We’ll see warmer than average temperatures around 60ºF to start the weekend before a cool off into the 50s Sunday. Temperatures rise again Monday into the upper-50s with a warm front approaching, then cold front bringing a chance of rain. Looking ahead at Thanksgiving temperatures seem like they should be mild we may see some rain in NYC.
Rest of today – sunny with highs generally in the upper-50s to near 60ºF. High pressure south of the region will lead to southwesterly flow that will bring us these mild temperatures. Overnight lows in the upper-50s.
Saturday – a cold front is forecast to move through during the day, however, this front should be deprived of any significant moisture. Temperatures should remain mild in the upper-50s to around 60ºF once again. It won’t be until the overnight hours when temperatures start to drop in response to the cold front passage, with winds turning towards the north and lows falling into the low-40s.
Weather Prediction Center surface forecast for 7AM Saturday, showing a cold front approaching from the northwest.
Sunday – mostly cloudy with high temperatures cooling off to around 50ºF. A warm front approaching from the southwest should stabilize temperatures and prevent much of a change overnight with lows barely budging in the upper-40s. The warm front, then a cold front following on its heels should bring us a round of showers.
Monday– rain diminishing early on. High temperatures in the upper-50s occurring early in the day prior to the cold front passage. Temperatures dropping steadily during the day after this into the 40s. Overnight lows in the upper-30s.
Looking ahead at Thanksgiving, there could be some rain coming our way though temperatures appear like they should be on the mild side.
GFS model 500 mb vorticity and height forecast for 7AM Thursday. A closed upper low over the Ohio valley is evident with lots of accompanying vorticity. Should this scenario actualize, we would expect to see some showers in our area during the day Thursday.
An upper low lingering over the Northeast results in unsettled weather to start this week. With the dynamics brought on by this upper low, there will be chances for isolated showers and thunderstorms each day esp. in the afternoon. High temperatures during this period should be generally in the low-80s. Luckily, this pattern should break in time for the Independence Day holiday weekend.
Rest of today – sunny with highs in the upper-80s to start. Chance for isolated showers and thunderstorms in the afternoon. Some of these thunderstorms could approach severe limits though we aren’t anticipating widespread severe weather today. Overnight lows around 70ºF.
Weather Prediction Center surface forecast for 8PM Monday.
Tuesday – more clouds resulting in cooler highs in the low-80s. Closed upper and surface lows over the northeast will provide for ongoing chances of showers and thunderstorms through the day. Coverage should again be scattered in nature. Overnight lows in the upper-60s.
Wednesday – similar day to Tuesday with highs in the low-80s, mostly cloudy with chances for showers and thunderstorms yet again. The closed upper low referenced above and visible in the graphic below will provide for a cold pool that should enhance lapse rates and increase chances for isolated severe thunderstorms. Overnight lows around 70ºF.
GFS model 500 mb temperature, height, and winds, valid for 2PM Wednesday.
Thursday– the nagging upper and surface lows will finally move off to the east. This should result in better conditions with sunny skies and no tangible risk for rain and thunderstorms. High temperatures should rebound into the upper-80s. Overnight lows in the low-70s.
After the first week of the WxChallenge (and part of this week), I’m second place in my class, tied with multiple others for #268 nationwide, and a little better than national consensus with 21.2 error points. I got hit the last day for going over on temperatures and winds, and will discuss that below. Hats off to one of my classmates who’s currently #44 nationwide!
Verifications
Below are the verified readings for each metric we were asked to forecast during last week, and a column showing error points I was assessed.
Forecast Day
Max Temp (°F)
Min Temp (°F)
Max Sustained Wind (kts)
Precipitation (inches)
Error Points Assessed
09/25/2018
82
50
11
0.00
4.0
09/26/2018
83
52
11
0.00
1.0
09/27/2018
84
52
9
0.00
2.5
09/28/2018
86
53
11
0.00
6.5
Post-Mortem
Day 1: went too aggressive on the max winds, and too warm on the low temps. The lower winds could explain the lower min temps (less mixing on clear nights). I think I was too optimistic about the possibility of funneling of winds from the ENE along the Columbia River Gorge.
Day 2: did pretty well, only got 1 point off for missing the high temp slightly. If I had stayed with my original forecast for that I would have had a perfect score! Much better on winds though.
Day 3 & Day 4: another decent day, but went a little too cool with the low temperatures. This low bias also bled into Day 4, where I was low on both the high, low, and max sustained wind speeds. I think if I were to go back and redo this, maybe I would have used the Delta Method (a form of moderate persistence) and been better off than looking at MOS, given how stable conditions were throughout the week.
Forecasting for KPDX October 2-5, 2018
Synoptic Set Up
Big changes in store for Oregon in the second week of the forecast challenge. The rex block and high pressure that brought a week of above normal warmth and clear skies last week will finally break down. The upper low associated with it will move northeast towards KPDX over the weekend. Local NWS forecasters currently (as of Thursday) noted considerable spread in forecast guidance about phasing of northern stream energy and a second upper low by the beginning of this forecast period, as well as interaction with outflow from Hurricane Rosa. AFD mentions longwave troughing as well, and this is backed up by GFS progs.
Rainy start to the week at KPDX possible
Coastal low coming ashore on Friday at KPDX
Forecast Rationale
The effects of the synoptic set up favor much cooler and unsettled conditions compared to last week. A drop in 500 mb heights with upper lows and longwave trough should result in temperatures close to or slightly below climatological norms. The prospect of this troughing means that precipitation will be in the mix as well at the start of the week. More substantial rain chances are in store for KPDX to end the week. Along with the rain Friday, we can expect cooler temperatures and windy weather as rain cooled air helps mix down some momentum from the lower atmosphere.
Forecasts Submitted
This only reflects finalized forecasts as of this posting, I’ve made small adjustments to the forecast based on checking MOS daily.
Enjoy the pleasant weather today if you can, because conditions will deteriorate going into the weekend. Wet weather will impact the NYC region starting tonight, lingering well into early next week. Rain could be heavy at times, and flash flooding is a possibility. Temperatures during this time will be considerably cooler than this past week with the influence of clouds and rain. We will be stuck under the influence of multiple shortwaves moving through at the upper level during this time. Starting next week, forecast models suggest that a closed 500 mb low will form, then linger in the area due to strong downstream ridging (high pressure) over the western North Atlantic. This cut-off upper level low will provide for persistent unstable conditions conducive for multiple rounds of rain and thunderstorms. I will be off the next two weeks on vacation and will not be posting updates unless there’s severe weather forecast for the area.
Rest of today – increasing clouds as a cold front approaches the area from the northwest but stalls out and dissipates overnight. High temperatures in the upper-80s. Chances for showers and thunderstorms increase overnight.
Saturday – multiple chances for showers and thunderstorms, starting early in the day, then again in the afternoon and evening hours. Much cooler with mostly cloudy skies and high temperatures only in the mid-70s. The cold front that passed through yesterday will return north as a warm front. Ahead of this, winds will be easterly and onshore, bringing the cool, damp influence of the Atlantic over the area.
Sunday – warmer with high temperatures in the low-80s but still mostly cloudy. Chances for rain throughout the day as the frontal boundary above remains in the area.
Monday – yet another impulse of shortwave energy aloft brings a surface low towards the area, so rain chances persist with a shot for thunderstorms as well. Mostly cloudy with highs in the low-80s.
