Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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
566 FXUS66 KOTX 011036 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 336 AM PDT Wed May 1 2024 .SYNOPSIS... The weather will stay unsettled and chilly until the week`s end, with a slight increase in temperatures from Thursday into Friday. The weekend forecast is looking more certain and its hedging toward another bout of cool and wet weather, particularly on Sunday. Expect cool temperatures and sporadic showers to persist into early next week. && .DISCUSSION... Today through Thursday Night...Today, the weather will get a bit warmer but remain cooler than normal by about 5 degrees with high temperatures in the mid 50s to low 60s. Shower will make a come back, mostly affecting the Idaho Panhandle and far northeast WA. With the temperatures rise, the precipitation will likely fall as just rain, not a mix of rain and graupel. Tonight`s temperatures will be slightly warmer but there is still a threat of frost with temperatures in the 30s. Tomorrow, the low will shift into eastern Montana, while another forms off the coast. Between the two lows, a weak ridge will build, with warmer temperatures reaching into the 60s. Shower coverage will be less again, with them mainly contained over the higher terrain in the ID Panhandle. The rest of the CWA will remain dry with clear to party clear skies. /KM Friday...The cool and unstable upper level low that region has been subject to the last couple of days will likely move east of the area on Friday as a shortwave ridge moves over the Inland NW. This should result in a relatively mild day compared to the last several days with 850 mb temperatures climbing into the 7-9C. This translates to high temperatures generally in the 60s with a few lower 70s over the LC Valley and lower Columbia Basin. Most locations will be dry as there is limited moisture and even less synoptic lifting. However they may be just enough orographic ascent and residual instability to trigger some light showers over the ID Panhandle mountains. Saturday...Another deep upper level low and associated occluded front is forecast to move onto the WA/OR coast which pushes the shortwave ridge into western MT by afternoon. This transition will also lead to a significant increase in atmospheric moisture with the precipitable water values rising from below normal on Friday to nearly 150% of normal by afternoon. Temperatures could prove tricky depending on the speed of the front. It now looks like the eastern third of WA and north ID could be as warm if not a little warmer than Fridays readings, however there is a lot of model spread with high temperatures ranging from the lower 60s to lower 70s in the Spokane area. Over central WA there is still a lot of model spread but good confidence that it will be cooler than Friday. Meanwhile precipitation amounts will generally range from 0.05-0.15 over central WA and generally less than 0.05 elsewhere. Saturday night into Sunday...Model confidence is growing about the track of the aforementioned upper level low. Yesterdays runs showed large deviations with most of the GEFS runs taking the upper low well south into NV, whereas the other model suites kept it over the northern half of Oregon. Now it seems the farther north solution is favored. This would result in a rather wet and cool forecast. Precipitation amounts will depend on where a deformation band, north of the upper low, is expected to set up. There is a wide variation in where that is expected to occur but it is likely to be somewhere over the Inland NW. There is a 40-50% of seeing precipitation amounts above a half inch during this period across SE WA into the central ID Panhandle with the Spokane/CdA seeing a 15-20% of seeing similar amounts. While the exact precipitation forecast will be difficult, suffice it to say most of the region will be wet. Whats more certain is the temperatures will plummet significantly due to the cloud cover and rain. It still seems the NBM is playing catch up with this cooling trend as it is on the warmer end of the model suites and is significantly warmer than most of the deterministic models. We could very well see highs remaining in the 40s. The chances of that are around 55% for Pullman, 45% for CdA, and 30-35% for the Spokane area. Needless to say those with outdoor plans on Sunday need to plan accordingly. Monday and Tuesday...Model consensus still looks much better than what we expect over the weekend. Although the deep trough is expected to drift east of the region, we will remain under the influence of a broad upper level trough focused over much of the PacNW. This will result in continued cooler than normal weather with occasional showers. fx && .AVIATION... 12Z TAFS: VFR conditions will prevail through the forecast. MVFR stratus will form between KGEG and KPUW but will likely remain away from TAF sites. Showers today will remain contained to the ID Panhandle with Central and Eastern Washington remaining dry. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Low confidence in MVFR stratus forming at TAF sites between KGEG and KPUW. ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports, please refer to the Aviation Dashboard on our webpage: https://www.weather.gov/otx/avndashboard && .PRELIMINARY POINT TEMPS/POPS... Spokane 59 34 62 36 66 46 / 20 10 10 0 0 10 Coeur d`Alene 55 33 60 37 63 43 / 30 20 20 10 0 10 Pullman 53 31 58 35 63 46 / 20 0 10 0 0 10 Lewiston 60 36 65 41 71 48 / 20 0 10 0 0 10 Colville 61 31 64 33 66 41 / 20 10 20 10 10 10 Sandpoint 53 36 59 36 61 42 / 50 30 40 20 20 10 Kellogg 48 36 55 36 61 43 / 60 30 40 20 20 10 Moses Lake 66 32 68 36 71 50 / 0 0 0 0 0 30 Wenatchee 63 39 66 42 67 51 / 0 0 0 0 10 30 Omak 65 37 69 40 68 49 / 10 10 0 0 10 20 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$