The weather looks pretty good for Saturday night, but Monday evening could be dicey, with "mostly cloudy" skies forecast. Check for weather updates. Urban lighting and thin clouds shouldn't hurt any. The ISS is very bright on these passes.

The first event comes Saturday evening, as the station passes over Lake Michigan and becomes visible from Central Maryland. Look for a very bright, star-like object rising in the northwest at 8:12 p.m. EDT. If it's blinking, has multiple or colored lights, it's an airplane. Keep looking. 

The ISS and its crew will climb high overhead, passing just above the moon in the western sky. It will climb as high as 69 degrees - more than two-thirds of the distance between the southwestern horizon and the zenith (straight up) by 8:15 p.m.

From there, the station will pass below the planet Mars in the southeast, disappearing over the Atlantic at 8:17 p.m.

The second pass comes on Monday evening, and it will look very much like Saturday's flyby. The station will rise in the northwest again, this time at 7:26 p.m. EDT. It will pass below the moon, 65 degrees above the southwestern horizon at 7:29 p.m.

From there it will slide off toward the southeast, passing between Mars and Sirius, the bright star to the lower left of the Constellation Orion, before vanishing at about 7:31 p.m. As always, drop back here after the show and share the experience.

The mercury out at BWI-Marshall Airport reached 70 degrees at 3:15 p.m. Thursday. It was the first time we've seen the 70s there since Nov. 15, when we touched 72 degrees

The Washington airports were in the same ballpark: 69 at Dulles at 3:59 p.m., and 71 down at Reagan National at 3:04, according to the NWS forecast office in Sterling, Va.

Here at The Sun, we reached 71 degrees at 3:30 p.m. It was 70 at the Maryland Science Center.

So, with spring officially less than 48 hours away, have we finally rid ourselves of all the February snow piles out there? The one behind my house has finally vanished. How about yours? How are the mall parking lot piles doing? Any more guesses on when the last of February's snows will finally trickle away?

(SUN PHOTO/Perry Thorsvik 1998)

The stowaway was probably a free-tail bat. It was spotted clinging to the surface of the shuttle's orange external fuel tank. Observers saw it moving around a bit, and they expected it would fly off before the countdown reached zero.

But it didn't, and it was seen on the tank as it began to rise toward orbit. NASA officials figure it was torn off the tank by wind during ascent and incinerated in the shuttle's rocket exhaust.

The bat may have had an injured wing. Here's more.

The National Oceanic and Atmospheric Administration has published its global and national data for February and for the past winter months. It demonstrates as clearly as anything could that what's happening locally, even nationally, does not necessarily reflect the global trends that we all need to be concerned about.

In the contiguous United States, February was cool, averaging 2.2 degrees below the long-term average.  Nearly two-thirds of the nation experienced below-normal temperatures. The averages were much below normal in the southeast, the Plains and mid-Atlantic states. Baltimore, Washington, Philadelphia, Pittsburgh, New York's Central Park and Wilmington, Del. all had their snowiest winters ever.

Florida had its fourth-coldest February since records began in the 19th century, and Louisiana had its fifth-coldest. On the other hand, Maine had its third-warmest winter on record. It was also warmer than average in the Northwest.

It was also a warm February - and a warm winter globally, according to NOAA. The combined global land and ocean surface temperature for February was the sixth warmest on record. The global land surface temperature alone for the month was tied with 1994 as the 14th warmest.

While it was unusually cold in the U.S., Mexico, Europe and Russia, most of the rest of the globe's land masses were warmer than average in February, especially Alaska, Canada, the Middle East and North Africa.

The winter as a whole was the fifth-warmest on record globally, just over one degree warmer than the 20th century average, NOAA said. Land temperatures were the 13th warmest on record.

While the United Kingdom had its coolest winter since 1978-79, much of Australia was warmer than normal. Western Australia, where drought has been a problem (photo), saw its warmest December through February period (summer) on record.

The Arctic saw its 12th consecutive February with below-average sea ice extent. February arctic sea ice has declined by 2.9 percent per decade since 1979. At the same time, on the other end of the planet, Antarctic sea ice has been expanding. The southern continent saw its eighth-largest February sea ice extent on record. It has increased by 3.1 percent per decade since the '70s.

Across the Northern Hemisphere, snow cover in February was the third-largest on record, after 1978 and 1972. For the winter, it was the second-largest snowcover on record. For North America alone, it was the largest, NOAA said. 

But the official arrival of spring on Saturday won't mean this kind of weather is here to stay. Forecasters say there's a cold front due to barrel through late on Sunday. That could bring thundershowers, and it seems certain to cancel the warmth we're enjoying now, especially for the snow-weary western counties.

The forecast calls for highs only in the 50s at BWI-Marshall on Monday and Tuesday, after the cold front blows through. The overnight lows will drop to near freezing again. That's actually about normal for this time of year in Baltimore. But after this week it's going to seem like a relapse into winter.

That will be especially true out in Garrett and Allegany counties. Westerly winds behind the front will mean upslope snow showers Monday and Monday night. Like they need more flakes to add to the 250 inches or more they've seen this winter.

This backsliding comes to us courtesy of the blocking features over the North Atlantic that controlled our weather for much of the winter. That Arctic high was responsible for the twist in the northern jet stream that kept the door to the eastern states open to cold Canadian air, and turned the parade of El Nino-fueled storms off the Pacific into snow-makers.

Eric the Red, a professional meteorologist in Baltimore, says that blocking high is back.

"You see, it's like Friday the 13th. You can't really kill Jason. And until further notice, you can't really kill the northern-Atlantic blocking high ... You don't have to be a meteorologist to see that bad things are coming our way. There's an initial surge of cold air over the nation's midsection, with another even-colder shot dropping out of Canada ... D'oh.

"I'm holding out hope that the switch back to cold doesn't last, but it's a little too early to say. Upper air forecast charts kinda imply the chilly weather might be back for a while."

That doesn't necessaily mean more snow. Heck, I heard my first spring peepers (photo) last night from the WeatherDeck in Cockeysville, even as the last basketball-sized pile of snow melted in the back yard.

But snow - even big snow - can happen in March in Baltimore. Steve Zubrick and Jared Klein, out at the NWS forecast office in Sterling, have been looking at the stats from the memorable (if you're old enough) winter of 1957-58.

They noted that the Arctic Oscillation - the same blocking high mechanism Eric the Red is talking about - was in a similar (negative) phase back then. In February 1958, Central Maryland was clobbered with a 15-inch storm, which until this winter ranked 9th on the all-time Top 20 snowstorm list. A month later, on March 19-20, the region was buried by a wet snowfall that topped 30 inches in Mount Airy, north and west of the city. Totals dwindled to 8 inches at Friendship (now BWI-Marshall) Airport because of a mix with rain and sleet; otherwise, that snowstorm would rank among the top 20 for Baltimore, too.

That March 1958 storm crippled transportation, ripped down power and phone lines and remains one of the most disruptive storms on the record books for this area. This weekend is the 52nd anniversary of that storm.

"Nice storm, if you love heavy, wet snow!," Zubrick said. "Winter can be tough here, even in March!"

(SUN PHOTOS/Top: Virginia Williams, 2010/ Bottom: Glenn Fawcett, 2007)

Nothing like a fine breakfast with a group of close friends. These vultures gathered this morning to dine beside Western Run on the carcass of a whitetail deer (barely visible, far left). The animal appeared to have been struck by a car on Ashland Road, then stumbled, or was dragged, to the edge of the woods.

The forecast calls for more sunshine today, and through the end of the week, with temperatures rising well into the 60s as the week rolls along.  

(SUN PHOTO: Frank Roylance, 3/16/10)

The assessments are made by the National Climatic Data Center. Meteorologists there use a ranking system developed to weigh not just the snow depth at any one location, but the depth, the geographic area and the population it affected over its full range.

Called the Northeast Snowfall Impact Scale (NESIS), the system was developed in 2004 by Paul Kocin and Louis Uccellini, of the National Weather Service. It's since been applied retrospectively to every major storm since 1956, and to all the big Northeast snowstorms that have occurred since the scale was developed.

The NESIS scale calculations generate an index number, which is translated into a five-level Category ranking similar to the Saffir-Simpson Hurricane Scale, including Notable, Significant, Major Crippling and Extreme. 

Category	NESIS Value	Description
1	1—2.499	Notable
2	2.5—3.99	Significant
3	4—5.99	Major
4	6—9.99	Crippling
5	10.0+	Extreme

Only two storms have been ranked as Cat. 5 "Extreme." They were the March 12-14, 1993 storm, which was given a NESIS number of 13.20; and the Jan. 6-8, 1996 storm, rated at 11.78.

Here, for comparison, with their preliminary rankings and NESIS numbers, are this winter's four biggest snowstorms. Only the three earliest had a major impact in Baltimore. And here's a link to the full list.

17. Feb. 23-29, 2010: 5.11, a Cat. 3 "Major" storm.

21. Feb. 4-7, 2010:  4.30, a Cat. 3 "Major" storm. (Map above.)

25.  Dec. 18-21, 2009:  4.03, a Cat. 3 "Major" storm.

26:  Feb. 9-11, 2010:  3.93, a Cat. 2 "Significant" storm.

First, the rain. Forecasters out at Sterling say we could see a few tenths of an inch more Monday and Tuesday before we finally shake free of this mess. Rivers and streams remain high, but the crests appear to have passed most points on the major rivers. 

The National Weather Service still has Coastal Flood Advisories posted until 11 p.m. Monday all around the Chesapeake Bay, with high tides expected to run 1.5 feet or more above predicted levels and minor coastal flooding possible.

Out along the Maryland beaches, the high tides will run 2 to 2.5 feet above normal, with minor flooding in Ocean City.

At Conowingo Dam, the waters of the Susquehanna River reached 22.12 feet at 9:30 a.m. Flood stage is at 23.5 feet. Minor flooding at Port Deposit, Md. begins when the river reaches 23.7 feet. The gauge at Conowingo was reporting 251,000 cubic feet per second flowing past the instruments this morning, a record for the date. 

On the tidal Potomac River, Coastal Flood Warnings are up until 11 p.m. Monday as high tides and the crest of the river flooding reaches the Washington, D.C. and Alexandria, Va. area.

The river flood crest is due in Washington around midday Monday, with Potomac River levels rising as high as 5 feet above normal at Georgetown. Major flooding is forecast at Wisconsin Avenue (chart below). More tidal flooding is expected in Old Town Alexandria. 

BWI-Marshall Airport reported 0.98 inch on Friday, another 2.31 inches on Saturday, and 0.29 so far on Sunday, for a three-day total of 3.58 inches. The average monthly rainfall for a March at BWI-Marshall is 3.93 inches.

Here on the WeatherDeck in Cockeysville, we have 1.98 inches on the gauge since Friday. The Sun's weather station at Calvert and Centre streets shows 2.34 inches since Friday.

Here are some other totals for the two days of rain, compiled from CoCoRaHS:

Elkridge, Howard County:  4.15 inches

Severn, Anne Arundel:  3.79 inches

Ellicott City, Howard:  2.86 inches

Elkton, Cecil:  2.74 inches 

Towson, Baltimore Co.:  2.70 inches

Columbia, Howard:  2.65 inches

Severna Park, Anne Arundel:  2.49 inches 

The National Weather Service has been reporting flooded roads in Elkridge, Thurmont and in Towson over the last 24 hours. The Potomac is in moderate flood at Paw Paw, W.Va., Point of Rocks, Md. (see chart), and at Wisconsin Avenue in Washington, D.C. Minor flooding is reported on Antietam Creek at Sharpsburg, and Harper's Ferry and Little Falls on the Potomac.

Heavy, peristent rain across the region is bringing small stream and creeks to their brims, while waters are rising to flood stage along the Potomac River, the Monocacy in Frederick County and other rivers.

BWI-Marshall has tallied more than 3 inches of rain so far from this storm. We have 1.6 on the gauge here on the WeatherDeck. Drop a comment and let us know what you're seeing.

The National Weather Service has posted Flood Warnings from Garrett County east to the Chesapeake, with more rain expected. Here is a bit of this afternoon's Forecast Discussion from Sterling:

"...THE FLOOD WARNING REMAINS IN EFFECT UNTIL 515 PM EST FOR URBAN
AREAS AND SMALL STREAMS IN BALTIMORE CITY...BALTIMORE...NORTHERN ANNE
ARUNDEL...HOWARD AND CARROLL COUNTIES...

"AT 219 PM EST NATIONAL SERVICE DOPPLER RADAR CONTINUED TO INDICATE
AN AREA OF HEAVY RAINFALL ACROSS THE BALTIMORE METROPOLITAN AREA.
ADDITIONAL RAINFALL AMOUNTS UP TO AN INCH ARE POSSIBLE.

"A FLOOD WARNING MEANS THAT FLOODING IS IMMINENT OR HAS BEEN REPORTED.
STREAM RISES WILL BE SLOW AND FLASH FLOODING IS NOT EXPECTED.
HOWEVER...ALL INTERESTED PARTIES SHOULD TAKE NECESSARY PRECAUTIONS
IMMEDIATELY."

