944 
FXUS65 KPSR 280402
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
902 PM MST Sat Jan 27 2018

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
A warming trend will continue through early next week with high 
temperatures nearing record levels in the 80s Sunday and Monday. 
High pressure gradually weakens thereafter allowing temperatures to 
cool slightly beyond the middle of the week, although still 
remaining above average. Next week looks to remain entirely dry. 

&&

.DISCUSSION...
As longwave troughing progresses into the Upper Midwest, pronounced 
ridging was building upstream into the SW Conus with 4-5dm height 
rises already sampled through southern CA/NV per 12Z soundings. Over 
the course of the next 36-60 hours, H5 heights will increase 
markedly from a 572-576dm range sampled this morning to a 580-584dm 
range under strongly subsident northerly flow. This sharp ridging 
configuration will promote notable pressure rises over the central 
Rockies/Great Basin such that stronger easterly flow will envelop 
much of the forecast area. The first vestiges of the warmer, 
breezier regime will arrive tomorrow with afternoon highs nearing 
the 80F threshold. 

However, the pinnacle of this warming trend will occur Monday with 
highs approaching record levels though recent model output indicates 
readings may fall just short. This appears to be a reflection of a 
very weak shortwave diving south into the region disturbing 
advective processes and helping enhance the pressure gradient and 
easterly wind through central AZ. In this case, there will be 
competing influences with an easterly wind pulling air from a cooler 
source region, yet also creating a deeper mixing depth resulting 
from the enhanced gradient. 

Of larger concern Monday afternoon will be impacts from these 
stronger easterly winds across south-central AZ. Though the number 
of newly plowed fields in the ag belt of Pinal County is uncertain, 
almost all similar wind events thus far this winter have produced 
dust streamers over open fields in this area. Therefore, have added 
a blowing dust mention for the traditional areas along the I-10/I-8 
corridors. In addition, fairly low relative humidity values and very 
dry fuels will lead to an elevated fire danger during the afternoon 
hours. 

Through the middle and end of next week, all signs point to a 
continued dry pattern for Arizona and southeast California under the 
influence of a dry northwest flow aloft. A large upper trof will 
settle over much of the central and eastern CONUS with Arizona on 
the far western periphery; at times, there will be high clouds 
embedded in the northwest flow and this will result in partly sunny 
skies at times. Heights aloft will slowly fall off and temperatures 
will fall back into the mid to upper 70s by about Wednesday. No 
precipitation is in the forecast for the foreseeable future.

&&

.AVIATION... 
South-Central Arizona including KPHX, KIWA, and KSDL: 

As high pressure continues to build in from the west, a light 
wind pattern is expected through mid to late Sunday morning. By 
late Sunday morning breezy east-northeasterly winds at 8-12 
gusting to about 15-20kt are expected and will continue until 
early evening. After that, light northeasterly winds will 
predominate. Skies will remain mostly clear to partly cloudy with 
periods of FEW-BKN high clouds. 

Southeast California/Southwest Arizona including KIPL and KBLH:

Light diurnal winds are expected across the region through late 
Sunday morning with some occasionally breezy northerly winds 
expected by late morning at 8-12kt. Skies will remain mostly clear 
to partly cloudy with periods of FEW-BKN high clouds through Sunday 
afternoon with clear skies thereafter.  

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Monday through Friday: 
A strong ridge of high pressure will lead to near record warmth 
early next week before temperatures cool only slightly from the 
middle of the week and beyond. The entire week will be characterized 
as warmer than normal and entirely dry. Correspondingly, afternoon 
humidity levels will fall into a 10-20% range while overnight 
recovery will generally be good. Winds will favor a northerly or 
easterly direction early in the week with the strongest gusts above 
25 mph (even stronger over ridge tops) occurring Monday. Along with 
these stronger winds, dry fuels and lower relative humidity values 
will result in an elevated fire danger Monday afternoon. A lighter, 
more typical wind trend will settle over the districts during the 
latter half of the week.

&&

.CLIMATE...

Record highs in jeopardy early next week:

Date      Phoenix           Yuma
----      -------           ----
Jan 28    83 in 1971      84 in 1986
Jan 29    83 in 1935      84 in 1986

&&

.SPOTTER INFORMATION STATEMENT... 
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

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DISCUSSION...MO/CB
AVIATION...Sawtelle
FIRE WEATHER...MO 
CLIMATE...MO