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Office: DMX

FXUS63 KDMX 200814
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
314 AM CDT Thu Sep 20 2018

.DISCUSSION.../Today through Wednesday/
Issued at 314 AM CDT Thu Sep 20 2018

Fairly quiet in the mid/long range with focus on today into tonight
with severe weather chances and heavy rain chances still through the
morning hours. Overall have a strengthening upper level trough
moving through the intermountain west which is expected to lift east
northeast through the region today into tonight. An associated
surface low pressure is centered across SW NE/NW KS and ERN CO with
a warm front stretching ENE through eastern NE and central/north
central Iowa. Moisture transport ahead of this system has been
oriented straight into NE Nebraska and northern IA through the
overnight hours with ongoing shower and isolated thunderstorm
activity in place across the northern third of the forecast area.
Backbuilding continues on the south side of the rain area which is
expected to continue through sunrise. However the entire area of
rain is expected to slowly ooze northward through this morning as
the warm front begins to lift north with the sfc low beginning to
lift ENE into central NE by mid morning. WPC had a moderate risk of
excessive rainfall across the north and that continues through 12z.
Rain rates have settled down some in the past few hours, but
continued fetch of moisture into the area and chances for heavy rain
still possible as moisture transport to strengthen even further
toward 12-15z. Therefore will continue the flash flood watch through
this morning.

Focus beyond early this morning, then shifts to the severe threat
for thunderstorms toward mid/late afternoon into tonight. The sfc
low off to the southwest to become situated near the Sioux City area
by 18z and then lift into SW MN toward 21z before moving into NW WI
by late evening. The associated warm front will continue to lift
northward into southern MN by this afternoon, with a trailing cold
front stretching from NW IA through central/eastern NE toward
mid/late afternoon. Some question as to how far north the warm front
will lift and expect development of storms along/south of the front
toward mid/late afternoon. With the sfc low expected to be in NW
IA/SW MN, could have a chance for some of the activity across far
northern Iowa. These storms are expected to be more discrete and
will bring the better chances for tornado development near the low
pressure area and the aforementioned warm front. CAPE values around
2000 J/kg or higher expected in the warm sector with strong low
level/deep layer shear in place. Some of the higher res models keep
the sfc low a bit further south tracking closer to the IA/MN border
which would increase the tornado threat across the far northern
forecast area near the triple point. Storms also expected to develop
along the sfc cold front extending S/SW from the sfc low through the
late afternoon hours. As the front slides across the area this
evening will see a continued chance for thunderstorms and severe
wind gusts. If can get some bowing segments in the line and
orientation of the 0-3 shear vector, could see some brief spinups
along the line of storms as well in addition to the damaging wind
threat. Enough instability and shear that could see some large hail
with the storms later today/tonight as well, but best chances will
be with the storms initially especially in any storms that remain
discrete. The front should exit the area by late tonight with precip
chances waning as well by Friday morning.

Other issue besides the severe weather will be gusty winds ahead of
the front across the forecast area today. Winds aloft to increase to
around 30 to 40 kts with a tightening sfc pres gradient. Harder to
get these winds to translate to the surface with mixing versus in a
CAA pattern, but still should get breezy to windy conditions. Would
not be surprised either if a few sites especially in the south/west
today hit advisory criteria at times. However do not feel it will be
widespread enough or consistent enough to issue a wind advisory for
now.

High pressure to then build into the area behind the system for
Friday into Sunday with dry and cooler conditions. Another system to
move through the region Monday into Tuesday bringing the next
chances for rain and storms with another system toward late next
week. More seasonable temperatures expected throughout the mid/long
range with a stronger cooldown looking probable just beyond the
forecast period.

&&

.AVIATION.../For the 06Z TAFS through 06Z Thursday night/
Issued at 1110 PM CDT Wed Sep 19 2018

Few changes to previous forecast. Looking for convection/low cigs
to MVFR/IFR to continue north sites through 13z at KMCW/KALO and
near KFOD as well. Farther south expecting VFR conditions through
at least 21z as upstream front will be slower to arrive. Mixing
winds will increase aft 13z over the region with gusts 25 to 35kts
from 19z through 22z...gusts continue into the evening. Front will
arrive far northwest by 22-23z moving southeast through 03z.
Another round of lower cigs/wind gusts and lower vsby possible.
/rev


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 1 PM CDT this afternoon for IAZ004>007-
015>017-023>028.

