The moisture will combine with slightly
unstable conditions (cape values of 150-200 j/kg and lifted
indices of -1 to -2) to give a chance for isolated thunderstorms
along/south of line from Wisdom-to-Ennis-to-Big Sky on Tuesday
aftn/eve. As for temperatures, most of the region will see middle 50s
today, then warming to the upper 50s to low 60s on Mon, and
increasing to upper 60s on Tuesday.

Tuesday night through Sunday...expect the weather pattern to slowly
become a bit more active as we move into the second half of the work
week. The upper level ridge of high pressure that will be over the
region for the first half of the week...will slowly begin to break
down during the second half of the week. With the airmass becoming a
bit unstable during the afternoon and evening hours...there will be
a chance for mainly afternoon showers and thunderstorms over central
and southwest Montana from Wednesday through Friday. Most of the thunderstorm
activity should be confined to the southern portions of the
region...where the airmass will be a bit more unstable. Temperatures
will be mild on Wednesday...then gradually cool a bit for Thursday
and Friday. For next weekend...both models have a weather system
moving through the region...but they differ on the exact timing and
strength. The GFS model is slower and produces along period of rain
and higher quantitative precipitation forecast amounts...while the ec is faster and not as wet. Thus
for now I increased probability of precipitation a bit for Saturday night into
Sunday...especially over southwest Montana. Most of the precipitation
will be rain...but there will be a chance for snow for elevations
mainly above 5000 feet by Sunday morning. Temperatures will also
cool to near normal readings by Sunday.


Preliminary point temps/pops...
gtf 54 33 63 38 / 0 0 0 0
ctb 54 32 63 37 / 0 0 0 0
hln 57 31 65 35 / 10 0 0 10
bzn 53 29 60 34 / 10 0 0 10
wey 50 27 55 28 / 10 10 10 0
dln 56 32 62 33 / 10 10 0 0
hvr 55 31 61 37 / 0 0 0 0
lwt 50 29 57 35 / 0 0 0 0


Tfx watches/warnings/advisories...



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