Flood warnings remain in effect in Harford and Cecil counties today as record rain and snowmelt in Pennsylvania and New York send high water down the Susquehanna River. The river has already passed flood stage at Marietta, Pa., about 35 miles upstream from Conowingo. It appears to have crested at Harrisburg.

UPDATED: The water below the Exelon Power Corp.'s Conowingo Hydroelectric Station is forecast to reach 25.5 feet by this evening, then begin to fall. At 10:30 a.m. it was at 24.5 feet. That is a foot above flood stage (23.5 feet). Minor flooding is occurring, according to the National Weather Service; "moderate" flooding is expected.

The forecast, if realized, would bring the river to Notification Level 5, with 21 to 25 of the dam's 53 gates open. At Level 5, backyards and basements on Main Street, and Tome's landing in Port Deposit begin to flood.

An earlier NWS forecast had predicted the river level would reach Level 6. An earlier version of this post indicated that level had already been reached. It has not. Your weather blogger regrets the error. Here's more on the Notification levels..

The webcam photo was taken in June 2006, during runoff from heavy rains. If anyone snaps some pictures there today, send them along and we'll post them.

Water was rushing through the dam this morning at a rate of 323,000 cubic feet per second. The previous record for a March 6 was 320,000 cf/s in 1979. The average for this date is 70,500 cubic feet per second. The all-time record high flow was 1.13 million cubic feet per second, on June 24, 1972, in the aftermath of Tropical Storm Agnes.

Below is a graph of the discharge rate at 9:30 this morning. You can get real-time data on the discharge by clicking here.

Posted by Frank Roylance at 10:24 AM | Permalink | Comments (2)
                    

Watch those smokes, folks. The National Weather Service has posted a "Red Flag Warning" from Arundel and Montgomery counties wouth into Virginia, as high winds and very low humidities turn grass, brush and leaf litter to tinder. It's the red zone in this map.

The forecast calls for winds gusting as high as 55 mph this afternoon. The really cold arctic air moves in late today, sending overnight lows into the teens tonight. This will be very dry air. Here's how the forecasters out at Sterling put it in their discussion yesterday:

"FOR SNOW LOVERS THIS WILL BE A WASTE OF COLD AIR. HIGH PRESSURE TO BUILD
INTO THE REGION SUNDAY NIGHT BRINGING VERY DRY (AND COLD) AIR. I CAN`T
RECALL THE LAST TIME I PUT SUBZERO DEWPOINTS IN THE ZONES. LOTS OF STATIC
ELECTRICITY WHEN YOU WALK AROUND AND TOUCH ANYTHING MON. MORNING."

Sub-zero dewpoints mean the air is so dry that temperatures would have to sink below zero before the air would become saturated, and the moisture condense and fall as snow. The dewpoints in Baltimore tonight will be minus-2 to minus-4 degrees.

I'll have to be careful with static charges. I've zapped my laptop once before with a spark from my finger to the screen. It went dark and I had to reboot.

Posted by Frank Roylance at 9:18 AM | Permalink | Comments (0)
                    

The National Weather Service has posted a coastal flood advisory for tonight as southerly winds drive water up the bay and send it lapping onto low-lying spots on the Western Shore of the bay and the tidal Potomac River. Check the advisory for high tide times at your location. Here's how the tide tracker saw it around 5 p.m. Tuesday. You can follow it yourself if you click here.

They're only talking about "minor" flooding, but it pays to keep a watch out, especially in flood-prone spots such as the Alexandria, Washington and the Annapolis City Dock. 

The flood threat will disappear during the morning tomorrow, as an approaching cold front crosses the region and turns the winds around to the west. But these will be strong winds. A wind advisory has been posted for the Baltimore metro area, from 5 a.m. Wednesday to 4 p.m. It warns of sustained winds reaching 15 to 25 mph, with gusts to 50 mph. Take that into account if you have to put trash out tomorrow.

Next up? Freezing rain late Thursday into Friday, with the best chance for icing west of I-95. Nice.

Posted by Frank Roylance at 4:54 PM | Permalink | Comments (0)
                    

UPDATE, 5:10 p.m.: The severe thunderstorm warning for Baltimore and Harford counties has been lifted. Watches remain in effect. Here's the latest watch/warning map. 