&&

$$

DISCUSSION...Beerends
AVIATION...REV

FXUS63 KDMX 200814
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
314 AM CDT Thu Sep 20 2018

.DISCUSSION.../Today through Wednesday/
Issued at 314 AM CDT Thu Sep 20 2018

Fairly quiet in the mid/long range with focus on today into tonight
with severe weather chances and heavy rain chances still through the
morning hours. Overall have a strengthening upper level trough
moving through the intermountain west which is expected to lift east
northeast through the region today into tonight. An associated
surface low pressure is centered across SW NE/NW KS and ERN CO with
a warm front stretching ENE through eastern NE and central/north
central Iowa. Moisture transport ahead of this system has been
oriented straight into NE Nebraska and northern IA through the
overnight hours with ongoing shower and isolated thunderstorm
activity in place across the northern third of the forecast area.
Backbuilding continues on the south side of the rain area which is
expected to continue through sunrise. However the entire area of
rain is expected to slowly ooze northward through this morning as
the warm front begins to lift north with the sfc low beginning to
lift ENE into central NE by mid morning. WPC had a moderate risk of
excessive rainfall across the north and that continues through 12z.
Rain rates have settled down some in the past few hours, but
continued fetch of moisture into the area and chances for heavy rain
still possible as moisture transport to strengthen even further
toward 12-15z. Therefore will continue the flash flood watch through
this morning.

Focus beyond early this morning, then shifts to the severe threat
for thunderstorms toward mid/late afternoon into tonight. The sfc
low off to the southwest to become situated near the Sioux City area
by 18z and then lift into SW MN toward 21z before moving into NW WI
by late evening. The associated warm front will continue to lift
northward into southern MN by this afternoon, with a trailing cold
front stretching from NW IA through central/eastern NE toward
mid/late afternoon. Some question as to how far north the warm front
will lift and expect development of storms along/south of the front
toward mid/late afternoon. With the sfc low expected to be in NW
IA/SW MN, could have a chance for some of the activity across far
northern Iowa. These storms are expected to be more discrete and
will bring the better chances for tornado development near the low
pressure area and the aforementioned warm front. CAPE values around
2000 J/kg or higher expected in the warm sector with strong low
level/deep layer shear in place. Some of the higher res models keep
the sfc low a bit further south tracking closer to the IA/MN border
which would increase the tornado threat across the far northern
forecast area near the triple point. Storms also expected to develop
along the sfc cold front extending S/SW from the sfc low through the
late afternoon hours. As the front slides across the area this
evening will see a continued chance for thunderstorms and severe
wind gusts. If can get some bowing segments in the line and
orientation of the 0-3 shear vector, could see some brief spinups
along the line of storms as well in addition to the damaging wind
threat. Enough instability and shear that could see some large hail
with the storms later today/tonight as well, but best chances will
be with the storms initially especially in any storms that remain
discrete. The front should exit the area by late tonight with precip
chances waning as well by Friday morning.

Other issue besides the severe weather will be gusty winds ahead of
the front across the forecast area today. Winds aloft to increase to
around 30 to 40 kts with a tightening sfc pres gradient. Harder to
get these winds to translate to the surface with mixing versus in a
CAA pattern, but still should get breezy to windy conditions. Would
not be surprised either if a few sites especially in the south/west
today hit advisory criteria at times. However do not feel it will be
widespread enough or consistent enough to issue a wind advisory for
now.

High pressure to then build into the area behind the system for
Friday into Sunday with dry and cooler conditions. Another system to
move through the region Monday into Tuesday bringing the next
chances for rain and storms with another system toward late next
week. More seasonable temperatures expected throughout the mid/long
range with a stronger cooldown looking probable just beyond the
forecast period.

