textproduct: Raleigh

WHAT HAS CHANGED

As of 245 PM Thursday...

* There is increased confidence in patchy fog over the northern/central Coastal Plain and far NE Piedmont early Fri morning. * Confidence is not high enough to warrant a Frost Advisory for tonight as temperatures should be at least several degrees warmer compared to last night. But patchy frost will still be possible.

KEY MESSAGES

As of 245 PM Thursday...

1) Patchy fog may develop over NE areas late tonight and early Friday morning, when isolated frost also can't be ruled out over the coolest parts of the Piedmont and northern Coastal Plain.

2) Fire weather concerns will remain elevated through early next week owing to dry conditions, low relative humidity and no rainfall forecast in the next 7 days.

3) Near record warm temperatures possible Tue through Thu.

DISCUSSION

As of 245 PM Thursday...

KEY MESSAGE 1... Patchy fog may develop over NE areas late tonight and early Friday morning, when isolated frost also can't be ruled out over the coolest parts of the Piedmont and northern Coastal Plain.

A ~1040 mb surface high centered over the North Atlantic will continue to ridge down the US East Coast through tonight. However, as it moves farther NE, the pressure gradient will lessen substantially, with mainly calm winds expected overnight. This combined with clear skies will result in decent radiational cooling conditions. However, with increasing low-level moisture as dew points rise into the 40s in eastern areas, high-res guidance is in good agreement that some patchy fog will develop across the northern/central Coastal Plain and far NE Piedmont late tonight and early Friday morning. This along with low-level thicknesses about 20- 30 m higher compared to this morning means confidence in frost development is lower, so opted to not issue a Frost Advisory at this time. However, patchy frost can't be totally ruled out in the usual cool outlying spots of the Piedmont and northern Coastal Plain, such as Roxboro and Siler City.

KEY MESSAGE 2... Fire weather concerns will remain elevated through early next week due to dry fuels, low relative humidity, and little to no rainfall forecast in the next 7 days.

Dry westerly flow will persist across the region between a broad upper trough over the northern US and strengthening ridge over the Gulf, limiting moisture return and resulting in a dry forecast through much of next week. A weak cold front will try to slip south into the Mid Atlantic states on Saturday, but will will most likely wash out as it reaches central NC, as the aforementioned ridge builds across the southern US. These warm and dry conditions, with daily afternoon RH of 20-35 percent, will worsen fire weather concerns, with only the relatively weak winds each day under high pressure helping to mitigate the threat. A cold front may approach NC from the northwest during the latter part of next week, which could result in higher RH and may help improve the fire conditions.

KEY MESSAGE 3... Near record warm temperatures possible Tue through Thu.

Mid-upper level ridging will steadily build over the Gulf and Southeast states through much of next week. Low level thicknesses will rise from 20-25 m above normal Mon to 40-50 m above normal by Wed/Thu, with Wed likely the hottest day. Temps are expected to be 15-20 degrees above normal Tue-Thu, within a category or so of records (see climate sections below). NWS Experimental Heat Risk reaches Level 2/Moderate/Orange by Wed, and this level of early- season heat could be dangerous, especially to those vulnerable to the heat. CPC outlooks extending beyond Thu suggest that temps are likely to stay much above normal into next weekend.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

As of 215 PM Thursday...

VFR conditions and dry weather will prevail across central NC through this evening, with light NE winds 7 kts or less. Scattered high clouds this afternoon will give way to clear skies this evening into tomorrow. The clear skies combined with mainly calm winds and increasing dew points from the east will result in possible patchy fog late tonight into early tomorrow morning across the northern/central Coastal Plain and far NE Piedmont. This signal shows up on the HREF as well as the HRRR, RAP, NAM and GLAMP. Confidence of this occurring is highest at RWI, where IFR and maybe even LIFR visibilities are possible. Included a TEMPO group for MVFR at RDU, as a lot of high-res guidance puts it on the western edge of any fog/mist that develops. Any fog will disperse by mid-morning, with light winds through the rest of the period.

Outlook: VFR and dry weather will prevail through early next week, with the possible exception of some fog and low stratus in the early mornings on Sunday and Monday.

CLIMATE

Record High Temperatures:

April 11: KFAY: 90/2001

April 14: KGSO: 90/1922 KRDU: 91/1941 KFAY: 93/1922

April 15: KGSO: 90/2006 KRDU: 92/1941 KFAY: 95/2006

Record High Minimum Temperatures:

April 13: KGSO: 61/2019 KRDU: 66/1930

April 15: KGSO: 65/2006 KRDU: 64/1993

RAH WATCHES/WARNINGS/ADVISORIES

None.