Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 280158 AAA

Area Forecast Discussion...UPDATED
National Weather Service GLASGOW MT
758 PM MDT FRI MAY 27 2016

.SHORT TERM...for northeast Montana...tonight through Sun...

Satellite visual imagery places a low pressure center and upper
level trough churning over the Northern and Canadian Rockies this
evening producing a strong southwest flow aloft over Western and
Central Montana. Later tonight and Saturday flow aloft over
Northeast Montana will back around to the southwest also. A weak
low centered over Southern Manitoba is pushing a cold front into
Nemont while the western trough is sending another cold front into
the local area. The resulting instability is producing isolated
showers and thunderstorms. The western front will eventually win
out and send heavier rain showers over our western zones tonight.
Modified pops. Otherwise few other changed needed.


Previous discussion...
Synoptic Setup: short term begins with zonal to southwestern flow
running from Oregon through southern Montana and into the Dakotas.
A meso Ridge runs north from northeast Montana through western
Saskatchewan while a large trough stretches north from Washington
up through the British Columbian coast.

This afternoon through Saturday: the remnants of a closed low
from yesterday and left over moisture moving in from the northeast
has allowed some showers and thunderstorms to form over the
northeastern third of the CWA. To the west an upper level cold
front has formed over western Montana. Extra lift has formed out
ahead of this front and is interacting with afternoon orographic
lift and the lee surface trough over the central Montana mountains
to form a few thunderstorms. As the front progress overnight these
thunderstorms may latch onto it and advect over the CWA. Lift with
this front will then progress across the CWA Saturday in a narrow
north-northwest/south- southeast band of about 50 to 100 miles.
Total QPF with this passage ranges from a hundredth of an inch to
two tenths for most of the CWA.

Saturday night through Sunday: flow will become more zonal with
warmer air aloft sneaking in from the south. This should stabilize
the atmosphere briefly and drive temperatures into the upper 70s
with partly cloudy skies and dry conditions. GAH

.LONG TERM...Sun night through Fri...
Very little change to the going forecast. Low pressure expected to
move across the region early next week still has enough
uncertainty to keep broad pop coverage from Monday through
Wednesday. However did start to taper pops off a little quicker.
Following the low passage, an upper ridge builds over the northern
Rockies for potentially drier conditions for the end of next week.

Previous long term discussion...The extended period begins Sunday
evening with a weak ridge in place over the Northern High Plains
and western flow aloft producing mild conditions. Off to the west
an upper trough will be digging into British Columbia and the
Pacific Northwest producing cooler conditions and widespread
precipitation there.

As the trough plows through the Northern Rockies upper flow over
Northeast Montana will begin to back to the southwest, introducing
moisture and instability. Expect rain showers sometime after
midnight, spreading east and increasing on Monday.

With the associated cold front moving across the area, convective
parameters become moderate to strong, enough to produce afternoon
and evening thunderstorms with the showers. Expect the upper and
lower low centers of this storm to stack up by Tuesday morning
into a compact cyclone with strong gusty winds and areas of heavy
rain. The storm will be a slow mover, not exiting the region until
Wednesday afternoon.

Wednesday evening a strong upper level ridge will have developed
over the West Coast producing northwest flow aloft over Montana.
This ridge will slowly progress eastward for the remainder of the
period, bringing warmer and drier conditions.

High confidence for the general upper flow pattern, and becoming
stormy by Monday, then diminishing the unsettled conditions
around late Wednesday, followed by increasing temperatures and dry
conditions late in the period. Generally continued the trend to
raise pops.




SYNOPSIS: An upper level trough over Western Montana will continue
to swing into the region overnight. This will bring a chance of
showers with it. Expect MVFR briefly with the showers as they
move through the region. Otherwise VFR shall continue to dominate
the flight category for the terminals.

Wind: The wind will remain under 15 knots through the period with
east wind becoming west late in the TAF cycle.           Proton




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