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Displaying AFOS PIL: AFDDMX Received: 2017-08-13 17:26 UTC
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803 FXUS63 KDMX 131726 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1226 PM CDT Sun Aug 13 2017 ...Updated for 18z Aviation Discussion... .SHORT TERM.../Today through Tonight/ Issued at 401 AM CDT Sun Aug 13 2017 Two areas of precipitation currently ongoing with one across southeast North Dakota and into west central Minnesota and the other over eastern Nebraska and into far west central Iowa. Each region is focused along the northern edges of two low level jet maxes and regions of strong theta-e advection and greater instability. The convection over eastern Nebraska has been weakening over the last several hours with cloud tops warming and lightning activity diminishing. CAM solutions have not been initializing well overnight and remain too aggressive with precipitation. Most solutions continue to focus over northwest Iowa where no activity is occurring. Furthermore, the current region of precipitation is moving east into a more stable and drier air mass as the large surface high pressure remains entrenched through the Mississippi Valley and Lake Michigan region. Expect a continued degradation in activity over the next several hours. Still uncertainty on how far east the precipitation will reach this morning as the low level jet does veer into the state. Overall most locations are expected to stay mostly dry though a period of brief light rain could reach east towards Interstate 35 before ending. Better instability arrives tonight and should have renewed convection over northwest Iowa that will gradually settle into central Iowa. .LONG TERM.../Monday through Saturday/ Issued at 401 AM CDT Sun Aug 13 2017 The main forecast concern was focused on periodic precipitation chances through mid-week. Leaned toward a blend of the ECMWF/GFS throughout the forecast period even though the NAM seems be in good agreement with these two through Tuesday. Overall, no significant changes to the ongoing forecast. Monday into Tuesday...weak upper level shortwave trough cuts across Minnesota during the day Monday and brings some decent forcing over northern Iowa. No significant deep moisture, but enough in the mid- levels (b/t 850-700mb) to provide the threat of elevated convection Monday. Low confidence in any heavy rain threat, at least widespread across the forecast area. Boundary lays up west to east across the state early Tuesday with another upper level vort max coupled with some 700-500mb theta-e advection looks to be enough for a few storms along and northern of Highway 30 to Minnesota border. Weak CAPE available, but enough present to warrant mention of thunder early Tuesday. Tuesday night into Wednesday...surface low pressure, 500mb shortwave trough, and associated cold front look to bring increasing rain chances late Tuesday night into Wednesday. Latest ECMWF run suggest Iowa will be split between two 500mb vort maxes placing the higher QPF amounts in Minnesota and Missouri but still enough across the state to keep with higher chance to likely pops. The GFS beginning to show this trend with the main vort max cutting across Minnesota during the same time and then a second shortwave trailing behind by Wednesday afternoon. Regardless of solution, Wednesday appears to be the state's best chance of any widespread convection and rainfall. Thursday into saturday...trough moves east and allows for surface high pressure to build into the state Thursday into Friday. ECMWF/GFS have a shortwave that tries to push into western Iowa by Friday morning but with the fairly strong surface high and plenty of dry air in place, low confidence with any pops Thursday night into Friday. Thus, decreased or removed them entirely during this time. && .AVIATION.../For the 18Z TAFS through 18Z Monday afternoon/ Issued at 1228 PM CDT Sun Aug 13 2017 VFR conditions have prevailed at the TAF sites with scattered showers moving across central Iowa this morning and early this afternoon. These showers may brush KALO and have mentioned it for the afternoon hours. Also cannot rule out a rogue shower affecting KMCW or KFOD, but have not mentioned at this time due to lower confidence. Have continued VCTS later tonight at the northern terminals and this is also where lower ceilings will arrive toward sunrise Monday with MVFR restrictions. It's possible these lower ceilings will reach farther south and east, but confidence is lower given SREF guidance maintains the best chance for lower ceilings over northwestern and north central Iowa. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Donavon LONG TERM...Podrazik AVIATION...Ansorge