Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 011546
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
945 AM MDT Fri Aug 1 2014

.DISCUSSION...
Update forthcoming. Have adjusted POP and sky grids for this
morning. General forecast theme remains unchanged with the pattern
similar to yesterday. Airmass thunderstorms likely to develop again
this afternoon. Highest CAPEs will again occur along the Rocky
Mountain Front and across the Hi-Line as well as higher dew points.
As was the case on Thursday, shear values are generally less than 30
knots and any storm reaching severe status will likely be isolated.
Temperatures look good.

$$

.AVIATION...
UPDATED 1200Z.
VFR conditions prevail with mostly sunny skies to start and
increasing clouds through the day. Another round of isolated showers
develop after 20Z. MVFR conditions are possible near thunderstorms.

&&

.PREV Discussion...Issued 409 AM MDT Fri Aug 1 2014

Today...Another hot day in store with highs in the low/mid 90s. One
feature to note will be a sfc pressure gradient and associated
northeasterly wind shift that develops over southern Alberta
and then slowly sags into far NC Montana by late afternoon/early
evening. This boundary will bring significantly higher
dewpoints...in the 50s to near 60 F...into areas along the
Hi-line...which will increase MLCAPE to near ~1500 J/kg and could
briefly exceed 2000 J/kg. 0-6 km shear will remain below 30 kts, so
only a few isolated stronger storms are possible across the far
north. Also, added environmental moisture means showers and storms
will be more efficient heavy rainfall producers compared to what we
have seen over the past few days.

NAM has a convectively-induced vorticity max, that is currently
over eastern Oregon, moving across the NW portion of my CWA late
tonight and into Saturday morning. Based on the track of this
feature and its dynamics, there may be a period overnight when sct
showers and storms affect the Rocky Mountain Front and adjacent
plains area.

Saturday afternoon and Sunday...As the aforementioned air mass moves
slowly southward into NC Montana PW will increase to near 1 inch as
far south as Great Falls. Isolated to scattered showers and storms
are expected with some storms likely producing brief heavy rain.
Highest instability will be found E/NE of Great Falls where MLCAPE
may approach ~1000-1500 J/kg. Sunday looks to be similar to
Saturday but convective activity may be more isolated as dewpoints
drop back into the 40s for most locations. Uttech

Sunday Night through Friday...A repeat of the current pattern
continues through the long term. Warm temperatures and isolated to
scattered thunderstorms will develop each afternoon, generally
starting up over terrain. With the showery nature of monsoonal
moisture, uncertainty remains with precipitation amounts and
coverage. Areas near higher terrain have the best chance of seeing
precipitation, namely the Continental Divide and Southwest Montana.
Latest forecast model runs suggest that increased coverage of
showers will develop Sunday afternoon/evening as a more defined
shortwave trough moves through the region. Drier conditions return
later next week as a high pressure rebuilds over the region.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  93  60  87  60 /  20  20  30  30
CTB  88  55  84  56 /  20  40  30  30
HLN  92  60  91  60 /  20  20  30  30
BZN  90  54  91  55 /  20  20  30  30
WEY  80  45  78  45 /  30  30  30  30
DLN  87  53  89  54 /  30  30  30  30
HVR  95  59  86  61 /  20  20  30  30
LWT  90  57  83  58 /  20  10  30  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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