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Monday, March 16, 2015

Spring Snow

3-20 -  Didn't get to update yesterday.  NAM held steady with .17 qpf for DXR.  GFS and Euro backed down the heaviest 6hr period from .4 to .25.  Though totals went down a little, they spread out .05 to .1" qpf over several 6hr periods.  That shouldn't accumulate.  This mornings HRRR and RAP still suggested 4-5", until the 13z run which has 3".  Temps slightly higher than forecast.  They were not forecast by any model to go above freezing, current temp is 33.2.  DP and WB temps still quite low, teens and lower 20's. 

3-18  Afternoon - GFS is now onboard

3-18  Euro still onboard with 3" of snow for the Danbury area.  QPF is .46 but looking at .39 for the 10:1 ratio time frame.  Temps do support snow.  No holes in any layer, just a matter of where the precip goes now.

Euro snow 3-18 0z run

ECMWF Deterministic FORECAST FOR:  LAT =  41.38  LON =  -73.46

                                            00Z MAR18
                               2 M     850     6 HR
                              TMP    TMP    QPF 
                               (C)      (C)     (IN)   
FRI 12Z 20-MAR  -6.2    -4.7      0.00    
FRI 18Z 20-MAR  -1.1    -7.3      0.05 
SAT 00Z 21-MAR  -2.2    -3.5    0.30    
SAT 06Z 21-MAR  -2.2    -1.9    0.09    
SAT 12Z 21-MAR  -1.9    -4.5    0.02    

GFS still at .1 qpf, for an inch of snow, but temps support snow as well.  0z and 6z NAM is also further south with QPF, but 12z may see some changes.

3-17  Euro continues on a 3-4" snow for the morning of the 21st for NYC/LI north. 850s well below 0 with surface temps at or below 0, so snow is supported.   .52 liquid qpf is currently forecast - snow ratio likely under 10:1, but it may be close.  1000-500 thickness in the 535 range, also supporting all snow.
                 2 M     850     6 HR    
                 TMP     TMP     QPF     
                 (C)     (C)    (IN)      
FRI 18Z 20-MAR   0.2    -6.9    .12         
SAT 00Z 21-MAR  -0.4    -2.9    .34         
SAT 06Z 21-MAR  -0.8    -4.6    06        
SAT 12Z 21-MAR  -1.7    -2.8    0.00      

0z GFS is less robust, with colder temps.  Only snow showers. CMC and UKMET more like Euro


DGEX brushes us with 1", but reloads and makes it look like we will get hit on the 25th.
Early NAM looks south - complete miss.
JMA from 12z yesterday has a nice deepening storm off New England 12z 3-21 after spreading .5 qpf.

3-16  First weekend of spring.... snow/rain.

Friday night into Saturday, Euro calls for 2-4 inches throughout Tristate.  This is coming from a southern storm, fairly weak, sliding to our south that will pull some cold air down and change from rain to snow.
850s and 925s support snow on this one, really most of the time. 
12z euro mslp

12z euro snow map
Then Sunday, some snow showers and perhaps another inch or two?? Scenarios where the precip chase the front don't usually work out, but there should at least be snow showers.  850s are warm ahead though.
Then a little flurries/snow showers as a warm front moves through on the 25th
3-25 warm front action
GFS supports Euro

12z GFS snow  6" for tristate

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