Saturday, February 28, 2009

"Hold on for one more day..."
- from the 1990 single Hold On by Wilson Phillips

BIG KAHUNA ALERT: SAT FEB 28 - 12:00 PM. NWS has issued a Winter Storm Watch for central Maryland - central and southwestern Virginia - Philadelphia metro - portions of northern DelMarVa. View map. Sterling, VA NWS projects 5 or more inches by Monday AM: Forecast discussion - HPC snow probability map - HPC short range discussion. Widespread school closings on Monday and delays Tuesday are a near certainty.

MY QUICK TAKE: While 6 to 10 inches may fall, a warm ground and higher sun angle may also negate much of that so actual accumulations on untreated secondaries/sidewalks/parking lots will be closer to 5 inches, with main roads receiving 3 inches or less. Closest comparison is the Feb 28-Mar 1 Kahuna of 2005: Heavy snow warnings of 6 - 10 inches in the Baltimore metro region yielded 5 or less for the same reasons.

PREVIOUS SYNOPSIS: FRI FEB 27 - 2:45 PM. I hope you're able to hold on for one more day, because if you want snow...things may be turning your way. A breakdown of weather impacts for eastern Mid-Atlantic/ I-95 corridor from DC to Philly:
FRIDAY: Mild windy conditions give way to showers this evening ahead of a cold front crossing the area overnight.
SATURDAY: Cold afternoon rain mixes with wet snow toward evening and changes to snow/sleet overnight.
SUNDAY: Colder air arrives by Sunday morning, with periods of snow and sleet that could accumulate 5 or more inches by evening on untreated secondaries and sidewalks, with up to 3 inches on main roads.
MONDAY: Sub-freezing temperatures throughout the day wind-driven snow on top of ice may produce widespread school closings from Virginia to DC and Baltimore into the Philly metro area. Cold winds in wake of the storm will deliver an unpleasant and disruptive start to the Spring sports season, so coaches, players and athletic directors alike should plan accordingly.
To stay current on storm developments, I encourage you to visit the following links: HPC probabilistic snow/ice, yesterday's prelim extended discussion, and the Baltimore/Washington forecast discussion. For comparison, here is Accuweather's take. A quick glance at the current precip timing charts for the GFS and NAM show roughly .50" of liquid equivalent snow, which for the Baltimore region could translate to a ballpark 2" by Sunday evening. A bigger picture of moisture potential is shown via the current QPF day 1-5 map (see all the purples and reds?) The current European model provides a general snapshot of 5000 foot temps and the storm's projected path. Taking all this into account, I hope you can plainly see it's worth holding on for one more day, even if it's barely enough to cover the grass.

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