Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
Issued by NWS Quad Cities, IA IL
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
301 FXUS63 KDVN 190825 AFDDVN Area Forecast Discussion National Weather Service Quad Cities IA IL 325 AM CDT Thu Sep 19 2024 .KEY MESSAGES... - There is a Slight or level 2 out of 5 Risk of severe thunderstorms late Thursday afternoon and into the evening west of a line from Delaware County southwestward to Keokuk County. A Marginal or level 1 out of 5 Risk of severe thunderstorms extends east of that line to the counties along the Mississippi River. - Above normal temperatures remain in the forecast through Saturday with near to slightly above normal temperatures from Sunday onward. - An active pattern will continue into next week. && .SHORT TERM /THROUGH TONIGHT/... Issued at 218 AM CDT Thu Sep 19 2024 There are pockets of showers and thunderstorms in a zone of 850 theta-e advection region that extends from southern Minnesota southwestward into eastern Nebraska and northern Kansas. Temperatures are warmer this morning and at 3 AM range from 58 degrees at Freeport to 68 degrees at Cedar Rapids. At 500 MB, a negatively tilted trough and vertically stacked closed low sit across North Dakota, Saskatchewan and Manitoba early this morning. This trough and vertically stacked closed low are forecast to lift into northeast Manitoba by 12 UTC Friday. At the surface, a cold front is forecast to move from central South Dakota and Nebraska this morning eastward and into east central Iowa by 12 UTC Friday. Dewpoints will be on the increase this afternoon into this evening with widespread dewpoints in the mid to upper 60s. High temperatures today will be similar to previous days and be in the mid to upper 80s. Pockets of scattered showers and storms associated with the theta-e advection are forecast to move into parts of east central Iowa this morning but slowly weakening as they move into a drier environment this morning. There are chances of showers and storms west of a Manchester to Cedar Rapids to Sigourney line 9 AM through 1 PM but expecting any of these to be weakening as they move into the area. The focus of the forecast then shifts to an approaching shortwave and midlevel jet streak that is forecast to move along the Iowa and Minnesota border later this afternoon and into this evening. After 00 UTC Friday, a 30 to 35 knot low level jet is forecast to develop across central Iowa and then veer into our area in the 3 to 06 UTC timeframe and think that most of the shower and thunderstorm activity will be associated with this feature with showers and storms sinking southeastward across the area through 12 UTC Friday. If thunderstorms can develop during the late afternoon and early evening associated with the approaching jet streak, Supercells are possible with 30 to 40 knots of 0 to 6 km shear and most unstable CAPE values of 1000 to 2000 J/KG. Model soundings show mainly elevated CAPE across the area with high LCLs expected. In the far western edge of CWA, northwest of Cedar Rapids model soundings show LCLs around 2000ft. Hodographs show good low level curvature with 0 to 1 km shear around 30 knots and SRH around 200 M^2/S^2. Although it appears that LCLs may be too high for a tornado threat there is a 2% tornado threat across pat of our area. It would seem that the developing low level jet may be able to aid in lowering LCLs resulting in a brief 1 to 2 hour threat for tornadoes mainly west of a Manchester to Cedar Rapids to Sigourney Iowa line before instability decrease this evening. Outside of the tornado threat, the primary threats will be damaging winds and hail. The Storm Prediction Center has a slight risk of severe thunderstorms west of a Manchester to Cedar Rapids to Sigourney line. There is a marginal risk of severe storms east of this line to the Mississippi River. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 218 AM CDT Thu Sep 19 2024 Active weather continues Friday through Monday with zonal west to east flow across North America. There are two closed 500 MB lows that will bring chances of showers and storms to the area during this time period. The first passes to our north Saturday into Saturday night. The second will lift from the southern High Plains and across the area Sunday through Monday when it is followed by another 500 MB trough. Models continue to disagree on the timing and placement of these storm systems and any interaction between the three late this weekend into early next week. This continues to result in broad brush POPS across the area through the period. This will also result in cooler high temperatures especially Sunday into early next week. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1230 AM CDT Thu Sep 19 2024 VFR conditions are forecast through the TAF period. There is a low chance of rain showers at KCID from 15 to 18 UTC but confidence is very low in this occurring so these were left out of the TAFs for now. A line of showers and thunderstorms are forecast to develop to our west during the late afternoon and move eastward across eastern Iowa from 00 UTC to 06 UTC. Have placed a prob30 group at KCID, KDBQ, and KMLI to account for this. Confidence is lower that this line of storms will move into KBRL before the end of the TAF period. MVFR ceilings and visibilities are possible in the strongest storms. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ SHORT TERM...Cousins LONG TERM...Haase/Cousins AVIATION...Cousins