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Posted at 5:00 AM ET, 03/ 9/2011

Forecast: Here comes more heavy rain

By Dan Stillman

Rainfall through Thurs. night could total 1.5-3"

Today's Daily Digit
 
A somewhat subjective rating of the
day's weather, on a scale of 0 to 10.

 

A cloudy, cool day with more rain on the way.
 
Get the 'Digit' on Twitter

EXPRESS FORECAST

Today: Cloudy. 40-50% chance of showers arrives from west to east. Mid-40s to near 50. | Tonight: Rain becomes steadier, heavier. Low 40s to near 40. | Tomorrow: Breezy with rain, heavy at times. Mid-50s to near 60. | A Look Ahead | Get Express Forecast by E-mail

FORECAST IN DETAIL

Another significant rain event is on the way, with the potential for as much or more rain than this past weekend's generally 1-2.5" soaking. The culprit is a system similar to the the weekend's - a cold front with an area of low pressure along it - that brings a chance of showers today and the likelihood of moderate to heavy rain late tonight and tomorrow. Some might see a smidge of snow and/or sleet at the storm's beginning and/or end, but the real concern is the chance of minor to moderate flooding issues late tonight and tomorrow.

Snow Potential Index: 1 (↑) - Any flakes Thurs. night shouldn't accumulate. Slight snow chance early next week, wouldn't put much stock in it yet.

 
The SPI is a daily assessment of the potential for accumulating snow for the next week on a 0-10 scale. Get the 'SPI' on Twitter
 


Radar & lightning: Latest regional radar shows movement of precipitation and lightning strikes over past two hours. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Today (Wednesday): Cloudy skies and onshore breezes, around 10-15 mph from the east/southeast, keep temperatures in check today with highs in the mid-40s to near 50. The western suburbs stand a 40-50% chance of showers as early as mid-to-late morning (there could even be a few pings of sleet if precipitation arrives early enough), then that 40-50% chance of showers advances to D.C. and east during the late morning or afternoon. Confidence: Medium

Tonight: A Flood Watch goes into effect this evening as steadier rain moves in from the southwest. The rain could be moderate to heavy at times overnight, with temperatures edging back to lows in the low 40s to near 40. Confidence: Medium

Keep reading for the forecast through the weekend...

Tomorrow (Thursday): Rain continues through much or all of the daylight hours, and it could be moderate to heavy at times. Watch for flooding on those same roads and low-lying areas that experienced flooding on Sunday. Winds from the southeast around 15-25 mph with higher gusts push highs to the mid-50s to near 60, before they shift to come out of the west and northwest during the afternoon into evening as temperatures fall through the 50s to near 50 or into the 40s. Confidence: Medium

Tomorrow Night: Rain should lighten during the evening and may come to an end by around midnight. However, a trailing area of low pressure in the upper atmosphere could keep the rain going longer or bring the return of some light rain toward dawn, especially west of D.C. where it might be cold enough for any rain to mix with or change to snow and/or sleet. Any accumulations more than a dusting or so are probably confined to west of Loudoun and Fauquier counties. Confidence: Medium

A LOOK AHEAD

Depending on the location and strength of the upper-level low, a chance of light rain may linger into Friday morning. The best chance of this would be from around D.C. and to the west. Any early-morning rain could mix with or change to snow and/or sleet mainly west of D.C. Again, this would be mainly non-accumulating except possibly west of Loudoun and Fauquier counties. Otherwise, we're looking at a breezy and colder day with highs in the upper 40s to low 50s under partly sunny to mostly cloudy skies. Lows Friday night fall back to near 30 to the mid-30s. Confidence: Medium

The weekend looks at least partly sunny and generally pleasant with highs in the mid-50s to near 60 on Saturday and 50s on Sunday. Can't rule out a passing shower Saturday afternoon or night with Saturday night lows in the upper 30s to mid-40s. Confidence: Medium

By Dan Stillman  | March 9, 2011; 5:00 AM ET
Categories:  Forecasts  
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Comments

Looks like it's time to build the Ark.....Accuwaether.com indicates Arnold, MD is to receive 3.38 inches of rain...Do you guys think this total is possible?

Posted by: jcmcgrath1969 | March 9, 2011 6:08 AM | Report abuse

Slight snow chance nect week, SWEET!!!!

Posted by: dannythe357 | March 9, 2011 7:03 AM | Report abuse

The headline for the day should have been, "SPI comes back to life!!!! and we might get some rain."

SNOW SNOW SNOW SNOW SNOW.

Posted by: ArlTeacherSnowman | March 9, 2011 7:18 AM | Report abuse

Yeah, Topper had a snowflake in his 7-day forecast last night around Monday night, but he basically admitted that it was a reach at this point.

