Tuesday, February 20, 2018

Rain, Rain, Then More Rain

How many different ways can you say it's going to rain?  I'm not very concerned about severe weather, but there is that chance Saturday mainly across the southeast half of the state.  However, let's first address the biggest weather story in the short range forecast, FLOODING.

There's a FLOOD WATCH and a FLASH FLOOD WATCH in effect for most of the state.  As of Tuesday morning, the flash flood watch is only in effect for far southwest Arkansas with a flood watch for the rest of the state.  While I think there's a good chance the flood watch is changed to a flash flood watch, what's the difference?

FLOOD WATCH - issued to indicate current or developing conditions that are favorable for flooding.  The occurrence is neither certain nor imminent.  A watch is typically issued within several hours to days ahead of the onset of possible flooding.  In situation where a river or stream is expected to be the main source of flooding, forecast confidence may allow for a FLOOD WATCH to be issued several days in advance

FLASH FLOOD WATCH - issued to indicate current or developing conditions that are favorable for flash flooding.  The occurrence is neither certain nor imminent.  A watch is typically issued within several hours to days ahead of the onset of possible flash flooding.

HUGE DIFFERENCE HUH?  That's sarcasm.  In my opinion, this falls into the "lake wind/wind advisory category".  The two need to be combined and made simpler.  I'm a big believer in the KISS method.   Keep It Simple, Stupid.  NOT insulting anyone, but to communicate a threat effectively, it must be made simple.  

Another example of this is the new "marginal" severe weather category from the Storm Prediction Center.  I'm willing to bet if you talk to 100 people out and about, only 1 will know what it means.  

AS OF TUESDAY MORNING.
How much?  Well, much will fall Tuesday PM through Thursday AM with more rounds following.  The highest amounts will likely be found across the northwest 1/2 of the state with some locations seeing 6'' or more.

How will this affect you?  Remember, turn around, don't drown.  The combination of heavy rainfall and dormant vegetation will contribute to the flooding threat.  Rivers and streams will also rise.  If you live in an area prone to flooding, please stay weather aware.

There is a remarkably cold air mass coming in tonight and Wednesday.  The temperature will fall drastically in a short period of time.  Temperatures will likely drop below freezing across far northwest Arkansas and for that reason, freezing rain will become likely.  Why not snow?  With strong southwest winds aloft, temperatures just above the surface will be quite warm.  This melting layer will prevent snow production.  The precip will fall as rain, then freeze on contact.  I expect winter weather advisories for far NW sections of the state.

If you are traveling to Oklahoma, Kansas, or Missouri, the icing will be worse.

When does the rain arrive?  HRRR and 3KM NAM from WeatherBell.com

6PM Tuesday

9PM Tuesday

Midnight Wednesday
6AM Wednesday covered up in rain.  Southeast Arkansas will get it shortly after.  Notice the freezing rain northwest.
Metro rain chances starting late Tuesday.  Notice how it decreases Thursday morning.  That should be the end of wave 1.  More after that.
But wait, there's more!  Another round of rain should be surging north late Thursday into Friday morning.  Notice the target area is once again the NW 1/2 of the state.
Euro rainfall totals through Friday show the NW 1/2 of Arkansas with 6 inches or more.  I think amounts could top 8'' in spots.

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