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Displaying AFOS PIL: AFDDMX Received: 2018-01-12 09:48 UTC
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625 FXUS63 KDMX 120948 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 348 AM CST Fri Jan 12 2018 .SHORT TERM.../Today through Tonight/ Issued at 324 AM CST Fri Jan 12 2018 Confidence: High Main concern will be the cold. High pressure heading south today with strong cold air advection continuing to push into the region early today. Gradient winds remain quite brisk at 08z with 15 to 20 mph sustained winds and gusts to near 30 mph at times. This has been keeping wind chills from 20 to 30 below over the north half of the region...generally along and north of US 30. Temperatures will remain quite cold by sunrise with winds dropping off a bit. Will monitor the US 30 corridor for possible extension of wind chill advisory. As well...a slow recovery is expected through the late morning with winds remaining about 12 to 15 mph. For the remainder of the afternoon some sunshine early today will allow afternoon highs to recover to the single digits north to the teens south. Already the next upstream system is spreading mid-level clouds into central South Dakota and western Nebraska. This will overspread the region by late afternoon with cloud cover remaining in the region at least through 09z tonight south of I 80 while the north again clears out by 12z Saturday. The weak lee side wave responsible for the cloud cover will spread some light snow across Nebraska today and this evening. Meanwhile only leftover moisture and very weak mid level lift will reach far western sections of the forecast area by this evening. There may be a few flurries in the far west this evening. The Northern Plains high will once again reassert itself tonight and clear out the northern half of the region by 12z. Along with that H850 temperatures will drop back to near -19 by 12z to - 15C south. This along with northwest sfc gradient winds of near 10 kts will once again push wind chill values down to the -20 to -30 F range from US 20 north to the border. It's likely that headlines for wind chills will again be needed for Northern Iowa tonight as the combination of cold lows...wind create similar conditions to early today. .LONG TERM.../Saturday through Thursday/ Issued at 324 AM CST Fri Jan 12 2018 In the long term concerns still revolve around the cold through the middle of next week. Temperatures will be coldest Monday and Tuesday. Headlines are still a strong probability Monday night as winds remain brisk through the overnight hours with temperatures of 15 below across northern portions of the forecast area. We are looking at wind chills of greater than 30 below in this time frame. Finally by mid-week the upper trough that is responsible for dumping the arctic air into the region shifts east and allows an upper ridge to build by late week. Beyond the long term, a trough appears to want to set up somewhere across the west placing a zonal to southwest flow across Iowa. If this happens, we will be back above freezing. As for precip chances in the long term, the best chance remains to be Sunday into Sunday night as a deep trough drops down out of Canada and into the Upper Midwest. Models have been consistent with timing and features. Forcing looks pretty strong and it is this feature combined with another arctic high that will bring our next shot of bitterly cold air to Iowa Monday/Tuesday. QPF appears a little overdone but given the amount of forcing, the consistency of the models and the higher snow ratios expected across the north central to northeast Iowa...we could see a couple inches of new snow out of this. Still in question is how far southwest to bring the higher PoPs with this system. For now, I stayed with consensus though I did increase the PoPs to likely across the northeast quarter to third of the forecast area. Other than this system Sunday, the long term does look pretty dry, though with as cold as it will be we can't rule out flurries should there be any subtle passing disturbance. && .AVIATION.../For the 06Z TAFS through 06Z Friday night/ Issued at 1134 PM CST Thu Jan 11 2018 Scattered MVFR ceilings are in place across the eastern half of IA at 06z. While recent radar and satellite trends suggest these may have now become false ceilings to due mixing and ice aloft, have error on the side of caution and continued these for a few more hours. Otherwise there is fairly high confidence in VFR conditions through the remainder of the valid period with clear skies into Fri until mid clouds increase late in the day. && .DMX WATCHES/WARNINGS/ADVISORIES... Wind Chill Advisory until 10 AM CST this morning for IAZ004>007- 015>017-023>028-033>038. && $$ SHORT TERM...REV LONG TERM...FAB AVIATION...Small