Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Glasgow Montana
754 PM MDT Monday Jun 1 2015
Short term...for northeast Montana...tonight through Wednesday...
Evening update... focus for the evening is on a developed and
cold front moving through the area and prohibiting strong convective
showers from developing in the southern and western zones. A
Theta-E ridge has develop on the southern and eastern sides of
this front and is running up the Yellowstone valley. This will
become the focus for remaining storm development after midnight in
the County Warning Area. Winds and dewpoint fields were updated to include this
change in forecast. Most other areas should still receive some
for of rain overnight but thunder will be limited. Gah
Previous short term discussion...
potent system kicks off first widespread severe potential for
eastern Montana this evening. Cold front starting to drop out of
Canada into north central Montana while the upper level short wave
is pushing into Idaho and the southwest portion of the state
where radar returns are showing some decent storms firing up.
Moisture evident with Theta-E analysis showing a bullseye over the
Black Hills...where storms are firing now in vicinity of 4000 cape...and
the axis pushing north along the Montana and ND border. Parameters and
timing are similar to this morning with the best chance of severe
being south of Highway 2. Have actually removed verbaige from the
area to the north of Highway 2.
One minute GOES-14 imagery (thank you CIRA-rammb) has been great
to use in the past half hour really showing where convection is
starting to fire things are starting to develop in central
Montana. Hrrr is indicating convection firing between Miles City
and Glendive by 21z and while the satellite imagery is showing
cells trying to form...they just aren't cutting it yet. The sseo
Page from Storm Prediction Center showed this earlier today giving confidence that
things will fire up over Fergus County area and move into
Petroleum and Garfield counties after 5-6 PM.
A special upper air run was released at 19z and data should be in
shortly. Data through 400 mb shows that precipitable waters have decreased by .2
of an inch since this morning with a bit of a dry sounding below
400 mb. The speed shear is fairly decent with less directional
shear to work with. Would anticipate most storms to be
multicellular/multicellular line in our County Warning Area with a greater
confidence of larger hail and strong to damaging winds. Supercells
have a better chance in the southern portion of the state.
Tonight transitions into a moderate rainfall event...especially
from kggw westward. Some areas will see in excess of a half inch
of rain as the shortwave continues it's push into Canada tonight
Southwest flow aloft will continue to bring weak waves into the
area tomorrow...but with temperatures around 20 degrees colder we
lose the instability and lift and expect more showers than
thunderstorms through Wednesday. Fransen
Long term...Wednesday night through Monday...
little change was made to the long range period with the inherited
forecast in excellent shape introducing a warming trend and
continued unsettled conditions as a series of shortwaves approach
embedded in the southwest upper flow. As an upper ridge builds
into British Columbia it will help turn the flow aloft
northwesterly...introducing drier weather conditions for Sunday
into early next week. The only real tweaks that were made were
simply for collaboration purposes. Maliawco
Previous long term discussion...
between Wednesday night and Friday night... southwest flow aloft
is expected over the area.
A shortwave ridge within the SW flow Wednesday night and a surface
high over North Dakota will allow for a period of dry weather
mainly over the northeast half of the forecast area. With moisture
ahead of a shortwave trough approaching from the SW for
Thursday...will need to maintain a chance of showers and
thunderstorms in the southwest half of the forecast area.
That wave will bring a chance of showers and thunderstorms to the
entire region Thursday and Thursday night. Another shortwave
trough on Friday will bring another chance of showers and
Meanwhile...an upper trough moving across the Canadian prairies
Friday and Saturday will turn the flow aloft over eastern Montana
to the northwest on Saturday. Will have yet another chance for
showers and thunderstorms on Saturday that could linger into
Sunday morning. Then...drier air mass into the area. With surface
high pressure... Sunday afternoon...night and Monday looks mainly
synopsis: a cold front continues to drop south through the state
this evening keeping the thunderstorms to the south of the
terminals this evening. Overnight showers and a few
thunderstorms with the thunderstorms mainly in the Yellowstone
valley. On Tuesday expect Post frontal conditions with lower
ceilings for most locations.
Flight category: VFR with MVFR after 12z moving into the region from
west to east.
Wx: thunderstorms over south central Montana will continue to move
northeast up the Yellowstone River Valley into kgdv and ksdy after
06z. Showers can be expected elsewhere starting at 03z in the
southwest and spreading into kggw and kolf after 06z.
Ceilings/vsby: VFR and lowering to MVFR ceilings after 12z. Otherwise brief
periods of MVFR/IFR can be expected with any thunderstorms. Proton