NOAA's Advanced Hydrologic Prediction Service is reporting minor flooding along the Potomac River near Williamsport, Little Falls (chart above) and Wisconsin Avenue in Washington, D.C.

The National Weather Service is also reporting flooding and closed roads on Route 77 near Cunningham Falls, near Thurmont in Frederick County and in Elkridge. Roads have been closed, also, in parts of Loudon County, Va., and Hampshire County, West Virginia.

(SUN PHOTO: Frank D. Roylance)

Also, the flood gauges so far show most rivers and streams in Maryland have not yet reached flood stage, although much of the runoff is not expected to reach the larger rivers until late today or tomorrow. You can follow the river flooding here. The chart below shows that water levels on the Potomac at Wisconsin Avenue in Washington have already climbed within a few inches of flood stage.

Here are some samples of the rain totals reported by this morning. The differences across the region are sharp. Where northern Arundel reported well over an inch, Towson saw barely a half-inch. Here on the WeatherDeck in Cockeysville, we've recorded less than three-quarters of an inch. NWS forecasters seem to be dialing back on their more dire rain forecasts of Friday afternoon.

Thurmont, Frederick Co.:  1.75 inches

Severn, Anne Arundel:  1.68 inches  

Severna Park, Arundel:  1.29 inches

Leonardtown, St. Mary's:  1.11 inches

Salisbury, Wicomico:  1.01 inches

Ellicott City, Howard:  0.94 inch

Columbia, Howard:  .81 inch

Sykesville, Howard:  0.66 inch

Towson, Baltimore Co.:  0.59 inch

In the meantime, Flood Warnings have been posted for Garrett, Allegany and Frederick Counties as snowmelt and rain push small streams and creeks over their banks. Waters are expected to continue to rise into Sunday.

UPDATE 11 a.m.: Flood Warnings have been extended to Baltimore County and City, northern Anne Arundel County, Howard and Carroll counties.

The advisories are in effect from Harford County south to St. Mary's, from midnight until 6 a.m. They will then upgrade to a Costal Flood Watch, in effect through Saturday afternoon.

High tides could rise two feet above predictions overnight due in part to the persistent east winds, and in part because of increased tidal levels related to the approach of the new moon. Minor flooding is expected. Higher tides are expected on Saturday. Here's more from the NWS: 

"STRONG EASTERLY WINDS WILL PERSIST THROUGH SATURDAY CAUSING TIDAL
ANOMALIES TO CONTINUE INCREASING. THE INCREASING TIDAL ANOMALIES
COMBINED WITH THE LUNAR CYCLE WILL BRING THE POTENTIAL FOR
MODERATE FLOODING NEAR TIMES OF HIGH TIDE.

"HIGH WATER LEVELS IN THE POTOMAC DUE TO HEAVY RAIN WILL ENHANCE THE THREAT FOR COASTAL FLOODING ACROSS THE UPPER TIDAL POTOMAC RIVER SATURDAY AFTERNOON
AND POSSIBLY INTO EARLY NEXT WEEK.

"EMERGENCY MANAGERS AND PEOPLE WITH INTEREST ON THE POTOMAC RIVER
AND THE WESTERN SHORE OF THE CHESAPEAKE BAY SHOULD BEGIN TO
PREPARE FOR POTENTIAL COASTAL FLOODING."

Next high tides:

HAVRE DE GRACE: 8:17 p.m. and 8:00 a.m.
FORT MCHENRY BALTIMORE: 4:47 a.m. and 5:39 p.m.

ANNAPOLIS U.S. NAVAL ACADEMY: 3:17 a.m. and 4:08 p.m.
SOLOMONS ISLAND: 12:09 a.m. and 1:00 p.m.
POINT LOOKOUT: 11:19 p.m. and 12:10 p.m.

There are Flood Watches posted for the entire state today through Saturday evening. Forecasters say the heaviest rain is due Friday night and Saturday, with 2 to 4 inches possible by the time things begin to taper off on Monday.

That much rain, coming on top of a heavy snow meltdown that has saturated the soil and kept the creeks full, will mean flooding for small creeks, streams and urban areas this weekend. And when all that reaches the larger rivers, we should expect those waters to spill over their banks, as well. You can track the flooding here.

The Flood Watches for the Eastern Shore call for even more rain - 3 to 5 inches. That's one to two months worth of normal rainfall in just four days. Do not attempt to drive through flooded roadways.