EARLIER: Thunderstorms pushing south and west out of New Jersey and Pennsylvania could reach Maryland this afternoon or evening. The National Weather Service has posted a severe thunderstorm watch for all of Central Maryland, the District and Northern Virginia, as well as the northern Eastern Shore and west to Allegany County. Large hail remains the primary worry.

Here's the radar loop. And the satellite view. Here's (as of 2:50 p.m.) where the watch was posted. Here is the forecast.  Here's a regional map of watches and warnings.

And here's a portion of the watch statement:

Posted by Frank Roylance at 2:45 PM | Permalink | Comments (0)
                    

UPDATE, 3:50 p.m.: Severe storm warnings for Harford and Baltimore counties have been cancelled. Severe storm watches remain in effect across the region. Here's a map that will provide current watches and warnings.

EARLIER: Baltimore and Harford counties are under severe storm warnings this afternoon as thunderstorms roll in ahead of a cold front from the north and west. The rest of the region is under a severe storm watch. Here is the latest forecast. Here is the current storm warning. And here is the local radar. For a wider view, click here.

Where's the lightning? Check here.

Here's how Sterling puts it:

STRONG THUNDERSTORMS ARE EXPECTED TO DEVELOP ALONG THE BLUE RIDGE
AND ACROSS THE BALTIMORE METRO AREA DURING THE MID
AFTERNOON...BRINGING A BRIEF HEAVY RAIN...DANGEROUS CLOUD TO GROUND
LIGHTNING...AND THE THREAT OF LOCALLY DAMAGING WIND GUSTS. THIS
ACTIVITY IS FORECAST TO MOVE SOUTHEAST ACROSS THE WASHINGTON DC
METRO AREA...INTERSTATE 95 CORRIDOR AND INTO LOWER SOUTHERN MARYLAND
DURING THE DINNER TIME HOURS.

And here are some severe weather safety rules to keep in mind. Be careful out there.

Posted by Frank Roylance at 2:31 PM | Permalink | Comments (0)
                    

Dry air and stiff winds have spurred the National Weather Service forecast office in Mt. Holly, N.J. to issue "red flag warnings" for northeastern Maryland and Delaware. That means conditions are ripe for the spread of brush fires. The warnings extend well beyond the Eastern Shore, north into New Jersey and eastern Pennsylvania.  So if you're in that area - or anywhere else for that matter - be careful with outdoor fires, and snuff your cigarettes in the ashtray. Here's our official forecast, from Sterling.

Ever wonder why much of Maryland's Eastern Shore gets its weather forecasts from a forecast office in New Jersey? Me too. It turns out that Maryland - one of the nation's smallest states - was carved up and parceled out to no fewer than four regional weather forecast offices, all located in other states. Here in Central Maryland, we're covered from the Sterling, Va. office. Garrett County, in far Western Maryland, gets its forecasts from the Pittsburgh office. Northeastern Maryland is handled from Mt. Holly, N.J.  And the Southern Shore, including Ocean City, is covered by forecasters in Wakefield, Va., west of Norfolk.

Go figure.

Posted by Frank Roylance at 8:39 AM | Permalink | Comments (0)
                    

Better put a rope on Toto today. Also bring in the garbage cans, secure your trash and put some muscle at the wheel of the Winnebago. Big wind's coming this afternoon as a cold front reaches the area from the northwest.

The National Weather Service has issued a wind advisory, warning of winds gusting in excess of 45 mph after the front reaches the I-95 corridor. Here's the advisory.

While our MarylandWeather.com forecast made mention of a possibility of thunderstorms arriving with the frontal passage, the National Weather Service discussion this morning downplays the possibility. We'll all find out in a few hours.

Behind the front we get into colder, drier air - colder than yesterday's highs in the 50s, and colder than the long-term averages for BWI at this time of year. But we won't be seeing the sort of arctic cold we saw last week, with lows in the teens and highs struggling to reach 30 degrees. Here's the official forecast.

Posted by Frank Roylance at 7:45 AM | Permalink | Comments (0)
                    

There are high wind watches up across our region. We're being told to expect sustained winds over 40 mph across most of the state tomorrow afternoon, with gusts above 58 mph, as this stormy cold front crosses the region. They're calling for high water along the bay shore, too - 1 to 2 feet above normal tides. They're already rising this afternoon, as this chart shows. (Click to enlarge.)

