2008 Spring Flood Situation

[CanisLupusArctos]

The National Weather Service just issued a flood warning for the Connecticut River at West Lebanon from now until Sunday night.

Rapid snow melt has brought the river to 16.7 feet (flood stage is 18 feet) and they are expecting a crest of 19 feet between now and Sunday night.

While not part of the Winnipesaukee watershed, it is a result of snow melt from up north, and therefore may be a sign of things to come.

It's starting to look like we might get temps in the 60s in the Wed-Fri timeframe. At this time of year, abnormally warm temperatures (75+) are not unusual, but are often not predicted until the day before. Usually the season's first 80-degree day starts off as a much cooler forecast and gradually gets warmer as the day approaches. Forecasters are usually unwilling to commit to a summery temp forecast at this time of year until it's right on the doorstep and knocking.

Last April, even after the way-below-normal temps we had from late January to early April, we still had a 76-degree day on April 23 (many parts of NH were in the low 80s.) Between the 21st and 24th the daytime highs were 66... 64... 76... 65. Such an occurrence this year could generate a lot of water from the snow upstream.

You probably wouldn't have more than 24 hours' notice of such temps... so best prepare as though the mountains were going to be in the 70s tomorrow and then you'll be ready for any flooding if it does happen before most of the snow melts. Watch the weathermap for warm fronts. They're common at this time of year as warm air makes its annual northward push from the Gulf of Mexico. Warm fronts can generate several hours of steady precip, followed by a sudden jump in temps after they pass.

[Airwaves]

River Flood Statement
National Weather Service Gray, Me
951 Am Edt Sun Apr 13 2008

...the Flood Warning Is Cancelled For The Following River In New
Hampshire And Vermont...

Connecticut River At West Lebanon Affecting Grafton...sullivan And Windsor Counties


National Weather Service Taunton Ma
1120 Am Edt Sun Apr 13 2008

...the Flood Warning Is Cancelled For The Following Rivers In
Connecticut...massachusetts...

Connecticut River At Thompsonville Affecting Hartford And Hampden Counties

...the Flood Warning Continues For The Following Rivers In
Connecticut..
Connecticut River At Hartford Affecting Hartford And Middlesex
Counties
Connecticut River At Middletown Affecting Hartford And Middlesex Counties

Continued Runoff From Snow Melt In Central And Northern New
England...combined With The Rainfall From Friday Night And
Saturday...will Keep The Lower Connecticut River In Minor
Flood At Hartford And Middletown Connecticut...probably Into
Tuesday...if Not Longer.

[Fargo]

Our dock has been right at lake level the last couple springs, last year it was covered with about 2" of water. The waves did structural damage to it and we have major repairs scheduled for this season. It appears that the lake has come up about 4" since I measured Thursday. I'm expecting the dock to be under water again real soon (another 20"). We're considering raising the dock another 12" just in order not to deal with this each season.

[jeffk]

Except for the Merrimack at Concord (above flood stage) and Manchester (very near flood stage) most of the river gages show that the levels are declining, including the Pemigewasset and Winni Rivers. I live along the Merrimack in Hudson and the levels are at normal spring highs, up a little after the weekend rain but OK. The lake level is about where it should be for this time of year. The forecast for the next 10 days at the lake is for almost no rain and temps in the 50's to low 60's, nightime around 40.

I would expect that melting would continue at an accelerated clip this week but without any significant rain I would bet that we'll get rid of a good amount of snow without any problems.

Unless we get another 3"+ rain storm within the next few weeks I think we may be OK.

[CanisLupusArctos]

For the most part I agree with that. No rain is in the forecast for the next several days, which will help keep melting to a trickle for at least the first part of the week as temps stay pretty cool.

I am getting gradually more concerned about Thursday-Friday. What started off as a 60-degree forecast for Thursday is now showing a warming trend with each update, and now looks like upper 60s/near 70 for both days. As I mentioned earlier, the season's first 80-degree day often starts off as a much cooler forecast because we're usually unwilling to commit to such a forecast until the day before. Therefore, I would not be surprised if Thursday and Friday ended up being 75-80 both days with a couple of places reaching low 80s. HOWEVER... I am not committing to that forecast. Only saying it's possible based on the trend I'm starting to see, and what it often means at this time of year. Keep watching the Thurs-Fri forecast to see if it works out that way.

