Area Forecast Discussion
Issued by NWS Glasgow, MT
FXUS65 KGGW 201452
Area Forecast Discussion
National Weather Service GLASGOW MT
852 AM MDT Thu Oct 20 2016
.SHORT TERM...for northeast Montana...today through Sat...
The forecast is in excellent working order depicting freezing
fog for parts of the area this morning. The freezing fog advisory
has been expanded to cover a larger area of the CWA based on
observations and trends. Maliawco
Forecast challenges will focus mainly on the presence and
persistence of freezing fog along the Yellowstone River Valley
this morning. Seems to have formed near the western edge of a
clearing bank of low level clouds. Fog has been not as dense for
Poplar and Wolf Point, but 1/4 mile visibility has set in at
Glendive and had persisted for more than one hour. Felt it was
best to proceed with a freezing fog advisory this morning for
Dawson and Richland counties. Some fog models are generally
showing this fog, but the RAP13 seems to have the best handle on
it for now and may indicate more northern expansion of the fog
after sunrise than what I have shown in the forecast and advisory.
The synoptic weather pattern basically oscillates from weak dirty
ridging to zonal through the remainder of the short term forecast
period. Models are showing some weak agreement that this pattern
will give rise to a passing sprinkle early Friday morning, then
more substantial rain showers near and north of the Milk River
Valley Saturday morning as SW flow aloft become more prominent.
Expect temperatures throughout to be warm enough to support only
rain as the precip type after this morning.
.LONG TERM...Sat night through Thu...
An upper ridge will be building over the northern plains through
the weekend, opening the region to southwest flow aloft. Warm and
generally dry condition are expected through Monday with high
pressure sliding from the northern plains into the upper midwest.
The upper trof digging off the Pacific Northwest will begin
ejecting shortwaves across the northern Rockies to break down the
ridge early in the week. Lee side low develops in southern Alberta
on Tuesday then pulls a cold front through Montana Tuesday night.
Precipitation chances increase behind the frontal passage on
Wednesday although timing and position of the moisture stream
decrease confidence for details.
A better chance for precipitation occurs by the end of the week
with the upper trof moving on shore. Ebert
FLIGHT CATEGORY: IFR improving to VFR by Noon.
SYNOPSIS: A surface boundary is retreating to the northwest. An
inversion exists to the northwest of this boundary and has trapped
moisture under it in the form of a low cloud deck. The boundary
and most of the low clouds should be gone by Noon. These low clouds
could generate some icing on wings in decent.
FREEZING FOG: where the boundary passes over the surface as it
retreats it will bring clouds to ground generating fog and
freezing of very high density. the times of low visibility will
be limited to only an couple hours as the front quickly retreats.
WINDS: light and variable initially, becoming south to southwest
at 5 to 15 kts with the passage of the front by Noon, becoming
west by the end of the cycle Friday morning.
Freezing Fog Advisory until noon MDT today for Daniels...