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Displaying AFOS PIL: AFDDMX Received: 2018-02-09 18:16 UTC
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438 FXUS63 KDMX 091826 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1216 PM CST Fri Feb 9 2018 .SHORT TERM.../Today through Tonight/ Issued at 410 AM CST Fri Feb 9 2018 Obvious primary concern will be precip trends and associated headline decisions this morning. The band of snow from Thursday evening was phased with decent H5/H6 frontogenetic Fn response and low static stability above per +/- zero H5/H4 EPV. The banding/frontogenesis has fallen apart recently however, but spotty patches of stronger echoes upstream suggest low stability remains in place and is likely creeping eastward crossing the MO river per H7/H5 EPV <=0. Recent RAP and HRRR runs seem to have a good handle on reality with a few weaker bands pushing south and east through the morning in the broader, departing warm advection. Visibilities are now generally several miles with just a few lingering 1-2sm reports so additional accumulations should be minimal at this point, <=1 inch. Thus have scaled headlines back quite a bit in time and space per the following. * All headlines along and NE of a Denison-Pocahontas-Forest City line where snow has ended and amounts relatively low have been canceled * Kept the Winter Storm Warning going along Highway 20 from Webster City toward Waterloo where light snow is still in progress but shallow blowing snow may be a concern in the heaviest snow accums * Downgraded western edge and Highway 30 warning sections to advisory where either no additional snow is anticipated or amounts were lighter than expected but blowing snow may be an issue. * Cancel portions of advisory I80 and south * All remaining headlines will end at 12z per RAP/HRRR simulated reflectivities and be replaced by an SPS Later today the aforementioned lower stability may still produce some isolated snow showers, which appear more convective in nature per the radar mosaic. Any accumulations should be less than an inch and sporadic. Looking ahead into the early evening hours the next surge of forcing in the Pacific NW short wave train along the jet should cross the MO river into IA. Much of this forcing will be mid level, and while there will be fairly deep moisture, QG subsidence and cold advection is in place 1-3km. This mid level UVM will be coincident with a somewhat deeper dendritic growth zone however so 1-3 inch accums will be possible south half by 12z due to a prolonged light snow. .LONG TERM.../Saturday through Thursday/ Issued at 410 AM CST Fri Feb 9 2018 The overall pattern and precip mechanism from tonight will linger into the start of this period with additional lingering light snow possible southeast into Saturday Night with more minor accums possible. Farther north cold temperatures will be the main theme through the weekend with lows in the single digits above and below zero and far northern sections flirting with headline criteria /-20F/ wind chills once again. The outlook into the next work week looks predominately dry and cool with Iowa still influenced by the broad mean central CONUS trough. There are some subtle precip chances late in the period, but these look minor and confidence is low. Models are uncertain on the evolution of the midweek Baja cutoff and its interaction with Pacific NW short waves of varied strength. && .AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/ Issued at 1216 PM CST Fri Feb 9 2018 VFR conditions expected over all but KOTM through 02Z. Next system to impact the southern TAF locations. KDSM on the fringe of this but will see IFR conditions from 03Z-09Z and KOTM roughly 06Z to 12Z. Mainly vsbys will drive the IFR conditions but lower cigs will occur at times as well. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Small LONG TERM...Small AVIATION...FAB