&&

.AVIATION.../For the 06Z TAFS through 06Z Thursday night/
Issued at 1110 PM CDT Wed Sep 19 2018

Few changes to previous forecast. Looking for convection/low cigs
to MVFR/IFR to continue north sites through 13z at KMCW/KALO and
near KFOD as well. Farther south expecting VFR conditions through
at least 21z as upstream front will be slower to arrive. Mixing
winds will increase aft 13z over the region with gusts 25 to 35kts
from 19z through 22z...gusts continue into the evening. Front will
arrive far northwest by 22-23z moving southeast through 03z.
Another round of lower cigs/wind gusts and lower vsby possible.
/rev


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 1 PM CDT this afternoon for IAZ004>007-
015>017-023>028.

&&

$$

DISCUSSION...Beerends
AVIATION...REV



Office: DVN FXUS63 KDVN 200819 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 319 AM CDT Thu Sep 20 2018 .SYNOPSIS... Issued at 317 AM CDT Thu Sep 20 2018 A warm front was located south of Interstate 80 with showers and a few thunderstorms north of this front in our northern counties early this morning. The heavier and more widespread rain and storms have been across northern IA/southern MN/southern WI. To the south of the front the atmosphere was capped and temperatures were in the 70s, but readings were in the 60s to the north of the front. Temperatures were only in the 40s and 50s in northern WI/northern MN and into the Dakotas. Low pressure was located in sw Neb (1002 mb). && .SHORT TERM...(Today and Tonight) ISSUED AT 317 AM CDT Thu Sep 20 2018 One last hot day of the season until next summer, then the long- awaited fall pattern becomes established. Today: A strong upper level wave moving out of the northern Rockies will intensify the cyclone in Nebraska. This will allow the warm front in our area to lift northward into MN and WI. Any lingering showers or isolated storms will end by early to mid morning in our far north. Then much of the day will be mostly sunny hot and humid as the atmosphere should be capped. As the cyclone deepens to 997 mb as it tracks to eastern MN, a strong low level jet will allow for gusty south winds this afternoon, gusting to 35 mph. Maximum temperatures will soar into the upper 80s to lower 90s, which will be near record highs (see climate section below). With dewpoints in the lower 70s the heat index values will push to around 100 for about 4 hours this afternoon, mainly south of Highway 30. Being that we recently had a string of hot days (acclimated?) was not planning on issuing a heat advisory at this time. This looks to be handled by a special weather statement and will mention in the HWO and weather story. Tonight: The cyclone will continue to deepen as it tracks into northern WI this evening. The bulk of the severe weather, (including tornadoes) should occur across southeast/eastern MN and into WI associated with the triple point area (enhanced risk there). The CAM's models suggest a line of thunderstorms sweeping into the dvn cwa later this evening and overnight. However, there should be a weakening trend to this line as CAPE diminishes and the better forcing lifts off to our north, as the surface low pushes northeast of Lake Superior by sunrise Friday. SPC has a slight risk barely in our far nw cwa for this evening. Much cooler air will be ushered into our nw cwa overnight with lows there in the upper 50s. Our se cwa will have lows in the upper 60s. .LONG TERM...(Friday through Wednesday) ISSUED AT 317 AM CDT Thu Sep 20 2018 The main message for this portion of the forecast is cooler and drier. Following the passage of the cold front early Friday morning a cool Canadian airmass will move in and take residence over the forecast area for the weekend. There could be some lingering showers over the far southern tier of counties early Friday morning, but this will quickly sink south with a dry forecast in play for the remainder of the day. After a hot day today, much cooler temperatures are expected for Friday, ranging from the low 60s to low 70s from northwest to southeast. Not only will temperatures be cooler, but dewpoints in the 40s and 50s keep the humidity low, so could make it seem chilly compared to the past week. Looking for below normal lows Friday night with lows generally in the 40s. The far northwest counties may see lows drop into the low 40s. This seems quite plausible as current observations in this airmass over North Dakota and Minnnesota are showeing readings in the low 40s. Winds will be fairly calm and with clear skies to help the boundary layer decouple, confidence is rather high in the lows for Friday night. Saturday will be cool and quiet with the surface high overhead, then on Sunday the high moves east with southerly flow bringing back a little warmer air. The southerly flow will be interupted by a front in place from Oklahoma into Virginia so there won't be a full feed from the Gulf of