Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 271406

Area Forecast Discussion
National Weather Service Glasgow MT
806 AM MDT Sun May 27 2018

Going forecast in good shape and little changes were made. Most of
the area will be dry today and cooler. Showers should stay to the
south of the CWA, but work their way back north tomorrow with a
marginal risk of severe thunderstorms in the SE zones. TFJ

Previous discussion...
Synoptic Setup: Short term begins with hot high pressure ridge
running north from New Mexico through the high plains of Colorado
and into the Dakotas. To the west of this south to southwest flow
runs from California through Montana and into the Canadian Prairie
Provinces pumping pacific moisture into the region. The base of a
trough embedded in the flow sits over Utah, Nevada, and southern
Idaho. A much large trough lies northwest over the Gulf of Alaska
and moving into northern British Columbia.

Today through tonight: Cooler air behind the previous disturbance
will filter into the region generating high pressure near the
surface for most of the CWA. The frontal boundary between this and
warmer air to the south and east will be around or south of I-94
over the Yellowstone Valley and may generate some afternoon and
evening showers.

Monday and Monday night: The trough over the Great Basin will
begin to break apart and send weak jet streaks into the region.
The first one will take what remains of the front across the
southeast and return it north increasing showers and thunderstorms
across the area during the afternoon and early evening, possibly
making a few isolated cells strong to severe. The remainder of the
trough should continue to evacuate northeast overnight
maintaining light showers and thunderstorms.

Tuesday through Thursday night: Flow will stay southwest
throughout these periods allowing for general thunderstorms.
However none look to be severe at this time with no upper level
support. Wednesday looks to be a very warm day with a sub-
synoptic ridge moving through the flow and this may taper down
convection for this period with highs again approaching 90.

Friday onward: Model agreement at this point goes out of phase
with general flow not being consistent from one main ensemble
member to the next. Thus far, a pattern change towards the cooler
side looks likely, but this could quickly change. Therefore,
confidence here onward is low. GAH




DISCUSSION: Cooler high pressure will move into northeast Montana
today with a stalled front around KGDV. This will keep most of
the terminals dry throughout the day with KGDV seing a possible
shower in the afternoon and evening hours.

WIND: Becoming northeast at 10 to 20 kts this afternoon...
reducing to 5 to 15 kts overnight.





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