Area Forecast Discussion
Issued by NWS Aberdeen, SD
Issued by NWS Aberdeen, SD
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
921 FXUS63 KABR 141725 AAD AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 1225 PM CDT Sat Sep 14 2024 .KEY MESSAGES... - Chances for storms this afternoon/evening in central SD (20-30% chance) with marginal (1 out of 5) risk for hail in excess of 1 inch in diameter and damaging winds. - Periodic and frequent chances for precipitation will be possible next week. Greatest confidence in widespread rainfall will be late Tuesday into Wednesday with a 50-80% chance for precipitation. && .UPDATE... Issued at 1222 PM CDT Sat Sep 14 2024 See updated aviation discussion below. UPDATE Issued at 1009 AM CDT Sat Sep 14 2024 Still some lingering fog across mainly along and just west of the Missouri River this morning, but visibilities are beginning to improve, so let the Dense Fog Advisory expire. The Marginal Risk area for severe weather late this afternoon and this evening has been expanded northward to include north central South Dakota. No changes made to winds or temperatures at this time. UPDATE Issued at 431 AM CDT Sat Sep 14 2024 Just a quick update to add a dense fog advisory in mainly north central South Dakota. && .SHORT TERM /TODAY THROUGH SUNDAY AFTERNOON/... Issued at 357 AM CDT Sat Sep 14 2024 Between the Missouri and James valley, fog is starting to develop, albeit sporadically across the area. Anticipate this will fill in under light winds and clear skies. Winds though the day re-organize and become southeasterly again as another southwest flow shortwave begins to lift into the region and a surface low develops across western South Dakota this evening and overnight. We end up with about a 10mb gradient across the state, with pressure falls about 5mb through the afternoon...with 1/2km winds increasing to about 25-35kts overnight. Winds should be a far cry from those on Thursday, however. The shortwave does provide the impetus for another round of convection later today/tonight. We will have mid-level warm advection and the NAM supports 2000j/kg MUCAPE today and about 1500j/kg overnight, though shear is only about 35kts at its peak. HREF is a tick lower in comparison, but probably still good enough for a localized SPC marginal risk as both HREF CIN and BUFKIT profiles suggest convection could be surface based with hodographs that show both, albeit weak, speed and directional shear. 850mb temperatures continue to increase into Sunday, at about a standard deviation above climo. Continued southeast low level flow will also increase humidity, with the NBM probability of seeing a dewpoint above 70 degrees at about 20-30 percent across northeast SD/western MN. && .LONG TERM /SUNDAY EVENING THROUGH FRIDAY/... Issued at 357 AM CDT Sat Sep 14 2024 The upper level flow across the CONUS will continue to exhibit a negative PNA pattern through most of this period as a Rex Block remains persistent across the eastern CONUS while upper troughing will continue to reload through the period across the western CONUS. The Rex Block in the east will lend to more uncertainty going forward in time through this next week although there is general agreement among deterministic/ensemble guidance as well as cluster analysis showing the persistent upper low will just continue to meander across the eastern U.S. through the end of the work week. This will lead to the aforementioned upper low/troughing in the west to continue to take up residence there leaving a quite active southwesterly flow aloft pattern over our region through the end of this period. Beginning Sunday night through Monday, one of several upper waves is progged by guidance to transit southwest to northeast across the Dakotas. This will help aid in the development of 20-40% PoPs mainly across the western half of the forecast area. Low confidence continues in any widespread rainfall with this system. Ensemble probs of seeing a 1/4 inch of rain remain 20% or less mainly across central portions of SD. BUFKIT profiles also aren`t very favorable looking with soundings taking on more inverted V patterns across central SD. Not that there won`t be some showers, but probably more scattered and lighter in nature is more the thought at this point in time. This wave will exit the region sometime early Tuesday. We will see a brief respite from the rainfall before next slug of moisture arrives late Tuesday and persists through at least the first half of Wednesday. Progs from guidance lends to more confidence in this being a more significant wave and rainfall producer. NBM probs of seeing a 1/4 inch in a 24-hr period ending at 7PM Wednesday currently sit at roughly a 40-60% range. Probs for seeing a half inch in the same time frame are 30-45% mainly south and east of a line from Eagle Butte to Britton. Windy conditions will return through the first part of the work week, especially on Tuesday. Our region will be located in between deepening low pressure across the Northern Rockies/Northern High Plains and high pressure across the Great Lakes. Gusty south to southeast winds look likely by Tuesday afternoon. NBM probabilities of wind gusts reaching or exceeding 40 mph are highest between the Missouri and James Valleys as well as across the Glacial Lakes area ranging from 50-70%. With a persistent and active upper flow pattern persisting, our forecast area will continue to see periodic chances for additional precipitation through the end of the work week. Right now, the window for drier conditions will be between late Wednesday and Thursday afternoon. NBM ensemble data has gone with a blanket of 30-50% PoPs from Thursday night through Friday night across the forecast area. As one might anticipate, this pattern will be conducive to the continuation of above normal temperatures and higher humidity values. We really don`t see much sign of any cool downs until perhaps very late in the period into the following weekend when readings could return closer to normal. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1222 PM CDT Sat Sep 14 2024 Terminals KABR,KATY,KPIR,KMBG For the most part, VFR conditons will prevail through the TAF period. The exception will be across central South Dakota late this afternoon and this evening, when periods of MVFR vsbys will be possible in areas of thunderstorm development. A few of the storms may become strong enough to produce large hail and strong wind gusts. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Parkin SHORT TERM...Connelly LONG TERM...Vipond AVIATION...Parkin