Mexico, but dewpoints will rise back into the 50s. This will keep lows in the 50s Sunday night. Synoptically, on Sunday a trough pushes onto the west coast, which will move east on Monday into Tuesday. The primary low with this system will be over Ontario, with a cold front that will drag behind it down into the southern plains. Warm air advection ahead of this front will give us another day in the mid to upper 70s, then prior to the front passing through on Tuesday evening showers and storms are expected across the region. As the front moves through, another Canadian airmass will move in behind it bringing another round of near to below normal air to close out the work week. By the end of this forecast cycle, another reinforcing cold front will be moving into the northern plains with 850mb temperatures around 0C. So, again the main story is a pattern change, with the region taking more influence from upper level troughing, rather than ridging. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) ISSUED AT 317 AM CDT Thu Sep 20 2018 Showers and isolated thunderstorms north of Interstate 80 will diminish this morning as a warm front lifts into WI. Much of Thursday will be hot and dry with VFR conds. A strong cold front will push across the taf sites Thursday night accompanied by a line of thunderstorms. South winds will be gusting to 25 knots Thursday afternoon ahead of this front. && .HYDROLOGY... Issued at 237 PM CDT Wed Sep 19 2018 One to three inches of rain has fallen in parts of north central and northeast Iowa over the past 24-36 hours. The current WPC rainfall forecast through Thu morning has a 100-150 mile wide swath of another 1 to 3 inches generally centered on and spanning along the Iowa/Minnesota border. For this reason, river forecasts for the Cedar River basin are forecast to rise above flood stage in the Day4 to Day7 time frame. Due to the uncertainty of amounts and placement of forecasted rainfall, I have issued new Flood Watches for the Cedar River at Vinton, Cedar Rapids, and Conesville. I have also continued the Flood Watch on the Iowa River at Marengo, which, although delayed 48 hours, still is forecast to exceed its flood stage early next week. As for current river flooding on the Lower Mississippi and Rock rivers, the levels on the Mississippi at Gladstone, Burlington, and Gregory Landing are expected to drop below their respective flood stages tonight. However, the Rock River at Joslin will continue to slowly fall; reaching its flood stage level Saturday. && .CLIMATE... ISSUED AT 317 AM CDT Thu Sep 20 2018 Record Highs for September 20... Moline.........94 in 2017 Cedar Rapids...93 in 1931 Dubuque........92 in 1895 Burlington.....93 in 2017 && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...Haase SHORT TERM...Haase LONG TERM...Brooks AVIATION...Haase HYDROLOGY...14 CLIMATE...Haase FXUS63 KDVN 200819 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 319 AM CDT Thu Sep 20 2018 .SYNOPSIS... Issued at 317 AM CDT Thu Sep 20 2018 A warm front was located south of Interstate 80 with showers and a few thunderstorms north of this front in our northern counties early this morning. The heavier and more widespread rain and storms have been across northern IA/southern MN/southern WI. To the south of the front the atmosphere was capped and temperatures were in the 70s, but readings were in the 60s to the north of the front. Temperatures were only in the 40s and 50s in northern WI/northern MN and into the Dakotas. Low pressure was located in sw Neb (1002 mb). && .SHORT TERM...(Today and Tonight) ISSUED AT 317 AM CDT Thu Sep 20 2018 One last hot day of the season until next summer, then the long- awaited fall pattern becomes established. Today: A strong upper level wave moving out of the northern Rockies will intensify the cyclone in Nebraska. This will allow the warm front in our area to lift northward into MN and WI. Any lingering showers or isolated storms will end by early to mid morning in our far north. Then much of the day will be mostly sunny hot and humid as the atmosphere should be capped. As the cyclone deepens to 997 mb as it tracks to eastern MN, a strong low level jet will allow for gusty south winds this afternoon, gusting to 35 mph. Maximum temperatures will soar into the upper 80s to lower 90s, which will be near record highs (see climate section below). With dewpoints in the lower 70s the heat index values will push to around 100 for about 4 hours this afternoon, mainly south of Highway 30. Being that we recently had a string of hot days (acclimated?) was not planning on issuing a heat advisory at this time. This looks to be handled by a special weather statement and will mention in the HWO and weather story. Tonight: The cyclone will continue to deepen as it tracks into northern WI this evening. The bulk of the severe weather, (including tornadoes) should occur across southeast/eastern MN and into WI associated with the triple point area (enhanced risk there). The CAM's models suggest a line of thunderstorms sweeping into the dvn cwa later this evening and overnight. However, there should be a weakening trend to this line as CAPE diminishes and the better forcing lifts off to our north, as the surface low pushes northeast of Lake Superior by sunrise Friday. SPC has a slight risk barely in our far nw cwa for this evening. Much cooler air will be ushered into our nw cwa overnight with lows there in the upper 50s. Our se cwa will have lows in the upper 60s. .LONG TERM...