Area forecast discussion
National Weather Service Great Falls Montana
1050 PM MDT Tue Jun 18 2013
..update to aviation...
Update...
a few strong thunderstorms continue to push northward through the
region. The thunderstorm watch will continue a bit longer where it
is currently in effect in case a severe storm develops. The flash
flood warnings will continue a bit longer as well. Expect a few
thunderstorms to continue after midnight. Otherwise current
forecast is on track. Brusda
&&
Aviation...
updated 0450z.
Widespread showers and thunderstorms will continue to move through
western portions of north central Montana through 10z. During this
time, areas of MVFR conditions in heavy rain remain possible along
with mountain obscurations. A surface cold front will push east of
the Continental Divide Wednesday afternoon then moves into eastern
Montana after 03z. Another round of strong to severe thunderstorms
will develop ahead of the frontal boundary but clearing skies and
calmer weather will move in behind the front. Mpj
&&
Hydrology...
more widespread showers and thunderstorms are possible along the
Rocky Mountain front and adjacent plains this afternoon and
evening and over most of the plains of north central/central
Montana on Wednesday. Some of these storms may produce brief heavy
rainfall. These periods will need to be monitored for possible
areal flood/flash flood highlights. The greater area of concern is
across eastern portions of north central and central Montana for
Wednesday that still have moist soil that would not be able to
absorb much rapid rainfall. If rainfall from storms today are
significant along the Rocky Mountain front additional rainfall on
Wednesday will increase the flooding threat there as well.
&&
Previous discussion...
/issued 555 PM MDT Tue Jun 18 2013/
today through Thursday...a low pressure system moving over the
Pacific northwest coast today will bring increased moisture and
instability to Montana. These factors will help generate showers and
thunderstorms over terrain this afternoon. A frontal boundary
associated with this system will also move into western Montana
today providing a good forcing mechanism for storm development. As a
result the Storm Prediction Center continues to keep western and
central Montana under a slight risk for severe thunderstorms. Storms
decrease overnight, but another round of potentially severe weather
is expected for Wednesday as the main system continues to move east
across the northern rockies. The most unstable conditions will also
shift northeast into central and eastern Montana, where the Storm
Prediction Center has a slight risk for Wednesday as well. The
potential for the strongest storms will be along and east of a
Havre-to-Stanford line as wind shear and instability are strongest
there. Precipitation from storms may be heavy adding the potential
for flash flooding. The system will lift northeast across the area
later Wednesday night into Thursday keeping high pops in the
mountains. Westerly down-slope winds will hinder shower/thunderstorm
development Thursday though. Winds strengthen along the Rocky
Mountain front Thursday making high wind highlights possible.
Temperatures cool Wednesday as the main front moves through the area.
Thursday night through Tuesday...no significant changes made to
the medium range forecast. An unsettled pattern will persist
through Saturday as a closed upper low will remain quasi-
stationary over northwest Montana. Short wave energy will
continue to rotate out from the base of the low and help initiate
shower and thunderstorm development each day. The strength of
these storms will depend on availability of low level moisture
and the strength of the divergent flow aloft. The models also
continue to differ on the upper low's position which, in turn,
will affect where and how strong thunderstorms will be. Because
of these differences, have continued to broad-brush the pops
through Saturday. By late Saturday, the models move the low to
northeast Montana and lift it out as an upper ridge begins
building over the Pacific northwest. The ridge breaks down on
Sunday as short wave energy ripples across the area within the
westerly flow aloft. Isolated thunderstorms will remain a
possibility Sunday and Monday. By Tuesday, weak upper ridging
returns though isolated showers will persist over the Southwest
Mountains. Temperatures will remain below seasonal averages to
start the period due to cloud cover and periodic cold advection
from transient shortwaves. Temperatures should rise above
seasonal averages to start the week.
&&
Preliminary point temps/pops...
gtf 54 76 46 67 / 40 80 80 20
ctb 52 73 45 64 / 100 100 90 30
hln 53 75 46 67 / 50 70 60 30
bzn 48 79 42 69 / 20 50 40 20
wey 38 70 32 61 / 10 30 20 20
dln 48 71 39 65 / 20 60 50 20
hvr 59 84 51 73 / 20 80 90 20
lwt 53 80 44 69 / 20 60 80 20
&&
Tfx watches/warnings/advisories...
none.
&&
$$
Weather.Gov/greatfalls
