Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 300406

Area Forecast Discussion
National Weather Service Tucson AZ
906 PM MST Mon May 29 2017

.SYNOPSIS...There is a chance of afternoon and evening thunderstorms
east of Tucson into Wednesday. Dry conditions will then prevail
Thursday into early next week. Daytime temperatures will moderate
closer to seasonal normals or a few degrees below normal by midweek,
then another warming trend will occur by the weekend.


.DISCUSSION...Dew points along the Arizona/New Mexico border have
increased 20-30 degrees over the past 24 hours due to low-level
southeasterly flow around a negatively tilted trough axis. This
moisture influx helped generate isolated showers and thunderstorms
during the afternoon, especially over the higher terrain along the
border. Activity has moved east this evening and conditions should
remain dry until afternoon convection kicks off again tomorrow. Even
with the extra cloud cover today, high temperatures still reached 3-
5 degrees above normal. The current forecast remains in good shape
and no significant changes were made. Please see the previous
discussion for further details.


.AVIATION...Valid thru 31/06Z.
SCT-BKN clouds above 20k ft AGL through the period, with FEW-SCT cu
developing tomorrow afternoon around 12k ft AGL. Terrain driven
light surface wind tonight will increase Tuesday afternoon sly to
swly 10-15 kts with gusts to 20 kts. Isolated to scattered -TSRA/-
SHRA also develop Tuesday afternoon mainly near the AZ/NM border.
Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Isolated to scattered afternoon and evening
thunderstorms will occur east of Tucson into Wednesday. The best
chance of wetting rains will be near the New Mexico border. Expect
gusty and erratic winds due to thunderstorm outflows. Dry conditions
will then prevail across southeast Arizona Thursday into early next


.PREV DISCUSSION /230 PM MST/...An upper level trough axis will
extend from the San Francisco Bay Area southeastward into southern
Baja California Tuesday. Backing of lower and mid-level winds should
promote a somewhat further westward development of showers/tstms
versus this afternoon. Based on the 29/12Z GFS/ECMWF/CMC/NAM
deterministic solutions as well as the Univ. of AZ WRF-NAM and WRF-
GFS, have maintained at least a slight chance of afternoon and
evening showers/tstms Tuesday across much of Greenlee and Graham
Counties, and about the eastern half of Cochise County.

The upper trough axis is progged to move gradually eastward into
southern Arizona Wednesday. Increasing southwesterly flow aloft will
shunt the bulk of deeper moisture east of this forecast area.
However, enough moisture should remain to support at least a slight
chance of showers/tstms Wednesday afternoon and evening across
eastern sections. The deterministic GFS/ECMWF/CMC then depicted any
measurable precip Thursday to be well east of this forecast area.
Based on these solutions, have opted for dry conditions area-wide
Thursday. Amplifying high pressure aloft will likely maintain precip-
free conditions Friday into Sunday.

Thereafter, there were differences between the GFS/ECMWF regarding
precip potential for next Monday. The ECMWF was considerably more
robust versus the drier GFS with various moisture parameters, and
depicted measurable rainfall to potentially return to near the New
Mexico border. For this forecast issuance have opted to favor the
drier GFS. Thus, have extended the dry forecast scenario into next

Expect no significant change in daytime temperatures Tuesday versus
this afternoon, with high temperatures Tuesday to generally average
about 2-5 degrees above normal. A few degrees of daily cooling is on
tap Wednesday and Thursday followed by another warming trend Friday
into next weekend.






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