Also expect brief, heavy rains in thunderstorms and rapidly falling temperatures.

It was nearly 72 degrees here this afternoon at The Sun's monitoring station at Calvert and Centre streets. BWI reported 71 degrees this afternoon, too. The record for a Nov. 30 in Baltimore is 74 degrees, set downtown in 1933. The overnight readings are forecast to fall to 37 degrees by tomorrow night, and to 27 degrees by Monday night.

Posted by Frank Roylance at 3:25 PM | Permalink | Comments (2)
                    

The National Weather Service has posted a freeze warning for tonight in Cumberland and other portions of Allegany County. Temperatures out west could dip as low as 30 degrees tonight as cold air continues to stream in from the Great Lakes and Canada, and clear skies allow plenty of the day's solar energy to radiate back out into space.

Of course, that also makes it a great night for stargazing. The big show this month remains Jupiter, brilliant in the southeast in the evening and just a couple of weeks past opposition - its closest and brightest apparition of the year. Binoculars should reveal as many as four of its moons, lined up on either side of the big planet.

If you get lucky while you're outside tonight, maybe you'll spot a fireball like this one. It was photographed from El Paso, Texas, on May 4.

Posted by Frank Roylance at 4:29 PM | Permalink | Comments (0)
                    

There are frost advisories up tonight in the Pennsylvania counties just north of the Mason-Dixon Line, bordering Carroll, Baltimore and Harford counties. I suspect weather conditions don't much respect political boundaries, even those as venerable as Mason's and Dixon's. So watch for frost in the normally colder valleys of north-central Maryland, too.

The latest recorded freezing temperature at BWI was a 32-degree reading on May 11, 1966

Posted by Frank Roylance at 6:21 PM | Permalink | Comments (0) | TrackBacks (1)
                    

Watch those smokes. Dry air and high winds have raised the risk of wildfires in Maryland the Virginia for tomorrow. "Red Flag" warnings have been posted for much of Virginia and the lower Eastern Shore. And the danger is only slightly less in Central Maryland. Here's how the weather service put it:

"...FIRE WEATHER WATCH REMAINS IN EFFECT FROM WEDNESDAY MORNING
THROUGH WEDNESDAY EVENING...


"THE COMBINATION OF DRY GROUND...DRY AIR...AND STRONG WINDS WILL
LEAD TO POTENTIALLY DANGEROUS FIRE CONDITIONS WEDNESDAY. WINDS
WILL REACH SPEEDS OF 20 MPH...WITH GUSTS TO 35 OR 40 MPH. MINIMUM
RELATIVE HUMIDITY VALUES WILL REACH 20 TO 30 PERCENT. ALTHOUGH
THIS MORNINGS SHOWERS WILL MOISTEN THE GROUND A LITTLE...
PERSISTENT WINDS TODAY AND TONIGHT SHOULD DRY FUELS...PRIMING THE
GROUND BY WEDNESDAY.

A FIRE WEATHER WATCH MEANS THAT CRITICAL FIRE WEATHER CONDITIONS
ARE FORECAST TO OCCUR. LISTEN FOR LATER FORECASTS AND POSSIBLE
RED FLAG WARNINGS."

The Red Flag warnings in Virginia cover all the areas in red on this map.  A Red Flag warning means:

"CRITICAL FIRE WEATHER CONDITIONS
ARE EITHER OCCURRING NOW...OR WILL SHORTLY. A COMBINATION OF
STRONG WINDS...LOW RELATIVE HUMIDITY...AND WARM TEMPERATURES WILL
CREATE EXPLOSIVE FIRE GROWTH POTENTIAL."

Posted by Frank Roylance at 5:33 PM | Permalink | Comments (1) | TrackBacks (1)
                    

Oh my, that air felt good this morning - 72 degrees on the car thermometer at 9:30 a.m. But this early breath of spring is also stirring up warnings of wildfire danger and coastal flooding today.

First, there's the forecast:  We're talking a high of 78 degrees this afternoon. Hello ? We haven't seen the 70's at Baltimore-Washington International Airport since Nov. 16, when it was 76 degrees. And we haven't had a 78-degree day since Oct. 6.

