National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS65 KTFX 150037
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
637 PM MDT Fri Jun 14 2013

.UPDATE...
Following the lead of the Billings weather office and am updating
to remove the mention of thunderstorms over southwest Montana for
this evening but will continue to mention them over north central
Montana. Also went more with partly cloudy skies over the north
in line with current observations and extended the mention of
precipitation a little farther west over the plains in line with
latest radar charts. Finally followed the lead of the Missoula
weather office and lowered the chances of precipitation slightly
over the far western zones for this evening. Blank

&&

.AVIATION...
Updated 2310Z.
VFR conditions are expected through the TAF period. An upper level
trough of low pressure will begin to push east allowing high
pressure to build into the area. This will bring increasing
stability and lighter winds to the region. Any lingering showers and
thunderstorms will diminish early this evening followed by clearing
skies. Langlieb

&&

.HYDROLOGY...
Point flood warnings remain in effect for the Big Sandy Creek near
Havre and Clear Creek near Chinook. Rain from recent thunderstorms
will keep water levels high in many creeks and streams. Drier
weather this weekend should result in gradually decreasing levels
into early next week.

&&

.PREV DISCUSSION...
/ISSUED 510 PM MDT Fri Jun 14 2013/
This Afternoon Through Sunday Evening...Upper level trof located over
central Alberta continues to make steady eastward movement thru MT
this aftn. Trof axis is currently located from just east of Havre
to near White Sulphur Springs with scattered showers and a few
small, short-lived thunderstorms occurring along the axis. A second
area of showers is also occurring along the Rocky Mtn Front and
over portions of southwest MT, some of which will push into
central MT this aftn. None of this activity is expected to become
particularly strong, but a few of the thunderstorms may produce
some pea-sized hail due to lower freezing levels aloft.
Precipitation will gradually taper off from west to east this
evening as the upper trof tracks into ern MT. Forecast still on
track for high pressure ridge to build into the Northern Rockies
starting tomorrow and continuing to strengthen through the
weekend, resulting in mostly fair skies and gradually warming
temperatures for Sat/Sun. Some forecast models continue to indicate
that a weak disturbance and small area of moisture may move into the
western side of the ridge on Sun aftn, sparking a few showers and
thunderstorms along the Rocky Mtn Front and over the southwest
mountains. So have kept a chance for precip in those areas but rest
of central and Hiline counties should remain dry with highs reaching
the mid to upper 70s.
Waranauskas

Sunday night through Friday...Models continue to be in good
agreement, but the overall progression of next week`s low pressure
system from the Pacific Ocean is about 24 hours slower than the
previous runs. Will address the changes below. An upper level ridge
of high pressure will linger over Montana through Monday night. The
airmass will warm to between 5 and 10 degrees above seasonal
averages, but weak steering winds aloft will keep the threat for
isolated thunderstorm activity over the higher terrain. The
aforementioned weather system will then deepen and move onto the
Pacific coast on Tuesday. The increasingly moist and unstable
southwesterly flow aloft ahead of the system will bring an
increasing chance of showers and thunderstorms mainly to the western
half of Montana. The flow aloft will also pump warmer air into the
area, causing temperatures to warm to between 10 and 15 degrees
above normal. As the system moves into the Pacific Northwest on
Wednesday, the flow aloft will become more southerly, unstable, and
diffluent. This, in turn, will bring a much better chance for
showers and thunderstorms to the area, especially over north
central/central Montana. Forecast CAPE values increase to between
1000 and 2000 J/kg Wednesday afternoon/evening, which hints at the
potential for a round of strong to possibly severe thunderstorms.
Would like to see run-to-run consistency with this feature before
mentioning severe potential in Hazardous Weather Outlook. Forecast
models differ with exact movement of this system beyond Wednesday.
GFS model moves the system into southern Alberta and Saskatchewan by
Friday, while the ECMWF model keeps the system over the Pacific
Northwest. The GEM is slow with movement of the system (moving it
over Montana), but it weakens the system. With this discrepancy,
have kept the chance for showers/thunderstorms near climatology and
will look to refine the details when the models come into better
agreement. Regardless, the models all bring a cold front through the
area Wednesday night, which should cool temperatures back to between
5 and 10 degrees below normal for Thursday through Friday and bring

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  43  74  46  76 /  10   0   0   0
CTB  44  72  44  74 /  10   0  10   0
HLN  43  74  47  78 /  10   0   0  10
BZN  39  73  43  79 /  20   0   0  10
WEY  32  67  37  74 /  20   0   0  10
DLN  37  72  42  78 /  10   0   0  10
HVR  47  75  49  76 /  20  10  10   0
LWT  42  70  46  72 /  20   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Flood warnings continue until further notice for Big Sandy Creek
near Havre and Clear Creek near Chinook.

&&

$$

SHORT TERM...BLANK
LONG TERM...LANGLIEB
AVIATION...LANGLIEB

weather.gov/greatfalls