9/28/15: Frosty Tuesday?

This morning the North Dakota Agricultural Weather Network (NDAWN) mesonet stations recorded lows  from near 60° in Campbell, MN to 29° in Froid, MT.

September 28, 2015 Minimums
September 28, 2015 Minimums

 

The colder air was found under an area of high pressure that is currently moving toward Williston.  That high pressure centered is progged to be in eastern North Dakota around sunrise tomorrow (Tuesday) morning.

12 PM Surface Analysis
12 PM Surface Analysis

 

Under the high pressure center will be light and variable wind and the highest radiative loss potential.  Therefore, eastern North Dakota into northwestern Minnesota will have the highest potential for frost on Tuesday morning.

Tuesday 12z
7 AM Surface projection for Tuesday, September 29, 2015

 

The NAM-WRF is projecting 30s across much of eastern North Dakota and northwestern Minnesota as you would expected given what the lows under that high were yesterday.  It will likely be a scenario where NOT everyone technically reaches 32°, but grass, roofs and cars will radiate heat more rapidly than the air, and therefore, many areas will have frost present tonight without the “official” air temperature reaching 32° (although some locations will).

Tuesday AM 7 AM temperature projections
Tuesday AM 7 AM temperature projections

 

Last week I mentioned that both Tuesday and Wednesday morning may record frost, but it appears that tonight (besides what happened this morning) will be the only main threat in North Dakota, although, many locations in Minnesota will drop into the 30s on Wednesday AM.

A weak disturbance will bring a slight risk of light showers on Wednesday into Wednesday Night, but otherwise, the week looks dry.  Western North Dakota is expected to record some light rain this weekend, but another area of high pressure that will move into northern Minnesota should keep that rain away from eastern North Dakota or Minnesota.  That rain in western North Dakota will also impact western South Dakota into Nebraska.    Eastern North Dakota and much of Minnesota is expected to remain dry (or mostly dry) until early next week.   Temperatures mostly in the 60s for maximums, with lows in the 40s, with of course the exception of the 30s expected on Tuesday morning.

The rain next week looks to be part of a pattern change that may bring a wetter pattern into the region, at least temporarily (a couple of weeks).

Daryl Ritchison