The warm air barreling into the Northeast from the Gulf states is rocking small cars and empty trucks. The National Weather Service says we should expect winds of 13 to 21 mph today, with gusts as high as 37 mph. You can watch the top wind speeds at BWI on the strip chart here.

Wind plus low humidity are contributing to increased wildfire hazards. The weather service has issued the following notice:

"...NEAR CRITICAL FIRE CONDITIONS ACROSS THE REGION THIS AFTERNOON...

MINIMUM HUMIDITY OF AROUND 30 PERCENT IS EXPECTED ACROSS PORTIONS
OF THE FIRE WEATHER FORECAST AREA THIS AFTERNOON. THESE VALUES ARE
NOT QUITE RED FLAG CRITERIA....HOWEVER WITH SUSTAINED SOUTHWEST WINDS OF 15 TO 25 MPH...COMBINED WITH VERY DRY FINE
FUELS...NEAR CRITICAL FIRE WEATHER CONDITIONS SHOULD BE
ANTICIPATED.

"THE GENERAL PUBLIC IS ADVISED
TO RESPECT ALL STATE AND LOCAL BURNING LAWS."

Red Flag warnings are posted for the upper Eastern Shore, Delaware and southern New Jersey.

High winds from the south or southeast are also pushing water up the bay, increasing the risk of coastal flooding. Here's the advisory:

"...MINOR TIDAL FLOODING AT TIMES OF HIGH TIDE THROUGH FRIDAY
AFTERNOON...

"STRONG SOUTHERLY FLOW WILL CREATE ABNORMALLY HIGH TIDE LEVELS
THROUGH THIS AFTERNOON. WATER LEVELS OF 1 TO 2 FEET ABOVE
ASTRONOMICAL PREDICTIONS MAY CAUSE MINOR TIDAL FLOODING IN AREAS
THAT ARE PRONE TO PROBLEMS FROM HIGHER THAN NORMAL TIDES.
ALEXANDRIA VIRGINIA AND ANNAPOLIS MARYLAND ARE TYPICALLY
SUSCEPTIBLE TO COASTAL FLOODING.

"UPCOMING TIMES FOR HIGH TIDES ARE AS FOLLOWS...

"ANNAPOLIS MARYLAND...2:49 PM FRIDAY
ALEXANDRIA VIRGINIA...4:54 AM AND 5:18 PM FRIDAY
KEY BRIDGE WASHINGTON DC...5:11 AM AND 5:35 PM FRIDAY
FT MCHENRY BALTIMORE...4:27 PM FRIDAY
BOWLEY BAR...5:18 PM FRIDAY"

You can watch the tides rise here.

Posted by Frank Roylance at 10:50 AM | Permalink | Comments (0) | TrackBacks (1)
                    

Rain and lingering cold in parts of Maryland could spell trouble for late-night (or early-morning) motorists tonight as a storm system moves in from the Ohio Valley. The National Weather Service has issued a freezing rain advisory for the northern tier of counties, from Harford west to Allegany. Normally colder valleys may be especially vulnerable.

Heading north? There are winter storm watches and warnings up for eastern Pa., northern N.J. and the NYC area. That means 4 inches of snow or more. Click here.

Things should warm up here in the morning - at least enough to erase the ice threat. And the rain will cease. But it won't be anywhere near the balmy 65 degrees forecast earlier in the week. The cold air to our north has lingered more than forecasters expected, and the warm weather to our south will stay there, holding temps here to about normal for this time of year - mid-to-upper 40s in the daytime, 20s at night.

But once we're clear of the rain tomorrow, the sun will come out, and stargazing should be good for the weekend. And forecasters seem confident that the coastal low that's expected early next week will not push far enough north to affect our region. If it does, cold air here could mean frozen precipitation.

Posted by Frank Roylance at 10:30 AM | Permalink | Comments (0) | TrackBacks (1)
                    

Stiff winds, low humidity and a promise of more to come have prompted the National Weather Service to post a "Fire Weather" Watch for most of Maryland west of the Chesapeake. There's plenty of fuel out there, too. Here's the latest Haines Index map, which shows relative wildfire hazards across the country. We're listed as "moderate."  And, there's no new precipitation in the forecast until Wednesday. So crush those smokes.

Posted by Frank Roylance at 5:59 PM | Permalink | Comments (0) | TrackBacks (1)
                    

The National Weather Service has posted a winter storm watch for far western Maryland -including Garrett and Allegany counties - beginning Saturday afternoon and extending to late Sunday. Accumulations in excess of 6 inches are possible in some spots. And counties in PA and WV to the north and west could see up to 8 inches. Here's the skinny:

"LOW PRESSURE OVER THE DEEP SOUTH WILL TRACK NORTH INTO QUEBEC BY
SUNDAY. AS THIS SYSTEM REACHES PENNSYLVANIA SATURDAY
EVENING...COLD AIR WILL FILTER IN VERY QUICKLY WITH RAIN CHANGING
TO SNOW LATE SATURDAY AFTERNOON. SNOW SHOWERS ARE EXPECTED TO
CONTINUE ALL DAY ON SUNDAY AS MOISTURE IS LIFTED UP THROUGH THE
HIGHER TERRAIN ON WESTERLY WINDS. AT THIS TIME...THERE IS THE
POTENTIAL FOR SNOW ACCUMULATIONS IN EXCESS OF SIX INCHES OR MORE THROUGH
SUNDAY NIGHT.

"A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
CONTINUE TO MONITOR THE LATEST FORECASTS."

Posted by Frank Roylance at 4:02 PM | Permalink | Comments (0)
                    

Better bring in the trash cans. As a storm center moves off the mid-Atlantic coast and intensifies this afternoon, colder air will move in behind the low, blowing in from the northwest with gusts as high as 40 mph this afternoon and tonight. There are gale warnings for the Bay. Here's the landlubbers' advisory from the weather service:

" LOW PRESSURE WILL INTENSIFY AS IT MOVES OFF THE DELMARVA TODAY.
THIS STORM WILL HELP TO GENERATE SOME STRONG WINDS. NORTHWEST
WINDS WILL GUST UP TO 40 MPH ACROSS THE REGION THROUGH EARLY
EVENING. THESE WINDS WILL ALSO USHER IN A MUCH COOLER AIR MASS WITH
TEMPERATURES FALLING INTO THE 30S BY LATE AFTERNOON IN MOST AREAS.

"SCATTERED SNOW SHOWERS WILL EVEN OCCUR IN THE HIGHER ELEVATIONS
WEST OF THE BLUE RIDGE...ALTHOUGH ANY ACCUMULATIONS WILL BE UNDER
ONE INCH.

"BE SURE TO SECURE ANY LOOSE ITEMS ON YOUR PROPERTY DUE TO THE
STRONG WINDS. MOTORISTS SHOULD ALSO USE EXTRA CAUTION."

But the cold blast tonight won't do much to bring in more seasonable temperatures. The forecast still calls for sunshine and highs this week in the upper 40s and low 50s. That's still 5 to 10 degrees above normal for this time of year.

Posted by Frank Roylance at 2:03 PM | Permalink | Comments (0) | TrackBacks (2)
                    

The National Weather Service has issued a flood watch for all of Maryland from Allegany County in the west, to the Chesapeake Bay in the east. Forecasters are calling for 3 to 5 inches of rain from Friday through Saturday afternoon, as the remnants of Tropical Storm Tammy collide with a cold front approaching from the west. The heaviest amounts should fall west of the Blue Ridge.

The watch actually extends from Northern Virginia, across Maryland and Pennsylvania, clear into central New York State, visible as dark green on this map.

Posted by Frank Roylance at 5:50 PM | Permalink | Comments (0)
                    

5:54 p.m.: The Weather Service is issuing severe thunderstorm warnings ahead of a storm now crossing Maryland ahead of a cold front. The warnings have been issued for Baltimore, Frederick and Montgomery counties. Watches are posted across most of the rest of the state.

Storms are crossing Carroll County, headed for the greater Baltimore region. Here's the radar image. And here's a wider view.

Just to give you an idea of what's happening, it's still 98 degrees in downtown Baltimore at this writing, but the storms and the passing cold front have already dropped temperatures in Westminster, Frederick and Hagerstown to about 81 degrees. It fell 18 degrees in 40 minutes in Westminster. Be careful out there.

