Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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
671 FXUS65 KTFX 031740 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1140 AM MDT Wed Jul 3 2024 .Aviation Section Updated... .SYNOPSIS... Unsettled weather continues today and tomorrow as upper level troughing helps promote the development of afternoon showers and thunderstorms. Temperatures begin to warm over the weekend and next week, setting the stage for the start of a heat wave next week. && .Update... Only minor updates this morning, mainly to nudge PoPs up through the morning hours to better match radar trends. Otherwise the remainder of the forecast remains on track an no other updates were needed. - Moldan && .AVIATION... 03/18Z TAF Period Unsettled weather is expected to continue through around 04/02Z before tapering off. During this time, expect intermittent showers and thunderstorms, periods of mountain obscuration, and periods of low-VFR to MVFR conditions. By later in the afternoon clouds are expected to break for KEKS, KWYS, KHLN, and KCTB while lingering mid to high level clouds will persist for all other sites through the rest of the period. -thor Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 540 AM MDT Wed Jul 3 2024/ Key Points: -Afternoon showers and a few thunderstorms continue today and Independence Day -Near to below average temperatures expected to continue through Independence Day -Temperatures begin to warm over the weekend and next week, with a heat wave likely beginning next week Short term (through Independence Day)... Broad upper level troughing remains through Independence Day across the Northern Rockies, which will result in a continuation of the recent cool and unsettled weather that we have seen the past few days. Early morning radar imagery shows widely scattered rain showers in an area bounded to the north by US 2 and to the south by a Lewistown to Great Falls to Lincoln line, and these showers are slowly moving east. These showers will continue through the day today, with the focus of the showers gradually shifting to the south over the higher terrain. With these showers around, temperatures will struggle to get out of the mid 60s, with just a few locations along the Missouri River managing to see 70 this afternoon. While the upper level trough will shift a bit for Independence Day, north westerly flow aloft will help to keep the atmosphere primed for a few instability showers in the afternoon, especially across Central Montana. With the axis of todays trough shifted a bit to the east, temperatures will manage to warm a bit, with most locations seeing highs in the 70s with a few isolated areas reaching 80 degrees. Extended (Friday through next Wednesday)... Temperatures begin to trend warmer to end this week as an impressively strong upper level ridge begins to develop over California/Nevada, with a ridge axis extending up the West Coast. Highs on Friday and Saturday will reach the upper 70s and low 80s for most of the lower elevations as the ridge builds with a few ring of fire thunderstorms developing on the fringes of this upper level ridge (the edges of upper level ridges like these tend to be favorable to some thunderstorm development, hence the nickname ring of fire). Depending on the timing of any showers or thunderstorms, some relief from the heat will be possible where the storms move through, especially if they manage to produce some cool outflow breezes. As we head into early next week, the ridge will continue to strengthen and shift eastward, putting us into what looks like the beginning of the first heat wave of the summer, with many locations seeing multiple days of temperatures exceeding at least 90 degrees as early as Monday (and even Sunday for the Helena valley). With the ridge overhead, any shower or thunderstorm activity will be incredibly isolated/nonexistent, which while not allowing for any atmospheric relief from the heat, will also reduce the risk for natural fire starts. Ensemble data for next week shows a high likelihood of this heat wave extending through at least all of next week, with some indications that it could last all the way through the following week as well (meaning at least 10 days), with some areas possibly seeing multiple consecutive days of temperatures over 100. Great Falls, for example, has multiple consecutive days with at least 50% of the ensemble members forecasting at least 100, with some of those exceeding the all time record high of 107 (July 25, 1933). While this degree of heat is not guaranteed yet, it is time to start preparing for the possibility of heat well outside the climatological norm. Ludwig && .PRELIMINARY POINT TEMPS/POPS... GTF 67 47 74 47 / 70 30 20 10 CTB 67 46 72 45 / 70 20 20 10 HLN 74 50 79 50 / 70 40 10 0 BZN 69 42 73 45 / 50 30 10 10 WYS 64 33 67 33 / 40 10 10 0 DLN 68 39 73 42 / 30 10 0 0 HVR 70 50 74 50 / 70 30 30 10 LWT 64 44 68 45 / 80 30 50 10 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls