NEG NAO Posted November 24, 2012 Share Posted November 24, 2012 PRELIMINARY EXTENDED FORECAST DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD 311 AM EST SAT NOV 24 2012 VALID 12Z WED NOV 28 2012 - 12Z SAT DEC 01 2012 ...HEAVY PRECIPITATION EXPECTED IN CALIFORNIA LATE THIS WEEK INTO THIS WEEKEND... ...MODERATE TO HEAVY SNOWS POSSIBLE FOR THE NORTHERN MID-ATLANTIC STATES AND INTERIOR NEW ENGLAND MID TO LATE NEXT WEEK... GENERAL FLOW PATTERN ==================== A REPETITION OF THE PATTERN SEEN OVER THE PAST FEW WEEKS IS EXPECTED, WITH AN AMPLIFIED TROUGH MOVING SLOWLY THROUGH THE EASTERN PACIFIC, WITH DOWNSTREAM RIDGING FORMING ACROSS THE WEST AND PLAINS, AND RENEWED TROUGHING ANTICIPATED ACROSS THE NORTHEAST WHICH IS EXPECTED TO CLOSE OFF INTO A DEEP CYCLONE AS IT MOVES INTO QUEBEC AND ATLANTIC CANADA. THE RIDGE/TROUGH COUPLET OVER THE LOWER 48 IS EXPECTED TO BE COMPOSED OF BROAD FEATURES OF RELATIVELY LOW AMPLITUDE, WHICH LEADS TO QUICK SHORTWAVE MOVEMENT/SYSTEM PROGRESSION THROUGH THE LOWER 48. MODEL PREFERENCES ================= THE 00Z ECMWF IS QUICK WITH A SHORTWAVE MOVING THROUGH THE EAST/WESTERN ATLANTIC EARLY IN THE PERIOD AND OUTPACES THE REMAINDER OF THE GUIDANCE LATE IN THE PERIOD NEAR THE WEST COAST, INCLUDING ITS OWN 12Z ENSEMBLE MEAN. ALOFT, THE NON-ECMWF GUIDANCE FITS THE 12Z ECMWF ENSEMBLE MEAN BEST ACROSS EASTERN CANADA FROM THURSDAY ONWARD (AND PLAYS INTO THE SLOWING/WESTWARD SHIFT SEEN IN THE OPERATIONAL ECMWF NEAR THE EAST COAST OVER ITS PAST COUPLE DAYS OF RUNS), THOUGH THE ECMWF ENSEMBLE MEAN SURFACE LOW NEVER COUPLES WITH ITS 500 HPA CIRCULATION (WHICH SEEMS UNLIKELY), SHOWING MINIMAL INTERNAL CONSISTENCY. BASED ON THE ABOVE, THE PRESSURES WERE BASED ON A 40/30/30 BLEND OF THE 00Z UKMET/00Z GFS/00Z CANADIAN THROUGH FRIDAY BEFORE SWITCHING TO A 50/50 BLEND OF THE 00Z GFS/00Z GEFS MEAN SOLUTION THEREAFTER. WHILE THIS MAINTAINED GOOD CONTINUITY NEAR THE WEST COAST, IT LED TO A MORE COASTAL CYCLONE TRACK LATE TUESDAY AND WEDNESDAY WHEN COMPARED TO FRIDAY AFTERNOON'S PROGS AND A GREATER SNOW THREAT FOR THE NORTHEAST. WEATHER IMPACTS =============== MODERATE PRECIPITATION IS EXPECTED TO SPREAD UP THE CENTRAL APPALACHIANS THROUGH NEW ENGLAND AND NORTHERN MID-ATLANTIC STATES TUESDAY THROUGH THURSDAY AS A LOW SWINGS OFFSHORE THE NEW ENGLAND COAST BEFORE MOVING INTO ATLANTIC CANADA THURSDAY. THIS PRECIPITATION COULD BE IN THE FORM OF MODERATE TO HEAVY SNOW ACROSS THE NORTHERN MID-ATLANTIC STATES AND INTERIOR NEW ENGLAND. RIDGING ACROSS THE WEST AND PLAINS SHOULD MINIMIZE ANY SIGNIFICANT GULF MOISTURE INFLUX THROUGH THE PERIOD, THOUGH LIGHT RAINS COULD RETURN INTO TEXAS AND THE MIDWEST THURSDAY THROUGH NEXT WEEKEND, LURED NORTHWARD BY WEAK FRONTAL WAVES ACROSS THE MID-SECTION OF THE COUNTRY CAUSED BY WEAK SHORTWAVES MOVING OVER THE TOP OF THE WESTERN AND PLAINS RIDGE. OUT WEST, HEAVY PRECIPITATION IS EXPECTED TO BEGIN IN CALIFORNIA AND PORTIONS OF THE NORTHWEST THURSDAY, AND CONTINUE THROUGH NEXT SATURDAY, WITH AREAL AVERAGE LIQUID EQUIVALENT (LEQ) AMOUNTS OF 4-6 INCHES EXPECTED...LOCAL LEQ AMOUNTS COULD EXCEED 10 INCHES IN THE TOPOGRAPHY OF NORTHERN CALIFORNIA WHICH COULD FALL IN THE FORM OF SIGNIFICANT HIGH ELEVATION SNOWS. ROTH Link to comment Share on other sites More sharing options...
