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Displaying AFOS PIL: AFDDMX Received: 2018-01-17 11:30 UTC
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270 FXUS63 KDMX 171130 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 530 AM CST Wed Jan 17 2018 .SHORT TERM.../Today through Tonight/ Issued at 358 AM CST Wed Jan 17 2018 There is little weather of concern in this period beyond temperature trends. The long wave trough will continue to depart with warm advection in place throughout the day. Moisture will be very limited however so there will be little in the way of cloud cover. The warm advection will wane somewhat into tonight however with the H85/H7 thermal ridge crossing the Plains into IA. Attention will turn to the current compact short wave/PV anomaly as it skirts the MN/Canada border later tonight. This will have little effect this far south however keeping skies mostly clear in our dry airmass. Current 09z obs show temps ranging from just above zero to the single digits below, but with the surface ridge moving through winds are fairly light. A few spots are showing wind chills near advisory criteria but this should be brief and not too impactful considering the light wind so no additional wind chill advisories this morning. Examination of soundings suggests highs today could rebound more than recently with the warm advection pushing highs closer to normal, into the lower to middle 20s. .LONG TERM.../Thursday through Tuesday/ Issued at 358 AM CST Wed Jan 17 2018 The initial but secondary concern in this period will be temp trends as we continue to warm, but the primary impact will be the large storm anticipated for the weekend. At onset, the aforementioned system will be passing through the Great Lakes with little impact here besides ushering in additional warm advection in its wake. Surface flow will change little through the work week with highs pushing back to or even just above normal by Thursday. The bigger question will be how warm can we get by Friday. The 00z NAM snow depth initialization was fairly good, but it changes little into Friday, which seems unlikely, especially south. Considering the persistent warm advection and favorable trajectories it would seem we could erode more of the inversion than depicted in soundings by that time, especially in the lesser snow depths south and west. Have not gone as aggressive of what MOS depicts, but have warmed temps further through the 40s. It is often difficult to get beyond mid 40s for highs with at least several inches of snow depth keeping readings there north, but 45-50 would seem attainable eroding at least a third of the inversion south and west. Would not be surprised to see some 50s depending on the degree of snow melt Thursday. Looking into the weekend there continues to be high confidence and good agreement in larger scale features and some of the sensible weather. The ECMWF/EPS and GFS/GEFS all have similar depictions of a deepening surface low advancing from the Plains into Great Lakes Sunday into late Monday. There are some timing and track differences at this time range of course which will diminish confidence in details, but some higher confidence broader things to key on at this point include strong winds as the system exits, likely stronger than currently depicted in the forecast until timing and location can be better defined, and the potential for accumulating, wind blow snow over some part of northwest Iowa. Dropping down to medium confidence will be a period of convection south and east in the warm sector, which has yet to be introduced until timing confidence increases, and likely drizzle or lighter precip in the shallow moisture along and south of the triple point track Saturday Night. Confidence decreases even further with regard to localized precip types early next week with surface temps and the location and extent of the potent dry slot all still in question. Both of these will have an appreciable impact on precip type and magnitude and will not be better defined until the coming days, if then. The current forecast only has rain or snow depicted, but all kinds of mixed wintry precip such as drizzle, freezing drizzle, and sleet are on the table wherever the transition zone lays out depending on the dry slot and ice introduction as well as warm layer and surface temps. Confidence may remain low with this system even right up to game time because of all these moving parts. PoPs will decrease later Monday as the system exits and will be followed by relatively benign NW flow aloft. The source region will have sufficient westerly component to keep our temps close to normal into early next week. There are some token low end PoPs to end the period, but confidence is low in model agreement and anything that does occur does not look too significant at this time. && .AVIATION.../For the 12Z TAFS through 12Z Thursday morning/ Issued at 529 AM CST Wed Jan 17 2018 There is high confidence in VFR conditions and essentially clear skies through the period. Winds will change little in speed or direction outside of minor peak heating speed increases, staying south-southwesterly. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...Small LONG TERM...Small AVIATION...Small