May 29, 2015: A look forward

A cold and windy day in progress this afternoon.  That cold air with temperatures only in the 50s this afternoon, in combination with the stiff north wind continuing to advect colder air into the state, should set up ideal conditions for possible frost conditions tonight.

2:40 PM Temperatures (May 29, 2015)
2:40 PM Temperatures (May 29, 2015)

Although the wind is still  brisk this afternoon, that is expected to diminish overnight as the Arctic High slowly moves closer to the region tonight.  Considering the average diurnal change in temperature (from low to high) is about 20° to 23° degrees this time of year, that would mean the prospect for 30s for overnight lows is certainly feasible.

2:40 PM Wind Speed and Direction
2:40 PM Wind Speed and Direction

 

The NAM-WRF takes lows into the lower 30s in many locations tonight.  Although I think that is too low in locations south of Interstate 94, low to mid 30s in north central and northeastern ND will clearly be possible with upper 30s elsewhere.

NAM-WRF Minimum Temperature Prog for Saturday, May 30, 2015
NAM-WRF Minimum Temperature Prog for Saturday, May 30, 2015

 

Because the ridge of high pressure (image below indicated by the blue line/arrow) will be over north central / northeastern North Dakota down toward the James River Valley, those area will be the most likely to record a temperature near or below 36°.  I always use 36° as the reference for frost as temperatures are measured near the 4-5 foot height, meaning with the usual strong inversions (warmer as you go up) that set up in the early morning hours, that the temperature near the surface can easily be around 32° even with a temperature being reported as 36°.

7:00 AM Surface Map Prog for Saturday, May 30, 2015
7:00 AM Surface Map Prog for Saturday, May 30, 2015

Beyond the chilly, but dry day on Saturday, warmer air will surge quickly north on Sunday.  That will probably induced some shower development on Sunday, but amounts look very light if any falls at all as many locations will likely stay dry that day.  Monday even warmer air moves in and the day looks dry, but thunderstorms are expected Monday Night into Tuesday as an area of low pressure moves across North Dakota.  Farther out, another round will be possible in the Thursday/Friday time frame late next week.  Temperatures should be near or above average Monday through Wednesday with even some 80s possible on Tuesday/Wednesday.  Slightly cooler air toward the end of next week, but near average.

Using the best analogs for what is happening in the atmosphere in recent weeks, I am currently projected June to be above average for temperatures (1°) with rain near average, although with thunderstorms there will be wide variations and near average perhaps being the overall trend.

Daryl Ritchison