textproduct: Raleigh

WHAT HAS CHANGED

* Bit of a downward trend in QPF for Saturday's system.

KEY MESSAGES

As of 218 AM Friday...

1) Chilly with widespread rain tonight and Saturday as a deepening surface low lifts along the NC coast.

2) Below normal temperatures Sunday trending above by Tue with potential showers and storms next Wed-Thu

3) Marginal fire concerns Monday and Tuesday within a dry and gusty airmass

DISCUSSION

As of 218 AM Friday..

KEY MESSAGE 1... Chilly with widespread rain tonight and Saturday as a deepening surface low lifts along the NC coast.

Sfc analysis this morning depicted a cold front moving south across the NC/SC border. A few isolated showers have developed along this front primarily in SC. Post-frontal nnely flow this morning will shift to ely and eventually sly as this weak boundary migrates back north. Increasing WAA/isentropic lift may generate isolated showers across our Sandhills/Coastal Plain (and perhaps as north as Raleigh) this morning through mid afternoon. QPF should be relatively low and isolated. Otherwise, highs today will max out around 70 with mostly cloudy skies.

As we pivot to later tonight, increasing isentropic lift associated with a developing offshore low with bring light rain to the area. The bulk of the rain should fall between ~06Z Saturday and 00Z Sunday. However, latest 00Z guidance has trended lower wrt to QPF over our area. The HREF and RREFS LPMM output only highlight a maximum of six to seven tenths in our far southeast to just a tenth in the Triad. Regardless, Saturday should remain chilly with persistent nely flow with highs in the mid to upper 50s. Rain should clear from west to east by early Saturday evening, with clearing skies expected overnight. While winds may stir a bit Saturday night, which may limit radiational cooling, the chilly airmass should still support lows in the upper 30s to lower 40s.

KEY MESSAGE 2... Below normal temperatures Sunday trending above by Tue with potential showers and storms next Wed-Thu

With the passage of Saturday's system, cool high pressure near the TN valley region Sunday will build east into early next week. The airmass in the wake of the offshore low will remain below normal on Sunday with highs generally in the 60s, some 10-12 degrees below seasonal normals.

The cool area of high pressure is forecast to rather quickly shift offshore Monday afternoon, with return flow to persist at least into midweek Wednesday. This will aid low-level thicknesses to trend from near normal Monday to above by midweek, with temperatures rising above normal into the upper 70s to middle 80s Tue and Wed.

The warm temperatures may very well extend into Thursday. However, we are watching another mid to late week cold front slated to approach either Wed or Thu. The 12z ensemble guidance is mixed on the timing, with the top two cluster solutions focusing precipitation chances mainly on Thu, while the other two cluster solutions show a deeper and faster trough, bringing showers as early as Wed afternoon or evening. The trough is fairly strong for early May across the OH valley, with southwest flow at mid-levels approaching 70-75 kt, supportive of strong deep-layer shear where low to perhaps mid 60s dewpoints could be present at the surface. Nearly all of the AI severe convective guidance models are thus indicating the potential for severe storms late Wed or Thu east of the cold front if the trough can materialize. That is a big if this far out, but is something we will be keeping a close eye on as we get closer.

KEY MESSAGE 3... Marginal fire concerns Monday and Tuesday within a dry and gusty airmass

As cool high pressure Sunday shifts offshore Monday, return flow will set in across the region. However, dewpoints will be slow to recover, resulting in low RH levels from the upper 20s to middle 30s. Southwest winds of 20-30 mph will be possible, especially on Tuesday across the Piedmont. As a result, with the breezy and dry conditions in place, marginal fire danger concerns cannot be completely ruled out. Depending on how much precipitation falls on Saturday, this may become more of an issue.

AVIATION /11Z FRIDAY THROUGH TUESDAY/

As of 636 AM Friday...

1030Z Update: Nely flow and VFR conditions persist this morning. As expected, a few isolated showers continue to trend east near KFAY this morning. Expect this to continue through much of today, with isolated showers possible at KFAY/KRDU/KRWI. Otherwise, introduced sub-VFR ceilings at KFAY and KRWI between 6 and 12Z tonight.

Previous discussion:

VFR conditions persist this morning as a cold front slides into South Carolina. A few isolated showers have popped up the past few hours along the advancing front. While no restrictions are expected, these showers could linger around KFAY this morning. As we progress throughout the day, the warm front will slowly retreat northward as low-level flow turns ely and then sly. Increasing isentropic lift may promote isolated showers in the KFAY vicinity through much of the day. Some guidance brings these showers closer to KRDU and KRWI, but confidence is too low to make a mention of -RA at these sites in this TAF package. Steadier rain and associated restrictions from Saturday's low pressure system are not expected to reach any of our terminals till after 06Z Saturday.

Outlook: Rain is expected to arrive late Friday night and early Saturday. CIGS will become MVFR to IFR then LIFR late Saturday morning through the afternoon. Slow clearing is expected Saturday night into early Sunday with a return to VFR Sunday. The longest duration CIGS/VSBYS should be around FAY/RWI/RDU, will accompany an area low pressure forecast to track along the coast of the Carolinas Saturday then offshore by early Sunday.

RAH WATCHES/WARNINGS/ADVISORIES

None.