Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tucson Arizona
900 am MST Wednesday Jul 30 2014
Synopsis...thunderstorms will be confined mainly to the south and
southeast of Tucson today. Increasing chances of thunderstorms will
start on Thursday followed by scattered mainly afternoon and evening
thunderstorms Friday through Sunday. Expect hotter daytime
temperatures today...then a moderation in high temperatures will
prevail this weekend.
Discussion...remnants of a thunderstorm complex over Sonora Mexico
last night continued to move northward into far Southeast Arizona
this morning. A slight increase in moisture and a weak circulation
associated with this feature will help increase the chances of
thunderstorms and showers across Cochise and Santa Cruz counties
today. The previous shift already adjusted pop values for this
area...so the short term forecast looked in good shape. Latest
models were still suggesting somewhat limited thunderstorm chances
again for Thursday before a noticeable upswing in activity on
Friday. Much better chances of thunderstorms can be anticipated
areawide on Saturday. Please refer to the previous discussion in
this product for more details.
Aviation...valid through 31/18z.
Isolated -tsra/-shra will be limited to mainly near the mountains
and near the international border south-to-southeast of ktus this
afternoon/evening. Otherwise...mostly clear skies will prevail west
of ktus through early Thursday morning. From ktus vicinity eastward
expect a few to broken cumuloform clouds at 8-12k feet above ground level this
afternoon and this evening...and cloud bases mainly above 15k feet above ground level
at other times. Surface wind will be mostly less than 10 kts into
early Thursday morning. Aviation discussion not updated for taf
Fire weather...expect thunderstorms to be limited mostly to locales
south-to-southeast of Tucson this afternoon and this evening.
Thereafter...scattered mostly afternoon and evening thunderstorms
will return starting Thursday and continue into this weekend as
deeper moisture moves into the area. Otherwise...normal diurnal wind
trends will occur with occasional gusts during the afternoon hours
due to daytime heating.
Previous discussion...expect scattered showers/thunderstorms Thursday
afternoon/evening east and south of Tucson with isolated
showers/thunderstorms from Tucson westward/nwwd into western Pima/south central Pinal
counties. Greater coverage of showers/thunderstorms will occur Friday due to
the prognosticated moisture increase and a more favorable southeasterly middle-level
flow. A scenario consisting of gusty outflows producing areas of
dense blowing dust is a possibility Friday afternoon into early Friday
evening...particularly northwest of Tucson. However...will defer depicting
areas of blowing dust in the gridded data weather field until
forecast confidence increases.
scattered to numerous mainly afternoon/evening showers/thunderstorms will
prevail as high pressure aloft becomes centered near The Four
Corners region. 30/00z GFS/European model (ecmwf) were fairly similar with depicting
an inverted trough/weak upper low to be over the area. This system
will enhance the potential for locally heavy rainfall and perhaps
GFS/European model (ecmwf) were similar with depicting drier air to advect into Southeast Arizona
from the southwest Monday as high pressure aloft becomes centered southeast of
the area. GFS/European model (ecmwf) continued to be similar with establishing an
upper high over the northern Gulf of California Tuesday. This scenario would
yield another drying trend early next week. Thus...have opted for a
gradual decrease in shower/thunderstorm coverage...with chance-category probability of precipitation
by Tuesday across eastern sections and dry conditions across western Pima County.
High temperatures this afternoon will generally be about 2-5 degrees f warmer
versus temperatures achieved Tuesday...and will average nearly 3-7 degrees f above
normal. A gradual cooling trend will then occur thur-sun...with
forecast high temperatures sun to be a few degrees below normal. A warming
trend is on tap Monday-Tuesday due to the expected drier regime.
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