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
953 FXUS63 KFGF 062320 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 620 PM CDT Mon May 6 2024 .KEY MESSAGES... - Strong southeast winds will continue this afternoon into tonight across eastern North Dakota and adjacent portions of Minnesota, with gusts up to 50 mph at times. - Showers and isolated thunderstorms will affect the region through Wednesday. && .UPDATE... Issued at 620 PM CDT Mon May 6 2024 No huge changes with this forecast update. Will slow down the arrival of likely precipitation chances for another few hours. Seems like there is more areal coverage of showers/storms organizing over eastern South Dakota now, but if they hold together as is, it will be a few more hours until they arrive in the southern FA. There is some lightning activity over southeast North Dakota, but nothing too concentrated or long lasting. As the previous shift noted, 850mb winds crank up to around 60 knots around or after sundown (and continue through most of the night), so the echoes on radar are moving very fast. && .DISCUSSION... Issued at 212 PM CDT Mon May 6 2024 ...Synopsis... A strong upper level trough is moving out of the Rockies into the central and northern High Plains as seen on water vapor satellite imagery. This is helping rapid deepening of a surface low in the western Dakotas, generating an expansive increased wind field as well as drawing in moisture and lift into the region. By Tuesday afternoon, the upper trough closes into an upper low, becoming stacked on top of surface low halting its deepening/strengthening. This also allows the low to stall over the Dakotas by Tuesday. A second upper trough moving through the Intermountain West Wednesday will then help the upper low move southeast out of the Dakotas by Wednesday night. Northwest flow aloft then develops with the help of upper ridging over the West around Friday, with ensemble guidance all depicting an open, progressive shortwave trough moving out of central Canada into the Upper Midwest. While there is strong consensus in this synoptic wave, there are differing scenarios in its progression and strength. Uncertainty in the upper pattern then degrades after Friday`s shortwave passage with either upper ridging out of the West becoming the dominate influencing mechanism for our weather, or upper troughing over the Great Lakes. Both would still favor average temperatures for our area, however. ...Strong winds today and tonight... Strong surface pressure gradient over our area and mixing of low level winds in the 40-50 kt range is contributing to sustained winds 25-35 mph with gusts up to 50 mph in eastern North Dakota into portions of adjacent northwest and west-central Minnesota. Southeasterly direction of winds is favoring strongest winds in the southern Valley with the help of downsloping within the southern Valley, as well as locally better mixing from daytime clearing. This will continue advisory-criteria winds through the afternoon into the evening. After sunset, daytime heating ceases, although the pressure gradient remains tightened over our area, along with some continued mixing with the help of either downsloping/terrain influences as well as transferred winds from aloft with the help of convection/weak thunderstorms tonight. Still thinking winds will remain near or at advisory-criteria after sunset until around midnight. Winds aloft increase over 50 kt tonight, which introduces some uncertainty in tapping into these near warning- type criteria. However, the chance in seeing warning-criteria winds is low, at around 10% between 7pm - 1am. ...Showers and thunderstorms through Wednesday... Lift and strong moisture transport into our area gives high confidence in widespread showers into eastern ND and west- central and northwest MN. Weak instability feeding into this moisture transport allows the chance for weak thunderstorms tonight into Tuesday. Tuesday midday, some high resolution guidance does bring a surface front through into our area, coupled with relatively warmer/more moist air mass. With forcing aloft and at the surface from convergence and frontal lift amid surface CAPE values 100-500 J/kg, clusters of semi-discrete and/or a line of thunderstorms are expected. In this same area, low level winds veer with height, with good ventilation aloft. Should thunderstorms remain semi-discrete and attach themselves on the boundary, funnels and/or a couple of quick tornadoes cannot be ruled out. This conditional chance is low, less than 10%, but still exists and would increase if more discrete mode and/or greater instability becomes more favored. The window of opportunity for such potential exists between 11am to 4pm. Otherwise, accumulated precipitation is forecast to range in the 0.20 - 0.75 inches, with locally higher amounts up to 1.5 inches in areas that see numerous rounds of showers and thunderstorms. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 620 PM CDT Mon May 6 2024 This will be a challenging set of TAFs, due to wind speeds and shower/isolated thunder chances. Also expect some LLWS around or after dark (up to 60 knots), continuing through most of the night. This amount of wind is not expected at the surface, but surface winds will stay gusty the entire night and into Tuesday. There could still be a few higher gusts at the surface associated with some of the shower activity. TAFs are pretty hard to write with showery convection, especially when it is fast moving and fairly high based initially. Trying not to include TEMPO groups every 4 hours as well. So will not be chasing TAFs too much tonight, as precipitation will be off and on. There may be some lightning around, but for the most part expect showers. Ceilings do tend to lower at most sites during the night (some closer to Tuesday morning), then lift again Tuesday afternoon as the first main band of precipitation either dissipates or moves into southern Canada. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Wind Advisory until 1 AM CDT Tuesday for NDZ006>008-014>016- 024-026>030-038-039-049-052>054. MN...Wind Advisory until 1 AM CDT Tuesday for MNZ001>004-007-027- 029>031-040. && $$ UPDATE...Godon DISCUSSION...CJ AVIATION...Godon