Snow_Miser Posted November 24, 2012 Share Posted November 24, 2012 FWIW, the NAM was less amplified on it's 06z run for this storm. It's the NAM at 84 hours though, so general fluctuations can probably be expected with the outcome of this storm at this range. Link to comment Share on other sites More sharing options...
MJO812 Posted November 24, 2012 Share Posted November 24, 2012 If we could get a strengthening storm on the benchmark, that might help the coastal areas. Link to comment Share on other sites More sharing options...
Snow_Miser Posted November 24, 2012 Share Posted November 24, 2012 12z GFS is a bit further south of the 00z and the 06z GFS. Also a bit colder for the area. Link to comment Share on other sites More sharing options...
MJO812 Posted November 24, 2012 Share Posted November 24, 2012 Link to comment Share on other sites More sharing options...
Snow_Miser Posted November 24, 2012 Share Posted November 24, 2012 Nice run for the area. This is the total precip through hr 96 and more is still falling. 850s stay below freezing the entire time. Not sure if there is a mid level warm layer or not. Soundings should be telling. Link to comment Share on other sites More sharing options...
PB GFI Posted November 24, 2012 Share Posted November 24, 2012 So my first idea of the storm not going to the lakes was right , BUT looks like my second idea of the storm being shunted was WRONG . The EURO s error yesterday was it left a piece behind and now all the models take it all out So a nice middle ground looks good now . Link to comment Share on other sites More sharing options...
MJO812 Posted November 24, 2012 Share Posted November 24, 2012 Looks like the GFS went towards benchmark hit just like the Euro. Link to comment Share on other sites More sharing options...
ag3 Posted November 24, 2012 Share Posted November 24, 2012 Nice run for the area. This is the total precip through hr 96 and more is still falling. 850s stay below freezing the entire time. Not sure if there is a mid level warm layer or not. Soundings should be telling. GFS still has that warm layer in the 900mb level and also the surface for NYC and east. Link to comment Share on other sites More sharing options...
Snow_Miser Posted November 24, 2012 Share Posted November 24, 2012 GFS still has that warm layer in the 900mb level and also the surface for NYC and east. How about for places further west and inland, like at KMMU/KSMQ/KHPN? Link to comment Share on other sites More sharing options...
ag3 Posted November 24, 2012 Share Posted November 24, 2012 How about for places further west and inland, like at KMMU/KSMQ/KHPN? Gets better just west of NYC. Link to comment Share on other sites More sharing options...
bluewave Posted November 24, 2012 Share Posted November 24, 2012 How about for places further west and inland, like at KMMU/KSMQ/KHPN? NYC looks to be the dividing line on this GFS run between rain and snow. The GFS is hinting that the city and Western LI could mix with wet snow between 84-96 hrs if the BL cools enough. Sleet shouldn't be a concern for any sections as there is uniform below freezing temps above 900 mb. Link to comment Share on other sites More sharing options...
Snow_Miser Posted November 24, 2012 Share Posted November 24, 2012 Gets better just west of NYC. NYC looks to be the dividing line on this GFS run between rain and snow. The GFS is hinting that the city and Western LI could mix with wet snow between 84-96 hrs if the BL cools enough. Sleet shouldn't be a concern for any sections as there is uniform below freezing temps above 900 mb. Thank you. Link to comment Share on other sites More sharing options...
