The current NWS forecast calls for 87°F tomorrow and 86°F on Thursday at Fairbanks airport, and I think that's a conservative prediction. This morning's GFS MOS forecast has 89°F tomorrow and 90°F on Thursday, which seems about right.
The chart below shows a time-height cross-section of temperature according to the GFS model, showing that 850mb temperatures are expected to reach about 17°C. If we trace that warm air down to the surface along a dry-adiabatic lapse rate, we get a surface temperature of 88°F at Fairbanks airport, and typically solar heating will boost temperatures a bit beyond that estimate. For reference, the last time 90°F was reached in Fairbanks was in June 2013; the high was 92°F on the 25th and 26th, but the lapse-rate method gave a temperature of 88°F. So lower 90s are certainly a possibility this week.
The one factor that might help keep temperatures down a bit is the high level of soil moisture remaining from recent wet weather; the moist ground will not heat up quite as much, and increased evaporation will soak up some energy compared to, say, 2013. It will certainly be interesting to see if 90°F can be reached - for only the 5th time in the past 20 years.
Update: here's a radar image from Tuesday evening (see comments below):
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ReplyDeleteLots of cumulus congestous forming over the hills this afternoon. I see no caping layer yet above the cloud tops but I'm sure it's getting there. Warm today, upper 70's around 2pm. I'm guessing low 80's today with an isolated shower possible off to the east.
ReplyDeleteWe're seeing a relative humidity rebound at 11pm Tuesday eve and some cooling as the Sun slips lower to the NW and scattered clouds shield...is that what you refer to in your last paragraph?
ReplyDeleteMaybe monitor the hourly data for the next few days and describe before the cold front forecast for this weekend descends from the Arctic. This may be our Summer's heat event.
Gary
Gary, indeed with a jump in dewpoint from 51F at 8pm to 62F at 10pm, and light winds, this looks like locally generated humidity finding itself trapped in the lowest levels of the atmosphere after solar heating eases and a low-level inversion forms.
DeleteA dewpoint of 62F ties the highest observed in Fairbanks since 2010.
The dew point for Fairbanks rose to 65F around midnight 6/13>6/14.
DeleteGary
Gary, that's close to an all-time record for Fairbanks. The highest credible dewpoint appears to be 67F.
DeleteActually it got closer...66F. Air temp,relative humidity, dew point.
DeletePAFA,07/13/2016 23:35 AKDT,71.62,83.13,66.2
PAFA,07/13/2016 23:50 AKDT,71.62,83.13,66.2
Well spotted, Gary. It's hard to be sure of the measurement, though, because unfortunately there is a processing issue with these intra-hourly ASOS observations that have become available lately. Apparently the integer Fahrenheit measurement is being converted to Celsius, then truncated (not rounded), then converted back to Fahrenheit.
DeleteYou can see for example at 06:53 AKDT today we have a temperature of 64.9F, but 64.4F on either side. In reality it was measured at 65F the whole time, but for the intra-hourly obs this was converted and truncated to 18.0C and then back to 64.4F. At :53 (the standard hourly measurement) a Celsius decimal point was retained (but only one decimal point), giving 65F = 18.3C = 64.9F.
The same thing is happening for dewpoint, so it appears the peak measured dewpoint must have been 67F, ending up as 66.2F after Celsius truncation.
To quote Rick Thoman yesterday on this: "what a mess".
Here's the relevant section from the ASOS documentation. The ASOS reports in integer F or nearest 0.1-degree C. The issue is with the processing after that point.
DeleteThe ASOS hygrothermometer continually measures the ambient temperature and dew point temperature and provides sample values approximately six times per minute. Processing algorithms in the hygrothermometer use these
samples to determine a 1-minute average temperature and dew point valid for a 60-second period ending at M+00. These data are passed to the ACU for further processing.
Once each minute the ACU calculates the 5-minute average ambient temperature and dew point temperature from the 1-minute average observations (provided at least
4 valid 1-minute averages are available). These 5-minute averages are rounded to the nearest degree Fahrenheit, converted to the nearest 0.1 degree Celsius, and reported once
each minute as the 5-minute average ambient and dew point temperatures. All mid-point temperature values are rounded up (e.g., +3.5°F rounds up to +4.0°F; -3.5°F rounds up to -3.0°F; while -3.6 °F rounds to -4.0 °F).
There was a fair sized thunderstorm which passed to the south east of Fairbanks last night. It dissipated around midnight.
ReplyDeleteLooks like it was small but intense. I've added a radar image to the post. Eielson reported thunder and a wind shift at 9:20pm as the cool outflow reached the station.
DeletePAEI 130522Z 18012G14KT 100V220 10SM VCTS SCT065CB SCT085 BKN200 27/13 A3003 RMK AO2A TS 6SE MOV W LTG SE WSHFT 20