Area forecast discussion
National Weather Service Great Falls Montana
1055 PM MDT Mon Jun 17 2013
..update to aviation...
Update...
current forecast is on track...with just a minor adjustment to
pops overnight. Isolated thunderstorms continue to redevelop over
southwest Montana and move northeastward into central/north central Montana.
Thus I added some isolated thunderstorms overnight generally along
the path the storms have been taking through the evening hours.
Most storms should only produce brief heavy rainfall...lightning
and small hail overnight. Overnight lows look on track.
Looking ahead...it should be a bit more active for severe weather
on Tue and Wed across much of the region. Storm Prediction Center has a slight risk of
severe weather both days over portions of central and north
central Montana and that looks good. Brusda
&&
Aviation...
updated 0455z.
Scattered showers and thunderstorms will continue to move across
central Montana through 09z with the khln and klwt areas most likely
to see convective activity. Skies will clear out by 12z but another
round of strong and possibly severe thunderstorms will develop after
20z and continue into the late evening. VFR conditions will prevail
but conditions may deteriorate to MVFR in heavy rainfall associated
with the strongest storms. Mpj
&&
Hydrology...
a stronger period of showers and thunderstorms are possible on
Wednesday, which may produce brief heavy rainfall. In fact, this
situation will likely need to be monitored for possible areal
flood/flash flood highlights across portions of north central and
central Montana that still have moist soil that would not be able
to absorb much rapid rainfall.
&&
Previous discussion...
/issued 543 PM MDT Mon Jun 17 2013/
Tonight through Wednesday...the high pressure ridge will continue to
keep the airmass relatively dry and shower/thunderstorm activity
will diminish this evening. The ridge will move east of the zones
Tuesday and a low pressure system over the eastern Pacific will
move over the West Coast. This will put central Montana underneath
moist, unsettled southwest flow aloft. The airmass will become
unstable during the day and a cold front will be crossing The
Rockies late afternoon and evening. Scattered thunderstorms are
expected across most of the region with numerous storms over The
Rockies and adjacent slopes. Convection may last well into Tuesday
evening along the eastern zones due to the slow eastward movement of
the cold front. The low pressure system will continue to approach
the region and heights aloft will continue to fall. And
thunderstorm activity will increase Wednesday as the airmass becomes
very moist and unstable. Heavy rain is possible across the central
and northern portions of the region, and large hail possible over
the northeastern zones.
Wednesday night through Monday...a somewhat unsettled pattern will
characterize the long term forecast. A low pressure system will push
slowly drift across the Pacific northwest through the long term.
Shortwave energy will continue to rotate out from the main trough
and move across the area from the southwest. Scattered showers
and thunderstorms will continue to develop over southwest Montana
and then move northeast across central Montana. The system will
reach northwest Montana Thursday morning before stalling and slowly
weakening. The low will lift out over southern Saskatchewan Sunday.
The models develop differences in their solutions by Monday with the
European model (ecmwf) building a ridge and the GFS maintaining weak cyclonic flow
over Montana. Uncertainty with the timing and placement of
convective activity has led to a broad-brushed approach with regards
to pop grids during the period. Due to cloud cover and periodic
advection of cooler air following shortwaves, temperatures will
remain generally below seasonal averages through Saturday. Highs
should climb above seasonal averages to start the week.
&&
Preliminary point temps/pops...
gtf 51 84 53 74 / 20 40 40 80
ctb 48 82 50 70 / 20 50 60 90
hln 51 84 51 73 / 30 50 30 70
bzn 45 85 45 76 / 20 50 30 60
wey 38 77 37 69 / 20 40 10 60
dln 47 82 47 68 / 30 40 30 70
hvr 54 87 57 80 / 20 30 30 90
lwt 49 82 53 79 / 10 40 50 70
&&
Tfx watches/warnings/advisories...
none.
&&
$$
Weather.Gov/greatfalls