Posted by: ThinkSpring | March 9, 2011 7:32 AM | Report abuse

note where our interest lies:
we're mostly talking about the remote chance of maybe possibly seeing a few inconsequential flakes before and/or after the potentially epic rainstorm that's on the way. (fyi: GFS=2.5-3", NAM=1.75")

i'm just "model-hugging", because that's all i know how to do in terms of predicting weather. NAM/GFS show NO snow on the "back end" (or the front end) of tomorrow's rain. i suspect the SPI of 1 is a reaction to what happened sunday.

and, sadly, next tuesday's snow storm has literally "gone south". the storm center now passes over north/south carolina dropping 0" of any kind of precip on us. i guess that'll please bombo - if it verifies.

but, there's always the next model run!

Posted by: walter-in-fallschurch | March 9, 2011 8:12 AM | Report abuse

I know we need the rain but personally we need a week or so of dry weather so our swamp will turn back into our yard & we can do some clean up.

Posted by: wadejg | March 9, 2011 8:20 AM | Report abuse

CWG,
Why has your site disappeared from the "home page" of the online Post? Yes, I can find you by doing several extra clicks, but why have you been hidden? And the same about Dr. Gridlock. Frankly, these two sites are the main reason I bother with WaPo online at all. Otherwise, I read the paper:)

Posted by: busgirl1 | March 9, 2011 9:26 AM | Report abuse

@busgirl1

I gather you're talking about the right sidebar of then national home page. It appears there may be an issue with those links disappearing sometimes depending on the vertical length of a given advertisement. We'll check on this, but also know that you can find a link to us at the top of postlocal.com, or you can link to us directly at washingtonpost.com/capitalweathergang, capitalweathergang.com, capitalweather.com, or just google "Capital Weather Gang" -Dan, CWG

Posted by: CapitalWeatherGang | March 9, 2011 9:39 AM | Report abuse

i often check this radar image showing the whole country (and, wow.. nice storm coming our way - too bad it's just rain...).

http://radar.weather.gov/Conus/full_loop.php

but it only shows what's happening over land. is there any radar or satellite composite or some sort of graphic loop that would show the moisture while it's still over the gulf of mexico?

Posted by: walter-in-fallschurch | March 9, 2011 9:47 AM | Report abuse

Curious if these had been snow storms and it was cold enough to accumulate - how much snow we might have gotten. Sigh.

Posted by: 3seasons | March 9, 2011 9:51 AM | Report abuse

Now that many of us have packed up our shovels & salt & are well into spring garden fever it's about time for a shocking & unexpected DC metro March snowstorm.

Posted by: FIREDRAGON47 | March 9, 2011 9:58 AM | Report abuse

3seasons,
sigh.... in general, as a rule of thumb, you can assume about 1" of rain = ~10" of snow. so, dan's estimate of 1.5 - 3" of rain would be about 15" - 30" of snow...

(the thing is, and maybe CWG can elaborate, i don't think this much liquid would be available if it were cold enough. i mean, we probably get several 1.5" rain storms every year, but 15" snow storms are (except for last winter) a once-a-decade, at best, occurrence.)

Posted by: walter-in-fallschurch | March 9, 2011 10:19 AM | Report abuse

"Otherwise, we're looking at a breezy and colder day with highs in the upper 40s to low 50s"

I love this statement! Why? Because not so long ago, highs in the upper 40s to low 50s would have been considered a HEAT WAVE. Bring on Spring!!

Posted by: SSpring1021 | March 9, 2011 10:26 AM | Report abuse

walter, on the next week storm many of the GFS runs of late (which did not show much here) still have a decent look at 500mb. Also, the EURO last night finally showed something from the system as well, about .4" up in this area to 1" down toward RIC -- those are liquid numbers, but much of it would be snow on the Euro. The system evolution is still problematic as it's mainly northern energy (like we've seen all winter).

Posted by: Ian-CapitalWeatherGang | March 9, 2011 10:31 AM | Report abuse

snow ratios in march are typically as good as 10:1 in DC. they are always very wet snows this time of year so the ratio would likely be half that.

Posted by: rapotter | March 9, 2011 11:02 AM | Report abuse

are typically NOT as good as 10:1 *****

critical type-o !

Posted by: rapotter | March 9, 2011 11:03 AM | Report abuse

@3seasons

walter is right when he suggests that often when it's cold enough for snow there's not as much moisture available. so the "How much snow would all this rain be?" question isn't always a fair one. But yes, with the same amount of moisture and assuming a 10-to-1 ration (10 inches of snow for every 1" of rain; this is just an approximation though and the true ration is different with different storms), then 1.5-3" of rain would equate to about 15-30" of snow. -Dan, CWG

Posted by: CapitalWeatherGang | March 9, 2011 11:03 AM | Report abuse

That disappearing link (mainly when I'm at work) was incentive enough for me to finally bookmark your site, rather than coming in through the main WPost site.