Much of the snow to the south of the lake has now melted so we're in good shape there... at least from floodwaters originating locally. If Thursday-Friday do end up having our first taste of summer (which is not unusual for mid/late April) it would be runoff from the mountains we'd have to deal with, and would be a matter of predicting how far downstream the "bulge" would go before the riverbed was wide/deep enough to swallow it. For that, we would turn to a different breed of scientists, the hydrologists. They've been doing a lot of number-crunching since this flood threat became apparent in late February.

[KEEPER]

http://www.des.state.nh.us/rti_home/...g_stations.asp

Here is the link to the snow pack data that DES collects. Another survey will be done tomorrow (4/15) and should be available by 2PM.

[SIKSUKR]

As of Tuesday the Merrimack in Manchester had already crested at just below flood stage and is currently almost at action stage or 1 ft below flood.Forecast is for the river to be 1 ft below action stage or 2 ft below flood stage by tomorrow and continue to drop.We've been real fortunate this year with a nice slow melt and low rainfall during the melt.Keeper can speak to this but it looks like this should help with being able to keep Lakeport flows high enough to keep Winni from flooding like last year unless we see very large rainfall amounts in the near future.

[Pepper]

SS - so glad to hear that, at least for now, you're not in danger of yet another flood. You've had enough of that to last a lifetime!

Keep us posted.

[SIKSUKR]

Thanks Pepper.The forecast is for the river to keep dropping through friday.If Waldo Peppers was in my location the last few years you would have needed a "float"plane to stay in business.All looks good right now.

[CanisLupusArctos]

Latest forecasts are indicating anywhere from 2-4 inches of rain falling between Monday afternoon and Tuesday afternoon. The NWS is considering flood watches for the area which may be issued during their overnight shift tonight.

They are looking at forecasts for the headwaters of the CT, Saco, and Pemi Rivers where most of the snow pack is now gone and river levels are below action stage but could rise quickly if enough rain falls in a short period of time.

This storm is shaping up like a wintertime Nor'easter except there is not enough cold air to create snow because it's April, but if this was 2 months ago we'd be getting a lot. Instead we will be getting a lot of the liquid equivalent.

At the very least, we will have basement flooding as well as flooding of low-lying areas (the usual places.) In addition, we will see flooding of areas near storm drains that have been clogged by debris left behind by the snowbanks this winter. Road crews haven't had more than the last few days to do much spring cleanup, so I suspect there are a lot of storm drains clogged by stuff the snowbanks left behind. And we'll know exactly where they are, come Tuesday, judging by the way the weathermaps look now.

One more concern is the fact that many roads are in various degrees of suffering from what winter did. So, it might not take the rain much effort to further damage or even wash out sections of roads that are already 'hangin' by a thread.'

Also, the lake is very near full. Since I'm not a hydrologist I can't say exactly what situation would push the lake above-full, but it's something you should start watching if you are on the waterfront.

Stay tuned to forecasts and any possible watches that may be issued. A watch is always issued for a general area and means "it's possible so get ready" while a warning is issued for a county and means "It's happening so put your plan into action, if you need to."

This will solve the fire danger problem we had this month.

[CanisLupusArctos]

The National Weather Service in Gray Maine has issued a flood watch for its entire forecast area including the lakes region until Wednesday.

The following is quoted from their forecast discussion written this morning (Technical terms have been translated after copying).

