Scientific Forecaster Discussion
fxus65 ktwc 290343
Area forecast discussion
National Weather Service Tucson Arizona
843 PM MST Tue Mar 28 2017
Synopsis...an area of low pressure over east central New Mexico
will continue to move away from the region, with dry conditions and
a warming trend occurring Wednesday and Thursday. The next system
will bring another chance of showers mainly northeast of Tucson
Friday through Sunday, along with strong and gusty winds on Friday.
Discussion...the system which brought spotty showers and gusty
winds today was shifting east of the region, with the center of the
low currently over east central New Mexico. The last vort lobe to
rotate through the back side of the circulation and affect Arizona
was over far western New Mexico, with just a few showers hanging on
in Arizona along portions of the Mogollon Rim and in the White
Mountains. These showers should come to an end by midnight as the
system continues to move east.
Winds have diminished considerably this evening, with northwest
winds generally at 7-12 mph. Overall, will continue to see a
general slackening of the winds through the rest of the night and
into the mid morning hours on Wednesday, before some breezy
northwest winds kick back up again. Satellite imagery indicates
generally clear skies west of the three most eastern counties
(greenlee, Graham and cochise). Eastern areas will become mostly
clear later tonight as the upper low tracks east into the Texas
Panhandle by early morning Wednesday.
Forecast morning lows on Wednesday across the area were generally a
few degrees below the latest guidance values. This seems reasonable
given the clearing skies and slackening winds. Also, with dewpoints
in the upper teens to lower 20s just upstream across the western
half of the state, not sure if we will hold onto dewpoints at
current levels in the upper 20s to lower 30s through the night.
Overall, forecast package looks to be in good shape. No updates. For
more information on the latter periods of the forecast, please refer
to the prev discussion section below.
Aviation...valid through 29/23z.
Expect sky clear conditions west of ktus and few-scattered clouds at 7-11k ft
above ground level east of ktus thru 29/06z. Aft 29/06z, mainly sky clear conditions
areawide. Sfc wind less than 10 kts thru 29/18z. Aft 29/18z, northwesterly
sfc wind at 8-16 kts, with the strongest wind in the upper Gila
River valley near ksad. Aviation discussion not updated for taf
Fire weather...afternoon breezes will continue Wednesday and
Thursday along with warmer temperatures. Another weather system will
then move in late Friday with gusty winds. Red flag conditions
possible Friday afternoon across far southern fire weather zone 152.
This system will also bring a chance of showers mainly northeast of
Tucson Friday through Sunday.
Previous discussion...wrap around moisture on back side of upper low
moving through west central nm this afternoon. Isolated showers/high
elevations snow showers for the remainder of the afternoon hours
into early this evening, mainly east of a Safford to Douglas line.
Gusty northwest winds this afternoon will diminish this evening.
Dry northwesterly flow aloft on Wednesday becoming westerly on Thursday which will
result in warmer high temperatures both days. Highs on Thursday will
be the warmest in the upcoming 7 day forecast period.
The next Pacific storm will impact the area Friday thru Sunday.
Models pretty similar on moving closed low into northern Arizona on
Friday with resultant increase in pressure gradient across the area
which will produce breezy to windy conditions. Uncertainties exist
on timing of cold front passage, which will have impact on daytime
highs and then the amount of moisture this system will have or will
briefly pick up from the Gulf of California. At this time, have
relegated the slight chance pops to areas NE of Tucson, but can't
rule out further areal coverage. I say this due to European model (ecmwf) producing
some light quantitative precipitation forecast Friday morning/afternoon while the GFS/GFS ensembles
remain dry. Something for later shifts to monitor. Highs on Friday
will be well below normal to close out March.
Unsettled conditions over the first weekend of April as several
disturbances aloft drop down eastern Arizona on the back side of the
upper low as it moves to the east. Again the best chances at this
time appear to be NE of Tucson. Warmer to end the weekend into early