Posted by: msienkiewicz | March 9, 2011 11:19 AM | Report abuse

I was trying to find out how much rain National recording during Hannah in 2008,and in the course of that I was reminded we had 4.66 inches in Sept of last year. I only barely remember that ... but it makes me think 1-2 inches will not be a big deal.

Posted by: mhardy1 | March 9, 2011 11:57 AM | Report abuse

Er ... 4.66 inches in a single day in September .. not the whole month.

Posted by: mhardy1 | March 9, 2011 11:59 AM | Report abuse

mhardy, max daily rainfall in March is not that much compared to some other months. The daily record is 2.79" on 3/9/1881. There are only 5 other daily records above 2". I'm still looking at two and three day numbers, but nothing more than about 3.5" seems to be out there. So, an event in the 2-3" range would be fairly atypical for March.

Posted by: Ian-CapitalWeatherGang | March 9, 2011 12:11 PM | Report abuse

I understand that our greatest rainfall events have often been the result of tropical systems, or moisture from tropical systems (like the flooding rains from Nicole last Sept. 30), but there also seems to be an increase in heavy-rain events that occur around here in May and June. There was a huge Potomac River flood in June 1889, and as recently as May 2008, a flood caused a lot of damage to Upper Marlboro. Any explanation for why that late spring period brings an increase in high-rainfall events to our area?

Posted by: marklandterrapins | March 9, 2011 12:19 PM | Report abuse

ian,
thanks for tossing me that bone. my interpretation of the latest (12z) GFS run is that the storm is going even further south - the "good part" now passing over SC/GA and the cold temps going north... :-/ a very bad trend... hopefully it's just a "wobble", not a trend, and it will wobble back.

tell me there's better news from those precip-withholding euro bastages...
-------------

btw, when i look at this page,
http://www.srh.noaa.gov/data/LWX/CLIDCA ,
is the 5.8" of snow in 1911 the record amount for march 8 or march 9? (that's the same figure they were showing there yesterday afternoon... weird)

Posted by: walter-in-fallschurch | March 9, 2011 12:30 PM | Report abuse

Outside of a possible stray flake, there is no accum. snow over the next 10 days. Odds on any accum. snow get lower everyday, any snow that would accum. would have 2 fall at night. Time to give up the snow hope.

Posted by: VaTechBob | March 9, 2011 12:45 PM | Report abuse

Hey guys, from reading the forecast it doesn't seem that winds will be significant enough to worry a lot (given I've got PEPCO, that really should say worry more than normal) about power outages with this rain. But, given how wet the gound will be and I've got a basement full of crap protected by a lone sump pump do you think there may be a decent chance at some power outages with this event?

Posted by: ftwash | March 9, 2011 1:16 PM | Report abuse

walter, the new Euro has a pretty wet storm mainly to our south that tries to "cut off" and stall around for a while. Ultimately it warms us up but not before about .5" liquid has fallen around D.C. as snow or mix. Regardless, the Euro seems to have at least temporarily moved toward the GFS solutions of yesterday before it "lost" the storm. Also, the figure noted is for the 8th. The record for the 9th is 8.4" on 3/9/1999.

Posted by: Ian-CapitalWeatherGang | March 9, 2011 1:54 PM | Report abuse

@ftwash, in my amateur opinion I'd say this time around, trees are more likely to topple due the wet ground more than winds.

Posted by: wadejg | March 9, 2011 2:01 PM | Report abuse

thanks so much ian. where did you find the snow record for today?

Posted by: walter-in-fallschurch | March 9, 2011 2:05 PM | Report abuse

walter, I pulled it from a spreadsheet but you can get the daily record info here (March data).

Posted by: Ian-CapitalWeatherGang | March 9, 2011 2:08 PM | Report abuse

thanks again. i've bookmarked that page - good stuff there. and, wow, a quick perusal of those numbers shows that the late 1800s were great for snow!!

Posted by: walter-in-fallschurch | March 9, 2011 2:19 PM | Report abuse

Folks, I'm beyond scared to death with all this rain coming. My shrink told me to buy an umbrella. I'm going to do that, but I'm still so worried. What happens if I get swept up by a raging Middle Patuxent Creek that runs about 1/2 mile behind my condo? Please, will someone help me? Should I buy some t-paper, milk and bread just in case?

Posted by: rpcv84 | March 9, 2011 3:08 PM | Report abuse

This report was Wednesday's!

You'd think The Post would go with REAL weather professionals!

Uh, scratch that. They wouldn't, would they?

Posted by: clitteigh | March 10, 2011 12:50 PM | Report abuse

This report was Wednesday's!

You'd think The Post would go with REAL weather professionals!

Uh, scratch that. They wouldn't, would they?

Posted by: clitteigh | March 10, 2011 12:51 PM | Report abuse

This report was Wednesday's!

You'd think The Post would go with REAL weather professionals!

Uh, scratch that. They wouldn't, would they?

Posted by: clitteigh | March 10, 2011 12:52 PM | Report abuse

The comments to this entry are closed.

 
 
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