Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 292139
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
230 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 next weekend.

&&

.DISCUSSION...Isolated showers were occurring from the White
Mountains southward to just northeast of the Chiricahua Mountains at
this time. A few lightning strikes were also detected during the
past 30-45 minutes near Hannagan Meadow. The precip echoes were
moving northeast around 10 mph. Storm Prediction Center mesoscale
analysis depicted an axis of 500-1000 J/kg MLCAPE extending from the
White Mountains southeastward into the New Mexico bootheel. The
Univ. of AZ 29/12Z WRF-NAM had a fairly close depiction of echo
coverage valid 21Z, but the echoes were stronger than reality.

Based on various NWP solutions, appears that any showers and
thunderstorms will be east of this forecast area by around 8 PM MST
this evening or so. Thus, have opted for chance-category PoPs across
the White Mountains early this evening, then dry conditions area-
wide later tonight.

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
Monday.

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.

&&

.AVIATION...Valid thru 31/00Z.
Isolated to scattered -TSRA/-SHRA mainly near the AZ/NM border
ending by 30/03Z. Isolated to scattered -TSRA/-SHRA east of a P13
(Globe) to FHU line Tuesday afternoon. Otherwise, FEW-BKN clouds
mostly above 12k ft AGL through the period. Surface wind this
evening into Tuesday afternoon sely to swly 5-15 kts with gusts to
20 kts. 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
week.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

Francis

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