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Area forecast discussion 
National Weather Service Great Falls Montana
950 am MDT Tuesday Apr 28 2015

Update...no forecast adjustments needed this morning. Axis of high
pressure ridge is currently just east of the Continental Divide and
will make its way through central Montana during the daytime hours. This
will keep skies mostly clear and we are on track to reach forecast
highs of middle- to upper 70s across the region today.
Waranauskas

&&

Discussion...

Today through Thursday...high pressure aloft will keep north
central and southwest Montana dry and mild through tonight with
southerly winds. Highs today will mostly reach the upper 60s to
middle 70s, as overnight lows only fall into the middle 30s to middle 40s.
A Pacific low pressure trough will then move into the Pacific
northwest on Wednesday, which will force a cold front east across
the area. Models are indicating that more moisture will accompany
this front than was originally expected. Have therefore increased
the chance for scattered showers and thunderstorms along and
immediately behind the front across southwest Montana and
northeast into the Lewistown and Havre areas of north central
Montana. With moderate instability as well (cape values up to 600
j/kg and lifted indices as low as -4), cannot rule out an
isolated strong thunderstorm. With moderate wind shear and
precipitable water values (pw of up to 0.75 inches) forecast,
potentially strong wind gusts and at least small hail are possible
with storms. Farther north, a dry slot will likely keep only a
chance of showers along the Continental Divide, while strong
westerly downslope winds behind the front will hinder shower
development along the east slopes of The Rockies. Middle level winds
are not exceptionally strong, so am not expecting high wind
criteria winds there, but the situation will continue to be
monitored. With the front moving to a Havre-to-Dillon line during
the afternoon, temperatures along and east of that line will
mostly warm into the middle 60s to middle 70s once again. However,
behind the front, highs will only reach the middle 50s to middle 60s.
The front will move east of the area overnight as the upper trough
moves into Montana, which will move the shower/thunderstorm
activity out of the area. The gusty winds will decrease somewhat
overnight, but the dry and breezy westerly flow aloft in the wake
of the trough will allow westerly surface winds to increase again
on Thursday with mostly sunny skies. In the wake of the cold
front, temperatures will only warm into the middle 50s to middle 60s on
Thursday. Coulston

Thursday night through Tuesday...dry...breezy and mild conditions
are expected early in the forecast period under westerly flow
aloft. Temperatures through Saturday will be around 10 degrees
above seasonal averages. By the later part of the weekend...long-
range forecast models differ on the timing...strength and track of
the next weather system expected to move out of Canada. The GFS
and Canadian forecast models keep the weather system farther north
with drier conditions over the Treasure state while the European model (ecmwf)
deepens a trough of low pressure over the northern rockies which
would result in cooler and wetter conditions. Based on these
differences have kept at least a slight chance probability of precipitation over much of
the forecast area on Saturday night and Sunday and also lowered
temperatures to near seasonal averages. By Monday a ridge of high
pressure will build over the western U.S. With a return to drier
and mild conditions with the exception of a slight chance for
showers over higher terrain. Mlv

&&

Aviation...
updated 1200z.
VFR conditions will persist through Wednesday
morning. High pressure will keep skies mostly clear through the
forecast period with few to scattered high clouds at times. South-
southeasterly winds will generally remain 10kts or less. An upper-
level weather system and associated cold front will bring an
increase in westerly winds as well as a chance for showers and
thunderstorms by early Wednesday afternoon. Mlv

&&

Preliminary point temps/pops...
gtf 76 44 72 40 / 0 0 10 10
ctb 77 41 64 34 / 0 0 10 10
hln 77 44 71 37 / 0 0 20 10
bzn 73 41 71 38 / 0 0 20 40
wey 68 28 65 29 / 0 0 10 20
dln 73 41 70 39 / 0 0 30 30
hvr 77 41 76 40 / 0 0 10 20
lwt 74 45 75 41 / 0 0 20 40

&&

Tfx watches/warnings/advisories...
none.
&&

$$

Weather.Gov/greatfalls

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