(Friday through Wednesday) ISSUED AT 317 AM CDT Thu Sep 20 2018 The main message for this portion of the forecast is cooler and drier. Following the passage of the cold front early Friday morning a cool Canadian airmass will move in and take residence over the forecast area for the weekend. There could be some lingering showers over the far southern tier of counties early Friday morning, but this will quickly sink south with a dry forecast in play for the remainder of the day. After a hot day today, much cooler temperatures are expected for Friday, ranging from the low 60s to low 70s from northwest to southeast. Not only will temperatures be cooler, but dewpoints in the 40s and 50s keep the humidity low, so could make it seem chilly compared to the past week. Looking for below normal lows Friday night with lows generally in the 40s. The far northwest counties may see lows drop into the low 40s. This seems quite plausible as current observations in this airmass over North Dakota and Minnnesota are showeing readings in the low 40s. Winds will be fairly calm and with clear skies to help the boundary layer decouple, confidence is rather high in the lows for Friday night. Saturday will be cool and quiet with the surface high overhead, then on Sunday the high moves east with southerly flow bringing back a little warmer air. The southerly flow will be interupted by a front in place from Oklahoma into Virginia so there won't be a full feed from the Gulf of Mexico, but dewpoints will rise back into the 50s. This will keep lows in the 50s Sunday night. Synoptically, on Sunday a trough pushes onto the west coast, which will move east on Monday into Tuesday. The primary low with this system will be over Ontario, with a cold front that will drag behind it down into the southern plains. Warm air advection ahead of this front will give us another day in the mid to upper 70s, then prior to the front passing through on Tuesday evening showers and storms are expected across the region. As the front moves through, another Canadian airmass will move in behind it bringing another round of near to below normal air to close out the work week. By the end of this forecast cycle, another reinforcing cold front will be moving into the northern plains with 850mb temperatures around 0C. So, again the main story is a pattern change, with the region taking more influence from upper level troughing, rather than ridging. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) ISSUED AT 317 AM CDT Thu Sep 20 2018 Showers and isolated thunderstorms north of Interstate 80 will diminish this morning as a warm front lifts into WI. Much of Thursday will be hot and dry with VFR conds. A strong cold front will push across the taf sites Thursday night accompanied by a line of thunderstorms. South winds will be gusting to 25 knots Thursday afternoon ahead of this front. && .HYDROLOGY... Issued at 237 PM CDT Wed Sep 19 2018 One to three inches of rain has fallen in parts of north central and northeast Iowa over the past 24-36 hours. The current WPC rainfall forecast through Thu morning has a 100-150 mile wide swath of another 1 to 3 inches generally centered on and spanning along the Iowa/Minnesota border. For this reason, river forecasts for the Cedar River basin are forecast to rise above flood stage in the Day4 to Day7 time frame. Due to the uncertainty of amounts and placement of forecasted rainfall, I have issued new Flood Watches for the Cedar River at Vinton, Cedar Rapids, and Conesville. I have also continued the Flood Watch on the Iowa River at Marengo, which, although delayed 48 hours, still is forecast to exceed its flood stage early next week. As for current river flooding on the Lower Mississippi and Rock rivers, the levels on the Mississippi at Gladstone, Burlington, and Gregory Landing are expected to drop below their respective flood stages tonight. However, the Rock River at Joslin will continue to slowly fall; reaching its flood stage level Saturday. && .CLIMATE... ISSUED AT 317 AM CDT Thu Sep 20 2018 Record Highs for September 20... Moline.........94 in 2017 Cedar Rapids...93 in 1931 Dubuque........92 in 1895 Burlington.....93 in 2017 && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...Haase SHORT TERM...Haase LONG TERM...Brooks AVIATION...Haase HYDROLOGY...14 CLIMATE...Haase