Comparing the last pre-event model runs: NAM 00Z 19 Dec 2009 vs NAM 12Z 05 Feb 2010

The last pre-event model run is in, and the snow looks to be intense: over 2.5" QPF, which would translate to 25" using a 10-1 ratio. I thought it'd be interesting to compare this morning's last pre-event forecast with the last pre-event model run from the 19 December 2009 storm. Both NAM forecasts show over 2.5" liquid-equivalent QPF for a bulls-eye centered on the northern Chesapeake. Interestingly, the NWS and associated agencies were discounting the NAM back in December as being "too wet" (the GFS was their model of choice, with its much more 'reasonable' QPF of 1.5") This time around, the NWS is not discounting the NAM at all, and is predicting record snows for our area -- 20-30 inches in the latest warning. Regardless of what ends up falling, we are in for a good dousing of snow.

**EDIT at 1145 a.m. light snow began falling in Annapolis**

Below are the NAM forecasts, for comparison: top figure is for this current storm; bottom figure, for the 19 Dec storm. The QPFs look amazingly similar.

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1154 AM EST FRI FEB 5 2010

DCZ001-MDZ003>007-009>011-013-014-016>018-501-502-VAZ021-025>031-036>040-042-050>057-501-502-WVZ050>055-501>504-060100-/O.CON.KLWX.WS.W.0006.000000T0000Z-100207T0300Z/
...
INCLUDING THE CITIES OF ...WASHINGTON ...BALTIMORE ...ANNAPOLIS...
1154 AM EST FRI FEB 5 2010

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 10 PM EST SATURDAY...

* PRECIPITATION TYPE...HEAVY SNOW.

* ACCUMULATIONS...WIDESPREAD STORM TOTAL ACCUMULATIONS OF 20 TO 30 INCHES...WITH SOME LOCATIONS IN EXCESS OF 30 INCHES.

* TIMING...SNOW WILL CONTINUE THROUGH SATURDAY EVENING. CONDITIONS WILL DETERIORATE RAPIDLY THIS AFTERNOON...WITH HEAVIEST SNOWFALL OCCURRING FROM SUNSET THROUGH SATURDAY MORNING. THE MOST HAZARDOUS CONDITIONS WILL OCCUR TONIGHT.

* VISIBILITIES...WIDESPREAD VISIBILITIES AROUND ONE-QUARTER MILE ARE EXPECTED TONIGHT IN HEAVY SNOW. STRONG WINDS WILL COMBINE WITH THE SNOW ALONG THE MARYLAND CHESAPEAKE BAY AND TIDAL POTOMAC RIVER TO REDUCE VISIBILITIES TO WELL BELOW ONE-QUARTER MILE...PRODUCING NEAR-BLIZZARD CONDITIONS TONIGHT THROUGH SATURDAY MORNING.

* TEMPERATURES...HIGHS IN THE LOWER 30S TODAY. TEMPERATURES WILL BE IN THE MID TO UPPER 20S TONIGHT AND SATURDAY.

* WINDS...BECOMING NORTHEAST 10 TO 20 MPH LATE TODAY. GUSTS OF 20 TO 30 MPH TONIGHT AND SATURDAY...HIGHER NEAR THE COAST.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS EXTREMELY DANGEROUS STORM IS EXPECTED TO PRODUCE RECORD SNOWFALL FOR THE BALTIMORE AND WASHINGTON DC METROPOLITAN AREAS. TRAVEL CONDITIONS TONIGHT ACROSS THE REGION WILL BE EXTREMELY HAZARDOUS AND LIFE-THREATENING. HELP YOUR LOCAL AND STATE GOVERNMENT FIRST RESPONDERS AND TRANSPORTATION AGENCIES BY STAYING OFF THE ROADS.

A WINTER STORM WARNING MEANS SIGNIFICANT AMOUNTS OF SNOW ARE EXPECTED OR OCCURRING. STRONG WINDS ARE ALSO POSSIBLE...ESPECIALLY NEAR THE COASTLINE.

KRAMAR