weekend weather in the Whites

[bikehikeskifish]

I've been following the site posted earlier (by BIGEarl), namely
http://www.crownweather.com/summitsforecast.html, during the winter.
I've read the listed descriptions for all the symbols here:
http://www.weather.gov/tdl/synop/mavcard.htm, and the symbols and
values all make sense. What doesn't make sense to me is the apparent
contradiction in the values. For example, I'm interested in the FEB
12 forecast, and I've removed some of the rows and half the columns
(for FEB 13) from the report to make it easier to read.

MOS FORECASTS

GFS MOS (MAV)
 KMWN   GFS MOS GUIDANCE    2/11/2008  1200 UTC                      
 DT /FEB  11/FEB  12               
 HR   18 21 00 03 06 09 12 15 18 21
 N/X                    -8         
 TMP -13 -9 -7 -5 -4 -2  0  2  4  7
 DPT -14-11 -9 -6 -7 -7 -8 -8 -5 -3
 CLD  OV BK OV OV SC OV FW FW SC BK
 WDR  31 31 31 31 30 30 31 31 29 27
 WSP  70 62 59 51 44 45 39 26 20 17
 P06         4     2     1     2   
 P12                     3         
 POS  94100100100100 98100100100100
 TYP   S  S  S  S  S  S  S  S  S  S
 SNW                     0         
 VIS   1  1  1  1  1  1  1  1  1  1
 OBV  BL BL BL FG FG FG FG FG FG FG

According to the CLD data, it will be OV (overcast), SC (scattered),
FW (few) and BK (broken) during the day. Likewise the P06/P12
(Probability of Precipitation during the last 6/12 hours) says
virtually none (4, 2, 1, 2).

Why then does the POS (Conditional probability of snow) show nearly
100% for most of the day?

Are there going to be good views or will the higher summits be socked
in tomorrow? Is it going to snow? Why or why not?

Thanks,
Tim

 

[DrewKnight]

I read it the same way you do...

I would interpret the chart the same way you did, Tim, but the POP figures don't jibe so much with the other outlets, either. Weather.com (not the source of record for mountain forecasting but still) is saying partly cloudy AM, becoming overcast PM, snow developing in the evening.

This is pretty consistent with the Mt Washington Observatory, which is showing summits in the clear under increasing clouds tomorrow. They're calling for temps in the single digits with pretty good winds on the higher summits, and, again, snow developing later on.

Based on my non-scientific read, I would assume you'd be able to see a lot farther than your boots early in the day, with things closing in later. Maybe Mattl or Grouseking have a better sense of why the apparent contradiction?

BTW, the CONUS snow accumulation forecast for Tuesday into Wednesday seems to be indicating 4 to 6" in the Whites, where Weather.com and the NWS seem to be hedging toward 5 to 8".

These are the times that try a winter-lover's soul... I have a really long commute and in the last week, four out of four AM drives have been white-knuckle affairs (complete with a couple of roll-overs on 93 and lots of time contemplating the value of Volvo stability control in my own car). Also, we're in the middle of building a house, and the framing crew had to quit this AM when their pneumatic nailers essentially froze up and stopped working. But -- my god! -- how good that powder felt yesterday.

 

[bikehikeskifish]

Get this, the forecast for Gorham (I'm thinking about Moriah) says (forecast.weather.gov):

Tuesday: Increasing clouds, with a high near 21. Wind chill values as low as -4. Calm wind.

Does that make any sense?!?

Tim

 

[DrewKnight]

Wow...

That right there is what you'd call a "study in contradictions".

By the way -- the roads north of Plymouth are still pretty greasy tonight, which was a bit surprising. If the weather goes according to plan tomorrow night, it could be very messy come Wednesday morning. Be careful out there, folks.