Quakertown needs snow Posted November 24, 2012 Share Posted November 24, 2012 2m is warm for many Link to comment Share on other sites More sharing options...
Allsnow Posted November 24, 2012 Share Posted November 24, 2012 Wow..more snow...can i get close to ten before december Link to comment Share on other sites More sharing options...
ag3 Posted November 24, 2012 Share Posted November 24, 2012 2m is warm for many Its not even the 2m temps that are concerning for me. Under a heavy band, 2m temps will cool. The 900mb warming keeps showing up on the models for the coast as the winds start off as SE before switching to the NE. Link to comment Share on other sites More sharing options...
Snow_Miser Posted November 24, 2012 Share Posted November 24, 2012 2m is warm for many The warmest it gets for inland locations looks to be the mid 30s at the surface. Link to comment Share on other sites More sharing options...
MJO812 Posted November 24, 2012 Share Posted November 24, 2012 Accuweather pro snow map shows 2-5 inches in NYC Link to comment Share on other sites More sharing options...
MJO812 Posted November 24, 2012 Share Posted November 24, 2012 12z Nogaps got a little colder. It still shows a benchmark storm. Warm for the coast. Link to comment Share on other sites More sharing options...
SVT450R Posted November 24, 2012 Share Posted November 24, 2012 12z GFS Total snowfall Link to comment Share on other sites More sharing options...
SnowGoose69 Posted November 24, 2012 Share Posted November 24, 2012 The GFS is likely a snow event for the coast. The soundings for JFK at 16Z before precip arrives show 37/25, its a marginal event for sure and will depend on if the precip is decently heavy but I think in this exact setup we're snowing. Link to comment Share on other sites More sharing options...
MJO812 Posted November 24, 2012 Share Posted November 24, 2012 12z GGEM came further north. Rain for the coast and snow inland. http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html Link to comment Share on other sites More sharing options...
snywx Posted November 24, 2012 Share Posted November 24, 2012 12z GGEM came further north. Rain for the coast and snow inland. http://collaboration...pe_gem_reg.html GGEM has your classic R/S line.. Ill take it Link to comment Share on other sites More sharing options...
Isotherm Posted November 24, 2012 Share Posted November 24, 2012 Wow..more snow...can i get close to ten before december Need 4" to reach the snowiest November on record, 16" in 1898, for here. 4.1" to break the all time record. Crazy think I'd be over a foot heading into December. Link to comment Share on other sites More sharing options...
MJO812 Posted November 24, 2012 Share Posted November 24, 2012 GEFS http://raleighwx.americanwx.com/models/gfsensemble/12zgfsensemblep12084.gif Link to comment Share on other sites More sharing options...
Saturn510 Posted November 24, 2012 Share Posted November 24, 2012 Isotherm, and Snowlover can attest to this... It seems the middlesex , monmouth and somerset counties which typically are on the rain snow line on marginal events have seem to done better snow wise than in the past. I think we used to get royally screwed in the past and the last few years we have done well. Link to comment Share on other sites More sharing options...
forkyfork Posted November 24, 2012 Share Posted November 24, 2012 at this point i'm thinking we could see 2-5" immediately west of the city Link to comment Share on other sites More sharing options...
earthlight Posted November 24, 2012 Share Posted November 24, 2012 We're going to need some heavy precipitation to get snow near the coast with this profile (From EWR). On the GFS we're looking at a few hours of snow changing to rain and ending as IP. The boundary layer is just way too warm during the height of the event (4 c) Link to comment Share on other sites More sharing options...
Chris L Posted November 24, 2012 Share Posted November 24, 2012 1 to 3 inches sounds like a shot of happening, however, like John said, the BL shown in the sounding is a bit too warm, but that can change with heavy rates. Link to comment Share on other sites More sharing options...
Storm At Sea Posted November 24, 2012 Share Posted November 24, 2012 Agreed. The only hope is that the system cranks a bit more. Stagnant cold airmass and little advection from the north. We're going to need some heavy precipitation to get snow near the coast with this profile (From EWR). On the GFS we're looking at a few hours of snow changing to rain and ending as IP. The boundary layer is just way too warm during the height of the event (4 c) Link to comment Share on other sites More sharing options...
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