ALL MODELS SHOWING
2 TO 3 INCHES OF RAIN OVER A MAJORITY OF THE FORECAST AREA BY 7 AM
TUESDAY. THESE NUMBERS MAY BE UNDER DONE CONSIDERING SLOW MOVEMENT
OF THE SYSTEM AND LONG FETCH OF ATLANTIC MOISTURE FEEDING INTO THE
SYSTEM WITH THE POSSIBILITY OF SOME DEGREE OF TROPICAL MOISTURE
GETTING INTO THE ACT LATE TONIGHT AND TUESDAY. FLOODING WILL
CERTAINLY BE AN ISSUE ON MOST MAIN STEM RIVERS IN THE
FORECAST AREA ALREADY NEAR BANK FULL DUE TO SNOW MELT...SO WILL BE
ISSUING A FLOOD WATCH FOR THE ENTIRE FORECAST AREA WITH THIS
PACKAGE. SEE HYDRO SECTION BELOW FOR DETAILS.

Hydro section...

HIGH LEVEL OF CONFIDENCE THAT FORECAST AREA WILL SEE 1 TO 2 INCHES OF RAIN TODAY THRU TUESDAY WITH 3 TO 4 INCHES POSSIBLE. THIS MUCH RAIN COULD LEAD TO FLOODING ESPECIALLY WITH RIVERS AND STREAMS SWOLLEN FROM RAPID SNOWMELT OF WHAT WAS A VERY DEEP SNOW PACK ACROSS THE FORECAST AREA. THUS A FLOOD WATCH HAS BEEN ISSUED FROM MIDNIGHT TONIGHT THRU EARLY WEDNESDAY MORNING.

[jeffk]

All the rivers (except for a few way north) are down 2 to 4 feet from their big melt high of last week so there is some capacity there for runoff. The southern part of the state had long been snow free and was very dry so south of the lake there is capacity for the soil to soak up some rainfall.

The Lakeport dam outflow is not unusually high so the operators there seem to be content to let the lake go up a bit more for now.

Bizer's lake level chart is very interesting because of its historic picture. Almost every year the lake starts rising steadily and then sometime between mid April to mid June there is a bump up that I would suspect is associated with either a single very big (6+ inch) rainfall or a rapid sequence of smaller rain events. Over all it is pretty common for the lake to go over "full" for a while in the spring.

The rest of the week is forecast to be dry. My seat of the pants guess is that if we get 2 inches or less not much exciting will happen. If we get 4 inches there will probably be flooding in the areas commonly prone to spring flooding and drying out in a day or two.

Do you think we could train Woolly bear caterpillars to do flood forecasts?

[CanisLupusArctos]

An inch of rain has fallen at Black Cat Weather Station from this storm. Radar indicates several areas of heavy rain (yellow) forming over New York State, Connecticut, and Rhode Island. This activity is moving toward NH and Maine. Moderate rain will continue until the heavy stuff gets here late tonight.

As in wintertime, a secondary low pressure area is expected to develop off the mid-Atlantic coast and create (wet) Nor'easter conditions on Tuesday. The energy associated with this system may be sufficient for thunderstorms to spring up within the greater storm. If these form, they could drop an inch of rain on specific towns in an hour's time. This rain would be in addition to whatever the surrounding area gets from the general rainfall.

The National Weather Service in Gray Maine said in their latest forecast discussion that flood warnings could be issued as early as 11 pm. These would likely be for smaller rivers or streams over-full. On Tuesday any thunderstorms embedded within the greater storm may result in localized flash flooding, when water levels on roads or near homes rise to several inches (or feet) deep within minutes due to an all-out downpour. If this happens, the NWS issues a flash flood warning for the specific area where it's occurring.

Localized flooding may also occur in areas where the recently-melted colossal snowbanks have left heaps of dirt and debris on or near storm drains. Washouts may occur where localized flooding flows across roads already chewed up by the hard winter.

The following is the latest public update (not the forecast discussion) from the NWS.


FLOOD WATCH
NATIONAL WEATHER SERVICE GRAY ME
843 PM EDT MON APR 28 2008

...A HEAVY SOAKING RAIN WILL CONTINUE THROUGH TUESDAY...

