Area Forecast Discussion
Issued by NWS Grand Forks, ND
Issued by NWS Grand Forks, ND
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
47
48
49
50
943 FXUS63 KFGF 190903 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 403 AM CDT Wed Jun 19 2024 .KEY MESSAGES... - Additional chances for thunderstorms and heavy rain are possible late Thursday through Saturday. - Active weather continues early next week, with another chance for showers and possibly strong thunderstorms Monday and Tuesday. && .DISCUSSION... Issued at 402 AM CDT Wed Jun 19 2024 ...Synopsis... Upper flow remains out of the southwest today into Thursday before favoring more of a zonal tendency. The H5 trough bringing rain over the past several days is pushing off to the northeast, which will serve to end our rain chances as we approach mid morning. A period of quiet weather prevails this afternoon through late Thursday ahead of our next system that is set to move through the area Thursday night through Saturday. Zonal flow then looks to remain in place through next week, with several transient shortwaves showing up in ensemble guidance at various times. Some of these shortwaves have enough pattern support to mention the possibility of strong to severe thunderstorms. Skies are expected to gradually clear from west to east today as this mornings showers move out of the area by mid morning. High temperatures should be able to reach the low 70s where we see the best clearing, with perhaps middle to upper 60s where cloud cover is more persistent. Rain is not expected after midday across the entire forecast area. For Thursday, 850 mb flow gradually shifts, starting northwesterly during the morning hours, then becoming southerly by late afternoon. This will allow some degree of moisture return into the low to mid levels, although some uncertainty remains regarding PW values. This will ultimately be determined by the H5 ridge over the eastern CONUS, and how much it weakens and elongates by late Thursday. Most guidance weakens the ridge, but there is still some disagreement to what extent it weakens. A stronger ridge allows better moisture return into the Northern Plains, which will set the stage for our next system heading into Thursday night and Friday. ...Heavy Rain and Thunderstorms Possible Thur through Sat... Rain chances increase on Thursday from south to north as a theta-e gradient lifts northward into the Northern Plains and Upper Midwest. While there is still uncertainty regarding moisture availability, there is support (60 percent chance) for at least 0.50 inch of precipitation across portions of the region south of I-94. The axis of development for this precipitation will be somewhat stationary Thursday night through late Friday, when a shortwave is expected to move across the area. MUCAPE ahead of the shortwave could be upwards of 2000 J/Kg according to model soundings, which could support a mention of isolated strong to severe thunderstorms, which would likely be elevated due to the overall lack of surface based instability. Shear in both the 0-3Km and 0-6Km layers are supportive of large hail and damaging wind gusts. Tornado risk will be heavily dependent upon whether or not convection becomes surface based, which would support tornadic storms should this be the case. At this time, this looks like a less likely scenario. The highest probability for severe storms will be Friday afternoon and evening, with perhaps another chance Saturday afternoon. ...Active Weather Continues into Next Week... A progressive and very active shortwave pattern is expected to persist into next week. Exact timing of these shortwaves is likely to change due to the progressive nature of the H5 pattern; however, there is good agreement that there will be several shortwave passages next week. The first wave could move through the area Monday into Tuesday, with good agreement between ensembles regarding the potential for strong to severe storms. At this time, GEFS probability for surface CAPE greater than 2000 J/Kg is over 70 percent Monday afternoon and evening. Model soundings also show a shear profile supportive of discrete cells. This will depend heavily on timing, which could change in the coming updates; however, pattern support remains strong for potentially impactful weather through a good part of next week. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 1030 PM CDT Tue Jun 18 2024 Low clouds make this period tricky. TSRA will continue to push to the east away from our TAF sites. Low clouds will linger into the morning hours of Wednesday for MN TAF sites, but clear quicker in ND TAF sites to MVFR or VFR levels. Winds will shift into tomorrow as a surface feature passes over, becoming more variable then southeasterly at 5 - 10 knots. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ DISCUSSION...Lynch AVIATION...AH