135
FXUS65 KTFX 130931
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
331 AM MDT Tue Aug 13 2013
.DISCUSSION...
Today through Thursday...A series of shortwave troughs will move
through the ridge of high pressure over the northern Rockies
through Wednesday. Moderate instability over the central Montana
this afternoon combined with lift will result in scattered
thunderstorms this afternoon and evening. A few thunderstorms may
become briefly severe but weak shear should limit the threat for
widespread severe storms. Monsoonal moisture, a moist low level
easterly flow, and slow storm motion will keep a threat for heavy
rainfall over central Montana. Instability will be weaker over
southwest Montana but gusty winds could occur with any of the
thunderstorms due to dry air below the thunderstorm cloud bases.
Drier air will work its way into the region on Wednesday from the
southwest. This should limit any thunderstorms to the far eastern
zones. Much warmer temperatures and dry conditions are expected on
Thursday. A few models forecast high temperatures near 100 in the
plains Thursday. Have bumped the temps up a few degrees with low
90s for the lower valleys and plains, in line with the model
consensus. Langlieb
Thursday Night through Tuesday...Medium range models are in pretty
decent agreement tonight. Period starts off with an upper level
ridge over the Rocky Mountain region for dry and very warm to hot
temperatures into Friday. Upper level troughing moves inland across
the Pacific Northwest Friday night and Saturday, pushing the ridge
into the Midwest. Troughing and an associated surface front moves
through Montana Saturday night bringing isolated thunderstorms to
the forecast area. As the trough moves east, a zonal flow aloft will
set up over the state, although temperatures will remain above
seasonal averages through the period. Model solutions are in much
better agreement tonight and keep the airmass dry and stable for
Monday and Tuesday so have kept precipitation below climatology. mpj
&&
.AVIATION...
UPDATED 0505Z.
Scattered thunderstorms continue across central and north central MT
from northeast of KGTF to east of KHVR, producing good amount of
lightning and moderate to locally heavy rainfall. Storms have also
been putting out gusty outflow winds of 25-35 kts. Storm cells are
expected to gradually dissipate between now and 08Z with ceilings
increasing to greater than 10000 ft at that time. Clear skies to
scattered clouds and light winds expected overnight. Tuesday will
be near-repeat of Monday's weather as scattered thunderstorms
develop again during the afternoon/evening.
Waranauskas
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 84 55 86 54 / 30 30 20 10
CTB 82 52 85 52 / 30 20 10 20
HLN 86 57 89 57 / 30 40 20 10
BZN 85 49 86 50 / 30 30 20 10
WEY 78 37 78 33 / 20 20 10 10
DLN 83 49 84 49 / 20 20 20 10
HVR 82 56 84 55 / 20 30 20 20
LWT 81 53 81 53 / 40 30 30 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...LANGLIEB
LONG TERM...mpj
AVIATION...mpj
weather.gov/greatfalls