textproduct: NWS Phoenix

KEY MESSAGES

- Slightly above normal temperatures with areas of moderate HeatRisk will prevail throughout the week before retreating closer to normal over the weekend.

- Other than a slight chance of a thunderstorm in eastern Arizona during the middle of the week, dry conditions under mostly sunny skies will prevail the next several days.

- Locally breezy conditions will develop late in the week and this weekend, particularly across the lower Colorado River valley and higher terrain communities.

SHORT TERM /Today through Thursday/

Objective analysis at midday today still showed an omega block across much of the northern tier of the Lower 48, as well as a weak low circulation off the west coast due west of LA and San Diego and subtle cyclonic curvature over portions of eastern AZ. Global guidance shows the omega block will break down over the next 24-48 hours and the weak coastal low will continue sliding SSE to central Baja Peninsula. Through this progression the height field over the local area will not change much from its current level. H5 heights are currently around 585dam and will increase up to 586-587dam through the remainder of the week. Heights at this level are slightly above normal for the beginning of June and respectively the high temperature forecast the rest of the week is a few degrees (4-6F) above normal. This means high temperatures across the lower deserts reaching up to 103-108F, with the hottest days looking to be Wednesday and Thursday. These above normal temperatures will result in widespread moderate HeatRisk across the lower deserts. These temperatures will also be well shy of daily records which are mostly in the 112-116F range.

Objective analysis also currently shows a tongue of higher moisture and unstable air across southern NM and into the White Mountains of AZ. This has already resulted in some midday convective showers developing in the White Mountains. As things continue to heat up a few thunderstorms may also develop, but storms will mostly stay in NM this afternoon. Heading into tomorrow, a retreating of the dry line further west across NM and westward-propagating thunderstorm outflows should push more moisture into eastern AZ. Consequently, isolated thunderstorms become even more likely near the White Mountains Wednesday and Thursday afternoon, potentially leaking into far eastern Gila County. Latest NBM PoPs show virtually no chance for showers or storms in southern Gila County Wednesday afternoon, but most HREF and REFS members develop a few showers and storms in parts of southern Gila County, particularly south and east of US-60. PoPs were increased slightly, up to 10-15%, to at least reflect a mention of thunderstorms in the forecast. The main impacts with any storms will be lightning strikes with little rainfall, capable of sparking wildfires in dry late spring fuels, and strong gusty outflow winds. The outflow winds may help generate new convection in Gila County and progress west-southwest toward lower deserts in the evening. How Wednesday evolves may dictate shower and storm chances for Thursday, but confidence is too low to make any significant PoP adjustments at this time.

LONG TERM /Friday through Monday/

Through the weekend, the full suite of ensemble members are in fair agreement depicting the northern Mexico shortwave slowly ejecting into the southern plains with some measure of ridging holding over the Southwest ahead of deeper negative height anomalies approaching the West coast. The trend among the majority of ensemble membership is towards a slower progression of this troughing across the East Pacific resulting in less local influence of height falls as the southern extent of wave lags the Southwest before lifting into the Great Basin. As a result, H5 heights may only decrease modestly over the weekend into a 582-585dm range and temperatures only cooling near the seasonal average. Numerical spread remains quite large during this time frame reducing forecast confidence with respect to temperatures. However, this pattern evolution will force an increased low level pressure gradient with afternoon/evening wind gusts becoming more pronounced and heightening the potential fire danger. Forecast confidence deteriorates further during the beginning of next week tied to the exact evolution of troughing entering the western Conus, but there are a growing number of ensemble members suggesting more predominant ridging and warming versus previous iterations.

AVIATION

Updated at 1100Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns are expected during the TAF period. Winds will follow diurnal trends with some occasional gusts in the mid to upper teens during the afternoon hours. Other than some exiting high clouds this morning and distant high terrain CU later, skies will be mostly clear through Wednesday morning.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are expected during the next 24 hours. Outside of some periods of VRB to calm conditions, mainly during the the remainder of the morning hours, winds will follow familiar diurnal trends with speeds generally aob 12 kt. Skies will be mostly clear through Wednesday morning.

FIRE WEATHER

The threat for a few lightning strikes with little rainfall in southern Gila County Wednesday and Thursday is the main fire weather hazard this week. With temperatures hovering several degrees above normal, winds will maintain a diurnal upslope/nocturnal drainage pattern. However, gusts will increase markedly towards the end of the week, particularly across the lower Colorado River valley and mountainous locations of eastern districts. This will result in periods of an elevated to near critical fire danger during the afternoon/evening, especially over the weekend. Minimum afternoon humidity levels will generally fall in a 5-15% range following a wide ranging poor to fair overnight recovery of 15-45%.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...None.