Here's AccuWeather.com's take on the rain, with their rainfall forecast map. And here is Mr. Foot's Forecast.

The wet weather is being brought to you by a slow-moving low-pressure system that has been dawdling our over the Central Plains. The counter-clockwise circulation around that low has been dragging warm, moist air off the Gulf and the Atlantic, and delivering about 0.66 inch of rain at BWI-Marshall overnight.

Next up: A secondary low now forming over the southeast coast. The counter-clockwise circulation around that coastal low will begin to throw onshore easterly winds across Delmarva from the Atlantic. By tonight and Saturday, the rains will become heavy at times, delivering the bulk of the weekend rainfall.

The whole mess will be slow to pull away, so we can expect the drip to continue through Sunday and into Monday. We should get back to sunny skies and mild temperatures by mid-week.

(SUN FILE PHOTO)

Here are the top 10 finishers, according to a Web site called Golden Snow Globe. No idea who they are, so I can't vouch for their numbers. I know the total listed for Baltimore (80.4 inches) is no longer valid. The National Weather Service forecast office at Sterling, Va. has recalculated and cut the official total for BWI-Marshall Airport to 77 inches. That pushed Mobtown to 5th place, instead of 4th as listed on the site.

Here's now it should look:

1. Syracuse, N.Y.: 106 inches 

2. Erie, Pa.:  90.9 inches

3. Rochester, N.Y.:  89.6 inches

4. Philadelphia, Pa.:  78.7 inches

5. Baltimore, Md.:  77 inches

6. Pittsburgh, Pa.:  76.9 inches

7. Buffalo, N.Y.:  74.1 inches

8. GrandRapids, Mich.:  70.2 inches

9. Fort Collins, Colo.:  69.6 inches

10. Lakewood, Colo.:   68.2 inches

(SUN PHOTO: Algerina Perna)

But sunny days in the 60s will give way this weekend to four days in the 50s, with rain. And, for the western counties, especially, the mild temperatures and rain will combine to melt down the snowpack that remains on the ground there. Forecasters say small stream and creeks will likely overflow their banks, and river flooding could follow.

The National Weather Service has already issued Flood Warnings for portions of West Virginia southwest of Maryland's Garrett County. There are Flood Watches up from Garrett east to Washington County, including the cities of Cumberland and Hagerstown, where as much as 4 inches of rain could fall through Saturday.

East of the mountains, there are Hazardous Weather Outlooks posted as far as Carroll, Howard and Montgomery counties.

UPDATE: 6 p.m.: Flood watches are now posted for all Maryland counties west of the bay, plus the Upper Eastern Shore

For Baltimore, the rain is forecast to begin late Thursday night into Friday, with more than an inch expected by early Saturday morning. The rain could be heavy at times late Friday and Saturday, with another two inches possible. Rain chances continue into Monday, so it appears the weekend will be a washout. But at least it's not snow. And our snow cover is gone, except for some lingering piles. So we won't have to add that water to the runoff. The rain will be quite enough, thank you.

Needless to say, though, we'll need to be on the lookout for wet basements, leaks through ice-damaged roofs and gutters, overflowing creeks and street flooding. And that can collapse roads, as this amazing video from Freeport, Maine demonstrates.

Never drive through flooded low spots. It's amazing how little water it takes to float a car and carry it downstream. I suspect we will be reading about water rescues, anyway, this weekend.

All this rain is approaching as a low-pressure system moves very slowly toward us out of the Midwest. The counter-clockwise flow around the low is drawing mild, wet air north from the Gulf and, eventually, the Atlantic.

The heaviest rain will arrive late Friday and Saturday. Here's a bit of this morning's forecast discussion from Sterling:

"ONE BATCH OF RAINFALL ONGOING FRIDAY MORNING MAY LIFT NORTH IN THE AFTERNOON...LEAVING CLOUDS AND DRIZZLE BUT ANOTHER MORE SIGNIFICANT AREA OF RAINFALL IS STILL ON TRACK TO AFFECT THE [FORECAST AREA] FRIDAY NIGHT AND SATURDAY. RAINFALL TOTALS OF 1 TO 3 INCHES...WITH POTENTIAL FOR HIGHER AMOUNTS IN UPSLOPE AREA...ARE LIKELY WITH THIS SIGNIFICANT AREA OF RAIN FRIDAY NIGHT INTO SATURDAY."

The chances for rain will continue into Monday as the storm makes its leisurely exit.