Posted by at 5:49 PM | Permalink | Comments (0)
                    

The National Weather Service has posted a severe thunderstorm watch for the entire state east of Garrett County until 10 p.m. tonight (Wednesday) as a strong cold front approaches from the northwest. The front will relieve our high temperatures once it pulls through. But in the meantime it's 96 at BWI and worse - 98 - at the Maryland Science Center. Radar shows some thunderstorms moving through Washington County, headed toward the Chesapeake Bay.

You can see the dramatic shift in the weather west of the front. It was 94 degrees just before 4 p.m. today in Harrisburg, Pa., and 77 degrees at State College, just 62 miles away to the west.

Posted by at 3:38 PM | Permalink | Comments (0)
                    

As suffocatingly hot as it was today, it looks like the high temperatures have fallen short of some of the direst predictions. Yesterday's forecasts warned of highs of 95 or 97 degrees. There were a few mentions this morning of 99 or even 100 degrees.

But the actual high at BWI will likely stick at 94 today, despite strong sunshine all day. (It's the 11th day in the 90s this month, and the warmest at BWI since Aug. 22, 2002, when it was 94.) The Science Center, in downtown Baltimore, reached 97.

With heat index predictions falling short of earlier expectations, the National Weather Service cancelled many of its "excessive heat" warnings for Wednesday, except for downtown Baltimore and Washington. And heat advisories will likely be cancelled later today for communities west of the mountains.

This is the beginning of the end of the heat wave. Wednesday should bring a "cold" front from the northwest, with clouds and cooler temperatures - the mid-80s - by Thursday.

Posted by at 6:00 PM | Permalink | Comments (1)
                    

With temperatures headed for the 90s again, and humidities to match, we're in for another stifling July day. The National Weather Service has issued a heat advisory, effective across the region through early evening.

"THE COMBINATION OF WARM TEMPERATURES AND HIGH HUMIDITIES WILL
CONTINUE THROUGH THE FIRST PORTION OF THE WORK WEEK. HEAT INDICES
ARE EXPECTED TO REACH THE 100 DEGREE MARK THIS AFTERNOON AND TUESDAY.

"A HEAT ADVISORY MEANS THAT THE COMBINATION OF HIGH TEMPERATURES
AND HUMIDITY WILL COMBINE TO CREATE A SITUATION IN WHICH HEAT
INJURIES ARE POSSIBLE. DRINK PLENTY OF FLUIDS...STAY OUT OF THE
SUN...AND CHECK UP ON RELATIVES AND NEIGHBORS.

"DO NOT KEEP CHILDREN OR PETS IN CARS WITH WINDOWS ROLLED UP...EVEN
PARTIALLY. TEMPERATURES INSIDE A CAR WITH WINDOWS UP CAN REACH
OVER 150 DEGREES QUICKLY...RESULTING IN HEAT STROKE AND DEATH."

Posted by at 1:12 PM | Permalink | Comments (0)
                    

AT 649 PM EDT...DOPPLER RADAR INDICATED STRONG THUNDERSTORMS ALONG A
LINE EXTENDING ACROSS NORTHERN AND WESTERN MONTGOMERY NORTHEASTWARD
INTO CENTRAL HOWARD COUNTY AND INTO WESTERN BALTIMORE COUNTY JUST
WEST OF BALTIMORE CITY. THIS LINE OF STORM IS MOVING SOUTHEAST AT 15
TO 20 MPH. THESE STORMS WILL BE CAPABLE OF PRODUCING WIND GUSTS TO
45 MPH. THROUGH 745 PM...THE DISTRICT OF COLUMBIA...SOUTHEASTERN
HOWARD...SOUTHEASTERN MONTGOMERY...ANNE ARUNDEL...NORTHERN PRINCE
GEORGES...BALTIMORE CITY AND SOUTH CENTRAL BALTIMORE COUNTIES WILL
BE AFFECTED BY THESE STORMS.

RESIDENTS SHOULD BE ALERT AND BE PREPARED TO SEEK SAFE SHELTER IF
THREATENING WEATHER APPROACHES OR A WARNING IS ISSUED.
- from: SHORT TERM FORECAST
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
652 PM EDT WED JUN 29 2005

Posted by at 8:19 PM | Permalink | Comments (0)
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