.LOW PRESSURE OVER NORTHERN NEW JERSEY THIS EVENING WILL
TRACK NORTHEAST...CROSSING NORTHERN ENGLAND TUESDAY AFTERNOON
AND EVENING. AHEAD OF THE LOW...A DEVELOPING SOUTHEAST FLOW WILL
BRING AMPLE AMOUNTS OF MOISTURE IN FROM THE ATLANTIC...RESULTING
IN LOCALLY HEAVY RAINFALL.

RAIN HAD OVERSPREAD THE ENTIRE REGION BY THE EVENING HOURS...AND
THE RAIN WILL CONTINUE OVERNIGHT INTO TUESDAY. THE RAIN WILL FALL
HEAVILY AT TIMES...ESPECIALLY LATER TONIGHT AND TUESDAY MORNING.
SINCE RIVERS ARE STILL RUNNING HIGH FROM THE RAPID SNOWMELT OVER
THE PAST TEN DAYS...THE EXPECTED 2 TO 4 INCHES OF RAIN MAY RESULT
IN RIVERS RISING TO BANKFUL OR HIGHER LATER TONIGHT THROUGH
WEDNESDAY MORNING.

[chipj29]

Indeed the streams in my area are running at pretty high levels. More rain today could start making things get ugly.

[CanisLupusArctos]

The National Weather Service issued an urban and small stream flood advisory for much of NH for today. It means the same thing as a river flood warning but on a smaller scale, so the stronger word, 'warning' is not necessary.

There is also a river flood warning in effect for the Saco River near Conway because the river is nearing flood stage this morning.

Lake Winnipesuakee is either at or above full level now. This is indicated by the submersion of Black Cat Shoals in the WeatherCam. The last reported lake level from DES was yesterday morning.

Black Cat Weather Station has received 1.99 inches of rain since 10 a.m. yesterday and more is likely for today. The good news is that the state has gotten into the 'dry slot' of this storm. Radar indicates very heavy rain over our neighboring states of Maine and Vermont, with a moisture feed coming off the Atlantic Ocean. The rain to our east will stay there, while the rain to our west is what we'll have to deal with today.

While the rain to our west is heavy, there isn't much of it, so it won't take more than a few hours to pass. After that, we'll taper to showers and skies should begin to clear later tonight.

[phoenix]

and to think that Saturday we couldn't burn because it was too dry

[CanisLupusArctos]

Black Cat Weather Station has received 2.36 inches of rain from the storm so far and more heavy rain is falling. Radar indicates bands of moderate and heavy rain rotating in from the ocean.

This storm is proving itself a wintertime system as advertised. Cold air is feeding into it from the northwest and this has caused a change to snow in Vermont at elevations above 1000 feet. This change may also take place in the mountains and foothills of New Hampshire before the day is out.

Temps here at the lake are 42 and dropping at a rate of 1.5 deg. per hour.

The National Weather Service has issued a freeze warning for parts of New York state for tonight and also frost advisories in southeastern Massachusetts. Tonight we are expected below freezing here as well.

It now appears that the dry weather to follow this storm may only last until the end of the week. A warm front will approach on Friday. If it pushes through here, we'll have a warm and springlike weekend. Models are now hinting that it will stall instead, allowing a continuous moisture feed into this area.

[CanisLupusArctos]

Just what you wanted to hear, I know... but there's another inch of rain on the way for today (Sunday.)

The warm front mentioned in my above post from a few days ago has stalled out to the south of here, and has been the cause of all this cloudiness we've had the last several days. This warm front is associated with the same low pressure system (storm) that just dumped record snow on the northern plains and tornadoes to the south and east of there. That storm is weakening as it moves into New York state, but we're back in the wintertime pattern which means the storm will spawn its offspring along the mid-Atlantic coast which will then become the dominant one.

This whole process will mean more rain... just like in February when it meant more snow, except its not that cold anymore.

Look for rain throughout Sunday, heaviest in the late morning and early afternoon. Highest rainfall totals will be to the south, less to the north.

A cold front will clear the whole mess out of here on Monday but will also result in below-normal temps for at least the first half of the week. It looks like we may get a few showers late in the week (maybe) and then next weekend is starting to look like "a typical day in Ireland." Yay.