Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/02/21

Area Forecast Discussion
National Weather Service Glasgow MT
231 PM MST Fri Jan 1 2021 .DISCUSSION... AFTERNOON DISCUSSION: Synoptic Setup: Forecast begins with a ridge of warm air being kicked out and a weak disturbance moving across northeast Montana overnight. Behind this a large ridge and trough exist over the Pacific Northwest with another ridge setting off the Pacific Coast. With flow being zonal this parade of pacific systems will be the main story through the forecast keeping things unseasonably warm or nearly 15 to 30 degrees above normal. This afternoon through Saturday: The ridge will exit the area around midnight with a weak cold front on its heels. This passage will have just enough moisture to put down a trace to maybe two hundredths of an inch of precip. With the very strong warm nose aloft much of the snow will melt into rain, which may in turn freeze on pavement. Timing of the passage is from around 09Z to 18Z. Models are in broad disagreement about QPF/PoPs with the passage of this system and about half the ensembles hint at no precip happening with the passage. So, confidence this close to the event is low with impacts being marginal. Therefore, have decided not to issues winter weather advisory for freezing rain yet and allow the the evening shift one last stab at it. Saturday night through Sunday night: While Saturday night will be uneventful with a ridge, the second the ridge exits a relatively strong cold front will come barrelling through. Its expected to hit around the middle of the day Sunday with CAA lasting well through the evening. Looking at lapse rates hitting nearly 8 *C/km and 850 mb windspeeds bumping to 50 kts in multiple models have high confidence and decided to go ahead and issue a High Wind Warning for southwest Phillips county. This could expand to surrounding areas down the line but for now other areas look marginal and not likely to hit that 40-50 kt range needed. Monday throuh Wednesday: These periods look similar to the previous forecast periods with unseasonably warm conditions continuing, if maybe trending down a degree or two each day. There is even another frontal passage with weak QPF expected and rain/snow/freezing rain possible Tuesday. Wednesday night onward: Models ensembles are too far apart to predict more than unseasonably warm conditions continuing. Confidence from here onward is low. GAH 815AM UPDATE: Changes to the forecast this morning were mainly to bring sky conditions back into alignment. The bulk of NBM`s ensembles appeared to previously had fog hanging in quite awhile today which increased sky coverage. With the GOES NightFog Product showing the bulk of it dissipating from southwest to northeast it should be gone by about 18Z. The latest model ensembles seem to have finally caught on are rapidly clearing the afternoon and evening hours to partly cloudy for the northern half of the CWA. GAH MORNING DISCUSSION: High pressure has brought some patchy areas of low clouds and freezing fog along the International border and near the Montana North Dakota state line that should last through the morning of the New Year. The weak ridge will keep conditions dry today with periods of sunshine for northeastern Montana. A trough currently off the US west coast will pass through the region, increasing the potential for light precipitation and stronger winds this weekend. Temperatures will continue to warm through this timeframe. Overnight temperatures will be cold enough for snow, but warm westerly winds will promote a variety of wintery options Saturday morning. Prepare for the potential for any precipitation type if you plan to travel, especially in the morning. Precipitation that falls in the afternoon should be rain. Once the sun sets, temperatures will cool to below freezing, and any POP and thus ptype will change over, but by then could be on its way into the Dakotas. On Sunday, some folks could have temperatures hitting 50 degrees. With 850mb winds in the 40 to 55 kt range across the area, confidence is growing for a breezy weekend with westerly wind gusts in excess of 40 mph. Higher lapse rates in the west and southwest in addition to potential downsloping from higher terrain may increase daytime high temperatures above model guidance and bring locally higher wind gusts to the surface on Sunday. A progressive pattern will continue through the forecast period, with warmer and drier than normal weather into next week. Episodic shortwaves will bring a couple more opportunities for moisture, however light. Roxy && .AVIATION... LAST UPDATED: 2130Z FLIGHT CAT: VFR DISCUSSION: A cold front will move through the area from 09-18Z. Very light precipitation will be possible but not likely with its passage. With ground frozen, any potential rain could easily freeze on contact with runsways increasing breaking distance. LLWS: Around 14Z Saturday to just beyond the end of the TAF cycle, low level wind shear will become a problem as a cold front works its way past northeast Montana. Strong winds above may not be able to reach the surface initially. This will create a strong speed shear difference for aircraft approaches. WIND: West and southwest at 5 to 10 kts this afternoon through tonight. Veering to the west and increasing to 10 to 20 kts Saturday afternoon. GAH && .GLASGOW WATCHES/WARNINGS/ADVISORIES... High Wind Warning from 11 AM to 11 PM MST Sunday for Southwest Phillips. && $$