Area Forecast Discussion
Issued by NWS Great Falls, MT
FXUS65 KTFX 200543
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1040 PM MST Wed Nov 19 2014
Aviation Section Updated.
Tonight...A cool, moist airmass remains over central and northern
potions of the region. Light surface flow will allow for widespread
fog to develop central and north. Areas of this will be dense and
the freezing fog advisory has been expanded. Also lowered overnight
temps across central portions of the zones. Zelzer
LIFR conditions in FZFG prevail at KCTB due to a stationary front in
the area. This fog will persist through early morning hours when a
lee trof develops and southwest winds develop. FZFG has become
widespread across North-central MT, including KGTF/KHVR/KHLN at
times. VFR conditions are expected at KBZN and KLWT. Winds remain
light and variable tonight, but strengthen Thursday afternoon. Mid
and high-level clouds will increase ahead of the next Pacific
weather system. Nutter
/ISSUED 445 PM MST Wed Nov 19 2014/
Tonight through Friday...Quiet weather pattern will persist
overnight. An area of low clouds and fog continues across portions
of North Central and Southwest Montana. Some gradual lifting of
the fog is possible by late afternoon but fog will likely redevelop
again after dark. An upper trof will move to the Continental
Divide Thursday afternoon allowing isolated showers to develop
over the western and southwest mountains. Westerly flow aloft will
increase Thursday with the strongest winds along the Rocky
Mountain Front. Friday looks to be dry as downslope winds aloft
keeps precipitation out of the plains. Temperatures will be near
seasonal averages though cold air may remain trapped in some of
the southwest valleys.
Friday night through Wednesday...Split flow across the Western US
late this week consolidates this weekend as a strong Pacific Jet
moves onshore with a fairly vigorous mid-level trough/surface cold
front sweeping east across MT Saturday. Surface winds increase
Friday night through Saturday morning ahead of the front with
potential for strong winds along the Rocky Mtn Front. Strong wind
potential also exists Saturday morning in the Norris Hill area of
Madison County where SSW flow is channeled. Precipitation will be
most widespread along the Continental Divide Fri night and Saturday
with a period of showers likely accompanying the frontal passage as
it moves across the remainder of the forecast area. There is also
the potential for a brief period of freezing rain on Saturday
morning in the Helena Valley and along the Milk River near Havre.
Confidence is low on if freezing rain will occur, however if the
current cold airmass does not mix out by Saturday morning, then the
chance for freezing rain will increase.
A cooler NW flow aloft follows Saturday night into much of next week
with several embedded impulses keeping conditions unsettled though
model differences increase significantly by the middle of next week.
ECMWF and GFS keep the main upper level Jet energy to SW of the
region, but the ECMWF keeps heights colder in a more cyclonic flow
aloft while the GFS has an anticyclonic curvature to the flow with
higher heights and farther east position of an upper level ridge
along the West Coast. ECMWF has been slightly more consistent over
the last several model runs while the GFS has fluctuated more so am
leaning slightly toward the ECMWF solution and have cooled
temps/raised pops through much of next week however confidence is
.PRELIMINARY POINT TEMPS/POPS...
GTF 17 43 31 44 / 0 10 10 10
CTB 15 42 28 42 / 0 10 10 10
HLN 17 36 27 42 / 10 10 10 10
BZN 12 38 17 38 / 10 10 20 10
WEY 7 31 13 29 / 10 30 30 20
DLN 20 40 20 37 / 10 10 10 10
HVR 8 36 22 41 / 0 0 10 10
LWT 16 46 27 44 / 0 10 10 10
FREEZING FOG ADVISORY until 9 AM MST Thursday Blaine...Cascade...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
FREEZING FOG ADVISORY from 3 AM to 9 AM MST Thursday Central and
Southern Lewis and Clark.